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Mapping of Changes Induced by Microwave Heating in a Common Photoelastic Plastic - Towards an Effective Control of Thermal Runaway
Journal article

Mapping of Changes Induced by Microwave Heating in a Common Photoelastic Plastic - Towards an Effective Control of Thermal Runaway

A Oloyede, Ayodele Olofinjana and Paul Goombridge
Non-Destructive Testing - Australia, Vol.39(2), pp.49-52
2002
url
http://www.ndt.net/apcndt2001/papers/9292/9292.htmView
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Abstract

Materials Engineering thermal runaway polymer joining microwave joining nano-indentation temperature control
Thermal runaway phenomenon is a major hindrance to the use of microwave heating in manufacturing. The mechanical properties of a material can be modified when the internal temperatures induced during processing increase too rapidly. As a result, recent research has focused on developing suitable control systems utilizing temperature feedback to prevent damage caused by thermal runaway. Whilst this is effective the control parameters are found from time-consuming trial and error exercises in which the external temperature is used to deduce the internal temperature. A better understanding of the heat distribution in bulk materials during processing would provide useful insight into the impact of thermal runaway effects on manufacturing processes and enable process parameters to be predicted for any given situation. The results of a study in which cubic photoelastic specimens were sliced into sections and put back together then heated using microwaves and later examined using a polariscope and an ultra micro indentation system(UMIS) are presented in this paper. A Hounsfield test was also used to determine the elastic modulus of the material. The stresses and hardness measured have enabled three-dimensional mapping of microwave-induced changes in this resin, and a concomitant temperature distribution evaluated from the theory of elasticity.

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