DYNAMIC RESPONSE OF A RIGID,PERFECTLY PLASTIC FREE-FREE BEAM STRUCK BY A PROJECTILE ATANY CROSS-SECTION ALONG ITS SPAN

I. INTRODUCTION The dynamic plastic response of free-free beams subjected to intense dynamic loading is a subject ofinterest for aerospace engineering applications. For example, when a rocket is attacked by a missile, itslarge plastic deformation behav…     

端部受冲击作用的悬臂曲梁的实验研究

本文报导了具有不同端部质量的90°圆弧悬臂梁端部受冲击载荷的实验结果.实验中观察到梁在撞击后程短时间内有塑性区段从端部附近移向根部,梁变形达最大后有明显的反向甩动.变形后梁上各点曲率改变量在梁中部附近有极大值,在根部达最大值.实验结果与理想刚塑性模型的计算结果进行了比较.     

The dynamic plastic response characteristics of circular beam

In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its tip in its own plane is investigated on the basis of rigid-perfectly plastic assumption. The analytical solution of the particle velocities is obtained as the function of travelling plastic hinge location. By analysing the solution, some special properties of circular beam problem are found.     

钢框架抗震耗能节点梁的极限承载力分析1）

为提高结构的抗震性能,框架结构中以翼缘削弱型节点为代表的延性耗能节点逐渐代替传统节点,为研究翼缘削弱型节点框架梁在单向比例加载时的极限载荷,对削弱梁极限状态进行了分析,判定极限状态下削弱梁塑性铰生成的位置并计算极限载荷,将计算结果和普通梁进行对比.分析结果表明：削弱梁越长承载力下降越明显,对短梁需要选择合适的削弱参数,才能避免塑性铰出现在梁端.研究结果可为削弱梁塑性设计提供依据,同时拓展结构力学极限载荷学习内容.     

钢框架抗震耗能节点梁的极限承载力分析

为提高结构的抗震性能,框架结构中以翼缘削弱型节点为代表的延性耗能节点逐渐代替传统节点,为研究翼缘削弱型节点框架梁在单向比例加载时的极限载荷,对削弱梁极限状态进行了分析,判定极限状态下削弱梁塑性铰生成的位置并计算极限载荷,将计算结果和普通梁进行对比.分析结果表明：削弱梁越长承载力下降越明显,对短梁需要选择合适的削弱参数,才能避免塑性铰出现在梁端.研究结果可为削弱梁塑性设计提供依据,同时拓展结构力学极限载荷学习内容.     

自由梁受集中质量两点撞击的刚塑性动力响应

对矩形截面自由梁在两端同时受到完全相同的集中质量横向撞击问题进行了理论上的研究 ,通过采用刚塑性的材料模型得到了其动力响应完全解。结合数值方法给出了梁的瞬态变形 ,并讨论了输入能量、质量比等参数对梁的最终变形、能量耗散的影响。针对典型算例将完全解的结果与MSC/Dytran的计算结果进行了比较 ,两者具有合理的近似 ,但理论预测的结果略高估计了梁的最终变形。     

直角刚架在撞击作用下的塑性大挠度响应

本文研究了悬臂直角刚架在其自由端受到自身平面内的横向撞击时的塑性动力响应在本文报告的实验中,利用空气炮射出的子弹加载使软钢材料制成的直角刚架产生大挠度塑性变形;同时,依据理想刚塑性材料模型,给出了一个大挠度瞬时模态解。理论分析得到的挠度-载荷曲线与实验结果符合得很好。     

冲击载荷下软钢梁早期响应的数值模拟和简化模型

冲击载荷作用下，梁的早期响应既有弹性变形也有塑性变形，两者相互耦合．有限元数值模拟的结果表明，弹性弯曲波的传播是梁早期变形的主要机制，刚塑性简化理论预言的初始阶段中梁的“移行塑性铰”实际上是不存在的．本文提出的弹性 理想塑性简化模型可以很好地模拟固支软钢梁的早期响应     

梁在纯弯曲力矩作用下的动态塑性断裂

本文采用刚塑性分析方法,研究了带裂纹有限长韧性材料梁在纯弯曲力矩作用下的动态塑性断裂过程,本文考虑了由于断裂引起的附加轴向力对断裂过程的影响,并在分析中考虑了应变率对断裂过程的影响。文章给出了断裂过程中断裂截面上弯曲力矩和轴向力随时间的变化规律,以及裂纹长度,裂纹扩展速度和加速度随时间的变化规律。     

周边切口短圆柱试件的杆杆型冲击拉伸试验系统的弹塑性有限元分析

基于一维试验原理提出了用带有周边切口的短金属圆柱试件进行平面应变型弹塑性动态断裂韧度的测试方法；对该复杂的动力学系统进行了轴对称的弹塑性有限元分析，并计算了动态围道^J积分；根据对试件功能转换关系的分析和Rice公式的物理意义，提出了用试件两端平功载荷－两端相对位移曲线（P^-△）推广Rice公式计算试件的远场J积分，由此得到的P^-△曲线基本上消除了与裂纹运动无关的质心运动动能的影响。论证了J积分作为裂端的表征参量，且当切口深度比大于70％时，Rice公式有较高的计算精度，为平面应变型弹塑性动态断裂韧度的表征与测试提供了依据。     

Study of the plastic zone near a crack in an anisotropic body

The plastic zone at a crack tip in a finite anisotropic body is studied. A boundary-value problem is formulated in terms of the components of the covariant displacement vector for small strains. Particular attention is given to the case of plain strain. In this case, a numerical solution is found for a long rectangular body with a central crack under tension. As a result, conditions for the occurrence and development of a plastic zone at the crack tip are established. A plastic zone on the lateral surface of the body is discovered. How both zones extend and coalesce is elucidated. The effect of anisotropy on the occurrence of a plastic zone is evaluated __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 29–44, July 2006.     

