【作者】 田羽；

【导师】 曹国荣；

【作者基本信息】 北京印刷学院 ， 材料物理与化学， 2007， 硕士

【摘要】 纸浆模塑衬垫对产品的保护作用是依靠缓冲结构单元的变形来实现的,所以对单元的结构设计是提高纸浆模塑衬垫力学性能的研究重点。但是到目前为止,纸浆模塑衬垫的结构设计和力学性能测试都存在较大问题。一方面,实际应用中的结构设计还采用经验设计法,缺少现代技术手段和设计标准,使设计出的纸浆模塑衬垫可靠性能差。为保证衬垫的结构强度,往往依靠增加衬垫厚度或采用较复杂的结构,这样既浪费了纸浆材料,又增加了模具成本,最终导致衬垫成本的增加;另一方面,纸浆模塑衬垫的力学性能测试也没有行业标准或国家标准可以依据,如果应用发泡塑料材料的测试标准则会带来较大的误差,以上两个问题已经成为纸浆模塑衬垫扩大应用领域和性能提高的“瓶颈”问题,严重制约了国内纸浆模塑衬垫的推广使用。论文提出利用有限元方法,在分析软件ANSYS中实现高效、合理的结构设计方法,研究结果实现了在ANSYS中有效的模拟纸浆模塑衬垫的结构单元,并在垂直方向上施加静态载荷,对实际响应过程进行仿真。为保证有效地模拟纸浆模塑衬垫的结构单元,有限元分析所需的原始材料参数采用实验方法测得,并且对纸浆模塑衬垫进行实际静态压缩测试,作为仿真计算结果的进一步比较修正,以确定二者之间的修正系数。同时对衬垫的动态力学性能(冲击缓冲性能和振动传递特性)进行测试研究。(1)通过对纸浆模塑材料的拉伸实验,得到模拟纸浆模塑材料参数:在22～26℃的室温下,含水量为7.8～8.1%的纸浆模塑衬垫材料的紧度为5.7e-7 g/cm3,弹性模量为150MPa,泊松比0.01,将以上各值作为结构单元模拟的材料原始参数。(2)测试衬垫的静态抗压性能,作为效验和修正仿真结果的依据。运用统计方法得到纸浆模塑衬垫的静态载荷成正态分布,因此可以利用其样本的期望值估计整体的抗压性能。由于整个衬垫的抗压强度与衬垫的结构单元数成线性关系,故可以通过对单个单元的静态压缩测试得到整个衬垫的抗压性能,这为纸浆模塑衬垫的力学性能测试提供了理论依据。(3)测试纸浆模塑衬垫的冲击缓冲性能,由于纸浆模塑衬垫的缓冲机理与其它材料不同,其缓冲曲线与其它材料有明显的不同,应依靠提高结构强度和优化结构设计来提高缓冲性能。(4)自行设计振动传递特性的测试方法,得到实验中的塔状纸浆模塑衬垫的共振区域在10Hz左右,最大传递率为1.370。(5)通过ANSYS模拟纸浆模塑衬垫的塔状结构单元和对其实际压缩响应过程进行仿真,分析单元侧面六个典型位置节点的载荷时间曲线和应力时间曲线,得出最大的极限载荷集中于侧面中心位置,并且曲线符合实际测试规律,因此以中心附近节点的力-位移曲线为准,研究单元高度对抗压性能的影响,垂直高度从7.5mm到47.5mm,每升高2.5mm做一次压缩仿真,得到模拟单元的抗压性能随高度增加而先增强后下降,在27.5mm高度时达到极限载荷最大的结论。更多还原

【Abstract】 The structure design of moulded pulp pad unit is the key point for its mechanics performance research, because the pad’s protection relies on the distortion of its structure unit. While some big problems exist in both structure design and mechanic performance test so far away. One hand the structure design methodology in daily manufacture mainly adopts experience running short of modern technology and standard, leading to unreliable production. In order to guarantee the structure intension of pad, the suppliers will increase its thickness or make it much more complicated, followed by waste of pulp and increase of pulp cost. On the other hand, there are not any industrial or national mechanics performance standards for the test of moulded pulp pad, and serious errors would be brought on if the standards for plastic materials are used for moulded pulp pad. The two problems mentioned have been the choke point for the application and elevation of performance of moulded pulp pad, as well as the restriction for the production’s popularization.This paper describes an efficient and logical finite element analyses method with CAE ANSYS to implement structure simulation for moulded pulp pad and imitation of static compression test.In order to imitate the structure unit of moulded pulp pad availably, the material parameter needed in the finite element analyses must be gotten from real test, and the analyses result must be compared and corrected by real static compression test result, to confirm the correction modulus between them. At the same time dynamic performance of pad are tested, including cushion performance under impact and librating transformation ratio.(1) Found the simulation parameters of moulded pulp material through draw experiments: tightening degree 5.7e-7 g/cm3 under 22～26℃and water contained 7.8～8.1%;Elastic modulus: 150MPa; Poisson ratio: 0.01. All of the parameters must be as basic material simulation data for the structure unit.(2) Static compression performance was tested to proof or correct the result of imitation. As normal distribution was found to be the static pressure distribution rule through statistics method, the expected value of swatch can be used to estimate the general performance. The whole pad’s static compression performance which has a linear relation to the number of the pad can be counted by that of single unit.(3) The moulded pulp’s cushion performance under impact was tested and the cushion curve is obviously different from other material, which is caused by different cushion mechanism. The conclusion is the efficient method to improve the cushion performance is to improve the structure intensity and optimize structure design.(4) Projected the librating transformation ratio test, and gained the resonance area of the tower shape moulded pulp pad is around 10Hz, and the biggest ratio is 1.370.(5) ANSYS was used to simulate the tower shape structure unit of the moulded pulp pad and imitate the real compression response process. Through analyzing the pressure-time and stress-time curves of six elements on typical position, the position where utmost pressure fastens is the center of the sides, and there the curves accord real test most. So we studied the relation between compression performance and the height of unit according to the pressure-displacement curves of the elements positioned near the center of sides. Imitated the units every 2.5mm from 7.5mm to 47.5mm height, and the conclusion is along with the increasing height the compression performance rises to apex until 27.5mm height and begins to fall down after that.更多还原