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5 tips to survive a Seminar successfully!

Seminars have always been an important aspect of education. It's an opportunity to either gain knowledge on an unknown topic or develop ideas regarding something you already know.It's a place where you meet highly skilled persons and get to know their recent researches.You should attend at least a couple of seminars annually to keep yourself updated about the advancements taking place in your field. I've seen many people who keep avoiding seminars, although interested, just because they have never attended a seminar before. If this is your case, then I've only one thing to say "There's always a first time." Until and unless you attend a seminar, how can you overcome the fright?     Attending a seminar for the first time does not mean that you'll feel low or less confident than others. Here are a few tips that can make you seminar-ready. Here are a few tips that can help you get through a seminar and actually learn from it.   1. Know the Topic Usually there are no prerequisites to attend a seminar but ideally you should know something about the seminar you're going to attend.First know the topic, yes the topic. I've seen a lot of people coming for a seminar and asking what the topic is! Know the meaning of each term related to the topic, like definitions, some dates, names of some important people in that field, etc. If you still have some time and energy left, know who the speaker is and his background. You can look for his area of study, some research works, etc. So now that you know what you need to know, I'll suggest you some ways by which you can know it.( I just hope I didn't confuse you. Oops, I did! ) Now-a-days you can literally find everything on the web,sometimes even the details you need about the speaker from his research works. Now that you have the basic knowledge of the topic, you can consult the faculties if you feel like. You can find lot of details online but only after talking to the profs you get to know which information is relevant for the seminar you're going to attend.Knowing more never goes in vain, but off course you wouldn't like to clog your mind with so many points. If you feel it hard to remember all the points, you can make short notes and take it with you to the seminar. Just make sure your focus is on the speaker as soon as the seminar starts and not on these notes.        2. A proper attire it's never mandatory to wear formals for attending a seminar but avoid fancy dresses. Remember you're in the professional world, dress up like that. If you like make-ups go for it, but keep it light and simple. Just make sure you're comfortable with your look. In most of the cases, dressing up properly makes people feel confident.         3. Non-verbal communication People can communicate a lot of things even without uttering a single word, through their body gestures, eye movement, etc. ere lies the importance of non-verbal communication. You can put a smile on you face just to show that you're there to learn and not to oppose the idea the speaker is going to present. Nodding your head sometimes during the speech can also communicate a lot about you. It means you're listening and understanding the topic as well.         4. Be attentive It's not important to understand each and every part of the speech but at least you should get the essence of the speech. Just remember that the seminars are designed to provide you with a usable content on a variety of relevant subjects and keep you updated with the latest advancements in your field. So, try to gain as much knowledge as possible.         5. Asking Questions It's the best way to get you ideas about the topic reviewed by an experienced person, you'll get to know if you're on the right track. Speakers also encourage questions and it's a way of learning on their part too. But whenever you ask a question, make sure you know exactly what you need to know clearly. Frame the question in your mind first, you certainly don't want to stumble while asking.
At this moment, I certainly don't want to demotivate you, just remember that silence is better than asking "silly questions".   So the next time you're going for a seminar, you already now what to do and how to do!                        Happy "Seminar-ing" !  

Tania Alam

Tania Alam

 

BUE formation during machining

What is a BUE? BUEs are built-up edges formed due to the accumulation of work-piece material against the rake face of the tool. How are BUE formed? During machining, the upper layer of the work-piece metal experiences a large shear force as it comes in contact with the tool-tip and an amount of the metal gets welded to the tool-tip. This is due to work hardening of the metal layer. The metal adhered to the tool becomes so hard that it is difficult to remove.     Why are BUE formed? BUE formation is common under a few conditions which are : Low cutting speed  Work hardeneability of work piece material High feed rate Low rake angle Lack of cutting fluid Large depth of cut In which materials is it observed easily?   BUE formation is usually noticed in alloys such as Steel rather in pure metals.It is also observed in soft materials like soft pure Alumunium, hot rolled low carbon steel. What are the effects of BUE? There are a few basic effects caused by the BUE formation like : Change in tool geometry Change in rake steepness Reduction in contact area between the chip and the cutting tool. What are the advantages of BUE? BUE formation can have a few advantages on the cutting tool and ease of machining like : Slight increase in tool life Reduction in power demand. What are the disadvantages of BUE? The count of disadvantages is actually more than the advantages it has on the machining process. Poor surface finish  Problems in dimensional control of the process Leads to flank wear (damaging the flank face)       How can the BUE formation be prevented?  BUE formation is a common machining problem but there's a soluion to every problem.Here are a few prevention steps to reduce BUE formation Increasing cutting speed Use of cemented carbide tool in place of HSS tool Introduction of free machining materials ( loaded or resulphurized steel) Application of an appropriate lubricant at low cutting speed   P.S. - Suggestions are always welcomed.

Tania Alam

Tania Alam

 

Types of Kinematic pairs

When two links (or elements) in a machine are in contact with each other, they form a pair. When the relative motion between these two links is completely or partially constrained, then the links are said to form a kinematic pair.
In simple words, a kinematic pair or simply a pair is a joint of two links having relative motion between them. 
 
Kinematic pairs can be classified on the basis of:   1) Nature of contact between the pairing elements 
(a) Lower pair – surface or area contact between the members of the pair
There are 6 types of lower pairs
I. Revolute pair (R)
II. Prismatic pair (P)
III. Screw or helix pair (H)
IV. Cylindrical pair (C)
V. Spherical or globular pair (G)
VI. Planar pair or Ebony (E)                 (b) Higher pair – point or line contact between the members of the pair 
Examples of line contact – 
I. Tooth gears 
II. Ball and roller bearings 
III. Wheel rolling on a surface                  
Examples of point contact – 
I. Cam and follower pair                
(c) Wrapping pair – similar to higher pair, but there are multiple point contacts, one body wraps over the other, comprises of belts, chains, etc. Examples – A belt driven pulley                        
2) Nature of mechanical constraint 
(a) Form or Self closed pair – the contact between the two bodies is maintained by geometric form
Examples – Screw pair (lower pair)         (b) Forced closed pair – the contact between the two bodies is maintained by application of external force
Examples – Ball and roller bearings         
(c) Open pair – links are not help together mechanically, contact due to the force gravity or some spring action.
Examples – Cam and follower pair        
3) Nature of relative motion of one link to the other in the pair 
(a) Sliding pair – sliding motion
Examples – Rectangular rod in a rectangular hole in a prism     
(b) Turning pair – turning or revolving motion
Examples – Circular shaft revolving inside a bearing     
(c) Rolling pair – rolling motion
Examples – Ball and roller bearings      
(d) Screw or Helical pair – both turning and sliding motion
Examples – Lead screw and nut of a lathe     
(e) Spherical pair – one link is in the form of a sphere and can turn inside a fixed link
Examples – Ball and socket joint P.S. ~ Suggestions are always welcomed.

Tania Alam

Tania Alam

 

