FD+E Weld Challenge 6: Solid Square Beam Notched/Welded, A36 Steel



Fatigue Design and Evaluation Committee members: T.Cordes, D.Lingenfelser
Web Page: https://fde.uwaterloo.ca/Fde/CaseStudies/Weld6_SQbeam/weld6_SQbeam.html
Date: June 2014
Data Reference: Contributed to Fatigue Design and Evaluation committee by support from anon.

Invitation (Sept. 25 2008)

Tom Cordes is making and testing samples for using in
comparing life predictions to actual results.  The basic
specimen is 1.5 inch square steel stock, 24 inches long, loaded in fully
reversed 4 point bending.  There are 2 specimen types.  

The challenge is to predict the number of cycles at +/- 5,000 pounds
(initial load estimate, actual test load may vary) load to break the bar.
The specimens will be monitored to assess the portion of life before a
crack is identified and a measure of crack growth versus cycles.
Tom will have results for discussion at the Oct 15 2008 FDE meeting.


(Click to enlarge)
Fig. 1: Overview of square beam

Some of the specimen details are in figure 1. While the figure
shows one specimen with a weld and a notch, actual specimens have either
2 welds or 2 notches at the locations shown. 


    Material was normalized A36 (77- 78 HRB or 137-140 BHN)

    The welds were made with a Lincoln Powerwave 455, STT Mode 22, 
    with 90/10 gas mixture using L50 0.045" diameter wire.

    Welder settings were 80/380/10
A large amount of further information can be found in a

        Presentation by T. Cordes (pdf 16Mb)



Material

The material is a normalized A36 structural steel in the form of a 1.5"
square bar. Strain controlled ASTM E606 axial specimen test results for ASTM A36 steel
can be found 
 
                  lowcarbon.html
Crack propagation da/dN vs ΔK data 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

Solid steel rod 1.5 inch square, 24 inches long, loaded in fully
reversed 4 point bending.  There are 2 specimen types.  

In each test specimen the two notches are either both grooves or both weld beads.
See figure 1 for other geometric details. Also see Presentation by T. Cordes (pdf 16Mb)
for pictures.

Load Histories



Four Samples tested in totally reversed (R=-1) bending for each load level.
Constant Amplitude load control at load levels: 

        1       6000 Lbs (26.689 kN), 

        2       5000 Lbs (22.241 kN)  

        3       3500 Lbs (15.569 kN)


Test Results

Tests were performed at Mississipi Stae Univ. and at AET in Wixom MI. 


   Notched Specimen Test Results Summary
            at +/- 5000 Lbs          
                                           Fatigue Life      Fatigue Life
                                             To First         To Failure
                                            Detectable         To Carry
       Testing Performed By                Crack (Cycles)    Load (Cycles)
-----------------------------------------     -------         ---------
Original FD+E Round Robin Test Result           5,000           21,975
Mississippi State University (MSU) Group 6      5,000           26,365
Mississippi State University (MSU) Group 5      5,504           24,443
Mississippi State University (MSU) Group 4      6,000           27,216
Mississippi State University (MSU) Group 3      7,200           24,985
Mississippi State University (MSU) Group 2     12,224           24,271
Mississippi State University (MSU) Group 1     14,097           24,034




   Other Welded and Notched Specimen
   Test Results Summary.

                 Load    First Crack     Crack all the    Obvious Edge     Failure
Specimen        R=-1.0   Indication(s)     way across        Crack       Two Pieces
Configuration     Lbs      Cycles           Cycles          Cycles         Cycles
 ----------     ------   -----------     ------------     -----------    ----------
    Weld         6,000     18,000           20,700           23,400        30,964
    Weld         5,000     55,300           94,000          168,000       198,282

   Notch         5,000      5,000            8,000           14,000        21,975
   Notch         3,500     62,000          106,000          115,000       154,494

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