International Journal of Automotive Technology

A dynamic lumped-parameter gear model incorporating the effects of a time-varying and asymmetric mesh stiffness and a backlash nonlinearity is formulated to analyze the spur gear rattle response under the idling condition. The proposed theory assumes a rectangular time-varying mesh stiffness function. The phase shift between the mesh stiffness for forward and backward contacts is examined. Numerical studies are employed to examine the effects of engine torque fluctuations and tooth surface friction on the gear rattle response and the corresponding tooth impact behavior. Comparisons between the results from the time-invariant mesh stiffness model and the proposed time-varying mesh stiffness model reveal differences in the gear responses, especially when the mean rotational speed of the fluctuating gear pair is non-zero. The analysis reveals significant effects on the high frequency response components. However, the idling gear dynamics are relatively insensitive to tooth surface friction.

This study aims to investigate the combustion characteristics of mixed fuel of liquefied propane gas (LPG) and biodiesel under compression ignition (CI) in an effort to develop highly efficient and environmentally friendly mixed fuelbased CI engines. Although LPG fuel is known to be eco-friendly due to its low CO2 emission, LPG has not yet been widely applied for highly efficient CI engines because of its low cetane number and is usually mixed with other types of CI-friendly fuels. In this study, a number of experiments were prepared with a constant volume chamber (CVC) setup to understand the fundamental combustion characteristics of mixed fuel with LPG and biodiesel in two weight-based ratios and exhaust gas recirculation (EGR) conditions. The results from the current investigations verify the applicability of mixed fuel of LPG and biodiesel in CI engines with a carefully designed combustion control strategy that maximizes the benefits of the mixed fuel. Based on the results of this study, ignition is improved by increasing the cetane value by using higher blending ratios of biodiesel. As the blending ratios of biodiesel increased, CO and HC decreased and CO2 and NOx increases.

In this paper, the power transmission dynamics of a metal v-belt continuously variable transmission (CVT) under external vibration conditions were investigated for the micro and macro slip regions. A CVT variator simulator was developed based on the CVT power transmission dynamics. Using the simulator, the influence of a slip on the external vibration transmission characteristics was analyzed in time and frequency domain. From the analysis results, it was found that the external vibration transmission characteristics were different between the micro slip region and the macro slip region. In the micro slip region, the vibrations of the primary and the secondary pulleys were coupled, which means that the vibration characteristics of the primary and secondary pulleys are determined by the torque vibrations characteristics of both the primary and secondary torque. However, in the macro slip region, the vibrations of the pulleys are decoupled and the vibration characteristic of each pulley is determined by the torque vibration of the corresponding side. Experiments were performed to validate the external vibration transmission characteristics for the load torque fluctuation. The test results were in good agreement with the simulation results. It is expected that the different vibration transmission characteristics of the micro and macro slip regions can be used to detect a macro slip in the CVT variator during actual operation.

This paper is devoted to the design and first implementation of a new head and neck safety device (NHNS) for race of motorcycles. The system aims to mitigate the effects of crash forces acting along almost every direction with respect to the head. The system is composed by a helmet, linked to a jacket by means of a number of cables and a by a number of stop surfaces to limit both the flexion and extension of the neck. Stop surfaces are provided also to limit the lateral leaning of the head. Preliminary numerical simulations, performed by a simplified human model, and experimental tests, ran by using a Hybrid III dummy, show that the NHNS has the potential to actually reduce the neck damage in some relevant crash situations. The effect of the device is reducing the load acting on the passenger’s neck and maintaining the vertebrae rotations within the physiological limits.

This paper presents shape optimization of lower control arm considering multi-disciplinary (stiffness, strength and durability) constraint conditions. As non-linearity of strength and durability is large out of the design constraint conditions and performance indexes are defined as min-max values, sensitivity is not reflected and instead, a sequential approximate optimization (SAO) method using a meta-model is suggested. In order to verify the efficiency of the suggested design method, shape optimization design of a 1 piece-typed lower control arm for compact cars is conducted. The design target aims to meet the multi-disciplinary (stiffness, strength and durability) design constraint conditions and at the same time, intends to minimize the weight. Design variables are 3 shape vectors and 1 thickness while design constraint conditions include 2 stiffness, 12 strength and 26 durability variables, featuring a big design problem. As a result, the design problem is solved in total 3 interation and the optimal model meets all of the design constraint conditions and reduces the weight by about 200 grams comparing with that of the initial model. Thus, the suggested design method is an appropriate method suitable for shape optimization design.