模拟深水环境爆炸容器动力响应实验研究

对可模拟200 m水深、10 g TNT当量的爆炸容器在不同加载静压和内部爆炸载荷下的动力响应进行了实验研究,通过监测容器6个特征点的动态应变波形,分析了容器壳体的振动特性和动力学强度。测试结果揭示了在加载静压和内部爆炸载荷条件下容器的动态响应规律,为模拟深水环境爆炸容器的设计研制提供了参考。     

三层柱形爆炸容器动力学响应的有限元模拟

对采用平封头的三层柱形爆炸容器在内部爆炸载荷作用下的动力学响应问题应用ANSYS／LS-DYNA非线性有限元程序进行数值模拟。结果表明,冲击载荷由爆心向两侧顺序加载,峰值逐次降低,达到峰值的时间也逐渐增加,但在封头处得到会聚增强,并且随着径长比越大,增强越明显;容器内壳之间的摩擦力有助于提高容器的抗爆性装药越多,容器的残余变形越大,但是残余变形和装药的重最不是简单的成比例关系总壁厚一定的情况下,里外厚中间薄的容器抗暴性明显比其它情况差。数值模拟结果为爆炸容器的经验设计和防护提供了科学依据。     

球形爆炸容器动力响应的强度分析

运用ＤＹＴＲＡＮ程序中的欧拉计算方法,模拟了作用于球形爆炸容器内壁的反射超压波形。运用解析法和三维有限元程序ＬＳ－ＤＹＮＡ,对容器壳体在反射超压作用下的动力响应进行了强度分析,给出了容器的几个特征点的等效应力历史和重要区域的等效应力云图。分析结果对类似爆炸容器的强度设计和安全使用具有参考意义。     

压杆应变式压力传感器在爆炸冲击波载荷测试中的应用

在容器内实施化学爆炸时，容器内壁上冲击波载荷的确定是进行爆炸容器结构动力响应分析、安全评估和工程设计的基础。获得比较准确、可靠的爆炸容器内壁上作用载荷的时间历程及分布情况，对研究结构动力响应意义重大。文章采用压杆应变式压力传感器来测量爆炸冲击波载荷，这种传感器解决了普通传感器在高频压力脉冲下频响低且容易损坏等问题。压杆应变式压力传感器为一细长弹性杆，爆炸冲击波作用在杆的一端，在杆中激发一维弹性应力波，通过测量杆上适当位置处的应变，利用一维弹性应力波理论可以计算出作用在杆端的爆炸冲击载荷。文章根据一维弹性波理论，设计了满足所需频响、上升时间、持续作用时间等参数要求的压杆应变式压力传感器，其材料为高强度钢，采用动态应变放大器和数据采集仪组成测量系统。通过实验，获得了比较完整的容器内壁上冲击波载荷曲线，测量结果的重复性和一致性很好。经分析表明，压杆应变式压力传感器能准确地测得容器内壁上冲击波荷载的幅值和比较完整的曲线，对爆炸冲击波载荷测试来说，是一种比较准确可靠的传感器。     

含预制孔容器内爆问题的FEM-SPH耦合算法模拟

考虑带预制孔容器内空气的影响,采用三维FEM-SPH自适应耦合算法程序对含预制孔容器在内爆载荷作用下的动态响应过程进行了模拟,与实验所得到的破坏特征参量吻合。同时也用LS-DYNA软件中ALE算法得到的计算结果与FEM-SPH自适应耦合算法得到的结果进行比较,进一步分析了FEM-SPH自适应耦合算法的有效性。FEM-SPH自适应耦合算法能够稳定再现内爆载荷作用下含预制孔容器的爆炸鼓包过程、预制孔毁伤破坏过程以及容器内空气运动过程,可以为容器内爆问题的数值模拟研究提供有效途径。     

爆室内爆炸流场演化与壳体动力响应研究

针对内爆炸载荷的特点,采用等效单自由度法与薄膜理论分别得出了等效静载动效系数的解析式与径向位移的动态表达式。将反射压力代入径向位移与动效系数表达式中,得到最大径向位移与等效静载的解析式。所得解析式计算值与实验和数值模拟结果符合较好。运用三维有限元编码与现场实测的方法对爆室内冲击波流场的演化及壳体动力响应规律进行了研究。结果表明：1.内爆炸加载容器的动力响应主要取决于首次压力脉冲。2.壳体的最大应变由近爆点向远爆点方向逐渐降低。研究结果为相似工程设计设计提供了参考。     

球形装药半无限土介质中爆炸动力学分析

通过对球形装药土中爆炸的数值模拟,研究了球形装药半无限土介质中爆炸作用下,土介质的动力学响应;空腔的形成发展规律及鼓包的运动规律等动力学问题．数值模拟结果与实验现象吻合较好。     

