finite element analysis of brain injury accidents

This sub-forum all discussions about this "lively" subject. All topics that are substantially about helmets will be moved here, if not placed here correctly in the first place.
Vorpal
Moderator
Posts: 17909
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

finite element analysis of brain injury accidents

Postby Vorpal » 17 Dec 2016, 11:37pm

I thought this was interesting....

https://www.researchgate.net/publicatio ... ment_study

A number of assumptions are built into this sort of thing, and I don't know enough to criticize any of them. Although I have done finite element analysis, I've never done it on people.

Main conclusions:
Strain in the brain tissue, which is associated with brain injuries, was reduced by up to 43% for the accident cases studied when a helmet was included. This resulted in a reduction of the risk of concussion of up to 54%. The stress to the skull bone went from
fracture level of 80 MPa down to 13–16 MPa when a helmet was included and the skull fracture risk was reduced by up to 98% based on linear acceleration. Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity. The results of this study show that the brain injury risk and risk of skull fracture could have been reduced in these three cases if a helmet had been worn.
Last edited by Graham on 18 Dec 2016, 1:44pm, edited 1 time in total.
Reason: No brians were hurt in the course of this study.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

User avatar
Cunobelin
Posts: 10140
Joined: 6 Feb 2007, 7:22pm

Re: finite element analysis of brian injury accidents

Postby Cunobelin » 18 Dec 2016, 9:13am

Howzabout..........


I do research into a life saving vaccine, and find one that reduces the risk of the disease by 54%

Then I use that evidence to ignore the group of 40 - 50 year olds that form the greatest number of patients, the 30-40 year old age group that has the more severe symptoms and then justify that vaccine for the 18-24 year age group only

Is that ludicrous -yes it is

Yet that is exactly the case here, the research applies to pedestrians, cyclists, vehicle drivers and passengers, yet let's see what they do with this "life saving" intervention

Stevek76
Posts: 510
Joined: 28 Jul 2015, 11:23am

Re: finite element analysis of brian injury accidents

Postby Stevek76 » 18 Dec 2016, 12:14pm

Well the study seems sound enough on the methodology.

The stand out problem to me is that the three impacts it considers are all largely within a helmet's design parameters.

What about at the speeds where you're actually going to die, and also snagging on vents.

User avatar
al_yrpal
Posts: 8285
Joined: 25 Jul 2007, 9:47pm
Location: Cully
Contact:

Re: finite element analysis of brian injury accidents

Postby al_yrpal » 18 Dec 2016, 12:19pm

Its just common sense, finite element analysis isnt needed for that. Firemen, construction workers, plant workers, miners, policemen and fighter pilots amongst many others understand it too.

Al
Touring on a bicycle is a great way to explore and appreciate the countryside and towns you pass through. What do you do to make a difference?

axel_knutt
Posts: 1513
Joined: 11 Jan 2007, 12:20pm

Re: finite element analysis of brian injury accidents

Postby axel_knutt » 18 Dec 2016, 1:34pm

Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity.

You would have thought it would have been obvious to them that increased risk taking isn't necessarily in the form of increased speed.
“I'm not upset that you lied to me, I'm upset that from now on I can't believe you.”
― Friedrich Nietzsche

Vorpal
Moderator
Posts: 17909
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: finite element analysis of brian injury accidents

Postby Vorpal » 18 Dec 2016, 1:45pm

axel_knutt wrote:
Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity.

You would have thought it would have been obvious to them that increased risk taking isn't necessarily in the form of increased speed.

It's the one they could account for, and arguably the primary one that significantly affects the inputs required for this study.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

axel_knutt
Posts: 1513
Joined: 11 Jan 2007, 12:20pm

Re: finite element analysis of brian injury accidents

Postby axel_knutt » 18 Dec 2016, 2:28pm

Vorpal wrote:
axel_knutt wrote:
Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity.

You would have thought it would have been obvious to them that increased risk taking isn't necessarily in the form of increased speed.

It's the one they could account for, and arguably the primary one that significantly affects the inputs required for this study.

Yes, but it's an attempt to discount the effect of risk compensation on the benefit of wearing a helmet.
“I'm not upset that you lied to me, I'm upset that from now on I can't believe you.”
― Friedrich Nietzsche

irc
Posts: 4673
Joined: 3 Dec 2008, 2:22pm
Location: glasgow

Re: finite element analysis of brain injury accidents

Postby irc » 18 Dec 2016, 2:49pm

Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity.


A complete misunderstanding of risk in cycling IMO. The effect of risk compensation for cyclists is more risks leading to more accidents. Not having higher speed accidents though higher speeds may be a component. IMO any crash is a lottery as the small but tragic number of walking speed or below fatal falls demonstrates (Natasha Richardson for example.) Safety for cyclists lies in avoiding crashes not crash protection.

I don't think if I'm doored at 20mph or 22mph there will be a significant difference in the outcomes. But risk compensation might mean some riders are more likely to take that risk of being doored in the first place. Both speeds of course are outwith the design speeds of helmets

I don't actually dispute that if I am going to crash a helmet is likely to give some protection. I assert that my cycling (touring, commuting, shopping) where I do it is not dangerous enough to require head protection. 40+ years of cycling without an injury accident (bar minor bruises/grazes) seems to support my view. As does the KSI stats which suggest the average cyclist will ride X miles before a fatal accident.

