Ensuring sufficient road surface friction is essential for maintaining traffic safety, particularly under adverse weather conditions. However, the current Korean design standards for the longitudinal friction coefficient (LFC) are primarily derived from foreign guidelines with limited empirical validation under domestic road and climatic conditions. This study aims to generate field-based LFC data across a range of road surface types and vehicle speeds and evaluate the appropriateness of the LFC values currently adopted in national road design standards. The field experiments were conducted at the Yeoncheon SOC Proving Ground. The five representative road surface conditions were dry, wet, slush, compacted snow, and icy. Driving tests were conducted for each surface condition at four speeds (30, 40, 50, and 60 km/h) using a test vehicle equipped with continuous friction measuring equipment. Twenty scenarios were tested with multiple repetitions to ensure statistical reliability. Consequently, the average LFC values were 0.748 for dry, 0.615 for wet, 0.232 for slush, 0.173 for compacted snow, and 0.133 for icy conditions. The results showed that road surface conditions had a significantly greater impact on the LFC than vehicle speed. Moreover, the values measured under low-friction conditions were consistently lower than those specified in the current Korean standards. These findings highlight the need to revise the existing LFC design values to better reflect domestic winter road environments. The data can also inform the development of road safety strategies such as variable speed limit systems, autonomous vehicle control algorithms, and automatic emergency braking systems suitable for winter operations.

V-type coupling, which is often applied to wastegate-turbochargers(WGT), is a mechanical fastener. Its radial forces generated from the bolt pretension load colse contact with each other to the axial direction for turbine housing and center housing rotating assembly(CHRA). In addition, the torsional stiffness between two bodies should be sufficiently secured to minimize the linkage angle change from the EWGA to the valve spindle. Therefore, in this study, the torsional stiffnesses according to the effects of positioning pins and friction coefficient, and the bolt pretension loads were calculated for V-coupling turbocharger. As a result, it can be seen that the torsional stiffness of the coupling according to the number of position pins is very small. And, when the friction coefficient and the axial force of the bolt are large, the torsional stiffness is greatly increased, and gradually decreasing when the bolt load of the coupling is about 6,000 N or more.

PURPOSES: The purpose of this study is to develop a method for distribution between superelevation and side friction factor by increasing design speed. METHODS: First of all, a method for distribution between superelevation and side friction factor and a theory for the functional formula of side friction factor in compliance with horizontal radius applied in South Korea and the United States are considered. Especially, design speed of 140km/h and numerical value of design elements are applied to the theory for the functional formula of side friction factor in AASHTO's methods. Also, the anxiety EEG upon running speed is measured to reflect ergonomic characteristics through field experiments at seven curve sections of the West Coast Freeway, and this data is applied to graph for the functional formula of side friction factor. RESULTS : Matching side friction factor against the anxiety EEG, the results that a critical points of driver's anxiety EEG sharply increase locate under existing parabola are figured out. CONCLUSIONS : Therefore, we could get a new type of the functional formula that driver's driving comfortability is guaranteed if the existing the functional formula of side friction factor goes down under boundary of the critical points of the anxiety EEG.

For a mobile robot that travels along a terrain consisting of various geology, information on tire force and friction coefficient between ground and wheel is an important factor. In order to estimate the lateral force between ground and wheel, a lot of information about the model and the surrounding environment of the vehicle is required in conventional method. Therefore, in this paper, we are going to estimate lateral force through simple model (Minimal Argument Lateral Slip Curve, MALSC) using only minimum data with high estimation accuracy and to improve estimation reliability of the friction coefficient by using the estimated lateral force data. Simulation is carried out to analyze the correlation between the longitudinal and transverse friction coefficients and slip angles to design the simplified lateral force estimation model by analysing simulation data and to apply it to the actual field environment. In order to verify the validity of the equation, estimation results are compared with the conventional method through simulation. Also, the results of the lateral force and friction coefficient estimation are compared from both the conventional method and the proposed model through the actual robot running experiments.