Improved Techniques for Thermomechanical Testing in Support of Deformation Modeling

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Abstract
The feasibility of generating precise thermomechanical deformation data to support constitutive model development was investigated. Here, the requirement is for experimental data that is free from anomalies caused by less than ideal equipment and procedures. A series of exploratory tests conducted on Hastelloy X showed that generally accepted techniques for strain controlled tests were lacking in at least three areas. Specifically, problems were encountered with specimen stability, thermal strain compensation and temperature/mechanical strain phasing. The present study was undertaken to identify the source of these difficulties and to develop improved thermomechanical testing techniques to correct them. These goals were achieved by developing improved procedures for measuring and controlling thermal gradients and by designing a specimen specifically for thermomechanical testing. In addition, innovative control strategies were developed to correctly proportion and phase the thermal and mechanical components of strain. Subsequently, the improved techniques were used to generate definitive deformation data for Hastelloy X over the temperature range, 200 to 1000°C.