×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Units Confusion

Units Confusion

Units Confusion

(OP)
I am having some unexpected results, Can someone check my units please as I always have confusion in them.

Units: N,mm
Length = mm
Force = N
Mass = Tonne (1.0E3kg)
Time = second
stress = MPa (N/mm^2)
Energy = J (J)
Density = Tonne/mm^3
Conductivity = J/(s.mm.C)
Specific Heat = J/(Tonne.C)

and the following numbers have been put in ABAQUS.
E of steel = 207000 (MPa)
Yield = 450 (MPa)
gav = 9807 (mm/s^2)
density of steel = 7.85 (ton/mm^3)

Is there a mistake there?

RE: Units Confusion

(OP)
Silly me. the gravity should be 9.807E-3

RE: Units Confusion

(OP)
Lol. To correct my last post, I think the gravity was correct as 9807 (mm^3).

However the density should be
7850 kg/m^3 = 7.85e-9 (ton/mm^3)

Is that correct?


RE: Units Confusion

Yes. Correct now.

RE: Units Confusion

actually every time i read any post about the units iam doubful again.so you stated above that used units:N,mm
should you define this at beginning or you are saying this comprehensively.can you further explain.
if a line for example is 10mm should i dimension the line as 10 or 0.01 the same also for pressure,1Mpa is simply one then or is it 10^6 in the pressure load.please reply soon

RE: Units Confusion

(OP)
I normally define the unit as a comment under the heading. So the user can read from the input file that what unit I am using.

This is what the input in ABAQUS I used

Units: N,mm
Length = mm       value= 1m     ABAQUS value= 1000
Force = N         value= 1N    ABAQUS value= 1
Mass = Tonne (1.0E3kg) value= 7850 kg/m^3 = 7.85e-9
stress = MPa (N/mm^2) value= 1Mpa ABAQUS value = 1

Moreover, the ABAQUS stress results has the unit above. Hence, the plot show 100 in misses plot will mean 100MPa.

RE: Units Confusion

(OP)
"Mass = Tonne (1.0E3kg) value= 7850 kg/m^3 = 7.85e-9 "

Should be

Density = ton/mm^3   value= 7850kg/m^3
              ABAQUS value= 7.85e-9

RE: Units Confusion

thanks very much,so the same for presure if it is 10Mpa abaqus values will be also 10.really good explanied from you

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources