Matec- VSR Manual

STREL-Q

Sahyog Enterprise, Bombay 400 069.

1

INSTRUCTION MANUAL

VIBRATORY STRESS RELIEVING

EQUIPMENT

STREL - Q

MANUFACTURED BY

SAHYOG ENTERPRISE

TARUN PLASTIC COMPOUND,

MOGRA VILLAGE ROAD,

ANDHERI (EAST),MUMBAI 400 069

PH: (022) 28200559, 26840346

Email : [email protected]

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VIBRATORY STRESS RELIEVING EQUIPMENT

GLOSSORY OF TERMS

• Accelerometer … It is a small sensor, which senses the

vibration acceleration and converts the signal into electrical

signal.

• Amplitude … is the peak-to-peak displacement of the work

piece during vibration.

• Damping … is the loss of vibration energy due to natural or

forced friction, like contact with floor.

• Frequency … The numbers of vibrations per second of a

vibrating body.

• ‘g’ … Acceleration due to gravity, 9.81 m/sec2

• Mode … The pattern of vibration of a component.

• Node … A still area or a line on a vibrating component.

• Resonance … It is the condition of maximum response. It

arises when the forced frequency of vibration is equal to the

natural frequency of the work piece.

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INTRODUCTION

It is found and universally accepted that residual stresses in a metal are

the main cause of dimensional instability. Residual stresses are mainly

developed in a component due to:

1. Differential cooling of the component

2. Cold deformation

3. Phase transformation

The residual stresses are the main cause of the dimensional instability of

the component. Residual stresses are hard to visualize, difficult to

measure and extremely difficult to calculate and predict. To achieve the

dimensional stability it is required to redistribute or reduce the residual

stress level in the component. This can be achieved mainly by three

different methods:

• Natural aging

• Thermal Stress Relieving

• Vibratory Stress Relieving

All the processes have their merits and demerits over each other.

While natural aging does not require any equipment for stress relieving, it

is a very long time consuming process, almost of the order of 8 to 12

months and hence the indirect cost involved is much higher compared to

other two processes.

Thermal Stress Relieving (TSR) requires a very large capital expenditure

and also it has a limitation by the volume of the furnace to handle the job.

The treatment cycle in TSR process is very long and is associated with

very high consumption of energy.

Vibratory Stress Relieving (VSR) brings the dimensional stability by

vibrating the component at its natural frequency. Because of the

simplicity of the process it has become widely popular over last decade.

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The major advantages of VSR process are:

• Very short treatment cycle compared to other two processes.

• High energy saving.

• Very less material handling charges, as the process goes to the

work piece.

However it should be noted that the VSR process is not the direct

replacement of the TSR process in certain applications. It has its own

limitations, which we shall discuss in the chapters to come.

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PRINCIPLE OF VSR

Any Stress relaxation is associated with the plastic deformation of the

stressed atoms inside the component. In VSR method the cyclic loading is

applied to the work piece by using the vibrator. These injected stresses

are supper imposed on the existing residual stresses. The resultant stress

value crosses the yield point of the component and it will undergo micro

plastic deformation. With series of micro plastic deformation the stress

reduction is achieved which in turn stabilizes the component to achieve

dimensional stability. The interesting feature of cyclic sinusoidal loading

is that the Stress-Strain curve takes the different shape than the original

shape, and hence the resultant yield stress comes down drastically and

hence the stress relaxation is achieved at very low energy consumption.

APPLICABILITY OF VSR

Generally in the following areas the VSR technique is applicable:

• A wide variety of cast iron and mild steel welded structure.

• Low alloys high strength structures.

• Stainless steel cast and welded structures.

• Almost all structures where the stresses have been induced due

to differential cooling pattern during manufacturing.

VSR has got limited applications in following areas:

• Severely cold deformed sections like cold rolled, drowned, or

strain hardened materials.

• Precipitation hardenable material.

• Stresses generated due to heat treatment for example heat-

treated hardened material.

It should be noted that VSR does not change the metallurgy of the

material hence code does not permit pressure vessel, pipe work etc to be

treated by VSR method. The change in metallurgy is required for

corrosion or high-pressure problems in pipe work and pressure vessels.

Hence it is recommended that the thermal stress relieving be carried out

for these applications.

