Joseph A. Wysocki

A System-Safety Process For By-Wire Automotive Systems

Steer-by-wire and other “by-wire” systems (as defined in this article) offer many passive and active safety advantages. To help ensure these advantages are achieved, a comprehensive system-safety process should be followed. Here we review standard elements of system safety processes that are widely applied in several industries and describe the main elements of our proposed analysis process for by-wire systems. The process steps include: 1) creating a program plan to act as a blueprint for the process, 2) performing a variety of hazard analysis and risk assessment tasks as specified in the program plan, 3) designing and verifying a set of hazard controls that help mitigate risk, and 4) summarizing the findings. Vehicle manufacturers and suppliers need to work together to create and follow such a process. A distinguishing feature of the process is the explicit linking of hazard controls to the hazards they cover, permitting coveragebased risk assessment.

Reductions in static fatigue of silica fibers by hermetic jacketing

The lifetime of stressed silica fibers is normally limited by moisture‐enhanced stress corrosion cracking known as static fatigue. We have developed a metal‐jacketing technique that provides a hermetic protection of the glass fiber surface. Fibers protected in this fashion appear to be immune to normal static fatigue effects. Lifetimes of stressed silica fibers with hermetic jackets have been observed to be more than five orders of magnitude longer than those of conventional plastic‐coated fibers.

Aging effects in bulk and fiber TlBr‐TlI

A study of optical aging in bulk and extruded fibers of thallium bromo‐iodide (TlBr‐TlI) is presented. A variety of techniques including secondary ion mass spectrometry (SIMS), powder neutron and x‐ray diffraction, infrared spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy are used to probe the chemical and structural properties of both pristine and aged material. High concentration levels of a hydrogen bearing impurity have been detected by SIMS and neutron scattering in aged TlBr‐TlI, and have been shown to be localized in the surface layers of fibers as well as bulk samples. We present EPR evidence which indicates that the hydrogen bearing impurity is water.

Optical and mechanical properties of fluorophosphate glasses for IR transmission

The use of fluorophosphate glasses for transmission in the mid IR and as optical fibers have been attempted for the first time. These materials are easy to prepare and are of relatively low cost. They can be attractively compared to either chalcogenide or heavy metal fluoride glasses for midIR transmission. Preparation techniques mechanical and optical properties are reported. 1 .

Aging Effects In Extruded Polycrystalline Thallium Bromo-Iodide Fibers

Optical aging in bulk and extruded fibers of thallium bromo-iodide is discussed. In particular, changes in optical attenuation with age are correlated with the physical properties of the material.

Sensors for process monitoring and control of polymer composites

Two sensors have been evaluated as components of a sensor suite to be used to characterize polymer composite cure; the evanescent wave visible light sensor (EWVLS) and the curing resin emission sensor (CuRE). These two sensors have been sued to characterize the cure of HEXCEL F650 BMI graphite fabric composite in a laminate process. Our results indicate that the EWVLS signature may be useful for process control and that the CuRE sensor provides important diagnostic information.

Reliability Of Optical Fibers For Missile Payout

General techniques for the quality control of long lengths of optical fiber for telecommunications applications have been developed during the past 10 years in concert with ongoing handling scenarios that involved cabled versions of the tested fiber. In the present work, we discuss the same quality control techniques, but apply the results to stand-alone fiber (primary or secondary buffer only). Furthermore, by modifying the normal quality control techniques, we have produced a stand-alone fiber that exhibits superior mechanical performance for missile payout applications when compared with standard telecommunications fiber. High quality optical fibers, which were produced to more exacting standards than long-haul telecommunications fibers, were subsequently exposed to high-stress bend tests along multikilometer lengths of the fiber. Mechanical failures during these tests could occur at stresses lower than the required 200 ksi proof test. The fracture surfaces for these failures were examined by normal fractographic techniques. These surfaces clearly showed that mechanical failure occurred at stresses below the proof stress. Furthermore, an appreciable number of these failures were accompanied by damage to the buffer, presumably preceding the mechanical failure. To correct the situation, we introduced changes in both the process and the testing for these fibers. During processing, the fibers were prepared with high quality silica substrate tubing, and all processing was carried out in a clean room environment. Proof testing subsequent to production was changed from a single test at 200 ksi to multiple testing at 100 ksi increments. Testing was further modified to include preinspection of the entire buffer surface for flaws of a serious enough nature to lead to mechanical damage to the underlying glass. The interaction of all of the previously noted changes helped to increase the reliability of the optical fiber for missile payout applications. Fractographs of the failures, proof test data, and identification of the buffer flaws, independent of fiber manufacturer or manufacturing process, will be discussed.