Advanced Materials Research Vols. 622-623

Abstract: The laser forming process is one of the last technologies on forming of sheet metals with laser beam heat distribution. In this process laser beam moves across the top surface of the sheet metal and the heated zone expands and causes a great moment that deforms the sheet metal. Subsequently, the heated zone gets cooled and provides a reverse strain and moment. The final bending angle is a combination of two phases. Due to the complexity of the process, it is studied with different approaches; FEM analysis and analytical as well as empirical methods. The laser forming is a sensible process regarding the material properties. Also, because of the temperature change during the process, it is important to use a temperature dependent model. In this study The FEM model is proposed for simulation of the mechanism. Based on the simulation results, an integrated analytical model is then developed by a new elasto-plastic material model considering linear strain hardening, combined with the temperature dependent mechanical and physical properties. In addition, the temperature dependent tangential modulus is used instead of the yield point of the material to improve accuracy in the plastic deformation phase. Finally, the analytical model is compared with the FEM standard code, which showed a great conformity.

Abstract: Process of high-speed trains manufacturing is a complicated task requiring strong professional background and practical experience. However, in China, the production mode is staying at the step that explore in actual production constantly, continue to discover and solve problems, low productivity but high manufacturing costs. In order to try to solve above problems, applications of virtual simulation in manufacturing process of high-speed trains is applied for the goals. According to the workshop’s two-dimensional (2D) designing, a digital factory is constructed using simulation software based on production manufacturing process of high-speed trains. Then production model is disaggregated analysis. When virtual simulation environment is accomplished, an assembly process turns to be run. An example of plug-door assembly process is presented to illustrate the effect and feasibility of the application of virtual simulation.

Abstract: Using dilatometric technique, it is the purpose of present research to quantify the kinetics of austenite decomposition during cooling after isothermal hot compression. To reach this aim, based on lattice parameters and thermal expansion coefficients of different phases, a new model was proposed. In this model, the contributions of both isotropic and non-isotropic dilatations were considered. The model was applied to 22MnB5 steel to predict formation of bainite and martensite. Furthermore, the model was developed in order to determine the final fraction of deformation induced ferrite (DIF).

Abstract: For what is believed to be for the first time, the device physics based modeling approach to derive the generic model current equations of organic thin film transistor (OTFT) is described. Firstly, the current model equation is derived by considering the dependence of mobility on gate voltage and doping density, which is more realistic and relevant to organic materials containing TFTs. To model small molecule or polymer TFT, the potential drop across contacts is taken into account as contacts are not ohmic due to some morphological disorders. Further the effect of contact resistance is included and accordingly the generic model current equation is modified. It shows a good agreement of proposed current equation with simulated results which validates the proposed OTFT model from ohmic to saturation regime. Moreover, the analytical model is used to extract the contact and channel resistances in linear and saturation region and these resistances are verified through potential cut line (PCL) and transmission line methods (TLM). The extracted parameters are not only used to verify the electrical characteristics but also exhibit insight on contact potential, charge injection and transport phenomenon for organic TFT operation.

Abstract: Micro Electrical discharge machining (µEDM) is an electro thermal process, the cutting force is negligibly small and material removal occurs irrespective of hardness of work piece material .Micro electrical discharge machining process is capable of machining of complex shape, which is difficult to machine in conventional machining process. Last decade, the EDM process involved demand for machining requirements with short period. Since the major risk of wire breakage, deflections of electrodes were affecting the performance accuracy of EDM operation. This paper describe about a comprehensive review of micro electro discharge machining process and its process optimization techniques used for last 10 years. Micro electro discharge machining has more important given to difficult to machine materials. In order to improve the surface integrity and performance of process, need to select proper process parameters. It reports on the Micro EDM research involving the optimization of the process parameters surveying the influence of the various factors affecting the machining performance and productivity.

Abstract: Bio Additive Manufacturing (BAM), an interdisciplinary field of Rapid Manufacturing (RM) and Tissue Engineering (TE), aims to manufacture the customised bone scaffold for bone replacement. The hydrodynamic stress induced in cells will depend not only on the culture medium flow rate, but also on the scaffold three- dimensional micro-architecture. This paper presents, the patient’s CT scan data in DICOM format is exported into MIMICS software to convert the 2D images into 3D IGES data. The customised bone scaffolds with pore size of 0.7mm and distance between adjacent edges of pores from 0.6mm to 1mm are created in modeling software (SOLIDWORKS 2011) and porosities of five customised bone scaffolds are determined. The above customised bone scaffolds are analysed in CFD software (ANSYS CFX) for the fluid density 1000 kg/m³ and viscosity 8.2 ×10^-4 kgm^-1 s^-1. The estimated Wall Shear Stress (WSS) at fluid velocities from 0.2mm/s to 1mm/s lies in the range of 7.05 x 10 ^-4 Pa to 43.4 x 10 ^-4 Pa., and these scaffolds are fabricated in Rapid Prototyping (RP) technique.

Abstract: This paper aims at determining the fundamental frequency of square perforated plate with square perforation pattern of square holes. Rayleigh’s method is used for the solution of this problem. Non homogeneity in Young’s modulus and density at the perforation is expressed by using greatest integer function i.e. floor function. Boundary condition considered is clamped on all edges. Perforated plate is considered as plate with uniformly distributed mass and holes are considered as non homogeneous patches. The deflected surface of the plate is approximated by a function which satisfies the boundary conditions. Finite Element Method (FEM) modal analysis is carried out to validate the results of the proposed approach.

Abstract: In the presented paper, the failure mechanism of 12Cr2Ni4A minitype straight bevel gear was analyzed by means of both experimental characterizations and numerical simulation techniques. Fractography and simulation were conducted to find the failure mechanism. 3D finite element models (FEMs) of the driven gear with different structure parameters were constructed and used to simulate the inherent characteristic and stress field in the tooth root. Fractography indicated that teeth of the straight bevel driven gear failed because of high cycle fatigue (HCF). Simulation results showed no resonance but stress concentration in the tooth root. It was concluded that this failure occurred due to high cycle fatigue (HCF) and high stress concentration caused by small tooth root fillet radius.

Abstract: Gas Turbines (GTs) are the beating heart of nearly all industrial plants and specifically play a vital role in oil and power industries. Significant research activities have been carried out to discover accurate dynamics and to approach to the optimal operational point of these systems. A variety of analytical and experimental system identification methods, models and control systems has been investigated so far for gas turbines. Artificial neural network (ANN) has been recognized as one of the successful approaches that can disclose nonlinear behaviour of such complicated systems. This paper briefly reviews major ANN-based research activities in the field of system identification, modelling and control of gas turbines. It can be used as a reference for those who are interested to work and study in this area.

Abstract: In the present study, a numerical simulation is performed for the detailed prediction of heat transfer, phase change and fluid flow in welding process with moving heat source. This process may be considered steady with respect to the reference frame attached to the heat source for a long metal block. The problem is formulated by considering the three-dimensional equations of continuity, momentum and energy based on enthalpy model. The equations is solved using a fully implicit, control-volume-based computational method for fixed grids. The calculation domain including solid and liquid phases is solved together as a continuous region. Solid phase velocity is corrected using suitable source terms in the momentum equations. Phase change is considered based on the latent heat of evolution as a source term in the energy equation.The effects of thermal buoyancy and Marangoni flow on melting process are analyzed.