發(fā)動機(jī)配件的變形和疲勞斷裂:
Deformation and fatigue fracture of engine accessories:
一)變形
1) Deformation
發(fā)動機(jī)在使用過程中,由于受力的作用,使零件的尺寸或形狀產(chǎn)生改變的現(xiàn)象叫做零件的變形。
During the use of an engine, the phenomenon of deformation of parts is called the deformation of parts, which results in changes in the size or shape of the parts due to the action of force.
發(fā)動機(jī)零件,特別是氣缸體、氣缸蓋等基礎(chǔ)零件的變形,將嚴(yán)重影響相應(yīng)總成的性能和發(fā)動機(jī)的使用壽命。研究零件變形的機(jī)理及其影響因素,對預(yù)防零件變形及變形件的維修具有十分重要的意義。
The deformation of engine components, especially basic components such as cylinder blocks and cylinder heads, will seriously affect the performance of corresponding assemblies and the service life of the engine. Studying the mechanism and influencing factors of component deformation is of great significance for preventing component deformation and repairing deformed parts.
零件的變形包括彈性變形和塑性變形兩種。彈性變形是指金屬在卸除外力后能完全恢復(fù)的那部分變形。彈性變形量很小,一般不超過材料原長度的0.1%-1.0%。塑性變形是指材料在外力除去后,不能恢復(fù)的那部分 變形。
The deformation of parts includes two types: elastic deformation and plastic deformation. Elastic deformation refers to the part of deformation that a metal can fully recover after removing external forces. The elastic deformation is very small, generally not exceeding 0.1% -1.0% of the original length of the material. Plastic deformation refers to the deformation of a material that cannot be restored after external forces are removed.
二)疲勞斷裂
2) Fatigue fracture
疲勞斷裂是指零件在反復(fù)多次的應(yīng)力或能量負(fù)荷循環(huán)后才發(fā)生的斷裂現(xiàn)象。零件在使用過程中發(fā)生的斷裂,約有60%-80%屬于疲勞斷裂。其特點(diǎn)是斷裂時(shí)應(yīng)力低于材料的抗拉強(qiáng)度或屈服極限。不論是脆性材料還是塑性材料,其疲勞斷裂在宏觀上均無明顯塑性變形的脆性斷裂。柴油發(fā)動機(jī)中齒輪輪齒的折斷、曲軸的折斷等多為疲勞斷裂的結(jié)果。
Fatigue fracture refers to the fracture phenomenon of a component that occurs after repeated stress or energy load cycles. About 60% -80% of the fractures that occur during the use of parts belong to fatigue fracture. Its characteristic is that the stress at fracture is lower than the tensile strength or yield limit of the material. Both brittle and plastic materials exhibit brittle fracture with no significant plastic deformation at the macroscopic level during fatigue fracture. The fracture of gear teeth and crankshaft in diesel engines is often the result of fatigue fracture.
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