粘滞阻尼和干摩擦对物品包装跌落冲击的最在加速度的影响

考虑了在跌落冲击时粘滞摩擦两种阻力同时存在对物品加速度的影响,导出了包装件受冲击作用时产品的最大响应加速度,并对之进行了了讨论。     

弹载加速度记录仪在冲击环境下的失效研究

在弹体侵彻过程中,首先分析高g值冲击对弹载加速度记录仪的影响,得出应力波作用下加载到弹体内记录仪的加速度值,并研究了加速度记录仪壳体、缓冲材料及电路板的动态结构响应,进而提出可能出现的失效模式：壳体结构的失效、缓冲材料缓冲性能的不足、芯片与PCB板相对运动导致芯片的裂纹。针对各失效模式,利用ANSYS/LS-DYNA对记录仪各防护单元进行了数值模拟仿真,得出各防护单元失效的临界冲击加速度值: 电路板失效的临界冲击加速度为1.93×104g,当加载冲击加速度为1.63×105g时,壳体发生屈曲;增大冲击加速度至5.63×106g时,缓冲材料失效。经过实弹侵彻试验,得出记录仪在1.5×105g的冲击加速度下失效。该实验结果对后续弹体实际侵彻弹载记录仪的设计及优化提供数据支撑。     

齿轮加速度噪声的研究

本文重点研究了齿轮啮合时由于冲击产生的加速度噪声,利用齿轮有误差,加载变形后齿轮的几何关系计算齿轮冲击加速度,并利用声学理论计算齿轮啮合冲击时产生的声压,由此可以定量地研究齿轮的几何参数、误差以及弹性变形对噪声的影响。     

高冲击加速度传感器横向效应及装配方式所致测试误差

针对高冲击测试只校准加速度传感器而忽略其安装方式所致测试误差,分析高冲击加速度传感器灵敏度横向效应产生原因与测试仪整体力学模型。通过Hopkinson杆冲击实验装置对传感器每轴横向效应实验分析,利用ANSYS软件分析测试仪在冲击加速度载荷20000 g时结构响应。结果表明,测试仪结构发生振动时传感器装配方式所致测试误差不可忽略。     

用爆炸式冲击试验台研究钢丝绳隔振器冲击特性

采用了一种新型的爆炸式冲击试验台，对HGGS-200型钢丝绳隔振器的冲击特性进行了试验研究。结果表明，在舰艇冲击环境下，钢丝绳隔振系统能有效的降低传递给负载压缩时的加速度幅值，但拉伸时的加速度幅值降低较少。其在承受冲击载荷时，在冲击载荷脉宽不变的情况下，随着冲击载荷幅值的增加，隔振器吸收的能量增大。     

包装间隙对包装件跌落时的影响研究

建立了产品在二次冲击时的运动微分方程,求出了发生二次冲击时包装件固有频率与跌落高度等参数的关系,得到了包装件二次冲击时加速度幅值等动态特性.     

变埋深条件下混凝土中爆炸加速度的传播规律

为了研究混凝土中不同埋深爆炸冲击质点振动加速度传播规律,运用量纲分析和自由场实验相结合的方法并引入等效当量系数的概念得出C30混凝土不同埋深爆炸冲击质点振动加速度预估公式。研究结果表明：对于C30混凝土,当装药比例埋深为0.25 m/kg1/3≤h≤1.0m/kg1/3时,随着装药比例埋深的增加,爆炸冲击质点加速度峰值随之增大,但加速度随比例埋深的衰减规律基本一致;对于不同强度的混凝土触地爆（h=0m/kg1/3）,随着混凝土强度的增大,爆炸冲击质点加速度峰值随之增大,加速度衰减规律基本一致;给出了C30混凝土不同埋深爆炸冲击质点振动加速度精度较高的预估公式。     

25kg TNT当量爆炸容器的冲击隔震研究

运用压电加速度计及精密电荷放大器，对25kg TNT当量爆炸容器在六种TNT当量加载下对邻近结构及基础产生的冲击振动进行了三点比较测试。研究结果表明，当与容器基座有直接接触的钢平台上的冲击加速度达100g时，隔振沟内的地面加速度仅4g，而隔震沟外的地面振动加速度则只有0．7g；隔振沟对振动加速度的衰减作用随载荷强度的增加而增强。     

