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The correct CHOICE is (c) 30,000,000

For explanation: The modulus of elasticity of a material is used in determining the normal elongation of a material. The modulus of elasticity of steel is 30,000,000 pounds PER SQUARE inch. For ALUMINIUM alloys, it is 10,000,000 Psi and for magnesium it is 6,500,000 psi.

The CORRECT option is (a) 1/250 of the REGISTERED LOAD

The best explanation: To obtain an accurate result, it is IMPORTANT for the test machine to be in appropriate condition. One of the important conditions is for a load being applied, the test machine must be SENSITIVE to a variation of 1/250.

Correct choice is (C) Exographs

Easiest explanation: The INSPECTION method of radiography can be performed in two ways. EITHER using gamma-rays called Gammagraphs or made by passing X-rays through the material being inspected, which are called exographs.

The correct option is (c) gamma-rays

To EXPLAIN I would say: Gammagraphs are a type of radiographs. HENCE, they are non-destructive in nature. They are obtained by PASSING gamma-rays through a material. Radiographs and Gammagraphs are ALSO called shadow pictures.

Right answer is (b) wire

For EXPLANATION: It is a NECESSARY requirement for wires to undergo torsion test. There are different types of tests available for different kinds of a SPECIMEN like bending test, HARDNESS test, HYDROSTATIC test and crushing test.

Correct option is (d) higher

To explain I WOULD say: The higher the impact value of a material, higher is its toughness value. The toughness of a material is its capacity to absorb energy and DEFORM WITHOUT FRACTURING. It corresponds with the impact energy of a material.

Right answer is (a) True

Easiest explanation: It is true that most aircraft materials need to undergo and pass a bending TEST. This GIVES the IMPRESSION and meets the requirement of needing a MATERIAL that is more ductile and not brittle in nature.

Correct option is (B) 90°

For EXPLANATION: In the reverse bend test, a single bend is usually considered to be 90° in each test. The MACHINE goes both back and forth each TIME 90°, making a total of 180°, but one bend is considered to be 90°.

Right CHOICE is (c) 6

The best explanation: The usual length of the BENDING test specimen, which is sheets or strips is 6 inches long. The specimen should not contain rough SPOTS or edges, as that can EFFECT the MATERIAL and hence the experiment.

Correct option is (B) 1/4

Easy explanation: The speed which a crosshead should not exceed until yield point is 1/16 for one inch per inch GAGE LENGTH per minute.

For 4 inches, it is – \(\FRAC{1×4}{16}\) = 1/4 inch.

Right CHOICE is (b) 0

Best explanation: Demagnetization is done on materials that have been SUBJECTED to the magnaflux inspection method. There are two METHODS to do it, and one of them is keeping the specimen in the coil and SLOWLY decreasing the CURRENT to zero.

Correct OPTION is (a) True

Explanation: The above STATEMENT is correct. There are three ways in which the magnaflux INSPECTION method is carried out. Circular magnetization, BIPOLAR magnetization and the continuous method.

The correct ANSWER is (a) 10^-11

The explanation is: Rays like gamma-rays, X-rays are CLASSIFIED based on their wavelengths. The WAVELENGTH bracket in which the rays are considered to fit the category of gamma-rays is around 10^-11 centimeters.

The correct answer is (a) 2000 rpm

To EXPLAIN: The SPEED of rotation of fatigue TESTING MACHINES is different for different machines. But, the typical speed is usually of the order of 2000 rpm. For machines that are high speed, it can be 12,000 rpm.

Correct option is (a) 10

For EXPLANATION I would SAY: The minimum length required for the specimen is ten inches if the wire being TESTED has a diameter of more the 0.333 inches in the torsion TEST. The length requirements vary depending on the diameter of the wire.

Correct choice is (c) 10 inches

Explanation: In the reverse band test, the minimum length of wire USED in the EXPERIMENT is 10 inches. The specifications to perform the experiment on the specimen truly DEPEND on the nature of the MATERIAL.

The correct OPTION is (b) False

For explanation: This STATEMENT is INCORRECT. Like an IZOD impact test, even the Charpy impact test requires a pendulum/ hammer for the experiment. It is used to cause a rupture in the test specimen being tested.

Correct OPTION is (B) Izod test and Charpy test

To elaborate: The Charpy impact test and the Izod impact test are STANDARD impact tests. They have some DIFFERENCES, but they both give the impact values of the specimen. Reverse BEND tests and flattening test are bending tests.

The correct ANSWER is (d) Required edge distance

The explanation is: Deflection CAUSED DUE to depression is ONE of the possibilities that have to be considered and avoided to obtain the correct result. It can be avoided by ENSURING that the experiment is being conducted at the required edge distance.

