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Showing most liked content since 07/18/2017 in Posts

  1. 2 points
    Amazing work, Murat!!! it often happens like this because the hand calculation consider 1-D effect (only the moment area not 1-D) while the FEA consider 3-D effect. if you make the FEA becomes line/ 1-D (Ansys and SW could do this), the answer would be much closer to hand calc.
  2. 2 points
    the result some different between hand solve and computer solve. why the results are ddifferent. I couldn't understand. you can learn more information about singularity method from this link:
  3. 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
  4. 1 point

    Non destructive testing

    How is it related to mechanical engineering? Isn't it more related to materials science?
  5. 1 point
    Iam very interested to study mechanical engineering in abroad. Can anyone please guide me
  6. 1 point
  7. 1 point
    Check out this website http://www.autozine.org/technical_school/chassis/tech_chassis.htm It lists different types of chassis including ladder type chassis
  8. 1 point

    Triple Rocker

    In terms of four-bar linkages, most of them obey Grashof's Law, but evidently a few do not. Those that do not are called "non-Grashofian" or "triple rockers." I have a difficult time visualizing a triple rocker. The name implies that no link can turn a full revolution. Can any of you point me to an example, a problem discussion, or any other information regarding a Triple Rocker linkage? DrD
  9. 1 point
    John Nduli

    Software used for Analysis

    I've only used the solidworks FEA tool to do analysis on my bodies. Anyone have any other tools they've tried? Also a comparison of tools used would be nice.
  10. 1 point
    I've been wracking my brain with this. I would like to calculate the displacement caused by the force on beam. I've simulated this on Solidworks and then started to calculate it by hand. The problem in this is the overhanging parts that do not give the right answer when calculating by hands while compared on simulation answer. Have I typed wrong value at some point or have I used wrong values? Material is S235J2G3 and beam is HE 300B. Recommendations and suggestions are welcome.
  11. 1 point
    assume theta is the angle at right pin support. http://www.mathalino.com/reviewer/strength-materials-mechanics-materials/solution-problem-696-697-beam-deflection-method-supe M = w (0.9) (0.45) = 121500 theta = (w L^3 / 24 EI) - (ML / 3 EI) - (ML / 3 EI) theta = [(300000 x 1.2^3) / ( 24 EI )] - 2 [(121500 x 1.2) / ( 3 EI )] theta = (21600 / EI) - (97200 / EI) = - 75600 / EI Your (right) end displacement should be delta = 0.9 theta = - 0.9 x 75600 / EI = - 68040 / EI E is based on material properties (for steel, E = 200 GPa = 200 x 10^9 Pa) I is the second moment area of the beam (for HE300B, I = 2.517 x 10^-4 m4) delta = - 1.3516 x 10^-3 m = - 1.3156 mm
  12. 1 point
    View this quiz Production engineering quiz 1 lets check your knowledge on production engineering Submitter saurabhjain Time 10 minutes Type Graded Mode Submitted 05/03/2017 Category Mechanical Engineering Quiz  
  13. 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).
  14. 1 point
    Are you sure that this question has any answer other than "enough"? Do you think that there is a general answer that covers all cases? I really doubt that, but I certainly cannot answer your question. I'm anxious for you to post an answer. DrD PS: The answer to the "why?" part is simply to do whatever needs to be done.
  15. 1 point

    Technical Report Writing

    Technical reports, like most other written documents, begin with an Introduction, continue with the Main Discussion, and end with a Conclusion. In the Introduction, you describe the situation that motivates the document. Why is this being written? In the Main Discussion, you make your argument, analysis, data interpretation, or whatever you have done. In the Conclusion, you state your finaly results, the conclusions drawn from the material in the main body that (we hope) address the questions opened in the Introduction. That's about it. DrD
  16. 1 point
    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)
  17. 1 point

    Variable Frequency Drives

    Introduction What Is a Variable Frequency Drive? Adding a variable frequency drive (VFD) to a motor-driven system can offer potential energy savings in a system in which the loads vary with time. VFDs belong to a group of equipment called adjustable speed drives or variable speed drives. (Variable speed drives can be electrical or mechanical, whereas VFDs are electrical.) The operating speed of a motor connected to a VFD is varied by changing the frequency of the motor supply voltage. This allows continuous process speed control. Motor-driven systems are often designed to handle peak loads that have a safety factor. This often leads to energy inefficiency in systems that operate for extended periods at reduced load. The ability to adjust motor speed enables closer matching of motor output to load and often results in energy savings.
  18. 1 point
    As I can see - you have added the quiz , but all questions has been added in the description.. The steps are as below 1 create a new quiz and write description 2 add question and add all answers to the question 3 select the write answer of the above question 4 Add another question You need to edit the quiz....to get it approved Regards Saurabh
  19. 1 point
    Abdulsamad Valiya

    hydraulic pumps

    Simply we can define Hydro static pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement (flow through the pump per rotation of the pump) cannot be adjusted, or variable displacement pumps, which have a more complicated construction that allows the displacement to be adjusted.
  20. 1 point

    hydraulic pumps

    Hydraulic pumps are the part of the hydraulic system .it is used in various purpose in mechanical engineering and big machine.in term of mechanical engineering we used in high voltage machine.using this we increase power of machine and can lot of work in easy manner. so they are backbone of mechanical work.
  21. 1 point

