Durability improvement of automotive V-belt pulley

Improving the durability of an automotive V-belt pulley, which is commonly used in an automotive powertrain to transfer power to other parts, is discussed. Fatigue life of the original V-belt pulley is predicted based on damage analysis by finite element analysis (FEA). Stress history of the pulley during operation was found by performing consecutive static analyses on the pulley as the pulley rotates. Assembly load (due to the tightening of the bolts) and operation load were considered to describe the actual load conditions in a durability test. The contact condition from the belt was calculated and applied to the surface of the pulley. Static analyses at 36 different positions of the pulley, every ten degrees of rotation, were performed to determine the stress history of the pulley during operation. Using stress history data calculated from FE analysis, damage over one rotation of the pulley was calculated and fatigue life, in number of rotations to failure, was estimated. An improvement to the durability of the pulley was investigated by modifying the design of the pulley using FE analysis results. Durability tests for the pulleys used in the analysis were carried out to verify the analytical results. Comparison between analysis and experimental results showed that analytical results correlated with the experimental results closely.     

Development of the FMECA process and analysis methodology for railroad systems

FMECA (Failure Modes, Effects and Criticality Analysis) is a procedure used to identify potential failure modes, determine causes and effects of failure modes and mitigate or remove its effects on system functional performance. For the last several decades, FMECA has been widely used in industry, and specialized versions of FMEA have been developed for several industrial sectors. For instance, MIL-1629a, SAE-J1739 and IEC-60812 have been mainly used in the military, automotive and electronics industries, respectively. However, there is no specialized FMECA method for the railroad industry yet, despite a need for highly reliable systems. Thus, in this study three specifications, MIL-1629a, SAE-J1739 and IEC-60812, were analyzed and compared with one another, and characteristics and requirements of railroad systems were summarized. Then a specialized FMECA procedure for railroad systems was proposed based on the processes documented in the specifications, characteristics and requirements of railroad systems. Finally, the procedure was applied to a railroad system in order to validate its applicability.     

Partial range scaling method based washout algorithm for a vehicle driving simulator and its evaluation

Unlike an actual vehicle, a vehicle driving simulator (VDS) has limited kinematics, workspace, and bounded dynamic characteristics making it very difficult to simulate dynamic motions of an actual vehicle. To solve these problems, a washout algorithm was developed. The developed algorithm restricts the workspace of the VDS to within the kinematic limit and makes the person driving the VDS perceive movement of an actual vehicle. However, the classic washout algorithm contains several problems, such as time delay and the generation of a wrong motion signal caused by characteristics of the filters. So the driver feels “simulator sickness,” such as fatigue, nausea, headache and so on because of differences between the sense of movement of the VDS and that of a real vehicle. In this paper, a partial range scaling method based washout algorithm, including a tilt coordination system, is developed to enhance the perception of motion and reduce simulator sickness. It is verified by a simulation, a survey, and a bio signal analysis using an electrocardiogram (ECG).     

Experimental study of the characteristics of idle vibrations that result from axial forces and the spider positions of constant velocity joints

The vibrational characteristics of automotives during idling were studied experimentally by considering the axial forces of the drive shaft and the spider positions in a constant-velocity joint. The generated forces, such as PF (plunging force) and GAF (generated axial force) in the assembly of the drive-shaft module, were measured directly by an experimental apparatus. Measurements of the GAF and PF did not show the same trends as the joint angles. They depended instead on the types of CV joints. In addition, the relationship between the offset values of the shaft and the spider positions in the tulip of the constant-velocity joint were studied. As a result, the idle vibration characteristics were affected by the variation of the spider positions and the vibrational characteristics in the axial direction of the shaft, including the amplitude and the harmonic periods.     

Simple design approach for improving characteristics of interior permanent magnet synchronous motors for electric air-conditioner systems in HEV

In this paper, a simple design method for improving the performance of an interior permanent magnet synchronous motor (IPMSM), for driving the air-conditioning compressor used in hybrid electric vehicles, is presented. There are many design methods that optimize the IPMSM. Each method deals with a variety of design factors, such as slot opening, pole arc, and rotor shape. However, as the number of design variables increases, a lot of modeling and analysis time is needed in order to improve the characteristics of an IPMSM. This paper demonstrates that the optimization of a double-layer IPMSM, satisfying the given design conditions, is possible with only a flux barrier shape design. Then, response surface methodology is applied as the optimization method, and the validity of the design approach is verified by comparison with test results.     

