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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Automotive Engineers
Journal Basic Information
Journal DOI :
The Korean Society of Automotive Engineers
Editor in Chief :
Volume & Issues
Volume 16, Issue 6 - Nov 2008
Volume 16, Issue 5 - Sep 2008
Volume 16, Issue 4 - Jul 2008
Volume 16, Issue 3 - May 2008
Volume 16, Issue 2 - Mar 2008
Volume 16, Issue 1 - Feb 2008
Selecting the target year
Method of Decreasing the Deviation of Corrected Engine Torque using Knock Correction Rate in Gasoline Engine Performance Test on Dynamometer
Cho, Yoon-Ho ; Kim, Woo-Tai ; Bae, Choong-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 1~7
Recent trends of development in small size gasoline engines are both to have higher compression ratio for the purpose of improved fuel consumption and to advance spark timing up to DBL in a low to mid engine speed region for a good acceleration performance of vehicles. However, there occurs the deviation of corrected engine torque results during engine performance test on dynamometer because test conditions influence the onset of knock. Therefore, this research shows the test deviation of corrected engine torque decreases when knock correction rate is used.
Headform Impact Test for Pedestrian Safety using Domestic Vehicles
Yong, Boo-Joong ; Kim, Si-Woo ; Yoon, Kyong-Han ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 8~13
Since hundreds thousands of pedestrians are killed or injured in car accidents every year, a variety of research efforts have been performed to protect pedestrians in pedestrian-vehicle crashes. The IHRA reports that injuries on the child head, the adult head, and the adult lower leg/knee are the most critical in the crashes. Identifying the current status of international activities on pedestrian protection, this study, in particular, carries out headform impact test using selected domestic vehicles categorized by three groups - Sedan, SUV (Sport Utility Vehicle), and 1 Box (One Box) Vehicle. According to the valuable findings from the test results, this paper proposes a methodology under which the Korean Technical Regulation for protecting pedestrians in pedestrian-vehicle crashes will be developed.
Finite Element-Based Fatigue Assessment of Engine Connecting-Rod Bolts
Cho, Sung-San ; Chang, Hoon ; Lee, Kyung-Woo ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 14~20
Fatigue fracture of engine connecting-rod bolts is encountered frequently during the developement of high-speed engines. Only the engine dyno test is a currently reliable fatigue durability assessment method. It is because the available rig tests cannot mimic the engine running condition completely, and because the finite element analysis cannot provide realistic stresses near the bolt thread that is modeled as a cylinder. This paper introduces a methodology to assess the fatigue durability of the connecting-rod bolts using the finite element analysis. The methods to contruct the bolt model, to extract the critical bolt stresses for the fatigue analysis, and to obtain the bolt fatigue endurance limit experimentally are discussed. Reliability of the method is verified indirectly.
Weight of Modularization using the Exchangeability of Product
Mok, Hak-Soo ; Jeon, Chang-Su ; Han, Chang-Hyo ; Song, Min-Jun ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 21~28
The exchangeability of subassembly has a good relationship with the modularization of product. This relationship can be found by the analysis of the characteristics of a product. The weight for decision factors for the modularization can be determined by the exchangeability of a product or subassembly. The functions, structure, materials of subassembly are used as the decision parameters of exchangeability. Using these selected parameters, the modularization of a product, the characteristics of product structure, and the product function are analyzed. And then, the weighting factors could be calculated quantitatively using this relationship and the parameters of the exchangeability. The calculated weight can contribute to help a designer design for recycling (DFR), design for energy (DFE) and Eco-design.
Vehicle Stability Analysis using a Non-linear Simplified Model
Ko, Young-Eun ; Song, Chul-Ki ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 29~37
Vehicle stability is a very important subject in vehicle design and control, because vehicle safety is closely dependent upon its dynamic stability. For the vehicle stability analysis, the nonlinear vehicle model of a mid-size car with three DOF - longitudinal, lateral and yaw - is employed. A rigorous method is used to determine the vehicle stability region in plane motion. An algorithm is used to materialize a topology theorem, which enables to find the exact stability region. A stability criterion for the critical cornering is proposed.
