172 research outputs found
Characteristics of Intermetallic Compounds in Dissimilar Friction Stir Welding: A Review
No full textIn the present paper, mechanical and metallurgical characteristics of different dissimilar weldments fabricated by friction stir welding were investigated. Existence of lamellar composite structure within the stir zone in addition to observation of interfacial intermetallic compounds (IMCs) was the main characteristics that were investigated throughout this research. Results indicated that the optimum IMCs layers, resulting in enhanced mechanical properties, met three criteria, thinness, uniformity, and continuity
Lean behavior impact towards lean management: a case study
No full textLean behavior is an essential element to create a continuous improvement culture in the service organization. Meanwhile, continuous improvement is defined as the never-ending efforts for improvement involving everyone in organization. The purpose of this study is to evaluate the changes of behavior practices after the introduction of lean tools and to discuss on how lean behavior in developing the continuous improvement culture in an office environment. This study focuses on self-administered questionnaire method to obtain the real time data for the analysis of behavior practices. Ford Questionnaire is used and distributed to the employees of different management levels in Business Development and IT department. The obtained results are analyzed using the Statistical Package for the Social Sciences (SPSS) software. The same questionnaire survey is conducted after the introduction of lean tools. The expected outcomes of this study is to determine the level of lean behavior practices in the office department and to provide a clear understanding on some lean behavior practices that need to be nurtured among the employees in order to produce a healthy work environment
Development of explicit finite difference-based simulation system for impact studies
No full textDevelopment of numerical method-based simulation systems is presented. Two types of system development are shown. The former system is developed using conventional structured programming technique. The system incorporates a classical FD hydrocode. The latter system incorporates object-oriented design concept and numerous novel elements are included.
Two explicit finite difference models for large deformation of several material characteristics are developed. The models are capable of handling impulsive and constant load, impact and gravitational force, etc. Their capabilities of handling relatively complex shapes, which are not possible to deal with using classical FD models, are shown and discussed. A robust algorithm is suggested to describe general stress-strain relationship, ranging from elastic-perfecdy plastic to multiple elastic modulii and plastic modulii with or without strain rate sensitivity. Hysteresis and Bauschinger effects are included as well.
Development of contact-impact treatments is presented. Three novel contact elements are designed, developed and validated. Node-node and node-element contacts are formulated with all the elements developed. The contact-impact treatments include a novel method in handling potential voids and overlaps at contact intersection. Rigid Coulomb’s friction model is incorporated to handle sliding conditions.
Formulation of a novel revolute joint element is illustrated and several possible methods are suggested for handling bending limits. Incorporation of resistive moment and damping effects are presented. The numerical stability of the revolute element is discussed and a stability criterion is proposed.
The latter simulation system is used to model an idealised human body. Information from literatures, such as height and weight ratio of human segments, and resistive moment of human joints, is incorporated into the human model. Simulations are carried out according to a 2k factorial design of experiment to find the main effect(s) contributed to human head/brain injury when subjected to frontal collision. A simple motorcycle model based on Malaysian KRISS 110 motorcycle is developed as well. The human model is successfully integrated into the motorcycle model. Possibility of solving such model with the developed simulation system is studied
Effect of energy losses during an impact event on the dynamic flow stress
No full textDetermination of stress-strain properties of material and formulation of suitable constitutive laws is very important on the study of: (i) the elastic-plastic response and collapse mode of structures can be analysed for improving subsequent design, and (ii) high speed metal cutting and metal forming processes may be analysed for better estimation of the process parameters and better understanding of material flow behaviour. This paper is devoted to establish the energy losses in an existing ballistic rig. The effect of energy losses due to impact into the study of dynamic flow stress of a material is examined. Results assuming loss of kinetic energy varying from 1 to 20% of the initial energy are presented and discussed for En-9 steel. The effects of friction, inertia, and temperature rise during the dynamic compression tests are also presented and discussed. © 2002 Published by Elsevier Science B.V
The influence of humidity on the deformation and fracture behaviour of PMMA
No full textThe effect of relative humidity on the tensile deformation and fracture of poly(methylmethacrylate) (PMMA) has been studied. Seven sets of samples were conditioned under different environment: as-received specimens; dry specimens (zero moisture content); outdoor exposed specimens; water saturated specimens; specimens conditioned at three different relative humidities (75.5, 85.1, and 94.6%) using saturated salt solutions (NaCl, KCl, and KNO3, respectively). The main objective of this study is to investigate the effects of sorbed water on tensile mechanical properties of PMMA. Properties investigated include development of crazing, tensile fracture stress, strain to fracture and fracture surface morphology
Wear resistance investigation of titanium nitride-based coatings
No full textThe wear of components while they are in service is a predominant factor controlling the life of machine components. Metal parts are often damaged because of wear-driven failures causing the loss of dimensions and functionality.
