EPE泡沫塑料在多次冲击下的缓冲性能

目的预测并分析多次冲击下EPE缓冲材料的缓冲性能。方法应用应力-能量法得到并分析多次冲击下的缓冲曲线,评价EPE缓冲材料的缓冲性能变化。结果 EPE试样在经受多次冲击后,厚度会减小,缓冲性能会下降。结论在缓冲包装设计中,要充分考虑环境因素,根据物流环境条件适当增加缓冲垫厚度,使产品得到充分防护。     

空气柱衬垫缓冲性能研究

目的对空气柱衬垫的缓冲性能进行分析研究。方法通过动态压缩试验和应力-能量法得到空气柱衬垫最大加速度-静应力曲线,研究其动态缓冲性及承载力。结果得到了空气柱衬垫在不同跌落高度不同厚度的动态压缩试验曲线。结论材料缓冲性和承载能力均随着厚度增大而加强,跌落高度增大,包装件所受冲击载荷也随之增大。研究结果为进行合理缓冲包装设计提供计算依据。     

EPE和EVA发泡缓冲材料吸能特性表征

研究了EPE和EVA两种发泡缓冲材料在动态冲击下的吸能特性。将落锤冲击试验得到的载荷位移数据进行处理,绘制得到了动态应力-应变曲线和动态能量吸收曲线,并重点讨论了材料厚度、密度和多次冲击等因素影响下的曲线特征。结果表明,密度和多次冲击对吸能特性影响显著。研究结论为产品包装材料合理选择和优化设计提供科学依据。     

工控设备缓冲包装跌落试验及其仿真分析

目的研究某工控设备缓冲包装的跌落数值仿真技术。方法建立一种工控设备缓冲包装的跌落仿真模型,从仿真结果中获得跌落加速度曲线和产品的等效应力云图,观察缓冲包装的变形动画;对比缓冲包装的跌落试验,验证了跌落仿真模型;基于验证的跌落仿真模型,研究EPE衬垫尺寸对缓冲包装跌落冲击响应的影响规律。结果跌落仿真与跌落试验的加速度曲线趋势基本吻合,峰值加速度相差仅0.8%;仿真的等效应力云图显示产品满足强度要求,未发生永久变形,与跌落试验结果一致。对EPE衬垫尺寸的跌落缓冲研究表明,相对于缓冲面积,缓冲厚度的大小对跌落加速度具有更为显著的影响。结论建立的跌落仿真模型具有较高的模拟精度,为产品的缓冲包装结构设计及其优化奠定了良好基础。     

发泡聚丙烯动态缓冲性能分析

目的研究发泡聚丙烯材料的动态缓冲特性。方法对发泡聚丙烯材料进行动态压缩试验,分析密度、厚度、跌落高度对发泡聚丙烯动态缓冲性能的影响。结果发泡聚丙烯密度越大,动态压缩特性曲线最低点对应的加速度和静应力越大,最小缓冲系数越大。发泡聚丙烯厚度越大,曲线最低点对应的最大加速度越小,对应的静应力越大。随着跌落高度的增加,曲线最低点对应的最大加速度逐渐增加,静应力逐渐减小。结论在安全范围内,考虑到轻量化和成本因素,选择缓冲材料时需要综合考虑材料的密度、厚度以及实际的运输环境。     

运用数学拟合方法绘制动态冲击缓冲曲线的研究

提出了一个研究发泡聚乙烯缓冲曲线的方法。该方法使用压力-能量曲线来研究缓冲包装用发泡聚乙烯的动态缓冲性能。由于获得动态缓冲曲线需要大量的冲击实验和有效的数据,该方法是获得同种材料在多种厚度、多种跌落高度条件下的动态缓冲曲线的简便方法。该方法能够提供充足的数据,并为缓冲包装设计提供最大加速度、静应力和缓冲系数的参考。     

聚乙烯发泡塑料冲击能量的吸收及振动传递率的分析

研究了聚乙烯(EPE)发泡塑料冲击能量的吸收及振动传递率,结果表明:密度为0.025g/cm3的发泡聚乙烯在100cm跌落高度下.其动态冲击曲线随厚度的增加而下移,不同厚度试样所适合的产品的脆值及静应力也不相同;在2.21kPa静应力下,激振频率为18Hz左右时,采用发泡聚乙烯包装的包装系统会产生共振现象.     

