• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.3
• /
• pp.368-374
• /
• 2008

Multi-axial simulation table(MAST) is widely used in motor companies as the multi-axial excitor for vibration fatigue of target component, which provides the vibrational condition as close as the vehicle test. However, the vibration fatigue performance of target component can be guaranteed with MAST system only in case the input profile covers the required severity of the target component on field test. In this paper, the signal processing for multi-axial vibration fatigue test on vehicle component is presented, from the data acquisition of the target component to the derivation of input profile. To compare the severity of vibration condition between field and proving ground, the energy principle of a equivalent damage is proposed and then, it is determined the optimal combination of special events on proving ground using a sequential searching optimal algorithm. To explain the vibration methodology clearly, seat and door component of vehicle are selected as a example.

• Journal of Biomedical Engineering Research
• /
• v.22 no.6
• /
• pp.543-550
• /
• 2001

In this study, ground reaction force(GRF) and energy consumption of fixed. single-axis and multi-axis Prosthetic ankle assemblies were investigated to show the biomechanical evaluation for trans-tibial amputees. In the experiments. two male and two female trans-tibial amputees were tested with fixed, sin91e-axis and multi-axis Prosthetic ankle assembly. A three-dimensional gait analysis was carried out to derive the ratio of GRF to weight as the percentage of total stance Phase for nine Points Energy consumption of each Prosthetic ankle assembly was measured while subjects walked at 2km/h. 3km/h and the most comfortable walking speed on the treadmill The results showed that multi-axis ankle was superior to the other two ankle assemblies for the characteristic of forwarding and breaking forces. Fixed ankle was relatively superior to the other two ankle assemblies for gait balancing and movement of the center fur mass Compared to the other ankle assembly. sing1e-axis type showed lower energy consumption over 2.3km/h walking speed .

• Tribology and Lubricants
• /
• v.28 no.1
• /
• pp.19-26
• /
• 2012

Rolling contact fatigue of an urban railway wheel was analysed during its rolling. A FEM analysis was performed using a 3D modelling of rail and wheel, considering the slope of the rail and nonlinear isotropic and kinematic hardening behavior of the rail and the wheel. The maximum von-Mises stress and contact pressure between the rail and wheel were 656.9 MPa and 1111.4 MPa, respectively, under axial load of 85 kN with friction coefficient of 0. The fatigue initiation life prediction relationships by strain-lifetime (${\varepsilon}$-N) and Smith-Watson-Topper method were drawn for the wheel steel as follows: $N_i=7.35{\times}10^6{\times}SWT^{-3.56}$ and $N_i=5.41{\times}10^{-9}{\times}(\frac{{\Delta}{\varepsilon}}{2})^{-5.77}$. The fatigue lifetimes of the wheel due to rolling contact were determined to be infinite by ${\varepsilon}$-N and SWT methods.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.2
• /
• pp.231-235
• /
• 2013

The purpose of this paper is to compare with estimation of equivalent fatigue load in time domain and frequency domain and estimate the fatigue life of structure with multi-axial vibration loading. The fatigue analysis with two methods is implemented with various signals like random, sinusoidal signals. Also an equivalent fatigue life estimated by rainflow cycle counting in time domain is compared with results estimated with probability density function of each signal in frequency domain. In case of frequency domain, equivalent fatigue life can estimate through Dirlik's method with probability density function. And the work proposed in this paper compared the fatigue damage accumulated under uni-axial loading to that induced by multi-axial loading. The comparison is preformed for a simple cantilever beam, which is exposed to vibrations of several directions. For verification of estimation performance of fatigue life, results are compared to those of FEM analysis (ANSYS).

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.316-321
• /
• 2000

The role of fatigue on the surface damage of 5% chrome cold milling work roll is evaluated. Uniaxial and torsional fatigue tests are carried out, and the baseline data for fatigue life evaluation are established. An appropriate multiaxial fatigue parameter is developed from the fatigue data. Fatigue tests are also performed under compressive mean stresses, and a mean stress model is formulated. A computer program is developed to assess the interaction of fatigue and grinding of the roll. The fatigue damage is computed for selected servicing conditions. It is found that the fatigue damage can be an important issue when the effect of mean stress is ignored, however the fatigue damage is negligibly small when the effect of mean stress including the residual stresses currently used is fully accounted. The result indicates that spalling due to the growth of thermal shock cracks is more important than fatigue damage in roll surface failure.

• Journal of the Korean Society of Safety
• /
• v.27 no.2
• /
• pp.1-6
• /
• 2012

Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7 MPa and 626 MPa, respectively. The uniaxial fatigue limit was 422.5 MPa, corresponding 67% of the ultimate tensile strength. The ratio of ${\tau}_e/{\sigma}_e$ was 0.63. Fatigue strength coefficient and exponent were 1319.5 MPa and 0.339, respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal fatigue condition.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.621-629
• /
• 2011

Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7 MPa and 626 MPa, respectively. The uniaxial fatigue limit was 422.5 MPa, corresponding 67% of the ultimate tensile strength. The ratio of ${\tau}_e/{\sigma}_e$ was 0.63. Fatigue strength coefficient and exponent were 1319.5 MPa and 0.339, respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal fatigue condition.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1999.04a
• /
• pp.321-326
• /
• 1999

In this study, fatigue crack propagation problem of plate under multi-axial loading is mainly considered To analyze this special problem, recently developed technique called EFGM(Element-Free Galerkin Method), one of the Meshfree Methods, and general fatigue crack growth raw herein Paris law are used Using the Implemented scheme, paths of fatigue cracks by constant-amplitude load fluctuation and multiple-crack growth behavior are examined. The failure mechanism of steel plate due to crack propagation is studied. As a result, an algorithm that treats multiple fatigue crack problems is proposed. A numerical example shows that the prediction of growing paths can be achieved successfully and efficiently by proposed algorithm.

• Proceedings of the KSR Conference
• /
• 1999.05a
• /
• pp.344-351
• /
• 1999

Stress analysis of bogie frame by using the finite element method has been performed for the various loading conditions according to the UIC (International Union of Railways) Code 615-4. Multiaxial fatigue damage models such as signed von Mises method and typical critical plane theories were reviewed, and multiaxial fatigue analysis program (MUFAP) has been developed. Fatigue analysis of bogie frame under multiaxial loading was performed by using MUFAP and finite element analysis results. The procedure developed in this study is considered to be useful for the life prediction in preliminary design stage of railway components under multiaxial loading conditions. 3-dimensional surface modeling, mesh generation and finite element analysis were performed by Pro-Engineer, MSC/PATRAN and MSC/NASTRAN, respectively, which were installed in engineering workstation.

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1125-1131
• /
• 2009

This paper presents the evaluation of fatigue life for a journal box attached to rolling stock bogie under random dynamic loading condition. Because a journal box was under random dynamic loading conditions, the fatigue life assessment due to these loads requires the analysis considering the multiaxial effect of random dynamic loading. To do this work, the finite element analysis has been conducted to calculate random dynamic response using multiaxial acceleration data. Then, the fatigue life assessment of component has been conducted using vibration fatigue analysis applying the power spectral densities of the responses obtained through the FEA The results of fatigue life assessment were compared to the damage from the strain measurement. This study shows that can be evaluated the fatigue life assessment considering real service condition about a component attached to rolling stock bogie.