B. Destructive Tests

Of the destructive or damageable tests, two of the most commonly used are: the tensile, and hardness types. The former consists of exerting a tensile (pulling) force on the specimen and carefully recording its characteristics until it breaks. The final, or breaking load is known as its' ultimate stress, and is denoted in tons per square inch of the material.

The hardness test consists of pressing into the surface of the specimen a very hard steel ball— usually of 10 mm in diameter. The pressure is applied evenly, and the extent of indentation resulting in the specimen is carefully measured across its diameter and depth.

Certain values (or numerals) have been adopted and tabulated for the relative degrees of hardness of various materials, from which comparisons can be made with specimens tested.

Other tests for a metal's hardness are also made.

EXERCISES

І. Answer the following questions:

1.What tests may be carried out on materials? 2.When are non-destructive testes used? 3.What is the X-ray test? 4. How can a cracked casting be detected? 5. What types of the destructive tests are most commonly used? 6. What does the hardness test consist of?

II. Complete the following sentences:

1. Non-destructive tests can be performed on any.... 2. The X-ray test is.... 3. The X-ray test is performed for detecting.... 4. A cracked -casting can also be detected if....5. The breaking load is denoted in....

III. Translate the following sentences:

1.The X-ray test serves for detecting internal flaws, blowholes, or cracks, in castings and welded work. 2. Non-destructive tests can be performed on any finished article. 3. The destructive test consists of exerting a pulling force on the specimen. 4. The hardness test consists of pressing a very hard steel ball into the surface of the specimen.

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