For 2015, the seven teams are conducting the following failure analysis investigations:

Los Tres Toreros: Aluminum Drive Belt Failure Investigation

A Drive Belt Tensioner assembly from a 1996 Chevrolet Camaro was submitted to the group to conduct a failure analysis. The analysis has been conducted to identify the processing techniques used to produce the assembly, a stress analysis of the assembly has been carried out, and a material analysis of the failed component has been completed. This has allowed the culprit of the failure to be determined and any inconsistencies with the manufacturing of the product to be identified.

No Mow Worries: Mower Deck Mandrel Housing Failure

The corners on a mowing deck mandrel housing from a riding lawn mower broke off during use. The failure occurred when the blades were engaged and the spindle in the mandrel started rotating. The mandrel was only used for one year and failed before its expected lifetime. Losses include that of the part, and consequently the other components attached to the mandrel suffered damage due to the mandrel failing during use. Testing of the mandrel included scanning electron microscopy of the fracture surfaces, surface replication, dye penetrant, chemical testing, and metallography. Data was analyzed to determine cause of failure and tests will be conducted and compared to that of an exemplar mandrel.

Save our Spring (#SOS): Spring Steel Coil Failure

Mills operate based on a series of springs and gears, which both provide and support stresses introduced during operation. In the MSU College of Engineering machine shop, a mill suddenly failed, the cause being the sudden break of a spring steel coil attached to the handle. This caused a slowdown in production due to the time and money required to replace the part. This failure investigation has determined the cause of failure, details which led to failure, and steps to avoid any future failures.

(left to right) Benjamin Humfleet,
Keith Leonard, Loren Racicot, Justin Roe

Fudd: Failure Analysis of a Winchester Model 1200 Gun Barrel

The end of a gun barrel from a Winchester model 1200 shotgun that failed in service has been studied. During the cycle of firing, the end of the barrel experienced catastrophic failure and “tuliped” out in multiple directions. Various petals of the barrel were removed and examined in order to determine the likely failure method. Numerous tests were run on the specimen in order to understand the cause of failure, including dye penetrant testing, X-ray diffraction, chemical testing, hardness tests, and bending tests. The microstructure of the steel was characterized and examined using optical metallography.

The Big Three: Half-shaft Low-load Torsional Fatigue Failure Analysis

Nexteer Automotive supplied our group with a half-shaft bar that failed during a low-load torsional fatigue validation test at an abnormally low number of cycles (~28,000), compared to the design specifications of 50,000 cycles to pass. A comparative analysis has been done vs. an exemplar, also provided by Nexteer, that failed at about 60,000 cycles. These half-shafts are made of induction hardened 1050 steel. The failed part has been analyzed using scanning electron microscopy, microhardness evaluation, optical metallography, and other techniques to determine the cause of failure.

The Breaker Bar-Barians: Breaker Bar Failure Investigation

The purpose of the failure investigation was to ascertain the contributing factors to the fracture of a breaker bar submitted for investigation. This part is used for removing tight fasteners, and it failed during service. At that time, the head of the breaker bar that is intended to be inserted into the fastener broke off from the rest of the body of the breaker bar. The methods to establish the details and causes of the failure included interviews, testing of the part by non-destructive, and destructive testing. Based on the analysis of the reasons for the failure of the breaker bar, a recommendation was made for the future design, manufacture, material choice, and use of this type of breaker bar.

(left to right) He Zhao, Laura Bartow-Goudie, Jennifer Andrews, Natalia Pajares

The Shock Squad: Failure Analysis of Rear Shock Absorber for Electric Bike

The central shaft of the rear shock absorber of an electric bike fractured during a routine road test. Our analysis of the failed part included evaluation of mechanical properties, microstructures, compositional variations, macroscopic defects, and fracture surfaces using a variety of microscopy and mechanical testing techniques, including SEM, EDS, 3-point bend, and stereomicroscopy. The goal of this analysis is to improve the safety of the bike and prevent future failures.