共查询到19条相似文献,搜索用时 203 毫秒
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研究材料断裂应变与应力三轴度的关系,从而建立其断裂失效模型,对分析6061-T6铝合金断裂失效过程具有重要理论意义和应用价值。分别借助数字图像相关(DIC)测量技术和Abaqus软件对6061-T6铝合金光滑圆棒试件与缺口圆棒试件准静态拉伸过程进行试验和数值模拟,基于所得结果对后者应力三轴度进行分析和修正,从而得到Johnson-Cook(J-C)失效模型的部分材料参数,并建立了6061-T6铝合金断裂应变与应力三轴度的关系模型。将建立的失效模型输入到Abaqus中进行断裂数值模拟,模拟结果与试验结果基本一致,验证了失效模型的正确性。研究表明:6061-T6铝合金的断裂应变随应力三轴度的增加而减小;采用J-C失效模型可以较好的描述6061-T6铝合金在不同应力三轴度下的断裂失效行为。 相似文献
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破裂是剪切旋压时最主要的失效形式。为实现对剪切旋压时破裂的精确预测,根据剪切旋压成形时变形区材料的受力特点,提出对基于材料压缩变形塑性本构模型的Oyane准则进行研究。以DP600高强钢为研究对象,通过ABAQUS软件的VUSDFLD子程序二次开发,将Oyane准则耦合到剪切旋压有限元模型进行断裂损伤的计算及断裂阈值的判断。通过椭球形芯模旋压试验对断裂预测结果进行验证。结果表明,基于Oyane准则模拟得到的断裂危险位置位于已变形区靠近变形区处并沿着切向均匀分布,与试验结果的分布规律一致;但基于模拟所得到的极限减薄率与试验结果之间的相对误差达到33.8%。在Oyane准则的基础上,通过考虑平均应力和最大剪切应力对韧性损伤过程的影响,构建出适用于剪切旋压成形的修正韧性断裂准则。结果表明,采用修正后的韧性断裂准则,模拟得到的极限减薄率与试验结果的相对误差仅为15.9%;与Oyane韧性断裂准则相比,相对误差减小了17.9%。获得适用于剪切旋压时的韧性断裂准则,为金属剪切旋压成形破裂的精确预测奠定理论基础。 相似文献
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通过对比铝合金平面直线翻边试验及基于集中性失稳模型得到的极限应变和开裂断口,研究了汽车用铝合金滚压包边的失效机理;基于韧性断裂、塑性增量法则和混合强化准则,理论推导得到了弯曲成形极限图,并通过试验对成形极限应力图进行了验证;最后,通过数值解析的方法,研究了韧性断裂准则在滚边成形中的适用范围。结果表明:基于韧性断裂准则的成形极限图,可以用来预测铝合金滚压包边过程中产生的开裂;包边变形过程中弯曲强化效应无法忽略,适用于拉弯成形极限预测的集中性失稳理论将无法应用于滚压包边成形。 相似文献
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《机械工程材料》2016,(7)
针对汽车用6061和6063铝合金薄壁结构,先进行了准静态拉伸试验和180°弯曲试验,得到了铝合金的真应力-真应变曲线;然后采用线性回归拟合的方法建立了铝合金韧性断裂的本构模型,在此基础上,建立了铝合金薄壁结构压缩失效的有限元模型,并通过轴向压缩试验验证了有限元模型的准确性。结果表明:拉伸后,6061铝合金的表面呈橘皮形貌,6063铝合金的表面比较光滑;两种铝合金的断裂均为韧性断裂,6063铝合金具有更好的韧性;6061和6063铝合金的韧性断裂准则参数分别为104.81 MPa和179.91 MPa;有限元预测得到的铝合金薄壁结构的失效行为与试验结果比较吻合,证明了铝合金韧性断裂本构模型的正确性。 相似文献
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以Lou-2013韧性断裂准则为理论基础研究5182铝合金板材的韧性断裂力学性能,设计圆孔试件、平面应变试件和平面剪切试件的拉伸试验来获取准则中的材料参数。通过该准则确定"断裂应变?应力三轴度"曲线,为ABAQUS软件中的韧性损伤材料模型提供损伤判据,构建5182铝合金板材的韧性损伤仿真模型。利用此模型对上述三个试件的拉伸过程,以及半球形凸模胀形试验过程进行有限元仿真,并通过数据分析绘制基础拉伸试验与半球形凸模胀形仿真相结合的5182铝合金板材成形极限图。试验与仿真表明,所建立的有限元材料模型能够准确地再现三种试件的力程曲线和断裂特征;通过基础拉伸试验与半球形凸模胀形仿真相结合求解出的成形极限图包含两条曲线:损伤成形极限曲线(Damageforminglimitcurve,Damage FLC)和断裂成形极限曲线(Fracture FLC)。与成形极限试验数据对比表明,采用Damage FLC判定板材破裂失稳偏于安全,为实测成形极限数值的下限,而采用Fracture FLC判定则偏于危险。 相似文献
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在金属韧性断裂的数值模拟中,韧性断裂准则阈值的选取对模拟结果的精度有非常大的影响.通过对GCr15棒材试样进行单向拉伸、压缩试验,得到材料应力应变曲线及最大断面收缩率.通过有限元计算获得了三种常用韧性断裂准则的材料断裂阈值,研究结果可供进行GCr15轴承钢断裂模拟研究时应用. 相似文献
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Ductile fracture of metal often occurs in the plastic forming process of parts.The establishment of ductile fracture cri-terion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining.The 3D ductile fracture envelope of AA6063-T6 was developed to predict and prevent its fracture.Smooth round bar tension tests were performed to characterize the flow stress,and a series of experiments were conducted to charac-terize the ductile fracture firstly,such as notched round bar tension tests,compression tests and torsion tests.These tests cover a wide range of stress triaxiality(ST)and Lode parameter(LP)to calibrate the ductile fracture criterion.Plas-ticity modeling was performed,and the predicted results were compared with corresponding experimental data to verify the plasticity model after these experiments.Then the relationship between ductile fracture strain and ST with LP was constructed using the modified Mohr-Coulomb(MMC)model and Bai-Wierzbicki(BW)model to develop the 3D ductile fracture envelope.Finally,two ductile damage models were proposed based on the 3D fracture envelope of AA6063.Through the comparison of the two models,it was found that BW model had better fitting effect,and the sum of squares of residual error of BW model was 0.9901.The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test,but both of the predicting error of both two models were within the acceptable range of 15%.In the process of finite element simulation,the evolution process of ductile fracture can be well simulated by the two models.However,BW model can predict the location of fracture more accurately than MMC model. 相似文献
