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Experimental and Analytical Study of Drawbead Restraining Force for Sheet Metal Drawing Operations

Oakland University-Natalia Reinberg, Ashutosh Mokashi, Saeid Nasheralahkami, Sergey Golovashchenko, Srecko Zdravkovic, Yurdaer Demiralp
  • Technical Paper
  • 2020-01-0753
To be published on 2020-04-14 by SAE International in United States
Design of sheet metal drawing processes requires accurate information about the distribution of restraining forces, which is usually accomplished by a set of drawbeads positioned along the perimeter of the die cavity. This study is targeting bringing together the results of finite element analysis and experimental data in order to understand the most critical factors influencing the restraining force. The experimental study of the restraining force was performed using drawbead simulator tool installed into a tensile testing machine. Based upon the experimental results, it was observed that the restraining force of the given drawbead configuration is dependent upon the depth of bead penetration, friction between the drawbead surfaces as well as the clearance between the flanges of the drawbead simulator. This clearance is often adjusted during stamping operations to increase or decrease material inflow into the die cavity without any modification in the die. Numerical simulation was performed with Autoform software following the geometry of the experimental drawbead tools used in this study. Two different surface conditions were used in the experimental tools: surface treatment…
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Analysis of Sheet Metal Joining with Self-Piercing Riveting

Oakland University-Srecko Zdravkovic, Sergey Golovashchenko
  • Technical Paper
  • 2020-01-0223
To be published on 2020-04-14 by SAE International in United States
Self-piercing riveting (SPR) has been in production in automotive industry since early 1990s. A substantial amount of experimental work was traditionally required in order to find an appropriate combination of rivet and anvil design to satisfy the required joint parameters. Presented study is describing the methodology of numerical simulation of SPR process and its experimental validation for Aluminum alloys and steels. Among material properties, the required information for numerical simulation includes stress-strain curves validated for the range of strains taking place in SPR process (up to 2.0 of true strain for sheets and up to 0.4 of true strain for the rivet) and parameters of fracture model for all involved materials: all sheets in the stack and the rivet material. Experimental data on stress-strain curves for extended range of strains was obtained based upon multistep rolling tensile testing procedure for the sheet metals. Parameters of the fracture model for sheets were defined by custom hole expansion test, and the parameter of the fracture model for the rivet was defined via expanding the tubular portion of…
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The Role of Second Phase Hard Particles on Hole Stretchability of Two AA6xxx Alloys

Oakland University-Sergey Golovashchenko
Pacific Northwest National Laboratory-Xiaohua Hu, Xin Sun
Published 2017-03-28 by SAE International in United States
The hole stretchability of two Aluminum Alloys (AA6111 and AA6022) are studied by using a two stages integrated finite element framework where the edge geometry and edge damages from the hole piercing processes were considered in the subsequent hole expansion processes. Experimentally it has been found that AA6022 has higher hole expansion ratios than those of AA6111. This observation has been nicely captured by finite element simulations. The main cause of differences have been identified to the volume fractions of the random distributed second phase hard particles which play a critical role in determining the fracture strains of the materials.
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Analysis of Tool Wear for Trimming of DP980 Sheet Metal Blanks

SAE International Journal of Engines

Ford Motor Company-Raj Sohmshetty
Oakland University-Saeid Nasheralahkami, Sergey Golovashchenko, Scott Dawson
  • Journal Article
  • 2017-01-0302
Published 2017-03-28 by SAE International in United States
In recent years, implementation of dual phase (DP) Advanced High Strength Steels (AHSS) and Ultra High Strength Steels (UHSS) is increasing in automotive components due to their superior structural performance and vehicle weight reduction capabilities. However, these materials are often sensitive to trimmed edge cracking if stretching along sheared edge occurs in such processes as stretch flanging. Tool wear is another major issue in the trimming of UHSS because of higher contact pressures at the interface between cutting tools and sheet metal blank caused by UHSS’s higher flow stresses and the presence of a hard martensitic in the microstructure. The objective of the present paper is to discuss the methodology of analyzing die wear for trimming operations of UHSS components and illustrate it with some examples of tool wear analysis for trimming 1.5mm thick DP980 steel. The results of die wear of D2 cutting inserts will be reported based upon measurements of the surface of the die and measuring of the burr height of the samples. Strong correlation between local chipping of the trim die…
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Sheared Edge Stretchability of Steels Suitable for Automotive Applications