基于激光多普勒原理的超高冲击加速度校准系统

超高冲击加速度传感器在武器研制、航空航天等高过载测量中发挥了重要的作用,为解决超高冲击加速度的校准问题,基于激光绝对法,建立了超高冲击加速度校准系统。本文介绍了系统的组成和优化方案,设计了合适的解调程序和滤波算法,对原始多普勒信号进行解调,实现了冲击加速度峰值1 × 10⁴ g ~ 2.5 × 10⁵ g,脉宽20 ~ 50 μs范围内半正弦冲击波形的绝对复现。最后对影响测量结果的不确定分量进行评定,超高冲击加速度测量不确定度为8%,对2 × 10⁵ g以上冲击加速度校准具有重要意义。     

冲击脉冲的速度变化量计量

冲击加速度峰值及脉冲宽度是描述冲击脉冲的两个重要参数,然而在实际应用中要产生标准的冲击波形会存在许多困难,这就使得冲击脉冲的速度变化量的计量变得尤其重要了。通过对冲击加速度产生过程的分析,我们将会看到,根据传统的概念将速度变化量按照加速度的积分来计算并不能反映冲击过程的真实情况,冲击脉冲的速度变化量应该为加速度绝对值的积分。     

On the measurement of the impact energy of ceramics at different loading rates in instrumented impact tests

Summary The impact energy of a ceramic is measured in instrumented impact tests by means of a novel high sensitivity striker tup. The measured impact energy shows a strongly increasing trend with increasing impact velocity. High speed cinematographic investigations indicate that a considerable part of the measured impact energy is transferred into kinetic energy of the moving specimen halves after impact. If this kinetic energy is subtracted from the measured values of the impact energy a quantity representing the true fracture energy is obtained which does not depend on the impact velocity.Published in Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 27, No. 6, pp. 23–27, November–December, 1991.     

An efficient method for estimating from sparse data the parameters of the impact energy variation in the ductile-brittle transition region

An efficient method is proposed for estimating from sparse data the parameters of the systematic variation of the Charpy impact energy in the ductile-brittle transition region of low-carbon weld steels. The parameter estimates are practically unbiased and with a very good precision even in the case of very large scatter of the absorbed impact energy. Furthermore, the parameter estimates determining the shape of the transition curve are not affected by its location along the temperature axis. The method is robust regarding the temperature corresponding to a specified impact energy level. Thus, for different type of scatter of the impact toughness and different lengths of the scatter intervals, the estimates of the temperature corresponding to a specified impact energy vary in narrow limits. The transition temperature corresponding to a specified impact energy level is estimated with a very good precision, which is important for quantifying the deterioration of properties due to embrittlement.     

刚性卵形头弹撞击角度对编织复合材料层合板侵彻特性的影响

利用一级气炮发射卵形头弹撞击2 mm厚度的编织复合材料层合板,撞击角度分别为0°、30°和45°,通过高速相机记录弹靶撞击过程,并获得弹体速度数据。基于拟合公式处理试验数据,计算获取弹道极限,分析撞击角度对弹道极限、靶板能量吸收率及其失效模式的影响规律及机制。结果表明：弹体撞击角度为45°时,靶板弹道极限最高,其次为0°,撞击角度为30°时最小。随着冲击角度增加,层合板损伤形状从菱形逐渐转变为椭球形,损伤面积随冲击速度增加而增大,且45°冲击时层合板损伤面积最大,0°和30°冲击时损伤面积近似相等。弹体初始撞击角度对靶体失效模式存在影响,弹体撞击角度为0°时,纤维断口主要是剪切应力导致的横截面。撞击角度为30°时,纤维断口主要是剪切应力和拉伸应力导致的斜截面。45°斜撞击时,纤维断口主要是拉伸应力导致的横截面。     

金属蒙皮飞机冲击威胁研究

飞机服役中会遭受外来物冲击威胁,对机身蒙皮造成冲击损伤。分别对国内南北方两航空公司的飞机维修记录进行了调研,得到了金属蒙皮飞机飞行过程中的冲击损伤分布规律;基于ABAQUS软件建立有限元模型,采用不含损伤的Johnson-Cook本构模型,研究铝板的低速冲击响应特性,设计并实施铝板低速冲击试验,对模型可用性进行了验证;得到了凹坑深度逆向推导冲击能量的计算公式,将损伤凹坑深度数据转化为冲击能量,并估算在一定概率水平下,金属蒙皮飞机可能遇到的最大冲击能量。结果显示,冲击能量较小时,铝板凹坑深度与冲击能量近似为线性关系;在指定的概率水平下,机翼、机身、翼身整体的最大冲击能量分别为21.3 J,25.5 J,33.8 J。     

