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This paper introduces the effect of the strain rate on the ductile fracture of DP980 1.2t steel sheet. Tensile tests of DP980 sheet are performed at a range of strain rates from 0.001 s?1 to 100 s?1 with three different shapes of specimens: the diagonally notched specimen for the in-plane shear test; the dog bone specimen for the uniaxial tension test; and grooved specimen for the plane strain tension test. To trace the strain on the surface of the specimen, 2-D digital image correlation (DIC) technique is adopted to encompass the remarkable transition of the fracture characteristics including the fracture strain, loading path and strain rate sensitivity. The negative stain rate sensitivity is observed on the equivalent strain to fracture which corresponds to the experimental results at low strain rate ranging from 0.001 s?1 to 0.1 s?1. The transition of thermal condition from isothermal to adiabatic comes into play to increase the equivalent strain to fracture at the intermediate strain rate from 0.01 s?1 to 1 s?1. The fracture loci incorporating with the Lou-Huh ductile fracture criterion are developed to identify the strain rate effect in the wide regime of triaxiality. 相似文献
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B. Ruan G. Q. Li Y. Chen P. Mitrouchev B. He L. X. Lu 《International Journal of Automotive Technology》2016,17(6):1033-1043
As concerns of dynamic tensile measuring, a new tension mechanism driven by liner motor in high-speed tensile testing machine is presented. It satisfies the requirements for testing the dynamic tensile properties of plastic materials with strain rates from 1 to 100 s-1, which is relatively difficult to test for currently available machines. For this purpose the idle stroke principle is used to realize the dynamic load of plastic material with static grip. Computer aided engineering is used: i) to analyze and optimize the tension mechanism thus allowing reducing the system shock caused by collisions. ii) to avoid the influence of plastic materials specimen stress and strain uniformity on the measuring system. The analysis results agreed well with the established empirical relationships based on experimental evidence. Two sets of experiments for different strain rate tensile were conducted thus allowing proving the reliability and credibility of the designed tension mechanism. 相似文献
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H. J. Kim M. W. Song H. I. Moon H. Kim H. Y. Kim 《International Journal of Automotive Technology》2014,15(2):317-324
This paper suggests a fatigue life calculation method (A fatigue life calculation method is suggested) for rubber components based on the dynamic crack growth considering shear effect. Dynamic tearing tests were carried out, and the crack length was measured using an optical microscope to calculate the dynamic crack growth rate which characterizes and determines the fatigue life. The algorithm was numerically implemented in finite element code, ABAQUS standard, by using the user subroutine and applied to several rubber components. In the finite element analysis, deformation mode of an