后峰锯齿形脉冲激励下洗衣机包装系统的冲击特性

研究了后峰锯齿脉冲激励下洗衣机缓冲包装系统的冲击响应。结果表明缓冲垫刚度参数β和δ可调整箱体和桶体的冲击谱，是重要的缓冲包装设计。     

发泡聚乙烯包装系统冲击谱研究

建立了发泡聚乙烯缓冲包装系统的缓冲模型,运用四阶变步长Runge-Kutta方法,计算出了此非线性系统在半正弦脉冲冲击下的冲击响应谱,并讨论了参数λ1,λ2和λ3对冲击谱的影响规律。     

缓冲包装分析软件开发

建立了各类缓冲包装系统在不同加速度脉冲激励下的统一的动力学模型，开发了缓冲包装分析系统应用软件。只要输入有关冲击、材料和产品特征参数，便可方便地显示缓冲包装的冲击响应。本软件为优化缓冲包装设计提供了有力工具。     

蜂窝型缓冲包装系统冲击特性分析

基于MATLAB对蜂窝型缓冲包装系统的冲击特性进行数值分析,研究了蜂窝型缓冲系统在半正弦波脉冲激励下的冲击响应谱,并讨论了相关参数对它们的影响,对该类系统的缓冲设计具有重要价值.     

过阻尼对缓冲包装设计的影响

根据单自由度、过阻尼的包装件动力学模型，导出包装件受冲击作用时产品的最大冲击加速度和缓冲材料的最大形变的公式。并与无阻尼系统进行了比较。     

悬挂式弹簧包装系统的冲击特性研究

以悬挂式弹簧缓冲包装系统为研究对象,建立了矩形脉冲激励下系统几何非线性无量纲动力学方程,得到了系统的最大冲击响应谱。讨论了无量纲脉冲激励幅值、悬挂角度以及系统阻尼等对冲击谱的影响规律。研究表明,无量纲脉冲激励幅值、悬挂角度、系统阻尼等对系统冲击响应峰值影响显著,增加系统阻尼可有效降低系统加速度响应峰值。研究结论可为悬挂式弹簧缓冲系统的设计提供理论依据。     

半正弦波冲击时发泡聚苯乙烯衬垫破损边界曲线的研究

为研究发泡聚苯乙烯缓冲衬垫包装材料在半正弦波脉冲激励下的冲击响应,建立了动力学模型,应用数值计算方法,从而得到产品包装系统的冲击谱和破损边界曲线,结果表明,脉冲幅值、发泡聚苯乙烯缓冲衬垫的系统参数(α、β)对系统冲击谱和破损边界曲线有显著的影响.     

矩形波冲击下C 楞瓦楞纸板系统的冲击谱研究

基于C 楞瓦楞纸板动态本构模型,建立了C 楞瓦楞纸板包装系统动力学模型。借助三维冲击谱、破损边界曲面的概念,利用Rnuge-Kutta 算法,研究了C 楞瓦楞纸板缓冲包装系统在矩形波冲击下,不同阻尼、线性参量、正弦参量、正切参量对C 楞瓦楞纸板包装系统易损件冲击谱和破损边界的影响。计算结果表明:C 楞瓦楞纸板缓冲性能受阻尼系数、线性参量、正弦参量及正切参量的制约,且对C 楞瓦楞纸板缓冲包装系统的冲击谱和破损边界有显著影响。     

立方非线性双层包装在矩形方波冲击下破损边界曲线的研究

建立了双层包装的非线性包装缓冲模型,运用四阶Runge-Kutta方法,算出模型冲击响应谱及其破顿边界曲线,得到了质量比、阻尼比、材料增长率比对冲击谱和破损边界曲线的影响规律.     

根据冲击响应谱(SRS)确定产品冲击脆值新概念

实践证明,缓冲设计五步法存在保守因素,尤其在确定产品冲击脆值时更为突出,最终致使包装结构为过度包装.现提出根据实际输入激励下冲击响应谱(SRS)确定新的产品冲击脆值概念,此概念可为缓冲包装设计克服上述弊端提供一个可行方法.     

