The Department o f Defense Trusted Computer System Evaluation C r i t e r i a (TCSEC) establishes a requirement f o r formal v e r i f i c a t i o n a c t i v i t i e s o f a TCB designed f o r Mandatory o r V e r i f i e d Protection [l]. As a r e s u l t , formal v e r i f i c a t i o n has become an i n t e g r a l p a r t o f todays t r u s t e d systems development w i t h i n t h e DoD C31 community. Design engineers must commit t o a broader understanding o f v e r i f i c a t i o n issues and be a c t i v e p a r t i c i p a n t s i n t h e v e r i f i c a t i o n process.

A series of foam-injected repairs was performed on a portland cement concrete (PCC) test section at the U.S. Army Engineer Research and Development Center. Repairs consisted of uncompacted backfill overlaid by a 9-in. rapid-setting cementitious cap. A series of injection tubes was inserted through the cap into the uncompacted debris backfill, and a two-component rigid polyurethane foam was injected into this backfill. The test matrix compared the performance of three different repairs using various volumes of injected foam. A fourth repair was constructed without injected foam as a control item. Three hours after cap construction, the repairs underwent simulated aircraft traffic with an F-15E load cart. The performance of the four repairs was measured by passes to failure. The results of traffic testing were used to evaluate foam-injection technology for rapid repair of PCC pavements. The performances of foam-injected repairs were also compared with poured foam and traditional full-depth backfill repairs, each capped with rapid-setting materials. Comparisons were made about pavement performance, costs, and total duration required for installing the repair. Results showed that injection of excessive foam was detrimental to the repair surface, because it induced cracking before traffic application, and could lead to premature development of foreign object damage. However, repairs using moderate amounts of foam and pure backfill sustained the required traffic levels, defined by the research sponsor, of 200 passes within 4 h of initiating the pavement repair. For cost and repair duration, those repairs that did not include foam were more effective.

No abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information TR-NAVFAC-EXWC-EX-1601 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR / MONITOR'S ACRONYM(S)Strategic System Programs Naval Postgraduate School NAVFAC Headquarters Asset Management NAVFAC HQ SPONSOR / MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTThe Remote Collaborative 3D Printing project is a collaboration between Strategic System Programs (SSP), the Naval Postgraduate School (NPS), NAVFAC Headquarters Asset Management -Facilities Integrated Product Support (IPS) Program, and the NAVFAC Engineering and Expeditionary Warfare Center (EXWC). The intent of the project was to investigate the end-to-end process of transferring, receiving, manipulating, and printing a digital 3D model into an additively manufactured component. Several digital models were exchanged, and the steps, barriers, workarounds, and results have been documented. This page is intentionally left blank.v EXECUTIVE SUMMARYThe Remote Collaborative 3D Printing project is a collaboration between Strategic System Programs (SSP), the Naval Postgraduate School (NPS), NAVFAC Headquarters Asset Management -Facilities Integrated Product Support (IPS) Program, and NAVFAC Engineering and Expeditionary Warfare Center (EXWC). The intent of the project was to investigate the endto-end process of transferring, receiving, manipulating, and printing a digital model into an additively manufactured component. Several digital models were exchanged, and the steps, barriers, workarounds, and results have been documented. As a process investigation, limited analysis was conducted on the actual quality of produced parts, however basic observations on printer settings, power consumption, economics, and material performance were made and documented. In addition to the original models sent for evaluation, several models sourced from online model exchanges and libraries were printed, and process and product lessons-learned were documented.EXWC has productively employed 3D printers in concept visualization and limited production prototyping for destructive testing applications. In 2015, EXWC printed over $50k worth of plastic, avoiding over $500k of traditional prototype fabrication costs. EXWC used two 3D printers for this investigation; a Stratasys Dimension SST 1200es, and a Lulzbot TAZ5. The Stratasys Dimension 1200es is an entry-level commercial-grade Fused Deposition Model (FDM) printer, costing approximately $35,000, and the Lulzbot ...