共查询到19条相似文献,搜索用时 93 毫秒
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材料疲劳恢复新途径的探索Ⅱ:脉冲电流对Ti—6Al—4V合金裂纹扩 … 总被引:1,自引:1,他引:0
研究了大电流脉冲对Ti-6Al-4V合金疲劳裂纹扩展行为的影响。结果表明,在疲劳裂纹扩展后,试样经大电流脉冲处理,对疲劳裂纹的扩展有阻滞作用。并可以延长其疲劳扩展寿命。 相似文献
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氮等离子体浸没离子注入技术改善轴承钢滚动接触疲劳寿命和机械性能的研究 总被引:4,自引:0,他引:4
研究了氮等离子体浸没离子注入(N-PIII)技术处理后GCr15轴承钢表面的滚动接触疲劳特征和机械性能。测试了改性前后试样的滚动接触疲劳寿命和磨痕光学形貌、摩擦磨损行为及纳米压痕硬度。结果表明,处理后试样的最大显微硬度较基体增大近一倍,摩擦系数从0.95下降到0.15。在赫兹接触应力为5.1 GPa,90%置信区间下的L10和L50寿命分别增加了99.6%和236.3%。分析不同处理参数下的Weibull分布曲线和光学显微形貌可知,脉冲偏压、材料内部缺陷、基体表面粗糙度、注入时间和N离子注入剂量对疲劳寿命均有很大影响。疲劳寿命和相关机械性能的改善主要源于N-PIII处理所导致的氮化物强化相和残余压应力的共同作用。 相似文献
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碳纤维增强铝合金层压材料的研究 总被引:1,自引:0,他引:1
本文探索了碳纤维增强铝合金层压材料(CFALL)的制备工艺,并制得了具有优异力学性能、耐温、耐疲劳的层压材料.就纤维含量、纤维取向及温度等对层压材料力学性能的影响作了探讨,并对它的疲劳性能以及预应变对疲劳性能的影响进行了研究.试验表明,CFALL具有轻质、高强、耐温、耐疲劳等特点,它的拉伸、弯曲强度超过了ARALL和GLALL,它的疲劳性能与ARALL相近. 相似文献
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Gears for structural machines require high fatigue strength for high performance. Generally, gears made of carbon steel easily corrode, thus, shortening their fatigue life. The aim of this paper is to improve the fatigue strength of carbon steel gears by means of heat treatment method which was nitriding composed of 95 % nitrogen gas as well as 5 % hydrogen gas, and to investigate its properties after nitriding. Therefore, in order to find the optimum nitriding temperature to increase the hardness and corrosion resistance of gears, the gas nitriding process was conducted at two different tube furnace temperatures: low (550 °C) and high (1150 °C), both for four hours. Microstructural and mechanical property evaluation of the low and high temperature nitrided low-carbon steel BS970-080A15 were studied and the results were compared to identify which gear had better performance in terms of hardness as well as corrosion resistance. The results from Vickers hardness test and weight loss analysis proved that high temperature nitrided carbon steel is harder and more corrosion resistant than the low temperature one. 相似文献
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《Materials Science & Technology》2013,29(12):1410-1418
AbstractA new carbide free bainitic rail steel was prepared, whose comprehensive mechanical properties are equal or superior to current premium pearlitic and bainitic rail steels. The new bainitic rail steel possesses better low cycle fatigue properties and approximate resistance to wear compared with current pearlitic rail steel. The carbon enriched film-like austenite between the ferrite of the new bainitic rail steel can delay crack initiation and propagation in fatigue processes, resulting in a relatively high low cycle fatigue life (about two times) compared to the pearlitic rail steel. Finally, a wear model during sliding wear and deformation model during the low cycle fatigue of pearlitic and bainitic rail steels were established. As a result, the bainitic rail steel with a relatively reasonable combination of wear and fatigue properties compared to pearlitic rail steel is obtained, in which the initiation and propagation of cracks may be partially or entirely removed during the wear process. 相似文献
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Ultrasonic testing method has been often used to investigate fatigue properties of various metallic materials. Since ultrasonic fatigue tests are conducted at a very high loading frequency, they are particularly convenient for fatigue tests in the very high cycle regime. Indeed, ultrasonic fatigue method allows us to conduct fatigue tests up to 109–1010 cycles in a definite period. However, due to the huge gap of loading frequency between ultrasonic testing method (around 20 kHz) and usual testing method (most of the cases in the range 1–100 Hz), the frequency effect on the fatigue property is still unclear. Low carbon steel is one of typical metallic materials to provide a significant discrepancy between fatigue strengths obtained under ultrasonic testing frequency and under usual testing frequency range.Thus, by preparing a lot of specimens of JIS S15C low carbon steel (0.15% C), fatigue tests were carried out in a wide range of the loading frequency. The frequency effect on the S–N property was first examined and a useful procedure was proposed to obtain a common S–N property normalized by the lower yield stress. In addition, micro-plasticity behavior such as the stress–strain hysteresis loop and the local misorientation were also measured and the frequency effect on the fatigue property was discussed. 相似文献
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Abstract— An examination of PSB data pertaining to the effects of an air-excluding environment and electric current on the fatigue life of polycrystalline Cu and 316 stainless steel in rotating bending reveals that the spacing and width of the PSBs are smaller throughout the fatigue test for those conditions which lead to increased fatigue life. Moreover, the life correlates directly with the square of the product of the surface area fraction of PSB patches and the density of the PSBs contained therein. These results suggest that in these cases slip-homogenization is responsible for the increased fatigue life and not a consequence of it. A model is proposed for the observed relationship between slip band parameters and fatigue life, which is based on the strain concentration that exists at or near the PSB-matrix interface. The mechanisms by which an air-excluding environment or an electric current can increase slip homogenization are considered. 相似文献
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Bo Zhao 《Thin solid films》2009,517(6):2012-2015
Ultrasonic nanowelding technique was used to improve the field emission properties of carbon nanotube (CNT) cathodes. Two kinds of welding heads were used and the effects of the head on the emission properties were studied. The results show that cathodes welded by Al2O3 flat head demonstrate excellent field emission properties with high emission current density and good current stability. The improved field emission performance is attributed to the reliable and low resistance contact between CNTs and metal substrates. Cathodes welded by steel matrix head show a lower turn-on electric field due to the protruding CNTs at the edge of the welded pits. 相似文献