Robert B. Mason

Update on alternatives for cadmium coatings on military electrical connectors

Summary The most promising candidate coating processes to replace cadmium and hexavalent chromium in electrical connector applications are technologies that are already being used on electrical connectors to some extent, or demonstrate both considerable promise for the application and sufficient maturity. These include: • Electroplated aluminum (AlumiPlate®) • Electroplated alkaline zinc-nickel (5–15% nickel in the deposit) • Electroplated tin-zinc (at least 20% zinc in the deposit) Future efforts will focus on these three most promising candidates. In addition, to support efforts being undertaken by electrical connector manufacturers, two EN-based technologies, both incorporating occluded particles, will also be evaluated. Coatings with both CCCs and TCPs will be considered, as available, and cadmium with CCC will be used as the control. The most promising candidate coating processes from emerging alternatives were also identified. These are technologies that show promise for electrical connector applications, but require further development for the electrical connectors employed by TARDEC. These include: • Alloys deposited from ionic liquids • Magnetron sputtered aluminum alloys • Tin-indium alloys Future efforts may consider these candidates as the technology matures and becomes more feasible for electrical connectors.

Alternatives to dichromate sealer in anodizing operations

Abstract Ogden Air Logistics Center (OO-ALC) is the primary facility within the United States Air Force for maintaining and overhauling aircraft landing gear. Aluminum landing gear components are anodized at OO-ALC to provide enhanced corrosion resistance, paint adhesion, and wear resistance; a sodium dichromate sealing operation usually completes the anodizing process. During sealing, the pores of the anodized (oxide) layer are hydrated, which fills the pores and provides improved corrosion resistance. However, this sealer contains hexavalent chromium, which is listed on the Environmental Protection Agencys list of industrial toxic chemicals that are targeted for voluntary reduction or elimination. The specification that outlines the sodium dichromate sealing process delineates three alternative processes that are approved for use: 1) boiling de-ionized water, 2) cobalt acetate, and 3) nickel acetate. While some research to support the use of these and other sealing processes has been gathered under past efforts, additional work must be conducted to fully integrate non-chromate sealers into OO-ALCs anodizing operations. To meet this need, the Air Force Research Laboratory tasked Concurrent Technologies Corporation to identify viable alternatives to the sodium dichromate sealer, conduct testing on these alternatives, and recommend the most promising sealer(s) for implementation based on the test results. This paper will describe the requirements for anodizing and sealing operations within OO-ALC, as well as the sealing technologies that are available and a path forward to demonstrate/validate the most promising alternatives for the specific needs and applications of OO-ALC.

Guidelines for reliability testing of microelectromechanical systems in military applications

Micro electromechanical systems (MEMS) and microsystems technologies are seeing increased consideration for use in military applications. Assets ranging from aircraft and communications to munitions may soon employ MEMS. In all cases, MEMS devices must perform their required functions for the duration of the equipments mission profile. Long-term performance in a given scenario can be assured through an understanding of the predominant MEMS failure modes. Once the failure modes have been identified, standardized tests will be developed and conducted on representative devices to detect the potential for these failures. Failure mechanisms for MEMS devices in severe environments may include wear and stiction. While corrosion is not usually a concern for commercial MEMS devices, as they are made primarily of silicon, other materials, including metallics, are being considered for MEMS to provide enhanced robustness in military applications. When these materials are exposed to aggressive military environments, corrosion may become a concern. Corrosion of metallic packaging and interconnect materials may also present issues for overall performance. Considering these corrosion and degradation issues, there is a need to implement standardized tests and requirements to ensure adequate long-term performance of MEMS devices in fielded and emerging military systems. To this end, Concurrent Technologies Corporation has been tasked by the U.S. Army to initiate efforts to standardize test methods that have been developed under previous activities. This paper presents an overview of the MEMS activities under the standardization effort and the MEMS reliability test guidelines that have been drafted as a first phase of this effort.

Radiographic Study of Humeral Stem in Shoulder Arthroplasty After Lesser Tuberosity Osteotomy or Subscapularis Tenotomy

