Deformation Of Contact Surface Research Articles

Концепция микромоделирования процесса соединения разнородных материалов пластической деформацией

Introduction. Bond strength between dissimilar materials is the most important characteristic of laminated composites, which determines the success of its development for industrial use. In order to develop the theory of joining materials by plastic deformation, it is proposed to perform computer simulation of joint deformation of representative volumes of dissimilar materials on a microscale and compare the parameters of the stress-strain state with the previously presented theoretical mechanism. The aim of this work is to analyze the stress-strain state of dissimilar materials under plastic deformation on a microscale and to establish the location of the onset of fracture of surface oxide films. To achieve this aim, the following tasks of the work are formulated: 1) to study the surface profiles of dissimilar materials to be bonded by plastic deformation; 2) to simulate by the finite element method (FE) the plastic deformation of contact surfaces of dissimilar materials on a microscale; 3) to study the stages of joint deformation of dissimilar materials on a microscale and verify of the theoretical mechanism. Research methodology. The study of three-dimensional topography and roughness was carried out on a Veeco Wyko NT1100 Optical Profiling System. Deform-3D FE simulation package was chosen as the main research tool. Aluminum alloys AMg3 and D16 were chosen as the materials under study. Results and discussion. In this work, computer FE simulating of the joint deformation of the surface layers of AMg3 and D16 alloys on a microscale was performed, an analysis of the surface profiles of materials after various types of processing was carried out, the parameters of the stress-strain state were studied and compared with the parameters of the theoretical mechanism. Based on the results of the comparison, the adequacy of the proposed theoretical mechanism was assessed, and the practical difficulties of theoretical simulation of the joint deformation of dissimilar materials on the microscale were noted. Microscale FE simulation made it possible to study the flow of plastic deformation in the near-surface layers of materials, as well as to identify areas of the most probable fracture of surface oxide films and, consequently, areas of primary bonding of dissimilar materials.

Design of hourglass-lattice metastructure with near-zero thermal expansion using structural optimization method

Zero thermal expansion (ZTE) is strongly demanded for critical components of spacecraft structures exposed to extreme temperature variations in space. In this paper, a lattice metastructure with near-ZTE is numerically achieved by structural optimization method. A sandwich panel with one single layer of hourglass-type lattice cells with variable cross-sectional and bi-material beams are assembled to produce either positive or negative thermal expansion (PTE or NTE). Then, a multilayered construction of metastructures is proposed by the combination of both PTE and NTE layers to realize the overall behaviors of near-zero deformation. The structural optimization with the gradient-based algorithm is utilized to obtain an extreme low value of coefficient of thermal expansion (∼10-9 /K). The shape constraint is adopted to regulate the thermal deformation of contact surfaces of each layer. Furthermore, bi-material prototypes with nylon and short carbon fiber reinforced composites are fabricated and tested, and the results demonstrate a NTE value of −6.32 × 10-5 /K, PTE value of + 1.28 × 10-4 /K, and ZTE value of 2.53 × 10-6 /K. This agrees well with the optimization result. Overall, the proposed hourglass-lattice metastructure with a high thermal stability is a promising solution to enable large-scale space structures such as space telescope, antenna, and radar, etc.

Telematics of new vehicles for the purpose of pedestrian safety

Pedestrians are a vulnerable group of traffic users who most often suffer serious physical injuries in collisions with motor vehicles, which very often have a fatal outcome. The modern automotive industry is investing great efforts in the development of active and passive protection systems for all traffic participants, including pedestrians. Pedestrian protection is tried to be achieved by changing the shape of the front parts of the vehicle, by using plastic materials with higher deformation potential which, in collision with the body of the pedestrian, will spend most of the impact energy on its own deformation and thus maximally spare the delicate biological tissue of the pedestrian. Instead of protruding, rigid metal structures of insignificant elasticity and deformation potential, today’s cars are characterized by appropriate body design, use of high elasticity materials and deformation of contact surfaces, specially shaped and integrated bumpers, elastic and raised bonnet, headlights integrated into the contour of the vehicle front which are capable of absorbing part of the impact energy. Modern research shows a certain efficiency of these improvements on modern cars. Most of these studies are of the experimental type and are done in strictly controlled conditions on dolls, often commissioned and funded by wealthy automobile corporations, while there is less research in real field conditions. Recently, experiments have been made with testing the active bonnet, the airbag under the bonnet, and the google model of gluing the pedestrian body.

The effects of material and structure of main bearing caps on crankshaft lubrication of diesel engine

The elastic deformation of the crankshaft and engine block has important effects on lubrication performance of main bearings of the diesel engine. But the effect of main bearing caps was rarely analyzed. The purpose of this article is to analyze and compare the tribological performances of main bearings of a 20-V medium-speed diesel engine with different materials and structures of main bearing caps. A coupled multi-elastic body and elasto-hydrodynamic model is established for a 20-V medium-speed diesel engine. The deformations of engine block, crankshaft and bearing caps are simulated with finite element modal condensation method. The bearing lubrication analysis is based on the extended Reynolds equation considering the deformation of contact surface and solved by finite difference method. Two materials and four structures of the main bearing cap are analyzed with the coupled model. The distribution of oil film pressure, thickness and bearing thermal loads are obtained and analyzed. The main bearing cap of iron is better than steel on bearing lubrication performance. With the lower edge stiffness of bearing cap, the maximum oil film pressure of bearing can be reduced by 13%. Meanwhile, the bearing thermal load can be reduced by 53%. The results show that when the bearing cap material is iron and with large trough on both sides of bearing cap, the peak value of edge pressure and the average heat load of main bearing can be reduced effectively under the premise of ensuring stiffness.

Rational hardness ratio of fuel equipment parts under static loading

The definition of a rational combination of hardness of parts is necessary to determine the resource indicators of products. This task is also relevant for parts of internal combustion engines, including parts of their fuel equipment of any type. In operation such parts are used under constant contact. There is a wide distribution of fuel systems such as Common Rail in Russia. The high fuel pressure in the cavities of such systems exists both at the time of injection and between injections as well. The development of production of the domestic common rail fuel type system makes the task of determining the rational ratio of hardnesses even more important. Its solution is necessary, for example, for connecting high-pressure fuel lines with nozzle fittings, high-pressure pumps and fuel batteries. Engine manufacturers in some cases indicate in the operating instructions the maximum intervals for the use of certain components, for example, high pressure fuel lines. At the same time, there are practically no methodological materials allowing one to choose one or another hardness ratio. There are only a few attempts in this direction made in higher education institutions, for example, in the Polzunov Altai State Technical University. In this paper, an attempt is made to estimate the deformation of contact surfaces in «sphere-by-cone» type joints, which are typical for modern fuel equipment with various combinations of component hardness. The criterion for the rationality of the combination of hardness is the width of the contact trace - the residual deformation of parts. It is shown that when evaluating the rationality of fuel equipment manufacturers are guided by what component is more appropriate to replace in operation.

Multiphysics Analysis of Hemispherical Bulk Conductor Hertzian Contact Under Uniaxial Mechanical Load

A multiphysics model of smoothed contact surface hemispherical contact under dynamic vibration stress is treated in this paper. The contact structure is applied to hemispherical conductor bulk materials. The structure electrothermomechanical (ETM) behavior is investigated based on the Hertz contact theory coupled with electrokinetic approach. An electrical circuit integrating the contact material properties is proposed. The contact surface deformation ETM expression is formulated. The transient variations of the contact conductor material temperatures in function of the mechanical vibrations are analytically described. The ETM parameters range versus the mechanical load stress is analyzed by considering aluminum alloy material hemispherical bulk with a radius varying from 10 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m to 1 mm. The contact radius can be totally deformed when the load is increased up to 20 kN. In addition, an innovative multiphysics computational method is validated numerically to determine the transient variation of the contact surface radius model from SPICE simulation by considering 0.5 kHz/1 kHz frequency presenting 0.5-kN amplitude sine wave, and arbitrary waveform dynamic vibrations. It was conjectured from numerical application, the hemispherical bulk contact temperature, and also the mechanism multiphysics phenomena governing the structure behavior. As ongoing research, the equivalent system tensorial statement illustrating the multiphysics interaction between the conductor contacts will be developed.

