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orthotropic materials modal analysis

Cholito

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hi to everyone, I just joined this forum as I would like some suggestions for a teaser I have to perform. I am a mechanical engineering student and for an examination I was asked to look for relationships between properties (e, g, nu) that define an orthotropic material of a mechanical component printed in 3d aluminum powder using modal analysis. Basically, prof. provided me with directions of print, masses and frequency of the first way of vibrating.
What I would like to understand is whether to simulate the different printing orientation is enough to rotate the 3 components of e, g and nu or does there exist another way?

Thanks right away for your help.
 
hi, honestly I have no experience in am. as first approximation could go well, because reasoning is logical. However it is a specific field, so it is better to wait for the opinion of experienced users, also because the issue is much more complex.
 
the prerogatives that apply for an orthotropic material, we say classic (how could it be a laminate, for example), being "printed" in 3d (with what technique?) how much they apply?
 
The question is interesting, I would like to know more about it. We await the contribution of some expert.
 
thanks for the contribution, the printing technique presumes to be sls with aluminum powders. my base were the isotrope properties of the aluminum alloy supplied by ansys which then modified in orthotropa and studied with an optimization with response surfaces. My audition of which I attach the photo, is analyzed with a connection bolted on the hole and then the first way to vibrate is measured with laser techniques. from the analysis I found that there is a practically linear correspondence between the freq. the first way and the young module along the length (the size greater) and which is reasonable since the first way oscillates perpendicularly. Unfortunately, however, from the rotations I can't find links and I think it's difficult since the different samples printed differently have different masses and very variable frequencies. I also attach the experimental results of the first ways of testing printed in different directions. Thanks again.
 

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using the sls printing technology, defined with xy the material storage plan and with z the direction of the development in height, for how the particular printed on the xy plane should not be found differences of mechanical properties, while you should get different results along the z direction, where the layers happen.
different would be the behaviour of the test if it printed with slm technology: in this case the granules of powder are melted selectively through a high-energy laser, without addition of low-melting elements, resulting in an object similar to that achieved through a traditional fusion process, therefore, in theory, isotropic.
I do not interpret the attached table well, but I assume that or, v and l are the printed auditions along the three directions and the first column indicates the weight (grams ?). I do not understand how three objects printed in the same direction, using the same g-code, can have different weights: maybe they are not cleaned properly by excess powder?
leaving modal analysis for the moment, if a static analysis should be carried out, you should get that the value of the elastic module and is maximum when the fibers are oriented in the sense of the maximum load endured. do you get comparable results with modal analysis?
For me too the question is interesting, and I would like to know the results, beyond my deduction and hypotheses.
 
Thank you for your answer. As regards printing technology, the professor was unclear. In any case, the first column is the grams and I can not explain the different masses of the auditions, maybe in some cases there were more retreats of the material or different density or maybe the print was not very accurate. However, I did not understand the part concerning static analysis. Would you be suggesting that I try to carry out a static analysis in ansys? for what purpose?
 
in the end the great question is how of the tests printed in the same way with dimensions that differ of 1/10 mm can and in the same direction can have such different vibration frequencies. see the passage from 131 hz to 119 hz. the bolted connection is made in the same way and are all screwed with the same force.
Could the starting position be relevant in the 3d printing of the audition?
 
vabe but first of all you have to verify the repeatability of the instrument. you can't claim that contactless vibration measures are very precise .. 10 hz dancing on 120 are not so many.

In addition, as you say, there will certainly be variability in the molding process, as also emerges from the weight measurement.. but we are talking about tenths of gram ..

You're an engineer, not a pharmacist. When you use these measures to desume the matrix of the elastic modules you will see that there will be no considerable differences using the first measure, the third or the average of the 3.
 
Stan9411 said:
vabe but first of all you have to verify the repeatability of the instrument. you can't claim that contactless vibration measures are very precise .. 10 hz dancing on 120 are not so many.

In addition, as you say, there will certainly be variability in the molding process, as also emerges from the weight measurement.. but we are talking about tenths of gram ..

You're an engineer, not a pharmacist. When you use these measures to desume the matrix of the elastic modules you will see that there will be no considerable differences using the first measure, the third or the average of the 3.
Click to expand...
Excuse me, how would you do to degrade the matrix of elastic modules? what explanation would give to frequency differences according to the direction of stamping?
 
Cholito said:
Thank you for your answer. As regards printing technology, the professor was unclear. In any case, the first column is the grams and I can not explain the different masses of the auditions, maybe in some cases there were more retreats of the material or different density or maybe the print was not very accurate. However, I did not understand the part concerning static analysis. Would you be suggesting that I try to carry out a static analysis in ansys? for what purpose?
Click to expand...
No, I'm not suggesting to run a static analysis. more simply, regardless of the analyses that are carried out, the same results must be obtained at the same time. is just a verification that you can do to support your calculation.

p.s.: I am not your professor, please do not give me “shes”. ...
 
Stan9411 said:
vabe but first of all you have to verify the repeatability of the instrument. you can't claim that contactless vibration measures are very precise .. 10 hz dancing on 120 are not so many.
Click to expand...
surely there is something that does not return on the repeatability of the instrument. for a minimum weight difference and (it is supposed) in size, there is no justification for a difference of about 10% in the frequency relief for two printed auditions in the same way, which therefore should have the same density.
 
I don't know. I have seen some modal analysis .. 7-8 hz dancing in finding a proper frequency are normal. 10 and vabe came out here. .

we say that surely 3 only measures each on 1 different try are few.

It is also quite visible ( net of denial from further measures) that the frequency of this affair is between 130 and 120 hz (I refer to the measures indicated by letter or). basically to you that you have to get a young module, it will not change almost anything.. you will dance a couple of gpas on dozens that you have the goal of finding (it seems to have understood that you are talking about aluminum, so I guess you have to come a 70 gpa regardless of the manufacturing process).
engineering is the same thing. .
 
the realized study leads me to have a practically linear dependence of the module of young in x direction (length) and the first way of vibrating that oscillates perpendicularly to this. However, it passes from about 90 gpa of 137 hz of l1 to 55 gpa of 109 hz of v2. so there is a good difference.
I don’t think it’s a repeatability problem, they have been tested using a closed-circuit shaker, with a very rigid expansion head so as to ensure the same level of excitement to the whole surface and also the connection dice have been tightened with a dynamometric key to the same torque value.

I personally find it sensible that you have a very strong link between ex and the first way but I do not understand why the other 8 elastic constants are influential.

Moreover, I do not think I can give an explanation regarding the direction of growth/print connected to the different frequencies.
 
biz said:
was only a supposition, about the repeatability, validity and accuracy of the measures carried out.
Click to expand...
Okay, thank you very much, I think the measures provided to me by the teacher are correct. so according to you can be that the different frequencies depend on different factors that I cannot try to understand only with a trivial modal analysis?
 
Of course I can't know, at the most I can assume, you should investigate the cause of this.
 

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