21-05-2021, 09:56 PM
(This post was last modified: 21-05-2021, 09:59 PM by Bob Culver.)
Sorry Tony
Here is a translation
Cranks fail from fatigue. In general the higher the final as finished tensile strength in tons per square inch (tsi) the greater the resistance to fatigue. But for complex shapes processes which place the surface layer in compression have a further greater effect. ie shot peening. On modern cars the fillets are rolled. Nitriding another method. The absorbed nitrogen compresses the surface layer.The effect of the latter on fatigue life is very considerable. But only a few steels are ideally suited to nitriding. EN40b is one. Hence its wide use for high performance cranks, and so its legendary status. If not to be nitrided no gain over other steels of same finished strength. But nitriding is very advantageous.
Most basic texts on metal fatigue include a graph comparing life of nitrided items with others. The gain is considerable and presumably expalins the success of Phoenix.
I am not trying to interfere but seems to me the basic decison is to adopt nitrided or not. Most else follows
Here is a translation
Cranks fail from fatigue. In general the higher the final as finished tensile strength in tons per square inch (tsi) the greater the resistance to fatigue. But for complex shapes processes which place the surface layer in compression have a further greater effect. ie shot peening. On modern cars the fillets are rolled. Nitriding another method. The absorbed nitrogen compresses the surface layer.The effect of the latter on fatigue life is very considerable. But only a few steels are ideally suited to nitriding. EN40b is one. Hence its wide use for high performance cranks, and so its legendary status. If not to be nitrided no gain over other steels of same finished strength. But nitriding is very advantageous.
Most basic texts on metal fatigue include a graph comparing life of nitrided items with others. The gain is considerable and presumably expalins the success of Phoenix.
I am not trying to interfere but seems to me the basic decison is to adopt nitrided or not. Most else follows