共查询到19条相似文献,搜索用时 187 毫秒
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冲击载荷作用下边界条件对方板的毁伤破坏具有很大影响。利用落锤试验机开展了不同边界支撑下固支方板的冲击试验,为获取固支方板边界撕裂的典型破坏模式,专门设计加工了与固支方板尺寸相当的冲击锤头和可改变倒角的方板支撑框架。研究结果表明:(1)冲击载荷作用下,固支方板呈现出塑性大变形、单边撕裂、双边撕裂等典型破坏模式,倒角越小,方板越容易撕裂;(2)边界支撑对固支方板中心位移、整体变形轮廓影响较小,但对方板的撕裂长度、临界撕裂阈值存在较大影响;(3)不同边界支撑主要改变方板边界处的剪切应变,边界支撑倒角越小,剪切效果越明显,方板边界临界撕裂应变位于[0.191,0.241]区间。 相似文献
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为揭示高强度水下爆炸冲击载荷作用下金属夹芯结构的抗冲击性能,在实验室开展小尺寸水下爆炸加载技术对金属蜂窝夹芯结构性能影响的实验研究。基于实验结果,开展了全尺寸数值模拟金属蜂窝夹芯结构在水下冲击载荷作用下的动态响应和抗冲击性能研究。结果表明,数值模拟、实验和理论模型计算的结果具有良好的一致性。由于蜂窝芯材相对密度对夹芯结构能量耗散方式和载荷传递机制的影响,结构动态响应、失效模式以及抗冲击性能随着冲击强度的变化表现出较为明显的不同。通过抗冲击参数分析,建立了反映金属蜂窝夹芯结构抗冲击性能的结构横向变形、固支反力、透射脉冲和塑性能耗随冲击强度和芯材相对密度变化的结构-载荷-性能量化关系。 相似文献
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钢筋混凝土靶板在弹丸冲击及爆炸载荷下响应的数值模拟 总被引:1,自引:0,他引:1
采用HJC混凝土损伤本构模型及LS-DYNA的流固耦合算法,分别对钢筋混凝土靶板在弹丸冲击和爆炸载荷作用下的响应进行了有限元数值模拟,其中模拟参数由实验数据拟合重新获取。将模拟结果与实验结果和经验公式进行对比分析,结果表明:数值模拟再现了弹体贯穿靶板过程中的开坑、隧道及漏斗碎裂区,计算得到的弹体弹道极限及残余速度与实验数据吻合较好;此外,数值模拟也很好地再现了炸药爆炸后冲击波的传播过程以及爆炸载荷作用下混凝土的破坏情况,模拟结果与实验现象具有良好的一致性。 相似文献
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对爆炸荷载下圆柱壳的动力学行为进行了实验研究及数值模拟。将外径均为100mm的3种壁厚的Q235钢质圆柱壳置于由TNT药柱产生的爆炸场中进行冲击实验,系统分析了在不同装药高度及壳壁厚度参数条件下圆柱壳的冲击变形模式,即迎爆面局部凹陷变形模式(ModeⅠ)、迎爆面局部凹陷与壳整体弯曲变形耦合模式(ModeⅡ)、整体变形失效模式(ModeⅢ)及局部穿透与整体变形失效耦合模式(ModeⅣ)。采用LS-DYNA有限元程序及Lagrangian-Eulerian流固耦合算法,对圆柱壳的非线性动力响应过程进行了数值模拟,分析了圆柱壳的变形历程及最终残余变形的情况,计算结果与实验现象吻合较好。研究结论可为圆柱壳结构爆炸破坏分级及抗爆技术设计提供科学依据。 相似文献
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为了研究延性薄靶的穿透性能,进行了90°锥头弹丸穿透薄钢板的准静态和动态实验。通过准静态实验,得到了4种不同厚度钢板的载荷-压入位移曲线及破坏模式;结合膜力理论模型及纯弯静塑性破坏模型,对实验结果进行了分析,得出:对于薄靶,大变形膜力起主导作用,随着靶厚增加,弯距在板整体变形过程中的影响逐渐增大。通过动态穿透实验,得到了弹丸穿透4种不同厚度钢板的入射速度、残余速度及靶板破坏模式,计算得到穿透耗能。最后,将准静态实验与动态实验结果进行了对比讨论。 相似文献
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The transition from localized to homogeneous plasticity during nanoindentation of an amorphous metal
Using nanoindentation, we examine the fundamental nature of plasticity in a bulk amorphous metal. We find that the mechanics of plasticity depend strongly on the indentation loading rate, with low rates promoting discretization of plasticity into rapid bursts. For sufficiently slow indentations, we find that plastic deformation becomes completely discretized in a series of isolated yielding events. As the loading rate is increased, a transition from discrete to continuous yielding is observed. These results are fundamentally different from the classical expectations for metallic glasses, in which the transition from discrete to continuous yielding occurs upon a decrease in deformation rate. The present experimental results are analysed with reference to the theoretical ideal-plastic strain field beneath an indenter and rationalized on the basis of mechanistic models of glass plasticity. 相似文献
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在高压、高应变率加载条件下,孪晶变形对材料的塑性变形具有重要的贡献,而目前孪晶对金属材料的动态屈服强度、冲击响应等的影响还没有被充分揭示.为此,本文考虑孪晶变形和晶粒碎化,针对铍(Be)材料在高应变率加载下的动态力学响应发展了含孪晶的热弹-黏塑性晶体塑性模型.经过和实验结果的对比,发现该模型可以更准确地预测Be材料在动态加载下,尤其是高压动态加载下的屈服强度.进一步,基于该塑性模型研究了Be材料在冲击加载下的准弹性卸载行为,结果表明剪切波速随着压力和剪应变的变化而发生变化是材料产生准弹性卸载现象的主要原因.此外,研究了冲击波卸载过程中Be材料孪晶的演化过程,发现Be材料卸载过程中也伴随着孪晶的产生. 相似文献