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THE VSR EQUIPMENT (STREL – Q)

The basic VSR Equipment (STREL – Q) consists of three main modules:

1. An Electro-mechanical vibration exciter unit

2. An electronic control console, which includes vibration

controlling and monitoring instrument. And the Strip Chart

Recorder.

3. Set of rubber isolators & necessary vibrator clamps.

1. Electro Mechanical Vibration Exciter :

The equipment is supplied with two vibration exciter. 0.37 kw (

VSRE 05) and 0.75 kw (VSRE 20). The VSRE 05 exciter may

be used from 300 kg to 5 Tons of job weight and the VSRE 20

exciter may be used from 2 tons to 20 tons of job weight.

This unit induces cyclic sinusoidal load into the work piece. The

basic features of this unit are:

• Generates variable frequency cyclic loading from

7.5Hz to 100 Hz with the help of electronic console.

• The cyclic load generated is 500 Kgf, for VSRE05

exciter and 1000 Kgf for VSRE 20

2. Electronic control console :

This unit consists of vibration controller, monitoring system and

the chart recorder. The controller part generates the variable

frequency, which is then fed to the Electro-mechanical vibration

exciter to generate variable cyclic loading. It requires 220V

single Phase input and generates 7.5Hz to 100 Hz output.

The monitoring part of this system indicates and allows

navigation through various VSR parameters, using touch screen.

The monitoring system analyses and processes the data and

displays the process parameters. With the help of these

parameters we can locate the resonant frequencies, which is the

most important parameter of VSR technique.

Another important element in this console is an accelerometer

sensor. An accelerometer is a transducer, which converts the

vibration signal to the electrical signal. It acts as a feed back

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device. With this we can have a closed loop control over the

entire VSR process. The accelerometer along with its cable is a

very sensitive and costly element and should be handled very

carefully during the process.

The strip chart recorder (Fig 1,part 7) is a device, which can

be utilized if the hard copy of the entire VSR process is

required. It plots the displacement v/s time during the VSR

process. It is a useful device for the validation process or to

compare the previous data for similar jobs.

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OPERATING INSTRUCTIONS

The following instructions should generally be followed for operating the

VSR Equipment:

1. Observe the work piece thoroughly for cracks. There should not

be any crack on the work piece.

2. Mount the Exciter on the work piece, at the convenient place

and hold it rigidly with the clamps. See supporting the

component and fixing the vibrator on page 11

3. Place the isolators below the work piece so that the work piece

is in balanced condition.

4. Give 220V, 1ph. Electric connection at single-phase socket

input at the back panel (Fig 1,part 12), Three phase output (Fig

1,part 11) to Exciter and the sensor cable at sensor terminal (fig

1,part 13). The other end of sensor cable is connected to the

accelerometer sensor.

5. Mount the accelerometer on a clean flat surface over the work

piece. Handle it very carefully; mount it using the permanent

Magnet provided with the sensor, or with any other means.

6. Start the process, put ON the mains switch (fig 1,part 4). The

well come screen will appear on the monitor ( Fig 1, part 3).

Wait for few seconds, the well come screen will change and the

equipment will enter into the Manual mode, Screen 2 of

Annexure 1 will appear.

7. Press the START button (on the touch screen), Screen 3 of

Annexure 1 will appear and Indicator lamp (Fig 1, Part 10) will

glow indicating the start of process. The Indicator lamp will not

glow if the sensor is open or Emergency switch (Fig 1, Part 8) is

pressed. To activate the process timer press the TIMER MODE

SELECT BUTTON on the screen. Set the TOTAL RUN TIME

in minutes. We recommend setting the timer to about 15

minutes. Put ON the Chart recorder (fig1, part 9) to take out the

process Time v/s Amplitude graph. The VSR operation is

carried as follows:

a) Sweep the frequency knob (fig1, part 1) of frequency

indicator from minimum to maximum slowly, while

observing the vibration meter simultaneously. Try to locate

the resonant frequencies (the resonant frequency and its

harmonics). The resonant frequency is located when the

maximum displacement is indicated on the analogue

resonance meter. The harmonics are located beyond the

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resonant frequency by locating, once again, the displacement

peak during the sweep. If the resonance deflection is very

small, change the RANGE switch (fig1, part 5) in position 1.

