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A side door impact beam absorbs energy and plays an important role in preventing intrusion of another vehicle into the occupant area. Impact beams are being actively researched to reduce vehicle weight while still meeting the strength requirements of environmental regulations and to improve fuel efficiency and enhance safety. No study has subjected a lightweight glass fiber-reinforced plastic (GFRP) impact beam to the Body in White (BIW) Federal Motor Vehicle Safety Standard (FMVSS)-214 quasi-static test. We compared three beams that differed in shape and stacking pattern. We performed three-point bending analyses, bending tests (including after bracket tightening), and static bending tests of door assemblies. The best GFRP beam (B) and a steel model were compared in terms of BIW static bending performance. The front-door GFRP beam exhibited an average reaction force 135% of that mandated by the FMVSS-214S test specification, an intermediate average reaction force 158% of that required, and a final force 154% of that required. In terms of bending performance, the initial average reaction force was 9.5% higher than that of the steel impact beam, and the rear door force was 6.6% lower. The reaction force of the GFRP beam decreased rapidly as breakage occurred after bending through 110.0–120.0 mm; however, the average reaction force was similar to that of the steel beam. Thus, the GFRP impact beam met the legal requirements but weighed 30% less than the steel beam.

Electromagnetic forming (EMF) is a high-speed method used to shape metals using a high-energy magnetic field generated by a forming coil. In this study, EMF experiments were conducted on heat-treated aluminum pipes in an attempt to improve the workability of the metal, in which the heating temperature was varied. Heating to 200 °C and 250 °C resulted in deformation displacements of 1 and 5 mm, respectively. Coupled EM-structural numerical analyses revealed that the EM force was lower by 16 % after heating at 250 °C due to the reduction in the conductivity of aluminum at higher temperatures, resulting in a higher resistance. However, the flow stress decreased by about 50 % at 250 °C. Thus, the increase in displacement despite the reduction in the EM force at higher temperatures indicates that the workability of metals during EMF can be improved with preheating.

AISI 1045 specimen was compared through a high-frequency heat treatment simulation and experiment considering metal phase transformation. Hardening zone predictions were confirmed through cooling and metal phase transformation simulations after obtaining the results from electromagnetic heat transfer simulations. The cooling process was modeled by applying the cooling coefficient of the cooling water in the same way as the actual heat-treatment process. To obtain the current flowing through the coil during high-frequency induction heating, the voltage was measured and applied using the resistance&ndash, inductance&ndash, capacitance circuit calculation method. Experimental and simulated results of the heating temperature and curing depth of an AISI 1045 specimen with a carbon content of 0.45% were compared, the comparison indicated good agreement between the two. Using the simulation results, we established a method for obtaining the current flowing through the induction coil for predicting the extent and depth of the hardening zone during high-frequency induction heat treatment.

Case hardening, or surface hardening, is the process of hardening of a metal object at its outer surface while allowing its core to remain relatively soft, thereby forming a thin layer of harder metal at the surface. Currently, induction heating using high frequency current is applied to carry out this hardening process. We modeled this hardening process using the powerful Abaqus finite element tool and validated the results of the numerical analysis by comparing them with experimental results. Our model accurately predicted the hardened area at the outer surface of the metal for a steel sprocket. Future research will optimize the coil geometry and other parameters.

This dissertation tried to analyze passenger behaviors after an accident with the possibilities of a variety of accidents open reflecting the phases...

