基于ANSYS/LS-DYNA 的示位标入水冲击仿真分析

无线电示位标投放入水时承受较大冲击载荷,可能会对其结构或内部元器件造成破坏。因缺少实际的冲击载荷参数,设计时为保证满足冲击要求留有较大的刚强度余量,增大了示位标的重量和体积,而通过有限元分析手段可以方便快速地得到较为符合实际的入水冲击载荷参数。文中将示位标假设为刚体,基于ANSYS/LS-DYNA对其入水冲击过程进行有限元建模及数值分析,得到了其以不同姿态、不同速度入水时的最大冲击加速度和冲击时间等参数,这些参数作为力学输入条件可以更好地指导示位标的结构设计。     

旋挖钻机设备油液智能分析与健康监测

为了对直升机盒段件入水载荷进行分析,开展了模型垂直入水冲击试验,同时采用有限元-光滑粒子流体动力学（finite element method-smooth particle hydrodynamics,简称FEM-SPH）耦合数值方法进行仿真分析,计算了不同材料构型和速度下的过载、压力及应变结果。与试验结果进行对比表明,仿真结果与试验值吻合较好,预测的结构失效破坏模式与试验结果基本一致,可为真实直升机入水冲击的结构设计提供参考。     

直升机盒段件垂直入水数值仿真与试验

为了对直升机盒段件入水载荷进行分析,开展了模型垂直入水冲击试验,同时采用有限元-光滑粒子流体动力学(finite element method-smooth particle hydrodynamics,简称FEM-SPH)耦合数值方法进行仿真分析,计算了不同材料构型和速度下的过载、压力及应变结果。与试验结果进行对比表明,仿真结果与试验值吻合较好,预测的结构失效破坏模式与试验结果基本一致,可为真实直升机入水冲击的结构设计提供参考。     

刚性α/β尖拱体垂直姿态高速入水冲击理论建模与仿真

首先对刚性圆锥体以垂直姿态高速入水这个特殊情况进行理论分析，引入Shiffman的圆锥体流体附加质量，进行相应的简化处理，在理论上，采用动量定理方法分析其单频次高速入水冲击现象；然后重点分析刚性α／β尖拱体垂直高速入水冲击问题，引进与液面隆起有关的沾湿因子以及采用等效液面代替水平自由液面，通过Baldwin等效锥方法进行理论建模，以充分贴合实际的入水冲击现象；最后给出不同初始状态入水冲击的仿真与分析，特别是讨论了液面隆起对α／β尖拱体垂直入水冲击的影响。     

斜入水高速冲击的理论建模及缓冲分析

以入水冲击的理论动力学和入水弹道学理论为基础,根据鱼雷头部尖拱的结构外型,采用精确形体法建立斜入水高速冲击运动学和动力学耦合模型,充分考虑入水冲击引起的液面隆起现象以及流体阻力的影响。编制入水冲击耦合冲击的时间步进仿真程序,比较液面隆起现象对高速入水冲击载荷的影响,以及给出了入水初始状态条件和入水冲击载荷之间的关系和入水过程中的转动力矩的变化规律。最后比较尖拱体和截头尖拱体以50°角斜入水高速冲击的过载值,分析采用尖拱体进行缓冲卸载和截头尖拱体起到防止弹跳的理论原因。这为缓冲头帽的结构优化,忽扑、击水弹跳现象或后继的弹道提供预报以及为入水冲击缓冲技术提供了理论依据。     

高速行驶工况下履带车辆车体刚强度分析

为研究履带车辆最大速度行驶时发动机冲击载荷对车体结构的影响,在分析履带车辆最大速度行驶时所受牵引力的基础上,建立了冲击载荷作用下履带车辆车体结构的有限元模型.在Pro/E和Hypermesh软件中建立简化模型,综合网格划分,建立有限元模型.将建立好的有限元模型导入ANSYS软件中,进行模态分析和发动机冲击载荷作用下的静力分析,验证履带车辆整车刚强度是否满足设计要求,为后续结构优化设计提供设计基础.     

