Suzana Jakovljević, Dražen Mezdić, Gorana Baršić, Hrvoje Skenderović: Investigation Into the Effects of Laser Texturing on the Wettability of Ti-6Al-4V Alloy

Laser surface texturing is a technology that enables us to achieve very complex surface geometries. In this study, geometries created on the Ti-6Al-4V surface were in the form of parallel grooves. Those geometries were obtained by changing the laser beam speed and the number of passes (one or two). The effects of laser texturing on the roughness and the contact angle of Ti-6Al-4V surfaces on the first day and after 80 days were investigated. The results of this study indicate that the samples treated with two passes of the laser beam and at a lower speed scan show regularities of roughness profile geometry while other laser-treated samples do not. It is shown that the surfaces laser-textured with either one or two passes of the laser beam show no significant changes in the surface wettability after 80 days. The statistical test proves that there is a significant difference (level α = 0.05) between the contact angles on the untreated sample on the first day and after 80 days of treatment.

Key words: Ti-6Al-4V, laser surface texturing, surface topography, roughness, wettability

Original scientific paper

Jiri Stodola, Petr Stodola: Analysis and Model of Corrosion Wear of Selected Materials Used in Special Vehicles

The paper deals with the evaluation and modelling of corrosion wear of two standard materials used in the construction of special vehicles. The experimental research on corrosion wear involved the testing of two steels, EN 10131 and EN C22R, in a salt spray at 35 and 50 oC for 24, 48, 120 and 144 hours. The model of the process of corrosion degradation of the tested materials uses the results of weight loss of the samples as a function of temperature and exposure time. The diagnostic macroscopic evaluation of corroded surfaces of the tested materials, using graphic (analogue) information of surfaces and its conversion into the digital form, is a completely new technology. The samples were photographed using a CCD camera, then pre-processed, segmented, and masks were created for the logic of deciding what corrosion is and what it is not. The final filtered image was created in binary values where logic 1 refers to a corroded and logic 0 to a non-corroded sample. The MATLAB software environment and the Image Processing Toolbox were used to process the results of the surface evaluation.

Key words: metal corrosion, salt spray corrosion tests, analysis, digital evaluation of material surfaces, evaluation and modelling of corrosion wear

Original scientific paper

Nima Mirzaei: Solar Collector Performance Analysis Using ANOVA Method

In this study, the thermal performance of a newly designed solar air heater was examined using a thoughtfully designed and analysed experimental methodology. In the analysis, three factors (collector type, bed height, and airflow rate) were adjusted and their effects on the performance of the system were evaluated; additionally, mesh layers were used to act as absorber plates. The single and counter flow collectors were also examined using different bed heights (3 cm, 5 cm, and 7 cm) at various airflow rates (0.011 kg/s, 0.035 kg/s, and 0.043 kg/s). Subsequently, the results obtained from this experiment were analysed using the analysis of variance (ANOVA) method. According to the data obtained from the ANOVA method and pairwise mean comparisons, the best configuration that yields the highest thermal performance was the one with counter flow passage (3 cm bed height, and 0.043 kg/s air flow rate). Moreover, a 99% confidence interval was utilized in estimating the lower and upper bounds of thermal performance for each system setup.

Key words: Solar air heater, ANOVA, Thermal performance, Experimental design

Original scientific paper

Reda M.S. Abdulaal, Omer A. Bafail: A New Slope Index for Solving NxM Flow Shop Sequencing Problems with Minimum Makespan

A flow shop sequencing problem is one of the classical problems in the production scheduling. In a flow shop, a particular case of manufacturing process follows a fixed linear structure. The purpose of this paper is to find the minimum total processing time (makespan) of sequencing ‘n’ jobs on ‘m’ machines for a flow shop problem in a static workshop. The proposed approach is based on the slope of each job on its journey from the first to the last machine. This approach is compared with five well-known heuristics (Palmer, Gupta, CDS, Dannenbring, Hundal) and one more recent technique that is based on the harmonic triangle. The results obtained from this study for different sizes of ‘n’x’m’ flow shop sequencing problems ranging from 4×4 to 50×20 indicate that the proposed approach is efficient with an encouraging percentage of improvements compared with all other six heuristic techniques.

