Free Essay

Welding

In: Computers and Technology

Submitted By abdullahkhalid
Words 927
Pages 4
Spur Gears
General: Spur gears are the most commonly used gear type. They are characterized by teeth which are perpendicular to the face of the gear. Spur gears are by far the most commonly available, and are generally the least expensive. The basic descriptive geometry for a spur gear is shown in the figure below.

Limitations: Spur gears generally cannot be used when a direction change between the two shafts is required.
Advantages:Spur gears are easy to find, inexpensive, and efficient.

Helical Gears
General: Helical gears are similar to the spur gear except that the teeth are at an angle to the shaft, rather than parallel to it as in a spur gear. (See the references for more specific information). The resulting teeth are longer than the teeth on a spur gear of equivalent pitch diameter. The longer teeth cause helical gears to have the following differences from spur gears of the same size: o o o Tooth strength is greater because the teeth are longer,
Greater surface contact on the teeth allows a helical gear to carry more load than a spur gear
The longer surface of contact reduces the efficiency of a helical gear relative to a spur gear

Helical gears may be used to mesh two shafts that are not parallel, although they are still primarily use in parallel shaft applications. A special application in which helical gears are used is a crossed gear mesh, in which the two shafts are perpendicular to each other:
The basic descriptive geometry for a helical gear is essentially the same as that of the spur gear, except that the helix angle must be added as a parameter.

Limitations: Helical gears have the major disadvantage that they are expensive and much more difficult to find
(at least insofaras an ME3110 student is concerned). Helical gears are also slightly less efficient than a spur gear of the same size (see above).

Advantages: Helical gears can be used on non parallel and even perpindicular shafts, and can carry higher loads than can spur gears.

Bevel Gears
General: Bevel gears are primarily used to transfer power between intersecting shafts. The teeth of these gears are formed on a conical surface. Standard bevel gears have teeth which are cut straight and are all parallel to the line pointing the the apex of the cone on which the teeth are based. Spiral bevel gears are also available which have teeth that form arcs. Hypocycloid bevel gears are a special type of spiral gear that will allow nonintersecting, non-parallel shafts to mesh. Straight tool bevel gears are generally considered the best choice for systems with speeds lower than 1000 feet per minute: they commonly become noisy above this point.
One of the most common applications of bevel gears is the bevel gear differential,

Limitations: Limited availability. Cannot be used for parallel shafts. Can become noisy at high speeds.
Advantages:Excellent choice for intersecting shaft systems.

Worm Gears
General: Worm gears are special gears that resemble screws, and can be used to drive spur gears or helical gears.
Worm gears, like helical gears, allow two non-intersecting 'skew' shafts to mesh. Normally, the two shafts are at

right angles to each other. A worm gear is equivalent to a V-type screw thread. Another way of looking at a worm gear is that it is a helical gear with a very high helix angle.
Worm gears are normally used when a high gear ratio is desired, or again when the shafts are perpendicular to each other. One very important feature of worm gear meshes that is often of use is their irreversibility : when a worm gear is turned, the meshing spur gear will turn, but turning the spur gear will not turn the worm gear. The resulting mesh is 'self locking', and is useful in racheting mechanisms.

Limitations: Low efficiency. The worm drives the drive gear primarily with slipping motion, thus there are high friction losses.

Advantages:Will tolerate large loads and high speed ratios. Meshes are self locking (which can be either an advantage or a disadvantage).

Racks (straight gears)
General: Racks are straight gears that are used to convert rotational motion to translational motion by means of a gear mesh. (They are in theory a gear with an infinite pitch diameter). In theory, the torque and angular velocity of the pinion gear are related to the Force and the velocity of the rack by the radius of the pinion gear, as is shown below: Perhaps the most well-known application of a rack is the rack and pinion steering system used on many cars in the past. Limitations: Limited usefulness. Difficult to find.
Advantages:The only gearing component that converts rotational motion to translational motion. Efficiently transmits power. Generally offers better precision than other conversion methods.

Gear

Parallel
Shaft

Spur Gear

Intersecting
Shaft

Helical Gear

Single
Helical
Gear

Bevel
Gear

Coniflex
Bevel Gear

Non-Intersecting and Non-parallel
Shaft

Crossed
Helical
Gear

Hypoid
Gear

Worm
Gear

Double Helical:
Herringbone
Gear

Zerol
Bevel Gear

Spiral
Bevel Gear

Miter
Gear

Angular
Gear

Crown
Gear

Gear

Low
Velocity
Gear

Medium
Velocity
Gear

High
Velocity
Gear

Gear

External
Gearing

Internal
Gearing

Rack and
Pinion

Figure 1: Spur Gear

Figure 2: Helical Gear

Figure 3: Crossed Helical Gear

Figure 4: Herring Bone Gear

Figure 5: Bevel Gear

Figure 6: Zerol Bevel Gear

Figure 8: Spiral Bevel Gear

Figure 10: Spiroid Gear

Figure 7: Hypoid Gear

Figure 9: Coniflex Gear

Figure 11: Angular Gear

Figure 12: Miter Gear

Figure 14: Worm Gear

Figure 13: Internal Gear

Similar Documents

Free Essay

Incident Report

... JULY INTAKE 2012 RESISTANCE WELDING REPORT NAME | TRAINEE ID | JACK LAI KAR HAO | 323265 | ALLEN LAW CHI SEAN | 323359 | L.F NAME : MOHD. FADZIL BIN MUSA CONTENTS m/s Overview and introduction 3 Variables in welding process 4 How is resistance welding work 5 Types of resistance welding 6 Advantages and disadvantages of resistance welding 10 Application of resistance welding 11 Conclusion 12 Overview of Resistance Welding Introduction In simplest terms, welding is a process by which two or more pieces of metal are joined by applying heat and pressure. Back in the good old days, blacksmiths and other crafty people would heat metals in a furnace and then weld them by hammering the red-hot metals together. By hammering the metals as they cooled, the weld would be made stronger. This heating-and-hammering method is known as forge welding. While forge welding worked quite well for most of the welding done back then, today's welding requirements are a bit more advanced.......

Words: 1221 - Pages: 5

Premium Essay

Lgal Doc

...SAFE WELDING WORK AREA.. PREPARING THE WORK PIECE ............. ALUMINUM WELDING PREPARATION ........ CONNECT WELDER GROUND .............. PRODUCT DESCRIPTION 5 5 5 5 5 OPERATION GETTING TO KNOW YOUR NEW WELDER .... SETTING THE CONTROLS ................. HOLDING THE GUN ....................... Position of the Gun to the Work Piece ......... Distance from the Work Piece ............... LAYING A BEAD .......................... CLEANING THE WELD BEAD ............... 19 19 19 20 20 21 21 21 SPECIFICATIONS ......................... WELDER CONTROLS AND THEIR FUNCTIONS. DUTY CYCLE ............................. INTERNAL THERMAL PROTECTION .......... ASSEMBLY AND INSTALLATION 6 6 6 7 7 7 8 8 8 9 UNPACKING YOUR WELDER ................ INSTALL THE GROUND CLAMP .............. INSTALL WELDING GUN ASSEMBLY .......... PROVIDE REQUIRED POWER ............... Power Requirements ....................... Connect Welder to Power Source ............. Extension Cord Use ........................ INSTALL TANK TRAY AND BRACKET .......... SELECT SHIELDING GAS ................... WELDING TECHNIQUES 22 22 22 23 24 TRAVELING WITH THE GUN ................ TYPES OF WELD BEADS .................. WELDING POSITIONS ..................... MULTIPLE PASS WELDING ................. SPECIAL WELDING METHODS 25 25 25 Gas Selection For Steel Welding With Steel Wire. 9 Gas Selection for Aluminum Welding .......... 9 Gas Selection for Stainless Steel Welding......

Words: 14464 - Pages: 58

Premium Essay

Welding Processes

...1 Arc welding - an overview 1.I History of welding Methods for joining metals have been known for thousands of years, but for most of this period the only form of welding was forge welding by a blacksmith. A number of totally new welding principles emerged at the end of 19th century; sufficient electrical current could then be generated for resistance welding and arc welding. Arc welding was initially carried out using carbon electrodes, developed by Bemados, and was shortly followed by the use of steel rods. The Swede Oskar Kjellberg made an important advance when he developed and patented the coated electrode. The welding result was amazing and formed the foundation of the ESAB welding company. Figure 1. I Principle of Manual Metal Arc ( M M ) welding. Another early method of welding which was also developed at that time was gas welding. The use of acetylene and oxygen made it possible to produce a comparatively high flame temperature, 3100°C, which is higher than that of other hydrocarbon based gas. The intensity of all these heat sources enables heat to be generated in, or applied to, the workpiece quicker than it is conducted away into the surrounding metal. Consequently it is possible to generate a molten pool, which solidifies to form the unifying bond between the parts being joined. Figure 1.2 Submerged arc welding. © 2003, Woodhead Publishing Ltd WELDING PROCESSES HANDBOOK Later, in the 1930s, new methods were developed. Up until then, all metal-arc......

