There is something inherently satisfying about watching a layer of heavy oxidation vanish instantly under a beam of light. But for engineering design managers and automation specialists, this isn't magic—it is Laser Ablation . In the field of industrial maintenance, non-contact surface cleaning is becoming the gold standard for restoring precision parts without altering the substrate tolerance. Advertisement The Physics: How Laser Ablation Works Laser cleaning operates on the principle of sublimation . The process relies on the differential absorption coefficients of the materials involved. When the high-energy pulse hits the surface, two things happen: The Oxide Layer (Rust): Has a high absorption rate. It absorbs the energy, heats up rapidly, and transitions directly from a solid state to a gas (plasma) phase. The Substrate (Steel): Has a high reflection rate. Once the rust is removed, the laser reflects off the shiny metal, eff...
Figure 1: The Critical Stress curve. Note how the J.B. Johnson parabola is tangent to the Euler curve at C c , creating a perfectly smooth transition between failure modes. The Danger of the Wrong Formula In Column Design (Part 4) , we introduced the Euler formula. However, Euler's equation assumes the column fails purely by elastic instability (buckling). If you try to apply Euler's formula to a Short Column (where the slenderness ratio KL/r is less than the transition value C c ), the results are dangerous. The formula will predict a critical load much higher than the column can actually support. In reality, the material will yield (crush) long before it buckles theoretically. Advertisement Search for Structural Analysis Books The J.B. Johnson Formula To accurately predict failure in short or intermediate columns, we use the J.B. Johnson parabolic formula. Recall: The Column Constant (C c ) Before...