2nd Last Final Draft Research Project 2013.docx

8/14/2019 2nd Last Final Draft Research Project 2013.docx

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SCHOOL OF ENGINEERING

DEPARTMENT OF MECHANICAL AND AERONAUTICAL ENGINEERING

VIBRATION EFFECTS IN SOLIDIFICATION OF A LOW MELTING POINT METAL

Compiled By

Student No

S i

MR. D.D. Jonker

28511141

MR P V d


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Supervisor MR P Vadazs

D.D. Jonker_28511141

MCS_412

MEGANIESE EN LUGVAARTKUNDIGE

INGENIEURSWESEMECHANICAL AND AERONAUTICAL ENGINEERING

INDIVIDUAL COVER SHEET FOR PRACTICALS / INDIVIDUELE DEKBLAD VIR PRAKTIKA

Name of Student / Naam van Student D.D. Jonker

Student Number / Studentenommer 28511141Name of Module / Naam van Module Research Project

Module Code / ModuleKode MSC 412

Name of Lecturer / Naam Van Dosent Mr. P. Vadazs

Date of Submission / Datum van Inhandiging 27 May 2013

Declaration:

1. I understand what plagiarism is and am

aware of the Universitys policy in this regard.

2. I declare that this reportis my own, original

work.

3. I did not refer to work of current or

previous students, memoranda, solution

manuals or any other material containing

complete or partial solutions to this

Verklaring:

1. Ek begryp wat plagiaat is en is bewus van die

Universi-teitsbeleid in hierdie verband.

2. Ek verklaar dat hierdie verslagmy eie,

oorspronk-like werk is.

3. Ek het nie gebruik gemaak van huidige of

vorige studente se werk, memoranda,

antwoord-bundels of enige ander materiaal wat

volledige of gedeeltelike oplossings van hierdie


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1 AbstractTitle: Vibration effects in solidification of a low melting point metal

Author: D. D. Jonker

Student Number: 28511141

Study Leader: Mr. P. Vadazs

The purpose of the research project is to produce metal casts subjected to sonic or mechanical

vibrations during the solidification process. The research involves the selection of; (1) a low melting

point temperature metal and, (2) a vibration source between either sonic or mechanical which will

be transmitted via a cylindrical mould. Theoretical time of the solidififcation should be produced and

comparatively discussed with the experimental findings (see Chap. 1).

A detailed literature review was carried out in order to fimiliarise the researcher of the subject

matter. The review include a look at how a casting process is practiced in foundries, available castingmetals or alloys characterised by low melting point temperatures, suitable materials used in making

of moulds, application of vibrations in a casting process and what are the influences of the induced

vibration on the solidification process of casts. A study was also conducted about different

thermocuoples suitable for experimentation, insertion of thermocouples in the moulds and the

eventual cooling curve generation. As a guideline, the literature was used in making certain decisions

on the different materials to be used in the experimental phase of the research (see Chap. 2).

The design and manufacturing of components required for the setup was carried in chapter 3 of the


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2 Table of ContentsAbstract .................................................................................................................................................... i

List of Figures ......................................................................................................................................... iv

List of tables ............................................................................................................................................ v

Abbreviations .......................................................................................................................................... v

List of Symbols ....................................................................................................................................... vi

1. Chapter 1: Introduction .................................................................................................................. 1

1.1. Background ............................................................................................................................. 11.2. Objectives and scope of research ........................................................................................... 2

1.2.1. Theoretical objectives ..................................................................................................... 3

1.2.2. Experimental objectives .................................................................................................. 3

1.2.3. Exclusions from scope ..................................................................................................... 3

1.3. Methodology ........................................................................................................................... 4

2. Chapter 2: Literature Review .......................................................................................................... 5

2.1. Metal casting ........................................................................................................................... 5

2.1.1. Casting methods ............................................................................................................. 6

2.2. Low melting point cast metals ................................................................................................ 7

2.2.1. Characteristics of pure metals ........................................................................................ 7

2.2.2. Characteristics of alloys .................................................................................................. 8

2.3. Mould materials ...................................................................................................................... 8

2 3 1 Pl t 8


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3.1.2. Required Pattern ........................................................................................................... 34

3.1.3. Required Casting Mould ................................................................................................ 34

3.2. Fixtures for mould attachment ............................................................................................. 35

3.3. Vibrating table design ........................................................................................................... 36

3.3.1. Platform ........................................................................................................................ 36

3.3.2. Vibration motor ............................................................................................................ 42

3.3.3. Suspension system ........................................................................................................ 45

3.3.4. Support stand ................................................................................................................ 49

3.3.5. Table technical specifications ....................................................................................... 51

3.4. Cost analysis .......................................................................................................................... 52

4. Chapter 4: Setup and procedure of the experiment .................................................................... 54

4.1. Experimental Setup ............................................................................................................... 54

4.2. Experimental procedure ....................................................................................................... 55

5. Chapter 5: Results and discussion ................................................................................................. 57

6. Chapter 6: References ................................................................................................................... 597. Chapter 6: Addenda ...................................................................................................................... 62

Addendum A.1: Selection of cast metal......................................................................................... 63

Addendum A.2: Selection of mould material/s ............................................................................. 64

Addendum A.3: Selection of vibration source ............................................................................... 64

Addendum B: Theoretical solidification time .............................................................................. 65

Addendum C.1: Detailed explanation of experimental setup components ..................................... 67

Add d C 2 E i t l d h kli t 73


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3 List of FiguresFigure 1: Various modes in which mould vibration can be applied ........................................................ 2

Figure 2: Typical experimental setup for mould vibration ..................................................................... 2

Figure 3: Casting process flow chart ....................................................................................................... 6

Figure 4: Classification of casting processes ........................................................................................... 6

Figure 5: Comparison of melting points and free energies of oxide formation for pure metals ........... 8

Figure 6: schematic of the melting process ............................................................................................ 9

Figure 7: Stages of shrinkage ................................................................................................................ 11

Figure 8: Formation of crystals of radius r in a molten metal homogeneous nucleation .................... 12

Figure 9: Cooling curve for a pure metal showing the degree of undercooling to initiate HN ............ 12

Figure 10: Formation of crystals of radius r in a molten metal heterogeneous nucleation ................. 13

Figure 11: The volume and surface free energy terms combined leads to a total free energy. .......... 14

Figure 12: Growth of a metal dendrite ................................................................................................. 15

Figure 13: Homogeneous nucleation and crystal growth into grains ................................................... 15

