摘要:

This work investigates the performance of TiN and TiN/TiCN/TiN physical vapor deposition (PVD)-coated carbide tools in continuous turning of Ti-6Al-4V. Significant improvement in tool life was achieved when machining Ti-6Al-4V with both PVD-coated tools under the optimum cutting conditions. Notching at the depth of cut (DOC) was suppressed and flank wear, chipping and flaking of tool material on the rake face and/or at the nose of tools were the dominant failure modes. Tool life equations of the coated tools (when machining Ti-6Al-4V) were achieved by using a statistical regression analysis of the experimental data.

ISSN:1040-2004    

DOI:10.1080/10402009708983632

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The wear process of tribological systems in general meaning is strictly analyzed and discussed in this paper. The dynamic model for the wear process and the characteristic parameters of wear condition have been established. The performance of wear has been well monitored with the parameters. In this paper, the wear process in the failure stage is analyzed and the concept of a “wear marginal failure state” is proposed. It is proposed that the wear process on the failure condition is composed of a few “marginal failure states.” The wear condition of the tribological system of the diesel engine is monitored with spectrometric oil analysis, and the results of monitoring agree with the views proposed.Printed as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Lahaina, Hawaii, October 16–20, 1994

ISSN:1040-2004    

DOI:10.1080/10402009708983633

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A finite-element analysis (FEA) of a generic, dimensionally normalized inner race of an angular-contact ball bearing was performed under varying conditions of speed and the press (or interference) fit of the inner-race bore on a journal. The FEA results at the ball-race contact were used to derive an equation from which the radius of an equivalent cylindrical bearing race with the same or similar hoop stress was obtained. The radius of the equivalent cylinder was used to obtain a generalized closed-form approximation of the hoop stresses at the ball-inner race contact in an angular-contact ball bearing. A life analysis was performed on both a 45 and a 120 mm-bore, angular-contact ball bearing. The predicted lives with and without hoop stress were compared with experimental endurance results obtained at 12,000 and 25,000 rpm with the 120 mm-bore ball bearing. A life factor equation based on hoop stress is presented.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983634

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The dry sliding friction and wear behavior of ternary blends of polyetheretherketone (PEEK), polyetherimide (PET) and a thermotropic liquid crystalline polymer (TLCP) was investigated as a function of operating temperature. Friction and wear measurements were performed at selected temperatures within the range of 20° to 250° C. The specific systems investigated consisted of binary PEEK/PEI 85/15 and 70/30 isotropic thermoplastic matrices and a thermotropic liquid crystalline copolyester acting as the reinforcing phase. Although individually both PEEK/PEI matrices and the TLCP were seen to undergo catastrophic tribological failure at their respective glass transition temperatures (Tg), the ternary PEEK/PEI/TLCP blends were able to maintain sliding at temperatures well in excess of the Tgof their constituent phases. This synergistic behavior is explained in terms of TLCP reinforcement and PEEK cold-crystallization. In the ternary blends investigated, PEI exhibits miscibility with both PEEK and the TLCP, a mutually immiscible pair of polymers. In view of this, PEI was expected to enhance, via blend compatibilization, mechanical properties and, ultimately, tribological performance at high temperatures. Comparison of the tribological performance of PEEK/PEI/TLCP and PEEK/TLCP blends indicated otherwise, however. The sliding friction and wear mechanisms of the PEEK/PEI/TLCP blends are described in relation to their micro-structures. The effects of TLCP concentration and thermal transitions 07i mechanical properties and tribological performance are also discussed.Presented as a Society of Tribologlsts and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983635

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A closed, form of the average Reynolds equation is derived for non-Newtonian inelastic fluids with roughness effects taken into consideration. The derivation of flow factors is carried out by means of the perturbation approach with Green's function technique. A coordinate transformation is also utilized to make the equations similar with the Newtonian ones. The results of flow factors are expressed as functions of the Peklenik numbers and the standard deviations of roughness heights of each surface, as well as functions of the film thickness ratio Final manuscript approved November 10, 1995 and the flow behavior index of the power-law fluid of the lubrication film. One can find a critical value for Peklenik number (γcr) from the expressions of pressure flow factors. When γ > γcr(γ < γcr), the pressure flow factors increase as n increases (decreases). A modified Peklenik number is defined to reveal the interactions between roughness orientations and the non-Newtonian flow. Furthermore, an appropriate combination of fluid properties and surface characteristics will introduce a flow with desired roughness effects. Finally, the static performance of near-contact recording in magnetic head disk files is analyzed, and Ike effect of the flow behavior index of the power-law fluid on load capacity is found more significant than that of the roughness.

