Assessment of Risky Cornering on a Horizontal Road Curve by Improving Vehicle Suspension Performance

Vehicle stability during cornering on horizontal road curves is a risky stage of travel because of additional factors acting. The main stability factor is centrifugal force, which depends on road curve sharpness and is very sensitive to driving speed usually controlled by the driver. However, the counterforce is produced at tire-road interaction, where different pavement types and states cause a wide variation of tire contact forces and vehicle stability. In the paper, the part of vehicle suspension performance while moving on a sharp horizontal road curve with different levels of pavement roughness was simulated by 14 degrees of freedom vehicle model. The model was built in MATLAB/Simulink software with available pavement roughness selection according to ISO 8608. The influence of variable suspension damping available in modern vehicles on risky cornering is analysed when a vehicle reaches the edge of the pavement with its specific roughness. Critical parameters of vehicle stability depending on road curvature, pavement roughness and driving speed are selected to assess the solutions for safe cornering.

Failure analysis of a re-design knuckle using topology optimization

In this study, a systematic design process is carried out for the design of the knuckle. A systematic method is proposed for the design and analysis of a lightweight steering knuckle in an electric vehicle. In the proposed approach, a finite element (FE) model of the knuckle is constructed based on an inspection of the suspension and steering requirements of the target vehicle and the results of a kinematic analysis. A two-stage topology optimization method is then applied to refine the material distribution within the FE model in such a way as to minimize the knuckle weight. Finally, FE simulations are performed to evaluate the strength of the knuckle under road impact conditions and to determine the fatigue life of the knuckle for four ISO 8608 road classes (A–D). The results show that the optimized knuckle has a weight of 3.64 kg (approximately 6.2 % lighter than the original knuckle of the same strength and material) and achieves fatigue lives of 2.512×1011, 2.972×108, 5.598×103 and 2.432×101 cycles for road classes A, B, C and D, respectively.

The vibrations induced by surface irregularities in road pavements – a Matlab® approach

Purpose The paper tackles the theme of evaluating dynamic load increases that the vehicle transfers to the road pavement, due to the generation of vibration produced by surface irregularities. Method The study starts from the generation, according to the ISO 8608 Standard, of different road roughness profiles characterized by different damage levels. In particular, the first four classes provided by ISO 8608 were considered. Subsequently, the force exchanged between the pavement and three typologies of vehicles (car, bus and truck) has been assessed by implementing, in Matlab®, the QCM (Quarter Car Model) characterized by a quarter vehicle mass and variable speed from 20 to 100 km/h. The analysis allows determining the amount of dynamic overload that causes the vibrational stress. Results/Conclusions The paper shows how this dynamic overload may be predetermined as a function of the pavements surface degradation. This is a useful reference for the purposes of designing and maintaining road pavements.

AN ADVANCED MEASUREMENT OF PADDY FIELD SURFACE ROUGHNESS BY STATIC LEVEL METHOD

Determination of accurate paddy field surface profile has great importance to designing the paddy tractor suspension system. With this aim, a new test rig has been designed and developed to measure paddy field surface profiles using static level method (sampled interval of 200mm). The data were analyzed through Matlab/Simulink software to obtain power spectral densities (0.05-3.5c/m) of the measured profiles on a log-log scale and it was found that the amplitude variation of the power spectral density (PSD) at low spatial frequency was higher than at high spatial frequency whereas the undulation of the PSD curve was largely changed from low to high frequency with roughness coefficient of 645.06x10-6 m3/cycle and slope value of 1.2399 representing the paddy field surface roughness under class D of ISO 8608 standards. This classification has great significance in the field of tractor vibration simulation work. Keywords: Paddy field surface, Rod and Level, Static level method, ISO 8608.