Figure 14: Solidification of metal in a cylindrical mould ....................................................................... 15

Figure 15: Schematic drawing of three types of cast growth structure ............................................... 16

Figure 16: Schematic illustration of different cast structures solidified in a square mould ................. 16

Figure 17: Temperature distribution in Air-Mould-Metal .................................................................... 17

Figure 18: Typical example of a cooling curve for pure metals ............................................................ 20

Figure 19: Ideal cooling curve of an alloy ............................................................................................. 20

Fi 20 T i l li f Al Si h t ti ll h i d li 21


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4 List of tablesTable 1: Some melting points and free energies of oxide formation of cast metals. ............................. 7

Table 2: Some melting points of alloys ................................................................................................... 7

Table 3: Ranges and tolerances for ASNI thermocouple types ............................................................ 22

Table 4: Thermocouple design and arrangement and their advantages .............................................. 24

Table 5: Recommended zinc cast allowances ....................................................................................... 32

Table 6: laboratory equipment to used ................................................................................................ 67

Table 7: Cast metal selection ................................................................................................................ 63

Table 8: Vibration source selection....................................................................................................... 64

Table 9: metal constants required for Chvorinov's rule equation ........................................................ 65

5 AbbreviationsTMT Temperature measuring technique

VTM Vibration testing machines

ext. dia. Extension diameter

HN H l ti


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6 List of SymbolsSymbol Definition Volume free energy Surface energy, r* Crystal radius Specific surface free energy of particleK ,

,

Thermal conductivity

Thermal diffusivity Density

c Specific heat Temperaturex Distance from mould-metal interface Heat flux AreaV Volume

Solidified metal thickness Time Latent heat of fusion Minimum mould thickness Biot number Heat transfer coefficient AmplitudeFrequency

A l f


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1. Chapter1: Introduction1.1. BackgroundThe process of solidification of metal during casting has been observation and practiced for many

years with the systematic researches in the subject only appearing a few hundred years ago. The

interest and development of the different techniques applied in casting solidification processes have

seen a sharp increase due to industrial demand of high security parts used in aerospace, automobile,

power generation, and related industries (Pirvulescu and Bruto, 2010). Vibration of molten metal

during the solidification process has been introduced in the field, since the documentation of the

numerous experimental studies conducted by Chernov in 1868 shown successful improvement in

physical properties of part being cast. Jahn and Reisenger (1935) introduced treatment of molten

metals with high frequency mechanical vibration in the early 1900. In their study, they found that

gas inclusions, dross and slag were raised to the surface by the vibration process which was credited

for the increase in the toughness, ultimate tensile strength, yield strength, and uniform, finer grain

size of the cast material. Recent investigations conducted at ACRC suggested that controlled

mechanical vibration of the mould may result in reduced solidification time and thus, reducing the

overall casting cycle time, as well as enhances the economic competitiveness of the process

(Makhlouf, 2012).

A review of several previous investigations on the effect of mould vibration during solidification

reveals a number of notable effects such as grain refinement, increased density, degassing, etc.


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Figure 1: Various modes in which mould vibration can be applied (Campbell, 1981)

In this method, it is required that a suitable mould material be selected with caution, as

conventional sand moulds turns to disintegrate when subject to vibrations. Throughout the

literature review, consistencies of moulds used for vibration testing were in the categories of either

permanent or plaster/ceramic moulds, although sand moulds with high binder level were also used.

A typical casting with mould vibration experimental setup consists of a platform with fixtures for

attaching the mould and a choice of the vibration source.


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1.2.1. Theoretical objectivesThe following theoretical aspects of the project should be achieved.

Calculations with regards to total solidification time without vibration should be conductedusing appropriate approximations.

Comparison of the calculations above and data obtained from experiments should be madeand discussed where necessary.

Calculations with regard to vibration platform should be carried out to find the naturalfrequency of the suggested experimental setup.

1.2.2. Experimental objectivesAn experimental setup need to be constructed in order to produce the metal casts. The dimensions

of a vibration platform and cylindrical mould need to be determined. The experiments will be

conducted as follows:

Five (5) vibration frequencies should be chosen starting from 0 Hz. Three to five (3 - 5) samples of metal casts should be produced per vibration frequency. The temperature of the solidifying metal need to be monitored by using thermocouples or

any other convenient method.

The samples produced will be used to investigate the effects of vibration on the metal withregard to solidification time only.

Graphs of metal temperature vs. solidification time should be produced for each frequency.


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1.3. MethodologyIn order to successfully achieve the all the objectives of the research project, the following

methodology is proposed:

A literature review of all aspects considered to be relevant to the successful completion ofthe thesis is conducted. The review will assist in the selection of the different materials and

vibration source for experimentation.

Calculations with regards to total solidification time without vibration should be conductedusing appropriate approximations.

Determine major components to be designed and manufactured. This may include thepattern, mould, vibration shaker, mould attachments on the platform.

Prescribe the experimental setup and validation of the setup. This will require setting upexperiment, attaching the mould, and running preliminary vibration test to check for faults

and satisfactory vibration transmission.

Conduction of the experiments. Capture data (solidification times, measured temperature). Data analysis and discussions


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2. Chapter2: Literature ReviewThis section outlines a literature review of all aspects considered to be relevant to the successful

completion of the thesis. Some major parts covered are metal casting, solidification of metals, and

vibration principles applied to castings.

2.1. Metal castingIn the manufacturing of metals, casting is perhaps one of the oldest and a more direct method of

producing metal parts (IBF, 1981). Although the fundamental processes in metal casting aretheoretically the same, the end products in casting have improved due to quality requirements,

usefulness, etc. in last few hundred years (BCS, incorporated, 2005). Metal casting involves pouring

of molten metal into a mould cavity, which is a vessel configured to the shapes and dimensions of

the finished form, where it solidifies into the desired shape. The industrial revolution in metal

casting methods since their inception has brought about numerous new innovations and has

enabled casting of vast variety of complex components of any metal or alloy with mass ranging from

less than an ounce to several hundred tons of a single part (IBF, 1981).

Metal casting is sometimes the only practicable means of developing shape in some alloys lacking

plasticity or machinability for alternative manufacturing processes (IBF, 1981). It is highly flexible in

relation to part configuration design. The inherent design freedom offered by metal casting allows a

combination of what would otherwise be several parts of fabrication into a single part. This type of

freedom is crucial when exact alignment must be held. For instance, housings that carry shafts

i i i i d id f il hil i i V i f fi i h


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Figure 3: Casting process flow chart (MMC)

2.1.1. Casting methodsCasting processes are categorised into three main groups, viz. expendable mould with permanent

patterns, expendable mould with expendable patterns, and metal or permanent mould processes

(seefigure 4). Each casting process has the capability of producing a part with estimated tolerance,

surface detail, and complexity. The melting point of metal or alloy greatly affects the choice of the

casting process as well as the mould material.

Pattern

Making

Core making

(If needed)

Mould

Making

Mould Material

Pre aration

Raw Metal

Or Alloy

Melting Pouring Solidification

And Cooling

Removal

from

Cleaning and

Inspection


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2.2. Low melting point cast metalsVirtually any metal and alloy that can be melted down to a liquid form can and is being cast. Cast

metal and alloys vary broadly when it comes to their physical properties and constitution (in the case

of alloys). Metals and alloys also have different castability characteristics based on their combination

of liquid-solid properties and solidification characteristics that support accurate and sound castings.

The choice of mould material is greatly influenced by the melting point of the cast metal or alloy. A

list of melting points of some low-melting metal and alloys is provided in table 1 and the selection

process of the cast metal to be used is provided Addenda A.

Table 1: Some melting points and free energies of oxide formation of cast metals (Beeley, 1972).

metal Melting point metal oxide Name SymbolAluminium Al 660 220.6

Antimony Sb 631 114.3

Bismuth Bi 271 167.9

Magnesium Mg 649 239.8

Lead Pb 327 76.4

Zinc Zn 420 134.4

Tin Sn 232

Table 2: Some melting points of alloys (Harocopos and Fisher, 1967)

l S b l M l i i


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Pure metals are known to melt and solidify at a constant temperature (melting point). When their

temperature is above the melting point, they are completely liquid and below which are solid.

However, pure metals exhibit certain characteristic properties such as high electrical and thermal

conductivity, high ductility, amongst others which make them favoured for specialised applications.

Figure 5: Comparison of melting points and free energies of oxide formation for pure metals

2.2.2. Characteristics of alloysAlloys are metals made by combining two or more metallic elements especially to modify or enhance

their properties. Alloys are generally stronger than their pure metal counterparts. In foundry,

ll i l b dd d i h h dli h i i f h l hi h


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dimensional accuracy, and low defects if made properly (Joseph, 1999). The plaster mixture is

relatively easy to handle and sets quicker.

2.3.2. Cement-bonded sandCement bonded sand mould uses sand aggregate as a base material and cement as a binder. The

mould mixture usually contains approximately 8-12% of Portland cement and 4-6% of water. The

mould shows improved dry strength properties upon setting. The moulding process is simplified by

using wooden frames which are removed once initial setting of cement bond enables the mould to

stand independently instead of the common moulding boxes for normal mould sands (Beeley, 1972).

The only major shortcoming of the cement bonded sand mould is the long waiting time (up to 72

hours) for setting as well as the drying through evaporation of excess water before it can be

assembled for pouring of cast metal (Harocopos and Fisher, 1967). This type of mould can be

constructed with considerable dimensional precision resulting in satisfactory castings.

2.3.3. MetallicMould made from dense, fine grained, and heat resistant metals. They have long life span and can

be reused many times before being discarded or rebuilt. Metallic moulds are constructed in two or

more pieces so as to facilitate removal of the casting and very good finish and dimensional accuracy

in castings are possible. They are suited to small and medium sized casting and have rapid cooling

rates.

2 4 M l i d i f l


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Specific heat for solid Specific heat for liquid Pouring temperature Melting temperature Starting temperature,

The energy efficiency of the melting process can be determined by dividing the amount oftheoretical energy needed to melt the metal and raise its temperature to the required pouring state

by the actual amount consumed (BCS, 2005).

The melting process of any metal involves the following factors and they must be managed in ways

that reduce the inefficiencies which waste energy.

Preparing the metal and loading Melting the metal Refining and treating molten metals Holding molten metal Tapping molten metal i l l


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by shrinkage can be remedied by employing a gating system such that the shrinkage is reduced or

moved into a non-critical region of the cast.

Figure 7: Stages of shrinkage


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2.6.1. Solidification processSolidification is a process by which a material undergoes a phase change from a liquid state to a solidstate. The process invariably requires the creation of new surfaces which use up the available energy

in order to isolate the liquid and solid phases (Beddoes & Bibby, 1999). Solidification process has

three major stages as described briefly below.

2.6.1.1. NucleationFrom the definition as given by Hohenberg and Halperin (1977), nucleation is one of the mechanisms

of first order transition phase in which a new phase is generated from an old phase whose free

energy has become higher than that of the emerging new phase. In metal solidification, nucleation

process starts off with the slow moving atoms bonding together and creating tiny, stable crystals in

some location in the liquid metal. As the new tiny crystals are formed and stabilises, they arrange

themselves into clusters. The clusters then form nuclei.


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The inclusions in the liquid phase greatly affect the rate of nucleation. According to Mullin (1993) in

his book on Crystallisation, quite often, the critical interfacial free energy between a crystal and a

solid surface is lower than that of crystal in contact with the solution. De Yoreo and Vekilov (2003)

suggested that the lower free energy in heterogeneous nucleation may be due to the tendency of

molecules in the crystal forming bonds with those in the solid surface that are stronger than the

bonds of liquid and also that the enthalpy contribution to the free energy comes primarily from

chemical bonding, therefore resulting in smaller interfacial free energy. For this reasons, a smaller

amount of undercooling is required to activate nucleation and form a stable nucleus in

heterogeneous.

Figure 10: Formation of crystals of radius r in a molten metal heterogeneous nucleation

Nucleation can also be stimulated through dynamic events of which Chalmers (1964) report that

there are three distinct types of such events, viz. friction, vibration, and pressure pulse. One of the

first experimental evidence that relate to dynamically stimulated nucleation is that of D. K. Chernov

who showed that a gentle vibration of the mould resulted in finer grains in steel casting (Campbell,

) f f ff


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Total energy is obtained from addition of the two energy terms with volume free energybeing negative and surface energy positive:

[Equation 3] The volume free energy () released in forming new tiny crystal must be greater than energyneeded to create the required solid-liquid interface. Once a cluster of crystals reaches a critical size,

it becomes a nucleus and continues to grow. The critical radius

of a nucleus representing the

minimum size of a stable nucleus is related to total free energy and can be derived mathematically

by taking the derivative of Eq_3 and setting it equal to zero.

When Therefore, critical radius

and

[Equation 4]


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Figure 12: Growth of a metal dendrite

The growth may take place in approximately a single direction under a pronounced temperature

difference, or may occur from within the undercooled liquid and proceeding radially outward (IBF,

1981). At some point near completion of solidification, the growing dendritic arms join together

forming grains. Depending on the metal or alloy and the solidification conditions, the grain structure

may take a solely equiaxed, columnar, or both types may be present. The process of nucleation and

crystal growth is illustrated in figure 13.


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Figure 15: Schematic drawing of three types of cast growth structure

The figure above illustrates the many small chill crystals with arbitrary crystallographic orientations

nucleating along the mould walls which eventually form a large region of long and thin grains with

similar orientation called columnar dendritic. There are other dendrites types which grow equally in

all directions from the central liquid pool forming oval shapes called equiaxed, and spherical growth

called equiaxed non-dendritic usually a characteristic of an alloy that solidifies with a widetemperature range. A typical cast structure solidified in a square container would resemble that

shown in figure 16.


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Figure 17: Temperature distribution in Air-Mould-Metal

According to Chalmers (1964), the rate at which heat is transferred from liquid metal, at a known

initial temperature; after it has been poured into a mould at some lower temperature can be

determined mathematically as long as the appropriate physical constants for the metal and mould

are known. Although the mathematical approaches followed are, in general, limited to idealised one

dimensional, semi-infinite system involving pure metals and the results of which are quite

challenging to attain in terms of experimentation. A brief review of the heat transfer mechanisms

are given below:


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Specific heat If the mould internal wall surface, initially at room temperature , is instantly raised to an interfacetemperature at time and held constant through solidification, then the solution fortemperature at any point after time in the mould is:

[Equation 6]With the error function, whose converging series is expressed as:

( ) Where distance from mould-metal interface To obtain the temperature gradient in the mould, the above equation is differentiated with respect

to

. The rate of heat removal from casting at any time

can be determined by applying the Fourier

heat conduction.

*+ *+ [Equation 7] Where Melting temperature of metal


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*+ Where Solidified metal thickness Density of metal Since heat flux away from mold-metal interface = heat flux to mold-metal interface due to

solidification, then:

*+ *+ [Equation 11]After some mathematical manipulation, the constant for a cast without superheat is:

0 1

[Equation 12]

If the metal is cast at a temperature above the melting point, a better approximation of the

proportionality constant is obtained by an addition of the superheat term in the previous form.

2 3

Where


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If any of the given conditions is satisfied, the time for solidification can be expressed as:

() [Equation 14]2.6.1.5. Cooling curveCooling curve is a temperature-time relation that begins at the moment when the metal is poured

into the mould and continues through the solidification period for as long as is desirable thereafter.

An idealised cooling curve for pure metals is shown infigure 18.In the figure, the solidification starts

off at some superheated temperature and the metal cools quite quickly to its melting point (A). Atthe melting point, latent heat is released as the metal continues cooling at constant temperature.

Only after the metal is completely solid (point B) can further cooling.


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In an actual lab experiment or industrial foundry, the cooling curves do not present the idealised

situation as shown in the above figure. In fact, the rate of local solidification is extremely high and

nucleation does not necessarily starts exactly at the melting point temperature. In most cases, liquid

metal temperature will drop considerably below the melting point during undercooling (see Figure

20). The degree of the necessary undercooling to activate spontaneous nucleation is always less than

20% of the absolute melting point temperature (Ruddle, 1957). Undercooling is, however decreased

to just a few degrees Celsius due to the present of foreign bodies.

Figure 20: Typical cooling curve for Al-Si hypoeutectic alloy showing undercooling

The graph above shows clearly that the superheat always disappears fast and since the cast metal


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2.7.1. Commercially available thermocouplesA thermocouple is a measuring device with two different wires joint at one end and open at theother. Their arrangement allows a voltage, usually in millivolts, to be produced along the wires and

increases in magnitude as the temperature difference between the joined end and the open end

increases (ABB, 2013). The measurement is obtained by taking the voltage at the open end and

converting it into temperature using the calibration of the wires. Figure 21 shows the arrangement

of the wires of a thermocouple.

Figure 21: Schematic view and application of a thermocouple (Kerlin, 1999)

The measurement system is made up of three components needed to make a measurement; sensor,

wiring, and instrumentation. There are different standards which regulate thermocouples in most

industrial application. These standards are compatible regarding their basic nominal performance as


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2.7.2. Thermocouple setupThe technique of measuring temperature using thermocouples enables the progress of both thebeginning and end of solidification process to be followed and also depict metal behaviour in the

neighbourhood where the temperature is at the liquidus and solidus. The arrangements of

thermocouples in the mould and/or casting are quite vital to the success of the TMT and some of the

requirements for designing and arranging of thermocouples are provided inTable 4.

There are different ways in which thermocouples can be employed to measure the decrease in

casting temperature. The arrangement will also differ with respect to position of the measurementto be recorded.

2.7.2.1. Metal temperatureThere are two different ways in which the temperature of the cast metal can be monitored. The

schematics below show thermocouples cantilevered into the mould cavity and fixture

accommodated thermocouples:

Figure 22 shows a thermocouple held in place on one side of the mould by a twin boredsheath (usually silica) exposing only the hot junction which is protected by refractory washes

at a certain distance from mould wall.


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Figure 24: Overhanging thermocouples

2.7.2.2. Metal/mould interface temperatureThe interface temperature is usually determined by inserting the thermocouple wire as infigure 25.

The sheathing is not necessary in this case because it only offer support with regard to insulation

and stopping dislocation of wires.

Figure 25: Thermocouple inserted into the mould


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2.8. VibrationsVibration refers to the dynamic excitation that may cause a dynamic response of a physical system(particles of an elastic body) that is exposed to that excitation (Piersol and Peaz, 2010). In

experimental techniques, the dynamic excitation generally appears as an input motion, or force at

the mounting points, or a pressure field over the exterior surface of the physical system of interest

(De Silva, 2007). Primarily, the focus of this thesis is in vibration testing, where the excitation signal

will be generated in a signal generator in accordance with the given specification, and transmitted to

test object through an exciter and a vibrating platform.

This type of vibration is referred to as forced vibration as the motion of the test object will be

occurring in response to a continuing excitation whose magnitude varies with time sinusoidally. As

stated in the research problem statement, forced vibration can be applied to test object in many

different way, but only the two will be considered.

2.8.1. Mechanical vibration2.8.1.1. Theoretical analysis of mechanical vibrationMechanical vibration is applied to the test object through vibration testing machines (VTM), also

known as shakers. VTM is usually a table for mounting the test object and includes bolting fixtures

for attaching payload directly (Piersol and Peaz, 2010). They are used in exploratory vibration tests

for the purpose of studying the effects induced by vibration or of evaluating the physical properties

of materials.


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Then a conservative maximum force estimate would be:

|| [Equation 17]

With ||being the peak value of the required response spectrum (RRS) Power rati ng

The output power is determined by using: 2.8.1.2. Use of mechanical vibration in metal solidificationAccording to the review by Campbell (1981), the effect of mechanical vibration during solidification

of metal was first investigated by D. K. Chernov around 1868 as mention earlier. Mechanical

vibration in solidification of metal can be applied in a variety of methods and has been linked to

numerous improvements of material properties and reduction of defects in metals (Campbell, 1981).

However, vibration of the mould is the most convenient and simplest method of all the processes

influencing solidification and the method is reported to give noticeable results for low frequency and

high amplitude vibrations, even though the effect is limited by the energy reflected near the mould-

casting interface (Kocutepe, 2007).

Muric-Nesic et al. (2009) investigated the use of low frequency mechanical vibration in composite

materials to reduce the void content. The range of vibration frequency covered was between 10Hz

to 50Hz for a duration varying from 10min to 30min. they found that for a duration of 10min, the

applied vibration were insufficient to reduce the voids throughout the specified frequency range


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Figure 28: Effect of vibration frequency on the cooling rate of the melt at different areas (Omura, et al., 2009).

The cooling time readings from Omura and colleagues cooling curves clearly shows that the metal


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In another investigation performed by Deshpande (2006) on effects of mechanical mould vibration

on aluminium alloys, a comparison of the cooling curves obtained indicate that mechanical vibration

significantly affect the cooling rate and ultimately, the solidification time. Vibration intensity wasvaried from 0 to 3g with intervals of 0.5 and the pouring temperature was taken as 740 degree

Celsius, about 100 degree above the liquidus temperature.

Figure 30: Setup and cooling curves for varying vibration intensity (Deshpande, 2006)

On the matter of mechanical shakers, Zhang, et al. (2009) conducted a series of experimentation in

which they proposed a relationship between the vibration parameters and the required power of

the system and related it to grain refinement. The relation is expressed as a function of vibration

acceleration and frequency as:


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compensated for the variations. A typical experimental setup of that can be used in solidification

with vibration using ultrasonic is provided infigure 31.

Figure 31: Schematic illustration of solidification with ultrasonic vibration (Das and Kotadia, 2011)

2.8.3.

The us e of ultrasonic vibration in metal solidification

The use of ultrasonic vibration to influence solidification process of casting was first suggested by

Seemann in 1936 (Campbell, 1981). Whenever ultrasonic vibration is introduced to melts, similar

crystallographic changes in the metal to mechanical vibration are reported in most of the

investigations. In foundry practice, ultrasonic treatments of melts are considered to be rather

uneconomical due to their cumbersome equipment requirements. An example of this point can be

seen in the study by Yao et al. (2011), where the experimental setup included a commercially


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2.9. Literature review conclusionThe literature review conducted included an investigation of metal casting, modes of solidificationprocess, heat transfer during casting, as well as the vibration shakers and how they are used in the

solidification of cast metals. It was of found that the majority of the experiments conducted using

mechanical vibration had frequency ranging from 0~300 Hz which is considered to be the

recommended low frequency testing. Hand calculations for the solidification time prediction were

performed. In order to assist with the second phase of the research, certain materials had to be

selected. More detailed information is provided inChapter 8: Addenda.

From this investigation, the following are important for the experimental phase:

Cast metal selection Mould material selection Vibration source selection and design Operational frequency range


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3. Chapter3: Design and manufacturing3.1. Pattern and mould design3.1.1. Sample and riser dimensionsThe cast will be produced from zinc metal with a cylindrical open-mould due to the simplicity of the

desired part. The dimensions of the cast sample are as follows:

Cast diameter:

Cast height: Mould cavity, and ultimately the cast itself, is made from a suitable solid pattern, a full sized model

of the cast sample. A loose pattern incorporating the necessary allowances should be manufactured

first. Recommended allowances for zinc casting are provided intable 5.

Table 5: Recommended zinc cast allowances

Allowance Recommended value

Shrinkage 4.2 % or 26 mm per m

Machine-finish 2.4 mm (approx. from brass)

Draft 0.25-1.0 degree

To produce a cast sample having particular final dimensions, the required mould into which zinc melt


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3.1.2. Required PatternFinal pattern dimensions

By combining the sample and feeding riser, the dimensions of the pattern that should be

constructed can be found. The schematic infigure 32 shows the expected end product.

Height: 172.6 mm Max. Width: 60 mm Estimated mass and volume of zinc cast: 1.175 kg and 21967.73 cubic millimetres Material: Aluminium extruded round bar 60mm


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Figure 33: Schematic diagram of the mould

Mould preparation

A cylindrical flask was first constructed from PVC pipe, a metal pattern as mentioned above, and

plywood which forms part of the flask bottom. Once the flask assembly is put together, grease is

used as a releasing agent for easy withdrawal of the pattern.

A slurry mixture containing equal amount of plaster of Paris and fine sand by weight is poured into

the flask that contain the pattern. After the waiting for setting of the slurry, the flask is removed and

the drying cycle to remove excess moisture from the mould begins.

The mould is baked in the furnace at a temperature of 300 degree Celsius for two hour and cooled in

the furnace itself. The holes of the thermocouple wiring are drilled using a 2mm drill bit.


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Table 7: Design requirements for platform of vibrating table

Constraints Free Variables Objective/s

Must be stiff enough to avoid distortion byclamping forces

Natural frequencies above maximumoperating frequency (to avoid resonance)

High damping to suppress resonance andnatural vibrations

Tough enough to withstand mishandling andshock

Material choice Length and width Thickness

Minimise massand power

consumption


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Then:

And thus, for a given stiffness and length, the expression for the thickness is:

Thickness of the platform: Substituting thickness h into the mass equation, the following is obtained:

( )( ) . /According to Ashby (2011) materials usually considered for construction of vibration components are

alloys of magnesium, aluminium, titanium, and steel. This is due to a high value of the ratio of

youngs modulus to density of the materials which is the controlling factor for natural frequency.

Only steel and aluminium alloy will be considered for construction of the platform because both

metals are readily available to the designer. The best compromise is obviously in using aluminium

alloy but steel would still be an acceptable choice.

Table 8: physical properties of steel and aluminium


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3.3.1.2.1. Static analysisThe platform was modelled as a 250 mm by 250 mm grid of thickness h square plate bendingelements with critical test load applied on a circular area in the middle and the self-weight due to

gravity applied on the top surface of the plate (Figure 36). In order to simplify the analysis and

reduce simulation time, the mirrored symmetry about two orthogonal planes was applied and one

fourth of the geometry was modelled. The goal of static analysis was to find the optimum platform

design that will minimise thickness by allowing the definition of the first few values of the thickness

for testing.


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Table 10: Static analysis results for aluminium and steel

h (mm) m (kg) Max

(MPa) Max. displ (mm)

Aluminium

3 0.5224 13.217 1.22E-01 2.43 3.13

5 0.8706 5.411 2.80E-02 5.94 7.64

8 1.4 2.837 7.53E-03 11.34 14.58

Steel

3 1.47 16.06 5.01E-02 5.81 6.62

5 2.44 7.13 1.23E-02 13.09 14.90

8 3.91 4.0019 3.58E-03 23.32 26.55

The simulation results in the above table indicate that a table of 3 mm thickness should be enough

to satisfy both the safety margin against yielding and ultimate tensile strengths. An aluminium plate

of thickness 3 or 5 mm will be used because it minimises the mass of the table.

3.3.1.2.2. Vibration analysisThe first natural frequency of the platform is the frequency of interest as it provides the frequency

coverage specification for the table. Again, the platform is modelled as a flat plate supported at the

corners and no loading is applied on the platform. The aim of the analysis was to maximise the

fundamental natural frequency of the platform and thus, increasing the operational frequency range


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In this case, the fundamental natural frequency (227.34 Hz) is less than the recommended highest

excitation frequency ( 300 Hz).

Figure 38: First four modes of platform (unstiffened)

The fundamental natural frequency for each model is provided intable 11 andfigure 39 displays a

graphical comparison of the three models. Both stiffeners were found to have a significant increase

in the first natural frequency (approx. 350 Hz > 300 Hz) but square tube stiffeners offers a better

mass to frequency ratio as compared to square solid bars. Therefore, square steel tubes will be used

as stiffeners should the need arise.


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Figure 39: Comparison of the natural frequencies of platform models

3.3.2. Vibration motorVibration motors can be placed on a number of different locations on the driven machinery

depending on the type of desired vibrations to carry out the vibration testing process. According to

Denver Concrete Vibrators the most effective motor placement is achieved when they are mounted

underneath the platform.


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Figure 41: Vibration types by motor placement of platform

The vibration type desired resembles the platform motion represented by either single motorvibrator or twin contra rotating motor vibrators. With the cost of the motor vibrator in mind, a single

motor vibrator configuration will be used. The following requirements were used to aid in selecting a

suitable motor vibrator.

Table 12: Design requirements and equipment data for motor selection

Constraint/s Free variable/s Objective/s


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3.3.2.2. Vibrator motor selectionVibrator motor selection process is usually the result of a specific know-how and experience due tolack of regulatory selection standards. However, a preliminary evaluation of the vibrator motor for a

specific application can be found from different suppliers and manufacturing companies. The

following table represents estimates of data used in selection procedures.

Table 13: Estimated vibration parameters and other data

Est. vibration parameters and other data

Type of vibration Circular vibrationFrequency range 0 - 100 Hz

Peak to Peak Amplitude range 0.1 - 1 mm

Platform mass 1 kg

Mould + cast mass + fixture 3.4 kg

Motor selection procedure - Visam electric motors(www.visam.it/en_US/guida-alla-scelta-del-

vibratore):

Given data - seetable 13 Calculations = 0.45 mm = 0.225 mm


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Figure 44: Simplest form of an isolator with spring (k) and viscous damper (c) supporting machine (m)

It is assumed that the operation of the machine generates a harmonically varying force

. Then, the resulting equation of motion of the machine with mass m can be expressed as: The transient solution to the above equation will fade out after some time, leaving only the steady

state solution given by:

The force transmitted to the foundation through the isolator is given by:


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3.3.3.1. Isolator selectionProblem statement: Vibrating table directly driven by 3000 rpm vibrating motor causing vibration

disturbance to the support stand on which it is mounted. The motor, platform, and test object weigh

45 kg. There are four mounting points for the isolators.

Known data:

Weight = 7 kg

Weight per mounting point = 7/4 kg

Estimated Isolation required = 90 %

Transmissibility at resonance


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The operation of the vibrating table dictates that as rpm of the motor increases, the disturbing

frequency of the motor would at some point pass through the natural frequency of the system. With

no or light damping, the build-up of the dynamic forces from the table to the support stand may bevery large, resulting in damages to equipment. Amplification of the forces at resonance would be

reduced by selecting isolator with higher degree of damping.

When resonance occurs and transmissibility is at maximum, then:

Get quotes:

1. Seals and devices, 30 ARNOLD STREET, ALRODE, ALBERTON, SOUTH AFRICA. +27 11 9084616, [email protected]

3.3.3.1.2. Horizontal vibration modeThe vibrating table will display horizontal rocking due to the circular vibratory characteristics of using

a single motor. This will result in two more natural frequencies, 1) a lower mode wherein the


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Aspect ratio:

FromFigure 45,the ratios of horizontal for mode 1 and 2 are found such that: 3.3.4. Support standThe support stand must support the platform, motor, and test object without buckling. The legs ofthe stand should be as solid as possible. 1 ASU workshop permitted the use of the waste material

cut-offs which the designer thought would aid in reducing the overall cost of the table. The material

was found for the stand was a 50x50x5 angle section, code 300W.

The legs of the stand are loaded in compression and held together by horizontal section as depicted

in FIGURE 46. The calculations carried out here are in accordance with clause 1.3.3.1/2 of SANS

10162 code and the REDBOOK 6th

Edition, and are to determine the suitability of the angle section

for the required design loads.


