GB/T 1927.7-2021Test methods for physical and mechanical properties of small clear wood specimens—Part 7: Determination of water absorption (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1. Structure and Drafting Rules of Standardization Documents" drafted.

This document is part 7 of GB/T 1927 "Test Methods for Physical and Mechanical Properties of Small Specimens of Wood without Defects". GB/T 1927 has been issued The following parts are distributed.

--- Part 1. Collection of test materials;

--- Part 2. Sampling methods and general requirements;

--- Part 3. Determination of growth ring width and latewood rate;

--- Part 4. Determination of moisture content;

--- Part 5. Density determination;

--- Part 6. Determination of dry shrinkage;

--- Part 7. Determination of water absorption;

--- Part 8. Determination of swelling properties;

--- Part 9. Determination of flexural strength;

--- Part 10. Determination of flexural modulus of elasticity;

--- Part 12. Determination of transverse grain compressive strength;

--- Part 17. Determination of impact toughness;

--- Part 18. Determination of impact indentation;

--- Part 19. Determination of hardness;

--- Part 20. Determination of splitting resistance.

This document replaces GB/T 1934.1-2009 "Wood Water Absorption Determination Method". Compared with GB/T 1934.1-2009, except for structural adjustment In addition to the adjustment and editorial changes, the main technical changes are as follows:

a) terms and definitions are added (see Chapter 3);

b) Changed the provisions on sawing of test materials and interception of samples (see 6.1, 5.1 of the:2009 edition);

c) Changed the test procedure (see Chapter 7, Chapter 6 of the:2009 edition);

d) Changed the time interval when measuring the maximum water absorption rate (see 7.3, 6.3 of the:2009 edition);

e) Changed the water absorption calculation formula (see 8.1, 7.1 of the:2009 edition);

f) Changed the provisions for the record of test results (see 9.1, 8.1 of the:2009 edition);

g) Changed the content of the test report (see 9.2, 8.2 of the:2009 edition).

Introduction

The standard of test methods for physical and mechanical properties of wood is used in wood scientific research, teaching, wood inspection, wood structure design, wood processing and production, etc.

It is widely used and is an important basic standard in the wood industry. In 1980, my country issued the first edition of the test methods for physical and mechanical properties of wood.

The domestic standard (GB/T 1927~GB/T 1943) was revised twice in:1991 and:2009 respectively. In recent years, with the development of wood science and technology The development of technology, ISO 3129:2012 "Sampling methods for wood physical and mechanical tests of small samples of wood without defects and "General Requirements" has been revised, and ISO 3130:1975 "Determination of moisture content by physical and mechanical tests of wood", ISO 3131:1975 "Wood 15 international standards for test methods such as "Determination of Density by Physical and Mechanical Testing of Materials" have been integrated and revised. Based on this, in order to be in line with international standards, This time, the third revision was made to the national standard for test methods for physical and mechanical properties of wood in my country, and the 22 scattered test methods were integrated and adjusted to The sub-part document of GB/T 1927 adopts the latest version of the international standard in the revision.

GB/T 1927 aims to establish a test method for the physical and mechanical properties of small sample wood without flaws, and is intended to be composed of 21 parts.

--- Part 1. Collection of test materials. The purpose is to describe the sample collection method for testing the physical and mechanical properties of wood with small samples without defects.

--- Part 2. Sampling methods and general requirements. The purpose is to establish a suitable test for the physical and mechanical properties of small wood samples without defects.

Specimen sawing, interception methods and general requirements to be observed when testing methods.

--- Part 3. Determination of growth ring width and latewood rate. The purpose is to characterize the growth ring width and latewood rate of small samples of clear wood method of determination.

--- Part 4. Determination of moisture content. The purpose is to describe a method for the determination of the moisture content of small wood samples without defects.

--- Part 5. Density determination. The purpose is to describe the density, air-dry density, absolute dry Methods for the determination of density and basic density.

