GMR Institute of Technology - Rajam

An Autonomous Institute Affiliated to JNTUK, Kakinada

Department Of Basic Sciences & Humanities

3rd

Sessional Examination- Key

Academic Year: 2014-15 Program: First B.Tech Semester: II

Course: EME Code: ME 1401 Date: 2.7.2015

Time: From 9.00AM to 10.30AM Max. Marks: 40

NOTE: Answer any FOUR of the following FIVE questions. Each question carries 10 Marks. Students

should write the answers in serial number i.e. 1a, b, 2a, b, 3a, b, etc. and in one space in the answer

book.

Q1. Two pulleys, one 450mm diameter and the other 200mm diameter are on parallel shafts 1.95m apart

and are connected by a crossed belt. Find the length of the belt required and the angle of contact

between the belt and each pulley. What power can be transmitted by the belt when the larger pulley

rotates at 200rpm, if the tension on tight side of the belt is 1kN and the coefficient of friction

between the belt and the pulley is 0.25? [10M]

Answers: Length of the crossed belt L= 4.975m

Angle of contact b/n the belt and each pulley==3.477rad

Power transmitted=P=2.74kW.

Q2. a) Differentiate between the hot working and cold working processes. [4M]

Cold Working:

Plastic deformation of metals below the recrystallization temperature is known as cold working. It is

generally performed at room temperature. In some cases, slightly elevated temperatures may be used to provide increased ductility and reduced strength. Cold working offers a number of distinct advantages,

and for this reason various cold-working processes have become extremely important. Significant

advances in recent years have extended the use of cold forming, and the trend appears likely to continue.

In comparison with hot working, the advantages of cold working are

1. No heating is required 2. Bettter surface finish is obtained

3. Better dimensional control is achieved; therefore no secondary machining is generally needed.

4. Products possess better reproducibility and interchangeablity. 5. Better strength, fatigue, and wear properties of material.

6. Directional properties can be imparted.

7. Contamination problems are almost negligible. Some disadvantages associated with cold-working processes are:

1. Higher forces are required for deformation.

2. Heavier and more powerful equipment is required.

3. Less ductility is available. 4. Metal surfaces must be clean and scale-free.

5. Strain hardening occurs ( may require intermediate annealing ).

6. Undesirable residual stresses may be produced

Cold forming processes, in general, are better suited to large-scale production of parts because of the cost

of the required equipment and tooling.

Hot Working:

Plastic deformation of metal carried out at temperature above the recrystallization temperature, is called hot working. Under the action of heat and force, when the atoms of metal reach a certain higher

energy level, the new crystals start forming. This is called recrystallization. When this happens, the old

grain structure deformed by previously carried out mechanical working no longer exist, instead new

crystals which are strain-free are formed.

In hot working, the temperature at which the working is completed is critical since any extra heat left in the material after working will promote grain growth, leading to poor mechanical properties of

material.

In comparison with cold working, the advantages of hot working are

1. No strain hardening 2. Lesser forces are required for deformation 3. Greater ductility of material is available, and therefore more deformation is possible. 4. Favorable grain size is obtained leading to better mechanical properties of material 5. Equipment of lesser power is needed

6. No residual stresses in the material.

Some disadvantages associated in the hot-working of metals are:

1. Heat energy is needed 2. Poor surface finish of material due to scaling of surface 3. Poor accuracy and dimensional control of parts 4. Poor reproducibility and interchangeability of parts 5. Handling and maintaining of hot metal is difficult and troublesome 6. Lower life of tooling and equipment.

b) What is soldering process? Explain about various flames used in Oxy-acetylene gas welding process.

[6M]

Soldering is defined as the process of joining two pieces of metals using a filler metal, known as solder, having a low melting point below the melting point of the work piece. It is often confused with welding

but the difference between them is, in soldering the work piece is not melted, they are joined using a filler

metal, but in welding work piece is joined by melting.

Neutral Welding Flame

Temperature Gradient of a Neutral Welding Flame

Carburizing Flame

Oxidizing Flame

Q3. Discuss in detail about the importance of Personal Protective Equipment (PPE) in the safety context

of an industry. [10M]

Personal Protective Equipment (PPE) includes all clothing and accessories designed to protect against

workplace hazards. In some situations the only available protection for employees will be the useof PPE

and often in emergencies, PPE will be required for the safety of the workers.

As required by federal and state regulations, personal protective equipment is essential for the protection

of eyes, ears, face and other body parts when working around hazardous machinery and equipment. All PPE must meet established standards (ANSI, NIOSH,OSHA, etc).

All Personal Protective Equipment (PPE) is provided by XYZ Manufacturing Company. Employees are

not allowed to provide their own PPE unless authorized by the Safety Director. As a general rule, only company provided PPE is allowed.

Hazard Assessments have been completed throughout the production and warehouse areas of XYZ Manufacturing Company.

PPE is required in the following areas:

Warehouse

All employees and visitors are required to wear approved hard hatsand eye protection. Steel-toed

shoes/boots required of warehouse workers.

Welding Shop

All employees and visitors are required to wear approved eye protection. Approved hard hats required of all welders. Approved hearing protection required of all welders. Welders are also required to don

approved PPE in the form of goggles, helmet, leather coat, apron, steel-toed work boot, gloves, no cuff

pants and other equipment as deemed necessary by the Safety Director. Mechanical ventilation is required

at all welding stations.

Paint Shop

All employees and visitors are required to wear approved eye protection. Spray painters are required to wear company provided work clothing (disposable shirt/pants). Approved respirators are required during

those times when spray painting, mixing, or clean-upis taking place. Steel-toed boots/shoes required of

paint sprayers. All spray painting is to be conducted within the paint spray booth. Mechanical ventilation system is to be in operation when spray painting takes place.

