PART A

PART A/BAHAGAIAN A

INSTRUCTION/ARAHAN:

Answer ALL questions / Jawab SEMUA soalan.

QUESTION 1 / SOALAN 1

Describe the influence of analysis and optimazation stage in a design process.

Huraikan pengaruh analisis dan tahap optimum dalam proses perekaan.

[Total/Jumlah: 5 marks]


Describe metal cutting process and the important factor for metal cutting operation.

Huraikan proses pemotongan logam dan faktor penting untuk operasi pemotongan logam



Explain the meaning of “flash” and formation of flash in closed forging operation.

Terangkan maksud “flash” dan pembentukan “flash” dalam operasi penempaan tertutup.

The meaning of the flash in forging is metal in excess of that required to fill

the blocking or finishing forging impression of a set of dies completely. Flash

extends out from the body of the forging as a thin plate at the line where the

dies meet and is subsequently removed by trimming. Because it cools faster

than the body of the component during forging, flash can serve to restrict

metal flow at the line where dies meet, thus ensuring complete filling of the

impression.In conventional closed die forging the formation of flash is

necessary for die filling

The process formation of flash in closed forging, a billet is formed (hot) in

dies (usually with two halves) such that the flow of metal from the die cavity

is restricted. The excess material is extruded through a restrictive narrow

gap and appears as flash around the forging at the die parting line.

Figure 14.7 (a) Stages in forging a connecting rod for an internal combustion

engine. Note the amount of flash required to ensure proper filling of the die

cavities..

Figure 14.7 (a)



Define tensile strength and Modulus of Elasticity and describe the relation.

Takrifkan “tensile strength” dan Modulus Keanjalan dan nyatakan hubungannya.

[Total/Juml ah: 5 marks]


Describe the flank wear and crater wear and significant factors that influence those

wear on cutty tool.

Huraikan kehausan “flank wear” dan “crater wear” dan faktor penting yang mempengaruhi

kedua-dua kehausan tersebut terhadap alat pemotongan.


[Overall Total/Jumlah keseluruhan: 25 marks]

PART B / BAHAGIAN B

INSTRUCTION/ARAHAN:

Answer ALL questions / Jawab SEMUA soalan.


a) What are the three main function of the cutting fluid in metal cutting?

Apakah tiga fungsi utama cecair pemotongan dalam pemotongan logam?

The three main function of the cutting fluids in metal cutting is to lubricate

the chip-tool and tool-workpiece interfaces, remove heat from the workpiece

and cutting zone and flush away chips from the cutting area (Shaw, 1942).

While each of these three functions can be employed as justification for

cutting fluid usage, it is widely believed that the primary functions of a

cutting fluid are lubrication and cooling.

b) Describe briefly two method of cutting fluid application during metal

cutting process.

Huraikan secara ringkas dua kaedah penggunaan cecair pemotongan

semasa proses pemotongan logam.

Every conceivable method of applying cutting fluid example flooding,

spraying, dripping, misting, brushing can be used, with the best choice

depending on the application and the equipment available. For many metal

cutting applications the ideal would be high-pressure, high-volume pumping

to force a stream of fluid directly into the tool-chip interface, with walls

around the machine to contain the splatter and a sump to catch, filter, and

recirculate the fluid.

One of the method that I want to describe is Flooding .

In flooding, a steady stream of fluid is directed at the chip or tool-work piece

interface. Most machine tools are equipped with a recirculating system that

incorporates filters for cleaning of cutting fluids. Cutting fluids are applied to

the chip although better cooling is obtained by applying it to the flank face

under pressure:

Second of the method that I want to describe is Mist applications.

Fluid droplets suspended in air provide effective cooling by evaporation of

the fluid. Mist application in general is not as effective as flooding, but can

deliver cutting fluid to inaccessible areas that cannot be reached by

conventional flooding. As illustrated in Fig. 3, two different mechanisms have

been proposed as sources for cutting fluid mist: atomization and

vaporization/condensation. Both mechanisms of mist formation will be

discussed and their significance explored.

