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1.
材料疲劳恢复新途径的探索Ⅰ──低碳钢疲劳寿命的延长   总被引:5,自引:0,他引:5  
研究了低碳钢经大电流脉冲处理后改善疲劳性能的可能性结果表明:在循环载荷作用一定周次后,经大电流脉冲处理,可使低碳钢的疲劳性能得以改善,并可延长其疲芳寿命约一个量级  相似文献   

2.
研究了大电流脉冲对 Ti—6 Al—4 V 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   

3.
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   

4.
脉冲磁处理改进疲劳性能MagneticProcessingSystemInc.发展了一种脉冲磁处理,能释放金属零件应力和改进疲劳性能。这种不加热工艺通过一个电磁场施加高能脉冲。对经过机加工、焊接、热处理过的零件的表面和亚表面缺陷有缓解作用,从而改进疲...  相似文献   

5.
研究了氢化处理对退火α-Ti 板材的组织、结构及性能的影响。α-Ti 在室温出现两种结构的氢化物:有序的fctγ相(TiH)和fccδ相(TiH_2)。分析了用X 射线衍射只查觉到δ相的原因。氢化物的数量及形态影响除氢后基体的晶粒组织。控制氢含量可以改善拉伸性能及疲劳性能。  相似文献   

6.
利用激光重熔技术对超音速火焰喷涂(HVOF)涂层进行改性处理,可改善涂层质量.采用HVOF技术在低碳钢表面喷涂Cr3C2-NiCr层,然后对其进行激光重熔处理,考察了熔覆后涂层的冲蚀性能.结果表明:HVOF层激光重熔后以不同角度冲蚀,30°冲蚀时冲蚀率最大,表现为塑性材料的冲蚀性能;激光重熔HVOF层在冲蚀初期冲蚀率较大,随着冲蚀次数的增加,冲蚀率降低,冲蚀性能最终优于低碳钢和HVOF层;HVOF层激光重熔后致密性提高.  相似文献   

7.
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   

8.
为了提高2024铝合金疲劳后的性能,先对其进行50%预疲劳再作激光冲击强化处理。采用显微硬度、残余应力测试,EBSD和疲劳试验等技术,研究了2024铝合金50%预疲劳和激光冲击强化后的组织结构和性能;讨论了激光冲击强化提高其预疲劳后性能的机理。结果表明:激光冲击强化可以明显改善2024铝合金50%预疲劳后的疲劳性能,200 MPa疲劳载荷下循环寿命比未强化前提高了1倍多。  相似文献   

9.
研究了能量脉冲对高能ZnO压敏电阻在可控硅整流电压下的静态老化性能的影响以及可控硅整流电压的过电压对压敏电阻的作用。过电压使压敏电阻流过频率为300Hz的脉冲电流,从而使晶界势垒高度下降和晶粒导电性增加;经受能量脉冲后的压敏电阻的静态老化电流增长速度远大于未经能量脉冲的压敏电阻的静态老化电流增长速度,即能量脉冲使静态老化性能严重变差。  相似文献   

10.
表面处理镁合金疲劳性能的研究现状   总被引:2,自引:1,他引:1  
随着镁合金应用的日益广泛,其疲劳性能也越来越受到人们的重视.对近年来有关表面处理镁合金疲劳性能的研究进行了总结,归纳了喷丸处理、滚压强化、阳极氧化、激光熔融等表面处理方法对镁合金疲劳性能的影响及机理.最后对改善镁合金疲劳性能未来应重点发展的表面处理技术进行了展望.  相似文献   

11.
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   

12.
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   

13.
Abstract

A 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   

14.
在低碳马氏体不锈钢中添加适量Cu,经过抗菌热处理,使不锈钢具有优良的抗菌特性。利用X射线衍射仪和恒电位仪分析了抗菌处理后相的分布和耐蚀性,并通过覆膜法测定其抗菌性。结果表明,随着Cu含量的增加,含铜马氏体不锈钢的硬度和抗菌性提高,维钝电流密度、致钝电流密度和致钝电压减小,更易于钝化。  相似文献   

15.
用高密度脉冲电流对服役后期的高锰钢辙叉进行表面处理,研究了对其组织结构的影响。结果表明,在较低的温度下(786 K)辙叉发生再结晶,再结晶晶粒尺寸约为29.3μm,远比处理前的晶粒尺寸小,处理后的显微硬度显著降低。在高密度脉冲电流作用下,位错运动能力、原子的扩散能力以及振动频率都提高了,从而使再结晶的形核速率显著提高,...  相似文献   

16.
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 SN property was first examined and a useful procedure was proposed to obtain a common SN 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   

17.
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   

18.
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   

19.
本文探讨了用冲击疫劳试验测定的疲劳寿命和疲劳裂纹扩展速率衡量热锤锻模材料疲劳抗力的合理性。研究了5CrNiMo钢在热锻模要求的硬度范围内,材料强度水平和表面强化对冲击疲劳性能的影响。试验结果表明,在相当小型锻模受载的低冲击能量作用下,适当提高材料强度可延长疲劳寿命;在相当大型锻模受载的高冲击能量作用下,提高材料塑性、韧性可提高疲劳寿命。软氮化并磨去脆性白层可显著提高低冲击能量下的冲击疲劳寿命。  相似文献   

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