Key words: scheduling, flow shop, sequencing, makespan, Gantt chart

Original scientific paper

Dimitar Dichev, Iliya Zhelezarov, Nikolay Madzharov: Dynamic Error and Methods for its Elimination in Systems for Measuring Parameters of Moving Objects

This paper presents a new block diagram for defining a dynamic error in instruments for measuring the angular position of moving objects. The diagram proposes a new concept for investigating dynamic error characteristics as well as for compiling algorithms, inventing methods, and employing means for elimination of the dynamic error as independent component. Based on that concept, a system for measuring the roll, pitch, trim, and heel of moving objects has been developed. The system features high accuracy ensured through a combination of the capacities of different micro-electromechanical sensors that are unified into a shared platform with a specific algorithm used to determine and eliminate a real-time dynamic error. In addition, the paper presents the results from experimental research work. The results confirm the large operational capacity of the proposed concept concerning measurement accuracy.

Key words: dynamic error, micro-electromechanical system, error analysis, error correction

Original scientific paper

Chenggang Li, Wenyan Zhang, Jing Chen, Jingjing You: A Comparative Study on Two Methods of Decoupling a Six-Axis Accelerometer without and with a Gyroscope

Methods of decoupling a 6-axis accelerometer are attracting more and more attention because of their great significance for the accuracy, efficiency and stability of acceleration calculation. This paper introduces the basic decoupling methods without and with a gyroscope first. The decoupling accuracies of numerical accelerations are compared based on the definition of the comprehensive error, and the efficiencies are compared based on the computational time. In order to compare the stability of the two methods, the influence of step size is given, and the comprehensive errors are compared. Possible error sources that affect the stability of the decoupling methods are listed and divided into three categories, and the influence of every error source is analysed and presented. In the simulation, the gyroscope-based method is verified to achieve better accuracy, efficiency and stability than in the case of the method without a gyroscope. The experimental results agree well with the theoretical analysis.

Key words: 6-axis accelerometer, decoupling methods, gyroscope, decoupling accuracy, stability

Original scientific paper

Adel Al-Shayea, Emad Abouel Nasr, Hisham Al-Mubaid, Abdulrahman Al-Ahmari, Ali K. Kamrani, Husam Kaid, Haitham A. Mahmoud: A New Association Analysis-Based Method for Enhancing Maintenance and Repair in Manufacturing

Maintenance and quality of products are absolutely crucial for any organization to succeed in the industrial and manufacturing engineering. Current research studies have confirmed the presence of a high correlation between these two factors, namely maintenance and quality of products, in industrial organizations. Nevertheless, no extensive research has been conducted in order to study the link between maintenance and the quality of products in manufacturing. In this paper, we conduct a study in this domain and examine the relationship patterns between maintenance and the quality of product using manufacturing data on maintenance and the product quality. Specifically, we employ association analysis and association rule mining with large and extensive sets of product quality, repair, and maintenance data. Our main objective is to discover interesting and non-trivial associations for feature failure resulting in the repair or maintenance of a product with unapproved quality. The results of evaluation are quite interesting. The resulting association rules with high values of confidence and lift suggest some essential associations between the product features and the failure; such findings have not been known and used before. This can help quality engineers and maintenance teams to enhance maintenance and repair operations and lower the overall cost of manufacturing.

Key words: Association Rule Mining in Manufacturing, Data Mining in Manufacturing, Quality Control, Maintenance and Repair in Manufacturing

Original scientific paper

Hamood Ur Rehman, Ferenc Boór, Muhammad Wasif, Syed Amir Iqbal: A Novel Method for Process Planning for Die and Mould Manufacturing Using Expert System Approach

Mould design and development are experience-oriented operations involving complex process planning integration and relatively time-consuming processes. A solution for integrating the process planning with manufacturing operations for mould design and development is presented. In this paper, the developed solution is related to cost and time. The main aim of the study is to optimize the whole process planning scenario and make it feasible and accessible for faster and optimum design to manufacture die and moulds for injection moulding applications. The developed method consists of group technology (GT) coding for part and tool linked to the manufacturing process and its criticalities. An impact factor rating system is established using the weighted average method to associate the manufacturing operations with time and cost combined with the matrix reduction method so as to produce an optimized sequence of operations. The effect of restricting certain criticalities (electric discharge machine usage, quality and complexity) on the GT code is also elaborated in reference to quality and other parameters. The resultant study presents a novel method of establishing an expert system (ES) that combines GT coding, manufacturing operations, weighted average and matrix reduction to optimize the process planning. The rationale behind the research is an effective use of the ES in optimizing process planning applications in digital manufacturing.

Key words: process planning, expert system, tool design, injection mould, group technology, digital manufacturing

Original scientific paper