Abstract: To eliminate geometric deviations of sheet metal subjected to an air-bending process from the geometry required by the designer, it is necessary to predict the accurate value of the springback. Springback is the elastic deformation observed upon removal of the load during a bending process. In order to predict the springback amount, a multidimensional function should be approximated. In this paper, a neural network metamodel (NNM) based on the back propagation algorithm is introduced to predict the springback value. A verified nonlinear finite element model is developed to generate NNM training data. To select the training data for the NNM, computer generated D-optimal designs are utilized. The NNM developed model in this research can be used in determination of the springback value in sheet metal bending.
Abstract: It is difficult to calculate dynamic equilibrium configuration in the mechanical systems, especially with the constraint conditions. In this paper, a method to calculate the dynamic equilibrium positions in the constrained mechanical systems is proposed. The accelerations of independent coordinates are derived in the algebraic form so that the numerical solution is easily obtained by the iteration method. The proposed method has been applied to calculate the dynamic equilibrium configuration for speed governor and the wheelset of railway vehicle.
Abstract: Stellite 6 was deposited by laser cladding on an austenitic stainless steel substrate (ASS) with energy inputs of 1 kW (ASS 1) and 1.8 kW (ASS 1.8). The chemical compositions and microstructures of these coatings were characterized by atomic absorption spectroscopy, optical microscopy and scanning electron microscopy. The microhardness of the coatings was measured and the wear mechanism of the coatings was assessed using a pin-on-plate (reciprocating) wear testing machine. The results showed less cracking and pore development for Stellite 6 coatings applied to the austenitic stainless steel substrate with the lower heat input (ASS 1). Further, the Stellite coating for ASS 1 was significantly harder than that obtained for ASS 1.8. The wear test results showed that the weight loss for ASS 1 was much lower than for ASS 1.8. It is concluded that the lower hardness of the coating for ASS 1.8, together with the softer underlying substrate structure, markedly reduced the wear resistance of the Stellite 6 coating.
Abstract: The aim of the work is to computationally investigate the influence of pipe diameters on shapes of air Taylor bubbles in small pipes, containing stagnant water. The examined pipe diameters are selected between 6.5 and 11 mm so that flows around the bubbles are laminar. The proper Taylor bubble shape of each pipe size is determined by varying the bubble shape until the air pressure distribution inside the bubble is uniform. Computational results show that the Taylor bubble shape will be slenderer if the pipe diameter is larger.
Abstract: The design of semi-monocoque frame by using the composite-steel joint is considered in this paper. The frame is designed with weight less than 30kg and torsional stiffness more than 1200 Nm/deg. In order to design the semi-monocoque frame, the analysis of the composite-steel joint has to be clearly investigated. Therefore, the stress analysis of composite-steel joint is performed and then the frame is designed. The double lab joint with two holes is tested and verified by the experiments. The carbon-fiber fabric laminated with the KEVLAR fabric composite laminate is used for composite part. From experiments, the joint’s strength can be increased by using the eccentric holes. Therefore, in order to meet the requirement of the SAE rules; load capacity more than 30 kN, the eccentric hole double lap joint is numerically designed and applied to semi-monocoque frame. The joint has strength of 32 kN and can be used in frame design. The semi-monocoque frame is designed and analyzed by finite element analysis. The maximum stress at maximum load is 208 MPa which is less than the yield strength of the materials so it can withstand the loads, the mass is 29.6kg, and the torsional stiffness of the frame is 1408 Nm/degree. Therefore, the semi-monocoque frame can be successfully designed.
Abstract: The threat of terrorism has led to increased awareness about protecting properties from damage in terrorist attacks. With the rapid growth of the computer industry and progress in the field of finite-element analysis, evaluations of conventional weapons focus more on simulations than on experiments. There are many approaches to simulate blast and impact. These include Eulerian, Lagrangian, multi-material arbitrary Lagrangian-Eulerian (MM-ALE), and the meshless approach of smooth particle hydrodynamics (SPH) methods. Each method has distinct advantages. In this study, finite-element analysis was applied to simulate a 1 kg trinitrotoluene (TNT) blast in front of a 20-mm-thick steel plate. Three different approaches were simulated: Eulerian, MM-ALE, and SPH. Each method gave different results for the von Mises stress distribution, peak pressure, and displacement of the steel plate. A comparison of the three results implies that using one of these three approaches may generate a significant blast simulation.
Abstract: Gear design is a state of art in mechanical design topic. In this paper, the systematic gear design concept was used to design the double output shaft gearbox for rolling mill, the aim to reduce cost of production. The design process starts from receive the requirement data, elaborate the data to the design specification. Make a conceptual design, embodiment design or preliminary design and finally detailed design. The all design methodology has suggested systematic decision-making procedures for early stages of the design. The design result is leading to change from the traditional two stage gearbox into the single stage gearbox ratios 1:2.3.
Abstract: The wave glider is an autonomous unmanned vehicle (AUV) which uses the power of the ocean to propel itself. The purpose of this study is using the well known slender model NPL in developing hull in an attempt to design the floating hull of wave glider. CFD and Maxsurf software are used to present a method focused on mesh generation to predict calm water resistance for the hull. Calculations are carried out for Froude numbers in the range of 0.10 to 0.40. Three different mesh sizes are used for CFD to calculate the mesh effects. The results of numerical predictions under the same conditions obtained from CFD and Maxsurf calculations are obtained and compared for accuracy of the solution parameters. The comparison shows a good agreement between the results. The method is useful and acceptable and the overall numerical scheme is suitable for resistance prediction.
Abstract: The objective of this paper is to design and develop a simple geometry of an underactuated mechanical gripper which can provide most common hand grasps, fingertip grasp and enveloping grasp. The gripper consists of 2 2-DOF fingers underactuated by a pulley-tendon system, and a movable pulley for underactuation between fingers. Each finger has 2 links and 2 pulleys. A parallel linkage is used to translate distal phalanx toward an object such that fingertip grasp is improved. This work implements stability and force isotropy criteria to optimize the design. The prototype has 0.43 of pulley-radius ratio and 1.72 of link-length ratio. From primitive-shape grasping test, the gripper is able to achieve the stable configuration.