Development of Weld Strength Testing Protocol

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Development of Weld Strength Testing Protocol

• Jason Harwood
• Advisors Dr Edward Morse, Brian Dutterer

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Project Overview

• Design a welding test for the Mechanical
  Engineering/Motorsports program
• Allow for evaluation of student welding abilities
• Visual inspection of welds
• Strength testing
• Based on existing national standards

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Basic Welding Gas

• Oxyacetylene Welding
• Heat comes from burning oxygen and acetylene
• Requires two gas tanks, torch
• Requires separate filler material to be added

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Basic Welding Electric

• MIG (Metal Inert Gas) welding
• Electrical arc forms between work and electrode
• Filler metal is fed in as a wire
• Shielding comes from coating on wire

Image courtesy www.earlbeck.com/Training20Catal
og.htm
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Basic Welding Electric

• TIG (Tungsten Inert Gas) welding
• Electrical arc again provides heat
• Tungsten electrode is not consumed
• Shielding comes from argon gas blowing past
  tungsten

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Why Welding?

• Welds can be as strong, or stronger than original
  material
• Requires no extra fixtures for components
• Very flexible in position and joint styles

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UNCC Motorsports Welding Uses

• Vehicle construction
• Roll cages and pickup points for Formula SAE,
  Baja teams
• Vehicle repair/maintenance
• Legends cars bumpers, Formula/Baja chassis
  modifications/repairs
• Student project assistance
• Helping with design projects, personal projects

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Step 1 Identifying the Needs

• Identifying needs of the program
• Primarily TIG welds
• Clean, precise welds
• Welder and filler metal readily available in shop
• Steel and aluminum welding both used
• Strong, consistent welds
• Able to withstand chassis flex, cornering loads,
  impacts

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Step 1 Identifying Resources

• Identifying existing welding standards
• ASME welding standards
• School equipment for tests
• Load frame
• Hardness tester
• Radiography
• Faculty Welding Experience
• Brian Dutterer

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Step 2 Understanding Welding

• Learning to weld
• Began basic TIG welding
• Using metal coupons, with and without filler
  metal
• Became familiarized with what to look for while
  welding

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Step 3 Establishing Test Criteria

• Evaluations based on ASME Boiler and Pressure
  Code, Section IX 1992 Edition
• Outlines all welding and brazing standards
• Three most common welds performed by students
• Aluminum (mainly plate)
• Steel plate
• Steel tube

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Step 3 Establishing Test Criteria

• Tailoring ASME code to UNCCs needs
• Code requires numerous positions and test
• Many uneconomical or not applicable
• Radiography machine resources couldnt be
  coordinated during project
• Readily available tests
• Tensile strength
• Bending
• Visual inspection

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Step 4 Tools for Testing

• Build fixture for steel tube welding
• ASME calls for tubing not to be rotated during
  test
• Simple fixture devised from steel plate, rod and
  aluminum rod

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Step 4 Tools for Testing

• Jig for guided bend test
• Allows for welds to be bent and stretched
• Shows cracks or lack of penetration in weld

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Step 4 Tools for Testing

• Tensile strength test
• Use load frame on second floor
• Machine weld area to 1/8 in2 area at weld
• Steel should hold 60-70 ksi, weld material rated
  to hold 80
• Sample should at least be as strong as original
  specifications
• Breaks not at the weld, and within 10 of
  original material strength, are acceptable

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Step 5 Finalizing the Test

• Part 1 Steel Plate Test
• Open groove, butt weld two steel coupons, each 5
  X 6.5
• Joint style requires gap between coupons, making
  weld more difficult than flush plates

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Step 5 Finalizing the Test

• Part 2 Steel Tube Test
• Weld 360o around 1 O.D., .065 wall thickness,
  cold worked steel tube (similar to chassis
  tubing)
• Piece is cut into 4 pieces, pieces are then
  pulled in load frame

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Step 5 Finalizing the Test

• Part 3 Aluminum Plate Test
• Butt weld Aluminum plate, 1/8 thick, 3000 series

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Accomplishments

• Learned basic TIG welding
• How welds should look during and after process
• Tweaking machine and heat to get proper heat
• Established basic welding test
• Covers most common materials used in shop
• Test gives quantitative and qualitative results

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Future Projects/Ideas

• Finish guided bend jig
• Explore radiography testing
• Hardness testing

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Lessons Learned

• Time Management
• Most tasks take twice as long as expected
• Nothing can take the place of money and materials
• Basic research structure
• Importance of following basic scientific method

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Acknowledgements

• James Phipps, Will Scotton, and Grant Cameron for
  welding tips
• Gary Hodgkin for load frame assistance