DETERMINING OPERATING LIFETIME OF LANDING WHEEL HUBS WITH PRD PORTABLE DIFFRACTOMETER

Transcription

1 Copyright JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume DETERMINING OPERATING LIFETIME OF LANDING WHEEL HUBS WITH PRD PORTABLE DIFFRACTOMETER A.V. Lutzau 1, B.N. Kodess 2, A.V. Kotelkin 1, S.A. Kononogov 2, D.B. Matveev 1, V. Mozalyov 1, and A.D. Zvonkov 1 1 MISIS, Moscow Institute of Steel and Alloys, Moscow, , Russia 2 Crystals Metrology Department, VNIIMS, Moscow, , Russia ABSTRACT A portable X-ray diffractometer with classic scheme of measurements (Sin 2 Ψ) was applied for the residual stress control. The example of residual stress determination in the landing wheel hubs with different service life (take-off-landing numbers) are presented. The assessment of the durability is based on the results of residual stress determination. INTRODUCTION Technologically important multicomponent materials used in modern constructions usually operate under conditions far from equilibrium and therefore may be highly sensitive to the external factors and conditions of previous heat and mechanical working. X-Ray nondestructive testing of products surface makes it possible to assess their durability (replacement life). Different semi-stationary and portable X-ray diffractometers [1-3] were designed to determine residual stresses directly under working conditions. To make the measurement procedure simpler two schemes are usually used: either the orthogonal incidence of the original beam when all the planes at the angles to surface less than the diffraction angles are not taken into account, or schemes realizing Ω-method in which the tilts of Bragg reflex at angle Ψ are simulated by tilt of normal to reflecting planes in Bragg reflex proper, which may also change the values determined by this methods. The classic measurement scheme of Sin 2 Ψ method [4] is realized in a used PRD diffractometer. The data on the changes of interplanar spacing are obtained from various tilts of diffraction plane, i.e. Bragg reflex turn around the line of its intersection with the product surface. The technique based on twostage determination of residual stress, operating and design rates of residual stress changes, mismatching factor for these rates was used to assess the replacement life of the landing wheel hubs. Figure 1. General view of PRD diffractometer A distinctive feature of the portable diffractometer PRD (Figure 1) used in the present studies is that its goniometer carries three low power air-cooled fine-focus X-ray tubes (2.4

2 This document was presented at the Denver X-ray Conference (DXC) on Applications of X-ray Analysis. Sponsored by the International Centre for Diffraction Data (ICDD). This document is provided by ICDD in cooperation with the authors and presenters of the DXC for the express purpose of educating the scientific community. All copyrights for the document are retained by ICDD. Usage is restricted for the purposes of education and scientific research. DXC Website ICDD Website -

3 Copyright JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume to 5.0 W), curve-shaped position-sensitive detector and focus-to-the-sample distance control. Total weight of XRPD does not exceed 20 kg (44 lbs). Its power source independence is achieved by inclusion of a compact 350W diesel generator. Usage of laptop-based control unit combined with short exposure time ( min) depending on material studied and monochromators used provides an ability to conduct real-time diagnostics procedures. The calibration and data reliability provide the set of Standard Reference Materials, CSRM, for diffraction method of measurements. In this paper we present the results of residual stress determination and analysis in the landing wheel hubs (Figure 2) with different service life (takeoff-landing numbers) using portable diffractometry Figure 2. View of a wheel hub [3]. RESULTS For residual stress measurements an X-ray tube with Cr target was operated at 25 Kv and 15 ma, Ψ angle values in Sin 2 Ψ method being 0, 15, 25 and 35 degrees. Time for data collection was 35 sec. for each Ψ angle (reflection from plane (311) for wheels). The measurement area used was about 10 mm 2. A new (not used) wheel (W 0 ) and two used wheels W 1 and W 2 were examined. According to the accepted practice all wheels had fuse units ( heat-witnesses ) for independent control of possible overheats. It should be noted that wheel W2 was tested after being subjected to extremely high loads as a result of which all heat-witnesses were found to be melted. Residual stresses in axial direction in surface zones of wheels lying at sections 1-3, (Figure 3) were obtained from a linear regression of deformation ε versus sin 2 Ψ as given by equations (1). ε = (d ψ -d 0 )/d 0 = - (σ 1 +σ 2 )µ/e + (1+µ)/E σ z (1) where d is the measured d-spacing, Ψ is the tilt angle, d 0 is the stress-free d-spacing, µ is the Poisson's ratio and E is Young's modulus.

