Product List
13416835050
Tel：0769-22024833
Contact：Dora
mobile：13416835050
Fax：0769-22024855
Email：sales@gd-kc.com
ADD：Pengdong Industrial Park, shuilian, Nancheng District, Dongguan City
Position：Home 》News
Discussion on the main factors affecting the fatigue strength of the spring
Published：2014.07.16 News Sources：kaichuang spring machinery Views：
Introduction: fatigue strength refers to the spring metal forming materials in infinitely many times under alternating load, the maximum stress without destruction of the material itself, the fatigue strength of metal materials is also called the fatigue limit. In practical application, metal materials is not possible for infinite times alternating load test, the spring fatigue strength in many tests after application, the fatigue limit is decreased. So, what are the main factors that influence the fatigue strength of the spring?
The yield strength of 1 spring material. Generally speaking, spring the yield strength of the material is high, the fatigue strength is also higher. Therefore, in order to enhance the anti fatigue strength, try to improve spring material yield strength or the yield strength and tensile strength ratio higher material. Compared with the same material, fine grain structure than the coarse grain microstructure has higher yield strength, the fatigue strength is high.
Surface quality of 2 spring material. The maximum stress surface condition usually occurs in the spring material surface, so the surface quality of spring has a great influence on the fatigue strength. For example, spring material in the rolling, drawing and winding (computer spring machine) cracks, defects and defects such as scars caused by the process is often the main cause of spring fatigue fracture.
The surface roughness is low, the stress concentration is small, the fatigue strength is also higher. The material effect of surface roughness on the fatigue limit is increased with the increase of roughness, the decline of fatigue limit. In the same roughness conditions, rolling method of different materials and different spring machine, the fatigue limit decrease to different extent, such as cold rolled spring to reduce the level of specific heat volume spring small. Because the steel coil spring and heat treatment, the oxidation of the spring material surface become rough and generating decarburization phenomenon, this will reduce the fatigue strength of the spring. This is why we sometimes grinding, for surface pressure, shot blasting and rolling processing, the main is to improve the fatigue strength of the spring.
3 size effect. The dimension of the material the greater possibility, due to defects caused by all kinds of cold and hot processing technology is high, the surface defects of the possibility is bigger also, these factors will lead to the decline of spring fatigue strength. Therefore in the application we calculated the fatigue strength of the spring to consider the influence of size effect.
The 4 metallurgical defects. Metallurgical defects refers to the non metal impurities, bubbles and the elements of the material in the segregation. Inclusions present in the material surface is a concentrated source of stress, will cause the fatigue crack prematurely between inclusion and matrix interface. Therefore, the use of measures of vacuum smelting and vacuum pouring in, can greatly improve the quality of steel.
5 corrosion medium. Spring working in corrosive medium, because the surface layer or grain boundary corrosion pitting surface and become the source of fatigue, with force will be gradually extended to the fracture phenomenon. For example, in freshwater spring steel, the fatigue limit is only 10%~25% in air. Influence of corrosive medium on the fatigue strength of the spring, and spring not only by the number of variable load, but also related to working life. So the design and calculation of spring by the corrosion effect, should be considered in the working life.
In practical application, the spring to consider working in corrosive condition, in order to ensure that the fatigue strength, the high corrosion resistance material, such as stainless steel, non ferrous metal, or on a spring surface treatment to increase protection layer, such as coating, oxidation, spraying, painting etc.. The practical application indicated that cadmium plating can greatly improve the fatigue limit of spring.
6 temperature coefficient. Fatigue strength temperature steel, down from room temperature to 120 ℃, from 120 ℃ to 350 ℃, temperature is higher than 350 ℃ drop again, no fatigue limit at high temperature. Spring under high temperature, to consider the use of heat resistant steel; under the conditions below room temperature, fatigue limit of steel has increased. The content of technical support from Kaichuang spring machine: http://www.kcmcnc.com/en/.
The yield strength of 1 spring material. Generally speaking, spring the yield strength of the material is high, the fatigue strength is also higher. Therefore, in order to enhance the anti fatigue strength, try to improve spring material yield strength or the yield strength and tensile strength ratio higher material. Compared with the same material, fine grain structure than the coarse grain microstructure has higher yield strength, the fatigue strength is high.
Surface quality of 2 spring material. The maximum stress surface condition usually occurs in the spring material surface, so the surface quality of spring has a great influence on the fatigue strength. For example, spring material in the rolling, drawing and winding (computer spring machine) cracks, defects and defects such as scars caused by the process is often the main cause of spring fatigue fracture.
The surface roughness is low, the stress concentration is small, the fatigue strength is also higher. The material effect of surface roughness on the fatigue limit is increased with the increase of roughness, the decline of fatigue limit. In the same roughness conditions, rolling method of different materials and different spring machine, the fatigue limit decrease to different extent, such as cold rolled spring to reduce the level of specific heat volume spring small. Because the steel coil spring and heat treatment, the oxidation of the spring material surface become rough and generating decarburization phenomenon, this will reduce the fatigue strength of the spring. This is why we sometimes grinding, for surface pressure, shot blasting and rolling processing, the main is to improve the fatigue strength of the spring.
3 size effect. The dimension of the material the greater possibility, due to defects caused by all kinds of cold and hot processing technology is high, the surface defects of the possibility is bigger also, these factors will lead to the decline of spring fatigue strength. Therefore in the application we calculated the fatigue strength of the spring to consider the influence of size effect.
The 4 metallurgical defects. Metallurgical defects refers to the non metal impurities, bubbles and the elements of the material in the segregation. Inclusions present in the material surface is a concentrated source of stress, will cause the fatigue crack prematurely between inclusion and matrix interface. Therefore, the use of measures of vacuum smelting and vacuum pouring in, can greatly improve the quality of steel.
5 corrosion medium. Spring working in corrosive medium, because the surface layer or grain boundary corrosion pitting surface and become the source of fatigue, with force will be gradually extended to the fracture phenomenon. For example, in freshwater spring steel, the fatigue limit is only 10%~25% in air. Influence of corrosive medium on the fatigue strength of the spring, and spring not only by the number of variable load, but also related to working life. So the design and calculation of spring by the corrosion effect, should be considered in the working life.
In practical application, the spring to consider working in corrosive condition, in order to ensure that the fatigue strength, the high corrosion resistance material, such as stainless steel, non ferrous metal, or on a spring surface treatment to increase protection layer, such as coating, oxidation, spraying, painting etc.. The practical application indicated that cadmium plating can greatly improve the fatigue limit of spring.
6 temperature coefficient. Fatigue strength temperature steel, down from room temperature to 120 ℃, from 120 ℃ to 350 ℃, temperature is higher than 350 ℃ drop again, no fatigue limit at high temperature. Spring under high temperature, to consider the use of heat resistant steel; under the conditions below room temperature, fatigue limit of steel has increased. The content of technical support from Kaichuang spring machine: http://www.kcmcnc.com/en/.