Words: 7587 - Pages: 31

Premium Essay

Asdasddsa

...Introduction Resistance welding covers a wide range of specific processes, mainly use for highly automated or even fully mechanized welding application, the majority in mass production. All these processes, except one (ESW, electroslag welding), need a mechanical clamping and pressurizing system to compress the workpiece areas intended to be welded prior to welding. Thus, these welding applications are categorized as resistance pressure welding processes (See figure 1-1) Figure 1-1 principal types of resistance weld In Resistance Spot Welding, passage of a relatively high welding current I [kA] throughout a locally compressed workpiece area (by means of an electrode force F [daN]) during a properly defined period of time t [cyc, ms] heats this area due to resistive heating following (Figure 1-2) Figure 1-2 principal of resistance of spot welding Values for Welding Force [daN], Welding Current [kA] and Welding Time [cyc, ms] are available in database format, and these values are commonly used to make a base setting to start from. Fine tuning within the parameter range (weldability lobe) can be done in order to optimise towards a specific application according to EN ISO 14327-2004 (Resistance welding – Procedures for determining the weldability lobe for resistance spot, projection and seam welding). Such a......

Words: 1388 - Pages: 6

Premium Essay

Hoha

... Cast iron is difficult, but not impossible, to weld. In most cases, welding on cast iron involves repairs to castings, not joining casting to other members. The repairs may be made in the foundry where the castings are produced, or may be made to repair casting defects that are discovered after the part is machined. Mis-machined cast iron parts may require repair welding, such as when holes are drilled in the wrong location. Frequently, broken cast iron parts are repaired by welding. Broken cast iron parts are not unusual, given the brittle nature of most cast iron.While there are a variety of types of cast iron, the most common is gray cast iron, and these guidelines are directed toward this type of material. A few facts about cast iron help in understanding the welding challenges. Cast iron typically has a carbon content of 2% - 4%, roughly 10 times as much as most steels. The high carbon content causes the carbon to form flakes of graphite. This graphite gives gray cast iron its characteristic appearance when fractured.When castings are made, molten iron is poured into a mold and allowed to slowly cool. When this high carbon material is allowed to cool slowly, crack free castings can be made. Remembering this is helpful when welding cast iron: during and after welding, the casting must either be allowed to cool slowly, or should be kept cool enough that the rate of cooling is not important.A critical temperature in most cast iron is about 1450 degrees F. When at this......

Words: 8583 - Pages: 35

Premium Essay

Electroslag Welding

...Electroslag Welding Electroslag Welding Electroslag Welding is a welding process, in which the heat is generated by an electric current passing between the consumable electrode (filler metal) and the work piece through a molten slag covering the weld surface. Prior to welding the gap between the two work pieces is filled with a welding flux. Electroslag Welding is initiated by an arc between the electrode and the work piece (or starting plate). Heat, generated by the arc, melts the fluxing powder and forms molten slag. The slag, having low electric conductivity, is maintained in liquid state due to heat produced by the electric current. Electroslag welding (ESW) is a highly productive, single pass welding process for thick (greater than 50 mm) materials in a vertical or close to vertical position. An electric arc is initially struck by wire that is fed into the desired weld location and then flux is added The slag reaches a temperature of about 3500°F (1930°C). This temperature is sufficient for melting the consumable electrode and work piece edges. Metal droplets fall to the weld pool and join the work pieces. Electroslag Welding is used mainly for steels. Electroslag Welding equipments Power source Wire feeder Electrode guide tube Retaining Blocks Welding head and Controls Power source 100 % duty cycle AC and DC (EP) power source 10,000 Amp OCV 60V (range is 30 V to 100 V) Remote controled Wire feeder Feed roller Drive motor Provide......

