**Figure 3.**

*Fatigue test set-up of welded aluminum hand-hole details.*

#### **Figure 4.** *Typical strain gage location and position around the hand-holes.*

as shown in **Figure 5** and installed on the surface of the tube adjacent to the fillet weld that joins the cast hand-hole to the tube. Strain gage placement was the same as the older study and was taken from [9]. A strain gage was placed at the 3 and 9 o'clock positions respectively, with the addition of a gage in the middle of the specimen. The center of the gage was placed within 2 ~ 3 times the tube thickness away from the welding throat. The strain gages were connected to the data acquisition system to measure the nominal stress ranges.

All of the specimens were cycled at 2 Hz and tested around the clock. Visual inspections of the hand-holes were conducted several times daily. Of the 16 hand-hole details tested, 15 failed.

 **Figure 5.**  *The position of strain gages installed around a hand-hole.* 

 The data shown in **Figure 6** reveals that changes to the weld detail do not have a drastic effect on fatigue life. In fact, some of the changes appeared to have a negative effect on the fatigue life. This was most prevalent in the milling of the cast insert. The only test that appeared to have any positive effect was when the hole itself was milled. In this case, the fatigue life was increased slightly. **Figure 7** shows the compilation of previous data compared to the change in details [ 11 ].

 During testing, cracks were first observed in the throat of the fillet weld that joins the tube to the reinforcement ring. These cracks were first observed along the minor axis of the hand-hole at either the 3:00 or 9:00 position in Ref. to a clock. A sample of one of these cracks may be seen in **Figure 8** . These cracks would normally start at the weld root and propagate through the throat of the weld and then progress around the handhole. **Figure 9** shows an example of the crack surface after failure. Note that this

 **Figure 6.**  *Fatigue test results of new weld hand-hole details.* 

*Fatigue Behavior of Reinforced Welded Hand-Holes in Aluminum Light Poles with a Change… DOI: http://dx.doi.org/10.5772/intechopen.106342*

**Figure 7.** *New weld detail vs. old 10in data.*

#### **Figure 8.**

*Fatigue crack through weld throat between reinforcement and tube.*

**Figure 10.** *Typical final failure of hand-hole details.*

is similar to that of a previous study conducted at the University of Akron [10]. The edges of the jagged surface appear to coincide with the weld bead ripples.

Final failure typically occurred as the crack progressed through the cast insert near either the 11:00 or 5:00 position (**Figure 10**). In these cases, the fatigue cracks spent most of the cyclic life while small. In every case there was a definite transition from the time of the development and propagation of visible fatigue cracks within the fillet weld throat to the final failure. In most cases, cracks would develop and progress around the hand-hole. At this point, they would appear to stop, and only after a significant number of load cycles were applied, would failure occur.
