Study on the four-point bending beam method to improve the testing accuracy for the elastic constants of wood

Using the static analysis of ANSYS 19, longitudinal, radial, and tangential beam specimens of spruce, Scots pine, and beech were subjected to stress and strain analysis under symmetrical four-point bending and asymmetrical four-point bending. The effects of wood grain on the surface of the specimen and its stress properties on the transverse and longitudinal strain at the center of the specimen surface were studied experimentally. The results show that the four-point bending beam method is suitable for testing the elastic modulus, Poisson’s ratio and shear modulus of wood. The elastic modulus, Poisson’s ratio and shear modulus of larch tangential, larch radial and Sitka spruce transverse specimens were tested by four-point bending beam method. Their effectiveness was verified by the axial tension method, square plate torsional strain method and free rod torsional vibration method. The four-point bending method of the two-group tests with the half bridge measurement method has successfully improved the test accuracy of the Poisson’s ratio of wood, and its effectiveness has been verified by axial tension method. The asymmetric four-point bending method adopts the ± 45°strain gauge full bridge measurement method, which is simple and effective in improving the measurement accuracy of wood shear modulus.