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力学性能不均匀性对焊接接头三点弯曲试样塑性区发展规律的影响 总被引:3,自引:0,他引:3
利用弹塑性有限元方法对焊接接头试样在三点弯曲试验中塑性区的发展情况进行了计算。分析了不同的裂纹深度、强度组配,焊缝宽度以及不同位置裂纹的焊接接头试样对塑性区形状发展的影响规律。分析结果显示,不同强度组配和几何特征的焊接接头试样对裂纹尖端塑性区的发展规律有较大的影响,由于裂纹尖端拘束程度的不同会造成塑性区的形状和尺寸的改变,因此在做焊接接头试样三点弯曲试验时,可能会得出与均质材料试样不同的驱动力曲线 相似文献
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《机械工程学报》2015,(16)
异种钢的焊接连接在发电设备中制造中扮演着重要角色,其中碳迁移是影响异种钢焊接接头服役性能的一个重要因素。研究9%Cr+2.25%Cr异种钢焊接接头的碳迁移现象及其对接头高温韧性的影响,发现该接头在9%Cr母材侧热影响区(Heat affected zone,HAZ)中形成富碳区,在紧邻的2.25%Cr焊缝一侧形成贫碳区,富碳区和贫碳区存在较大的硬度差异。在对接头HAZ的高温(500℃)准静态断裂韧度测试中,发现位于焊缝的贫碳区裂纹容易扩展。富碳区断口形貌以准解理为主,贫碳区断口形貌以浅韧窝为主。有限元计算结果表明,在贫碳区中有塑性应变集中现象,导致其损伤加剧,成为裂纹扩展过程中的较弱环节。结合断口形貌以及有限元计算结果,对控制该接头断裂过程的机理进行分析,认为弹性能与塑性能储备能力的不同是导致断口形貌差异的主要原因。 相似文献
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TC17-TC11异种钛合金线性摩擦焊接头弯曲性能分析与改善 总被引:1,自引:0,他引:1
分析了TC11和TC17异种钛合金线性摩擦焊接接头的弯曲性能,探寻了焊缝区弯曲塑性的薄弱区。通过测试焊接接头的硬度、分析焊缝区组织、断口形貌,特别是弯曲试样表面滑移线形态,研究了弯曲断裂机制。通过焊后超声冲击以及高温固溶+时效热处理,探索了改善焊接接头弯曲塑性的工艺方法。研究结果表明,采用接头弯曲性能试验,可以更好地表征TC11和TC17异种钛合金线性摩擦焊接接头焊缝区的宏观性能;经焊后时效热处理的线性焊接头的弯曲角度只有TC17母材的38%,TC11母材的30%。弯曲塑性是其力学性能的薄弱环节;焊合区及TC17侧变形区是接头弯曲塑性的薄弱区,弯曲断口均呈脆性断裂特征。焊合区断口为细小等轴晶粒的晶间断裂,焊接界面对TC17侧的滑移有明显的阻碍作用,容易在焊合区TC17侧形成微观裂纹;TC17变形区的弯曲起裂断口是大面积滑移剪切所形成的剪切韧窝,而TC17侧变形区晶粒大而长,有利于形成更长的滑移线和更集中的位错聚集,所以弯曲试验时TC17侧变形区最容易开裂。焊后进行超声冲击处理,在试件表面形成了约20 μm厚度的变形层,接头的弯曲角度相对提高34%;接头进行高温固溶+时效处理后,接头的弯曲塑性提高,最高平均弯曲角度达到31.2°,相对提高82%。为钛合金线性摩擦焊接接头的宏观塑性性能分析与改善提出了一个有意义的研究方向。 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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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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小范围屈服条件下复合材料裂纹尖端塑性区分析 总被引:1,自引:1,他引:0
基于复合材料力学,推导Tsai-Hill强度准则在平面应力和平面应变条件下的一般表达式,得到了小范围屈服条件下,含中心裂纹无限大板Ⅰ型裂纹、Ⅱ型裂纹和Ⅰ/Ⅱ复合型裂纹尖端塑性区的解析解。针对不同裂纹倾角及泊松比 和,对裂尖塑性区进行了计算和分析。结果表明平面应变条件下塑性区范围小于平面应力条件下塑性区范围,参数、和 对复合材料裂尖塑性区范围和形状有明显的影响,不同的参数值得到的塑性区结果差别很大。另外,该解既适用于各向异性复合材料,也适用于各向同性材料。 相似文献
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Mudaser Ullah Chuan Song Wu Faisal Qayyum 《Journal of Mechanical Science and Technology》2018,32(8):3625-3635
Effect of solidification rate on crack tip plastic zone size at various crack lengths was calculated analytically and numerically by simplified Sih’s and Irwin’s models, respectively. Influence of plastic zone size is explained in terms of COD and elastic stress intensity factor within valid range of small scale yielding approximation. Up to plastic zone size range of 4–5 mm, a good agreement between numerical and analytical plastic zone size and elastic stress intensity factor for all weldments was observed. For high loads and greater crack lengths, experimentally obtained COD values were found 15–19 % more than simulation ones due to rapidly induced plasticity at high crack dimensions. Solidification rate showed a significant influence on FCPR, for solidification rates 13.75 °C/s, 6.97 °C/s and 4.32 °C/s the obtained fatigue strength was 35.29 MPa, 36.26 MPa and 41.32 MPa, respectively. 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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针对冷胀对6005铝合金疲劳裂纹产生和扩展的影响,用单边预切口试样研究了含缺陷结构冷胀后的疲劳寿命,分析了不同情况下新裂纹产生的循环数;并用ANSYS软件进行了数值模拟,确定冷胀产生的残余应力场和塑性区及在不同参数下冷胀度对其的影响.结果表明:孔径和冷胀度对最大残余压应力值影响不大,都在材料屈服强度1~1.1倍的限定范围内,而冷胀度对塑性变形区和残余压应力区大小的影响则非常显著. 相似文献
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加筋板广布疲劳损伤的剩余强度分析 总被引:3,自引:1,他引:3
给出加筋板广布疲劳损伤的两种损伤类型和两个剩余强度判据,剩余强度判据是净截面塑性区屈服判据和裂尖韧带屈服判据.给出蒙皮带有多裂纹和蒙皮带有多裂纹且桁条也带有裂纹时应力强度因子的近似工程估算方法.文中也给出加筋板含多裂纹时剩余强度净截面塑性区屈服判据和裂尖韧带屈服判据的表达式及塑性区尺寸估算方法.对三种损伤的加筋板进行剩余强度试验,指出多裂纹尤其是桁条也带裂纹时剩余强度降低较多.用上述两种判据进行加筋板广布疲劳损伤剩余强度预测,预测结果和试验结果比较符合. 相似文献
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The anti-plane shear problem of bonded elastic materials containing a crack at an arbitrary angle to the graded interfacial
zone is investigated in this paper. The interfacial zone is modeled as a nonhomogeneous interlayer of finite thickness with
the continuously varying shear modulus between the two dissimilar, homogeneous half-planes. Formulation of the crack problem
is based upon the use of the Fourier integral transform method and the coordinate transformations of basic field variables.
The resulting Cauchy-type singular integral equation is solved numerically to provide the values of modeIII stress intensity factors. A comprehensive parametric study is then presented of the influence of crack obliquity on the stress
intensity factors for different crack size and locations and for different material combinations, in conjunction with the
material nonhomogeneity within the graded interfacial zone. 相似文献
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Y. M. Tsai 《International Journal of Mechanical Sciences》1984,26(4):245-252
The Dugdale hypothesis is adapted to the problem of a penny-shaped crack contained in a thick transversely isotropic plate. The problem is solved using the techniques of Hankel transform.Exact expressions for the finite-stress condition and the crack shape function are obtained and calculated numerically for both composite materials and metallic substances. The normal stress is shown to be continuous at the value of the material yield stress along the outer circle of the inelastic zone. The example materials give both real and complex characteristic roots. The effects that the material anisotropy has on the inelastic zone size, the crack shape, and the crack opening displacement are clearly revealed in the numerical results presented. The effects of material anisotropy for the composites are compared to those for the metallic substances. 相似文献