Residual stresses: how to mitigate them to guarantee the quality of the machined parts

giugno 14, 2023

Residual stresses are a common phenomenon that can occur during machining processes. The internal ones remain in the material after being subjected to processes such as turning, hobbing or shaving. While the surface of the part appears stable, residual stresses can cause significant problems if not addressed correctly.

How do residual stresses appear?

These appear in different forms and with various alarm bells. Among the most common are geometric distortions. A machined part can deform or take on a different shape from the desired one due to the residual stresses present inside it. For example, a turned shaft could bend or deviate from its expected straightness even many hours after machining.
Dimensional deformations are another symptom of residual stresses. These can cause unwanted variations in the dimensions of the part after machining. A turned part, for example, could contract or expand, leading to discrepancies from required tolerances.

Furthermore, the residual stresses can cause unforeseen deformations after the heat treatment phase. Especially in treatments that take place at high temperatures such as carburizing and hardening, excessive residual stresses can lead to unwanted deformations that compromise the quality of the piece.

How to reduce the impact of residual stresses?

Fortunately, there are several techniques that can be used to mitigate residual stresses in machined parts and ensure their quality.

Let's have a look at some of the most common strategies:

Targeted heat treatments: their application can help reduce residual stresses. The annealing or quenching and tempering process of the blank can allow the material to gradually relax, reducing internal stresses.

Straightening or controlled deformation: In some cases, they can be applied to reduce residual stresses. These processes involve the plastic deformation of the part in a controlled way, allowing the effects of residual stresses to be corrected.

Controlled sequential machining: can help reduce residual stresses. This may include using progressive machining steps or alternating between cutting and stress relief operations to minimize stress buildup.

Optimization of cutting conditions: cutting speed, feed and the use of appropriate tools can help reduce residual stresses. Correct choice of tools and machining parameters can reduce stress buildup during the process.

It is important to consider the material, part geometry and machining specifications to choose the most appropriate residual stress mitigation techniques. Sometimes, a combination of several strategies may be required to achieve optimal results.

In conclusion, residual stresses can be a significant problem for machined parts. However, with the adoption of the right mitigation strategies, it is possible to guarantee the quality of the parts, minimizing the negative effects of residual stresses. In GSI, thanks to our technical office, we are able to support projects to adopt the right strategy and prevent residual stresses.

Residual stresses: how to mitigate them to guarantee the quality of the machined parts

How do residual stresses appear?

How to reduce the impact of residual stresses?

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