水果卡车运输模拟振动的研究

论述了水果运输模拟振动试验的目的，探讨了水果运输的振动损伤与振动加速度、振动次数的关系，分析了运输模拟试验的振动频率、振动加速度、振动时间等参数的确定方法。     

果蔬运输振动频谱检测分析及对水果损伤的研究

检测了不同路况下,钢片弹簧悬架的卡车运输黄花梨过程中车厢前后垂直振动,并且比较了卡车车厢内不同装载位置梨的损伤情况.试验结果表明:卡车在运输过程中,振动加速度最大值发生在2.5～4Hz之间.在2～40Hz之间,车厢后部的振动加速度显著高于车厢前部,梨的损伤程度与其在车厢内的不同位置的振动水平有关.车厢后部的梨损伤要高于车厢前部同样高度堆放的(P＜0.05),在车厢内同一位置,装在顶部塑料箱内的梨损伤情况显著高于装在底部塑料箱的(P＜0.05).     

基于LSTM和响应分解的冲击载荷识别方法研究

同一量级的冲击载荷所产生的动响应要远大于静态响应,因此准确识别冲击载荷对于航空器结构件的动强度设计、校核与结构健康监测都具有重要意义。该文章提出的方法主要针对一般线性结构的冲击载荷识别问题,从实测冲击响应应变信号出发,主要解决了冲击载荷与响应信号样本长度不一致这一突出矛盾。首先基于冲击响应信号分解方法来进行振动信号特征提取,然后基于长短期记忆神经网络对载荷和响应信号样本特征进行映射,从而实现冲击载荷识别。通过对挂架模型实测冲击载荷信号进行识别,结果表明4种工况下,该方法识别的冲击载荷的均方根相对误差小于0.6,相关系数大于0.94。结果初步表明,在理想的试验环境中,该方法具备一定的识别精度。     

冲击载荷下包装物随机响应的数字特征

据跌落高度变化样本值,用最大似然法求得冲击加速度峰值的概率密度函数,据此得出该随机变量加速度峰值的数字特征。假设包装件为单自由度结构系统,由其加速度激励的频率响应函教而求出包装物响应加速度峰值的数字特征,以此作为缓冲包装设计的依据。     

主推进轴系振动特性和冲击响应预估

１　前　言近代舰船由于各种原因,产生严重艉部振动的现象时有发生,导致该种现象的因素很复杂,其中不乏由主推进轴系引起的振动,因此,在轴系设计阶段精确预估轴系的振动特性和动态响应显得越来越必要了。从７０年代后期起,很多研究包括转子数学模型和方程的求解已经做了大量工作。如最常用的传递矩阵法［１］、运用有限元技术,写出转子振动微分方程,并由子结构或模态方法缩减自由度数目［２］［３］。在舰船设计和评估中,冲击响应是一个重要的参数,最常用是冲击试验来模拟各种冲击条件,如可用跌落式冲击机进行冲击激励,但由于…     

粘滞阻尼三次函数弹性缓冲包装系统的跌落冲击响应

研究具有粘滞阻尼和三次函数强非线性弹性缓冲包装系统的跌落冲击响应。基于系统 时的响应特征和渐近法的原理，得到了阻尼系统冲击响应的一次和二次渐近解，所得响应表达式对缓冲包装设计具有重要价值。     

浅论商品在冲击振动作用下的响应

商品包装缓冲，防震方法和技术设计必须针对商品流通过程中商品在冲击，振动作用下的响应规律进行。商品缓冲、防震的原理就是选择适当的缓冲材料和包装结构，使传递到商品上的冲击力和振动力小于商品自身的强度，商品在冲击，振动作用下的响应与环境条件参数，商品属性参数和缓冲材料参数密切相关，现试将这四者之间的关系作初步论述。     

连续冲击载荷对包装产品的影响

本文通过理论与实验分析后认为，运输过程中的连续冲击载荷会引起产品发生破损，它应作为运输包装设计的参数之一。     

利用冲击试验获得缓冲材料振动传递率的研究

基于冲击信号是一非周期信号,在冲击脉冲作用下通过测量冲击激励和在该激励下的冲击响应,对其进行频谱分析,最后得出振动传递率.本文论述了这一方法的理论依据以及可行性.     

Illuminating Origins of Impact Energy Dissipation in Mechanical Metamaterials

Elastomeric mechanical metamaterials have revealed striking ability to attenuate shock loads at the macroscopic level. Reports suggest that this capability is associated with the reversible elastic buckling of internal beam constituents observed in quasistatic characterizations. Yet, the presence of buckling members induces non‐affine response at the microscale, so that clear understanding of the exact energy dissipation mechanisms remains clouded. In this report, the authors examine a mechanical metamaterial that exhibits both micro‐ and macroscopic deformations under impact loads and devise an experimental method to visualize the resulting energy dissipation mechanisms. By illuminating the dynamic distribution of strain in the metamaterial, the authors uncover a rational way to program the macroscopic deformation and enhance impact mitigation properties. The results emphasize that mechanical metamaterials clearly integrate materials science and structural engineering, encouraging future interdisciplinary studies to capitalize on the opportunities.

     

Effects of Stacking Sequence and Impactor Diameter on Impact Damage of Glass Fiber Reinforced Aluminum Alloy Laminate

The methods of numerical simulation and test are combined to analyze the impact behavior of glass fiber reinforced aluminum alloy laminate (GLARE). A new failure criteria is proposed to obtain the impact failure of GLARE, and combined with material progressive damage method by writing code of LS-DYNA. Low velocity impact test of GLARE is employed to validate the feasibility of the finite element model established. The simulation results have been shown that progressive damage finite element model established is reliable. Through the application of the finite element model established, the delamination of GLARE evolution progress is simulated, various failure modes of GLARE during impact are obtained, and the effects of stacking sequence and impactor diameter on the impact damage of GLARE are obtained.     

