共查询到18条相似文献,搜索用时 78 毫秒
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本文研究了六升超高强度钢瓶疲劳裂纹扩展特征。气瓶疲劳失效方式不仅与材料的性能K1c 和σ0-2 有关,而且与主要疲劳裂纹源半长度C0 和两相邻疲劳裂纹源中心距L0 有关。气瓶撕裂的主要原因是多疲劳裂纹源扩展汇合成一个新的大疲劳裂纹源所致。 相似文献
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针对铸铝合金A356-T6开展了不同环境湿度下的超声疲劳裂纹扩展试验和实验室环境湿度下的常规疲劳裂纹扩展试验。由试验结果可知,超声疲劳在干空气环境中的疲劳裂纹扩展速率最低,而在蒸馏水环境中的疲劳裂纹扩展速率最高。常规疲劳在实验室环境中的疲劳裂纹扩展速率和超声疲劳在蒸馏水环境中的疲劳裂纹扩展速率几乎一致。针对Wei建立的环境湿度对铝合金材料疲劳裂纹扩展速率预测模型进行了修正,得到了铸铝合金A356-T6在任意环境湿度和试验频率下的疲劳裂纹扩展速率预测模型。 相似文献
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针对高强钢在硫化氢环境中腐蚀疲劳数据极为缺乏的现状,研究高压气瓶材料4130X在硫化氢腐蚀介质中的疲劳裂纹扩展速率.结合气瓶实际运行的环境和应力状态,应用改进型WOL(wedge-opening-loading)试样,在自行改造的专用低周腐蚀疲劳试验机上,完成0.006 7 Hz超低频率下饱和H_2S溶液、中等浓度H2S溶液和空气三种环境下的腐蚀疲劳试验,并用Paris公式进行两段式拟合,得出da/dN-ΔK的数学表达式.将试样微观断口的变化与宏观应力强度因子K的变化进行对比研究,给出不同环境中三个阶段K值的定量结果.结果表明:相同条件下,H_2S环境中的疲劳裂纹扩展速率比空气环境中大20倍以上;但当H_2S浓度达到一定范围后,对da/dN影响并不按比例增长,浓度相差11倍时,da/dN相差2.4倍,H_2S腐蚀介质的存在加速了疲劳破坏. 相似文献
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PD3和U71Mn钢轨钢疲劳裂纹扩展速率研究 总被引:7,自引:0,他引:7
利用MTS试验机, 在常温下对两种钢轨PD3和U71Mn进行疲劳裂纹扩展速率试验研究,根据Paris公式确定两种钢轨的疲劳裂纹扩展速率,利用极大似然估计法计算带有一个随机变量描述的疲劳裂纹扩展速率的概率方程.结果表明,裂纹扩展速率曲线符合一般疲劳裂纹扩展规律;PD3的强度性能优于U71Mn,但U71Mn表现出更好的抗疲劳裂纹扩展性能,扩展速率低于PD3钢轨;疲劳裂纹扩展速率的不确定性方程与试验结果相符. 相似文献
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建立了新型损伤容限性钛合金TC21的疲劳裂纹扩展模型;研究了疲劳裂纹扩展速率da/dN与疲劳裂纹扩展门槛值之间的关系。该模型预测了TC21钛合金的疲劳裂纹扩展速率,其预测结果与实验结果非常吻合。 相似文献
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采用电液伺服疲劳试验机对2205双相不锈钢进行不同过载比(1.0,1.5,2.5,3.5)下的疲劳裂纹扩展试验,研究了单峰过载对疲劳裂纹扩展速率的影响。结果表明:过载比越大,2205双相不锈钢裂纹扩展停滞的时间越长,疲劳裂纹扩展速率下降的幅度越大;当过载比小于3.5时,单峰过载引起裂纹尖端发生钝化或闭合,疲劳裂纹扩展速率明显下降甚至暂时停滞;当过载比为3.5时,裂纹尖端发生偏折及分叉,疲劳裂纹扩展完全停止。 相似文献
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A complete life model for the nucleation and growth of a fretting fatigue crack has been developed. The nucleation of a fretting crack is predicted by superimposing the crack growth rate experienced under fretting conditions onto S–N fatigue data for the alloy. The growth model utilizes small crack growth rate data and a fretting fatigue stress intensity factor to account for the small crack sizes and higher stresses experienced under fretting fatigue conditions. The development of the propagation model within the established fatigue crack growth code AFGROW allows this approach to be readily used by members of the aerospace industry. 相似文献
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Choon Yeol Lee Han-Kyu Jeung Jae-Do Kwon 《Journal of Mechanical Science and Technology》2016,30(11):4937-4940
Several studies have been conducted on the fretting fatigue limit characteristics of Inconel alloy tube material used in steam generators of nuclear power plants. Nevertheless, additional research on fretting fatigue crack initiation and propagation behavior is necessary in order to evaluate its fretting fatigue life more accurately. In this study, crack growth tests of fretting fatigue are conducted, and the characteristics of fatigue crack initiation and propagation are analyzed on Inconel 690 alloy. Also, plain fatigue crack growth tests are performed on the same material, and the results are compared with those of fretting fatigue crack growth tests. From both of the plain and fretting fatigue crack growth test results, the ΔK-da/dN diagrams are obtained and the crack growth rates are compared. It is found that the crack growth rate for fretting fatigue tests is faster than that for plain fatigue tests under a certain value of DK. However, over this value of DK, the crack growth rate for fretting fatigue tests becomes slower than that for plain fatigue tests due to debris which is produced by fretting and trapped in the propagated cracks. Finally, the fracture surfaces examined by an optical microscope, and the initiation angles of the oblique cracks are determined under various applied stresses. Also, the microstructure of the fracture surfaces is observed by a Scanning electron microscopy (SEM). 相似文献
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16MnR钢在不同应力比下的疲劳裂纹扩展的试验研究及模拟 总被引:1,自引:0,他引:1
采用3.8 mm厚带有圆形缺口的CT试样,研究了16MnR钢在不同应力比的恒幅循环载荷作用下的疲劳裂纹扩展。开发了一种基于疲劳损伤的方法来模拟疲劳裂纹扩展速率。将16MnR钢的循环塑性本构模型通过用户材料子程序UMAT嵌入到ABAQUS中。把有限元计算得到的疲劳裂纹尖端附近区域的弹塑性循环应力应变结果,代入到疲劳损伤模型中,得到每个加载循环在裂尖各点产生的疲劳损伤值。通过疲劳损伤准则,导出疲劳裂纹稳定扩展速率的计算公式。疲劳裂纹扩展试验验证了模拟结果。实验结果和模拟结果都表明,该试样厚度下,应力比对裂纹扩展速率几乎没有影响。 相似文献
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通过对不同热处理后获得3种典型显微组织的粉末高温合金FGH96合金试样在650 进行保载90 s和5 s并恒载荷循环应力作用下的疲劳试验,研究组织特征对疲劳裂纹扩展速率的影响规律,确定不同载荷条件下孕育期、萌生期、扩展期及瞬断期所占的比率。结果表明,γ相特征显著影响疲劳裂纹扩展速率;疲劳行为对保载时间存在敏感性,随保载时间的延长,在疲劳-蠕变的交互作用下会明显加快合金疲劳裂纹扩展;在整个疲劳破坏过程中,萌生比率均高于扩展比率,说明该合金抗裂纹萌生的能力要高于抗裂纹扩展的能力;此外,该合金疲劳裂纹扩展四个阶段在整个断裂周次所占的比率分配上,孕育期比率一般较小,萌生期和扩展期比率较大,瞬断期的比率很小,表明该合金裂纹扩展一旦失稳将高速扩展并迅速断裂。 相似文献
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基于机器视觉技术的疲劳裂纹自动检测实验系统 总被引:2,自引:1,他引:1
为解决现有传统的金属疲劳裂纹检测方法存在的精度不高、操作繁琐、抗干扰性差和不易实现自动记录等问题,将虚拟仪器和图像处理技术应用到金属疲劳裂纹检测系统中,进行了疲劳裂纹长度在线测量和疲劳扩展速率计算。通过系统的整体设计和原理介绍,提出了疲劳裂纹在线非接触式的机器视觉检测方案;并基于LabVIEW的实验平台,进行了疲劳裂纹扩展试验,通过使用NI的IMAQVision实现了图像处理功能。研究结果表明,由该方案建立的基于图像处理技术的裂纹检测系统在线测量得到的最大裂纹长度测量误差为0.148mm,且由拟合裂纹长度一时间曲线的导函数可得到裂纹扩展速率,是一种较理想的疲劳裂纹在线检测方法。 相似文献
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N. I. I. Mansor S. Abdullah A. K. Ariffin 《Journal of Mechanical Science and Technology》2017,31(10):4719-4726
This paper discusses the fatigue life behaviour of the API X65 steel tested under constant amplitude loading in ambient temperature. The influence of repeated loading at a particular stress ratio would favour the initiation of fatigue cracks that would consequently affect the fatigue crack growth. The main objective of this paper is to evaluate the load ratio effects on fatigue crack growth rate, taking into account their statistical characteristics. The fatigue crack growth test was carried out using compact-tension specimen at different load ratios of 0.1, 0.4 and 0.7. The experimental results showed the crack growth rate was dependent on the applied load. It was observed that the load ratio effect was less significant in stable crack growth regions. The result was consistent with the multiple regression test obtained by the least square method at a significance level of 0.05. The empirical model of Paris and Walker was utilised to evaluate the effects of load ratio on the fatigue crack growth rates. The approximation of fatigue life lies between 10-25 % of error using conservative model and 6 % error using the Walker model. The experimental data was scattered within a factor-of-2 correlation line suggesting that the accuracy of the experimental data towards the estimated values was high. 相似文献