A European project to develop an easy-to-use, affordable non-destructive tool using ultrasound to detect flaws in spot welds under automotive repair is reaching its field trial phase. We look at the work carried out by the consortium so far.
When considering the thousands of spot welds present in the make-up of a car, it is inevitable that some will need to be remade when the vehicle undergoes repair. Clearly, it is not possible to destructively test repair welds. Matching test samples could be made for some reassurance but there is currently no suitable method to ensure the integrity of welds going into service.
The SpotTrackTM project aims to meet the need and is developing an automated spot weld inspection device.
Project partners (Vermon, Tecnitest, ACT, Nardoni, TWI, KTU, CAB, Tofas and Karl Vella) first worked to assess market requirements, then, using a combination of numerical modelling and experimentation, designed the device.
The numerical modelling results provide visualisation of the sound field throughout the whole volume at any point in time during the weld test. This enables a deeper understanding of the effects of test variables on the reliability of the results.
SpotTrack
TM uses an array probe to allow greater inspection resolution with a multiplexer, which allows signals to be collected without the need for expensive phased array equipment. The inspection system hardware will comprise a hand held probe, an ultrasonic unit and a laptop to view the results.
As part of the development work, the project team also created a set of samples to ensure that SpotTrack
TM could reliably determine the quality of spot welds. Samples included good welds and a range of defective welds: undersized; stuck (where the zinc coating melts and sticks the two plates together but a proper bond is not achieved); oversized (burnt); and porous. The team used the data from these tests to develop novel signal processing algorithms for the inspection system.
The next step for the project is to take the device to a body shop for field trials on cars that are under repair.
Examples of spot weld macro sections and the decision made using the newly developed algorithm on specimens made with identical
welding parameters:
- a) Undersized;
- b) Oversized/Burnt;
- c) Loose/Stuck;
- d) Good.
For more information please contact:
Ruth Sanderson or
An Nguyen-Dinh.
The SpotTrack project has received funding from the European Union under the Seventh Framework Programme [FP7/2007-2013] and grant agreement no 284471.