5.Conduct machining operations prior to surface treatments to reduce the potential for crack  initiation. Machining of the holes after applying the anodic coating likely influenced crack initiation of  ~12 μm (4.7E-4 in) depth through the anodic coating and into the base material. The tooling hole  machining process may have contributed to the fatigue crack initiation. MSFC failure analysis noted that ‘[h]ard anodized coatings reduce the fatigue life and increase the number of crack initiation site  [sic] when applied to aluminum 7050-T7451.’ There is evidence that ‘[a]nodic oxidation of light alloys  reduces bending endurance limits by as much as 39 percent'.   6.Utilize dedicated tooling for locking patch process development. This prevents unneeded  cycling of the test article or flight unit’s threads during the locking patch development. 7.Utilize visual movement indicators (e.g., to rque striping) for threaded joints. The umbilical strut  had torque stripes applied to certain indicators that were of high value during the investigation. However, not all threaded interfaces had torque stripes so the state of some could not be  ascertained. Torque striping is typically very easy and inexpensive to apply. 8.Conduct testing to determine the required lim its on running torque for joint designs not  conforming to available sta ndards and specifications . The running torques and preload torques  found in most tables have been determined through testing of specific joint combinations. Applying  those torques to configurations other than those from which the values were derived may result in  large differences from what is needed. In the case of this strut, the material modulus was three times lower than a steel fastener and the threaded body was hollow, generating a much different stiffness in the joint than assumed in the torque tables.  9.Perform a bounding fatigue analysis in all po ssible orientations on mechanism components  that are subject to rotation. The fatigue analysis assumed that the strut remained in its ideal  rotational alignment, resulting in the tooling holes being at the neutral axis of the strut. However,  normal limits of rotation allowed by the strut design could move these holes somewhat out of the neutral axis and begin to have an impact on fatigue life. Fatigue analysis (as well as all other  analyses) should examine the worst-case orientations allowed by the design, not just the ideal  orientation. 10.Review requirements, references, and methodologies used in analyses for design  applicability. The requirements and analysis methods utilized in the assessment of joint preload did  not consider bending as a potential source of joint separation. Additionally, the references are  primarily focused on typical bolted joints and fasteners, the definitions of which are not completely applicable to the spring strut joints. This resulted in a false confidence in the understanding of the behavior of these joints. 11.Assess the contribution of assumed secondary eff ects (e.g., CG offset s, induced compression  spring static torques, nonlinear behavior, etc.) to  the analysis results, and perform an analysis  and correlation study that reflects the major contributors. Assumptions about what will be a  small contributor to strut response to environments are appropriate for initial design phases, but those  assumptions should be checked via sensitivity studies or other means once the design and analysis are more fully developed. In this case, some of the factors assumed to be unimportant turned out to have non-negligible effects on the hardware. 403