Advanced Materials Research Vols. 264-265

Abstract: This paper aims to demonstrate the effectiveness of Multi-Objective Genetic Algorithm Optimization and its practical application on the automobile engine valve timing where the variation of performance parameters required for finest tuning to obtain the optimal engine performances. The primary concern is to acquire the clear picture of the implementation of Multi-Objective Genetic Algorithm and the essential of variable valve timing effects on the engine performances in various engine speeds. Majority of the research works in this project were in CAE software environment and method to implement optimization to 1D engine simulation. The paper conducts robust design optimization of CAMPRO 1.6L (S4PH) engine valve timing at various engine speeds using multiobjective genetic algorithm (MOGA) for the future variable valve timing (VVT) system research and development. This paper involves engine modelling in 1D software simulation environment, GT-Power. The GT-Power model is run simultaneously with mode Frontier to perform multiobjective optimization.

Abstract: The investigated 34CrNiMo steel is traditionally used for highly loaded components with very high hardenability, fatigue strength and toughness. There were obtained very good experiences with this material, therefore there is no demand for change of the material, but for the material full potential utilization. This goal could be attained by application of thermo-mechanical treatment to the material of interest. There are compared several materials states obtained by conventional thermal treatment with new thermo-mechanically processed states in the current study. Conventionally treated materials exhibit about half tensile strength of the material after the thermomechanical treatment. The material fatigue life is related to tensile strength of the material. Therefore for representative comparison it is useful to compare materials with similar tensile properties, if the advantage of thermomechanical over heat treatment is to be evaluated. Samples of material of similar tensile strength to thermomechanically treated state were prepared by heat treatment. Fatigue tests were performed for traditionally treated samples with thermomechanically treated state and heat treated state. Thermo-mechanically treated state exhibits superior strength and fatigue life in comparison to all other states investigated. There was also performed metallographical investigation of microstructures of compared states providing information on what sort of microstructures were obtained by which treatment, that could be related to mechanical properties. The study presented here shows potential of thermo-mechanical treatment of traditionally used steels.

Abstract: Sintering is a key step in the preparation of metal foams. The present work focuses on the sintering effects on the properties of titanium foam prepared using the slurry technique. Sintering affects the density as well as the mechanical properties of the sintered parts. To achieve a high density of the titanium alloy foam, the effects of various parameters including temperature, time profile and composition have to be characterized and optimized. This paper reports the use of the Taguchi method in characterizing and optimizing the sintering process parameters of titanium alloys. The effect of four sintering factors: composition, sintering temperature, heating rate and soaking time to the density has been studied. The titanium slurry was prepared by mixing titanium alloy powder, polyethylene glycol (PEG), methylcellulose and water. Polyurethane (PU) foam was then impregnated into the slurry and dried at room temperature. This was later sintered in a high temperature vacuum furnace. The various factors were assigned to an L9 orthogonal array. From the Analysis of Variance (ANOVA), the sintering temperature was found to give the highest percentage of contribution (34.73) followed by the composition of the titanium alloy powder (26.41) and the heating rate (0.64). The optimum density for the sintered titanium alloy foam was 1.4873±0.918 gcm-1. Confirmatory experiments have produced results that lay within the 90% confidence interval.

Abstract: Dissimilar joints between CP-Ti and 304stainless steel were produced using diffusion welding technique in the temperature range of 800-950 °C, under a uniaxial pressure of 7 MPa in argon atmosphere. Mechanical assessment of the joints was carried out employing shear testing. The shear strength was found to be a function of joint surface area and volume fraction of brittle intermetallic phases such as σ, FeTi, and Fe2Ti which were detected by scanning electron microscopy and energy dispersive spectroscopy. Increasing the temperature and time of the diffusion welding process increased joint surface area and accelerated elemental diffusion across the joint interface which enhanced the shear strength value. However, as the volume fraction of the brittle intermetallic phases and Kirkendall voids increased at higher temperature and time, the bond shear strength decreased. Optimum shear strength was found to be 168 MPa which related to the joint produced at temperature and time of 900°C and 30 min, respectively.

