ESDU Engineer

SHAFTS WITH INTERFERENCE-FIT COLLARS

In February 2007 amendments to the following Data Items were issued: ESDU 68002, “Shafts with interference-fit collars. Part I: some factors affecting the design of an assembly”; ESDU 68003, “Shafts with interference-fit collars. Part II: nominal elastic interface pressures and stresses”; and ESDU 68004, “Shafts with interference-fit collars. Part III: procedure for calculation of nominal elastic interface pressures and stresses in assemblies of three or more elements”. ESDU 68005, “Shafts with Interference-fit collars. Part IV: fatigue strength of plain shafts”, which completes the series, was also
re-issued.

ESDU 68002 outlines the main aspects of the design of interference-fit collars on rotating shafts insofar as the design is affected by the interference fit. It deals with the following design criteria: (i) design such that the maximum stresses do not exceed specified allowable values for the particular materials chosen; (ii) freedom from general slip under specified working conditions; and (iii) design to specified minimum fatigue strength.

The data presented in ESDU 68003 are obtained from plane stress elastic theory and apply to collars of constant thickness with an axially uniform initial interference. The data may also be used for tapered fits. The graphical presentation of the data accommodates a wide range of shaft and collar diameters, Young’s moduli, etc., for materials having a Poisson’s ratio of 0.3. The effects of a uniform temperature change and rotation are considered and two worked examples are presented. The amendment to ESDU 68003 consists mainly of the addition of a new Fortran program, ESDUpac A6803, for the calculation of the nominal elastic interference pressures and stresses.

ESDU 68004 gives a procedure for calculating the nominal interface pressures and stresses in a set of three or more uniform circular rings with axially uniform initial interferences. The effects of rotation and of a uniform temperature change are also considered. The procedure is based on plane stress elastic theory. The equations are stated in a general form for any number of rings and a complete worked example is provided. As with ESDU 68003, the amendment toESDU 68004 consists mainly of the addition of a new Fortran program, ESDUpac A6804, to calculate the nominal elastic interface pressures and stresses in assemblies of three or more elements. This program also deals with the calculation of the effects of temperature change, rotational velocity and diametral interference on the interface pressure.

ESDU 68005 discusses the results of about 170 fatigue tests on shafts of constant diameter with plain collars subjected to rotating bending loads. The data, which are presented graphically, encompass both untreated shafts and rolled or induction-/flame-hardened shafts. The shafts and collars were manufactured from forged or cast steels with tensile strengths in the range 510 to 765 N/mm2 (74 000 to 119 000 lbf/in2); the shaft diameters are between 10 and 240 mm
(0.4 and 9.5 in).

Queries regarding this article should be directed to Dr Dorothy Downs, Engineer, Strength Analysis Group: dorothy.downs@ihs.com

Selected current work

Listed below are some examples of work currently being undertaken by our Engineers

Fluid Mechanics
Flow in rotating machinery/labyrinth seals, flow in straight pipes, flow through orifice plates

Aerodynamics
Study of the aerodynamics of parachutes

MMDH ESDU 00932
Supplement 47, consisting of 41 new and updated Data Sheets, will be added to the internet, CD and paper versions of MMDH shortly

Fatigue
Strain-life data for aluminium and titanium alloys and steels

For more information visit www.esdu.com.