共查询到17条相似文献,搜索用时 265 毫秒
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纯Ⅱ型载荷作用下裂纹的三维厚度效应研究 总被引:1,自引:0,他引:1
采用修正的边界层模型,利用有限元计算方法对纯Ⅱ型裂纹的厚度效应进行分析和研究,通过比较三维裂纹纯Ⅰ型和纯Ⅱ型裂纹尖端的应力、应变以及J积分和裂尖张开位移等参数,得到纯Ⅱ型载荷作用下厚度效应影响弱的认识。与Ⅰ型结果相比可以看出,在Ⅱ型载荷作用下裂尖的应力、应变场的厚度效应不明显,但三维影响区的大小与Ⅰ型基本相同,在裂尖前方半厚度以内存在着很强的三维效应区,从半厚度到1.5倍厚度范围应力在不同的厚度位置有显著的变化,在1.5倍厚度以外的区域表现为平面应力场的特性。在纯Ⅱ型载荷的作用下,三维J积分J^local沿厚度分布不随载荷变化,且基本没有厚度效应,裂尖滑动位移(crack tip sliding displacement,CTSD)也没有厚度效应;沿不同厚度截面,J^local积分和CTSD存在线性关系。 相似文献
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平面应力Ⅰ型准静态扩展裂纹尖端场的弹粘塑性分析 总被引:1,自引:1,他引:0
由于材料率敏感性的影响,蠕变材料中裂纹尖端场的分析更加复杂.采用弹粘塑性力学模型,并假设粘性系数为等效塑性应变率的幂函数,推导出理想弹塑性材料的一种率敏感型本构关系.通过量级匹配表明裂纹尖端场具有幂奇异性,奇异性指数由粘性系数中的幂指数唯一确定.推导出平面应力条件下准静态扩展裂纹尖端场的控制方程,并给出Ⅰ型裂纹的边界条件.采用双参数打靶法,结合各材料参数的可能取值范围,对控制方程进行了数值求解,并讨论裂尖场特性随各材料参数的变化规律.结果表明当材料服从理想塑性规律时,裂纹尖端的应力场是连续的,不存在某些无粘性解中出现的不合理间断线.裂尖场应力强度由材料的粘性所控制,泊松比对于裂尖场没有影响,并且不存在弹性卸载区. 相似文献
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复合型裂纹小范围屈服下裂尖塑性区统一解 总被引:9,自引:0,他引:9
采用俞茂宏统一强度理论,推导Ⅰ、Ⅱ复合型裂纹在小范围屈服条件下裂尖塑性区尺寸的统一解析解.给出材料参数在不同拉压比α、泊松比v和中间主应力影响参数b下的一族裂尖塑性区形状与大小的轨迹.讨论以上参数对裂尖塑性区变化的影响,其中拉压比α对塑性区影响较大,α≠1导致塑性区在裂纹上下表面处不连续,b=0和b=1分别对应裂尖塑性区的上限、下限边界.同Tresca准则、Mises准则的解进行比较分析,已有解均是它的特例或线性逼近,该理论解具有理论的统一性和对不同材料的普适性. 相似文献
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采用金相观察和图形分析相结合的方法研究裂尖区域的晶粒变形,可以对试件内部断裂过程区受载后的塑性变形进行直接的定量测试,从而为分析复合型裂纹的破坏机理和断裂过程提供实验依据.本文研究表明,Ⅰ-Ⅱ复合型裂尖延伸区的破坏以空穴机理为主导,较低的塑性变形即可引起韧窝型起裂;锐化尖角区可以承受很大的累积塑性变形,是集中剪切型断裂的起点.研究结果还表明,拉伸试件的等效塑性变形远低于Ⅰ-Ⅱ复合型裂纹锐化尖角区的变形,用拉伸试件得到的应力应变曲线不能满足分析复合型裂纹尖端应力应变的需要. 相似文献
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给出计算一般平面裂纹问题应力强度因子的半权函数方法。该方法引入两个满足裂纹面零应力条件、平衡方程以及裂尖位移具有r^-1/2奇异性的虚拟位移与应力函数的解析表达式,即半权函数。从功能互等定理出发,结合从裂纹下缘到上缘绕裂尖任意路径的位移与应力的近似值,得到Ⅰ、Ⅱ复合型应力强度因子KⅠ和KⅡ积分形式的表达式。由于在积分中避开了裂尖的奇异性,因此即使采用较粗糙的模型或方法得到的近似值,也可以得到精度较高的KⅠ、KⅡ。相对于权函数法,本方法的限制条件较少,半权函数易于获得,实用性强;相对于有限元法计算量小,模型建立简便。 相似文献
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利用Mises屈服准则从理论上分析了Ⅰ-Ⅱ复合型裂纹尖端前缘的塑性区分布。推导出了由三轴应力约束参数Tz参与表征的裂纹尖端前缘塑性区尺寸rp的表达式,并绘制出了Ⅰ-Ⅱ复合型裂纹在单轴、双轴载荷作用下裂纹尖端塑性区的分布图。 相似文献
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Finite element analysis (FEA) is the most popular numerical method to simulate plasticity-induced fatigue crack closure and
can predict fatigue crack closure behavior. Finite element analysis under plane stress state using 4-node isoparametric elements
is performed to investigate the detailed closure behavior of fatigue cracks and the numerical results are compared with experimental
results. The mesh of constant size elements on the crack surface can not correctly predict the opening level for fatigue crack
as shown in the previous works. The crack opening behavior for the size mesh with a linear change shows almost flat stress
level after a crack tip has passed by the monotonic plastic zone. The prediction of crack opening level presents a good agreement
with published experimental data regardless of stress ratios, which are using the mesh of the elements that are in proportion
to the reversed plastic zone size considering the opening stress intensity factors. Numerical interpolation results of finite
element analysis can precisely predict the crack opening level. This method shows a good agreement with the experimental data
regardless of the stress ratios and kinds of materials. 相似文献
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Hyeon Chang Choi 《Journal of Mechanical Science and Technology》2000,14(4):401-407
