Becoming a detective in stress analysis requires both experience, training and studying two major fields:

Failure avoidance, which is also known as condition based maintenance (CBM) and failure analysis.

Several articles that were published in STRAINBLOG, one on using strain gages for failure avoidance, and the other on using Advanced Sensors Technology foil strain gages on failure analysis – bring to mind ( we prefer growth mindset than fixed mindset)  the use of mechanical failures to supplement undergraduate engineering instruction in mechanics, materials, and design.

Fractures and failed parts in Automotive, Marine, Aerospace, Engine testing, Civil Engineering, Renewable energy, Oil and Gas, Medical, PC Board and more, when constructively exploited, can be uniquely effective resource materials for course enrichment. The fracture face on a broken part, for example, often contains a remarkably detailed record of the condition and events leading to the failure.

In the case of fatigue failures ( such as in many bridges or dams) , the service history of the part can sometimes be read from the fracture face in a manner similar to the way a knowledgeable forester interprets the growth rings of a tree. Fracture patterns in glass, and in fine-grained brittle metals, can also be very revealing to the origin and progression of the fracture, and thus to its likely cause.

Fundamental to an understanding of design for failure avoidance is an equally thorough understanding of why and how materials, in their fabricated forms, fail. Creating real-world service loading conditions using typical testing and fatigue machines found in the laboratory is challenging. Laboratory fractures can be quite different in appearance from fractures typically found in manufactured parts subjected to real service environments and to real load spectra.

The instructional opportunities in failed parts are manifold – stress concentration, welded joints, fatigue, metallurgy, heat treatment, design considerations, wear phenomena, corrosion, etc. Handling, studying, and analyzing a broken part can give the student a learning experience not readily equaled by any textbook, online video or laboratory exercise. Since the failure normally represents a severe deviation from the expected or desired performance of the part, the lesson learned may have profound and long-lasting implications, which greatly transcend its purely technical content.

In the 21th century, broken and failed parts are (unfortunately!) quite easy to obtain for instructional purposes. Any concerned and interested teacher can readily establish a “morgue” of failures, classified by principle cause: design, material, manufacturing, and service environment. The effective use of such a collection can help immeasurably in rectifying what is otherwise a serious omission in engineering education.

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Yuval Hernik

StrainBlog Editor in Chief