Types of Hydraulic Turbines

Turbines are machines which convert fluid energy to mechanical energy. When the fluid used is water, they are called hydraulic turbines.  Hydraulic turbines may be classified on the basis of four characteristics :       On the basis of the type of energy at the turbine inlet Impulse turbine total head of the incoming fluid is converted in to a large velocity head at the exit of the supply nozzle ( entire available energy of the water is converted in to kinetic energy.) water entering the runner of a reaction turbine has only kinetic energy the rotation of runner or rotor (rotating part of the turbine) is due to impulse action Flow regulation is possible without loss Unit is installed above the tailrace Casing has no hydraulic function to perform, because the jet is unconfined and is at atmospheric pressure. Thus, casing serves only to prevent splashing of water. It is not essential that the wheel should run full and air has free access to the buckets. eg - Pelton wheel turbine ( efficient with a large head and lower flow rate.)     Reaction or Pressure turbine the penstock pipe feeds water to a row of fixed blades through casing that convert a part of the pressure energy into kinetic energy before water enters the runner water entering the runner of a reaction turbine has both pressure energy and kinetic energy the rotation of runner or rotor (rotating part of the turbine) is partly due to impulse action and partly due to change in pressure over the runner blades Water leaving the turbine is still left with some energy (pressure energy and kinetic energy)  It is not possible to regulate the flow without loss Unit is entirely submerged in water below the tailrace Casing is absolutely necessary, because the pressure at inlet to the turbine is much higher than the pressure at outlet. Unit has to be sealed from atmospheric pressure. Water completely fills the vane passage.  eg - Francis and Kaplan turbines ( efficient with medium to low heads and high flow rates )           On the basis of the direction of flow through the runner Tangential flow turbine   Direction of flow is along the tangent of the runner  eg - Pelton wheel turbine.     Radial flow turbine   Direction of flow is in radial direction radially inwards or centripetal type, eg- old Francis turbine radially outwards or centrifugal type, eg -Fourneyron turbine           Axial flow turbine   Direction of flow is parallel to that of the axis of rotation of the runner the shaft of the turbine is vertical, lower end of the shaft is made larger which is known as hub (acts as runner)   eg - Propeller turbine ( vanes are fixed to the hub and they are not adjustable )        Kaplan turbine (vanes on hub are adjustable )     Mixed flow turbine   Water flows through the runner in the radial direction but leaves in a direction parallel to the axis of rotation of the runner  eg- Modern Francis turbine.               On the basis of the head at the turbine inlet High head turbine net head varies from 150m to 2000m or even more small quantity of water required eg -: Pelton wheel turbine.   Medium head turbine net head varies from 30m to 150m moderate quantity of water required eg -: Francis turbine. Low head turbine net head less than 30m large quantity of water required eg -: Kaplan turbine.   On the basis of the  specific speed of the turbine Before getting into this type, one should know what the specific speed of a turbine is. It defined as, the speed of a geometrically similar turbine that would develop unit power when working under a unit head (1m head).
  Low specific speed turbine specific speed is less than 50. (varying from 10 to 35 for single jet and up to 50 for double jet )  eg -: Pelton wheel turbine.
  Medium specific speed turbine specific speed varies from 50 to 250 eg -: Francis turbine
  High specific speed turbine specific speed more than 250 eg -: Kaplan turbine       References : 1. Course contents on NPTEL website 2. A textbook of Fluid Mechanics and HydraulicMachines - R.K. Bansal 3. Fluid Mechanics: Including Hydraulic Machines - A.K. Jain 7 hours, 59 minutes ago

Tania Alam

Tania Alam

 

Advanced Polynomial Curve Fitting

Mechanics Corner
    A Journal of Applied Mechanics & Mathematics by DrD, #33
    © Machinery Dynamics Research, 2016
Advanced Polynomial Curve Fitting
    The use of polynomials to fit engineering data is a common engineering practice. In school, we learn that "A data set consisting of n data points ((x_{i},y_{i}), i=1,2,3,…n) can be exactly fitted with a polynomial of degree n-1. Thus three data points can be fitted exactly with a quadratic expression, four data points can be fitted exactly with a cubic expression, and so on. If this approach is pursued much further, something ugly appears: while a polynomial of degree n-1 will pass exactly through n data points, for large values of n, it will oscillate wildly in between the data points. Since one of the most common reason for using a polynomial fit in the first place is for interpolation -- to be able to estimate a function value at locations between the known data points -- this wild oscillation is devastating. It is at this point that least squares fitting is usually introduced to give an approximate fit using a much lower order polynomial. A different approach is employed here. AdvancedPolynomialCurveFitting.pdf

DrD

DrD

 

Braced Cantilever

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 32
    © Machinery Dynamics Research, LLC, 2015
Braced Cantilever Introduction     Anyone who has actually gotten into machine design is familiar with this difficulty. Consider the situation where a project is well advanced, many plans have been made, and it is all based on the assumption of the adequacy of one particular part. When you finally get to the detailed analysis of that part, the calculations show that it is not adequate. What can you do?
    To make the problem much more concrete, consider the cantilever beam shown in Figure 1. It supports a weight W at the free end, and when someone finally makes the calculation, the tip deflection, δ, is unacceptably large. The whole system design has been developed on the assumed adequacy of that cantilever, and there is no room to put in a beam with a larger section to give more stiffness. What can be done?     Any of countless machine design texts, mechanics of materials texts, etc., give the formula for the end deflection, δ=(WL³)/(3EI)     where
    E= Young's modulus for the beam material
    I= area moment of inertia for the beam cross section
    L= length of the beam
    W= tip load value
    While we can argue that someone should have checked this earlier, finger-pointing does not fix the problem.   BracedCantilever.pdf

DrD

DrD

 

What is the name of this mechanism.

good morning Someone could tell me what the name of this mechanism or how can I find a way to design it. It is a shaft that moves in a straight line vertically and along the way makes a 180 ° worst shaft never leaves his line of action . these links you can see the operation of the mechanism     Thank you Imagenes del giro.docx

Daniel Barco

Daniel Barco

 

ODE Solution --- Fail!!