Correct choice is (b) Storing

Easy explanation: DUE to the properties of the material, the HARDNESS and subsequently tensile STRENGTH are affected. Processes LIKE buffing influence the surface of the material. Porous areas and decarburizing ALSO affect the material.

The correct choice is (d) 0

To elaborate: The dial on the Rockwell hardness test method is where the value can be FOUND. There are two sets of numbers on the dial, black and red. Before the major LOAD is APPLIED on the test specimen, the DIRECT reading dial on the MACHINE has to be fixed to zero.

Correct ANSWER is (d) 10mm

To ELABORATE: The BRINELL test method involves pressing a hard BALL made of steel, with a particular pressure onto the surface of the test specimen. The DIAMETER of the steel ball being used is 10 mm.

Right option is (C) Circular magnetization

For explanation: There are two ways in which a specimen in the magnaflux process can be MAGNETIZED. Circular magnetization and bipolar magnetization. Angular magnetization does not EXIST in this process.

The correct choice is (b) False

To ELABORATE: This statement is not TRUE. Materials that have been SUBJECTED to heat-treatment have higher tensile strengths, (not lower) compared to materials that are annealed. They ALSO have higher fatigue limits.

Correct choice is (d) 2,000,000

Explanation: Performing a fatigue test on a material is a very DIFFICULT TASK. The amount of test CYCLES required to be performed on HARD steels is 2,000,000. For SOFT steels, the number of cycles required is 10,000,000.

Correct choice is (a) capacity of a material to withstand the twisting load

The best I can EXPLAIN: The capacity of a material to withstand the twisting load is called torsional strength. It is ALSO called modulus of rupture. Gravitational FORCE is the force of ATTRACTION present between particles.

The correct choice is (B) APPLICATION of pressure and BLOW from a hammer

To elaborate: The bending in the bending test is usually achieved by either applying a constant source of pressure or by DELIVERING blows from a hammer. The usage of the hammer creates a much HIGHER impact on the specimen than the other method.

Correct ANSWER is (C) Instrument should be fixed rigidly

The BEST explanation: The instrument should be fixed rigidly in a particular position to avoid MOVEMENT during the experiment. If any movement happens, it might AFFECT the accuracy of the obtained hardness number.

Correct answer is (d) ductility

For explanation I would say: BENDING tests are conducted to obtain the ductility of material and MAKE SURE that it does not have more BRITTLENESS than ductility. The hardness TEST is conducted to measure the hardness of the material.

Right CHOICE is (c) rectangular

Explanation: For a specimen being tested that is heavy in weight, the rectangular cross section should be PRESENT. The cross section can be obtained by APPLYING a smooth FILE at the CORNER of the test specimen.

Right option is (a) diamond

For explanation: A diamond PENETRATOR is used in a Vickers/diamond pyramid HARDNESS test. The penetrator consists of a pyramid that has a square BASE. A Steel ball is used in BRINELL and Rockwell hardness TESTS.

Right option is (B) Rockwell HARDNESS

The explanation: The method of hardness testing usually preferred for aircraft manufacturing purposes is the Rockwell hardness method. This is because it is easy to OPERATE and is RELIABLE. DIVIDER method is used to determine the yield point of a material. It is not a hardness testing method.

Correct answer is (a) 3

The best I can explain: X-rays can be USED to inspect materials MADE up of steel sufficiently up to a thickness of THREE inches. If the material being inspected is not as dense as steel, it can also be TESTED for a HIGHER thickness value.

The correct option is (d) Vickers

The BEST explanation: BRINELL hardness numbers are usually similar to Vickers hardness or Diamond pyramid hardness numbers. But HARD MATERIALS are the only exception to this rule as they are not similar in this CASE.

Right choice is (B) DIVIDER METHOD

The explanation: There are two methods to DETERMINE the YIELD point of a material. One is divider method, and the other is drop of beam method. In that, drop of beam method uses a pair of dividers. Set method is a method of determination of yield strength.

Right choice is (c) 5kg

The best I can explain: The loads being APPLIED in the ROCKWELL HARDNESS method usually on the penetrator(steel ball or DIAMOND cone) being used and the test specimen. The loads applied are typically 100kg, 150kg and 60KG.

Right option is (c) Filing

To ELABORATE: The requirements of the specimen for Brinell testing METHOD is similar to the remaining test METHODS. There are several ways to prepare the MATERIAL for the test. Grinding, filing and polishing using emery paper are done. Layering is not ONE of the methods.