The existence of tensions among important characteristics of glass products and is a criterion for their general physical and mechanical strength. There are two types of stress in the glass Residual internal stress and controlled imported.
– The first type is the result of improper process water cooling products /tempering/ neprosredstveno after molding them. This gives rise to a compressive force and tension between rapid solidification surface layer of glass and this in depth. In this case, the stresses are randomly located and if they exceed the permissible norm cause the destruction of the glass due to minimal mechanical or self-destruction without the intervention of any external factor.
– The second type is when tensions are kontrolilano imported. These are thermally toughened glass or so-called special purpose lenses – safety glasses and dangerous. As an example, these are all glass doors, glass walls, etc. . In this case, the voltages are made by special technology of heating and subsequent quenching. They are evenly distributed, which is the reason for their high physico- mechanical and thermal resistant to this type of glass. Another reason why they are preferred building product is that in case of breakage, they are broken into small pieces nerezheshti and without risk of injury. There is also a technology imported controlled internal stresses in the glass by a special chemical treatment of already produced izdeliya. This category includes refractory glass products and a special glass located prolozhenie military industry. We measure the stresses in the glass with polyariskop – polarimeter. In the Republic of Bulgaria, there are several polyariskopa in different laboratories, but polarimeter can boast just us. The principle of measurement is quantitative and the unit is nanometer to centimeter thick. The method is optical and based on the birefringence of the light that occurs in the glass under the action of the internal stress. The test was performed by the method of compensation, and the quantitative determination of the difference in the beam path. We use compensator Senarmont. The field of vision of the compensator is a size of 250 mm.
