Deflection Test Plan
and Results
T-F-001
Multidisciplinary Senior Design 1
Project 12007
Guide: Dr. Elizabeth DeBartolo
Objective: To determine the deflection of a 0.25” thick, 6061-T6 aluminum plate in order to compare to data gathered via simulations using SolidWorks software.
Failure Criteria:
1. Proposed plate design deflection must be half of the deflection of the current plate design or less.
2. No feeling of movement in the plate when stoop upon.
Equipment: 1. Dial Indicator
2. Four, 0.125” thick aluminum supports (1” x 1” square)
3. 165lb weight (A friend)
Test Set Up: 1. Center aluminum plate over the dial indicator plunger
- Indicator must measure the dead center of the plate where the plate will experience the greatest deflection
2. Place aluminum supports in each of the corners of the plate
3. Zero dial indicator once plate and supports are in place
Test: 1. Place weight (ask friend to set onto plate) in the center of the plate
2. Measure the deflection from the dial indicator
3. Remove weight (ask friend to set off of plate)
4. Re-zero the dial indicator
5. Repeat steps 1-4, 9 more times
Data:
Trial # / Plate Deflection (in)Thin Plate Design (t = 0.25”) / Current Plate Design (t = 0.375”) / Proposed Plate Design (t = 0.375”)
1 / 0.0510 / 0.0180 / 0.0290
2 / 0.0510 / 0.0190 / 0.0290
3 / 0.0505 / 0.0175 / 0.0290
4 / 0.0495 / 0.0170 / 0.0280
5 / 0.0515 / 0.0185 / 0.0280
6 / 0.0505 / 0.0180 / 0.0300
7 / 0.0515 / 0.0190 / 0.0295
8 / 0.0500 / 0.0180 / 0.0295
9 / 0.0520 / 0.0170 / 0.0280
10 / 0.0495 / 0.0175 / 0.0280
Avg / 0.0507 / 0.0181 / 0.0288
Conclusions:
The test showed an average deflection of 0.0507 inches for the thin plate, 0.0181 inches for the current plate, and 0.0288 inches for the propose plate when they were place under a 165lb load. It can be seen that the proposed plate design does deflect about 0.0200 inches more than the current plate. However, the proposed plate deflects about 0.0220 inches less than the thin plate. This is close to the failure criteria in that the proposed design was not to deflect more than 0.0250 inches. It is assumed that +/-0.003 inches is not detectable under one’s weight. Also, no noticeable deflection was felt by the test subject compared to testing the thinner plate. From this, the proposed plate design passes the failure criteria.
Some sources of error were experienced during testing. First, the plate itself is not perfectly flat and therefore did not sit on all the corner supports perfectly. As the weight was added, the plate most likely shifted on the supports and may have skewed the deflection measurements. Another error was the placement of the force on the plat. Although it was attempted, the test subject did not step onto the plate in the exactly spot every time. In addition to that, the subject admitted that more of their body weight was concentrated in their heel which could have caused the plate to deflect more in the back than the front.
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