Nagoya R and D Laboratory

Japan

Nagoya R and D Laboratory

Japan
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Yoshida T.,A-D Technologies | Uenishi A.,A-D Technologies | Isogai E.,Hirohata R and D Laboratory | Sato K.,Nagoya R and D Laboratory | Yonemura S.,Kimitsu R and D Laboratory
Nippon Steel Technical Report | Year: 2013

Improving the prediction accuracy of springback simulation are one of the most important problem because springback is major forming defect in sheet metal forming using high strength steel sheets. By applying the mixed hardening model by Lemaitre- Chaboche, which is possible to consider the Bauschinger effect under reverse loading path, prediction accuracy of springback were improved. And influences of material parameters of this model on springback deformation are investigated. To investigate the mechanism of the 3D springback, theoretical evaluation of simulation results before springback is carried out. It was found that 3D springback were reduced effectively by countermeasures obtained from that analytical results applied to the rear member model tests.


Uenishi A.,A-D Technologies | Isogai E.,Hirohata R and D Laboratory | Sugiura N.,Kimitsu R and D Laboratory | Ikematsu Y.,Hirohata R and D Laboratory | And 2 more authors.
Nippon Steel Technical Report | Year: 2013

The material behavior at large strains is one of the most important properties in sheet steel, for it undergoes severe plastic deformation in its use. We focus on the relationship between the work hardening behavior at large strains and the evolution of microstructure during deformation by experimental and numerical methods, with attention to the crystal orientation. The work hardening behavior of ferritic single crystal with different orientations has been characterized by simple shear experiments. At the same time, TEM observations have been performed to study microstructures after shear deformation. The work hardening behavior depends largely on the crystal orientation. The observed microstructures may be classified into three types. The work hardening behavior could be correlated to the type of microstructure via the activity of slip systems. Crystal plasticity analysis revealed that the behavior in macroscopic and microscopic scales could be attributed to the activity of slip systems and their interaction.


Sato K.,Nagoya R and D Laboratory | Yoshida H.,A-D Technologies | Hashimoto K.,A-D Technologies
Nippon Steel Technical Report | Year: 2013

Automotive industry has been facing the challenge of body-lightweight against the background of environmental issues. Near-net-shape and high-strength-steel has been progress in order to solve these problems, for which are being deployed the mission and power train as well as body-in-white. Therefore, thick steel plate is used for cold forging process not only by the steel bar and rod, so called the "sheet forging" which has been an increase in recent years. In this paper, it will be introduced the mechanical properties and the basic material properties of thick steel plate, the evaluation of formability of thick steel plate with thickness variation plate, and also introduced the three-dimensional local bifurcation theory with its effectiveness.


Yonemura S.,Kimitsu R and D Laboratory | Uenishi A.,Steel Research Laboratories | Kosugi S.,Mathematical Science and Technology Research Laboratory | Yoshida T.,A-D Technologies | And 2 more authors.
Nippon Steel Technical Report | Year: 2013

Bake-hardenable steel sheets are often used in exterior automotive body panels, such as doors, hoods, and fenders, because these applications require high strength for dent resistance as well as low yield strength for surface deflection. The dent resistance depends on the yield strength of materials after work hardening by forming and strain ageing by paint baking. In this study, the anisotropy of yield strength has been investigated in a uniaxially prestrained and baked bakehardenable steel. On the other hand, surface deflection is investigated by press forming experiments and their numerical simulations of the exterior door panel model. Emphasis is placed on the effects of mechanical properties and press forming condition on surface deflection are discussed. Furthermore, a new system for evaluation and visualization of surface deflection using Gaussian curvature is presented.