General Production Areas

Approved eye protection required of all who enter shop. Visitor glasses (eye protection) are available in main office as well as next to loading dock door and warehouse entrance.

XYZ Manufacturing Company will reimburse employee (maximum -$100) each 24 months for the purchase of approved steel-toed boot/shoe.

XYZ Manufacturing Company will provide prescription eye wear (approved safety eye protection) for those individuals requesting same. See Safety Director for additional information.

Q4. a) Explain the following: Need for training foremen and safety rules. [5M]

Safety & Training

All in-house Safety & Training sessions will be coordinated by (Name of Safety Director).

Foremen and Assistant Foremen are required to be trained in Accident Investigation Procedures by the

Safety Director Operators of forklift trucks are to be trained in-house in accordance with federal/state requirements.

Operators must attend classroom instruction as well as behind the wheel training. All employees who work with, or are exposed to, hazardous chemicals are to be trained in Hazard Communication, in accordance with federal and state regulations.

All employees who don respirators are to be trained in accordance with federal and state regulations.

Those individuals who donrespirators are required to have annual physicals. All employees who don Personal Protective Equipment (PPE) will be trained in the proper use of such

equipment.

First-aid training and training will be conducted by (Name of Hospital) and the local chapter of the

American Red Cross. Machine/Equipment operators are to be trained in-house. Emphasisis to be placed on point of operation

guarding. No employee is allowed to operate a machine unless it is properly guarded.

Employees who operate company vehicles are required to participate in an in-house Defensive Driving Program.

All production, shipping, and warehouse employees are required to attend a 4 hour in-house safety

training session on an annual basis. This partial day session is held each January in the conference room. The Safety Director will decide the

topic material; however each annual session is to place emphasis on material handling and machine

guarding.

All employees, at time of hire, are to be trained in Emergency Action and proper evacuation of building in case of an emergency. Each employee is to be given instruction/training on where to exit and where to

locate in the event of an emergency.

Foremen and Assistant Foremen are to meet with the Safety Director on a quarterly basis to discuss training needs and goals.

Safety Rules

All safety rules must be obeyed. Failure to do so will result in strict disciplinary action.

All injuries must be reported as soon as possible.

No alcohol, or drugs allowed on premises.

No alcohol usage allowed during lunch break.

PPE must be worn as prescribed by management.

All tools/equipment must be maintained in good condition.

Only appropriate tools shall be used for specific jobs.

All guards must be kept in place.

Only authorized personnel can operate forklift vehicles.

Smoking allowed only in lunchroom.

Seat belt use required of all drivers/passengers.

b) Define extrusion process and explain about forward extrusion and backward extrusion processes.

[5M] Extrusion is a Manufacturing process in which a softened blank of a metal or plastic material is forced through a shaped metal piece or die to produce a continuous ribbon of the formed product.

Direct extrusion:

The metal billet is placed in a container and driven through the die by the ram. The dummy block or pressure plate is placed at the end of

the ram in contact with the billet. Friction is at the die and container

wall requires higher pressure than indirect extrusion.

Indirect extrusion:

The hollow ram containing the die is kept stationary and the container

with the billet is caused to move. Friction at the die only (no relative

movement at the container wall) requires roughly constant pressure. Hollow ram limits the applied load.

Metal is forced to flow in the same direction as the punch. The punch

closely fits the die cavity to prevent backward flow of the material.

Metal is forced to flow in the direction opposite to the punch movement.

Metal can also be forced to flow into recesses in the punch

Q5. Explain in detail about various steps involved in a sand casting process. [10M]

1. Initially a suitable size of molding box for creating suitable wall thickness is selected for a two

piece pattern. Sufficient care should also be taken in such that sense that the molding box must

adjust mold cavity, riser and the gating system (sprue, runner and gates etc.).

2. Next, place the drag portion of the pattern with the parting surface down on the bottom (ramup)

board.

3. The facing sand is then sprinkled carefully all around the pattern so that the pattern does not stick

with molding sand during withdrawn of the pattern.

4. The drag is then filled with loose prepared molding sand and ramming of the molding sand is

done uniformly in the molding box around the pattern. Fill the molding sand once again and then

perform ramming. Repeat the process three four times.

5. The excess amount of sand is then removed using strike off bar to bring molding sand at the same

level of the molding flask height to completes the drag.

6. The drag is then rolled over and the parting sand is sprinkled over on the top of the drag.

7. Now the cope pattern is placed on the drag pattern and alignment is done using dowel pins.

8. Then cope (flask) is placed over the rammed drag and the parting sand is sprinkled all around the

cope pattern.

9. Sprue and riser pins are placed in vertically position at suitable locations using support of

molding sand. It will help to form suitable sized cavities for pouring molten metal etc.

10. Fill the cope with molding sand and ram uniformly.

11. Strike off the excess sand from the top of the cope.

12. Remove sprue and riser pins and create vent holes in the cope with a vent wire.

13. Sprinkle parting sand over the top of the cope surface and roll over the cope on the bottom board.

14. Rap and remove both the cope and drag patterns and repair the mold suitably if needed and

dressing is applied.

15. The gate is then cut connecting the lower base of sprue basin with runner and then the mold

cavity.

16. Bake the mold in case of a dry sand mold.

17. Set the cores in the mold, if needed and close the mold by inverting cope over drag.

18. The cope is then clamped with drag and the mold is ready for pouring.

Prepared by: PNLP, PGR, KPR, GVSS, MAK, PSR and MVR.