淀粉/PP基发泡缓冲包装材料动态冲击性能研究

目的 研究不同初始应变率和湿度条件下,淀粉/PP基发泡缓冲包装材料的动态冲击性能,并构建基于湿度及应变率的动态本构模型。方法 应用冲击试验机对淀粉/PP基发泡缓冲包装材料进行不同初始应变率及相对湿度下的动态冲击实验,得到其应力–应变曲线,并构建动态本构模型。结果 动态冲击下,材料的应变率效应较为明显,该材料的应力和能量吸收随着初始应变率的增加而增加。在相对湿度为50%的条件下,当应变为0.6时,随着初始应变率由30 s⁻¹分别增加至34.6、38.6 s⁻¹,材料的应力分别增加了36.1%和50.4%,能量吸收分别增加了25.8%、36.4%。该材料对环境湿度较为敏感,该材料动态冲击力学性能随着相对湿度的增加显著降低,在初始应变率为38.6 s⁻¹条件下,当应变为0.6时,随着相对湿度由50%增加到70%、90%,该材料的应力分别下降了9.7%和11.3%。另外,构建了基于初始应变率和湿度的淀粉/PP基发泡材料的动态冲击本构模型。结论 初始应变率与湿度对材料的缓冲性能有一定的影响。基于初始应变率和相对湿度的动态冲击本构模型,通过实验进行了验证,实验数据和本构模型一致性较好,该本构模型可用于预测该材料的动态冲击应力–应变曲线。     

外包装瓦楞纸箱对缓冲性能的影响研究

目的研究外包装瓦楞纸箱对整体缓冲性能的影响。方法实验设定400,600,750 mm等3个等效跌落高度,设置单种EPE与EPE/瓦楞纸板组合材料的对比实验组,测定试样的动态压缩残余应变、最大加速度变化率,并绘制应力-应变曲线、最大加速度-静应力曲线及缓冲系数-最大应力曲线。结果EPE/瓦楞纸板的缓冲性能明显优于单种EPE,最大加速度值平均减小5%~13%,缓冲系数减小2%~10%,同时极值点的承载能力提高了20%左右。结论瓦楞纸板组合材料的缓冲性能明显增强,考虑外包装箱瓦楞纸板的缓冲作用具有实际应用意义。     

确定缓冲曲线的应力-能量法研究

应力-能量法是确定缓冲材料缓冲曲线的主要方法,其能预测任意高度的缓冲曲线,操作简便,且基于试验所得数据进行推算,可以得到较为精确完整的缓冲曲线,但由于应力-能量法是以假定缓冲材料在受到冲击过程中没有能量损失为前提,且该法较易受人为因素的影响,故利用应力-能量法的动能量公式计算得到的能量不够精确.现有对应力-能量法的应用研究可分为直接应用和改进应用两个方面,今后的研究可适当减少能量水平和跌落次数,进一步优化数据拟合函数的选取以及试验数据,从而更大程度地节省材料及试验时间,以获得更准确的缓冲曲线.     

电脑主机缓冲包装结构缓冲效果的高速摄像评价

为了评价电脑主机缓冲结构的缓冲效果,利用高速摄像测量方法,对电脑主机运输包装件冲击实验进行了冲击响应分析,研究了电脑主机包装件中EPE缓冲垫对电脑主机的防护作用。实验中分别取5,10,15 cm 3个跌落高度,利用跌落冲击瞬间缓冲垫、主机、水平滑台三者冲击作用的瞬态图像,通过采集图像进行处理和分析,得到了电脑主机的位移-时间、加速度-时间曲线以及水平滑台的加速度峰值和衬垫冲击传递率。结果表明,随着冲击高度的增加,电脑主机加速度响应随之增大,缓冲垫的冲击传递率达到50%左右,显示出EPE缓冲结构具有显著的缓冲效果。     

Impact Oscillator Model for the Prediction of Dynamic Cushion Curves of Open Cell Foams

Cushion curves enable packaging designers to optimize a design solution for a given product fragility and expected distribution environment drop height. The industry accepted techniques for developing these curves are time intensive and devoid of a physical understanding of the materials and the physics involve in energy absorption. This paper delves into a qualitative understanding of the dynamics of a platen impacting an open cell foam cushion material. An hyperelastic material model is used to describe the foam's nonlinear stress–strain relationship, while its damping and hysteretic behaviour are represented with linear viscoelasticity. Using a simple nonlinear, discontinuous model of a drop test along with numerical simulations, the study examines the physics of the impact. The numerical studies show that the model is able to provide predictions of the shock pulse's shape, duration and amplitude at various static stresses and drop heights. The dynamic cushion curves generated by the model retain the characteristic concave upward ‘trough’ shape of the experimental curves. Furthermore, the model shows that the optimal amplitude of shock absorbed for a given set of drop conditions depends on the foam's thickness and cross‐sectional area. Lastly, the model is validated using the comparison of a predicted curve and experimental data captured using a cushion tester. Copyright © 2014 John Wiley & Sons, Ltd.     

Generation of cushion curves from one shock pulse

Three methods for generating performance information relative to the shock absorbing ability of cushioning materials are discussed. The conventional method, which follows the test standard ASTM D1596, requires enormous amounts of test data and can be quite expensive in material costs, laboratory time and equipment. Two methods based on generating the dynamic stress vs. energy density curve for the material are discussed. This single curve replaces all of the published cushion curves. One method requires only 10-20 drops and predicts peak G to within ± 5% of the published values. A new method proposed here produces the same stress vs. energy curve from only one drop.     

Evaluation of Static and Dynamic Cushioning Properties of Polyethylene Foam for Determining Its Cushion Curves

A comparison of static and dynamic cushioning properties of polyethylene foam is discussed in this paper. A dynamic factor function is defined and obtained from the analysis on the experimental data from compression and cushion tests. The deformation energy per unit volume is taken into consideration to make an estimate of the maximum strain and dynamic stress data in an impact, and the peak acceleration can be predicted from the compression data corrected for the dynamic effects by the dynamic factor function. Then, the cushion curves at almost every test condition, such as different drop heights or thickness of cushioning material, can be approximated by a specially developed computer code using Matlab. This research can assist in determining the accuracy of cushion curves for all variants of a particular cushioning material from the dynamic factor function and compression test data. This new procedure will greatly simplify the experimental process for determining cushion curves. Copyright © 2014 John Wiley & Sons, Ltd.     

基于本构模型的发泡聚乙烯缓冲特性曲线研究

目的 建立EPE本构模型,并基于本构模型研究EPE缓冲系数-最大应力曲线。方法 通过静态压缩实验得到EPE应力-应变曲线,利用三次Bezier曲线拟合实验曲线,根据拟合曲线求得缓冲系数,从而得到缓冲系数-最大应力曲线。结果 利用三次Bezier曲线拟合得到了EPE分段本构模型,基于本构模型建立了EPE分段缓冲系数-最大应力曲线参数方程。本构模型、基于本构模型建立的EPE缓冲系数-最大应力曲线均收敛于分段点（0.3,0.1075）,且当拟合应力值为0.4529 MPa时,得到缓冲系数最小值（5.0362）。结论 利用三次Bezier曲线拟合得到的应力-应变曲线与实验曲线有很好的拟合度,分别基于本构模型建立的和由实验数据得到的2条EPE缓冲系数-最大应力曲线有较好的拟合度,基于三次Bezier曲线拟合的本构模型研究EPE缓冲特性曲线是可行的。     

发泡聚乙烯最大加速度-静应力曲线快速获取方法研究

目的 研究快速、准确预测最大加速度-静应力曲线的方法。方法 首先利用落锤冲击试验机获取了5个不同高度下,5种不同厚度的发泡聚乙烯的最大加速度-静应力曲线。在此基础上,分析对比文中3种不同的改进拟合法与已有的动应力与动能量多项式拟合法的区别。结果 研究发现,当不区分高度的情况下,以最大加速度因子为函数值,以跌落高度、衬垫厚度、静应力为变量进行拟合时,其代表预测精度R²的平均为0.835,相比动应力与动能量多项式拟合法的0.299 6要高。但曲线右侧的预测精度偏低。引入以静应力为变量的多项式作为修正因子后,R²的平均值为0.934。预测精度有所提高,右侧的预测偏差减小,但仍存在。在区分高度的情况下,以带有修正因子的公式进行预测时,R²的平均值为0.984,曲线向右侧预测偏差逐渐增大的现象明显改善。结论 区分高度情况下,利用带修正因子的预测公式可以快速且较准确地预测最大加速度-静应力曲线,可以为冲击防护设计及相关软件的开发提供一定的帮助。     

Predicting the Effect of Temperature on the Shock Absorption Properties of Polyethylene Foam

Polyethylene (PE) foam is a material used commonly in protective packaging for its shock absorption properties. When developing a package design intended to mitigate shock to the product, decisions are typically made based on established cushion evaluation procedures performed at standard laboratory conditions. Distribution environment temperatures, however, can vary greatly from the condition at which these materials are assessed. The research presented in this paper utilizes the stress–energy method of cushion evaluation and highlights trends in the stress–energy equations of PE foam tested at 12 different temperatures, ranging from ?20°C to 50°C. A quadratic polynomial is used to describe the variation in the stress–energy equation coefficients over the temperature range evaluated. The model developed enables cushion curve prediction for any static stress, drop height, material thickness and temperature expected over the intended range of use of the material. This model is validated by performing additional impact testing of samples at various temperatures and comparing experimentally obtained acceleration values to those predicted by the model. Further model analysis is performed to estimate the optimal static stress for the material at any temperature within the range tested and to study the variation with temperature of this optimal point. Results reveal that the model developed is capable of predicting the shock absorption properties of the material within the range of parameters tested and that the optimal static stress of the material decreases as temperature increases from ?20°C to 50°C. Application to cushion design is made to recommend an approach to designing a PE cushion system for use over a range of temperatures. Copyright © 2016 John Wiley & Sons, Ltd.