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Jing Hongyang 《机械工程学报(英文版)》2000,13(2):122-125
0INTRODUCTIONAttemptsarebeingmadebymany.,.areh..[I~41toaPPlyfracturemechanicstestresultstofractureperformanceevaluationofstmctundcomponents.Thelinkbetweenthefmeturemechanicstestresultsandthefmeturebehaviorofrealisticstructuralcomponentsiscalledfoetransferability.Recently,acProgressivemathalshavebeenp~edtoaddressthetransferability.OneistheJ--TandJ-Qtheori.,L51,wheretheT-stressandQ-p~terhavebeendevelopedtOqUantifythedifferencebetWeenthefull-fieldsolutionforthenearcracktipstressdistribu… 相似文献
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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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Liviu Marsavina Tomasz Sadowski Nicolae Faur 《Journal of Mechanical Science and Technology》2011,25(2):309-315
Ceramic-metal interfaces are often present in composite materials. The presence of cracks has a major impact on the reliability
of advanced materials, such as fiber or particle reinforced ceramic composites, ceramic interfaces and laminated ceramics.
The understanding of the failure mechanisms is very important, as is as the estimation of fracture parameters at the tip of
the crack approaching an interface and crack propagation path. A cracked sandwich plate loaded with axial uniform normal stress
was numerically investigated using plane strain Finite Element Analysis. The numerical results for the singularity orders
were compared with the analytical solution. The influences of the material combination and crack length on the radial and
circumferential stresses and displacement distributions were investigated. The Stress Intensity Factors were determined based
on numerical results using a displacement extrapolation method. The results for the non-dimensional stress intensity factors
show that at lower crack lengths the influence of material mismatch is lower, but this influence increases with increasing
crack length. 相似文献
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CrMnFeCoNi高熵合金的优异力学性能使其具有广阔的工程应用前景。材料力学行为的本构描述对其工程服役行为的安全评估至关重要,但是描述CrMnFeCoNi高熵合金拉伸断裂行为的本构模型少见报道。基于晶体塑性本构模型,利用Cohesive单元在多晶代表性体积单元内部植入含损伤破坏机制的晶界,模拟了CrMnFeCoNi高熵合金在单轴拉伸下的晶间断裂过程。模拟结果与试验所得的应力-应变曲线吻合较好,且能准确描述断裂发生时的应力下降过程,说明采用晶体塑性本构模型与Cohesive本构模型可以有效描述材料的宏观响应行为和断裂失效行为。进一步分析表明:裂纹从应力集中处开始萌生;随着应变的持续增加,裂纹沿着晶界扩展,最终造成断裂;晶粒随机取向对裂纹萌生位置与扩展路径有显著影响,但对宏观拉伸应力-应变曲线几乎没有影响。 相似文献
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In This study we investigate the dynamic fracture characteristics of a tungsten carbide cobalt (WC-6wt%Co) composite material.
The dynamic fracture initiation toughness and some of the dynamic fracturing characteristics are evaluated by using the Instrumented
Charpy Impact Testing (ICIT) procedure. The dependence of measured time-to-fracture on the tup impact velocity and the dynamic
fracture toughness for the WC-6wt%Co composite material are obtained by using ICIT. The effect of the loading rate on fracture
initiation toughness is found to be negligible when the time-to-fracture is on the order of 50μsec. At significantly higher
rates of loading it is impossible to determine the apparent dynamic fracture initiation toughness because of the influence
of the inertia force on fracture loading. It is found that the impact velocities affect the time-to-fracture significantly
at lower impact velocities for various engineering materials. It is shown that with the decrease of tup impact velocities
the time-to-fracture is increased and the dynamic fracture initiation toughness converges to static fracture toughness. 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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Bahadir Uyulgan Hakan Cetinel Tevfik Aksoy 《Journal of Mechanical Science and Technology》2011,25(9):2171-2177
In this study, 17Mn4 (P295GH) pressure vessels steel and AISI304 stainless steel were welded with ER309L austenitic consumable.
