Papers by Keyword: Contact Stress

Abstract: This research evaluates analytical, semi-empirical, and numerical models for predicting contact stresses in the interaction between rock-destroying elements and rock formations, a critical factor influencing wear, cutting efficiency, and energy consumption in drilling operations. The Hertzian analytical model, semi-empirical model with experimental calibration, and a Finite Element Method model incorporating plastic deformation via the Drucker-Prager criterion are compared for accuracy and applicability. Mock experimental data, based on rock mechanics literature, validates the models, revealing average prediction errors of 28%, 12%, and 4% for the Hertzian, semi-empirical, and Finite Element Method models, respectively. The Hertzian model is computationally efficient but inaccurate in nonlinear conditions, the semi-empirical model balances accuracy and practicality in calibrated scenarios, and the Finite Element Method model excels in complex formations despite high computational demands. Graphical comparisons within the contact radius highlight the Finite Element Method model’s ability to capture plastic effects, making it ideal for optimizing rock-destroying elements design in challenging geological environments. The findings underscore the importance of selecting models based on operational requirements, with the Finite Element Method model recommended for high-precision applications in deep or unconventional drilling.

Abstract: An interface crack between two semi-infinite piezoelectric/piezomagnetic media under out-of-plane mechanical load and in-plane electric and magnetic fields parallel to the crack faces is examined. A portion of the faces is electrically conducting and kept at a uniform magnetic potential, while the remaining portion is electrically and magnetically permeable. The coupled fields are represented by functions analytic in the plane outside the crack. With these representations, the mixed crack-face conditions lead to a combined Dirichlet–Riemann and Hilbert boundary-value problem, which is solved in closed form for arbitrary conductive versus permeable segment lengths. The solution yields explicit expressions for stresses, electric and magnetic fields, and the crack-face sliding (displacement jump). The singular behavior at both crack tips and at the transition between conducting and permeable zones is characterized, and intensity factors are defined accordingly. Parametric results illustrate how applied electric and magnetic fields modulate the fracture driving force; in particular, suitable magnetic loading can markedly reduce the mechanical stress intensity at the permeable tip. The formulas supply benchmark data for verification and enable design guidelines for tailoring electrode coverage and field application to mitigate interface fracture. The approach provides an analytic framework for mixed electromagnetic conditions in magnetoelectroelastic interface fracture.

Abstract: The reported paper presents a field pattern of sliding lines in a plastic zone of flow chip formation in the process of cutting metals considered for front and rear angles on the cutting blade other than zero. Equations of sliding lines for these conditions are proposed. Using calculation data, plasticity zone border lines are plotted for positive and negative front angles. The paper suggests methods and calculation data on average stress and plane stress state components in nodal points of the plastic zone of chip formation. The study provides data for plotting distribution diagrams of normal and tangential stresses of contact stresses on work surfaces of a cutting blade.

Abstract: A new solution Karman’s equation with the Mises plasticity condition is proposed for determining contact stresses in the slip zones for hot strip rolling. Replacement of the precise plasticity condition by an approximate condition in terms of primary stress leads to a substantial decrease in the length of slip zones and to increase of the rolling force. It was shown that, even at high frictional coefficients, the length of slip zones forms a significant part of the length of deformation region. On the basis of the obtained solutions the techniques for plotting curves of the normal contact stresses, determining the length of the slip zones, the neutral position of the cross section and rolling force refined.

Abstract: Spur gear is the most basic type of parallel-axis gear. In this study, contact stress and fatigue life of spur gear for different modules and for different materials were studied. The commercially available Solidworks 2016 is used for modelling and ANSYS Workbench tool for discretizing and solving. The analysis has been performed on the gear models of modules 1mm, 2mm and 3mm to observe the distribution of contact stress and life. The graphic results obtained were compared and it was found that contact stress decreases as the module increases and also aluminium alloy was having the least stress and high fatigue life among the selected materials. Hence from the finite element analysis, it’s found that the contact stress depends on the module and material used. Similarly fatigue life of gear purely depends on the material chosen.

