P18351: Sandia Passive Vacuum Detection Team A
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Subsystem Build & Test

Table of Contents

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Team Vision for Subsystem Level Build & Test Phase

Summarize: In this phase, our team set out to complete the following:
  1. Pressure testing for repeatability
  2. Finalize vibration testing requirements and have test completed
  3. Locate centrifuge apparatus to complete continuous G-Force testing

We were able to accomplish:

  1. Pressure testing for repeatability with rudimentary characterization of diaphragm behavior
  2. Make appropriate design improvements according to design requirements and testing results

We are working with Delphi in order to better understand the scope of their vibration and G-force testing. Testing of full prototype is expected within weeks.

Test Plan and Setup

Diaphragm Testing

A small hand pump was used to pressurize the sealed vessel. A pressure sensor was used to monitor the internal pressure, while a dial indicator was used to measure the total deflection of the diaphragm. A complete test system setup is shown in the image below.
Diaphragm Testing Setup

Diaphragm Testing Setup

Test Plan

  1. Bolt switch and diaphragm housings together
  2. Place assembly on rigid support
  3. Connect air hose to all three exits of a T-quick disconnect fitting.
  4. Connect 1 hose to the QD fitting on the diaphragm housing, 1 into the pressure sensor, and 1 into the outlet of the check valve
  5. Connect hand pump to inlet of check valve with air hose
  6. Pump a small amount of air into the system and observe the pressure reading to check for leaks. If pressure drops, take measures to ensure that all fittings are leak-proof
  7. Relieve pressure from the system
  8. Place dial indicator tip on center of un-deformed diaphragm
  9. take initial dial indicator reading
  10. Increase pressure with hand pump to desired pressure value
  11. Record pressure value and diaphragm deflection
  12. Relieve pressure from the system and record ending diaphragm deflection. This measurement will also serve as the beginning measurement for the next test
  13. Repeat steps until desired number of tests have been completed

Switch Testing

A micrometer was used to determine the activation point and repeatability of our snap action switch. The switch plunger was depressed using the micrometer, and the activation reading was recorded with reference to a known datum. This measurement will be used to accurately place our switch on our final design so that the activation points lines up precisely with the total diaphragm deflection.

Switch Testing Setup

Switch Testing Setup

Test Results Summary

Diaphragm Testing

Testing Results

Testing Results

From our preliminary testing, we are able to roughly characterize the deflection of our diaphragm in relation to pressure. We can use this characterization to get an idea of our deflection distances to set up for more robust vacuum testing.

Switch Testing

Switch Activation Measurements

Switch Activation Measurements

From testing of out switch we found that the switched activated at the same exact distance for every trial. We are confident that the activation distance from our datum is 0.501 in.

Updated Design

Updated Design

Updated Design

A big design change is the removal of a large amount of material on the back of the assembly casing. This allows for plenty of air flow in the open atmosphere side of our assembly. It also opens up a flat, rigid surface for the switch to be mounted on.

Risk and Problem Tracking

Risks

Risks

Problem Tracking

Problem Tracking

Functional Demo Materials

Include links to:

Plans for next phase

For the next phase, we would like to have all dimensions finalized. All vacuum testing will be completed and an accurate relationship will be developed for deformation distance of the diaphragm in order for this to occur. Vibration and g-force testing will be done within the next 3 weeks as well.


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