Throughout their collegiate careers, TU engineering students are encouraged to experiment with original ideas and tackle product design from scratch. For more than 20 years, Professor John Henshaw, chair of the Department of Mechanical Engineering, has tasked his students with performing failure analysis on commercial products. In 2014, the project became a class competition, and the winning team featured three female engineers.
Seniors Hannah Emnett, Hannah O’Hern and Katy Riojas, a 2015 Goldwater Scholar, under the team name KH2, conducted a failure analysis on a pair of German double-action bone-cutting forceps, used primarily in cardiovascular surgery. Of the eight independent analyses conducted by the team, Riojas said all pertained directly to the forceps’ material properties. “For example, in order to determine the specific type of steel used to create the forceps, we performed a microhardness test and a metallurgical analysis,” she said.
The students were required to answer three questions: How the forceps failed, how they functioned and how they could be redesigned to prevent additional failures. Team KH2 determined the forceps failed from mechanical overload caused by the stress concentration at the base of the device’s pincer. According to the team, the force required to cut a bone is much less than the force required to fracture the forceps, suggesting the forceps failed from misuse. Additionally, the surface clearly indicated a brittle fracture, which was further evidence of failure from misuse.
“Our mission was to take the design one step further and improve the safety of the forceps to prevent future failures, even those caused through misuse,” Emnett said.
KH2 recommended increasing the radius at the base of the pincer to minimize the stress concentration. Also, increasing the cross-sectional area at the base of the pincer would alleviate induced stress on the forceps. The redesign reduced maximum stress by 42 percent.
In addition to teaching students the importance of thorough product testing, Riojas said the process has confirmed her desire to pursue a career in medical device testing and design. She and the KH2 team received Lowe’s gift cards as the inaugural class winners of the Hackworth-Wilson Prize for Excellence in Failure Analysis, a new award named in honor of mechanical engineering alumni Matt Hackworth (BS ’96, MS ’98, PhD ’00) and Kelly (Wilson) Hackworth (BS ’96, MS ’98), former TU classmates who are married and now serve on the TU Mechanical Engineering Industrial Advisory Board. Matt’s project as a student in the mechanical engineering course involved the analysis of an exploded soda can under the mentorship of Henshaw.
“Matt and I did close to $1 million in external research for Alcoa, Coca-Cola, Anheuser-Busch and others,” Henshaw said. “When he and Kelly asked how they might give back to TU in a creative way, we established the Hackworth-Wilson Prize.”
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