Collaborative optimization design of lightweight and crashworthiness of the front-end structures of automobile body using HW–GRA for Pareto mining

To collaboratively improve the lightweight and frontal collision safety performance of the automobile body, the material–structure–performance integrated multi-objective optimization design of the front-end structure was implemented in this study. The hybrid weight–grey relational analysis (HW–GRA) method was proposed to address the problem that the Pareto optimal compromise solution of multi-objective optimization cannot be easily selected. The design variables of the material and structural parameters were recorded through material type coding and model parameterization. To satisfy the basic static–dynamic performance constraints of the body, the RSM–Kriging surrogate model, design of experiments, and multi-objective particle swarm optimization algorithm were used to optimize the material and structural parameters to improve the lightweight and crashworthiness of the body. The Pareto optimal compromise solution was determined using the HW–GRA method. The decision result of the proposed method was more robust and rational than those of single weighting techniques combined with GRA and hybrid weighting approach combined with TOPSIS. After the multi-objective optimization and decision-making, the basic static–dynamic performance of the body demonstrated a change of less than 2.0%, which satisfied the constraint requirements. The mass of the body was reduced by 2.4 kg, and the frontal collision safety performance of the body was significantly improved.

Improving the Appearance of a 3-Coat-1-Bake Coating Film by Minimizing the Shrinkage Difference between the Three Layers

The 3-coat-1-bake coating system has been widely employed in automobile body painting. This study examined whether the appearance (waviness) of the coating film can be improved by reducing the difference in the shrinkage percentage (by weight) between the primer surfacer and the basecoat and the clearcoat after flow/leveling stops in the clearcoat while baking. To delay the time of flow/leveling stops in the clearcoat (tC) and to reduce the difference in the shrinkage percentage between the basecoat and clearcoat, solventborne clearcoats were prepared by blocking all or part of the isocyanate group with 3,5-dimethylpyrazole (DMP). tC was measured using the electric-field tweezers system while baking at 140 °C. The respective shrinkage percentages of the primer surfacer, basecoat, and clearcoat (ωS, ωB, and ωC, respectively) were measured after tC. tC increased as the DMP content of the solventborne clearcoat increased. The ωC value is lower than the ωS and ωB values when the DMP content is zero; however, the ωC value increased when tC increased, and the ωS and ωB values decreased as tC increased. Wavescan Wa, Wb, Wc, and Wd decreased (i.e., improved the appearance) as |ωS − ωB| + |ωB − ωC| decreased. We confirmed that reducing the difference in the shrinkage percentage between the primer surfacer, basecoat, and clearcoat after tC is an effective way to improve the appearance.

Study on application of MSOT method for lightweight design of automobile body structure

In this study, the integrated MSOT (M-Multi-dimensional factor autobody model, S-Screening autobody component, O-Optimization of plate thickness, T-Testing, and validation) integration method is adopted to optimize the automobile body structure design for weight reduction. First, a multi-dimensional factor body model is established, then components of the vehicle are screened for the most important targets related to weight reduction and performance, and a multi-objective optimization is performed. Virtual experiments were carried out to validate the analysis and the MSOT method were proposed for lightweight design of the automobile body structure. A multi-dimensional performance model that considers stiffness, modality, strength, frontal offset collision, and side collision of a domestic passenger car body structure. Components affecting the weight of the vehicle were identified. Sheet metal thickness was selected as the main optimization target and a multi-objective optimization was carried out. Finally, simulations were performed on the body structure. The comprehensive performance, in terms of fatigue strength, frontal offset collision safety, and side collision safety, was verified using the optimized Pareto solution set. The results show that the established MSOT method can be used to comprehensively explore the weight reduction of the body structure, shorten the development process, and reduce development costs.

PENGARUH PARAMETER SPRAY GUN TERHADAP KEKILAPAN PADA PELAPISAN BAJA KARBON RENDAH (ST37)

Two purposes of painting of the automobile body, i.e. protection and aesthetic. For the aesthetic one, scientifically measured its glossiness. The purpose of this study was to determine the effects of painting parameters using a spray to its glossiness. Three parameters varied were: (i) comparison of paint composition and thinner (1:1.2; 1:1.4 and 1:1.6), (ii) spraying distance (110 mm, 130 mm and 150 mm), and air pressure (3.5 bar; 4.5 bar and 5.5 bar, while the glossiness measured in gloss unit (GU) using a gloss meter. The experimental design method used was the response surface method with Box-Behnken design. A series of tests were carried out prior to ANOVA and optimization with Minitab: (i) lack of fit test, (ii) simultaneous parameter test, (iii) the coefficient of determination test, (iv) identical test, (v) independent test and (vi) normal distribution test. Out of three parameters, the most influential one is composition with a coefficient of mathematical equation of 6.592. In this study, the highest value in the 10th trial was 57.3 GU which was occurred when the parameters used were: distance of 130 mm, composition 1: 1.6 and pressure 3.5 bar. On the contrary, the smallest value GU in the 7th experiment was 35 GU with a distance of 110 mm, composition 1:1.4 and pressure 5.5 bar. From processing data using Minitab, the maximum gloss value was 58.76 GU with distance 116.86 mm, composition 1: 1.6 and pressure 3.5 bar. Keywords: painting, Box-Behnken design, gloss meter