ISSN:1040-2004    

DOI:10.1080/10402009708983636

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The tribology of tri-pad sliders is investigated for hydrogenated and nitrogenated carbon overcoated disks. Friction and stiction during contact-start-stop testing are measured for both types of disks and the acoustic emission signal is studied to investigate the modes of slider vibrations during steady-state flying. Finite element simulations of the steady-state slider vibrations are performed and the results are compared with experimental observations. The optical fluorescence spectra are studied for the aluminum oxide and aluminum oxide-titanium-carbide (Al2O3TiC) portions of the slider. In addition, wear of the rear pad of a tri-pad slider is determined for fixed-track testing using nanoindentations.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983637

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two test series were conducted to study the effect of low speed and high load on the rolling-element fatigue life of 30 mm and 40 mm bore cylindrical roller bearings at inner race speeds from 19 to 3725 rpm and lubricant film parameter Lambda (λ) ratios from 0.03 to 1.2. Maximum Hertz stress ranged from 2.24 to 4.2 GPa (325 to 609 ksi). A total of 387 bearings were tested out of which 123 failed. Bearing life was directly related to transit contact lime (TT). As TT increases, life also increases. That is, bearings which run slower have longer lives in terms of bearing revolutions. A transit time life factor (LF) is suggested to be used with STLE life factors for slow moving industrial equipment roller bearings. Both TT and the total number of stress cycles affect the magnitude of measured surface residual stress induced during bearing operation. There was a relation observed between the decomposition of retained austenite and induced compressive residual stress measured on the inner-race surface.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983638

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

One of the most important problems of rotor-bearing systems, the stability problem, especially in the case that the rotor is in misaligned position in respect with the bearing, is examined in this paper. Lyapunov's direct method was preferred in this analysis instead of a classical eigenvalue analysis in order to obtain the stability conditions in the form of analytical, expressions.

ISSN:1040-2004    

DOI:10.1080/10402009708983639

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The transient response of a point-mass rotor supported in turbulent flow, externally pressurized fluid film bearings is presented. The equations of motion are solved numerically with local linearization at each integration time step. The bearing reaction forces are calculated from the numerical solution of unsteady bulk-flow equations including fluid inertia, turbulence, variable fluid properties and thermal energy transport. Examples for the transient response of damper seals and hydrostatic bearings under a variety of external loads are presented. Transient responses based on an approximate model which uses constant rotordynamic force coefficients are also included and shown to compare well with the full nonlinear responses. The nonlinear model needs small time steps with large execution times, while the simple linear model provides reliable results in a minute fraction of time.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983640

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Seventy-percent straight-rail, taper-flat sliders were made from A12O3-TiC, Mn-Zn ferrite, SiC, Si3N4and ZrO2and tested, on lubricated thin-film disks. The tests involved low speed (0.44 m/s) continuous contact drag testing at a fixed radius for a maximum of one. million revolutions or to disk failure. SiC did not cause the disk media, to fail, even, out to five million revolutions, and the friction force had. consistently low modulation throughout the test. Si3N4did not cause any disk failures but exhibited higher friction force with more modulation. A2O3-TiC, Mn-Zn ferrite and ZrO2exhibited high failure, rates (>50%), even though the initial friction forces were. low. The failure rates of these ceramics can be explained by the catalytic activity of Al2O3, TiC, Fe2O2and ZrO2on the degradation of the disk lubricant. Another explanation is the localized surface oxidation of SiC and Si3N4sliders resulted, in a softer slider material exhibiting more wear, leading to higher contact area and lower contact stresses at the slider/disk interface.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983641

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor