Heating a Metal Target Subjected to Pulsed Laser Radiation

Results are given of the investigation of the mechanisms of energy transfer to a target in different modes of a microsecond pulse of laser radiation acting a metal target in standard-density air.     

硬化期受扰动混凝土的抗硫酸盐侵蚀性能

凝结硬化期间的施工扰动,可能使混凝土产生砂浆微裂缝与骨料位移,进而影响其强度及耐久性.为分析硬化期扰动对混凝土抗硫酸盐侵蚀性能的影响,采用振动台模拟工程扰动,借助超声波和扫描电子显微镜(SEM)等测试手段,系统研究了硬化期受扰混凝土抗硫酸盐侵蚀的劣化规律,探讨了其损伤劣化机理.结果表明:临近初凝(贯入阻力值为3.5～11.5 MPa)和临近终凝(贯入阻力值为19.5～28.0 MPa)的扰动对混凝土影响较小,受侵蚀后试件质量和相对动弹模量的变化规律与未受扰混凝土基本一致.硬化中期(贯入阻力值为11.5～19.5 MPa)的扰动对混凝土性能影响明显,使混凝土抗压强度降低14％,抗折强度降低20％;硫酸盐腐蚀进程中,混凝土质量在90次循环后开始出现明显下降,相对动弹模量在130次循环后出现急剧下降,经250次循环后达到0.60,此时基准混凝土的相对动弹模量仍为0.90;SEM结果表明,受扰混凝土内部微裂纹增多,结构密实性变差,硬化期扰动加速了混凝土在硫酸盐侵蚀环境下的劣化.     

浸没的圆柱壳在冲击波作用下动响应的Galerkin解法

研究了无粘、无旋和不可压缩流体中两端简支圆柱壳在给定冲击波作用下的动响应。圆柱壳的运动方程中考虑了流体动压力和冲击波压力的共同作用，通过将冲击波压力分布函数表示为Ｆｏｕｒｉｅｒ级数有限项形式，并利用Ｇａｌｅｒｋｉｎ方法对耦合方程进行数值求解，得到了圆柱壳在冲击波作用下的位移响应特性     

硬化期受扰动混凝土的抗硫酸盐侵蚀性能

凝结硬化期间的施工扰动,可能使混凝土产生砂浆微裂缝与骨料位移,进而影响其强度及耐久性。为分析硬化期扰动对混凝土抗硫酸盐侵蚀性能的影响,采用振动台模拟工程扰动,借助超声波和扫描电子显微镜(SEM)等测试手段,系统研究了硬化期受扰混凝土抗硫酸盐侵蚀的劣化规律,探讨了其损伤劣化机理。结果表明:临近初凝(贯入阻力值为3.5~11.5MPa)和临近终凝(贯入阻力值为19.5~28.0MPa)的扰动对混凝土影响较小,受侵蚀后试件质量和相对动弹模量的变化规律与未受扰混凝土基本一致。硬化中期(贯入阻力值为11.5~19.5 MPa)的扰动对混凝土性能影响明显,使混凝土抗压强度降低14%,抗折强度降低20%;硫酸盐腐蚀进程中,混凝土质量在90次循环后开始出现明显下降,相对动弹模量在130次循环后出现急剧下降,经250次循环后达到0.60,此时基准混凝土的相对动弹模量仍为0.90;SEM结果表明,受扰混凝土内部微裂纹增多,结构密实性变差,硬化期扰动加速了混凝土在硫酸盐侵蚀环境下的劣化。     

Investigation of Flow in the Vicinity of Porous Material on a Cylindrical Body Subjected to Flow

The results are given of an experimental investigation of the distribution of velocity components in a flow of air in the vicinity of a hemispherical permeable blunting of a cylindrical body under conditions of low injection intensity. A numerical simulation of the flow structure is performed for the parameters corresponding to those used in the experiments. Comparison of the results of physical and numerical simulation revealed a number of special features of flow in the boundary layer on a curved surface under conditions of its gasdynamic conjugation with the inner cavity.     

Buckling of Cracked Laminated Composite Cylindrical Shells Subjected to Combined Loading

A series of finite element analysis on the cracked composite cylindrical shells under combined loading is carried out to study the effect of loading condition, crack size and orientation on the buckling behavior of laminated composite cylindrical shells. The interaction buckling curves of cracked laminated composite cylinders subject to different combinations of axial compression, bending, internal pressure and external pressure are obtained, using the finite element method. Results show that the internal pressure increases the critical buckling load of the CFRP cylindrical shells and bending and external pressure decrease it. Numerical analysis show that axial crack has the most detrimental effect on the buckling load of a cylindrical shell and results show that for lower values of the axial compressive load and higher values of the external pressure, the buckling is usually in the global mode and for higher values of axial compressive load and lower levels of external pressure the buckling mode is mostly in the local mode.     

