Experimental Determination of Residual Stresses
Stress determination on a base of advanced interferometric measurements of deformation response induced by local mechanical influence
Tech Area / Field
- SAT-AER/Aeronautics/Space, Aircraft and Surface Transportation
- INS-MEA/Measuring Instruments/Instrumentation
- PHY-OPL/Optics and Lasers/Physics
8 Project completed
Senior Project Manager
Kulikov G G
Central Aerodynamic Institute, Russia, Moscow reg., Zhukovsky
- Universität Stuttgart / Institut fuer Technische Optik, Germany, Stuttgart\nDeutsches Zentrum für Luft- und Raumfahrt e.V. / Institute of Materials Research, Germany, Köln
Project summaryIntroduction. The main project objective is a development of sophisticated methods for stress determination, metrological parameters of which considerably exceed analogous characteristics of known techniques, especially for curved cylindrical shells and tubes. Remarkable feature of the technique involved resides in a capability of recognizing a stress state type proceeding from whole-field initial experimental data. This fact is an essential condition of reliable characterization of both residual and actual stresses. The main research directions include investigations of residual stresses near welded joints and their influence on fatigue crack behavior. Residual stresses, which often appear during different stages of the manufacturing process of structural elements or their operating, may exert a considerably negative influence on both the structure's static strength and fatigue life-time. From the other hand, an accurate taking into account actual residual stress distributions often reveals new beneficial operating capabilities for some types of structural units. Residual stress evaluation represents by itself the most sophisticated problem in both a mechanical formulation and modelling predictions. The point is that residual stresses are inherent in most manufacturing processes involving material deformation, heat treatment, machining or processing operations that transform the shape or change the properties of a material. In many situations both a source and history of residual stress arising can not be established within the accuracy that is large enough for reliable numerical simulation. Such a simulation has to be based on prescribing a wide set of unknown parameters, which can not be characterized without doubts. Thus a problem of incorporating residual stress analysis into design, which is of the great importance in aerospace, nuclear and other critical engineering industries, rigorously demands involving experimental information.
Expected results and their applications. The main project results are related to both the stage of applied research and further development of created techniques. Applied research are directed toward a high-accurate characterization of both residual and actual stress components. All techniques to be developed are oriented on obtaining results, which are essential for a design and strength analysis of welded joints but can not be reliably established without solid experimental foundations. These techniques can be supported with patents thus representing a product that is capable of promoting in research institutions related to aerospace, nuclear, gas/oil, and other critical industries:
- Universal technique for reliable determination of both membrane and bending residual stress components in thin-walled structures by means of inverse problem solution proceeding from data of both two-side and eventually one-side measurements near drilled small hole. Established approach is of both metrological and applied importance, especially for investigations of residual stress fields in advanced aircraft structures of redundant type.
- Advanced high-accurate technique for residual stresses determination in curved both thin-walled shells and thick-walled tubes, accuracy and reliability parameters of which can not be achieved by any other destructive or non-destructive methods. The technique to be developed and possible results of its implementing are of great both scientific and applied importance because there is a deficiency of reliable information related to residual stress distributions near welds in curved shells and tubes.
- Advanced method for an evaluation of values of fracture mechanics parameters based on drilling small holes at the crack tip proximity and whole-field interferometric measurement of required deformation parameters. The technique is mainly directed toward studies, which are essential for describing a process of fatigue crack propagation in residual stress fields inherent in aircraft structures.
- Non-destructive technique for stress determination by combining the ball indentation method and whole-field displacement measurements. Metrological parameters of this unique method are high enough for reliable engineering estimations of both residual and actual stresses in thick-walled structures. There are two ways of further development of the created techniques, which can be formulated as the following project results:
- Obtaining reference set of initial residual stress distributions, which are inherent in typical welded joints of aluminium thin-walled structural elements at different stages of their operating. The second fragment of the catalogue includes information related to an influence of residual stress fields of different type on crack initiation and propagation. These data are of great importance for a process of substituting routine pin and rivet joints traditionally used in structural elements with advanced welded joints. There are good chances for a wide promotion of main results obtained in both research and industrial applications in the field of aerospace engineering.
- Design and manufacturing a prototype of the portable device that is capable of reliable stress evaluating on a base of both the hole drilling and ball indentation method. The device is founded upon digital speckle pattern interferometer and can be used for a fast inspection of various structures inherent in aerospace, nuclear and other critical industries. Main scientific essence of the project resides in the following project result:
- A manuscript of the book titled “Residual stresses determination on a base of whole-field interferometric measurements” will be prepared during a short period after a project finishing. The book preface and content, which are developed in detail together with collaborators Prof. W. Osten and Dr. H. Doeker, are attached to the project description. It is assumed that a book volume will be not less than 500 double-spaced printed pages with 200 figures. The book is mainly aimed at researches and engineers whose field of expertise is connected with experimental determination of residual stresses in metallic materials. It may be also useful for specialists in computer-aided stress analysis and design of welded joints. This book can serve as a guide to post-graduates and students in understanding the problems related to advanced analysis of residual stresses on a base of holographic and speckle-interferometry data.
Technical approach and methodology. The project includes four streamlines, which mainly coincide with the first four project results. Most of techniques, on which the project is founded upon, have been developed and have to be developed by the authors of the project. All these techniques correspond, as minimum, to the current state of the art. Some of them are of unique character. Detailed information related to approaches used for reaching the project objectives is contained in the following works:
- Shchepinov V.P., Pisarev V.S. Strain and Stress Analysis by Holographic and Speckle Interferometry. Chichester: John Wiley, 1996.
- Pisarev V.S., Dzuba A.S., Grigoriev V.D., Chumak S.V. Reference fringe patterns as effective tool for local strain analysis based on holographic interferometry data. In: Juptner W., Osten W., Editors. Fringe 2001. Proceeding of the 4th Int. Workshop on Automatic Processing of Fringe Patterns. Paris: Elsevier, 2001: 475-488.
- Pisarev V.S., Balalov V.V., Aistov V.S., Bondarenko M.M., Yustus M.G. Reflection hologram interferometry combined with hole drilling technique as an effective tool for residual stresses fields investigation in thin-walled structures. Optics & Lasers in Engineering. 2001; 36(6): 551-597.
- Pisarev V.S., Balalov V.V., Aistov V.S., Bondarenko M.M., Chumak S.V., Grigoriev V.D., Yustus M.G. Metrological justification of reflection hologram interferometry with respect to residual stresses determination by means of blind hole drilling. Optics & Lasers in Engineering, 2004; 41(2): 353-410.
- Pisarev V.S., Balalov V.V. A role of fringe pattern catalogue in the course of interferometrically based determination of residual stresses by the hole-drilling method. Optics & Lasers in Engineering, 2004; 41(2): 411-462.
- Pisarev V.S., V.V. Balalov V.V., Bondarenko M.M. Classification of holographic fringe patterns inherent in through hole drilling in residual stress field. Optics & Lasers in Engineering, 2004; 42(6): 673-702.
- Pisarev V.S., V.D. Grigoriev V.D., Balalov V.V., Chumak S.V. Residual stresses deriving from holographic interferometry data on a base of inverse problem solution. Optics & Lasers in Engineering, 2004; 42(6): 703-726.
- Razumovsky I.A., Medvedev M.V., Fomin A.V. Methods for investigations inhomogeneous residual stresses fields. In book: Handbook of Residual Stress and Deformation of Steel /Ed. G.Totten, M.Howes, T. Unoue. ASM International, USA, 2002, P. 125-138.
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