Study On Size Effect Of Refractory Fracture Parameters

Refractory materials are mainly used as lining materials of high temperature vessels, which can be damaged by various stress in the process of use, in which the mechanical damage is one of the important factors. The new refractory strength test standard increases the distance between the bearing and supporting mouth. The practice shows that the resistance of the refractory material decreases with the increase of the distance. As a kind of quasi brittle materials, refractory material fracture failure exist size effect, at present for refractories research mainly concentrated in different materials with the effect of ratio on the performance of this material, and for the size effect is less studied. The effect of size effect on the judgment and evaluation of the real strength, durability and bearing capacity of refractory materials is an important aspect of the research and application of refractory materials.Firstly, this paper reviews the research history of the problem size effect and about the study on the size effect of three kinds of basic theory, namely Bazant energy release size effect theory, Weibull statistical size effect law, crack fractal theory. The magnesia carbon brick and magnesia alumina brick as the experimental material, through the flexural specimen explores the bearing from the mouth to the influence of flexural strength. Use of carbon free unburned corundum brick used in ladle as raw materials, fixed taller than that made of five dimensions of strip sample and normal temperature in the electric bending machine bending experiment to explore size effects. The results show that the size effect is the general character of refractory materials, and the change of the distance between the supports and supports is the cause of the size effect of refractory materials. Based on Bazant energy release size effect rule proposed a carbon free does not burn just jade ladle lining brick modified flexural strength size effect formula. Experimental results show that modified flexural strength size effect formula is more practical and can be used to predict the free carbon does not burn just jade steel package lining brick with different sizes under the room temperature flexural strength.Finite element analysis is an important method of scientific research. It can overcome the shortage of experimental conditions, waste materials and other obstacles, and get more accurate results. In this paper, the use of software ANSYS15.0 first, we simulate the ordinary magnesia bricks under the different size of compressive strength at room temperature, numerical simulation results show that, common magnesia brick compressive strength at room temperature is decreased with the increase of the size of sample model showed a significant size effect. In addition, this paper also with a three point bending beam to analog form, a reasonable set of bonding element of the fracture zone, to specimen span, height, crack depth ratio as variables, were obtained from the simulation under different conditions of fracture. The results show that specimen height and gap ratio is constant, and the fracture energy decreases with the increase of span; when the span and crack depth must and fracture of the specimen can increase with the increase of the height of; when the span and height is certain, the fracture of the specimen can decreases with increasing crack depth ratios, and fracture of the specimen can exhibit a pronounced size effect, simulation results and the experimental results are in good agreement.It should be pointed out that, although the results of the experiments and simulation are consistent with the actual trend of the fracture, the strength of the refractory is very large, and the factors which affect the fracture are also varied.