Multimodal route choice in maritime transportation: the case of Korean auto-parts exporters

Global offshoring has increased the need for transport of half-finished goods and components, along with finished goods. The auto-parts industry in Korea has also entered the global market as Korean car manufacturers have started to build overseas factories. Maintaining cost competitiveness by minimising total logistics costs will thus be a critical strategy for the industry. This research compares the total annual costs of four feasible transport routes from Korea to the US using the inventory-theoretic model, which encompasses direct transport costs, in-transit carrying costs, and warehouse inventory costs. We apply this model to real transport data collected from a Korean auto-parts company. A static analysis shows that inventory costs can play a decisive role in altering the cost competitiveness of different routes. In addition, sensitivity and scenario analyses with changes in variables and the market situations reveal that the cost structure of each route plays an important role in determining their relative cost competitiveness in varying market conditions.     

A study of fatigue crack propagation at a web stiffener on a longitudinal stiffener

Predicting fatigue crack growth after its detection during in-service inspection is necessary to prevent a loss of serviceability, such as the oil and/or water tightness of critical compartments. This paper focuses on the most typical fatigue cracks that start at the weld joint between a flat bar stiffener on a transverse web frame and the flange of a longitudinal stiffener on a bottom plate or inner bottom plate. An experiment is carried out to observe the fatigue crack propagation for two kinds of flat bars at the abovementioned connection. The experimental results, especially the surface crack growth on the flange (which dominates during the total fatigue life of the longitudinal stiffener), are compared with crack growth curves predicted using a few existing formulas. Based on the comparative study, a formula that shows the best agreement with the experiment results is selected. Weld toe magnification factors for the web stiffener are computed from the crack propagation rates measured in the experiment, and two equations for the magnification factors versus crack depth are developed for two types of web stiffeners. The selected existing formula and the proposed equations are applied to two connections at the inner bottom and side longitudinal bulkhead of an LNG carrier. The equivalent stress approach based on a long-term distribution is employed to avoid the complexity involved in dealing with the actual stress history. Using this prediction, the remaining service life until an oil or water leakage occurs at a tank boundary can be estimated when a fatigue crack at the connection is detected.     

Wet Single Clutch Engagement Behaviors in the Dual-Clutch Transmission System

A frictional torque was generated by a lubricated slip contact between a wet clutch pad and a steel separator during a wet clutch engagement. It is necessary to understand the generation of frictional torque to improve the performance of the frictional torque transfer and the durability of the wet clutch system. The analytical modeling of wet clutch torque transfer considers the effects of surface roughness, permeability, the elastic modulus of the frictional material, lubricant viscosity, temperature, etc. Experimental apparatus for wet clutch engagement was designed for the measurement of frictional torque transfer during wet clutch engagement. The experimental results were compared with the analytical results under various operational conditions for the verification of the theoretical analysis to evaluate the performance of the wet clutch system. Some correlations were investigated between the experimental and analytical results. We found that computation by analytical modeling can predict the effects of oil temperature, applied force, and slip speed, as well as engagement period and frictional torque transfer shapes.     

Sequential Approximate Optimization of MacPherson Strut Suspension for Minimizing Side Load by Using Progressive Meta-Model Method

In a MacPherson strut suspension, the side load is inevitably generated and it causes friction at the damper reducing riding comfort. In this paper, to solve this problem, progressive meta-model based sequential approximate optimization (SAO) is performed to minimize the side load. To calculate the side load, a wheel travel analysis is performed by using flexible multi-body dynamics (FMBD) model of suspension, which can consider both finite element method (FEM) and multi-body dynamics (MBD). In the optimal design process, meta-model is generated by using extracted sampling points and radial basis function (RBF) method. As a result of optimal design, spring setting positions that minimize the side load are obtained and by using optimal spring setting positions, the suspension FMBD model was constructed.     

Simulation Study on Thermal Management Strategy to Achieve 99 % SCR Efficiency of a Heavy-Duty Diesel Engine over a Transient Cycle

In this study, NOx conversion characteristics of a urea selective catalytic reduction (SCR) system equipped on a heavy-duty diesel engine were evaluated through engine dynamometer bench tests over a scheduled world harmonized transient cycle (WHTC). Also, based on transient SCR simulations, the thermal management strategy to improve SCR NOx conversion efficiency was investigated. As a result, it was found that a selective increase in exhaust temperature at low temperature period would be a useful measure to increase SCR efficiency on WHTC mode. From the baseline SCR efficiency of around 98 % on WHTC mode, the current simulation results have shown that around 99 % level of SCR efficiency would be achievable by increasing exhaust temperatures with modifying diesel exhaust fluid (DEF) dosage. Another valuable contribution of this study is that the design guidelines for controlling exhaust temperature and DEF injection to obtain a target NOx conversion efficiency are presented for SCR systems of heavy-duty diesel engines on transient operating conditions.