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  1. K

    B Could Archimedes' problem have been solved a little differently?

    When I was reading this page to understand Archimedes' 'story' I got a question: According to the example shown, Archimedes found the density of crown by finding the apparent weight. What if he had just measured the volume of water...
  2. K

    How to solve spring mass damper system manually?

    The other day when I solved a spring mass damper system in Matlab, I was curious how in olden days would have people solved the equation. We all know the 2nd order differential equation of the system: However if I know the time, damping coefficient, stiffness and mass, will I be able to find...
  3. K

    Job Skills What next for manual gearbox design engineers?

    Simple questions are sometimes difficult to ask. I am a mechanical design engineer of automotive gearboxes with a UG qualification and 12 years of experience. My core expertise is into gears and special interest in NVH. In the recent years I see the automotive OEMs cutting down research cost of...
  4. K

    Will steam generated inside an oven not break it?

    Disclaimer first: Though the question is around cooking, IMO it certainly is to with physics / engineering. Yet, if the admins find this post inappropriate, pl. delete it. I am planning to make some rice cakes which is prepared by steaming a mix of rice powder and water. Because I don't have...
  5. K

    Automotive Modal analysis - Input and boundary conditions given?

    My understanding in modal analysis is very limited. All I know is it helps to find a specific mode of vibration and the natural frequency corresponding to it. While I was discussing about this with my NVH team colleague, he told me that there is no force input or excitation input given to a...
  6. K

    I Palmgren-Miner equation derivation

    Summary: This equation is used in ISO standard ISO 6336-6. I want to understand how it is derived. This equation helps to consolidate damage caused by multiple torque, cycle bins. A bin means a torque applied for a given number of cycle. As an outcome of the equation, a single equivalent...
  7. K

    MATLAB Spring mass impact system in Matlab - How to correct it?

    I am new to Simulink and I wanted to start practicing using a spring mass damper system. My first tutorial was this: Later, I wanted to model a spring system where a mass moving at a known velocity hits the spring. The governing equation and a similar modeling method given in the previous...
  8. K

    How to find the deceleration of a mass colliding on a spring?

    Problem Statement: A known mass at a know velocity collides on a spring of known stiffness. What is the equation that governs the deceleration of the mass, so that the force on the spring could be found? Relevant Equations: 1/2 m*V^2 = 1/2*k*x^2 + 1/2*m*(Vo)^2 Kinetic energy of mass before...
  9. K

    Automotive Mathematical modeling of driveline impact test of an automobile

    I am in a process of making a mathematical model of an automobile driveline validation procedure called "Driveline impact". In this test, after the engine in cranked, first gear is selected. While clutch pedal is still pressed, engine rpm is raised unto its max. torque deliverable speed. In this...
  10. K

    What is the governing equation of a spring with sinusoidal excitation?

    Hi, Most of the spring vibration lectures assume spring to be fixed on one end and mass on the other end [Example]. In my case, spring has a sinusoidal excitation on one end and mass on other end. Pl. refer the image below. How to get the governing equation? With that I also want to find the...
  11. K

    Automotive Why don't motorcycle clutches need torsional damper springs?

    I was reading the difference in construction between a car clutch (dry, single plate) and a motorcycle clutch (wet, multiplate). I understand wet multiplate clutches do not have torsional springs in them. How is the Engine vibration damped then? Can we not use this same arrangement in a car?
  12. K

    Automotive Dual mass flywheel clutch - How does it make a difference?

    I was going through these two documents: My primary interest was to understand why and how Dual Mass Flywheel (DMF)...
  13. K

    Relative velocity and force relationship

    This is something related to my job. There are two components A & B both travelling the same direction but at a different velocity. I can find out the exact velocity of both the components when they just hit each other, thus relative velocity is known. Is there a way I find out the force...
  14. K

    I Mathematical series in physics - Why and when do we need them?

    Hi, Before I post my question, let me admit that my foundation on mathematics is poor. I am trying to work on it, specifically on the application part. When I came through the following image, I was stuck to understand why I will need one like Taylor's series in a simple case like "F+ΔF = F...
  15. K

    Max. acceleration of a pendulum changes with its length and mass?

