13th International Conference on the Technology of Plasticity (ICTP 2021): Yasuhisa Tozawa Honorary Symposium
Program Organizers: Glenn Daehn, Ohio State University; Libby Culley, The Ohio State University; Anupam Vivek, Ohio State University; Jian Cao, Northwestern University; Brad Kinsey, University of New Hampshire; Erman Tekkaya, TU Dortmund; Yoshinori Yoshida, Gifu University

Friday 9:15 AM
July 30, 2021
Room: Virtual: Room A
Location: Virtual

Session Chair: Takashi Ishikawa; Yoshinori Yoshida, Gifu University


A Plasticity Framework for Forming Applications: Frederic Barlat1; Toshihiko Kuwabara2; 1Pohang University of Science and Technology; 2Tokyo University of Agriculture and Technology
    This presentation reviews the key features of a plasticity framework developed by the author and his co-workers over the last two decades. The purpose is to define an accurate macroscopic plasticity theory applicable to numerical simulations of practical forming processes in industry. The constitutive relationships are developed for anisotropic materials with an anisotropic hardening assumption. The framework relies on mathematical concepts, physical understanding of deformation mechanisms and experimental results. Lower scale simulation results are essential for the introduction of relevant features in the macroscopic framework. The experimental investigations on plasticity conducted by Professor Tozawa in the 1960’s and 70’s is of fundamental importance for the development and validation of the theory. An application of the approach for numerical forming process simulations of a complex sheet product is described as an illustration.

Prof. Yasuhisa Tozawa's Achievements in the Field of Metal Forming: Takashi Ishikawa1; 1Chubu University
    Prof. Yasuhisa Tozawa’s achievements in the field of metal forming is introduced and reviewed. He has consistently been involved in the study of metal forming. (1) Sheet metal forming, especially bending accuracy and bending fracture and deformation behavior of sheet materials under multiaxial stresses. (2) Strip rolling, especially its three-dimensional analysis. (3) Cold forging, especially evaluation of flow stress and fracture of forging materials. He has been active internationally as a member of CIRP and ICFG. As an excellent educator, he was also enthusiastic about teaching guidance for undergraduate and graduate students, or company engineers, and nurtured many leading researchers and engineers.

Surface Quality of Extruded Sidewall in Cold Backward Cup Extrusion with Low-frequency Torsional Oscillation: Ryo Matsumoto1; Seiji Takatsuka1; Hiroshi Utsunomiya1; 1Osaka University
    The surface quality of an extruded sidewall of a workpiece was investigated in cold backward cup extrusion with torsional oscillation. In this extrusion process, a cylindrical aluminum workpiece lubricated with a mineral oil was simultaneously extruded in the axial direction and twisted in the circumferential direction between extrusion and knockout punches with an axial speed of 0.1 mm/s, an alternating amplitude of 5deg, and a maximum angular speed of 0.5 rpm at room temperature. The sidewall of the workpiece was axially extruded and circumferentially rotated with approximately 25% lower contacting pressure with the container, so that the surface of the sidewall was uniformly smoothed. Furthermore, the circumferential profile of the sidewall height of the extruded workpiece was close to uniform because the workpiece was uniformly lubricated by the circumferential rotation of the workpiece.

Anisotropic Ductile Fracture Estimation of Diagonal Cracks in Flange-shaped Parts: Atsuo Watanabe1; Kunio Hayakawa2; Shinichiro Fujikawa3; Tatsumi Takeshita4; Mika Furutani4; 1Nissan Motor Co., Ltd. and Graduate School of Science and Technology, Shizuoka University; 2Graduate School of Science and Technology, Shizuoka University; 3Nissan Motor Co., Ltd.; 4Jatco Ltd.
    Inclined rotary forming (IRF) is a combined process of bending and axial compression with rotation, which is used to forge flange shaft-structured parts from round rod billets. Although the forming load is less than that of conventional processes, cracks may develop during the IRF process. However, it is difficult to predict cracks by applying the conventional ductile fracture prediction equations. In this paper, an equation for predicting ductile fractures is proposed that considers anisotropic ductile fractures. The proposed equation was expressed as a second rank tensor resulting from the product of the stress tensor and strain increment tensor. The proposed equation was verified through a uniaxial tensile test conducted on a notched round bar and the compression test of cylindrical specimen referring to the past literature. The proposed equation was applied to the IRF process. Consequently, it was possible to estimate the lubrication conditions that make diagonal cracks smaller.

Prediction on Microstructure of Large Scale Hot Forged Ni-based Super Alloy: Nobuki Yukawa1; Takayuki Yamada1; Chihiro Osawa1; Eiji Abe1; 1Nagoya University
    Recently, it has been more important to realize the higher combustion temperature of a gas turbine for air crafts. In order to attain that, it is necessary the material gets an excellent mechanical property like tensile strength. The grain size of the material has a large influence on the mechanical property. Therefore, it is imperative to predict recrystallization behavior under hot forging and heat treatment for controlling the grain size. In this study, we focused on Alloy 718 of a Ni-based superalloy and developed a prediction model for the fractions of dynamic recrystallization and the grain size under a large scale hot forging. The calculated results are good agreements with experimental results of the fractions of dynamic recrystallization and grain size.

