低附带/不敏感炸药作用下战斗部联接强度的计算方法

某些采用低附带/不敏感炸药的战斗部以及有些威力可调战斗部,其联接强度对装药反应状态、爆炸型式变化、各反应所占的百分比以及各部件最大过载等有着较大影响,是装药选择、结构设计、装药形式等需要重点考虑的因素之一。鉴于此,研究了采用螺纹联接战斗部在低附带/不敏感炸药作用下联接强度的计算方法,给出了联接强度的计算公式,并通过钢质与钢、铝、尼龙材质的配合部件进行实验,实验表明该计算公式与实际十分吻合,为未来相似战斗部联接强度的计算提供了理论依据。     

Experimental-theoretical correlation on the containment of explosions in closed cylindrical vessels

Approximate containment design formulas are developed for prediction of the maximum wall deformation of a cylindrical vessel due to detonation of a centrally located bare spherical high-explosive charge. Vessel wall response due to both the initial impulse loading and the long-term pressure build-up is considered. Formulas, which incorporate a rigid-plastic material model including strain hardening and strain rate sensitivity, are written in terms of elementary functions suitable for containment design calculations. Wall response predictions compare favorably with the results of a limited experimental program performed on mild steel containment vessels closed with massive end caps.     

电站冷凝器用钛钢复合板结合界面均匀性研究

采用高低爆速炸药分段式铺药的方式对钛/钢复合管板进行爆炸焊接.对爆炸复合法制备的电站冷凝器用29 m2、材料为Gr.2/Gr.70的管板结合界面的微观组织和力学性能进行了分析,结果表明,采用2250～2300 m/s的高低爆速和分段布药工艺制备的大面积钛/钢复合板,在无损检测时无杂波,结合界面均匀,力学性能符合ASTM...     

一种超细晶材料的混合硬化模型及其数值模拟

针对超细晶材料强度高、塑性能力不佳以及饱和应力跟晶粒尺寸和应变率等因素有关的特点,在Johnson-Cook模型的基础上引入Hall-Petch关系式,再与Armstrong-Frederick非线性随动硬化规律进行叠加,提出一种同时包含各向同性硬化和非线性随动硬化的混合硬化模型。该数学模型不仅考虑了超细晶材料的尺寸效应,还计及了加工硬化和包辛格效应的组合效应。在推导出该混合硬化模型的积分算法的基础上进行有限元数值分析和试验数据的对比分析。对比结果表明,不同晶粒大小与不同应变率下的超细晶材料的数值仿真结果与试验数据均吻合较好,进而证明该数学模型的合理性。因此,该混合硬化模型不仅丰富了塑性力学的内容,也可为超细晶材料的结构件设计提供一定的理论依据。     

热冲压硼钢B1500HS高温本构方程的研究

硼钢的高温本构方程是热冲压数值模拟不可缺少的数学模型,它反映了流动应力与应变、应变速度以及温度之间的依赖关系。为了研究热冲压硼钢B1500HS高温时的流变力学行为,采用Gleeble 1500D热模拟试验机,在600～900℃温度区间,分别以0.01 s–1、0.1 s–1、1.0 s–1、10 s–1的应变速度对硼钢B1500HS试样进行等温单向拉伸试验,计算得到各相应测试条件下的正应力—应变曲线。采用包含变形激活能和变形温度的双曲正弦形式修正的Arrhenius关系来描述硼钢奥氏体组织的热激活变形行为。通过对试验数据进行拟合回归分析,得到与应变量相关的各材料参数,以及与应变速度、变形温度相关的流变应力关系式。试验结果显示,流动应力随着变形温度的降低而增大,随着形变速度的升高而增大。计算结果表明:流变应力关系式的计算结果与试验数据的吻合度较好。     

Constitutive relations for compressible granular materials using non-Newtonian fluid mechanics

This paper is about constitutive relations which can model the flow of granular materials with cohesion, friction, and collisions between particles. The constitutive model represents compressible viscoplastic fluids with second-order effects, in which the Cauchy stress tensor depends on the velocity components and on the rate of volume distribution. An alternative model employs the maximum volume distribution to take second-order effects into account. It is shown that the simplification of the model in which compressibility and second-order effects are neglected leads to the constitutive model of Diez and Godoy. The formulation is employed to solve the flow through an inclined channel, for which the problem reducesto a one-dimensional situation. Explicit solutions are obtained for this case, and are presented in some detail for different degrees of approximation. The results are compared with theoretical values by other authors and with experimental data available in the literature, by Drake and Walton and by Savage, with excellent agreement. The constitutive equation in which second-order terms are a function of the volume distribution is the most general of the constitutive relations presented.     

用亏测量炸药在有限空间内爆炸特性的试验装置

为了表征炸药在有限空间内的爆炸特性,分别设计了密闭和半密闭爆炸试验装置。采用传感器测量了典型炸药在半密闭环境下的爆炸场温度和压力特性,并测量了其在密闭条件下的爆炸场温度特性。研究结果表明,2套装置满足炸药在有限空间爆炸测试要求,能够测量出有限空间条件下炸药的温度及压力特性,从而反映出不同炸药的杀伤能力大小,为炸药配方设计提供依据。     

基于改进温度模型的300M钢本构方程参数识别

为了提高通过切削实验获取材料本构方程参数的精度,提出了将基于移动热源理论的温度分布模型沿剪切面积分计算剪切区平均温度的方法,结合不等距剪切区模型求得等效应变和应变率,建立了材料Johnson-Cook(J-C)本构方程参数的求解模型。根据切削实验获取的切削力和切屑厚度数据并采用遗传算法求得了300M钢J-C本构方程参数。与AdvantEdge FEM软件自带的300M钢本构模型相比,用所求模型参数仿真得到的主切削力、进给力和切屑厚度的精度有显著提高,验证了所建本构方程参数求解模型的有效性。     

钢管混凝土构件的爆炸荷载试验研究

针对钢管混凝土结构构件在爆炸冲击荷载作用下的动力响应进行研究,试验对象为相同管径三种不同壁厚的钢管混凝土结构构件在简支状态下,受到两种不同爆炸冲击荷载的作用,测量了两种不同爆炸空气冲击波的压力时间曲线、构件跨中的应变时间曲线和构件跨中的最终挠度值,并对测量结果进行分析,为钢管混凝土构件的抗爆炸荷载设计提供有益的试验成果,也为后续进一步研究提供有效的基础数据和可靠的对比参照.     

0Cr18Ni9不锈钢本构模型及其对切削力预测影响分析

利用MTS材料试验机和分离式Hopkinson压杆(SHPB)实验装置对经过1100℃固溶处理后的0Cr18Ni9不锈钢的静态力学性能和动态力学性能进行了测量,用Johnson-Cook模型拟合了材料的本构关系,用正交切削实验识别了Johnson-Cook模型材料参数。将SHPB实验和切削实验两种方法得到的Johnson-Cook材料模型应用于切削力的预测,分析了不同实验方法得到的材料模型在切削力的预测中的适用性,为不锈钢切削研究中的分析模型和数值计算中的材料流动应力模型选择提供参考。     

Pressure measurements in laboratory-scale blast wave flow fields

The present study examines the effects that temporal and spatial averagings due to finite size and finite response time of pressure transducers have on the pressure measurements in blast wave flow fields generated by milligram charges of silver azide. In such applications, the characteristic time and length scales of the physical process are of the same order of magnitude as the temporal and spatial characteristics of the transducer. The measured pressure values will then be spatially and temporally averaged, and important parameters for the assessment of blast effects may not be properly represented in the measured trace. In this study, face-on and side-on pressure transducer setups are considered. In the experiments, face-on and side-on readings at the same distance from the charge as well as time-resolved optical visualization of the whole flow field are obtained simultaneously for the same explosive event. The procedure of data extraction from the experimental pressure traces is revisited and discussed in detail. In the numerical modeling part of the study, numerical blast flow fields are generated using an Euler flow solver. A numerical pressure transducer model is developed to qualitatively simulate the averaging effects. The experimental and numerical data show that the results of pressure measurements in experiments with small charges must be used with great caution. The effective averaging of the pressure signal may lead to a significant underestimation of blast wave intensities. The side-on setup is especially prone to this effect. The face-on setup provides results close to those obtained from optical records only if the pressure transducer is sufficiently remote from the charge.     

