共查询到19条相似文献,搜索用时 62 毫秒
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利用数字激光动态焦散线实验系统(DLDC),对含不同层理角度(30°,45°和60°)的3组有机玻璃板(Polymethyl methacrylate, PMMA)试件进行三点弯落锤冲击试验,借助高速相机记录了试件的断裂过程和裂纹尖端的动态焦散斑形状变化过程,得到了其Ⅰ、Ⅱ型动态应力强度因子的变化特征,并分析了其裂纹尖端位移及速度曲线.结合离散格子弹簧模型(DLSM),对比分析了试件的断裂形态,得到了裂纹尖端的应力场和运动场的变化规律,研究了应力波在层理处的透射和反射特征,最后利用DLSM分析了层理参数对介质断裂特性的影响.结果表明,试件的断裂特征,裂纹的起裂时间等都随层理角度的变化而不同,裂纹在不同角度层理内扩展速度不同;试件的断裂表现出拉剪复合特征;裂纹在抵达层理前速度在某一数值上下波动;层理的弹性模量和厚度都会对试件的动态断裂特性产生影响. 相似文献
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基于刀具破岩的非爆机械化开采有望成为深部矿山开采的主要替代方法之一。矿岩可切割性是制约刀具破岩的关键因素,其受到受限应力条件和岩石性质的影响。因此,研究不同种类岩石在不同受限应力条件下的可切割性,可为机械刀具破岩提供理论依据和关键技术参数支撑。首先在不同受限应力条件下,对花岗岩、大理岩、红砂岩和磷矿石进行了截齿破岩试验。然后,以试验结果为基础,对脆性指数、受限应力条件与截齿破岩峰值载荷和破岩比能之间的关系分别进行了回归分析。最后,利用熵权法评价了岩石强度特性和受限应力条件对截齿破岩峰值载荷和破岩比能的影响权重。结果表明:所建立的回归模型具有良好的预测精度,单向受限应力和脆性指数对截齿破岩峰值载荷和破岩比能的影响均呈非线性变化;单向受限应力和岩石强度特性对截齿破岩性能均有显著影响,且单向受限应力的影响权重略大于岩石强度特性。研究结果可为深部矿山非爆机械化开采可行性判别以及破岩参数设计提供理论依据。 相似文献
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利用CEAST 9340落锤式冲击试验机,通过高周期疲劳方式加载,测试冲击功、球表面积、WC-Co硬质合金球齿衬底厚度及聚晶金刚石层(PCD)层厚度对复合片球齿抗冲击性能的影响;利用ANSYS软件对PCD层厚度对球齿抗冲击性能的影响进行有限元分析;利用JSM-6360LV型扫描电子显微镜对样品断口形貌进行观察。研究结果表明:球齿的冲击破碎率随冲击功的增大而升高,随WC-Co硬质合金球齿衬底厚度增加及PCD层厚度减小而下降;在相同冲击功条件下,增大球齿球表面积则导致冲击破碎率下降;球齿抗冲击性能随WC-Co硬质合金球齿衬底厚度减小及PCD层厚度增加而下降。直径为14 mm和16 mm球齿部分可满足低风压抗冲击性要求但无法满足高风压抗冲击性能要求。 相似文献
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《中国钨业》2016,(1):74-80
通过冲击破碎仿真模拟能使多尺度内聚颗粒呈现出较明显的弹性变形阶段、塑性变形阶段以及断裂破碎阶段。文章利用EDEM与ADAMS的双向耦合,对基于离散元法构建的钨矿石多尺度内聚颗粒模型进行冲击破碎仿真试验,通过仿真模拟发现,矿石多尺度内聚颗粒模型在冲击破碎过程中具有较明显的弹性变形阶段、塑性变形阶段以及断裂破碎阶段;分析得到了不同冲击角下破碎黏结键数目、冲击破碎力随时间的变化曲线,二者与冲击破碎能呈线性关系;对碎后的粒度进行筛分、统计,得到多尺度内聚颗粒模型破碎后粒度分布具有一定的单峰偏度正态特性,并与破碎试验结果进行对比,两者一致性较高,证实了利用多尺度内聚颗粒模型模拟矿石冲击破碎的可行性。 相似文献
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利用背散射电子衍射技术对高速冲击前后高锰钢样品强制剪切区域的晶粒进行准原位观察,分析了剪切区域不同位置晶粒的相变情况,并借助有限元模拟及受力计算对不同晶粒相变程度差异的原因做了进一步分析.结果表明,在高速变形下,应力应变水平、奥氏体取向及晶粒间的相互作用共同影响TRIP行为:应力应变水平越高,相变程度越大;由于帽型样中剪切应力的存在,相比于近〈111〉取向奥氏体,近〈100〉和近〈110〉取向奥氏体相变程度更大,近〈110〉取向相变程度最大.具有有利取向的奥氏体,晶粒尺寸越大,其相变行为受周围晶粒影响越小,越容易充分相变;具有有利取向的长条状奥氏体晶粒,若其两侧晶粒难相变,则该晶粒相变将受到束缚;带有尖角的晶粒,变形时应力集中难以释放,易发生相变;当晶粒的孪生分力大于滑移,但其最大和次大的孪生分力相差不大,可能导致在这两个方向孪生互相竞争,反而不易相变.高速变形时体心马氏体多在晶界应力集中处产生,很少在晶粒内部大量产生,形态多为细片状,变体选择强. 相似文献
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The free vibration of the laminated composite anticlastic doubly curved stiffened shells is investigated using the finite element method. The stiffened shell element is obtained by appropriate combination of the nine-node doubly curved isoparametric thin shallow shell element with the three-node curved isoparametric beam element. The shell forms include the hyperbolic paraboloid, hypar, and conoidal shells. The accuracy of the formulation is validated by comparing the authors’ results of specific problems with those available in the literature. The additional problems are taken up for parametric studies to include the effects of fiber orientation and lamina stacking sequence of shells and stiffeners. Moreover, the effects of number, types, and orientations of stiffeners, and stiffener depth to shell thickness ratio on the fundamental frequency are also included in the present study. Further, mode shapes corresponding to the fundamental frequency for typical cases are obtained to verify the parametric trend of the results of the fundamental frequency. 相似文献
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As part of the quest to add the infraply scale to high-fidelity simulations of damage evolution in composites, a model of the phenomenon of delamination jumping across transverse plies is formulated by using nonlinear cohesive fracture models in the augmented finite element method (A-FEM). The nonlinearity of the fracture process zone and the interaction between multiple cracks combines to determine the details of how the delamination jump occurs. Simulations reveal that the jumping process starts with the triggering of a sequence of kinking cracks branching from the propagating delamination crack into the transverse plies. The first few kinking cracks arrest within the transverse plies just above the further interface because of the crack-retarding effects of the nonlinear process zone and the effects of material heterogeneity. Eventually, one kinking crack reaches the interface and initiates a new delamination crack, a step that is accompanied by a significant load spike. The competition between delamination and kinking cracks shows global-local coupling: kinking cracks are triggered when the local stress satisfies a critical condition, but a kinking crack does not reach the second interface and initiate the new delamination crack until the global energy release rate reaches the kinking crack toughness. This suggests that the jumping process is controlled more by deterministic load and geometrical factors than by stochastic flaw populations. 相似文献
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Alemdar Bayraktar Ahmet Can Altuni?ik Fatma Birinci Bar?? Sevim Temel Türker 《Canadian Metallurgical Quarterly》2010,24(1):46-52
This paper presents the analytical modeling, modal testing, and finite-element model updating for a two-span masonry arch bridge. An Ottoman masonry arch bridge built in the 19th century and located at Camlihemsin, Rize, Turkey is selected as an example. Analytical modal analysis is performed on the developed 3D finite-element model of the bridge to obtain dynamic characteristics. The ambient vibration tests are conducted under natural excitation such as human walking. The operational modal analysis is carried out using peak picking method in the frequency domain and stochastic subspace identification method in the time domain, and dynamic characteristics (natural frequencies, mode shapes, and damping ratios) are determined experimentally. Finite-element model of the bridge is updated to minimize the differences between analytically and experimentally estimated dynamic characteristics by changing boundary conditions. At the end of the study, maximum differences in the natural frequencies are reduced on average from 18 to 7% and a good agreement is found between analytical and experimental dynamic characteristics after finite-element model updating. 相似文献
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A. Varadarajan K. G. Sharma C. S. Desai M. Hashemi 《Canadian Metallurgical Quarterly》2001,1(1):83-107
Strain‐controlled triaxial tests have been conducted using servo‐controlled loading system on three schistose rocks from a hydropower project in the Himalaya. A constitutive model based on the disturbed state concept is used to model the behavior of the rocks. Predictions are made using a single point method and finite element method. The constitutive model is found to provide satisfactory predictions. The DSC model is used to predict observed behavior of a powerhouse cavern; the relevant paper, “Analysis of a Powerhouse Cavern in the Himalaya,” appears in this issue. 相似文献
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风化成土过程中稀土元素地球化学特征 总被引:19,自引:0,他引:19
探讨了稀土元素在风化成土过程中轻、重稀土分异、富集、迁移规律以及 Ce、Eu异常特征。分别讨论了成土母质、气候条件、水化学性质、氧化还原条件及其它因素对稀土元素地球化学行为的影响。并提出了当前风化成土过程中稀土元素研究中存在的一些问题。 相似文献
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《钛工业进展》2019,36(6):13-18
TC18钛合金在退火状态下的屈服强度非常高,进行动态力学性能测试存在一定困难,可优先考虑采用数值模拟方法对其动态力学性能进行研究,而数值模拟结果的精确性主要取决于合金本构方程的精确性。为了减少数值模拟与实验结果之间的差异,在Johnson-Cook模型的基础上做了调整,利用ABAQUS软件的子程序接口自定义了材料本构子程序UMAT,以代码的形式来扩展ABAQUS程序的功能。通过与ABAQUS/Standard软件分析结果以及实验结果的对比,验证了自定义材料本构子程序UMAT计算结果的精确性与可靠性。该研究可为TC18钛合金的结构设计提供参考。 相似文献
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The characteristics of rare earth elements in the Devonian and Carboniferous volcanic rocks were studied in the north Altay. And the mechanism of formation of volcanic rocks were discussed by using the rare earth elements. The correlativity of rare earth elements and major elements shows that the fractional crystallization is undistinguishable during the formation of Devonian and Carboniferous volcanic rocks, and the mechanism of formation of volcanic rocks may be the partialmelting. The further study of the relationship of manifold rare earth elements shows that the mechanism of formation of Devonian and Carboniferous volcanic rocks in the north Altay is the partial melting. And the result also shows that the rare earth elements in the Devonian and Carboniferous volcanic rocks inherited the characteristics of those in its source materiels. 相似文献