This paper deals with the problem of forming a surface roughness profile of a machined surface and a definition of the optimal depth of penetration in ball burnishing which would allow minimization of surface roughness. The assumptions, which have been numerically and experimentally verified, claim that maximum surface quality, i.e., minimum surface roughness, Ra, is achieved when the depth of ball penetration into the workpiece material is approximately equal to the maximum peak height, Rp. For the purpose of numerical simulations, a surface roughness model based on milling kinematics was used. Numerical simulations and the used roughness model support the claim that penetrating with a stiff tool up to the mean line of the roughness profile yields best surface quality. The authors maintain that ball penetrations, which exceed Rp, cannot significantly improve surface quality. Furthermore, the phenomenon of profile peak deformation is substantially clarified. The analysis of internal stresses within the workpiece after ball burnishing allowed a relationship to be established between internal stress distribution along the depth of the hardened layer and ball penetration depth.
One of the most frequent manual occupational tasks involves the pushing and pulling of a cart. Although several studies have associated health risks with pushing and pulling, the effects are not clear since occupational tasks have social, cognitive and physical components. The present work investigates a real case of a pushing and pulling occupational task from a manufacturing company. The study initially characterizes the case in accordance with Standard No. ISO 11228-2:2007 as low risk. An experiment with 14 individuals during three modalities of pushing and pulling was performed in order to further investigate the task with the application of electrophysiology. At the end, a simple questionnaire was given. The results show electrophysiological differences among the three modalities of pushing and pulling, with a major difference between action with no load and fully loaded with a full range of motions on the cart to handle.
Paper aims is analysis of the current situation in SME in Serbia, identification, analyse and description of the main barriers to the management of OHS in SMEs in Serbia and points to the possibilities of overcoming barriers. Based on interviews and observations, results indicate that the different groups at different hierarchical levels experience different types of barriers. Main barriers in SMEs in Serbia were classified into four categories: lack of top management support, financial capability, lack of employee's skill and expertise and organizational culture. The number of barriers increases with the size of the enterprise. Also, in this paper authors presented the key factors that affect health and safety at work in SMEs. The most important are: management commitment, air safety, competence and motivation of employees, training and education in the field of security, the implementation of regulations in the field of OHS etc.
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