SUB: MECHANICAL TESTING and QUALITY CONTROL (3Rdsem Mechanical)

K.S. POLYTECHNIC

No. 14, Raghuvanahalli, Kanakapura Road,

Bengaluru-560062

SUB: MECHANICAL TESTING AND QUALITY CONTROL (3rdsem mechanical)

IMPORTANT VIVA QUESTION

Define co-efficient of friction

Theforcerequiredto movetwoslidingsurfacesovereachother,divided bytheforceholdingthemtogether is called co-efficient of friction.

What is mean by flash point and fire point.

Thefire pointof a fuel is the lowest temperature at which the vapour of that fuel will continue to burn for at least 5 seconds after ignition by an open flame. At theflash point, a lower temperature, a substance will ignite briefly, but vapor might not be produced at a rate to sustain thefire.

Define viscosity.

Viscosityis an internal property of a fluid that offers resistance to flow.

SI unit: = (N·s)/m2

What is impact strength.

Theimpact strengthdescribes the ability of a material to absorb shock and impact energy without breaking.

Define hardness.

In metallurgyhardnessis defined as the ability of a material to resist plastic deformation.

Define yield stress.

Ayield strengthoryieldpoint is the material propertydefinedas thestressat which a material begins to deform plastically.

Define ultimate stress.

ultimate strength, is the capacity of a material or structure to withstand loads tending to elongate.

Define breaking stress.

The maximum stressa material can stand before it breaks is called thebreaking stress.

Define young modulus.

it is defined as the ratio of tensile stress to tensile strain.

Define compressive strength.

Compressive strengthorcompression strengthis the capacity of a material or structure to withstand loads tending to reduce size.

What is shear stress.

The stress induced in a body,which subjected to two equal and opposite forces which are acting tangentially across the resisting section called shear stress.

Define accuracy,precision,sensitivity,range.

Accuracy: It is defined as the closeness of agreement between a measured value and the true value.

Precision: the precision of an instrument is its ability to reproduce a certain reading with a given accuracy.

Sensitivity: it is the ability of a measuring device to detect small difference in a quantity being measured.

Range: the range of a measuring system describe the value of the measurand to which that measuring system will respond properly.

What is pitch diameter?

The pitch diameter is the diameter where the thread thickness is equal to the space between the threads.

Mention some of the angle measuring instrument.

Bevel protractor,sine bar etc.

What is the formula to find out the angle in sine bar.

Sin*=h2-h1/L

What is the use of limit gauges?

In mass production a large number of identical component are manufactured.there to use of micrometer, vernier or other measuring instrument to check the dimension will be time consuming.for this purpose we can use limit gauge.it can check holes,diameter,externaldimension,etc.

Mention the parts of a vernier caliper.

Jaws(for measuring inner and outer dimension)

Vernier scale,main scale,stem,locking screw

What is the unit of viscicity?

Si unit is NS/m2

What is the role of CMM machine

Coordinate measuring machine is a device for measuring the physical geometrical characteristic of an object.It is also a device used in manufacturing and assembly process to test a part.

What is the use of spirit level.

Aspirit level, bubblelevelor simply alevelis an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb).