Fatigue strength of a fork-pin equivalent coupling in terms of the local strain energy density

Abstract The fork-pin coupling of the front suspension of a motorbike is very important for the reliability and the safety of the entire vehicle. One of the more important causes of failure of the component is fatigue under fully reversed bending load. In this work, the fatigue behaviour of fork-pin equivalent couplings made of 39NiCrMo3 steel is analysed by means of simplified specimens obtained by the interference of a cylindrical pin in a hollow cylinder reproducing the same static stresses present on the contact surfaces of the real component. The contact of the two bodies is modelled by means of Ansys® 9.0 and the stress field due to the interference is analysed and compared with that obtained by a strain gauge located on the external surface of the equivalent hub during the press-fit operation. By means of the same three-dimensional model, the local strain energy density (SED) averaged in a control volume, defined under mode I loading and surrounding the critical zone of the pin, is evaluated to summarize all fatigue strength data. The data, expressed in terms of the local energy, fall in the same scatter band with some other new data from plain and V-notched specimens made of the same material subjected to tension loading. Altogether about 60 new fatigue results are now available and presented in the paper.

[1]  G. Pluvinage.  Fracture and Fatigue Emanating from Stress Concentrators , 2003 .

[2]  D. A. Hills,et al.  Recent developments in the understanding of fretting fatigue , 2013 .

[3]  S. Timoshenko,et al.  Theory of elasticity , 1975 .

[4]  Zohar Yosibash,et al.  Failure criteria for brittle elastic materials , 2004 .

[5]  D. Hills,et al.  On the mechanics of fretting fatigue , 1988 .

[6]  Shigefumi Kihara,et al.  A STRENGTH EVALUATION METHOD OF A SHARPLY NOTCHED STRUCTURE BY A NEW PARAMETER, "THE EQUIVALENT STRESS INTENSITY FACTOR" , 1991 .

[7]  Dario Croccolo,et al.  Friction Coefficient Definition in Compression-fit Couplings Applying the DOE Method , 2008 .

[8]  K. L. Edwards,et al.  Materials for rotationally dynamic components: rationale for higher performance rotor-blade design , 2006 .

[9]  K. L. Edwards,et al.  Linking materials and design: an assessment of purpose and progress , 2002 .

[10]  Paolo Lazzarin,et al.  A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches , 2001 .

[11]  Oguz Kayabasi,et al.  The effects of static, dynamic and fatigue behavior on three-dimensional shape optimization of hip prosthesis by finite element method , 2007 .

[12]  Filippo Berto,et al.  Multi-axial fatigue behaviour of a severely notched carbon steel , 2006 .

[13]  Hong Tae Kang.  Fatigue prediction of spot welded joints using equivalent structural stress , 2007 .

[14]  Paolo Lazzarin,et al.  Fatigue strength of steel and aluminium welded joints based on generalised stress intensity factors and local strain energy values , 2005 .

[15]  G. Sih.  Strain-energy-density factor applied to mixed mode crack problems , 1974 .

[16]  Dario Croccolo,et al.  The design and optimization of fork-pin compression coupling in front motorbike suspensions , 2007 .

[17]  F. Berto,et al.  Some Expressions for the Strain Energy in a Finite Volume Surrounding the Root of Blunt V-notches , 2005 .

[18]  P. Castro,et al.  Methodologies for failure analysis: a critical survey , 2004 .

[19]  Ciro Santus,et al.  Fretting fatigue of aluminum alloy in contact with steel in oil drill pipe connections, modeling to interpret test results , 2008 .

[20]  C. M. Sonsino,et al.  A notch stress intensity approach to assess the multiaxial fatigue strength of welded tube‐to‐flange joints subjected to combined loadings , 2004 .

[21]  Filippo Berto,et al.  Local strain energy density and fatigue strength of welded joints under uniaxial and multiaxial loading , 2008 .

[22]  M. R. Kianoush,et al.  Fatigue failure assessment of engineering components under service loading conditions , 2007 .