装载机工作装置载荷识别模型与载荷测取方法

为了研究装载机铲装作业时所受外载荷大小及变化特性,根据铲斗铰点力与斗尖力关系建立工作装置外载荷识别模型。以国产LW900K装载机为试验样机,提出了三向力销轴传感器法和动臂截面弯矩法两种载荷制取方法,进行典型作业姿态下的载荷验证和铁矿粉物料下的载荷测试试验。结果表明:提出的三向力销轴传感器法和动臂截面弯矩法都能够准确获取外载荷识别所需要的铰点载荷,销轴传感器法结果精度高于动臂截面弯矩法;试验样机工作装置所受大载荷出现在物料铲掘和卸载时刻,测得卸料时的惯性冲击载荷峰值约为400kN;通过雨流计数得到外载荷合力的均值服从正态分布,幅值服从三参数威布尔分布。载荷测试和分析结果能够有效解决装载机工作装置外载荷难以获取的问题,为载荷谱编制和疲劳特性分析提供依据。     

不同加载下的TBM刀盘瞬态动力学分析

以滚刀破碎岩石时所受冲击载荷作为瞬态载荷输入,运用有限元软件分析得到了刀盘承载规律与承载的薄弱位置并与静力学分析结果相比较。结果表明:支撑筋与法兰连接处应力存在大幅度的突变,冲击载荷对刀盘应力大小影响明显,且最大等效应力大于静力学分析结果。     

楔形体入水冲击响应的试验研究及应用

结构物在入水过程中会受到较大的冲击载荷,严重影响结构和结构内部人员的安全,因此入水问题的研究在航空航天和军事领域具有实际意义。以简单的楔形体为研究对象,进行了垂直入水的冲击试验,采用高速摄像机采集了楔形体入水过程的图像,并且考察楔形体入水过程的加速度的响应,通过滤波消除高频信号,得到合理的加速度响应值。结果表明:楔形体密闭空腔对加速度响应有重要影响。依据相似准则,通过试验模型的数据,预测了实际大尺寸的飞机结构的入水冲击响应,研究结果对入水结构的设计具有一定的参考价值。     

弹射座椅的冲击动力学分析研究

将冲击动力学和有限元分析方法相结合，建立了复杂结构在冲击载荷作用下的分析计算方法。通过对军用飞机弹射座椅所受不同冲击载荷的对比计算，分析了弹射座椅的响应规律和可能的失效形式。通过仿真计算有利于在设计阶段掌握弹射座椅薄弱环节，其方法对同类复杂结构的冲击动力学分析计算具有参考价值。     

一种旋转式液固两相流冲蚀磨损试验装置的研制

针对目前液固两相流冲蚀磨损试验装置存在实际冲角误差大、浆体浓度不均匀等问题,研制了一种旋转式冲蚀磨损试验装置。该装置允许的冲角范围为0°~90°,冲击速度为0~28.5m/s连续可调,利用搅拌叶片和导流槽实现不同冲击速度下浆体浓度的均匀性,具有速度稳定、可同时测试8个不同冲角下的试样、操作方便等特点。对低碳钢在不同冲击速度和冲角下的试验表明,所测得试验数据误差在6.8%以内,冲蚀磨损规律与经典结论一致。因此,该装置有望作为一种准确可靠的冲蚀磨损试验研究新平台而应用于耐冲蚀磨损优化设计和寿命预测等领域。     

The ricochet of dumb-bell shaped projectiles

Retardations and rotations were measured for five double-ended or dumb-bell shaped (d.s.) projectiles having spheres separated by a light weight rod at specific distances. The projectiles were fired into sand at approximately 100 m/sec and at an impact angle of 10°. Experimental data indicate that for identical sizes of sphere, initial speed, impact angle and projectile mass, the forces of ricochet are independent of the interspherical distance and seem to depend only on the geometry of the leading face.Tests were also carried out with two spherical and five d.s. projectiles at various entry speeds with 5°, 10° and 15° impact angles and it was found that the crater volume in sand is proportional to the initial momentum of the projectile.     

Average Velocity Measurements in Six Automotive Torque Converters Part II: Turbine Measurements

The internal flow fields of two automotive Plexiglas torque converter turbines with three different pumps were examined. A laser velocimeter was utilized to measure the velocity flow field at the turbine inlet and mid-planes in the six different geometry combinations; the stator was the same for all combinations. The turbine geometries differed only by the inlet blade angle, while the pump geometries differed only by the exit blade angle. The torque converter was operated at three different turbine/pump rotational speed ratios: 0.065 (near stall), 0.600, and 0.800 (near coupling point). For all geometries at the inlet plane the flow is fairly uniform in the blade-to-blade direction at all speed ratios. Velocities are most uniform in the core-to-shell direction at high speed ratios, but high velocities move near the shell at lower speed ratios. At the mid-plane, at low speed ratios the velocities are significantly higher near the pressure surface but as the speed ratio increases, the gradient decreases. At low speed ratios velocities are higher near the shell but this distribution becomes uniform at higher speed ratios. In general the flow became more uniform as the speed ratio increased. Variations in the pump exit blade angle had effects on both inlet and mid-plane velocity distributions and are documented. Variations in turbine inlet blade angle altered the inlet and mid-plane flow fields, but less so than the pump variations. A clockwise circulatory secondary flow pattern at the turbine inlet plane was observed for all geometries and, conversely, counter-clockwise circulatory secondary flow patterns at the mid-plane were recorded. Resulting vorticities were found to depend on geometries and speed ratios. The turbine leading edge incidence angles were found to strongly depend on the speed ratio, ranging from positive to negative, as well as pump and turbine blade angles.     

Electrochemical behaviour of stainless steel 304 alloy in erosion–corrosion conditions and synergism effect

Abstract

A study has been made of the erosion–corrosion behaviour of stainless steel (SS) 304 in tap water in the presence and the absence of solid particles. Water at ambient temperature impinged in various angles (15–90°) on specimen surfaces at different velocities (7·85–14 m s^–1) and sand concentrations (0·43–2%). In this research, potentiodynamic, electrochemical impedance spectroscopy and weight loss measurements were used to study the damage mechanism and to estimate corrosion rate. The SEM micrographs and optical microscopy images were used to study the corrosion morphology. Under test conditions, protective passive film and non-protective film formations formed on SS 304 surface. It was found that maximum corrosion–erosion rate happened at the impact angles between 60 and 75°. The synergism effect was positive in all conditions and it was greater for the lower angles, the higher velocities and the higher solid contents.     

不同工况下机车车体碰撞过程数值模拟

对铁路内燃机车正面碰撞进行仿真分析,得到了在撞击质量和撞击速度变化时,机车车头部位的变形、速度、碰撞力以及能量的变化规律,并将碰撞力和能量的变化拟合成三维曲面形式。结果表明,碰撞产生的塑性变形主要集中在车体前端,在撞击质量或撞击速度较小时,将较快出现碰撞反弹现象;由数据点拟合的三维曲面可得到任意撞击速度和撞击质量的碰撞力和碰撞能量,为相关机车车体设计和碰撞试验提供基本数据参考。     

Mapping erosion–corrosion of carbon steel in oil–water solutions: Effects of velocity and applied potential

In this study, the erosion–corrosion performance of carbon steel was investigated in crude oil, reservoir water, and a mixture of both solutions at a range of applied potentials, velocities and impact angle. The application of such work is to upstream and downstream oilfield conditions, where the proportions of hydrocarbon and water may vary during the extraction process over time. Following exposure of the carbon steel in the crude oil, the extent of erosion was greater than that of corrosion, whilst in the reservoir water, the erosion and corrosion contributions were similar. Regimes of erosion–corrosion were proposed based on the variation in erosion behaviour at various impact angles and applied potentials in the environments studied. Mechanistic changes were identified on erosion–corrosion maps as a function of velocity and applied potential at various impact angles, indicating important transitions in erosion–corrosion processes in the oil/water environments.     

