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The purpose of this paper is to analyze the failure of the left waterwall tube of a boiler furnace in the steam power plant which led to cracks and rupture. Macro visual observation showed the rupture like a fish mouth with slag adhering at the outer surface of the tube. Magnetite as a protective layer was peeled off. Changes in the thickness were analyzed through dimensional measurement. In this research, an analysis to find the cause and determine the fracture mechanism is presented.

A physical analysis was performed through visual observation of changes in the thickness. Micro visual testing with a metallography test provided the data required to measure the change of grain size. The mechanical analysis used Von Mises criteria and API 530 standard and provided the pressure limits data.

The thickness of the tube decreased at the peak curvature of the tube. The smallest thickness at the peak curvature of the tube was 0.108 inches. The working pressure was 40.74 percent from permit limits with Von Mises calculations. The percentage of pressure calculated by the API standard was 48.42 percent from permit limits. Larger crystal grains occurred only in the nearby area of the oxide layer and at the end of the crack tip. It indicated that part of the inner surface had a relatively high temperature and plastic deformation occurred because of the pressure from inside the tube. Combining all these factors ruptured the tube at this location because the cross-section could not hold up the pressure.

The analysis of this discussion focuses on the combined effect of those factors causing the ability to decrease stress being received. It restricts the tube from holding up the stress and furthermore it will generate fractures.

The purpose of this paper is to investigate prediction and optimization of multiple performance characteristics in the wire electrical discharge machining (wire-EDM) process of SKD 61 (AISI H13) tool steel.

The experimental studies were conducted under varying wire-EDM process parameters, which were arc on time, on time, open voltage, off time and servo voltage. The optimized responses were recast layer thickness (RLT), surface roughness (SR) and surface crack density (SCD). Arc on time was set at two different levels, whereas the other four parameters were set at three different levels. Based on Taguchi method, an L18 mixed-orthogonal array was selected for the experiments. Further, three methods, namely grey relational analysis (GRA), backpropagation neural network (BPNN) and genetic algorithm (GA), were applied separately. GRA was performed to obtain a rough estimation of optimum drilling parameters. The influences of drilling parameters on multiple performance characteristics were determined by using percentage contributions. BPNN architecture was determined to predict the multiple performance characteristics. GA method was then applied to determine the optimum wire-EDM parameters.

The minimum RLT, SR and SCD could be obtained by setting arc on time, on time, open voltage, off time and servo voltage at 2 ms, 3 ms, 90 volt, 10 ms and 38 volt, respectively. The experimental confirmation results showed that BPNN-based GA optimization method could accurately predict and significantly improve all of the responses.

There were no publications regarding multi-response optimization using a combination of GRA and BPNN-based GA methods during wire-EDM process available.

The purpose of this paper is to present the current status of a quality management practice in Serbia, in terms of the development and application of integrated managements systems (IMS), and research and implementation of Six Sigma and the related techniques.

Two main aspects of total quality management (TQM) have been considered: institutional (organisational or strategic) aspect that corresponds to standardised management systems and their integration, and technical (quality engineering) aspect whose main contributor is Six Sigma. The findings of a comprehensive study on IMS implementation in Serbia have been presented, based on the results of a questionnaire that was sent to 54 organisations during 2013. Also, the significant technical improvements and tangible benefits of a recently conducted Six Sigma project were shown, including the application of the advanced quality engineering techniques within DMAIC method.

Good QM practice in Serbia is improving, both in terms of the organisational (IMS) and technical (Six Sigma) aspect, that server as a good basis for the adoption of TQM in manufacturing companies from various sectors. It could be anticipated that these results will facilitate the adoption of an overall TQM culture in Serbia and leverage its future sustainability.

This paper offers key insights into IMS and Six Sigma implementation in Serbia. This could encourage manufacturing organisations in developing countries to adopt IMS and Six Sigma, in order to boost the overall TQM culture and gain a competitive advantage.