Material fatigue is a concern in aviation safety. Airplanes are exposed to significant mechanical stress during flight. Over time, this can lead to material fatigue that jeopardizes the airplane’s structural integrity. For a better understanding of material fatigue in aviation, keep reading.
Overview of Material Fatigue
Also known as metal fatigue, material fatigue is a phenomenon that involves the gradual weakening of a material due to repeated stress. It often involves the formation of hairline or microscopic cracks. Repeated stress over a prolonged period can cause small cracks to form at points of concentrated stress.
Material fatigue isn’t the same as overload failure. Overload failure involves a single instance of force or stress that exceeds the material’s strength, whereas material fatigue involves repeated stress. With overload failure, damage occurs instantly after the initial stress exposure. With material fatigue, damage occurs over time after being exposed to stress many times.
Common Causes of Material Fatigue
What causes material fatigue in airplanes exactly? Cabin pressurization and depressurization is a common cause. As airplanes ascend, they typically pressurize their cabins to provide passengers with a safe and comfortable environment. As they descend, conversely, they depressurize their cabins. These pressurization-depressurization cycles can take a toll on an airplane’s fuselage, resulting in material fatigue.
Temperature fluctuations can contribute to material fatigue. The air is thinner and cooler at high altitudes. At 30,000 feet — cruising altitude for most commercial airliners — the air can be as cold as minus 50 degrees Fahrenheit. Exposure to this cold air can pave the way for material fatigue.
Aerodynamic forces can cause material fatigue in airplanes. Drag, for instance, can take a toll on airplanes. It’s the main resistance that an airplane experiences during flight. Over time, excessive drag can weaken various parts, leading to material fatigue.
How Engineers Prevent Material Fatigue
While material fatigue is common in aviation, there are ways to prevent it. Most airplanes, for instance, have strict pressurization guidelines. Commercial airliners are typically pressurized to a maximum of 8,000 feet, which is about 11 to 12 pounds per square inch (PSI). By staying within this pressure limit, they can protect their cabins from excessive pressurization and related material fatigue.
Engineers design airplanes using materials that can withstand fatigue. The wings, for example, are designed to bend when exposed to drag. This bending action allows the wings to flex so that material fatigue is less likely to occur.
Another way engineers prevent material fatigue is redundancy. They design airplanes so that if one part or system fails, there’s at least one other backup part or system to perform its task.