Three-dimensional Analysis of Strip Rolling by Coupling Elastic Deformation of Rolls and Rolling Mills: Jun Yanagimoto1; 1The University of Tokyo
     This paper will describe the characteristics of three-dimensional stress field of strip and plastic deformation which is affected by the elastic deformation of rolls and rolling mills. FE analysis results will be presented. Elementary three-dimensional numerical analysis of strip rolling will be presented to compare the results obtained by FEM.(This presentation is a part of session dedicated to Prof. Tozawa)

Characterisation of Anisotropic Material Behaviour: Erman Tekkaya1; Till Clausmeyer1; Felix Kolpak1; Oliver Hering1; Florian Gutknecht1; Heinrich Traphöner1; 1TU Dortmund
    During metal forming processes the workpiece material undergoes large plastic strains. The material develops anisotropic behavior as it is plastically deformed. This anisotropy effects not only the material flow during forming but also the properties of the formed part such as the residual stresses, the yield strength, the damage level etc. Pioneering studies on the determination of anisotropic hardening behavior has been conducted by Professor Tozawa in the seventies. This presentation focuses on the anisotropic hardening behavior of metals at very large strains and describes experimental techniques to quantify anisotropic hardening.

Analysis of Orientation Behavior of Plate-like Particles in Differential Speed Powder Rolling: Kazunari Shinagawa1; Kentaro Kudo1; 1Kyushu University
    Rolling of powder compacts has been used to develop grain-orientated microstructures, especially for anisotropic magnetic material, but can also be applied to piezoelectric ceramics. To obtain a thick ceramic green sheet, powder rolling may be an effective way to actualize higher productivity, compared with a conventional process consisting of slip casting and subsequent laminating of thin sheets. However, the rolling condition to reach high orientation of plate-like ceramic particles, in bodies plasticized with organic binders, has not been studied sufficiently, and should be clarified based on the theoretical consideration. In this study, the effects of differential speed powder rolling on the orientation behavior of plate-like particles are examined by using the Folgar-Tucker model. The change in orientation angle distribution is computed under assumption of a simple velocity field in rolling process. It is shown that the shear deformation in advance of compression is effective to obtain higher degree of orientation.

Control Theory for High End Press Brake: Zhigang Wang1; 1Gifu University
    This paper proposes a control theory of V-bending of sheet metals for high end press brake. The control theory consists of the basic relationship between the product angle and the punch stroke, inflexion point and bending load. The proposed control theory has been applied to the high end press brake and gives a great performance.

The Process Design to Control the Yield Ratio of Yield-Ratio-Control-Steel on Both Wire Production and Forging Process: Youngseon Lee1; 1Korea Institute of Materials Science
    Yield-ratio-control-steel(YRCS) is a steel which the yield strength can be controlled although the same tensile strength. The lower yield ratio steel is more effective for cold forging since the forging load is lower and tool life is enhanced. The yield ratio of YRCS metal is controlled by plastic deformation amount and cooling rate. So, the yield ratio is changed cooling rate after wire rolling as well as plastic deformation during cold wire drawing. Moreover, precision forged part can be used directly without post-heat-treatment(quenching/tempering) because the strength of forged part is increased by work hardening and grain refinement. Three major process variables are considered to get the proper yield ratio on cold forging of bolt which tensile strength is over 800 MPa. The cold drawing amount of wire is major variable to change the yield ratio, while cooling rate is the most important variable affected on their strength.

Surrogate Modelling of Search Range in Polyhedron Flow Stress Model Identification with Inverse Analysis and Cylindrical Compression Test: Yoshinori Yoshida1; Junpei Samukawa1; Takeshi Nishiwaki2; Masanobu Murata3; 1Gifu University; 2Daido University; 3Nagoya Municipal Industrial Research Institute
    Identification of flow stress is conducted with inverse analysis based on finite element analysis. In this procedure, the search range space of equivalent strain and equivalent strain rate should be figured out. In this research, surrogate modeling of maximum value of the strain and strain rate is performed with compressed cylindrical specimen shape with machine learning.

Hole Expansion Simulation of Steel Sheet Considering Differential Hardening: Toshihiko Kuwabara1; Shunya Nomura1; 1Tokyo University of Agriculture & Technology
    The deformation behavior of a steel sheet in hole expansion forming (HEF) using a flat-bottomed cylindrical punch has been investigated both experimentally and analytically to investigate the effect of material modeling on the accuracy of the finite element analysis of HEF. The elastic-plastic deformation behavior of a test material is precisely measured using the biaxial tensile test with cruciform specimens and the multiaxial tube expansion test with tubular specimens. Many linear stress paths in the first quadrant of stress space are applied to the specimens to measure the contours of plastic work and the directions of plastic strain rates to determine appropriate material models assuming either isotropic hardening or differential hardening. The accuracy of HEF simulation is improved by using the differential hardening model.