塑料盖收缩裂口成因分析

Analysis on the Formation Mechanism of the Contraction Crack of Plastic Covers

研究盖的收缩裂口位置及其产生原因与收缩应力的关系,分析盖型结构的力学特性。结果表明,圆盘的径向和弦向收缩率相等,对实际发生在盖边沿的裂口无影响。经分析高分子材料及其成型特性、结晶规律和结构受力情况以及结构退让性,计算得出了盖的环圈收缩外翻倾向对其本身经纬向收缩率的重大影响,提出了减轻盖的内应力的方法。

The relationship among the contraction crack, crack position and shrinking stress of plastic cover structure was studied. It was proved that the shrinking ratio of radial vertical direction is equal, so that it's no effect on the edge crack. It was analyzed that the forces about the cover in different ways such as the characters of plastics and their formed process, relative contraction ratio in different directions, crystal orderliness with plastics and the structural reform ability. It was calculated that the stress of the circle of the influence of the horizontal stresses and vertical ones. The evagination of the cover's circle by the structure combination was the most important factor to cause the cracks. It was suggested to reduce the stress in the cover to solve the problems.