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Within this paper, electro-mechanical long-term tests on a thrust bearing were presented. The effects of an additional electrical load on the bearing raceways and the used lubricant were investigated. Chemical investigations and viscosity measurements were presented, which show the changes in the lubricant. These investigations were compared with the electrical loads and the occurring raceway damage. In addition, a comparison was made with mechanical reference tests. This procedure makes it possible to classify the changes that occur due to the electrical load and to distinguish the effects from each other. The background to these investigations is the increased occurrence of parasitic currents in electric motors, which can lead to damage to machine elements. The phenomena that occur here are new challenges in the development of drive trains.

In the presented work, a parametric multibody simulation model is presented that is capable of predicting the friction torque and kinematics of tapered roller bearings. For a highly accurate prediction of bearing friction, consideration of solid and lubricant friction is mandatory. For tapered roller bearings in particular, the friction in the contact between the rolling element and raceway is of importance. Friction forces in the contact between the rolling element end face and inner ring rib as well as roller cage pocket contacts are also considered in the model. A large number of tests were carried out to validate the model in terms of the simulated frictional torque. Influencing variables such as speed, axial load, radial load, and temperature were investigated. The simulation results show good agreement with the measured friction torque, which confirms that the model is well suited to predict frictional torques and therefore the kinematics of tapered roller bearings.

A multiscale approach for the fatigue life estimation of rolling bearings is presented in this paper and applied to inner rings of cylindrical roller bearings of the type NU208. The forces acting in the rolling contact are determined from system-oriented modeling at the macro level. The microscale contact simulations are carried out in a half-space contact model. The stresses on the inner ring are determined and used in the local fatigue approach, according to Fatemi–Socie, for fatigue life estimation. Four surface variants were investigated, one ideally smooth surface and three real (rough) surfaces. The three rough surface variants used different finishing processes: fine ground, hard turned, and rough ground were produced. A load case with a maximum pressure of 2.4 GPa in the roller-inner ring contact was investigated. In addition to the fatigue life estimation, the plasticity behavior (surface topography, resulting contact pressure, and residual stress) of the three manufactured surfaces stood in the focus of the work. As the comparison between experimental and simulated results confirms, good predictions can be made with the simulation model.

Polytetrafluoroethylene (PTFE) exhibits excellent non-stick properties and a very low coefficient of friction under tribological stress, but it is incompatible with almost all other polymers. In the first part of this study, we presented the generation of the novel tribological material based on unsaturated oil, radiation-modified PTFE and Polyamide 66 (PA66). To get a better understanding of the chemical properties and chemical composition of the compounds, the PA66-PTFE-oil-cb (chemically bonded) compounds were examined by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). In this part, the mechanical properties of the compounds are compared with plain PA66 and PA66-MP1100-cb. The tribological investigation was carried out using the block-on-ring tribometer. It was detected that the mechanical properties of PA66-PTFE-oil-cb with 20 wt% PTFE-oil-cb only show slight differences compared to PA66, but the tribological properties of the compounds were significantly improved through chemical coupling between the three components.

Radial shaft sealing rings (RSSR) are important machine elements used in rotating and oil lubricated systems. Their main task is to prevent oil from exiting the system and dirt particles from entering the system. When this function is not fulfilled, a leakage can occur and cause excessive damage after certain operating times, such as gear failure due to insufficient lubrication. This is the reason for the high level of current research interest in seals. The sealing function of RSSR occurs in the contact area between the sealing lip and the shaft. The contact takes place over a very small contact width of approximately 1 μm. These extremely small dimensions and the complex relationships between the functional influencing variables on the radial shaft sealing system make it difficult to simulate wear on the sealing ring. The energetic consideration of the wear process offers the possibility of quantifying influencing variables more easily by their energetic contribution, which can be determined experimentally. Based on experimentally measured total friction moments, and with the help of a semi-analytical (SA) solid contact model based on the half-space theory, this paper presents a modelling approach for the calculation of wear at the sealing ring. The model presented in this work differs from the existing models in two ways. The first particularity is the coupling of SA method with finite element method (FEM) for the resolution of the contact between the sealing lip and the shaft, allowing a fine discretization of the contact zone (by SA method) and the consideration of the structural behavior (by FE method). The SA method compared to the commonly used FEM presents a great saving in computation time. The second particularity is the use of the real data obtained during the wear tests. Most existing simulation models are based purely on contact pressure. This means that through the contact pressure obtained by simulation and a given sliding distance value, a friction energy will be estimated which will be used in a next step using a wear model such as Archad’s to calculate the wear rate. In this publication the value of friction energy was obtained directly on an experimental basis and a more appropriate wear law, such as Fleischer’s, taking into account the friction conditions, was used to estimate the wear rate.