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( )

( )

* +

0 1


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Still to be finalised

Table design done

Insolation/dampers done

Modal analysis done

3.3.5. Table technical specificationsParameter Specification Comments

Frequency range

Maximum amplitude

Maximum acceleration

Maximum payload

CAD drawings


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4. Chapter4: Setup and procedure of the experimentThis section deals with the planning of the experimental setup and the methodology of conductingthe experiments such that appropriate set of data can be collected for further analysis.

4.1. Experimental SetupThe proposed setup consists of a mechanical vibrator, vibration measuring unit (VMU), cylindrical

plaster mould, temperature measuring unit (TMU), and furnace with its accompanying parts. A

schematic representation of the setup with the apparatus used is illustrated infigure 47.

Figure 47: Schematic representation of the experimental setup (not to scale)


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Recall that one of the experimental objectives of this research is monitor the temperature of the

solidifying metal. The method employed for the task at hand utilises thermocouples to take the

measurements. The strategic locations for taking the temperature measurements as well as thenumbers of the thermocouples are shown in the schematic diagram of the cylindrical mould below.

Figure 49: Schematic diagram of the locations of TCs in the cylindrical mould

4.2. Experimental procedureThe following pre-testing and experimental procedure were followed in conducting the experiments


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checklist for this procedure was generated for convenience and can be view in Addendum C.2:

Experimental procedure checklist.

Table 14: chemical composition of the AZIM6 used in the experiment

PRODUCT DATA SHEET FROM ZINCHEM

ZINC ALLOY DESIGNATION AZIM 6

SOURCE ASTM B240

ELEMENT Percentage (%)

Zinc (Zn) Rem.

Aluminium (Al) 4.1 - 4.3

Magnesium (Mg) 0.57 - 0.98

Copper (Cu) max 3.0 - 3.6

Iron (Fe) max 0.015

Lead (Pb) max 0.003

Cadmium (Cd) max 0.001

Tin (Sn) max 0.001

NICKEL (Ni) max 0.001


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5. Chapter5: Results and discussionDifficulties encountered during the experiments

Observation

0 frequency: Pouring zinc melt at 450 degrees Celsius into the plaster mould resulted in boiling-like

fluid motion with countable droplets coming out of the mould. The smoke started coming out as

well which could be the result of the plaster mould releasing trapped water.

5.1. ResultsCooling curves

Discussion of the results


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6. Chapter 6: ConclusionConclusion

Recommendations


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7. Chapter 7: References[1] Hohenberg P. C, & Halperin, B. I. 1977. Theory of dynamic critical phenomena. Rev Mod Phys

49: 435-479

[2] De Yoreo, J. J. & Vekilov, P. G. 2003. Principles of crystal nucleation and growth. Reviews in

Mineralogy and Geochemistry 54 (1): 57-9. [online]. Available:

https://secure.hosting.vt.edu/www.geochem.geos.vt.edu/bgep/pubs/Chapter_3_DeYoreo_

Vekilov.pdf [26 march 2013]

[3] Mullin, J. W. 1993. Crystallization. 3rd

ed. Oxford: Butterworths-heinemann

[4] The Institute of British Foundrymen (IBF). 1981. Typical microstructures of cast metals. Newrevised ed. Boultbee, E. F. and Schofield, G. A. (editors). Working Group P9 of the Technical

Service Co-ordination Committee. Birmingham: IBF.

[5] Ruddle, R.W. 1957. The solidification of castings. 2nd

ed. Institute of metals monograph and

report series. No.7. Suffolk: Richard clay and company

[6] Taylor, H. F., Flemings, M. C., & Wulff, J. 1959. Foundry Technology. New York: .John Wiley &

Sons.

[7] Chalmers, B. 1964. Principles of solidification. London: John Wiley & Sons

[8] Beeley, P. R. 1972. Foundry technology. London: Butterworth

[9] Beeley, P. R. 2001. Foundry technology. 2nd

ed. London: Butterworth Heinemann.

[10] Flinn, R. A. 1963. Fundamentals of metal casting. Massachusetts: Addison-Wesley.

[11] Heine, R. W., Loper, jr, C. R., & Rosenthal, P. C. 1967. Principles of metal casting. 2nd

ed. new

York: McGraw-Hill.

[12] Adams, C. M., Jr. 1953. Heat flow in the solidification of casting. Thesis; MIT. [online].


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[20] Kerlin, W. T. 1999. Practical Thermocouple Thermometry. Instrument Society of America.

(ISA). [Online]. available: http://0-

www.knovel.com.innopac.up.ac.za/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=3324&VerticalID=0 [04 May 2013]

[21] ABB in South Africa. 2013. Product Guide: Thermocouples (TC). ABB Asea Brown Boveri Ltd.

[Online]. Available:

http://www.abb.co.za/product/ap/seitp330/38f6d1e7005d4fb4c1257315003661ba.aspx [05

May 2013]

[22] Piersol, A. G. & Paez, T. L. 2010. Harris shock and vibration handbook. 6th

ed. New York:

Mcgraw-Hill[23] De Silva, C. W. 2007. Vibration monitoring, Testing, and instrumentation. Boca Raton: CRC

Press

[24] Vibco. 2011. Product: Vibrating Tables Custom/Standard. [Online]. Available:

http://www.vibco.com/products/vibrating-tables [29 April 2013]

[25] Kacutepe, K. 2007. Effect of low frequency vibration on porosity of LM25 and LM6 alloys.

Material and design 28: 1767-1775.

[26] Muric-Nesic, J. et al. 2009. Effect of low frequency vibrations on void content in composite

materials. Composites: Part A 40: 548-551.[27] Kocatepe, K. 2007. Effect of low frequency vibration on porosity of LM25 and LM6 alloys.

Materials and Design 28: 17671775.

[28] Taghavi, F., Saghafian, H., & Kharrazi, Y.H.K. 2009. Study on the ability of mechanical

vibration for the production of thixotropic microstructure in A356 aluminium alloy. Materials

and Design 30: 115121.


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Worcester Polytechnic Institute, USA. [Online]. Available:

http://www.wpi.edu/Images/CMS/MPI-ACRC/Vibrations_with_Sizzle_Fact_Sheet.pdf

[37] Abed, E. J. 2011. The influence of different casting method on solidification time andmechanical properties of AL- Sn castings. International Journal of Engineering & Technology

IJET-IJENS. Vol: 11 No: 06. 34-44

[38] Yao, L. et al. 2011. Effects of ultrasonic vibration on solidification structure and properties of

Mg8Li3Al alloy. Transactions of non-ferrous metals society of china. 21: 12411246.

