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A three-dimensional study of frictional contact in a helical splined coupling for the assessment of macroscopic fretting variables is presented. The study is based on an experimentally validated finite element model of the coupling under combined torque and axial loads. The effect of axial profile modification for reduced contact stresses in spline teeth and the effect of friction coefficient are considered. The motivation for the work is the need for representative information about fretting variable distributions in splined couplings for the development and application of simplified fretting test configurations.

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Single transgene copy, vector backbone-free transgenic crop plants are highly desired for functional genomics and many biotechnological applications. We demonstrate that binary vectors that use a replication origin derived from the Ri plasmid of Agrobacterium rhizogenes (oriRi) increase the frequency of single copy, backbone-free transgenic plants in Agrobacterium tumefaciens mediated transformation of soybean, canola, and corn, compared to RK2-derived binary vectors (RK2 oriV). In large scale soybean transformation experiments, the frequency of single copy, backbone-free transgenic plants was nearly doubled in two versions of the oriRi vectors compared to the RK2 oriV control vector. In canola transformation experiments, the oriRi vector produced more single copy, backbone-free transgenic plants than did the RK2 oriV vector. In corn transformation experiments, the frequency of single copy backbone-free transgenic plants was also significantly increased when using the oriRi vector, although the transformation frequency dropped. These results, derived from transformation experiments using three crops, indicate the advantage of oriRi vectors over RK2 oriV binary vectors for the production of single copy, backbone-free transgenic plants using Agrobacterium-mediated transformation.

The frictional contact conditions in a helical spline joint coupling under torsional and axial loads are studied using finite element analyses. Comparisons of spline root torsional stresses are made with photoelastic measurements. Surface contact tractions, relative slip distributions and subsurface localized stress component and equivalent stress distributions are presented for both the external and the internal spline contact surfaces. The work is important as a basis for understanding and predicting the fatigue, contact fatigue, fretting fatigue, wear and fretting wear characteristics of the coupling. A representative test specimen concept is presented which seeks to capture the local contact variable distributions in the spline coupling, with a view to predicting the wear and the contact and fretting fatigue performance of the coupling.NOTATION a contact half-width for the punch-on-flat configuration a 1 axial direction contact width a 2 tooth flank (profile) direction contact width d width of representative specimen D pitch circle diameter D b inside diameter of the external spline shaft D re root diameter of the external spline teeth D ri root diameter of the internal spline teeth D te tip diameter of the external spline teeth D ti tip diameter of the internal spline teeth D o external diameter of the internal spline shaft F axial force applied to spline coupling; also, force applied to the female bar of the representative specimen F n normalized axial force F th force per unit length calculated for the punch-onflat equation F m yp maximum elastic axial force capacity of the nominal male shaft L f distance from the tooth centre to the end of the slot on the female load arm L m distance from the tooth centre to the run-out radius on the male load arm N number of spline teeth p contact pressure along the spline contact surface p i contact pressure at node i in the full spline model p x contact pressure at point x for the punch-on-flat configuration p 0 mean contact pressure for the spline contact surface r p radius of the pitch circle R A , R B radial positions along the involute t A , t B transverse tooth thicknesses at radii R A and R B respectively t f thickness of the female load arm t m thickness of the male load arm T torque T n normalized torque T m yp maximum elastic torque capacity of the nominal male shaft x external spline tooth flank (profile) coordinate direction; also, distance from the centre of contact for the punch-on-flat configuration x l tooth-flank length of the contact elements in the spline joint finite element analysis y internal spline tooth flank (profile) coordinate direction z axial direction along the spline contact region z i axial coordinate of face i of the finite element model z 0 axial coordinate of the first (unrotated) face of the finite element model 521The MS was

The fatigue behaviour of a representative high-performance aero-engine spline coupling is investigated under test conditions designed to simulate in-service conditions. The test load cycles consist of major cycle torque and axial load, simulating maximum thrust, combined with minor cycle rotating bending moment and fluctuating torque, simulating life-limiting conditions at take-off. The objective of the study is to develop understanding of the fatigue behaviour of the coupling over a range of loading conditions, including interaction between low-cycle fatigue, fretting fatigue and fretting wear. This information is necessary for the development of fatigue and fretting-fatigue life prediction techniques. The test results are interpreted with the help of three-dimensional finite element models, which include the frictional contact between the spline teeth.