Yoshida T.,A-D Technologies | Sato K.,Nagoya R and D Laboratory | Isogai E.,Hirohata R and D Laboratory | Hashimoto K.,A-D Technologies
Nippon Steel Technical Report | Year: 2013

Springback is one of the most difficult problems in applying high strength steel sheets to automotive body parts. The mechanism of springback behavior classified by the phenomenon and countermeasures based on each mechanism were reported. It was made clear that section opening of member parts was reduced by crash forming and wall tension control. And torsion and camber of complicated shape parts were possible to decrease by planer stress control using the developed analytical methods of CAE. In addition, about the buckling torsion of panels, the mechanism of the occurrence was studied and effects of countermeasures were reported. Basic concept of countermeasure for springback is expected to design the part high rigidity at first, utilize the stress control methods and minimize the compensation of die tools.


Hirose S.,A-D Technologies | Yonemura S.,Kimitsu R and D Laboratory | Uenishi A.,Steel Research Laboratories | Hiwatashi S.,Nagoya R and D Laboratory
Nippon Steel Technical Report | Year: 2013

The accuracy of crash analysis is important for design of car body with crashworthiness and depends on some properties of applied material. Strain rate dependency of flow stress and bake hardenability caused by painting process of car body are of particular significance to crash analysis. Here, developed technologies for evaluation of their properties were introduced.


Furusako S.,Welding and Joining Research Center | Murayama G.,Welding and Joining Research Center | Oikawa H.,Welding and Joining Research Center | Nose T.,Welding and Joining Research Center | And 3 more authors.
Nippon Steel Technical Report | Year: 2013

Application of high strength steel for the auto body has been increasing, because lightness is required in order to reduce CO2 emissions at the same time as the high collision safety. This paper focused on technology trend and research progress concerning welding techniques which are being used for the assembly of auto bodies. On the resistance spot welding, the following results were introduced: 1) stress analysis by FEM in case of cross tension test for joint using high strength steel sheet, 2) improvement technique of cross tension strength based upon the FEM analysis, 3) welding technique of three steel sheets with a combination of substantially different thicknesses and 4) welding tecnique of an open section component like a hydroformed one.


Fujita N.,Quality Management Div. | Matsumura K.-I.,Hirohata R and D Laboratory | Tomokiyo T.,Yawata Steel Works | Kusumi K.,Steel Research Laboratories | Nonaka T.,Nagoya R and D Laboratory
Nippon Steel Technical Report | Year: 2013

Application of ultra-high strength steel sheets is one of the most important methods to satisfy weight reduction and crash safety of a vehicle. Recently, there is a trend to apply ultra-high strength steel sheets widely to auto-body parts. In this report, present situation of ultra-high strength steel sheets, especially with tensile strength more than 980MPa and 1,470MPa by hot-stamping, have been introduced.


Yoshida H.,A-D Technologies | Sato K.,Nagoya R and D Laboratory | Matsuno T.,A-D Technologies | Yoshida T.,A-D Technologies | And 2 more authors.
Nippon Steel Technical Report | Year: 2013

By using of high strength steel sheets for autobody parts and chassis parts, crack initiation of burring process and stretched flange is one of the most important problems in sheet metal forming. Although the factor of crack initiation is complicated procedure due to various cutting conditions and inhomogeneous distribution of stress or strain, we could evaluate this phenomenon by developing forming method of the parts, side bending test method and "limit diagram of stretch flange-ability". To prevent from crack initiation of burring process, we also developed original die shape and piercing methods for improving condition of the cutting edge.


Mizumura M.,Forming Technologies Research Laboratory | Sato K.,Nagoya R and D Laboratory | Suehiro M.,Forming Technologies Research Laboratory | Wada M.,Forming Technologies Research Laboratory | And 2 more authors.
Nippon Steel Technical Report | Year: 2013

Hydroforming has applied for many kinds of auto parts in Japan since 1999. In order to expand hydroforming market, increasing of hydroforming limit and joining technology between hydroforming component and other component are important. Therefore authors developed following five new hydroforming technologies, (1) high branch forming technology with moving dies, (2) forming technology of two branches with right angle each other, (3) large expanding technology by means of expanding method with restricted expanding direction and crossing moving dies and counter punches each other, (4) hydro-burring and nut-inlaying technology and (5) full length flange forming technology.

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