Welding vs. Adhesives II: Working Together

Transcription

1 Welding vs. Adhesives II: Working Together ASC Fall Convention and Expo October 17-19, 2016 Dr. George W. Ritter Principal Engineer Materials Technology Group EWI

2 2 Agenda EWI and ASC Differences between Welding and Bonding Advantages of Welding and Adhesive Bonding Types of Welding Weldbonding and Rivetbonding Summary and Conclusion

3 3 Range of Technical Services Materials Selection Manufacturability Formability Joining Constraints Joint Designs Process Selection Design Optimization Analytical Modeling Process Validation Automated Systems Development Process Monitoring and Controls Tooling Development Concept Feasibility Preliminary Design Detailed Design Manufacturing Transition Production Weldability Analysis Process Feasibility Joining Trials Property Characterization Process Development Prototyping Testing and Analysis Equipment Specification NDE System Design NDE Process Development Life Assessment Failure Analysis

4 Do Welding and Adhesives Compete? Synopsis from: The Threat of Welding vs. Adhesives or Vice Versa? ASC Spring Convention and Expo

5 5 Adhesive and Welding Culture Characteristic Adhesive Bonding Welding Joint Content Heterogeneous bonding material Largely homogenenous Joint Material Usually organic or polymeric Metallic Mechanical Performance Lower modulus and tensile strength than the metal Similar modulus and tensile strength to the metal Temperature Limits Useful to 230 C and 35 MPa Useful to limits of material Function HAZ, Change in Metallurgy, Change in Material Properties Bonds materials and transfers stress through the joint None Joins materials, BUT they must be welding compatible Possible

6 Technology Space and Marketing Space 6 Welding can only weld materials that are allowed : Usually means something to itself Will not work with most dissimilar materials May not work with materials having widely differing properties. Adhesives can join anything to anything: Bond surfaces Does not change bulk material chemistry or properties Rarely distorts shapes. Blue Ocean do not compete, define: Understand welding processes and what they cannot do Market to those applications where welding is impossible. Also look for areas where the two can work together.

7 Welding Methods Resistance Welding Friction Stir Welding Laser Welding Ultrasonic Welding

8 8 Welding Methods Resistance Spot Welding F 1 F 1 F 1 F 1 Heat is generated internally by electrical resistance heating: High currents High squeeze pressure Multiple stack-ups.

9 Welding Methods Resistance Projection Welding 9 Projection concentrates heat. Important for high conductivity metals like aluminum. Can also serve to set adhesive gap. (a) (b) (c) (d) [Reference: Welding Handbook, Vol. 2, p. 566, AWS]

10 Welding Methods Friction Stir Welding 10 Parts are rigidly fixtured to machine table. Uses cylindrical tool with cylindrical pin extending from shoulder. Tool is rotated to desired rpm and plunged into joint. After short dwell time, tool is traversed along joint. At end of joint, tool is lifted and rotation is stopped.

11 Welding Methods Friction Stir Spot Welding 11 Friction Stir Spot Welding Plunge is made. Special tool fills the divot. No traverse. In production with aluminum structures.

12 Welding Methods Ultrasonic Metal Welding 12 Lateral-Drive System Transducer Booster Static Force Vibration Power Supply Horn/Sonotrode Anvil Workpieces Asperities Bonding Mechanism Oxides, Contaminants Static Force Sonotrode Vibration Workpieces Weld Zone Anvil

13 Welding Methods Ultrasonic Metal Welding 13 Scrubs two pieces of metal together. Can weld dissimilar metals. In production on battery assemblies. Not in production on other metal structures.

14 Welding Methods - Laser Processes 14 Focused laser energy. Very rapid process. Power > 20 kw.

15 Weldbonding and Rivetbonding Joint Design Basic Methods Synergistic Performance

16 Bonding Joint Types 16 Double Lap Shear Pi Joint Center-line thrust. Excellent shear loading. Derived from aerospace. Bond anything to anything.

17 Weldbonding Derivation of Joint Concepts 17 Combining welds or rivets with good bonding practice to achieve maximum joint efficiency.

18 Weldbonding - Projection Weld-Bonding 18 Weld-through adhesive depicted with a projection weld in aluminum. Projections can set adhesive thickness.

19 Weldbonding Laser Weldbonding 19 Use a shim between the metals to permit metal-metal bonding. Adhesive is outside the weld zone. Shim sets adhesive thickness.

20 Weldbonding Laser Weldbonding 20 Adhesive is outside jointline. Welds provide ~ 2 peel over adhesives alone. Adhesives provide ~ 3 shear over welds alone. Weldbonding provides fatigue life over either alone. Ritter, G.W., Eastman, J., Talwar, R., and Bolser, D.R., Laser weldbonded aluminum structures, Proceedings of the 28 th Annual Conference of the Adhesion Society, (2005).

21 Weldbonding Other Methods 21 Friction Stir Spot Weldbonding Ultrasonic Spot Weldbonding

22 Rivet-Bonding Self-Piercing Rivets 22

23 23 Summary and Conclusions Welding and adhesive bonding have different process cultures. Many materials and combinations cannot be welded. A few welding processes lend themselves to combination with adhesives. Weldbonded and rivetbonded structures are increasingly important for lightweighting.

24 QUESTIONS & DISCUSSION