Test device and method for parallel-to-grain tensile properties of ancient building wood materials

Abstract

The invention provides a test device and method for parallel-to-grain tensile properties of ancient building wood materials. The device comprises a test sample composed of an ancient building wood rawmaterial, hardwood gaskets and a resistance strain gauge, wherein the portions with a wider section at both ends of the test sample are clamping portions, the portion with a narrower section in the middle is a test portion, and all the portions are transitioned through circular arcs; the tester is clamped at both ends of the sample by a horizontal clamp and applies a tensile force. The method comprises the following steps of fabricating and processing the ancient building wood raw material, pasting the hardwood gaskets processed with meshes on both sides of the clamping portions by glue, drawing a cross in the middle of the test portion for positioning, pasting a vertical strain gauge, pasting a strain gauge below, causing the strain gauges at both sides in the same direction to be at thesame height, and clamping the gasket with the horizontal clamp to ensure that the longitudinal axis of the sample is in the same direction as the tensile force. The test device and method provided bythe invention are suitable for the research on the tensile properties of ancient building wood materials with limited raw materials, and have the advantages of simple sample processing, simple test operation, reliable test result and high test efficiency.

Description

technical field [0001] The invention relates to the technical field of wood property testing, in particular to a testing device and method for the along-grain tensile properties of ancient building wood materials. Background technique [0002] Wooden structure is the main architectural form in ancient my country, and it is also an important part of the traditional culture of the Chinese nation. The understanding and protection of the wooden structure of ancient buildings is inseparable from the testing of the mechanical properties of its constituent materials. The tensile mechanical properties of wood along the grain is one of its basic mechanical properties. However, different from the test conditions for the tensile properties of new wood materials, the tensile properties of ancient building wood materials have the following problems: [0003] (1) The limitation of test materials. Different from new wood materials, ancient building wood structure materials have cultural ...

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Problems solved by technology

[0004] (2) Quantitative evaluation is difficult to achieve

Combined with the limitation of materials, whether it is based on the Chinese national standard GB / T 1938-2009, the Japanese standard JIS Z 2101:2009 or the American standard ASTM D 143-94, it is impossible to simultaneously take into account the size requirements and Quantitative evaluation requirements that the test itself should meet

[0005] (3) Complexity of wood sample processing

The processing of wood tensile samples in the three standards mentioned above is relatively complicated. Due to the size characteristics and processing difficulty of wood tensile samples, the utilization rate of materials is reduced, which further increases the demand for raw materials.

[0006] (4) There is no uniform test method for the tensile elastic parameters of wood

At present, none of the existing testing standards provides the testing method for the tensile elastic modulus of wood. The methods used in the literature include the resistance strain gauge method, the extensometer method and the approximation method (replacing the tensile elastic modulus with the bending elastic modulus of wood) etc. Different methods lead to the inability to make a uniform comparison between the test results

And for the research on the tensile Poisson's ratio of wood along the grain, it is rarely involved.

[0007] Wood is an anisotropic material, and it is inaccurate to use its compressive or bending properties to approximate tensile properties. For ancient wooden structures, such an approach will undoubtedly have adverse effects on structural safety assessment or maintenance decisions. influences

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