P19432: Murphy's Stage
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# Build & Test Prep

### Team Vision for Build & Test Prep Phase

What we planned to do:

• Make updates to Risk Management, Project Plan, and individual plans for week 6 subsystem demo.
• Complete Test Plan and start problem tracking system

What did we actually do:

• Continually populated problem tracking, risk management, and test plans
• Design optimizations
• BOM refinement and sourcing
• Preparations for machining
• Work with Interior Design Department on stage aesthetics

## Project Plan

Preliminary Gantt Chart for all of MSD II

A link to the live Gantt chart document can be viewed here

## Test Plan Summary

Example of Test Plan

The test plans encompassed both our engineering requirements and additional testing to ensure the stage functions beyond the given requirements. These included:
• Testing the stage's acoustic properties
• Testing the stage under abnormal loading conditions to check for potential binding
• Testing the stage with uneducated users to observe how the setup process is followed intuitively

The full slate of tests can be viewed in the spreadsheet linked below. View live test plan here.

## Analysis

Analysis was formally derived for to ensure the concrete bolts will not pull through the concrete.

Assumptions:

• The strength of the concrete is rated to 4000 psi and is not significantly worn or cracked.
• The pullout force of the concrete bolts is 1,100 lbs. This comes from the datasheet on McMaster-Carr.
• Wooden 4x4s are sufficiently ridged to distribute the force from the gas springs evenly over all concrete anchor brackets

Below is a diagram depicting the free body diagram of the structure anchored into the concrete.

Concrete anchor structure diagram

The equations below show the process of determining the force associated with the loading condition induced by the gas springs. Where:

• n(posts) is the number of 4x4 posts
• n(gs) is the number of gas springs
• n(bolts) is the number of bolts per side of the concrete anchor bracket to prevent tipping. This value is 2 since there are 4 bolts in total (2 on each side)
• M(post) is the moment at the base of the post induced by the gas springs
• F(gs) is the force induced by the gas springs
• h is the height of the 4x4

Concrete anchor equations

The factor of safety is 3.42 which is safe for our application.

The stage should withstand a load of 150 lbf over the entire surface. Please see "Detailed Design" phase for this analysis.

A concentrated load on a flooring surface according to the 2018 International Building Code is the maximum load that surface should be expected to withstand if the load is evenly distributed over a 2.5' x 2.5' area. This analysis was performed using ANSYS Classic and the results and inputs can be seen in the table below.

The yield strength of aluminum is 37,000 psi and the Inverse Tsai-Wu criterion estimates the inverse of the safety factor for the sandwich structure.

• A factor of safety of 1 is achieved at 3000 pounds which is equivalent to flooring in a heavy manufacturing scenario.
• A factor of safety of 2 is achieved at 1300 pounds. No more weight than 1300 pounds is recommended on this stage on a concentrated area

Below are the results of the inverse Tsai-Wu failure criterion as well as stage deflection. At 1500 pounds, the stage deflects 0.118 inches.

Concentrated Load Stage Deflection at 1500 pounds over Worst Case Area

## Risk and Problem Tracking

Updated Risk Management as of 1/23/19

#### Problem Tracking

A live problem tracking document was created to aid the team in the management of problems that arise during MSDII. Each problem goes through 6 stages:

1. Identifying and selecting problem
2. Analyzing problem
3. Generating potential solutions
4. Selecting and planning solution
5. Implementing solution
6. Evaluating solution

As problems come up they are added to the list and evaluated as the team moves through the problem stages. This helps the team to stay organized and recognize which problems have been addressed and which ones need to be addressed.

View live problem tracking here.

View live risk management here.

## Plans for next phase

Individual 3 week plans: