PREDICTION OF THERMAL DISTORTION AND THERMAL FATIGUE IN SHOT SLEEVES
Abstract (Summary)In the horizontal cold chamber die casting process, shot sleeves experience alternate heating and cooling as well as intensification pressure at the biscuit end – all of which influence the shot sleeve service life. Since the shot sleeve failure is expensive in terms of cost and downtime, it is important to understand the effects of design parameters and process conditions on shot sleeve failures. Due to the difficulties of measuring shot sleeve temperature and distortion in the actual manufacturing process, computer simulation is not only a useful method to understand and predict failures in shot sleeves, but also a tool to guide shot sleeve design. The 2-D plane strain computer models were developed at the beginning of the work. The simulation results from the 2-D models were compared with the existed experimental data, and the best model was identified. Based on the experimental data, accurate heat transfer coefficients between the shot sleeve and molten metal were determined. To model the shot sleeve radial distortion at biscuit end, the plane strain model was extended to 3 dimensions in order to properly apply boundary conditions. Based on the available commercial shot sleeve geometry and process data, the radial distortions of large shot sleeve with thin/thick wall thickness were studied. Based on the computer simulated strain range results from the same 3-D model, a thermal fatigue life prediction method (Universal Slope Method) was then developed for service life prediction. Compare the predicted thermal fatigue life with commercial sleeve fatigue data, the predicted thermal fatigue life is well matched with the actual operation shot sleeve thermal fatigue life. Combining the small ID and large ID shot sleeve simulation results, it can be concluded that control of the “out of roundness” of the ID dimensional changes is the key factor for large ID shot sleeve clearance design between its ID and plunger tip.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/2002