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 31
      Machinery Dynamics Research, 2016
ODE Solution --- Fail!!      Introduction     Digital computation has become a major tool for engineers, and it is a great benefit. It can also lead to many pitfalls for the unwary. This note is about the latter, a potential pitfall that many engineers risk on a daily basis, most of them with little awareness of the danger.
    Early in the development of digital computation, every problem required that the user write a program specific to the problem at hand. If speed was a very important issue, the programs were written in machine language, so that they would execute as fast as possible. If speed was a little less critical, programs were written in so-called "high level languages." This included FORTRAN, BASIC, ALGOL, C, C++, and a host of other such names. But even with a high level language, there was the problem of generating a program for the solution of the specific problem at hand.
    As things have continued to evolve, it was soon evident that a lot of the work in writing each program was the same from one problem to the next. The major mathematical operations, such things as numerical integration, matrix operations and the solution of systems of linear equations, plotting, and many other steps were re-usable from one problem to the next. It was natural that this would eventually lead to the development of general purpose programs, able to solve broad classes of problems. This group includes programs like Mathematica, Maple, MatLab, SciLab, Maxima, TKSolver, and numerous others. Most of those just mentioned have built-in capability to solve ordinary differential equations, in some cases by analytical means, and in practically all cases, by numerical means. This has taken the sting out of working with differential equations
from many engineering problems, and we must all be grateful for that.
    At the same time, we must also be somewhat skeptical about any general purpose solver when applied to a particular problem. How do we know that the solution generated is correct? How do we even know if it is reasonable? Most of the time, when engineers resort to numerical solutions, it is because there is no readily available analytical solution. Thus, when faced with a problem that cannot be solved in closed form, how can we know when to trust the numerical solution? This is a very serious question, one that all must consider. It you blindly trust a numerical solution, the old excuse, "The computer said it was OK" will not get you very far. The computer cannot be fined, fired, or (in extreme cases) possibly sent to prison, but all of these things can happen to an engineer!
    So, what can the engineer do when the differential equation has no known solution? Well, there are several options.
    (1) He can resort to any physical principles that apply to the situation. For example, if the system is such that energy should be conserved, then he can add code to calculate the total system energy at every instant. Just verifying that energy is conserved does not "prove" that the solution is correct, but if energy is not conserved when it should be, you can be sure there is an error in the solution.
    (2) He can try various approximations that may apply to see if they are in reasonable agreement with the computed solution.
    (3) He can verify the solution code by applying it to a similar problem for which there is a known solution. It is this last approach that I want to talk about in this post. ODE_Soln_Fail.pdf

DrD

DrD

 

Where is this?

Does anyone recognize where this video is shot? Is it a group of students at a school (what school?), or is it an industrial site (what company)? I am anxious for someone to locate this for me, please. DrD   Saurabh Jain, our host, has identified this location for me, and that is much appreciated. When I watched the video, I was aghast at all those nearly bare feet in a machine shop! I can appreciate that in Indian culture, the simple sandals are socially quite acceptable, but from a safety perspective, this is an absolute horror. Think of all the opportunities for something to drop on a foot, a tool, a machine part, sparks, etc.   Some years ago (quite a few years ago), I worked in a steel mill. We were required to wear hard hats and steel toed shoes at all times in the mill. And these were not just any old steel toed shoes. These shoes came up ankle high, and had massive steel toes and an additional steel plate, called a metatarsal plate, that came up over the top of the foot almost to the ankle. Each shoe weighed 4 lb, and it was very tiring simply to walk around wearing them. But, .... and this is the key part .... they added much to our safety. Even today, in my advanced old age, I have a pair of steel toed boots (but not metatarsal plates) for when I go into an industrial environment.   What is shown in this video is actually a cautionary tale, a warning of just about everything not to do from a safety perspective. Take heed! Be warned, or you could easily loose all your toes on one foot of the other.   DrD  

DrD

DrD

 

Did I Go to School to Make Copies?

I did not write the linked article. I should have since you will not learn this in school. When we finish 4 or more years of an ME education we are all wound up. We have been working at a pace which would kill us if tried it indefinitely. What shocked me when I entered industry was the trivia that engineers must be involved with. Perhaps like a soldier, you train to fight, but you don't do it 8-12/hr per day for 30 years. I don't know if the following article is accurate for small companies but it is for large corporations. I recall being bored and asked my supervisor for more work. He looked at me for a second or two then asked if I could make him a copy of some document. I said to him if this is what I get when I ask for more work I will eventually stop asking. My suggestion to young engineers is to keep in mind what one of my ME professors told us. “The best thing you can do is to get a job that keeps you as busy as I did.” I don't know if that is possible but I would keep that in mind. The article suggests too much complacency in my opinion. I think you need to know what is coming but don’t settle for making copies.

JAG Engineering LLC

JAG Engineering LLC

 

A Question for Readers

Many of you have asked me various questions, so now it is my turn. Let me lay a bit of background first, and then the questions.   I have had some conversations recently with JAG (one of the other writers here at ME Forums) regarding the choice of software for 3D modeling and analysis. JAG has made some excellent suggestions, specifically a cloud based program called Onshape. Unfortunately, for reasons that are unclear, my computer cannot run Onshape; I have worked with their help people for several hours, all to no avail. JAG recommends this in part because there is a "free version for the hobbyist" and a relatively inexpensive "full version for the professional." That is pretty attractive, but since I can't run it, I'm stuck.   I gather that virtually all engineering colleges these days are teaching some sort of 3D modeling and analysis software, but that raises a few questions in my mind. 1. If your college teaches brandX 3D software, what will you do when you go to work for a small company that cannot afford anything more than 2D drafting (simple CAD), with no analysis capability at all? How will you do your job then? You probably have your own pocket calculator, but will you have your own copy of ANSYS or Pro-E? 2. What software does your school teach (every students should have an answer to this question, so I expect lots of replies on this one!)? 3. If you have used software extensively for analysis of engineering problems (beam deflections, stress analysis, fluid flow, heat transfer, etc), are you confident  that you will be able to work all of those problems if there is no such software available to you on the job?   I might add, as sort of a postscript, most of you know that I am older than dirt (I just had another birthday, so the situation is even worse!), so I tend to look at things from an elderly perspective. One of my great fears as a working engineer was "What will happen when I'm ask to do something that I don't know how to do?" It happened more than once, and it usually resulted in a flurry of intense research to come up to speed on whatever topic was involved. I could usually do that because I have a pretty good library, and I knew how to use a university library as well. But in terms of software, I was always concerned that I had no FEA program, so how could I do problems that others were doing by FEA? I have come up with some interesting work-arounds, including writing my own FEA for some problems, but I never wanted to be dependent on software that I could not afford to own. So, back to my questions about: How are you going to buy your own copy of ANSYS? DrD

DrD

DrD

 

Rule and equation

Hi guys, can someone here help me to understand this better, explain in a teoretical way to understand Chvorinov's Rule and Bernoulli`s equation? Not just in a simple way, but deeper, can someone here do that, or knows how?   Thanks in advance!!!!

Ajarn Basin

Ajarn Basin

 

Nobody Told Me This Was a Math Class

Since a lot of young people visit this forum I thought it could be of value repeat what I learned 40 years ago. I did learn the following from one of my professors not in the classroom but during a meeting with her as my adviser. I did not fully appreciate what she suggested though I did follow her advice and it was the correct thing for me. I was in a city community college (CC). The four year city colleges were somewhat prestigious. The CC prepared students to transfer within the city university system and planned the curriculum to match the methods at the four year city colleges. I had the option to take mechanics (statics and dynamics) at the CC or wait until I went to a 4 year college. At that time I thought a class was class was a class. My advisor suggested that I take statics and dynamics at the CC if I were to go to the 4 year city college. That would better prepare me for the more theoretical approach I will find at the city college. If I planned to attend a particular private college, which the adviser had attended and taught, that I was better to take statics and dynamics at the private school. Here the subject matter was taught on a more applied and practical bases. I now appreciate how subject matter can be presented in different ways. This is important because not all people can absorb material the same way. If you are still in the planning mode for college or an advanced degree do some research about how the material is presented. A coworker several years ago commented about his master’s degree from a famous college in the San Francisco Bay Area. He said "regardless of the tile of the class, the professors turned it into a math class. Only one class was of any practical value to me."
 

