13th International Conference on the Technology of Plasticity (ICTP 2021): Sheet Forming I
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
Wednesday 10:20 AM
July 28, 2021
Room: Virtual: Room A
Location: Virtual
Session Chair: Edurne Iriondo, University of the Basque Country
Analysis of Material Work Hardening and Fracture Strains for Sheet Metal Stamping Processes: Sergey Golovashchenko1; Srecko Zdravkovic1; Natalia Reinberg1; Saeid Nasheralahkami1; Weitian Zhou1; 1Oakland University
Experimental study of sheet material flow curves was performed using combined methods of cold rolling for prestraining material to targeted strain and then tensile testing. Experimental studies revealed that aluminum alloys show tendency for flow curves saturation which substantially lowers sheet work hardening. Performed numerical simulations of cup drawing illustrated that this effect leads to earlier material wrinkling compared to power law approximation of the flow curve. Examples of numerical simulation with Autoform software comparing various cases of flow curve approximation will be provided.Analysis of fracture strains was performed by combined gridding and paint spraying on the sheet surface. This approach enabled measurements of local strains in the area closely adjacent to fracture without having continuous access to this area by video camera. This approach was used for sheet hole expansion, sheared edge stretchability along straight cut, hemming, and self-piercing riveting for ultra high strength steels and aluminum alloys.
Finite Element Simulation and Punch Design for Tube Hydro-piercing: Yeong-Maw Hwang1; Wei-Han Dai1; Pin-Chen Lin1; 1National Sun Yat-sen University
This study is focused on punch shape design in tube hydro-piercing processes of aluminum alloy A6005 tubes. The flow stresses of the aluminum alloy tubes obtained by tensile tests are used in the finite element simulations of tube hydro-piercing process with software “DEFORM 3D”. The ductile fracture criterion of normalized Cockcroft and Latham is used during the FE simulations. The critical damage values for the criterion are obtained by comparing simulation results and tensile test data. The effects of various parameters such as the stroke, internal pressure, etc. on hydro-piercing processes and deformation mechanism are discussed. Experiments are conducted and the experimental shearing surface heights are compared with the simulation results to verify the validity of the analytical models. The effects of various parameters on shearing surface heights are also discussed by hydro-piercing experiments.
Formability of Functional Corrugated Cup: Yasunori Harada1; Yuki Nishikubo1; 1University of Hyogo
The formability of the corrugated clad cup was investigated to enhance the functionality of the cup. The drawn cup with a corrugated structure on the side wall was formed by deep drawing. Since the side wall of the cup had a wave shape, the wave shape was reproduced by using a unique die in which steel balls were arranged without the gaps in the shoulder of the die. In the experiment, the materials were low carbon steel SPCC, stainless steel SUS304, and pure titanium JIS-TP340. In the deep drawing process, the round blanks were employed and the flat sheet blanks were formed into a circle by a punch. The laminated sheets were successfully drawn without the cracks. It was found that the corrugated clad cups were successfully formed by using the roller die.
Fine-piercing of Electrical Steel Sheets by Edge-sharpened Diamond-punch: Tomomi Shiratori1; Tatsuhiko Aizawa2; 1Komatsu Seiki Kosakusho, Co., Ltd.; 2Nano Coat Film, llc.
EV-motors required for much reduction of iron loss in the motor cores. Distortion of magnetic zones by piercing each electro-magnetic steel sheets of motor cores, is notices as one of the largest issues toward this reduction of iron loss. In the present paper, the edge-sharpened diamond punch was developed to significantly reduce the plastic strained area as well as the elastic recovery of pierced sheets. First, the femtosecond-laser trimming method was employed to reduce the edge curvature of diamond coating as well as the surface roughness. Micro-piecing experiments with use of EBSD analysis on the microstructure were utilized to demonstrate that plastic zones were narrowed along the shearing line.
Experimental Analysis on Granular Media Based Tube Forming with Active Axial Feed: Eike Hoffmann1; Christian Löbbe1; A. Erman Tekkaya1; Siddharth Upadhya1; 1Institute for Forming Technology and Lightweight Components (IUL), TU Dortmund
Production of high strength, high stiffness and safety-relevant profile parts is feasible through the sequence of media based forming and in-die quenching. As forming media, solid granular media have been recently introduced (Chen, 2016). In this work, the granular media tube press hardening process with additional axial feeding is investigated in order to enhance the tube thickness distribution and to enlarge the process window. The experiments show that, compared to the process with frictional feed, the limits for insufficient forming and wrinkling are unaffected by the change of the feeding system, while the area for intolerable thinning is reduced. Additionally, through the new feeding system a higher degree of design freedom could be achieved, e.g. shoulder angles of 90° are possible. Furthermore, for the design of the process an advanced FEM simulation has been developed, which is based on the Drucker Prager cap model and covers also the thermal interactions.
Effects of Servo Press Forming on Various Strain Path Failures: Laura Zoller1; Tom Feister1; Hyunok Kim1; 1EWI
Utilizing a servo press for sheet metal forming provides benefits for users such as a fully adjustable slide motion and blank holder force control during the stroke. These allow users to program unique profiles based on position and velocity. This paper will discuss how unique servo press profiles can improve various strain path failures that may occur in final formed parts. Standard crank motion, variable blank holder force, and attach-detach slide motion were used to evaluate biaxial, plane strain, and uniaxial failure paths of three variations of bake hardened steel and three variations of GEN-3 steel. It was determined that different strain failure paths require different servo press programs to improve the overall part quality.
