13th International Conference on the Technology of Plasticity (ICTP 2021): Sheet Forming II
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
Thursday 10:20 AM
July 29, 2021
Room: Virtual: Room C
Location: Virtual
Session Chair: Celalettin Karadogan, Institute for Metal Forming Technology - University of Stuttgart
Development of Adhesion Preventing Method during Deep-drawing of Titanium Alloy Sheets: Yusuke Okude1; Taku Iwaoka1; Isao Nakamura1; 1Tokyo Metropolitan Industrial Technology Research Institute
To prevent the adhesion during press forming of titanium alloy sheets, it is necessary to prevent the surface oxide film peeling caused by sliding between workpiece and die material with high surface pressure. Hence, we have focused on the method to prevent the titanium surface oxide film peeling during press forming to prevent the adhesion. The workpieces with surface oxide film by atmospheric and anodic oxidation was utilized to demonstrate the effect of titanium surface oxide film on formability in deep-drawing process. Additionally, the method to prevent the adhesion during deep-drawing process was developed. In this study, the compressed air was applied into die and the blank holding force (BHF) with vibration technique was utilized during circular-cup deep-drawing of TP340 sheets. As the results, the occurrence of adhesion was prevented significantly by application of developed methods.
Localized Contact Pressure of Blankholder for Stamping Irregular Sheet Parts by Configuring the Height of the Supporting Elements: Kuang-Jau Fann1; Mathias Liewald2; Kim Riedmueller2; 1National Chung Hsing University; 2University of Stuttgart
This paper presents an engineering procedure for stamping irregular sheet metal parts with an elastic blankholder providing a localized contact pressure to ensure stamped parts without failures of cracks and wrinkles. This is done by arranging the height of the blankholder supporting elements in a die set, which is made by standard manufacturing quality and implemented in a press line equipped with standard die cushion. However, the contact pressure is very sensitive to the height of supporting elements. To eliminate the inherent noise from the GD&T of the die set, a finite element model for optimization of the contact pressure must be created according to the actual die set geometry. In this study, the blankholder geometry for stamping a fender-like part was scanned by GOM-ATOS and the height of cylindrical supporting elements was realized by inserting feeler gauges between blankholder and them according to the outcomes of finite element analysis.
Size Effect on Cyclic Deformation Behavior and Springback Prediction of Ultrathin Superalloy Sheet: Weilin He1; Bao Meng1; Bingyi Song1; Rui Zhao1; Li Zhang1; Min Wan1; 1Beihang University
Springback is a challenging issue in the processing of superalloy ultrathin components, and its prediction is affected by the size effect. In this research, the cyclic shear tests of superalloy sheets with different grain sizes were performed to clarify the relation between size effect and cyclic deformation behavior. The experimental results indicated that the Bauschinger effect is affected by the geometrical and grain size effects. To explore how the size effect affects the springback of ultrathin superalloy sheet, U-bending tests were performed on specimens with different grain sizes and thicknesses. In addition, different hardening models were compared by multiscale U-bending tests. The results showed that the YU model can well describe the cyclic deformation of superalloy sheet at various scales.
On the Determination of the Forming Limits by Necking and Fracture of Polycarbonate Sheet: Ana Rosa-Sainz1; Gabriel Centeno1; M. Beatriz Silva2; J. Andrés López-Fernádez1; Andrés J. Martínez-Donaire1; Carpóforo Vallellano1; 1University of Seville; 2University of Lisbon
This research evaluates experimental methodologies for determining forming limits by necking and fracture in polycarbonate (PC) sheet by proposing developments of recent methodologies usually used in sheet metal forming [1,2]. With this purpose, Nakajima tests with different blank geometries are performed on 1 mm thickness polycarbonate (PC) sheet. The experimentation included the use of Digital Image Correlation (DIC) for the evaluation of strains and thickness measurements for the determination of failure strains. The results provided accurate formability limits by necking and fracture, establishing a general framework for analysing specific forming processes (such as incremental forming) on polymeric sheet. Differences in the shaping of the FLC and FFL curves for PC compared to those obtained in metal sheet are also discussed. REFERENCES. [1] A.J. Martínez-Donaire, F.J García-Lomas, C. Vallellano (2014). Materials and Design 57:135-145.[2] P.A.F. Martins, N. Bay, A.E. Tekkaya, A.G. Atkins (2014). International Journal of Mechanical Sciences 83:112–23.