Economical Robotic Vacuum cleaner

Robotics brings together several very different engineering areas and skills. There are various types of robot such as humanoid robot, mobile robots, remotely operated vehicles, modern autonomous robots etc. This survey paper advocates the operation of a robotic car (remotely operated vehicle) that is controlled by a mobile phone (communicate on a large scale over a large distance even from different cities). The person makes a call to the mobile phone placed in the car. In the case of a call, if any one of the button is pressed, a tone equivalent to the button pressed is heard at the other end of the call. This tone is known as DTMF (Dual Tone Multiple Frequency). The car recognizes this DTMF tone with the help of the phone stacked in the car. The received tone is processed by the Arduino microcontroller. The microcontroller is programmed to acquire a decision for any given input and outputs its decision to motor drivers in order to drive the motors in the forward direction or backward direction or left or right direction. The mobile phone that makes a call to cell phone stacked in the car act as a remote. 27_Shahul Gasnikhal__Economical Robotic Vacuum cleaner.pdf  

Shahul Sgk

Shahul Sgk

 

The Dumbest Guy in the Room.

Over the years I have witnessed a particular mistake repeated. It is usually with an old product that has a problem, or the old product requiring a change or a feature added. The mistake manifests itself with everyone believing they carry the true operation and understanding in their heads. Aside from Scotty aboard the USS Enterprise, most should assume there is something they may not know. When a new product is being developed the team usually follows some development process with defined tools. Oversight is likely in place with design reviews and gatekeepers of some kind. But humans grow complacent and subconsciously assume these systems must be as they believe it to be. After all we have been making it or using it for years. If you get involved with Value Stream Mapping you will come to realize everyone has their own reality of how things work. This could almost be a money making parlor tick. Do a demonstration of some process with 15-20 steps to an audience of 20 people. If two in the audience come up with the same detailed step by step process after watching the demonstration, I would be surprised. Usually 2 or 3 people are asked and I have never witnessed two agreeing or any of them being correct on the first pass. The tasking of writing it down will indentify to others what was missed. With repeated passes a complete process can be documented. Having been a manager of experts in a variety of specialties I have often been the dumbest guy in the room. I know what I don’t know and I am less likely to develop a mental understanding good enough to convince myself I understand. One example in particular comes to mind. I sat in a meeting to develop a system consisting of electronic devices. This was an add-on or a fix – not new product development where checks and balances are in place. I can’t recall the specifics but the experts were discussing this with great confidence. I was lost and asked that the oral conversation to be turned into a block diagram on the white board. Just as with Value Stream Mapping the first attempt at the block diagram received corrections from people who a few minutes ago were in oral agreement. I believe it took seven iterations of the block diagram before all the experts agreed. This is not an attempt to discredit experts. Without them the job would not get done. This illustrates that experts, except Scotty of course, can easily get over confident. When a team is involved it is seldom the case that everyone knows everything. Add the element of time for aged products/systems and it is almost a certainty. If you are part of a meeting where everyone is in oral agreement it would be prudent to ask for a flow chart or block diagram. The dumbest guy in the room may save the day.
 

DIY 3D Printer Kits From StuffMaker

3D printing technology is attracting every science and technology enthusiast whether it is a mechanical, civil, architecture, electrical, manufacturing or medical application. Everybody is interested in creating models, prototype using 3D printing technology. It’s not a technology but a 3D printing evolution. The pace at which this industry is growing and the novelty that 3D printing has introduced, it is predicted that additive manufacturing will affect almost all the fields of daily life including trade and commerce in near future.     Checkout these Affordable & High Performance 3d Kits From Stuffmaker

Arpit.v

Arpit.v

 

