THE EFFECT OF A TEMPERATURE-GRADIENT ON RESIDUAL-STRESSES AND DISTORTION IN INJECTION MOLDINGS
THE EFFECT OF A TEMPERATURE-GRADIENT ON RESIDUAL-STRESSES AND DISTORTION IN INJECTION MOLDINGS
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DOI：
10.1002/pen.760240402
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发表时间：
1984-01-01
影响因子：
3.2
通讯作者：
WHITE, JR
中科院分区：
文献类型：
--
作者：
THOMPSON, M;WHITE, JR
已经检查了由聚苯乙烯、聚丙烯和玻璃纤维填充聚丙烯注塑成型并随后置于温度梯度中的杆的变形。测量了成型状态和温度梯度退火后的残余应力分布。在模塑状态下，所有模塑件显示出通常的残余应力分布，表面附近有压应力，内部有拉应力。在所有三种材料中，发现在梯度退火时，拉应力可以在较热的表面附近产生，并且当棒冷却并允许弯曲以恢复内部平衡时，拉应力仍然保持在该表面处。因此，它表明，除了发生的尺寸变化，这可能使模具不能使用后，温度梯度退火，另一个不希望发生的变化，使模具更容易从表面裂纹断裂。均匀退火被发现是不太可能导致应力逆转和应力保持平衡，使失真是最小的。
Distortion of bars injection‐molded from polystyrene, polypropylene, and glass‐fiber‐filled polypropylene and subsequently placed in a temperature gradient has been examined. Residual stress distributions have been measured both for the as‐molded state and after annealing in a temperature gradient. In the as‐molded state all moldings showed the usual residual stress distribution with compressive stresses near the surface and tensile stresses in the interior. In all three materials it was found that tensile stresses could be developed near to the warmer surface on gradient annealing and that tensile stresses still remained at this surface when the bar was cooled and permitted to bend to restore internal equilibrium. It is shown therefore that in addition to the dimensional changes which occur and which may render the molding unserviceable after temperature gradient annealing, another undesirable change takes place, leaving the molding much more susceptible to fracture from a surface flaw. Uniform annealing is found to be much less likely to cause stress reversal and the stresses remain balanced so that distortion is minimal.