轴向冲击作用下泡沫铝填充圆管吸能特性研究

基于金属圆管移动塑性铰理论,建立一种考虑偏心率效应和相互作用效应的泡沫铝填充圆管轴向冲击移动塑性铰分析模型,利用LS-DYNA软件对填充结构进行冲击仿真试验.结果表明,移动塑性铰模型和静态塑性铰模型相比,移动塑性铰模型计算的理论结果与仿真结果具有更好的一致性.泡沫铝填充圆管的平均压溃载荷与偏心率m有关,m存在最优值,冲击速度越大,m的最优值也越大.受轴向冲击载荷压溃时,泡沫铝与圆管之间存在明显的相互作用效应,在分析吸能特性时应加以考虑.     

水下爆炸载荷作用下加筋圆柱壳的响应分析

运用MSC．DYTRAN软件，首先比较了网格划分密度的改变，耦合法的选取及边界条件对计算的影响。并在合理的网格划分和耦合方法选用的基础上，设置符合实际的边界条件，在壳体的迎爆面，侧爆面和背爆面各选取一个点，在分析光壳的响应的基础上，详细计算了加筋圆柱壳对水下爆炸冲击波的响应。比较分析了不同的尺寸参数对结构抗爆性能的影响，并做了综合讨论，计算中考虑了材料的应变率强化效应。在此基础上验证了增加壳体厚度，减小加筋间距和增加加筋高度等有利于提高加筋圆柱壳抗爆性能的方法，同时得到了一个适合本例计算的较优化模型。     

Brittle Cracking of a Cylindrical Spiral Gear of Axle Gearbox

A cylindrical spiral gear of locomotive axle gearbox failed after standing in site for 10 days. The failed gear had been assembled with the spiral gear-shaft. Inspection in site found that cracking occurred on the spoke plate between the shaft bore and the oil-pressed hole. The gear teeth are required to be carburized, but the surfaces of the shaft bore and the oil-pressed hole of gear are surface-coated to prevent carburizing. The crack initiated from the surface of oil-pressed hole and propagated along the radial of the oil-pressed hole. Metallurgical examination reveals that anti-carburizing measure was not conducted on the surface of oil-pressed hole as the specification. A simplified evaluation of the maximum hoop tensile on the wall of oil-pressed hole subjected to internal pressure for swelling bore is far insufficient to lead to brittle fracture. Delayed fracture of gear, the predominance of intergranular fracture micro-mechanism, and the presence of several secondary micro-cracks in the depth of case layer on the oil-pressed hole surface are a clear indication of hydrogen embrittlement. Hydrogen absorption occurred during gas carburizing process.     

Endurance of VT1-0 Titanium Alloy Subjected to Solid-Solution Surface Hardening

We study the influence of solid-solution hardening (by the method of thermal-diffusion saturation from a rarefied oxygen-containing atmosphere) of the surface layers of VT1-0 titanium alloy on its fatigue resistance in bending with rotation. It is shown that the dependence of fatigue limit on the degree of surface hardening has a maximum whose value depends on the depth of the hardened zone. We managed to increase the original fatigue limit of the alloy by 38% for a relative increment of the surface hardness K of 70% and a depth of the hardened zone l of 30 μm. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 3, pp. 119–122, May–June, 2005.     

水下爆炸气泡对内加筋圆柱壳结构毁伤机理分析

以内加筋圆柱壳为研究对象,对近距离非接触爆炸作用下气泡的脉动载荷以及气泡溃破高速射流对内加筋圆柱壳结构的毁伤机理进行计算分析,并且探讨结构参数、药包位置等相关物理量对结构变形特征与毁伤模式的影响。研究结果表明,水下爆炸气泡膨胀产生的膨胀脉动冲击造成结构的整体变形,另一方面气泡溃破所造成的高速射流(速度 > 100 m/s)则会对局部区域造成严重破坏,弹塑性边界以及自由液面效应会对气泡的形状产生显著的影响。     

Analysis of Metal Matrix Laminated Cylindrical Panels Subjected to Nonuniform Temperature Loading

The moderately large deflection response of metal matrix composite (MMC) cylindrical panels to nonuniform thermal loading is addressed. Temperature dependence of both elastic and viscoplastic properties of the metallic matrix is taken into account; this suggests that a nonuniformly heated panel should be considered as a nonhomogeneous structure. At each loading increment, a micromechanical analysis is performed to establish the instantaneous thermoinelastic constitutive law at each point of the panel. This is followed by a structural analysis that yields quasi-static thermal response of antisymmetrically laminated MMC panels. Results are presented for simply supported and clamped graphite-aluminum panels and for two types of in-plane boundary conditions. The effects of boundary conditions, lamination angle, panel's curvature, length-to-thickness ratio, and different types of spatial temperature distributions are illustrated. Comparisons with results obtained using an approach that treats the effect of temperature-dependent material properties in a simplified manner are shown. Comparisons with the corresponding elastic solutions (which neglect the inelastic effects in the metallic matrix) are given.     

