水晶梨运输包装件振动冲击性能实验研究

针对目前水晶梨在储运过程中的主要包装形式以及造成破损的情况,选择市场较为流通的运输包装件,按照国家测试标准进行定频、扫频、堆码、垂直冲击和跌落实验,研究水晶梨包装件损坏的主要原因。实验证明,包装件的共振频率为25.88 Hz,最大堆码层数为8层,包装件的脆值为90.88g,最大允许跌落高度为450mm。最后评价了包装件在储运过程中对水晶梨的防护能力,并提出了改进建议。     

运输包装件振动试验系统研究

在流通环境振动分析的基础上，进行了运输包装件各种振动试验的特点比较，并对随机振动试验系统的方案和实施过程等做了一定的研究，为运输包装件的优化设计打好了基础。     

果品物流运输包装件堆码振动传递性能的实验研究

以贵妃富士苹果为测试对象,模拟了其在实际运输过程中的振动载荷,进行了运输包装单件扫频振动实验,测出了其固有频率;对10层堆码进行扫频振动传递性能实验,分别测出了底层、中间层(第6层)和顶层运输包装件的固有频率、最大响应加速度和振动传递率。最后探讨了最大响应加速度、振动传递率随时间的变化规律,分析了固有频率和振动传递率峰值与堆码高度之间的关系,研究了其在模拟振动条件下的损伤规律,找出了现有包装的不足,提出了合理的包装设计方案。     

运输包装件振动特性的计算机仿真

应用有限元法对计算机主机在运输过程中的振动特性进行了计算机仿真。首先利用Pro/E建立几何模型，然后基于ANSYS进行有限元动力分析，求出了包装件的固有频率与固有振型，以及频域／时域的动态响应。     

运输包装件低气压振动模拟试验方法

目的 在常温下通过控制低气压和振动双危害因素,研究一种模拟运输的试验方法,用于评估物流包装对产品的保护性能.方法 研发一种低气压振动试验装置,将其与振动系统相结合,在实验室内模拟高原运输或飞机运输中的低气压环境条件.实现一种能够在特定的温湿度下控制低气压和振动综合环境因素的试验方法.结果 低气压振动试验系统能够满足ISTA 3A中的试验要求,根据国内外低气压试验标准和随机振动试验标准,制定了低气压振动综合试验方法.结论 对于评价高海拔卡车、铁路和航空运输包装件的模拟试验提供了可行性依据.     

包装件可控水平冲击试验

通过对国内外现状的分析,认为在实验室内进行可控水平冲击试验具有较好的模拟性能,更接近实际流通情况。试验以控制输入等级为基础,测定包装件承受各种运输环境危险的能力,可用于包装研究。     

信号采集仪运输包装件缓冲性能研究

通过对信号采集仪包装件进行振动试验和跌落试验,研究了纸浆模塑缓冲衬垫的抗振和缓冲能力.研究发现:在定频(频率4.6Hz)振动试验中,激振加速度为7.5m/s2时,产品振动响应的最大加速度为1.32g,包装件并没有发生失效、失灵或商业性破损.在扫频振动试验中,测得其共振频率分别为34.80Hz(包装件平放)和29.16Hz(包装件立放).在跌落实验中,面跌落的最大冲击加速度峰值为67.98g;棱跌落的最大冲击加速度峰值为61.50g;角跌落的最大冲击加速度峰值为24.05g.跌落实验后产品发生了严重破损.即包装件可以通过振动试验,但是在跌落试验中会产生严重损坏,所以此包装为欠包装.     