Numerical Modelling of Damage Response of Layered Composite Plates

The paper addresses the problem of impact on layered fibre composites. The behaviour of composite laminates under impact loading is dependent not only on the velocity but also on the mass and geometry of the impactor. Using micromechanical Mori-Tanaka approach, mechanical properties of the laminate have been calculated utilizing the material constants of the fibre and matrix. General purpose FEM software ABAQUS has been modified by means of user written subroutines for modelling of composite laminate and rigid impactor. The kinematics of the impact has been simulated using transient dynamic analysis. Employing user defined multi point constraints, delamination zones have been modeled and visualised     

果品运输中的机械损伤机理及减损包装研究进展

果品在贮运过程中承受静载、挤压、振动、冲击等载荷形式的作用,形成了以塑性变形为主的现时损伤和以粘弹性变形为主的延时损伤.果品采后由于贮运引起的机械损伤和耐贮性的下降是果品采后损耗的主要原因.采用科学有效的措施减少果品采后机械损耗具有重要意义.文中综述了国内外这方面的研究成果,着重论述了果品的流变特性、运输过程中果品的损伤机理与规律、模拟试验技术以及减损包装技术.     

移动式预冷设备在果蔬保鲜中的应用

本文讨论了发展移动式预冷设备的必要性,具体介绍了冰水预冷、注冰预冷、小型机械制冷冷库预冷、差压预冷、蓄冷板预冷、真空预冷、蒸发冷却预冷等实用的移动式预冷设备,指出移动式预冷设备在果蔬保鲜中具有广阔的应用前景。     

猕猴桃电商包装随机振动响应及果品损伤研究

目的 研究猕猴桃在5种不同电商包装形式内的振动响应和损伤情况，为猕猴桃电商包装提供理论基础和科学指导。方法 以“红阳”猕猴桃为研究对象，对目前市场常见的5种形式的猕猴桃电商包装(EPE衬垫、EPS衬垫、PET带盖托盘、瓦楞隔板和EPE网套)分别进行扫频振动和随机振动试验研究，获得各包装内猕猴桃的共振频率、振动传递率、果品损伤面积、硬度、质量损失率、可溶性固形物含量等参数，分析包装形式对猕猴桃果实振动响应和振后损伤的影响。结果 PET带盖托盘和EPE网套包装下猕猴桃的共振频率较小，在20~30 Hz，处于公路运输振动范围内，易发生共振受损。瓦楞隔板包装的猕猴桃共振频率最大，在50~75 Hz内，受到的振动能量较低。5种包装下猕猴桃的振动传递率从大到小为EPE网套、EPE衬垫、瓦楞隔板、EPS衬垫、PET带盖托盘，PET带盖托盘包装的振动传递率最低，为1.68，隔振效果最好;EPE网套和EPE衬垫包装的振动传递率较高，为3.16~3.72，隔振效果较差。振后24 h果实硬度下降了13.5%~48.7%、软化率提高了9.0%~40.4%、质量损失率提高了6.7%~100.0%、可溶性固形物含量(SCC)提高了3.2%~15.0%、损伤面积为981~6 931 mm²。结论 5种包装中PET带盖托盘包装对果实的保护效果最佳，瓦楞隔板和EPE网套包装的保护效果较差。     

Evaluation of Damage in Concrete Under Uniaxial Compression by Measuring Electric Response to Mechanical Impact

The paper proposes a method of evaluating damage in concrete under uniaxial compression. The evaluation procedure is based on measuring the electric response to mechanical impact. Measurements are made periodically while the external load is gradually increased. The experiment is carried out using samples of normal weight concrete. The algorithm for evaluating concrete degradation under uniaxial compression is based on analyzing signals in terms of time and frequency. The paper analyzes a number of measured and computed parameters of the electric response: the energy attenuation coefficient of the electric responses; the correlation coefficient of the signal spectra prior to and during the loading; the spectral centroid of the signal spectrum and the frequency of the dominant spectral peak. Experimental results show that the array of the collected data allows for evaluation of cracking processes in concrete under an external compressive load. The proposed method can be used to monitor the development of damage in concrete under uniaxial compression.     

Carbon Nanotube Sensing Skins for Spatial Strain and Impact Damage Identification

Impact damage, excessive loading, and corrosion have been identified as critical and long-term problems that constantly threaten the integrity and reliability of structural systems (e.g., civil infrastructures, aircrafts, and naval vessels). While a variety of sensing transducers have been proposed for structural health monitoring, most sensors only offer measurement of structural behavior at discrete structural locations. Here, a conformable carbon nanotube-polyelectrolyte sensing skin fabricated via the layer-by-layer technique is proposed to monitor strain and impact damage over spatial areas. Specifically, electrical impedance tomographical (EIT) conductivity mapping techniques are employed to offer two-dimensional damage maps from which damage location and severity can be easily and accurately quantified. This study deposits carbon nanotube-based sensing skins upon metallic structural plates with electrodes installed along the plate boundary. Based on boundary electrical measurements, EIT mapping captures both strain in the underlying substrate as well as damage (e.g., permanent deformation and cracking) introduced using an impact apparatus.     

制冷机房设备振动传递及防治措施

本文探讨空调制冷机房设备振动的产生、传递途径、设备减振、管道系统隔振的设计和防治措施等问题。