Thermal residual stresses in injection mouldings result from the non-uniform cooling of the melt in the mould. Normally, compressive stresses develop at the surface and tensile ones within the core of the mouldings. The magnitude of these residual stresses was examined for an acrylonitrile-butadiene-styrene copolymer (ABS) under various injection moulding conditions. Although the occurrences of thermal stresses are inevitable, the warpage results only when the residual stresses are out of balance. The imbalance of the residual stresses are caused by the non-uniform temperature distribution through the thickness of the mouldings which may be caused by variation in cross section, part geometry and temperature difference between the two surfaces. The magnitudes of thermal residual stresses in injection moulded ABS flat plaques were determined using a layer removal technique. The development of warpage in a 3D component (an L-shaped bracket) was modelled using the residual stresses obtained for the flat plaques and the predictions were compared with the experimental warpage measurements.
From M. Akay | S. Ozden
School of Electrical and Mechanical Engineering, University of Ulster at Jordanstown, Newtownabbey, Co. Antrim, N. Ireland
Appeared in International Polymer Processing 1996/02, Page 179-187
Direct link: http://www.polymer-process.com/IPP960179
An Assessment of Thermal Stresses in Injection Moulded ABS Copolymer [1,07 MB]
Free access for subscribers. PPS-Members: For Access Password please contact your Society.
|© 2013 by Carl Hanser Verlag|