element was classified into tension and shear, and a weighting factor was multiplied to a strain energy density according to the degree of shear strain. Tension and compression of an elliptic dumbbell specimen was simulated in order to verify the material parameters of the suggested fatigue life prediction equation and to enhance the reliability of the algorithm. Finally, the fatigue life of a vehicle suspension bushing was calculated and compared with test. There were good agreements in the failure location and the magnitude of the fatigue life. 相似文献
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本文采用密栅云纹实验解析法研究方板对角拉伸的起皱过程,得到了在起皱临界状态下的位移,应变和应力的全场的瞬间和连续变化信息。发现了起皱是局部的塑性失稳现象,它与横向压力分布的区域性和区域不均匀性直接相关,它可为研究大型覆盖件成形缺陷机理开辟一条新的途径。 相似文献
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为揭示变剪应力作用下黏土的流变特性,建立了一维剪切弹黏塑性模型。参照Yin等提出的等效时间流变模型的建模思路,将剪切应变速率分为弹性剪切应变速率和黏塑性剪切应变速率。弹性剪切应变速率与加载路径无关,用非线性函数模拟。而对于黏塑性剪切应变速率,首先基于Singh等提出的常剪应力作用下的蠕变速率经验公式推导黏塑性剪切应变、等效时间与剪应力之间的函数关系式;然后参照Yin等提出的等效时间法,把该关系式通过等效时间代入蠕变速率经验公式,获得以剪应力和剪应变为变量的黏塑性剪切应变速率式。弹性剪切应变速率式与黏塑性剪切应变速率式之和即为一维剪切流变的等效时间线本构关系式,再通过淤泥质黏土的分级加载试验和黄土的加卸载试验与该本构关系式剪切应变表达式之间的比较,验证该模型在变剪应力加载下的适用性。研究结果表明:所构建模型的预测曲线和分级加载试验曲线、加卸载试验曲线吻合较好,这说明该模型在变剪应力加载下具有较好的适用性;模型良好的预测性也说明其建模过程中用到的等效时间法不仅适用于一维压缩流变,还适用于一维剪切流变,拓展了等效时间法的应用范围。 相似文献
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深长岩溶隧道掘进过程中掌子面和隧道两侧壁将出现大量裂隙,裂隙在远场应力与水压力的共同作用下将发生扩张膨胀,使得通过裂隙的水流量增大并最终导致隧道发生大范围的突水突泥事件。受水压致裂技术的影响,一般认为裂隙内部水流作用的机制是由水力劈裂和水压扩径造成的。基于断裂力学和流体力学,在平面受力情况下求解含水裂隙发生劈裂破坏和压剪破坏所需的临界水压值,并将两者进行比较后发现,同一裂隙发生水力劈裂破坏所需的临界水压大于其发生压剪破坏所需的临界水压,得出压剪破坏是含水裂隙破坏的主要形式。 相似文献
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针对目前应用越来越广泛的斜腹式、鱼腹式箱梁,阐述了其剪应力计算不同于矩形截面梁的地方,并指出其剪应力计算不符合传统的矩形截面梁剪应力计算的假定。针对上述问题,分别采用平面梁单元和空间块体单元对拟定的斜腹式、鱼腹式箱梁截面的剪应力进行计算对比。结果表明,采用传统的矩形截面梁的剪应力计算公式来计算斜腹式、鱼腹式箱梁腹板上的剪应力,结果将有较大的误差。为此,提出了腹板抗剪有效厚度的概念,为斜腹式、鱼腹式箱梁剪应力计算提供了一个简便的、可行的方法。 相似文献
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汽车用TRIP高强度钢板的成形行为试验研究 总被引:1,自引:0,他引:1
对冷轧TRIP600钢板在单向拉伸、双向拉伸和平面应变变形模式下的成形行为进行试验研究,在此基础上建立描述TRIP效应的计算模型,并用扫描电镜方法分析TRIP钢变形过程中微观组织的变化。试验结果表明:在单向拉伸、双向拉伸和平面应变中,平面应变最有利于TRIP效应的发挥,双向拉伸次之,单向拉伸最不利。 相似文献
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有限元强度折减法在膨胀土路堑滑坡分析中的应用 总被引:3,自引:1,他引:3
膨胀土路堑滑坡机理复杂,传统边坡分析方法无法对它进行分析并得出合理解释。而有限元强度折减法可采用岩土材料的非线性弹塑性本构关系,能考虑膨胀力等因素的作用,通过计算坡体的应力与应变,合理分析土坡变形过程和潜在滑动面,并采用安全系数评价边坡稳定性,较好地解决了膨胀土边坡稳定性及滑坡处治效果分析问题。应用有限元强度折减法,分析了南友路膨胀土滑坡规律,以及柔性支挡的处治效果。 相似文献
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RAP中细集料的老化沥青含量大,再生利用价值高,将RAP应用于应力吸收层混合料,可最大资源化提升RAP再生利用价值,降低应力吸收层混合料建设成本。采用车辙试验、小梁弯曲试验、预切缝半圆弯拉试验、复合梁试件扭剪试验、拉拔试验、扭剪疲劳试验、Over Test评价热再生应力吸收层混合料的高低温性能、层间抗剪切性能、抗剪切疲劳性能和抗反射裂缝性能。结果表明:随着RAP掺配比例增大,热再生应力吸收层混合料的油石比降低、高温性能增强,但增大RAP掺量导致热再生应力吸收层混合料低温弯曲应变、断裂能、扭剪强度、拉拔强度、扭剪疲劳寿命和抗反射裂缝性能均降低。在50%RAP掺量下,热再生应力吸收层混合料的动稳定度3 604次/mm,低温弯曲应变4 890με,且Over Test(OT)加载达到了1 200周期,聚合物胶粉复合改性沥青热再生料应力吸收层混合料具有优异的高温韧性和低温延展性与抗反射裂缝性能。 相似文献
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结合统一强度理论和极限分析法,对水平加筋增强体复合地基承载力进行了研究。通过对已有以主应力表达的统一强度理论关系式进行变换,导出了以任意平面上的剪应力和正应力表达的统一强度理论关系式;将统一强度理论与相关联流动准则相结合,解决了基于统一强度理论进行极限分析的基本问题;并结合加筋材料对地基极限承载力的影响,对水平加筋材料复合地基进行了极限分析,得到了水平加筋材料复合地基极限承载力计算公式。最后结合工程算例对地基极限承载力的影响因素进行分析,对实际工程具有一定指导意义。 相似文献
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