engleski

RESIDUAL STRESSES CAUSED BY SHRINKING IN MULTI BODY POLYMER - MODELS

To solve spatial technical problems by three dimensional photoelasticity it is necessary to fix the optical effect in the model. In order to avoid the well known disadvantages of the classical freezing method ionising irradiation is used for that purpose [1, 2]. With this method it is not necessary to enlarge the scaling-factor for the displacement which is in some cases very important especially when shrinking is used to develop the fringe pattern. In addition fixation with ionising irradiation can be carried out without elevated temperatures. The most important advantage compared with the freezing method is given by the fact that Poisson’ s ratio of the polymers is in this way practically the same as in the simple two dimensional photoelasticity. This is very important because using the classical freezing method temperature treatment above the glass temperature is needed and in this temperature range Poisson’ s ration of the polymer is practically the same as in plasticized zones so that by using the classical freezing method it is not possible to distinguish between the elastic and the plasticized zones of the model. The mentioned features were already shown in case of two dimensional contact problem [3]. New materials introduced by Beer at all [2] opened additional possibilities in modelling more complex problems. However dealing with models consisting of two (or even more) different parts we have to keep in mind that shrinking in such models causes residual stresses and for that reason an accompanying rheological process is going on. To distinguish between these processes additional information, not available by photoelasticity, is needed.

three dimensional photoelasticity; gamma irradiation; shrinking

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