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.

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.

Numerical Simulation of the Effect of Punch Paths on the Quality of Sheet Metal Stretch Forming

2012 ◽  
Vol 217-219 ◽  
pp. 2002-2005
Author(s):  
Chang Jiang Wang ◽  
Diane J Mynors ◽  
Tarsem Sihra
Keyword(s):  
Numerical Simulation ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Finite Element Modelling ◽  
Metal Strip ◽  
Stretch Forming ◽  
Forming Quality ◽  
Element Modelling

Presented here is the simulation of uniaxial stretch forming using two punches in a sheet metal forming operation. In the finite element modelling, the sheet metal strip was held by two bank holders and two punches are able to move in two directions to stretch the sheet metal. Due to the friction between the punch and sheet metal, it was found that friction affects the sheet metal forming quality, however by adopting an optimal punch path the effect of friction in sheet metal forming can be reduced. The effect of punch paths on the quality of the sheet metal are also reported in this paper.

Bending and Stamping Processes of FSWed Thin Sheets in AA1050 Alloy

2014 ◽  
Vol 622-623 ◽  
pp. 459-466 ◽  
Author(s):  
Michela Simoncini ◽  
Lorenzo Panaccio ◽  
Archimede Forcellese
Keyword(s):  
Mechanical Properties ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Preliminary Investigation ◽  
Thin Sheets ◽  
Microstructural Investigation ◽  
Bending Tests ◽  
Friction Stir ◽  
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.

A Finite Element Based Die Design Algorithm for Sheet-Metal Forming on Reconfigurable Tools

2000 ◽  
Vol 123 (4) ◽  
pp. 489-495 ◽  
Author(s):  
Simona Socrate ◽  
Mary C. Boyce
Keyword(s):  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Design Procedure ◽  
Die Design ◽  
Tool Geometry ◽  
Stretch Forming ◽  
Design Algorithm ◽  
Die Surface

Tooling cost is a major contributor to the total cost of small-lot production of sheet metal components. Within the framework of an academic/industrial/government partnership devoted to the development of a reconfigurable tool for stretch forming, we have implemented a Finite Element-based procedure to determine optimal die shape. In the reconfigurable forming tool (Hardt, D. E. et al., 1993, “A CAD Driven Flexible Forming System for Three-Dimensional Sheet Metal Parts,” Sheet Metal and Stamping Symp., Int. Congress and Exp., Detroit, MI, SAE Technical Paper Series 930282, pp. 69–76.), the die surface is created by the ends of an array of square pins, which can be individually repositioned by computer driven servo-mechanisms. An interpolating polymer layer is interposed between the part and the die surface to attain a smooth pressure distribution. The objective of the die design algorithm is to determine optimal positions for the pin array, which will result in the desired part shape. The proposed “spring-forward” method was originally developed for matched-die forming (Karafillis, A. P., and Boyce, M. C., 1992, “Tooling Design in Sheet Metal Forming using Springback Calculations,” Int. J. Mech. Sci., Vol. 34, pp. 113–131.; Karafillis, A. P., and Boyce, M. C., 1996, “Tooling And Binder Design for Sheet Metal Forming Processes Compensating Springback Error,” Int. J. Tools Manufac., Vol. 36, pp. 503–526.) and it is here extended and adapted to the reconfigurable tool geometry and stretch forming loading conditions. An essential prerequisite to the implementation of the die design procedure is the availability of an accurate FE model of the entire forming operation. The particular nature of the discrete die and issues related to the behavior of the interpolating layer introduce additional challenges. We have first simulated the process using a model that reproduces, as closely as possible, the actual geometry of the discrete tool. In order to optimize the delicate balance between model accuracy and computational requirements, we have then used the information gathered from the detailed analyses to develop an equivalent die model. An automated algorithm to construct the equivalent die model based on the discrete tool geometry (pin-positions) is integrated with the spring-forward method, to generate an iterative die design procedure that can be easily interfaced with the reconfiguring tool. The success of the proposed procedure in selecting an optimal die configuration is confirmed by comparison with experimental results.

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

2011 ◽  
Vol 110-116 ◽  
pp. 1437-1441 ◽  
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.

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.

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