摘要:

An extraction replica method is described by means of which thin solid film on worn surfaces may be removed from selected areas for examination in the transmission electron microscope. A scratch or several scratches are made on the worn surface with a pointed stylus. Displaced or loosened fragments of material are removed by means of a plastic extraction replica. After subsequent processing of the replica, sufficiently thin fragments can then be examined by transmission electron microscopy, electron diffraction, and the allied methods of x-ray energy dispersive analysis and electron energy loss spectroscopy. The latter two methods permit the determination of chemical composition which can then be correlated with crystallographic and microstructural observations. Application of the scratch extraction replica method is illustrated with examples of films removed from worn 52100 steel surfaces.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981598

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Core yielding has been identified as a major source of premature failure in case-hardened ball and roller bearings. Design criteria have been established and accepted to prevent core-crushing failures in these bearings. Vendors have made substantial advances in understanding core yielding and in designing to prevent failures. However, the user is in need of a simplified, straightforward method of assuring himself that core failure will not occur. A simplified computational method is constructed from the established design criteria and presented. With minimal geometry information and a case-core specification, the core-yield limit, in terms of maximum allowable element load, can be computed for a given bearing. Numerous hand-calculation methods for arriving at maximum element loads from applied loads exist. In this manner, core-yield adequacy can be easily verified. A numerical example is presented.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981599

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Metallurgical and mechanical changes occurring during high-speed rubbing of Ti-6Al-4V blade specimens against an abradable, nichrome aircraft engine seal material were studied using optical microscopy, electron microscopy, and microhardness techniques. Evidence of temperatures above the beta transus of Ti-6Al-4V (1000°C) and of thermal hardening was found on blade tips that exhibited undesirable abrading characteristics resulting in high forces of interaction, high temperatures, and smearing. The material within the layer of the corresponding seals was found to be work-hardened to a depth of about 0.1 mm and showed evidence of densification extending to a depth of about 0.5 mm below the rubbed surface. Wear particles produced by rub interactions that generated cleanly abraded seal surfaces were found to be several times larger than those produced during interactions which showed evidence of surface smearing and seal densification.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981600

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Annular pressure seals act as powerful hydrostatic bearings and influence the dynamic characteristics of rotating machinery. This work, using the existing concentric seal theories, provides a simple approximate method for calculation of both seal leakage and the dynamic coefficients for short seals with large eccentricity and/or misalignment of the shaft. Rotation and surface roughness effects are included for leakage and dynamic force calculation. The leakage calculations for both laminar and turbulent flow are compared with experimental results. The dynamic coefficients are compared with analytical results. Excellent agreement between the present work and published results have been observed up to the eccentricity ratio of 0.8.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981601

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper presents the results of a study combining experimental and analytical techniques to characterize the role played by near-surface inclusions in the pitting of gears. Experimental test results pertaining to failures induced by inclusions are presented in photomicrographs and discussed in terms of metallurgical considerations. A model is proposed to explain the phenomena observed in roller test specimens in terms of theoretical subsurface stress distributions that include the effect of inclusions. The model is shown to be qualitatively consistent with test results concerning microstructural alterations and microcrack propagation behavior. Finally, practical considerations pertaining to material selection and further research in this area are discussed in light of the present results.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981602

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Despite the long-time acceptance of melt-lubrication of rotating bands by the Army scientific community, all of the evidence supporting this conclusion has not been collected and, indeed, some has never been published. The melt-lubrication of rotating bands is very important because then sliding is lubricated and friction and wear is determined by the characteristics of the molten film and the amount of melting at the sliding interface. Melt-lubrication results in much less resistance and much less severe wear than would otherwise be the case. Both friction and wear and metallographic evidence from examination of recovered projectiles and fired cannon tubes show that melt-lubrication of projectiles sliding on a gun bore has, in fact, occurred. Melt-lubrication is caused by the production of a thin surface film of molten rotating band material. Such a molten surface layer can also be produced on the surface of materials other than copper alloys contacting the bore at high surface loads and velocities.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981603

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Critical components in coal-liquefaction system, like letdown value trim and valve seats, are subject to severe wear from the erosive coal slurries. The slurry-erosion behavior of candidate valve trim and seat materials, like WC-Co cermets and hard ceramics (SiC, B4C), was studied by measuring the wear rates in a slurry-jet impingement test and by examining the wear craters in a scanning electron microscope. The erosion rates of the WC-Co cermets decreased monotonically with decreasing cobalt volume fraction in the range 36.9 to 5.1 Percent. The mechanism of erosion changed systematically from one involving preferential removal of binder and release of undamaged WC grains in high-binder alloys to a uniform transgranular wear of WC grains in the low-binder alloys. A sintered grade of SiC and a hot-pressed grade of B4C showed wear rates less than those of the cermets.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981604

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Titanium implantation has been shown to produce superior tribological surfaces on hardened steels. Low-friction (μ = 0.3), wear-resistant surfaces have been formed on polished and abraded (600 and 120 grit Sic) AISI-52100 steel by appropriate implantation conditions. On flat surfaces implanted at normal incidence, the required fluence of Ti ions increases from 2 to 5 × 1017Ti/cm2as the energy increases from 50 to 200 KeV/ion. On curved surfaces (e.g., bearings, cutting tools, etc.) higher fluences are necessary due to effects of implantation at angles off normal incidence (i.e. the combined effects of higher sputtering rates, decreased range, and changes in the carburization process associated with duty cycles). Optimal benefits of Ti implantation are associated with the formation of a modestly thick (>20nm) fully carburized layer.Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

ISSN:0569-8197    

DOI:10.1080/05698198508981605

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor