Razlogi za močno obrabo zobnika so naslednji:
(1) The greater the adhesive wear load and the higher the surface temperature, the more serious the adhesion phenomenon. For metal materials with a certain hardness, wear tests are performed under different pressures to obtain a graph of the relationship between wear rate and pressure. When the pressure reaches more than 1/3 of the hardness of the material, severe wear will occur. According to the stress distribution diagram, it can be seen that the maximum stress contact point is the maximum pressure, and its value is 884.4 MPa. Because the quenching hardness of the chain socket is HRC4852, the corresponding hardness value is 4800MPa. Therefore, the pressure is far less than 1/3 of the material's hardness, so adhesive wear is not the main form of sprocket wear.
(2) Kontaktna obraba zaradi utrujenosti
The friction pair of the sprocket and the chain is an alternating contact stress, which is prone to fatigue pitting on the friction surface. The index for judging the contact fatigue strength of metals is the contact fatigue limit, that is, the maximum stress at which pitting corrosion does not occur under a certain number of stress cycles. The contact fatigue limit of 40Cr is σ0H=HRC17 plus 200 after surface quenching treatment, and σ0H=1016MPa is calculated. According to the stress distribution diagram, the maximum stress value of the sprocket socket is 884.4 MPa. Its value is very close to the allowable contact fatigue limit of the sprocket surface, and it is easier to cause pitting failure at the maximum stress. However, due to the poor lubrication conditions of the sprocket and the chain, pitting corrosion is too late to form and has caused wear. At this time, the main form of damage is wear rather than pitting. Contact fatigue wear is the main form of sprocket wear, which basically determines the service life of the sprocket.
(3) Abrazivna obraba
Ker veriga neizogibno pride v stik s premogom v prahu, je na njej majhna količina premoga v prahu, ki se pripelje do kontaktne točke vtičnice verige zobnikov. Premog v prahu vsebuje malo ostrega peska, zaradi česar bo površinski material zobnika med trenjem odpadel. To je abrazivna obraba. Obraba abraziva je povezana s trdoto tornega materiala in trdoto abraziva. Iz grafa vpliva trdote abraziva na obrabo je razvidno, da ko je trdota abraziva blizu trdote tornega materiala, bo to povzročilo -hitro obrabo tornega materiala. Ker je premog v prahu pomešan z malo ostrega peska, je to tudi eden od glavnih razlogov za pospešeno obrabo zobnika.
