微孔贯通机制的韧性多裂纹扩展研究
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摘要
拉伸载荷作用下,裂尖附近具有较高的应力三轴度,微孔洞体积扩张及随后内部韧带颈缩是主导韧性裂纹扩展的细观机制。为基于微孔洞损伤机制模拟裂纹扩展,需要建立合理的孔洞贯通准则。基于三维体胞分析,建立了2524-T3铝合金的宏观等效应变失效准则。通过假设孔洞在贯通前保持球形扩张,将塑性极限载荷准则推导为仅依赖于宏观应变的形式。这两种准则分别与Gurson-Tvergaard-Needleman(GTN)模型结合在一起,形成了GTN-E及GTN-L模型,对2524-T3铝合金薄板中的韧性多裂纹扩展过程进行了模拟。模拟结果与试验结果的对比表明,可以有效地分析韧性多裂纹的扩展连通过程。
For the pre-cracked specimen under tensile loading,due to the high stress triaxiality ratio near the crack tip,microvoid dilation and subsequent coalescence by reduction of the inter-void ligament dominates the failure mechanism. Void coalescence criteria should be established properly to simulate the crack extension based on the void damage mechanism. Firstly,the results of 3 D cell computation were used to establish a macroscopic equivalent strain criterion for 2524-T3 aluminum alloy. Thereafter,a new form of the plastic limit-load criterion only depending on macroscopic strain is derived with the assumption that voids keep the spherical expansion until coalescence. Finally,these two void coalescence criteria are combined with Gurson-Tvergaard-Needleman( GTN) model to form GTN-E and GTN-L models,respectively. The ductile multiple-crack extension process in 2524-T3 aluminum alloy sheet was simulated. Comparison vith the test results shows that the predictions of the fracture behaviors,including crack extension,coalescence and final fracture,have a good agreement with the experiment data,which also validates the current approach.
For the pre-cracked specimen under tensile loading,due to the high stress triaxiality ratio near the crack tip,microvoid dilation and subsequent coalescence by reduction of the inter-void ligament dominates the failure mechanism. Void coalescence criteria should be established properly to simulate the crack extension based on the void damage mechanism. Firstly,the results of 3 D cell computation were used to establish a macroscopic equivalent strain criterion for 2524-T3 aluminum alloy. Thereafter,a new form of the plastic limit-load criterion only depending on macroscopic strain is derived with the assumption that voids keep the spherical expansion until coalescence. Finally,these two void coalescence criteria are combined with Gurson-Tvergaard-Needleman( GTN) model to form GTN-E and GTN-L models,respectively. The ductile multiple-crack extension process in 2524-T3 aluminum alloy sheet was simulated. Comparison vith the test results shows that the predictions of the fracture behaviors,including crack extension,coalescence and final fracture,have a good agreement with the experiment data,which also validates the current approach.
引文
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[10]GAO X S,ZHANG G H,ROE C. A study on the effect of the stress state on ductile fracture[J]. International Journal of Damage Mechanics,2010,19(1):75-94.
[11]PARDOEN T,HUTCHINSON J W. An extended model for void growth and coalescence[J]. Journal of the Mechanics and Physics of Solids,2000,48(12):2467-2512.
[12]THOMASON P F. Three-dimensional models for the plastic limit-loads at incipient failure of the intervoid matrix in ductile porous solids[J]. Acta Metallurgica,1985,33(6):1079-1085.
[13] KHAN A,LIU H. A new approach for ductile fracture prediction on al 2024-t351 alloy[J]. International Journal of Plasticity,2012,35:1-12.
[2]JIANG W,LI Y Z,SU J. Modified GTN model for a broad range of stress states and application to ductile fracture[J].European Journal of Mechanics-A,2016,57:132-148.
[3]姜薇,李亚智,刘敬喜,等.基于微孔洞细观损伤模型的金属剪切失效分析[J].华中科技大学学报(自然科学版),2015,43(1):24-29.
[4]GURSON A L. Continuum theory of ductile rupture by void nucleation and growth. Part I. Yield criteria and flow rules for porous ductile media[Z]. Office of Scientific and Technical Information(OSTI),1975.
[5] TVERGAARD V,NEEDLEMAN A. Analysis of the cupcone fracture in a round tensile bar[J]. Acta Metallurgica,1984,32(1):157-169.
[6]KIM J,ZHANG G H,GAO X S. Modeling of ductile fracture:Application of the mechanism-based concepts[J]. International Journal of Solids and Structures,2007,44(6):1844-1862.
[7] NAHSHON K,HUTCHINSON J W. Modification of the Gurson Model for shear failure[J]. European Journal of Mechanics-A,2008,27(1):1-17.
[8]ZHOU J,GAO X S,SOBOTKA J C,et al. On the extension of the Gurson-type porous plasticity models for prediction of ductile fracture under shear-dominated conditions[J]. International Journal of Solids and Structures,2014(51):3273-3291.
[9]ZHANG Z L,THAULOW C. A complete Gurson model approach for ductile fracture[J]. Engineering Fracture Mechanics,2000,67(2):155-168.
[10]GAO X S,ZHANG G H,ROE C. A study on the effect of the stress state on ductile fracture[J]. International Journal of Damage Mechanics,2010,19(1):75-94.
[11]PARDOEN T,HUTCHINSON J W. An extended model for void growth and coalescence[J]. Journal of the Mechanics and Physics of Solids,2000,48(12):2467-2512.
[12]THOMASON P F. Three-dimensional models for the plastic limit-loads at incipient failure of the intervoid matrix in ductile porous solids[J]. Acta Metallurgica,1985,33(6):1079-1085.
[13] KHAN A,LIU H. A new approach for ductile fracture prediction on al 2024-t351 alloy[J]. International Journal of Plasticity,2012,35:1-12.