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Impact resistance of plastic underbody parts was studied using simulated injection-molded specimen which can be tested according to different types of material used, injection molding variants like position and number of injection molding gates, and features of ribs. Material applied was glass fiber reinforced polyamide which can be used in underbody parts. Test was performed using several combinations of injection molding gates and rib types. From the test result, optimal design guide for plastic underbody parts was determined. Also, new high impact resistant plastic material made of glass fiber reinforced polyamide 66 (PA66) and polyamide 6 (PA6) alloy was developed and the material properties useful for CAE were determined. As a case study, oil pan and muffler housing were designed following the optimal design guide and CAE. And the reliability of the sample muffler housing designed was verified.

A semi-empirical index to evaluate the noise propensity of brake friction materials is introduced. The noise propensity index (NPI) is based on the ratio of surface and matrix stiffness of the friction material, fraction of high-pressure contact plateaus on the sliding surface, and standard deviation of the surface stiffness of the friction material that affect the amplitude and frequency of the stick-slip oscillation. The correlation between noise occurrence and NPI was examined using various brake linings for commercial vehicles. The results obtained from reduced-scale noise dynamometer and vehicle tests indicated that NPI is well correlated with noise propensity. The analysis of the stick-slip profiles also indicated that the surface property affects the amplitude of friction oscillation, while the mechanical property of the friction material influences the propagation of friction oscillation after the onset of vibration.

A piston in a diesel engine is subject to the high pressure and the high thermal load. The high structural reliability is required to the piston in the automotive diesel engine and it is important to confirm the design parameters of piston in initial design stage. There are lots of research works proposing new geometries, materials and manufacturing techniques for engine pistons. But, the failures of piston occur frequently in development stage. Failure mechanisms are mainly fatigue related. This paper presents failure mechanisms of the high cycle fatigue and low cycle thermal fatigue cracks which occur on the piston during durability test using engine dynamometer. In this study, FE analysis was carried out to investigate the root cause of piston failure. The analysis includes the FE model of the piston moving system, temperature dependent material properties, mechanical and thermal loadings.

Various polymer-based coatings are applied on piston skirt to reduce friction loss between the piston skirt and cylinder bore which is one of main factors of energy loss in an automotive engine system. These coatings generally consist of polymer binder (PAI) and solid lubricants (graphite or MoS₂) for low friction property. On the other hand, the present study found that PTFE as a solid lubricant and nano diamond as hard particles can be used to improve the low friction and wear resistance simultaneously. In the process of producing coating material, diamond particles pulverized to a nano size tend to agglomerate. To prevent this, silane (silicon coupling agent) treatment was applied. The inorganic functional groups of silane are attached to the nano diamond surface, which keep the diamond particles are apart.

Copper has been regarded as one of the indispensable ingredients in the brake friction materials since it provides high thermal diffusivity at the sliding interface. However, the recent regulations against environmentally hazardous ingredients limit the use of copper in the commercial friction material and much effort has been made for the alternatives. In this work, the role of the cuprous ingredients such as copper fiber, copper powder, cupric oxide (CuO), and copper sulfide (CuS) are studied using the friction materials based on commercial formulations. The investigation was performed using a full inertial brake dynamometer and 1/5 scale dynamometer for brake performance and wear test. Results showed that the cuprous ingredients played a crucial role in maintaining the stable friction film at the friction interface, resulting in improved friction stability and reduced aggressiveness against counter disk.

A new noble material for automotive bumper fascia has been developed by compounding of ethylene-propylene block copolymers with ethylene-α-olefin copolymers and some additives. Also mineral fillers are added, if necessary. This material is suitable for injection molding of large parts including automotive bumper fascia. By using selected rubbers which have proper melt viscosity, molecular weight, and co-monomer content, and adding modified polymer containing polar group, it has enhanced processibility and paintability maintaining general properties such as tensile strength, impact strength at low temperature, and thermal and UV stability. The remarkable characteristics of this material is good processibility compared to the conventional TPOs. This material has especially high melt flow index(20∼30g/10min at 230°C) and stable flow behavior at the processing conditions.

The mechanical energy of an engine is lost by engine friction and in driving the engine's auxiliary components, which is then transferred to transmission. Thus, it is very important to know the exact value of engine friction and the driving torque of engine's auxiliary components in order to reduce fuel consumption of an engine by reducing these losses. And, it is also helpful to know the braking torque of an engine in actual vehicle so as to improve vehicle's driving performance. For these reasons, present study developed an engine torquemeter for in-vehicle application, and measured braking torque of an engine in vehicle and analyzed fuel consumption contributions of engine's auxiliary components.

Suspension system of vehicle is very important because it has an effect on ride comfort and safety. And the leaf spring is one of the major parts of commercial vehicle. By that reason it has to be designed to operate under severe condition to ensure enough endurance. But the traditional method for fatigue design needs repeated fatigue tests for each design according to its geometry, material, and operating condition. This means that a lot of time and money is needed for those tests. Thus, in this paper, a fatigue design method for leaf spring based on numerical analysis is proposed. At first, stress analysis is performed to get the stress under operation load or rig tests. And fatigue analysis is performed to get the fatigue life and to ensure the safety of leaf spring. Through this study, design parameters that play vital role in fatigue life of the leaf spring can be found out.

The use of light-weight materials in automotive engine components has increased in order to achieve better fuel efficiency and engine performance. In this study, Al alloy (AI5056) valve spring retainer can reduce a weight by 63% in comparison to steel and improve the upper limit of engine speed by about 500rpm. The Al valve spring retainer was fabricated by cold forging and coated with hard anodizing, DLC (diamond like coating), cold spray and thermal spray for better wear resistance and durability. We conclude that among these materials the DLC coating improves the wear resistance of Al valve spring retainer and has a sufficient durability after endurance testing.

Depending on the scatter of material properties, geometrical shapes and load conditions, the fatigue life of mechanical components has wide range of scatter although they were tested under same conditions. This scatter is the main reason of different results between observed and predicted fatigue life. This study shows how to estimate the fatigue life distribution by analysis. Dominant factors for fatigue life distributions and their scatter could be obtained by comparing the analysis results and fatigue test results. Applying the scatter of these factors to fatigue analysis, it was possible to predict fatigue life distributions. This will improve the reliability of fatigue life estimation, therefore a more robust and reliable component design is possible.

In this paper, the distortion analysis in spot welded area of car body - front side member, it is found out that the optimum condition for panel assembly is closely related to the welding sequence, location of clamping system, number, shape and welding force. The distortion resulting from welding sequence is minimized starting from the surroundings of the clamping system and in the way that the value of the welding force is from large to small. The MCP is determined from the positions inducing the minimum distortion in panel through calculating the deformation and reacting force of the panel. The welding force originating from the manufacturing tolerance of assembly is a critical design factor determining the welding sequence and the clamping system that yield minimum distortion in spot welding of body panel.

The tube hydroforming technology (THF) has been extensively used as auto-body structural members such as engine cradle, frame rail etc. in order to meet the urgent need of vehicle weight and cost reduction as well as high quality. In this paper we experimentally investigate the mechanical properties for hydroformed tubes with various bulging strains under the plane strain mode. Axial compression tests for hydroformed tubes are performed to investigate the collapse load and collapse absorption capacity through the collapse load-displacement curves. Moreover the collapse absorption capacities are compared and discussed between as-received, hydroformed, and press formed tubes. Results demonstrate that the hydroformed tubes show higher collapse absorption capability in comparison with the as-received tube and the press formed tube, because of its high yield strength due to strain hardening.

Recently, upon customer’s needs for noise-free brake, carmakers are increasingly widely installing damping kits in their braking systems. However, an installation of the damping kits may excessively increase softness in the brake system, by loosening stroke feeling of a brake pedal and increasing compressibility after durability. To find a solution to alleviate this problem, we first conducted experiments to measure compressibility of shims by varying parameters such as adhesive shims (e.g., bonding spec., steel and rubber thickness), piston’s shapes (e.g., different contact areas to the shims), and the numbers of durability. Next, we installed a brake feeling measurement system extended from a brake pedal to caliper. We then compared experimental parameters with brake feeling in a vehicle. Finally, we obtained an optimized level of brake feeling by utilizing the Design for Six Sigma (DFSS).

Creep groan noise occurs in a just moving vehicle by the simultaneous application of torque to the wheel and the gradual release of brake pressure in-vehicle. It is the low frequency noise giving the driver a very uncomfortable feeling. Recently, the field claims regarding the creep groan noise are increasing. So far, creep groan noise has been improved by means of chassis modification the transfer system. But vehicle body the response system does not. In this paper, the effect between vibration characteristics of vehicle body, creep groan noise was analyzed. Then presented analysis method for vehicle body effect regarding creep groan noise.

