Dislocations – Something We Must Live With

What impact can material dislocations have? And could they affect something as ordinary as a car body?

The story begins with the world’s first jet-powered passenger aircraft, the de Havilland Comet. In the early 1950s, four aircraft crashed within a short period of time. The cause was later identified as metal fatigue — what we today understand in terms of microscopic dislocations in the material structure.

Using electron microscopy, investigators discovered structural fractures around door openings and window corners. These were areas exposed to repeated stress cycles during pressurization and depressurization. The Comet, introduced in 1954, featured an all-metal wing design with four engines mounted directly to the wings. After significant structural modifications, the aircraft operated safely for nearly 30 years before being retired with honor.

This became one of the first widely recognized examples of what uncontrolled material fatigue can lead to.

In simple terms, dislocations in steel are irregularities within what should otherwise be a uniform atomic lattice. Under repeated stress, these microscopic imperfections can accumulate strain. The material moves from the elastic region into the plastic region — and eventually, failure occurs.

No steel is entirely free from dislocations. In addition, finished steel components may suffer from stress corrosion cracking or intergranular corrosion. Under certain conditions, these phenomena can develop long after manufacturing.

In earlier decades, lower-quality steel could sometimes result in small surface “blisters” under paint — rust forming from within the structure. Sandblasting and repainting would not solve the problem permanently, as the corrosion originated internally. In severe cases, entire body panels had to be replaced.

We often say that rust requires water (H₂O) and oxygen. Remove one of those elements, and corrosion cannot occur. Yet stress-related corrosion mechanisms can sometimes begin even when metal is heavily protected — slowly developing over time.

Fortunately, advances in metallurgy and production standards have dramatically reduced such issues in modern manufacturing. Today’s automotive industry applies far stricter quality control over materials than in the past.

Even so, the lessons remain relevant. Material science matters. Structural integrity matters. And quality control matters.

In the automotive sector — including components such as wheels and structural parts — quality assurance has become a central focus. Companies operating in the tyre and wheel industry, such as Dekksperten, emphasize reliable sourcing and material standards to ensure durability and safety in everyday driving.

Dislocations are a natural part of material reality. The key is not to eliminate them entirely — that is impossible — but to understand them, manage them, and design around them.

History has shown us what happens when we fail to do so.