Influence of Hole Shape and Pattern on the Prediction of Limiting Strain for Perforated Commercial Pure Aluminium Sheets

2012 ◽  
Vol 232 ◽  
pp. 961-965 ◽  
Author(s):  
G. Venkatachalam ◽  
S. Narayanan ◽  
S. Patel Nilay ◽  
Prabhakar Nishant ◽  
C. Sathiya Narayanan
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sheet Material ◽  
Pure Aluminium ◽  
Numerical Techniques ◽  
Local Necking ◽  
Hole Shape ◽  
Reliable Knowledge ◽  
Aluminium Sheets

One of the needs of modern sheet metal forming is reliable knowledge about the formability of a given material. In sheet metal forming formability is usually related to the ability to have high values of the strain until failure, where this failure can be local necking and/or fracture. This high values of strain is called limiting strain which is not only influenced by material but also by the geometric features of sheet material. In this work, influence of hole shape and the patterns in which holes are arranged on limiting strain, are studied using experimental and numerical techniques. Both experimental and numerical analysis reveals the same.

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.

Modelling of Forming Limit Strains of AA5083 Aluminium Sheets at Room and High Temperatures

2016 ◽  
Vol 1135 ◽  
pp. 202-217 ◽  
Author(s):  
José Divo Bressan ◽  
Luciano Pessanha Moreira ◽  
Maria Carolina dos Santos Freitas ◽  
Stefania Bruschi ◽  
Andrea Ghiotti ◽  
...  
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Stress Rupture ◽  
Forming Limit ◽  
Limit Curve ◽  
Local Necking ◽  
Localized Necking

Present work analyses mathematical modelling to predict the onset of localized necking and rupture by shear in industrial processes of sheet metal forming of aluminium alloy 5083 such as biaxial stretching and deep drawing. Whereas the AA5083 sheet formability at room temperature is moderate, it increases significantly at high temperature. The Forming Limit Curve, FLC, which is an essential material parameter necessary to numerical simulations by FEM, of AA 5083 sheet was assessed experimentally by tensile and Nakajima testing performed at room and 400°C temperatures. Tensile test specimens at 0o, 45o and 90o to the direction of rolling (RD) and Nakazima type specimens at 0o RD of aluminium AA5083 were fabricated. Simple tensile tests at room and 400°C temperatures were performed to obtain the coefficients of plastic anisotropy and material strain and strain rate hardening behavior at different temperatures. Nakazima biaxial tests at room and high temperature, employing spherical punch were carried out to plot the limit strains in the negative and positive quadrant of the Map of Principal Surface Limit Strains, MPLS, of aluminium AA5083 sheet. The “Forming Map of Principal Surface Limit Strains”, MPLS, shows the experimental FLC which is the plot of principal true strains in the sheet metal surface (ε1,ε2), occurring at critical points obtained in laboratory formability tests or in the fabrication process of parts. Two types of undesirable rupture mechanisms can occur in sheet metal forming products: localized necking and rupture by induced shear stress. Therefore, two kinds of limit strain curves can be plotted in the forming map: the local necking limit curve FLC-N and the shear stress rupture limit curve FLC-S. Localized necking is theoretically anticipated to occur by two mathematical models: Marciniak-Kuczynski modelling, hereafter M-K approach, and D-Bressan modeling. Prediction of limit strains are presented and compared with the experimental FLC. The shear stress rupture criterion modeling by Bressan and Williams and M-K models are employed to predict the forming limit strain curves of AA5083 aluminium sheet at room and 400°C temperatures. As a result of analysis, a new concept of ductile rupture by shear stress and local necking are proposed. M-K model has good agreement with both D-Bressan models.

The Effect of Forming Half-Apex Angle on Incremental Sheet Metal Forming

2010 ◽  
Vol 139-141 ◽  
pp. 1514-1517 ◽  
Author(s):  
Liu Ru Zhou
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Tool Path ◽  
Sheet Material ◽  
Sheet Thickness ◽  
Apex Angle ◽  
Forming Limit ◽  
Forming Technology ◽  
Incremental Sheet Metal Forming

The incremental sheet metal forming technology is a flexible forming technology without dedicated forming dies. The locus of the forming tool can be adjusted by correcting the numerical model of the product. The effect of forming half-apex angle on forming process with all kind of sheet material, sheet thickness and ironing ratio is researched. The limit half-apex angle is different for all kind of sheet material and thickness. The limit half-apex angle is smaller for the larger thickness of sheet metal. It will succeed in square conical box incremental forming in a single tool-path if the forming is carried out with an angle which is larger than the forming limit half-apex angle θ. The ironing ratio ψt is decided by the forming half-apex angle θ. The ironing ratio ψt varies with θ. The ironing ratio ψt is smaller when is larger.

