Contact Force Distribution and Static Load-carrying Capacity of Large Size Double Row Four-point Contact Ball Bearing

Clearance not only affects the startup torque,rotation precision and stiffness of bearing,but also affects the load distribution,load-carrying capacity and life of bearing.A computational model in which the clearance of bearing is first included is presented for determining the contact force distribution and static load-carrying capacity of a double row four-point contact ball bearing which is subjected to the combined radial,axial and overturning moment loadings.The relation between the negative axial clearance and the contact force distribution is analyzed.The static load-carrying capacity curves are established,and the effects of the changes in negative axial clearance,curvature radius coefficient of raceway groove and initial contact angle on the static load-carrying capacity are analyzed.The results show that,with the increase in the absolute value of negative clearance,the maximum contact load decreases first and then increases.The clearance values in the range of 0.2 mme0 mm have little effect on the static load-carrying capacity of bearing.With the increase in the curvature radius coefficient of raceway groove and the decrease in the initial contact angle,the static load capacity of bearing decreases.

Construction of Burkholderia pseudomalleiΔrelA mutant and comparison of their biological characteristics

Objective: The relA gene,a gene associated with the synthesis of rigorous response signaling molecule (p)ppGpp in Burkholderia pseudomallei, was knocked out and its effects on the biological functions of bacterial growth, motility and biofilm formation were investigated. Methods: The plasmids with trimethoprim resistance (TPR) were modified by enzyme digestion and enzyme ligation method. The TPR fragment was linked to the suicide plasmid pK18mobSacB containing SacB sucrose killing gene by Bgl Ⅱ enzyme digestion site, and trimethoprim resistance was obtained Plasmid(TPR-pK18mobSacB);The relA gene of Burkholderia pseudomallei HNBP001 was knocked out by homologous recombinant gene knockout method, and the relA mutant was obtained. The growth, motility and biofilm phenotypes of Burkholderia pseudomallei HNBP001 were compared before and after the deletion of relA gene. Results: The relA mutant was successfully constructed. The growth rate, motility and biofilm formation of ΔrelA decreased. Conclusion: The modified plasmid TPR- pK18mobSacB can improve the knockout efficiency of HNBP001 strain, which can be widely used in the gene knockout of Burkholderia pseudomallei, and provide convenience for the laboratory to study the gene function of Burkholderia pseudomallei at the molecular level;The mutant of the relA gene inhibits the growth, motility and biofilm formation of HNBP001.