• Subject Code : 300597
• University : Western Sydney University
• Subject Name : Engineering

## Modelling and Simulation of Sheet Metal Forming Processes

### Introduction to Numerical Simulation of Metal Bending Process

Metal bending refers to a manufacturing process of bending of strip, sheet and plate. A metal is deformed after application of force, bending it to desired shape. This process is used to produce parts for different industries such as ships, railways, automobiles and aircraft. There are different types of bending processes but the most common bending process is V shaped die bending.

To bend metal sheet, a press brake tool (uses a punch or a die) is used. There are various types of press brakes such as

• Mechanical
• Pneumatic
• Hydraulic
• CNC

The conventional methods of manufacturing processes are casting, forming, cutting, joining, sheet metal forming, and deep drawing etc. A special case of sheet metal forming is deformation in which flat sheet of metals are converted into desired shape without fracture. Deformation process is used to produce majority of metallic parts. The shaping of material in solid state is known as forming process. It is a vital feature when material is subjected to deformation. A huge amount of energy is required in this process according to type of material, capital investment and expenditure. The material cross section stay same but its shape changes in sheet metal working operations. The tools (die and punch) are used to carry out operations on thin sheet (< 6mm). Forming depends on sheet kind, die and punch. The processes involve in sheet metal forming are bending, punching, drawing, stretching and some other processes. Generally, V-bending is selected for forming of metal sheet. During forming of sheet metal, the common issues are shape distortion, puckering and wrinkling, characterizing by a high ratio of surface area to thickness. There is no single test that indicates the accuracy of sheet metal forming operations as these operations are diverse in rate and type (Oliveira and Fernandes, 2019).

### Literature Review of Numerical Simulation of Metal Bending Process

Panthi, S.K. et al. performed finite element simulation to analyze elastic recovery in bending of sheet metal. He studied the impact of load on spring b reverse with changing die radius and thickness (B.Pati and Badhe, 2017).

Bahloul R.et al. used finite element simulation to predict punch load and distribution of stress during wiping-die bending process. Elastic plastic theory coupled with Lemaitre's damage approach was modeled with numerical simulation. Finite element simulation was carried out with ABAQUS. Response surface methodology (RSM) was used to predict punch load and distribution of stress.

The impact of friction forces under punch and blank holders was studied by Guo, Y.Q.et.al. They optimized deep drawing and initial blank contour (B.Pati and Badhe, 2017).

The effect of different on spring back (2D drawing bending) was studied by Papeleux, L.et.al.

The ability of Finite element simulations in order to forecast distribution of strain and blank shapes in sheet metal forming was investigated by Lee C.H.et.al. They devised an algorithm that can be applied to square cup, cylindrical cup drawing, and oil pan drawing. Their work and numerical simulations results were close to each other.

According to Karafillis, A.P. and Boyce, M.C., there is a requirement of proper design of binder and tooling shape together. To evaluate this manufacturing process, they used finite element methodology. The algorithm with input from finite element methodology was numerically designed. CNC machines was used to manufacture tooling. It was found that tooling was producing accurate parts which implies that finite element methodology was efficient.

The detail literature review regarding Finite element analysis in deep drawing optimization features was provided by Joshi, Patil and Satao. This article clearly highlighted the significance of Finite element analysis in metal bending process.

The various features of tube hydro forming process using Finite element analysis was optimized by Shinde, R.A., Patil, B.T. and Joshi, K.N.

Finite Element (FE) Method is the most common method that is applied for numerical simulation (Brünig, Gerke and Schmidt, 2017). Currently, the widely used programs for simulation of sheet metal forming are

• AutoForm Incremental.
• PamStamp (core is from Dyna public, it is an original FE program). ESI group developed PamStamp.
• LS-Dyna and DynaForm (core is from PamStamp but Livermore Software developed it)

The same input data is required by all programs. VDA or IGES format is used for input of component surface geometry and the metal sheet. Special functions in the programs are used to build tool surfaces geometry. There is another method in which tool surfaces are built in any 3DCAD program and then import it to numerical software. In numerical simulation, it is assumed that tool is entirely rigid as compared to sheet metal. Therefore, the surfaces of the tool that interact in forming process are required to be imported.