Lesser tuberosity osteotomy (LTO) and subscapularis tenotomy (ST) are used for takedown of the subscapularis during shoulder arthroplasty. LTO offers the theoretical but unproven benefit of improved healing and function of the subscapularis. However, humeral stem subsidence and loosening may be greater when osteotomy is performed, which may compromise functional outcomes. Our hypothesis is that no difference in proximal collar press-fit humeral stem subsidence or loosening exists, with no impairment of functional outcomes using the LTO technique. Radiographs of 39 shoulders from 35 patients who underwent shoulder arthroplasty with a minimum of 1 year of radiographic follow-up were included in the study cohort. All patients received the same press-fit implant (Bigliani-Flatow; Zimmer Biomet). We collected data including demographic information; radiographic measurements, including humeral-acromial distance (HAD); subsidence; subluxation index; the presence of lucent lines >2 mm; and functional outcome scores using the Western Ontario Osteoarthritis of the Shoulder Index, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, and the Constant score. Subsidence was 2.8 ± 3.1 mm for LTO vs 2.5 ± 3.1 mm for ST (P = .72). HAD did not differ between the LTO and ST groups preoperatively (9.5 ± 2.4 mm vs 10.9 ± 2.7 mm, P = .11). The first postoperative and final follow-up films for HAD for the LTO and ST groups showed a statistically significant difference (first postoperative film, 11.9 ± 3.7 mm vs 15.9 ± 4.5 mm, P = .005; final follow-up film, 11.8 ± 3.2 mm vs 14.5 ± 3.9 mm, P = .03). We identified no differences in subsidence, lucent lines >2 mm, posterior subluxation, and Constant, and DASH functional outcome scores for patients undergoing total shoulder arthroplasty via the LTO vs ST techniques with the same proximal collar press-fit humeral stem at short-term follow-up.

Development of Reliability Test Guidelines for Microelectromechanical Systems in Military Applications

Micro-electromechanical systems (MEMS) and microsystems technologies are being increasingly considered for use in military vehicles and weapon systems. Assets ranging from aircraft and communications to munitions may soon incorporate MEMS technologies. These MEMS devices must perform their required functions for the duration of the equipments mission profile. Long-term performance in a given scenario can be assured through an understanding of the predominant MEMS failure modes. Once the failure modes have been identified, standardized tests can then be developed and conducted on representative devices to detect the potential for these failures. However, there is a need to implement standardized tests and requirements to ensure adequate long-term performance of MEMS devices in fielded and emerging military systems. To this end, Concurrent Technologies Corporation has been tasked by the U.S. Army to initiate efforts to standardize test methods that have been developed under previous activities. This paper presents an overview of the MEMS activities under the MEMS reliability assessment program and describes the MEMS reliability test guidelines that are being developed under this effort.

SENSOR REQUIREMENTS TO MONITOR THE REAL TIME PERFORMANCE OF A GAS TURBINE ENGINE UNDERGOING CO MPRESSOR BLADE EROSI ON

This investigation of sensor technologies needed for measuring the real time performance of gas turbine engines was motivated by the fact that under certain severe environmental operating conditions, such a s a sand storm, a helicopter engine ingests particulate matter. Exposure to such environments leads to compressor component erosion, which decreases compressor efficiency. This decrease in compressor efficiency subsequently results in a decrease in deliv ered shaft horsepower, which can be reduced to the point where there is an inadequate amount of power delivered to the helicopter main rotor to produce lift for takeoff and sustained flight. Although real time engine health monitoring systems are currently available and installed aboard some aircraft, none have the capability to monitor sand ingestion and provide the pilot with a display of remaining engine power margin based upon compressor blade damage incurred by such ingestion. In order to better und erstand the physical parameters that an onboard sensor suite would have to measure, work focused on relating gas turbine engine particulate ingestion to the engine remaining power margin. The engine remaining power margin, which can be utilized by the pil ot to effectively assess engine health, can be displayed in real -time. The information resulting from this work provides an understanding of what type of data a gas turbine engine contaminant ingestion sensor (GTECIS) suite would be expected to provide, including particle size, particle number density, and volumetric flow rate of air. As a result of a better understanding of the data that this type of sensor suite would have to measure, an effort was initiated to establish a set of physical and operationa l parameters that the sensors would have to meet in order to provide the data required for real time engine health monitoring in the presence of compressor blade erosion. The established physical and operational parameters can be used to benchmark sensors during laboratory and subsequent field validation testing. To begin with, a Venn diagram was constructed that showed the interrelationships among the physical measurements desired and the operational sensor requirements, and which illustrated the param eters necessary to qualify a sensor suite as a suitable choice for use as a real time engine health monitoring system. This paper will provide quantitative parameters relating to the Venn diagram for a variety of operational environments and engine types and will provide the requirements for a GTECIS.

Update on the Developments of the SAE J2334 Laboratory Cyclic Corrosion Test

The Corrosion Task Force of the Automotive/Steel Partnership has developed the SAE J2334 cyclic laboratory test for evaluating the cosmetic corrosion resistance of auto body steel sheet. [Ref. 1] Since the publishing of this test in 1997, further work has improved the precision of J2334. In this paper, the results of this work along with the revisions to the J2334 test will be discussed.