“Three-point flexural test”的意思、由来-开放百科全书

The three-point bending flexural test provides values for the modulus of elasticityin bending

, flexural stress

, flexural strain

and the flexural stress–strain response of the material. The main advantage of a three-point flexural test is the ease of the specimen preparation and testing. However, this method has also some disadvantages: the results of the testing method are sensitive to specimen and loading geometry and strain rate.

Testing method

The test method for conducting the test usually involves a specified test fixture on a universal testing machine. Details of the test preparation, conditioning, and conduct affect the test results. The sample is placed on two supporting pins a set distance apart.

Fracture toughness testing

The fracture toughness of a specimen can also be determined using a three-point flexural test. The stress intensity factor at the crack tip of a single edge notch bending specimen is^[3]

where

is the applied load,

is the thickness of the specimen,

is the crack length, and

is the width of the specimen. In a three-point bend test, a fatigue crack is created at the tip of the notch by cyclic loading. The length of the crack is measured. The specimen is then loaded monotonically. A plot of the load versus the crack opening displacement is used to determine the load at which the crack starts growing. This load is substituted into the above formula to find the fracture toughness

The predicted values of

are nearly identical for the ASTM and Bower equations for crack lengths less than 0.6

Standards

See also

References

1. ^{{cite book | title = Biomaterials – The intersection of Biology and Material Science | publisher = Pearson Prentice Hall | location = New Jersey, United States | year = 2008 | chapter = Chapter 4 Mechanical Properties of Biomaterials | page = 152}}
2. ^{{citation | author = Zweben, C., W. S. Smith, and M. W. Wardle | title = Test methods for fiber tensile strength, composite flexural modulus, and properties of fabric-reinforced laminates | journal = Composite Materials: Testing and Design (Fifth Conference) | publisher = ASTM International | year = 1979}}
3. ^{{cite book | title=Applied mechanics of solids | author=Bower, A. F. | year=2009 | publisher=CRC Press.}}
4. ^ {{citation | title = ASTM D5045-14: Standard Test Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials | publisher = ASTM International | location = West Conshohocken, PA | year = 2014}}
5. ^ {{citation | title = E1290: Standard Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement | publisher = ASTM International | location = West Conshohocken, PA | year = 2008}}