Determination of Shearing Properties for Tubular Pinewood under Torsion

Abstract

In this study, tubular pinewood ( Pinus sylvestris L. ) specimens are tested and shear strain measurements are performed by applying torsion in z direction in the consideration of light weight aircraft engineering. The objective of this paper is to contribute and generate the nonlinear material model in terms of shear modulus presented with power functions under the consideration of nonlinear behavior of wood under torque. Strain gauge measurements are performed for the maximum shear stresses which develop on the tubular specimen, along the radial r ( rin , rout ), circumferential Φ ( Φin , Φout ) and z directions, in a point-wise manner. The data is gathered and examined for the determination of the local variations of empirical shear modulus functions on transversely isotropic surfaces of the specimens. The coordinate dependent shear modulus functions of GzΦ ( r ), Gz Φ ( Φ ), GzΦ ( z ) are derived for GzΦ ( r , Φ , z )as the function of r , Φ and z , respectively, by analyzing the gathered data. It is proposed to represent the shear modulus functions, GzΦ ( Φ ) and GzΦ ( z ) with the parabolic polynomials, and, to represent the shear modulus function GzΦ ( r ) with a linear equation.