Fengchong Lan

Notice of Retraction Influence of tooling geometric parameters on clinching joint properties for steel-aluminum hybrid car-body structures

In order to solve the difficulties in connecting different materials used in steel-aluminum hybrid car-body structures, the mechanical clinching was chosen as the research object to study the feasibility and the effects of geometric parameters of clinching tools on the joint performance for joining high-strength steel SPFC590 and aluminum alloy A5052-H34. The results show that the mechanical clinching method is feasible to connect the two different materials. When connecting HSS and aluminum alloys, the stamping direction has a great influence on the joint performance, and the obtained joint strength is higher when A5052-H34 is close to punch. In addition, the geometric parameters of the tooling also have important impact on the shear strength and tensile strength of the joints. For upper A5052-H34, neck thickness decreases with the increase of punch radius, punch conical angle and die depth, but increases with the increase of die conical angle. Undercut value reduces with the increase of punch conical angle and die conical angle. With the punch radius increases, undercut value is increased first and then decreases, and there is an optimal value of punch radius. Due to the complex influence law of each parameter, the geometric parameters of clinching tools should be scientifically optimized in order to obtain a joint with excellent performance.

Control algorithm of electric vehicle in coasting mode based on driving feeling

Coasting in gear is a common driving mode for the conventional vehicle equipped with the internal combustion engine (ICE), and the assistant braking function of ICE is utilized to decelerate the vehicle in this mode. However, the electric vehicle (EV) does not have this feature in the coasting mode due to the relatively small inertia of the driving motor, so it will cause the driver cannot obtain the similar driving feeling to that of the conventional vehicle, and even a traffic accident may occur if the driver cannot immediately adapt to the changes. In this paper, the coasting control for EV is researched based on the driving feeling. A conventional vehicle equipped with continuously variable transmission (CVT) is taken as the reference vehicle, and the combined simulation model of EV is established based on AVL CRUISE and MATLAB/Simulink. The torque characteristic of the CVT output shaft is measured in coasting mode, and the data are smoothed and fitted to a polynomial curve. For the EV in coasting mode, if the state of charge (SOC) of the battery is below 95%, the polynomial curve is used as the control target for the torque characteristic of the driving motor, otherwise, the required torque is replaced by hydraulic braking torque to keep the same deceleration. The co-simulation of Matlab/Simulink/Stateflow and AVL CRUISE, as well as the hardware-in-loop experiment combined with dSPACE are carried out to verify the effectiveness and the real-time performance of the control algorithm. The results show that the EV with coasting braking control system has similar driving feeling to that of the reference vehicle, meanwhile, the battery SOC can be increased by 0.036% and 0.021% in the initial speed of 100 km/h and 50 km/h, respectively. The proposed control algorithm for EV is beneficial to improve the driving feeling in coasting mode, and it also makes the EV has the assistant braking function.

Joints Parameters Identification in Numerical Modeling of Structural Dynamics

The dynamics of assembled structures are significantly dependent on joints. Joints parameters, owing to be difficultly measured, are always ignored by pure rigid in numerical modeling and it will result in unreliable or even error descriptions. 1 3 Hz deviations may cause resonance especially in engineering optimization issues; hence it is necessary to identify joints parameters for structural dynamics investigation. In present work, multiobjective optimization algorithms are used to identify joints parameters by approaching actual test results in each series of structure to decrease unreliable or error for numerical modeling. Taking automotive dynamics with seam-welding and spot-welding as examples, the relationship of joints parameters perturbation and structural dynamics is derived to give the selecting reason of parameters’ identification. The actual dynamics of an SUV’s frame and a thin-walled part in BIW (body in white) are utilized to validate the methodology. Results demonstrate that the validated model has enough accuracy to reflect the dynamics of the actual structure. The methodology provides reliable guarantee for dynamic analysis and the design of structure.

Automobile crashworthiness improvement by energy-absorbing characterisation of aluminium foam porosity

Abstract Aluminium foam has been adopted as one of the light filler materials in auto body structural components because of its excellent energy-absorbing ability and lightweight which play a key role in reducing weight and improving safety. This paper combines the porosity of aluminium foam material and the application in cars crashworthy structures to present the energy-absorption behavior and its effect evaluation. First, the paper focuses on the effect of porosity on the energy absorption by experimental study. All the experiments were performed with the specimens subjected to quasi-static axial loadings. As the experimental results, the energy-absorbing properties on porosity are presented, implying that the porosity is a very sensitive factor to energy absorption and the best porosity of aluminium foam in energy-absorption capacity was obtained. A case study on aluminium foam-filled material for automobile front rails was carried out by collision simulations, the improved crashworthiness was verified.

