Analytical Prediction of Large Radius Bending by Circular Approximation

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Vitalii Vorkov ◽  
Richard Aerens ◽  
Dirk Vandepitte ◽  
Joost R. Duflou
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
High Ratio ◽  
Coefficient Of Determination ◽  
Engineering Practice ◽  
Analytical Prediction ◽  
Large Radius ◽  
Forming Process ◽  
Air Bending ◽  
Wide Range

An accurate analytical method is normally the preferred choice in engineering practice since this approach usually does not require additional software and can be applied for different situations. A number of analytical methods have been proposed for the air bending process, however, none of them has the capacity to deal with large radius bending. Large radius bending is characterized by a high ratio of the punch radius to the die opening and it is often applied for high-strength steels because of their limited bendability. This bending mode is used to fulfill the imposed level of maximum strain during the forming process. This contribution develops an analytical solution based on the assumption that the bent plate profile can be represented by two straight lines and a circular segment. Three different hardening laws—linear, Swift, and Aerens—are used for the bending moment calculation. Unit moment measurements are used in order to avoid extrapolation of hardening curves obtained by tensile testing. The model is compared with a wide range of experiments using the coefficient of determination, relative and absolute average errors, in addition to the mean standard error. The analytical prediction based on the circular approximation is found to be an accurate and robust tool for the calculation of the major bending characteristics for large radius air bending of high-strength steels.

Investigations on the Mechanical Properties and Formability of Friction Stir Welded Tailored Blanks

2007 ◽  
Vol 344 ◽  
pp. 143-150 ◽  
Author(s):  
Gianluca Buffa ◽  
Livan Fratini ◽  
Marion Merklein ◽  
Detlev Staud
Keyword(s):  
Mechanical Properties ◽  
Stress Condition ◽  
Research Effort ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Friction Stir ◽  
Tailored Blanks ◽  
Sheet Stamping ◽  
Wide Range

Tight competition characterizing automotive industries in the last decades has determined a strong research effort aimed to improve utilized processes and materials in sheet stamping. As far as the latter are regarded light weight alloys, high strength steels and tailored blanks have been increasingly utilized with the aim to reduce parts weight and fuel consumptions. In the paper the mechanical properties and formability of tailored welded blanks made of a precipitation hardenable aluminum alloy but with different sheet thicknesses, have been investigated: both laser welding and friction stir welding have been developed to obtain the tailored blanks. For both welding operations a wide range of the thickness ratios has been considered. The formability of the obtained blanks has been characterized through tensile tests and cup deep drawing tests, in order to show the formability in dependency of the stress condition; what is more mechanical and metallurgical investigations have been made on the welded joints.

Springback Analysis in Bilayer Material Bending

2017 ◽  
Author(s):  
Chetan P. Nikhare
Keyword(s):  
Fuel Consumption ◽  
Elastic Recovery ◽  
Dissimilar Materials ◽  
High Strength Steels ◽  
Thick Layer ◽  
High Strength ◽  
Geometric Error ◽  
Forming Process ◽  
Tailor Welded Blanks ◽  
Geometric Defect

Exponential increase in the use of auto vehicles, and thus the fuel consumption, which relates to the air pollution, vehicle industry are in a strict environmental regulation from government. Due to which the innovation related to light-weighting is not only an option anymore but became a mandatory necessity to decrease the fuel consumption. To achieve this target, industry has been looking in fabricating components from high strength to ultra-high strength steels. With the usage of these material the lightweight was achieved by reducing a gage thickness. However due to their high strength property often challenges occurred are higher machine tonnage requirement, sudden fracture, geometric defect, etc. The geometric defect comes from elastic recovery of a material, which is also known as a springback. Springback is commonly known as a manufacturing defect due to the geometric error in the part, which would not be able to fit in the assembly without secondary operation or compensation in the forming process. Due to these many challenges, other research route involved is composite material, where light materials can be used with high strength material to reduce the overall vehicle weight. This generally includes, tailor welded blanks, multi-layer material, mechanical joining of dissimilar material, etc. Due to the substantial use of dissimilar materials, these parts are also called as hybrid components. It was noted that the part weight decreases with the use of hybrid components without compromising the integrity and safety. In this paper, a springback analysis was performed considering bilayer metal. For this two dissimilar materials aluminum and composite was considered as bonded material. This material was then bent in a channel forming set-up. The bilayer springback was compared in different condition like aluminum layer on punch side and then on die side. These results were then compared with the baseline springback of only aluminum thin and thick layer. It was found that the layer, which sees the punch side, matters due to the differences in elastic properties for both material and thus it directly influences the springback.

Investigation of EN AW 5754 Aluminum Alloy’s Formability at Elevated Temperatures

2017 ◽  
Vol 885 ◽  
pp. 98-103 ◽  
Author(s):  
Dávid Budai ◽  
Miklós Tisza ◽  
Péter Zoltán Kovács
Keyword(s):  
Elevated Temperatures ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Composite ◽  
Alloy Sheet ◽  
High Mass ◽  
Mass Reduction ◽  
Forming Process ◽  
Forming Temperature ◽  
Operating Distance

Nowadays, mass reduction is the most often used term in the automotive industry. Car manufacturers are continuously working on getting ever lighter models than the previous ones, because of the global competition and the rigorous emission rules. A light car has many advantages: lower consumption, better handling, longer operating distance, etc. The emission rules forced the car brands to start new researches to find new solutions for mass reduction. The formula is relatively simple, using lighter or less materials or both and the car will be lighter. In the recent solutions there are three different ways: application of high strength steels, aluminum alloys, and carbon-composite elements. Our investigations are focusing mainly on aluminum, because of its high mass reduction potential. The biggest problem with the aluminum is its low formability. The formability of aluminum is lower than the steel, and it causes problems for the manufacturers. To increase the formability of the aluminum is a hot topic in the research and development area. Forming at elevated temperatures is one of the best solutions to increase the formability of aluminum. The relation between the formability and the forming temperature is not linear, furthermore beyond the optimum forming temperature the formability decreases. We need dozens of investigations to describe the perfect relation, but sometimes a good approximation is enough to form sheet products safely. In our work we investigated the EN AW 5754 aluminum alloy sheet at room temperature, 130°C, 200°C and 260°C. From these tests we could obtain FLC curves of the alloy at different temperatures. Using these curves, the process engineers could find the optimum parameters of their forming process.

Forming Limit Extension of High-Strength Steels in Bending Processes

2014 ◽  
Vol 611-612 ◽  
pp. 1110-1115 ◽  
Author(s):  
Mohamed El Budamusi ◽  
Andres Weinrich ◽  
Chrstioph Becker ◽  
Sami Chatti ◽  
A. Erman Tekkaya
Keyword(s):  
Hydrostatic Pressure ◽  
Metal Forming ◽  
Fem Simulation ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Forming Limits ◽  
Air Bending ◽  
Forming Technology ◽  
Bending Process

Bending is a commonly used forming technology in metal forming. The occurring springback and low forming limits of high-strength steels especially during air bending are the main disadvantages. In this paper, the conventional air bending process is applied with a hydrostatic pressure in the bending zone. This was done using an elastomer tool. The advantage of this method is that the flexibility of air bending is maintained by reducing the springback while the forming limits are extended. Furthermore, different geometries for the elastomer tool were investigated by means of a FEM simulation. The investigation leads to a reduction of the process forces by minimizing the springback and to an extension of the forming limits.

Frictional Behaviors of a Mild Steel and a TRIP780 Steel Under a Wide Range of Contact Stress and Sliding Speed

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Chongmin Kim ◽  
Jeong-Uk Lee ◽  
F. Barlat ◽  
Myoung-Gyu Lee
Keyword(s):  
Mild Steel ◽  
Contact Pressure ◽  
High Strength Steels ◽  
Diffraction Method ◽  
High Strength ◽  
Contact Stresses ◽  
Minor Amount ◽  
Sliding Speed ◽  
Normal Contact ◽  
Wide Range

