Material properties -- Elastic and Plastic deformation in automobile crashes

[shk]

Homework Statement:

The question has been attached and my answer can be seen below.
Would you please check my answer?

Relevant Equations:

Elastic and plastic deformation

a)plastic deformation because of permanent deformation
b) the other parts that have been destroyed have stored the energy and this saved the passenger compartment.
C) the alloy crash barrier is stronger than the car body and and saves more of the energy by deforming shape.

I'm not sure about my answers especially about the answer to part c.

I appreciate your help.

 

[Lnewqban]

Your answers seem to be correct.
Note that C) is asking about the struts supporting the central barrier.
I would replace the reference to strength with one about the different rates of elastic and plastic deformations, which seem to be the goal of the exercise.

 

[shk]

Your answers seem to be correct.
Note that C) is asking about the struts supporting the central barrier.
I would replace the reference to strength with one about the different rates of elastic and plastic deformations, which seem to be the goal of the exercise.

Thanks for the reply. So do you think if I say the barrier is stronger than the body car , is enough for part c ?

 

[Frabjous]

these are really open ended questions ...
a) the entire car body has undergone elastic deformation. There are undeformed parts which have come to a stop. The deformed parts deform elastically “first.” Parts of the car body have undergone plastic deformation which is detectable by permanent deformation.
b) I would say absorbed or dissipated the energy not stored
c) the struts are stronger and exhibit less plastic deformation because they are designed to prevent the vehicle from crossing lanes. They transfer energy to the ground. the car body is softer because it is designed to prevent energy from being absorbed by the passenger department, by dissipating the energy via permanent deformation

 

[shk]

these are really open ended questions ...
a) the entire car body has undergone elastic deformation. There are undeformed parts which have come to a stop. The deformed parts deform elastically “first.” Parts of the car body have undergone plastic deformation which is detectable by permanent deformation.
b) I would say absorbed or dissipated the energy not stored
c) the struts are stronger and exhibit less plastic deformation because they are designed to prevent the vehicle from crossing lanes. They transfer energy to the ground. the car body is softer because it is designed to prevent energy from being absorbed by the passenger department, by dissipating the energy via permanent deformation

Wow, your explanation really helped.
Thank you very much . I now completely understand this.
Thank you

 

[haruspex]

these are really open ended questions ...
a) the entire car body has undergone elastic deformation. There are undeformed parts which have come to a stop. The deformed parts deform elastically “first.” Parts of the car body have undergone plastic deformation which is detectable by permanent deformation.
b) I would say absorbed or dissipated the energy not stored
c) the struts are stronger and exhibit less plastic deformation because they are designed to prevent the vehicle from crossing lanes. They transfer energy to the ground. the car body is softer because it is designed to prevent energy from being absorbed by the passenger department, by dissipating the energy via permanent deformation

Just one quibble.. the barrier struts are stiffer (not just stronger) yet still, preferably, inelastic to avoid bouncing the car into other lanes.

 

[shk]

thank you very much . Yes you are right, I should use the word stiffer and inelastic for the struts. your message was very helpful . thank you