1. Spot Weld Mechanical Properties 2 Cross Tension Ductility Ratio Torsion Test

2. Mechanical Properties 2 Lesson Objectives When you finish this lesson you will understand: Cross Tensile and Torsion Mechanical testing techniques Factors which effect performance in these mechanical tests The importance of these test for part design Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook 5.Do Homework Keywords Cross Tensile Test, Ductility Ratio, Torsion Test, Twist Angle

3. Mechanical Properties of Spot Welds Peel Tests Chisel Test Tensile Test – Tensile Shear Tensile Test - Cross Tension Tensile Shear Ratios Torsion Test Impact Tests Fatigue Test

4. Dickinson, “Welding in Auto Industry, AISI, 1981 Direct Tension Testing

5. Tensile Shear Material Thickness on Direct Tension Heuschkel, “Some Metallurgical Aspects…” Welding Journal, Oct 1947 Higher Carbon Material lower Strength Because Brittle Nuggets

6. Effect of Weld Current (Sheet Thickness) On Cross Tension Tensile Shear Pollard, “Spot Welding Characteristics…” Welding Journal, Aug 1974

7. Effect of Nugget Size (Current) Small Nugget Interfacial Tearing Strength Determined By Nugget Size Strength Determined By Weld Ductility Above Expulsion Erratic Behavior

8. Effect of Weld Time Low Current Intermediate Current High Current High Currents = increase heat input to HAZ reducing cooling rate so that less hard martensite present Thus peak may be chemistry dependent Increase in time = larger nuggets thus higher direct tensile strength

9. Effect of Hold Time - Direct Tension Tensile Shear The More the Interfacial Mode The lower the Direct Tensile Strength Note Difference between Tensile Shear and Direct Tensile Sawhill, “Spot weldability for High Strength Steels”, SAE 810352, Feb 1981

10. Effect of Carbon Content Tensile Shear Note Difference between Tensile Shear and Direct Tension Heuschkel, “The Expression of Spot Weld Properties”, Weldign Journal, Oct 1952

11. Effect of Steel Cleanliness Small Nugget Interfacial Tearing Strength Determined By Nugget Size Strength Determined By Weld Ductility Above Expulsion Erratic Behavior Lamellar Type Tears 50% lower

12. Effect of Base Metal Strength Slightly Raises Cross Tension Strength Small Nugget Interfacial Tearing Strength Determined By Nugget Size Strength Determined By Weld Ductility Above Expulsion Erratic Behavior Lamellar Type Tears 50% lower Yamauchi, “Spot Weldability of High …” IIW III-644-80, 1980

13. Effect of Post Weld Temper

14. Upslope/Downslope, Hold Time, & Temper Weld Current Temper Current Electrode Pressure Current Squeeze Time Weld Time Off Time Hold Time Upslope Downslope Temper

15. Temper Improvement Degradation

16. Analytical Approach Heuschkel, J. “The Expression of Spot Weld Properties”, Welding Journal, Oct. 1952

17. Mechanical Properties of Spot Welds Peel Tests Chisel Test Tensile Test Tensile Shear ( Ductility) Ratios Torsion Test Impact Tests Fatigue Test

18. Balasubramanian, S. et al “Improvement of Resistance Spot Weld Characteristics”, Welding Research Abroad, Nov 1978 Pollard, B., “Spot Weldability of HSLA Steels”, ASM/ADDRG Seminar on the Application of High-Strength-to-Weight Metals for Automotive Components, Nov 1974.

20. Heuschkel, J. “Some Metalurgical Aspects of Carbon Steel Spot Welding”, Welding Journal, Oct 1947.

21. Williams, NT, “Spot Weld Size and Fracture Mode in Low Carbon Mild Steels”, Metal Construction, Oct 1979

22. Cold Rolled Steels Hot Rolled Steels Sawhill, J, “Spot Weldability Tests for High Strength Steels”, SAE Paper 810352, Feb 1981

23. Schneider, EJ Pollard, B, “Titanium-Bearing High Strength Cold Rolled Steels”, Proceedings of the AIME Mechanical Working Conference Oct 1980.

24. Balasubramanian, S. et al “Improvement of Resistance Spot Weld Characteristics”, Welding Research Abroad, Nov 1978

25. Mechanical Properties of Spot Welds Peel Tests Chisel Test Tensile Test Tensile Shear Ratios Torsion Test Impact Tests Fatigue Test

26. Dickinson, “Welding in the Automotive …” AISI, !981

27. Dickinson, “Welding in the Automotive …” AISI, !981 Angle taken as Failure Angle

28. Torsion Test Factors Affecting Angle of Twist (Ductility) Sheet Thickness Material Strength Carbon Content & Chemistry Post Weld Heat Factors Affecting Torque Sheet Thickness Material Strength Post Weld Temper Hold Time

29. Effect of Sheet Thickness & Material Strength Bibber, “Spot Weldability of Low Carbon….” Welding Journal, Dec 1943 Sheet Buckling Twist Angle Reduces With Increased Thickness Stronger Material

30. Nugget Defects At Short Hold Martensite Harder Martensite Effect of Hold Time, Carbon Content, Post Weld Temper Joumat, P. “Assessment of Spot Quality…” British Welding Journal, May 1955

31. Effect of Chemistry Heuschkel “The Expression of Spot Weld Prop..” Welding Journal, Oct 1952

32. Effect of Post Weld Heat on Twist Angle Torque Joumat, P. “Assessment of Spot Quality…” British Welding Journal, May 1955

33. Effect of Hold Time on Torque Sawhill, “Spot Weldability for HS Steels” SAE Paper 810352, Feb, 1981

34. Effect of Steel Type on Angle and Torque French “A Comparison of Methods of Assessing….” British Welding Journal, Nov 1957

36. High Tensile Loaded Joint Assignment 3