Why did the brake drum fail during operation?
Release Time:
2019-08-21
During the use of automobile brake drums, if brake drum failure occurs, it will pose a danger to us. What causes brake drums to fail during operation? Let's find out! Sampling analysis was performed on failed brake drums (including one each with longitudinal cracks, creep cracks, and surface hard spots). The working environment of brake drums is relatively harsh. Under the impact of thermal stress caused by frequent braking (each braking event is equivalent to an impact thermal stress), generally speaking, thermal shock can occur if the heating or cooling rate is greater than 93, or if heating is very rapid and uneven, or if temperature fluctuations in the casting exceed 102. Due to poor heat dissipation conditions of the brake drum, the temperature rises. When the temperature reaches about 730℃, if the stability of pearlite is not good, it will decompose, and its volume will expand, causing phase transformation stress. If the superimposed peak value of phase transformation stress and thermal stress exceeds the thermal fatigue stress, thermal fatigue cracking will occur. Similarly, if the environment is extremely harsh or the thermal conditions are very poor at this time, and the temperature rises above the eutectoid transformation temperature, austenite will form. Under strong cooling conditions, such as water cooling or strong air cooling, hardening phases such as martensite, bainite, or troostite will form. This explains why failed brake drums exhibit both cracking and the formation of hard spots on the surface.
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