Nürnberg, University, Diss., 2003--Erlangen. / Parallelt.: Das Verschleiß- und Korrosions-Verschleißverhalten von Wolframkarbid-Kobalt-Hartmetallen bei der Holzzerspanung und unter Drei-Körper-Abrasivverschleiß Erscheinungsjahr an der Haupttitelstelle: 2002.

Techn. Universiẗat, Diss., 2002--Berlin.

The wear process in three-body contact causes problems of abrasion such as volume loss and changes of geometry of the triboelements. The wear problem leads to increased failure and high costs for repairing or replacing equipment. To understand the nature of the wear behaviour and to predict the wear rate in advance, experimental investigation and numerical simulation of the wear process are required. In this work, the wear process is analysed and the influencing parameters governing the wear behaviour are investigated experimentally to develop a new wear model. Main influential factors are considered such as kinematics of abrasive particles, contact stiffness of the particle layer, friction characteristics, and wear factors. The experiments to study kinematics of particle layers are performed on a new observation tester. To define the contact stiffness of abrasive particles, experiments are conducted by the uniaxial spindle compression tester. Moreover, a tribometer test rig with applied load up to 200 N and velocity up to 1000 mm/s is used to investigate the friction characteristics and the wear behaviour of three-body tribosystem. Analyses of influential factors on the wear behaviour in dependency of predefined process parameter are carried out. Additionally, based on the results of the experimental investigations, approximation equations representing the relation of the influential factors and the process parameters are determined. A three-body wear model is build up to represent the wear behaviour by physical wear laws. Furthermore, these approximation equations and the relevant parameters obtained by experimental investigations are included in the Fleischer’s wear equation to simulate the wear process. With the coupled model the wear process of the sample can be simulated twodimensional over the sliding distance. It is possible to predict the wear depth and the wear intensity, which can be used to estimate the wear rate. Additionally, from the results of the wear simulation the worn surface and the local contact pressure in the contact region are determined which provide a deeper insight into the wear process. With this simulation the understanding of the wear behaviour can be improved which is important to solve wear problems.

The wear process in three-body contact causes problems of abrasion such as volume loss and changes of geometry of the triboelements. The wear problem leads to increased failure and high costs for repairing or replacing equipment. To understand the nature of the wear behaviour and to predict the wear rate in advance, experimental investigation and numerical simulation of the wear process are required. In this work, the wear process is analysed and the influencing parameters governing the wear behaviour are investigated experimentally to develop a new wear model. Main influential factors are considered such as kinematics of abrasive particles, contact stiffness of the particle layer, friction characteristics, and wear factors. The experiments to study kinematics of particle layers are performed on a new observation tester. To define the contact stiffness of abrasive particles, experiments are conducted by the uniaxial spindle compression tester. Moreover, a tribometer test rig with applied load up to 200 N and velocity up to 1000 mm/s is used to investigate the friction characteristics and the wear behaviour of three-body tribosystem. Analyses of influential factors on the wear behaviour in dependency of predefined process parameter are carried out. Additionally, based on the results of the experimental investigations, approximation equations representing the relation of the influential factors and the process parameters are determined. A three-body wear model is build up to represent the wear behaviour by physical wear laws. Furthermore, these approximation equations and the relevant parameters obtained by experimental investigations are included in the Fleischer’s wear equation to simulate the wear process. With the coupled model the wear process of the sample can be simulated twodimensional over the sliding distance. It is possible to predict the wear depth and the wear intensity, which can be used to estimate the wear rate. Additionally, from the results of the wear simulation the worn surface and the local contact pressure in the contact region are determined which provide a deeper insight into the wear process. With this simulation the understanding of the wear behaviour can be improved which is important to solve wear problems.

Abrasivity is a characteristic property of rocks. Rock abrasivity has influence on tool wear, energy consumption and construction time and is therefore an important parameter in rock engineering. Over the years, a number of testing methods have been developed to define and quantify the abrasive potential of rocks. Due to simple design and convenient handling, Cerchar abrasivity test and its index, Cerchar abrasivity index, are most commonly used to assess the rock abrasivity. Besides the abrasivity index, various parameters can be derived from the Cerchar test thanks to the development of a special designed testing device. Diverse parameters like scratching force, applied work and specific energy can be used to estimate the cutting efficiency. Moreover, a new composite parameter named Cerchar abrasion ratio is proposed, which considers both, the wear on the stylus tip and the material removal on the rock surface and can be regarded as an indicator to evaluate the cutting effectivity. Since the development of Cerchar abrasivity test, major attentions are focused on the abrasion of the stylus, but minor attentions are paid to investigate the mechanical behavior of rocks against the action of the stylus during the scratching process. The scratch groove produced on the rock surface is observed under a scanning electron microscope. The Cerchar wear mechanism can be explained as follows: mineral grains are detached from damaged surface by fracturing after plastic deformation on stressed surface. Transition from plastic deformation-induced to cracking-induced wear are related to the rock microstructure. For the Cerchar test, various factors affecting the Cerchar abrasivity index have been studied, which can be divided into testing condition-based and geotechnical-based factors. The influence of some dominant testing condition-based factors including surface condition, testing distance and velocity on the test result is investigated by using the new designed testing device, in which the sliding distance and scratching velocity can be exactly controlled during the test. Results show that the surface condition can affect the result of Cerchar index, especially for hard and inhomogeneous rocks, while the testing distance and velocity have no obvious influence on the Cerchar index. As far as it is known, in rock mechanics, anisotropic features of rocks can affect the experimental results significantly. In the original Cerchar specification, testing procedure for stratified or foliated rocks is not specially discussed. Due to this, the influence of rock anisotropy on the Cerchar abrasivity index is investigated based on two intact metamorphic rocks of slate and gneiss. However, no significant dependency is found. Cerchar scratch test is simulated based on a quasi-homogeneous model made of sandstone with respect to its mineralogical-mechanical properties. The numerical simulation is conducted by using the discrete element method-based particle flow code of PFC3D. As a result, the simulated scratching force shows a good agreement with the experimental result. A gap between numerical and experimental studies can be attributed to the testing condition-based factors, such as rock mineralogy and microstructure, scratching velocity and depth of scratch, tool abrasion and temperature. Based on the calibrated sandstone model, numerical simulations of rock cutting are conducted under different testing conditions. The influence of tool geometry like tip shape, tip angle and tip wear, and cutting parameters including cutting velocity, depth of cut and rake angle on the cutting force and crack pattern is studied.