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  1. 5 points
    1. pressure represent intensity of external forces acting at a point. but stress represent intensity of internal resisting forces develop at a point.2. pressure is always acts normal to the surface. but but stress may also act either normal or parallel to the surface.3. magnitude of pressure at a point in all direction remain same. but magnitude of stress at a point in all the direction are unequal.4. pressure can be measure by using measuring device.like pressure gauge. but stress can't be measure directly by using any device.
  2. 2 points


    One of the most interesting examples of automation that I have worked on is a paper cup making machine. Everyone has seen paper cups. They come in many different forms, from simply conical forms to more complex truncated cones with a flat bottom. The come in small, medium, and very large sizes. How do you make such things cheaply, cleanly, and fast? Starting with a long coiled sheet of paper, the pattern must be cut out, rolled up, a bottom added, and the whole thing sealed. This is quite a sequence of operations, and the machines that do this consist of a number of stations, each station performing one operation and then passing the work piece on to the next station. The machines that I worked on were all cam controlled, which is to say they were a form of hard automation. Cam driven systems are extremely repeatable, but they are fairly difficult modify for a different product. They are also capable of operating at incredible speeds. I saw machines making 1200 paper cups per minute. The literally come flying out the end to be caught and packaged for distribution. The machines are quite expensive, but the number of paper cups they can make is absolutely huge! DrD
  3. 2 points
    I can offer a few suggestions. 1. I would take your birth date off the resume. It really is not relevant, unless you want birthday cards. 2. I see several different type faces (not including headings). I would use the same for all (except headings), and surely do not use a smaller font for your experience. 3. In item #3 of your university projects, you did not calculate parameters. Parameters are things like the acceleration of gravity, the area of the parachute, the initial drop height, etc. You calculated results, not parameters. I'd re-word this section. 4. There is a misspelled word in one of your university projects. For goodness sake, use spell check!! 5. In item #4, I really doubt that you calculated anything at EVERY point on the beam. Much more likely you did this at many points. 6. Course titles like "Intro to Electrical Engineering" and "Analysis of Engineering Systems" do not tell the reader very much. Add some detail if you want this to count, something like "circuit theory" or "systems modeling" or "systems simulation" or whatever is appropriate. Go Mountaineers!! DrD
  4. 2 points
    I read somewhere that the Romans known for their great engineering feats used brute force to accomplish said feats. Human power was used when horses were available and domesticated. Even then there were worries about unemployment and labor unrest if the human labor was replaced (aka automation) with "high tech" methods. http://www.jagengrg.com/blog/-dump-trucks-vs-donkeys
  5. 2 points
    One of the problems with many of these software packages mentioned above is their expense. If you work for company "A" where you get very proficient in software X, what happens when you take a position with company "B" that uses software Y? Presumably the software packages X and Y do similar things, but in their own formats, and they are not compatible. Further, if you want to work on something on the side, for your own interest, will you be able to use the company's software for your personal work? Years ago (before the end of the Ice Age), engineers all used slide rules, but every engineer provided his own slide rule at work. There were many different brands (K&E, Dietzen, Post, etc.) but they all worked about the same (some small variations), and they gave the same results. You could use your slide rule at work and on your home projects; it was yours. For this reason, I encourage people to use public domain software, rather than proprietary software. Several folks above have mentioned MatLab, but no one has mentioned SciLab. SciLab is public, available for free, and works just about like MatLab. Why do so few use public software? This baffles me. There are other similar situations regarding other types of software. DrD
  6. 2 points
    Well, not really. Stress is a second order tensor while vectors are first order tensors. Confused enough? How about if we say that stress requires a square matrix for full representation, while a vector can be fully represented by a single column (or row) matrix. To JAG above ... Well, you're no fun at all. I want to play as well. DrD
  7. 2 points
    Sirazz92 has given a fairly good answer. Pressure usually refers to a distributed external load applied to a body. Stress is the distributed internal loading associated with displacement under load. DrD
  8. 2 points
    Pressure is the force acting upon the surface of an body.(Action) Stress is the resisting force developed in a body when an external force acts on a body.(Reaction)
  9. 1 point
    What is difference between stress and pressure?
  10. 1 point
    List of Seminar topics for Mechanical Engineers Hello 2 all engineers and Engineering students Every one look for good seminar topics lets make collection of good topics.. and latest intresting topics... Use Reply to add the topics u know.. keep updating it
  11. 1 point
    Pressure and stress are both force unit per area. Pressure applies to fluid (liquid or gas). It is a force per unit area applied perpendicular to a surface. Stress is more often used in solids, a force per unit area that can act parallel to a surface and/or perpendicular to it (vector).
  12. 1 point
    That was my best guess. Sometimes offering a solution to an ambiguous question, gets the questioner to realize how ambiguous the question is, and they can better form the question.
  13. 1 point
    Depend on you bolt/washer material, you could calculate it using VDI 2230 Part 1 and Part 2. I don't have it on hand right now. Other than that you could use this http://www.tribology-abc.com/calculators/e3_6a.htm Input the correct size and material, you minimum torque should be in column Total tightening torque MA
  14. 1 point
  15. 1 point
    Henry Kurniadi

