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Yang, Lianxiang
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Research on the different Behavior of Edge Cracking Limit by Adopting the Laser Cutting Method

Oakland University-Junrui Li, Wan Xu, Boyang Zhang, Lianxiang Yang
Published 2019-04-02 by SAE International in United States
The edge fracture occurs more frequently during the forming procedure by using the material with higher strength. To avoid the edge fracture that happens during the manufacturing, the edge cracking limit at different pre-strain level needs to be determined. The edge of the part under forming is conventionally manufactured by mechanical cutting, and the edge cracking limit under this circumstance is already heavily studied. In recent years, laser cutting is more applied in the automotive industry to cutting the edge due to the following advantages over mechanical cutting: easier work holding, higher precision, no wearing, smaller heat-affected zone, etc. The change cutting method could lead to a different behavior to the edge cracking limit at different pre-strain level. In this paper, the edge cracking limits of sets of pre-strained coupons with different pre-strain levels are tested. Half of them is cut by the conventional punch method, and the other half uses laser cutting. These cut pre-strained half dog-bone coupons are loaded under a uniaxial tension to acquire the edge cracking limit. The thinning strain is…
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Experimental Drawbeads Design Research

Oakland University-Boyang Zhang, Wan Xu, Zhenpu Zhang, Rong Wang, Lianxiang Yang
Published 2019-04-02 by SAE International in United States
In order to constrain the restraining force and control the speed of metal flow, drawbeads are widely used in industry. They prevent wrinkling or necking in formed panels, reduce the binder force, and minimize the usage of sheet metal to make a part. Different drawbead configurations can satisfy various stamping production. Besides local design of drawbeads, other factors like pulling directions, binder angles and single or multiple beads play an important role too. Moreover, it was found that the same beads configuration can own a different rate of change of pulling force on different gaps by experience. In this paper, to study the effect of each factor, the Aluminum and Steel sheet metals were tested to obtain the pulling force as they passed through a draw bead. Three gap cases between a male and a female beads are set to figure out the trend of pulling force. Drawbeads are installed in a Stretch-Bend-Draw-System (SBDS) test device while a tensile machine was used to record the pulling force. The results validate that the sensitivity of drawbeads…
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Bendability Study of 7xxx Aluminum Alloy Based on the DIC Technique

Oakland University-Wan Xu, Junrui Li, Wen Ma, Lianxiang Yang
Published 2019-04-02 by SAE International in United States
Bendability is a critical characteristic of sheet metal during the stamping process in automobile industry. Bending operation plays an important role in the panels forming of vehicles. In this study, the recently developed “Incremental Bending” method was utilized to evaluate the ambient bendability of 7xxx series avoiding bending crack. A 3D digital image correlation (DIC) measurement system is improved to capture the displacement and strain information on the stretched side of the sheet samples. The background, experimental method and data post-procedure are introduced in detail. After several sequential images acquisition and data processing, the major strain histories on the stretch zone of the samples are measured. With different bending process and parameters, the location of peak strain and the surface major strain distribution were evaluated as a function of R/T ratio (the inner radius over sheet thickness). The experimental results showed how the bending parameters, such as the tooling radius, bending process, and angle influenced 7xxx AA sheet. The potential applications of the relationship between the peak strain and R/T ratio are proposed.
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Experimental Study of Springback (Side-Wall-Curl) of Sheet Metal based on the DBS System

Oakland University-Wan Xu, Boyang Zhang, Zhenpu Zhang, Lianxiang Yang
Published 2019-04-02 by SAE International in United States
Springback is a common phenomenon in automotive manufacturing processes, caused by the elastic recovery of the internal stresses during unloading. A thorough understanding of springback is essential for the design of tools used in sheet metal forming operations. A DBS (Draw-bead Simulator) has been used to simulate the forming process for two different sheet metals: aluminum and steel. Two levels of pulling force and two die radii have been enforced to the experimental process to get different springback. Also, the Digital Image Correlation (DIC) system has been adopted to capture the sheet contour and measure the amount of side-wall-curl (sheet springback) after deformation. This paper presents the influence of the material properties, force, and die radius on the deformation and springback after forming. A thorough understanding of this phenomenon is essential, seeing that any curvature in the part wall can affect quality and sustainability. The data collected during this experimental procedure, in addition, to evaluate the springback characteristic of different sheet metals and is crucial for simulation validation within the automotive stamping industry. Moreover, it…
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Test of Inclined Double Beads on Aluminum Sheets

FCA US LLC-Dajun Zhou, Changqing Du, Kaiping Li, Bazzi Rawya
Oakland University-Boyang Zhang, Wan Xu, Guobiao Yang, Junrui Li, Lianxiang Yang
Published 2018-04-03 by SAE International in United States
Draw beads are widely used in the binder of a draw die for regulating the restraining force and control the draw-in of a metal blank. Different sheet materials and local panel geometry request different local draw bead configurations. Even the majority of draw bead is single draw bead, the alternative double draw bead does have its advantages, such as less bending damage may be brought to the sheet material and more bead geometry features available to work on. In this paper, to measure the pulling force when a piece of sheet metal passing through a draw bead on an inclined binder, the AA5XXX and AA6XXX materials were tested and its strain were measured with a digital image correlation (DIC) system. Five different types of double bead configurations were tested. The beads are installed in a Stretch-Bend-Draw-System (SBDS) test device. The clearance between a male and a female bead is 10% thicker than the sheet material. A tensile machine was used to record the pulling force. The comparison of pulling force and strain are reported in…
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Friction Coefficient Evaluation on Aluminum Alloy Sheet Metal Using Digital Image Correlation

Engineering Quality Solutions, Inc.-Danny Schaeffler
Oakland University-Junrui Li, Hao Wang, Lianxiang Yang
Published 2018-04-03 by SAE International in United States
The coefficient of friction between surfaces is an important criterion for predicting metal behavior during sheet metal stamping processes. This research introduces an innovative technique to find the coefficient of friction on a lubricated aluminum sheet metal surface by simulating the industrial manufacturing stamping process while using 3D digital image correlation (3D-DIC) to track the deformation. During testing, a 5000 series aluminum specimen is placed inside a Stretch-Bend-Draw Simulator (SBDS), which operates with a tensile machine to create a stretch and bend effect. The friction coefficient at the contact point between an alloy sheet metal and a punch tool is calculated using an empirical equation previously developed. In order to solve for the unknown friction coefficient, the load force and the drawback force are both required. The tensile machine software only provides the load force applied on the specimen by the load cell. Thus, the drawback force requires an indirect method of measurement. In this presentation, a method is proposed that uses DIC to measure tensile strain on a specimen’s surface to acquire the drawback…
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Study of Incremental Bending Test on Aluminum Sheets

Aleris-Zhi Deng, John Mcguire, Raj Dasu
FCA US LLC-Changqing Du, Dajun Zhou
Published 2018-04-03 by SAE International in United States
Bendability is one of the most important formability characteristics in sheet metal forming, so it has to be understood for robust aluminum stamping process designs. Crack is one of the major failure modes in aluminum sheet bending. In this study, a new “incremental bending” method is proposed to reduce the risk of bending failure. A novel laboratory test methodology is conducted to test the 5xxx series aluminum sheet bendability with 3D digital image correlation (DIC) measurement system. The designs of test apparatus and test procedure are introduced in this paper. Through the data processing and evaluation of a sequence image acquisition, the major strain histories within the zone of the through thickness crack of test samples are measured. Testing results show that incremental bending is capable of reducing peak strain on the outer surface obviously compared with traditional non-incremental bending. The more step, more movement, the more peak strain reduction. Based on the experimental results, potential applications of incremental bending are discussed and proposed.
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Property and Fiber Orientation Determination for Carbon Fiber Composite

Ford Motor Company-Danielle Zeng
Oakland University-Junrui Li, Xiangning Zhu, Wan Xu, Boyang Zhang, Lianxiang Yang
Published 2018-04-03 by SAE International in United States
Unexpected severe failures occur during the warm forming procedure of carbon fiber material due to the existence of extremely large deformation/strain. To evaluate this failure, a good understanding the accurate material property under certain loading is important to evaluate the forming feasibility of carbon fiber material. Also, a clear connection between the fiber orientation and the material property helps to increase the accuracy of the forming prediction. Therefore, an experimental test is needed to evaluate the material property as well as the fiber orientation. In this paper, a uniaxial tension test for the prepreg carbon fiber under the warm forming condition is performed. A halogen lamp is used to heat the specimen to reach the warm forming condition. A 3D Digital Image Correlation (3D-DIC) is utilized to measure the material property and the fiber orientation in this test, along with a DIP system. The strain distribution, dimension change, and the fiber orientation are measured throughout the test. The detailed experimental procedure is demonstrated, and the result is also analyzed.
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Experimental Validation and Optimization of Computational Methods for High Pressure Fuel Pipe Brazed Joints

Oakland University-Issam Mashal, Boyang Zhang, Xiangning Zhu, Guobiao Yang, Lianxiang Yang
Published 2018-04-03 by SAE International in United States
A V-engine high pressure fuel pipe have experienced several failures during dyno engine validations at brazed joints due to combination of static and dynamic engine loads. The braze fillet experience high local stress concentration with large gradients and it was critical to capture strain contour at this spot to properly understand the failure. Strain gauges was used to measure strain but was incapable of capturing the braze fillet due to the small fillet radius and lack of real estate to install the gauge (braze fillet radius ~ 0.10 mm). A whole field optical experiment method Digital Image Correlation was utilized to successfully captured strain contour at area of interest and results fed back to computational model.In this paper, experimental investigation and theoretical simulation have been carried out to measure and analyze the strain at braze fillets. 3D CAD modeling software Siemens NX was used to design and manufacture a light weight fixture which was used to install the high pressure fuel pipe in uniaxial tension compression machine and perform displacement control compression test. Digital Image Correlation…
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Study on Frictional Behavior of AA 6XXX with Three Lube Conditions in Sheet Metal Forming

FCA US LLC-Changqing Du, Dajun Zhou, Bazzi Rawya, Michael Szymanski
Hefei University of Technology-Xinya Gao
Published 2018-04-03 by SAE International in United States
Light-weighting vehicles cause an increase in Aluminum Alloy stamping processes in the Automotive Industry. Surface finish and lubricants of aluminum alloy (AA) sheet play an important role in the deep drawing processes as they can affect the friction condition between the die and the sheet. This paper aims to develop a reliable and practical laboratory test method to experimentally investigate the influence of surface finish, lubricant conditions, draw-bead clearances and pulling speed on the frictional sliding behavior of AA 6XXX sheet metal. A new double-beads draw-bead-simulator (DBS) system was used to conduct the simulated test to determine the frictional behavior of an aluminium alloy with three surface lubricant conditions: mill finish (MF) with oil lube, electric discharge texture (EDT) finish with oil lube and mill finish (MF) with dry lube (DL). The experimental results could be utilized to distinguish the frictional performance of the three different sheets aforementioned under the same test condition, as well as simulate draw dies process and validates draw bead force models based upon either the finite element method or analytical…
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