GB/T 1927.4-2021Test methods for physical and mechanical properties of small clear wood specimens - Part 4: Determination of moisture content (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 4 of GB/T 1927 "Test methods for physical and mechanical properties of wood with small samples 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 1931-2009 "Wood Moisture Content Determination Method", compared with GB/T 1931-2009, except for structural adjustment and

In addition to editorial changes, the main technical changes are as follows:

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

b) Changed the content of the principle (see Chapter 4, Chapter 2 of the:2009 edition);

c) Changed the balance accuracy and the function of the oven (see 5:1 and 5:2, 3:1 and 3:2 of the:2009 edition);

d) Changed the size and number of test specimens (see 6:1, 4:1 of the:2009 edition);

e) changed the level of precision reported (see 7:1, 5:1 of the:2009 edition);

f) Changed the level of precision of the result calculation (see Chapter 8, Chapter 6 of the:2009 edition);

g) Changed the equipment, sample size, balance accuracy, test procedure and reporting accuracy level (see Appendix B,:2009 edition of the appendix

Record A);

h) Added record and report of test results (see Chapter 9);

i) Added the record table of Appendix B (see Table B:1):

This document is modified to adopt ISO 13061-1:2014 "Test methods for the physical and mechanical properties of wood with small specimens without defects - Part 1: Moisture content

Measurement":

The technical differences between this document and ISO 13061-1:2014 and their reasons are as follows:

--- Regarding normative citation documents, this document has made adjustments with technical differences to adapt to the technical conditions of our country and the circumstances of the adjustment:

The situation is reflected in Chapter 2 "Normative References", and the specific adjustments are as follows:

* Replace ISO 3129:2019 with GB/T 1927:2-202X which is modified to adopt international standard (see 9:2);

* Deleted ISO 24294, the terms of logs and sawn timber are not involved in this document, so this reference standard is deleted;

* Added LY/T 1788-2008 (see Chapter 3):

The following editorial changes have been made to this document:

--- In order to harmonize with existing standards, the name of the standard is changed to "Test Methods for Physical and Mechanical Properties of Small Specimens of Wood without Defects - Part 4: Contains

Water rate measurement";

--- Removed references:

Please note that some content of this document may be patented: The issuing agency of this document assumes no responsibility for identifying patents:

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 measurement:

--- 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 rate of small sample wood without defect:

--- 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:

Test method for physical and mechanical properties of wood with small sample without defect

Part 4: Determination of moisture content

1 Scope

This document describes the principles, equipment, samples, test procedures, calculation of results and test records for the determination of the moisture content of wood in small unblemished samples:

record etc:

This document is applicable to the determination of moisture content in the test of physical and mechanical properties of wood with small flawless samples:

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

(ISO 3129:2019, MOD)

LY/T 1788-2008 Terms of wood properties

3 Terms and Definitions

The terms and definitions defined in LY/T 1788-2008 and the following terms and definitions apply to this document:

3:1

wood moisture content of wood

The moisture mass contained in the wood as a percentage of the total dry wood mass:

[Source: LY/T 1788-2008, 3:3:6, with modifications]

4 Principles

By weighing the mass of the sample before and after drying, calculate the water mass contained in the sample, and use the water mass contained in the sample and the full dry test

The percentage of the sample mass, indicating the moisture content in the sample:

5 Instruments and equipment

5:1 Balance, the accuracy of the balance (minimum reading) should be determined according to the requirements of the moisture content accuracy: Water with a moisture content of a sample with an absolute dry mass of 10g

The accuracy of the balance and balance is shown in Table 1: For other samples of absolute dry mass, the accuracy (minimum reading) of the balance should be appropriately adjusted proportionally: