铅壳柔爆索冲量作用下圆柱壳体结构响应实验研究

通过设计排布在圆柱壳体周围的柔爆索的间距及柔爆索与圆柱壳体间的距离 ,得到了沿圆柱壳体周向呈余弦分布的冲量载荷 ,并设计了柔爆索加载的结构响应实验装置 ,对圆柱壳体的动态力学响应进行了实验研究。测得的圆柱壳体残余变形局限于 70左右的范围 ,0方向径向变形最大。     

球形和等长径圆柱装药在爆炸近区内载荷差异的实验研究

为了研究爆炸近区内装药形状对爆炸载荷的影响,运用压杆法测量了爆炸容器内壁的压力。通过 实验发现,对于圆柱装药径向方向上的正反射爆炸载荷,等长径圆柱装药的压力峰值、冲量与相同当量下球形 装药对应量的比最大超过2。还通过实验验证了数值模拟,并运用数值模拟获得2种装药形状下爆炸载荷的 静水压、密度、粒子速度,得到爆炸近区内2种装药形状载荷的差异以及该差异随爆心距离的变化规律。     

圆柱形爆炸容器的内壁爆炸载荷

爆炸容器内壁所受爆炸载荷的确定是容器动态响应特征研究、容器结构设计及安全评估的基础。对自行研制的组合式圆柱形爆炸容器开展了系列内爆加载试验,测量了容器内壁几个典型位置所受爆炸载荷,并利用ANSYS/LS-DYNA软件对容器内爆载荷的形成和传播全过程进行了数值模拟。通过对试验结果进行分析,获得了容器内壁所受爆炸载荷的特征及其分布规律,并拟合出容器圆柱形壳体部分所受载荷首脉冲的峰值压力、正压作用时间和比冲量经验计算公式、容器内部准静态压力经验计算公式。通过对数值模拟结果进行分析,阐明了容器内壁所受爆炸载荷特征和分布规律的形成机理。研究结果表明,椭球端盖内壁产生的马赫反射波在端盖极点汇聚,使得极点所受载荷峰值压力及单次脉冲比冲量峰值总是所有测点中最大的,峰值压力最高可达圆柱壳所受最大压力的2.79倍,应予以足够重视。     

圆柱形爆炸容器的内壁爆炸载荷

爆炸容器内壁所受爆炸载荷的确定是容器动态响应特征研究、容器结构设计及安全评估的基础。对自行研制的组合式圆柱形爆炸容器开展了系列内爆加载试验,测量了容器内壁几个典型位置所受爆炸载荷,并利用ANSYS/LS-DYNA软件对容器内爆载荷的形成和传播全过程进行了数值模拟。通过对试验结果进行分析,获得了容器内壁所受爆炸载荷的特征及其分布规律,并拟合出容器圆柱形壳体部分所受载荷首脉冲的峰值压力、正压作用时间和比冲量经验计算公式、容器内部准静态压力经验计算公式。通过对数值模拟结果进行分析,阐明了容器内壁所受爆炸载荷特征和分布规律的形成机理。研究结果表明,椭球端盖内壁产生的马赫反射波在端盖极点汇聚,使得极点所受载荷峰值压力及单次脉冲比冲量峰值总是所有测点中最大的,峰值压力最高可达圆柱壳所受最大压力的2.79倍,应予以足够重视。     

用十字形超细药条离散群同步起爆实现超低比冲量加载

余弦分布载荷的化爆加载技术是高空核爆软X射线辐照下空间结构动态响应考核的主要手段。为适应新型空间飞行器结构考核的复杂构型、高同步性和低比冲量载荷设计要求,提出了一种用十字形超细药条离散群同步起爆实现超低比冲量加载的方法。实验结果验证表明：(1)所制作的十字形超细药条,最小截面尺寸为0.33 mm×0.5 mm,传爆性能稳定,并可通过直径0.5 mm的柔爆索直接起爆;(2)与相同布药密度的条状布药方式相比,布药空间均匀度提高了76.7%;(3)所采用的21点柔爆索同步起爆网络,起爆率达100%,起爆不同步性小于1μs。进一步建立了离散片炸药加载数值计算模型,分析了离散片炸药群同步起爆加载的比冲量空间分布和匀化规律,将匀化过程分为扩散段、叠加段和均匀段3个阶段;对比了方形、十字形、短条形3种形状药片阵列的比冲量演化过程,发现十字形药片所需匀化距离最短、均匀度最高,仅需约0.8倍布药间距即可使比冲量均匀度偏差降至10%以下。     

钢质圆柱壳在侧向爆炸荷载下的动力响应

将壁厚为2.75mm、外径为100mm的钢质圆柱壳置于75g裸装圆柱形压装TNT药柱产生的爆炸场中进行冲击实验,获得了不同装药条件下圆柱壳的变形破坏特征。实验表明:非接触爆炸条件下,壳壁迎爆面局部破坏呈现碟型凹陷,同时沿壳体轴线方向产生了整体屈曲变形,且装药距离较大或药柱轴线与壳体轴线垂直放置情况下对壳体损伤程度较大;而接触爆炸时,壳壁发生破裂形成破口及破片。利用动力有限元程序LS-DYNA及Lagrangian-Eulerian流固耦合方法对圆柱壳的非线性动态响应过程进行数值模拟,分析了壳壁的屈曲变形过程及迎爆曲面中心点速度、位移时程曲线,计算结果与实验吻合较好。并基于数值计算确定了壳壁发生破裂的临界装药距离。     