外部空间与初始温度对氢气与空气混合气体爆炸过程的影响

为了研究容器形状和初始温度对氢气与空气预混气体爆炸过程的影响,分别采用20 L球形容器和20 L圆柱形容器对氢气与空气混合气体的爆炸过程进行了研究。首先,通过壁面压力传感器获取了两种容器内的最大爆炸压力,并采用高速摄影装置拍摄了球形容器内部爆炸火球的发展变化过程。其次,利用计算流体力学方法对氢气爆炸过程进行了数值模拟,获取了三维爆炸压力场、火焰温度场等爆炸参数,对比分析了容器内不同位置处的压力曲线,并探讨了初始温度对氢气爆炸压力的影响。实验结果表明:在常温下,最大爆炸压力出现在氢气体积分数为30.0%的条件下,略高于理论当量浓度。数值模拟结果表明:两种容器内,火焰传播初期均呈球面往外发展;容器内上壁面的压力均低于右壁面的压力;由于壁面不规则的反射作用,圆柱形容器第1个压力峰值后的压力振荡周期不同步;在体系初始压力不变的情况下,初始温度提高20%,容器内部总的物质的量减少,最大爆炸压力下降15%。     

远场水下爆炸结构动态响应的数值模拟方法研究

远场水下爆炸载荷作用下结构动态响应的数值模拟方法的研究一直是国内外专家关注的热点。针对远场爆炸中冲击波传播的消散过程,将爆炸冲击波载荷直接加载于结构附近的水域面,基于DAA和Taylor板理论,提出简化的改进数值计算方法。采用有限元软件模拟水下爆炸的冲击波传播,通过与经验公式对比,表明只有当水域网格较小时,才能比较真实的模拟冲击波传播过程。最后通过文献中的实验验证了改进方法的准确性,该方法可有效的分析远场水下爆炸下结构的非线性动力高频响应。     

高压容器试验仓安全评估计算方法研究

文章分析了高压容器爆炸对试验仓产生的三种危害模式,并采用等效TNT药量爆炸替代高压容器气体爆炸,对这三种危害模式的计算方法进行了研究。通过计算模型的建立和计算结果分析,对高压容器的爆炸危害安全评估进行了实例模拟和数值计算,为高压容器气体密封试验仓的结构设计和材料选择提供了一种计算方法。     

Calculation with MCNP of capture photon flux in VVER-1000 experimental reactor

The aim of this study is to obtain by Monte Carlo method the high energy photon flux due to neutron capture in the internals and vessel layers of the experimental reactor LR-0 located in REZ, Czech Republic, and loaded with VVER-1000 fuel. The calclated neutron, photon and photon to neutron flux ratio are compared with experimental measurements performed with a multi-parameter stilbene detector. The results show clear underestimation of photon flux in downcomer and some overestimation at vessel surface and 1/4 thickness but a good fitting for deeper points in vessel.     

Finite plane strain deformations of rubberlike materials

A finite element program capable of analysing finite plane strain deformations of incompressible rubberlike (Mooney–Rivlin) materials has been developed. Two problems, namely a long wall loaded uniformly in two directions and a thick-wall cylindrical pressure vessel loaded internally, have been solved. The computed values of displacements, strains, stresses and hydrostatic pressure agree very closely with their values obtained analytically.     

25kg TNT当量爆炸容器的冲击隔震研究

运用压电加速度计及精密电荷放大器，对25kg TNT当量爆炸容器在六种TNT当量加载下对邻近结构及基础产生的冲击振动进行了三点比较测试。研究结果表明，当与容器基座有直接接触的钢平台上的冲击加速度达100g时，隔振沟内的地面加速度仅4g，而隔震沟外的地面振动加速度则只有0．7g；隔振沟对振动加速度的衰减作用随载荷强度的增加而增强。     

Burst Pressures for Torispheres and Shallow Spherical Caps

Abstract:  Burst pressures are computed for shallow spherical caps and torispheres loaded by uniform static pressure. They are defined as maximum pressures at which proposed plastic strain criteria are met. The criteria are taken from true stress–true strain curves of uniaxial tensile tests. Experimental tests, carried out on pressure vessel components made from aluminium alloy 6061 and mild steel, provide experimental results against which the proposed criteria for burst pressures are benchmarked.     

Numerical simulations of a tanker collision with a bergy bit incorporating hydrodynamics,a validated ice model and damage to the vessel

Numerical simulations of a collision between a loaded tanker and a bergy bit have been conducted using LS-Dyna™ software. The simulations incorporated hydrodynamics, via LS-Dyna's ALE formulation, and a validated crushable foam ice model. The major portion of the vessel was treated as a rigid body and a section of the hull, located on the starboard side of the forward bow where the ice contact occurred, was modeled as typical ship grillage that could deform and sustain damage as a result of the collision. Strategies for dealing with the highly varying mesh densities needed for the simulations are discussed as well as load and pressure distribution on the grillage throughout the course of the collision. Realistic movement of the bergy bit due to the vessel's bow wave prior to contact with the ice was observed and the damage to the grillage resembled published results from actual grillage damage tests in the lab. A load measurement from the lab tests compared reasonably well with a rough estimate from the simulation. The collision eventually ruptured the hull in a ripping fashion resembling documented incidents of vessel impacts with ice masses.     

