Penile stress/strain relationship

OMG I must have too much free time in my hands. I have just done a little lab experiment on my penis. I decided to measure the elongation of my penis under a range of weights from 0.150kg upto 2.70kg.

This in effect allowed me to to plot a classic stress/strain graph. For those unfamiliar with engineering

stress = force/area
strain = increase in length/original length

The strain is caused by the stress.

I thought even if it only illustrates the bleeding obvious it would still be interesting to get some figures on how much weight produces how much strain.

I measured by drawing a horizontal line across my dick about an inch from the base and using that as the reference point for measuring to the tip. As I hang weight my hanger sucks on the glans and the skin on the shaft is not stretched so my base reference line remained pretty static.

Results
Here’s what I measured

Kg L(cm)
0.00 9.0
0.15 9.0
0.30 9.5
0.40 10.0
0.60 10.7
0.80 10.8
1.20 12.3
1.60 12.2
2.00 12.4
2.70 12.6

To calculate the strain for each weight it is (L-9)/9 so

Kg Strain
0.00 0.0
0.15 0.0
0.30 0.06
0.40 0.11
0.60 0.19
0.80 0.20
1.20 0.26
1.60 0.24
2.00 0.27
2.70 0.29

Here’s the weight/strain relationship in the form of a graph.

Cool. Can you tell from this whether you’re in elastic or plastic deformation?

You might want to consider that, as time went by, your unit was probably also elongating due to visco-elastic extension. To account for this effect, you might try repeating your experiment but reversing the order. If you did the lightest weight first and increased the weight linearly, try doing the heaviest weight first and decreasing it linearly.

I only experimented upto 2.7kg (6lb) since my vacuum hanger is not able to take bigger weights. If anyone is interested in experimenting at higher weights please remember this is non-destructive testing - stop short of sample failure!:(

Conclusions
Firstly it appears that weight of less than 250g (0.5lb) does nothing to strain the penis. Perhaps, since a flaccid penis probably only weighs 100g, that is why there is no growth from a lifetime of gravity pulling on our flaccid members. The little buggers aren’t heavy enough to be effected.

Secondly the strain increases rapidly between 250g and about 1200g. At 1200g the strain is about 90% of that produced by 3kg (and probably much higher weights as well)

Of course none of this answers the question “How much strain is needed to promote growth”.

I’d have to say elastic in the sense that the bastard thing always goes back to the same size!:)

Yes your second point is something I thought about in terms of creep. I will try hanging my heaviest weight and try to detect any “creep” over a period of time. My feeling is that as I got the weights on and off there wasn’t a great deal of change in the measurements over the few minutes I hung each weight.

I also thought of repeating the experiment with applied heat to see if I could detect any difference.

Interesting that the strain is less at 1.60 than it is at 1.20. Do you take into account skin stretch with the line you are using?

If I remember correctly, the region where the line ‘flattens out’ marks the inelastic (plastic) region - this is where the material being stretched yields and ‘gives’ permanently. Before this point, stretching will not cause any permanent extension.

It’s like a spring, stretch it a little and it pings back. Stretch it beyond it’s designed length and suddenly it ‘gives’ and lengthens greatly, and then stays that way.

Obviously the penis is not a metal spring but the same basic principle of plastic deformation should apply, implying that below a certain stress (ie Weight) no permanent deformation will occur.

Agreed.

I think it also shows that high weights are not required for permanent elongation and as the graph shows no yield point (which would have been nice), then creep is the most likely mode of permanent elongation and thus provided the weight is sufficient, time is the crucial factor in determining gains.

Very interesting mbuc.

Am I right in thinking that you were measuring how much the penis stretched rather then lig stretch?

I am interested because after manual stretching I attach a stainless steel weight (19oz about 1.25lbs) to my penis with the intention of letting the ligs heal in the elongated state.
Is this enough weight for that?

I think of “creep” as being temporary. It’s a slowly changing effect, which I think has something to do with driving water out of the tissues. Things stretch more as you wring out the water. Eventually, the water diffuses back, and you’re back where you started.

Really?

You don’t think it is possible that creep is the mechanism by which permanent deformation takes place? How else would you define it?

Creep is defined as permanent deformation achieved over long periods of time, at stress well below the yield point of a material.

To me, that is exactly what happens when hanging for long periods with low weights.

I think the data recording for length at a weight of 1.6kg is probably slightly low but is within any realistic margin of experimental error. (After all I wasn’t aiming to build a space probe. If you’d seen me hanging assorted weights including tins of fruit you’d think it was a miracle the final data came out so well! LOL)

Like I said before I don’t get skin stretch on my shaft the way I hang so my base line remained pretty static.

Kudos on the lab work mbuc. :thumbs:

Does this show that guys trying to hang thirty pounds after getting the Bib right from the Post office aren’t doing themself any favors?

AH

I have a feeling that the vast majority of the strain comes from soft tissue shear strain. Ligaments only strain like 6% before damage.

Probably, since any lig stretch would probably move my base line and so would not be measured, but I wouldn’t be too sure.

Like you I use an ADS weight and part of the reason I did this little experiment was to see how much stretching I could expect at different weights. Looking at the chart at 1.25lb (570g) you’re still on a steep part of the curve and if you could up the weight by 1lb you would get a good bit of extra stretch. That would take the weight up to 1kg and after that it is a case of diminishing returns in terms of added stretch. Of course the more weight the harder it is to comfortably wear. At the moment I’m using 1.5lb (750g) and will try to up it to 1kg.