If deflection is out of range change the RANGE switch in

next higher position i.e. ‘2’ or ‘3’ for better readability.

b) Run the vibrator at all the selected resonant frequencies. The

minimum time duration for effective VSR treatment should

be 5000 cycles for CI or MS fabricated jobs. For example, if

the resonance found at 25 Hz. The process time would be

5000/25 i.e. 200 seconds. If the vibrations are applied for

longer duration nothing wrong will happen to the job.

c) During the process take out the recorded chart from the strip

chart recorder. Refer the chart recorder manual supplied

separately.

d) Repeat the entire process with the different position of the

vibrator (generally 90 degree to previous position.)

e) To terminate the VSR process at any stage, press

EMERGENCY (Fig 1 , Part 8) button.

Following are the few thumb rules of VSR techniques and should

generally be followed during the process if possible:

(a) Vibration isolators should be placed below the job so that

the job is in balanced condition. Wooden planks, Rubbers

or tyres may be used as isolators. For small jobs, say

below 2000 kg, use rubber isolators provided with the

equipment.

(b) If at the first harmonic frequency the structure vibrates as

a whole block i.e. there is no relative movement between

the adjacent layers of the component, avoid this

resonance frequency and go for the next resonance

frequency for stress relieving.

(c) Run the vibrator at all the selected resonant frequencies

for about 15 to 20 minutes using the Timer provided on

the monitoring screen.

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Precautions:

The following precautions should be observed during the VSR

process:

1. Use the proper Exciter for the VSR treatment based on the

weight of the job.

2. The accelerometer and the cable should be handled very gently

as these are very sensitive and costly elements and the damages

are not repairable.

3. If any unusual noise is heard during the VSR process, stop the

process immediately by pressing the EMERGENCY switch

provided on the front panel. Observe the work piece for any

damage or crack. Or the vibrator may have got loosened.

4. If during the process, the amplitude decreases, then reduce the

frequency and try to achieve the resonance. If still resonance is

not obtained, increase the frequency and try to locate the

resonance. This means that the resonance frequency might have

sifted slightly towards lower side or slightly towards upper side.

However if the resonance has sifted towards the lower side, it is

clear indication of stress reduction.

5. During process the fault condition arises due to low voltage,

over voltage, over current, short circuit or any internal panel

fault, the process Exciter will stop. Immediately switch off the

mains, after 5 minutes start the process again. If still the trip

conditions prevail, consult factory.

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Supporting the component and Fixing the vibrator:

When light powdery material is sprinkled on the job during vibration,

they form the so-called nodal lines, under resonance condition. The nodal

pattern indicates the dynamic shape of the job. If these lines are parallel

to each other, then the job is said to be in the bending mode. If they are

90 degrees to each other then the job is said to be in torsion mode. At

nodal lines the vibration force is negligible, i.e. the sinusoidal force

passes through the neutral point.

The position or type of support isolator is critical only in case of light and

precision parts. Good quality isolators of suitable type are selected first.

The job or component, which is to be stress relieved, should be supported

so that the job is in balanced state. The support isolators should be placed

in such a way that there is minimum static deflection while ensuring

maximum dynamic deflection. If possible move the support isolators

below the nodal line keeping in mind that the job is in balanced condition.

The Vibration Exciter should be mounted conveniently on the job,

preferably parallel to but away from the nodal lines. It should be rigidly

clamped with the job. The vibrator can be mounted in any plane but

preferably in the horizontal plane. The job should be vibrated with

different position of vibrator, preferably at 90 degrees to the original

position.

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Accelerometer functioning and handling:

The Accelerometer is a device, which senses the vibration acceleration,

converts this signal into electrical signal, and feeds this signal to the

vibration meter. An accelerometer with its cable is the most costliest and

delicate part of the entire VSR system and hence it should be handled

very gently during the operation.

The accelerometer should be mounted rigidly on the job, away from the

nodal line, preferably corner of the structure is ideal. The peak reading of

this signal on vibration meter indicates the resonance. During operation,

prevent all loose parts from moving, otherwise some wrong readings will

be indicated with regards to the resonance which may be misleading.

Once again we remind you to avoid mishandling of accelerometer and

cable, as these are very costly items and the damages caused are not

repairable.

