动态加载条件下青贮PE膜的机械特性研究  

Study on mechanical properties of silage polyethylene film under dynamic loading conditions

作　　者：高东明[1] 魏丹丹 万其号[2] GAO Dongming;WEI Dandan;WAN Qihao(School of Computer and Artificial Intelligence,Beijing Technology and Business University,Beijing 100048,China;Grassland Research Institute,Chinese Academy of Agricultural Sciences,Hohhot 010010,China)

机构地区：[1]北京工商大学计算机与人工智能学院,北京100048 [2]中国农业科学院草原研究所,呼和浩特010010

出　　处：《中国塑料》2025年第1期48-56,共9页China Plastics

基　　金：内蒙古自治区科技计划项目(2023YFDZ0024)。

摘　　要：针对青贮聚乙烯(PE)膜在实际工况条件下处于动态拉伸,现有相关标准基于静态加载测得机械特性难以更好表征青贮PE膜实际工况条件下的相关特性。文章对PE膜的纵向(MD)、横向(TD)方向试样进行了不同拉伸速率下的单轴拉伸试验(应变范围控制在200%以内),以及不同初始延伸率下的应力松弛试验。结果表明,PE膜的应力-应变(σ-ε)曲线呈现显著的速度依赖性和方向依赖性。拉伸过程中PE膜MD、TD方向均经历了二次屈服,随着拉伸速率增加,第二屈服伸长率减小。MD方向的第一、第二屈服强度与拉伸速率的对数(ln v)呈良好线性映射关系。拉伸速率增加可以提高PE膜的屈服强度,以实现对青贮草捆的紧密包裹,但是达到一定速率后,屈服强度变化将不再明显,而且还会降低PE膜的韧性。室温下,在较低(10%)到较高的固定初始延伸率(70%)范围内,MD、TD方向PE膜均出现了应力先快速后缓慢降低现象。广义七元件Maxwell模型能较好的描述PE膜应力松弛行为,可用于预测其长期应力松弛特性。随着延伸率增加,应力松弛量降低,应力衰减率降低,松弛模量降低,应力缓慢下降阶段模量更稳定。为实现对青贮的有效密封,要求PE膜兼具刚度和一定抗松弛能力,青贮裹包时PE膜延伸率控制在50%~70%之间较为合理。The current standards are difficult to measure the characteristics of silage polyethylene(PE)film under actual working conditions.In this study,uniaxial tensile tests at different tensile rates with a strain range within 200%and stress relaxation tests at different initial elongations were conducted on the PE film specimens in the machine direction(MD)and transverse direction(TD).The tensile test results indicated that there was a pronounced dependency on both stretching speed and direction in the stress-strain(σ-ε)profiles,and the films exhibited a secondary yielding phenomenon in both MD and TD orientations.With an increase in the tensile rate,there was a decrease observed in the elongation at the second yield.The first and second yield strengths in the MD direction showed a good linear mapping relationship with the logarithm of tensile rate(ln v).An increase in the tensile rate could improve the yield strength of the PE film.How-ever,the yield strength reduced the toughness of PE film after reaching a certain rate.Stress relaxation tests indicated that both the MD-and TD-oriented films presented a rapid decrease followed by a gradual reduction in stress across a range from a low initial stretch level(10%)to the high one(70%).The generalized seven-element Maxwell model could accurately describe the stress relaxation behavior of the PE film,which offered insights into its long-term stress re-laxation characteristics.The quantity of stress relaxation and rate of stress decay decreased with an increase in the stretch level.This indicated a reduction in the relaxation modulus as well as a more stable modulus during the slow stress decline phase.These findings suggest that to realize the optimal silage sealing,the PE films should balance stiffness with resil-ience to relaxation with an ideal stretch range of 50~70%during wrapping.

关 键 词：青贮PE膜 机械特性 拉伸速率 屈服伸长率 应力松弛 

分 类 号：TQ325.12[化学工程—合成树脂塑料工业]