Simulation of orbital debris impact on the Space Shuttle wing leading edge

A series of three dimensional hypervelocity impact simulations has been performed to study the effects of orbital debris impact on the Space Shuttle wing leading edge. The simulations employed an improved hybrid particle-finite element method and an orthotropic elastic-plastic material model recently developed for reinforced carbon–carbon. The simulation results are consistent with the available experimental data, and suggest the use of momentum scaling to estimate damage effects for impact conditions outside the range of current light gas gun technology. Projectile shape and orientation effects appear to be modest for flat plate projectiles at impact velocities above the ballistic limit.     

Physics of deformation and fracture at impact loading and penetration

The structure, dislocation substructure, and mechanical properties of the targets made of four aluminum alloys after a impact loading by kinetic energy projectile have been investigated. The formula for approximation of the ballistic limit velocity by indentation technique is proposed. It has been shown that the maximum nonequiaxiality of the grain shape, increase of dislocation density, and decrease of dislocation cell size correspond to the 40–70% of plastic deformation at static compression for the investigated aluminum alloys.     

Large-scale molecular dynamics simulations of hyperthermal cluster impact

Using multimillion-atom classical molecular dynamics simulations, we have studied the impact dynamics of solid and liquid spherical copper clusters (10–30 nm radius) with a solid surface, at velocities ranging from 100 m/s to 2 km/s. The resulting shock, jetting, and fragmentation processes are analyzed, demonstrating three distinct mechanisms for fragmentation. At early times, shock-induced ejection and hydrodynamic jetting produce fragments in the normal and tangential directions, respectively, while sublimation (evaporation) from the shock-heated solid (liquid) surface produces an isotropic fragment flux at both early and late times.     

基于重构规则的企业应用系统影响分析方法

企业应用系统需进行频繁重构以响应变化，如何保证重构的完备性和正确性是重构工程中需要解决的一个关键问题。重构需求作用于业务模型，进而映射为相应软件系统的变化。该文给出了基于业务规则的业务元模型与重构元模型，并基于该模型简要地描述了应用系统的统一重构过程。随之对重构操作进行了分类，定义了重构规则的表达形式，并给出了基于重构规则的影响分析方法。最后给出了应用实例。     

Characterization of Material Properties of HPS-485W (70 W) TMCP for Bridge Girder Applications

There are currently two methods of production for A 709 Grade HPS-485W (70 W)—quenching and tempering (Q&T) and thermomechanical controlled processing (TMCP). The TMCP enables plates to be rolled in longer lengths than is possible with Q&T; however, because of its recent introduction and a lack of material testing, relatively little is known concerning the effect of this new production method upon the intraplate variability of both tensile strength and toughness. Data from 96 tensile tests show that yield and ultimate strengths of HPS-485W (70 W) TMCP may be dependent upon plate thickness and orientation. The average yield strength was found to be lower than the 485 MPa (70 ksi) limit, while the average ultimate strength was within acceptable limits. Seventy-five Charpy V-Notch (CVN) specimens were tested, and all met the 48 J at ?23°C (35 ft-lb at ?10°F) AASHTO Zone III requirement for minimum toughness. Overall it was seen that HPS 485W (70 W) TMCP shows promise for bridge girder applications, but thicker plates do not currently meet all the ASTM A 709 standards, and should be reevaluated before being used in bridge construction on a large scale.     

Optimizing the design and impact behavior of a polymeric enclosure

This paper focuses on the application of finite element analysis to design an electronic enclosure with improved impact resistance properties. With the growing push towards miniaturization there is a constant decrease in the wall thickness of the enclosure applications. This necessitates use of ribs to enhance the impact resistance. This study aims at investigating optimal design of ribs for improving impact resistance. The ‘DSGZ’ phenomenological constitutive model, which uniformly describes the entire range of stress–strain constitutive relationship of polymers under any monotonic loading mode is used to predict the plastic failure energies. Several simulation runs were performed based on the design parameters using a 2³ factorial design of experiments. The results from these simulations were used to analyze and study the various design parameters and its influence on the impact energy. It was found that when designing enclosures with ribs with an objective to maximize the impact failure energy, stress should be laid on optimizing the ratio of wall thickness to rib height within permissible limits while center-to-center spacing between the ribs and rib thickness do not have a significant effect.     

Projectile Attack of Surface Scattered Munitions Comparing Closed Form Theory with Live Trials

This paper describes research that has been undertaken to develop a low‐cost vehicle‐mounted gun system to provide for the rapid disposal of surface deployed munitions (principally mines) from up to 100 m distance. Inert high‐shock projectiles with optimized internal, external and terminal ballistic performance have been developed during this study. Work on shock wave interaction was reviewed in terms of the Rankine‐Hugoniot jump equations, and Walker and Wasley criterion has been employed using two modifications from James to predict initiation in this divergent shock application.     

反击式破碎机的发展

指出反击式破碎机在破碎过程中发挥的重要作用。对其结构特点作了介绍,并叙述了在国内的发展状况及发展方向。     

8240同承滚道断裂原因剖析

某雷达交用户使用一年多,天馈系统中的8240轴承滚道发生断裂,从其所承受的动载荷或静载荷看,安全裕量是足够的。作者在对系统进行深入分析的基础上,结合阵地的实际情况,分析了问题产生的原因,阐述了防止类似事故的设计原则。     

硅酸铝纤维／铝合金复合材料的高温疲劳特性

采用加压铸造法来制备硅酸铝短纤维增强铝合金材料,并通过与ZL109合金的对比试验,研究高温下材料的冲击疲劳特性。结果表明;在本试验条件下硅酸铝短纤维增强铝合金复合材料的高温冲击疲劳性能不如ZL109合金,但是随试验温度的提高,ZL109合金的抗冲击疲劳能力下降的速率比硅酸铝短纤维增强铝合金复合材料的快。