1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Energy waves from impact in a solid

  1. Jul 17, 2012 #1
    So i'm supposing a scenario where you have energy transfer into a solid and waves propagating out from the impact point and i want to measure the energy at different distances from the "epicenter" with sensors.

    the relationships i've been pointed to are basically conservation of energy at the different distances and something along the lines of the double integral of the full circle of the wave and of the distance from the epicenter multiplied by things like wave strength and thickness, which can then be converted to an integral of wave speed over time.

    then ive also been pointed out that with a piezoelectric sensor, that can further be converted to a measure of voltage squared integrated over time multiplied by a series of things, but then the distance from the wave source is pulled out as a constant.

    my question involves this supposition then that the energy of a wave at a specific point and distance from the wave source will be proportional to the integral of the voltage squared over time, MULTIPLIED by the distance.

    Is this indeed a valid relationship? so would it be correct to say that there is a distance and voltage where a sensor further away from a source than another might regardless measure a larger energy? what kind of relationship is this? cuz apparently its not the linear one i thought it would be.
  2. jcsd
  3. Jul 17, 2012 #2
    First question is

    Is this solid as in (a) solid ground or (b) a vibrating solid object such as a musical triangle or cymbals?

    For (a) you need to look up seismic geophysical methods

    and for (b) you need to look up mechanical vibarations and resonant excitation
  4. Jul 17, 2012 #3
    i suppose it would be a mechanical vibration in a solid object like a block of wood or steel
  5. Jul 17, 2012 #4
    Go on?
  6. Jul 17, 2012 #5
    You really do need to describe your setup much more fully to get an answer.

    Sensors can be velocity sensitive or acceleration sensitive.

    Look here to learn about sensors

    http://www.wilcoxon.com/knowdesk/TN16_Sensor%20Selection%20Guide.pdf [Broken]

    The entire solid object can be vibrating as a whole like my triangle example or a guitar string.

    Or the waves can be like seismic waves in the earth which only move a small part of the body at a time a they travel through it.
    I think you mean this type but you need to confirm it.

    Once you have confirmed that you need to specify the position and orientation of the transducer as the waves can be transverse ( up and down ) or longitudinal (side to side - backwards and forwards). These waves have different characteristics when they travel through large solid objects.

    Or they may be composite surface waves which are different again.
    Last edited by a moderator: May 6, 2017
  7. Jul 17, 2012 #6
    the relationship i saw was for piezoelectric sensors with some capacitance that measure a voltage depending on the deformation of the sensor. if squeezed, a positive voltage, if squeezed harder ,a more positive voltage, if stretched, a negative voltage, etc

    i imagine this would an assortment of seismic waves traveling thru the body. lets simplify it and say its an infinitely long plane of iron with finite thickness in a perfectly inelastic collision with a body significantly less massive then the infinite plane and a line of sensors at regular intervals from the site of the collision.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook