Papers by Author: Byeong Wook Noh

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Authors: Byeong Wook Noh, Young Woo Choi, Sung In Bae
Abstract: Automobile pedal which is loaded by driver’s input is transmitting load to throttle cable, braking device and clutch device and controlling automobile. Measuring working condition and applying equivalent damage are needed for reliability of developing pedal. The measuring working condition is requiring more investigation with various respects because of widely ranged drivers, road condition and environmental condition. Additionally, when equivalent damage is applied, there are not suitable for test condition if equivalent damage is too high level to apply or unused region. In this study, load history is measured with 95percentile customer. Measured load history is converted to stress history about critical area of pedal by FEM. There are drawn up histogram of pedal cycles and load from stress history with rain flow cycle counting method, calculated relative damage of extended stress history with Palmgren-Miner rule. From the results, calculated total relative damage is applied to calculation method of test time and load. Calculation method for test condition is carried out with three methods which are enforcing with total stress by rain flow cycle counting, representative load and blocked load. Accelerated durability test condition of pedal using with relative damage and acceleration factors are proposed.
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Authors: Byeong Wook Noh, Sung In Bae, Kyung Chun Ham
Abstract: A fatigue analysis program to calculate fatigue lives of mechanical components and structures from FE(Finite Element) results is developed. The useful characteristic of this program is operated under Web environment. So, any designer who design fatigue strength of components and structures can use without other program installation. For the assessment of multi-axial fatigue damage, signed equivalent stress method and critical plane approach have been employed. Each method is compared and the results of Signed von Mises stress method has similar to the results of Smith-Waston-Topper's parameter using critical plane approach. The results were compared with those from commercial program FE-Fatigue6.0 and it was observed that fatigue life and cumulative damage distribution calculated applying same fatigue resistance curve. The results of calculated fatigue life using Web based program agree well with those from FE-Fatigue6.0.
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Authors: Byung Il Kim, Byeong Wook Noh, Young Woo Choi, Sung In Bae, Jung I. Song
Abstract: Impact behaviors of Aluminum Honeycombs Sandwich Panel (AHSP) by drop weight test were investigated in this study. Two types of specimens with l/2" and l/4" cell size were tested by two impactors with the weight of 5.25kgf and 11.9kgf respectively. Transient, contact and elastic-plastic analyses were performed by finite element method. Impact behavior of AHSP about impact sites appeared nearly the same in low impact energy, but it was different in high impact energy. Face was the strongest about impact and short-edge was the weakest. The damaged area of AHSP was enlarged with the increase of impactor weight that is corresponding to impact energy. After 3-point bending test, fracture modes of AHSP were analyzed with AE counts, lower face sheet was fractured in the long-edge direction first, and then separation between face sheet and core happened. In the short-edge direction after core wrinkled, lower face sheet was torn, impact behavior by FE analysis were increased localized damage in high velocity because the faster velocity of the impact was, the smaller the stress of core was. Consequently, impactor weight had an effect on widely damaged area, while the impact velocity gave rise to localized damaged area.
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Authors: Byeong Wook Noh, Young Woo Choi, Jung I. Song, Sung In Bae
Abstract: The Combine is necessary equipment in the agricultural industry. The components of the Combine are worked for a long time under inferior environmental condition. Especially reaping knife is worked in high frequency domain, and submit fatigue load while use. So, fatigue test was performed to obtain the S-N curve of real component, and load history is measured through field test. The local stresses due to these loads have been calculated by FEM. These results have been used as the input values for the multi-axial fatigue analysis of real components. For the assessment of multi-axial fatigue damage, the critical plane methods have been employed. The used parameters of critical plane methods are Morrow’s, Smith-Waston-Topper’s, and Brown-Miller’s, those were modified for the high cycle fatigue region within elastic behavior. In addition, design improvement is performed about shape of reaping knife to increase the endurance limit, and durability test for improved knife is performed. It is found that the fatigue life of improved reaping knife is increased, and durability test result show that life of reaping knife is increased enough.
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Authors: Young Woo Choi, Byeong Wook Noh, Kyung Chun Ham, Sung In Bae
Abstract: In this study, the fatigue life evaluation of automatic transfer devices under stress concentrations due to the notch effect is performed. To investigate residual life of a notched component, load histories were obtained through strain measurement. A fatigue test was performed on a specimen imitating a real component and results were compared with each notch root radius of the concentration area. Three-dimensional finite element analysis was also performed to evaluate the local stress fields. Miner’s rule was used to predict the fatigue life calculation. As a result, the predicted life of a notched component was in good agreement with a real component and introduced a special method for measuring load using real machine components.
1269
Authors: Young Woo Choi, Byeong Wook Noh, Jung I. Song, Sung In Bae
Abstract: The fatigue life of hexagon head and socket head bolts, attached to vehicle a wheel, is assessed and the estimation of the residual life of existing bolts in vehicle wheel is investigated. Fieldmeasured load histories were applied in this test. Tensile tests and fatigue tests were performed to evaluate the effect of tightening torque and to obtain the basic experimental data. Miner’s rule was used to predict the fatigue life of bolts. The results indicate the prediction of fatigue life of the bolts was in good agreement with the real life of vehicle wheel bolts in this test.
819
Authors: Young Woo Choi, Byeong Wook Noh, Kyung Chun Ham, Sung In Bae
Abstract: The fatigue life of hexagon head and socket head bolts, attached to vehicle a wheel, is assessed and the estimation of the residual life of existing bolts in vehicle wheel is investigated. Field- measured load histories were applied in this test. Tensile tests and fatigue tests were performed to evaluate the effect of tightening torque and to obtain the basic experimental data. A three-dimensional finite element analysis was also performed to evaluate the local stress fields. Miner’s rule was used to predict the fatigue life of bolts. The results indicate the prediction of fatigue life of the bolts was in good agreement with the real life of vehicle wheel bolts in this test.
1770
Authors: Byeong Wook Noh, Jung I. Song, Sung In Bae
Abstract: In this study, fatigue strength of load-carrying cruciform fillet welded joints were evaluated using a new method proposed by Yamada, for geometric or structural stress in welded joint, that is, one-millimeter stress below the surface in the direction corresponding to the expected crack path. Validity of the method is verified by analyzing fatigue test results for load-carrying cruciform welded specimens has different size of weld toe radius, leg length and plate thickness reported in literature. Structural stress concentration factor for 1mm below the surface was calculated by finite element analysis for each specimen respectively. When compared to the basic fatigue resistance curve offered by BS7608, the one-millimeter stress method shows conservative evaluation for load-carrying cruciform fillet welded joints.
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