    internal combustion engines

    Ignition delay, the time from when the fuel injection starts to the onset of combustion.
  16. 1 point

    Simple Mechanical Analysis

    Thanks Henry!
  17. 1 point
    Hello everyone, Thank you so much for joining this club. But we still need more members os that we can have better discussions and increase the numbers of ideas and views shared here. These are the things you can do for the club: 1. Share this club to all you social media profiles, pages, group, etc. 2. Add the link to this club on all your websites, blogs, etc. After you're done, take a screenshot and post it here to inspire others to do the same. Off course we all want to be recognized and appreciated for what we do I've recently added the link to this club on my Autodesk profile. Check it out here: https://knowledge.autodesk.com/profile/L0IN4VI34RYS5 You'll also find some screencasts there, hope you enjoy them too!
  18. 1 point
    Ditto the last sentence. A membership card is expensive with little return on its own. Being active in a local chapter is very valuable.
  19. 1 point
    I thought I had written a post on professional societies some time ago in the Mechanics Corner, but I cannot find it now. Therefore, I'll address a few of these ideas now. I think the simple answer to your question is "yes," at least up to a point. If you see someone list a half dozen or more societies, you can be confident that they are not active in all of them, and most likely active in none. Therefore, I recommend that you join at least one and no more than three technical societies. The society I recommend most strongly for MEs is SAE (formerly the Society of Automotive Engineers, but now simply SAE). SAE is one of the most active societies in terms of holding conferences, publishing research and also standards, and aiding students. The definitely accept student members, and you should try to get a Student Chapter at your school if it does not already exist. The SAE mini-Baja race competitions, Formula 1 race competitions, etc. do a whole lot to build student interest and enthusiasm. I have been an SAE Faculty Adviser long ago, and I was really impressed with the way they supported student work. By the way, SAE is more than just automotive now. The describe themselves as the mobility society, so anything that moves is part of their interest area. Another well known (but not nearly as active) society is the American Society of Mechanical Engineers (ASME) and in the UK, the Institution of Mechanical Engineers (IMechE). There are dozens of special interest societies, such as these: American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) Society of Naval Architects and Marine Engineers (SNAME) American Institute of Aeronautics and Astronautics (AIAA) Japan Society of Mechanical Engineers (JSME) Institute of Electrical and Electronic Engineers (IEEE) There are literally hundreds of other societies, and as far as I know, they all take student members. I strongly recommend joining one or a few societies, and then take an active part. Attend meetings, serve on committees, make presentations, etc. You get out of the society what you put into it. DrD
  20. 1 point

    The New Way or the Old Way?

    Long, long ago, in a land far away, I was an undergraduate engineering student. I knew some of my fellow students who studied a course called "Kinematics," and that puzzled me. Kinematics had been one of the parts of my first course in dynamics, so I wondered what else there was to the matter; I really did not know much at all. I borrowed a textbook for the Kinematics course, and it looked interesting, particularly the aspect that seemed to deal with real machines. I liked that. But then I asked about the course and I learned that it was a lot like the drafting course that we were all required to take. Specifically, the solutions were all obtained by scale drawings. With that bit of information, my interest in Kinematics cooled completely. Now way back then, I was a pretty good draftsman, and I certainly was not put off by that in itself. I enjoyed drafting, and I had begun doing it for fun back in junior high school. But for kinematics, to major difficulties were immediately evident: (1) No matter how sharp you make your pencil point, drawn lines have width (without width, we could not see them). This very substantially limits the accuracy of a drawn solution. Jumping ahead some years, when I worked for Hamilton Watch Company, our draftsmen would make greatly oversized drawings to graphically check clearances, and other mechanism features. The common scale was 40:1, meaning that the drawing was 40 times the actual size. This was before CAD had really taken hold, so these huge drawings would be spread out on drafting tables and everything was carefully drawn to scale. (2) A single drawing can only show one mechanism position. Since most mechanisms operate through a considerable range of motion, the graphical analysis in one position was of little value for understanding velocities and accelerations in a second position. This could lead to the need to make many drawings, one for each position of interest. I was rapidly losing interst at the prospect of repeating essentially the same drawing, in slightly shifted positions, time and again! The long and short of it is that, I did not seriously study kinematics of machines until some 15 years after I finished my PhD. It happened when i was called upon to teach Theory of Machines at Texas A&M University. As I began reviewing textbooks in preparation for this course, I found that much had changed in the intervening time. There were still some books focused on the old graphical techniques. They claimed that this gave the student a feel for the motion, an intuitive understanding. It also gave him at most 3 digit accuracy. On the other hand, there were books out there that presented new methods, particularly based on the idea of a closed vector loop. While it is useful to have a sketch to identify the variables in this method, there are no graphical constructions involved in obtaining the results. It is all mathematical, and can be carried out to whatever level of precision the user wants. Usually 8 decimal digits is common, but 14 to 20 digits are readily available. No more worrying about how sharp your pencil point is!! I immediately adopted the mathematics based vector loop method for my own work and for teaching, and I have done so ever since that. The vector loop method has enabled me to answer many vexing questions that I would have never resolved by the graphical method. I went so far as to write a Theory of Machines textbook based on vector loop kinematics, and cannot imagine doing these problems any other way. An then, in the last few years, I have come to ME Forum, where I encounter folks who are still solving kinematics problems graphically. I know that they have access to computers; that is how I encounter them, at an Internet website. Thus I have to ask, Why are you still using graphical solutions? I simply do not understand. I hope that there will be some comments that will shed light on this question. DrD
  21. 1 point
    Dr D, I can't answer your question directly but I have an example of something I did recently. I was reviewing literature about rigging for lifting objects. An example had a two legged cable of different lengths. The unequal lengths were to compensate for a center of gravity not centered on the object being lifted. The example provided two trigonometric equations for determining the length of the short and long cables. Almost out of instinct I recreated it graphically vs. working through the trig to convince myself that the equations provided were correct. I think the approach one takes has to do with comfort level. You did not come upon the vector loop until post PhD. You would have had a lot more math experience than most at that point. If I were to venture into vector loop today, I would likely continue with a graphical approach as a sanity check. After many applications I may begin to develop a comfort level as I have with algebra. I often can tell an answer is wrong before I know why it is wrong. Math can be like a black box. When we add 2 + 2 we may not consciously think 2 objects + 2 objects as when teaching a child but I think something similar is going on in our mind. When I look at a complicated equation I have to take it on faith it is correct or work from first principles to verify it is correct. If I can't do that with confidence, or not at all, I will not use the equation unless it is published in multiple independent sources. With the trigonometric example above I could have worked through the trig, but the graphical method was faster and easier to trust. For a cable length the accuracy is not as critical as a cam dimension in an engine, so my example is not the best, but your question got me thinking. You and I have discussed differential equations. Having had little opportunity to use what was presented in class years ago; my confidence using them is low. I would have to use another approach or two to arrive at the answer. Fortunately none of the work I do requires using differential equations. And for the trigonometric equations in the example I mentioned, there was a glaring error I did not see at first. The author repeated the same equation for both lengths. The graphical vs. the equation results did not agree. I instinctively measured the other leg and got the correct answer. I then realized the problem. I have yet to work through the trig to get correct equation for the other leg. Joe
  22. 1 point
    I have been using autocad from two years. now i wish to learn a advanced software of designing. please suggest me which software to learn. as i am a mechanical engineering student for me which designing software will be important .
  23. 1 point
    Shalini Chakraborty


    Industrial Automation is the new trend in the new millennium. There has been numerous technological advancement and researchers in the field of Industrial Automation. One can definitely realize that the world is easily transcending towards the philosophy of production in huge volumes with increased precision and quality with minimized human intervention. The PLCs have completely surged the market and with the advent of cheaper digital technologies, the implementation of them in different industries has been easier. The Internet of Things is one of the most prevalent topics discussed in the current global world. The ongoing developments have intensified with the aim of low cost, higher performance, and high valued industrial automation systems. Innovative industrial automation has taken one step further with systems using PLM, ERP, asset management, operation management and so on which has further enhanced the flexibility and efficiency of the manufacturing systems. The simultaneous development of Lean Automation Architecture, Smart Sensors, Cooperative Robots and what on!!!! The developments have been rampantly going on and on. Hence, companies and individuals who are thriving for change will sustain themselves easily by adapting the new global rules and services and we can together step up to discuss pros, cons, new innovations and amazing future possibilities yet to come.
  24. 1 point
    How many manholes should be there on boiler? Why?
  25. 1 point


