The present work develops an explicit dynamic finite element model of soil–disc interaction for a notched harrow disc, aiming to quantify how APS coatings, soil type and disc–soil friction influence stresses in the disc and surrounding soil. The model reproduces a four-gang offset harrow operating at 7 km/h, 0.15 m working depth, with 18°disc angle and 15° tilt angle, and compares an uncoated steel disc with three APS-coated variants (P1 Metco 71NS, P2 Metco 136F, P3 Metco 45C-NS). Mechanical properties of the substrate and coatings are obtained from micro-indentation tests and introduced via a bilinear steel model and Johnson–Cook plasticity for the coatings, while disc–soil friction coefficients are calibrated from microscratch measurements. Soil behaviour is described using the AUTODYN Granular model for four representative agricultural soils, spanning sandy loam to saturated heavy clay. Results show that the uncoated disc develops von Mises stresses in the disc–soil contact region of ≈150–220 MPa, with intermediate-stiffness soils being most critical. APS coatings significantly alter both the level and distribution of stresses: P2, the stiffest ceramic, yields the highest stresses (≈421–448 MPa), P1 keeps stresses near the baseline while shielding the substrate through extended plastic zones, and P3 provides an intermediate, more uniformly distributed stress regime. Increasing disc–soil friction systematically amplifies von Mises stresses in the contact region, especially for P2. Overall, the calibrated explicit model captures the coupled influence of soil properties, coating stiffness and friction, and indicates that P1 is better suited for light-to-medium soils, P3 offers the most balanced response in medium-to-stiff soils, whereas P2 should be reserved for highly abrasive conditions and used with caution in cohesive soils.

An analytical model was developed for angular contact ball bearings running at high speeds. The model presented in this paper was designed for the 7206 C angular contact ball bearings and considers the geometrical parameters as well as the interactions between the raceways and the rolling elements involved while bearings are in operation. Using an original methodology, the effects of centrifugal forces generated by the rolling elements have been evidenced both on the normal contact load distribution and contact angles between balls and the two races. The effect of centrifugal forces was considered as a “supplementary clearance” included in a general model developed by Houpert for static conditions. Some simulations for various axial and radial loads and high rotational speeds have been presented. The results confirm important deviations of the static contact angle and the load distribution on both races.

Estimation of the power loss in miniature ball bearing grease lubricated is a complex problem. Usually the applied loads (radial and axial) have small values and the methodologies recommended by the bearing companies are cannot applied for these conditions. For a ball bearing, some friction processes have differential contribution to the total friction torque and power loss. For very low loads, the lubricant is the most important source for friction torque. In the present paper the authors determined experimentally the friction torque both in a standard 7000C angular contact ball bearing (ACBB) and a modified 7000C ACBB containing only 3 balls without cage, operating with very low axial load and lubricated with lithium soap grease. The experimental values of the friction torque have been correlated with the theoretical Houpert’s IVR model developed for hydrodynamic rolling resistances in ball race contacts considering the viscosity of the base oil of grease.

In the past decades, Mg alloys have been studied intensively as potential orthopedic applications. The present research work, the FEA of the obtained contact stresses in the case of the load applied on Mg-0.5Ca-xMn alloys has been investigated. It has been used the NCB Curved Femur Shaft Plate type as a model in order to establish the necessary modeling parameters. The objective of the present work was to highlight the strain values at the contact point on the surface of the Mg-0.5Ca-xMn alloys. The results showed that the highest stresses observed near the gaps of the plate and in the screws. It means that all mechanical loads are sustained by the plate and screws, and the patient’s femur can be recovered.

Using an unidirectional oscillator including a mass-spring system, the authors evidenced the important variations of the static friction coefficient both for very low contact pressure (0.002 MPa) and for high contact pressure (386 MPa).The experiments were realised by the CETR UMT-2 Tribometer with a variation of the sliding speed between 0.02 mm/s to 8 mm/s. The oscillator mass have 0.242 grams and the stiffness of the elastic spring had 77 N/m. The contact surface of the oscillator mass have a roughness Ra = 0.1 μm and the opposite plane surfaces have roughness of Ra = 0.1 μm and Ra = 2.5 μm. Two types of experiments were realized: the sliding between two plane surfaces with a nominal pressure of 0.002 MPa and the sliding between a plane surface and three steel balls of 6 mm with a maximum Hertz contact pressure of 386 MPa. For very low pressure the obtained static friction coefficient varied between 0.08 to 0.3 and the dynamic friction coefficient varied between 0.08 to 0.16. For high pressure the obtained friction coefficient varied between 0.2 to 0.4 and the dynamic friction coefficient varied between 0.15 to 0.2. To simulate the sliding speed the model of Zuleeg [5] for dynamic friction coefficient has been adapted to the experimental parameters and the dynamic equation of mass displacement as function on time has been numerical integrated.

