用柔爆索构成沿圆柱壳体周向呈余弦分布的冲量载荷

利用柔爆索爆炸加载模拟脉冲X射线辐照产生的汽化反冲冲量进行结构响应实验研究,需要对柔爆索载荷的分布特征进行直接的实验测定。按照优化设计结果在圆柱壳体周围排布一定数量的柔爆索,测量柔爆索爆炸在圆柱壳体表面不同角度处产生的冲量。测量结果表明通过优化设计柔爆索间距及柔爆索与圆柱壳体之间的距离可得到沿圆柱壳体周向呈余弦分布的冲量载荷。     

强脉冲激光束引起圆柱壳动屈曲破坏的理论估算

1 引言研究强激光对靶材破坏的机理,主要目的在于确定破坏阈值.高强度短脉冲激光束辐照靶材时,靶面物质由于汽化、电离向外喷射对靶材产生反冲冲量,高速冲击可能引起材料层裂等早期材料破坏效应以及由于大变形和大应变而产生的后期结构破坏效应,结构破坏阈值一般比材料破坏阈值低.本文先假设一均匀的强脉冲激光束辐照到铝材料的圆柱壳体时,壳体将受到一余弦分布的脉冲载荷,然后根据Andcrson 的假设认为壳体的变形达到某一临界值时,就会     

核爆X光辐照铝靶产生的脉冲应力波的简化解析估算

高空核爆炸大约有７０％的能量以Ｘ射线形式向外辐射，高能通量密度的Ｘ射线辐照在空间结构物上，在其表面的能量沉积将产生脉冲应力波（通常又称为热击波），这样的脉冲应力波可造成壳体材料的动力学破坏。对于试验研究人员来说希望采用简化解析模型对于其参数作出直观、快速的预测。并以简化模型估算了核爆Ｘ射线谱的特征、Ｘ光辐照铝靶产生的脉冲应力波的初始参数及其沿铝靶厚度的衰减特性。     

金属电阻率模型

修正了Burgess电阻率模型中的错误公式和算法流程,获得了与文献中结果完全相同的电阻率曲 线。采用Burgess电阻率对Z装置上的磁驱动飞片实验进行数值模拟,计算的自由面速度曲线与实验结果相 差较大。由于液体到达汽化点时,是气液混合体,因此从汽化点到临界温度的Burgess电阻率公式不应采用 气体计算公式,应改为气液混合体的计算公式。采用从汽化点到临界温度阶段修改为气液混合体的电阻率公 式进行数值模拟,计算的自由面速度曲线与实验结果、文献计算结果相吻合。     

薄片炸药与固体靶冲量耦合的计算模型

薄片炸药可用于模拟强脉冲X射线辐照下空间结构的响应,其与固体靶的冲量耦合作用是进行模拟载荷设计的基础。本文中基于有限元模拟技术,研究不同直径薄片炸药的边界稀疏作用和安装支座的反射作用对薄片炸药与固体靶冲量耦合的影响,结果表明:边界稀疏作用对薄片炸药的比冲量起到减弱的作用,由边界稀疏作用引起的薄片炸药比冲量的变化量和薄片炸药直径的倒数近似成线性关系;薄片炸药安装支座的反射作用对薄片炸药的比冲量起到增强的作用,由支座反射作用引起的薄片炸药比冲量的变化量和薄片炸药直径的平方近似成反比;随着薄片炸药直径的增加,薄片炸药比冲量趋于定值,边界稀疏作用和支座反射作用可以忽略;存在一个临界直径,当薄片炸药的直径为临界直径时,薄片炸药的边界稀疏作用和支座反射作用达到平衡,其比冲量大小和薄片炸药的直径为无穷大时的比冲量值相等。     

弹-塑性流体动力学数值模拟计算的一种新自由面格式

提出了适用于电子束或X射线辐照、爆炸和高速碰撞等问题的弹-塑性流体动力学数值模拟计算的一种新自由面格式。一些数值模拟计算的结果表明,所给出的新自由面格式明显优于目前一直沿用的Richtmyer格式,尤其适用于电子束及X射线辐照材料时产生的热-力学效应的数值模拟计算。     

双线性材料模型机械自紧厚壁圆筒的弹塑性分析

考虑了实际材料的应变硬化和Ｂａｕｓｃｈｉｎｇｅｒ效应，利用合理的简化假设、通过弹塑性分析，得到了计算机械自紧厚壁圆筒的应力、位移、过盈量与自紧度、残余胀大量和冲头推力等机械自紧技术的关键计算公式。本文的理论计算结果与实验值相符合。     