包装件在重复冲击下响应加速度计算

根据瞬态振动理论和冲击下响应迭加效应,计算单自由度包装件的响应加速度及其最大值。     

包装件跌落冲击研究现状

目的介绍包装件的跌落冲击研究现状。方法从跌落冲击机理、冲击动力学、试验和仿真模拟等方面详细讨论其发展现状,并指出各方面存在的问题。结果对于跌落冲击机理,太多的经验公式忽略了时间、阻尼、摩擦等因素的影响,物理试验不仅试验周期长、试验成本高,且很难观察到包装产品内部冲击后的变化特性,理论分析只局限于对简单的单自由度包装系统的研究,模拟仿真技术解决了物理实验和理论分析的弊端。结论目前的模拟仿真技术还很不成熟,很多数据库还未建立。     

包装件中易损零件的振动规律

根据包装件动力学模型,导出包装件受简谐激励时的易损零件振幅公式。先不考虑零件阻尼,分析衬垫阻尼比和刚度比对易损零件振动的影响,然后分析易损零件的质量比和阻尼比对自身振动的影响。在上述分析的基础上,总结了易损零件振动的基本规律。     

Stability of fruit juice drinks in aseptic packages

Cashew and passion fruit juice drinks were aseptically filled in cartons and in three types of plastic packages (with oxygen transmission rate‐OTR of 1,40; 2,96 and 13,74 cm³ (STP)/m²/day at 25 °C, 75% RH and 1 atm), with nitrogen gas flushing. No adverse effect on product sterility was found, neither were any significant changes in pH and acidity detected during storage at 25 ± 2°C. A decrease of the oxygen concentration in the headspace of the cashew juice drink plastic packs was observed, which appears to be caused by consumption of that gas in oxidation reactions. The shelf‐life of the cashew juice drink was limited to 45–70 days, after which period sensory changes attained objectionable levels (development of dark colours and deterioration of the typical fruit flavour). Passion fruit juice drink proved to be less sensitive to oxygen than cashew, since an increase of the oxygen concentration was detected in the headspace of the three plastic packs. The shelf‐life of passion fruit juice drink was limited to 70–90 days, due to deterioration of the typical passion fruit flavour and colour. Copyright © 2001 John Wiley & Sons, Ltd.     

Mathematical models and program packages for calculating pollutant transport in the atmosphere

Three mathematical models and program packages for modeling pollution of the atmosphere and the ground surface with pollutants from a source of technogenic dusting are presented. Experimental data are used to verify the programs. Translated from Inzhenerno-Fisicheskii Zhurnal, Vol. 71, No. 3, pp. 509–515, May–June 1998.     

Practical mathematical model to predict the performance of insulating packages

Thermal insulation is used in a variety of applications to protect temperature‐sensitive products from thermal damage. Several factors affect the performance of insulating packages. These factors include the packaging material, the geometry of the package, the geometry of the product, and the degree of contact between the product and the package. In this study, a comprehensive model which includes all of these factors was developed to predict the performance of the insulating package. First, an equation was derived for the calculation of the thermal resistance of a multilayered wall. The wall resistance was then used in a mathematical model which included the aforementioned factors. Basic heat transfer principles covering conduction, convection and radiation were applied to the model and the package heat penetration rate was calculated. Based on this model, several factors affecting the performance of the insulating package were discussed. Examples of the use of this model for ice requirement calculations were also included. Copyright © 2007 John Wiley & Sons, Ltd.     

Simulation of drop-weight impact and compression after impact tests on composite laminates

This paper presents finite element simulations of two standardized and sequential tests performed in polymer–matrix composite laminates reinforced by unidirectional fibers: the drop-weight impact test and the compression after impact test. These tests are performed on laboratory coupons, which are monolithic, flat, rectangular composite plates with conventional stacking sequences. The impact and the compression after impact tests are simulated using constitutive material models formulated in the context of continuum damage mechanics. The material models account for both ply failure mechanisms and delamination. Comparisons with experimental data are performed in order to assess the accuracy of the predictions.     

