Nicolae Ungureanu

The effect of active surface morphology of grinding wheel with zone-diversified structure on the form of chips in traverse internal cylindrical grinding of 100Cr6 steel

The article presents the results of experimental investigations to determine the effect of active surface morphology of grinding wheels with a zone-diversified structure on the form and size of chips generated during traverse internal cylindrical grinding of 100Cr6 steel. In the grinding process involving grinding wheels with a zone-diversified structure, chip formation phenomena differ in the rough and finish grinding zones of the tool. In order to expand one’s knowledge of this phenomena, the microtopography measurements of the grinding wheel active surface in the rough and finish grinding zones were made, as well as scanning electron microscopic observations of these areas after the dressing cut and following internal cylindrical traverse grinding. The conducted studies showed that chips in the rough grinding zone of the grinding wheel active surface are usually several hundred micrometers in length. In the finish grinding zone, however, mainly micro-chips were generated whose length does not exceed 100 µm (usually around 10 µm in length). In the rough grinding zone, shearing-type and flowing-type chips dominate with a few examples of spherical melted chips. Moreover, in the finish grinding zone, mainly slice-type and knife-type micro-chips were observed.

Measurements of the Friction Coefficient: Discussion on the Results in the Framework of the Time Series Analysis

Tribology studies the interaction between surfaces in relative motion with a particular focus on the principles of friction, wear and lubrication. The measurement of the friction coefficient (COF) is extremely sensitive to experimental friction force fluctuations thus making COF direct measurement not a trivial task. In this manuscript, a novel approach toward the understanding of the friction coefficient behavior during reciprocating tests is proposed. The proposed procedure represents a first approach for a deep investigation about measured COF distribution during tribological tests. It is based on the analysis of COF data measured during the tests in the framework of time series analysis and it was applied to several real tests in dry-friction showed as example of application. Output parameters (i.e., friction, traction force) were investigated to detect trends, connected to running-in period of the tribo-couple, seasonal, connected to the periodicity induced from reciprocating motion, and residual components. After “smoothing” the COF data set by removing the trend and seasonal components, the residual component was analyzed to check the stationary of the COF data set which represents the most characteristic interval in friction measurements.

Fluid Film Pressure Description in Finite Turbulent Lubricated Journal Bearings by Using the Warner’s Theory

The purpose of this paper is to propose a method for the analytical description of the non-steady fluid film for the liquid-lubricated finite journal bearings operating in a fully developed turbulent regime. The analytical description takes in account a symmetrical rigid rotor supported on two lubricated journal bearings under the classical assumptions of the Reynolds theory. The proposed methodology represents an extension of the Warner’s approach and allows to solve analytically in approximate way the equation governing the distribution of pressure in the bearing oil gap and then to obtain the analytical expressions for the unsteady fluid film forces giving particular attention to their continuity in the entire definition domain, introducing original analytical functions called “jump function”. The proposed model allows not only to minimize the computation time without any significant loss of accuracy in the nonlinear dynamic analysis of rotors on turbulent journal bearings but also permits a better readability of the parameter effects on the system unsteady behavior.

Contributions to the Development of an Ontology in Logistics of Manufacturing

In this paper are presented some contributions to the development of an ontology in logistics of manufacturing. In the paper are presented the basic conditions required by logistics of manufacturing and the main activities of logistics of manufacturing. Also are presented the main definition of ontology, the evolution of ontology and the ontological approach to the logistics problems of manufacturing. Are proposes a core ontology that specifies the main concepts used in logistics operations. In the end of paper are presented the future directions of research for the development of an ontology in logistics of manufacturing.