Compositional and Microchemical Evidence of Piezonuclear Fission Reactions in Rock Specimens Subjected to Compression Tests

Abstract: Energy‐dispersive X‐ray spectroscopy (EDS) is performed on different samples of external or fracture surfaces belonging to specimens used in piezonuclear tests [Strain 45, 2009, 332; Strain (in press); Phys. Lett. A. 373, 2009, 4158]. For each sample, different measurements of the same crystalline phases (phengite or biotite) are performed to obtain averaged information of the chemical composition and to detect possible piezonuclear transmutations from iron to lighter elements. The samples were carefully chosen to investigate and compare the same minerals both before and after the crushing failure. Phengite and biotite, which are quite common in the Luserna stone (20 and 2%, respectively), are considered owing to the high iron concentration in their chemical compositions. The results of EDS analyses show that, on the fracture surface samples, a considerable reduction in the iron content (～25%) is counterbalanced by an increase in Al, Si, and Mg concentrations.     

含铝炸药爆炸作用下的水中圆柱壳动态响应数值研究？

为了研究圆柱壳在含铝炸药水下爆炸载荷作用下的响应规律,利用非线性动力学软件AUTODYN计算了3种不同配方含铝炸药的远场冲击波特性,并将计算值与文献实验值进行对比,计算误差能够稳定在5％以内,之后结合ABAQUS程序模拟了含铝炸药冲击载荷作用下水中圆柱壳的动态响应。在30 kg药量下分析比对了圆柱壳体加速度、速度及有效塑性应变的变化规律,随后确定了各炸药致使圆柱壳结构失稳的临界药量,并以PBXW-115为例研究了临界药量作用下的圆柱壳破坏模式。结果表明,AUTODYN与ABAQUS程序的联用,能够有效地模拟圆柱壳在含铝炸药远场冲击波作用下的动态响应;含铝炸药致使圆柱壳单元达到屈曲失效所需药量普遍低于理想炸药RDX。     

静水压对加筋圆柱壳受水下爆炸冲击载荷作用的影响

应用有限元法，分析静水压对受水下爆炸载荷时的加筋圆柱壳体的变形及破坏模式的影响。通过对壳体结构及外部水域进行建模，并考虑流固耦合及空泡因素，模拟出结构受水下爆炸载荷及静水压力联合作用下的响应。通过比较有和没有外部压力时，不同冲击波下结构的破坏形式，得出外部水压对耐压结构受爆炸载荷时响应的影响。     

深水环境中水下爆炸冲击波作用下圆柱壳动态响应的数值模拟研究

基于通用有限元程序ABAQUS,运用静力分析和动力分析相结合的研究方法,对深水环境中圆柱壳在水下爆炸冲击波作用下的动态响应进行了数值模拟研究,分析了深水中圆柱壳动态响应的影响因素,研究了圆柱壳的破坏随深度而变化的规律.研究结果表明:在同样的冲击波载荷作用下,圆柱壳的毁伤程度随着所处深度的增大而逐渐加重;爆距不变时,不同爆心方位所对应的圆柱壳的响应不同;预应力的存在使圆柱壳毁伤程度有所增加,并且预应力对圆柱壳响应的影响与爆心方位有关;能够导致圆柱壳破坏的炸药质量随深度增加而迅速减小;圆柱壳在浅水中和深水中的破坏机制不同,前者是由于冲击波的作用,而后者是冲击波和静水压力联合作用的结果.     

Generalization of the Classical Formula of Stability of Cylindrical Shells to the Case of Spiral Stiffeners

The stability of a cylindrical shell with eccentric spiral stiffeners in the case of axial compression is considered. A simple computational formula for determination of the critical stress has been obtained. The formula contains all the necessary mechanical and geometric characteristics of the shell and the stiffeners and is, in essence, a generalization of the well-known and widely used classical formula for isotropic smooth shells. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 197–200, July–August, 2005.     

Static and Dynamic Strength of Paperboard Containers Subjected to Variations in Climatic Conditions

The variability in climatic conditions during product distribution, especially across large distances, can be significant and is well known to affect the mechanical properties of many packaging materials. As the use of environmentally friendly materials, such as paperboard and bio‐cushions, increases, the challenge associated with overcoming the effects of extremes in temperature and relative humidity in the distribution chain becomes critical. To date, in the case of paperboard boxes, this is dealt with by accounting for the loss of static (compression) strength with increasing relative humidity. However, no method exists to address the dynamic loads induced by vehicle shocks and vibrations especially for configurations that involve stacked boxes and where the vibration intensity within the stack is influenced by the dynamic characteristic of the boxes themselves. In such scenarios, it is the variation in the stiffness of the box as a function of environmental conditions and dynamic load that needs to be established. This paper describes the evaluation of the fatigue resistance of paperboard boxes subjected to random excitation and compares the results with those obtained from quasi‐static compression tests under various environmental conditions. Results reveal a lack of correlation between the static and dynamic tests. This finding is attributed to changes in internal damping of the paperboard box samples which, when reduced, results in increased dynamic force. The paper concludes that static testing alone is insufficient to establish the fatigue resistance of stacked packaging subject to variations in climatic conditions. Copyright © 2017 John Wiley & Sons, Ltd.