03-09-2012, 03:33 PM
METAL FORMING
METAL FORMING.ppt (Size: 2.22 MB / Downloads: 87)
Large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces
The tool, usually called a die, applies stresses that exceed yield strength of metal
The metal takes a shape determined by the geometry of the die
Stresses in Metal Forming
Stresses to plastically deform the metal are usually compressive
Examples: rolling, forging, extrusion
However, some forming processes
Stretch the metal (tensile stresses)
Others bend the metal (tensile and compressive)
Still others apply shear stresses
Material Properties in Metal Forming
Desirable material properties:
Low yield strength and high ductility
These properties are affected by temperature:
Ductility increases and yield strength decreases when work temperature is raised
Other factors:
Strain rate and friction
Bulk Deformation Processes
Characterized by significant deformations and massive shape changes
"Bulk" refers to workparts with relatively low surface area‑to‑volume ratios
Starting work shapes include cylindrical billets and rectangular bars
Sheet Metalworking
Forming and related operations performed on metal sheets, strips, and coils
High surface area‑to‑volume ratio of starting metal, which distinguishes these from bulk deformation
Often called pressworking because presses perform these operations
Parts are called stampings
Usual tooling: punch and die
METAL FORMING.ppt (Size: 2.22 MB / Downloads: 87)
Large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces
The tool, usually called a die, applies stresses that exceed yield strength of metal
The metal takes a shape determined by the geometry of the die
Stresses in Metal Forming
Stresses to plastically deform the metal are usually compressive
Examples: rolling, forging, extrusion
However, some forming processes
Stretch the metal (tensile stresses)
Others bend the metal (tensile and compressive)
Still others apply shear stresses
Material Properties in Metal Forming
Desirable material properties:
Low yield strength and high ductility
These properties are affected by temperature:
Ductility increases and yield strength decreases when work temperature is raised
Other factors:
Strain rate and friction
Bulk Deformation Processes
Characterized by significant deformations and massive shape changes
"Bulk" refers to workparts with relatively low surface area‑to‑volume ratios
Starting work shapes include cylindrical billets and rectangular bars
Sheet Metalworking
Forming and related operations performed on metal sheets, strips, and coils
High surface area‑to‑volume ratio of starting metal, which distinguishes these from bulk deformation
Often called pressworking because presses perform these operations
Parts are called stampings
Usual tooling: punch and die