共查询到17条相似文献,搜索用时 311 毫秒
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9Cr2凸模半埋藏疲劳裂纹电磁热止裂的实验与模拟研究 总被引:1,自引:0,他引:1
电磁热效应止裂技术的发展为金属模具中半埋藏裂纹的止裂问题提供了有效的解决途径。文章采用实验和数值模拟分析方法研究了对带有半埋藏裂纹的9Cr2凸模进行脉冲放电,实施电磁热止裂。实验结果表明,脉冲放电瞬时半埋藏裂纹尖端附近金属温升超过熔点,裂尖熔化形成焊口,并且由于裂纹是半埋藏状态,熔化的金属在裂尖处形成堆焊,其周围发生有利于遏制裂纹扩展的组织细化,有效地遏制了裂纹的扩展;数值模拟结果表明,脉冲放电瞬间,裂纹尖端附近很小的区域内,温度和温度梯度变化极大,裂纹尖端金属迅速熔化,导致半埋藏裂纹尖端曲率半径增加几个数量级,数值模拟分析结果与实验结果相吻合。 相似文献
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《塑性工程学报》2017,(3)
对含单边裂纹的40Cr Ni Mo钢构件进行脉冲放电止裂,分析了脉冲放电止裂后结晶区、相变区和基体区的显微硬度变化。结果可知,止裂后的裂纹尖端变得圆钝,曲率半径增大,应力集中得到消除,有效地阻止了裂纹的继续开裂;结晶区晶粒得到细化,相变区晶格畸变及位错密度增大导致塑性变形抗力增大,两者的显微硬度得到了不同程度的提高。应用Eshelby等效夹杂原理对脉冲放电止裂后单边裂纹尖端发生组织转变的相变应力进行了理论和数值计算,最终获得相变应力的计算方程;采用ANSYS有限元软件对于含单边裂纹构件脉冲放电止裂进行数值模拟,验证体积变化和屈服强度变化对相变应力的影响。最后,简述了含单边裂纹构件脉冲放电止裂技术对于异种材料焊接裂纹的止裂修复工程应用。 相似文献
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A. V. Ivanov A. V. Sinchuk A. S. Ruban 《Surface Engineering and Applied Electrochemistry》2012,48(4):348-354
The characteristics of a pulse discharge current flowing through a conductor made from Al-7% Si alloy within the temperature range of 700–500°C are experimentally investigated. It is found that the cooling and phase transition of a conductor from a liquid to solid state is accompanied by the contraction of the amplitude of the pulse sine wave current, by the increase of the damping decrement and of the oscillation period, and by the displacement of the oscillatory spectrum to an area of lower frequencies. A peculiarity of the temperature dependences of the pulse characteristics is the occurrence of discontinuities and excesses at the characteristic liquidus and solidus points. It is assumed that the observed changes are due to the increase of the active resistance and reactance (inductive) components of the full resistance during the cooling and solidification. 相似文献
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The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding (GMAW) is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation. 相似文献
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Based on the numerical calculation of 3-D potential distribution in aluminum reduction cells, current distribution in the metal pad is calculated under the following conditions: 1) pot ledge ideally formed; 2) ledge extension to below anode; 3) different metal heights; 4) AC and 5) Spike. It is found that Jy in metal pad increases first to a highest point and then decreases along anode length. At normal status, the largest Jy is about 0.4 A/cm^2 and it locates at about 2/3 of anode length. With longer ledge, the maximum value of Jy decreases and its position moves center-ward. The longer the side ledge, the larger the negative current flowing center-ward at side channel. Jy in metal pad increases with anode length and it is not affected by metal height; while Jy increases with metal height. At AC, current flows toward metal under new anode. At spike, current concentrates at spike rather than evenly distributes. Normally, Jy is almost negligible in metal pad. 相似文献
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V. N. Tsurkin A. V. Mel’nik A. V. Ivanov 《Surface Engineering and Applied Electrochemistry》2011,47(1):56-60
The spectral analysis results for the time dependences of the pulse current at the electric current treatment of the melt are shown. It is established that the most favorable conditions of treatment are reached at the oscillating discharge mode. The possibility to control the parameters of the impact by means of the duration of the current pulses is shown. 相似文献