Standard Test Method for Uniaxial Pre-strain and Thermal Free Recovery of Shape Memory Alloys

Abstract

5.1 This test method is used to measure a specimen's material and shape memory effect properties in response to a uniaxial deformation and then cycling through a full thermal transformation to recover all or a portion of the deformation. A material's martensitic stress-strain response, martensite residual strain, austenite recovered strain, and unrecovered strain (or plastic deformation) after thermal cycling is determined. 5.2 Measurement of the specimen's motion closely parallels many shape memory applications and provides a result that is applicable to the function of the material. 5.3 This test method may be used for, but is not limited to, wire, round tube, or strip samples. It is able to provide an assessment of the product in its semi-finished form. 5.4 This test method provides a simple method for determining transformation temperatures by heating and cooling specimens through their full thermal transformation after uniaxial pre-straining in the martensite state. 5.5 This test method can be used on trained and processed material in a semi-finished form to measure Two Way Shape Memory Effect (TWSME) by comparing the strain in the austenite state and martensite states with minimal applied stress. The force is set to a minimum value not to exceed a corresponding stress of 7 MPa (in accordance with Test Method F2516). 5.6 This test method is useful for quality control, specification acceptance, and research. 5.7 Transformation temperatures derived from this test method may not agree with those obtained by other test methods due to the effects of strain and stress on the transformation. 5.8 Components such as springs or other semi-finished parts can be tested using this method as agreed upon by the customer and supplier. Units of stress and strain can be replaced with force and displacement.