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THE STUDY OF THE SHAPE MEMORY EFFECT IN NI-TI AND CU-BASED ALLOYS WITH SPECIAL ATTENTION TO THE HYSTERESIS EFFECTS

Objective

The aim of the proposed R&D work is to propose solutions for regu lating mechanisms for which there is a large demand in space technology, robotics and other high technologies. Therefore, a fundamental study of the transformation characteristics of these alloys has to be made in order to determine and to understand the influence of the different parameters. This should lead to the proposal of novel technological applications in the field of shape memory alloys.
The project aimed at producing performing nickel titanium and copper based alloys for new applications in regulating mechanisms in space technology and robotics.

The macroscopic behaviour of shape memory alloys, for example the hysteresis curve (or effect gap remaining when the cause is cyclically decreased), it difficult to control and predict due to internal material properties and transformations under thermal and mechanical stimulus. Reciprocally, knowledge of the inner material transformations and shape memory performances would allow optimisation of the use of these alloys for sensitive regulating devices. The project studied the 2-way memory effect (training, to which hysteresis is directly related) and its degradation (to which effectiveness of the alloy is inversely related). Three aggregation levels were studied: nucleation, growth mechanisms and hysteresis of martensite (the result of quenching steel) variants; relations between nucleation and transformation instability; and macroscopic observations of the 2-way memory effect and relations between force, deformation and temperature and training and degradation. Specialised instruments had to be built or adapted to perform the observations. The project has increased the knowledge of the possibilities and limits of use of copper zinc aluminium based alloys. In particular, the transformation creep is much smaller between As and Af, allowing regulating mechanisms to operate better between the two.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

KATHOLIEKE UNIVERSITEIT LEUVEN
Address
De Croylaan 2
3030 Heverlee
Belgium

Participants (2)

ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE
Switzerland
Address

Lausanne
UNIVERSIDAD DE LAS ILLAS BALEARES
Spain