8.53 the data for any parameter that is found in successive tests, the fewer such tests are needed to establish any given level of confidence in the accuracy of the data. So an optimum number of samples cannot be established in advance. The assumed Shuttle can easily transport enough plates to meet any reasonable sampling requirements as they arise. VIII.8.4: Assembly Inspection: All plates, crack stoppers, and welds are inspected after assembly. Inspection can begin as soon as all assembly operations are completed on the compartment being inspected, so that inspection proceeds on the partially completed hull while construction is still in progress. Compartment subassemblies can be inspected before installation, but all parts subject to handling and joining stresses must be reinspected after final installation. All mechanical fastener holes must be inspected immediately before fastener installation. Ultrasonic inspection is used to check for cracks in the plates, flaws in the crack stoppers, and ba_d welds. A portable version of the automatic plate inspection transducer array is used for assembly inspection. The array is guided along the plates in the same manner as the welding head. Extra transducers looking sideways at the crack stoppers are added to the array, as well as sets of delta-scan weld inspection transducers. This system simultaneously inspects a plate, its attached crack stoppers, and their mutual welds. Fastener holes are inspected with eddy current probes. Automatic probes can inspect about two holes per minute (8.27). Accuracies much better than the assumed 2.5 mm have been achieved, but only at very slow inspection speeds (8.32). Some techniques for inspecting fasteners and holes together have been proposed (8.27), (8.33), (8.34), but insufficient field use data is available to support their inclusion in design and assembly considerations. VIII.8.5: Overall Structural Proof Testing: Proof testing stress levels are established by a proof test factor a = rjc (8.35), where Klc = 70 ksi/In and Kl= 1.1 (~)l/ 2 Mk (see S~cti8n VII.5). The outer hull has the highest design operational and failure stress levels and the lowest margin between them, so it is the worst case
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