The measurement of thermal stress distributions along the flow path in injection‐molded flat plates
The measurement of thermal stress distributions along the flow path in injection‐molded flat plates
复制标题
注射成型平板沿流路热应力分布的测量
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
G. Schennink
中科院分区：
文献类型：
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作者：
C. V. Hastenberg;P. C. Wildervanck;A. Leenen;G. Schennink
注塑件中的内应力是热、流动和压力历史的结果。内部应力可大致分为热应力和流动引起的应力。本文提出了一种修正的分层去除法来确定注塑平板的热应力分布。用这种方法，一个矩形试样的曲率后，从一个表面上删除一层确定。该曲率通过最初由Treuting和Read导出的数学关系转换为应力。通过确定连续层去除后的局部曲率，在单个试样内获得沿流路沿着的应力分布。这种改进的层去除方法的验证。获得了良好的再现性。该方法可视为半定量。平板由三种无定形聚合物注塑成型：聚苯乙烯、聚碳酸酯和聚苯醚/高抗冲聚苯乙烯共混物。一般来说，平板横截面呈三区域应力分布，平板表面和芯部均为拉应力区域，中间区域为压应力区域。采用改进的分层去除法研究了模具温度、退火处理和压力历史对热应力分布的影响。提高模具温度导致整体应力水平降低，而压应力区域转移到表面。退火处理显著降低了整体应力水平，而不影响应力模式。沿流道沿着的应力分布受从模腔入口到模腔末端的压力变化历史的影响。的应力分布的各种功能的解释的压力衰减率在注塑过程中的影响。
Internal stresses in injection-molded parts are the result of thermal, flow, and pressure histories. Internal stresses can be roughly divided into thermal and flow-induced stresses. In this paper, a modified layer-removal method is presented to determine thermal stress distributions in injection-molded flat plates. With this method, the curvature of a rectangular specimen is determined after the removal of a layer from one surface. This curvature is converted into a stress via a mathematical relation, originally derived by Treuting and Read. By determining the local curvatures after successive layer removals, stress distributions along the flow path were obtained within a single specimen. Validation of this modified layer-removal method is described. A good reproductibility was obtained. The method can be regarded as semi-quantitative. Flat plates were injection-molded from three amorphous polymers: polystyrene, polycarbonate, and a polyphenylene ether/high-impact polystyrene blend. In general, the flat-plate cross-section shows a three-region stress distribution with a tensile stress region both at the surface and in the core of the flat plate and an intermediate region with compressive stresses. The modified layer-removal method was used to determine influences of mold temperature, annealing treatment, and pressure history on the thermal stress distributions. Increasing mold temperature results in a decreasing overall stress level, while the compressive stress region shifts to the surface. An annealing treatment significantly reduces the overall stress level, without affecting the stress pattern. Stress distributions along the flow path were influenced by the varying pressure histories from the entrance to the end of the mold cavity. The various features of the stress profiles are explained by the influence of the pressure decay rate in the injection-molding process.