Development of a New Ecological Lubrication System for Sheet Metal Forming Based on CO2 in Liquid

2015 ◽  
Vol 651-653 ◽  
pp. 480-485 ◽  
Author(s):  
Markus Singer ◽  
Mathias Liewald ◽  
Anne Feuer
Keyword(s):  
Sheet Metal ◽  
Contact Area ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sheet Material ◽  
Lubrication System ◽  
Blank Holder ◽  
Tribological System ◽  
Micro Holes

Ecological aims and political requirements today are increasing demands on lubricants in sheet metal forming and their impact on environment. For that reason, metal forming industry wants to reduce the amount of lubricants containing polluting additives with a long-term goal of avoiding lubrication entirely. Additionally, dry metal forming will reduce the cleaning steps after the forming operation. This paper shows a new tribological system in which lubrication is replaced by CO2 in a liquid state. Here, CO2 is expanding directly into contact area between workpiece and tool surface and changes its state from gas to solid. The combination of this particular dry ice as well as the pressure of approximately 57 atm affects resulting friction coefficient significantly. After forming operation, CO2 medium vaporizes and a dry component can be used immediately for the next process steps. In this case, the lubricant is applied directly into the contact area. Therefore, laser drilled micro holes are located in the contact area of the tool. Very first gained experimental results disclose such feasibility, the effects and the potential of this new lubrication system at that moment is based on strip draw tests. Different numbers of micro holes are examined to support blank holder pressure ranging between 5 MPa and 6 MPa. In this investigation a mild strength steel DC04 is used as sheet material. This knowledge is aimed to be used for further investigation and later transfer into real deep and stretch forming processes.

scholarly journals Revisiting Veerman’s interpolation method

2016 ◽  
Vol 233 (2) ◽  
pp. 189-196
Author(s):  
Peter Christiansen ◽  
Niels Bay
Keyword(s):  
Sheet Metal ◽  
Metal Forming ◽  
Theoretical Foundation ◽  
Interpolation Method ◽  
Sheet Material ◽  
Forming Limit ◽  
Fe Simulations ◽  
Bulge Testing ◽  
Aluminium Sheets ◽  
Lagrangian Interpolation

This article describes an investigation of Veerman’s interpolation method and its applicability for determining sheet metal formability. The theoretical foundation is established and its mathematical assumptions are clarified. An exact Lagrangian interpolation scheme is also established for comparison. Bulge testing and tensile testing of aluminium sheets containing electro-chemically etched circle grids are performed to experimentally determine the forming limit of the sheet material. The forming limit is determined using (a) Veerman’s interpolation method, (b) exact Lagrangian interpolation and (c) FE-simulations. A comparison of the determined forming limits yields insignificant differences in the limit strain obtained with Veerman’s method or exact Lagrangian interpolation for the two sheet metal forming processes investigated. The agreement with the FE-simulations is reasonable.

Simulation of Ironing Process for Earring Reduction in Sheet Metal Forming

2013 ◽  
Vol 465-466 ◽  
pp. 91-95 ◽  
Author(s):  
Agus Dwi Anggono ◽  
Waluyo Adi Siswanto
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Deep Drawing ◽  
Metal Forming ◽  
Sheet Material ◽  
Anisotropic Properties ◽  
Multi Stage ◽  
Cylindrical Cup ◽  
And Control

Manufacturing of beverage cans is porcessed by using multi-stage ironing following deep drawing from the sheet material of aluminum and steel. An earing profiles are develops during deep drawing of cylindrical cup due to the planar anisotropic properties of sheet. Therefore, the analysis of earing is important to evaluate and control the development of earing. This paper describes a simulation of the cold ironing process in the forming cylinder cap. The ironing process in this study was focused on the prediction of height increasing, earing and thinning. Two different materials of aluminum AA5042 and AKDQ steel were selected for comparison. The results show that the increasing of cup height was in the same trend.

Hydrodynamic Lubrication in Hemispherical Punch Stretch Forming

1986 ◽  
Vol 53 (2) ◽  
pp. 440-449 ◽  
Author(s):  
Kuo-Kuang Chen ◽  
D. C. Sun
Keyword(s):  
Strain Hardening ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Model Problem ◽  
Hydrodynamic Lubrication ◽  
Sheet Material ◽  
Stretch Forming ◽  
Variable Friction ◽  
Hemispherical Punch

The existence and consequence of hydrodynamic lubrication in sheet metal forming is demonstrated using a model problem of hemispherical punch stretch forming. The problem is solved by incorporating a lubrication analysis into an incremental plasticity analysis. The sheet material is assumed to be elastic plastic with strain hardening, and the lubricant is assumed isoviscous. The study identifies two dimensionless parameters controlling the condition of lubrication. The resulting variable friction at the punch-sheet interface is found to affect significantly the distribution of strains in the sheet metal and its formability.

Incorporation of the strain-rate-sensitive constitutive relations in the analysis of sheet metal forming

1990 ◽  
Vol 25 (1) ◽  
pp. 15-20 ◽  
Author(s):  
C H Toh
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
High Speed ◽  
Constitutive Relations ◽  
Sheet Material ◽  
The Finite Element Method ◽  
Thickness Strain ◽  
High Speed Forming ◽  
Hemispherical Punch

Two forms of rate-sensitive constitutive equations, additive and multiplicative, are examined in the analysis of sheet metal forming using the finite element method. Results are obtained for hemispherical punch stretching of an AK steel sheet material with various punch speeds. The computed results in thickness strain distributions and load-displacement curves are almost identical for the two constitutive laws at a low punch speed. However, the additive law provides better agreement in the thickness strain distributions with the experimental trends for high-speed forming.

Material Flow Curve Influence on Macroscopic Residual Stresses in the Workpiece Bottom in High-Pressure Sheet Metal Forming

2006 ◽  
Vol 524-525 ◽  
pp. 173-178
Author(s):  
Rainer Krux ◽  
Werner Homberg ◽  
Matthias Kleiner
Keyword(s):  
High Pressure ◽  
Residual Stresses ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Flow Curve ◽  
Material Flow ◽  
Sheet Material ◽  
Detailed Knowledge ◽  
Process Strategy

The further development of innovative forming processes like sheet metal hydroforming is only possible with the help of detailed knowledge about the workpiece properties and their formation depending on the process strategy. Up to now, the knowledge about the formation of macroscopic residual stresses in high-pressure sheet metal forming (HBU), regarding the influence of the sheet material properties, is still insufficient. The characteristics of the specific forming procedure HBU lead to specific stress and strain gradients in the sheet cross-section, and therefore lead to a characteristic distribution of the induced macroscopic residual stresses, particularly in the workpiece bottom zone. This paper decribes the investigations on the influence of the sheet material flow curve on the macroscopic residual stress distribution in the workpiece bottom.

ИССЛЕДОВАНИЕ ТОЧНОСТИ ДЕТАЛЕЙ, ПОЛУЧАЕМЫХ ПРИ РАЗДЕЛИТЕЛЬНЫХ ОПЕРАЦИЯХ В ПЕРЕНАЛАЖИВАЕМЫХ ШТАМПАХ

2018 ◽  
pp. 52-63
Author(s):  
Е. А. Фролов ◽  
В. В. Агарков ◽  
С. И. Кравченко ◽  
С. Г. Ясько
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Balance Method ◽  
Experiment Planning ◽  
Practical Recommendations

To determine the accuracy of the readjustable punches for separating operations (perforation + punching out) of sheet-metal forming, the accuracy parameters were analyzed using the random balance method using the method of experiment planning. Analytical dependencies are obtained to determine the values of deviation of the outer and inner contour dimensions of perforated and punched out sheet parts. From the dependencies obtained, it is possible to estimate and predict the value of deviation in the dimensions of the resulting part at any time during the operation of the punch. Practical recommendations on the calculation of the actuating dimensions of the working elements (stamping punch, matrix) of readjustable punches are offered.

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