Calculation Of Contact Pressure Research Articles

Assessment of Tractor Tires Used in Forest Conditions in Terms of Traction Performance and Impact on Ground

This paper presents the assessment of selected tractor tires used in forest conditions. The first element of this assessment is related to tractive properties, while the second part concerns the potential negative impact of the tires on the ground. The research was conducted on the skid trail located in a lowland pine stand in Poland (Lower Silesian District). The 9.5-24, 400/55-22.5 and 11.2R24 tires were used for the experiment, and the following tractive parameters were analyzed: traction force, pulling force and rolling resistance. These parameters were determined during the experiment using special measure stand mounted on a 3-point linkage of the tractor. In addition to the traction properties, the impact of the wheel on the ground was determined – this evaluation included measurements of footprint areas and calculation of contact pressures. Based on the obtained results, it was shown that the increase of the vertical load and reduction of the inflation pressure of tires can cause an increase in net traction force of as much as 35% and 16%, respectively. The analysis of contact areas and pressures showed that the widest tire (400/55-22.5) had the least negative impact on the ground. The reducing of inflation pressure allowed to obtain higher traction force, higher contact area and smaller contact pressures.

An analytical model for pressure distribution in automated fiber placement on irregular surfaces and its application in aeronautical manufacturing

Automated fiber placement (AFP) is a key technology in the fabrication of composite aeronautical components, but the layup defects associated with uneven and insufficient contact pressure limit its application on irregular surfaces. Existing methods for pressure optimization in AFP are mostly based on extensive compaction experiments, which lacks theoretical basis and is not applicable to complex surfaces. In this paper, an analytical model of pressure distribution in AFP is proposed, which is suitable for any irregular surfaces. The influence of mechanical properties of contact materials and the mold curvatures on the calculation of contact pressure is taken into consideration. The Hertz theory is also extended to the three-dimensional contact area to suit the practical needs. Furthermore, an algorithm for pressure calculation along any layup path is proposed to rapid construct the pressure field. Then three sets of experiments are carried out on two aeronautical molds to validate the proposed model. The results show that the model can accurately calculate the contact pressure distribution in AFP, and compared with the previous model, the comprehensive prediction accuracy of the peak pressure is improved by 27.25 %. Combined with the layup path information, this model can be used to analyze the mechanical mechanism of layup defects, which provides a theoretical basis for the optimization of AFP parameters based on pressure distribution.

Analysis of Sealing Performance of Metal B-ring Self-Tightening Structure

Process industries often use B-ring self-tightening sealing structures and rely on interference assembly to meet the initial sealing requirements. Therefore, determining reasonable B-ring material, size and interference is crucial to ensure the sealing performance of the structure. In this paper, based on elastic deformation analysis, the deformation co-ordination equation of a B-ring sealing structure was established, and a sealing contact pressure calculation formula was obtained, with discussion of the main factors affecting sealing performance. With the finite element method, transient temperature field analysis was carried out for startup and shutdown load cases, and contact analysis was carried out for interference assembly, startup and shutdown. Based on the evaluation criteria of sealing performance with proposed sealing rate and leakage parameters, the effects of material properties, interference, B-ring size, etc., on sealing performance were investigated, revealing that although a B-ring with high material yield stress can meet the sealing requirements, both the B-ring and the sealing surface of a reactor body will yield plastic deformation. B-rings with a low material yield stress exhibit obvious plastic deformation during startup and leak during shutdown. However, leakage parameters can be minimized by smaller interference and moderate wave radius.

Research of the reasons of increased drop in cotton seeds after generation with reduced density of raw roller

Results of researches on definition of influence of density of the raw roller on pubescence of cotton seeds are given in article. The received mathematical model for calculation of contact pressure and movement of the raw roller in the form of a system from six equations with six unknown. The numerical results calculated on the computer. Sizes of shift and contact pressure for the set physic-mechanical and geometrical parameters of a system are determined. It is established that contact pressure significantly depends on elasticity (density) and angular speed of the raw roller. On the basis of the graphic data of contact pressure and contact movement of the raw roller received results of calculations the conclusion that with reduction of density of the raw roller conditions of capture of a short cotton slice worsen. The fact that the contact pressure and movement fluctuate during time is the reason of it, i.e. in the beginning the short cotton slice contacts to a saw, but during fractions of a second this contact is lost, also contact pressure similarly changes. Results of theoretical researches proved increase in a full pubescence of seeds after gin with reduction of density of the raw roller, i.e. one of the reasons of it is deterioration in conditions of capture of short cotton slices a saw - fluctuations of contact pressure and contact movement of the raw roller.

