FD+E Weld Challenge 2: T-Tube Welded, A36 Steel, Variable Amplitude



Fatigue Design and Evaluation Committee members:
J.Bonnen, Ford, P.Kurath, UoIllinois, M.El-Zein, J.Deere
Web Page: https://fde.uwaterloo.ca/Fde/CaseStudies/Weld2_TtubeVA/weld2_TtubeVA.html

Data Reference:
Specimens fabricated and donated to Fatigue Design and Evaluation committee by J.Deere.
Tested at U.of Illinois and Ford Sci. Res Lab,





Fig. 1: Specimen



Invitation :



How good are you with a Real history?

Here are the parameters for the weld challenge. Two variable amplitude load
levels, using the grapple skidder torque history will have been run by the time
of the next meeting.

First test:
       
    Peak load = 6106 lbs  ( = 19.2 times the loads in load file )

We have at least two tests done.


Second test:

    Peak load = 8618 lbs  ( = 27.1 times the loads in the file )

Pete and I (John Bonnen) hope to have two tests (his will probably
be done -- I'm not sure my test frame can stand the 8618lb max loads.
The brace broke near the end of the last test.)
Load history location:

     https://fde.uwaterloo.ca/Fde/Weld2/grpltorWeld.html


Details and a brief discussion showing the test piece fixturing (contraint) 
during testing can be found at

     https://fde.uwaterloo.ca/Fde/Weld2/testgeom.html

Incidentally, calibrating the "model" that you have to the previous
results from Weld Challenge 1 is considered poor sportsmanship. One should make
predictions without consideration of the error between one's prediction and
previous results.
Thanks,
John J. Bonnen
mailing: Ford Motor Co.


Material

The material is an ASTM A36 structural steel in the form rectangular tubes.
Yield was given as "about 50 ksi" 
 


Note that the original stress-strain life crack initiation data file used
by many of the simulators is not available.   The files indicated below are
felt to be reasonably similar.

Crack Initiation:
Strain controlled ASTM E606 axial specimen test results for ASTM  A36 steel 
can be found
                          here 

Note that these are not tests from the same tube material, but were collected
from other studies.


Crack propagation  
The da/dN vs ΔK data for A36 steel was not available during the original
tests and simulations, but became available later.  It was collected from presentations
and papers (Refs.: [1-4]) and is plotted in figure 2.


Fig. 2 : Collected A36 and similar low carbon steel da/dN vs ΔK data.



Geometry

(Click figure to enlarge)
Fig. 3 : Component Geometry.

Notes on section properties available
(Click figure to enlarge)
Fig. 4 : Section properties





Test Fixturing


Test overviews:

Some close-ups of 4"x4" end fixture:



Strain Gage Measurements

A study was made of the strain response at the two known critical locations by P.Kurath and M.El-Zein: kurath_ElZein__Challenge2strains.pdf



Load History


Fig. 5:
(June 2014: There is some question as to the lever arm being 12.5", TBD)

The load history file is located here:
https://fde.uwaterloo.ca/Fde/Weld2/grpltorWeld.html



Fig. 6: Grapple Skidder torsion history

When one runs a "hilo" on the history file the extrema are: 

            hilo2 Starts. Usage:  hilo2  out
            #The 1st data line has  1 columns of numbers
            #Done. Scanned         5728  data lines.
            #Total lines=         5750
            #Highs:   318.00000    
            #Lows :  -238.00000




Fig. 7: Rainflow counted cycles of Grapple Torsion History
( Sorted by range: Largest range cycles on left, smallest on right ) 


 

First test:

    Peak load = 6106 lbs  ( = 19.2 x values in the history file )


Second test:

    Peak load = 8618 lbs  ( = 27.1 x values in the history file )




Test Results

# Experimental test results 

                        (1 Block =  2864 cycles)

      Test Lab.       Load Pk.     No Crack     30mm Crack    Final Crack   Location
                        lbs         blocks        blocks     (blocks : mm)
  ------------        --------     --------     ----------    ----------    --------------

 Ford Research         +6106                       1750
                         "                         8618
 U. of Illinois          "                         2181                     Partial penetration
                         "                        10962

 Ford Research         +8618                        450                     Partial penetration
                         "                         1850                     
 U. of Illinois          "                        not obsv.                 Partial penetration
                         "                         1505
( Click figure to enlarge }

Further information on the testing and results can be found here:

bonnen__ResultsforWeldChallenge2.png

References:

  1. Dindinger, P., "A36 Strain Life Fatigue Test Data," Fat.Des.and Evaluation Comm. Meeting, Oct.18,2011, Stork Technimet, 3200 South 166th St, New Berlin, WI

  2. Neuman, J., "Fatigue Crack Growth Rate Behavior of A36 Steel using ASTM Load-Reduction and Compression Precracking Test Methods," Fat.Des.and Evaluation Comm. Meeting, Oct.18,2011, Stork Technimet, 3200 South 166th St, New Berlin, WI

  3. El-Haddad, M.H. "A Study of the Growth of Short Fatigue Cracks Based on Fracture Mechanics," Ph.D. Thesis, U.of Waterloo, Canada, Aug. 1978.

  4. Klingerman, D.J., K.H. Frank, J.W.Fisher, " Fatigue Crack Growth in A36 Steel," Lehigh Univ., Fritz Engr. Lab Rep. No. 358.31, May 1971.

  5. Miller, G.A. and H.S.Reemsnyder, "Strain-Cycle Fatigue of Sheet and Plate Steels I: Test Method Development and Data Presentation," SAE Paper 830175, Detroit MI, Feb28-Mar.4, 1983

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