Words: 2360 - Pages: 10

Premium Essay

Welder

...WELDING TECHNICIAN I always loved doing activities with my hands, crafting different items out of raw materials. I remember when I took woodshop and welding class at high school and I enjoyed how I had the opportunity to create and sculpt items. That’s why I feel becoming a welding technician would be great for me. Welders are needed all over the world, its like you have endless work . Welders are in high demand they‘re need for everything when it comes to manufacturing. It just sounds like everything i'm looking for in a career. The reason I chose this profession was because I’m a hands on kind of guy. I like to get my hands dirty. Ever since I was a little kid, I was always dismantling things around the house. I stayed in trouble with my mom. As I become older, I started to notice that I was pretty good with my hands. My mom was always asking me to repair things around the house, like the dvd player or the lawn mower or just odd jobs around the house. But what really interested me in the welding job was my welding class. I had a teacher named Mr. Green who taught us the safety procedures, proper clothing to wear and welding using the basic methods. I found the class very interesting, We created tables, chairs, and a barbeque pit and even statues from raw metals. This class really made me want to become welding technician. Based on my personality assessment from type focus, my personality type is “introversion, intuition, thinking and perceiving”. This...

Words: 939 - Pages: 4

Premium Essay

Paper

...BODY WELDING - CAN IT BE FLEXIBLE? BODY WELDING - CAN IT BE FLEXIBLE? Some 250~300 pressed panels from in-house and vendor facilities are brought to different subassembly stations of Body Weld Shop. Subassemblies of pressed components are carried out mainly by resistance welding and other joining methods in a planned sequence at number of stations. Some subassemblies are done in off-line manufacturing cells and fed in at appropriate locations into the main assembly line. Fig. 6.1 shows a layout of a typical Body Weld Shop. Front end, rear floor, and front floor, are transported to underbody body line, where all these are welded together in sequence to form the floor structure. Underbody is then transferred to main body welding station. Right hand and left hand body side panels are brought from two sides to main body weld station, after completion of all subassembly operations in separate lines. Preframing of body structure is carried out on special fixture. At same or next station, roof is added to form the body shell, Fig. 6.2. Thereafter, rear doors, front fenders, hood and decklid/ tailgate fitments are carried out to complete the body-inWhite. If necessary, a metal finish line may be added for minor repair of Body-in-White before it moves for painting. Fig. 6.3 illustrates the sequences of subassemblies and the main body weld. Typically, Body weld shop activities cover fixturing, welding, and transportation between the work stations, and the related support services....

Words: 7585 - Pages: 31

Free Essay

Welding Techniques

...Processes in Design DT1410 Chapter 15 Case Problem 1: Welding Thin Materials I have to disagree with both, the experienced welder and the production supervisor. Arc welding is not the ideal process for thin metals. It takes many years for a welder to acquire the skills to arc weld thin metal and ever the most experienced welders mess up and ruin product. TIG welding would work with the thin metal but will take a lot longer and cost a lot more. It also takes the longest to master. Gas MIG (GMAW) is the process I recommend for the thin metal. I will explain the three processes in the following paragraphs. Arc Welding is one of the oldest welding processes around. It can be the cheapest to start with as there is not a lot of equipment needed. It is also very versatile as there are a lot of specialized electrodes available. These specialized electrodes are used for different types of preferences which include: hardening, high-strength, stainless, mixed, cast iron and other meter alloys. This process requires a flux coating to shield the weld and the flux will have to be cleaned from the weld. This process is very difficult to accomplish of thin metals of all types. Therefore, takes a considerable amount of training and practice to master. Also this process requires no gas or wire feeder which allows this process to be portable. This process works of AC (used on aluminum) or DC (used on ferrous metals (steels)). TIG welding is also very versatile and produces the......

Words: 622 - Pages: 3

Premium Essay

The Welding Experience

...The Welding Experience. The sun's rays hit my eyes as if to cause a prick as I opened the gigantic mahogany door, commanding my reflexes to quickly pull out my hand to cover some amount of the beams for better visibility. It was one of those hot summer afternoons. The temperature levels were very high. Conversely, I felt cooler in comparison with close to 120 degrees temperature of my area of work. I pierced my eyes through the parking lot as I shielded them from the bright glare of light that bounced off the windscreens. I had somehow succeeded in avoiding the sun though my sight remained blurred due to the sweat sipping into my eyes. This gave the feeling of swimming in the salty waters with eyes wide open. My clothes were no exception, it emphasized the likeness of me having been swimming in the ocean. Unknowingly, I tried to wipe the perspiration using my shirt but my reflexes for the first time betrayed me. I had worsened the situation since my attire was also a victim of the excretion. Luckily, I was now able to figure out the sense of the surrounding and the parking lot at large. I quickly maneuvered towards my automobile. Regrettably, General Electric owns a parking space that would rival most major parks. Executives and actual employees did not have a problem reaching their parking spot, unlike us welding interns who were reserved parking at the very behind of the lot, roughly a mile away from the building. I had been dodging cars as I walked across the parking......

