• Journal of Mechanical Science and Technology
• /
• v.17 no.6
• /
• pp.836-843
• /
• 2003

The polymer composites contain numerous internal boundaries and its structural elements have different responses and different resistances under the same service environment. Fatigue phenomenon is much more complex in composites than homogeneous materials. An understanding of the fracture behavior of polymer composite materials subjected to constant and cyclic loading is necessary for predicting the life time of structures fabricated with polymers. There is a need to acquire a better understanding of the fatigue performance and failure mechanisms of composites under such conditions. Therefore, in this study the analyses of fiber orientation and fracture mechanism for low cycle fatigue crack have been studied by SEM and LM for observing the ultrathin sections.

• Advances in aircraft and spacecraft science
• /
• v.3 no.4
• /
• pp.447-470
• /
• 2016

Limit cycle oscillations (LCO) as well as nonlinear aeroelastic analysis of a swept aircraft wing with cubic restoring moments in the pitch degree of freedom is investigated. The unsteady aerodynamic loading applied on the wing is modeled by using the strip theory. The harmonic balance method is used to calculate the LCO frequency and amplitude for the swept wing. Finally the super and subcritical Hopf bifurcation diagrams are plotted. It is concluded that the type of bifurcation and turning point location is sensitive to the system parameters such as wing geometry and sweep angle.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.7
• /
• pp.168-177
• /
• 1999

Fatigue damage is the phenomena which is accumulated gradually with loading cycle in material. It is represented by fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$. Fracture mechanical parameters estimating large crack growth behavior can calculate quantitative amount of fatigue crack growth resistance in engineering material. But fatigue damage has influence on various load, material and environment. Therefore, In this study, we propose that artificial intelligent fatigue damage model can predicts fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$ simultaneously using fracture mechanical and nondestructive parameters.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.3
• /
• pp.28-38
• /
• 2003

Finite element analysis of cylinder heat/block compound under assembly, thermal and firing condition were performed. FE model including two cylinders with gasket, head bolts, liners and valve seats was used. FE modeling method and boundary conditions were introduced. Stress distribution and deformation of cylinder head and block under each loading condition were presented. Gasket pressure distribution and bore distortion level were predicted. Measured data of bore distortion was compared with the analysis results. The analysis result showed similar trends with the experimental data. High cycle fatigue analysis on the basis of this result has been performed in order to find the critical areas of the engine assembly.

• Journal of the Korean Society for Railway
• /
• v.3 no.4
• /
• pp.194-202
• /
• 2000

Fatigue behavior of shear joints between the combined reinforced concrete(RC) and the reinforced steel fiber concrete(SFRC) specimens has been experimentally investigated. Experimental parameters used are the amount of steel fiber and the type of shear joint. Six specimens have been tested under static load, and eight specimens have been subjected to the fatigue load in a range of 50 % and 5 % of the ultimate static load. The purpose of this research is to propose an empirical formula for fatigue shear behavior of the combined RC and SFRC structures on the basis of experimental result. It can be observed from experimental results that addition of steel fibers to concrete specimen increases the static ultimate load by approximately 25 %, enhances the fatigue behavior, and also reduces vertical and lateral displacements at the shear joint for a given load cycle after the occurrence of first crack.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.427-433
• /
• 2005

Railway wheelset is the most essential part which undergoes severe cyclic loadings. In recent years, there has been increasing need for insuring the safety of running as the speed of the railway vehicles is getting higher. So it is required on the assessment of fatigue characteristics of the wheelset to consider plastic deformation which might be probable in the severe loading condition. In this study, total-strain controlled low cycle fatigue(LCF) test were performed to observe the LCF behaviors of the railway wheels and axles using companion specimens method. From the experimental results, the cyclic mechanical properties have been evaluated and total strain amplitude versus life relationship have been derived using the empirical Coffin-Manson law.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.6
• /
• pp.830-836
• /
• 1986

In this study, the effect of hydrogen absorbed in welding process on the fatigue behaviour of the weld bond was quantitatively made clear. The influence of cyclic loading rate on the fatigue characteristics of the manual arc weld bond was inspected under the condition of constant amount of hydrogen. Moreover, the fatigue cracking mechanism concerning the diffusible hydrogen in the welded part was discussed in connection with fractographs of the fracture surfaces.

• Computational Structural Engineering : An International Journal
• /
• v.2 no.1
• /
• pp.19-23
• /
• 2002

A reliability-based cost-benefit model for the risk management of oil platforms in the formulation of optimal decisions based on life-cycle consideration is proposed. The model is based on structural risk assessments and the integration of social issues and economics into the management decision process. Structural risks result from the platform's exposure to the random environmental loading associated with the offshore site where it is located. Several alternative designs of a typical platform are proposed and assessed from the cost-effectiveness viewpoint. This assessment is performed through the generation of cost/benefit relationships that are used, later on, to select the optimal design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.334-337
• /
• 2007

Austenitic stainless steel is used as high temperature components such as gas turbine blade and disk because of its good thermal resistance. In the present investigation, tensile and low cycle fatigue(LCF) behavior of stainless steel for turbine disks was studied at wide temperature range $20^{\circ}C\;{\sim}\;750^{\circ}C$. In the tensile tests, it was shown that elastic modulus, yield strength, ultimate tensile strength decreased when temperature increased. The effect on fatigue failure of the parameters such as plastic strain amplitude, stress amplitude and plastic strain energy density was also investigated. Coffin-Manson and Morrow models were used to adjust experimental data and predict the fatigue life behavior at different mean strain values during cyclic loading of high temperature components.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.133-138
• /
• 2007

The balance shaft housing in the recent engines tends to have the high cycle fatigue crack caused by increased engine power. In this paper, a CAE procedure is introduced to predict the durability of the balance shaft housing. The procedure is performed through two analysis steps. In the first step, the multibody dynamic simulation is used to obtain more accurate loading boundary conditions applied to the finite element model for the following step. Next, the finite element analysis is performed to predict the durability of the balance shaft housing through the calculation of the safety factor. Through this CAE procedure, the revised balance shaft housing was developed to improve the durability. And the durability of the housing was confirmed experimentally.