    Hi, If I find out the tangential force on the bob at position 1, it turns out to be m*g*sinθ. From this if I find out acceleration by dividing this equation by m, I get only g*sinθ. Does it mean the max acceleration of pendulum has got nothing to do with its length or mass but theta?
  16. K

    Pitch and amplitude of sound wave Vs its volume

    Hi. If I know the pitch and amplitude of a sound wave, will I be able to calculate its volume. I can understand volume of devices vary betwerb brands and other categories. For the sake of discussion, lets assume volume to be a consistent unit or if db is the right unit, lets take that.
  17. K

    I Need a help in solving an equation (probably differentiation

    I am trying to find out the interference condition between tool and a part. The below attached snapshot is the equation between interference and machine feed. At dy/dx = 0, I will have max. interference, which I intend to find. Except x and y every alphanumeric character in the following...
  18. K

    Is EN353 cold forgeable as much as SCM420

    Hi, We are doing a gear box for a two wheeler (for the first time). Most of our benchmarks are of Suzuki and Honda bikes. All their gears are made of SCM420. Surprising part is these gear teeth are formed by cold forging. No machining at all! Now, I was comparing the chemical composition of...
  19. K

    I Angle of repose - Trying to understand the formula

    I recently posted a question on similar line and got few good explanations as well. Still, I am unable to understand clearly. Hence I am going more specific this time. In the given picture taken from internet, friction force acting between an inclined plane and an object is defined as Fr = W x...
  20. K

    Derivation of angle of repose - Friction

    Hi, Recently I came across this image in deriving an equation for angle of repose of an object in an inclined plane: "W" is the weight of the component which acts vertically down. "Rn" is the normal reaction by the inclined plane "W cos alpha" is the component of the weight of the object...
  21. K

    Need a simple accelerometer for a demo kit

    Hi, I am trying to build a demo kit to show the velocity and acceleration of a slider that reciprocates. I am from mechanical engineering background and hence need help in finding good acceleratio measurement device. My requirements are this: 1. Should be something like a ready to fit. 2. Needs...
  22. K

    Automotive Why is an FFT done after a noise signal is captured?

    Presently there is a gear whine noise issue in a vehicle transmission. Our NVH team captured the noise signal using a microphone and then did an FFT of the signal and gave us a frequency plot. What exactly can I take out of it? Can I assume every harmonic belongs to a noise generated by a gear...
  23. K

    Protuberance in gears - Why doesn't shaving operation finish

    Just because shaving doesn't finish the root of a gear, a protuberance is given during hobbing. This, most of the time, leads to an undercut. To avoid this, can shaving operation clear root of the gear as well? Thus, I can avoid protuberance. Another question - Can grinding clear root? Thanks.
  24. K

    Notch factors in FEA method

    Hi, I want to understand how stress concentration factor or notch factor is considered in FEA method. Lets assume a case of stepped shaft which has got the left end of the shaft fixed with rigid wall and the other end being pulled by an axial load. In the case of conventional calculation...
  25. K

    Hysteresis in helical coils springs

    Hi, Do helical springs have hysteresis. Say I do an exercise of plotting deformation Vs load curve of a helical spring, one way will be starting from load zero and increasing till the spring achieves solid length. The other way will be loading the spring till solid length and measuring...
  26. K

    Clutch stiffness and hysteresis - Role in gearbox NVH

    Hi, There is a rattling noise in one of the automobile passenger car gearboxes that we designed. After few experiments and observations, it was found that the noise is because of incorrect clutch stiffness and hysteresis behavior. I have got some fundamental questions about both: 1. Clutch...
  27. K

    Fourier transform - Other possible wave forms

    Hi, I am totally a non-math guy. I had to attend a training (on automobile noise signals) that had a session discussed about Fourier Transform (FT). Let me pl. write down what I understand: "The noise signal observed at any point in the transmission line can be formed using a sum of many sine...
  28. K

    Effects of harmonics in NVH

    I had a chance to go through a lecture on general NVH issues in Automobile engineering. The faculty used to say "first harmonic", "second harmonic" etc. during the course. I found in wikipedia to know that harmonics are multiples of frequency of vibration. What has harmonics got to do in NVH...
  29. K

    Why is a vibration that reaches natural frequency so detrimental?

    Why are we not supposed to operate a machine on its natural frequency condition? I read max. energy transfer happens at this condition. What exactly does it mean? When we swing a pendulum it just oscillates on its natural frequency. Nothing goes wrong there. So what makes it different for a...
  30. K

    Overlap ratio or axial contact ratio in helical gears

    Hi, I am trying to understand the Overlap Ratio (OR) / axial contact ratio of a helical gear pair. Unlike transverse contact ratio, I am unable to understand OR so easily. What does it mean if the OR is exactly 1? What will happen practically when it goes less than one? Thanks.