基于Z箍缩X射线源的热-力学效应实验

材料或结构对强脉冲X射线的响应如热激波的传播和喷射冲量等,统称为X射线热-力学效应,在抗辐射加固研究、天体物理、行星科学等领域具有重要应用。利用驱动电流近10 MA脉冲功率装置上的丝阵Z箍缩X射线源开展了初步的热-力学效应实验。采用20 mm直径的双层铝丝阵产生了约230 kJ的X射线总辐射能,其中铝的K壳层产额约为30 kJ,距离源中心5 cm处的样品上的X射线能注量为732 J/cm2。受辐照样品为厚度2 mm、直径10 mm的铝制圆盘,其背面设置有铝衬套,样品与衬套的总质量为585 mg。采用全光纤光子多普勒测速（PDV）系统来测量受辐照样品后表面的运动过程。PDV测量的样品后表面速度历程显示,当热激波到达后表面时的自由面速度为2.12 km/s,样品最终的整体运动速度为180 m/s。根据冲击波关系式以及动量守恒原理,推导出X射线在样品中产生的热激波应力为19.2 GPa,单位面积上的喷射冲量为1341 Pa·s,进而由喷射冲量和X射线能注量测量结果可以推出冲量耦合系数为1.83 Pa·s·cm2/J。同时,对实验测量结果的可靠性和不确定度进行了讨论和分析。这些实验结果初步验证了将PDV技术应用于热-力学效应研究的可行性。     

γ射线辐照聚四氟乙烯复合材料的结构和摩擦磨损性能研究

通过γ射线辐照聚苯酯改性聚四氟乙烯(PTFE/POB)复合材料,利用红外光谱、X射线衍射、DSC等对辐照前后材料的化学组成、结晶结构等进行了表征,并与γ射线辐照纯PTFE材料作对比,考察了热稳定性能、拉伸性能和摩擦磨损性能. 结果表明:γ射线辐照并未造成PTFE/POB 材料的化学组成和热稳定性能的明显变化,但使得PTFE分子量降低,结晶度增大;相比纯的PTFE材料,POB的加入一定程度上提高了PTFE的抗辐照能力,延缓了PTFE分子量下降程度和再结晶化能力. 辐照对PTFE/POB材料的耐磨性能影响并不显著,但摩擦系数均有不同程度的降低,且随着辐照剂量的增大,呈现先增大后减小的变化趋势,这与辐照后PTFE的分子量、结晶度及带晶尺寸变化,以及POB自身的抗辐照能力等密切相关.      

激光辐照固体推进剂材料的冲量耦合机制分析

利用流体反应动力学编码对火箭推进剂材料的脉冲激光点火过程进行了一维数值分析,并对计算结果进行了分析和讨论。初步分析结果表明,火箭推进剂材料的激光冲量耦合增强机制较为复杂,包含两种主导机制,并受推进剂组分及其物理性质、激光参数等多因素影响。     

Elastic-plastic aluminium ring response to pulsed electron beam impulse

Aluminum alloy 6061-T6 and 7075-T73 rings with lead and tin blowoff overlays were exposed to the Hermes II pulsed electron beam. The resultant energy deposition and subsequent expansion of the overlay produced an impulse load on the ring. High speed framing camera photographs permitted determination of the peak impulse and the variation of the impulse with angular location. The framing camera photographs also yielded the time dependent ring deformation profiles. Favorable comparisons were obtained between the UNIVALVE calculated response and the observed ring response.     

Effect of the recoil pressure induced by evaporation on motion of powder particles in the light field during laser cladding

A model is proposed, which takes into account acceleration of powder particles by a force induced by recoil of material vapors from the irradiated region of the particle surface. Results of a numerical analysis of heat and mass transfer in the case of motion of individual stainless steel powder particles in a gas flow and in a light field of laser radiation under conditions of laser cladding are presented. Acceleration of particles is found to depend on their diameter, carrier gas velocity, powder material properties, laser radiation power, and degree of attenuation of the power density in the laser beam in the direction of its action on the substrate. The calculated results are compared with experimental data on light-propulsion acceleration of individual particles (of aluminum, aluminum oxide, and graphite) under the action of pulsed laser radiation.     

Numerical modelling of thermal radiation absorption during the dispersion of dense gas clouds in the atmosphere

A numerical model is presented for the prediction of thermal radiation absorption in dense gas clouds during accidental release in the atmosphere. The model is based on the discrete transfer method (DT method) that was originally developed for modelling radiation in combustion chambers. The radiation model assumes a number of representative rays of predetermined orientation fired from each of the domain boundaries. Each ray is traced through the domain elements until reaching another boundary where it is terminated. Radiation sources are calculated for each element by performing an energy balance across each element for each ray passing through it. The energy sources recovered are fed into the finite element flow solver for every time step in the energy equation. The model proved accurate, and memory and computer time efficient. It showed that accounting for radiation effects lead to improved predictions. It also showed that in certain scenarios, radiation effects could be predominant. © 1998 John Wiley & Sons, Ltd.     