Near-tip fields for a crack growing along an elastic perfectly plastic interface

The stress and deformation fields near the tip of an anti-plane crack growing quasi-statically along an interface of elastic perfectly plastic materials are given in this paper. A family of solutions for the growing crack fields is found covering all admissible crack line shear stress ratios. The project supported by the National Natural Science Foundation of China     

环形含内钝缺口试件在斜加载作用下弹塑性场的分布特征

运用有限元数值计算方法,对含内缺口的环形试件在受到与缺口对称面成不同角度的载荷作用下,缺口前端附近的弹塑性场分布特征进行了研究,得到了缺口前端应力和应变场以及塑性区的变化情况,此外,选取缺口弧度不同的模型,探讨了缺口顶端钝化程度对弹生场的影响,为了对计算结果的可靠性进行评价,运用高精度云纹干涉实验力学方法进行了验证性试验,试验得到的位移,应变分布情况与计算结果基本吻合。文中得到的结果为钝口试件的材     

端部受斜撞击作用悬臂梁的弹塑性动力响应模式

基于大变形动力控制方程并利用有限差分离散分析,研究了斜撞击作用下弹塑性悬臂梁的动力响应．通过对屈服函数以及弯矩、轴力在动力响应过程中分布规律的分析,阐明了斜撞击下恳臂梁的弹塑性动力响应模式和斜撞击的轴向分量对变形机制的影响．研究表明,弹塑性响应过程可划分为四个阶段,对应的变形模式为：“压缩塑性区扩展”模式,“广义移行塑性铰”和“压缩塑性区收缩”混合模式,“驻定塑性铰”模式,“弹性自由振动”模式．与刚塑性分析所假定的两相变形模式比较,弹塑性应响分析证实了响应早期的瞬态轴向压缩模式和梁根部“驻定塑性铰”模式的存在性,肯定了刚塑性分析所假定变形模式的主要特征．斜撞击的轴向分量在撞击发生的瞬时主导了梁的变形,使梁呈现同承受横向冲击明显小同的变形规律．随着响应的深入,轴向分量迅速衰减,其对截面屈服的贡献非常微弱,由横向分量引起的弯曲挠动在大部分时间内主导和控制梁的变形．数值计算结果表明,斜撞击载荷的质量、撞击速度和角度是影响梁动力响应的重要因素．     

Two-parameter failure criterion for elastoplastic bodies with mode I cracks

The generalized Dugdale crack model is used to formulate two-parameter failure criteria for the cases of quasibrittle state and developed plastic zones at a mode I crack tip. The failure criteria relate the fracture strength characteristics and the stress mode at the crack tip through the plastic constraint factor. The critical state of bodies with cracks under uni-and biaxial loading is analyzed in the cases of plane stress and plane strain using the Tresca and von Mises yield criteria. A small-scale yield criterion, which is an analytic relation between the critical stress intensity factor and T-stresses, is established __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 47–57, July 2007.     

弹塑性球形薄壳在冲击载荷作用下的动力分析

通过曲面弯曲的等度量变换，给出了受冲击球壳的变形模态；接着，分别假定材料力弹性或刚塑性，基地能量守恒，得到了壳本和撞击体在运动过程中控制方程；最后，对所得到的控制方程进行了数值求工与实验数据作了比较，发展二者具有较好的一致性。     

Formation of a plastic zone in an anisotropic body under loads acting along a crack

The effects of tension and compression along a crack on the plastic zone in a finite anisotropic body under plane strain are studied. The formation pattern for the plastic zone with increasing load is established by numerically solving a boundary-value problem for each of the cases. In particular, a new plastic zone is revealed. It occurs at the crack face under a compressive load of certain magnitude. How this plastic zone interacts with that at the crack tip is established __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 5, pp. 3–19, May 2007.     

端部受斜冲击的刚塑性悬臂梁的双铰模型

斜冲击载荷作用在刚塑性悬臂梁的端部,引起作用在梁横截面处的弯矩以及轴力;在发生塑性变形截面处,弯矩及轴力满足交互作用屈服条件。广义应力在移行铰的邻域不违背屈服条件,屈服函数可在移行铰的背面取极大值,移行铰处的剪切力不必为零。如果悬臂梁足够长,在响应的初始阶段移行铰处非零的剪力会在梁上引起多铰变形。通过对双铰模型与单铰模型的比较发现,双铰模型计算的结果与单铰模型计算的结果很接近,单铰模型作为一个近似模型具有一定的合理性。     

PERFECTLY PLASTIC FIELDS AT A RAPIDLY PROPAGATING PLANE-STRESS CRACK TIP

Under the condition that all the perfectly plastic stress components at a crack tiP arethe functions ofθonly,making use of the Mises yield condition,steady-state movingequations and elastic perfectly-plastic constitutive equations,we derive the generallyanalytical expressions of perfectly plastic fields at a rapidly propagating plane-stress cracktip.Applying these generally analytical expressions to the concrete crack,we obtain theanalytical expressions of perfectly plastic fields at the rapidly propagating tips of,modesⅠandⅡplane-stress cracks.