Fly Line Stretch and Viscoelasticity

[Merlin]

Gordy

What amount of load did you use for your experiment?
I shall see what I find with my large deflection file.

Merlin

[gordonjudd]

What amount of load did you use for your experiment?

Merlin,
There was no tip load. The bend was due to the inertial load produced by the rho_l*g distributed force of the line's linear mass density.

I will send you the resulting bending shape values so you can compare your flexural modulus value with mine.

Gordy

[gordonjudd]

"quite low" is not defined, but you don't loose all energy after one oscillation.

Torsten,
What was the initial PE value (in Joules) that corresponded to the 100% energy value in your plot of the PE and KE in your damped oscillation measurement?

Would the PE for a .5N load be around (.5/(9.82*.5) )^2 = .01 of the PE value you got for a 500 g mass?
Gordy

[Merlin]

Hi Torsten

Testing a dynamic model for the stretching of the line shows a wavy response having the same level on average, by comparison to the static analogy. It means that I do not see a dynamic coefficient associated to this phenomenon.

The potential of internal losses remains low at this stage, maybe there could be a non linear issue behind.

Merlin

[Merlin]

Hi Torsten

You can find below a comparison between static vs dynamic approach of the energy related to stretch for the scenario I used.

The static case corresponds to the direct application of energy computing just as if the line would instantaneously respond to tension (0.00011J). The model used is a classic (Pearson) which is similar to GB analogical model.

In the dynamic case I consider the line as a spring with skin drag as the only energy loss source. It is a car & brick type of model (without brick), the velocity and leg length history being directly taken from the other (Pearson) model. Things become unstable at the end of the flight, likely a problem of time increment versus spring frequency (which rockets to high values as leg length shortens to zero).

The elastic energy value is about twice the static estimate (0.00021 J), so a possible dynamic coefficient is 2. However, the amount of potential loss due to viscosity of line material is still extremely small by comparison to the energy lost by skin drag (0.7 J).

Merlin

[Merlin]

Here is an update with a damping function (damping ratio = 0.06):

Figures are confirmed, the losses are small in dynamic conditions.

Merlin

[VGB]

Figures are confirmed, the losses are small in dynamic conditions.

Did you use both temperature and frequency sweeps on the DMA?

Vince

[Merlin]

I'm looking forward seeing DMA measurements for soft saltwater flylines in high temperature conditions.
A moodel is ready for runs.

Merlin

[VGB]

What is a soft saltwater fly line Daniel and how high is high?

Vince

[Merlin]

Vince

Ask James, I think he knows the answer. My comment was a best guess of a possible worst situation.
Something interesting to read:
https://www.researchgate.net/publicatio ... _Materials

Merlin