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  • saurabhjain

    Calling Mechanical Engineers to collaborate on Twitter

    By saurabhjain

    If you are a mechanical engineering professional and have a twitter account .. we invite you in our mechanical engineering  campaign to collaborate on twitter.. Retweet the following status on https://twitter.com/mechportal/status/646544243649961985 Look forward for your presence. Regards Mechanical Engineeirng forum
    • 5 comments
    • 1,478 views
  • DrD

    A Question for Readers

    By DrD

    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
    • 28 comments
    • 2,878 views
  • DrD

    #20 -- A Question of Stability (Revised)

    By DrD

    Mechanics Corner
        A Journal of Applied Mechanics and Mathematics by DrD, #20
        © Machinery Dynamics Research, 2015
    A Question of Stability Introduction     The word stability in its several forms is widely used in nontechnical communication. A person whose life it highly consistent from day to day is said to have a stable life. When the political situation in a particular area appears to be unlikely to change, it is said to be stable. A person who is well balanced and unlikely to be easily provoked to anger is said to be a stable person. When the medical condition of a sick or injured person ceases to get worse, the person is said to be stabilized. A company on the verge of bankruptcy is said to be an unstable company. But what does the word stability mean in a technical context? Each of the foregoing examples hints at the technical meaning without really being explicit about it.   A factor g = accel of gravity was missing in the potential energy expression. That is now corrected.
        
     
        Stability.pdf
    • 16 comments
    • 5,709 views
 

Boilers: Introduction and Classification

The boiler system comprises a feed-water system, steam system, and fuel system. The feed-water system supplies treated water to the boiler and regulate it automatically to meet the steam demand. Various valves and controls are provided to access for maintenance and monitoring. The steam system heats and vaporizes the feed water and controls steam produced in the boiler. Steam is directed through a piping system to the application. Throughout the system, steam pressure is regulated using valves and monitored with steam pressure gauges. The fuel system consists of all equipment used to supply of fuel to generate the necessary heat. The equipment required in the fuel system depends on the type of fuel used in the system. Boilers Classification: There are a large number of boiler designs, but boilers can be classified according to the following criteria: 1. According to Relative Passage of water and hot gases: Water Tube Boiler: A boiler in which the water flows through some small tubes which are surrounded by hot combustion gases, e.g., Babcock and Wilcox, Stirling, Benson boilers, etc. Fire-tube Boiler: The hot combustion gases pass through the boiler tubes, which are surrounded by water, e.g., Lancashire, Cochran, locomotive boilers, etc. 2. According to Water Circulation Arrangement: Natural Circulation: Water circulates in the boiler due to density difference of hot and water, e.g., Babcock and Wilcox boilers, Lancashire boilers, Cochran, locomotive boilers, etc. Forced Circulation: A water pump forces the water along its path, therefore, the steam generation rate increases, Eg: Benson, La Mont, Velox boilers, etc. 3. According to the Use: Stationary Boiler: These boilers are used for power plants or processes steam in plants. Portable Boiler: These are small units of mobile and are used for temporary uses at the sites. Locomotive: These are specially designed boilers. They produce steam to drive railway engines. Marine Boiler: These are used on ships. 4. According to Position of the Boilers: Horizontal, inclined or vertical boilers 5. According to the Position of Furnace Internally fired: The furnace is located inside the shell, e.g., Cochran, Lancashire boilers, etc. Externally fired: The furnace is located outside the boiler shell, e.g., Babcock and Wilcox, Stirling boilers, etc. 6. According to Pressure of steam generated Low-pressure boiler: a boiler which produces steam at a pressure of 15-20 bar is called a low-pressure boiler. This steam is used for process heating. Medium-pressure boiler: It has a working pressure of steam from 20 bars to 80 bars and is used for power generation or combined use of power generation and process heating. High-pressure boiler: It produces steam at a pressure of more than 80 bars. Sub-critical boiler: If a boiler produces steam at a pressure which is less than the critical pressure, it is called as a subcritical boiler. Supercritical boiler: These boilers provide steam at a pressure greater than the critical pressure. These boilers do not have an evaporator and the water directly flashes into steam, and thus they are called once through boilers. 7. According to charge in the furnace. Pulverized fuel, Supercharged fuel and Fluidized bed combustion boilers.

Rishabh Pandey

Rishabh Pandey

 

Strength calculation

hello All,  i am working as a design engineer and i am working on sheet metal structures. i am looking at the calculations to decide on the thickness of sheet metal to carry a particular load. i calculated the sectional modulus of the design based on the cross sectional area of sheet metal and it is well within the sectional modulus of material. I would like to know werher the approach is right or are there other calculations which i should do before deciding the thickness?. request to suggest on the above please find the image below for reference

abhilashNJ

abhilashNJ

 

Pre- Crash Sensors for Pre-Crash Safety

Many research and development have been conducted  to meet society needs for safer vehicles. Particularly, occupant protection system such as air bags, developed and introduced in order to reduce occupant injuries in crashes, are currently installed in most vehicles making significant contribution to safety.   Meanwhile, many studies have been made into the development of active safety technologies that help to avoid crash accidents. Unfortunately the current situation is that the active safety technologies are not sufficient spread. Adaptive cruise control has been commercialized since 1995, but its primary use has not been convincing.Some audible warning system  are also being offered, but have not yet reached widespread use.   Toyota Motors corporation has explored the possibility of producing an active safety system employing Intelligent Transport System (ITS) technologies,through participation in the Advanced Safety Vehicle (ASV) projects started in 1991 and led by ministry of land , infrastructure and transport.   Critical basis ITS technologies for application to ASV includes a surround monitoring sensor and an obstacle determination algorithm which combines information from the surround monitoring sensor with other information to identify obstacles with which the vehicle is likely to actually crash.   The sensors and crash determination algorithm for an active safety system should be capable of reliably determining that  a crash will not occur in non-crash situation. Advanced technologies are required to make these predictions and judgments correctly while also taking into account the driver's operation and behavior and this has hampered widespread of active safety systems.   Pre-crash safety system has been developed which operates only when it is judged that a crash cannot be avoided by most drivers under normal driving conditions. Determining unavoidable crashes is restricted to a short time period immediately before the crash so as to improve the reliability of the judgement. In addition the pre-crash system is made with a mechanism and system that will not place the driver and the running vehicle in an unsafe condition even if the system is operated unnecessarily. As a result the world's first commercial system has been achieved.              

saurabh kumar tiwari

saurabh kumar tiwari

 

V2V (Vehicle to Vehicle) Communication

The objective of ambient intelligence is to create an intelligent daily space, which is immediately usable and integrated into our homes, our offices, our roads, our cars, and everywhere. This new concept must be invisible; it must blend in with our normal environment and must be present when we need it.   One of the application of this concept consists of providing our cars and roads with capabilities to make road more secure (information about the traffic, accidents, dangers, possible detours, weather, etc.) and to make our time on road more enjoyable (Internet access, network games, helping two peoples follow each other on the road, chat, etc). These applications are typical example of what we call an Intelligent Transport System (ITS) which goal is to improve security, efficiency and enjoyment in road transport through the use of new technologies for information and communication.   Traditional traffic management systems are based on centralized infrastructures where cameras and sensors implemented along the road collect information on density and traffic state and transmit this data to a central unit to process it and make appropriate decisions. This type of system is very costly in terms of deployment is characterized by a long reaction time for processing and information transfer in a context where information transmission delays is vital and is extremely important in this type of system. In addition, these devices on roads requires periodic and expensive maintenance. Consequently, for large scale deployment of this type of system, important investment is required in communication and system infrastructure. However, with the rapid development of wireless communication technologies, location and sensors, a new decentralized architecture based on vehicle to vehicle communications has created a very real interest in these last few years for car manufacturers, R&D community and telecom operators. This type of architecture relies on a distributed and autonomous system and is made up of the vehicles themselves without the support of fixed infrastructure for data routing.     The main objectives of an intelligent transportation system includes:   the improvement of trip security the improvement of global efficiency of the transportation system by reducing travel time and congestion the integration of transportation in a durable development policy particularly by reducing gas emissions for light vehicles and heavy trucks and  by optimizing maintenance of the infrastructure the improvement of user comfort by providing him with a selection of information, decision support, guidance and internet access services.                  

saurabh kumar tiwari

saurabh kumar tiwari

 

Automated Manual Transmission

MT (manual transmission) uses simple spur gears providing excellent transmission efficiency and thus typically get 10% or better fuel mileage than current ATs (automated transmissions). The object of the ATM (automated manual transmission ) is to automate starting and gear shifting while retaining this excellent fuel efficiency. A round of fierce competition was triggered among European manufacturers to see who would be the first to develop what is generally known as a conventional AMT that attempts to automate the shifting of MT. The problem with this design is that the drive torque is momentarily interrupted during shifting. This results in a very different shift feeling from an AT, and thus never saw the wide spread acceptance as a replacement for the conventional AT in mainstream vehicles. This was more recently followed by a twin clutch AMT that is receiving great deal of attention. Supporting smooth and responsive shifting much like an AT, the twin-clutch AMT has been installed by European vehicle manufacturer on some high engine capacity sport cars beginning last fall. Hitachi group has now developed an original torque-assist AMT that is fundamentally different from these other two approaches.   TORQUE-ASSIST AMT
In order to achieve widespread acceptance as a replacement for conventional transmissions, the next generation must provide the good fuel economy of an MT, the effortless shifting of an AT, and must also be compact and affordable. Unfortunately, the conventional AMT fails to achieve the seamless shifting of an AT and the twin clutch AMT is difficult to implement compactly and cost effectively.   Hitachi Group has proposed a third way that does meet all the above requirements a torque assist AMT and is now in the process of developing this system. A key advantage of this approach is that it can be implemented with relatively little modification to existing AMTs by simple adding a friction clutch called as assist clutch to the transmission. Action of the assist clutch effectively solves the torque interruption  problem of the conventional AMT while providing the smooth gear shifting of an AT.  A compact and economical torque assist AMT could thus be implemented fairly easily for application on mainstream FF (front-engine front-drive) compact vehicles with engine displacement with 2 liters.                    

saurabh kumar tiwari

saurabh kumar tiwari

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