The application of advanced high-strength steels (AHSS) generally makes it necessary to use higher tool-sheet contact pressures compared with those used for forming low-strength steel, and it leads to significant changes in frictional behavior, which in turn change the final product characteristics. In order to understand frictional behaviors between steel sheets and tool materials under high contact stresses present in real stamping conditions, a novel friction tester was conceived, fabricated, and used. This tester can generate high normal loads, as high as 625 MPa, whereas traditional friction testers were limited to 10 MPa or less. A mild steel and a TRIP780 steel were paired with Cr-coated D2 tool steel, and friction behaviors were observed under various conditions, including the use of two lubricants, wide ranges of sliding speeds, and normal contact stresses. The coefficient of friction (COF) decreased at a low contact pressure as the sliding velocity increased. The contact pressure had a significant effect, albeit too complex to be explained by simple models. It was also evident that lubricant effects must be studied coupled with the contact pressure and sliding speed. In a nonlubricated condition at normal stresses roughly half of the steel’s yield strength, the friction event caused plastic deformation that reached up to 0.2 mm from the surface. In this deformed region, the amount of retained austenite in the TRIP steel decreased substantially, and significant residual compressive stress, reaching 350 MPa, also developed in the ferrite phase (plus a minor amount of martensite, which is undistinguishable from ferrite by the X-ray diffraction method used herein). The magnitude of change of friction constant due to changes in contact conditions was enough to significantly affect springback of automotive body panels.

Modeling and FE Simulation of Quenchable High Strength Steels Sheet Metal Hot Forming Process

2010 ◽  
Vol 20 (6) ◽  
pp. 894-902 ◽  
Author(s):  
Hongsheng Liu ◽  
Jun Bao ◽  
Zhongwen Xing ◽  
Dejin Zhang ◽  
Baoyu Song ◽  
...  
Keyword(s):  
Sheet Metal ◽  
Fe Simulation ◽  
High Strength Steels ◽  
High Strength ◽  
Hot Forming ◽  
Forming Process

Experimental Study on Galling Behavior of Advanced High Strength Steel in Sheet Metal Forming

2012 ◽  
Vol 502 ◽  
pp. 36-40
Author(s):  
Ying Ke Hou ◽  
Shu Hui Li ◽  
Yi Xi Zhao ◽  
Zhong Qi Yu
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sheet Material ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Process ◽  
Advanced High Strength Steels ◽  
Sheet Materials ◽  
Materials Used

Galling is a known failure mechanism in many sheet metal forming processes. It limits the lifetime of tools and the quality of the products is affected. In this study, U-channel stamping experiments are performed to investigate the galling behavior of the advanced high strength steels in sheet metal forming . The sheet materials used in the tests are DP590 and DP780. In addition to the DP steels, the mild steel B170P1 is tested as a reference material in this study. Experimental results indicate that galling problem becomes severe in the forming process and the galling tendency can be divided into three different stages. The results also show that sheet material and tool hardness have crucial effects on galling performance in the forming of advanced high strength steels. In this study, DP780 results in the most heaviest galling among the three types of sheet materials. Galling performance are improved with increased hardness of the forming tool.

The Influence of Temperature on Zinc Abrasion in Deep Drawing Processes

2014 ◽  
Vol 611-612 ◽  
pp. 1039-1046 ◽  
Author(s):  
Peter Sachnik ◽  
Wolfram Volk ◽  
Roland Golle ◽  
Hartmut Hoffmann
Keyword(s):  
Deep Drawing ◽  
High Strength Steels ◽  
High Strength ◽  
Heating System ◽  
Sheet Metals ◽  
Process Stability ◽  
Forming Process ◽  
Whole Process ◽  
Different Temperatures ◽  
The Impact

Due to the development of corrosion-resistant lightweight, todays automotive manufacturers typically use zinc coated sheet metals in the forming process. However, zinc abrasion in industrial presses decreases the process stability and often causes interruption of the whole process. The application of high strength steels leads to a significant increase of the temperature due to the plastic work. So far a detailed, quantitative analysis of the relation between temperature and zinc abrasion is not available. Therefore, this paper examines the impact of the temperature on abrasion behaviour in sheet metal processes. To achieve this, a progressive die was built. The deep drawing stage of this tool is connected to a cooling / heating system in order to obtain a constant temperature during the forming process. A variety of different galvanized sheet metals compared to commonly used tool materials has been tested. For each combination of materials five experiments at different temperatures were performed to determine the effect of the temperature on the zinc abrasion. Applying the method of total reflection x-ray fluorescence (TXRF) the quantity of zinc abrasion was measured. A relation between low temperatures and reduced zinc abrasion can be clearly observed. Industrial experiments revealed that temperature exerts a high influence on the zinc abrasion. The new insights into the impact of the temperature show a significant way to lower the zinc abrasion and therefore increase the process stability in deep drawing processes.

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