The material data needed for numerical simulation are

• Friction coefficient
• Specific mass density
• Poisson’s number
• Strain-hardening curve parameters according to material type
• Material law parameters according to material type
• Young’s modulus
• Forming limit curve parameters according to material type

The simulation is performed after creation of simulation model with the following steps

• Gravity is applied in order to attain deformation or shape of metal sheet when set on binder
• Forming process is the first step to close binder. Binder move towards die and it forces sheet against die.
• Drawing, punch moves down in die and simulates the forming process
• Trimming, component is separated from scrap
• Spring back, the surfaces of tool are removed and the strain elastic part of the component could relax

### Methodology of Numerical Simulation of Metal Bending Process

The following three sheets will be used for Finite Element Analysis in ANSYS

Aluminum:

Aluminum is a silver gray metal and has the lowest density. It is ductile. The extraction of Aluminium from ores is difficult but it forms strong bonds and the strength of aluminium is high. These properties of aluminium make it to be used in various sectors. The analysis of aluminium type of sheet metal will be performed and various parameters are analyzed after application of 115 N force. For forming process, the sheet metal of 240X65X1 mm dimension will be used. The properties of this metal are

Density (g/cc) 2.7

Ultimate Tensile strength (MPa) 45

Yield Tensile strength (MPa) 18

Poisson’s ratio 0.35

Young Modulus (MPa) 70000

B.Mild steel:

The most common form of steel is mild steel. It exhibits low-tensile strength. After application of force of 105 N, static analysis on mild steel sheet metal will be done and various parameters are analyzed. For forming process, the sheet metal of 240X65X1 mm dimension will be used. The properties of this metal are

Density (g/cc) 7.9

Ultimate Tensile strength (MPa) 420

Yield Tensile strength (MPa) 350

Poisson’s ratio 0.25

Young Modulus (MPa) 210

C.Stainless Steel of Type 303:

Stainless steel is also called inox steel. The different between carbon steel and stainless steel is that they have different weightage of chromium in both metals. For forming process, the sheet metal of type 303 will be used after application of force of 260 N and various parameters are analyzed. The properties of this metal are

Density (g/cc) 8

Ultimate Tensile strength (MPa) 690

Yield Tensile strength (MPa) 415

Poisson’s ratio 0.25

Young Modulus (MPa) 210

#### ANSYS (Finite Element Analysis)

The model of die, punch and sheet metal will be drawn in SolidWorks. Then, this arrangement is meshed and refined. After arranging the set up in required format, different metal sheets will be placed and then subjected to forces. The required parameters are calculated by placing sheet metal on 70oV-dieV-metal. UTM is used to calculate forces after deforming type of each sheet. For calculation of parameters, static analysis will be performed using ANSYS V12 (Abhinav and Annamalai, 2013).

After application of fixed support on base die punch and force on punch (that acts vertically downward), a sheet metal is deformed. The analysis of the required parameters is needed. The required parameters are

• Deformation
• Maximum principal elastic strain
• Equivalent stress and maximum principal stress

### Results of Numerical Simulation of Metal Bending Process

The graphs of required parameters will be plotted and comparison is conducted.

• Maximum normal stress of stainless steel, mild steel and aluminum will be plotted on graph and analyze which metal has highest maximum normal stress and compare them with analytical results.
• Total deformation of stainless steel, mild steel and aluminum will be plotted on graph and analyze which metal has highest total deformation and compare them with analytical results
• Maximum principal elastic stress of stainless steel, mild steel and aluminum will be plotted on graph and analyze which metal has maximum principal elastic stress and compare them with analytical results
• Equivalent stress of stainless steel, mild steel and aluminum will be plotted on graph and analyze which metal has highest equivalent stress and compare them with analytical results
• Maximum principal stress of stainless steel, mild steel and aluminum will be plotted on graph and analyze which metal has maximum principal stress and compare them with analytical results

### References for Numerical Simulation of Metal Bending Process

Abhinav, K. and Annamalai, K., 2013. Analysis of sheet metal bending by using Finite Element Method. International Journal of Engineering Research & Technology (IJERT), 2(1).

Brünig, M., Gerke, S. and Schmidt, M., 2017. Experiments and numerical simulation of stress-state-dependent damage in sheet metal forming. Journal of Physics: Conference Series, 896, p.012077.

B.Pati, N. and Badhe, S., 2017. Review of Finite Element Simulations in Sheet Metal Forming Processes. International Research Journal of Engineering and Technology (IRJET), 4(5).

Oliveira, M. and Fernandes, J., 2019. Modelling and Simulation of Sheet Metal Forming Processes. Metals, 9(12), p.1356.

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