Key Engineering Materials Vols. 297-300

Abstract: An integrated vehicle collision-avoiding radar and intelligent cruise control system is proposed. Collision-avoiding radar measures the distance of a vehicle-to-vehicle and roadblocks automatically, and then Cruise Control System design optimal acceleration for the vehicle-to-vehicle distance control. An integrated radar and intelligent cruise control law has been proposed. Using this control law, the brake controller forces the vehicle acceleration to converge to the desired acceleration. It has been shown via the simulations with good distance control performance in both high speed and low speed stop and good driving situations. Vehicle Collision-avoiding Radar System and Intelligent Cruise Control System have very important significance on improving vehicle active safety and reducing driver’s fatigue. Collision-avoiding Radar System and Intelligent Cruise Control System will be the necessary equipment in future vehicle.

Abstract: Among welded structure bogies used for high speed freight cars, failures in an end beam have been found in a number of bogies manufactured in between 1999 and 2000. A freight car suffers from a harsher loading condition and it uses a tread brake without a secondary suspension system. It is presumed that the cause of the failure on the end beam is not the vertical loading by the cargo and the vehicle but the force exerted by the brake. The failure at the end beam makes the brake system useless and can cause a derailment in the worst case. In this study, we propose a simple torsion-free brake shoe holder hanger to remove torsion of hanger bracket. Also performed are the finite element analysis and the on-board test for the developed part. Comparison tests verified the applicability of the torsion-free brake shoe holder hanger.

Abstract: Suspension system of light commercial vehicle (LCV) has enough endurance to protect passenger and freight. Leaf spring is major part of LCV suspension system. Thus, fatigue strength evaluation of leaf spring based on road load response was carried out. At first, the strain of leaf spring was measured on the city mode driving condition and proving ground driving condition. And , the damage analysis of road load response was carried out. After that, fatigue test of leaf spring was also carried out. Based on ε-N life relation, fatigue life of leaf spring was evaluated at Belgian mode, city mode and drawing test specification called the 3 steps test mode. Next, it is compared the design life of leaf spring and evaluated fatigue life by the 3steps test mode. From the above, new target of Belgian mode and city mode was proposed to gratify design specification of leaf spring. It is expect that the proposed target can be satisfied leaf spring fatigue endurance at specific road condition.

Abstract: Steel-wire-rope (SWR) is a key part of the electric-glass-lifter (EGL) in a car, which has a strong effect on the life and reliability of EGL. This paper investigates the operation process and the fracture surface morphology of the SWR of EGL under three different conditions. Experimental result indicates that the fracture character of the SWR of the EGL in car is the typical microvibration- fatigue fracture, which results from micro-crack propagation of the contacting microasperities on the surface of the SWR. In addition, the fracture mechanism of the SWR is analyzed.

Abstract: We designed the compound CVT (Continuously Variable Transmissions) by combining power circulation mode and power split mode, which have been proposed for connecting 2K-H II differential gear to the V- belt type CVU (Continuously Variable Unit), as an input coupled type. With the designed compound CVT, we carried out theoretical analysis and performance experiments. We proved that the compound CVT had a better performance than either of the power circulation mode or power split mode.

Abstract: Ironwork, especially steel roll coil, is usually transported to the customers over land or by sea. For fast and safe transportation of steel roll coil without damaging it, it is necessary that steel roll coil is surely fixed. These days, apitong, which is fully imported from abroad, is being used to fix the steel roll coil. However, because of apitong harshness, it often damages the coil that would be hard to fix. Recovering damaged coil is almost impossible, and we have to look for a new type of dunnage, which would be able to substitute apitong. This paper discusses various types of reinforcement, as well as rectangular and trapezoid dunnages. We will consider how rolling occurs and what happens when the carrier starts and stops moving. Thus, it will be possible to design a dunnage, which would not damage ironwork and had better recovery and softness than the existing apitong.

Abstract: This paper has performed the fatigue strength evaluation for the bogie frame of Korean tilting train. In order to verify the structural safety of the bogie frame, we firstly investigated the loading condition imposed on the bogie frame. The bogie frame of the tilting train is exposed to the more severe loadings compared with the conventional one because of the tilting of the carbody and the high-speed curve negotiation. We have conducted some multi-body dynamic analyses to extract the load condition by tilting on curve. The finite element analysis is used to obtain the stress distribution. Through this study, we could make sure the safety of the tilting bogie frame.

Abstract: The torque of the continuously variable transmission system with friction drive mechanism is transmitted by contacting roller with input and output disks. For the higher transmitted torque, it is necessary to apply large load in order to get higher friction force, which in turn generates severe high stress on the contact surfaces of roller and disks. The toroidal type CVT system has simple component arrays that have three contact points between roller and each input or output disk to get the torque transmitted. However, compact assembly design of the three sets of rollers contacting with input and output disks needs the roller to stay with unsymmetrical angled position with each other. Therefore, the contact shapes between roller and disk vary according to the transmission ratio and should be investigated to avoid the excessive contact stress over than ~1.8 GPa. In this study, the contact geometries of roller and disks in the toroidal type CVT system are computed during the gear ratios. The contact area of which the size depends on the material elasticity, curvatures of roller and disk, and applied load are all of elliptic shapes because of the convex and concave curvatures of roller and disk shapes, respectively. From the computed results considering the size of roller diameter, roller stroke and applied load, it is found that the shapes of contact area changes the sizes of major and minor elliptical diameters in the rolling direction during the gear ratios due to the unsymmetrical angled position of roller.

Abstract: Durability assessment for the suspension system of the vehicle is very important. Particularly, corrosion fatigue strength of coil spring depends on many factors including mechanical and environmental properties. In this paper, residual stresses by multiple shot peening were analyzed using finite element analysis, and evaluated its effect on corrosion fatigue strength. And also, a corrosion fatigue design criterion for coil spring of light commercial vehicle (LCV) based on proving ground response was proposed.

Abstract: Through defining a piece of viscoelastic medium as a thermodynamic system described by the generalized coordinates in the stress relaxation process, the evolution equation is derived by making use of the 1st law of thermodynamics, the 2nd law of thermodynamics and the Onsager’s principle. Based on the general solutions of the evolution, the constitutive expressions of uniaxial stress relaxation are obtained for both ideal viscoelastic solid materials and ideal viscoelastic fluid one respectively, in terms of the situation whether the coordinates participating in the entropy production are in stable or neutrally stable equilibrium state. As the result, whether the stress relaxes to a constant or zero depends on whether the free energy in viscoelastic medium is left or not.