机电系统损坏与消除次冲击的必要性

本文阐述了在跌落冲击试验时主冲击与次冲击的特点。计算了产品系统对整个冲击过程的响应,并分析了产品损坏的原因。当产品进行精密冲击试验时,消除次冲击是很有必要的。     

爆炸分离冲击试验分析

论述了爆炸分离冲击环境的特点,介绍了一次模拟爆炸冲击试验时所采用的试验方案以及针对试验中暴露的问题所采取的措施;并结合试验结果,对如何适应爆炸冲击环境提供了参考意见。     

温度湿度对产品的影响分析

环境应力试验是产品质量鉴定及保证不可缺少的条件之一。论述了温度、湿度及冷热冲击等不同的环境应力对产品的影响。试验证明,通过必要的环境应力试验,可以减少产品的循环,去除缺陷产品,降低产品故障率。     

激光冲击次数对1Cr11Ni2W2MoV不锈钢高周疲劳性能的影响

高周疲劳是航空发动机部件的主要故障之一。通过对1Cr11Ni2W2MoV不锈钢进行不同次数的激光冲击强化(LSP)处理,研究冲击次数对激光冲击强化材料高周疲劳性能的影响。对不同处理状态的试件进行常温振动疲劳试验,采用X射线衍射(XRD)应力分析仪、扫描电镜(SEM)、金相显微镜等手段研究冲击次数对材料组织和力学性能的影响。试验结果表明,随着LSP冲击次数的增加,1Cr11Ni2W2MoV不锈钢表面粗糙度增大,组织细化层厚度没有变化,残余应力梯度变小,残余压应力层深度增加,1次冲击后,残余压应力层深为1.8mm,3次冲击后为2.5mm。表面残余压应力随着冲击次数增加而逐渐趋于饱和,饱和值接近于-100%σ0.2。振动疲劳试验结果表明,疲劳寿命随着LSP次数增加而提高,但提高幅度减小。在σmax=640MPa应力水平下,1次冲击后试样疲劳寿命是未强化试样的3.8倍,3次冲击后试样疲劳寿命是未强化试样的5倍。经分析,多次冲击时的冲击波叠加效应使得冲击波传播到材料的更深层,从而使材料组织变形层和残余应力影响层更深,高周疲劳寿命提高更大。     

振动与冲击试验

电信终端产品入网前,要经过一项重要的检验过程,就是振动与冲击试验。该试验旨在模拟产品送达用户之前可能发生的诸如运输、搬运、挤压及跌落等力学方面的破坏作用,以检验产品的抗损毁能力。 所谓冲击试验,就是在一个较短的时间内,将一个高量级的输入脉冲力加到试品上进行试验。冲击是一种迅速运动,可激发试验样品的动态响应(谐振),但总体挠曲(应力)却很小。试品的加速度响应通常作为测量的试验变量。冲击试验不能代替加速度试验,反之亦然。     

集成电路机械冲击试验的研究

机械冲击是集成电路检验中评估元器件特性的关键试验,试验目的是测定元器件能否承受中等程度的冲击,这种冲击是模拟器件在装卸、运输或现场操作中由于突然受力或运动状态的改变而产生的。文章主要分析了集成电路机械冲击试验的原理,论述了冲击加速度值、脉冲持续时间与冲击台底座材料之间的关系,提出试验过程中操作人员应该注意的问题。     

冲击响应谱分析

传统的冲击试验采用的是典型冲击脉冲源,不能完全模拟真实的冲击环境,冲击响应谱通过冲击引起的响应大小来衡量冲击的破坏力,将传统试验方法中对冲击环境的模拟转变为对冲击损伤的模拟,从而使冲击试验具有对实际冲击环境更加真实的模拟效果。     

通信机楼冲击电流浅析

当通信机楼停电,油机启动保障时,如果机楼冲击电流太大,将影响油机使用寿命甚至无法启动。文中通过对单套整流电源和对整栋机楼的冲击电流试验,研究了影响冲击电流的相关因素,并讨论了减小冲击电流的相应方法。     

冲击响应谱试验参数的设置

与经典冲击相比,冲击响应谱试验可以更真实地模拟军用设备在使用和运输过程中所遇到的复杂冲击环境.文中介绍了冲击响应谱的基本概念,阐述了冲击响应谱试验参数的设置方法及同一参数不同设置对试验的影响.验证试验结果表明,按此方法进行试验参数设置可获得较高的冲击响应谱试验精度.     

7050航空铝合金激光冲击强化残余压应力研究

用激光冲击强化处理装置对重要航空铝合金结构材料7050T7451、7050T7452不同工艺条件下进行了冲击强化处理,并对试件激光冲击区存在的残余压应力进行了测量。结果显示经激光冲击处理后试件表面具有极高的残余压应力,可达-200MPa以上;经过两次迭加冲击处理能够极大提高强化效果,其残余压应力相比单次冲击处理提高1倍以上;单面两次迭加处理与双面依次迭加冲击处理相比,试件正面(先冲击一面)残余压应力水平相当,且双面依次迭加处理试件反面(后冲击一面)的残余压应力远小于正面。以上一系列重要结果均为首次通过试验发现,对激光冲击强化处理技术的实际工程应用具有指导性意义。最后还给出了相应的表层组织结构分析和疲劳寿命试验结果。     

Succession-dependent shock models

A system that is subject to external shocks of different types is studied. Each shock can lead to a breakdown or an accident, stopping the system performance with a certain probability, depending on the succession of shock arrivals and times since the latest shocks. A case of a fixed number of shocks is treated for illustration. Another model presents shocks arriving according to a non-homogeneous Poisson process or a renewal process.     

