How to estimate vibrations Measurements can be done Experimental modal analysis

# How to estimate vibrations measurements can be done

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How to estimate vibrations? Measurements can be done Experimental modal analysis Estimates only natural frequencies and damping Running vibration measurements Actual levels can be obtained All of these can be done only on existing products Mathematical modeling Lumped parameter models Single and multi degree-of-freedom Distributed parameter models Infinite degrees-of-freedom Can be solved only for simple structures 6 / 61
Building a vibration model Objective to improve ride comfort Models of varying complexity can be built How does one decide ? Mouli (IIT Madras) Lecture @ NITK Jan 2014 7 / 61
Simplest model Vehicle operating at low speeds Long wavelength road input ) Compared to wheel base In this case only vertical motion important Pitch can be neglected Mouli (IIT Madras) Lecture @ NITK Jan 2014 8 / 61
Bounce and Pitch model Vehicle operating at higher speeds Shorter wavelength road input ) Compared to wheel base Vertical and pitching to be included Mouli (IIT Madras) Lecture @ NITK Jan 2014 9 / 61
Separate Rider model Rider response to road input Sensitive to 4-9 Hz inputs Vertical and pitching to be included ) Both short and long wavelength road inputs Mouli (IIT Madras) Lecture @ NITK Jan 2014 10 / 61
Another example Model to study cutting tool dynamics Assume that tool and turret are quite rigid Force from tool transferred through turret/slide to bed The interface between the bed and turret is compliant? How about the bed? Mouli (IIT Madras) Lecture @ NITK Jan 2014 11 / 61
Vibration model Model to study cutting tool dynamics Workpiece flexibility taken into account by cantilever model Turret to bed interface compliance considered Machine bed compliance modeled as a fixed-fixed beam Mouli (IIT Madras) Lecture @ NITK Jan 2014 12 / 61

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• Fall '16
• 1981, January, 1990, IIT Madras

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