4 Copyright JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume Section 3 Section 1 Section 2 Level 1 Level 2 Level 3 Figure 3. Schemе of measurements on the wheel surface Determination of operating lifetime. Based on the measurements performed the level of axial stress σ z0 = -340 MPa was obtained for the fresh wheel W 0 Table 1. Results of the residual stress determinations. Level Wheel 1 Wheel 2 σ z, МПа Assessment of residual resource. For each section the most weak point, i.e. zone with σ 2max was chosen for wheels. The change in residual stress in each section was determined as difference of residual stress in the first and second testing stage of maintenance (σ 2max - σ z0 ); σ max = (σ 2max - σ z0 ). Experimental rate of residual stress change V exp max during the service life determined as the number N of take-off-landings is calculated as V exp max = (σ 2max σ 0 ) / N. Maximum change in the residual stress level was determined as σ res des max =(1 0.9) σ σ des + σ 0. Design rate V des was calculated according to V des = σ res des max / R des. Mismatching factor K V for operating and design rates was determined from К V = V exp / V des. replacement life R o is equal

5 Copyright JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume to R o = R des / К V. Figure 4 schematically shows replacement life mismatching factor relation, while К V < 1 R o > R des, while К V > 1 R o < R des, and when К V = 1, R o = R des. σ, MPa σ 0,2 В σ 0,2 В-σ д К V >1 K V =1 K V <1 σ max Р э <Р п τ, hours Р э =Р п σ о Р э >Р п -σ 0,2 В Figure 4. Influence of mismatching factor for rates on replacement life. According to above procedure the calculation was performed for the landing wheel operating lifetime (Table 2).

6 Copyright JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume Table 2. Results of the replacement life calculation. Index Wheel W 1 Wheel W 2 σ exp max, MPa σ exp max, MPa N, number of take-offlandings V exp max, MPa/number of take-off-landings R des, number of take-offlandings V des, MPa/number of take-off-landings K V R o, number of take-offlandings The calculated operating lifetime for wheel W 1 used for 5740 take-off-landings was Thus the wheel can withstand about 9000 additional take-off-landings. Calculation of limiting operating lifetime for the second wheel W 2 (with melted-out heat witness) gives only 926 takeoff-landings. The relative error of calculation was about 2% (the real number of take-offlandings before removal from service was 942). CONCLUSION The analysis of pre-faulty state of particularly critical structures and constructions without disruption of their links is one of the main methods of nondestructive testing. Periodical testing of technical conditions based on the determination of stressed-deformed state of the material using portable diffractometry of new generation makes it possible to control the material state before its application, to promptly remove a construction unit from service prior the formation of cracks, and to prevent running the main crack and thus to prevent material destruction resulting in an emergency. The good agreement of real replacement life and those calculated using X-ray diffractometry has been demonstrated by the example of studying the landing wheel hubs.

7 Copyright JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume REFERENCES [1] Catalogue for LXaD and ixrd diffractometers < Proto Manufacturing Ltd, Ontario, Canada. [2] XSTRESS 3000 < X-Ray Stress Analyzer. AST/Stresstech Catalogue XR3000/Sep 799/TS-S. [3] Kodess B.N., Lutzau A.V., Kotelkin A.V., Zvonkov A.D., Matveev D.V., Surface. X- ray, Synchrotronic and Neutron Investigations. (Poverkhost`. Rentgenovskiye, Synkhrotronnye i neitronnye issledovaniya 2002, 9, (in Russian)) [4] Umansku Ya.S., Skakov Yu. A., Ivanov A.N., Crystallography, X-ray and Electron Microscopy, Metallurgy, Moscow, 1982, , (in Russian).