An elastic-plastic finite element analysis is performed to investigate detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The finite element analysis performed under plane stress using 4-node isoparametric elements can predict fatigue crack closure behavior. The mesh of constant element size along crack surface can not predict the opening level of fatigue crack. The crack opening level for the constant mesh size increases linearly from initial crack growth. The crack opening level for variable mesh size, is almost flat after crack tip has passed the monotonic plastic zone. The prediction of crack opening level using the variable mesh size proportioning the reversed plastic zone size with the opening stress intensity factors presents a good agreement with the experimental data regardless of stress ratios. 相似文献
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非均质焊接接头裂纹尖端塑性区 总被引:2,自引:0,他引:2
采用平面应力弹塑性大应变有限元法分析了非均质焊接接头裂纹尖端塑性区的扩展规律,指出在非均质焊接接头中存在着塑性变形的不同时性与不均匀性,且焊缝金属强度匹配、材料本构关系以及裂纹长度(韧带长度)对塑性区的发生发展均有重要影响。 相似文献
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Bing Yang Zhanjiang Wei Zhen Liao Shuwei Zhou Shoune Xiao Tao Zhu Guangwu Yang Mingmeng Wang 《机械工程学报(英文版)》2021,34(4):196-207
In the digital image correlation research of fatigue crack growth rate,the accuracy of the crack tip position determines the accuracy of the calculation of the stress intensity factor,thereby affecting the life prediction.This paper proposes a Gauss-Newton iteration method for solving the crack tip position.The conventional linear fitting method provides an iterative initial solution for this method,and the preconditioned conjugate gradient method is used to solve the ill-conditioned matrix.A noise-added artificial displacement field is used to verify the feasibility of the method,which shows that all parameters can be solved with satisfactory results.The actual stress intensity factor solution case shows that the stress intensity factor value obtained by the method in this paper is very close to the finite element result,and the relative error between the two is only-0.621%;The Williams coefficient obtained by this method can also better define the contour of the plastic zone at the crack tip,and the maximum relative error with the test plastic zone area is-11.29%.The relative error between the contour of the plastic zone defined by the conventional method and the area of the experimental plastic zone reached a maximum of 26.05%.The crack tip coordinates,stress intensity factors,and plastic zone contour changes in the loading and unloading phases are explored.The results show that the crack tip change during the loading process is faster than the change during the unloading process;the stress intensity factor during the unloading process under the same load condition is larger than that during the loading process;under the same load,the theoretical plastic zone during the unloading process is higher than that during the loading process. 相似文献
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A. A. Ostsemin 《Russian Engineering Research》2011,31(2):128-132
An equation characterizing the stability loss in elastoplastic deformation is proposed for a complex stress state under the influence of the transverse-deformation coefficient. The influence of the transverse-deformation coefficient on the radius of the plastic zone at the crack tip is determined in the cases of a plane stress state and plane deformation. 相似文献