Mechanical Fastening of Dissimilar Metals in Car Bodies

In this section

Back to Core Research Programme AMorph – 4D Printing for Field Morphing Structures Automation of Composite and Hybrid Joining Process Coaxial Wire Additive Manufacturing Processes and In-Line Monitoring Tools Development of Coded Excitation Technique for Non-Metallic Pipes Inspection Development of Digital Twin technology as a demonstrator for real-time integrity assessment of crack growth in tensile specimens Development of Friction Stir Welding (FSW) for Hydrogen Fuel Storage Tanks Development of Leak-Before-Break Hydrogen Storage Composite Pressure Vessels With Polymeric Liner Establishing Assessment Methods for Determining Safe Service Limits of High-Temperature Materials in Extreme Environments Fracture toughness in aggressive environments: effect of crack monitoring techniques on test results In-process detection and non-destructive testing of electron beam weld imperfections Internal Bore Coatings for Applications in Corrosion and Hydrogen Environment Joining of Additively Manufactured Materials Long term behaviour of polymeric liner materials/coatings in hydrogen service Techniques for High Temperature Ultrasonic Inspection of Arc Welding Ultimate Leverage Fund

Project Code: 30185

Objectives

Perform a critical assessment of all available means of mechanically joining steel and aluminium for automotive structures
Investigate what range of materials (strength and gauge) can be joined with each technique to help determine its range of applicability
Benchmark the performance of each technique against critical automotive production requirements
Provide wider production economics data including the cost of equipment, cost of consumables, weight of each joint and time to produce each joint

Project Outline

TWI will perform a benchmarking study on the full range of mechanical fastening technologies for steel to aluminium joining. Each technique will be tested against critical performance criteria:

A first level assessment will be performed looking at the following for each technique:

What grades and gauges of steel and aluminium can be joined
How well do the processes work in combination with structural adhesives
How sensitive are the joints to loosening or deformation as a result of differential thermal expansion of steel and aluminium in a typical automotive paint baking cycle
What are the relative joint strengths in tensile shear and cross tension

The following areas have been identified as requiring solutions:

Lack of reliable NDT techniques available for nearly all mechanical fastener types
Production rates of fastening techniques are considered too slow (and costly) in most cases
Single sided joining processes desired
The size and weight of many fasteners is considered too great
Post-crash repair techniques are not available for all fasteners
The perfect fastener solution is not yet available on the market

Relevant Industry Sectors

Automotive

Industry Need

The automotive sector is reducing vehicle weight to achieve present and future performance and emission targets. Many car companies see a multi-materials strategy as the best way to achieve weight savings, with a hybrid structure of steel and aluminium being the goal of most automotive producers.

In recent years the automotive sector has seen significant technology development in the area of mechanical fastening for the joining of similar and dissimilar materials. Today a modern automobile can contain; self-pierced rivets (SPR), clinched joints, blind rivets, blind rivet studs and bolts, flow drill screws, high speed joints, friction rivets (Ejot-weld), resistance element welds, solid punch rivets. Although many possible techniques now exist for dissimilar materials joining, each has advantages and disadvantages in terms of joint strength, production speed, cost, weight and range of materials that can be joined. At present much confusion exists regarding when and where each technique should be used.