摘要
注塑成型制品的翘曲变形作为评定制品质量的重要指标之一,其研究有着重要的应用价值。为提高具有复杂几何形状的塑件翘曲变形预测精度,对聚丙烯基热塑性弹性体(Thermal plastic olefin,TPO)分别进行了拉伸加载-卸载实验、压力-体积-温度(Pressure-volume-temperature,PVT)实验、复杂注塑制品翘曲变形的测量和数值模拟。材料的PVT曲线显示冷却过程中材料的热膨胀系数会发生非线性变化。拉伸应力应变曲线表明,材料未表现出明显的屈服,应变速率越大则弹性模量就越大,而在卸载时弹性模量小于初始弹性模量,并随总应变极限的增加而减小。修正Chaboche粘塑性模型并将其应用于高分子复合材料,对各温度和应变速率下的应力应变曲线进行拟合获得本构方程参数,编写子程序UMAT并嵌入到TPO复杂注塑制品的翘曲变形有限元模型中,所得模拟结果不仅能成功预测试样取样位置上翘曲变形的趋势,还能够发现在套筒位置和加强筋处的过度收缩。
The warpage of injection molded part is one of the most important criteria to validate the quality of plastic part.In order to increase the accuracy of warpage prediction,the tensile loading-unloading tests at different strain rates and elevated temperatures,the pressure-volume-temperature(PVT)test,the deflection measurement and warpage simulation are conducted for the polypropylene based thermal plastic olefin(TPO).The PVT curves indicate that the coefficient of thermal expansion varies nonlinearly in the transition zone.The stress-strain curves show that the material has no obvious yielding.The Young′s modulus increases with the increasing of strain rate.The slope of the stress-strain curves in the unloading path is different from the initial Young′s modulus and dependent on the loaded strain limit,and it decreases when the loaded strain limit increases.The Chaboche viscoelastic constitutive relationship is adopt and modified to describe the mechanical behavior of TPO composite.The user subroutine UEXPAN and UMAT are developed to calculate the thermal and mechanical strain respectively.The warpage of injection molded part with complex geometry is simulated and compared with the measuredresult.The predicted distribution of deflection exhibits a good agreement with the measured one.The area,in which the excessive shrinkage happens,can also be predicted in the simulation.
出处
《南京航空航天大学学报》
EI
CAS
CSCD
北大核心
2015年第5期752-759,共8页
Journal of Nanjing University of Aeronautics & Astronautics
基金
美国福特汽车公司中国大学研究基金(2009-5041R)资助项目
江苏高校优势学科建设工程资助项目
江苏省普通高校研究生创新计划(CXLX11-0190)资助项目
南京航空航天大学研究基金(1006-KFA13731)资助项目
关键词
热塑性弹性体
复杂塑件
注塑成型
翘曲变形
数值模拟
thermal plastic olefin(TPO)
complicated plastic part
injection mold
warpage
numerical simulation