Formability Analysis of a Local Heat-treated Aluminium Alloy Thin-walled Tube: Antonio Piccininni1; Joao Magrinho2; Beatriz Silva3; Gianfranco Palumbo1; 1Politecnico di Bari; 2Istituto Superior Tecnico, Universitade de Lisboa; 3Istituto Superior Tecnico, Universitade de Lisboa
The environmental concerns to save energy are driving the attention toward alternative ways to match light alloys with innovative manufacturing processes. Moreover, the need to increase the material formability has led the adoption of local heat treatment to gain relevance over the last years. The present work is focused on the evaluation of the room temperature formability of thin walled Aluminium alloy tube locally annealed by laser. The formability limits were preliminarily determined in the “as-received” conditions (tube expansion with elastomer). Numerical analyses were performed to define the experimental conditions to obtain different strain paths. Tube expansion tests were assisted by the Digital Image Correlation (DIC). Subsequently, the local laser treatment was investigated and Locally Annealed Tubes (LATs) were subjected to tube expansion tests. LATs strain paths and failure strains were compared to those in the “as-received” condition, allowing to evaluate the effect of the local modification on the formability.
Novel Roll Bonded Stainless Steel / Boron-steel Multilayer under Hot Stamping Conditions: Mike Kamaliev1; Marco Teller2; Christian Löbbe1; Gerhard Hirt2; A. Erman Tekkaya1; Markus Stennei1; 1Institute of Forming Technology and Lightweight Components (IUL), TU Dortmund University; 2Institute of Metal Forming (IBF), RWTH Aachen University
Aluminium-silicon coated boron-steels are regarded as standard material in direct hot stamping processes. Nevertheless, the material brings along some disadvantages such as the requirement of a long dwell time in the furnace for the generation of a resistant diffusion layer. In this paper a multilayer steel sheet, with a boron-steel core and stainless steel outer layers, is introduced and the manufacturing process by hot roll bonding is described. Due to the stainless steel surfaces, a coating for hot stamping is no longer necessary. The multilayer is characterized by hot tensile tests and compared with the monolithic multilayer-partners. Hot stamping experiments are conducted on a laboratory scale. Corresponding hardness measurements show that the core is hardened while the outer layers remain ductile. The new multilayer sheets offer the potential to deliver components with higher formability due to tailored properties along the sheet thickness and the use of rapid heating methods.
Experimental and Numerical Investigations into the Influence of the Process Parameters during the Deep Drawing of Fiber Metal Laminates: Thomas Heggemann1; Werner Homberg1; Hüseyin Sapli1; 1Universität Paderborn
Reducing fuel consumption and climate-damaging CO2 emissions are important current challenges for the automotive industry. These goals can be achieved by reducing the weight of the car. Extremely lightweight car bodies can be achieved by using exclusively composite materials, which have the major disadvantage of high costs and unsuitability for large scale production. A promising approach to the automated, large-scale production of lightweight automotive structures with a high stiffness to weight ratio is the combination of high strength steel alloys and CFRP prepregs in a hybrid material – fiber metal laminate (FML) – which can be processed by specially adapted forming technologies such as deep drawing. The paper presents recent results of the combined curing and forming process. The influence of the process parameters, the process limits, the necessary tool systems and the process strategies are similarly covered by the paper.
Hydro-mechanical Deep Drawing of Locally Solution Treated Aluminum Alloy Sheets: Takeshi Nishiwaki1; Ryota Sako1; Hideo Tsutamori1; 1Daido University
Improvement of formability of aluminum alloy sheets is desired because of their lower drawability than mild steel. Therefore, the special sheet forming methods such as a hydro-mechanical forming and a tailor heat treated blank have been developed for aluminum alloy sheets. In this study, we combined the both methods and investigated the limit of drawing ratio of tailor heat treated blanks in a hydro-mechanical forming process. Tailor heat treated blanks of A6061-T6 sheets were produced by the locally solution treatment which was conducted by heat transfer from metal plates heated to a high temperature. Hydro-mechanical deep drawing tests were performed using a cylindrical punch. The limit of drawing ratio of tailor heat treated blanks in a hydro-mechanical forming process was higher than that of simple hydro-mechanical forming and that of simple tailor heat treated blanks.
Development of Warm Press Forming Process Method of Ti-6Al-4V Alloy Sheet: Yusuke Okude1; Taku Iwaoka1; Isao Nakamura1; Takashi Katagiri1; 1Tokyo Metropolitan Industrial Technology Research Institute
Because of the low ductility of Ti-6Al-4V alloy at the temperatures between room temperature and 600℃, fracture easily occurs during press forming. Hence, a method of press forming of Ti-6Al-4V alloy sheets at 300℃ was developed. In this method, the punch motion and blank holding force were applied separately to prevent fracture at the punch radius until the maximum punch load was reached, and the deep-drawing process was demonstrated from the maximum punch load until finish forming to prevent the fracture at end of the flange. In addition, by applying the developed method, we were able to prevent the decrease in wall thickness at the punch shoulder, compared with that in press forming. As a result, warm press forming of Ti-6Al-4V alloy sheets at 300℃ was achieved without fracture of the formed cup or local decrease in the wall thickness by applying the developed method.