Effects of friction layer characteristics on the tribological properties of Ni3Al solid-lubricating composites at different load conditions

This paper investigates the effects of friction layer characteristics of Ni3Al matrix self-lubricating composites (NMCs) on the tribological properties sliding against ceramic ball Si3N4 at dry friction process at the different load conditions. The characteristics of friction layer are performed in terms of hardness of wear scars, thickness and elemental distributions of friction layer. The results show that the microhardness of wear scars of NMCs increases with the increase of the sliding time and applied load, which results in friction coefficient reduced and wear rate decreased, indicating that the tribological performance of NMCs is obviously affected by microhardness of wear scar. However, under excessive applied load, the performance of friction layer of NMCs is deteriorated for the spalling of wear debris and deformation of contact surface. Therefore, selecting appropriate load conditions during the sliding contact, at the transition to the optimal properties of friction layer maybe occur. NMCs exhibits excellent tribological properties at 15N, which leads to the lowest friction coefficient (0.386) and wear rate (2.48 × 10−5 mm3 N−1 m−1), as well as the smoothest surface of wear track compared with the other load conditions. Meanwhile, the elemental distributions analysis of cross-section of friction layer of NMCs shows that the frictional structures can be divided into three main layers. The thickness of the friction-affected layer varies with the changing of applied load. These results could provide a reference for preparing the solid-lubrication materials with better tribological properties.

Tribological performance studies of micro-patterned seal-shaft contacts

Surface texturing is a technique where well defined micro-patterns are created on the tribo-surfaces to have a tailored surface topography instead of random. It helps in improving the tribological behaviour and life of mechanical seals used extensively in industry. Among the different attributes related to textures, the stress concentration and deformation of contact surfaces is not seen reported in literature so far. In this paper, both finite element (F.E.) and experimental studies have been reported exploring the performance of contacts during dry and lubricated unidirectional motions. Experimental studies have limitations in employing a large number of texture patterns to study the performance behaviors due to cost and time constraints. Hence it is essential to develop finite element models. The results showed that the stress concentration around micro features is strongly depended on load. The experimental studies conducted on a pin-on disc apparatus showed that, the coefficient of friction is reduced at the contact in the presence of surface textures. The presence of lubricant is found to have reduced the material loss of seal when in contact with hardened steel.

Modeling and experimental validation of a linear ultrasonic motor considering rough surface contact

Linear ultrasonic motor is driven by the interface friction between the stator and the slider. The performance of the motor is significantly affected by the contact state between the stator and slider which depends considerably on the morphology of the contact interface. A novel fiction model is developed to evaluate the output characteristics of a linear ultrasonic motor. The proposed model, where the roughness and plastic deformation of contact surfaces are considered, differs from the previous spring model. Based on the developed model, the effects of surface roughness parameters on motor performance are investigated. The behavior of the force transmission between the stator and the slider is studied to understand the driving mechanism. Furthermore, a comparison between the proposed model and the spring model is made. An experiment is designed to verify the feasibility and effectiveness of this proposed model by comparing the simulation results with the measured one. The results show that the proposed model is more accurate than the spring model. These discussions will be very useful for the improvement of control and the optimal design of linear ultrasonic motor.

Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E−3, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.

