An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

Micro-pitting fatigue lives of lubricated point contacts: Experiments and model validation

A study of spur gear pitting under EHL conditions: Theoretical analysis and experiments

Comparison of material properties: Steel 20MnCr5 and similar steels

Influence of real surface topography on the contact area ratio in differently manufactured spur gears

Twin disc micropitting tests

This publication is intended to serve as a key to the results of the research project Simulation-based design process of smart machines (KONEMASINA). The basic idea of the project was that the simultaneous design of different technical processes is inevitable in order to develop modern, optimized products. The project had three principal themes: simulation-based design, control of machine reliability and operability and the interaction between these two. The project included development of simulation-based design processes and particularly application of computer simulation tools and methods on these processes, and actual modellingand simulation-related practices in managing complex sub-models as well as an overall system simulation model base. Methods and tools were developed for the use of real-time simulators and virtual technologies in the product development process, such as condition monitoring, operator training and determination of a customers needs regarding new procedures and products. The practical process of determining dynamic properties of components for simulation work was developed. This study aims to enhanced simulation model with adequate methods and tools focused on an interactive human machine system. A new concept for modeland simulation-based machine operability and reliability was studied. This publication also represents methods for reliability analysis and real time simulation applications, as well as load monitoring applications and solutions for estimating remaining lifetime. Methods to control safety and reliability in product design, applications of probability-based design methods and ways to control various uncertainties were studied.

Simulation-based design process of smart machines

There are several interacting factors in grease lubrication of bearings. They include e.g. the grease quality, grease supply quantity and interval, bearing housing construction, rotational speed, load, temperature, sealing as well as grease removal. In order to find out the major problem areas with respect to grease lubricated bearings, a survey was carried out within industrial companies representing mainly pulp and paper industry. The most common problems experienced with grease lubrication included poor grease removal, overlubrication, deficient lubrication and contaminants. The most prominent reason for bearing failures according to the survey was lack of lubrication or lubricant. Monitoring of the lubricant film thickness in grease lubricated bearings is more demanding than in the case of oil lubrication. It is commonly accepted that in grease lubrication the viscosity index or κ-ratio does not give a reliable estimate of the lubricant film thickness. Whereas acoustic emission can be used to determine the critical rotational speed below which boundary lubrication conditions apply in an oil lubricated bearing, it is possible in grease lubricated bearings that the lubrication conditions remain good at far lower speeds or that lubrication becomes instable such that it varies between properly functioning and boundary lubrication. The grease contained within the bearing also has a vibration damping effect. On the other hand, if there is insufficient amount of lubricant available for the roller path and the necessary pressure formation required for elastohydrodynamic (EHL) lubrication cannot be realised, the contact area may become deficient of grease even in conditions where oil lubrication should theoretically be good. In this paper results are reported from experimental studies with a rolling element bearing test rig using vibration based monitoring methods, with the objective of detecting the condition of deficient lubrication and optimising the lubrication. The test rig enables also experimental research on the effects of overgreasing, different grease supply and removal methods or the effects of contaminants in grease.

Risto Parikka

Papers

Twin disc micropitting tests

Simulation-based design process of smart machines

Monitoring of grease lubrication