Grinding Characteristics of MoS_(2)-Coated Brazed CBN Grinding Wheels in Dry Grinding of Titanium Alloy

As an important green manufacturing process,dry grinding has problems such as high grinding temperature and insufficient cooling capacity.Aiming at the problems of sticking and burns in dry grinding of titanium alloys,grinding performance evaluation of molybdenum disulfide(MoS_(2))solid lubricant coated brazed cubic boron carbide(CBN)grinding wheel(MoS_(2)-coated CBN wheel)in dry grinding titanium alloys was carried out.The lubrication mechanism of MoS_(2)in the grinding process is analyzed,and the MoS_(2)-coated CBN wheel is prepared.The results show that the MoS_(2)solid lubricant can form a lubricating film on the ground surface and reduce the friction coefficient and grinding force.Within the experimental parameters,normal grinding force decreased by 42.5%,and tangential grinding force decreased by 28.1%.MoS_(2)lubricant can effectively improve the heat dissipation effect of titanium alloy grinding arc area.Compared with common CBN grinding wheel,MoS_(2)-coated CBN wheel has lower grinding temperature.When the grinding depth reaches 20μm,the grinding temperature decreased by 30.5%.The wear of CBN grains of grinding wheel were analyzed by mathematical statistical method.MoS_(2)lubricating coating can essentially decrease the wear of grains,reduce the adhesion of titanium alloy chip,prolong the service life of grinding wheel,and help to enhance the surface quality of workpiece.This research provides high-quality and efficient technical support for titanium alloy grinding.

Residual stress model of pre-stressed dry grinding considering coupling of thermal, stress, and phase transformation

Pre-stressed dry grinding can result in a hardened layer on the part surface while the surface residual stress is controlled.Considering the factors of the thermal field,pre-stress,and microstructural transformation,a proximate model of surface residual stress for pre-stressed dry grinding is established using the ANSYS finite element simulation method and verified through experiment.The variation laws and mechanisms of the residual stress along with the grinding parameters are revealed.Under the comprehensive effect of pre-stress and phase transformation,the residual stress of pre-stressed dry grinding is revealed mainly as compressive stress.This increases as the pre・stress and grinding depth increase.Under the coupling effect,pre-stress has larger influence on the residual stress than the grinding depth.The model can analyze and predict the residual stress of pre-stressed dry grinding in general.

Experimental Research on Performances of Dry-grinding Fine Cement for Grouting

The performances of dry grinding fine cement (DFC) in grouting procedure were experimentally studied.The measurement of its fineness and simulated test for injectability showed that this DFC could be used to inject rock mass with micro fissure.In order to improve the grouting quality,the water cement ratio and discarding time of slurry should be controlled precisely.If the water cement ratio is over 2∶1 in slurry that is made from DFC,it is not suitable to grout.Finally,the influence of different mixing times on strength of hydrated cement made from the DFC is explained by microstructure analysis with SEM.