Hiroyasu Miyakawa

Bio: Hiroyasu Miyakawa is an academic researcher from Industrial Research Institute. The author has contributed to research in topics: Femoral neck & Conformal cooling channel. The author has an hindex of 2, co-authored 2 publications receiving 84 citations.

Multi-objective optimization of injection molding process parameters for short cycle time and warpage reduction using conformal cooling channel

Abstract: In this paper, cooling performance of conformal cooling channel in plastic injection molding (PIM) is numerically and experimentally examined. To examine the cooling performance, cycle time and warpage are considered. Melt temperature, injection time, packing pressure, packing time, cooling time, and cooling temperature are taken as the design variables. A multi-objective optimization of the process parameters is then performed. First, the process parameters of conformal cooling channel are optimized. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using a radial basis function network is used to identify a pareto-frontier. It is found from the numerical result that the cooling performance of conformal cooling channel is much improved, compared to the conventional cooling channel. Based on the numerical result, the conformal cooling channel is developed by using additive manufacturing technology. The experiment is then carried out to examine the validity of the conformal cooling channel. Through numerical and experimental result, it is confirmed that the conformal cooling channel is effective to the short cycle time and the warpage reduction.

Inversion of the acetabular labrum causes increased localized contact pressure on the femoral head: a biomechanical study.

Abstract: Although studies suggest that subchondral insufficiency fracture of the femoral head may cause rapidly progressive osteoarthritis of the hip, the mechanism of that relationship remains unclear. Our biomechanical study aimed to provide more data in this area by quantifying pressure distribution on the femoral head for normal and inverted hips and by determining the effects of labral inversion on pressure distribution across the joint, focusing on types of fracture under load. We tested mid-sized fourth-generation composite femurs at 15° of adduction, and applied 1 mm/min of axial compressive force to the femoral heads until failure. Additionally, single loads (3000 N) were applied using Prescale film to investigate pressure distribution on the femoral head, with or without silicone rubber representing entrapment of an inverted acetabular labrum. In tests with an external load of 3000 N, the mean pressure for 10 × 5 mm of silicone rubber was 11.09 MPa, significantly greater (about 5.7-fold) than 1.94 MPa without silicone rubber. Different fracture patterns were observed with and without the 10 × 5 mm silicone rubber; when the 10 × 5 mm silicone rubber specimens were used, all eight cases showed fractures in the anterior femoral head. When silicone rubber representing an inverted acetabular labrum was placed between a hemispherical metallic platen and a composite bone model, the silicone rubber areas were subjected to extreme concentration of stress. The fractures that developed at the silicone rubber areas clearly represented subchondral fractures of the femoral head, rather than fractures of the femoral neck.

Design and optimization of conformal cooling channels for injection molding: a review

Abstract: The recent developments in the additive manufacturing make easier and affordable the fabrication of conformal cooling channels (CCCs) compared with the traditional machining techniques. Conformal cooling channels (CCCs) achieve better cooling performances than the conventional (straight-drilled) channels during the injection molding process since they can follow the pathways of the molded geometry while the conventional channels fail. Cooling time, total injection time, uniform temperature distribution, thermal stress, warpage thickness, etc. are some of the objectives that are improved via CCC applications. However, the CCC design process is more complex than the conventional channels; therefore, computer-aided engineering (CAE) simulations have significant importance for the effective and affordable design. This review study presents the main design steps of CCCs as follows: (1) a background of the CCC fabrication process is projected, (2) the thermal and mechanical models are presented with respect to the 1D analytical model, (3) the CAE-supported design criteria are discussed for the 3D models of CCCs and relevant mold materials, (4) some of the illustrative CAE simulations are explained in detail according to the computational thermal and mechanical objectives, and (5) the single- and multi-objective optimization procedures are defined. By following the aforementioned steps, clearer and effective CAE steps can be obtained for the designers before the on-site fabrication of CCCs.

Challenges and Status on Design and Computation for Emerging Additive Manufacturing Technologies

Abstract: The revolution of additive manufacturing (AM) has led to many opportunities in fabricating complex and novel products. The increase of printable materials and the emergence of novel fabrication processes continuously expand the possibility of engineering systems in which product components are no longer limited to be single material, single scale, or single function. In fact, a paradigm shift is taking place in industry from geometry-centered usage to supporting functional demands. Consequently, engineers are expected to resolve a wide range of complex and difficult problems related to functional design. Although a higher degree of design freedom beyond geometry has been enabled by AM, there are only very few computational design approaches in this new AM-enabled domain to design objects with tailored properties and functions. The objectives of this review paper are to provide an overview of recent additive manufacturing developments and current computer-aided design methodologies that can be applied to multimaterial, multiscale, multiform, and multifunctional AM technologies. The difficulties encountered in the computational design approaches are summarized and the future development needs are emphasized. In the paper, some present applications and future trends related to additive manufacturing technologies are also discussed.