By: Henry Karpovas Lisak Have you ever seen footage of the Tacoma Narrows Bridge collapse or read about the tragic failures of the de Havilland Comet, the world’s first commercial jet airliner? These are not just dramatic moments in engineering history – they are powerful reminders of how unexpected material failures can bring down even the most advanced structures. As a sophomore mechanical engineering student at the University of Minnesota, I’ve been exploring these concepts in MATS 2001: Introduction to the Science of Engineering Materials, taught by Professor Chris Haas. This course has been fundamental in helping me understand the relationship between material structure, mechanical properties, and real-world performance – and how failure often results from overlooked or misunderstood mechanisms. Fatigue: The Silent Accumulator Fatigue is one of the most common and dangerous forms of material failure. It occurs when a material is subjected to repeated loading and unloading, even when the loads are below the material’s yield strength. Over time, microcracks form and grow with each cycle until the material fails suddenly. A textbook example of this is the de Havilland Comet. In the 1950s, this jet experienced multiple in-flight breakups due to fatigue cracks that developed around the sharp corners of its square windows. The fuselage underwent cyclic pressurization with each flight, and the stress concentrations at the window corners accelerated crack growth, ultimately causing catastrophic failure. This tragedy led to major advancements in fatigue testing and design, including the adoption of rounded windows in all future aircraft. Creep: Deformation Over Time Creep is another critical mode of failure, especially in high-temperature environments. It refers to time-dependent deformation that occurs when a material is under constant stress at elevated temperatures. Early jet engines, for example, suffered from creep damage in their turbine blades, which operate under extreme heat and rotational stress. Over time, these blades would elongate and lose their shape, reducing engine performance and potentially leading to mechanical failure. Addressing this required the development of high-performance materials, such as nickel-based superalloys and single-crystal blades, which resist creep and maintain integrity over long periods. Torsion: Twisting into Instability The Tacoma Narrows Bridge collapse in 1940 is one of the most iconic failures in engineering history, often cited in materials and structures courses. Although not a case of material strength failure, it demonstrated the danger of torsional instability. Under steady winds, the bridge began to oscillate in a torsional mode due to aeroelastic flutter. The bridge lacked the necessary torsional stiffness, and the twisting oscillations amplified until the structure tore itself apart. This failure underscored the importance of considering dynamic forces – not just static loads – in structural design. Shear: Sliding at the Breaking Point Shear failure happens when a material or component fails along a plane due to forces acting parallel to each other. A real-world example is the collapse of the World Trade Center towers on September 11, 2001. While many factors contributed to the collapse, one mechanism involved the failure of shear connections between floor trusses and vertical columns. As intense fires weakened the steel, these connections were unable to resist the shear forces imposed by sagging floors. Once enough shear connections failed, the building’s structure could no longer support the upper floors, leading to a progressive and total collapse. Conclusion: Learning from Material Failures These historical examples show that materials can fail in many ways – through fatigue, creep, torsional instability, or shear – and understanding these mechanisms is essential to prevent future disasters. Courses like MATS 2001 have helped me develop a foundation in analyzing how materials respond to stress, temperature, and time. By learning from past failures, engineers can design safer, more resilient systems that stand the test of time. Henry Karpovas Lisak: Henry is a Mechanical Engineering student at the University of Minnesota with a Management minor, interested in innovation within the automotive and aerospace industries. He serves as Vice President of ASHRAE at UMN, organizing workshops, networking events, and company tours to support student engagement in HVAC&R fields. Outside the classroom, Henry is actively involved in Jewish campus life as Vice President of Campus Relations for Minnesota Hillel and a student government representative. He participates in several leadership programs, including the Voice of the People Fellowship, the Israel on Campus Coalition’s Community Impact Fellowship, and the inaugural Campus Commons Program, where he focuses on Jewish advocacy and community-building. A former member of the Minnesota Men’s Crew team, Henry brings a collaborative and disciplined approach to his academic, leadership, and service work, aiming to make a thoughtful impact both within engineering and his broader community. You can connect with him on LinkedIn at linkedin.com/in/henry-karpovas-lisak

By: Henry Karpovas Lisak As I fly back from my latest trip to Israel—connecting in Dubai on my way to Minnesota—I caught myself admiring the magnificence of the tallest structure ever built by mankind. The Burj Khalifa rises so high above the Arabian desert that it’s visible for miles, shimmering through the desert heat. At 828 meters tall, this monstrous, futuristic sculpture sparked hours of reflection during my 13.5-hour flight. The Burj Khalifa Wikipedia contributors. (n.d.). File:Burj Khalifa.jpg . Wikipedia. https://en.wikipedia.org/wiki/File:Burj_Khalifa.jpg And as we approached Chicago for our second layover, that flame of awe ignited again. Out the window stood the Willis Tower—what once held the title now claimed by the Burj Khalifa. How incredible are our engineering skills! Humanity has reached the point where we can create such massive, awe-inspiring structures. I’ve always been fascinated by these state-of-the-art, unbelievably large accomplishments of human ingenuity. But that sense of wonder was soon joined by another, perhaps even more profound feeling. The following Monday, I started my summer Co-Op at CPC, a leading manufacturer of couplings, fittings, and tubing connectors. There, I wasn’t working on skyscrapers or bridges—I was working with parts you can hold in the palm of your hand. And yet, I felt a surge of excitement even greater than what I’d experienced in Dubai. It hit me: we often celebrate the big, the majestic, the record-breaking. But behind every towering structure lies an army of meticulously designed small parts—every nut, bolt, and connector essential to the whole. Without these, the grandest designs would never stand. In just my first day on the job, I learned about soldering techniques, ultra-specific application requirements, and how tiny details can make or break a solution. It was fascinating. It reminded me that for every bridge like the Golden Gate, there are thousands of precision parts that make its construction possible. We don’t often stop to wonder how a screw is made. But someone had to design it, test it, and manufacture it—likely with painstaking effort and little recognition. Yet that humble screw holds your TV rack together so you can enjoy your PS5 instead of flipping through a manual. So next time you see a structure that earns the title of “tallest in the world,” remember what blink-182 sang: 🎵 All the small things... 🎵 Henry Karpovas Lisak: Henry is a Mechanical Engineering student at the University of Minnesota with a Management minor, interested in innovation within the automotive and aerospace industries. He serves as Vice President of ASHRAE at UMN, organizing workshops, networking events, and company tours to support student engagement in HVAC&R fields. Outside the classroom, Henry is actively involved in Jewish campus life as Vice President of Campus Relations for Minnesota Hillel and a student government representative. He participates in several leadership programs, including the Voice of the People Fellowship, the Israel on Campus Coalition’s Community Impact Fellowship, and the inaugural Campus Commons Program, where he focuses on Jewish advocacy and community-building. A former member of the Minnesota Men’s Crew team, Henry brings a collaborative and disciplined approach to his academic, leadership, and service work, aiming to make a thoughtful impact both within engineering and his broader community. You can connect with him on LinkedIn at linkedin.com/in/henry-karpovas-lisak

The AJES team has been working on some really interesting interviews with amazing personalities.....stay tuned!!!!