空中强爆炸冲击波地面反射规律数值模拟研究

为准确预测空中强爆炸产生的冲击波载荷分布,基于欧拉坐标系建立了能够模拟具有高密度比、高压力比的强激波问题的二维多介质流体数值方法。结合网格自适应技术,对1 kt TNT当量的空中强爆炸在不同爆炸高度下的冲击波地面反射过程进行了数值模拟,并考虑了真实气体状态方程和空气随高度不均匀分布的影响。计算得到了地面上距爆心投影点大尺度范围内的反射超压和冲量等冲击波载荷分布,并给出了冲击波载荷随爆高的变化规律。     

爆炸荷载在圆截面桥梁墩柱上的分布规律

墩柱是桥梁结构的主要承载构件,研究爆炸荷载在墩柱上的分布规律是分析爆炸荷载作用下桥梁结构动态响应的前提。以圆截面桥梁墩柱为研究对象,基于LS-DYNA软件建立了桥梁墩柱的有限元模型,综合考虑炸药当量、爆心高度、爆炸距离和墩柱直径等影响因素,基于数值模拟得到爆心高度低于0.3倍墩柱高度,比例距离为0.5～2.1 m/kg1/3和墩柱直径为0.15～1 m时,爆炸荷载冲量沿墩柱高度和横截面方向上的分布。结果表明:沿墩柱高度方向,地面爆炸或爆心高度为0.1倍柱高时,墩柱前表面冲量近似“单线性”分布,当爆心高度距地面0.2和0.3倍柱高时,墩柱前表面冲量近似“双线性”分布;沿横截面方向的平均净冲量与其前表面冲量之比为常数。基于上述爆炸荷载冲量分布规律,进一步提出了爆炸荷载作用在桥梁墩柱上总净冲量的计算方法,从而为桥梁墩柱抗爆响应分析与设计提供一定的理论基础。     

夹芯圆柱壳在水下爆炸载荷作用下的抗冲击特性

采用声固耦合方法对夹芯圆柱壳和等质量的普通圆柱壳在爆炸载荷作用下的应变、速度和加速度进行有限元计算。结果表明:夹芯防护层对爆炸冲击波可起到较好的衰减作用,即通过芯层的塑性变形,耗散了冲击过程中产生的大部分能量,对里面的圆柱壳体起到较好的保护作用,由于夹芯防护层的存在,与等质量的普通圆柱壳相比,夹芯圆柱壳能够承受更强的爆炸冲击波,降低结构的整体变形。     

近场近地爆炸下建筑柱爆炸荷载分布规律及简化模型

为了快速评估近场近地爆炸荷载下建筑柱的动力响应和破坏模式,通过数值仿真方法,探究了近场近地爆炸工况下冲击波在建筑柱迎爆面的分布规律,并提供了该工况下的爆炸荷载简化模型。为此,首先利用已有实验数据验证数值模型,并建立典型近地近场爆炸工况的数值模型,然后研究比例爆距和比例爆高对建筑柱冲击波特征参数的影响规律,最后拟合出柱迎爆面反射冲量和正相超压持续时间的计算公式,将柱迎爆面各点爆炸荷载转化为等效三角形荷载模型,为工程实践中建筑柱遭受近场近地爆炸作用下的抗爆设计提供荷载输入。研究结果表明：当比例爆高小于0.3 m/kg^1/3、比例爆距在0.4～0.6 m/kg^1/3范围时,最大反射冲量沿柱高可简化为三折线分布;当比例爆距在0.6～1.4 m/kg^1/3范围时,最大反射冲量沿柱高可近似简化为双折线分布;在同一比例爆距和比例爆高工况下,随着炸药当量的增加,柱迎爆面相同比例高度处反射超压峰值保持不变而反射冲量正比于当量的立方根。     

用于柱形爆炸容器周向大变形历程测量的应变丝技术

为了测量柱形爆炸容器的动态周向大变形历程,开发了应变丝测量技术。选用性能良好的合金丝沿爆炸容器周向固定,容器膨胀变形驱动合金丝同步伸长,配合适当的电路,检测合金丝的电阻变化,从而获得容器的变形历程。在钢筒的中心进行了120 g TNT当量球形装药下的爆炸加载实验,获得了峰值超过20%的钢筒周向变形历程。测量结果与实验后钢筒变形实测结果及数值模拟结果吻合较好。     

Fracture behavior of brittle plates and cylindrical shells subjected to concentrated impulse loading

The influence of impact velocity and geometry in the fracture patterns produced by a concentrated impulse loading on brittle plates and cylindrical shells has been studied both experimentally and theoretically. The experiments were performed by impacting plates and cylindrical shells made of plaster with a steel ball. The fracture behavior was photographed by a camera with a flash. The crack-initiation time was measured using a memoriscope. The fracture behavior is explained using the theory of flexural motion of a plate and a cylindrical shell. With the addition of impact-fracture criteria to these theories, the fracture patterns of brittle plates and cylindrical shells are predicted and the resemblance is discussed.     

