CFSP - Wichita State University - Two electronic Non-Destructive Evaluation (e-NDE) algorithms for Friction Stir Welding (FSW) have been successfully developed in collaboration with Wichita State University (WSU) and South Dakota School of Mines and Technology (SDSM&T). According to the Probability of Detection (POD) analysis based on the maximum-likelihood method, the e-NDE method gave significantly better detection performances compared to the conventional ultrasonic-phased-array and the X-ray techniques. In addition, from examining a series of cross-sectional macrographs taken from along the weld path, it was found that the e-NDE method tested was sufficiently sensitive to predict volumetric defects even before voids emerged during the welding process. This is accomplished through examining only the feedback signals generated by the process events.

The implementation of e-NDE promotes FSW into a “green-squared” technology. FSW is considered as a “green” welding technology that does not produce any toxic gas or use of filler material. Thus, utilizing e-NDE adds to the “greenness” of FSW by reducing expensive post-weld inspection procedures. Moreover, the development of e-NDE algorithms is the crucial step towards creating an intelligent closed-loop control system for FSW to achieve the highest quality friction stir joints.

 

 

 

 

 

 


CFSP - South Dakota School of Mines & Technology - Friction stir welding has shown the potential to repair defective or damaged areas in metals, and to reduce scrap rates in welded parts by reworking select areas.  Parts repaired this way showed an enhancement in fatigue performance returning it to a level comparable to the unaffected base material.

This demonstrates the potential to repair damaged parts to like new condition, presenting significant cost savings, and a reduced environmental impact.  That is because it generally takes much less energy to repair a part than to make an entirely new part and reycle or dispose of the old one.

Many of the aircraft flying today do not have approved repair procedurs using today's advanced materials processing technologies, like friction stir welding, because they were not common practice or invented when the planes were first designed and qualified.  Consequently, many parts are simply replaced rather than repaired.  This study is working at answering the important questions that need to be understood in order to begin taking advantage of these new developing technologies.
 

Contact email: Michael.west@sdsmt.edu

 


CFSP - Wichita State University - Advancements in weld tool designs for friction stir welding (FSW) have enabled the development of a prototype lightweight automotive bumper / crash box assembly. Assemblies fabricated with FSW and Gas Metal Arc Welding (GMAW) were subjected to crash sled and drop tower testing to provide a comparison in performance under dynamic loading conditions. The FSW development work included micro-structural examination and static mechanical testing. Results from coupon-level development were compared against results from component-level testing of prototype articles using micrographs and an advanced electronic (signal/frequency analysis) non-destructive evaluation (e-NDE) technique in order to detect weld anomalies primarily in the form of voids. Due to the geometry of the welded part joint, conventional mechanical testing methods (tensile and peel test) were not applicable. Therefore, a wedge test was devised to test the relative toughness of the FSW joint.

A drop tower test fixture was also fabricated using friction stir welding. Finite Element Analysis (FEA) was used to compare the predicted damage to the actual damage in FSW bumper and FSW test fixture joints. According to the bumper test results, friction-stir butt welds performed as well as or better those produced by GMAW.

 

 

 

 

 

 


CFSP - Brigham Young University - Figure 1 shows a weld that started in RPM control mode then given a temperature command 51°C lower than the current temperature.   The overshoot was 29%, rise time 3.325 seconds, 10% settling time of 17.3 seconds and 1°C settling time of 29.5 seconds. After the 1°C settling time, the temperature was held at 425°C with a standard deviation of 0.717°C for non-filtered temperature and 0.312°C for filtered temperature.   Welds were run using the same gains as the weld shown in Figure 1 in various plate thicknesses, commanded temperatures, backing plates and feed rates.  In all cases temperature control functioned properly and the commanded temperature was held with a standard deviation of less than one degree.   Similar results have been obtained for welds run using PCBN tools.