A New Approach for the Production of Burr-free Sheet Metal Components Having Significantly Increased Residual Formability: Sergei Senn1; Mathias Liewald1; 1University of Stuttgart Institute for Metal Forming Technology
Shear cutting induces high strains and work hardening into the shear-affected zone, thus reducing the formability of the sheet metal material during subsequent forming operations. A common method for increasing the residual formability of shear-cut component edges is to shave the surfaces. The shaving process allows highly hardened areas to be removed from a pre-cut contour, resulting in a comparatively high residual formability of the cutting surface. However, as with normal cutting, a burr remains on the shear surface when shaving. For this reason, a new process has been developed which combines counter-cutting and shaving, enabling the production of burr-free shear surfaces having high percentages of clean-cut proportions and significantly higher hole expansion ratios (factor 1.7) than conventional cutting surfaces. The present paper deals with numerical and experimental investigations carried out in the course of the process development with the high strength sheet metal material DP600.
Effects of Press Ram Vibrations on the Production Quality: Bernd-Arno Behrens1; Kai Brunotte1; Richard Krimm1; Oliver Commichau1; 1Institute of Forming Technology and Machines
An indicator for the quality of products that are formed in an embossing process is the product contour. Highest contour quality is achieved, if the shape of the forming tool is perfectly imprinted into the material. However, contact pressure and tribological effects, that occur during the forming process, produce tool wear and thus impair the shape setting progress. To improve product quality, an electromagnetic actuation unit is presented in this paper, which applies horizontal vibrations into the press ram during the forming process. The actuation unit consists of two strong linear solenoids, which generate oscillating force with variable levels and frequencies. The vibrations improve the shape setting during the embossing process. The concept, design and the functioning of the actuators are presented in this paper. Additionally, experimental studies on an embossing process in a production environment were performed to study the quality improvement by means of press ram vibrations.
Study on the Effect of Embossing on the Bending Properties of High Strength Sheet Metals: David Briesenick1; Stefan Walzer1; Mathias Liewald1; 1Institute for Metal Forming Technology
Selective embossing of sheet metal blanks, prior processing, offers the possibility of locally modifying material properties. Small indentations applied on the sheet metal surface by a punch lead to increased material strength due to the induced strain hardening. Moreover, such locally embossed sheet metals show an enhanced process window with regard to forming processes and an improved performance under different loading conditions. The experimental study presented in this paper investigates the bending properties of high-strength steel sheets em-bossed on the tension or the compression surface of the bent blank. The effect of embossing on the bending resistance of two different materials (DP500 and TRIP780) were analyzed by varying the embossing patterns by density and depth. As a result, bending forces required in the tests rise when increasing the proportion of em-bossed surface. Therefore, the paper reveals potentials of local embossing with regard to a specific modification of bending properties of sheet metal components, thus enabling their use in lightweight constructions.
Effect of Machining Induced Microstructure Changes on the Edge Formability of Titanium Alloys at Room Temperature: James Kwame1; Evgenia Yakushina1; Paul Blackwell1; 1University of Strathclyde
The difficulty of forming titanium alloys at room temperature is well researched and is mostly attributed to their ability to form a strong crystallographic texture during plastic deformation. Also, one major issue of concern linked to the forming of such alloys is their high sensitivity to surface inhomogeneity. Various machining processes are utilised in preparing sheet hole edges for edge flanging applications. However, the response of edge forming tendencies of titanium to different edge surface finishes is not well investigated. The hole expansion test was used in this project to elucidate the impact of selected cutting techniques and edge finish integrities on the edge formability of CP-Ti (Grade 2) and Ti-3Al-2.5V alloys at room temperature. The results show that, the quality of the cut edge surface finish has major effect on the edge formability of the material. The paper explores the reasons and consequences for this for industrial forming operations.