A Weibull stress model to predict cleavage fracture in plates containing surface cracks

This study applies recent advances in probabilistic modelling of cleavage fracture to predict the measured fracture behaviour of surface crack plates fabricated from an A515-70 pressure vessel steel. Modifications of the conventional, two-parameter Weibull stress model introduce a non-zero, threshold parameter (σ_w-min ). The introduction of σ_w-min brings numerical predictions of scatter in toughness data into better agreement with experimental measurements, and calibration of this new parameter requires no additional experimental data. The Weibull modulus ( m ) and scaling parameter (σu ) are calibrated using a new strategy based on the toughness transferability model, which eliminates the non-uniqueness that arises in calibrations using only small-scale yielding toughness data. Here, the Weibull stress model is calibrated using toughness data from deep-notch C(T) and shallow-notch SE(B) specimens, and is then applied to predict the measured response of surface crack plates loaded in different combinations of tension and bending. The model predictions accurately capture the measured distributions of fracture toughness values.     

THE SIZE EFFECT OF MICROSTRUCTURAL IMPLICATIONS OF THE WEAKEST LINK MODEL

Abstract— CT specimens made of a reactor pressure vessel steel were loaded at—40°C until final failure occurred by cleavage fracture. The samples of J _lcl values obtained in these tests are analysed using the weakest link model. The size effect observed with specimens of different thicknesses is compared with the predictions of the weakest link model. A formula is derived for the distribution of the locations of fracture origins which have been determined for almost all specimens with a scanning electron microscope. The distribution of the size of the "weak spots" is calculated from the distribution of the fracture origins using two different models for the stress field ahead of the crack tip. These fractographic results and the J _lcl data confirm the basic ideas of the weakest link model. The deviations observed between the quantitative predictions of the weakest link model and the data can partly be explained by the change in the stress state ahead of the crack tip caused by a change in the specimen thickness.     

Aspirin-loaded electrospun poly(ε-caprolactone) tubular scaffolds: potential small-diameter vascular grafts for thrombosis prevention

Thrombosis is the main cause of failure of small-diameter synthetic vascular grafts when used for by-pass procedures. The development of bioresorbable vascular scaffolds with localized and sustained intra-luminal antithrombotic drug release could be considered a desirable improvement towards a valuable solution for this relevant clinical need. For this aim, we present the fabrication and characterization of aspirin-loaded electrospun poly(ε-caprolactone) tubular scaffolds as a vascular drug-delivery graft. Three different drug concentrations were considered (i.e., 1, 5 or 10 % w/w). Although a fibrous structure was clearly observed for all the collected scaffolds, aspirin content was directly implied in the final microstructure leading to a bimodal fiber diameter distribution and fused fibers at crossing-points (5 or 10 % w/w). Mechanical response highlighted a direct relationship for modulus and stress at break with the aspirin content, while the elongation at break was not remarkably different for the investigated cases. The temporal drug release was strongly dependent from the amount of loaded aspirin, reaching a steady state release after about 50 h. Finally, the adhesion assay confirmed the capability of the electrospun scaffolds to reduce platelet adhesion/aggregation onto aspirin loaded polymeric fibers. Aspirin-loaded electrospun tubular scaffold could represent a feasible candidate to develop a novel bioresorbable drug-releasing graft for small-diameter vessel replacements.     

运输中紧急制动时贮液容器的应力分析

在运输中的紧急制动情况下,贮液容器器壁受内部液体惯性的作用,将产生附加内力。分析了不同边长比长方体容器和不同高径比圆柱形容器的受力状态,探讨了长方体容器在不同装载方向时边长比对器壁应力水平的影响及圆柱形容器动荷系数随高径比的变化规律,对运输时贮液容器的安放方式和容器设计有一定的指导作用。     

Shear band development in dynamic loading of a viscoplastic cylinder containing two voids

Summary We presume that plane strain state of deformation prevails when the interior of a long gun barrell or a cylindrical pressure vessel is dynamically loaded. The viscoplastic material of the body is taken to exhibit strain-rate hardening and thermal softening. Two thin ellipsoidal voids located symmetrically on the horizontal axis and near the center of the cylinder wall act as nuclei for the initiation of shear bands. We note that deformations of the cylinder are nonhomogenous even in the absence of the voids. It is therefore interesting to investigate when the bands initiate from the void tips and the interaction, if any, among them.It is found that shear bands initiate first at void tips closer to the center of the cylinder. These bands propagate faster to the inner surface of the cylinder as compared to those initiating from the other void tips which propagate towards the outer bounding surface of the cylinder. Whereas contours of constant maximum principal logarithmic strain originating from the outer void tips spread out laterally in both directions as they propagate into the cylinder, those originating from the inner void tips spread out in only one lateral direction as they propagate into the body.