Kensuke Funada

Bio: Kensuke Funada is an academic researcher from Kobe Steel. The author has contributed to research in topics: Pillar & Finite element method. The author has an hindex of 2, co-authored 7 publications receiving 10 citations.

Design optimization and application of hot-stamped B pillar with local patchwork blanks

Abstract: The demand for new structural concept design of automotive parts has grown with weight reduction and improvement of crash safety in automotive industry. In this study, the established local patchwork hot stamping technology was used in structural design of hot-stamped automotive parts and expected to obtain maximum lightweight efficiency while maintaining crash performance by using local patchwork blanks instead of conventional reinforcement. Firstly, the technical feasibility of this technology was verified in an experimental method, and an optimization method was proposed to determine the optimal position and shape of local patchwork blanks. Then it was used for the improvements of two parts as examples, a top-hat channel created based on a conventional B pillar cross section and a B pillar. Finite element (FE) analysis models of these two parts were established based on the deformation of B pillar during full vehicle side impact and validated through experiments. It was confirmed that both the top-hat channel and the B pillar optimized have the same crashworthiness but became lighter compared to the original parts with reinforcement. Furthermore, the effects of local patchwork blank thickness, material strength and outer thickness on the optimal position and shape of local patchwork blanks and lightweight efficiency were investigated. Finally, the effectiveness of a hot-stamped B pillar with local patchwork blanks was verified through full vehicle side impact simulations. It can be concluded that the established local patchwork hot stamping technology and the proposed optimization method can be used as a dependable tool to design and manufacture hot-stamped parts with local patchwork blanks.

Manufacturing method of press-formed article and press forming apparatus

Abstract: A manufacturing method of press-formed article according to the present invention includes a step of placing a flat plate member (10) between a first die (11) and a second die (12), and a step of causing a first press portion (14A) and a second press portion (15A) approach each other, thereby pressing the flat plate member (10). In the step of placing, the flat plate member (10) is placed so that a first main surface (10C) and a second main surface (10D) align with a vertical direction. In the step of pressing, the flat plate member (10) is vertically pressed by causing the first press portion (14A) and the second press portion (15A) to approach each other in the vertical direction, and a thick portion is formed on the flat plate member (10) by causing a part of a material of the flat plate member in the vertical direction to flow into a thickened portion-forming section (16) formed on a first opposing surface (11A).

Method for manufacturing press-molded product and press-molding device

Abstract: PROBLEM TO BE SOLVED: To provide a method for manufacturing a press-molded product for which a cost can be reduced and also a space can be saved by simplification of a metal mold structureSOLUTION: A method for manufacturing a press-molded product comprises: a process of locating a flat plate member 10 between a first metal mold 11 and a second metal mold 12; and a process of pressing the flat plate member 10 by causing a first press part 14A and a second press part 15A to approach each other In the process of locating the flat plate member 10, the flat plate member 10 is located so that a first principal surface 10C and a second principal surface 10D are along a vertical direction In the pressing process, the first press part 14A and the second press part 15A are caused to approach each other in the vertical direction, thereby pressing the flat plate member 10 in the vertical direction Further, in the pressing process, a part of material of the flat plate member 10 in the vertical direction is made to flow into a thickening formation part 16 formed on a first opposite surface 11A, thereby forming a thick portion on the flat plate member 10SELECTED DRAWING: Figure 3

Manufacturing method of press-formed article, press-formed article, and press forming apparatus

Abstract: A manufacturing method of a press-formed article includes arranging a member to be pressed between first and second dies, and relatively moving the first and second dies so as to approach each other, thereby press forming to a portion to be pressed so that a height of the portion to be pressed decreases. In the press forming step, while first bent portions in a pair each bent in a protruded shape toward the second die on the portion to be pressed are held by groove-shaped holding portions in a pair separated from each other on the second die, a second bent portion bent in a protruded shape from a position between the first bent portions toward the first die on the portion to be pressed is pressed and deformed by a pressing portion of the first die.

Press molding manufacturing method, press molding, and press molding apparatus

Abstract: PROBLEM TO BE SOLVED: To provide a press molding manufacturing method for obtaining a desired shape more properly.SOLUTION: A press molding manufacturing method comprises: a step of arranging a pressed member 30 between a first mold 10 and a second mold 20; and a step of pressing a pressed part 31 so that the height of the pressed part 31 may be reduced by bringing the first mold 10 and the second mold 20 may be relatively moved to approach to each other. At the pressing step, a pair of first bent parts 31A bent to bulge toward the second mold 20 in the pressed part 31 are held by a pair of holding parts 20B disposed to leave each other at the pressed part 31. In the pressed part 31, a second bent portion 31B to be bent to bulge from the position between the paired firs bent portions 31A to the first mold 10 is pressed and deformed by the pressing part 14 of the first mold 10.SELECTED DRAWING: Figure 8

Energy absorption performance of fully clamped curved tubes under transverse loading

Abstract: Curved tubes are widely used on autobody to suffer the transverse bending loads. This paper studies the energy absorption performance of curved tubes under transverse bending load. Firstly, three-point-bending and fully clamped bending experiments are conducted for three kinds of curved tubes with different radii. It is found that the curvature has a significant impact on the energy absorption effect under the fully clamped condition. However, the influence is limited and it will be easily ignored in the three-point-bending condition. Under fully clamped condition, tubes with large radii have three-plastic-hinges, and curved tubes with small radius have five-plastic-hinges. Due to the participation of axial force, the energy absorption of the curved tubes under fully clamped condition is 2.8–4.1 times that of the three-point-bending condition. Subsequently, FE models of curved tubes with different radii are established to analyze the effect of curvature on the deformation mechanism and energy absorption. It is found that whether the shortening of the plastic hinges can meet the requirements of geometric compatibility determines the deformation modes of curved tubes. The influence of loading (loading direction) and geometric (cross-section and thickness) factors are also discussed. Finally, a theoretical model of curved tubes with three-plastic-hinges mode is proposed to predict the energy absorption performance.

Experimental and numerical investigation into the dynamic impact responses of CFRP header rail

Abstract: The application of composite materials in vehicle thin-walled structure has attracted more and more interest by carmakers. This study aimed to investigate into the dynamic impact responses of the carbon fiber reinforced plastic (CFRP) header rail subjected to the vertical (Z-direction) and horizontal direction (X-direction) loading. The lightweight CFRP header rail was first fabricated using the wet compression molding process, special fixtures were designed and prepared for drop weight impact tests. The failure modes, force responses, energy absorption characteristics and the structural responses to different directional loads were compared. The global peak forces in X-directional tests were higher than those in Z-directional counterpart, but the energy absorption ratios were lower. It is shown that the impact performance of the specimens under Z-directional impact was better than under X-directional impact with same loading magnitude. The finite element (FE) models were then established in both impact directions for exploring the failure mechanisms. The simulated impact process, force–displacement curves and failure modes were found to be consistent with the experimental counterparts. After validation, damaged and weak areas of the specimen could be identified from the simulations, and the models could effectively predict the global peak force and energy absorption ratio. • Dynamic responses of CFRP header rail were investigated under vertical and horizontal impact. • The impact performance of the specimen was better under vertical impact than horizontal impact. • Failure modes and main contributors to energy absorption between different tests were compared. • Damaged and weak areas of the specimen were identified from the FE simulations.

Energy absorption behaviors and optimization design of thin-walled double-hat beam under bending

Abstract: Thin-walled hat-shaped structures have gained growing interest attributed to their excellent performance and wide application in the vehicle industry. However, few systematic studies have been conducted on the design of hat-shaped structures with irregular sectional shapes. In present research, thin-walled double-hat beam (DHB) with different sectional configurations under dynamic three-point-bending are investigated by performing numerical simulations. First, the energy absorption mechanism of DHB is explored, and then an in-depth parametric study, including shape parameters o, p, q and thickness parameter k, is performed. The results show that all DHBs deform in bending with indentation mode. And compared with single-hat beam (SHB), the DHB has a significant advantage in loading capacity. When the design space is held fixed, the shape parameter o has the greatest influence on the bending behaviors of DHB, followed by parameter p, while parameter q has the least influence. In addition, it is also found that a larger thickness of the top hat leads to the increase of the SEA and PCF and the decrease of the hammer displacement. Finally, a multi-objective optimization based on lower confidence bound matrix (LCBM) criteria is conducted to determine the optimal design of DHB. The numerical results of the optimal DHB suggest that increasing the initial impacting velocity will make the SEA and PCF increase while make the displacement decrease.

Lightweight Design Optimization of Nonpneumatic Tires under Radial-Stiffness Constraints

Abstract: Nonpneumatic tires (NPTs) have good safety and a good load-carrying capacity, and they replace the function of air in pneumatic tires with a solid spoke component. The radial stiffness and weight are the important indexes for evaluating the performance of an NPT. In this research, we designed an NPT according to the requirements of vehicle Chery eQ1 based on weight minimization. Taking the radial stiffness related to the bearing-capacity performance as the constraint condition, a topology-optimization algorithm is proposed to find the best thickness distribution of the spokes with the objective of minimizing the mass. First, the mechanical properties of the material were obtained with the test. Then, the FE model of an NPT with a Fibonacci spoke structure was built and validated with a radial-stiffness test on a five rigid test machine. The optimization algorithm was carried out by searching for the best thickness distribution of the spoke after verifying the reliability of the FE model. Finally, the optimized tire was manufactured, and the stiffness test was carried out to verify the feasibility of the optimization results. The results show that the spoke mass can be reduced by 9% by using the proposed optimization algorithm while satisfying the radial-stiffness constraint.