What is Residual Stress?

Generalized:
Residual stress refers to the material or workpiece in the processing process after the temperature and no external force and restraint, in order to achieve the balance of force exists in the object within the elastic stress.​

Residual Stress
∥
Elastic Stress

In terms of atomic point of view, when the material is subjected to larger external energy (processing), it causes the displacement of the atomic group, which is the formation and accumulation of the poor row, which is the distortion of the lattice. Lattice twist under the lattice and lattice between the internal existence of the "lattice strain energy", the strain can be called residual stress; when the internal lattice strain energy, the greater the residual stress. Since the twisted lattice is a spring-type resilient mechanism, the residual stress is the same as the elastic stress.​
​

Residual Stress Sources And Hazards​

🔥Casting
🔥forging
🔥welding
🔥Heat treatment
🔥Machining
🔥other
🎈Cumulative contraction
🎈Rapid expansion
🎈Hot cracking
🎈Grain deformation​

Residual Stress

✔Thermal Stress
✔Phase change stress
✔Solidification shrinkage stress
✔Plastic working stress​​

Elimination Of Residual Stress

(So that the internal distortion of the material lattice row row of energy to move again to become the perfect lattice)​

What is Vibration To Eliminate Stress

  • In terms of atomic point of view, when there is residual stress in the material, it will cause lattice distortion, this time there is a "lattice strain energy", the greater the internal lattice strain energy, that is, the greater the residual stress. The twisted lattice belongs to the spring-type springback mechanism, so the residual stress is the same elastic stress, when there is a new external energy to stimulate the twisted lattice, so that the original stuck lattice by external energy stimulation, elastic recovery To the initial position into a perfect lattice (perfect lattice that is no difference row, no strain energy lattice structure), that is, the release of residual stress.
  • When the material is subject to larger external energy (processing) will cause the atomic group of the shift, which is the formation and accumulation of poor row, and move the accumulation of the difference is the release of the stress phenomenon, to move the difference row only by shear stress Of the role, so the greater the shear stress is to promote the effect of poor row movement better. And fluctuation is the best source of shear stress inside the material.
  • According to the above two described, through the vibration to produce fluctuations in the energy of the material to twist the lattice by the poor row of movement, has reached the release of residual stress into a perfect lattice, the process of vibration to eliminate stress.
Twisted lattice
Stress relief
Perfect lattice

Vibatory Stress Relief(V.S.R)

The use of vibration to the energy into the material inside, and thus reduce the residual stress within the material technology. Residual stress has a considerable impact on the metal components, so the metal components in the processing process must pay attention to the existence of residual stress in order to create precision meet the requirements and have excellent quality components. This technology has been shown to be effective in reducing residual stresses, reducing metal component deformation and enhancing the strength of metal materials, and vibration technology with energy saving, pollution, low cost, high efficiency, easy operation and so on.

There are many metal processing industry application oscillation technology to achieve the following items:

(1) to improve the welding quality (2) to avoid deformation (3) to prevent stress corrosion
(4) to enhance the service life of the workpiece (5) to save heat treatment costs up to 95%

Synchronous Vibration Welding​

The residual stress release after welding is the culprit in the deformation, cracking, and future strain of the weld, so it is the most distressing problem for the welding designer. The residual stress occurs due to the non-uniform thermal stress caused by the heat applied during welding, or the multiplication effect of the coefficient of thermal expansion which varies between the bead material and the base material, and the residual stress value after welding is abrupt Uneven magnification. If the application of welding at the same time into the oscillation energy can affect the molten pool solidification of the organization, in the molten gold crystal will break the columnar crystal is too large growth, increase the grain nucleation rate, grain refinement, reduce the columnar crystal Blindly melting the phenomenon of vertical melting line, thus breaking the coherence of grain growth direction and slow down the phenomenon of segregation of the weld structure, based on the general concept of the material can be said to be improved bead organization.
    In the perspective of the formation of stress interpretation, the weld temperature from the melting point and down to room temperature, the internal stress value from zero to the highest, just as the material within the binding of the situation is proportional to, so the molten pool is about to be formed when the stress That is, with the increase in binding and gradually release the internal stress, when the weld can be achieved to achieve the best effect of stress relief; Moreover, at higher temperatures due to the expansion of the vibration between atoms, resulting in reduced row of obstacles from the additional energy required, At this point the addition of the oscillation can just be multiplied by its energy, and play the best difference row effect. So it will be in the residual stress to get a greater stress relief effect, so this method can be done after welding to do more stress relief effect is better.
No synchronous welding lattice

V.S
Synchronous welding lattice​

Applicable Material​

All kinds of carbon steel, alloy steel, tool steel, stainless steel, manganese steel, chromium-nickel alloy, aluminum alloy, titanium alloy, cast iron, cast steel, aluminum die casting castings, forgings and welding structure.

