Spot Weld Mechanical Properties 3

Impact Testing

Mechanical Properties 3

Lesson ObjectivesWhen you finish this lesson you will understand:• Impact Mechanical testing techniques• Factors which effect performance in Impact tests• The importance of these test for part design

Learning Activities1. View Slides; 2. Read Notes, 3. Listen to lecture4. Do on-line

workbook

KeywordsImpact Test, Ductile-Brittle Transition, Tensile Shear Impact Test, Direct Tension Impact Test

Mechanical Properties of Spot Welds

• Peel Tests• Chisel Test• Tensile Test• Tensile Shear Ratios• Torsion Test• Impact Tests• Fatigue Test

Impact Testing of Tensile Shear Samples

Low Temp Ductile to Brittle Temp Fine “Evaluation of a new, Dua Phase..”SAE Paper 780136, Fgeb 1978

Bibber, “Spot Weldability of Low Carbon and other Aircraft Steels”,Welding Journal, Dec 1943

Effect of Sheet Size on Impact Test Results

Pollard, “Spot Welding Characteristics of HSLA Steel..”,Weldign Journal, Aug 1974

Effect of SheetThickness on Impact ResultsTensile ShearSamples

Tensile Shear Direct Tension

Sawhill, “Spot Weldabiloity of High Strength Steels”,Welding Journal, Jan 1980

Effect of Nugget SizeOn Impact Test ResultsComparison of Test Samples

Effect of Weld Time (for same nugget diameter)

Increased weld time may have resulted in nugget softening

Unger “Behavior of Spot Welds Under Impact”Welding Journal, 1942

Effect of Hold TimePlain Carbon Steel

No Effect on Tensile Shear

Slight DecreaseIn Impact EnergyFor Cross Tension

No Similar Data Found for Other Materials

Dinsdale “A Comparison of Static and Impact Strength…”Sheet Metal Industries, Aug 1977

Dinsdale “A Comparison of Static and Impact Strength…”Sheet Metal Industries, Aug 1977

Hess “Spot Welding of SAE…”Welding Journal, Oct 1943

Effect of Chemistry

0.1 –0.2 Carbon Steels0.2 – 0.5 Carbon Steels

Effect of Chemistry - 40 ksi HSLA different microalloy

Ti free = Higher ImpactPartial Nugget Failure = Higher Impact

Fine “Spot Weldability of High Strength..”SAE Paper 790005, Feb 1979

Effect of Material Strength

IncreaseStrength

Bibber “The Spot Weldability of Low Carbon..”Welding Journal, Dec 1943