Tribology in Industry

149-155

Authors: M. Bachraty, M. Tolnay, P. Kovac, V. Pucovsky

This paper presents a part of research on power consumption differences between various cutting fluids used during turning operations. An attempt was made to study the possibility of artificial neural network to model the behavior function and predicting the electrical power consumption. Friction factor of examined cutting fluids was also measured to describe a more complete picture of investigated cutting fluids characteristics. It was discovered that wide spectrum of characteristics is present in today’s market and that artificial neural networks are suitable for purpose of modeling the power consumption of the lathe during machining. This paper could be used as a foundation for later database building where it would be possible to predict how certain cutting fluid will behave in a specific machining parameter combination.

163-175

Authors: F. Beyer, M. Löffler, K. Willner, U. Engel, M. Merklein

The aim of this work is the improvement of a constitutive friction law which has been identified for the specific demands of sheet-bulk metal-forming. The constitutive friction law determines the friction shear stress in dependency on the plastic smoothing of the surface roughness, which also affects the real contact area. An experimental setup is introduced to determine the change of the surface roughness, which is influenced by the tensile bulk stress in the workpiece. In order to model the experimental results, a well-established half-space model is presented and improved to consider strain hardening. The half-space model is used to determine the change of the contact area as a function of the tensile bulk stress. This interdependency is also reflected by the proposed constitutive friction law.

186-196

Authors: J. Javorova, A. Mazdrakova, I. Andonov, A. Radulescu

The purpose of this paper is to study the performance of a finite length journal bearing, taking into account effects of non-Newtonian Rabinowitsch flow rheology and elastic deformations of the bearing liner. According to the Rabinowitsch fluid model, the cubic-stress constitutive equation is used to account for the non-Newtonian effects of pseudoplastic and dilatant lubricants. Integrating the continuity equation across the film, the nonlinear non-Newtonian Reynolds-type equation is derived. The elasticity part of the problem is solved on the base of Vlassov model of an elastic foundation. The numerical solution of the modified Reynolds equation is carried out by using FDM with over-relaxation technique. The results for steady state bearing performance characteristics have been calculated for various values of nonlinear factor and elasticity parameters. It was concluded that in comparison with the Newtonian lubricants, higher values of film pressure and load carrying capacity have been obtained for dilatant lubricants, while the case was reversed for pseudoplastic lubricants.

214-220

Authors: A.P. Markopoulos, N.E. Karkalos, N.M. Vaxevanidis, D.E. Manolakos

In this paper, orthogonal cutting finite elements models are built for the investigation of the impact of large negative rake angles on the friction coefficient in the tool-chip interface in machining. The simulation results give an insight on the mechanism of chip formation in processes with large negative active rake angle, such as machining with chamfered tools, grinding and micromachining. For the present analysis, cutting conditions resembling the qualitative and quantitative characteristics of the aforementioned processes were selected. More specifically, tool rake angles varying from -10o to -55o and Coulomb friction with constant friction coefficient were considered. The results indicate that friction coefficient is greatly affected by the negative tool rake angle, exhibiting values well above 1 for the high extreme of the examined rake angle spectrum.

229-234

Authors: M. Stojilković, M. Kolb

The annual consumption of lubricants in the world is around 40 million tons out of which less than 40 % are collected and properly processed meaning regeneration, re-refining and controlled incineration while the rest is disposed without control thus contaminating soil, water and atmosphere. It's one of the reasons that the last twenty years the environmentally friendly lubricants are more and more used. For the production of environmentally friendly lubricants are mostly used vegetable oil. In the field of the application of environmentally friendly lubricants attention should be given to the technical requirements including protection from the wear, corrosion protection, high load carrying properties and fulfilment of all the requirements imposed by the producer of the mechanical system. This paper presents development and testing of the biodegradable universal tractor transmission oil (UTTO) based on the vegetable oils. Tribological properties of the oils based on rapes oil, sunflower and soya, after corresponding testing, compared with the features of the commercially available mineral universal tractor transmission oil.

241-248

Authors: C. Fragassa

This paper describes an accelerate aging procedure used for investigating the surface alteration of PTFE gaskets commercialized by two alternative producers. These gaskets are installed in modern process plants where tires moulds are cleaned inside a multistage ultrasonic process. The surface of gaskets degrades inexplicably under ordinary operative conditions after a relatively short period. Even if these gaskets are exposed to a combination of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the possibility of severe erosion phenomena as highlighted during the real utilization. A possible explanation could be represented by the presence of unexpected chemical compounds emerging from the disaggregation of highly reacting elements from the tire composition. In particular, it is believed that the unpredicted combination of fluorides and chlorides could explain the violent chemical attack highlighted on steel tanks and on their gaskets. But no evidence exists. Thus, the experimental characterization of PTFE properties has to follow an appropriate accelerated aging, aiming at actuating the specific mechanics of wearing as in industrial use.

255-266

Authors: B. Dan-asabe, A.S. Yaro, D.S. Yawas, S.Y. Aku, I.A. Samotu, U. Abubakar, D.O. Obada

A banana particulate reinforced polyvinyl chloride (PVC) composite was developed with considerabley low cost materials having an overall light-weight and good mechanical properties for potential application as piping material. The specimen composite material was produced with the banana (stem) particulate as reinforcement using compression molding. Results showed that density and elastic Modulus of the composite decreases and increases respectively with increasing weight fraction of the particulate reinforcement. The tensile strength increased to a maximum of 42 MPa and then decreased steadily. The composition with optimum mechanical property (42 MPa) was determined at 8, 62 and 30 % formulation of banana stem particulates (reinforcement), PVC (matrix) and Kankara clay (filler) respectively with corresponding percentage water absorption of 0.79 %, Young’s Modulus of 1.3 GPa, flexural strength of 92 MPa and density of 1.24 g/cm3. Fourier Transform Infrared (FTIR) analysis of the constituents showed identical bands within the range 4000–1000 cm-1 with renown research work. Scanning Electron Microscopy (SEM) result showed fairly uniform distribution of constituents’ phases. X-Ray Fluorescence (XRF) confirms the X-ray diffraction (XRD) result of the presence of minerals of kaolinite, quartz, rutile and illite in the kaolin clay. Comparison with conventional piping materials showed the composite offered a price savings per meter length of 84 % and 25 % when compared with carbon steel and PVC material.