An Investigation on Formability of Ti6Al4V Alloy in the Three-layer Sheet Hot Stamping Process: xiaoming yang1; Baoyu Wang1; chuanbao Zhu2; 1University of Science and Technology Beijing; 2Shandong Zhongxing Auto Parts Ltd Company
In the hot stamping process, the sheet will lose a lot of heat which results in poor formability of the sheet. So, a novel hot stamping process for the three-layer sheet is proposed in this paper, which uses two steel sheets to clamp the titanium alloy sheet for transferring and stamping. In this paper, the hot stamping depth is studied by experiments and simulation under the single/three-layer sheet hot stamping condition. The results show that the temperature of the titanium alloy sheet can be controlled effectively by using the three-layer sheet hot stamping process, and the stamping depth can be improved. Compared with the single-layer sheet hot stamping process, the depth of the titanium alloy parts can be increased by 135.7% under the three-layer sheet hot stamping process at 900°C, and the thickness distribution of titanium alloy parts obtained by three-layer sheet hot stamping process is more uniform. The finite element analysis results show that the temperature and stress distribution of titanium alloy sheet by three-layer sheet stamping process is more uniform, and the temperature difference is small through the sheet. The distribution of thickness obtained by simulation has good consistency with the experimental results. Under the three-layer sheet hot stamping process, the titanium alloy sheet has good deep drawing.
Investigation on Springback Behavior of Multi-intersecting High Stiffened Structure in Die Forming: Qiyuan He1; Weidong Li1; Min Wan1; Cailing Li2; Chao Cui2; 1School of Mechanical Engineering and Automation, Beihang University; 2Beijing Space Craft, China Academy of Space Technology
Multi-intersecting high stiffened structures have potential application in aerospace components, which are the main load-bearing structure of manned space station. However, its springback behavior is very complicated due to the interaction of multi-intersected ribbons and intersecting patterns during die forming. For the typical spherical shaped multi-intersecting stiffened structures, a new approach is proposed to quantize the influence on flexural neutral layer of multi-intersected ribs. The strain distribution along thickness at different radial positions of ribs is derived in theoretically. Reverse loading method is used to calculate springback radius of each position. Consequently, the final profile of the panel after springback is calculated by numerical integration. To verify the effectiveness of this method in predicting springback, finite element simulations based on ABAQUS software and experiments are both implemented. Comparison shows that the results are of good agreement, proving the method is capable of predicting springback of multi-intersecting stiffened structures.
Evaluating the Reliability of a Nondestructive Evaluation (NDE) Tool to Measure the Incoming Sheet Mechanical Properties: Fernando Alamos1; Clare Gu1; Hyunok Kim1; 1Edison Welding Institute
Today, the automotive OEMs and part suppliers are increasing their material suppliers globally. Therefore, the same grade steels are supplied by different steel mills and batch conditions to meet this requirement. However, the variation of the incoming material properties can significantly influence the stamping quality associated with necking, wrinkling, and cracking. This increases the overall manufacturing costs and lowers productivity. Nondestructive evaluation (NDE) tools have become useful to reduce this uncertainty by measuring incoming material properties. The measured data can be used during production in a feed-forward control to select the optimal process parameters or as forming process parameter optimization, using simulations. A detailed evaluation of a 3MA (micromagnetic, multiparametric microstructure, and stress analysis) Fraunhofer’s device and its viability of implementations in a production environment is introduced. The 3MA device was incorporated into an industrial robot and a practical calibration procedure was developed and validated for advanced high-strength steels.