Cornfields and Characterization: A Story of Failure Analysis

Dr. Jordan Moering, U.S. Eastern Sales Manager, EDAX

It was an icy morning in early November where I found myself, freezing, staring at a chunk of mangled aluminum, carbon fiber, and hickory nestled against mounds of pumpkins in a largely empty cornfield in Sussex County, Delaware. As the sun began to rise over the frosty ground, the carnal wreckage was investigated, pondered over, poked and prodded, touched, and engaged in any other means of characterization at the disposal of the rag-tag cohort of farmers, engineers, enthusiasts, and politicians surrounding me. In hindsight, this scenario seems like something out of a science fiction novel or perhaps a post-apocalyptic memoir, but I can assure you that this is a common sight to behold. Common, at least, at the World Championship Punkin Chunkin.

As it turns out, the twisted composite beam was one of the first instances I experienced in witnessing true engineering failure firsthand. Although the beam failed in some of our early testing, it had previously been attached to a world-class, 7-ton, torsion catapult capable of launching pumpkins over a kilometer at nearly the speed of sound. It could withstand tensile loads exceeding the weight of a Boeing 747 and extended nearly 20 feet in length. All of that impressive performance was a thing of the past as I closely examined the jagged features at the fracture surface, the twists along the flanges of the I-beam, and the shards of carbon fiber shattered amongst the corn husks.

Figure 1. Replacing the broken “Throwing Arm” with a convenient spare that we had brought with us.

Although I was just a student at the time, I already recognized the characteristic ductile fracture surface before me. I might have squinted my eyes and imagined some fatigue striations within the metal surface, but sadly this was the only means at my disposal of diagnosing the problem at the time. In a laboratory setting, I would have been able to not only characterize the elemental composition of the beam (it was a gift from a benevolent team sponsor) but also fully describe the crystalline structure with techniques like EBSD, XRD, and EDS. This type of material identification study is routine with modern analytical instruments, but recent advancements have taken this a step further. Had I known then what I know now, the unprecedented capabilities of high-resolution EBSD and ultra-high sensitivity of direct detection could have allowed me to understand and quantify, quite literally, the stressed state of the surrounding metal at the fracture surface.

Figure 2. The most frequently used deconstruction and characterization device we had at our disposal – an angle grinder.

While my first foire into failure analysis lacked the sophistication of modern analytical capabilities, it did spark an intense curiosity into this critical line of work. The modern electron microscopist, lab technician, or researcher has a wealth of opportunity at his/her disposal for understanding how materials fail. Sometimes these failures originate at some inclusion or material defect that could have previously been detected by methods like micro-XRF or EDS elemental analysis. Other times, inherent weaknesses in the system concentrate stress in ways that might not be apparent to the naked eye. Techniques like high-resolution EBSD and X-ray diffraction might be used to prevent these calamities. The list goes on and on.

I’ve only been working at EDAX for several months now, but every day I wake up and get to work with individuals who face scenarios, not unlike my previous encounter with twisted beams and flying pumpkins. Although a researcher at semiconductor foundry might not be surrounded by farmers in the middle of a cornfield, they certainly may find themselves staring at an improperly functioning device, wondering where things went wrong. In this capacity and many others, I find myself relating to our customers. I empathize with their challenges, and I am excited to help them uncover solutions to some problems that they previously were not aware of.

Because if there is one thing I have learned from Punkin Chunkin and Advanced EM Characterization, it is that you never know what you will find under the surface of your material.

The video below is of the beam in operation prior to its demise:

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