Advanced Materials Research Vol. 633

Abstract: Throughout the 1990s, the European Union achieved, through introducing the New and Global Approach to technical harmonization and standardization, significant improvements to conformity assessment of products, by integrating safety requirements into the design process. This was achieved through preventative analysis and quantification of risk levels, with the objective of determining the scope of the required safety systems. On the other hand, we have witnessed the rapid development and implementation of holistic approaches to risk management in enterprises, collectively known as Enterprise Risk Management (ERM). Along these lines, this chapter presents the basis of the New and Global Approach, and provides a proposal for the integration of New Approach Directives risk assessment into the holistic approaches of risk management in organizations, such as ERM.

Abstract: Precise determination of the time-to-failure for conveyor idlers allows the planning of regular conveyor system maintenance and well-timed replacement of worn conveyor garlands. Incidental delays in power plant coal supply leads to a significant reduction in overall thermal power plant efficiency. This paper describes a test stand for the laboratory testing of conveyor idlers, under the influence of different radial loads, which was developed by the Faculty of Mechanical Engineering at the University of Belgrade. Data acquisition and processing are also considered, which includes control, monitoring and automatisation of the test stand. Machine protective systems, which ensure a high level of machine safety, were specifically redesigned due to the importance of operator safety and health.

Abstract: Development of passive safety elements is a key component in the design and manufacture of railway vehicles. Proper functioning of these elements is of great importance and has a direct influence on the safety of passengers, goods and vehicles. Different types of railway vehicles require absorption elements of different geometries and absorption power. Over the last twelve years, new types of absorption elements have been investigated in Serbia. Research has begun on steel tubes and square cross-sections, which absorb energy based on the principles of folding tubes. Research progressed to seamless tubes with circular cross sections on the basis of two methods of energy absorption: expansion and shrinkage of the tube. The best characteristics were obtained using the shrinking method. The most recent research was based on shrinking tubes in combination with folding tubes in parallel operation. This combined method was chosen as the resulting absorber has higher absorption power with smaller dimensions, which is a key consideration given the available and very limited space for the mounting of the absorber behind the buffer. Experimental investigation of the combined absorber through a scale model was conducted on a Zwick Roell HB250 material testing machine at the Faculty of Mechanical Engineering, University of Belgrade. The recorded parameters showed a gradual increase in force values, a decrease in maximal force values at the start of the folding process, and a significant increase in the absorbed energy compared to the shrinking or folding process alone.

Abstract: Modern mechanical systems are required to have high reliability characteristics. To attain them, it is necessary to take particular care (aside from laboratory and in service reliability examinations) of reliability design from the early development stages of a mechanical system. Reliability design for a new system includes an allocation of reliability to system elements which should meet specified requirements. In order to meet certain technical and economic system requirements, a method has been developed using Lagrange multipliers to determine "the best" reliability allocation from the basis of achieving minimum system cost (C_Smin) for a specified system reliability (R_S). In addition, this method offers the possibility of achieving maximum system reliability (R_max) for a specified system cost (C_S). This paper presents a reliability allocation method allowing the techno-economic requirements imposed on the system to be satisfied in an appropriate way. The method was developed considering some specific factors in the construction of mechanical systems and the relationship between system cost and reliability. In addition, a procedure was developed which permits the determination of "the best" reliability allocation using the multi-criteria ranking method and compromise programming, where system cost and reliability represent the criteria for choosing "the best" solution. The described allocation model was employed in the reliability allocation for an automotive gearbox.

Abstract: Transport of ground and coal at the surface coal dig in Kostolac, Serbia, is done using transportation belts (3 - 5 kilometres in length) using the systems of BTR (Bagger-Transporter-Remover) and BTM (Bagger-Transporter-Mill). The transporter belt during circular movement is suspended on carry-rollers (during transport of weight) and on support-rollers (without weight). Two or three carry-rollers, or three support-rollers make a garland. Garlands (5 carry and 3 supporting) are built into a section and they enable the movement of belt over them. The number of sections depends on the transportation system length. Reliability of these systems is governed by the reliability of the carry and support rollers. In order to determine the reliability of the BTR and BTM systems, reliability analysis of both carry and support rollers was performed using the method of Fault Tree Analysis (FTA) and Reliability Block Diagrams (RBD). In this paper the assessment of roller reliability is described using the FTA method with failure elements. The reliability function was determined on the basis of the RBD in the case where all of the constructive elements of the rollers are in operation the complex relationship, and when some of the elements are in failure mode the quasi-complex relationship.

Abstract: This paper presents a modern systematic approach to the improvement of the management system for auxiliary mechanization operations at an open-pit coal mine. The approach is based on an integrated model (IM) of business processes and information systems (IS). Within IS/ICT system development, implementation of GPS/GPRS technologies is also described in this paper. Experimental research on this holistic approach was performed at the thermal power plants and open-pit coal mines in Kostolac, Serbia. Results confirmed the importance of this concept for auxiliary mechanization operations management based on selected KPIs (e.g. working moto-hours of the machine) and technical parameters (e.g. readiness).