Words: 1018 - Pages: 5

Free Essay

Welding

...The Art of Welding Welding is defined as the process of joining together metal pieces or parts by heating the surfaces to the point of melting using a blowtorch, electric arc, or other means, and putting them together by pressing or hammering. Welding is more of an art rather than a skill. It takes a special person to be able to completely master the art. Skills that a welder would need to have would be a very detail-orientated mind set. (Welding Basics) anyone can weld, but nobody is going to pay someone to weld something together crappily. The reason I am doing my research on welding is because I want to figure out if this is what I would like to do the rest of my life. I only have minor experience with welding. But, the experience I have had so far has been fun and exciting. Most of the work I have done with welding has involved my cars which is most likely the biggest reason that I have become so interested in this field of study. I have figured out that training for welding workers can range from a few weeks of school or on-the-job training for low-skilled positions, to several years of combined school and on-the-job training for highly skilled jobs. Training is available in high schools, and other types of institutions such as technical institutes, community colleges, and private welding schools. The Armed Forces have welding schools as well. (Jeffus,153) While some employers provide basic training, they prefer to hire workers with experience or more formal......

Words: 1137 - Pages: 5

Premium Essay

Flash Butt Welding Report

...SCHEDULING FRAMEWORK FOR TRACK LINKING IN RAILWAY PROJECTS First Review Report By Andrew George Cherian Under the guidance of Dr. Koshy Varghese Building Technology and Construction Management Department of Civil Engineering Indian Institute of Technology, Madras October 2015 TABLE OF CONTENTS Contents 1. INTRODUCTION 4 2. PROBLEM STATEMENT 4 3. OBJECTIVE 5 4. SCOPE OF WORK 5 5. METHODOLOGY 6 6. LITERATURE REVIEW 7 7. PILOT STUDY 8 7.1 RAIL WELDING 8 7.1.1 FLASH BUTT WELDING MACHINE 8 7.2 PRE-REQUISITES FOR LAYING THE TRACK 9 8. PROBLEM VALIDATION 12 9. ISSUE IDENTIFICATION 13 10. PROJECT TIMELINE 16 11. REFERENCE 16 TABLE OF FIGURES Fig1. Methodology Flowchart 6 Fig 2. Sequence of activities 10 Fig 3. Work Sampling Chart 10 Fig 4. Idle time distribution 11 Fig 5. Snapshot of planning assumptions 12 Fig 6. DPR for welding for a typical month 13 Fig 7. Snapshot of Internal Hire Charges 15 Fig 8. Project Timeline 16 1. INTRODUCTION Railway track construction started in India in 1859, with first operational line between Mumbai and Thane. It is the most critical transportation system of the country for passengers and goods. Spread of the railway track across any country is a key indicator of infrastructure and economy of a country. As of 2014-2015 India has a spread of more than 65000 route km of railway track (Indian Railways,2015). A typical railway construction project involves the construction......

Words: 2726 - Pages: 11

Free Essay

Welding Safety

...your First project Welding technology offer's society many beneficial ability's in enginering, construction, architecture, and also creates varied safety Concern's for the individual tradesmen' "tradeswomen"and their environment's. Welding Cover's a temperature range from 1500 F - 3000 ººF (800 ºC - 1635 ºC) and poses certain inevitable inherent risk's. As a skilled worker in this industry, one must proactively plan, prepare for any and all possible problem's, determine solution's and prepare preventative measures to use in case they arrive. Many welders reflecting on thier welding shop experience can admit they have acquired scars, acknowledge the dangers, and admit the necessity of demonstrating a professional respect for proper personal safety equipment and techniques. it has been said “If you play with fire you get burned” There are three main different risk's associated with welding including , heat, inhaling toxic fumes and electrical shock that are the most hazardous to your health, other various danger's include Gas leak, fire's and explosion's. In addition the extreme heat welding creates can burn you in many ways if not properly protected. There is ultraviolet light generated by the welding arc “electrical connection between welder and workpiece” that can cause severe radient heat, sunburns and increase your risk of skin cancer. Sparks can burn right through your gloves, boots and multiple layers of clothing even specialized welding coats! Using personal......

