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How to write the statement for MAX and MIN safety margin?

How to write the statement for MAX and MIN safety margin?

How to write the statement for MAX and MIN safety margin?

(OP)
How to write NASTRAN statement for output of safety margin:
MAXMIN (DEF) TTTT (BEAM,10) MAXALG(10) MINALG(10)?

I know the how to write the ourput for stress and forces but don't know which word in NASTRAN is used for safety margin (replacing TTTT in the above statement). I tried to find it in the manual but could not.

Thanks!

RE: How to write the statement for MAX and MIN safety margin?

Dear alin09,

Conventions for BEAM elements:
• M.S.-T: Minimum margin-of-safety in tension.
• M.S.-C: Minimum margin-of-safety in compression.
• Minimum M.S. found over entire length of element

Definition of Margin-of-Safety (M.S.):
======================================
The M.S. in tension is: M.S.–T = (ST / S-MAX) – 1.0, where ST is the tension allowable given on the MAT1 entry and S-MAX is the maximum stress given in the output, S-MAX = max (SA-MAX, SB-MAX). M.S. in tension is computed and printed if and only if ST is greater than zero and S-MAX is greater than zero.

The M.S. in compression is: M.S.-C = (–SC / S-MIN) - 1.0, where SC is compression allowable given on the MAT1 card and S-MIN is the minimum stress given in the output, S-MIN = min (SA-MIN, SB-MIN). M.S. in compression is computed and printed if and only if SC is greater than zero and S-MIN is less than zero.

The output I have using FEMAP & NX NASTRAN 7.0 is the following:
                                  S T R E S S E S   I N   B E A M   E L E M E N T S        ( C B E A M )
                    STAT DIST/
   ELEMENT-ID  GRID   LENGTH    SXC           SXD           SXE           SXF           S-MAX         S-MIN         M.S.-T   M.S.-C
0         1
                  1   0.000   -4.220390E+03 -4.220390E+03  4.220390E+03  4.220390E+03  4.220390E+03 -4.220390E+03  3.7E+00  6.1E+00
                  2   1.000   -3.798351E+03 -3.798351E+03  3.798351E+03  3.798351E+03  3.798351E+03 -3.798351E+03   

Best regards,
Blas.



 

RE: How to write the statement for MAX and MIN safety margin?

(OP)
Blas,

Thanks for the reply.
I know the meaning of margin of safety and how to calculate. But I don't know how I can get the first 10 maximum and minimum values of margin of safety by using the statement MAXMIN (DEF) TTTT (BEAM,10) MAXALG(10) MINALG(10) in NASTRAN input file? What do I use to for "TTTT" to represent margin of saftey?

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