[39] Zhang, Z-q. et al. 2010. Effect of high-intensity ultrasonic field on process of semi-continuous

casting for AZ80 magnesium alloy billets. Transactions of non-ferrous metals society of

china. 20: 376381.[40] Qingmei, L. et al. 2007. Influence of ultrasonic vibration on mechanical properties and

microstructure of 1Cr18Ni9Ti stainless steel. Materials and Design. 28: 19491952

[41] Dasa, A. & Kotadiab, H.R. 2011. Effect of high-intensity ultrasonic irradiation on the

modification of solidification microstructure in a Si-rich hypoeutectic AlSi alloy. Materials

Chemistry and Physics. 125: 853859

[42] Ashby, M. F. 2011. Materials Selection in Mechanical Design. 4th

ed. London: Butterworth-Heinemann

[43] Siswanto, W. A. et al. 2011. Shaker Table Design for Electronic Device Vibration Test System.

IACSIT International Journal of Engineering and Technology, Vol. 3, No. 6.

[44] Muhlenkamp, M. J. 1997. Analysis, design and construction of a shaking table facility. Thesis:

Rice University. Houston, Texas: UMI Company.


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8. Chapter8: Addenda


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8.1. Addendum A.1: Selection of cast metalMetal selection is one of the most important considerations in casting. There are many factors which are used in determining a suitable metal for casting,

especially for a known application. In this research project, properties provided in the table below are used and not mechanical properties such as tensile

strength, hardness, etc. The use of the lowest cost material for the experimental phase is essential for a financially successful project. Hence, Zinc metal will

be used.

Table 15: Cast metal selection

Metal Melting Point 300C Density Cost Reactivity Health Effects

Tin 232C 7310 R239.9 per kg Relatively unaffected by both waterand oxygen at room temperatures.

Reacts with steam and oxygen athigher temperature.

Toxic (poisonous)- If inhaled, can cause problems such

as nausea, diarrhoea, vomiting, and

cramps.

Zinc 419.5C 7140 R20.6 per kg Fairly active element Does not react with oxygen in dry

air but in moist air, however, it

reacts to form zinc carbonate. The zinc carbonate forms a thin

white crust on the surface which

prevents further reaction.

Zinc is an essential micronutrientfor humans.

Breathing zinc dust may causedryness in the throat, coughing,general weakness and aching,

chills, fever, nausea, and vomiting

Bismuth 271C 9780 R23.54 per kg Reacts slowly with oxygen at roomtemperature.

Bismuth and its compounds arenot thought to be health hazards.

Lead 327.4C 11342 R203.6 per kg Moderately active Does not react with oxygen in the

air readily

Toxicity is a major drawback oflead.

It is toxic when swallowed, eaten,or inhaled and causes both

immediate and long-term health

problems


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8.2. Addendum A.2: Selection of mould material/sThe mould material to be used is plaster of Paris. The material possesses good refractory characteristics and can withstand high temperatures of the

selected cast metal.

8.3. Addendum A.3: Selection of vibration sourceStill to be completed

Table 16: Vibration source selection

Vibration source Number of

components

Frequency range Advantages Disadvantages

Mechanical shaker 01000 Hz Provides low and mediumfrequencies

Simple transmission of thesignal

Ultrasonic shaker 20 kHz and above Complex and expensiveequipment.

Requires separation from thedangers associated with

casting process

Difficulties such as energyreflection from joints,

interfaces, and unforeseen

waveguide changes.

Requires adjustment of thefrequency during solidification

to maintain resonance.


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8.4. Addendum B: Theoretical solidification timeMetal cast of the selected low melting point metal will be produced in the experimental phase of the

study in two different ways; 1) normal cast solidification, and 2) cast solidification subjected to

vibration. This section provides an approximation of the solidification time of the metal cast without

vibration and the results will later be compared to the experimental data. The importance of the

theoretical solidification time is to predict when it is safe to remove the cast from the mould.

The equations to be used are:

2 () 3 Table 17: metal constants required for Chvorinov's rule equation

Metal Zinc (Zn)

Plaster of

Paris mouldProperty

Ambien temp 25 -Melting temp 420 -Pouring temp 480 -Density 7140 1100Specific heat 0.39 solid/0.48 liquid 0.84


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This equation means that the temperature at the outer surface of the mould does not change

substantially above the ambient temperature, and L is the thickness of mould.

Governing equation: ( ) The governing equation will reach maximum when the bracketed term in the error function reaches

the value of about two according to the figure below.

Figure 50: Gaussian error function (Beddoes and Bibby, 1999)

k


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8.6. Addendum C.1: Detailed explanation of experimental setupcomponents

Table 18: laboratory equipment to used

Equipment Function/s

Mechanical vibration system

Vibration table

Plate table top with mould clamp

Modified angle grinder motor Power control module and potentiometer On/off safety switch Isolators

Generate the input vibration signal andtransmit it to mould/casting.

Vibration measuring unit

Spider 8 system Accelerometer

Measures the input vibration signal asreceived from the shaker

Assist in fine tuning the signal to the userspecified values

Record the input vibration signalCylindrical plaster mould

Mould Holds the melt throughout the solidificationprocess.

Mould clamp/fixture Mould fixtures are necessary for supportingthe mould subjected to vibrations

Temperature measuring unit

D D J k 28511141


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Figure 51: Mechanical vibrating table

D D J k 28511141


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D D J k 28511141


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D D Jonker 28511141


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Cylindrical plaster mould

The mould used is cylindrical in shape and made from plaster of Paris and sand. The mould is

mounted onto the table platform which is fitted with clamp fixture for securing the mould.

D D Jonker 28511141


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to an Agilent data acquisition system shown in Figure 53 (e) which records the temperature at

intervals of five seconds for each sampling vibration inputs.

Figure 53: Preparation and positioning of thermocouples in mould

Furnace and accompanying parts

Zinc ingot melting process was made up of a small electric furnace with a temperature controller,

crucible, skimming metal rod and a medium-sized tongs.


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8.7. Addendum C.2: Experimental procedure checklist

1. Mould preparation

Cleaning

Clamping mould onto

platform

2. Melting of zinc metal Crucible with enough metal chunks in furnace

Pouring T = 450C

Skim the surface

4. Pour melt into a vibrating

mould

3. Set required vibration parameters of table

Check frequency

Check amplitude


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8.8. Addendum D: Protocol8.9.

Documents

2nd Last Final Draft Research Project 2013.docx