Abstract: In the field of Engineering and Technology, Gear is one of the most significant and essential component in mechanical power transmission system. General devices have major applications in various fields like automotives, industrial rotational machines, lifting devices, etc. Gears are usually subjected to fluctuating loads while in action. Gear tooth mainly fails due to excessive bending stress and excessive contact stress. Thus while designing the gear it is very necessary and vital to analyze the stresses induced in the gear for its safe operation. Weight reduction of gear is also one of the main design criteria as it has a great role in improving the efficiency of the entire system. Nowadays engineering components made up of composite materials and plastics find increasing applications. The components made by the composite materials provide reasonable mechanical properties with minimum weight. The objective of this research is to develop the spur gear and pinion assembly model using engineering simulation PTC Creo and imported to 3-D design software ANSYS workbench 16.0 for working on the static structural analysis. The analysis was carried out by considering different materials for gears like structural steel, polycarbonate and 20%AlSiC. From the observed results it was found that, 20%AlSiC composite material has mass reduction of about 45%, hence it is suitable for light weight applications.

Abstract: The paper is focused on the interaction of the fibre reinforced concrete slab and the subsoil using both the results of experimental measurements on the experimental stand. Performed experimental measurements include monitoring of the concentrically loaded concrete slab with the dimensions of 2 m x 2 m and thickness of 0.15 m. This slab is in the interaction with subsoil of sandy clay character. The experimental load is applied in sequential steps by using a hydraulic press. During the tests the strain gauges and hydrostatic levelling method were used for the monitoring of the settlements of the slab. The contact stresses and the stresses corresponding to a certain depth below the slab were monitored by using a flat pressure cells. In the conclusion of this paper there are formulated the basic aspects of concrete slab-subsoil interaction, the results of various performed experimental measurements and the comparison of stress below the surface resulted from interaction of soil and slab of different degree of reinforcement.

Abstract: The main causes of pressure ulcer are the unrelieved contact stresses between the cushion and the human body and the deterioration of the skin condition caused by the impregnation of sweat and urine, especially the region around ischial tuberosities where the local pressure concentration appears. Pressure ulcer-preventing cushion that relieves the pressure concentration in a seated situation could help to decrease the incidence of pressure ulcer. A new concept of such cushion is to fill the cushion with small polyethylene elastic beads, which can redistribute the sitting pressure onto a larger supporting area and help to improve microcirculation. Then the local maximum sitting pressure falls and the skin will be maintained in fine condition. Both the human body buttock thigh modal and the cushion modal are built with ANSYS 14.5 to simulate the sitting condition and analyze the local maximum pressure with different diameters of the polyethylene beads and different filling ratios. The equivalent Young’s modulus of the cushion is analyzed using the homogenization method. With the local maximum pressure for index, the influence of diameters and filling ratios of the polyethylene beads on the pressure relief performance has been thoroughly investigated. Those results could give guidance on the design of cushions with proper material characteristic to lower the pressure ulcer prevalence rate.

Abstract: One of phenomena which cannot be avoided in the hip prosthesis due to sliding contact as a product of human activity is wear on the surface of contact interaction Wear in the bipolar model is more complicated than the unipolar model. There are two contact interaction in the bipolar model, while the unipolar model has only one contact interaction. Wear on the liner and cup surfaces of the bipolar model itself can be early estimated by investigation the contact stresses due to their contact interactions. The contact stress on the liner surface of unipolar model can be estimated using analytical method. However, the estimation of contact stress on the liner and cup surface of the bipolar model using analytical method still need to consider. The aiming of this paper is to study the contact stresses on the liner and cup surfaces in the bipolar model of hip prosthesis using the finite element simulation. There are three model of hip prostheses which are simulated in this research, i.e. the unipolar, bipolar and big head unipolar models. The result showed that the maximum contact stress on the liner surface of bipolar model is higher than the unipolar model. The maximum contact stress on the cup surface of the bipolar model is lower than the big head unipolar model. Based on this results, it can be concluded that the contact stress on the liner and cup surfaces of the bipolar model cannot be estimated using analytical method.

Abstract: Bearings have been used in various environments. Recently, small and light-weight bearings are developed in order to downsize mechanical components. Polymer bearings, such as PEEK (Poly-Ether-Ether-Ketone), PTFE (Poly-Tetra Fluoro-Ethylene) and PPS (Poly-Phenylene-Sulfide-Resin), are designed because of advantages of light weight, high corrosion resistance and self-lubricating. However, industrial design standards of these bearings have not been established yet, i.e., the relation between working conditions, shape, geometry, and lives of bearing components under RCF (Rolling Contact Fatigue) is not fully understood as well as crack propagation, wear and/or failure. In this study, we focused on the manufacture process of groove curvature decreasing contact stress, and observed cracks and flaking failures on groove surfaces and cross sections. Based on these observations, we investigated the relation between the groove geometry and lives of all-PEEK thrust bearings in water.