INSTRON Testing - Bending from Drag/Lift, Shear Force

Objectives

  • Understand how defects in previous fin cans impact overall strength 

  • Reference for making a 6” fin can for future spaceshot rocket

  • Future comparison to aluminum fin can


Heuristic Moment Comparisons 

 

 

Hermes III

Phoenix

Max. Q

9160 lb/ft^2

2735 lb/ft^2

Fin Area

0.392 ft^2

0.128 ft^2

Product

3588 lb

349 lb

 

Risks

  • Unfamiliarity with derivation and analysis

    • get trained! Go over procedure before actual testing to avoid having to test over and over again

  • Compatibility of INSTRON with setup

    • Communicate with Pierce to make necessary modifications

 

 

Bending Jig

INSTRON applies load on the faces of the fins that mimics moments from drag and lift

Fin can unconstrained around mandrel

Testing Procedure

  • Test in 10% load increments through proof load

  • Observe deformation throughout 

    • Stress strain curve 

    • Video 

Risks
 

  • Fin itself bending or twisting

    • Calculate distance from fillet to bend fixture 

    • Make sure bend fixture spans the length of the fin

  • Uneven application of loads

    • Account for jig, differences in manufacturing, testing 2 fins at once

    • Observe and take video to see if anything else deforms




 

Drag Jig

INSTRON clevis attaches to leading edge and pushes down to mimic shear from drag

Fin can unconstrained around mandrel

Testing Procedure

 

  • Test in 10% load increments through proof load

  • Observe deformation throughout 

    • Stress strain curve 

    • Video 


Risks
 

  • Load not well distributed / twisting / slipping

    • Revise jig edge / clevis setup 

    • Observe and take video to see if anything else deforms

  • Off-axis → base plate taking load

    • Can’t test to failure 

    • Proof load small tests 

    • Create bigger design to center the fin can and press on all 4 fins

 

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