--- Part 6. Determination of dry shrinkage. The purpose is to describe the measurement of radial, chordwise and volume drying shrinkage of unblemished small sample wood. determined method.

--- Part 7. Determination of water absorption. The purpose is to describe the determination method of 6h, 24h and the maximum water absorption of small sample wood without defects.

--- Part 8. Determination of swelling. The purpose is to describe the measurement of radial, chordwise and volumetric swell of unblemished small wood samples. determined method.

--- Part 9. Determination of flexural strength. The purpose is to describe a method for the determination of the flexural strength of small wood samples without defects.

--- Part 10. Determination of flexural modulus of elasticity. The purpose is to describe a method for the determination of the flexural modulus of elasticity of small wood samples without defects.

--- Part 11. Determination of compressive strength along grain. The purpose is to describe a method for the determination of the compressive strength along the grain of small wood samples without defects.

--- Part 12. Determination of transverse grain compressive strength. The purpose is to describe the transverse grain compressive proportional ultimate strength of small unblemished wood samples, including Methods for the determination of the total compressive proportional ultimate strength of the horizontal grain and the partial compressive proportional ultimate strength of the horizontal grain.

--- Part 13. Determination of compressive elastic modulus of transverse grains. The purpose is to describe the measurement of the transverse-grain compressive elastic modulus of unblemished small samples of wood. determined method.

--- Part 14. Determination of tensile strength along grain. The purpose is to describe a method for the determination of the along-grain tensile strength of unblemished small samples of wood.

--- Part 15. Determination of transverse grain tensile strength. The purpose is to describe a method for the determination of the transverse grain tensile strength of small wood samples without defects.

--- Part 16. Determination of shear strength along grain. The purpose is to describe a method for the determination of the shear strength along the grain of small wood samples without defects.

--- Part 17. Determination of impact toughness. The purpose is to describe a method for the determination of the chordwise impact toughness of small unblemished wood samples.

--- Part 18. Determination of impact indentation. The purpose is to describe a method for the determination of the impact indentation resistance of unblemished small samples of wood.

--- Part 19. Determination of hardness. The purpose is to describe a method for the determination of radial, chord, and longitudinal hardness of small, unblemished wood samples.

--- Part 20. Determination of splitting resistance. The purpose is to describe the method for the determination of the splitting resistance on the radial and chord surfaces of small wood samples without defects.

--- Part 21. Determination of nail holding force. The purpose is to describe a method for the determination of the nail-holding force of small samples of wood without defects.

1 Scope

This document describes the principles, test equipment, test specimens, test procedures, calculation of results, and test results for the determination of the water absorption of small unblemished wood samples. Results records and reports.

This document applies to the determination of the water absorption of wood in small samples without defects.

2 Normative references

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, dated citations documents, only the version corresponding to that date applies to this document; for undated references, the latest edition (including all amendments) applies to this document.

GB/T 1927.2-2021 Test methods for physical and mechanical properties of wood with small unblemished samples - Part 2. Sampling methods and general requirements

GB/T 1927.4-2021 Test methods for physical and mechanical properties of wood with small samples without defects - Part 4. Determination of moisture content

LY/T 1788 Terms for wood properties

3 Terms and Definitions

Terms and definitions defined in LY/T 1788 apply to this document.

4 Principles

Wood is a porous natural polymer material with the ability to absorb moisture. Water absorption of wood Use wood to absorb water to saturation or within The mass of water absorbed in a given time, expressed as a percentage of the mass of the whole dry wood.

5 Test equipment

5.1 Container for dipping the sample.

6 Samples

6.1 The sawing of the test material and the interception of the sample shall be carried out in accordance with the provisions of Chapter 4 of GB/T 1927.2-2021.

6.2 The size of the sample is 20mm×20mm×20mm. The precision and inspection of sample production shall be as specified in 5.2 of GB/T 1927.2-2021 conduct. END. Draft Version (GB/T 1927.7-2021)