What Is Plastic Bending?

Bending strength refers to the maximum stress that a material can withstand under a bending load or reach a specified bending moment. This stress is the maximum normal stress during bending, in MPa (megapascal) units. It reflects the material's resistance to bending and is used to measure the bending performance of the material.

Bending strength refers to the maximum stress that a material can withstand under a bending load or reach a specified bending moment. This stress is the maximum normal stress during bending, in MPa (megapascal) units. It reflects the material's resistance to bending and is used to measure the bending performance of the material.
Chinese name
Bending strength
Foreign name
bending strength
Nature
Performance of materials when subjected to bending loads
Unit
MPa

Definition of Bending Strength

Bending strength refers to the maximum stress that a material can withstand under a bending load or reach a specified bending moment. This stress is the maximum normal stress during bending, in MPa (megapascal) units. It reflects the material's resistance to bending and is used to measure the bending performance of the material. When the transverse force is bent, the bending moment M varies with the position of the section. In general, the maximum normal stress max occurs on the section with the largest bending moment and the farthest from the neutral axis. Therefore, the maximum normal stress is not only related to the bending moment M, but also to the cross-sectional shape and size. The formula for calculating the maximum normal stress is:
Where Mmax is the maximum bending moment and W is the bending section coefficient. [1]

Bending strength performance and experimental method

Bending strength strength performance

When a member is bent, the upper part of its section is the compression zone, and the lower section is the tensile zone. Taking a rectangular homogeneous section as an example, the strength of the outermost edge of the compression and tensile zone is called bending strength. It is proportional to the bending moment and inversely proportional to the section modulus.
It can be expressed by the following formula: = KM / W where K is the safety factor, M is the bending moment, and W is the section modulus. Different sections have different section modulus which can be found in the Handbook of Materials Mechanics.
Different materials have different test methods and national standards. For example, the flexural performance of plastics is determined by GB / T 9341-2008, the flexural strength of hard rubber is determined by GB1696-2001, the test method of high-temperature flexural strength of engineering ceramics is GBT14390-1993, and the flexural strength test method of natural facing stones is GBT9966.2-2001 and so on.

The main experimental method of bending strength

Test method for natural facing stone Test method for flexural strength
Standard name Test method for natural facing stone Test method for flexural strength
Standards of the People's Republic of China
Standard name (English) Test methods for natural facing stones Test method for flexural strength
International code UDC691.21: 620.1
Standard number: GB99666.2-88
Figures Figure 1;
Standard text
1 Theme content and scope
This standard specifies the testing equipment, specimens, test procedures,
Calculation and test results.
This standard applies to the bending strength test of natural facing stone and block.
2 Equipment and measuring tools
2.1 Material testing machine, the relative error of the displayed value does not exceed ± 1%. The maximum load for specimen failure is in the range of 20% -90% of the scale of the material testing machine.
2.2 Vernier caliper: The scale is 0.02 mm.
3 sample
3.1 Specimen size 160 mm in length, 40 ± 0.5 mm in width, 20 ± 0.5 mm in height, the parallelism of the bearing surface is within 0.08 mm, and two groups of vertical and parallel laminated samples . There are two groups of samples without stratification, five in each group.
3.2 The specimen shall be marked with the direction of rock bedding.
3.3 The two bearing surfaces of the sample were polished with 500-grit fine sandpaper. Edges, corners and visible cracks are not allowed.
3.4 Mark the two points and the force points (see the figure below for the dimensions), and measure the width of the two fulcrum points and load points of the sample.
With high dimensions and take the arithmetic mean.
Water level.
4 test steps
4.1 Dry the sample in an oven at 105 ± 2 for 24 hours, then put it in a desiccator to cool to room temperature.
4.2 Adjust the distance between the supports to 140 ± 0.5 mm, place the sample on the support, apply a load to
At a rate of two millimeters per minute until the specimen breaks, read the load value at break.
5 result calculation
The bending strength is calculated as follows:
3P · L
Rt =
2b · h2
In the formula: Rtthe bending strength of the sample, MPa (kgf / cm2);
P a-specimen fracture load, N (ksf);
L1distance between fulcrum points, cm;
b a sample width, cm;
hsample height, cm.
6 test results
Calculate the arithmetic mean, maximum and minimum values for different layers of the sample.
Additional information:
This standard was drafted by the Institute of Artificial Crystals of the State Building Materials Industry Bureau.
The main drafters of this standard are Yang Meiju and Meng Bingfen.

Calculation formulas related to bending strength

1 Set the arm to hF, the width of the dangerous section to SF, and the nominal bending stress of the dangerous section of the tooth root to be
2 Taking into account the load coefficient K, coincidence coefficient Ye, and stress correction coefficient Ysa, the check formula for the bending fatigue strength of the root of the tooth is
3 Design formula of tooth root bending fatigue strength

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