Regarding impact testing
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Regarding the impact test, the owner’s documents require that the ratio between the elastic limit E and the steel tensile strength R shall not exceed 0.85. What is the purpose of this requirement? Is there any source?
The shape strength ratio should not be greater than 0.85; consult the material’s yield limit/strength limit – low-strength materials should be used, and high-strength steels should be employed with caution.
Steel must possess good strength as well as a certain degree of plasticity and toughness; in addition, it should have an appropriate yield strength ratio. This is a fundamental requirement. However, for standard materials used in pressure vessels, these performance criteria are certainly met
The yield strength ratio is an indicator of a material’s plasticity reserve. It isn’t the case that the lower this ratio, the better; what’s important is that it be appropriate enough to ensure that when the material yields, it can undergo a certain degree of plastic deformation in order to counteract the further increase in stress, thus preventing the material from breaking. On the other hand, an excessively high yield strength ratio results in insufficient plastic buffering capacity after the material yields, leading to rapid fracture, which is quite dangerous in engineering practice. For the pressure vessel industry, this indicator is of little significance. This is because our design failure criteria generally involve plastic failure; that is, when the material reaches its yield point, it is considered that the equipment has failed, without taking advantage of the material’s inherent plasticity reserve.