Metal Testing by Metallurgical Associates, Grass Valley, California, Robert C. Helminiak - Principal Technician  and Lab Manager Metallurgical Associates
Metal Testing/Failure Analysis, Welding Tests, Certification & Evaluation

Grass Valley, California, USA
(Between Sacramento, California and Reno, Nevada)
Serving California, Nevada and Worldwide by Arrangement

Robert C. Helminiak
Principal Technician and Lab Manager
530 272-6052

Failure Analysis



Failure Analysis by Metallurgical Associates, Grass Valley, California, Robert C. Helminiak - Principal Technician  and Lab Manager A Ford van had a rear wheel fall off and cause a considerable amount of damage. Upon removing the intact hubcap, we found the lug nuts still intact with the broken wheel studs (see photo on left). Fatigue cracks were noted on the fracture surfaces (see photo on right). The Ford van had aluminum wheels which require the studs to be torqued to a specific tightness. Our conclusion was that the mechanic who rotated the tires failed to properly torque the wheel nuts (they were too loose) causing cracks to occur in the stud threads which progressed until failure Failure Analysis by Metallurgical Associates, Grass Valley, California, Robert C. Helminiak - Principal Technician  and Lab Manager
Failure Analysis by Metallurgical Associates, Grass Valley, California, Robert C. Helminiak - Principal Technician  and Lab Manager Failure Analysis by Metallurgical Associates, Grass Valley, California, Robert C. Helminiak - Principal Technician  and Lab Manager Failure Analysis by Metallurgical Associates, Grass Valley, California, Robert C. Helminiak - Principal Technician  and Lab Manager
A fractured connecting rod from an eight-cylinder Bugatti race car was submitted for analysis. Examination of the part's fracture face revealed a ¾" long crack. A cross-section of the connecting rod's surface adjacent to the fracture revealed forging laps which were quite soft in comparison to the matrix. Knoop 500 gm. Microhardness Tests were used to detect the soft areas. It was concluded the soft zone adjacent to the ¾" long crack was a stress riser causing a crack to start.
Tool Steeel Die Failure A metals heat treater sent us a very expensive die made from tool steel which developed a crack after quenching. The groove cut in the die had no radius at the corners. A stress riser was created when the metal cooled and rapidly a crack started - ruining the part.


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