Analysis of the occlusal stress distribution on the periodontal support of a 5-unit intermediate abutment prosthesis with rigid connector it is still of real interest. Aim. Forces, with vertical directions, were applied simultaneously on the entire mandibular prosthesis having as intermediate pillar the second premolar, but also separately on each supporting tooth. Matherial and Methods. A three-dimensional rigid mandibular fixed prosthesis, retained on the canine (mesial pillar) and the second molar (distal pillar), with intermediate support on the second premolar, was simulated three-dimensionally (3D, soft - CATIA V15 R19). It was subjected to vertical stresses. The forces were applied continuously, simultaneously on the entire prosthesis and separately, for each supporting tooth. Results. In the case of vertical forces, the highest concentration of stress was observed in the canine, the most distal pillar. Conclusions. In clinical situations where the fixed prosthesis with rigid connectors includes intermediate teeth, occlusal balancing, especially is essential for the perenity of the restoration.

In this study was addressed the problem of the contact stress simulation, generated in the case of the loads applied on thermal spray coatings, by finite element modelling. Starting from the characteristic lamellar morphology of this type of coatings, consisting of splats, voids, oxidized or unmelted particles, the studied layers were assimilated to an anisotropic material. Thus, it was tried to establish the parameters necessary for modelling, so that they define as accurately as possible the studied material. The purpose of this study was to identify the maximum value of the tension developed in the point contact, on the depth of the analysed layer. This value was subsequently used to determine the limit values for in practice use of the coatings.

This paper highlights the simulations of the contact stresses generated in the case of the load applied on biodegradable alloys based on Mg (Mg-0.5 Ca-xY), starting from previous studies done on these alloys and the homogeneity of the materials in different areas. Thus, it was tried to establish the parameters necessary for modeling, so that it would define as accurately the material studied. The main purpose of this paper was to identify the maximum values of the strain developed at the point of contact on the surface of the biodegradable alloys. This value was subsequently used to determine the limit values, for the practical use of these biodegradable alloys.

A well designed muffler means a compromise between its acoustic performance, backpressure, size and cost criteria. The acoustic performances of engine mufflers, in terms of insertion loss (IL) constitute the major aim of this paper. An experimental investigation of two manufactured mufflers with different inner configurations is realized. Insertion loss investigation is performed in an anechoic room and the experimental setup agrees the ISO 7235:2009 requirements. The analysis in third-octave band of measured noise gives us the sound pressure level on each frequency of interest. Sound attenuation and pressure results are highlighting the influence of mufflers inner configurations on their acoustical behaviour. A FEM analysis completes our study and simulations based on pressure results are performed in order to evaluate the critical displacements correlated to vibration eigenmodes. Our manufactured mufflers realize a good sound attenuation depending of their internal configuration.

Surface engineering has been conquered in recent decades by the versatility of the layers produced by thermal spraying, both in terms of spraying methods, of the materials types and their applications. In some cases, the coatings can be subjected during operation to rolling contact fatigue, with the main wear factors: thermal spray coatings structure and state of stress and strain in the contact area. In this paper was studied how three types of coatings deposited by APS (Atmospheric Plasma Spray) behaved at the contact fatigue tests. Subsequently they were carried out simulation of pressures and von Mises stresses distribution. It has been observed that the presence of asperities on the surface causes the development of local micro-contacts and therefore high values of pressure and local stresses in the vicinity of the surface.

The normal pressure distribution on contact area and depth distribution of von Mises equivalent stress are of major importance in prediction of various failure phenomena (e.g. rolling contact fatigue, scuffing) of the contacting surfaces. The paper reveals the relationship between roughness amplitude and stress state developed in the loaded material. The study was performed on a double rows spherical roller bearing under three levels of radial loading, and three significant values for the surface roughness. The numerical simulation was used to generate Gaussian rough surfaces with imposed values for Ra parameter. A semi-analytical method was used to solve the non-hertzian contact between rough surfaces. For the same loading level, the depth distribution of von Mises stress for rough surfaces is close to the distribution found for smooth surfaces, except the shallow layer close to the contacting surfaces. For medium and especially high loads, the contact between rough surfaces develops, inside this shallow layer, von Mises equivalent stresses higher than the fatigue limit stress.

