Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) on “Testing of Mechanical Properties”.
1. Mechanical testing of material or casting involves deformation and breakage of materials.
a) True
b) False
Answer: a
Clarification: Mechanical testing often involves deformation and breakage of samples of materials. A machine called UTM (Universal Testing Machine) is conventionally used, in which specimen is loaded or fixed at the chuck side and it performs various types of test like tension test, compression test etc.
2. In testing materials, only un-notched specimen of standard shape and size can be used.
a) True
b) False
Answer: b
Clarification: The simplest test specimens are smooth and un-notched, but more complex geometries can be used to produce conditions resembling those in actual engineering components. Notches like holes, slots or grooves that have defined radius can be machined in specimens. This gives more accurate information about the material.
3. Apart from UTM machine, servo-hydraulic systems are also used for testing materials which can be controlled manually.
a) True
b) False
Answer: b
Clarification: Various equipment are used for mechanical testing which ranges from simple, hand-actuated devices to the complex type of equipment, for example, servo-hydraulic system is one of the complex type which is used in testing and completely controlled through computer interfaces.
4. The tension test is generally used or performed for determining static properties of materials.
a) True
b) False
Answer: a
Clarification: The tension test is the commonly used test for determining static properties of materials. The data obtained from the test is mainly used to predict failure of parts subjected to more generalized stress states. Static properties are basically related to the strength and hardness of the material.
5. Tension test of brittle material may cause unexpected failure of the material.
a) True
b) False
Answer: a
Clarification: A direct tensile load is difficult to maintain because of misalignment of specimen grips and some bending usually occurs. It has no problem while testing ductile materials because local yielding can redistribute the stress, so uniformity remains; however, in brittle materials, local yielding is not possible and cause the failure of specimen in an unexpected way.
6. In tension test, the elongation or strain in the elastic region of material can be measured with the help of extensometer.
a) True
b) False
Answer: b
Clarification: The load in the specimen can be read directly from the testing machine, while the elongation is measured with the help of extensometer. But in the elastic region, the strains are so small that cannot be measured by extensometer, so some type of magnification of the deformations are generally required to measure the strains.
7. Which of the following categories is not the part of hardness testing of materials or castings?
a) Scratch test
b) Indentation test
c) Shear test
d) Rebound test
Answer: c
Clarification: In the mechanical properties of material, hardness is basically defined as the resistance of a material to penetration. To characterize hardness, it can be divided into three primary categories such as scratch test, rebound test and indentation test. Shear test is not the part of hardness testing; it is used to measure shearing strength of the material.
8. Which of the following properties of a material is assessed by the rebound test of hardness?
a) Toughness
b) Ductility
c) Malleability
d) Resilience
Answer: d
Clarification: The rebound test of hardness has generally employed some techniques to assess the resilience of material by measuring changes in potential energy of the material. For example, testing employs a hammer that is dropped onto the surface of the material being tested; same is also used for polymers testing.
9. In indentation testing of material, the hardness is a function of force and size of the impression.
a) True
b) False
Answer: a
Clarification: Indentation test actually creates a permanent impression on the surface of material. And the hardness is a function of force and size of the impression, so the force and size of the impression can be related to the hardness which can be objectively related to the resistance of material to the permanent penetration.
10. Which of the following types of indenter is employed in Brinell hardness test?
a) Diamond pyramid
b) Diamond ball
c) Titanium ball
d) Steel ball
Answer: d
Clarification: In this test, a large steel ball of generally 10 mm diameter is used with a force of relatively large magnitude. This force is usually compatible with either 3000 kg for relatively hard materials such as cast iron and steel or 500 kg for soft materials such as aluminium and copper alloys. For very hard materials, a tungsten carbide ball is preferred.
11. In testing of mechanical properties of material, torsion test is more preferred than the tension test.
a) True
b) False
Answer: a
Clarification: The torsion test is more preferred than the tension test because shear stress and shear strain are found directly in the torsion test, rather than tensile stress and tensile strain as in the tension test. And all the deformations of ductile materials are by shear, so the torsion test is more fundamental.
12. Which of the following devices is used for the measurement of angular deformation in torsion test?
a) Tachometer
b) Extensometer
c) Troptometer
d) Slip gauges
Answer: c
Clarification: A device known as troptometer is basically used to measure angular deformation in torsion test. This device mainly consists of two collars which are clamped to the specimen at the desired gauge length, in which one collar is equipped with a pointer and the other with a graduated scale.