Regarding the Question of Calculation of Contact Pressure in Metal-Polymer Plain Bearings during Wear

Regarding the Question of Calculation of Contact Pressure in Metal-Polymer Plain Bearings during Wear

FEM-based wear simulation for fretting contacts

This article presents a robust Finite-Element-Method-based wear simulation method, particularly suitable for fretting contacts. This method utilizes the contact subroutine in a commercial finite element solver Abaqus. It is based on a user-defined contact formulation for both normal and tangential directions. For the normal contact direction, a nodal gap field is calculated by using a simple Archard's wear equation to describe the depth of material removal due to wear. The wear field is included in the contact pressure calculation to allow simulation of wear and contact stress evolution during the loading cycles. The main advantage of this approach is that all contact variables are accessible inside the routine, which allows full coupling between normal and tangential contact variables. Also, there is no need for mesh modifications during the solution. This makes the implementation flexible, robust and particularly suitable for fretting cases where friction and tangential contact stiffness play an essential role. The method is applied to the bolted joint type fretting test case. The methodology is also fully applicable to complex real component simulations.

Determination of Contact Pressure during Double-T Section Rolling in Universal Beam Groove

Based on application the physical constraint equations of state of stress and strain of the metal for the isotropic medium, we get expressions for components of stress tensor. The new theoretical method for calculation of contact pressures and rolling force during rolling of double-T section in a universal beam groove was developed. Reliability of the method is confirmed by the results of experimental verification for conditions of rolling of H-beam No 35B1, 40K2 and 45B2 from steel 15CrSiNiCu on the universal beam mill of "NTMK". The average calculation error is 6.4%. The new method is recommended for calculation pass design and technological modes of H-beam rolling on rail-beam and section mills, equipped with universal stands.

Prediction of contact condition and surface damage by simulating variable friction coefficient and wear

Abstract A simulation method to predict the reliability of clamped metal contacts under cyclic loading is presented. The main idea is to predict the development of contact condition of a joint by simulating a spatially variable coefficient of friction (COF) and wear. Frictional energy dissipation drives the COF evolution rule, and classic Archard's equation is employed as the evolution rule for wear depth. As both the COF and wear evolution are considered, the presented approach is capable of predicting changes in the contact condition over time. The approach is based on the Finite Element Method (FEM) and is generally applicable to industrial cases. The method is implemented as a subroutine to a FEM solver Abaqus to define a contact formulation in both normal and tangential directions. The subroutine allows full coupling between normal and tangential contact variables, which makes the approach robust also in complex industrial applications. As the effect of wear is described in the contact pressure calculation, there is no need for mesh modification. The presented approach was validated by simulating cylinder-on-plane configuration. The presented method provides similar results obtained with a simulation where geometry is updated due to wear. The results of the case study were qualitatively verified against a bolted joint type fretting experiment. The area of slip after stabilized COF distribution corresponds well with the experimental fretting scars. However, Archard's wear law seems to be limited, at least in partial slip cases, as it overestimates the amount of wear without considering entrapment of wear debris in the contact. A case study of medium speed combustion engine component is presented to show how the simulation method can be used in engine development to ensure reliable contact interfaces.

Mathematic model for describing the stress-tension behavior of an autoclave with integrated heating element

This paper describes a mathematical model and the method for determining the thermal stress fields in a cylindrical wall element of a pressure vessel with a built-in heating element and a layer of heat insulating material. The method presented is based on the calculation of contact pressures.

Teeth geometry and contact pressure calculation of external cycloidal gears

Teeth geometry and contact pressure calculation of external cycloidal gears

An improved simplified model of rough surface profile

Abstract In order to obtain accurate characteristic parameters of contact between rough surfaces, such as curvature radius of asperity, a new method of asperity definition based on the reference line and the height of peak and valley is proposed in this paper. The real profile of the rough surface is described by parabolas. To improve the stability of contact calculation of the rough surface, the nominal contact line is taken as a simplified reference line. The simplified results show that: 1) the mean square error between the parabolas simulated by the proposed method and the real profile is smaller; 2) the calculation of contact pressure, contact area and other contact performance parameters have better stability.

Investigation of the process of thread extrusion using the ultrasound

We investigated and modelled the process of ultrasonic extrusion of a thread when imposing the ultrasonic oscillations. Based on the rheological model of deformation of the perfect elastic-plastic body, we constructed dependences for the calculation of contact pressures and specific friction force. In carrying out the present research, in order to simplify a mathematical model, the assumption was made on that the phenomenon of surface strengthening exerts little effect on the magnitude of contact pressure and friction force at plastic deformation. This mathematical model describes complex motion of the tool (rotational and oscillatory motion of the tap). The system of the derived dependences, which describes the influence of oscillation amplitude, oscillation direction, deformation rate, and mechanical properties of the machined material on the magnitude of contact pressure, makes it possible to estimate parameters of the process of plastic deformation when imposing the ultrasound. By employing such a description, it is possible to derive the value of contact pressure and friction forces for each region of the load chart. During analysis of the obtained results it was established that an increase in the amplitude of oscillations leads to a decrease in the time of contact between a tool and the machined surface, which is why contact pressure, specific friction of axial and torsional oscillations over a period decrease accordingly within a change in the examined factors. The benefit of the present study is a detailed analysis of the contact interaction between a tool and a part, as well as consideration of mechanical properties of the machined material, which makes it possible to choose the modes of treatment and to provide maximum operational performance

Mathematical models of tires and calculation of contact pressure on soil

When developing a new vehicle for certain tasks, their various characteristics are compared: engine power, mass, payload, etc., the calculation of which is sufficiently reliable. The tire pressure on the contact spot is one of the most important characteristics for determining the index of the off-road flotation of a wheeled vehicle, the determination of which directly depends on the mechanical properties of the tire, the roadway and their interaction. Ground pressure is the pressure exerted on the soil by tires or traces of a motorized vehicle, and is one of the indicators of its potential mobility, especially on softer ground. This article is devoted to the study of tire models and methods for determining the pressure of a wheeled propeller on the soil. The article contains information on the interaction of the tire with different support surfaces, as well as various approaches to the issue of determining the flotation of wheeled vehicles. Modeling the real contact area or the contact profile of the tire provides certain difficulties. Most solutions are based on a contact profile using a helix or an equivalent hard wheel, using a larger hypothetical wheel radius. One of the main models for calculating the tire's contact pressure on the soil is the MMP developed by D. Rowland to assess the maximum pressure of various tires intended for off-road and tracks on soft soils. It is established that, despite scientific achievements in the field of vehicle patency, there are still difficulties in determining the optimum parameters of the wheeled propulsion device to achieve the maximum mobility and environmental friendliness.

Development of Removal Amount Estimation Method Based on Calculation of Elastic Deformation of Superabrasive Stones During Multistage Superfinishing of Sapphire

In planarization processes of sapphire, lapping process takes a long time because sapphire is a hard material. In contrast, superfinishing, which involves fixed abrasive machining, can substitute for lapping, and it would be possible to shorten the amount of processing time. In this work, vitrified-bonded diamond superabrasive stones with different grain diameters are developed. Then, multistage superfinishing is investigated by combining these stones. Results indicate that the multistage process is capable of producing a 2 nmRa surface, equivalent of a lapped surface in less than 10 min. To improve the process of multistage superfinishing, a removal amount estimation method is developed based on the real contact pressure calculation. The working area ratio of the stone was calculated by considering elastic deformation during superfinishing. The contact ratio of sapphire is calculated considering the roughness of the pre-finished surface and grain depth of cut. Accordingly, the real contact pressure is calculated to estimate the removal amount during superfinishing and finished surface roughness was expected.

3D modelling of tyre-pavement contact pressure

Pavement design assumes uniform contact loading because of bottom-up traditional cracking (far from loading), but nowadays more and more surface damage (top-down cracking and rut) due to new technology in pavement and tyre design is observed. Then, a more realistic tyre–pavement contact modelling has to be considered. In order to go towards more realistic tyre–pavement contact, finite element method consumes a lot of calculation time; so in this article, we propose a semi-analytical model developed for the calculation of ball bearings. The contact is considered as a Hertzian contact, and the surface of the road is flat and that the tyre is smooth. Calculation of contact pressure is compared and validated with experimental data using a device called Stress-In-Motion, which allows contact pressure measurement. Different parameters are assumed in the modelling such as tyre pressure, axle loading and tyre shape. We have now a successful tool to analyse the tyre–pavement contact, more accurate and realistic and especially faster than those used at the moment.

Определение контактного давления при прокатке двутавровых профилей в универсальном балочном калибре

Solution of the problem of determining contact pressures and rolling forces in a universal groove is presented using physical equations of linking stressed and strained states of metal in the deformation zone. The variational principle of full power minimum was used to state and solve the problem of determining stressed and strained states of metal during rolling a double-T section in a universal four-roll groove. Deformation of the neck and flanges was considered as rolling of rectangular beams on a smooth surface of rolls, assuming that drafting of flanges occurs from the vertical roll direction only. From the solution of this problem the components of the strain rate tensor and intensity of shear deformation were determined using known conditions of mechanics. A new theoretical method of calculation of contact pressures and rolling forces during rolling double-T sections in a universal beam groove was developed. Its reliability is confirmed by the results of experimental tests. The method of determination of contact pressures and rolling forces was implemented as a Mathcad software package program for calculations on a personal computer. Calculations of rolling double-T sections No. 35B1, 40K2 and 45B2 made of 15KhSND steel at a universal beam mill of JSC “NTMK” were performed for the experimental verification of this method. Comparison of calculated data with the results of experimental studies revealed an average error of 6.4 %.

Selection Of Analytical Computational Model Of Contact Pressure

Abstract This paper presents a comparison of two contact pressure calculation methods between two real rough surfaces: a calculation based on FEM (Finite Element Method) using commercial software tool ANSYS and a calculation based on FDM (Finite Difference Method) using analytical functions implemented in programing tool MATLAB. This comparison, lately, leads to the selection of the most appropriate analytical contact model useful for time-effective and precise contact pressure determination. Surface data for numerical simulations are obtained by optical profilometry. For the case of the modelling process of 3D FEM models of rough surfaces the description of their building is included in this article. Furthermore, this paper discusses all challenges connected with the convergence of such simulations and essential post-processing of FEM simulation results, together with their comparison, along the results obtained by user-written MATLAB functions.

Theoretical and experimental studies for wind turbine’s shrink disk

With the wide application of multi-layer interference fit in many engineering fields, as for key component in the wind turbine generator, wind turbine’s shrink disk uses interference fit to transmit rated torque and axial force. In order to ensure the work reliability of shrink disk during the actual operation, the paper presents a more precise method on the design calculation of contact pressure on the mating surfaces with interference fit. In accordance with the order from the inside to the outside, the contact pressure of spindle-to-sleeve surface can be calculated based on the rated load required to transmit. Combining with Thick-wall Cylinder Theory and Lame Equation, taking into account the impact of fit clearance, the checking method of the bushing was used to calculate the contact pressure on mating surface of bushing-to-inner ring; and the stress analysis of the inner ring was used to calculate the contact pressure on mating surface of inner ring-to-outer ring. At the same time, the effects of frictional coefficient, fit clearance, and other design parameters on theoretical results were also analyzed. The pressure distribution of each mating surface was obtained by Abaqus software simulation, which showed that the results from improved method was closer to simulation results and had higher accuracy than traditional method by comparing the results with three different methods. Finally, the test was designed to verify whether the shrink disk could bear the load or not on the test platform of shrink disk, and the results indicated that it could meet the requirements of given loadcase.

Modeling the edge contact effect of finite contact lines on subsurface stresses

Finite contact line conditions lead to subsurface stress distributions determined by the free boundaries. Combined with a correction procedure, Semi-Analytical Methods (SAMs) accurately include the free boundary effects, and represent a rapid alternative to the Finite Element Method (FEM) for contact pressure calculation. This paper extends the free boundary correction procedure to the evaluation of surface and subsurface stresses from SAMs. The investigation integrates a validation based on a two-level factorial comparison confronting the stress distributions established with the developed procedure to results obtained from FEM models. The comparison examines three dimensionless factors, and shows that the stress distributions are evaluated with a high level of precision. The model also offers evaluation more than 125 times faster than FEM simulations.

Leak behaviors of steam generator tube-to-tubesheet joints from room temperature to 320 °C

To address concerns about excessive leakage from throughwall cracks in nuclear reactor tube-to-tubesheet joints under accident conditions, leak rates were measured experimentally by using tube-to-collar joint specimens and nitrogen gas. Rates were dependent on differential pressure between the tube internal surface and the crevice (i.e., the tube-to-collar interface region) and on temperature. As specimen temperature was raised to 320 °C, leak rates decreased gradually due to changes in gas properties and to differential thermal expansion between the Alloy 600 tubes and the SA508 collars. The leak rates did not change even after repeated temperature excursions to 320 °C, suggesting that thermally induced creep and subsequent contact pressure relaxation is negligible below that temperature. When considering factors that could increase flow resistance, such as oxidation, or debris on top of the tubesheet, the measured leak rates in this work are considered to be conservative. The test results were further used to validate the contact pressure calculation and a leak rate model.