耦合温度效应晶体塑性的TWIP钢变形行为研究

为探究TWIP钢高温条件下的塑性变形机理,建立了耦合温度效应的晶体塑性本构模型,考虑温度对TWIP钢滑移和孪生的影响,提出了耦合温度效应的流动法则和硬化法则。结合在500 ℃和750 ℃条件下的原位SEM高温拉伸试验,建立了描述TWIP钢热变形过程的晶体塑性有限元模型。模拟获得不同温度条件下的应力应变曲线、应变硬化率和孪晶体积分数与试验结果相吻合,验证了该模型的正确性。进而,基于所建立的模型研究了温度对TWIP钢塑性变形过程滑移、孪生演化及应变硬化过程的影响规律,结果表明：滑移阻力、孪生阻力和应变硬化率随温度的升高呈不均匀降低的趋势,且断后伸长率呈现降低的趋势,由25 ℃时53.4%降低至750 ℃时16.5%。同时,随温度升高,孪生受到抑制,但滑移受温度的影响较小,表现为滑移主导的塑性变形机制。     

Influence of salt addition and confinement on explosive welding parameters

Experimental data is presented for obtaining a wide range of detonation and flyer plate velocities by salt addition and inertial confinement of the explosive.     

H13钢超塑成形性能研究

对 H13钢的超塑性能进行了试验研究 ,得出了变形温度和应变速率对 H13钢超塑性能的影响规律。结果表明 :H13钢经 10 0 0℃三次循环淬火后 ,晶粒度可达 13级 ;在温度为 840℃ ,应变速率为 1.6× 10 - 4 s- 1的条件下拉伸 ,其最大延伸率为 185 % ,流变应力为 31MPa,m值为 0 .2 6。本研究为 H13钢的超塑性成形工艺提供了最佳工艺参数。     

Melting rate of electrode wire in arc welding

A mathematical model is proposed for the melting rate of electrode wire during the arc welding of low-alloy steel in protective gases. The discrepancy with experimental data is no more than 4%.     

Computational prediction of deformation behavior of TRIP steels under cyclic loading

A constitutive equation accounting for strain rate, temperature and applied stress system dependencies of strain-induced martensitic transformation is given. A series of computational prediction of monotonic and cyclic deformation behavior including tension, compression and shearing of typical 304 austenitic stainless steel, have been performed under different environmental temperatures from 77 to 353 K. The effect of stress range, pre-strain, temperature and applied stress system on such responses of TRIP steels as the evolution of martensitic phase, the accumulated plastic strain, and the asymptotic nature of the stress–strain relation with an increase in the number of cycles is clarified. The predictability of the present constitutive model is checked against the experimental results. Furthermore, simulation of the cyclic deformation behavior of TRIP steel bars with ringed notch is performed.     

SIMULATION OF CHIP FORMATION IN ORTHOGONAL METAL CUTTING PROCESS: AN ALE FINITE ELEMENT APPROACH

Lagrangian and Eulerian finite element formulations have been traditionally used for modeling of the orthogonal metal cutting process. In this paper it is shown that a more general formulation, the arbitrary Lagrangian-Eulerian method (ALE), may be used to combine the advantages and avoid the drawbacks of both methods in a single analysis. Due to the characteristics of the cutting process, ALE formulation offers a very efficient modeling approach for the cutting process. A comprehensive ALE model along with strain rate and temperature dependent constitutive equations and a contact/friction algorithm is used to analyze the thermo-elasto-plastic process of plane strain orthogonal cutting. Simulation results for cutting of low carbon free cutting steel are presented and compared with available experimental data obtained under similar cutting conditions. Good agreement between the numerical and experimental results is observed.     

压电复合悬臂梁非线性模型及求解

基于功能材料的复合悬臂梁涉及多物理场耦合,其本构关系的非线性影响悬臂梁的输出及控制精度,采用Helmholtz Gibbs自由能关系建立压电材料的非线性本构模型。基于Boltzmann原理,该模型的内核函数由热能和Gibbs能量平衡决定。将模型与悬臂梁结构进行耦合,利用边界和初始条件导出压电复合悬臂梁的强解形式,并对强解进行弱化,采用Galerkin法对弱解进行离散化,利用三次B样条函数得到悬臂梁的数值解。研究结果表明,与已有文献的实验进行比较,所建立的压电材料非线性本构模型能够较好地预测复合悬臂梁的行为。