The impact absorption of different metals such as low carbon steel, industrial pure iron and T8 steel at different temperatures was measured by impact test. The ductile-brittle transition temperature of low carbon steel was measured and the transition properties of the metal were obtained.
Toughness is the ability of a material to absorb energy during elastic deformation, plastic deformation, and fracture. The toughness of the material does not suddenly occur under the service conditions, so that safety is guaranteed.
The principle of measurement of impact absorption work is that a part of the energy existing in the form of pendulum potential energy before impact is absorbed by the sample during the fracture after being impacted. The difference between the starting height of the pendulum and the maximum height it reaches after the sample is broken can be directly converted into the energy consumed by the sample during the breaking process. The work absorbed by the sample is called the impact energy.
A series of impact specimens of a series of simply supported beam at different temperatures were subjected to a one-time strike with a pendulum of a predetermined height to measure the impact absorption work of each sample when it was broken. The test temperature is varied and a series of impact tests are performed to determine the temperature range at which the material transitions from human to brittleness, referred to as the "impact test." The ductile-brittle transition temperature is the temperature at which the Ak value on the Ak-T curve is significantly lowered. The middle portion where the curve impact energy changes significantly is called the conversion zone, and the temperature at which the brittle zone and the plastic zone each account for 50% is called the ductile-brittle transition temperature. When the crystallization or cleavage-like brittle zone on the fracture reaches 50%, the corresponding temperature is called the fracture morphology transformation temperature.
1. Brittle fracture: The material will exhibit brittle fracture at low temperature fracture. Brittle fracture is a rapid fracture. The energy absorbed during the fracture process is very low. There is no obvious plastic deformation before fracture and accompanied by fracture process.
2. Ductile-brittle transition: The energy absorbed by the material in a limited temperature range will be greatly changed by the impact load. This phenomenon is called the ductile-brittle transition of the material.
3. Cleavage fracture: When the applied normal stress reaches a certain value, the phenomenon of transgranular fracture that occurs along a specific crystal plane is called cleavage; the basic microscopic features of the cleavage fracture are steps, rivers, snake patterns, and so on.
4. Full-toughness fracture: the percentage of the area of the fractured crystalline area is set to 0%; the total brittle fracture: the percentage of the crystalline area of the fracture is set to 100%;
5. Ductile and brittle fracture: The percentage of the area of the fractured crystalline area needs to be measured by a tool microscope. The fracture surface of the fractured specimen is observed under a microscope. The brittle fracture is generally distributed with no dark spots. The brittle fracture can be obtained by measurement. The area of the trapezoid.
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