Cutting fluid is atomised by a jet of air and the mist is directed at the cutting zone

[Total/Jumlah: 10 marks/markah]

Ref :

1. Mahdi, S. M., and R.O. Skold, ``Ultrafiltration for the Recycling of a

Model Water-Based Metalworking Fluid: Process Design

Considerations,'' Lub. Eng., Vol. 47/8, Aug. 1991, pp. 686-690.

2. Marano, R. and G. Mac, ``Analytical Studies of Soluble Oil Cutting

Fluids - IV. Filtration Equipment and the Importance of Fine Particle

Removal System 97 - Dearborn Engine Plant,'' Ford Research Technical

Report No. SR-88-124.

3. Silliman, J.D., Cutting and Grinding Fluids: Selection and Application,

Society of Skold, R. O., ``Field Testing of a Model Waterbased

Metalworking Fluid Designed for Continuous Recycling Using

Ultrafiltration,'' Lub. Eng., Vol.47/8, Aug. 1991, pp. 653-9.


a) Describe the difference between brazing and soldering.

Huraikan perbezaan di antara “kimpalan loyang” dan “pematerian”.

The joining techniques of soldering and brazing have many similarities;

however, each process has its own characteristics and specific indications for

use. Generally, the criteria for selecting one process over the other depend

on the physical and economic requirements of the base metals and/or end-

use of the assembly being joined. The difference between brazing and

soldering is temperature As with brazing, soldering does not involve the

melting of the base metals. However, the filler metal used has a lower

melting point (often referred to as “liquidus”) than that of brazing filler

metals (below approximately 840° F, or 450° C) and chemical fluxes must be

used to facilitate joining. In soldering operations, heat may be applied in a

number of ways, including the use of soldering irons, torches, ultrasonic

welding equipment, resistance welding apparatus, infrared heaters, or

specialized ovens. A major advantage of soldering is its low-temperature

characteristic which minimizes distortion of the base metals, and makes it

the preferred joining method for materials that cannot tolerate brazing or

welding temperatures. However, soldered joints must not be subjected to

high stresses, as soldering results in a relatively weak joint. In brazing

operations, heat is generally supplied by an oxyfuel-type torch (manual or

automated), a controlled-atmosphere or vacuum furnace, a chemical dip

(salt bath), or specialized equipment using resistance, induction, or even

infrared technologies. Brazing is especially well suited to high volume

production (automation) and for joining thin sections and parts with complex

geometrie

Figure 1.0 – Show that the soldering temperature for soldering in pipe

installations

is approximately 250°C – for brazing the temperature is between 670°C and

730°C.

Brazing above 450 0 C

Soldering Below 450 0 C

Table l. Differences between soldered and brazed joints

Joining Method Joint Strength Distortion Aesthetics

Soldering Poor Noon Good

Brazing Excellent Minimal Excellent

Ref

1. The Brazing Book, Handy & Harman, New York (1985)

2. Brazing Handbook, 4th Edition, American Welding Society, Miami

(1991)

3. “The Effect of Atmosphere Composition on Braze Flow,” (Prepared for

14th Annual AWS/WRC Brazing and Soldering Conference, Philadelphia,

PA), Air Products and Chemicals, Inc. (1983)

4. Eichelberger, D.P., Garg, Diwakar, "Nitrogen-Based Atmospheres

Emerge as Brazing Option," Heat Treating, October 1993

5. "Furnace Brazing Theory & Practice" (Corporate Presentation), T.

Philips, Air Products and Chemicals, Inc.

b) Describe the difference between Brinell Hardness and Vickers Hardness Test.

Huraikan perbezaan di antara “Brinell Hardness” and “Vickers Hardness Test”

The many hardness tests listed here measure hardness under different

experimental conditions, such as indenters made in different shapes and

sizes and materials, and applied with varying loads. Further, the

experimental data is evaluated using different formulae. The difference

between a Brinell and a Vickers hardness tester is the type of indenter used.