EFP侵彻圆柱形带壳装药影响因素的数值分析

基于ANSYS LS-DYNA软件对EFP侵彻圆柱形带壳装药的数值模拟.通过对不同形状、不同速度以及不同侵彻角度EFP倾彻圆柱形带壳装药的分析,来研究其几个主要影响因素规律.仿真结果发现,准球形EFP比尾翼型和直杆型EFP更容易引爆带壳装药.同种形状的EFP,垂直冲击时效果最好.     

负泊松比曲边内凹蜂窝结构的面内冲击动力学数值研究

利用数值方法研究了具有负泊松比效应的可变弧角曲边内凹蜂窝结构的面内冲击动力学性能,讨论了冲击速度和弧角对曲边内凹蜂窝结构的变形模式与吸能能力的影响。研究结果表明:改变冲击速度和弧角的大小会影响曲边内凹蜂窝结构的变形失效模式;当冲击速度较高时,蜂窝结构内的应力波动范围较大,结构的体能量吸收值随弧角的增大逐渐增大;当冲击速度较低时则不存在上述现象。当弧角大于120°时,曲边内凹蜂窝结构具有负泊松比效应,该结构的吸能能力高于其他弧角所对应的正泊松比蜂窝结构的吸能能力,该现象与冲击速度无关。     

基于调车工况的车辆纵向冲击数值模拟研究

根据由车钩缓冲器和心盘组成的铁路货车纵向受力特点,利用Matlab软件建立铁路货车调车冲击的动力学模型,分别研究不同轴重车型、不同刚度阻尼、不同制动阻力状态及不同冲击模式对车辆纵向冲击特性的影响。结果表明,随着我国铁路货车轴重的增大,车钩连挂处、车体与转向架连接处承受的纵向惯性力也随之增大。阻抗特性呈凸型的缓冲器能吸收更多的车辆冲击能量,可适应更大的调车冲击需求。较小的车体底架结构刚度及车体与转向架连接刚度有利于缓和车辆的纵向冲动。被撞车的制动阻力作用会使车辆速度衰减的更快,但也将引起更大的车钩和心盘冲击。冲击模式对车钩和心盘处的冲击影响差异很大,三重冲三重模式下的车钩力最大,三重冲一空模式下的心盘力最大。     

RETRACTED ARTICLE: Penetrator strength effect in long-rod critical ricochet angle

3D numerical simulations were performed in order to further investigate the role of penetrator strength in the interaction of long-rods and oblique targets. Three distinctive regimes resulting from oblique impact depending on the obliquity, namely simple ricochet, critical ricochet and target perforation, were investigated in detail. Critical ricochet angles were calculated with a full 3D explicit finite element method for various impact velocities and strength of target plates and projectiles. Numerical predictions were compared with existing two-dimensional analytical models and test results. It was predicted that critical ricochet angle increases with decreasing impact velocity and that higher ricochet angles were expected if higher strength target materials are employed. But there are differences between analytical models and 3D numerical simulation results or test results. The causes for these discrepancies are established by numerical simulations which explore the validity of the penetrator strength parameter in the analytical model as a physical entity. As a matter of fact, in this paper we first investigate the role of penetrator dynamic strength using two-dimensional simulation which resulted in different penetrator strengths out of different impact velocities. Next, by applying these amounts for penetrator strength in Rosenberg analytical model the critical ricochet angle is calculated. Finally, a comparison between the present analytical method with the 3D simulation and test results shows that the new analytical approach leads to modified results with respect to Rosenberg ones. This paper was recommended for publication in revised form by Associate Editor Jeonghoon Yoo Kamran Daneshjou, is University Professor at Iran University of Science and Technology. He studied his MSC and PhD at aeronautical Engineering de-partment of Imperial college of Science and Technology in London. His own research is at the interface of solid mechanic, finite element and electromagnetic lunchers to address the sustainable development of aerospace and solid mechanic projects. His publications include 7 books and over 100 scientific papers. This article has been retracted due to copyright issues that cannot be resolved.