Two-unit standby reliability system subject to effective and non-effective random shocks

This paper considers a system consisting of two units. The system experiences shocks after certain random intervals. These random intervals are independently and identically distributed each with a general probability density function. Further, the shocks are classified into three types according to the effect of the shocks on the system: Type I, the shock that has no effects on the system, Type II, the shock increases the failure rate and Type III, the shock that fails the system. The system can fail either due to a shock of Type III or due to the internal stress and strain of the operation of the unit or due to two successive shocks, the first shock being of Type II. The repair times of the units are assumed to be exponentially distributed. The mean time to system failure (MTSF), steady state availability of the system and expected number of times the repairman is required are investigated. Finally, MTSF-shock rate and steady state availability-shock rate figures are drawn for special cases and certain interesting results are observed therefrom.     

中空激光加载下板料位移和厚度分析

采用数值仿真的方法,研究了中空激光加载下板料成形过程中位移和厚度参量的变化过程,通过试验对中空激光冲击成形后板料的位移和厚度进行了测量,并与实心激光下板料的位移和厚度进行了对比。结果表明,加载区域内板料首先获得速度产生位移并向外扩展,带动中心板料快速成形并产生最大位移;厚度减薄首先发生于加载区域边界并向外扩展,板料中心和加载区域内板料快速减薄。中空激光冲击成形后板料的截面轮廓呈高斯曲线分布,板料中心区域减薄最多,其次是加载区域,其变形均匀性优于实心激光冲击下的板料变形。研究工作对提高激光冲击成形性能具有重要意义。     

激光冲击铜薄膜的应力波传播特性模拟分析

为了研究冲击波的传播特性,采用有限元分析方法模拟不同参量激光冲击铜薄膜的过程,结合应力波理论分析了膜-基系统的动态应力波传播特性。结果表明,激光能量为30mJ时,冲击波为弹性波,薄膜在单次冲击作用下,其内质点速率最大为-0.018mm/s,3次冲击作用下,薄膜内部质点速度与残余应变变化较小;激光能量为120mJ时,冲击波为弹塑性波,3次冲击比单次冲击质点最大速率减小了26.44%,残余应变深度增加了35.48%。这对研究冲击波传播具有指导意义。     

On the development of a successive damage shock model based on Palm probability

Given that a system is susceptible to habitual shocks, each shock causing damage to the system leading to ultimate system failure on receipt of a threshold number of shocks (which is a random variable); the problem comprises of obtaining the expected survival time of the system right from the point it receives the first shock. The technique of Palm probability has been employed to develop the model and estimations of the parameters have been made by the method of moments.     

激光斜冲击强化曲轴

激光加工连杆轴颈与曲柄连接处圆角区域曲面时、激光光束不能保证与曲面上每点切线方向始终是垂直的,这个过程就是激光斜冲击强化过程.本文用江苏大学激光技术研究所生产的YAG激光器,斜冲击强化连杆轴颈与曲柄连接处圆角区域.冲击后在受冲击区域显微硬度比未冲击区域提高了65%-75%左右,残余应力比未冲击区域提高了80%-100%左右,使用寿命提高了150%.而这种显微硬度和残余压应力的提高对提高材料的疲劳寿命、抗磨损能力和抗腐蚀能力等表面机械性能都是有益的.激光斜冲击曲轴连杆轴颈与曲柄处圆角,残余应力和显微硬度提高最大处为圆角中心处,而这个位置正是易产生疲劳裂纹处,而圆角边缘处是疲劳强度非敏感区,对裂纹的产生影响不大.     

The availability of inspected systems subject to shocks andgraceful degradation

This paper studies maintained systems with nonself-announcing ("hidden") failures that deteriorate due to both shocks and graceful degradation. Shocks occur according to a Poisson process, shock magnitudes are i.d.d. random variables, and between shocks, deterioration occurs at a constant rate. Inspections are performed periodically. Using regenerative arguments, an expression is derived for limiting average availability. This expression provides insight into the effect of system life distribution on availability, and suggests opportunities for more effective inspection strategies     

Poisson shock models leading to new classes of non-monotonic aging life distributions

Suppose a device is subjected to a sequence of shocks occurring randomly in time according to a homogeneous Poisson process. In this paper we introduce a class of non-monotonic aging distributions, the so-called New Worse then Better than Used in Failure Rate (NWBUFR) and New Worse then Better than Average Failure Rate (NWBAFR). It is shown under appropriate conditions on the probability of surviving a given number of shocks that the non-monotonic aging classes NWBUFR and NWBAFR arise from suitable Poisson shock models.     

Transistorized ground-fault interrupter reduces shock hazard

The ground-fault interrupter is the most successful device for eliminating the hazard from low-voltage electric shocks in the home, on the farm, and in industry. It is the newest of four recognized means?isolation, insulation, grounding, and shock interruption?for reducing the danger from electric shock and it is, by far, the most radical.     

An economic discrete replacement policy for a shock damage model with minimal repairs

A discrete replacement model for a repairable system which is subject to shocks and minimal repairs is discussed. Such shocks can be classified, depending on its effect to the system, into two types: Type I and Type II shocks. Whenever a type II shock occurs causes the system to go into failure, such a failure is called type II failure and can be corrected by a minimal repair. A type I shock does damage to the system in the sense that it increases the failure rate by a certain amount and the failure rate also increases with age due to aging process without external shocks; furthermore, the failure occurred in this condition is called type I failure. The system is replaced at the time of the first type I failure or the n-th type Il failure, whichever occurs first. Introducing costs due to replacement and mininal repairs, the long-run expected cost per unit time is derived as a criterion of optimality and the optimal number n∗ found by minimizing that cost. It is shown that, under certain conditions, there exists a finite and unique optimal number n∗.