Introduction to metalforming 1

METAL FORMING

Metal Forming refers to a group of manufacturing

methods by which the given shape of the workpiece (a solid

body) is converted to another shape without change in the

mass or composition of the material of the workpiece.

Introduction to metalforming 2

Characteristics of Deformation Methods

• The loads and stresses required for deformation are very high.

• The majority of the parts are completely deformed.

• Because of the high costs of machinery and tools

- High productivity and short production time

- High accuracy

- Good mechanical properties of the component

Introduction to metalforming 3

Example of parts produced by metal forming processes

METAL FORMING

Automobiles and Machine tools COMPONENTS

HAND TOOLS hammers, pliers, etc.

FASTENER screw, bolt, nut, rivet

CONSTRUCTION ELEMENT

pipe, roof

FITTING used in building construction

OTHERS

Introduction to metalforming 4

Classification

- According to the part produced

- According to the shape of raw materials PRIMARY PROCESS SECONDARY PROCESS

METAL FORMING

BULK FORMING PROCESS SHEET FORMING PROCESS

METAL FORMING

- According to the working temperature

HOT WORKING COLD WORKING WARM WORKING

METAL FORMING

Introduction to metalforming 5

BULK FORMING SHEET FORMING

SHEARING

BENDING

DEEP DRAWING

UPSETTING

FORGING

ROLLING

EXTRUSION

DRAWING STRETCH FORMING

SPINNING

Introduction to metalforming 6

Die open Die close

MACHINE

TOOL

Introduction to metalforming 7

Area 1 : Plastic Zone

Area 2 : Characteristic of the workpiece before deformation

Area 3 : Workpiece characteristic

Area 4 : Boundary area

Area 5 : Forming Tool

Area 6 : Surface reaction

Area 7 : Machine Tool

Area 8 : Auxiliary equipment

Introduction to metalforming 8

Mechanical Properties

Metallurgical Properties

Physical Properties

Properties of Deformed Materials

Flow curve

Yield strength

Ductility

Plastic strain ratio

Friction

Lubrication

Surface Roughness

Crystal Structure

Lattice Defect

Dislocation

Strain hardening

Introduction to metalforming 9

FLOW CURVE

0A

F s

A

F

0

01

l

l-l e

0

1

l

lln

Engineering stress

Engineering strain True stress

True strain

Introduction to metalforming 10

Example

A tensile specimen with a 12 mm initial diameter and 50 mm gage length reaches maximum load at 90 kN and fractures at 70 kN. The minimum diameter at fracture is 10 mm. Determine the engineering stress at maximum load (the ultimate tensile strength) and the true fracture stress. Determine the engineering strain at fracture and true strain at fracture.

Introduction to metalforming 11

Example

Determine the engineering strain, the true strain and the reduction in area for each of the following situations:

• Extension from L to 1.1L • Compression from h to 0.9h • Extension from L to 2L • Compression from h to 0.5h • Compression to zero thickness

The advantage of using true strain

Introduction to metalforming

12 Consider a uniform cylinder which is extended to twice its original length.

To achieve the same amount of negative linear strain in compression

Example 1

Example 2

The total true strain is equal to the sum of the incremental true strains.

Consider a rod initially 50 mm long that is elongated in 3 increments

Increment Length of rod (mm)

0 50

1 55

2 60.5

3 66.55

Introduction to metalforming 13

PLASTIC STRAIN RATIO (r)

ANISOTROPY FACTOR

strain Thickness

strainWidth = =

t

wr

Introduction to metalforming 14

4

2 = 90450 rrr

rm

2

r+2r-r = 90450r

*Ref.“Standard Test Method for Plastic Strain Ratio r for Sheet Metal” Annual book of ASTM standard vol.3 E 517-81