Two bump foil journal bearings with different surface roughness of bearing housing's cylindrical hole surface were manufactured.The test-bed was established by exploiting bump foil journal bearing to test the static stiffness and lift off speed of bump foil journal bearings using friction torque method.By comparing test results of each bump foil journal bearing

the effects of friction between bump foil and bearing housing on static stiffness and lift off speed of bump foil journal bearing were studied.The results indicate that reducing surface roughness of bearing housing's cylindrical hole surface can weaken the friction between bump foil and bearing housing

decrease the bearing static stiffness and lift off speed under the same bearing load capacity.It has engineering significance to improve the bearing structure design and extend the bearing life due to lower the wear of bearing surface.Moreover

the static stiffness of bump foil journal bearing has strong nonlinear characteristic

and increases with the increasing foil deformation

so it is necessary to consider the nonlinear foil structural stiffness when modeling the bump foil journal bearing.