共查询到18条相似文献,搜索用时 125 毫秒
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用某压力容器实际工况载荷波动所编制的载荷谱,对材料为16MnR的CCT试件进行了变幅载荷谱下的疲劳裂纹扩展试验。根据试验数据,分析了裁荷谱中大载荷级和小载荷级分别对裂纹扩展量的贡献,并对考虑和不考虑超载迟滞效应对小载荷裂纹扩展行为的影响进行了对比。作为这方面的初步探索,本研究获得了一些有意义的结论。 相似文献
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报告了在 P_x∶P_y=0,0.5和1三种双轴载荷作用下,对倾斜角等于0°、30°和45°的表面裂纹所作的疲劳扩展研究。讨论了表面裂纹扩展速率的计算方法,指出必须考虑不同的裂纹倾斜角和不同的双轴载荷比造成的裂纹扩展驱动力的变化对斜表面裂纹扩展速率的影响。因而采用裂纹投影法来处理斜表面裂纹的疲劳扩展问题并提出了修正的 Paris 方程。按照修正的 Paris 方程,根据不同的双轴载荷比和裂纹倾斜角分组整理了试验数据,并作了回归分析、假设检验,给出了含表面裂纹的16MnR 板材在三种不同的双轴载荷比情况下的裂纹扩展速率方程。 相似文献
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界面脱黏是纤维增强密封复合材料界面破坏的主要表现形式,其可视为一种特殊的裂纹扩展。本文基于剪滞模型研究了纤维增强密封复合材料中纤维和基体界面在交变载荷作用下的裂纹扩展规律。在考虑疲劳加载引起的脱黏界面损伤和损伤分布不均匀性以及材料泊松比影响的基础上,建立了等效Paris公式,得到了疲劳裂纹扩展长度、扩展速率、界面上摩擦系数和加载次数之间的关系。 相似文献
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研究了双向载荷作用下对焊接头表面裂纹的疲劳扩展规律。采用经精确标定应力强度因子幅值的双向十字形试样,在电液伺服双轴向疲劳试验机上对母材分别为16MnR 和 Q235-B 这两种钢的对焊试板进行了疲劳裂纹扩展试验。同时,将其结果分别与单向应力下对焊接头及母材的疲劳扩展速率进行了比较,为制定我国在役压力容器缺陷评定规范提供了参考数据。 相似文献
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高温高压蒸汽分支管线的变幅值热疲劳裂纹扩展寿命研究 总被引:1,自引:0,他引:1
研究了一条高温高压蒸汽分支管线失效面上周向焊缝外表面裂纹在17级温度载荷谱作用下的变幅值热疲劳裂纹扩展寿命。计算中涉及到管子周向焊缝外表面裂纹K的求取、超载模型的选用及谱载下裂纹扩展寿命计算等 相似文献
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研究了双轴向应力状态下Ⅰ型穿透裂纹的疲劳扩展规律,采用构形合理且经精确标定应力强度因子值的双向十字形试样,在电液伺服双轴向疲劳试验机上对低合金钢(16MnR)进行了多种载荷比的疲劳裂纹扩展速率试验,得到了双轴向应力状态下的Paris方程,为目前按缺陷评定规范依据单轴向疲劳试验所得数据对工程构件进行疲劳评定提供参考数据,并就当前研究者们对于双向应力场中横向载荷对疲劳裂纹扩展行为的影响的不同看法进行分析探讨。 相似文献
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报告了在不同的双轴载荷比和不同的裂纹倾斜角的情况下,表面裂纹疲劳试验的某些试验结果,并首次从裂纹扩展驱动力的角度,揭示了裂纹宏观疲劳断口的变化规律。 相似文献
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以玻璃/环氧复合材料层合板二级栽荷下的疲劳寿命试验数据为基础,结合非线性损伤累积理论,拟合出第二级载荷下的剩余寿命计算公式,并推广到三级以上多级栽荷的寿命计算。采用本文给出的寿命预测公式计算出第二级载荷下的剩余寿命,并与试验结果进行对比,证明了计算公式的有效性。进而利用剩余寿命计算公式分析了加载次序对疲劳寿命的影响。 相似文献
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A. H. Al-Ghamdi I. A. Ashcroft A. D. Crocombe M. M. Abdel-Wahab 《The Journal of Adhesion》2003,79(12):1161-1182
The main aim of this article is to investigate the effect of frequency on fatigue crack propagation in adhesively bonded joints. Adhesively bonded double-cantilever beam (DCB) samples were tested in fatigue at various frequencies between 0.1 and 10 Hz. The adhesive used was a toughened epoxy, and the substrates used were a carbon fibre-reinforced polymer (CFRP) and mild steel. Results showed that the crack growth per cycle increases and the fatigue threshold decreases as the test frequency decreases. The locus of failure with the CFRP adherends was predominantly in the adhesive layer, whereas the locus of failure with the steel adherends was in the interfacial region between the steel and the adhesive. The crack growth was faster, for a given strain energy release rate, and the fatigue thresholds lower for the samples with steel adherends. Tests with variable frequency loading were also carried out, and a generalised method of predicting crack growth in samples subjected to a variable frequency loading was introduced. The predicted crack growth using this method agreed well with experimental results. 相似文献
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Unidirectional and cross-ply Nicalon fiber-reinforced calcium aluminosilicate (CAS) glass-ceramic composite specimens were subjected to tension–tension cyclic fatigue and static fatigue loadings. Microcrack densities, longitudinal Young's modulus, and major Poisson's ratio were measured at regular intervals of load cycles and load time. The matrix crack (0° plies) density and transverse crack (90° plies) density increased gradually with fatigue cycles and load time. The crack growth is environmentally driven and depends on the maximum load and time. Young's modulus and Poisson's ratio decreased gradually with fatigue cycles and load time. The saturation crack densities under fatigue loadings were found to be comparable to those under monotonic loading. A matrix crack growth limit strain exists, below which matrix cracks do not grow significantly under fatigue loading. This limit coincides with the matrix crack initiation strain. Linear correlations between crack density and moduli reductions obtained from quasi-static data can predict the moduli reductions under cyclic loading, using experimentally measured crack densities. A logarithmic correlation can predict the Young's modulus reduction in a limited stress range. A fatigue crack growth model is proposed to explain the presence of two distinct regimes of crack growth and Young's modulus reduction. 相似文献
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《Journal of the European Ceramic Society》1999,19(9):1705-1715
The fatigue and fracture characteristics of a partially-stabilized fine-grained zirconia with spinel additions, (Mg,Y)–PSZ, were studied. Fracture toughness, crack growth resistance curves and fatigue crack growth (FCG) behavior, under both sustained and cyclic loading, were evaluated. Mechanical fatigue effects were clearly evidenced by (1) remarkable crack growth rate differences under cyclic and static loading and (2) significant loading ratio effects. Comparing the cyclic and the static FCG behavior allows to deduce a higher cyclic fatigue sensitivity of the fine-grained (Mg,Y)–PSZ with respect to a commercial peak-aged Mg–PSZ used as a reference material. By in situ observation of crack extension under cyclic loading, the fatigue mechanisms could be resolved. Mechanical degradation of bridging ligaments, as already known for coarse-grained Mg–PSZ, is one source of cyclic fatigue. An additional source attributed to the particle dispersed microstructure of the (Mg,Y)–PSZ is the interaction between crack faces and hard spinel particles. The sensitivity of (Mg,Y)–PSZ and Mg–PSZ to cyclic fatigue is discussed in terms of the respective microstructures, prevalence and operativity of distinct mechanical fatigue mechanisms. 相似文献