Determination of Optimal Flat-End Head Geometries for Pressure Vessels Based on Numerical and Experimental Approaches

The experimental and numerical analyses of the pressure vessels with different flat ends are presented and discussed in the paper. The main aim of the study is to propose the optimal flat head end geometry. The analyses are focused on the comparison of standardized geometries and with the proposed elliptical cut-out. The experimental tests with the application of strain-gauge measurements and numerical modeling of the pressure vessel are conducted. The behavior under low and high pressures and the influence of the residual welding stresses, material properties, and geometrical tolerances on the level of the plastic deformation in the flat end is discussed. It is presented that the rules given in the recent standard are not sufficient for optimal selection of the optimal geometry. It is observed that in certain geometries the deviations of the pipe thickness may lead to a significant increase of the equivalent stresses. The residual welding stresses have a significant influence on the stress and strain level—particularly in the stress relief groove (SRG). The performed study and comparison of the different geometries allow for the proposal of the optimal shape of the flat end. It appeared that the pressure vessels with SRG are the most optimal choice, particularly when elliptic shapes are in use. In some cases (i.e., pipe with wall-thickness equal to 40 mm and the flat end with circular SRG), the optimal configuration is reached for dimensions beyond the admissible by code range.

INCREASING THE OPERATING PROPERTIES OF THE MACHINE PARTS BY THE SURFACE RELIEFS

The article discusses the direction of improving the operational properties of machine parts by applying regular reliefs to the surface/ Purpose - to develop a model, plan and methodology for experimental studies of regular reliefs and create their classification by purpose and methods of obtaining. The object of research - regular reliefs on the surface of machine parts. The hierarchy of the main factors that affect the profile of reliefs formed by triangular grooves is determined. This is the normal penetration force of a linear indenter, hardness and elongation of the experimental material. The optimization parameter is the groove depth. A mathematical model and research plan have been developed 23. The methodology and devices for conducting experiments are determined. These are hydraulic presses, linear indenters, optical microscopes, microhardness testers, test materials, instruments, and measuring instruments. Materials for research: alloyed and stainless steel, gray and malleable cast irons, bronze and brass, aluminum and titanium alloys. Classifications of reliefs according to the methods of obtaining and destination are developed. Production methods are based on cold plastic deformation and cutting. The basic methods for the study are static methods: the introduction of a dividing element with discrete drawing and a single protrusion of the shaped mandrel during reduction. The dependence of the depth and double angle of the relief groove on the normal force is shown. A new method for obtaining the surface of a part, including the alternation of supporting platforms and grooves is proposed. The method is carried out using machining and subsequent deformation pulling. A distinctive feature of the method is the use of an intermediate elastic sleeve. KEYWORDS: REGULAR RELIEF, COLD PLASTIC DEFORMATION, LINEAR INDUCTOR, SURFACE OF PARTS, COATING, MODEL OF FORMATION OF RELIEF.

Reliability design of relief groove for torque shaft of shearer

On cutting coal, the cutting resistance of a shearer may change suddenly due to uneven coal quality. It can lead to sudden acceleration of the cutting motor, deceleration, overload shutdown, and even burnout of the motor. We studied the dynamic, static, and working characteristics of the torque shaft of a typical shearer to ensure that the torque shaft of the cutting unit can transfer the torque from the cutting motor to the gear reducer in the rocker under rated conditions and be turned off immediately to protect the motor in case of overload. A method of radial size design of the relief groove of torque shaft based on combining positive, reverse reliability with unloading coefficient has been presented, and the flow chart using this design method has been provided. The positive and reverse reliability torsional test of strength of the experimental torque shafts without relief grooves using three different materials and the measurement test of unloading coefficient of various types of relief grooves were performed. The experimental results obtained through our investigation achieve and even surpass the design purpose. More importantly, to serve the industry it is designed for, the torque shaft designed using this method has high reliability.

Optimization of Flat Ends in Pressure Vessels

The application of flat ends in pressure boilers is inevitably associated with the presence of stress concentration, which is observed in the vicinity of the junction of the cylinder and the closing flat plate. The analyzed flat end plates with stress relief grooves fall into the group of solutions recognized by the respective Standards of Calculations of Pressure Vessels. Unfortunately, no clear evidence is given in the Standards on how to choose the best groove parameters. This opens up the problem of the optimal choice of the groove parameters providing a minimum stress level. Even for the optimal values defining the stress relief groove geometry, certain plastic deformations are observed in the groove area for materials which exhibit elastic-plastic properties. Such a situation is completely unacceptable during exploitation, and a suitable reduction of the operating pressure is necessary. This paper discusses the effectiveness of other designs for flat ends used in pressure vessels. The proposed modifications took the form of external ribs applied around the top of the endplate circumference. The dimensions of these ribs were set using parametric optimization. The results of the study encouraged the authors to perform a more general analysis with the use of topology optimization. The results of all performed studies proved that the reduction of stress concentration and the full elimination of plastic deformation are possible. All numerical calculations were made using the finite element code (FEM), Ansys.