Preliminaries:[ویرایش]
Creep is very important in industry and engineering and cannot be ignored easily
Creep is especially important in industries such as military, aircraft and bridge industries
Definition:[ویرایش]
The tendency of a material to change shape at high temperature due to constant stress or force
And it is called gradual and irreversible creep.
The amount of creep depends on various factors such as material type, time, temperature and amount of stress
In the diagram opposite, the amount of creep in time is shown,
Under constant stress, initial creep occurs rapidly
Then the creep speed decreases and the graph moves with a relatively constant slope
And finally, the creep speed increases and it goes towards rupture
Creep test: This test is done in two ways[ویرایش]
The first type (constant stress): In this test, by applying constant stress (the force changes according to the change in the shape of the object's cross-section so that the stress remains constant) at high temperatures, the object's resistance to change in shape is measured. This type of test is Because it is expensive, it is only done at the laboratory level and is not widely used in the industry
The second type (constant force): In this method, by applying a constant force (without considering the change in the shape of the cross section), the tendency of an object to change its shape at high temperatures is measured.
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The stress diagram in terms of rupture lifetime value shows:
As the amount of stress increases, the creep increases and as a result it goes towards rupture (the life span of rupture decreases) If we compare different temperatures, it can be seen that creep increases with increasing temperature | |
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