Prototype impact tests on ultimate impact resistance of PC rock-sheds

To confirm the ultimate impact-resistant capacity of Prestressed Concrete (PC) rock-sheds constructed over the highways in Japan, prototype impact tests are conducted by using two types of PC rock-shed frames: inverted L frame and fully rigid frame. The two types are of equal dimensions: span length=10.1 m, upper flange width=150 cm, column height=4.65 m. The impact tests are performed by iteratively and freely dropping a 3000/5000 kg steel weight onto the center of each frame covered with a 90 cm thick sand cushion. The results obtained from this study are as follows: (1) the fully rigid frame has more than 1.7 times the impact-resistant capacity of the inverted L frame with reference to input impact energy; (2) the fully rigid frame can effectively disperse the sectional forces over the whole structure; (3) the inverted L frame and fully rigid frame PC rock-sheds designed based on allowable stress design procedure have more than three and five times the margin against collapse, respectively.     

Modelling transport phenomena in refrigerated food bulks, packages and stacks: basics and advances

Transport phenomena, comprising airflow, heat and mass transfer, are key processes in refrigerated storage. This paper gives a review of approaches to modelling transport phenomena in food bulks, packages and stacks. Darcy–Forchheimer porous media models have been successfully used. Ergun theory was found not directly applicable when foods are stored in packages, which cause flow confinement and vent hole resistance, invalidating traditional theory. Heat and mass transfer in food bulks has been modelled using single- and two-phase models. Suggested modifications were demonstrated to not be generally valid, leaving much scope for further development of models for refrigerated system design. Direct CFD approaches were shown to be successful alternatives to achieve this goal.     

双声源法测量有源多层板声学性能的实验研究

采用双声源法对有源多层板声学结构的声学性能进行了测量,以压电陶瓷片作用在被激励板上使之振动产生次级声源,验证了以往研究中的一系列理论。实验研究结果表明:多孔材料可以实现多层板有源声学结构在高频范围的吸声;以最小声压为目标函数,利用FxLMS算法获得最优次级声源强度进行有源控制,可以提高结构在共振频率上的隔声量;为保证隔声量测量误差不超过5 dB,必须选择测量幅度误差小于±0.5 dB的传声器,且传声器间距必须满足一定的数学条件;传声器精度一定时,传声器间距为测试频率1/4波长的整数倍,隔声量测量误差达到最小值。     

单个蛋白质气泡的振动特性分析

根据粘弹性材料有限变形的应变能密度函数、Maxwell模型的松弛函数及气泡的变形梯度张量,推导出蛋白质气泡有限变形的应力方程.并结合气泡的动力学方程,得到气泡在内外压力差、弹性有限变形应力及粘性耗散应力共同作用下内径的非线性振动方程.利用该方程,通过数值模拟方法,对蛋白质气泡有限变形时的振动特性进行了分析,研究了气泡内外压力差、膜的厚度、膜的粘性以及气泡大小对气泡振动特性的影响.结果表明,蛋白质气泡的振动具有非线性特性,当初始压力差不同时,气泡的振动频率、振幅、速度的变化是不同的,停止振动时的大小也不相同;增加膜的厚度和膜的粘性会抑制气泡的振动,增强气泡承受载荷的能力;对于大小不同的气泡,尺寸较小的气泡振动频率高,速度衰减慢.     

多层工业厂房的振动测试及裂缝病害分析

针对多层织造厂房的振动及裂缝病害问题,采用有限元建模分析结构的振动特性,并进行了现场振动测试和裂缝病害调查。根据实测数据的时域和频域分析结果,研究了厂房及机器的振动频率和能量分布特点;结合振动幅值的对比分析,探究厂房结构裂缝病害的原因,提出了改进措施,为厂房的减振设计和裂缝预防提供建议。     

Interpretation of signals from dropweight impact tests

A spring-mass model has been developed to describe the dropweight impact response of CFRP panels. The model separates the effects of the main impact impulse, high frequency oscillations and free vibrations and can be used as a reliable guide for effective digital filtering of signals from dropweight impact tests. Whilst the model at present does not account for damage, the onset of high frequencies towards the peak impact force indicate the onset of damage in the panel. The oscillations become larger and extend over a wider plateau as the perforation threshold energy is approached.