Induction welding is a fast, clean, noncontact process that often uses a metal-mesh susceptor to facilitate localized controlled heating, however, the metal mesh presents various problems. In this study, the induction heating behavior of a 450 &mu, m thick thin-film susceptor, fabricated by mixing magnetite (Fe 3 O 4 ) nanoparticles (NPs) and PA6/carbon fiber (CF) (30%) thermoplastic resin, was examined with respect to the weight ratio of Fe 3 O 4 (50, 67, 75, and 80 wt%). The useful induction heating behavior of the 75 wt% Fe 3 O 4 susceptor suggested its suitability for additional heat treatment experiments, carried out at 3.4 kW at a frequency of 100 kHz. This susceptor attained the same maximum temperature during 10 cycles of repeated induction heating and cooling. It was then used to weld two thermoplastic composites, with 60 s of induction heating followed by 120 s of simultaneous cooling and pressing. The resulting welded joints had lap shear strength values of 36.8, 34.0, and 36.4 MPa under tensile test loads of 884, 817, and 874 N, respectively. Scanning electron microscopy images confirmed a uniform weld quality. Thus, the proposed manufacturing method, involving the incorporation of Fe 3 O 4 NPs into thermoplastic resin, should help expand the range of applications for thermoplastic composites.

High frequency induction heating (HFIH) is used in many industries and has a number of advantages, including reliability and repeatability. It is a non-contact method of providing energy-efficient heat in the minimum amount of time without using a flame. Recently, HFIH has been actively studied using the finite element method (FEM), however, these studies only focused on the accuracy of the analysis. In this paper, we can measure joule heat distributions by the electromagnetic analysis for HFIH and the temperature distribution from the heat transfer analysis by applying joule heat for a sprocket. The sprocket is heated over 850℃ due to joule heat and then cooled to under 200℃ by using cooling 20℃ water. These processes were used to calculate the FEM and then compared to our experimental results. The calculated outcome may be used to predict hardening depth in HFIH.

Induction heating is being actively studied, and High frequency induction heating (HFIH) is widely used for various industrial applications. The reason for highlighting induction heating is that it has many advantages compared with previously used heating methods. The performance of HFIH is governed by a number of variables, including the applied frequency and power, shape of the coil, and duration of the process. We assumed that two of these variables are dominant. The first variable is the shape of the coil. The second variable is the frequency related to the skin effect. We found the optimal hardening conditions by changing these variables. The HFIH process was simulated using FEM and compared with results from experiments. We believe that the results of this study will be helpful for users of HFIH in the near future.

Springback occurs at the end of sheet metal forming process where the geometric changes takes place in the part when the load is removed. It is an important factor to determine the quality of sheet metal forming. In this paper, the factors which affects the springback is determined and its influence over springback is studied analytically. The sheet metal forming process is performed using finite-element tool ABAQUS, so as to obtain the springback value for different process parameter. Punch radius and clearance gap along the horizontal axis between punch and die are the two process parameters considered for this study. For this study, 2D metal forming process has been performed and the springback angle is calculated at the corner area close to the holder. Kriging interpolation technique is used to build the surrogate model for the optimization process. Finite element method provides the data to build the metamodel which also helps in reducing the number of the real tests. Kriging or Gaussian process regression is an interpolation method which interpolates the values, modeled by a Gaussian process governed by prior covariance to optimize the smoothness of the fitted values. Kriging was applied to simulate the complex springback process. The sample data required to build the surrogate model was generated using MATLAB. Latin hypercube sampling technique has been utilized to generate the input sample points. The meta- model built with help of kriging interpolation for the sheet metal forming process is validated using RMSE method. With help of this approach we are able to predict the best process parameter which results in lower springback for the sheet metal forming is obtained, thereby reducing the spring back considerably. This paper gives a new approach that involves in reducing the springback phenomenon in sheet metal forming process with help of meta-model technique.

The widlass base frame which is currently used is designed by lots of volume and costs so as to obtain high rigidity in spite of the greatly external load. The purpose of this research is to draw conceptual design of optimal design which can satisfy high rigidity existing windlass base frame has and lessening the body at the same time. Therefore, it progressed conceptual design by applying Topology optimization and Size optimization based on the finite-element analysis for the early model and indicated the result by comparing the early model with optimized model. As the result of Topology optimization, its stress was increased by about 6MPa and weight was decreased by about 560kg in comparison with the early model. In addition, in case of Size optimization, its stress was increased by about 7MPa and weight was decreased by about 1,560kg in comparison with the early model.

