Both mild steel and higher tensile steel plates and sections built into a
ship are to be produced at works approved by the appropriate classification
society.
Destructive tests are made on specimens obtained from the same product as
the finished material in accordance with the societies’ requirements which may
be found in the appropriate rules. These tests usually take the form of a
tensile test, and impact test.Tensile Test
A specimen of given dimensions is subjected to an axial pull and a minimum specified yield stress, ultimate tensile stress, and elongation must be obtained. In order to make comparisons between the elongation of tensile test pieces of the same material the test pieces must have the same proportions of sectional area and gauge length.Impact Tests
The Charpy V notch test or Charpy U notch test is commonly specified and therefore described in this text. The object of the impact test is to determine the toughness if the material.
In the figure above, the principle of the Charpy test machine is illustrated and also is the standard test specimen for a Charpy V notch test. This specimen is placed on an anvil and the pendulum is allowed to swing so that the striker hits the specimen opposite the notch and fractures it. Energy absorbed in fracturing the specimen is automatically recorded by the machine. Basically, making allowances for friction, the energy absorbed in fracturing the specimen is the difference between the potential energy the pendulum possess before being released and that which it attains in swinging past the vertical after fracturing the specimen. A specified average impact energy for the specimens tested must be obtained at the specified test temperature.
