The strain softening characteristics analysis of 12Cr1MoV streel friction welding pipe joints.which were removed from heating apparatus pipes ager over 9 and is yearly of service, was undertaken. It is concluded that ...The strain softening characteristics analysis of 12Cr1MoV streel friction welding pipe joints.which were removed from heating apparatus pipes ager over 9 and is yearly of service, was undertaken. It is concluded that the evident softening did not occur in the weld metal and HAZ during serice. whereas it did in the base metal 2mm apart from the center of the weld metal. The difference is due to the restriction of the pipe hoop, which is formed on the joint during friction welding. The bainite. microstructure in the weld metal and HA Z, which is harder than the pearlite, pecrostpucture in the base metal, makes contpibution too. ThIS phenomenon is peculiar to the friction weldings pipes.展开更多
The Moody Diagram is widely used to determine the friction factor for fluid flow in pipes. The diagram combines the effects of Reynolds number and relative roughness to determine the friction factor. The relationship ...The Moody Diagram is widely used to determine the friction factor for fluid flow in pipes. The diagram combines the effects of Reynolds number and relative roughness to determine the friction factor. The relationship is highly non-linear and appears to have a complex interaction between viscous and boundary roughness effects. The Moody Diagram is based on predictions from an equation developed by Colebrook in 1939. The relationship requires an iteration process to make predictions. While empirical relationships have been developed that provide good predictions without an iteration process, no one has fully explained the cause for the observed results. The objective of this paper is to present a logical development for prediction of the friction factor. An equation has been developed that models the summed effect of both the laminar sublayer and the boundary roughness on the fluid profile and the resulting friction factor for pipes. The new equation does not require an iteration procedure to obtain values for the friction factor. Predicted results match well with values generated from Colebrook’s work that is expressed in the Moody Diagram. Predictions are within one percent of Colebrook values and generally less than 0.3 percent error from his values. The development provides insight to how processes operating at the boundary cause the friction factor to change.展开更多
文摘The strain softening characteristics analysis of 12Cr1MoV streel friction welding pipe joints.which were removed from heating apparatus pipes ager over 9 and is yearly of service, was undertaken. It is concluded that the evident softening did not occur in the weld metal and HAZ during serice. whereas it did in the base metal 2mm apart from the center of the weld metal. The difference is due to the restriction of the pipe hoop, which is formed on the joint during friction welding. The bainite. microstructure in the weld metal and HA Z, which is harder than the pearlite, pecrostpucture in the base metal, makes contpibution too. ThIS phenomenon is peculiar to the friction weldings pipes.
文摘The Moody Diagram is widely used to determine the friction factor for fluid flow in pipes. The diagram combines the effects of Reynolds number and relative roughness to determine the friction factor. The relationship is highly non-linear and appears to have a complex interaction between viscous and boundary roughness effects. The Moody Diagram is based on predictions from an equation developed by Colebrook in 1939. The relationship requires an iteration process to make predictions. While empirical relationships have been developed that provide good predictions without an iteration process, no one has fully explained the cause for the observed results. The objective of this paper is to present a logical development for prediction of the friction factor. An equation has been developed that models the summed effect of both the laminar sublayer and the boundary roughness on the fluid profile and the resulting friction factor for pipes. The new equation does not require an iteration procedure to obtain values for the friction factor. Predicted results match well with values generated from Colebrook’s work that is expressed in the Moody Diagram. Predictions are within one percent of Colebrook values and generally less than 0.3 percent error from his values. The development provides insight to how processes operating at the boundary cause the friction factor to change.
