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Tribology Lubricants and Lubrication 2012 Part 3

Tham khảo tài liệu 'tribology lubricants and lubrication 2012 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 42 Tribology - Lubricants and Lubrication 1 S2 i S1 -V 2 E 1 E 4 into Eq. 2 ends up with the following expression 1 _ p V 2S2ơp sin2 V S1 Ơ1 ơ2 5 For hardened steel isotropic grain distribution is assumed. The measurement of seven specimen tilt angles V from -45 to 45 symmetric about V o in equidistant sin2v steps is sufficient to reliably derive the desired ơp value from the slope of the straight line fitted to the data of a Dp V or gp V plot against sin2v for constant p Nierlich Gegner 2008 . High accuracy is already achieved by replacing Do with the experimental Dp V at V o Voskamp 1996 . Recommendations for the X-ray elastic constants of the relevant steel microstructure are given in the literature Hauk Wolfstieg 1976 Macherauch 1966 . For the XRD analyses reported in the present chapter 1 S2 5.811x10-6 MPa-1 is applied. 3.2.3 Two stage diffraction line analysis and peak maximum method Besides X-ray intensity gain in the beam path the second major task of rapid macro residual stress measurement is thus an efficient routine for the involved line shift evaluations. Accelerated determination of the diffraction peak position 29 is achieved by an automated self-adjusting analysis technique tailored to the a-Fe 211 interference. The method is explained by means of Figure 8 Fig. 8. Illustration of the self-developed peak finding procedure with a martensite diffraction reflex of full width at half maximum FWHM line breadth of 7.28 The pre-measurement at reduced counting statistics across the indicated fixed angular range of 5 provides the peak maximum with an error of 0.2 . This rough localization suffices to define appropriate symmetric evaluation points in an interval of 3 around the identified center for the subsequent highly accurate pulse controlled main run. The peak position is deduced from a fitting polynomial regression. A significant additional saving in acquisition time of 60 compared to the standard procedure is achieved by this skillful analysis .