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What are the main reasons for the mechanical properties of the propeller? (two)
Jan 11, 2018

What are the main reasons for the mechanical properties of the propeller? (two)

3. The alloy contains gas

There is gas in the alloy, which causes the specimen to have gas holes, which has a great influence on the plasticity of the propeller alloy. The study of plasticity in alloy steel shows that when the micropores increase from 0 to 5%, the plasticity decreases obviously and the elongation decreases by about 20%. This is also the case in the propeller. In the aluminum brass of propeller, when the gas content exceeds 3.4ml/100g, the plasticity is reduced by 30%, while the plasticity of the bronze propeller alloy decreases by about 40%. The hole in the test rod has serious discontinuities in the properties of the alloy. When the tensile force is concentrated, the crack source at the initial stage of fracture is formed, and the brittle fracture is accelerated. At the same time, the pores in the alloy will form coalescence and coalescence in the tensile deformation slip zone, and finally collapse, resulting in fracture, which will decrease the plasticity index of the alloy.

4, the influence of the size effect of the sample

The size effect refers to the same alloy material with the same structure, but the mechanical properties are different when the size of the sample is different. Under the static load, the performance of the size effect is reduced and the brittleness tends to increase.

This size effect also exists in the propeller copper alloy. In the same furnace alloy, chemical composition, pouring temperature and other material samples were the same, pouring the same sample and two kinds of different samples, and finally processed into 14mm in diameter and diameter of 10mm bar tensile test found there are some differences between the mechanical properties, especially the plasticity index. The elongation of the 10mm rod is higher than the 15~20% of the elongation of 14mm. The difference is due to the increase of the casting solidification conditions and the increase of size when the samples with different sizes are added. The probability of forming defects increases, and the index of plastic decreases. At the same time, because of the increase of the size and the strengthening of the constraint conditions, the tendency of brittleness is increased, and the mechanical properties of the alloy are reduced.


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