具脱层轴对称层合圆柱壳的振动模态分析

对具环向贯穿脱层的轴对称层合圆柱壳进行振动模态分析.首先,采用Heaviside阶梯函数,构造了一种适合于脱层壳的位移模式.通过对脱层壳的能量分析,应用瑞利--里兹法后,得到用时间函数表示的系统振动控制方程,然后对其求解,得到脱层壳模态分析的特征方程式.算例中,讨论了不同的脱层位置、脱层大小和脱层深度对脱层壳振动模态的影响.     

Thermal gradient effect on the free vibration of a cardioid cross-section cylindrical shell

For the first time, a new cross-section profile and efficient method are developed for the vibration analysis of isotropic and orthotropic cylindrical shells having circumferentially varying profile of a cardioid cross-section expressed as an arbitrary function, under thermal gradient effect. The governing equations of orthotropic cylindrical shells with varying thermal gradient around its circumference are derived as a boundary-value problem and solved numerically as an initial-value problem, based on the framework of Flügge's shell theory, transfer matrix approach and Romberg integration method. As a semi-analytical procedure, the trigonometric functions are used with Fourier's approach to approximate the solution in the longitudinal direction and also to reduce the two-dimensional problem to one-dimensional one. The thermal gradient is assumed to arise due to the variation of Young's moduli and shear modulus, along the circumferential direction of the shell. The results are obtained to indicate the effects of cardioid cross-section on the natural frequencies and corresponding mode shapes in the thermal environment as well as the sensitivity of the vibration behavior to the thermal gradient ratio and the orthotropy of the shell is also investigated for different types of vibration modes. In general, close agreement between the obtained results and those of other researchers has been found.     

Mixed boundary value problems for a cylindrical shell

Two mixed boundary value problems in potential theory for a semi-infinite cylindrical shell are solved. The first is interpreted as a heat conduction problem for an insulated shell containing a circumferential obstruction. The second is the torsion of a cylindrical shell containing a circumferential crack. For both problems the normal derivative of the potential function is taken as zero on the inner and outer shell walls. The boundary conditions at the end of the shell are mixed with respect to the potential function and its normal derivative. The problems are formulated using integral transforms in a manner leading to a singular integral equation which can be solved by numerical means. Intensity factors along the circumference separating the mixed conditions are computed.     

Wave Deformation Modes of Fluid-Containing Cylindrical Shells Under Periodic Force

The forced nonlinear vibrations of a cylindrical shell fully filled with a fluid in instability zones of single-mode deformation are analyzed. It is shown that the deformation mode of the shell in these zones is traveling bending waves propagating in the circumference direction. The effect of the fluid on the characteristics of these waves is studied__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 5, pp. 76–82, May 2005.     

ELASTIC PULSE BUCKLING OF CYLINDRICAL SHELLS UNDER RADIAL IMPULSIVE LOADING

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Flow around a flexible cylindrical shell by a plane stream of an ideal liquid

The flow by a plane stream of an ideal liquid around a cylindrical shell of zero flexural stiffness (a soft cylindrical shell), or a gas bubble on the boundary of which forces of tension act, was studied in [1–6]. The flow around an elastic plate in a linear formulation was considered in [7, 8]. We consider the flow, around a flexible cylindrical shell which possesses a flexural stiffness and at the same time admits large displacements, by a plane system of an ideal incompressible liquid. An application of methods of the theory of functions of a complex variable leads to an effective solution of the problem. The shape of the shell, the forces in it, the forces acting on the shell, and the field of velocities of the flow of the liquid are determined.     

Response of a thin cylindrical panel with constrained edges

Static and transient responses of a thin cylindrical panel constrained from motion along its straight edges and simply supported along its curved edges are treated analytically. Independent of modulus, and for a range of geometric parameters, static deformation along the panel’s circumference from a uniform radial pressure exhibits an indentation. This indentation does not appear in transient response of the panel from an impulse of short duration. Extensional boundary constraints strongly affect peak stress in static and transient response.     

Stresses around elliptic holes in circular cylindrical shells

The stress state around an elliptic hole in a circular cylindrical shell under axial loads is measured. The test cylinders which are made of aluminum are loaded both in tension and compression. Stress-concentration factors around the hole for different eccentricities of the ellipse and different curvature parameters are evaluated. Stress-concentration factors away from the edge of the hole are also determined. The results obtained are compared with theoretical results available in the literature. The effect of bending on the stress concentration as related to the eccentricity of the elliptic hole and to the curvature parameters of the shell is discussed. The results from tension test and those from compression test are also compared, and the sensitivity of the shell to any imperfection and possible local buckling at the hole in the case of compression test are demonstrated.