ASC Fall Convention and Expo

October 17-19, 2016

Welding vs. Adhesives – II:

Working Together

Dr. George W. Ritter

Principal Engineer

Materials Technology Group

EWI

614.688.5199

gritter@ewi.org

Agenda

EWI and ASC

Differences between Welding and Bonding

Advantages of Welding and Adhesive Bonding

Types of Welding

Weldbonding and Rivetbonding

Summary and Conclusion

2

Range of Technical Services

FeasibilityPreliminary

DesignDetailedDesign

Concept

– 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

– 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

ProductionManufacturing

Transition

3

Do Welding and Adhesives

Compete?

Synopsis from:

The Threat of Welding vs. Adhesives – or Vice Versa?

ASC Spring Convention and Expo - 2016

Adhesive and Welding Culture

Characteristic Adhesive Bonding Welding

Joint Content Heterogeneous bonding material Largely homogenenous

Joint Material Usually organic or polymeric Metallic

Mechanical PerformanceLower 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

FunctionBonds materials and transfers

stress through the joint

Joins materials, BUT they must

be welding compatible

HAZ, Change in

Metallurgy, Change in

Material Properties

None Possible

5

Technology Space and

Marketing Space

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.

6

Welding Methods

Resistance Welding

Friction Stir Welding

Laser Welding

Ultrasonic Welding

Welding Methods –

Resistance Spot Welding

F1

F1

F1

F1

Heat is generated

internally by electrical

resistance heating:─ High currents

─ High squeeze pressure

─ Multiple stack-ups.

8

(a) (b) (c) (d)

[Reference: Welding Handbook, Vol. 2, p. 566, AWS]

Welding Methods –

Resistance Projection Welding

Projection concentrates heat.

Important for high conductivity metals like aluminum.

Can also serve to set adhesive gap .

9

Welding Methods –

Friction Stir Welding

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.

10

Welding Methods –

Friction Stir Spot Welding

Friction Stir Spot Welding

Plunge is made.

Special tool fills the divot.

No traverse.

In production with aluminum structures.

11

Lateral-Drive System

Oxides,

Contaminants

Asperities

Bonding Mechanism

Static Force

Horn/Sonotrode

Transducer

Anvil

Workpieces

Vibration

Power Supply

Booster

Static Force

Sonotrode

Vibration

Workpieces

Anvil

Weld Zone

Welding Methods –

Ultrasonic Metal Welding

12

Welding Methods –

Ultrasonic Metal Welding

Scrubs two pieces of metal together.

Can weld dissimilar metals.

In production on battery assemblies.

Not in production on other metal structures.

13

Focused laser energy.

Very rapid process.

Power > 20 kW.

Welding Methods -

Laser Processes

14

Weldbonding and

Rivetbonding

Joint Design

Basic Methods

Synergistic Performance

Bonding –

Joint Types

Double Lap Shear

Center-line thrust.

Excellent shear loading.

Pi – Joint

Derived from aerospace.

Bond anything to anything.

16

Weldbonding –

Derivation of Joint Concepts

Combining welds or rivets with good bonding practice to achieve maximum joint efficiency.

17

Weldbonding -

Projection Weld-Bonding

Weld-through adhesive depicted with a projection weld in aluminum.

Projections can set adhesive thickness.

18

Weldbonding –

Laser Weldbonding

Use a shim between the metals to permit metal-metal bonding.

Adhesive is outside the weld zone.

Shim sets adhesive thickness.

19

Weldbonding –

Laser Weldbonding

Adhesive is outside jointline.

Welds provide

~ 2⨯ peel over adhesives alone.

Adhesives provide

~ 3⨯ shear over welds alone.

Weldbonding provides

10-20⨯ fatigue life over either alone.

Ritter, G.W., Eastman, J., Talwar, R., and Bolser, D.R., “Laser weldbonded aluminum structures”,

Proceedings of the 28th Annual Conference of the Adhesion Society, (2005).

20

Weldbonding –

Other Methods

Friction Stir Spot Weldbonding Ultrasonic Spot Weldbonding

21

Rivet-Bonding –

Self-Piercing Rivets

22

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.

23

QUESTIONS &

DISCUSSION