Development of a novel large stroke 2-DOF micromanipulator for micro/nano manipulation

An electromagnetic actuated XY micromanipulator with completely decoupled characteristics is proposed in this paper. The design process, stiffness and kinematics analysis, and experimental study are performed. In order to improve the accuracy and decoupling performance, contact surface deformations, tensile and compression deformations of the flexures are taken into consideration. The mathematic models in terms of stiffness and kinematics models are derived based on the matrix displacement method, and then validated by using ANSYS and MATLAB software. A prototype is fabricated, and electromagnetic actuator is adopted due to the merits of low-cost, large stroke and non-contact driving. Each axis of the manipulator is driven by two actuators, so the end-effector can realize four quadrant motions. On account of model uncertainty, a repetitive controller is introduced. Open-loop and closed-loop experiments are conducted. Experimental results indicate that the proposed manipulator can be widely used in micro/nano positioning and manipulation applications.

Investigation of mucosa-induced residual ridge resorption under implant-retained overdentures and complete dentures in the mandible.

This study aimed to investigate and compare the residual ridge resorption (RRR) induced by an implant-retained overdenture (IRO) and associative biomechanics and by a conventional complete denture (CD) without implants. Cone beam computed tomography was used to quantify RRR in a three-dimensional (3D) manner before and after 1 year of treatment with either IROs or CDs. Twenty patients were treated with IROs, and nine patients were treated with CDs in the mandible. Their maximum bite forces were recorded. The same sets of high-resolution scan images were used to create patient-specific 3D finite element analysis models. The hydrostatic stresses, contact surface deformation, and strain energy absorption in soft tissue mucosa were correlated with the changes in RRR for patients with and without implants. With the IROs, contact surface deformation on the mucosa was two times greater than with CDs (0.32 ± 0.23 mm vs 0.16 ± 0.06 mm) and was in agreement with the amount of RRR measured, which was also two times higher for the IRO than the CD (-3.8% ± 4.5% vs -1.9% ± 0.4%). Taking into account the differences in bite forces with and without implants, which again were twice as high with IROs, the hydrostatic stress within the mucosa was found to correlate well to the RRR map measured over the 1-year interval of treatment. IROs resulted in at least twice the RRR as CDs. This could be caused by the higher hydrostatic stress and less effective energy absorption capabilities of the mucosa underneath the IRO. While implants associated with the IRO provide stronger bite force, they could potentially concentrate hydrostatic stress and cause greater RRR compared to a conventional CD.

Lubrication Analysis for a Line Contact Covering from Boundary Lubrication to Hydrodynamic Lubrication: Part I-Micro Contact Results

The paper presents an analysis for a line contact where physical adsorbed layer boundary lubrication or hydrodynamic lubrication may occur, considering the boundary film dynamic and noncontinuum effects, the contact surface thermo-elastic deformation, the surface pressure effect, the contact surface shear stress effect on the contact surface deformation and the contact surface elastoplastic deformation. Exemplary calculations were first made for a micro contact. The obtained results show that in a micro line contact the contact surface thermo-elastic deformation has a negligible influence on the central film thickness for modest sliding speeds and loads, however it can yield a more than 10% reduction of the contact load-carrying capacity for very high sliding speeds and heavy loads due to the contact severe frictional heating. When the contact is in boundary lubrication, for a given load, a non-continuum boundary film model gives a considerably higher central film thickness than a continuum lubricating film model whenever the contact is in elastic, elastoplastic or fully plastic deformation, and a strong boundary film–contact interaction gives a greatly increased central film thickness and a much more insensitive central film thickness-load variation than a weak boundary film–contact interaction, which sustains a considerably high central film thickness in the contact even for heavy loads. The boundary film compressibility caused by the boundary film–contact interaction reduces the contact load-carrying capacity. The surface pressure and the contact surface shear stress were analyzed to have no influence on the total contact surface deformation and the central film thickness.

The Influence Factor Analysis for Coupling Performance of HSK Tool System

The coupling performance of tool system is the important factor for the machining quality of high speed machining. Based on the deformation of contact surfaces of HSK tool system, the paper makes the academic analysis by elasticity theory and finite element simulation to high speed spindle/tool shank coupling system. The property of the contact stress and the radial deformation as well as the torsional stiffness with different amount of interference has been analyzed. In this method, the paper brings forward how the amount of interference will affect the coupling performance. Thus, it will give academic evidence to design and select tool system in the process of high speed machining.