Fiber bragg grating (FBG) sensors are currently in use in various fields. However, it is difficult to use these sensors to obtain strain measurements at locations where it is not physically possible to connect the fibers to each other. In the present study, we performed strain measurements using many FBG sensors connected to a single optical fiber and a pair of collimators. The single optical fiber connected to the FBG sensors was installed on a cantilevered beam with another optical fiber line connected to a stationary optical interrogator. The two optical fiber lines were connected by a pair of collimators making use of the fact that light travels in a straight line through space. Our experiment demonstrated that the wavelength of the light changed linearly as it passed between the two collimators, and that this change increased with the applied strain. Accurate strain measurements could be obtained by applying a proposed collimator collection factor.

A load cell is the representative converter that changes load to the quantity of electricity. The load cell is used to a large mechanical structure and offshore structures to measure the force. Currently, the load cell using electrical strain gauges are commonly used. Basic measuring principle of electrical strain gauge is the electrical method. A load cell with electrical strain gauges is not available in the electromagnetic and corrosion environment. A Fiber Bragg Grating (FBG) sensor is not affected by the EMI (Electro Magnetic Interference)/EMC (Electro Magnetic Compatibility) and is strong in corrosion under the sea water. In this paper, we use the FBG sensors to make a load cell under the sea water condition and the electromagnetic environment and show FBG sensors' availability.

Recently, Fiber Bragg Grating(FBG) sensors are being used in various fields. However, it has difficulty to measure at the place where it is not possible to connect fibers each other physically. In this study, using FBG a collimator, we have measured strains with a single optical fiber with many FBG sensors where FBG sensors on one optical fiber line is installed on the beam and the other optical fiber line is connected with an optical interrogator installed at stationary side. The optical fiber lines between an optical fiber line with FBG sensors on the beam and the other optical fiber line on the stationary part are connected by the collimator which makes the use of light's unique characteristic - light travels through space. The experiment showed that the wave length of the light were changed to be linear as strains increased, and the accurate strains were measured by applying the collimator collection factor, which was proposed in this paper.

Cohesive models are increasingly applied to simulate fracture and fragmentation processes in various materials. The multiple-domain boundary element method (MDBEM) may be more suitable than the often-applied finite-element method (FEM) because debonding is also a boundary surface problem. In this study, a modified damage initiation criterion possessing a linear relationship to the MDBEM is proposed for the cohesive model. Numerical examples are presented to demonstrate the validity of this procedure.

The reliability and safety of MEMS parts are important factors in industrial MEMS applications. Most MEMS parts are made from multigrain polysilicon, an orthotropic material with random material direction. Analyzing the stress and displacement and knowing the effective material constant are important when using MEMS in industrial applications. We developed a computer program to calculate the effective material constant of polysilicon using the boundary element method with the microstructure evolution method. The results obtained using the boundary element method were compared to those obtained using the finite element method to confirm the validity of the program.

Most of the MEMS parts are made of multi-grain silicon wafer, which is the orthotropic material and its material direction is arbitrary. The reliability of the parts must be guaranteed in order to use for the commercial usage. The need of the structural analysis of its parts emerges an important factor. The material properties of the MEMS parts are calculated by the numerical method in order to reduce a material test. In this study, the effective elastic modulus and its Poisson’s ratio are calculated by the boundary element method(BEM) and are compared with the results by the finite element method(FEM). 1. 서 론 MEMS 부품의 신뢰성 평가 및 미세 부품의 안전성 파악은 MEMS 부품을 적용함에 있어서 중요한 요소이다. 이들 연구에서 계산역학을 적용하여 MEMS 재료의 재료상수를 구하는 방법을 개발하여 실험을 최소로 하는 연구가 진행되고 있다. 유효탄성계수와 푸아송비의 추출에 관련된 연구로 den Toonder 등 (1) 은30 개의 각 입자에 대해서 다른 재료 방향각을 가지는 이방성 재료에 유한 요소법을 적용하여 유효탄성계수들을 계산하였다. Mullen 등 (2) 은 다결정 박판의 유효탄성계수를 Monte-Carlo 법으로 (3)모사하였으며, Yin 또한 같은 방법으로 (4)유효탄성계수를 추출하였다. Chu는 Johnson-Mehl 형상을 적용하여 다결정 재료의 유효탄성계수를 추출하였다. Sharpe등

