共查询到10条相似文献,搜索用时 62 毫秒
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Accurate measurement of short (<1 mm depth) elliptical fatigue cracks that grow from the toes of fillet welds has proved to be an obstacle to the application of fracture mechanics principles to welding fatigue. This paper reports a DC potential drop technique which allows continuous measurement of the depth of such elliptical cracks. A delicate compromise between sensitivity and accuracy, combined with superior electrical stability displayed by the measurement apparatus, has allowed detection of: 1 — crack growth less than 0.01 mm and; 2 — crack growth rates less than 10?7 mm/cycle for cracks less than 1 mm deep.Preliminary results have indicated the relative importance of stress ratio, defect size and material variation on the growth of these short elliptical cracks. When the weld toe is subject to high stress ratios the phenomenon may be considered propagation dominated whereas low stress levels increase the influence of threshold and initiation mechanisms. 相似文献
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Experimental and numerical investigation of fatigue crack growth in the cracked gear tooth 总被引:1,自引:0,他引:1 下载免费PDF全文
X Zhang L Li X Qi J Zheng X Zhang B Chen J Feng S Duan 《Fatigue & Fracture of Engineering Materials & Structures》2017,40(7):1037-1047
The numerical simulation was conducted to analyse the fatigue crack growth in gear with the finite element codes ansys (ANSYS, Inc. Canonsburg, Pennsylvania, USA.) and franc 3d (Fracture Analysis Consultants, Inc. Ithaca, New York, USA.), and the corresponding fatigue test was also carried out. During the simulation, the location of maximal stress induced by the external force was first determined by the code ansys , and then the obtained results were imported into the franc 3d to analyse the crack growth. The analysed results were input into the codes ansys and franc 3d again to compute the stress and the stress intensity factor in the following steps. After several rounds of analysis, the results of the fatigue crack propagation were obtained. The investigations show that the crack mode I is dominant during the crack growth and the stress intensity factor KI raises with increase of crack growth length and a series of quarter‐elliptical cross sections of the ruptured gear tooth are obtained. The simulation results are in good accordance with experimental findings. 相似文献
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Molecular dynamics simulation of crack initiation and propagation in bcc iron under load within spur gear tooth root 下载免费PDF全文
Spur gears are widely used in practice, and one of their typical failures is tooth breakage. In general, the tooth breakage occurs at tooth root, and the amount of crack growth during a meshing cycle is in atomistic scale. This work aims at identifying the mechanisms of crack initiation and propagation at tooth root by using molecular dynamics simulation. The results prove that there are phase transition regions and edge dislocations at crack tips. According to the distribution characteristic of the atomic potential, its concentration can be observed obviously by visualization software. In these concentration regions, microvoids come into being and expand gradually, which results in the subcrack initiation. Additionally, the microvoids and subcracks propagate along the high potential direction and then come together to accelerate the crack growth. Through carrying out a comparative simulation, the effects of heavy load at single meshing area on crack initiation and propagation are addressed. 相似文献
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Gear mesh stiffness plays a very important role in gear dynamics and it varies in the presence of gear fault such as crack. The measurement of stress intensity factor can lead to the determination of gear tooth mesh stiffness variation in the presence of crack in a spur gear system. In this paper, the technique of conventional photoelasticity has been revisited to explore the possibility of using it as a supplementary technique to experimentally measure the variation of gear mesh stiffness. An attempt has been made to calculate the variation of mesh stiffness for a pinion having a cracked tooth and a gear tooth with no crack of a spur gear pair. An analytical methodology based on elastic strain energy method in conjunction with total potential energy model has been adopted and implemented within the mesh stiffness calculations. To visualize the state of stress in a structure using finite element and other currently available methods, photoelasticity is considered to be one of the oldest and most developed experimental technique. An experimental methodology based on conventional photo-elasticity technique for computing stress intensity factor (SIF) for cracked spur gear tooth is presented for different single tooth contact position and crack length. The relation between contact position, crack length, crack configuration, SIF and the variation of total effective mesh stiffness have been quantified. Finally, a comparison has been made and the results obtained from finite element method (FEM) based on linear elastic fracture mechanics (LEFM), analytical method and proposed experimental method has been outlined. 相似文献
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S. PODRUG D. JELASKA S. GLODE 《Fatigue & Fracture of Engineering Materials & Structures》2008,31(5):327-339
A computational model for determination of the service life of gears with regard to bending fatigue at gear tooth root is presented. In conventional fatigue models of the gear tooth root, it is usual to approximate actual gear load with a pulsating force acting at the highest point of the single tooth contact. However, in actual gear operation, the magnitude as well as the position of the force changes as the gear rotates. A study to determine the effect of moving gear tooth load on the gear service life is performed. The fatigue process leading to tooth breakage is divided into crack‐initiation and crack‐propagation period. The critical plane damage model has been used to determine the number of stress cycles required for the fatigue crack initiation. The finite‐element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth. 相似文献
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为避免传统设计和加工的近似球面渐开线齿形螺旋锥齿轮存在的缺陷,提出了一种新型螺旋锥齿轮设计方案.从齿面精确组成和形状特征出发,将球面渐开线理论应用于齿面基本曲线的方程表达式求导中,实现了齿面曲线的分段参数化.然后,对组成齿面的各区域分别求取齿面离散点数据,并采用三次均匀B样条曲面方法进行初步的拟合与拼接.为了进一步提高齿面精度,借助NURBS方法对拼接后的齿面进行了统一的NURBS精确拟合,并给出了齿面统一参数化的优化方法.最后的算例表明了相关方法的精确性和可行性,为螺旋锥齿轮的数字化设计与NURBS加工提供了新的思路与途径. 相似文献
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局部均值分解在齿轮故障诊断中的应用研究 总被引:3,自引:6,他引:3
局部均值分解(Local Mean Decomposition,简称LMD)作为一种新的自适应的时频分析方法,在故障诊断领域开始得到研究。本文利用仿真信号研究了LMD算法的特性,验证了LMD处理描述齿轮故障信号特征的多分量调幅调频信号的有效性;在此基础上将LMD综合应用于断齿、磨损和剥落三种齿轮故障诊断中,并与传统解调方法进行了对比。结果表明,LMD方法可以有效提取故障齿轮的故障特征,消除虚假成分的影响,从而提高了齿轮故障诊断的准确性 相似文献