**Introduction to GBT 4741-1999: Method for Testing Bending Strength of Ceramic Materials**
This standard outlines the procedure for determining the room temperature bending strength of ceramic materials using a three-point loading method. It covers the necessary testing equipment, sample preparation, test procedures, calculation of results, and data processing. The method is applicable to ceramic materials and related auxiliary substances.
**Standard Test Method for Bending Strength of Ceramic Materials**
Released by the National Bureau of Quality and Technical Supervision, this standard was proposed by the National Light Industry Bureau. It defines the scope, equipment, and steps for measuring bending strength.
**Definitions**
Bending strength refers to the maximum stress a specimen can withstand under static bending before breaking. It is calculated as the ratio of the bending force to the section modulus at the point of fracture.
**Equipment Required**
- **Bending strength testing machine**: Must have an error margin of no more than 1%, with a constant-speed loading function and blades of 10 mm ± 0.1 mm in diameter.
- **Vernier caliper**: Accuracy of 0.2 mm.
- **Oven**: Capable of maintaining 110°C ± 5°C.
- **Desiccator**
- **Balance**: Sensitivity of 0.1 g.
**Sample Preparation**
- Specimens should be 10 cm long, with a width-to-thickness ratio of 1:1.
- They must be manufactured under the same conditions as the actual production process.
- The samples must be free of visible defects and well-machined.
**Test Procedure**
1. Dry the samples in the oven at 110°C ± 5°C until they reach constant weight, then cool them in a desiccator.
2. Place the sample on the support blades, ensuring that the distance outside the supports is 10 mm.
3. Apply load gradually at an average speed of 10–50 N/s until the sample breaks. Record the maximum load.
4. Measure the width and thickness of the fractured area using a vernier caliper.
**Data Processing**
- If the maximum relative deviation exceeds 10%, discard the most deviated sample and recalculate.
- If more than 4% of samples are discarded, retest.
- Use the arithmetic mean of valid samples as the final result, rounded to 0.1 MPa.
**Test Report**
Include details such as the sample supplier, name, number, span, loading speed, dimensions, and any data exclusions. Also, note the test date, personnel, and institution.
**Determination of Water Absorption, Apparent Porosity, and Bulk Density**
This section describes methods for measuring water absorption, apparent porosity, and bulk density of ceramic tiles. Two techniques are used: boiling and vacuum saturation.
**Scope**
The standard applies to ceramic tiles, with boiling suitable for classification and vacuum for detailed porosity and density measurements.
**Principle**
Dry ceramic tiles are suspended in water after being saturated, allowing the calculation of mass differences to determine key parameters.
**Instruments**
- Oven (110 ± 5)°C
- Boiling heater, heat source, balance (0.01% accuracy), deionized water, desiccator, sponge, suspension rings, glass containers, and vacuum system.
**Specimens**
- 10 whole bricks per type.
- For larger bricks, adjust the number accordingly.
- Ensure each sample weighs between 50–100 g if individual pieces are light.
**Procedure**
- Dry the samples in the oven until constant weight.
- Saturate using either boiling or vacuum methods.
- Weigh the samples in both dry and wet states, recording all values accurately.
**Implementation Date**
Approved on November 1, 1999, and implemented on January 1, 2000.
This comprehensive guide ensures accurate and consistent evaluation of ceramic material properties, supporting quality control and product development in the industry.
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