“With shot peening, you have a random spattering of shot going everywhere, and you might hit one point a half-dozen times before you hit the spot next to it. He added that control is what differentiates LPB from traditional burnishing and other stress-relief processes like shot peening. “As long as you do that as little as possible, you can keep the bulk of the cold-working low in the material.” “You plastically deform in tension in order for it to rebound with residual compression,” Prevey explained. The process might at first glance look like traditional burnishing, during which a tool applies pressure and smooths the material surface. “Early on, we learned that there is a lot of benefit to being able to put in the compressive stresses while keeping cold-working low.”įrom this came LPB. Lambda’s roots go back to the 1970s, when it was primarily a laboratory that studied surface treatments and residual stresses. That was Mike Prevey, vice president of enigneering and manufacturing at Lambda Technologies Group, Cincinnati. And you can impart some residual compressive stresses while you’re doing it.” You’re basically rolling a tool-in old-school burnishing, it’s usually a wheel-type tool-across a piece of metal to smooth the surface. Burnishing of railroad axles is a common application. “Conventional burnishing has been around for decades. It’s called low-plasticity burnishing, or LPB. Another option is burnishing, an old-school process that, like shot peening, has a high-tech cousin. Shops might apply heat (like in postweld heat treatments) vibratory stress relief shot peening or even shot peening’s high-tech cousin, laser shock peening. Unfortunately, the very act of fabrication stresses the material, so fabricators will need to employ various techniques to mitigate the effects of that stress.

Those that win the work will (ideally, at least) propose fabrications designed to last. With infrastructure spending set to rise, so will opportunities for metal fabricators.

The untreated portion of this weld has evidence of stress corrosion cracking (SCC).

Typetool crack