Accounting method for residual technological stresses in modeling the stress-deformed state of a railway wheel disk. Report 2

The actual problem of increasing the service life of stamped-rolled railway wheels is a complex problem. Residual technological stresses, which cannot be completely eliminated, have a significant effect on the stress-strain state of the wheel as a whole and its disk in particular. At different stages of roughing wheels machining, the residual stress field is continuously changing. This makes it difficult to take into account the residual stresses in the wheels strength calculations. In Report 1 of this work, an accounting method for residual technological stresses was proposed, the essence of which is to set the value of interference between hub and axle when modeling is greater than the actual one. This approach made it possible to obtain additional stresses in the wheel, which adequately reflect the effect of residual technological stresses. In this part of the work, the authors have carried out practical implementation of the developed method and assessment of the degree of residual technological stresses influence on stress-strain state of the wheel disk under the action of operational loads. With regard to the design of a 957 mm diameter wheel with a flat-conical disk (GOST 10791 – 2011), calculations of stress-strain state of the disk under the action of mechanical types of load have been performed. The 60 % increase in the interference between hub and axle realized in the calculations made it possible to establish that the presence of residual technological stresses in the wheel causes an increase of 5 – 38 % in maximum equivalent stresses in the disk zones most loaded during operation. Thus, the proposed method for residual technological stresses accounting allows obtaining an upper estimate of the wheels strength characteristics, and, therefore, more adequately predicting their service life.

Accounting method for residual technological stresses in modeling the stress-deformed state of a railway wheel disk. Report 1

The work is devoted to development of a method for accounting residual technological stresses in wheel disks, which will provide both the versatility of the approach and the accuracy of calculations. The analysis of stresses in the wheel disk from the action of assembly (interference between the hub and the axle) and operational loads is carried out on basis of the results of finite element modeling. Verification of adequacy of the used model was made by comparing the calculated information with the experimental data of JSC “VNIIZHT”. The analysis of calculated and experimental values of radial stresses was carried out for the most loaded (critical) zones of the disk during operation – the zones of its interface with the rim and the hub. It was found that by setting the interference fit value to be greater than the actual one, it is possible to obtain the formation of additional stresses in the wheel, which, with a sufficient degree of accuracy, reflect the effect of residual technological stresses on its stress-strain state. On the example of calculating a wheel with a flat-conical disk (GOST 10791 – 2011), it is shown that an increase in the interference fit value by 60 % (from 0.25 mm to 0.4 mm per diameter) makes it possible to adequately predict the magnitude of stresses in the most critical disk elements. The maximum relative deviations of the calculated values of radial stresses from the experimental ones, both along the outer and inner sides of the wheel, do not exceed 14 %. Despite the simplicity of implementation, the proposed method provides an increase in the accuracy of predicting the strength characteristics of wheels, as well as the possibility of using it for various standard wheel sizes.

Simulation of vehicle tires based on the finite element method

Modeling of wheeled vehicles is one of the main directions of development and practical appli-cation of software systems based on modeling the dynamics of body systems. In this paper, a tech-nique for analyzing a vehicle tire by the finite element method under various types of loading is considered in order to identify the parameters of its simplified dynamic models. Based on the finite element method, a refined tire model is created. It takes into account the complex geometric shape of various tire parts, their material properties, as well as the contact interaction of the tire with the support. The efficiency of this model was tested, both when performing static calculations of the stress-strain state of the tire from the action of an external load, and when solving the generalized eigenvalue problem. The great influence of external load on the natural frequencies and vibration modes of the tire is confirmed. One of the possible applications of the considered method of finite element modeling of a tire is the performance of refined calculations of the dynamics of wheeled vehicles in the “Universal Mechanism” software package. There are several variants of dynamic tire models that can be used to study the dynamics of off-road wheeled vehicles, including a model based on the method of discrete elements and a model based on the method of coupled substruc-tures. A model based on the method of discrete elements represents a number of absolutely solid bodies-particles, connected to each other and by a wheel disk by a set of elastic-dissipative ele-ments. Each particle of this model has three linear degrees of freedom relative to the wheel disk. The results of calculations of the refined finite element model of the tire are necessary to identify the mass and elastic-dissipative properties of this dynamic tire model. In the model based on the method of connected substructures, the elastic displacements of the tire are represented as the sum of the admissible shapes of the elastic body. Static and natural vibration modes are used as permis-sible forms of an elastic body, calculated using a refined finite element model of the tire.

Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk. The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.

Influence of Deformation of the Wheel Disk-Type Body on the Tooth Load Distribution over the Facewidth in Helical Gears

The article demonstrates one of the ways to reduce uneven load distribution along the width of the gear wheels which can be used in place of expensive modifications of the tooth flanks (crowning). This can be achieved by appropriate selection of the shape of the gear wheels for example the disk shape. The presented numerical example illustrates the above possibility taking into account deformability of the wheel body.