GB/T 1927.2-2021Test methods for physical and mechanical properties of small clear wood specimens - Part 2: Sampling methods and general requirements (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 2 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 1928-2009 "General Principles of Wood Physical Mechanics Test Methods" and GB/T 1929-2009 "Wood Physical Mechanics"

Test material sawing and sample interception method", compared with GB/T 1928-2009, GB/T 1929-2009, except for structural adjustment and editorial changes

In addition, the main technical changes are as follows:

--- Changed the schematic diagram of the method of marking the test material (see 4:2:1:2, 3:2 of GB/T 1929-2009);

--- Added sampling method for center board and sawn timber (see 4:2:2 and 4:2:3);

--- Added the relevant provisions for the matching of green and dry wood samples (see 4:5);

--- Changed the drying room temperature conditions (see 4:6:3, 4:3 of GB/T 1929-2009);

--- Increase the moisture content adjustment of the raw material test material (see 4:6:4);

--- Increased the average value of the coefficient of variation of the equilibrium moisture content (see 5:1:2);

--- Increased the moisture content adjustment of green samples (see 5:3:2 and 5:3:3):

This document is modified and adopted ISO 3129:2019 "Sampling methods and general requirements for wood physical and mechanical tests of small samples of wood without defects":

This document has the following structural adjustments compared to ISO 3129:2019:

--- Chapter 4 corresponds to Chapter 5 and Chapter 6 in ISO 3129:2019, of which 4:1~4:5 correspond to ISO 3129:2019

Chapter 5, added 4:2:1, 4:6 corresponding to Chapter 6 in ISO 3129:2019;

--- Chapter 5 corresponds to Chapter 7, Chapter 8, Chapter 9 and Chapter 10 in ISO 3129:2019, of which 5:1~5:3 correspond to

Chapter 7 in ISO 3129:2019, 5:4~5:5 correspond to Chapter 8 in ISO 3129:2019, 5:6:1~5:6:3 correspond to

Clause 9, 5:6:4 in ISO 3129:2019 corresponds to Clause 10 in ISO 3129:2019:

The technical differences between this document and ISO 3129:2019 and their reasons are as follows:

--- This document does not cite the international original text quoted in the ISO 3129:2019 normative reference document, because it does not involve logs and sawn timber

vocabulary;

--- Changed the log interception plan to conform to the type of test material actually collected (see 4:2:1, 5:2:2 of ISO 3129:2019);

--- Changed the adjustment method of the moisture content of the test material, in line with the adjustment method of the moisture content of the test material in my country, and the operation is more convenient (see 4:6, ISO 3129:

6:1 of:2019);

--- Changed the method for determining the number of samples, only specifying the number of samples for mechanical sampling, and deleted the original random sampling and selective sampling:

The number of samples, the uniform number of test pieces facilitates the operability of the comparison of test results (see 5:1:1, 7:5 of ISO 3129:2019);

--- Changed the coefficient of variation of hardness to 20%, in line with the coefficient of variation of hardness of major wood species in my country (see 5:1:2, ISO 3129:

7:5:4 of:2019);

--- Changed the allowable error of sample accuracy to +/-0:5mm, which is in line with the actual machining accuracy level in my country (see 5:2:2, ISO 3129:

7:3 of:2019);

--- Change the moisture content of the sample and adjust the relative humidity to be kept at (65+/-3)%, which is in line with the accuracy level of the equipment of the constant temperature and humidity chamber in my country (see

5:3:1, 7:6:1 of ISO 3129:2019);

--- Changed the laboratory temperature and humidity conditions: If the temperature (20 +/- 2) degrees C and relative humidity (65 +/- 3)% conditions cannot be maintained, the adjusted content

The samples after the water ratio should be placed in a closed container when sent to the laboratory, and taken out during the test: The perfect laboratory does not meet the temperature and humidity conditions:

Specimen preservation method under conditions (see 5:4, 8:1 of ISO 3129:2019):

The following editorial changes have been made to this document:

--- In order to harmonize with the 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 2: Take

Sample Methods and General Requirements":

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, ISO 3130:1975 "Determination of moisture content by physical and mechanical tests of wood", ISO 3131:1975

15 international standards for test methods such as "Determination of Density in Physical and Mechanical Tests of Wood" have been integrated and revised: Based on this, in order to connect with international standards

This time, the third revision of the national standard for test methods for physical and mechanical properties of wood in my country will be carried out, and the 22 scattered test methods will be integrated and adjusted:

The whole is a sub-part document of GB/T 1927, and the latest version of the international standard has been adopted 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:

This time, GB/T 1928-2009 and GB/T 1929-2009 are integrated and revised into GB/T 1927:2, and the structure of the document is further adjusted:

structure and complete the content of the document: The sawing and sampling methods of logs, center boards and sawn timber are mainly considered, and the variation of equilibrium moisture content is increased:

The average value of the difference coefficient was used to clarify the matching of the green and dry samples and the adjustment method of the moisture content of the green wood: By establishing a clear flawless small sample

Sampling methods and general requirements for physical and mechanical properties of wood, so that test operators can rely on the physical and mechanical tests of wood, so as to improve the test results:

Accuracy of test methods and performance evaluation, and better promote trade, exchanges and technical cooperation:

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

Part 2: Sampling methods and general requirements

1 Scope

This document describes the method of sawing and intercepting the specimens collected in the test method for the physical and mechanical properties of unblemished small specimens:

general requirements:

This document is applicable to the sawing, intercepting and testing of various physical and mechanical properties of the sample in the physical and mechanical test method of wood with no 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 8170 Numerical Rounding Rules and Representation and Judgment of Limit Values

GB/T 1927:4 Test methods for physical and mechanical properties of wood with small flawless specimens - Part 4: Determination of moisture content (GB/T 1927:4-

2021, ISO 13061-1:2014, MOD)

3 Terms and Definitions

There are no terms and definitions that need to be defined in this document:

4 Sampling method

4:1 Selection of test materials

The test materials include logs, center boards, and sawn timber: Specimen selection takes into account the purpose of the test and ensures that the sample obtained is representative of the population:

4:2 Distribution of test materials

4:2:1 Logs

4:2:1:1 After the collected log test material is transported to the test site, it should be sawed off as soon as possible:

At the lower end of each log test material, three sections of 300 mm were cut in sequence: One of the wood segments is cut 300mmx70mmx according to Figure 1

70mm wood strips, cut out one sample blank for hardness and nail-holding force from each wood strip; cut out 300mm x 300mm from the other wood section according to Figure 2

35mm x 170mm radial wood strips, and the radial tensile, radial compressive elastic modulus, and radial shear sample blanks are taken from each wood strip:

One; from the last wood section, cut 300mmx35mmx170mm chordwise wood strips according to Figure 3, and cut the chordwise resistance from each wood strip:

One each of tensile, chordwise compressive elastic modulus and chordwise shear specimen blanks: The above wood strips do not contain pith: