23. Lower penetration is required for shearing the sheet of
a. Harder and thicker metal
b. Softer and thinner metal
c. Harder and thinner metal
d. Softer and thicker metal
Answers
Answer:
Sheet metal process unit 4 notes
1. Sheet-Metal Forming Processes COMPILED BY M.BALASUBRAMANIAN
2. Metal Characteristics affecting Sheet Metal Processing • Elongation- Determines the capacity of the sheet metal to be stretched without failure • Anisotropy - Different behavior at different planar directions • Grain Size - Grain size determines the mechanical properties of the material • Residual Stress - Since this being a cold working process, residual stress may lead to distortion or cracking. • Spring Back - Elastic recovery of a plastically deformed work piece • Wrinkles - If the w/p is not clamped properly or clearance is not provided, wrinkles may occur
3. Basic Types of Sheet Metal Processes 1. Cutting – Shearing to separate large sheets – Blanking to cut part perimeters out of sheet metal – Punching/ Piercing to make holes in sheet metal 2. Bending – Straining sheet around a straight axis 3. Drawing – Forming of sheet into convex or concave shapes
4. Various Sheet Metal Forming Process • Roll Forming • Stretch Forming • Drawing • Stamping • Rubber Forming • Spinning • Super Plastic Forming • Peen Forming • Explosive Forming • Magnetic Pulse Forming
5. Shearing • Shearing is a process for cutting sheet metal to size out of a larger stock such as roll stock. • Shears are used as the preliminary step in preparing stock for stamping processes, or smaller blanks for presses • Name the three phases in shearing i) Plastic deformation ii) Penetration iii) Fracture
6. EMU Shearing of sheet metal between two cutting edges: (1) just before the punch contacts work; (2) punch begins to push into work, causing plastic deformation; Shearing of sheet metal between two cutting edges: (3) punch compresses and penetrates into work causing a smooth cut surface; (4) fracture is initiated at the opposing cutting edges which separates the sheet. Sheet Metal Cutting - Shearing
7. EMU Blanking and Punching Blanking - sheet metal cutting to separate piece (called a blank) from surrounding stock Punching - similar to blanking except cut piece is scrap, called a slug (a) Blanking and (b) punching.
8. Punching and Piercing • A slug (the material punched out) is produced in punching operations but not in piercing work • Piercing is “forming a hole in sheet metal with a pointed punch with no metal fallout (slug).” • In this case, a significant burr or deformed sharp edge is created on the bottom side of the material being pierced. EMU PIERCE PUNCHES
d. Softer and thicker metal.