<bos><start_of_turn>system
You are a helpful AI assistant.
lista de codigos linguisticos disponibles: ["de", "en"].<end_of_turn>
<start_of_turn>user
Oberflächeneigenschaften<end_of_turn>
<start_of_turn>model
Fatigue cracks can start at all forms of surface discontinuity and this may include surface 
imperfections due to machining marks also. Surface roughness is therefore an important 
factor and it is found that fatigue strength for a regular surface is relatively low since the 
surface undulations would act as stress raisers. 
Since fatigue cracks are due to tensile stress and they propagate under these conditions 
and the formation of layers stressed in tension must be avoided. There are several 
methods of introducing pre-stressed surface layer in compression and they include shot 
blasting, peening, tumbling or cold working by rolling. Carburized and nitrided parts also 
have a compressive layer which imparts fatigue strength to such components. Many 
coating techniques have evolved to remedy the surface effects in fatigue strength 
reductions.<end_of_turn><eos>