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A basic evaluation of a new press forming technique using in-plane shear deformation was carried out to suppress fracture and wrinkle of parts bent in the height direction, supposing auto body parts such as the front side member rear. This two-step technique comprises two processes. The first process is deep draw forming with a rectangular blank to induce in-plane shear strain in the blank. The second process is bending the pre-formed blank into a part shape with a U-shaped cross section. According to experiments, in-plane shear deformation was induced in the blank in the first process when the press stroke changed along the part longitudinal direction, and increasing the induced in-plane shear deformation made it possible to form a part with a higher bent angle in the height direction in the second process. The results suggested that complex bent parts which were difficult to form by the conventional press forming technique can be formed without fracture or wrinkle when appropriate in-plane shear deformation is induced in the blank in the first process.

A new springback cause analysis method was developed for sheet press forming with measured 3-dimentional shapes of dies and a formed part. In conventional springback cause analysis, a stress distribution is calculated by elasto-plastic FEM analysis of press forming. The newly developed method can be directly applied to a press formed part and its forming dies: an elastic FEM analysis of press forming is conducted using measured shapes of both a pressed part and forming dies, and a stress distribution which causes springback is obtained; and then a springback cause analysis is carried out based on the stress distribution. This calculation method is easier than that of conventional press forming simulation because plastic material properties and friction parameters are not required in its procedure. The philosophy of the new method and an example of application to an automotive part are described in this paper.

Springback is one of the most serious problems in high-strength steel-sheet forming to produce automotive body parts. A springback-root-cause analysis method was developed to identify the areas of stresses at the bottom dead point, which are the most influential in springback. The analysis method of using springback driving stresses, that is, the difference between stresses before and after springback, is more accurate to eliminate the effect of the residual stresses on springback. This analysis method was applied to both a simple model and the forming of an actual part to verify this analysis method. The areas of stresses that have a major impact on springback were identified. A countermeasure against the actual part springback based on this result was devised and it was clarified that the countermeasure is effective on the springback.

Background and Aim White opaque substance (WOS) in gastric neoplasias is a unique finding visualized in magnifying endoscopy (ME) with narrow band imaging (NBI) and it represents intramucosal accumulation of lipid droplets using oil red O staining. Methods Subjects were 26 WOS-positive (13 adenomas and 13 well-differentiated adenocarcinomas) and 27 WOS-negative gastric epithelial neoplasias. We carried out immunohistochemical staining using a monoclonal antibody specific for adipophilin as a marker of lipids. Immunoelectron microscopy was used to evaluate morphology of the lipid droplets. Results Adipophilin was detected in 24 of 25 (96.0%) WOS-positive neoplasias, but it was detected in only two of 27 (7.4%) WOS-negative neoplasias. Lipid droplets were only seen in the surface epithelium in 10 of 11 (91.1%) adenomas, whereas the lipid droplets also existed in the cryptal epithelium in seven of 13 (53.8%) adenocarcinomas. Immunoelectron microscopy revealed numerous lipid droplets mainly existing in the subnuclear cytoplasm of the epithelium. The shape of the lipid droplets in adenomas was round and uniform, whereas that in adenocarcinomas was irregular. Conclusions The present study confirmed that the presence of WOS in gastric neoplasias was dependent upon intramucosal accumulation of lipid droplets using anti-adipophilin staining. Intraepithelial distribution and morphology of the lipid droplets differed between adenoma and adenocarcinoma.

The effect of strain gradient on the stretch flange deformation limit of steel sheets was investigated by hole expansion test under some forming conditions and by FEM. Hole expansion ratio was changed by changing initial hole diameter and punch shapes. It was clarified that a limit stretch flange deformation strain basically depends on not the initial hole diameter and the punch shape by themselves but the strain gradient in the radial direction. The strain gradient along the direction toward the maximum principal strain did not affect limit deformation strain. The limit deformation thickness strain of the stretch flange portion could be changed by changing strain gradient. These results suggest that the formability of stretch flange deformation area should be determined from not only the maximum principle strain but also the strain gradient and blanking clearance.

The present paper deals with a computer-aided process design for tension leveling based on finite element analysis. A FE code developed specifically for that purpose, which involves a sophisticated constitutive model of cyclic plasticity, enables the accurate performing of a numerical simulation. The very short computation time in numerical simulation by this FE code is due to a novel calculation algorithm to solve the steady elasto-plasticity problem based on the incremental deformation theory of plasticity. From the results of numerical simulation for some tension leveling processes, it has been concluded that a series of work rolls should be set in the final stage of the leveling process such that the roll-intermesh gradually decreases along the stream line and approaches zero at the final roll.

The development of press-forming analysis technologies is important to expand the application of high strength steel sheets to automotive body structures. In general, there are various problems in the forming process of high strength steel sheets. In this study the improvements in the prediction accuracy of stretch-flange-fracture and springback were especially focused. In terms of the prediction accuracy of stretch-flange-fracture, a new stretch-flange-fracture prediction technology was developed based on a maximum principal strain gradient. It enables the accurate prediction of stretch- flange-fracture in press-forming of practical parts. On the other hand, springback prediction technologies were developed to solve springback problems. It is very important to clarify the root cause of springback in order to control. Therefore, a new method of springback factor analysis was developed, which can extract the areas and residual stresses which have major impacts on springback at press-forming.

White opaque substance (WOS) in gastric neoplasias is a unique finding visualized in magnifying endoscopy (ME) with narrow band imaging (NBI) and it represents intramucosal accumulation of lipid droplets using oil red O staining.Subjects were 26 WOS-positive (13 adenomas and 13 well-differentiated adenocarcinomas) and 27 WOS-negative gastric epithelial neoplasias. We carried out immunohistochemical staining using a monoclonal antibody specific for adipophilin as a marker of lipids. Immunoelectron microscopy was used to evaluate morphology of the lipid droplets.Adipophilin was detected in 24 of 25 (96.0%) WOS-positive neoplasias, but it was detected in only two of 27 (7.4%) WOS-negative neoplasias. Lipid droplets were only seen in the surface epithelium in 10 of 11 (91.1%) adenomas, whereas the lipid droplets also existed in the cryptal epithelium in seven of 13 (53.8%) adenocarcinomas. Immunoelectron microscopy revealed numerous lipid droplets mainly existing in the subnuclear cytoplasm of the epithelium. The shape of the lipid droplets in adenomas was round and uniform, whereas that in adenocarcinomas was irregular.The present study confirmed that the presence of WOS in gastric neoplasias was dependent upon intramucosal accumulation of lipid droplets using anti-adipophilin staining. Intraepithelial distribution and morphology of the lipid droplets differed between adenoma and adenocarcinoma.