Words: 659 - Pages: 3

Free Essay

Mos 5201 Case Study

...MOS 5201 – Columbia Southern University October 14, 2013 Introduction When it comes to safety rules and regulations, there are many different sources to look for safety and health facts. In this paper we will be examining the safety and health facts for confined spaces, chromium and nickel in welding fumes, and thoriated tungsten electrodes, as they are presented in both the American Welding Society (AWS) safety and health fact sheets, as well as the course textbook, Occupational & industrial safety health management and engineering (2nd Custom ed.) and other official safety and health expert sources. It can be seen that there many similarities amongst safety regulations, as well as differences, depending on the topic at hand. Confined Spaces Confined Spaces are considered to be a very dangerous hazard for all industries. Cleaning, repair, or maintenance can often require entry inside confined spaces such as small rooms, pits, underground utility vaults, sewers, storage tanks, and so on, often where hot work will need to take place. Hot work in a confined space is characterized by limited space for entry or exit, and poor ventilation of air and other hazardous gases and fumes (Asfahl, Hammer, & Price, 2004/2001). OSHA 1910.146 specifies a permit-required confined space as an area that has one or more of the following characteristics: contains or has the potential to contain a hazardous atmosphere; contains a material that has the potential to engulf......

Words: 1840 - Pages: 8

Free Essay

Arx Welding Conditions

...মেসে থাকার নিয়মাবলী ১। প্রতি মাসের ২৫ - ৩০ তারিখের মধ্যে পরবর্তী মাসের খাওয়া ও থাকার সম্পূর্ন টাকা পরিশোধ করতে হবে। ২। কোন ধরনের নেশা / মাদক দ্রব্য ক্যান্টিন এর ভিতরে ব্যবহার ও সংরক্ষন করা নিষেধ। ৩। ক্যান্টিনে খাওয়ার সময় অবশ্যই ID কার্ড প্রদর্শন করতে হবে, ID কার্ড হারিয়ে গেলে সাথে সাথে কর্তৃপক্ষকে জানাতে হবে এবং ১০০ টাকা জরিমানা দিয়ে পুনরায় কার্ড সংগ্রহ করতে হবে। ৪। মেস ও সেন্টারের আশে পাশের কোন জায়গায় বিশৃঙ্খলা সৃষ্টি করা যাবে না। ৫। কেন্টিন এর নিয়ম অনুযায়ী নির্ধারিত সময়ের মধ্যে খাওয়া দাওয়া করতে হবে, সময় শেষ হওয়ার পর খাওয়া না পেলে কর্তৃপক্ষ দায়ী নয়। ৬। যার যার রুম নিজ দ্বায়িত্বে পরিস্কার করতে হবে। ৭। রুমে থাকা অবস্থায় রুমমেটের সাথে কোন ধরনের সমস্যা হলে সাথে সাথে কর্তৃপক্ষকে জানাতে হবে, মারামারি বা ঝগড়া করা যাবে না। ৮। কর্তৃপক্ষকে না বলে ৭ দিন মেসে না থাকিলে ভর্তি বাতিল বলে গন্য হবে। ৯। ভাড়া পরিশোধের পরে সেই ভাড়া ফেরতযোগ্য নয়। ১০। নিজ নিজ মালামাল টাকা ইত্যাদি নিজ নিজ দায়িত্বে রাখতে হবে, কোন কিছু হারিয়ে গেলে কর্তৃপক্ষ দায়ী নয়। ১১। প্রতি মাসের ১৫ তারিখ পর্যন্ত ভর্তির ক্ষেত্রে সম্পূর্ন মাসের টাকা এবং ১৫ তারিখের পর ভর্তির ক্ষেত্রে অর্ধেক মাসের টাকা পরিশোধ করতে হবে। ১২। কর্তৃপক্ষ যে কোন সময় যেকোন নিয়ম পরিবর্তন এবং ছাত্র বহিস্কার করার ক্ষমতা বহন করে। |দিন |সাপ্তাহিক খাবার তালিকা ও সূচি | | |সকাল |দূপূর |রাত ...

Words: 312 - Pages: 2