MATHEMATICAL MODELING OF OPERATION OF THE PALLET CARS’ GRATE BARS MADE OF STEEL 40Kh24N12SL

To determine the reasons that decrease life of the grate bars of pellet cars from steel 40Kh24N12SL during the operation, a compara­tive analysis of the results of macro-investigations of the grate bars af­ter operation with the results of modeling the operating conditions for the grate was performed. The modeling of the operating conditions was carried out using the finite element method, which allowed achieving high reliability of the obtained results. For the reliability of the model­ing results, the maximum possible number of boundary modeling con­ditions was obtained, obtained from both macro-examples conducted earlier and from the scientific literature. The application of the finite element method made it possible to determine that a high temperature gradient with local overheating zones is formed along the section of the component. It is shown that the nature of overheating is predictable and is related to the conditions of the coolant supply to the working area during operation of the part. It is established that zones with large values of internal stresses and deformations are locally formed during operation. The regularity of appearance of these zones is shown, which highly dependents on the presence of inhomogeneities in the structure of the part, and is also supposedly related to geometric complexity of the casting. It is also established that in the presence of shrinkage shells, all values of stresses and deformations increase sharply, espe­cially in local maximums. In this case, the distribution of local zones with high stresses and deformations in the presence of shrinkage shells remains practically unchanged. An analysis of the location of zones with high stresses and strains made it possible to explain the existing principle of the destruction of the grate by cracking during operation. It is proved that one of the main causes of buckling, cracking and fracture of the grates of the pellet cars made of steel 40Kh24N12SL is the pres­ence of shrinkage shells in the metal structure. As a result of modeling the operating conditions, mechanism of the occurrence of buckling, cracking and fracture of the grates of steel 40Kh24N12SL during op­eration is described, which completely coincides with the results of macro-investigations and observations obtained during operation.