• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.32-38
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• 2018

In this study, the one-piece propeller shaft composed of carbon/epoxy was designed and manufactured for 4 wheel drive automobiles that can bear the target torsional torque performance of 3.5kN.m. For the CFRP tube, braiding machine was used to weaving carbon fiber and it was formed the braided yarns with the braid angle ${\pm}45^{\circ}$ and axial yarns to improve strength of the lengthwise direction. The final CFRP tube of propeller shaft was evaluated through the torsional torque test. The CFRP propeller shaft satisfied requirement of the target torsional maximum torque of 3.5kN.m. Also, it was found that the one-piece composite propeller shaft with CFRP tube had 30% weight saving effect compared with a two-piece steel propeller shaft.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.38-49
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• 1994

In this study, grindability of some representative engineering ceramics are experimentally investigated using resin bond diamond wheel with conventional surface grinding machine, and proper grinding conditions which can be obtained from various experimental results are established also for mechanical components which are proper to domestic circumstances with high reliability. And through the results of experiment, it is confirmed that grinding energies of the ceramics, especially in the case of $Al_2O_3$, are lower than steel with same machining condition in the conventional grinding because of their fine-brittle fracture mode type removal process, though the ceramics are well-known to unmachinable materials. And moreover, the total pass numbers needed for spark-out process to be completed are depend on their mechanical properties because that grinding stiffness is different from each other. The grinding force, ginding power and ground surface roughness are also measured and compared. Furthermore, the experiments carried out in this study, some useful results are obtained with can guide to grind engineering ceramics with conventional surface grinding machine.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.309-314
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• 2021

Due to the superior corrosion resistance and mechanical properties of TiAl alloy at high temperature, it has been utilized as a turbine wheel of a turbocharger. The dissimilar metallic bonding is usually applied to combine the TiAl turbine wheel with the SCM440 structural steel which is used as a driving shaft. In this study, the TiAl and SCM440 joint were fabricated by using a friction welding technique. During bonding process, to suppress the martensitic transformation and the formation of cracks, which might reduce a strength of the joints, Cu was used as an insert metal to relieve stress. As a result, the intermetallic compounds (IMCs) layer was observed at TiAl/Cu interface while no IMC formation was formed at SCM440/Cu interface. Since understanding of the IMCs effects on the mechanical performance of welded joint is also essential for ensuring the reliability and integrity of the turbocharger system, we estimated the nanohardness of welded joint region through nanoindentation. The relation between the microstructural feature and its mechanical property is discussed in detail.

• Steel and Composite Structures
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• v.47 no.1
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• pp.91-102
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• 2023

To study the evaluation standard and control limit of mortar filling layer void length, in this paper, the train sub-model was developed by MATLAB and the track-bridge sub-model considering the mortar filling layer void was established by ANSYS. The two sub-models were assembled into a train-track-bridge coupling dynamic model through the wheel-rail contact relationship, and the validity was corroborated by the coupling dynamic model with the literature model. Considering the randomness of fastening stiffness, mortar elastic modulus, length of mortar filling layer void, and pier settlement, the test points were designed by the Box-Behnken method based on Design-Expert software. The coupled dynamic model was calculated, and the support vector regression (SVR) nonlinear mapping model of the wheel-rail system was established. The learning, prediction, and verification were carried out. Finally, the reliable probability of the amplification coefficient distribution of the response index of the train and structure in different ranges was obtained based on the SVR nonlinear mapping model and Latin hypercube sampling method. The limit of the length of the mortar filling layer void was, thus, obtained. The results show that the SVR nonlinear mapping model developed in this paper has a high fitting accuracy of 0.993, and the computational efficiency is significantly improved by 99.86%. It can be used to calculate the dynamic response of the wheel-rail system. The length of the mortar filling layer void significantly affects the wheel-rail vertical force, wheel weight load reduction ratio, rail vertical displacement, and track plate vertical displacement. The dynamic response of the track structure has a more significant effect on the limit value of the length of the mortar filling layer void than the dynamic response of the vehicle, and the rail vertical displacement is the most obvious. At 250 km/h - 350 km/h train running speed, the limit values of grade I, II, and III of the lengths of the mortar filling layer void are 3.932 m, 4.337 m, and 4.766 m, respectively. The results can provide some reference for the long-term service performance reliability of the ballastless track-bridge system of HRS.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.131-138
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• 2005