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Investigation of the viscous and thermal effects on ductile fracture in sheet metal blanking process
Ahmad Rafsanjani Saeed Abbasion Anoushiravan Farshidianfar Nilgoon Irani 《The International Journal of Advanced Manufacturing Technology》2009,45(5-6):459-469
In this paper, a methodology is proposed to predict the ductile damage in the sheet metal blanking process using a coupled thermomechanical finite-element method. A constitutive material model combined with the ductile fracture criteria was used. The effect of material softening due to the heat generated during plastic work in a specimen was considered in blanking simulations. To verify the validity of the proposed model, several blanking simulations are performed and the results compared with those obtained from an experimental study. The interaction of fracture initiation and temperature distribution in the sheet metal during the process was studied. The effect of velocity and the clearance on the product shape were examined. It was seen that at high punch speeds the viscous and thermal effects have significant effects on product quality. 相似文献
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《Wear》2002,252(11-12):911-933
An upper bound model has been proposed for the single-grit rotating scratch with a conical tool on a rigid perfectly-plastic material. The model was validated experimentally with a newly-developed technique to make scratches on annealed pure titanium. It has been realized that the built-up edge (BUE) governs the material removal process of the rotating scratch. The current model makes use of the modification of BUE to the tool configuration so that the discretization of plastic region in the vicinity of the tool becomes feasible. The features of side-ridge and front-ridge, BUE and sub-layer plastic zone have been found to be evolving in different ways during the rotating scratch. Three material removal mechanisms were uncovered to be involved with the rotating scratch process, namely, plastic (shear) deformation, contact friction and ductile fracture. In the first-half of the scratch, the first two mechanisms dominate the process, while in the second-half, the ductile fracture plays an active role as evidenced by the extensive tearing along the both banks of scratch. 相似文献
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Ductile fracture criterion is key limitation parameter in material forming. Accuracy predicting surface and internal failure in plastic deformation process affects on the technology design of workpiece and die greatly. Tension, compression, torsion and shearing test on 45# steel are utilized for providing the experimental values of the critical values at fracture, and 11 widely used ductile fracture criterion are selected to simulate the physical experiments and their relative accuracy for predicting and quantifying fracture initiation sites are investigated. The comparing results show that metal forming process under high triaxiality can be estimated successively using both Normalized Cockcroft-latham and the Brozzo ductile fracture criteria, but the Ayada and general Rice-Tracey model work very well for the low triaxiality cases. 相似文献
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V. P. Golub H. J. Christ J. Byrne 《International Journal of Mechanical Sciences》2002,44(5):1017-1032
The problem of long-term strength prediction of structural materials under uniaxial and biaxial creep conditions, which give rise to ductile fracture, is considered. A new approach to long-term fracture modelling based on constitutive equations of the “isochronous creep theory” and criteria of ductile fracture is suggested. The change in the momentary tangential modulus specifies the materials rheological behaviour and a value tending to zero is assumed as the ductile fracture criterion. Using the model the times to fracture of rods, beams and thin-walled tubes made of high-temperature and heat-resistant materials are estimated and they show good agreement with experimental data. 相似文献
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