IMPLICATION OF INITIAL OBSERVATIONS
The initial fractographic observations allow the investigator to draw some conclusions regarding the cracking mechanisms for the attachment bolt and the saddle clamp bracket. If a fatigue crack exists, there is a prima facie case for pursuing litigation against the service company that performed the rebuild. The corrosion product enables us to determine, qualitatively, whether a crack existed in the component for an extended period of time, and may provide evidence to support a accusation of negligence or lack of due care.
The relevant pictures are shown below as thumbnail images, which can be clicked on to download a larger image.
 Figure 3 Inboard attachment bolt |
 Figure 4 Saddle clamp fracture - undercarriage leg side at top of picture |
 Figure 6 Higher magnification view of saddle clamp |
 Figure 7 SEM view |
- The inboard attachment bolt has failed by a cup-and-cone mechanism (refer to the Fractography resource).
- The saddle clamp has a much flatter fracture surface with three distinctly different regions apparent.
- These three regions are shown in the optical fractograph given as Figure 5 - in the top light grey region, some ridges are present (see Fractography Resource)
- This light grey region is shown at higher magnification in the SEM fractograph of Fig. 6, and some parallel lines which outline a semi-elliptic shape are apparent. Some irregular holes can also be seen in this region, particularly at the left in the middle of the three bands of crack growth.
This information can be assembled to provide some initial ideas regarding the mechanism and causes of the failure.