fragile materials vs ductile materials

[amedeo]

Hello, everyone. .
The thesis work I'm facing poses a question to me....when designing a device for the absorption of titanium alloy shocks, I was asked why a fragile material is used for its construction instead of a ductile material. . .
waiting for some answers, I greet all and thank you in advance

 

[davide_r]

take my answer "with the pliers" since I am not an engineer, but first of all it is necessary to determine whether it is titanium in the state called "pure" (i.e. not tied with aluminum and vanadium). In fact, titanium not tied in addition to being light and corrosion resistant is relatively ductile. by experience I know that the greatest difficulties for titanium processing are when this is in the form of alloy.

 

[amedeo]

hi davide...senti...the titanium is alloy-shaped...exactly ti-6al-4v...my doubt comes especially regarding the use of such alloy on the device I designed, not so much in the production phase of the alloy...
what I would like to know is precisely because you prefer to use a material with fragile characteristics compared to a ductile material. . .

 

[davide_r]

depends on the fact that you want to obtain a controlled deformation using the mechanical characteristics of the material, in fact the tial6v4 alloy besides being particularly light has a high breaking load and a low elongation percentage. If the material was too ductile, a permanent deformation would not be able to absorb the shock.

 

[amedeo]

I thank you so much. .however other answers to further deepen the topic....
Hi.

 

[guitarfenix]

Hi.
I think you're wrong...the alloy you have is perfect for the type of construction you're planning...and it's certainly ductile and not fragile.
Of course compared to the excellent characteristics of the steels is more fragile but cmq above the characteristics of aluminum and magnesium.

an important feature is the good ductility (then high elongation to break, about three times higher than that of aluminum and steel) that especially in pure titanium prevents from sudden breaks of brittle type as well as allowing good workability.

the use of titanium can be partially considered for armoring vehicles for safety. despite the balistic demands of potential light titanium constructions are poor, one could expect good results from the application of such metal in the construction of light weapons and in the anti-granata protection, it was used in the American American m2a tank for the construction of some of its details.

...if I can tell you a link...which is about tanks but with a lot of information you might need. . .http://www.ing.unitn.it/~colombo/mototitaniomoto.htm#proprietàtechnological... let me know and good work!
Hi.

 

[amedeo]

thank you very much for the straight guitarfenix.... great also the link you sent me... I will let you know as soon as possible. . .

 

[guitarfenix]

...of nothing!

Hi.

 

[stevie]

I agree with guitarfenix, the alloy mentioned above has very high ductility characteristics, superior to steel.
In addition, in the case of shocks and energy absorption, the key factor in my opinion is the tenacity, which is precisely the energy absorbed by the material before breaking (by volume unit) and that in the sigma/eps diagram is represented by the area suspended at the curve.

 

[Fulvio Romano]

the choice if to use ductile or fragile materials depends on the application.

- ductile materials absorb more energy during deformation. if after the impact you decide not to replace the piece, the machine is not safe

- fragile materials typically absorb less energy. this is measurable with charpy pendulum. the only advantage that comes to mind is that the piece breaks and must be replaced. I look like this not to be underestimated in some machines.

 

[cacciatorino]

Sometimes in the cinematic chain there is a weak mebro that makes it "fusible" for the mechanism, that is so that in the presence of overloads he breaks instead of more expensive components, but surely if this was the logic you wouldn't do it in titanium!

 

[matteoso]

Sometimes in the cinematic chain there is a weak mebro that makes it "fusible" for the mechanism, that is so that in the presence of overloads he breaks instead of more expensive components, but surely if this was the logic you wouldn't do it in titanium!

quoting and adding that you choose a "sacrifice" component also depending on the easy accessibility to replace it.

 

[Fulvio Romano]

However I did not understand why titanium... usually these alloys are used to have high resistance with low weight, but for industrial applications I have never heard of them.

But I must say that I have no experience on this.

 

[amedeo]

then...I thank all for the interest given...

the answer he gave in his first speech is the one that approaches what I needed. . .
the device that I am planning will have to be installed in the front of the sae formula car...it must in practice be able to absorb a possible shock...the mechanism will have to dissipate energy deforming... .
the choice of titanium is due to the fact that the absorber will be realized with a trabecular structure (i.e. formed by a series of cylindrical rods joined together in order to connect the center of an ideal tetrahedron) and the only technology to be able to realize this device is e.b.m. technology: Such technology can run the desired models only using titanium or chromocobalt alloys. . . .

 

[Bradi88]

from my experience in designing a shock absorber, what you need to look for is a material that has a high percentage elongation value. clearly the material you use must be less rigid possible, so a low module of young, otherwise, as you will know, the more a body is rigid, the more the shock is absorbed by the soft parts. I think the proper behavior you have with a ductile material, more than fragile, as for the latter you cannot appreciate a deformation before the breakup. your material, instead, will have to deform to absorb energy! look well what concerns also the influence of deformation speed and in particular the law of cowper-symonds