Sheet Metal

Question 1

What is the objective for this lab?

Answer 1

The objective of this lab is to demonstrate the shearing and drawing processes and to investigate the formability of sheet metal. The lab will focus on understanding how the shape of the punch affects the strain on the sheet metal during the drawing process. Additionally, it aims to measure the formability of the sheet metal, specifically how it deforms during drawing without tearing or necking, using tests such as the Swift cupping test.

Question 2

What is the procedures for this lab? Part 1

Answer 2

Part 1: Shearing and Preparing Coupons
1. Setup the Shearing Die in the Press:

Mount the punch and die in the 50-ton press.
Secure the lower and upper dies using strap clamps.
Ensure alignment by adjusting the horizontal straps.

2. Shear Coupons:

Apply grease to the punch and die.
Insert the steel strip, align it, and press to shear the coupons.
Repeat to make 6 large and 6 small coupons.

3. Measure and Mark Coupons:

Measure thickness with Vernier calipers (avoid edge burrs).
Mark the center by scribing three diameter lines (120° apart).
Punch center points and create patterns using a template and spring clamp.

4. Prepare for Measurements:

Sand the coupon surface to smooth burrs and punch marks.
Use the Microscribe to measure distances between punched points:
Define the origin and axes using the Microscribe arm.
Record point coordinates in Excel for each coupon.

Question 3

What is the procedures for this lab? Part 2

Answer 3

Part 2: Drawing Process
5. Setup Tinius Olsen Press:

Turn on the press and let the hydraulic motor stabilize.
Replace any tensile test jaws with the appropriate drawing setup.

6. Drawing Coupons:

Grease both sides of a coupon and place it on the lower die.
Attach the pressure pad snugly (avoid over-tightening to prevent wrinkling).
Use the square punch to draw large coupons to a depth of 0.25 inches:
Record press force at 0.05-inch intervals until the coupon tears or the force drops.

7. Experiment with Variations:

Repeat the drawing process for:
Round punch on both large and small coupons.
Different speeds (2.25, 4.5, and 7 inches/min).
Observe depth at tearing and maximum press force.

8. Final Measurements:

Use Microscribe to remeasure distances on deformed coupons.
Calculate strains using the recorded data.

Question 4

What is the conclusion for this lab?

Answer 4

In this lab, we explored the importance of sheet metal formability by analyzing the shearing and drawing processes commonly used in industry. The results revealed a distinct pattern in drawing force, which initially increased linearly before decreasing as the material transitioned into the elastic region. Tangential and radial strains grew with distance from the coupon’s center, while thickness strain decreased, with its highest value observed at the punch’s center. Minor inaccuracies, likely due to human error, were noted. Additionally, slower punch speeds demonstrated better material control, reducing the risk of failure. Overall, this lab underscored the critical role of strain measurements in assessing the formability of sheet metal.

Question 5

Specific things to remember

Answer 5

50-ton Press for shearing (Part 1, Step 1).
Tinius Olsen Press for drawing (Part 2, Step 5).
Microscribe Arm for measuring distances (Part 1, Step 4; Part 2, Step 8).
Vernier Calipers for measuring thickness (Part 1, Step 3).

Different speeds (2.25, 4.5, and 7 inches/min).

Use the square punch to draw large coupons to a depth of 0.25 inches:
Record press force at 0.05-inch intervals until the coupon tears or the force drops.

Repeat to make 6 large and 6 small coupons.

Mark the center by scribing three diameter lines (120° apart).

Q: How do you ensure the strap clamps are properly aligned when mounting the shearing punch set?
A: Adjust the heel to make the strap horizontal before tightening.