In the course of increasing electric mobility, the effect of electricity on parts of machines is more significant than before. Rolling bearings and their lubrication, as a part of electric motors, are subjected to harmful currents, which lead to damage in the bearing in the long term. In order to avoid such damage, the influence of the lubricant in the bearing is becoming increasingly important. The electrical behaviour of the system can be investigated by analysing the discharge currents and the breakdown voltage in rolling bearings with lubricants of different compositions. This paper presents a procedure for characterizing the breakdown voltage at the rolling bearing and the influence of conductivity of the lubricants on harmful electrical phenomena.

At the Institute of Machine Elements, Gears, and Transmission (MEGT, University of Kaiserslautern) a spherical roller bearing has been modeled in an multi body system (MBS) environment. The use of the commercial MBS (multi-body system) software (MSC ADAMS) allows the development of user-written subroutines for contact recognition and the calculation of contact forces. Those subroutines can help understanding the principles of friction phenomena inside spherical roller bearings, while the measurement of those effects is difficult.Measurements on a friction torque test rig for roller bearings are used to validate the MBS models. Since the sum of all contact forces equals the friction of the bearing, this test stand provides a way for validation of the contact and friction calculations.

Polymeric cages endowed with MoS2-particles serve the purpose of lubricant depot and thereby enhances the service life of solid-lubricated bearings. This contribution provides the investigation of cage pocket wear and the transfer process at the ball-cage pocket contact with the help of experimental and simulation methods. Thus, it helps to gain a better understanding and reliable prediction about the wear processes. In order to do so, an existing four-bearing-vacuum-testrig is used to carry out the bearing tests, and a Tribometer is employed to investigate the tribological characterization of the cage material. Additionally, simulations are performed to study the overall bearing dynamics. Primary results are presented here.

This research focuses on the significant role of Corporate Social Responsibility (CSR) in shaping employees’ behavior towards the reduction of food waste in the hospitality industry that has been under scrutiny for its environmental impact. The study aimed at understanding how CSR, coupled with employees’ moral attitudes, admiration for their organization, and climate change awareness influences sustainable practices by realizing the complex interplay between company initiatives and personal psychology. The participants were staff members who worked in several hotels in China where there were active CSR programs. Using established scales, we collected 422 valid responses over three waves to strengthen our data collection process. Empirically, it was found that CSR directly influenced food-waste-reduction behavior. Additionally, it was discovered that this relationship was mediated by moral attitudes and employee admiration as well as moderated by awareness of climate change. The findings have substantial theoretical implications regarding the interaction between emotional and cognitive factors within the CSR framework to influence behavior among employees. This paves the way for creating well-rounded strategies that appeal to staff and encourage sustainability in the hotel business. While focused on China’s hospitality industry, this research creates room for future studies in other places around the world using various methods. The conclusions drawn underline the critical role of CSR in promoting environmental sustainability in the hospitality industry, providing a pathway for organizations to engage employees in meaningful and impactful sustainability initiatives.

Driving and timing chains are widely used machine elements which are continuously improved regarding wear and energy efficiency. Especially for timing chains, reducing wear is of high importance as it is critical for the function of the combustion engine. To achieve this goal, the wear in the chain joint has to be measured precisely which is usually done by measuring the length of the entire chain. With this method, no information about the distribution of wear between the contacting bodies, pin and bush, is available. An additional measuring and analyzing technique using a standard roundness instrument is developed with which more detailed information about the wear in the chain joint is obtained. With this method, unworn chain joint components are characterized and the wear on worn components is measured and compared for pins with different surface treatments. Furthermore, approaches to use the measured data in simulation and calculation are presented.