some important viva questions for foundry and forging lab

what is shear strength?

ans. shear strength is the ability or capacity of a material to resist a shear force applied on it.

shear force as shown above in the figure can also be referred to as a tangential force.

what is tensile strength of a material? ans. Tensile strength of a material is the ability or capacity of a material to resist tensile forces applied on it.when tensile forces are applied on a material then the material produces internal stresses to resist those forces applied on it.

what is compressive strength? ans.Compressive strength of a material is the ability or capacity of a material to resist tensile forces applied on it.when compressive forces are applied on a material then the material produces internal stresses to resist those forces applied on it.

what is the difference between strength of a material and stress in a material?
ans. As a matter of fact most of the properties related to these two are almost same.so it would be better not to define them.The most important difference between them is that strength of a material remains the same no matter what the size of the specimen is.Even in the molecular state,its strength is the same.whereas when stress is considered,it changes with the area of the specimen.so the stress of a specimen is inversely proportional to the area of the specimen but strength is not.

what is the use of conducting permeability test on a specimen? ans.The permeability test is very important test.when the molten metal is poured in the prepared mould,the gases(hot) escape from the molten metal and penetrate through the mould. these gases get trapped in the mould producing small globules containing gases.the permeability test is conducted to find the condition of the mould sand after the metal is poured into it n check whether or not these globules are present.

How many types of sand are there which are used in the foundry and forging lab?

ans.There are two types of sand that is used in this lab,namely:-
1. river sand
2. gre.en sand.

what is grain fineness number? ans.A system developed by AFS for rapidly expressing the average grain size of a given sand. It approximates the number of meshes per inch of that sieve that would just pass the sample if its grains of uniform size. It is approximately proportional to the surface area per unit of weight of sand, exclusive of clay.

what are the types of hammers used? ans.you can check out the picture above(top of the page).the only one missing there is a sledge hammer.

what are blacksmith's tongs? ans.

History

1. The art of the blacksmith goes back to before recorded history and starts with the invention and cultivation of fire. Fire allowed budding blacksmiths to shape soft metals found in the earth, like bronze, into sharp and hard spear points and daggers. Iron became the metal of choice, with its use rising from 1200 B.C. forward. Wootz steel was created by blacksmiths in India by combining iron with various materials, including charcoal and glass. In the western world, the Romans began perfecting steel techniques, making complicated suites of plate and chain mail for their soldiers. Today, the art of the blacksmith is fading. Horseshoes and various as-needed products still require a blacksmith's hands, but the advent of machine production has led to the decline of this ancient skill.

Function

2. The function of a blacksmith's tongs is simple. Metal gets very hot when heated to the temperature needed to shape it. A blacksmith must have a way of holding the heated metal without seriously burning himself. Tongs were the perfect solution. Tongs allow a blacksmith to grip, lift and rotate red-hot metal in his forge. They also allow the blacksmith to place metal deep into burning coals so that it can be heated quickly.

Types

3. There are several different types of blacksmiths' tongs, each used for something different.:
   
   Flat tongs have flat, rectangular grabbing points and are used to grip flat pieces of metal.
   
   Bolt tongs have a rounded grabbing point and a stem that allows bars of iron or steel to be clasped, as well as metal with holes to be gripped and lifted from the hole.
   
   Box jaw tongs and variations on them have commonly been used in sword making. The box-style grabber allows a blade of heated metal to be held inside the tongs without warping the shape.

Size

4. Blacksmith tongs vary in size, depending on the intended use. Smaller tongs for more delicate work usually come in at around 8 inches in length and resemble typical pliers of today. Larger tongs for things like sword and horseshoe making are usually between 14 and 15 inches. However, custom tongs can be made by a blacksmith to be just about any size if needed.

Warning

5. A blacksmith's art is a dangerous one and should not be tried without the proper training and supervision. Due to the use of fire as a main component, burns and property damage are significant risks. Also, the striking of hot metal with a hammer sends sparks and shards flying in different directions, and without proper safety equipment can cause blindness.

check out the various tongs as shown in the picture on the top of the page.




and then there are some bookish questions like :

what is the composition of the moulding sand?
what is the use of cope and drag?
what are the types of cores?
what is theuse of a core?
what are the types of moulding processes?

all of these stuff can be found in the 1st chapter of the manufacturing processes-1.

if u still have any unanswered questions please write it back to me.

And i wanna tell u some basic stuff before i end this post.

** except for tensile test,all the strength tests use a cylindrical mould.In tensile test we use a bone shaped specimen.

**for clay content test we use a different sand.for all other tests we use a common sand.

**we have not made the model in forging with a hexagonal head.so just a piece of advice.make the specimen as that of the round headed bolt n then keep rotating and hitting the end of the round shape.this will give you the desired shape.