1A1-D07 反射型触覚センサにおける汎用性の高い形状復元手法の提案

We are developing a reflection type tactile sensor, which is simple and sensitive one. This sensor measures deformation of contact surface from reflection image. In order to solve the inverse problem, we formulated new method of shape reconstruction employing three dimensional vectors. We evaluated our proposed method by reconstructing deformed surface from reflection images produced by simulation.

Indentation contact behavior of copper–graphite particulate composites: Correlation between the contact parameters and the electrical resistivity

The elastoplastic contact surface deformations of copper–graphite particulate composites are examined in instrumented Vickers/spherical indentation tests. The composites include various contents of metallic Cu-particles with various sizes and shapes originated from the starting powders, that are mixed with flaky natural graphite having various sizes. The elastoplastic surface deformations of the composites are characterized in term of the elastic modulus E′, contact hardness H, and the relative residual depth ξ r of hardness impression. The surface deformations of the composites are well correlated to their microstructures and electrical resistivities. It is concluded that the evolution of the percolation structures of Cu-phases is essential in controlling the electrical resistivity and the plastic ductility of the composite.

Evaluation of scuffing behavior of single-crystal zirconia ceramic materials

Scuffing, described as sudden catastrophic failure of lubricated sliding surfaces, is usually characterized by a sudden rapid increase in friction, temperature, and noise, and is an important failure mode on sliding surfaces. In metallic materials, scuffing results in severe plastic deformation of surfaces in contact. This study evaluated the scuffing behavior of two variants of zirconia (ZrO 2) ceramic. Using a block-on-ring contact configuration and unformulated polyalphaolefin (PAO) lubricant, step-load-increase scuffing tests were conducted with single crystals of cubic ZrO 2–9.5% Y 2O 3 and tetragonal ZrO 2–3% Y 2O 3. Phenomenological “scuffing”, characterized by a sudden rise in friction coefficient and noise, was observed in the cubic material. For this material, “scuffing” occurred by sudden fracture at the end of test. The tetragonal material underwent no sudden failure (scuffing). This lack of scuffing is attributed to the sequential operation of three plastic deformation mechanisms: ferroelastic domain switching, tetragonal-to-monoclinic phase transformation, and dislocation slip as the frictional stress and energy dissipation pathway.

Modeling of dry stiction in micro electro-mechanical systems (MEMS)

Stiction, a term commonly used in micro electro-mechanical systems (MEMS) to refer to adhesion, is a major failure mode in MEMS. Undesirable stiction, which results from contact between surfaces, can severely compromise the reliability of MEMS. In this paper, a model is developed to predict the dry stiction between uncharged micro parts in MEMS. In dry stiction the interacting surfaces are assumed to be either hydrophobic or placed in a dry environment. In this condition the van der Waals (vdW) and asperity deformation forces are dominant. Here a model is developed for the vdW force between rough micro surfaces, and the new model is combined with a newly developed multiple asperity point model for the elastic/plastic deformation of rough surfaces in contact to solve the equilibrium condition of the forces. This in turn will yield the equilibrium distance between micro surfaces, using which the apparent work of adhesion can be found. The theory result is compared with the available experimental data from the literature. The developed model can be easily used for design purposes. If the topographic data and material constants are known, the desirable adhesion parameters can be quickly found from the model.

517 接線応力法によるフレッティング疲労強度評価の有効性(OS フレッティング摩耗と疲労)

Fretting fatigue test of NiCrMoV(JIS-SNCM439) was carried out using pads of same material and specimens of three kinds of height. There was little difference in the time strength of fretting fatigue between the heights of specimen, however a slight difference in the fatigue limits was observed: the fretting fatigue limit increases slightly as the height of specimen is extremely smaller. Fretting fatigue strengths in overall life range were successfully predicted by using an assumed stress-strain curve on the pad material for considering the deformation of contact surface by fretting wear.

Deformation of contact surface between an agricultural tyre and soils

Deformation of contact surface between an agricultural tyre and soils