    You speak of automation as though it was a brand new idea, new in the 21st century. Are you unaware of the automation that took place in the 20th century? It is certainly true that new developments continue, but the whole idea is not nearly as new as you make it sound. Automation has been around for a very long time. You might want to Google the term "Luddite" for a bit of history. DrD
  26. 1 point
    Ahmed Diaa

    Heat Exchangers

    It depends whether it is a design process or ratting process ......for Design process you want to find the area so you must know the following :;:; Hot fluid mass flow rate . Heat capacity and temperatures (in and out ).cold fluid mass flowrate ..heat capacity and temperatures too .and you need to know the over all heat transfer coefficient. For ratting ;:;:: You must know the area the mass flow rate ..the heat capacity and the overall heat transfer coefficient . ...trying to know the output temperatures and that is called ratting . Remember that you must define the type of the heat exchanger first Ahmed diaa
  27. 1 point
    There are a list of Huge Softwares used by us... U might be knowing only few. names and so this thread has been created..... If u know one name and me another , and we exchange we will be knowing abt two softwares..... Please Use Post Reply to Add Software name Also write what it deals with .... What r its capabilities...Specialization ...and more u know abt it... Hardware requirements!!!! Whose Developer : Company name Email to friend to email this topic to all Mechanical Engineers You know.....so that we can have great list here.... Looking forward for great list....
  28. 1 point


    I'd be inclined to start by trying to select appropriate tooth numbers for the gear pair. Do you want exactly 5:1, or simply something approximating that ratio? This is significant because of the wear problems associated with gear pairs that have a common factor in both tooth numbers. Moving past the tooth number matter, I'd look at the speed, lubrication, and power to be transmitted. Select a face width that will keep the tooth stresses low enough to give infinite life (unless this is a short term application), and consider the heat generated. DrD
  29. 1 point
    Yup ,,, Pressure can causes stress but stress can't ....
  30. 1 point
    Most of above answers are good and almost explains the difference. only one point to add: 1. pressure is a scalar while stress is a vector. Don't know much, but i will try to answer. First of all some definitions: 1. MoE: It is the ratio of stress to the strain developed. strain is dimensionless and hence the units of MoE are same as that of Stress i.e. N/m2 or Psi. 2.Strength: or i can say maximum strength or Ultimate strength. is the maximum force that a material( in our case steel) can withstand just before fracture. 3.Yield strength: it is the value of stress at which sample starts yielding. i.e. going plastic deformation. as seen from the above definitions all three are not same. e.g. for pure aluminum. the MoE is 10^7 psi, Ultimate strength : 110*10^6 psi and Yield strength: 95*10^6 psi for different steel there is same MoE but different strength as shown in the image.
  31. 1 point
    I would like to add a story here. There are a limited number of units in this world. Different properties share the same units and combination of units though the meanings are VERY different, as DrD and sirazz92 explained. Two values that are very related are stress and modulus of elasticity (MoE). Both have the units of pounds per square inch. I once witnessed a complete misunderstanding of the relationship. The engineer, a very proficient ProE user when it came to building models, ran an FEA routine. He was under the mistaken belief that as long as the stress was below the MoE the load was ok. Dr D is now holding his head. The MoE for steels are usually taken as 30,000,000 psi. This is good enough for classroom work. When you are doing real world work you will find values vary, but not by large percentages. Some steels are very strong but I am not aware of any that yield or fail at 30,000,000 psi. On a somewhat related topic a group of us were discussing a stress issue and a question came up that also showed a lack of understanding the basics. I too had to stop and think for a while. Though I was long past confusing MoE with the strength of a material, a basic understanding had grown stale. QUESTION: If all steels have about 30,000,000 psi for MoE, how can they have different strengths? I would like to see answers from students and recent graduates. Dr D knows the answers all too well so he is not allowed to answer.
  32. 1 point
    Name :G. Vu Engineering college: University of Civil Engineering Location (City/ Country): HN/Vietnam/Japan Engineering Batch: 2008 Engineering Company/ Dream company to work for: Oil drilling industry Area of Interest: Vibration/ Reliability for maintenance Project undertaken: Environment & maintenance dept. Any other info you want to share
  33. 0 points