In this study, advanced computational analysis system for nonlinear static aeroelastic problems has been successfully developed by the composite structure (FEM)-fluid (CFD) combined method with internal iteration steps. Major focus of the present study is to investigate the static aeroelastic characteristics of laminated composite wings including the strong normal shock waves in the transonic and low-supersonic flow regions. The results importantly indicate that the effect of airfoil camber on the load distribution of laminated composite wing models can be nonlinear due to the variation of ply orientations.

In the present study, an unsteady three-dimensional flow simulation based on the RANS (Reynolds Average Navier-Stokes) equations with k-e turbulence model and Singhal et al.’s cavitation model is conducted to study the cavity development behavior of two slender bodies, that is, a flat-headed cylinder and a step-headed cylinder of 50 mm in length and 10 mm in diameter. Using so called VOF method to track the liquid-vapor phase interface, time dependent solutions with varying approach speed range from 10 m/s to 55 m/s are obtained and analyzed to provide key information such as cavity initiation speed, drag coefficient and the cavity shape and size (max. length and diameter). The implemented numerical model is validated for flows over a flat disk cavitator against the experimental correlation. According to the present simulation results, slender bodies with two different head shapes, that is, a flat cylinder and a stepped one, respectively, showed very close behavior in their cavity initiation speed, maximum developed cavity diameter and length, but consistently lower drag coefficient with the step-headed cylinder case, which suggests the possible advantage of seeking optimized cavitator shape.Copyright © 2015 by KSME

Modern aircraft are designed using the damage tolerance concept. Fatigue cracks will be occurred at the initial flaw such as micro flaws in the material and scratches during the material manufacturing process. And stress concentration on notches, fillets and rivet holes under random loads caused to initiate the crack. This crack will propagate by repeated loads and finally failure. Therefore aircraft parts must be performed the damage tolerance test to prove the safety of the design life under the loads during operation. In this study, we have tested and analyzed the crack propagation behavior of aluminum alloy 2024-T3 plate under random loads. The crack lengths measured by the fractography analysis were compared to the analysis results with the retardation effect.

Two‐noded curved beam elements, CMLC and IMLC, are developed on the basis of Timoshenko’s beam theory and curvilinear co‐ordinates. These elements are developed by the separation of the radial displacement into the bending and the shear deflection and the projection of the shear deflection into bending deflection. In the CMLC element, field‐consistent membrane strain interpolation is adapted for removing the membrane locking. The CMLC element shows the rapid and stable convergence on the wide range of radius, thickness and length of the curved beam. The field‐consistent membrane strain and the separation of radial displacement produce the most efficient linear element possible.

A variational formulation for a Timoshenko beam element is derived by the separation of the deformation mode into the bending deflection and shear deflection. Shear deflection is projected into bending deflection and the projection matrix is constructed by using the equilibrium equation and the relation of force and displacement. The exact stiffness matrix of the Timoshenko beam element can be obtained by the present method. Examples are solved in order to show the effectiveness of the beam element in comparison with other elements.

A numerical procedure is developed for the solution of the two-dimensional frictional contact problems with Coulomb's law of friction. The formulation for this procedure is reduced to a complementarity problem. The contact region is separated into stick and slip regions and the contact stress can be solved systematically by applying the solution technique of the complementarity problem

A numerical procedure is developed for the solution of contact problems with Coulomb friction based on a complementarity problem formulation. Two-dimensional elasticity problems discretized by the boundary element method are used for detailed derivation of the complementarity equations for an incremental step. The dependency of the contact stress state on loading path is clearly shown and illustrated by examples.