New Tool to Assess Torque During Inertia Welding
Inertia welding is a well-established, friction-based,
solid-state joining process. Many different applications use this welding
process, ranging from aircraft engine parts to air bag inflators to hand tools.
Process parameters associated with inertia welding (spindle speed, welding
force, inertia, and displacement) have been widely studied since the process
gained traction in the late 1960s. One characteristic that has received less
scrutiny is the torque generated during the process. Torque is known to vary
widely during a given welding event. Resulting torques occurring during welding
are a key factor in tooling designs and may offer further insight into the
quality of the joint.
Most of the previous work performed to understand torque
variations during inertia and direct-drive friction welding was done with strain
gauges attached to the part or the tooling. Attaching strain gauges presents
two drawbacks. First, the data can only be collected once, as the strain gauge
is a consumable attached to the workpiece. Second, the gauges are often
destroyed during the welding process, which limits usable data. Attaching strain
gauges to the tooling does not totally reflect the torque generated.
Recently, EWI developed a monitoring capability for assessing dynamic torque during welding. Here, the tailstock of a Model 120B inertia welder was modified to allow for free rotation during welding. A torque arm was then mounted on that tailstock and coupled to a load cell. The combination enabled direct and calibratable measurement of reaction torques during welding. For comparison, measured torques from the developed system were compared to that from strain gauges placed on a bar that holds the stationary test sample.
The EWI system offers opportunity to directly assess the
physical requirements for joining new candidate applications. This information
has the potential to improve sizing of equipment and reduce risk in specific
tooling designs. In addition, the described monitoring system can provide
additional information allowing understanding inertia and friction weldability
of specific materials and dissimilar metal combinations.
To learn more about this system, contact Tim Stotler, Principal Engineer, at [email protected].
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