The AASHTO wheel load distribution factor (LDF) equation has been with us since 1931 and has undergone minor modifications. In 1994, an entirely new procedure was introduced in the AASHTO LRFD code based on parametric studies and finite element analyses. However, this LDF equation involves a longitudinal stiffness parameter, the design of which is not initially known. Thus, an iterative procedure is required to correctly determine the LDF value. The increased level of complexity puts undue burden on the designer resulting in a higher likelihood for misinterpretation and error. In this study, based on current AASHTO LRFD framework, a new simplified equation is developed that does not require an iterative procedure. A total of 43 representative composite steel girder bridges are selected and analyzed using a finite element model.The new simplified equation produces LDF values that are always conservative when compared to those obtained from the finite element analyses and are generally greater than the LDF obtained using AASHTO LRFD specification. Therefore, the proposed simplified equation is expected to streamline the determination of LDF for bridge design without sacrificing safety.

• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1252-1262
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• 1999

The effect of microstructures on the strength-flangeability of Nb bearing hot-rolled high strength steel was investigated in order to improve the strength-flangeability of conventional TS 580MPa grades HSLA steel for the automotive wheel disc. The low temperature coiling method using 3-step controlled cooling pattern after hot rolling was effective to produce the Nb-bearing high strength steel with the polygonal ferrite and bainite duplex microstructures. It was suggested that the suppressed precipitation of grain boundary cementites and the decreased hardness difference between ferrite matrix and bainite cause the excellent stretch-flangeability of ferrite-bainite duplex microstructure steel. Therefore, the formation and propagation of microcracks were suppressed relative to the conventional HSLA steel with ferrite and pearlite microstructure. In addition, the elongation was improved as compared with that of hot-rolled steel sheets using conventional early cooling pattern because the volume fraction of polygonal ferrite was increased.

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.17-28
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• 2000

The current specifications for bridge decks requires the same amount of upper and lower reinforcement mats. There have been many empirical activities that the partial elimination of upper reinforcing bars was not caused the structural integrity of a deck. A simplified method is derived based on thin plate theory for three and four-girder-span bridge decks. A simplified method for bridge deck considering the effect of girder deflection is proposed based on a closed-form solution that shows good agreement with the results of finite element models. In this research, a new design approach for deck slabs is proposed based on the simplified method. The negative bending moments in a deck can be evaluated with the simplified method based on the position of a wheel load, the aspect ratio and relative stiffness and the span length. This new approach can lead to a significant reduction of the quantity of the top reinforcing steel bars in a deck. Reducing the quantify of the top reinforcement not only reduces the construction costs for bridge decks, but also reduces the corrosion of reinforcement to a minimum.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.204-209
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• 2003

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important for dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations. Therefore, by modifying the constitutive equation fur a nonlinear viscoelastic incompressible material developed by Lianis, the data fur the elastomeric bushing material was obtained and this data was used to derive the new load-displacement relation for radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed, Solutions were allowed fur comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.727-736
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• 2000

The present study investigates the influences of vehicle induced loads on the thermal buckling behavior of straight and curved continuous welded rail (CWR) tracks. Quasi-static loads model is assumed to determine the uplift region, which occurs due to the vertical track deflection induced by wheel loads of vehicle. The lateral loads of vehicle induced by weight, the speed, the superelevation and curvature of track, and other dynamic vehicle track interaction, are included in the ratio of lateral to vertical vehicle load. Parametric numerical analyses are perfomed to calculate the upper and lower critical buckling temperatures of CWR tracks, and the comparison between the results of this work and the previous results without vehicle is also included.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.415-419
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• 2003

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important for dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations. Therefore, by modifying the constitutive equation for a nonlinear viscoelastic incompressible material developed by Lianis, the data for the elastomeric bushing material was obtained and this data was used to derive the new load-displacement for radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed. Solutions were allowed for comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.