Applicable Industry​

  1. High output, high variety, high production efficiency requirements of large and medium-sized machinery factory, to meet the machinery factory to eliminate residual stress applications.
  2. Aircraft, ships, weapons and other military projects, can enhance the weapons and equipment manufacturing technology to ensure that the focus of military equipment, quality and accuracy.
  3. Steel bridge, steel construction, oil and electricity transport pipelines, chemical storage tanks and other public works, can solve the public facilities of fatigue corrosion and deformation damage, to ensure that the public facilities life and safety.

V.S.R. And Heat Treatment Comparison Table​

Project
TST-VSR
Heat Treatment
Operating costs
Cheap, cost per kilogram of 0.1 or less​
Expensive, cost about $ 30 or more per kilogram (at current price)​
Operation procedure
Simple, only four hours of education and training​
The setting is simple, but it must be done according to the table​
Operating time​
Short, about an hour or so (depending on the size of the workpiece)​
Long, about several hours or even dozens of hours (depending on the procedures required)​
Side effect​
At room temperature operation, no decarburization, oxidation, rust and other troubles​
Material due to gas oxidation, resulting in rust and other troubles​
Material ingredient
Room temperature operation, no element diffusion oxidation and other issues​
Decarburization, alloying elements to soften the material​
Material restrictions
Non-metallic material restrictions​
There are metal material restrictions, such as: stainless steel​
Mechanical properties
Does not affect at all
Will soften the material, the intensity becomes low, causing corrosion concerns​
Processing deformation
Completely without deformation, apply to the process of stress relief​
Will lead to deformation, not applicable to finished products​
Effect
Stress relief can reach 40 ~ 70% or more, confirmed by stress measurement​
Only the annealing part can eliminate most of the stress, but other processes will produce stress (such as: normalization, quenching), and no measurement confirmed​

Examples Of Cases​

Product Name
Material
Purpose And Effect
Aluminum die-casting mold​
SKD-61
Improve the accuracy, manufacturing accuracy, service life, reduce the mold when the secondary processing deformation​
Casting products​
FC,ADC
Improve the accuracy, reduce the working hours and secondary processing of deformation, to prevent post-casting strain​
Plastic molding mold​
SKD-61
Improve the accuracy, manufacturing accuracy, service life, reduce the mold when the secondary processing deformation​
Forging machine tools​
SC
Reducing the stress and the weld crack generated by the change in temperature drop after welding​
Automotive exterior sheet stamping die​
FCD
Improve the accuracy, manufacturing accuracy, service life, reduce the mold when the secondary processing deformation​
Slide rail, machine tool base​
FC
Improve accuracy, reduce processing steps, improve product accuracy, extend the service life​
Steel columns, steel structures, racks,
Welded structural parts​
SS
Improve the welding quality and service life, weld grain microstructure fine​
Turbine housing, turbine blades​
FC
Improve the accuracy, improve the deformation before or after processing or prevent the strain after casting​
Large metal pipelines,
Gas (oil) tank
Mn alloy​
Reduce the weld bead and the bead structure is miniaturized​
Aluminum alloy skin​
AL
Reduce fatigue strain, and improve the solderability, reduce the weld crack and weld the structure of the subtle

TST-VSR Equipment Technical Principles

The vibration vibration principle of the TST-VSR equipment is developed by the use of a low-frequency vibration of the exciter to stimulate the natural frequency of the special high frequency band inside the workpiece itself, thereby eliminating its own residual stress, This technology is the company's high-frequency wave (the essence of this technology, has obtained the US patent), this vibration technology is the most consistent and most effective application of the appropriate vibration energy to stimulate the twisted lattice into a perfect lattice technology. Can be for each kind of metal material, size, shape, weight automatically find its special frequency and automatically perform vibration to eliminate stress.​

High Frequency Wave​

Through the low-frequency vibration in the 100HZ scan, the resulting signal through the computer conversion, to find the high frequency of the workpiece frequency, and then the specific energy to vibration, resulting in fluctuations (alternating shear stress) to promote the poor row of movement. Plastic yield, thereby reducing the peak residual stress, while the distribution of residual stress uniformity. This technology is exclusively owned by Taiwan Stress Co., Ltd.​