GB/T 3074.1-2021The test method for flexural strength of carbon materials (English PDF)

Foreword

This document was drafted in accordance with the provisions of GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.

This document is Part 1 of GB/T 3074.GB/T 3074 has been published in the following parts.

-- GB/T 3074.1 The test method for flexural strength of carbon materials;

-- GB/T 3074.2 Method for the determination of the elastic modulus of graphite electrodes;

-- GB/T 3074.3 Method for the determination of the oxidation resistance of graphite electrodes;

-- GB/T 3074.4 Method for the determination of the coefficient of thermal expansion of graphite electrodes.

This document replaces GB/T 3074.1-2008 Method for the determination of the flexure strength of graphite electrodes. Compared with GB/T 3074.1-2008, in addition to structural adjustments and editorial modifications, the main technical changes of this document are as follows.

-- The scope of application has been modified (see Chapter 1; see Chapter 1 of the 2008 edition);

-- The normative references have been modified (see Chapter 2; see Chapter 2 of the 2008 edition);

-- The chapter "Terms and definitions" is added (see Chapter 3);

-- The principle of the four-point loading method is added (see 4.2; see Chapter 3 of the 2008 edition);

-- The instruments and equipment are modified (see 5.1, 5.2, 5.3, and 5.4; see Chapter 4 of the 2008 edition);

-- The specimen dimensions and processing requirements are modified (see Chapter 6; see Chapter 5 of the 2008 edition);

-- The test procedures are modified (see Chapter 7; see Chapter 6 of the 2008 edition);

-- The calculation formula for the flexural strength of parallelepiped specimens is added (see 8.2);

-- The content of the test report has been modified (see Chapter 9; see Chapter 8 of the 2008 edition).

1 Scope

This document specifies the principles, instruments, equipment, specimens, test procedures, result calculations, and test reports for determining the flexural strength of carbon materials.

This document is applicable to the determination of the flexural strength of carbon materials by using the four-point loading method at room temperature.

2 Normative references

The provisions of the following documents constitute the essential clauses of this document through normative references in this text. Among them, for referenced documents with dates, only the versions corresponding to the dates are applicable to this document; for referenced documents without dates, the latest versions (including all amendments) are applicable to this document.

GB/T 1427 Sample method of carbon material

GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values

3 Terms and definitions

There are no terms or definitions that require definition in this document.

4 Principle

4.1 Flexural strength is a measure of the maximum load that a material can withstand when it is bent and fractured by an external force. Its value is the magnitude of the normal stress on the cross-section of the specimen when it is bent and fractured.

4.2 Four-point loading method. Place the specimen on two load-bearing blocks and apply load at their center until the specimen breaks.

5 Instruments and equipment

5.1 Vernier caliper. The measuring range is 0 mm~200 mm, and the accuracy is 0.02 mm.

5.2 Micrometer. The measuring range is 0 mm~50 mm, and the accuracy is 0.01 mm.

5.5 Test fixture. The fixture shall ensure that the force applied to the specimen is normal and has no eccentricity through the adjustment of the spherical bearing seat or roller bearing assembly. The distance between the upper and lower indenters can be adjusted to meet the needs of samples of different sizes. The fixture shall have a device to prevent the specimen from sliding. The device is shown in Figure 1.

6 Specimens

6.1 Sampling and processing shall be in accordance with the provisions of GB/T 1427.

6.2 For products that are not specified in GB/T 1427, the specimen dimensions and processing requirements are as follows.

6.3 All planes of the specimen are required to be flat, with parallelism better than 0.1 mm/100 mm and surface roughness better than Ra3.2 µm.

7 Test steps

7.1 The specimen shall be dried in an air blast drying oven at 110 °C±5 °C for 2 hours and stored in a desiccator to cool to room temperature for use.

7.2 Measure the dimensions of the specimen. For cylindrical specimens, measure the diameter.

7.3 Place the specimen on the lower indenters of the testing machine, align the center of the specimen with the center of the spacing between the upper indenters, and make the axes of the upper and lower indenters perpendicular to the specimen axis. Adjust the anti-slip device to prevent the specimen from sliding.

8 Result calculation

8.1 The flexural strength of the cylindrical specimen is calculated according to formula (1).

9 Test report

The test report shall at least include the following contents.