The influence of the publication delay on journal rankings according to the impact factor

Summary  The inter-citation journal group is defined as a group of journals with inter-citation relations. In this paper, according to the 2003 JCR, an inter-citation relation matrix of 10 medical journals is established. Based on the transfer function model of the disturbed citing process, the calculation formula of journal impact factor disturbed by publication delays of certain journal in the group is deduced and a changing process of every journal's impact factor caused by the increase of each journal's average publication delay is simulated. In the inter-citation journal group, when a journal's publication delay increase, impact factors of all journals will be decreased and rankings of journals according to the impact factor may be changed. The closer a citation relation between two journals, the stronger the interaction of them and the larger the decrease of their impact factors caused by the increase of their publication delays.     

Approximate determination of the magnitude of the critical size in the problem of the evolution of an impact

The evolution of a nonlinear dynamic system after the action of a localized effect (impact) is examined. A semiquantitative method is suggested for determining the critical size of the impact upon exceeding which the diffusional mode of decay in the system is replaced by a wave mode of propagation. The use of the proposed technique to evaluate the critical size of an impact in a realistic model of an oceanic ecological system is demonstrated.P. P. Shirshov Institute of Oceanology, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 4, pp. 398–404, April, 1994.     

On the rigid projectile model for low velocity impacts

Most of the studies about low velocity impact aimed to determine the impact force and the impact duration. The influence of the interaction law between the projectile and the target on the response has been examined; the influence of the structure model on the response has been addressed as well. However when the projectile is much more rigid than the structure, it has always been considered as an infinitely rigid mass. This paper shows that such a model tends to overestimate the maximum impact force and underestimate the impact duration; however, a 2-degree-of-freedom (dof) model has been suitable to recover the impact force very well. Moreover, it is shown that this rigid projectile may be viewed as a rigid mass associated with a modified Hertz law. These results have been established for a sphere–sphere impact and a sphere–beam impact as well. Nevertheless, it has been shown that the 1-dof model is definitively relevant to determine the structural response: in fact the displacement of the structure provided by the 1-dof model and the 2-dof model are the same, as indicated in the last section.     

蝶形拱桥的动力冲击系数研究

通过建立车桥耦合动力学模型,编写计算程序研究了行车速度、偏载距离、结构阻尼、路面不平度、行车方向、轴距、车间距、车辆数及结构设计参数等对蝶形拱桥各构件动力冲击系数的影响。结果表明：主吊索力的冲击系数整体上随着速度的增大而增大;偏载侧主拱拱顶横向位移的冲击系数随着偏载距离的增大迅速增大,而竖向位移的冲击系数却呈现迅速下降的趋势;阻尼比使得各构件的冲击系数均有所降低;构件的冲击系数随着路面不平度等级的不同而不同;异向行驶时,左右对称的各构件冲击系数差别较大;存在某个矢跨比值使得主梁跨中挠度的冲击系数最小;采用尼尔森体系,各构件的冲击系数明显减小。     

An empirical investigation of the influence of collaboration in Finance on article impact

We investigate the impact of collaborative research in academic Finance literature to find out whether and to what extent collaboration leads to higher impact articles (6,667 articles across 2001–2007 extracted from the Web of Science). Using the top 5 % as ranked by the 4-year citation counts following publication, we also follow related secondary research questions such as the relationships between article impact and author impact; collaboration and average author impact of an article; and, the nature of geographic collaboration. Key findings indicate: collaboration does lead to articles of higher impact but there is no significant marginal value for collaboration beyond three authors; high impact articles are not monopolized by high impact authors; collaboration and the average author impact of high-impact articles are positively associated, where collaborative articles have a higher mean author impact in comparison to single-author articles; and collaboration among the authors of high impact articles is mostly cross-institutional.     

Progress and development in the instrumented Charpy impact test

Toughness is the most important characteristics for structural component materials and has been evaluated widely by Charpy impact test. Charpy test has been presented firstly in 1901, and instrumentation to record load history during impact has been attempted since 1920's. Various methods to estimate quantitative fracture toughness values under dynamic loading condition have been presented. In the development of fracture mechanics, one of the authors has successfully developed the new dynamic fracture toughness testing and evaluation system using the instrumented Charpy impact test, which is called “CAI system”. This paper introduces history of instrumented Charpy impact test and CAI system. Moreover, instrumented impact testing method on brittle materials is also mentioned. Worldwide standard on dynamic fracture toughness evaluation by the instrumented impact testing is highly expected to be established.