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Numerical simulation and experimental validation of residual stress induced constrained shrinkage of injection molded parts

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Azdast T. , Behravesh A. H. , Mazaheri K.

2008

tom T. 53, nr 4

304-310

In this paper a numerical analysis of in-mold constrained shrinkage of injection molded parts is presented, considering the residual stresses produced during the packing and cooling stages. Residual stresses are the main reasons of shrinkage and warpage of the injected parts. In regards to the viscoelastic characteristics of polymeric materials, mold constraints have noticeable effects on the final dimensions of the molded parts. A numerical analysis was developed and experimentally examined for constrained shrinkage using a case study: a plate containing the holes (as constraints). The results indicated a good agreement between the numerical solution and the experimental data.

Przedstawiono podstawy analizy numerycznej wymienionego w tytule zagadnienia w odniesieniu do skurczu na etapach docisku i chłodzenia w formie. Naprężenia własne stanowią główną przyczynę skurczu i odkształcania kształtek. Na końcowe ich wymiary wyraźny wpływ wywierają przeszkody w gnieździe formy wtryskowej. Wnioski wynikające z obliczeń symulacyjnych (rys. 4 i 6) porównano z wynikami doświadczalnymi otrzymanymi w badaniach z zastosowaniem kształtki o specjalnej konstrukcji (rys. 3) wykonanej z terpolimeru akrylonitryl/butadien/styren, uzyskując dobrą zgodność (rys. 7).

Comparative evaluation of various experimental and numerical simulation methods for determination of t8/5 cooling times in HPAW process weldments

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Sajek A. , Nowacki J.

tom Vol. 18, no. 2

583--591

The aim of this article is to provide a quantitative comparison and efficiency verification of the methods of estimating t8/5 cooling time in the process of HPAW of S960QL steel. The measurements of t8/5 welding time were conducted at the face of weld with the use of thermoelectric, pyrometric and thermovision methods. A FEM model of the joint was made, and welding simulation was done. The results of the calculations were then confronted with experimental data, and measuring methods were evaluated. Differences in the results of t8/5 time measurements were determined for the analysed methods and arranged according to the precision of results presented; the applicability of FEM for predicting the value of t8/5 time was investigated. The usability of temperature measuring methods for determining cooling time was determined, the weaknesses of non-contact measurement in terms of diversification of cooling time in a section of a welded joint were shown, and the advantages of numerical method were demonstrated. It was established that joining experimental methods for measuring cooling time of a joint with FEM analysis allows to obtain a desired resolution of prediction. In this way, the technology for hybrid welding of advanced high-strength steels can be designed more efficiently.