Abstract: The ability of mortarless wall to restrain/sustain lateral load become important aspect to be consider in the design of wall. Therefore, this paper presents analyses of mortarless wall subjected to in-plane combined loading using finite element programs. The developed 2D finite element program is used in this research. The finite element models are developed based on micro modelling approach where each constituent of masonry (block and dry joint) connected each other by joints at their actual position. Eight nodded isoparametric plane element and six nodded zero thickness isoparametric interface element are used to represent block unit and dry joint respectively. The developed models are analysed under nonlinear environment. The most relevant results concern the strength response of the dry joint masonry walls subjected to in-plane combined compressive and shear loading. The results of finite element analysis compared with corresponding experimental results and its show good agreement. Parametric study also performed to consider the important parameters that effect the design of wall under combined loading. Significant features of the structural behaviour, ultimate capacity and observed failure mechanisms are addressed and discussed.

Abstract: The photoalignment technology for the alignment of liquid crystal molecules has lately gathered much attention because its advantages over the conventional rubbing of polyimide coating and several different approaches for the realization of photoalignment have been presented. Due to its non-contact nature, a photoalignment eliminates generation of dust and electrostatic charges as well as mechanical damage to the surface. Up to now, the study of the photoalignment effect has been focused mostly on uniform substrates through linearly polarized light. With the aim to achieve such a bistable liquid crystal device by means of unpolarized UV light, we have proposed a single-step laser patterning on a photoalignment layer using a photomask to achieve an equilibrium configuration of LC molecules in contact with a periodically patterned substrate. The patterns were formed by stripes of alternating random planar and homeotropic anchoring in a sub-micron scale on the order of 0.5 micron. We proposed two possible configurations of bistable LC cells that can be obtained by combination of micro-patterned surface formed with alternating random planar alignment with either planar alignment or homeotropic alignment surfaces. In this study, we have investigated the alignment properties and switching behaviours of both proposed models.

Abstract: The problem of resource allocation and scheduling is considered for a flexible job shop composed of several work centers with multiple identical machines. Each machine has its own setup time that depends on the current and the arriving batch types. The optimal number of machines at each center and the optimal batch size for each job type is to be determined for several dispatching rule. The objective of the study is to assist the scheduler in selecting the best dispatching rule with respect to a desired performance measure along with its corresponding batch size and optimum number of machines in each center. Several measures are considered including the average flow time, sum of earliness and tardiness, and the number of tardy jobs. The simulation package ProModel is used to build the model and its optimization tool called SimRunner is used for optimization.

Abstract: Use of hydrogen as a temporary alloying element in Ti alloys is an attractive approach to improve the mechanical properties of the materials, enhance processability and thereby reduce manufacturing costs. In this paper, the hydrogen diffusion process and the phase transformation both between Ti particles and in Ti sheets were simulated to analyze the mechanism of hydrogen diffusion in different phases (α-Ti, β-Ti and TiHx). With the simulation based on the kinetics and thermodynamics, quantitative behaviors of the hydrogen diffusion and the phase transformation were analyzed. The simulation results provide an insight into the diffusion process and improve the fundamental understanding of the mechanism of diffusion and phase transformation.

Abstract: This study investigated on cooling characteristics of thermoelectric cooling system using thermoelectric materials as Bi-Te alloy. The thermoelectric module used as thermoelectric materials of thermoelectric cooling system can achieve heating and cooling by change of electricity direction. When thermoelectric module and cooling fan received 12V from DC power source, the cooling region was occurred in thermoelectric cooling system. Also, the piezoelectric actuator was applied to improve the cooling effect and investigate the heat transfer phenomenon. The temperature distribution of cooling region was measured to investigate cooling characteristics of thermoelectric cooling system. The flow phenomenon of cooling region was visualized using visualization device such as He-Ne laser, optical lens, image grabber and CCD camera. When the piezoelectric actuator was applied to the heat transfer process of thermoelectric cooling system, acoustic streaming was occurred in the cooling region. The acoustic streaming was occurred forced convection flow, and was regularly formed the temperature distribution in the cooling region. In the end, the results clearly show that the acoustic streaming is one of the prime effects to enhance the convection heat transfer and cooling effect.

Abstract: Although cold ring rolling (CRR) process is largely used in the manufacturing of profiled rings like bearing races, research on this purpose has been scant. In this study, based on a validated finite element (FE) model, CRR process is simulated regarding the variable and constant feed speeds of the mandrel roll which lead to constant and variable values of the ring's diameter growth rates respectively using a 3D rigid-plastic finite element method (FEM). Major technological problems involved in the process including plastic deformation behavior, strain distribution and its uniformity, Cockcroft and Latham damage field and final outer diameter of ring are fully investigated. The results of simulations would provide a good basis for process control especially feed speed controlled mills and guiding the design and optimization of both cold and hot ring rolling process.