effect of variation in applied force on transformation

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EFFECT OF VARIATION IN APPLIED FORCE ON TRANSFORMATION TEMPERATURES OF NITINOL SMA Prepared By: Shashin Vyas

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Page 1: Effect of variation in applied force on transformation

EFFECT OF VARIATION IN APPLIED FORCE ON TRANSFORMATION

TEMPERATURES OF NITINOL SMA

Prepared By:Shashin Vyas

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CONTENTS Abstract

Introduction

Experiment Setup

Results And Discussion

Conclusion

References

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ABSTRACT Phase Transformation Temperature is one of the

most important parameters for the Shape Memory Alloys (SMAs).

Because of offering large deformations and forces, SMAs are promising materials for actuation in space applications.

For determining transformation temperatures of the SMA Nitinol, a novel method is carried out which uses dead weight.

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ABSTRACT The wire is heated up to approximately 80 degree

Celsius with direct current. And then the temperature is decreased to cool down the wire.

All the temperatures are obtained and recorded with variation in applied force.

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INTRODUCTION Shape memory alloys are metal alloys that remember their

original shape.

If deformed, they recover their original shape upon heating.

One type of shape memory alloy is Ni-Ti (Nitinol).

It has two stable phases, the high temperature Austenite phase and the low temperature martensitic phase.

It is quite fascinating field of research mainly in aviation technology and Medial Science.

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INTRODUCTION For Designing and Optimizing The Application of

SMAs it’s required to understand its behavior.

The Phase Temperature for the Shape Memory Alloys Such as the Austenite Start (As), Austenite finish (Af), Martensite start (Ms), Martensite finish (Mf) are the Basic Temperatures that should be determined before designing the system.

In This Experiment a Linear Variable Displacement Transducer (LVDT) consisting of a stack of masses actuated vertically by an SMA wire is used.

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INTRODUCTION The Experimental setup contains force sensors

displacement measurement and thermocouple to determine the phase transformation temperatures.

The Wire was heated up with the direct current and the testing was done with different value of dead-weight load to the wire.

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INTRODUCTION

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EXPERIMENTAL SETUP The Nitinol wire of 0.5mm diameter and length

351mm was used for the study.

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EXPERIMENTAL SETUP The Setup used for the experiment are:

DC regulated power supply, a clamping device for SMA wire, a type J-thermocouple for temperature measurement, multimeter and linear variable displacement transducer (LVDT) As Shown in above figure.

Through Physical Loading of dead weights from 0.5kg to 3.15kg In steps, Stress is induced in the SMA wire. And displacement in initial condition is set to zero.

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EXPERIMENTAL SETUPThe Experiment is divided into two parts:

1] Heating Cycle: The wire is heated and as the temperature increases, it starts to contract. The temperature is increases to the maximum level of 75 degree centigrade.

2] Cooling Cycle:The DC Power supply is turned off and the wire is allowed to cool. The data of change in temperature and displacement were taken as the wire returns to its original condition.

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RESULTS AND DISCUSSION

In The Fig. 2, The Strain V/S Temperature plot for a particular load is given.

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RESULTS AND DISCUSSION

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RESULTS AND DISCUSSION

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RESULTS AND DISCUSSION

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RESULTS AND DISCUSSION

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RESULTS AND DISCUSSION

Here, Austenite Start (As), Austenite finish (Af) Temperature will be obtained from the heating process curve while Martensite start (Ms), Martensite finish (Mf) Temperature from the cooling process curve.

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RESULTS AND DISCUSSION

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CONCLUSION This method is one of the simple methods for

Determining Phase transformation temperatures for the shape memory alloys.

It can be observed that For NiTi wire, Austenite start and finish temperatures are 38.3 and 46.6 degree Celsius. While martensite start and finish temperatures are 29.9 and 27.9 degree Celsius respectively.

The phase transformation temperatures are affected by the applied force. And it increases with increase in applied force.

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REFERENCES Mohammad H Elahinia and Mehdi Ahmadian,

2005, an enhanced SMA phenomenological model:II. The experimental study, smart meter. Struct 14, 1309-1319.

J. Rena and, K.M. Liewa, “Meshfree modelling and characterisation of thermomechanical behavior of NiTi alloys,” Engineering Analysis with Boundary Elements 29 (2005) 29–40.

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Any Query ?

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