Development of simple thermal fatigue test method using low-thermal expansion restraining holders
Ikuno Hajime; Iwanaga Shogo; Awano Yoji
Abstract:A new test method of evaluating the thermal fatigue resistance of aluminum alloy has been developed. In this test method, a small test piece was clamped between a pair of holders consisting of low-thermal expansion materials, mainly Incoloy 904 superalloy. The test piece was alternately heated and cooled with constraining longitudinal thermal expansion. The compressive and tensile strains were generated during the heating and cooling periods, respectively. The total strain range was determined by the thermal expansion of the test piece and holders, and by the size and shape of the test piece. The initial strain could be controlled by changing the clamping temperature of the test piece. The temperature distribution along the test piece was within 5K. The total strain range was almost constant during the test in spite of softening of the material. Thermal stress and strain were quantitatively estimated using high-temperature strain gages by compensating the temperature dependence of the gage factor and elastic modulus of holders. By using this test method, it has been quantitatively clarified that decreasing total strain range and reducing porosity increased the thermal fatigue lives of JIS AC2B aluminum alloy castings. Key Words:thermal fatigue, test method, restraining holder, AC2B alloy casting, porosity, total strain range, high-temperature strain gage