Investigation of sheet metal forming by bending—Part IV: Bending and wrinkling of circular sheets pressed by a hemispherical punch

The present investigation aims at studying post-welding forming operations of friction stir welded AA1050 aluminium thin sheets. A preliminary investigation has allowed to define the rotational and welding speed values leading to friction stir welded joints with high mechanical properties. Then, formability and elastic springback were evaluated using the hemispherical punch and bending tests, respectively. A microstructural investigation has allowed to relate the mechanical properties of joints to microstructure. Finally, the friction stir welded assemblies were subjected to air bending and stamping experiments in order to evaluate their attitude to undergo to sheet metal forming operations.

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Numerical Prediction of Forming Limit in Hemispherical Punch Bulging by Lemaitre's Ductile Damage Model

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.110-116.1437 ◽

2011 ◽

Vol 110-116 ◽

pp. 1437-1441 ◽

Cited By ~ 1

Author(s):

Farhad Haji Aboutalebi ◽

Mehdi Nasresfahani

Keyword(s):

Sheet Metal ◽

Sheet Metal Forming ◽

Metal Forming ◽

Damage Mechanics ◽

Thin Sheet ◽

Damage Model ◽

Ductile Damage ◽

Forming Limit ◽

St14 Steel ◽

Hemispherical Punch

Prediction of sheet metal forming limits or analysis of forming failures is a very sensitive problem for design engineers of sheet forming industries. In this paper, first, damage behaviour of St14 steel (DIN 1623) is studied in order to be used in complex forming conditions with the goal of reducing the number of costly trials. Mechanical properties and Lemaitre's ductile damage parameters of the material are determined by using standard tensile and Vickers micro-hardness tests. A fully coupled elastic-plastic-damage model is developed and implemented into an explicit code. Using this model, damage propagation and crack initiation, and ductile fracture behaviour of hemispherical punch bulging process are predicted. The model can quickly predict both deformation and damage behaviour of the part because of using plane stress algorithm, which is valid for thin sheet metals. Experiments are also carried out to validate the results. Comparison of the numerical and experimental results shows good adaptation. Hence, it is concluded that finite element analysis in conjunction with continuum damage mechanics can be used as a reliable tool to predict ductile damage and forming limit in sheet metal forming processes.

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Hydrodynamic Lubrication in Hemispherical Punch Stretch Forming

Journal of Applied Mechanics ◽

10.1115/1.3171778 ◽

1986 ◽

Vol 53 (2) ◽

pp. 440-449 ◽

Cited By ~ 9

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.

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

The Journal of Strain Analysis for Engineering Design ◽

10.1243/03093247v251015 ◽

1990 ◽

Vol 25 (1) ◽

pp. 15-20 ◽

Cited By ~ 1

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.

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ИССЛЕДОВАНИЕ ТОЧНОСТИ ДЕТАЛЕЙ, ПОЛУЧАЕМЫХ ПРИ РАЗДЕЛИТЕЛЬНЫХ ОПЕРАЦИЯХ В ПЕРЕНАЛАЖИВАЕМЫХ ШТАМПАХ

Open Information and Computer Integrated Technologies ◽

10.32620/oikit.2018.81.06 ◽

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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