In order to reduce wear, researchers follow two paths: (i) use new, wear resistant materials or (ii) improve the wear resistance of materials by adding alloying elements or performing surface treatments. Thin film hard nitride coatings are seen as a viable way to enhance the wear resistance of metallic materials, thus extending the lifespan of products. This paper reviews the wear resistance of titanium nitride-based coatings obtained using physical vapor deposition (PVD), chemical vapor deposition (CVD), and thermal spraying techniques. The results of thin film coatings deposition on the wear performance and on the coefficient of friction are investigated. The advantages and disadvantages of coating methods are discussed. Finally, recent developments and new possibilities for coating manufacturers to produce films with enhanced wear performance are briefly discussed.NPRP award NPRP 5–423–2–167 from the Qatar National Research Fund (a member of The Qatar Foundation). Hanyang University (201500000000438)
Cobalt effect on structure, cutting ability and erosion resistance of W-Mo-V high speed steels
No full textDevelopment of genetic algorithm-based fuzzy rules design for metal cutting data selection
No full textFuzzy rules optimization is always a problem for a complex fuzzy model. For a simple 2-inputs-1-output fuzzy model, the designer has to select the most optimum set of fuzzy rules from more than 10000 combinations. The authors have developed fuzzy models for machinability data selection (Int. J. Flexible Autom. Integrated Manuf. 5 (1 and 2) (1997) 79). There are more than 2×1029 possible sets of rules for each model. The situation would be more complicated if there were a further increase in the number of inputs and/or outputs. The fuzzy rules (Turning Handbook of High-Efficiency Metal Cutting, General Electric Co., Detroit) were selected based on trial and error and/or intuition. Genetic optimization has been suggested in this paper to further optimize the fuzzy rules. The development of a Fuzzy Genetic Optimization algorithm is presented and discussed. An object-oriented library to handle fuzzy rules optimization with genetic optimization has been developed. The effect of constraint rules is also presented and discussed. Comparisons between the results from the optimized models and literature are made
Simulated annealing with auxiliary knowledge for process planning optimization in reconfigurable manufacturing
No full textIn this paper, three simulated annealing based algorithms that exploit auxiliary knowledge in different ways are devised and employed to handle a manufacturing process planning problem for reconfigurable manufacturing. These algorithms are configured based on a generic combination of the simulated annealing technique with; (a) heuristic knowledge, and (b) metaknowledge. Capabilities of the implemented algorithms are tested and their performances compared against a basic simulated annealing algorithm. Computational and optimization performances of the implemented algorithms are investigated and analyzed for two problem sizes. Each problem size consists of five different forms of a manufacturing process planning problem. The five forms are differentiated by five alternative objective functions. Experimental results show that the implemented simulated annealing algorithms are able to converge to good solutions in reasonable time. A computational analysis indicates that significant improvements towards a better optimal solution can be gained by implementing simulated annealing based algorithms that are supported by auxiliary knowledge
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