Spherical contact mechanical analysis of roller cone drill bits journal bearing

Fang contact model is introduced to analyze stress of the spherical fixed ring journal bearing.Developed calculation programs in the MATLAB software which are utilized to calculate the contact characteristics of roller cone drill bits spherical fixed ring journal bearing.In addition,effects of external load,radius clearance values,and material parameter on the mechanics performance were investigated.The results show that the value of external load has a direct pronounced effect on the contact characteristics of journal bearing.There is a significant positive correlation between contact pressure and external load,radius clearance value,and the Young's modulus of material.However,there is an evident negative correlation between contact radius of journal bearing and radius clearance value,and the Young's modulus of material.The smaller radius clearance value of journal bearing is,the more centralized contact region will be,so the corresponding contact pressure will be higher.From the perspective of reducing friction and wear,we need select the materials which have high strength and good toughness.Not only might this can improve the wear resistance,it also effectively decreases the contact pressure.In this case,we can prolong the service life of roller cone drill bits journal bearing.

Fabrication of Ceramic-Polymer Piezo-Composites with Triply Periodic Minimal Interfaces via Digital Light Processing

The geometry of the phase interface in co-continuous piezoelectric composites is critical in improving their piezo-electric properties.However,conventional co-continuous piezoelectric composites are mostly simple structures such as wood stacks or honeycombs,which are prone to stress concentrations at the joints,thus reducing the fatigue service performance and force-electric conversion efficiency of piezoelectric composites.Such simple structures limit further improvements in the overall performance of co-continuous piezoelectric composites.In this study,based on the digital light processing 3D printing method,we investigated the influence of three dif-ferent structures-the gyroid,diamond,and woodpile interfaces-on the piezoelectric and mechanical properties of co-continuous ceramic/polymer piezoelectric composites.These findings demonstrate that the gyroid and di-amond interfaces outperformed the ceramic skeleton of the woodpile interface in terms of both mechanical and electrical properties.When the ceramic volume percentage was 50%,the piezo-composite of the gyroid surface exhibited the greatest hydrostatic figure of merit(HFOM),reaching 4.23×10^(−12) Pa^(−1),and its piezoelectric coeffi-cient(d_(33))and relative dielectric constant(εr)reached 115 pC/N and 748,respectively.The research results lay the foundation for the application of co-continuous piezoelectric composites in underwater communication and detection.