The authors investigated analytically and experimentally the friction torque in a modified thrust ball bearing operating at very low axial load in dry conditions by using only three balls and a cage. The experiments were conducted by using spin-down methodology. The results evidenced the influence of the sliding friction between the cage and the balls on the total friction torque. It was concluded that at very low loads the friction between cage and balls in a thrust ball bearing has an important contribution on total friction torque.

A spherical roller bearing under high radial loading, constant speed and imposed roughness for the contacting surfaces was chosen as case study. Different lubrication regimes were obtained by varying oil viscosity through the operating temperature. For bearings with especially machined contacting surfaces, λ-ratio is firstly determined and its value is used to estimate the particular value of the lubrication parameter κ. Using the λ-ratio approach the paper reveals the relationship between roughness amplitude and the modified rating life of rolling bearings. The roughness values corresponding to good manufacturing practice are possible to be determined for each particular case. Three groups of random Gaussian roughness were generated with the same values for the Ra parameter as used in the modified lives investigations. For medium and especially high radial loads, the contacts between rough surfaces develop, inside the shallow layer, von Mises equivalent stresses higher than the fatigue limit stress. For condition of lack of lubricant or starved lubrication, these findings explain the initiation of the rolling contact fatigue in the shallow layer, close to contacting surfaces.

The authors investigated experimentally the friction torque in a thrust ball bearing operating at very low axial load and lubricated with mineral oils. The experiments were conducted using spin-down methodology and the results were compared with the theoretical values determined by the SKF methodology for friction torque. The values of the friction torque obtained in the experiments are higher than the analytical values obtained with SKF equations, the differences being explained by the important influence of the friction in balls–cage contacts.

Based on a theoretical model and an experimental methodology for defining the friction torque for lubricated conditions in a modified thrust ball bearing having only three balls, the authors experimentally investigated the influence of the lubricant parameter Λ on friction torque for mixed IVR (isoviscous rigid) and EHL (elastohydrodynamic) lubrication conditions. The experiments were conducted using ball diameters of 3 mm, 3.97 mm and 6.35 mm loaded at 0.125 N, 0.400 N and 0.633 N. Two oils of viscosity 0.08 Pa·s and 0.05 Pa·s were used and rotational speed was varied in the range 60–210 rpm to obtain a lubricant parameter Λ varying between 0.3 and 3.2. The experiments confirmed that the measured friction torque can be explained using hydrodynamic rolling force relationships respecting the transition from an IVR to an EHL lubrication regime.

Based on a theoretical model and an experimental methodology for defining the friction torque in a modified thrust ball bearing having only 3 balls and presented in [2], the authors experimentally investigated the influence of the ball diameter on friction torque when operating in mixed and full film lubrication conditions and maintaining the normal load, the race curvature and oil viscosity constant. The experiments were realized using ball diameters between 7.938 mm and 3 mm corresponding to maximum Hertzian pressure between 0.264 GPa and 1 GPa and a rotational speed between 60 rpm to 240 rpm. The experiments confirmed that the measured friction torque can be explained using hydrodynamic rolling force relationships respecting the transition from IsoViscous Rigid (IVR) to ElastoHydrodynamic Lubrication (EHL) regime presented in [2].

The behavior of the contact surfaces between the gear teeth has a significant influence on the gear service properties. An analytical research concerning this behavior by considering a non Hertzian model was developed. A mathematical model of the surfaces of the teeth flanks for modified involute spur gears with crowning and relieving was presented. The pressure distribution, displacement and contact surfaces were analyzed, on considering the load, material characteristics and geometry of the contact surfaces and using a numerical method.

The authors experimentally determined the friction coefficient in simulated contacts between gear teeth flanks having the slide-to-roll ratio between 0.045 to 0.15 and operating in mixed lubrication regimes. The dependence between friction coefficient in mixed lubrication regime and lubricant parameter λ has been verified according to the others models. Also, the variation of the friction coefficient with the slide-to-roll ratio was obtained.

The authors have developed a methodology and a computer program to evaluate the lubrication regimes and minimum film thickness in a spur gear transmission. For given geometrical conditions in a lubricated point contact spur gear, was generated the map of lubrication regimes according to the viscosity parameter g(v) and elasticity parameter g(e). The map of lubrication was generated in three contact points on the gear tooth flank: top, pitch and end of the pinion tooth. For given operation conditions (power, rotational speed, lubricant viscosity and temperature) was determined, both the lubrication regime and minimum film thickness. Also the ratio between minimum film thickness and gear teeth flanks roughness has been determined and the risk of scuffing failure was evidenced.