Where Brinell uses a round ball indenter to press materials, Vickers utilizes a

square or diamond-shaped indenter. It’s the same basic principle as the

Brinell, but the user has a device to measure more defined indentations

rather than Brinell’s harder-to determine round indentation. (See

illustration.)

Brinell Hardness

Brinell hardness is found out by impressing a hardened ball of diameter D to

the test sample by force F directed perpendicularly to the sample surface for

a specified period of time. After relieving, the impression diameter d is

measured. Diameter D is normally 1 mm, 2,5 mm, 5 mm or 10 mm. Ball

diameter depends on thickness t of measured materials. It applies that the

minimum thickness is ten times the impression depth. Otherwise the base

hardness might influence the results.

The Brinell Hardness Test is commonly used for metallic materials and

determines hardness by applying a known load of 500, 1500, or 3000 kgf to the test

specimen via a hardenedsteelordiamondballwhichis10mmindiameter. The size of

the impression on the specimen surface is calculated into a Brinell Hardness

Number(HB) using the formula:

A measurement is not considered valid unless the diameter of the impression is in

the range of 2.5 to 4.75 mm, although slightly exceeding this limit is tolerable. The

3000 kgf load yields Brinell hardness results from 160 and 600; the 1500 kgf load

yields an HB value of 80 to 300; and the 500 kgf load will produce HB values of 26

to 100. Smaller loads of 100, 125 and 250 kgf can be utilized for softer metals.

According to American Society for Testing and Materials (ASTM) Standard E10-66, a

steel ball may be used up to HB 450, and carbide should be used up to HB 630. Use

of the Brinell test on materials harder than HB 630 is not recommended as

deformation of the ball indenter itself may occur, leading to errors in test result

values

Vickers Hardness Tester

A diamond square pyramid of a specified apex angle is impressed to the

tested material under loading force F (acting to the sample surface

perpendicularly) for a specified period of time. Afterwards, the mean length

of both impression diagonals is measured. The testing loading force normally

varies between 10 and 1000 N. The loading is chosen from 10 up to 180 s.

The load applied is recorded in the identification, such as HV 100 (HV 100 =

215). For practical reasons, we use tables where appropriate hardness is

specified depending on the diagonal length d and force F applied.

The Vickers Hardness test can be applied to different materials across a

broad range of harnesses. The Vickers test uses a square-bottomed diamond

pyramid that has a 136º point angle. The load is usually 50 kgf, but can be 5,

10, 20, 30, or 120 kgf. The load is applied via the pyramid-shaped indenter

against the well-supported, smooth, flat surface of the test specimen for 30

seconds. The resulting hardness reading is calculated based on the load and

the area of the pyramid impression according to the formula:

Ref :

1. H.E. Boyer, in: Hardness Testing, ASM International, Metals Park, Ohio, 1987 2. J.Kising, W. Weiler and I. Winckler, VDI-Berichte, 583 (1986), p. 371-391.

3. Wrilreus, S. R. (1942) Hardness and hardness measurements, Cleveland: American Society of Metals, p. 167-762.

[Total/Jumlah: 10 marks/markah]

[Overall Total / Jumlah Keseluruhan: 20 marks/markah]

ENDS OF QUESTION PAPER / KERTAS SOALAN TAMAT

If optimal characteristics can only be built into a design at a late stage in development, the cost implications are huge and the potential design variations are usually severely constrained. The use of virtual prototyping techniques overcomes this limitation in the development process and enables multiple attributes to be assessed much earlier, when design changes are less constrained. However, there is a critical need for system-level simulation processes, which predict the impact of modifying components and sub-systems on the full system-level response as well as on component-level performance, and enable trade-offs between conflicting attributes, even including customer ‘subjective’ inputs to the design process.

Documents

PART A