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The question of how the static strength of angle-plied nylon cord-reinforced rubber composites simulating aircraft tire carcass is affected by damage accumulation or materials degradation was examined in this study. Upon cyclic loading at 1 Hz, residual tensile strength was gradually lowered with the progression of fatigue damage. The degradation of the residual strength became more drastic toward the end of the fatigue life because of worsening delamination. In contrast, the residual strength after cyclic loading of 10 Hz exhibited a rapid decrease at the beginning of the fatigue life, presumably due to thermal degradation, and then remained virtually constant throughout the life. Acoustic emission (AE) activities were monitored to assess the extent of damage and to explore a possibility of indirect monitoring of residual strength of composites.

This paper presents follow-on material and conclusions to a previously published paper that presented work to develop and validate life prediction models for SiC device packaging [ 1 ]. The first step in this work was to determine the most probable failure modes in the device packaging. After determining the expected dominant failure modes of a SiC semiconductor packaging, appropriate models were identified and applied to the packaging in order to track remaining useful life. Once failure modeling was completed, the life prediction models were validated. Validation consisted of accelerated life testing designed to stress specific parts of the device package so as to stimulate the desired failure mechanism. This paper will review the three testing methodologies designed to excite the three dominant failure mechanisms in the electronic packaging. These tests can be broken into two types of general tests: power cycling and high temperature reverse bias testing (HTRB).

The intrinsic wear behavior of tire tread materials bonded to carcass plies was examined under static footprint load and static axial pretension. Relying on a specially designed test apparatus, the abrasion action was induced with constantly changing directions and cyclic change of sliding speed. A series of wear tests was performed for parametric studies. The morphology of resulting wear surfaces was examined to understand wear mechanisms. The wear process of tire tread materials consisted of a mechanical mode of abrasion when sliding speed was below a critical level. For this range of sliding speed, the extent of tread wear was found to be simply dependent on the cumulative number of abrading head revolution which reflects the total sliding distance. The relationship between the amount of wear and cumulative number of abrading head revolution deviated from linearity when the rotational frequency of abrading head reached a critical level.

The use of aluminum is rapidly gaining acceptance for structural applications in the automotive industry. While laser beam welding offers many advantages for joining of aluminum alloys, it also possess certain inherent characteristics that differentiates laser beam welding of aluminum alloys from ferrous materials. These characteristics include aluminum's high reflectivity, large differences in vapor pressure between aluminum and many of its alloying constituents, and relatively low surface tension and viscosity in the molten state. This paper addresses process requirements for effective laser beam welding of aluminum alloys designed primarily for automotive applications and characterization of welded joints commonly used in the automotive industry.

The effect of minimum stress on the fatigue life has been assessed for an angle-plied nylon cord-reinforced elastomer composite which represents the bias aircraft tire carcass. The S-N curves were established under constant minimum stress rather than constant R-ratio. In this manner, all data points in each S-N curve could be associated with the same level of creep stress. Composite laminate specimens exhibited a normal failure sequence of fiber-matrix debonding developing into the delamination under cyclic tension. A trend of longer fatigue life of the composite was clearly observed at a given stress amplitude with a higher level of minimum stress. The use of a higher level of minimum stress also caused the increase of the fatigue endurance limit of the composite. The trend of longer fatigue life with a higher level of minimum stress stems from the fact that the stress and strain are not linearly related to each other.

The advent of stainless steel automotive exhaust systems presents a significant opportunity for powder metallurgy (P/M) parts and the inherent economic advantages of this near net shape metalworking technology. A study was performed to determine the viability of ferritic P/M stainless steel parts for exhaust applications such as coupling flanges and hot exhaust gas oxygen sensor (HEGOS) bosses. In order to help achieve the automotive industry's stated goal of extending the functional life of exhaust components while remaining competitive, the authors developed a program to develop a database of the mechanical properties and performance characteristics of several grades of P/M stainless steel. Among the data generated and analyzed for these ferritic alloy systems are room temperature, tensile stress-strain curves, fatigue and endurance properties, hardness levels, and corrosion resistance.

Delivery of a lubricant as a vapor mixed with a carrier gas provides a method of controlling the delivery rate of the lubricant. Temperatures in the range of 370 to 800 C are high enough to produce a lubricating film from tricresyl phosphate [TCP] vapor delivered in nitrogen as a carrier gas. The solid film lubricant formed by this delivery system provides excellent lubrication for a four-ball wear tester run at 370 °C. Deposit rates are compared for TCP vapor delivered lubrication over a temperature range using stainless steel and quartz surfaces. The deposit rate is sensitive to TCP concentration in the carrier gas. The deposit rates of the TCP decomposition products versus time are reported. Having been demonstrated in laboratory tests, the Vapor Phase [VP] concept is being pursued for hot section lubrication of the advanced (low heat rejection) diesel engines.

A multi-axial dynamic test instrument was designed to perform wear testing of actual aircraft tires as well as tread/carcass composite specimens under laboratory loading conditions which simulate the elements of take-off, landing and taxiing operations. The wear tester consists of a self-spinning abrading head, mounted on the actuator of a servo-hydraulic test system, which faces either (1) the tread surface of a composite specimen clamped by a horizontal stretch frame or (2) the tread region of actual inflated tires. The test concept has been partially proven in the case of tread/carcass composite specimens by building a proto-type test apparatus and operating it successfully. In the current test set-up, the specimen is subjected to static tension to simulate a circumferential load in the tire footprint and the tread surface is in periodic contact with an abrading head under a specific level of pressure.