Use of the Chart Recorder:

With wider implication of the quality standard like ISO 9000, proof of

treatment, method of deployment, and component identification are

increasingly in demand. For this to accomplish, a stylish representation of

the graph can be produced with the help of a chart recorder. It forms a

reliable QA tool and contains useful design data. Requirements will very

from company to company.

Although the use of chart recorder is envisaged here, the process can still

be employed without it. Once the operator has become fully conversant

with the treatment method, the recorder may not be required. However, a

chart recorder may be regarded as an essential tool for QA system or ISO

9000 standard.

The chart recorder gets the signal from the vibration meter corresponding

to the accelerometer signal. This signal is traced on the hard copy chart

paper with respect to the time.

Read the chart recorder instruction manual thoroughly, provided

separately, before using it.

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Frequently Asked Questions

• What is Stress?

For metallurgical purpose the stress can be defined as the force

experienced between any parts of the body of continuous material.

Normally they are in a state of equilibrium and balanced internally

• What is Residual Stress?

The Stresses in the body, which are not in the state of equilibrium and are

not balanced internally, is known as the Residual Stress.

• What is the effect of Residual Stress?

Residual Stress is the main cause of dimensional instability of the

component. Hence they cause the premature failure of the component if

not relieved or redistributed for equilibrium.

• How the stress level is evaluated & weather we can know that the

stresses have been relieved?

Unfortunately there is no non-destructive technique available to indicate

the Stress level. However, X ray defraction is the latest technique by

which the effectiveness of the VSR is evaluated at CMTI, but again it is

the destructive and the laboratory method. In Heat Treatment also no test

is applied for the efficacy, and the procedure is blindly applied.

• How Reliable and effective VSR is?

VSR is equally reliable as TSR for achieving the dimensional stability of

the metal. It has been tested and proved at CMTI, a Govt. recognized

research institute. However it is not the direct replacement to thermal

treatment for annealing, hardening or any other treatment where

metallurgical changes are required in the metal.

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• Weather this process is approved under any code or standard?

Though the process was invented during the Second World War and

practiced widely over the world, somehow or the other it has not been

standardized. However in India CMTI, National Physical Laboratory and

other institutions recognize the process. Many large organizations have

also accepted and use the VSR technique. In fact in India the VSR

equipment was first developed by CMTI.

• How big jobs can be stress relieved by this process?

This method does not have any limitation by size, shape or weight of the

Job. Large or heavy jobs are no problem but small jobs may need certain

fixtures to be prepared to carry out the process.

• What should be the frequency and the duration of the vibration?

Every component has its own natural frequency. To maximize the effect,

the job should be vibrated to its natural frequency and its harmonics. The

typical duration can be 10 minutes at a given frequency. Most jobs get

stabilized when treated for 15 minutes each at two different harmonic

frequencies.

• Weather the job can be treated at site?

The VSR equipment is a portable machine and can be easily carried to the

site. The job is to be isolated from the ground and then the process is

applied at the site itself. Also almost all metals can be treated by VSR

method except the precipitation hardenable materials and severely cold-

formed materials. We carry out the job at your site for VSR treatment

provided the quantum permits.

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Annexure I

WELCOME SCREEN

Wait for few seconds to go to next screen

SCREEN 2

Note:

• If during the process Emergency switch is put on, the process will

terminate at any stage.

MANUAL INDEX SCREEN

MANUAL.

SETUP &

MONITORING

M/S SAHYOG ENTERPRISE 5, Tarun Plastic Industrial Estate,

Mogra Village Rd, Andheri (E), Mumbai-69.

EMAIL: [email protected]

VSR EQUIPMENT

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SCREEN 3

SET TOTAL RUN TIME: Sets the VSR operation time for the selected

frequency

TIMER MODE SELECT : Selects the mode of operation Timer/ Manual

START : Starts the VSR process at selected frequency

INDEX : Goes to manual index screen.

SENSOR OPEN : sensor open will appear on the screen if the

sensor is not connected or the sensor has

failed. The process will stop

EMS : EMS will appear when Emergency switch is

pressed during the operation and the process

will stop.

MANUAL SETUP & OPERATION

MANUAL SET

VIBRATION FREQ.

