Stress, Fatigue, and my Jet Engine Internship

Or, what fracture mechanics can tell us about our minds.

Disclaimer: This piece is a reflection of my experience at my summer internship with Pratt and Whitney Canada (which was a very good experience). I thought it would be interesting to summarize approximately what I had done with one of our greatest tools: the metaphor.

Photo by Inspirationfeed on Unsplash

The 7:38 yellow line to Station Longueuil-Universite de Sherbrooke is not an exciting one. In the warm, muggy metro car filled with people of all ages and walks of life, there are those that stare blankly into space, wires running out of their ears, and those that are staring blankly into a book, hoping the train would be less bumpy this time. Those that are standing are halfway into a dazed sleep, and those that are sitting squint at their phones through thick-rimmed glasses, avoiding eye contact.

Photo by Manny Fortin on Unsplash

It’s not hard to imagine that the 7:38 train is just a train like any of the other hundreds of trains that shuttle people to their jobs in Longueuil each morning, carrying tired office workers and engineers and salespeople and the folks that fake-smile and tell you to have a ‘good day, too,’ who have not reached their ultimate limit, but are on their way there. Fatigue is at work each morning on the 7:38 train, filled to the brim with people who experience its cyclic loading and subsequent deloading, day after day. The blare of n’oubliez pas vos effets personnels signals that it is time to deboard. Cracks nucleate at dislocations on their psyche’s surface, maybe in the drudgery of it all, or the angry slamming of their child’s door. The strains on their lives start from the outside and work inwards. These cracks propagate slowly but surely, cycle by cycle, drifting not against their consciousness, but with it. Cracks slide along slip planes, shearing, not pressing.

The commuting victims never notice. Fatigue doesn’t do its work through a flurry of emotional blows, but rather through the accumulation of losses, a propagation of dislocations in their minds that they mistake for the throes of life, creeping up on them until it is too late. The metro’s mindless journeys have changed their minds and lifestyles to point of no return- they can’t snap back to who they were before. The cracks are growing at an exponential rate, tempting the ever chomping jaws of fatigue’s beast.

“It’s okay,” they might say, “it’ll just be these few years of the commute and then I’ll move closer to my job.” Unfortunately, this may not solve their problems. The never-ending cycles have done their damage, and crack has made its way off the train, into their lives. Fracture is always unexpected.

Life has a way of piling on stress at the most inopportune times. It’s not only that they have 51 error messages when they run their programs, that they can’t seem to replicate the most simple tasks, and that budget cuts loom like guillotines. It’s their long hours and accelerating deadlines and missing out on a mortgage payment. The cracks are amplifying their stresses, raising monsters that can’t be fought. What had been manageable grows beyond their control, and in a vicious cycle, it doesn’t stop.

The cracks have lowered their available mental strength to bear the burdens of life, increasing the wear on their remaining faculties. Weekdays pass, the 7:38 train screeches by, n’oubliez pas vos effets personn -

Catastrophic failure.

What can be done about the scourge of every living thing, the repeated loads we take upon our shoulders? Fatigue and stress concentration are inevitable parts of any ordinary schedule, but how we can improve our precarious fate?

Engineers at Pratt and Whitney Canada may have a solution. It’s not a panacea, nor even a vaccine, but it will do a serviceable job to get you where you need to go. Heck, it’ll even get you to go beyond where you need to go. The engineers use a process called shot-peening to induce compressive residual stresses to prevent those life-threatening cracks from propagating. By shot-peening ourselves, say by exercise, or managing our time with smaller, self-imposed deadlines, we can build up a resistance to succumbing to the tractions of life that pull us every which way. We, as sentient plastic vessels, shape ourselves to prevent cracks from shaping, and subsequently destroying, us. Depending on the temperature of operation, however, our shot-peening may not prove to be of much help.

Groups of teens enter the 1:03 train at Jean Drapeau Station, complaining about the heat. They push toward the middle of the car and settle with a deep scowl, starting to sweat. The beating sun and crowds of office workers taking a lunch break, part-time workers, and ‘have a good day, too’ park employees contribute to the MR-63 Dutch oven. They feel their stoic composure starting to tremble and their shot-peened exterior begin to buckle. By the time they hear terminus they are already pouring out of the car, fragile and brittle creatures.

If not through shot-peening then, there must be another way to maintain our mental and structural integrity after the low-cycle taffy stretch that has become our norm. Luckily, at Pratt and Whitney Canada, there are other options.

Employees get vacation days and flex hours, carefully calculated by experts in fatigue management and fracture avoidance. Using complex statistical analysis, the experts create a lifing model for the usable working time of employees that takes into account both stress concentrations and peening effects. The fatigue experts compare real data from the floor to intricate computer-generated models to see the actual failure time of randomly sampled workers. They measure the arrival of the 7:38 train and the temperature and the screech of the unoiled doors to the office. They observe the microwave lines and shouting managers and rolling hills of unopened emails.

The unified lifing model, while not perfect, provides a level of unsurpassed safety to avoid fatigue failure by instantiating service periods. The vicious cycle has been broken.

You get two weeks this year, maybe three. Relax, take your Mediterranean cruise, and let the cares of your world sink below the billowing sails. Forget about the slogged commute, the sweaty holding-bars, just missing your bus. Forget about the project, someone else is taking care of it, just as you will for them when they leave. Forget about the 7:38 yellow line to Station Longueuil-Universite de Sherbrooke and forget about the crowds of people in their lonely bubbles, but always, always remember-

N’oubliez pas vos effets personnel.

Some helpful resources:

https://web.mit.edu/course/3/3.11/www/modules/frac.pdf

https://en.wikipedia.org/wiki/Fracture_mechanics

http://www.fracturemechanics.org/

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