Numerical study on the influence of superstructure configuration on coach rollover resistance performance

Coach rollover is one of the most dangerous accidents with respect to fatalities and injuries. The superstructure of a coach has an essential and vital impact on the rollover crashworthiness. To design the optimal superstructure of a coach requires that the effects of superstructure configuration on rollover crashworthiness are thoroughly understood. In order to find the design guidelines for superstructure configurations, this paper studied the influence of coach superstructure configuration on rollover resistance performance. A baseline finite element (FE) model of an intercity coach with semi-integral body is developed. Seven FE models are derived on the basis of the baseline model considering different superstructure configurations, such as closed rings, joints between the side-wall and floor, side window pillar structure as well as distances between the window rails and waistrail. Numerical simulations of rollover test are performed in accordance with the technical prescriptions in ECE Regulation 66. Performance indices, including residual space intrusion amount, energy absorption of each assembly, deformation mode and impact force are calculated and investigated. Results show that the closed rings, the joints between the side-wall and floor assembly as well as structural configurations of the side window pillars have significant effects on the rollover crashworthiness, but the rollover resistance is not sensitive to the distance between the window rail and waistrail. Design guidelines are proposed for coach superstructure to improve rollover crashworthiness based on comparative analysis on performance indices.

Notice of Retraction Bus skeleton lightweight design based on reduced model and mixed variables optimization

A new method integrating reduced model and mixed design variables is proposed and applied in the lightweight design of a bus skeleton for the purpose of mass reduction without loss in structural performance. A whole skeleton model and a reduced model are built. All parts except chassis and floor assembly are reduced out using static reduction method. Reduced model is verified with finite element analysis (FEA) results compared with those from whole model. The study shows that a close agreement of computed results of whole and reduced models is obtained in terms of deformation and displacements at load-bearing nodes and normal mode shapes. While slight discrepancy in first mode frequencies is observed because the static condensation method for reduced model is approximate for mass matrix. As a result, the reduced model saves computation time by about 50 per cent compared to whole model. A structural size optimization is carried out for bus skeleton lightweight issue. Considering size specifications of structure members, three computer-aided engineering (CAE) models with fully discrete design variables, mixed design variables (combination of continuous and discrete variables) and fully continuous variables are built and solved respectively. A comprehensive comparison is examined on the basis of optimized results such as mass reduction, structural performance and computation cost. The results show that adopting the optimization model (scheme) with the reduced model and the mixed design variables, a compromise with 4 per cent mass-saving is obtained between lightweight objective and computing cost. Moreover, optimized results totally accord with size specifications of bus skeleton, which means no manual adjustment is required and makes the proposed method feasible for engineering application.

Multiple Dynamic Heat Sources Thermal Modeling of a Pouch LiFePO4 Lithium-ion Battery

To research the temperature field of lithium-ion battery for electric vehicle during working condition, a thermal model of a pouch LiFePO4 lithium-ion battery is established to obtain more accurate and dynamic changing distribution of battery temperature field. Time varying heat sources model, coupling thermal effect of plate lug, was established based on the characteristic of heat generation in battery caused by its internal resistance. The analysis of battery heat generation character, heat transfer character, and heat dissipation character are also carried out. Three dimension temperature field of battery are analyzed, and the corresponding experiments are conducted. The experimental result indicate that, the multiple dynamic heat sources thermal model built in this research can preferably reflect the real temperature of the pouch LiFePO4 lithium-ion battery.

A New FE Modelling Approach to Spot Welding Joints of Automotive Panels and Modal Characteristics

This paper presents a new finite element modeling technique for spot-weld connection. Unlike the conventional one that depends on node-node model, using this method, while meshing, it is not necessary to consider the correspondent relationship of the positions between the nodes and the actual welding spots. It performs a shortcut and shows high efficiency in a large number of spot-weld models as established easily and rapidly, especially for automotive cab, body frames and panels, etc. It is significant for reducing workload in pre-process of carbody finite element, enhancing the modeling precision and reliable CAE analysis. In addition, based on the orthogonal experiments, the effect of the parameters of spot-welding structure, such as overlap proportion, spot pitch, etc., on the modes of the connected panels has been emphatically investigated, and its law is obtained. The law is significant in engineering applications providing with an approach to reduce the NVH level of products where a large number of spot-welding connection structures is used, such as vehicles, airplane, etc.