TIMER MODE

SELECT

TIME

LAPSED

MANUAL CYCLE

OFF

# #

VIBRATION FREQ.

AMPLITUDE.

CURRENT.

12

min

123.45 HZ

123.45 HZ

1234 micron

123.4 amps

START

SET TOTAL RUN

TIME

MANUAL

INDEX

min

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INTERNAL INSPECTION REPORT

1. Description: Stress Relieving Equipment ( Vibratory Type) 2. Specifications: As per PO- MATEC-SET/PO-001-10 3. Consignee: Machine Automation Joint Stock Company. 4. Size of Lot: 1 Set 5. Offered for inspection: 1 Set 6. Date of inspection: 24/04/2010 7. Place of inspection: Sahyog Enterprise, 5, Tarun Industrial Estate,

Mogra village road, Andheri East, Mumbai 400069 Main Equipment : Model VSR AT

A. VSR Equipment Make : SAHYOG ENTERPRISE B. Exciter VSRE 05 & VSRE 20 make: Good Earth Engineering

Industries C. Sensor with cable : ACD make, accelerometer sensor D. Clamps : 2 nos Big Clamps and 2 nos small Clamps E. Rubber isolators : 12 nos assorted

8. Specifications:

Main Equipment: Value Specified Value Observed Supply Voltage 230V, 1ph, 50Hz 230V, 1ph, 50Hz Exciter Rating 0.37Kw, 3ph, 220V, 0 to 100

Hz variable model VSRE 05

0.37Kw, 3ph, 220V, 0 to 100 Hz variable model VSRE 05

Exciter Rating 0.75Kw, 3ph, 220V, 0 to 100 Hz variable model VSRE 20

0.75Kw, 3ph, 220V, 0 to 100 Hz variable model VSRE 20

Frequency 0 to 100 Hz variable using potentiometer

0 to 100 Hz variable using potentiometer

Vibration Exciter Electromechanical type Electromechanical type Type of recorder pen type chart recorder, 100

mm width with 3 speeds pen type chart recorder, 100 mm width with 3 speeds

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Control Indications Value Specified Value Observed Frequency 0 to 100 Hz 0 to 100 Hz Displacement Amplitude

0 to 6000microns 0 to 6000 microns

Chart Widh 100 mm 100 mm

Timer Programmable Programmable through touch screen

Sensor

Specified : Piezoelectric voltage output type, vibration sensor, with low impedance cable with magnetic base. Observed : Piezoelectric voltage output type, vibration sensor, with low impedance cable with magnetic base.

Accessories

Value Specified Value Observed

C Clamps small 2 nos. 2 nos. C Clamps Big 2 nos. 2 nos. Set of Rubber for isolation

12 nos 12 nos.

Electric Input & Output cable

1no. Each 1no. Each

9. Test/ Inspection:

Sr. No. Perameter Specified Oberservation Remark

1 Vibrator Type Electro mechanical

Electro mechanical OK

3 Type of

recorder Pen type Pen type OK

4 Chart Width 100mm 100mm OK 5 Control Input 230V, 1

Phase,50Hz 230V, 1 phase, 50Hz.

OK

6 Output frequency

0 to 100 Hz 0 to 100 Hz OK

7 Sensor Piezo electric, voltage output type with low impedance cable and magnetic base

Piezo electric, voltage output type with low impedance cable and magnetic base

OK

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8 Accessories Clamps- Small 2Nos., Clamps- Big 2 Nos., Set of rubbers- 12 Nos., Input-output cable- 1 No each, Chart pen – 5 nos, Chart Paper – 5 nos

Clamps- Small 2Nos., Clamps- Big 2 Nos., Set of rubbers- 12 Nos., Input-output cable- 1 No each, Chart pen – 5 nos, Chart Paper – 5 nos

OK

10. Performance Report: The equipment was tested on the small job with VSRE 05 exciter along with sensor and cable. The parameters are as follows:

VSRE 05 Exciter Resonance Frequency 22 Hz

Amplitude, (Microns). 600 microns Time duration, Minutes.

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11. Conclusion:

Specification, performance confirms specification as mentioned in PO.. Hence equipment found acceptable. SAHYOG ENTERPRISE

Partner

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Matec- VSR Manual