Determination of the anisotropic permeability of a carbon cloth gas diffusion layer through X‐ray computer micro‐tomography and single‐phase lattice Boltzmann simulation

An investigation of the anisotropic permeability of a carbon cloth gas diffusion layer (GDL) based on the integration of X‐ray micro‐tomography and lattice Boltzmann (LB) simulation is presented. The method involves the generation of a 3D digital model of a carbon cloth GDL as manufactured using X‐ray shadow images acquired through X‐ray micro‐tomography at a resolution of 1.74 µm. The resulting 3D model is then split into 21 volumes and integrated with a LB single‐phase numerical solver in order to predict three orthogonal permeability tensors when a pressure difference is prescribed in the through‐plane direction. The 21 regions exhibit porosity values in the range of 0.910–0.955, while the average fibre diameter is 4 µm. The results demonstrate that the simulated through‐plane permeability is about four times higher than the in‐plane permeability for the sample imaged and that the corresponding degrees of anisotropy for the two orthogonal off‐principal directions are 0.22 and 0.27. The results reveal that flow channelling can play an important role in gas transport through the GDL structure due to the non‐homogeneous porosity distribution through the material. The simulated results are also applied to generate a parametric coefficient for the Kozeny–Carman (KC) method of determining permeability. The current research reveals that by applying the X‐ray tomography and LB techniques in a complementary manner, there is a strong potential to gain a deeper understanding of the microscopic fluidic phenomenon in representative models of porous fuel cell structures and how this can influence macroscopic transport characteristics which govern fuel cell performance. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of the time structure of laser pulse on the temperature distribution in homogeneous body with coating

In the present paper an analytical solution of the transient heat conduction problem for the nonhomogeneous body, consisting of bulk foundation and thin coating of different material, is presented. This body is heated through the outer surface of coating by heat flux generated due to absorption of pulsed laser radiation. The dependence of nonstationary temperature on the thermophysical properties of the foundation and coating were studied.     

Application of fractional-derivative standard linear solid model to impact response of human frontal bone

The impact of a rigid body on a thin plate with a buffer is investigated in this paper. A buffer is assumed as a linear spring fractional derivative dashpot which exhibits the viscoelastic features. The fractional-derivative standard linear solid model is suggested for describing the shock interaction of the impactor with a circular elastic plate. We assume that a transient wave of transverse shear is generated in the plate and the reflected wave does not have sufficient time to interact with the plate before the impact process is completed. The ray method is used outside the contact spot, but the Laplace transform method is applied within the contact region. The time-dependence of the contact force is determined. A numerical example is carried out by considering crash scenarios in frontal impacts of the human head which could estimate brain injury risks.     

Effect of Radiation Scattering on the Dynamics of the Transitional Zone During Solidification of a Semitransparent Material

The effect of isotropic scattering in a two-phase zone on the velocity of boundaries, thickness of the transitional zone, and distribution of the solid phase over the two-phase zone thickness in the course of solidification of a semitransparent material is considered. A generalized model of phase transition in a semitransparent medium is used. The results of numerical calculations show that radiation scattering can exert a significant effect on the structure and size of the two-phase zone and also on heat transfer (temperature gradient) in the crystal being formed.     

Non-LTE radiation transport in high radiation plasmas

A primary goal of numerical radiation transport is obtaining a self-consistent solution for both the radiation field and plasma properties, which requires consideration of the coupling between the radiation and the plasma. The different characteristics of this coupling for continuum and line radiation have resulted in two separate sub-disciplines of radiation transport with distinct emphases and computational techniques. LTE radiation transfer focuses on energy transport and exchange through broadband radiation, primarily affecting temperature and ionization balance. Non-LTE line transfer focuses on narrowband radiation and the response of individual level populations, primarily affecting spectral properties. Many high energy density applications, particularly those with high-Z materials, incorporate characteristics of both these regimes. Applications where the radiation fields play an important role in the energy balance and include strong line components require a non-LTE broadband treatment of energy transport and exchange.We discuss these issues and present a radiation transport treatment which combines features of both approaches by explicitly incorporating the dependence of material properties on both temperature and radiation fields. The additional terms generated by the radiation dependence do not change the character of the system of equations and can easily be added to a numerical transport implementation. A numerical example from a Z-pinch application demonstrates that this method improves both the stability and convergence of the calculations. The information needed to characterize the material response to radiation is closely related to that used by the linear response matrix (LRM) approach to near-LTE simulation, and we investigate the use of the LRM for these calculations.