The methods for numerical research of "body-suspension-wheel-soil" system in assessment problems of flotation ability and ride comfort of wheeled vehicles are proposed. The use of the methods allows to take into account the pecu- liarities of interaction between the wheels and the deformable support surface in simulation of wheeled vehicles move-ment on soils with different physical and mechanical properties in prospective areas of operation. Numerical simulation is based on the finite element method in a nonlinear dynamic formulation.
A computational and experimental method is presented for assessing the influence of the roughness of a rigid surface on the stiffness and damping properties of automobile tires. The method is based on the solution of tire-ground contact problem using finite-element analysis. In the paper, the influence of two types of irregularities (peaks and pits), their size and shape and tire air pressure on tire enveloping properties is analyzed.
Calculations are presented on the state of strain in pipe joints to equipment and pressure vessels used in the chemical and oil industries. Various model approaches are considered for calculating reinforced pipe joints. Calculated results are given for a pipe joint as a welded joint between three cylindrical shells (body, ring, and pipe). A complete solution is presented for the three-dimension contact problem and a two-dimensional solution obtained with the SAIS program.There are usually pipe joints (PJ) in the apparatus and vessels used in the chemical industry, petrochemical industry, oil refining, and adjacent areas of industry, in which the main load comes from the internal excess pressure. A local state of stress arises in the PJ, which is characterized by a high stress level.A pipe joint is usually welded, and the highest stresses in the body and pipe arise near the weld. The stress concentration here is the cause of microplastic strain, which in the presence of cyclic loading may lead to crack initiation and failure. Research on stress concentration effects in PJ regions is thus important in the general strength analysis of such structures.At present, GOST 24755-89 deals with the standards and calculation methods for PJ on cylindrical and conical shells and on elliptical and spherical base plates and other such vessels made in Russia. In foreign practice, the most familiar standards are the American ASME Code and the British standard BS 5500, which contain rules and recommendations for choosing the basic geometrical parameters and other such information. However, such documentation cannot reflect all practical aspects of structures of this type, particularly as there are wide ranges of variation in the geometrical parameters of pipes and bodies.The body of the apparatus and the pipe are shells of rotation, which are often thin-walled (particularly the body of the apparatus or vessel), so usually the PJ is considered as the joining of intersecting shells differing in geometrical form. The stress state in the shells in the region of their intersection is inhomogeneous. The stresses vary considerably in the direction of the intersection between the shell surfaces (outside or inside) and also along the intersection line. The character of the maximal stresses in the shells (predominance of membrane or bending components) is extremely important for strength evaluation.To reduce the maximal stresses in a PJ, it is best to use various types of local reinforcement: monolithic (integral) mounting; fitted ring; transitional section (rim or toroidal insert); and lining tubes.There are possible forms of combined local PJ reinforcement, e.g., a pipe with locally thickened wall (monolithic reinforcement) and a welded ring attached to the body.One chooses the local reinforcement method on the basis of the performance (reduction in the maximal stresses in the shells), with allowance for the object (body or pipe), the soundness of the reinforcement, and so on. Local reinforcement is also favorable from the viewpoint of PJ...
To ensure fatigue strength of metal structures in mechanical engineering, various approaches are practiced. One of them allows for the appearance of cyclic stresses in details with amplitudes exceeding the fatigue limit. Typically, this approach is justified where the loads are fairly regular and ample opportunities for fatigue testing exists, but the requirement of a minimum metal consumption is critically important as well. Another approach to ensuring fatigue strength does not allow the possibility of cyclic stresses with amplitudes exceeding its endurance limit in the designed structure. With regard to the supporting elements of locomotives and electric multiple units (EMU) to ensure the fatigue resistance characteristics in Russia and the CIS countries, the second of these approaches has been implemented and successfully practiced for many years. Its purpose is to ensure the absence of fatigue damage in the parts of the carriage and the body during the designated service life. Relevant requirements for strength and dynamic qualities for these types of rolling stock, as well as the method of conducting dynamic strength tests are currently formalized in the standards. The article presents the main provisions of the methodology currently used on the railways of the Russian Federation and CIS countries to control the strength requirements of load-bearing structures of locomotives and EMUs, as well as the admission of these types of rolling stock to operation. Types of dynamic strength tests are described, strength indicators are listed, methods for their determination are indicated. Today, this technique successfully solves the problem of the strength of load-bearing structures of traction rolling stock.
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