In experimental part of the study, tensile tests were conducted on welded plates and variation of hardness values along specimen
was measured. J-integral fracture toughness values were investigated for different crack locations. In order to determine
the regions where plastic deformation did not take place due to constraint, uni-axial tensile test was performed on welded
tensile specimen after attaching strain gauges. In numerical part of the study, finite element (FE) analyses were conducted
by fixing 2-D models precracked on different locations by using ANSYS software. In these models, stress triaxiality and plastic
deformation characteristics around crack tip were determined for each crack locations after stress — strain analyses. The
limitation on the extension of plastic deformation at diffusion line causes extra increase in stress triaxiality at crack
tip. 相似文献
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M. Rakin O. Kolednik B. Medjo F.D. Fischer 《International Journal of Mechanical Sciences》2009,51(7):531-540
The effect of thermal residual stresses in bimaterial structure with initial crack located near a sharp interface is discussed in this paper. Bimaterial compact tension (CT) specimen is used in the analysis, and the residual stresses are introduced by cooling of the specimen. The residual stresses affect the stress and strain fields near the crack tip, and the crack-driving force is different compared with that in the homogeneous material without residual stresses. This difference can be quantitatively expressed through an additional crack-driving force term—the material inhomogeneity term, Cinh. In this paper, it is evaluated using the post-processing procedure based on the concept of configurational forces, following a finite-element analysis. The results indicate that accurate numerical analysis of pre-cracked bimaterials should include the effect of thermally induced residual stresses. This effect cannot be neglected, even for bimaterials with homogeneous mechanical properties and inhomogeneity in thermal properties only (e.g. welded joints of ferritic and austenitic steel). Based on the obtained results, data from this study can be used in engineering practice to improve integrity and work safety of various inhomogeneous structures. 相似文献
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Damage accumulation and failure behaviors are crucial concerns during the design and service of a critical component, leading researchers and engineers to thoroughly identifying the crack evolution. Third-generation synchrotron radiation X-ray computed microtomography can be used to detect the inner damage evolution of a large-density material or component. This paper provides a brief review of studying the crack initiation and propagation inside lightweight materials with advanced synchrotron three-dimensional (3D) X-ray imaging, such as aluminum materials. Various damage modes under both static and dynamic loading are elucidated for pure aluminum, aluminum alloy matrix, aluminum alloy metal matrix composite, and aluminum alloy welded joint. For aluminum alloy matrix, metallurgical defects (porosity, void, inclusion, precipitate, etc.) or artificial defects (notch, scratch, pit, etc.) strongly affect the crack initiation and propagation. For aluminum alloy metal matrix composites, the fracture occurs either from the particle debonding or voids at the particle/matrix interface, and the void evolution is closely related with fatigued cycles. For the hybrid laser welded aluminum alloy, fatigue cracks usually initiate from gas pores located at the surface or sub-surface and gradually propagate to a quarter ellipse or a typical semi-ellipse profile. 相似文献
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D.M. Rodrigues L.F. Menezes A. Loureiro 《International Journal of Mechanical Sciences》2004,46(10):1481-1488
In order to study the influence of the heat-affected zone softening on the fracture behaviour of welds with cracks in the weld metal centre line, a large variety of weld geometries and undermatch conditions of the heat affected zone mechanical properties, relative to the weld metal and base material, were addressed in this study. With this aim, the opening stress distribution in notched welded specimens was analysed using the numerical simulation of the three-point bending test. The numerical results show a reduction in the stress levels ahead of the crack tip for welded specimens with severe heat-affected zone undermatch. The stress distribution is strongly influenced by the crack position relative to the weld material/heat-affected zone interface, independently of heat-affected zone width. 相似文献
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SiC/Al梯度功能材料各梯度层由不同体积浓度的陶瓷和金属组成,由于材料组分梯度变化,克服了双材料界面的应力突变问题,从而获得优异的使用性能。文中应用Ansys软件和激光云纹干涉法,对具有四个梯度层的SiC/Al梯度功能材料紧凑拉伸试件在三种工况下的力学行为进行研究。通过Ansys分析得出试件裂纹扩展的规律以及裂前4mm处的应变分布,后续实验采集试件随各载荷变化的位移场云纹图,根据位移与条纹级数的关系以及小变形条件下应变与条纹级数关系式,得到梯度功能材料紧凑拉伸试件预制裂纹区的应变分布。通过两种方法相应结果对比分析,得出有关梯度功能材料的裂纹扩展准则的适用性方面的结论;同时,就实验获得的应变测量结果,讨论梯度功能材料的物性变化规律,以及材料组分和梯度层结构对材料整体物性参数的影响。 相似文献
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结合焊接结构的工程安全评定,针对焊接接头熔合线上容易出现缺陷的问题,本文利用有限元计算方法,编写了断裂参量J积分计算的有限元程序,并对裂纹位置不同时的焊接接头进行了有限元计算。结果表明,无论是平面应变还是平面应力条件下,焊接接头J积分值都与全母材和全焊缝材料不同;与此同时,裂纹位于熔合线上和裂纹处于焊缝中,焊接接头的J积分值也是有所差异的,并且,这种差异在平面应变状态下表现得更加明显。在实际工作中,对焊接接头的断裂参量的计算必须考虑裂纹所处位置的影响。 相似文献