Nanosecond pressure pulses propagating at anomalously high velocities in metal foils

We have studied the process of nanosecond compression pulse propagation in metal (aluminum, copper, and steel) foils. It was found that the compression pulse velocity in the foil may significantly exceed the longitudinal sound velocity in the corresponding bulk material. The results emphasize the necessity of very carefully interpreting the data for submicrosecond and shorter impact loading. The presence of a sufficiently long nonstationary shock wave process at the surface subjected to a short impact perturbation (with the wave characteristics significantly differing from those of a steady-state wave process) requires a more detailed analysis of the mechanism of shock wave formation in solids taking into account their discrete structures.     

FATIGUE BEHAVIOUR OF A RAIL STEEL UNDER LOW AND HIGH LOADING RATES

Abstract— In this study, both sinusoidal wave loading and rectangular pulse (impact) loading are applied to a sample of rail steel in order to compare the growth rates for a surface fatigue crack. The results show that the rectangular pulse (impact) loading gives a crack growth rate on average 5 times that of the sinusoidal wave loading but can be almost 100 times in some instances. There are distinct differences between the fractograph patterns under the two modes of loading. The fractograph under sinusoidal wave loading clearly exhibits the pearlite structure of the material but under impact loading this microstructure is not revealed; only a quasicleavage pattern is observed. Analysis of the experimental fatigue crack growth data indicated that the surface fatigue crack growth rate behaviour could be described by the Paris-type relationship.     

两装药水下爆炸毁伤目标振动信号时频分析

针对某水下目标抗水下爆炸试验数据,研究两装药水爆炸下冲击波的相互作用及气泡脉动的相互作用现象,分析非平稳结构响应信号时频特征,分别提取前爆冲击波、后爆冲击波及前爆气泡脉动三个不同时段信号进行能量与频率分析,并由此确定不同时段对目标毁伤的影响。结果表明,后爆冲击波能量最大,前爆冲击波与后爆冲击波均处于较宽频率范围,主要作用在780 Hz以上,前爆气泡脉动能量主要作用在100～400 Hz内。与结构自振频率频段重合,因此前爆气泡脉动作用不可忽视。     

Prediction of cushion curves of polymer foams using a nonlinear distributed parameter model

Polymer foams are commonly used in the protective packaging of fragile products. Cushion curves are commonly used within the packaging industry to characterize a foam's impact performance. These curves are two-dimensional representations of the deceleration of an impacting mass versus static stress. Cushion curves are currently generated from exhaustive experimental test data. This study represents the first time that the physics of the mass-cushion impact have been analysed by modelling the foam as nonlinear, continuous rod. Using a single mode of vibration and excluding the effects of damping, the maximum displacement during the impact can be obtained from a polynomial describing the maximum elastic energy in the foam. The displacements can be used to recover the amplitude of the deceleration shock pulse. Numerical and analytical analysis of the model with damping is considered in its ability to predict the shock pulse shape, duration, and amplitude at various static stresses, foam thickness, and drop heights as compared with experimental data. Furthermore, both the analytical and numerical results agree and are primarily within the expected lab-to-lab variability of 18% documented in ASTM D1596 - Standard Test Method for Dynamic Shock Cushioning Characteristics of Packaging Material.     

食品模拟液对抗菌涂层中Nisin扩散性的影响

影响抗菌剂扩散性的因素有很多,食品模拟液是其中一个重要的因素。将1gNisin加入到壳聚糖中制备成抗菌涂层,涂覆于薄膜后分别接触100ml2％的蔗糖溶液、2％NaCl溶液以及水,在25℃下用考马斯亮蓝法测量Nisin的扩散量,通过计算扩散系数来评价在不同食品模拟液中Nisin的扩散性。结果表明,Nisin在2％蔗糖溶液中的扩散系数最大,其次是水和2％氯化钠溶液。     

水下爆炸载荷作用下加肋圆柱壳应变响应研究

采用加肋圆柱壳结构模型模拟潜艇结构,对其在水下爆炸冲击载荷作用下的响应过程进行试验研究。结果表明:采用应变测量的方法对结构进行模态分析是可行的;受附连水质量的影响,加肋圆柱壳结构的低阶湿模态频率较干模态频率显著下降;在爆炸载荷作用下,距离爆炸点越近结构承受的冲击作用越严重,越容易产生塑性破坏;应变的最大响应是冲击波载荷和一次脉动压力载荷共同作用的结果,第二次脉动压力对结构的动态应变响应贡献不明显。     

光电脉搏波信号处理中呼吸干扰的抑制

动态光谱的检测精度与光电脉搏波的幅值检测精度直接相关．为了获取较高的幅值检测精度,抑制光电脉搏波中的呼吸干扰,采用基于相干平均的脉搏波特征参数重构滤波和小波变换相结合的方法对光电脉搏波原始测量信号进行处理．首先用相干平均法获取脉搏波特征参数并重构光电脉搏波信号;然后对原始信号减去光电脉搏波后的剩余部分进行小波频率分析,并提取呼吸干扰,处理结果表明,本文的方法可以提取到高精度的光电脉搏波幅值信息,抑制大部分的呼吸干扰,从而改善动态光谱的检测精度．     

On the errors associated with the use of large diameter SHPB, correction for radially non-uniform distribution of stress and particle velocity in SHPB testing

The large diameter (up to 100 mm) Split Hopkinson Pressure Bar (SHPB) setup is used throughout the world to test large-cell heterogeneous materials, small structures, etc. This paper proposes a correction method to take into account the non-uniform distribution of stress and particle velocity (non-plane wave effect) in large diameter setups, following the theory of wave propagation in an infinite cylindrical elastic or viscoelastic rod. Such a non-plane wave effect depends on the pressure bar diameter and the high-frequency components contained in the signals. This correction procedure can be performed together with the wave dispersion correction, which is already incorporated for many large diameter bars used. For the various metallic and Nylon viscoelastic bars (up to 60 mm diameter) available in our laboratory, the relative difference between the average values of the particle velocity (and stress) in a cross-section and that calculated with a standard one-dimensional analysis is found to be inferior to 5%. However, this difference increases with a higher impact velocity, because signals containing more important high-frequency components are generated by higher impact velocities. In order to find an upper limit of the potential error for bars of various diameters, the theoretical pulse signal for a perfect impact between two infinite cylindrical rods is used, which gives the highest signal spectrum. With this theoretical pulse, such an upper limit of the potential error for different bar diameters (up to 200 mm) is found. It shows that the potential average error can reach up to 12% for a 100-mm-diameter bar currently used in the world.     

冲击波形调节器的原理分析

在碰撞试验中,一般的阻尼制动器对制动加速度的波形调节并无特殊要求,对有特殊要求的阻尼制动器需要使用额外的波形调节装置。文章对一种波形调节器的结构及其工作原理进行介绍与分析,通过对设计参数的仿真研究,证明调节器的设计在原理上是可行的,可方便地通过调节阀芯的运动速度来改变制动过程中冲击波形的脉宽和幅值,从而满足不同的冲击试验要求。     

Method of measurement of the dynamic strength of concrete under explosive loading

Within the framework of the search for the method of determination of the strength properties of concrete under the action of an explosion or high-velocity impact, suitable for large scale concrete samples, the evolution of the compression pulse in plates or rods made of concrete with compressive strength of 30 MPa was investigated. It was found that wave configuration consisting of the ramped elastic precursor with insignificant stress jump at the front followed by a dispersed plastic shock wave is formed in the plates under uniaxial shock compression. In this experimental configuration, the compressive strength of the material is not identified. Experiments with concrete rods of various diameters have demonstrated the scalability of the wave process. It was established that the compressive fracture of the rods occurs at a distance of around twice their diameters and is accompanied by the fast decay of the load pulse after that weakly decaying elastic wave was propagated along the rods. The measurements of parameters of the compression pulse at the end of the fracture zone allowed us to determine the value of the dynamic compression strength of concrete equal to \(105\pm 20~\hbox {MPa}\), which turned out to be 3.5 times higher than the static strength.