GB/T 38978-2020 PDF English
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Refractory products-Determination of stress-strain (three-point bending method)
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GB/T 38978-2020: PDF in English (GBT 38978-2020) GB/T 38978-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 81.080
Q 40
Refractory Products - Determination of Stress-strain
(three-point bending method)
ISSUED ON: JULY 21, 2020
IMPLEMENTED ON: JUNE 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Principle ... 4
4 Equipment ... 4
5 Specimens ... 7
6 Test Procedures ... 8
7 Result Calculation ... 9
8 Test Report ... 9
Refractory Products - Determination of Stress-strain
(three-point bending method)
1 Scope
This Standard specifies the principle, equipment, specimens, test procedures, result
calculation and test report of the determination of stress-strain of refractory products.
This Standard is applicable to shaped fired refractory products, chemically bonded
refractory products and unshaped refractory materials.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 4513.5 Monolithic (unshaped) Refractory Products - Part 5: Preparation and
Treatment of Test Pieces
GB/T 8170 Rules of Rounding off for Numerical Values & Expression and Judgement
of Limiting Values
GB/T 10325 Shaped Refractory Products - Rule of Acceptance, Sampling and
Inspection
3 Principle
At room temperature, or heat the specimen to the test temperature and maintain the
temperature for a specified time. Apply a load that increases at a certain rate on the
upper surface of the specimen, until the specimen breaks. On the lower surface of the
specimen, measure the central deformation of the bent specimen. Record the load and
the corresponding central deformation, so as to calculate the stress and strain of the
specimen.
4 Equipment
4.1 The equipment mainly includes test furnace, loading device, specimen deformation
measuring device and temperature measuring device, etc. The principle of the test is
mm.
4.2.5 The loading device shall be able to uniformly load the specimen at the specified
loading rate, and shall be equipped with a device to record or indicate the load when
the specimen breaks, and the accuracy of the indication shall be 2%.
4.3 Deformation Measuring Device
4.3.1 The precision needs to reach 1 m and shall be regularly calibrated.
4.3.2 When the contact-type displacement sensor is used, the deformation of the
specimen is transferred to the displacement sensor through the transmission
mechanism. When the extensometer is used for measurement, the precision of the
extensometer is not lower than Level B-1. The precision of the extensometer used at
high temperature can be calibrated at room temperature, but an attempt shall be made
to calibrate it together with the high-temperature extension rod. For the automatic
recording chart extensometer, before each test, the precision shall be calibrated on the
site of the test.
4.3.3 Non-contact measurement may adopt laser, but it shall satisfy the accuracy
requirements.
4.4 Test Furnace
4.4.1 The test furnace shall be able to simultaneously heat the loading device and the
specimen. During the test, the temperature on the specimen shall be evenly distributed,
and the temperature difference shall not exceed 10 C.
4.4.2 For easily oxidized specimens, for example, specimens containing carbon, the
atmosphere around the specimens in the test furnace shall be neutral or reductive, so
as to protect the specimens from being oxidized.
4.5 Temperature Measuring Device
4.5.1 The temperature shall be measured through a thermocouple near the midpoint
of the tension surface of the specimen.
4.5.2 The relations between the measured temperature and the midpoint temperature
of the tension surface of the specimen shall be determined in advance and regularly
checked.
4.5.3 During the test, the midpoint of the tension surface of the specimen shall be
maintained at the test temperature.
4.6 Electric Drying Oven
It shall be controlled at the temperature of (110 5) C.
treatment is usually required. The conditions of pre-treatment need to be negotiated
by relevant parties and indicated in the test report.
6 Test Procedures
6.1 Room-temperature Test
6.1.1 Symmetrically place the specimen on the lower cutting edge. Install a
displacement measuring device at the center of the contact surface between the
specimen and the lower cutting edge.
6.1.2 Vertically and uniformly load the upper cutting edge in the middle of the pressure
surface of the specimen, until the specimen breaks. The stress increase rate shall
comply with the following stipulations:
---dense refractory products: (0.15 0.015) MPa/s;
---thermal insulating refractory products: (0.05 0.005) MPa/s.
6.1.3 Record the load value that the specimen bears and the corresponding central
deformation during the loading process.
6.2 High-temperature Test
6.2.1 The test temperature shall be determined by relevant parties through negotiation.
It is recommended to use multiples of 100 C (such as: 1,000 C, 1,100 C and 1,200
C, etc.); if necessary, multiples of 50 C (such as: 1,050 C, 1,100 C and 1,150 C,
etc.) may also be used.
6.2.2 Symmetrically place the specimen on the lower cutting edge in the test furnace.
At a specified rate, raise the temperature, generally at 4.5 /min ~ 5.5 C/min. For
dense shaped refractory materials, when the temperature exceeds 500 C, the heating
rate of 10 C/min may be used.
6.2.3 When the test temperature is used, maintain the specimen at this temperature
for a period of time, so that the temperature distribution on the specimen is uniform.
The temperature difference shall not exceed 10 C; the temperature-holding time
shall be indicated in the test report.
6.2.4 When the specimen is heated to the test temperature, start the timing of the
temperature-holding time. For the fired refractory materials, the temperature-holding
time is 30 min. For the unshaped refractory materials which have received thermal
treatment, the temperature-holding time is 30 min. For the unshaped refractory
materials which have not received thermal treatment, the temperature-holding time
may be 60 min, or be determined by relevant parties through negotiation. The
temperature-holding time and thermal treatment conditions of unshaped materials
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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