• Smart Structures and Systems
• /
• v.20 no.4
• /
• pp.473-481
• /
• 2017

This study suggests a simple, convenient and non-destructive method for investigation of the Young's modulus detection in stepped shafts which only utilizes the first-order resonant frequency in flexural mode and dimensions of structures. The method is based on the impulse excitation technique (IET) to pick up the fundamental resonant frequencies. The standard Young's modulus detection formulas for rectangular and circular cross-sections are well investigated in literatures. However, the Young's modulus of stepped shafts can not be directly detected using the formula for a beam with rectangular or circular cross-section. A response surface method (RSM) is introduced to design numerical simulation experiments to build up experimental formula to detect Young's modulus of stepped shafts. The numerical simulation performed by finite element method (FEM) to obtain enough simulation data for RSM analysis. After analysis and calculation, the relationship of flexural resonant frequencies, dimensions of stepped shafts and Young's modulus is obtained. Numerical simulations and experimental investigations show that the IET method can be used to investigate Young's modulus in stepped shafts, and the FEM simulation and RSM based IET formula proposed in this paper is applicable to calculate the Young's modulus in stepped shaft. The method can be further developed to detect mechanical parameters of more complicated structures using the combination of FEM simulation and RSM.

• Journal of Mechanical Science and Technology
• /
• v.14 no.7
• /
• pp.715-721
• /
• 2000

Residual stress is one of the causes which makes defects in engineering components and materials. These residual stresses can occur in many engineering structures and can sometimes lead to premature failures. There are commonly used methods by which residual stresses are currently measured. But these methods have a little damage and other problems; therefore, a new experimental technique has been devised to measure residual stress in materials with a combination of electronic laser interferometry, laser heating and finite element method. The electronic laser interferometer measures in-plane deformations while the laser heating and cooling provides for very localized stress relief. FEM is used for determining the heat temperature and other parameters. The residual stresses are determined by the amount of strain that is measured subsequent to the heat-up and cool-down of the region being interrogated. A simple model is presented to provide a description of the method. In this paper, the ambiguity problem for the fringe patterns has solved by a phase shifting method.

• Nuclear Engineering and Technology
• /
• v.55 no.4
• /
• pp.1365-1381
• /
• 2023

In this paper, a procedure for evaluating the structural integrity of the PCSG (Printed Circuit Steam Generator) unit block is presented with a simplified FE (finite element) analysis technique by applying the homogenization method. The homogenization method converts an inhomogeneous elastic body into a homogeneous elastic body with same mechanical behaviour. This method is effective when the inhomogeneous elastic body has repetitive microstructures, and thus the method was applied to the sheet assembly among the PCSG unit block components. From the method, the homogenized equivalent elastic constants of the sheet assembly were derived. The validity of the determined material properties was verified by comparing the mechanical behaviour with the reference model. Thermo-mechanical analysis was then performed to evaluate the structural integrity of the PCSG unit block, and it was found that the contact region between the steam header and the sheet assembly is a critical point where large bending stress occurs due to the temperature difference.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.2
• /
• pp.158-163
• /
• 2022

The test method on the Type II high-pressure hydrogen storage tanks made of the metal wire hoop winding is a complex and high risk. Also closeup on the tank being test is difficult. In this study, we studied a mechanical test method for a high-pressure hydrogen tanks. This method must be simple, risk-free and possible to observe the change in microscopic behavior of a metal wire on a liner. As the results, it was possible to observe the microscopic behavior on the metal wire by the mechanical test method. Also, a simple and risk-free test was possible compared to the conventional test method for high pressure hydrogen tanks.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.10
• /
• pp.1671-1677
• /
• 2001

Cracks at mechanical fastener holes usually nucleate as elliptical comer cracks at the faying surface of the mechanical joints and grow as elliptical arc through cracks. The weight function method for elliptical arc through cracks at mechanical fastener holes has been developed and verified in the part I of this study. In part H, applying the weight function method, the effects of the amount of clearance on the mixed-mode stress intensity (actors are investigated and the change of crack shape is predicted from the analysis for various crack shapes. The stress intensity factors leer inclined crack are analyzed and critical angle at which mode I stress intensity factor becomes maximum is determined.

• Journal of Mechanical Science and Technology
• /
• v.20 no.9
• /
• pp.1382-1389
• /
• 2006

Dynamic responses of a simply supported beam with a translational spring carrying a moving mass are studied. Governing equations of motion including all the inertia effects of a moving mass are derived by employing the Galerkin's mode summation method, and solved by using the Runge-Kutta integral method. Numerical solutions for dynamic responses of a beam are obtained for various cases by changing parameters of the spring stiffness, the spring position, the mass ratio and the velocity ratio of a moving mass. Some experiments are conducted to verify the numerical results obtained. Experimental results for the dynamic responses of the test beam have a good agreement with numerical ones.

• Structural Engineering and Mechanics
• /
• v.58 no.3
• /
• pp.443-458
• /
• 2016

In this paper, we propose a method for taking into account uncertainties based on the projection on polynomial chaos. Due to the manufacturing and assembly errors, uncertainties in material and geometric properties, the system parameters including assembly defect, damping coefficients, bending stiffness and traction-compression stiffness are uncertain. The proposed method is used to determine the dynamic response of a one-stage spur gear system with uncertainty associated to gear system parameters. An analysis of the effect of these parameters on the one stage gear system dynamic behavior is then treated. The simulation results are obtained by the polynomial chaos method for dynamic analysis under uncertainty. The proposed method is an efficient probabilistic tool for uncertainty propagation. The polynomial chaos results are compared with Monte Carlo simulations.

• Journal of Mechanical Science and Technology
• /
• v.16 no.2
• /
• pp.211-218
• /
• 2002

This paper proposes an unstructured tetrahedral meshing algorithm for CAD models in the IGES format. The work presented is based on the advancing front method, which was proposed by the third author. Originally, the advancing front method uses three basic operators, namely, trimming, wedging, and digging. In this research, in addition to the basic operators, three new operators splitting, local finishing, and octahedral-are added to stabilize the meshing process. In addition, improved check processes are applied to obtain better-shaped elements. The algorithm is demonstrated and evaluated by four examples.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.304-310
• /
• 2001

Cracks at mechanical fastener holes usually nucleate as elliptical comer cracks at the faying surface of the mechanical joints and grow as elliptical arc through cracks after penetrating the opposite surface. In this study mode I, II and III stress intensity factors at two surface points of elliptical arc through cracks at mechanical fastener holes are analyzed by applying weight function method. The weight function method for two dimensional mixed-mode problem is extended to three dimensional one and it is verified.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.934-937
• /
• 2001

It is well-known that the micro fabrication technology of micro parts are the high energy beam or silicon-based micro machining method such as LIGA Process, Laser machining, photolithography and etching technology. But, for fabricating complex 3-D structure it is better to use mechanical machining. This machining method by the mechanical machine tool with nanometer accuracy is getting attention in some field-especially micro optics machining such as grating, holographic lens, micro lens array, fresnel lens, encoder disk etc.. In this study, we survey the micro fabrication by mechanical cutting method and set up the mechanical micro machining system. And we carried out micro cutting experiments for micro parts with v-shape groove.