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The forced and free dynamic response of plates with cut-outs formulated in Part I [1] is used to investigate the effect of cut-outs on the natural frequencies of clamped-clamped plates. The size, shape and location of the cut-out is expressed as a displacement dependent external loading. The plates considered are homogeneous and anisotropic. Lagrange's equations of motion lead to an infinite system of differential equations in time-dependent generalized co-ordinates with generalized forces which include the effects of the cut-outs. There is an infinite system of frequency equations for free vibrations. The infinite system is truncated to a finite system of equations depending upon the accuracy desired in frequency values. Results are given for square, clamped-clamped plates with centrally located square cut-outs for different modulus ratios. Good agreement is obtained when results for isotropic plates with cut-outs are compared with available theoretical and experimental results. 相似文献
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强冲击下的物质变形、破坏及诱发的轻重介质混合问题,是内爆压缩科学和工程应用领域的研究重点.本文针对爆轰波对碰条件下的复杂加载动力学过程及其动载破坏形态特征,开展数值模拟研究与极曲线理论分析.设计了爆轰波对碰驱动平面锡飞层的计算模型,获得了爆轰加载动力学过程及波系相互作用物理图像,分析了锡飞层对碰区自由表面速度历史的典型特征.给出了锡飞层中折射激波对碰发生马赫反射的临界条件,解读了三波结构的传播行为,阐明了对碰区内存在"一维正冲击"区域,一维区外存在单次斜冲击向两次斜冲击过渡的复杂加载动力学过程,提出了对碰区冲击动力学模型,揭示了影响对碰区动载行为特征的机理.数值模拟结果与极曲线理论分析结果相互印证,符合较好.本文的研究成果,将为深入理解和解读对碰区特殊的物质破坏及混合现象提供重要的理论支撑. 相似文献
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On the basis of modification of the relaxation model of plasticity developed previously for the case of single loading, a new model of cyclic deformation is formulated. It is shown that the introduction of only one constant time parameter dependent on the material structure makes it possible to compose a simple calculation scheme of accumulation of residual strains under multiple cycling of samples. 相似文献
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Elastoplastic solutions for thin plates and disks are sensitive to loading and plasticity conditions [1–5]. The plasticity
condition for a number of metal materials depends on the mean stress [6–8]. In this case, when using the associated flow rule,
plastic deformations do not satisfy the incompressibility condition, which is commonly accepted in statements of boundary-value
problems for thin elastoplastic plates and disks [9–13]. It is of interest to determine the effect of plastic compressibility
on the behavior of solutions for such structures. In this paper, a hollow disk in a rigid container subjected to a uniform
temperature field is considered. The plasticity condition proposed in [14] is accepted. A general study of the set of equations
including this plasticity condition and the associated flow rule was performed in [15]. The solution under the Mises plasticity
condition was obtained in [1]. 相似文献
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Lingyan Shen 《Phase Transitions》2013,86(8):755-771
In this paper, temperature evolution in shape-memory TiNi alloys was in situ measured in the process of phase transition under shock loading tests. It was shown that the temperature increased during loading, while unloading, it would keep the maximum value constant or decreased, depending on the strain rate. The corresponding dynamic response indicated that the hardening property is related to phase transition strain and the transformation path has remarkable strain-rate effect. The reason for this phenomenon is essentially due to the temperature dependence of the phase transformation stress. Moreover, the evolution of temperature was consistent with the change of stress, suggesting that this dynamic phase transition deformation is uniform. The theoretical calculation shows that the mechanism of temperature evolution results from the release of latent heat and the hysteresis dissipated energy. The results of this investigation provide insight into intriguing strain-rate-dependent phenomena intrinsic of TiNi alloys. 相似文献