Oakland University-Saeid Nasheralahkami, Sergey Golovashchenko, Collin Malek, Daniel Kowalsky, Weitian Zhou
Sweet Briar College-Erika Rugh
Published 2017-03-28 by SAE International in United States
In recent years, dual phase (DP) Advanced High Strength Steels (AHSS) and Ultra High Strength Steels (UHSS) are considered as prominent materials in the automotive industry due to superior structural performance and vehicle weight reduction capabilities. However, these materials are often sensitive to trimmed edge cracking if stretching along sheared edge occurs in such processes as stretch flanging. Another major issue in the trimming of UHSS is tool wear because of higher contact pressures at the interface between cutting tools and sheet metal blank caused by UHSS’s higher flow stresses and the presence of a hard martensitic phase in the microstructure. The objective of the current paper is to study the influence of trimming conditions and tool wear on quality and stretchability of trimmed edge of DP980 steel sheet. For this purpose, mechanically trimmed edges were characterized for DP980 steel and compared with other steels such as HSLA 350 and BH210. Sheared edge stretchability of these materials was analyzed by performing the tensile tests. Local elongations were measured by grid analysis and digital image correlation…
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Effect of Tool Stiffness and Cutting Edge Condition on Quality and Stretchability of Sheared Edge of Aluminum Blanks

Oakland University-Nan Wang, Sergey Golovashchenko
Published 2016-04-05 by SAE International in United States
Stamping die design recommendations attempt to limit the production of burrs through accurate alignment of the upper and lower trimming edges. For aluminum automotive exterior panels, this translates to a clearance less than 0.1 mm. However, quality of sheared edge and its stretchability are affected by stiffness of the cutting tool against opening of the clearance between the shearing edges.The objective of the study is to investigate the influence of stiffness of trimming or piercing dies against opening of the cutting clearance on sheared edge stretchability of aluminum blanks 6111-T4. For experimental study, one side of the sample had sheared surface obtained by the trimming process while the other side of the sample had a smooth surface achieved by metal finish. Burr heights of the sheared edge after different trimming configurations with 10% clearance were measured. Subsequently, sheared edge stretchability of the specimens was evaluated by measuring major strains of 2 mm circle grids electro-etched on the surface of the samples along the sheared edge. Comparison of burr height and sheared edge stretchability was analyzed…
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Characterization of Trimmed Edge of Advanced High Strength Steel

Arizona State Univ.-Lindsay Brown
Oakland Univ.-Saeid Nasheralahkami, Sergey Golovashchenko, Bindiya Gugnani
Published 2016-04-05 by SAE International in United States
In recent years, implementation of dual phase (DP) Advanced High Strength Steels (AHSS) and Ultra High Strength Steels (UHSS) is increasing in automotive components due to their superior structural performance and vehicle weight reduction capabilities. However, these materials are often sensitive to trimmed edge cracking if stretching along sheared edge occurs in such processes as stretch flanging. Tool wear is another major issue in the trimming of UHSS because of higher contact pressures at the interface between cutting tools and sheet metal blank caused by UHSS’s higher flow stresses and the presence of a hard martensitic in the microstructure. The objective of the present paper is to study the influence of trimming conditions and tool wear on quality of trimmed edge of DP980 steel sheet. For this purpose, mechanically trimmed edges were characterized for DP980 steel, sheared with six different cutting clearances (from 4% to 40% of the sheet thickness). In addition, the burr height for DP980 has been compared to two other sheet materials including IF and HSLA350. It has been shown that the…
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Experimental Study of Stretchability of Sheared Edge of Aluminum Sheet 6111-T4

Exvoa. Materials Testing, Calibrating and Advising Co.-Quochung Le
Oakland Univ.-Nan Wang, Sergey Golovashchenko
Published 2015-04-14 by SAE International in United States
Experimental results on influence of trimming conditions on the shape of the sheared surface are combined with the results of stretching sheared samples after trimming. The objective of the research described in this paper is to study the mechanism of fracture initiation and cracks propagation during half-a-dog bone tensile test representing sheared edge stretching condition. One side of the sample had sheared surface obtained by the trimming process while the other side of the sample had a smooth surface. Significant attention was paid to understanding of fracture sources. An interrupted tensile test approach was employed to track fracture initiation and propagation during stretching of sheared surface. The results of the experimental study indicated that multiple sources of fracture were observed in the burr area for trimming with clearances exceeding 10% of the material thickness.
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Analysis of Methods for Determining Sheared Edge Formability

Ford Motor Co.-Sergey Golovashchenko
Oakland Univ.-Andrey Ilinich, Lorenzo Smith
Published 2011-04-12 by SAE International in United States
Imposing tensile stress on an edge of a sheet metal blank is a common condition in many sheet metal forming operations, making edge formability a very important factor to consider. Because edge formability varies greatly among different materials, cutting methods (and their control parameters), it is very important to have access to an experimental technique that would allow for quick and reliable evaluation of edge formability for a given case. In this paper, two existing techniques are compared: the hole expansion test and the tensile test. It is shown that the hole expansion test might not be adequate for many cases, and is prone to overestimating the limiting strain, because the burr on the sheared edge is typically smaller than what is observed in production. The tensile test represents an effective alternative to the hole expansion test. Advantages and disadvantages of each case are discussed. Additionally, the strain gradient effect in the hole expansion test is investigated by means of finite element analysis.
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