INTERVIEW QUESTIONS AND ANSWERS – MECHANICAL ENGINEERING DESIGN, SAFETY AND MAINTENANCE

Mechanical Engineering Interview Questions and answers for freshers on design, safety and maintenance. 1) What is an accident ?
An accident is a unexpected and unforeseen event which may or may not injury to a person or a machine tool. 2) What are the standard sizes of drawing board as per Indian Standards? As per Indian Standards :1250×900,900×650,650×500,500×350,350×250 sizes are available. 3) What are the functions of a scale ? (a) To measure distance accurately.
(b) For making drawing to scale either in full size, reduced size or enlarged size. 4) What is a sketching ? This is freehand expression of the graphic language. 5) What do you mean by First Aid ? First Aid is immediate and temporary care given to a person who affected accidental injury or a sudden illness before the arrival of doctor. 6) What is a Drawing ? It is a graphical representation of a real thing to define and specify the shape and size of a particular object by means of lines. 7) What is Engineering Drawing ? A drawing which is worked out an engineer for the engineering purpose is known as Engineering Drawing. 8)  What are the methods of extinguishing fire ? 1) Starvation. Separating or removing the burning material from the neighbour hood of the fire.
2) Blanketing. Preventing the air flow to the fire.
3) Cooling. Lowering the heat created by burning materials. 9)  What are the precautions to be taken to avoid fire ? 1) The buckets along with sand should be placed inside the workshop.
2) Switches and other electrical parts must be made of fireproof material.
3) Carbon dioxide gas should be place at required points in special containers.
4) Fire extinguishers of suitable type should be placed at accessible places.\ 10) What safety precautions should be observed while working in the workshop ? 1) Keep shop floor clean, free from oil and other slippery materials.
2) Wear proper dress and avoid loose clothing and loose hair.
3) Wear shoes and avoid chapels.
4) Avoid playing, loose talk and funning inside the shop floor.
5) Keep good housekeeping and put all unnecessary items and rejected items in scrap box.
6) Learn everything about the machine before starting and clear all the doubts.
7) Keep a safe distance from rotating and sliding parts.
8) Never store inflammable materials inside or around the shop.
9) Never play with electricity, fire, parts with sharp edge etc.
10) Keep fire buckets and extinguishers ready for use.

saurabhjain

saurabhjain

 

Becoming An Expert -- Part 3

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD
    © Machinery Dynamics Research, 2016
Becoming An Expert -- Part 3      Introduction     In the previous article on Becoming An Expert--Part 2, I mentioned that there were two big issues for the engineering analysis section at my Houston position, the first being the matter of seismic survivability and the second being torsional vibration. The first item was dealt with in Part 2, and in this article we will take up the second item of concern.
    When I joined the engine distributor in Houston in the mid-1970s, the company was about 65 years old, and the torsional vibration problem was not new. This was a problem that they had been dealing with, in one way or another, for many years. There were lots of old torsional vibration analysis reports available to study. I was not at all familiar with torsional vibration of machine trains; I had not studied anything quite like that in school and it had not come up in my previous industrial experience. So I eagerly began reading the old reports, and that is when the problem became acute for me: They did not seem to make any sense. I could not, with any integrity, continue to write reports like that when I thought they were complete nonsense, but I did not know how to analyze the problem correctly. I was in a jam!
    There were three major difficulties:
    1. The entire crank assembly rotates endlessly, so the stiffness matrix for the system is singular. This results in a zero eigenvalue, something that did not take too long to figure out.
    2. It is obvious that the system does more than just go round-and-around; it goes up and down as well. I was baffled for a long time about how to deal with the kinematics and their impact on the dynamics.
    3. It is apparent that there is a torque acting on the crank, but it is not directly applied to the crank by the combustion process. There is the slider-crank mechanism between the two, and I was at a loss as to how to transfer the cylinder pressure into a crank torque. This is again directly related to the kinematic problem mentioned just above. BecomingAnExpert--Part3.pdf

DrD

DrD

 

A Comment Remembered

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD
    © Machinery Dynamics Research, 2016
A Comment Remembered     
    Recently, in connection with one of the posts on Becoming An Expert, one of the ME Forum readers made a comment to me, something about seeing everything in terms of differential equations. That comment brought to mind a comment made to me many years ago that I want to pass along to you today.
    Most of my college education was at the University of Texas at Austin. It was there that I received BS, MS, and PhD degrees in engineering, and I was there studying for most of a decade. After I finished my PhD, I was asked to stay on the faculty for a year as an Assistant Professor, so that was my first post-graduate teaching position as well.
    One of the well known faculty members at UT-Austin was Dr. E.A. Ripperger, a man with a national and international reputation for his work in plastic stress wave propagation. In addition to his teaching responsibilities, Dr. Ripperger directed a laboratory at the Balcones Research Center, a research arm of the University. He had many graduate students working under his direction, and he was riding high in terms of his reputation. He was a rather august figure, somewhat austere and above everyone else.
    While I was still a struggling and confused undergraduate, one of Ripperger's graduate students had taught my Mechanics of Materials course, and I had done well in that class. This fellow liked me, and when a job opening came up out at the lab, he let me know about it and helped me to land it. Thus I was working a few hours a week as a lab assistant for this particular graduate student who was himself working under Dr. Ripperger. Before long, I signed up to take a class in Intermediate Dynamics, and Dr. Ripperger was the assigned teacher. Truth to tell, he was only mediocre teacher, nothing to get excited about.
    The class was fairly difficult, and I was having trouble keeping up with it all. In particular, the solution of the many differential equations just overwhelmed me. Since I was working out at the lab, and Dr. Ripperger was out there from time to time, I thought it might be a good idea to go in to to see him at the lab to discuss the class. I found him at his desk one afternoon, and screwed up my courage to go into talk with him.
    I told him that I was finding the class difficult, even though I thought I had a good understanding of dynamics. I told him that my difficulty was particularly with the differential equations, not with dynamics. He listened quietly while I spoke, and then he fixed me with a withering gaze when he spoke, calling me first by name and then saying, "Did you think there was anything else besides the differential equations?"
    He said no more, and I slunk away to lick my wounds! I don't think I ever spoke to him again.
    
