: +86 29 86033971   : zhao.wanbao@dcsxsm.com
You are here: Home » News » Knowledge » Eight main factors affecting the fatigue strength of metal materials

Product Categories

Contact Us

 :  +86 29 86033971
 : +86 29 86033972
 zhao.wanbao@dcsxsm.com
 : The Innovation Industrial Park, No.36, Jingwei Road ,Xi'an Economic and Technological Development Zone,Xi'an City,Shaanxi Province,China
Industry News

Eight main factors affecting the fatigue strength of metal materials

Views: 1     Author: Site Editor     Publish Time: 2022-04-18      Origin: Site

Eight main factors affecting the fatigue strength of metal materials

The fatigue strength of materials is very sensitive to various external and internal factors. External factors include the shape and size of parts, surface finish and use conditions, and internal factors include the composition of the material itself, organizational state, purity and residual stress. The slight change of these factors will cause the fluctuation or even large change of the fatigue properties of materials.

The influence of various factors on fatigue strength is an important aspect of fatigue research, which will provide basis for rational structural design of parts, correct selection of materials and reasonable formulation of various cold and hot processing technologies to ensure that parts have high fatigue performance.

1. The impact of stress concentration

Conventional fatigue strength is measured by carefully processed smooth samples. However, there are inevitably gaps insingle double cardan half shaft supplier - Xinsanming different forms in actual mechanical parts, such as steps, keyways, threads and oil holes. The existence of these gaps causes stress concentration, so that the maximum actual stress at the root of the gap is far greater than the nominal stress borne by the parts, and the fatigue failure of parts often starts from here.

2. The influence of size factor

Due to the inhomogeneity of the material's structure and the existence of internal defects, the increase of the size leads to the increase of the failure probability of the material, thus reducing the fatigue limit of the material. The existence of size effect, is the laboratory small sample measured fatigue data used in the large size is an important problem in the actual parts, because cannot make the actual size of the parts of stress concentration and stress gradient completely similar to reappear in the small sample, resulting in the laboratory results with some specific parts touch each other between the fatigue damage.

3. The influence of surface machining state

There are always uneven processing marks on the machined surface, which are equivalent to tiny gaps, causing stress concentration on the surface of the material, thus reducing the fatigue strength of the material. Experiments show that for steel and aluminum alloys, the fatigue limit of rough machining (rough turning) is reduced by 10% to 20% or more than that of longitudinal fine polishing. The higher the strength of the material, the more sensitive it is to surface finish.

4. Loading experience effects

In fact, no part works under the condition of absolute constant stress amplitude, and the overloading and secondary loading in the actual work of materials will affect the fatigue limit of materials. The test shows that the phenomenon of overloading damage and secondary loading exercise generally exists in materials.

The so-called overload damage refers to the material running under a load higher than the fatigue limit for a certain period of time, will cause the material fatigue limit to decline. The higher the overload, the shorter the cycle required to cause damage.

In fact, under certain conditions, a few times of overloading will not cause damage to the material, but also strengthen the material due to deformation strengthening, crack tip passivation and residual compressive stress, thus improving the fatigue limit of the material. Therefore, the concept of overload damage should be supplemented and modified.

5. Chemical composition

There is a close relationship between the fatigue strength and tensile strength of materials under certain conditions. Therefore, any alloying element that can improve the tensile strength can improve the fatigue strength of materials under certain conditions. Comparatively speaking, carbon is the most important factor affecting the strength of materials. Some impurity elements forming inclusions in steel have adverse effects on fatigue strength.

6. Effects of heat treatment and microstructure

Therefore, the effect of heat treatment on fatigue strength is essentially the effect of microstructure. Due to different heat treatment, the same static strength can be obtained for materials with the same composition, but the fatigue strength can vary in a considerable range due to different structures.

At the same strength level, the fatigue strength of flake pearlite is obviously lower than that of granular pearlite. For granular pearlite, the smaller the cementite particles, the higher the fatigue strength.

The effect of microstructure on the fatigue properties of composites is not only related to the mechanical properties of the composites themselves, but also to the grain size and the distribution characteristics of the composites. Refinement of grain can improve the fatigue strength of the material.

7. Effects of inclusions

The inclusions themselves or the holes generated by them are equivalent to tiny notches. Under the action of alternating loads, stress concentration and strain concentration will be produced, which will become the crack source of fatigue fracture and have a bad effect on the fatigue properties of materials. The influence of inclusions on fatigue strength depends not only on the type, nature, shape, size, quantity and distribution of inclusions, but also on the strength level of materials and the level and state of applied stress.

8. Influence of surface property change and residual stress

Besides the surface finish mentioned above, the influence of surface state also includes the change of surface mechanical properties and the influence of residual stress on fatigue strength. The mechanical properties of the surface layer may be caused by the chemical composition and structure of the surface layer or by the deformation strengthening of the surface layer.

Quick Links

Products

Contact Us

  : +86 29 86033971
 : +86 29 86033972
  :  zhao.wanbao@dcsxsm.com
  : The Innovation Industrial Park, No.36, Jingwei Road ,Xi'an Economic and Technological Development Zone,Xi'an City,Shaanxi Province,China
Get In Touch
Copyright © Xi'an Xin Sanming Auto Parts Co.,Ltd All Rights Reserved. | Sitemap