In this paper, grind-hardening experiment on nodular cast iron QT400 was done with a surface grinder.The effects of the time discrepancy(TD) between the rst cut-out of the grinding wheel and the second cut-in of the two-pass grinding on the grinding force, microstructure, micro-hardness and uniformity of the hardened layer depth were studied. Then, by using the measured tangential grinding force, the simulation model of grinding temperature eld is established. We concluded that, with the same grinding parameters, increasing TD can reduce micro-hardness and harden layer depth, but the uniformity of the hardened layer increases. However, the change of TD has no noticeable in uence on the grinding force and microstructure of the hardened layer. The simulation results show that with the same grinding parameters, reducing the TD can increase the temperature of the workpiece in the second grinding. The experimental results are consistent with the simulation results, and the relative error of the hardened layer depth is 9%. Under the consistent grinding parameters, when TD =6s, the hardened layer depth is moderate and its uniformity is good.
A dry running experiment was to evaluate the anti oil-interruption ability of a novel cageless bearing, and the failure mechanism was investigated. The results reveal a distinct and singular modification in the bearing temperature profile, characterized by a distinctive shape resembling a "hump" after the oil-interruption. Additionally, the temperature of the outer ring decreased following the oil-interruption due to the newly cageless bearing reduced levels of frictional heat. The experimental data demonstrated that the bearing exhibited a functional lifespan of 88 minutes under dry conditions, indicating a notable anti oil-interruption ability. In summary, the premature failure of bearings can be attributed to significant sliding of the rolling elements, which caused by inadequate lubrication and cyclic contact. This study contributes to understanding the performance of cageless bearings and failure modes under extreme operating conditions, which provides a foundation for further research.
In this paper, grind-hardening experiment on nodular cast iron QT400 was done with a surface grinder. The effects of the time discrepancy(TD) between the first cut-out of the grinding wheel and the second cut-in of the two-pass grinding on the grinding force, microstructure, micro-hardness and uniformity of the hardened layer depth were studied. Then, by using the measured tangential grinding force, the simulation model of grinding temperature field is established. We concluded that, with the same grinding parameters, increasing TD can reduce micro-hardness and harden layer depth, but the uniformity of the hardened layer increases. However, the change of TD has no noticeable influence on the grinding force and microstructure of the hardened layer. The simulation results show that with the same grinding parameters, reducing the TD can increase the temperature of the workpiece in the second grinding. The experimental results are consistent with the simulation results, and the relative error of the hardened layer depth is 9%. Under the consistent grinding parameters, when TD =6s, the hardened layer depth is moderate and its uniformity is good.
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