High-Speed Tensile Teste

Team: Blair Fairbanks, Spencer Kenison, Katherine Odell, Karter White

Sponsor: Autoliv

What is the High-speed Tensile Tester?

Autoliv designs airbags that open at high speeds to protect passengers. Regular tensile testing instrumentation exists to test fabric and threads at low speeds, but little numerical data is known about the stress & strain performance of airbag threads in high speed and high stress environments. This project aims to collect data to better understand the performance of airbag thread put under high load at speeds of up to 100 m/s (224 mph).

Timeline

Timeline read from top-down: Develop SOw Sept 24, Oct 24, Proof of Concept, Preliminary Design Review, Nov 24, Critical Design Review, Dec 24, Jan 26, Build Phase, Feb 26, Test Phase, Mar 26, Delivery, Apr 26

Testing and Performance

  • Numerical simulations used to predict system performance.
  • Low-speed tensile testing to validate pneumatic system.
  • Testing at range of pressures to analyze pressure/velocity relationship.
  • System review to ensure system met physical requirements.
Requirement Target Threshold Predicted Actual
Extension rate 100 m/s 50 m/s 95 m/s 25 m/s
Speed accuracy +/- 5 m/s +/- 10 m/s +/- 2 m/s +/- 10 m/s
Extension accuracy +/- 5% +/- 10% +/- 0.19% +/- 1%
Force accuracy +/- 5% +/- 10% +/- 10% +/- 3.4%
Data points 50+ 30+ 35 5
Elongation limit 75% 50% 100% 75%
Total cost $5000 $7000 $5,578 $3389
Cost per cycle $10/cycle $15/cycle $1.03 $9.40
Cycle time 2 min 3 min 2.42 min 3.45 min
Part sourcing 80% COTS 50% COTS 88% COTS 94% COTS
Assembly Length 12 ft N/A 11 ft 8 in 13 ft 5 in
Analysis Results graph
Test Results graph

Major Subsystems

The high-speed tensile tester uses a pneumatic propulsion system with a quick-release piston valve to pull the thread sample at high speeds. A moving gripping mechanism holds and rapidly pulls one end of the thread sample. Stress data is recorded using a strain gauge load cell with strain data collected by an ultrasonic sensor. Collected data is fed into a NI myDAQ which interfaces with a python script for data analysis. The fast-moving thread grip is slowed by a magnetic braking system after the thread breaks.

Data Collection System

Data Collection System, read left to right: Coputer (Python), Ni myDAQ, (branches) (top-branch) Load Cell Amplifier, Load Cell. (bottom-branch) Ultrasonic Sensor
Labeled model diagram. Moving clockwise from the top left-hand side: Magnetic Braking System, Load Cell, Pneumatic Propulsion System, Ultrasonic Sensor, Moving Grip

Looking Forward

Prototype laying on the ground inside of the Metal factory

Results: As desired, the prototype high-speed tensile tester demonstrated the viability of a pneumatic propulsion system and magnetic braking system. The design also demonstrated low-cost PVC and instrumentation were not suitable for high-speed tensile testing

Lessons Learned: Manufacturability must be considered when creating a mechanical design. Buffer time to resolve issues should always be built into project schedules.

Future Work: For more consistent high-speed testing at increased speeds, the prototype should be rebuilt with high-pressure steel piping, proper instrumentation, and a reinforced Lexan safety enclosure.

Acknowledgements:

The team would like to thank the following people for their support: Quinn Soderquist, Young Jung, and the Autoliv OTC team.