【Mechanical Equipment Technology Exchange Edition】Mechanical Equipment 【Daily Question】20190717
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Question: What is low-cycle fatigue of metallic materials? What is the fatigue strength limit? There are no answers provided for this series of posts; fellow netizens are free to share their own opinions – just reply with what you understand. Replies earn rewards ranging from 5 to 15 points; all forum members are welcome to participate actively and support the development of the forum! ! ! Chemical Equipment and Machinery
Low-cycle fatigue: Fatigue that occurs when the stress levels acting on parts and components are high, with the number of cycles to failure generally being less than 104–105; this type of fatigue affects items such as pressure vessels and gas turbine components. The maximum stress that a material can withstand under infinite cycles of variable loading without breaking is known as the material’s fatigue limit
Low-cycle fatigue: Fatigue that occurs when the stress levels acting on parts and components are high, with the number of cycles to failure generally being less than 104–105; this type of fatigue affects items such as pressure vessels and gas turbine components. The maximum stress that a material can withstand under infinite cycles of variable loading without breaking is known as the material’s fatigue limit
The fatigue limit refers to the median fatigue strength at a specified number of cycles; when the number of cycles is different, it is called the conditional fatigue limit for that number of cycles, and it is sometimes simply referred to as the fatigue strength at that number of cycles. Definition of low-cycle fatigue: Fatigue failure with a fatigue life of 102 to 105 cycles is referred to as low-cycle fatigue. Low-cycle fatigue involves high cyclic stresses, which are often greater than σs, leading to plastic deformation until fracture; hence it is also known as plastic fatigue or strain fatigue. Fractures of things such as airplanes, ships, and bridges are sometimes caused by low-cycle fatigue.
Low-cycle fatigue: Fatigue that occurs when the stress levels acting on parts and components are high, with the number of cycles to failure generally being less than 104–105; this type of fatigue affects items such as pressure vessels and gas turbine components. The maximum stress that a material can withstand under infinite cycles of variable loading without breaking is known as the material’s fatigue limit
Low-cycle fatigue: Fatigue that occurs when the stress levels acting on parts and components are high, with the number of cycles to failure generally being less than 104–105; this type of fatigue affects items such as pressure vessels and gas turbine components. The maximum stress that a material can withstand under infinite cycles of variable loading without breaking is known as the material’s fatigue limit
#Should fatigue stress be considered for static equipment here? #quickreply
Low-cycle fatigue: also known as the conditional fatigue limit, or “low-cycle fatigue”. Refer to the stress limit value that the component can withstand based on the number of times it may be used during its working cycle. The fatigue limit refers to the median fatigue strength at a specified number of cycles; when the number of cycles is different, it is called the conditional fatigue limit for that number of cycles, and it is sometimes simply referred to as the fatigue strength at that number of cycles.
When a material or component is subjected to alternating stresses (stresses that change periodically over time), after a period of time, tiny cracks may form locally at internal defects or stress concentration areas. These cracks gradually expand, leading to sudden brittle fracture even when the stress is much lower than the yield point or strength limit. This phenomenon is known as fatigue. Low-cycle fatigue: high stress, low number of cycles.
The stress levels acting on parts and components are high, and the number of fatigue cycles before failure is generally below 10^3–10^4, as in the case of fatigue in pressure vessels, gas turbine components, etc； The maximum stress under which a metal material can withstand an infinite number of alternating stresses without fracturing is known as the fatigue limit or fatigue strength.
The fracture of metal materials under the action of low-cycle stress is known as low-cycle fatigue of metal materials. When a material is subjected to loads that vary over time, the stresses generated in it also change periodically as time goes by. If these alternating stresses exceed a certain limit strength and act repeatedly over an extended period, it will lead to the failure of the material; this limit is known as the material’s fatigue strength limit