Formation of Fibrous Macrostructure in a Bearing Ring at Stamping and Rolling

The numerical modeling of the technological process of stamping and unrolling of a bearing ring is carried out. By using the method of finite elements, we obtained a numerical solution of the problem on thermal conductivity and the contact problem on thermo-viscous-plasticity for determining the shape-changing of the billet of a bearing ring in the process of stamping and unrolling. When modeling, at each subsequent step of the solution of a boundary problem, we assign as the initial state a distribution of the temperature field of the billet of a bearing ring, which was established at the end of each technological operation. An analysis of distribution of the Lagrange lines revealed changes in the distribution of fibrous structure of the billet material of a bearing ring at sequential technological operations of die forging and unrolling. It is proposed to use double-pass molding and, additionally, unrolling for displacing the exit of fibers from the raceway to the surface of board and forming the rational fibrous macrostructure of the bearing ring billet. Results of numerical simulation with an accuracy of 4.7 % coincided with the distribution of fibrous macrostructure of material during metallographic analysis of the experimental sample of a bearing ring billet

Establishment of the Dependence of the Strength Indicator of the Composite Material of Pressure Hoses on the Character of Single Damages

Experimental studies are presented and the dependence of the change in the strength of the material of a pressure head fire hose of type T with an inner diameter of 77 mm in the longitudinal direction is established, taking into account single damages. The work describes the plan of the experiment and carried out a number of field experiments to determine the effect of the length ld and the depth K damage on the strength F of the hose material, that is, obtaining the dependence F=f (ld, K). A mathematical method of experiment planning was used and a plan was drawn up for a complete multivariate experiment of type 2k with an acceptable model accuracy of 5 %. The limits of variation of the factors are set taking into account a priori information, experimental capabilities and on the basis of the results of preliminary search experiments. The dependence in the coded and natural values of the factors is obtained. The reliability of the relationship was checked using the Fisher test, the calculated value of which was 5.98, which confirms the adequacy of the described process with a probability of 95 %. Analyzing experimental studies of the dependence of the change in the strength of the hose material on the length and depth of damage, it can be said that the change in the strength of the hose almost linearly depends on the specified damage parameters. It is found that with increasing damage, the strength of the hose material significantly decreases. When varying the length factor and the greatest depth of damage, K=0.4 mm, the strength of the hose material decreases from 11.67 kN to 8.77 kN, and in percentage terms by 25 %. The results obtained can be used in practical units of emergency rescue teams, when diagnosing hidden damage in pressure head fire hoses in order to prevent their failure in case of fire