The market demands for CO2 reduction and fuel economy have led to a variety of new gear set concepts of automatic transmissions with 4 planetary gear sets and 6 shift elements in recent years. Understanding the relationship between the torque of clutch and brake and gear ratio in the design stage is very important to assess new gear set concepts and to set up the control strategy for enhancing shift quality and to reduce the heat generation of clutch and brake. In this paper, a new systematic approach is used to unify the relationship between torque and gear ratio during the gear shift for all multi-step planetary automatic transmissions. This study describes the unified concept model with a lumped inertia regardless of the specific transmission layout and derives the principal unified relationship equations using torque and energy analysis, which prove that the sum of brake torque is always gear ratio -1 in every in-gear.

This paper presents a transient vibration analysis of a nonlinear full-vehicle. The full-vehicle model consists of a powertrain, a trimmed body, a drive line, and front and rear suspensions with tires. It is driven by combustion forces and runs on a road surface. By performing time-domain simulation, it is possible to capture nonlinear behavior of a vehicle such as preload due to gravitational force, large deformation, and material nonlinearity which cannot be properly treated in the conventional steady state analysis. In constructing a full-vehicle, validation process is essential. Validation process is applied with respect to the assembling sequence. The validation starts with component levels such as tires, springs, shock absorbers, and a powertrain, and then the full-vehicle model is constructed. Model validation is done in two aspects; one is model accuracy and the other is model efficiency.

The current sensor for motor control is one of the main components in inverters for eco-friendly vehicles. Recently, as the higher performance of torque control has become required, the current sensor measurement error and accuracy of motor controls have become more significant. Since the response time of the sensor affects the motor output power, the response delay of the sensor causes measurement errors of the current. Accordingly, the voltage vector changes, and a motor output power deviation occurs. In the case of the large response delay of the sensor, as motor speed increases, then difference between motoring and generating output power becomes larger and larger. This results in the deterioration of power performance in high-speed operation. The deviation of the voltage vector magnitude is the main cause of motor output power deviation and imbalance through the simulation.

Professional bus drivers are highly exposed to physical fatigue and work-related injuries because driving task includes complicated actions that require a variety of ability and cause extreme concentration or strain. For this reason, there has always been some sense of concern regarding driver fatigue, especially for drivers of commercial vehicles. In this study, we have tried to analyze quantitative fatigue degree of urban bus drivers by measuring their physiological signals. The investigation is made up of the following approaches: a traditional questionnaire survey and video-ethnographic method with 4-way cameras. The close-circuit cameras are installed to observe the upper and lower body of real drivers when they are in driving or even resting. This approach can help to understand urban bus drivers' behaviors and fatigue-related issues. Based on the video-ethnographic investigation results above, we have got certain patterns of drivers.

In case of cooling module rotated by belt, many sources (vehicle’s vibration, belt’s tension and thrust force by rotated fan) are acting on it. Because it is not easy to analyze them individually, there were no rig test modes for pre-validation while developing a new vehicle. In this study, we correlated the strain gauges signal to belt’s tension and fan’s thrust force, and measured acceleration of a vehicle and cooling module by driving a vehicle on the several test roads. In that case of measured acceleration data, we could analyze it by using PDF and construct the representative rig test modes considering vibrational fatigue characteristics by using the FDS. These modes can be utilized while developing a new vehicle without measuring anymore. Also, we could understand each load’s characteristics. It is confirmed that the factors affecting the fatigue were not only the vehicle’s vibration but also the belt’s installation tension.

In this study, a co-operative regenerative braking control algorithm was developed for an electric vehicle (EV) equipped with an electronic wedge brake (EWB) for its front wheels and an electronic mechanical brake (EMB) for its rear wheels. The co-operative regenerative braking control algorithm was designed considering the road friction characteristic to increase the recuperation energy while avoiding wheel lock. A powertrain model of an EV composed of a motor, and batteries and a MATLAB model of the control algorithm were also developed. They were linked to the CarSim model of the vehicle under study to develop an EV simulator. The EMB and EWB were modeled with an actuator, screw, and wedge to develop an EMB and EWB simulator. A co-simulator for an EV equipped with an EWB for the front wheels and an EMB for the rear wheels was fabricated, composed of the EV and the EMB and EWB simulator.