Method for testing shearing modulus of material based on torsional mode of cantilever plate

Abstract

The invention provides a method for testing shearing modulus of a material based on a torsional mode of a cantilever plate, which is simple and convenient, rapid and accurate and is applicable to testing of the shearing modulus of isotropic materials and orthogonal aeolotropic woods. The cantilever plate has the length of l, width of d and thickness of h; one end of the cantilever plate in the length direction is fixed; an accelerometer is mounted at a part, which is 0.2 to 0.3l away from a fixed end, of a long edge of the cantilever plate; the corner of a freed end of the cantilever plate is hammered to motivate the cantilever plate to vibrate freely; a vibration signal is received through the accelerometer and is converted into an electric signal for outputting; the electric signal is amplified and filtered and then is subjected to AD (Analogue / Digital) conversion, and an analogue signal is changed into a digital signal; signal and system analysis software is used for processing and an acceleration frequency spectrum is displayed; first-order bending frequency fb and first-order torsional frequency ft of a test piece are read from the frequency spectrum; the density of the woods is rho; elastic modulus E and the shearing modulus G are calculated according to the following formulas: E=48pi<2>rhol<4>fb<2> / (1.875)<4>h<2> and G=(rhopi<2>l<2>b<2>ft<2> / C1betah<2>)-C2E, wherein beta is about equal to 1 / 16[16 / 3-3.36h / b(1-h<4> / 12b<4>)]; values of vibration form coefficient C1 and C2 are related to the variety of materials and the size of the cantilever plate.

Description

technical field [0001] The invention relates to a method for material shear modulus, specifically, a method for testing materials such as wood and low carbon steel based on the torsional mode of a cantilever plate Background technique [0002] Elastic modulus is one of the basic parameters of material properties, and the finished materials produced in North America are marked with their elastic modulus value. The wood processing industry has applied the elastic modulus of the finished timber to derive its finished timber strength. In the early days, the continuous testing machine was used to test the elastic modulus of the finished product, but because the continuous testing machine needs a huge initial investment, it is not a suitable equipment for testing the elastic modulus of the finished product. Since the 1980s, the stress wave method and dynamic vibration method of non-destructive testing have been used in China to test the elastic modulus of finished products. Amon...

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Problems solved by technology

Due to the profound principles and technical difficulties of dynamic shear modulus testing, the progress of dynamic shear modulus testing of wood and wood-based composites has been relatively slow, and few research articles have been published in this area.

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