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基于概率断裂力学理论和Mome Caflo模拟方法,本文进行了自紧身管临界裂纹尺寸的可靠性研究。自紧身管内表面的疲劳裂纹考虑为半椭圆形式。裂纹尖端处的应力强度因子由内压和自紧残余应力共同产生。自紧残余应力采用了符合身管材料具有强化和包辛格效应性能推导的公式计算,它产生的应力强度因子通过权函数方法得到。根据断裂准则,可计算出自紧身管的临界裂纹尺寸。实例分析表明,对数正态分布为临界裂纹尺寸的最佳分布,同时给出了在各种置信度和可靠度下自紧身管的临界裂纹尺寸。 相似文献
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提出了计算带单边裂纹三点弯曲试样动态应力强度因子的新方法.首先由权函数的普遍形式和两种参考载荷下的应力强度因子,得到了带单边裂纹三点弯曲试样的权函数,然后考虑试样的转动惯性和剪切变形,根据振动理论推导出无裂纹梁内的动应力响应和分布,最后由权函数的思想推导出了带裂纹三点弯曲试样动态应力强度因子公式.通过有限元数值计算,验证了该方法的正确性,结果比较表明公式具有较高的精度.另外,还研究了冲击载荷下三点弯曲试样的动态应力强度因子随裂纹长度和加载速率的变化规律. 相似文献
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A new formula is obtained to calculate dynamic stress intensity factors of the three-point bending specimen containing a single
edge crack in this study. Firstly, the weight function for three-point bending specimen containing a single edge crack is
derived from a general weight function form and two reference stress intensity factors, the coefficients of the weight function
are given. Secondly, the history and distribution of dynamic stresses in uncracked three-point bending specimen are derived
based on the vibration theory. Finally, the dynamic stress intensity factors equations for three-pointing specimen with a
single edge crack subjected to impact loadings are obtained by the weight function method. The obtained formula is verified
by the comparison with the numerical results of the finite element method (FEM). Good agreements have been achieved. The law
of dynamic stress intensity factors of the three-point bending specimen under impact loadings varing with crack depths and
loading rates is studied. 相似文献
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不同于实心结构纳米粒子,中空结构Pt纳米粒子具有低密度、高孔隙率和大的比表面积等特点,具有特殊的物理化学性质,在催化、光电子和药物输送领域有重要的应用.纳米粒子热稳定性和形变特性对其合成、应用具有重要的影响.利用分子动力学模拟研究中空结构Pt纳米粒子结构稳定性和形变过程,对不同壳层厚度的Pt纳米粒子进行分析,结果表明:在弛豫过程,温度为0.1 K时,壳层厚度为0.5 nm的Pt纳米粒子结构将发生形变,壳层厚度为1 nm、1.5 nm、2.0 nm、2.5 nm和3 nm纳米粒子结构保持几乎不变;升温过程,中空结构Pt纳米粒子塌缩时对应的温度随着壳层厚度增加而升高;塌缩过程所经历的温度区间很窄,空心结构短时间内突变为实心结构,另外,中空结构纳米粒子塌缩后,内部原子重新排列,仍保持有序的fcc结构. 相似文献
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The equation of stress intensity factors(SIF) of internally pressurized thick- walled cylinder was used as the reference case.SIF equation of rotating thick-walled cylinder containing a radial crack along the internal bore was presented in weight function method.The weight fumction formulas were worked out and can be used for all kinds of depth of cracks,rotating speed,material,size of thick-walled cylinder to calculate the stress intensity factors.The results indicated the validity and effectiveness of these formulas.Meanwhile,the rules of the stress intensity factors in rotating thick-walled cylinder with the change of crack depths and the ratio of outer radius to inner radius were studied.The studies are valuable to engineering application. 相似文献
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针对当前人才培养存在的问题, 如实践动手能力差、 创新能力颇弱, 笔者在光电子技术基础原有的教学
中, 在注重光电子技术的基础知识、 原理的同时, 适当加入了相关技术的前沿动态、 应用成果, 并在业余时间鼓励学
生参加组建创新团队, 去企业参观、 实习, 建立比较全面的师生评价体系, 采用多样化的课程考核方式, 建立专用的
实验室, 结合多样化的教学手段, 充分激发学生学习和创造的积极性, 培养学生应用型创新能力, 满足众多光电产业
的专业素养需要和创新能力需要, 为整个社会的发展提供最佳的后备人才 相似文献
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