    DrD is a retired Professor of Mechanical Engineering in the USA. He can be reached for comments, questions, or requests via the ME Forum message system. Be sure to check back soon at www.http://mechanical-engineering.in/forum/blog/206-mechanics-corner/ for more articles.

DrD

DrD

 

Becoming An Expert -- Part 2

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD
    © Machinery Dynamics Research, 2016
Becoming An Expert -- Part 2      Introduction     In the previous article on How To Become An Expert, I covered a lot of points in generalities with some short anecdotes from my own experience. In this article and the next, I will describe in considerably more detail a critical period in my own formation, an time of considerable professional embarrassment which was a real spur to learning.
    In the summer of 1974, I took a position as the head of the engineering analysis section with a large diesel engine distributor in Houston, TX. This company purchased diesel engines, mostly from General Motors (GM) and packaged them on a skid with some driven machine such as a generator, a pump, air compressor, or other driven machine, along with the required controls. For me, it was a fascinating place to be as I had always been intrigued by diesel engines. I soon found out how little I actually knew about the whole matter.
    The analysis section consisted of three other engineers (two men from India and a lady from Turkey) and myself. The men were there before I came, and I hired the lady. They were all good workers, but they were best at following directions. They did not ask "Why?" very often. If this is the way it had been done previously and nobody objected, they would repeat that same pattern over and over without wondering why we do it that way. More about that aspect later.
    This was a time of great activity in terms of nuclear power plant construction in the USA, and the company was building a lot of very large engine-generator sets to serve as standby power in nuclear power plants. In a nuke plant, pumps continuously supply cooling water to the core to take away the heat and as a means to move heat to the steam generators. If those pumps fail for any reason, the core can over heat and meltdown, a major catastrophe. The great fear was that the pumps would lose power from their regular supply, in which case the standby generators would need to start up and provide power to the pumps. The proposed cause of loss of power was an earthquake, and that meant that the standby generator set must survive the earthquake and be able to start and run. BecomingAnExpert--Part2.pdf

DrD

DrD

 

How To Become An Expert

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD
    © Machinery Dynamics Research, 2016
How To Become An Expert      Introduction     This is going to be another of those personal experience/opinion pieces, so if these bore you, be warned! This may be the time to click on something else.
    A reader recently wrote to me asking how to become an expert. I have to tell you, I don't spend much time thinking about being an expert, but I suppose on some reflection, the shoe probably fits. (Most of the time, I see myself as simply a tired old man, still enjoying the things I have done almost all my working life.) In the discussion below, I will describe a few events and observations that seem to relate to the question at hand. Find Your Place     Nobody can hope to be an expert on everything, there is simply too much to know. You have to find the area that excites you, the area that really makes you want to dig in more. If you do not really enjoy it, you will never be an expert!
    I was very fortunate in this regard. When I was in High School, I was rather good in Mathematics, and my school advisers all told me, "You should become an engineer." Sadly, I really had no idea what that meant, and neither did they. The town where I grew up had rather little industry, and no one in my family knew an engineer of any sort. I did a little bit of research on engineering (this was thousands of years before the Internet), and it sounded interesting in a very vague way; there seemed to be little specific information available to me. But I went off to college, intending to study mechanical engineering, whatever that was.
    In my first semester of college, I took a Physics course in classical mechanics, and I really enjoyed it. This was exactly what I wanted to do, I just did not know the right name for it. I thought Newton's Second Law was the greatest thing ever discovered, and when implemented with Calculus, it was really fun. I was astounded at the power of it all, the questions that could be answered. If I could just get a job doing mechanics problems, I was sure I would be happy. HowToBecomeAnExpert.pdf

DrD

DrD

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