Recent content by JolileChat

I'm reading it.

I don't think so. You will need to find out the equation of the elastic line of your beam. You will need to consider the inclination of the rod. A good startup is: http://www.efunda.com/formulae/solid_mechanics/beams/theory.cfm

My sugestion: a counter rotating eccentric mass exciter. It is very easy to build and operate, and it will do the job as you want.

Control surfaces of airplanes are good candidates.

http://www.uni-siegen.de/fb11/nm/aktuelles/downloads/trebuchet_adams.pdf This might be useful for you, in particular the model described in figure 5(c).

When we consider the mass of the spring, the equivalent mass is equal to the particle mass plus one third of the spring mass. Let us perform two tests, with two mass configurations. For the mass configuration #1, you will attach a mass M_1 to the spring. For the mass configuration #2, the...

The quality factor Q is a measure of the sharpness of a peak of resonance and also the damping. For small values of the damping factor \zeta, that is, \zeta \leq 0.1 , Q = \frac{1}{2 \zeta} For mechanical systems, it is useful to get a measure of the equivalent viscous damping. In your...

6.75 Hz doesn't seem to be related with the frequencies you have found after the modal analysis (10 Hz and 60 Hz). By the way, 60 Hz is a suspect frequency, be sure it is not coming from the AC electric power. How much is the initial displacement? And the length of the beam? Can you repeat...

Lisa, please let me know what is exactly the bump test. You "bump" the beam only one time or you keep bumping the beam at a fixed frequency? Now let's talk about the initial condition response. When you impose a displacement to the tip of your beam, it will assume a shape that is very close to...

Hi, Studiot. The extra term is the forcing term, and it does not change the natural frequency of the beam. Natural frequency and damping are properties of the system, therefore it does not matter if we are talking about the forced response or the response to initial conditions.

Hi Lisa. How did you adjust the sampling rate and the length of the time domain acquisition?

No, it is a static case where the displacement is large enough to invalidade the linear theory, which permits us to find the traditional deflection and equivalent stiffness expressions.

Hello. Supose that we have a cantilever beam. For a small force P applied at the free side of the beam, we can find an expression for the maximum deflection: \delta=\frac{P l^3}{3 E I} If we want to use this beam as a string, we can find its equivalent stiffnes noting that P=K_{eq} \delta, so...

I guess he tried to express the excitation as: F=cos(w*t-pi/2)

Ok, let me try to figure out what you are trying to find. It's a FRF of a structure, where both input and output are measured by accelerometers. What do you mean by a realization? The system is being excited continuously, and a realization is a period of time where you perform the signal...