    Variable Frequency Drives

    It is true that VFDs offer some real advantages for motor applications. It is also true that they can just about destroy your motor if not applied with great care. The switching that is used to synthesize the variable frequency AC waveform creates all manner of high frequency content on the output of the VFD. The cable connecting the VFD to the motor needs to be very carefully matched to the motor such that resonances are avoided. If resonance occurs, extremely high voltage can develop due to ringing of the output circuit, with the resulting destruction of the insulation in the cable and more importantly destruction of the motor insulation. This can require a very expensive motor replacement soon after the application of the VFD due to the insulation failure. So the long and short of it it, properly applied VFDs can be really very useful. Improperly engineers VFDs can be very costly and destructive. Oh, and they are always expensive, bulky, and heavy, if that matters.
  22. 1 point

    Variable Frequency Drives

    Applications Variable speed drives are used for two main reasons: • to improve the efficiency of motor-driven equipment by matching speed to changing load requirements; or • to allow accurate and continuous process control over a wide range of speeds. Motor-driven centrifugal pumps, fans and blowers offer the most dramatic energy-saving opportunities. Many of these operate for extended periods at reduced load with flow restricted or throttled. In these centrifugal machines, energy consumption is proportional to the cube of the flow rate. Even small reductions in speed and flow can result in significant energy savings. In these applications, significant energy and cost savings can be achieved by reducing the operating speed when the process flow requirements are lower. In some applications, such as conveyers, machine tools and other production-line equipment, the benefits of accurate speed control are the primary consideration. VFDs can increase productivity, improve product quality and process control, and reduce maintenance and downtime. Decreasing cost and increasing reliability of power semiconductor electronics are reasons that VFDs are increasingly selected over DC motors or other adjustable speed drives for process speed control applications. Motors and VFDs must be compatible. Consult the manufacturers of both the VFD and the motor to make sure that they will work together effectively. VFDs are frequently used with inverter-duty National Electrical Manufacturers Association (NEMA) design B squirrel cage induction motors. (Design B motors have both locked rotor torque and locked rotor current that are normal.) De-rating may be required for other types of motors. VFDs are not usually recommended for NEMA design D motors because of the potential for high harmonic current losses. (Design D motors are those that have high locked rotor torque and high slip.) Additional Benefits of VFDs In addition to energy savings and better process control, VFDs can provide other benefits: • A VFD may be used for control of process temperature, pressure or flow without the use of a separate controller. Suitable sensors and electronics are used to interface the driven equipment with the VFD. • Maintenance costs can be lower, since lower operating speeds result in longer life for bearings and motors. • Eliminating the throttling valves and dampers also does away with maintaining these devices and all associated controls. • A soft starter for the motor is no longer required. • Controlled ramp-up speed in a liquid system can eliminate water hammer problems. • The ability of a VFD to limit torque to a user-selected level can protect driven equipment that cannot tolerate excessive torque.
  23. 1 point

    Variable Frequency Drives

    I nduction motors, the workhorses of industry, rotate at a fixed speed that is determined by the frequency of the supply voltage. Alternating current applied to the stator windings produces a magnetic field that rotates at synchronous speed. This speed may be calculated by dividing line frequency by the number of magnetic pole pairs in the motor winding. A four-pole motor, for example, has two pole pairs, and therefore the magnetic field will rotate 60 Hz / 2 = 30 revolutions per second, or 1800 rpm. The rotor of an induction motor will attempt to follow this rotating magnetic field, and, under load, the rotor speed "slips" slightly behind the rotating field. This small slip speed generates an induced current, and the resulting magnetic field in the rotor produces torque. Since an induction motor rotates near synchronous speed, the most effective and energy-efficient way to change the motor speed is to change the frequency of the applied voltage. VFDs convert the fixed-frequency supply voltage to a continuously variable frequency, thereby allowing adjustable motor speed. A VFD converts 60 Hz power, for example, to a new frequency in two stages: the rectifier stage and the inverter stage. The conversion process incorporates three functions: • Rectifier stage: A full-wave, solid-state rectifier converts three-phase 60 Hz power from a standard 208, 460, 575 or higher utility supply to either fixed or adjustable DC voltage. The system may include transformers if higher supply voltages are used. • Inverter stage: Electronic switches - power transistors or thyristors - switch the rectified DC on and off, and produce a current or voltage waveform at the desired new frequency. The amount of distortion depends on the design of the inverter and filter. • Control system: An electronic circuit receives feedback information from the driven motor and adjusts the output voltage or frequency to the selected values. Usually the output voltage is regulated to produce a constant ratio of voltage to frequency (V/Hz). Controllers may incorporate many complex control functions. Converting DC to variable frequency AC is accomplished using an inverter. Most currently available inverters use pulse width modulation (PWM) because the output current waveform closely approximates a sine wave. Power semiconductors switch DC voltage at high speed, producing a series of short-duration pulses of constant amplitude. Output voltage is varied by changing the width and polarity of the switched pulses. Output frequency is adjusted by changing the switching cycle time. The resulting current in an inductive motor simulates a sine wave of the desired output frequency (see Figure below). The high-speed switching of a PWM inverter results in less waveform distortion and, therefore, lower harmonic losses. The availability of low-cost, high-speed switching power transistors has made PWM the dominant inverter type.