Advances in Fracture and Failure Prevention

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Authors: Soon Suck Jarng, Je Hyeng Lee, Y.J. Kwon
Abstract: This paper describes the application of the coupled FE-BEM (finite element-boundary element method) for the numerical harmonic analysis of the linear dynamic behaviour of a magnetostrictive Terfenol-D rod in water. The magnetostrictive rod is three-dimensionally modeled to transduce applied electric current in a helical coil around the rod to mechanical displacement. The steady-state resonance response of the displacement is shown.
Authors: Li Xing Huo, Min Liu, You Feng Zhang, Fang Juan Qi
Abstract: To increase the accuracy of R-F method, it is necessary to solve the problems of the linear expansion of failure function and non-normal variables. In this paper, the improved FOSM method was applied to calculate the failure probability of welded pipes with cracks. The examples show that this method is simple, efficient and accurate for reliability safety assessment of welded pipes with cracks. It can save more time than the Monte Carlo method does, so that the improved FOSM method is recommended for general engineering reliability safety assessment of welded pipes with cracks.
Authors: Xiu Guang Song, Xiu Yuan Ma, Jin Zhang Liu
Abstract: Based on the conception of dynamic shape function, a finite dynamic element method (DEM) is developed for the computation of dynamic consolidation. Formulae of the DEM are also derived. This method overcomes the shortcomings of conventional finite element methods, i.e., the vibration characteristics of the soil to be consolidated cannot be considered. Therefore, it practically reflects the dynamic characteristics of consolidation. The programs for the DEM are also written. Results of practical calculation show that the method is correct and feasible.
Authors: Q. Li, H.Z. Liu, Zhuo Zhuang, S. Yamaguchi, Masao Toyoda
Abstract: A numerical algorithm using equal-order linear finite element and fractional two-step method is presented in this paper, which is used for analysis of incompressible viscous fluid flow with free surface problems. In order to avoid severe mesh distortions, ALE method is used for dealing with the free surface sloshing. For numerical integration, the fractional step method is employed, which is useful because the same linear interpolation functions for both velocity and pressure could be carried out in the finite element formulation. The present algorithm has been applied to some examples and proved to be accurate and more efficient.
Authors: S.I. Huh, S.W. Jung, C.K. Jung, Kyung Seop Han
Abstract: This study simulated the Scoring process and the Can opening process of Easy Open End by finite element method. A FEM model was developed to predict the limitation of the scoring depth and the opening force at the End of steel Can using ABAQUS. In spite of a complex 3D structure, the shape of the Can End was simplified 2D axisymmetric model and analyses were focused on the change of materials and score shapes. Adaptive meshing was applied to the region of the score in the scoring process in order to suppress large deformation of elements. The critical depth of the scoring was observed because necking occurred at the panel during the scoring process. Necking could be restrained by changing the shape of the score punch. For the opening simulation, the shear failure model was utilized. The opening force was predicted with various materials, residual thickness, panel thickness (thickness ratio) and score shapes. The influence of these factors changed with the thickness ratio. Synthetically, the score condition of the steel Can End that the opening force is similar to the aluminum End was proposed.
Authors: Hoon Cheol Park, Yanti Rachmadini, Sang Min Lim, Sang Ki Lee, Kwang Joon Yoon, Gene Joo, Deog Kwan Kim, Myeong Kyu Lee, Dan Bi Hong
Abstract: Finite element analysis for thick composite structures is rather complicated. Two-dimensional modeling, which is relatively easy to make, can cause inaccurate result since the plane stress condition cannot be applied, while three-dimensional modeling is hard to make. In the three- dimensional modeling, it is difficult to model all the layers with different material properties and ply orientation in the structure. In this paper, an equivalent modeling is proposed and numerically tested for analysis of thick composite structures. The method has been verified for the modeling of composite plate and circular composite tube in order to find their bending deflection and natural frequency. MSC/NASTRAN and PATRAN are used for the calculation. It has been confirmed that three-dimensional analysis must be conducted for thick structures and the equivalent modeling is proven to be accurate when layers with same characteristics are properly grouped. The proposed modeling technique has been applied to analyze hingeless composite rotor hub system designed by Korea Aerospace Research Institute (KARI). Detailed three-dimensional modeling for this structure is almost impossible to make due to its complex geometry of thick composite structures. Using the proposed equivalent modeling technique, failure analysis was performed based on stress/strain criterion and the safety of each part was checked. Deflection of the hub system was validated comparing with the result from the simple analytical beam model, and the numerical result will be used for the next design cycle of the composite hub system.
Authors: Jae Yeol Kim, Lee Ku Kwac, Jae Ho Han
Abstract: Recently, the world is preparing for new revolution, called, ‘IT(Information Technology), NT(Nano-Technology), and BT(Bio-Technology).’ NT can be applied to various fields such as semiconductor-micro technology. Ultra precision processing is required for NT in the field of mechanical engineering. Because of radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts. In this paper, stability of ultra precision cutting unit is investigated and this unit is the kernel unit in ultra precision processing machine. According to alteration of shape and material of hinge, stability investigation is performed. Hinge shapes of micro stage in UPCU (Ultra Precision Cutting Unit) are designed in two types, where, hinge shapes are composed of round and rectangularity. Elasticity and strength are analyzed on micro stage with respect to hinge shapes by FE analysis. The micro stage in ultra precision processing machine has to keep hinge shape under cutting condition with 3-component force (cutting component, axial component, and radial component) and to reduce modification against cutting force. Then we investigated its elasticity and strength under these conditions. The material of the micro stage is generally used for duralumin with small thermal deformation. Since the elasticity and the strength quiet become important, the stability of the micro stage is investigated. Used materials are composed of aluminum of low strength and cooper with medium strength and spring steel with high strength. Through this stability investigation, trials and errors are reduced in design and manufacture at the same time, and we are accumulated foundation data for a unit control.
Authors: Hong Gun Kim
Abstract: A seat frame structure in automotive vehicles made of polymer matrix composite(PMC) with reinforced by X-shape steel frame was developed to obtain weight reduction at low cost. The frame structure was designed and analysed using finite element analysis(FEA) and was compared with experimental impact test to verify the structural safety after fabricated. The design model based on safety was analysed with appropriate boundary conditions and loading conditions. Each result was utilized to modify the actual shape to obtain a lighter, safer and stabler design. It was found that the substitution of PMC material reinforced by an X-shaped steel frame resulted in a weight reduction effect with equivalent strength, impact characteristics and fracture property.
Authors: Gang Fang, P. Zeng
Abstract: Fine blanking process with V-ring was simulated with FEM. The geometric parameters of the die, the punch, the serrated ring and the sheet are modeled. In this paper, some other assumptions are made for the analysis. The workpiece is considered as elastic-plastic material, while the tools are defined as rigid bodies. The damage model taking into account the influence of hydrostatic stress is used to simulate material fracture in blanking. The stress status and forming process are analyzed. Authors also investigated the effect of distance from tooth to die edge on roll-over high. The simulation can reflect the laws of fine blanking process.
Authors: L.S. Ma, Tie Jun Wang
Abstract: Based on the first-order shear deformation theory of plate, governing equations for the axisymmetric buckling of functionally graded circular/annular plates are derived. The coupled deflections and rotations in the pre-buckling state of the plates are neglected in analysis. The material properties vary continuously through the thickness of the plate, and obey a power law distribution of the volume fraction of the constituents. The resulting differential equations are numerically solved by using a shooting method. The critical buckling loads of circular and annular plates are obtained, which are compared with those obtained from the classical plate theory. Effects of material properties, ratio of inter to outer radius, ratio of plate thickness to outer radius, and boundary conditions on the buckling behavior of FGM plates are discussed.

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