An Experiment Study on the Combustion Characteristics with BD20 according to Ultrasonic Energy Irradiation Duration and Injection Delay in a Diesel Engine
Im, Seok-Yeon ; Lee, Ho-Gil ; Ryu, Jeong-In ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 38~46
An object of this study is to understand the correlation between the characteristics of an engine performance and combustion characteristics, applying BD20 fuel reformed by ultrasonic energy irradiation to diesel engines. Before conducting the main experiment, an experiment was performed to determine the optimum injection timimg of reformed BD20 by ultrasonic energy irradiation. To control the duration of the ultrasonic energy irradiation, the capacity of an ultrasonic energy fuel supply system was tested with 550cc and 1100cc chambers. As the result of the analysis of the regular BD20 and reformed BD20 by ultrasonic energy irradiation, the BSFC and the Power of the reformed BD20 was improved 3% and 6%, respectively compared to those of non-irradiated BD20. When the fuel injection timing was delayed by
, the engine power was improved by 3%, and the BSFC was improved by 2%. The maximum cylinder pressure of reformed BD20 was improved by a maximum of 6% in comparison to that of regular BD20, and demonstrated a synergistic effect of 3% by delaying the injection timing
A Study on the Characteristics of the Oil-free Turbocharger for Diesel Engine Vehicles
Park, Dong-Jin ; Kim, Chang-Ho ; Lee, Yong-Bok ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 47~55
Turbocharger has a main purpose on recycling of the exhaust gas from the engine cylinder. On the basis of the facility characteristics, the turbocharger supported on floating ring bearings has some problems such as the large volume, oil supplement for lubrication and high power loss due to high operating torque. The air foil bearing has been studied as the bearing element to be able to alternate the floating ring bearing without the problems of the floating ring bearing. In this study, the air foil bearing has 2 parts; journal and thrust bearings, and the test facility consists of the engine, exhaust and intake parts. In addiction, the specification of the turbocharger follows a small turbocharger for SUV engine. The engine speed is varied from 750 (idle rpm) to 2,500 rpm and then, the rotating speed of the turbocharger rotor is accelerated from 0 to 100,000 rpm. From those experiments, the comparison between the performances of the air foil bearing and floating ring bearing is conducted and the results show that the air foil bearing has less power loss, maximum 770 watt, than the floating ring bearing, maximum 5,110 watt. This result verifies that the air foil bearing is more efficient and able to output more power under the same condition of the input power.
An Experimental Study on Variations of Exhaust Gas Temperature and Concentration with Synthetic Gas Combustion in Exhaust Manifold
Cho, Yong-Seok ; Lee, Seang-Wock ; Yang, Seung-Il ; Song, Chun-Sub ; Park, Young-Joon ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 56~62
A synthetic gas reformed from hydrocarbon-based fuels consists of
, CO and
. Hydrogen contained in the synthetic gas is a very useful species in chemical processes, due to its wide flammability range and fast burning speed. The ESGI (Exhaust Synthetic Gas Injection) technology is developed to shorten the light-off time of three way catalysts through combustion of the synthetic gas in the exhaust manifold during the cold start period of SI engines. Before the ESGI technology is applied to the test engine, the authors set a test rig that consists of gas temperature and composition controllers, an exhaust pulse generator and an exhaust manifold with a visualization window, in order to optimize the point and conditions of injection of the synthetic gas. Through measuring burned gas temperatures and taking photographs of synthetic gas combustion at the outlet of the exhaust manifold, the authors tried to find the optimal injection point and conditions. Analysis of burned gas composition has been performed for various
concentrations. As a result, when the synthetic gas is injected at the port outlet of the cylinder No. 4 and
concentration exceeds 4%, combustion of the synthetic gas is strong and effective in the exhaust manifold.