Vorpal
Moderator
Posts: 17909
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: finite element analysis of brian injury accidents

Postby Vorpal » 18 Dec 2016, 2:55pm

axel_knutt wrote:
Vorpal wrote:
axel_knutt wrote:You would have thought it would have been obvious to them that increased risk taking isn't necessarily in the form of increased speed.

It's the one they could account for, and arguably the primary one that significantly affects the inputs required for this study.

Yes, but it's an attempt to discount the effect of risk compensation on the benefit of wearing a helmet.

I'm not sure I understand how you came to that conclusion. They looked at specific injury accidents. In other words, that a a crash had already occurred was a given, so crash rates and risk taking could not otherwise be considered.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

User avatar
[XAP]Bob
Posts: 17178
Joined: 26 Sep 2008, 4:12pm

Re: finite element analysis of brain injury accidents

Postby [XAP]Bob » 18 Dec 2016, 8:49pm

I haven't read the whole paper...

Two things stand out from above - linear acceleration is the first.
We already know that the brain deals well with simple linear trauma, it's the rotation that is really damaging.

The other is that the result is so strong that it should easily be identified in the real world. Since it isn't I assert that there is an discrepancy between their assumptions and reality. One possible error is my first point...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

irc
Posts: 4673
Joined: 3 Dec 2008, 2:22pm
Location: glasgow

Re: finite element analysis of brain injury accidents

Postby irc » 18 Dec 2016, 10:39pm

skull fracture risk was reduced by up to 98%


Helmets have improved then from the days when they only prevented 85% of injuries.

tanglewood
Posts: 138
Joined: 14 Jan 2011, 7:14pm

Re: finite element analysis of brain injury accidents

Postby tanglewood » 19 Dec 2016, 5:23am

If I fall from a roof onto a mattress will I get fewer injuries than if I fall onto bare concrete? Of course.

Am I more likely to do something risky on the roof (like reach out to paint that corner instead of moving the ladder again) if there is a mattress beneath me? Yes.

If humans were entirely rational we would always move the ladder and never reach out and also have a mattress beneath, moving it every time we move the ladder of course.

But humans are not like that.

Me - I will move the ladder, use a good one, keep it well maintained, and stay sober.

Others - let them put a mattress on the ground and I hope when they fall they land on it.


I'm a trendy consumer. Just look at my stupid phone.

profpointy
Posts: 476
Joined: 9 Jun 2011, 10:34pm

Re: finite element analysis of brian injury accidents

Postby profpointy » 19 Dec 2016, 8:44am

Vorpal wrote:
axel_knutt wrote:
Vorpal wrote:It's the one they could account for, and arguably the primary one that significantly affects the inputs required for this study.

Yes, but it's an attempt to discount the effect of risk compensation on the benefit of wearing a helmet.

I'm not sure I understand how you came to that conclusion. They looked at specific injury accidents. In other words, that a a crash had already occurred was a given, so crash rates and risk taking could not otherwise be considered.


When you say "crash which had already occurred" did they take account of the increased size od the helmetted head, and thus you'd likely hit your head twice as often? Thus half the unhelmetted crashes would miss the head compared to wearing a helmet.

Vorpal
Moderator
Posts: 17909
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: finite element analysis of brian injury accidents

Postby Vorpal » 19 Dec 2016, 8:48am

profpointy wrote:
Vorpal wrote:
axel_knutt wrote:Yes, but it's an attempt to discount the effect of risk compensation on the benefit of wearing a helmet.

I'm not sure I understand how you came to that conclusion. They looked at specific injury accidents. In other words, that a a crash had already occurred was a given, so crash rates and risk taking could not otherwise be considered.


When you say "crash which had already occurred" did they take account of the increased size od the helmetted head, and thus you'd likely hit your head twice as often? Thus half the unhelmetted crashes would miss the head compared to wearing a helmet.

Crash rate, or likelihood of vicitms hitting their heads was not considered at all. That's what I was trying to say. They looked at specific cases where a crash had already occurred, and considered whether a helmet would have been of benefit.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

Bez
Posts: 1217
Joined: 10 Feb 2015, 10:41am
Contact:

Re: finite element analysis of brian injury accidents

Postby Bez » 19 Dec 2016, 10:00am

al_yrpal wrote:Its just common sense, finite element analysis isnt needed for that. Firemen, construction workers, plant workers, miners, policemen and fighter pilots amongst many others understand it too.


Research is good*, because "common sense" is often wrong. People's "sense", common or otherwise, is frequently unreliable. The fact that your examples are all of hard-shell helmets, almost all with minimal padding and without designed-in absorption by failure, is an illustration of this. Show me a miner or a construction worker who wears a polystyrene hat with large vents and a thin shell that has little more than an aesthetic function. (Also, show me a cycling scenario where there is a reasonable chance of falling masonry, rockfalls, explosions, rocket attack or physical assault with a weapon**.)

* I've not yet read this paper, though.
** Ok, there are examples of the last one.