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Disposable mechanical elements are widely used in many fields such as aerospace and military industries. It is known for their extremely short work time which is quite different from general mechanical elements. The stress level of disposable mechanical elements is much higher than general mechanical elements. In this situation, the traditional fatigue fracture failure will be replaced by fatigue elastic failure used in the design of disposable mechanical elements. The fatigue elastic failure is closely related to the ratcheting properties of materials. Therefore, this paper focuses on the ratcheting properties of typical cyclic softening materials steel 45 and 42 CrMo. The fatigue elastic failure phenomenen of these two materials are shown through the stress control tests.

Disposable mechanical elements with extremely short lives are widely used in the aerospace and defense fields. To reliably evaluate the life of disposable mechanical elements, many attentions were concentrated in the fatigue properties of disposable mechanical elements. According to the different meanings of static strength for metals, disposable mechanical elements are divided into two groups with different fatigue properties: extremely low cycle fatigue module for Type I with ultimate strength as design stress and low cycle fatigue module for Type II with yield strength as design stress. The Kuroda model and a cumulative damage model consisting of the Miners rule and the sequential law are used in the fatigue design process of the Type I. To the Type II, the Manson-Coffin model is suitable for conventional applications but more attempts are still conducted to further improve stress levels. The Type II with increasing load sequences are specially treated, since the cyclic yield strength of certain materials under pulsating stress closing to the yield strength increase with the deepening of fatigue damage. Consequently, under the increasing pulsating cyclic loading, the later load whose amplitude is higher than the initial yield strength will be permitted.

In this paper a new kind of finite element analysis model towards metallic microstructure of titanium alloy is established based on a common metallic microstructure picture. By the simulation of tensile test on this new kind of FEA model performed by finite element analysis software Abaqus, the tensile curve in the state of simulation is obtained. Meanwhile, in order to verify the accuracy of the simulation results, a series of tensile tests are designed and performed and the tensile curves under experimental conditions are obtained. Comparing the experimental results with the simulation results, the conclusion can be verified that the new microstructure FEA model can illustrate the metallic microstructure very well. And this model provides a new perspective to study the mechanical properties of metallic materials.

Recently advances in testing methods and study of the inorganic salt establish the high temperature phase change energy storage materials as a promising candidate for solar thermal power generation, industrial process heat use and waste heat recovery. In this paper, a phase change model related to the warming-cooling method was established to test the phase change temperature and the heat of LiCl-NaCl(1.08-1) and Ca(NO3)2-NaNO3(4-7). The result tested by the warming-cooling method is mainly in line with the one tested by other method. The data allows a promising development of the energy storage.