Fatigue Design of Bevel Gear for Automobile by Shot Peening
Lee, Dong-Sun ; Cheong, Seong-Kyun ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 63~68
The fatigue characteristics of bevel gear used for differential gear of automobile was investigated in this paper. From the A-N(Almen intensity-Number of fracture)curve of bevel gear it was shown that there was a specific time that have a maximum fatigue life. Optimal peening condition was 65m/s of project velocity and 8min of project time. Fatigue life was also investigated from the S-N curve between optimal peened specimen and unpeened specimen. Another very significant point is that the crack initiation of bevel gear by shot peening was generated in the subsurface from fractography. This paper shows that shot peening process tremendously improve fatigue characteristics of bevel gear.
Thermal-Structural Coupled Field Analysis of the Circumferential Pressing Type Brake Disc
Kim, Hyeong-Hoon ; Lee, Seong-Wook ; Han, Dong-Seop ; Han, Geun-Jo ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 69~74
The heat generated by the brake system of vehicles results in reduction of friction force on the brake surface and vibration during a braking. To solve these problems, extensive research for the brake shape has been conducted such as drilling cooling holes on the brake disc, accommodating ventilated holes and etc. In this study, we suggest the circumferential pressing type brake disc in order to improve its cooling performance. In order to compare the cooling-down efficiency between the conventional side-pressing type and the circumferential-pressing type, we adopted the FMVSS 105-77 as thermal analysis conditions and This newly proposed concept has been verified using Thermal-structure Coupled Field Analysis along with comparative analysis with the existing ventilated disk.
The Characteristics on the Engine Performance, Smoke and NOx Emission for Variation of Fuel Injection Timing in an IDI Diesel Engine Using Biodiesel Fuel
Choi, Seung-Hun ; Oh, Young-Taig ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 75~80
Biodiesel fuel(BDF) can be effectively used as an alternative fuel in diesel engine. However, BDF may affect the performance and exhaust emissions in diesel engine because it has different physical and chemical properties from diesel fuel such as viscosity, compressibility and so on. To investigate the effect of injection timing on the characteristics of performance and exhaust emissions with BDF in IDI diesel engine, it was applied the BDF derived from soybean oil in this study. The engine was operated at seven different injection timings from TDC to BTDC
and six loads at a single engine speed of 1500rpm. When the fuel injection timing was retarded, better results were showed, which may confirm the advantages of BDF. The simultaneous reduction of smoke and NOx was achieved at some fixed fuel injection timings of an IDI diesel engine.
The Energy Absorption Control Characteristics of Al Thin-walled Tubes for Crashworthiness Enhancement
Yang, Yong-Jun ; Kim, Sun-Kyu ; Yang, In-Young ; Sim, Jae-Ki ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 81~87
In this study, concerns the crashworthiness of the widely used vehicle structure, square thin-walled tubes, which are excellent on the point of the energy absorbing capacity. An experimental investigation was carried out to study the energy absorption characteristics of thin-walled square tubes subjected to dynamic crushing by axial loading to develop the optimum structural members. The impact velocity was tested in the rage
. To efficiently review the collapse characteristics of these sections, the simulation have been carried out using explicit FEM package, LS-DYNA. The solutions compared with results the impact collapse experiment. Here, the controller are introduced to improve and control the absorbed energy of thin-walled square tubes in this paper. To predict and control the energy absorption, we designed it in consideration to the it's influence, height, thickness, wide ratio in this study. When the controller used, the experimental results of crushing of square tubes controlled by the controller's elements showed a good candidate for a controllable energy absorption capability in impact axial crushing.
Effects of an Inlet Guide Vane on the Flowrate Distribution Characteristics of the Nozzle Exit in a Defrost Duct System
Kim, Duck-Jin ; Lee, Jee-Keun ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 88~96
Effects of the duct inlet guide vane on the flowrate distribution characteristics of the defroster nozzle exit in a defrost duct system were investigated experimentally to design the optimum heating, ventilation and air conditioning (HVAC) system applied in an automotive compartment. A 3-dimensional hot-wire anemometer system was used to measure the velocity field in the vicinity of the defroster nozzle jet flow and the velocity distributions near the windshield interior surface. At first, two cases of with- and without-duct inlet guide vanes were considered as the test condition, and then three cases of the duct inlet guide vane were tested to determine the optimum guide vane shape and their positions. The arrangement of the duct inlet guide vanes has an effect on the improved flowrate distribution at the defroster nozzle exit and near the windshield interior surface. However, the application of the lots of guide vane to control the flow direction leads to increase the flow resistance, resulting in the decreased flowrate issuing from the defroster nozzle. The shape of the duct inlet guide vane affects not only the flowrate distribution between the driver side and the assistant driver side but also the reduction of the flow resistance in the defrost duct system.
A Study on Vibration Characteristics of Engine Mount System of a Medium Duty Truck at the Key On/Off
Kuk, Jong-Young ; Lim, Jung-Hwan ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 97~102
The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system have direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key on/off of a medium truck by experiment and simulation. The analysis model consists of the engine, a body including the frame, front and rear suspensions and tires. The force element between the body and the suspension is modeled as a combination of a suspension spring and a damper. The engine shake obtained from the experiment was compared with the result of the computer simulation, and by using the verified computer model, parametric study of the body shake on engine key on/off is performed with changing the stiffness of an engine mount rubber, the engine mount angle, and the position of engine mounts.
Analysis on the Shift Characteristics of Semi-Spherical CVT using 2-dimensional Friction Model
Kong, Jin-Hyung ; Lim, Won-Sik ; Park, Yeon-Gil ; Kim, Jung-Yun ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 103~109
Semi-spherical CVT(SS-CVT) is one of friction drives, which transmits power via the friction force between a spherical shaped variator and output disks. The variator varies the speed ratio of SS-CVT continuously as well as transmits input power into the output shaft. Therefore two friction forces are normally applied on the variator; one is the longitudinal friction force for power transmission and the other is the lateral for shifting. In order to investigate the dynamic behavior of SS-CVT, we introduced a numerical model of 2-dimensional friction force using a function of slip ratio and slip angle. And a dynamic model, which describes the shifting mechanism of SS-CVT, is developed through 3-dimensional vector analysis. Finally we presented numerical results of the shift characteristics focused on the transient behavior of the variator's slip ratio and slip angle. The numerical results also show the typical CVT shifting characteristics of SS-CVT and stable shifting behaviors of the variator.
Unified Modeling and Performance Prediction of Diesel
and PM Reduction by DOC-DPF-SCR System
Jung, Seung-Chai ; Yoon, Woong-Sup ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 110~119
Computer methods with simplified mathematical models in conjunction with empirical model parameters can be efficiently practiced into an optimization of a diesel aftertreatment system. Components of prime interests are diesel particulate filter, diesel oxidation catalyst and de-
catalytic converter. de-
, de-PM, and de-HC processes in each part are individually modeled, formulated and then combined into an integrated analysis procedure for a unified simulation of the diesel emission aftertreatment. The model is empirically tuned and validated with comprehensive engine and laboratory data. The effects of emission species and space velocity on the
and soot reductions are parametrically investigated. A lowered
ratio due to PM oxidation in DPF contributes to promote the
reduction by SCR at intermediate gas temperatures.
reduction is inert to the PM oxidation at high temperatures. Rate of PM trapping strongly depends on temperature and
Virtual Fatigue Analysis of a Small-sized Military Truck Considering Actual Driving Modes
Suh, Kwon-Hee ; Lim, Hyeon-Bin ; Song, Bu-Geun ; Ahn, Chang-Soon ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 120~127
A military vehicle undergoes normal to extreme driving conditions, which consequently induce the fatigue and fracture of cabin and frame. So, it is important to estimate the fatigue life of two components at an initial design stage. In this paper, Modal Superposition Method(MSM) was applied to evaluate the durability performance of a small-sized military truck. For reliable durability analysis, a Virtual Test Lab(VTL) Model was established by correlation with experimental results. These data were extracted from actual driving test, modal test, and SPMD(Suspension Parameter Measuring Device) test. This process shows that Virtual Fatigue Analysis can be a useful approach in the development of military vehicles as well as commercial vehicles.
Hydropneumatic Modeling and Analysis of a Heavy Truck Cabin Air Suspension System
Shin, Hang-Woo ; Choi, Gyoo-Jae ; Lee, Kwang-Heon ; Ko, Han-Young ; Cho, Gil-Joon ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 128~134
In this paper, a hydropneumatic modeling and analysis of a heavy truck cabin air suspension system is presented. Cabin air suspension system is a system which improves ride comfort of a heavy truck and it can reduce vibration between truck frame and cabin. The components of the system, air spring, shock absorber, leveling valve and full cabin system are mathematically modelled using AMESim software. Simulation results of components and full cabin system are compared with experimental data of components and test results of a cabin using 6 axis simulation table. It is found that the simulation results are in good agreements with test results, and the hydropneumatic model can be used well to predict dynamic characteric of heavy truck cabin air suspension system.
Characteristic Investigation of Design Parameters on the Hydraulic Power Steering Gear Box
Jang, Joo-Sup ; Yoon, Young-Hwan ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 135~142
Hydraulic power steering system has been adopted in seniority passenger and commercial vehicle system for an easy maneuverability and a smoother ride. In this study, hydraulic power steering system analysis model which includes hydraulics and mechanical sub-systems was developed using commercial software, AMESim in order to predict characteristics for various steering components. Each component which constructs system was modeled and verified by experimentally obtained characteristics curves of each components. The parameter sensitivity analysis such as valve opening area, torsional stiffness of torsion bar for system design are carried out by the analysis and experimental method. The predicted results by the development model were a good agreement with experimentally obtained results. The sensitivity investigation results rotary torque when changing an input shaft edge width, was most sensitive, to change in angle and slot width and supply flow of input shaft edge is not a lot sensitively.
A Study on Application of On/Off Type EGR and Optimal EGR Rate for Gasoline-Hybrid Engine
Park, Cheol-Woong ; Choi, Young ; Kim, Chang-Gi ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 143~150
EGR(exhaust gas recirculation) is an attractive means of improving the fuel economy of spark ignition engines, as it offers the benefits of charge dilution (lower pumping and cooling losses) while allowing stoichiometric fuelling to be retained for applications using the three-way catalysts. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate in Gasoline-Hybrid engine should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel economy, combustion stability, engine performance and exhaust emissions. EGR tolerance with load variation was found to be more sensitive than with rpm variation. With optimal EGR rates, the fuel consumption was improved by 5.5% while a combustion stability was guaranteed.
Start of Combustion Detection Method for Gasoline Homogeneous Charge Compression Ignition Engine
Choe, Doo-Won ; Lee, Min-Kwang ; SunWoo, Myoung-Ho ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 151~158
Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion is a new combustion concept. Unlike the conventional internal combustion engine, the premixed fuel mixture with high residual gas rate is auto-ignited and burned without flame propagation. There are several operating factors which affect HCCI combustion such as start of combustion (SOC), residual gas fraction, engine rpm, etc. Among these factors SOC is a critical factor in the combustion because it affects exhaust gas emissions, engine power, fuel economy and combustion characteristics. Therefore SOC of gasoline HCCI should be controlled precisely, and SOC detection should be preceded SOC control. This paper presents a control oriented SOC detection method using 50 percent normalized difference pressure. Normalized difference pressure is defined as the normalized value of difference pressure and difference pressure is difference between the in-cylinder firing pressure and the motoring pressure. These methods were verified through the HCCI combustion experiments. The SOC detection method using difference pressure provides a fast and precise SOC detection.
Coordinated Control of EGR and VGT in the Diesel Engine
Huh, Jun-Young ; Chung, Jin-Eun ; Jin, Young-Wook ; Kang, Woo ; Chung, Jae-Woo ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 159~164
In diesel engine technology the drive to reduce emissions and fuel consumption with improved performance targets has led to many advances. In particular, Exhaust Gas Recirculation (EGR) and Variable Geometry Turbocharger (VGT) have played a key role in achieving these aims by permitting flexible control of the engine inlet gas charge. The full potential of these devices are difficult to achieve due to limitations in the classical control methods. However, fuzzy logic is particularly appealing due to its simple heuristic nature. The controller used in this work was designed using the Matlab Fuzzy Logic Toolbox. The overall object is to access the potential for emissions and fuel consumption reductions during transient events whilst maintaining and even improving driveability. Classical control methods (PID), as used on production engines, are examined and contrasted with an coordinated control that utilizes fuzzy logic.
A Study on the Injection Characteristics of Urea Solution to Improve deNOx Performance of Urea-SCR Catalyst in a Heavy Duty Diesel Engine
Jeong, Soo-Jin ; Lee, Chun-Hwan ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 165~172
Urea-SCR, the selective catalytic reduction using urea as reducing agent, has been investigated for about 10 years in detail and today is a well established technique for deNOx of stationary diesel engines. In the case of the SCR-catalyst a non-uniform velocity and
profile will cause an inhomogeneous conversion of the reducing agent
, resulting in a local breakthrough of
or increasing NOx emissions. Therefore, this work investigates the effect of flow and
non-uniformities on the deNOx performance and
slip in a Urea-SCR exhaust system. From the results of this study, it is found that flow and
distribution within SCR monolith is strongly related with deNOx performance of SCR catalyst. It is also found that multi-hole injector shows better
uniformity at the face of SCR monolith face than one hole injector.
Real-Time Model-Based Fault Diagnosis System for EHB System
Han, Kwang-Jin ; Huh, Kun-Soo ; Hong, Dae-Gun ; Kim, Joo-Gon ; Kang, Hyung-Jin ; Yoon, Pal-Joo ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 173~178
Electro-hydraulic brake system has many advantages. It provides improved braking performance and stability functions. It also removes complex mechanical parts for freedom of design, improves maintenance requirements and reduces unit weight. However, the EHB system should be dependable and have back-up redundancy in case of a failure. In this paper, the model-based fault diagnosis system is developed to monitor the brake status using the analytical redundancy method. The performance of the model-based fault diagnosis system is verified in real-time simulation. It demonstrates the effectiveness of the proposed system in various faulty cases.
Optimum Design of Welding Pitch Considering Fatigue Life of Spot Welding Nuggets
Lee, Sang-Beom ; Jeon, Sang-Hoon ; Yim, Hong-Jae ;
Transactions of the Korean Society of Automotive Engineers, volume 16, issue 4, 2008, Pages 179~185
The purpose of this paper is to propose a systematic method on the weld pitch design of a vehicle sub-frame considering the fatigue life of spot welding points. The input data, which perform the fatigue analysis on the spot welding nuggets, are obtained by both the dynamic analysis of the multi-body vehicle model passing through the virtual proving ground of a typical Belgian road and the quasi-static analysis with the finite element model of the vehicle sub-frame. By utilizing the life cycle data obtained from the fatigue analysis, the welding points to perform the pitch change are determined. The sensitivity analysis on the fatigue life of the welding points is carried out by using the three-level orthogonal array design, and through the results of the sensitivity analysis, the best combination on the welding pitch is determined. This study shows that as compared with the baseline design, the sub-frame redesigned by the proposed technique improves the fatigue life about 7 percent while reducing the number of welding points about 19 percent.