A program to calculate principal stresses, Ordering the variables in the sub-directory – HP 50g Graphing Calculator User Manual

Page 753

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Page 22-38

information tell us is that somewhere between

φ

= 58

o

and

φ

= 59

o

, the shear

stress,

τ’

xy

, becomes zero.

To find the actual value of

φ

n, press $. Then type the list corresponding to

the values {

σx σy τxy}, for this case, it will be

{ 25 75 50 } [ENTER]

Then, press

@CC&r. The last result in the output, 58.2825255885

o

, is the actual

value of

φ

n.

A program to calculate principal stresses

The procedure followed above to calculate

φ

n, can be programmed as follows:

Program PRNST:
«

Start program PRNST (PRiNcipal STresses)

INDAT

Enter data as in program MOHRCIRC

CC&r

Calculate

σc, r, and fn, as in MOHRCIRC

φ

n” TAG

Tag angle for principal stresses

3 ROLLD

Move tagged angle to level 3

R C DUP

Convert

σc and r to (σc, r), duplicate

C R + “

σPx” TAG

Calculate principal stress

σPx, tag it

SWAP C R - “

σPy” TAG

Swap,calculate stress

σPy, tag it.

»

End program PRNST

To run the program use:
J

@PRNST

Start program PRNST

25˜

Enter

σx = 25

75˜

Enter

σy = 75

50`

Enter

τxy = 50, and finish data entry.

The result is:

Ordering the variables in the sub-directory

Running the program MOHRCIRCL for the first time produced a couple of new
variables, PPAR and EQ. These are the Plot PARameter and EQuation variables

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