Classification of residual stresses in metals(vibration stress relief equipment)？

Residual stresses in metals can be classified based on their origin, magnitude, and spatial distribution. Here are the main classifications:

1. By Origin:

a. Thermal Stresses:

These arise from non-uniform temperature distributions during heating and cooling processes. They occur when there is a mismatch between the thermal expansion and contraction rates of different regions within a metal. Examples include stresses induced during welding, casting, and quenching.

b. Mechanical Stresses:

These result from mechanical processing operations such as cold working, rolling, forging, and machining. Plastic deformation due to these processes causes dislocation movement and rearrangement, leading to residual stresses.

c. Phase Transformation Stresses:

These occur when phase transformations take place during heat treatment or cooling, and the new phases have different volumes or elastic properties. An example is the transformation of austenite to martensite in steels, which can cause significant residual stresses.

2. By Magnitude:

a. Macroscopic Stresses:

These are stresses that affect large areas or entire sections of a metal component. They are usually caused by significant thermal or mechanical processes and can lead to visible distortions or failures if not managed properly.

b. Microscopic Stresses:

Also known as "microstresses," these are localized stresses that occur at the grain or subgrain level. They are often the result of localized plastic deformation or phase transformations within individual grains.

3. By Spatial Distribution:

a. Uniform Stresses:

These are relatively constant throughout a given plane or volume of material. They do not vary significantly over the affected region.

b. Non-Uniform Stresses:

These vary across the material, either along a single axis or in multiple directions. They can be highly localized or spread over larger areas, depending on the nature of the process that induced them.

4. By Sign:

a. Tensile Stresses:

These are stresses that attempt to stretch the material apart. They can be detrimental to the integrity of the metal, especially under cyclic loading conditions, as they can promote crack initiation and propagation.

b. Compressive Stresses:

These are stresses that try to compress or squeeze the material together. Compressive residual stresses can be beneficial, as they can counteract externally applied tensile stresses and improve fatigue resistance.

Understanding the classification of residual stresses is crucial for selecting appropriate stress relief methods, such as heat treatment, mechanical stress relief, or vibration stress relief, to mitigate their negative effects on material performance and longevity. Residual stress measurements and analysis are often conducted using techniques like X-ray diffraction, neutron diffraction, hole drilling, and other strain gauge-based methods to quantify and characterize these stresses accurately.