# Discussion Forum

## Heaviside function simulate Acoustic emission signal

 Topics: 4.2a
RSS feed   |   Turn on email notifications   |   5 Replies   Last post: February 4, 2013 2:26pm UTC

Nuno Gueiral

January 30, 2013 4:02pm UTC

Heaviside function simulate Acoustic emission signal

Hello,

I need to apply a Heaviside function difference to simulate a Acoustic emission burst signal. Can help, how can I do this? What model should I use? I'm new working with COMSOL.

Thanks,

Nuno Gueiral

Ivar Kjelberg

January 30, 2013 6:10pm UTC in response to Nuno Gueiral

Re: Heaviside function simulate Acoustic emission signal

Hi

the Heavyside functions of 3.5 are now readily available as Definitions - Functions : such as step, or rectangle or ramp ... , all with smoothing

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Good luck
Ivar

Nuno Gueiral

January 31, 2013 5:45pm UTC in response to Ivar Kjelberg

Re: Heaviside function simulate Acoustic emission signal

Hello,

I'm using de COMSOL 4.2a version.

Best regards,
Gueiral

Ivar Kjelberg

February 1, 2013 5:52am UTC in response to Nuno Gueiral

Re: Heaviside function simulate Acoustic emission signal

Hi

in v4 look under Model - Definitions - Functions, and check the step, rect or ramp functions, these have Heavyside smoothing included

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Good luck
Ivar

Stevie89

February 1, 2013 10:07pm UTC in response to Ivar Kjelberg

Re: Heaviside function simulate Acoustic emission signal

Hi

The ramp function worls perfectly fine, but if your lazy like me and u use the Heaviside function often, its easier to use COMSOL's inbuilt Heaviside function

flc1hs(X,scale)

Nuno Gueiral

February 4, 2013 2:26pm UTC in response to Stevie89

Re: Heaviside function simulate Acoustic emission signal

Hello,

I need to insert in COMSOL a function or a expression like this:
f is a impact force
f = F_max [flch2(t,t_rise )-flch2(t-t_width ,t_fall )]
where
F=max( F )/ S_max ( N / m 2 )
and
S_max=pi*(2.5e-3/2)^2

F : maximum force (2-5N)

and I don't know how? Could you help me?

Best Regards

Nuno

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