Residual Stress of steel tube and its harm

When the precision seamless steel pipe is deformed because of the external factors (such as force, humidity, temperature field, etc.), the internal forces that interact with each part of the object are produced to resist the effect of the external cause, and try to restore the object from the post deformation position to the position before the deformation.

The internal force at a certain unit area of the cross section is called stress. Perpendicular to the cross section is called normal stress or normal stress. The tangent to the cross section is called shear stress or shear stress.

How to measure stress?

A stress gauge or strain gauge is an instrument for measuring the internal stress of an object. Generally, the signals of strain gauges are collected and converted into electrical signals for analysis and measurement.

The method is to put the strain sheet on the measured object to stretch together with the strain of the measured object so that the metal foil inside is elongated or shortened with the strain. The resistance of many metals will change with mechanical elongation or shortening. The strain gauge is based on this principle, which is measured by measuring the change of resistance. The sensitive grid of general strain gauges is copper chromium alloy, whose resistance change rate is constant and proportional to strain.

Through the Wheatstone bridge, the proportional relation of the resistance can be transformed into voltage. Then different instruments can transform the voltage change into measurable data.

For the stress meter or strain gauge, the key indicators are the test accuracy, the sampling speed, the number of channels that can be supported, the dynamic range, the support of the strain gauge and so on. And the software of the stress meter is also very important, it needs to be able to display real-time, real-time analysis, real-time recording and other functions. The high-end software also has various signal processing capabilities.

In addition, some instruments are designed by means of spectrum, diaphragm and so on.

So what is the harm of stress?

1. Crack

Because of the existence of stress, after exposure to the external effect (such as exposure to chemical solvents or baking at the back of the paint at the back end of the paint), the stress release can be induced to crack in the residual stress position. Cracking is mainly concentrated at gate or excessive filling.

2. Warpage and deformation

Because of the existence of residual stress, the product will have a long time internal stress release at room temperature or the process of residual stress release in a short time. At the same time, the product has a poor local position, and the product will be warped or deformed at the residual stress position.

3. Product size change

Because of the existence of stress, if the environment reaches a certain temperature in the process of product placement or treatment, the product will change due to stress release.

If you have any problem of precision seamless steel tube, you can contact with Raymond company by email or whatsapp on website.