The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Michael B Prime - One of the best experts on this subject based on the ideXlab platform.
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beyond the streetlight effect a united future for relaxation and diffraction methods for Residual Stress Measurement
Advanced Materials Research, 2014Co-Authors: Michael B Prime, Michael L SteinzigAbstract:Residual Stress Measurement techniques can be categorized as either relaxation or diffraction methods. Practitioners often advocate a particular category and sometimes a specific technique (hole drilling, contour, XRD, neutron, etc) based on their experience or capability rather than using the best technique for the particular application. This paper considers some of the implications from applying this “drunkard’s search” or “streetlight” approach by examining examples where the critical Stress could be hidden from both relaxation and diffraction Measurements. A better approach to planning Residual Stress Measurements would begin with a detailed consideration of why the Stresses should be measured and how the results will be used. Only then can the most appropriate Measurement plan be developed. Since a single Measurement technique cannot reveal the full state of Stress, especially in challenging parts, the use of multiple Measurement types often provides the most useful information to customers.
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laser surface contouring and spline data smoothing for Residual Stress Measurement
Experimental Mechanics, 2004Co-Authors: Michael B Prime, Robert J Sebring, J M Edwards, D J Hughes, P J WebsterAbstract:We describe non-contact scanning with a confocal laser probe to measure surface contours for application to Residual Stress Measurement. (In the recently introduced contour method, a part is cut in two with a flat cut, and the part deforms by relaxation of the Residual Stresses. A cross-sectional map of Residual Stresses is then determined from Measurement of the contours of the cut surfaces.) The contour method using laser scanning is validated by comparing Measurements on a ferritic steel (BS 4360 grade 50D) weldment with neutron diffraction Measurements on an identical specimen. Compared to lower resolution touch probe techniques, laser surface-contouring allows more accurate Measurement of Residual Stresses and/or Measurement of smaller parts or parts with lower Stress levels. Furthermore, to take full advantage of improved spatial resolution of the laser Measurements, a method to smooth the surface contour data using bivariate splines is developed. In contrast to previous methods, the spline method objectively selects the amount of smoothing and estimates the uncertainties in the calculated Residual Stress map.
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Residual Stress Measurement by successive extension of a slot the crack compliance method
Applied Mechanics Reviews, 1999Co-Authors: Michael B PrimeAbstract:This article reviews the technical literature on the determination of a Residual Stress profile by successive extension of a slot and Measurement of the resulting strains or displacements. This technique is known variously in the literature as the crack compliance method, the successive cracking method, the slotting method, and a fracture mechanics based approach. The article briefly summarizes the chronological development of this method and then, to facilitate more detailed review, defines the components that make up the method. The theory section of the article first considers forward method solutions including fracture mechanics, finite element, analytical, and body force methods. Then it examines inverse solutions, including incremental inverses and series expansions. Next, the article reviews all experimental applications of the crack compliance method. Aspects reviewed include the specimen geometry and material, the details of making the slot, the deformation Measurement, and the theoretical solutions used to solve for Stress. Finally, the article makes a brief qualitative comparison between crack compliance and other Residual Stress Measurement methods. In many situations, the crack compliance method offers several advantages over other methods: improved resolution of Residual Stress variation with depth; the ability to measure both small and very large parts; Measurement of Stressmore » intensity factor caused by Residual Stress; Measurement of crack closure Stresses; increased sensitivity over other material removal methods; and the ability to measure non-crystalline materials. 77 refs.« less
Michael E. Fitzpatrick - One of the best experts on this subject based on the ideXlab platform.
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Surface preparation for Residual Stress Measurement of an accelerated corrosion tested welded marine steel
Corrosion Science, 2015Co-Authors: Bilal Ahmad, Michael E. FitzpatrickAbstract:Residual Stress Measurement is often required for the assessment of structural integrity of components. Measurement of Residual Stress in corrosion tested specimens is challenging owing to the difficulty of accessing the surface because of the rust layer. This study explored the potential methods for the surface preparation of an ultrasonically-peened and accelerated corrosion tested DH36 marine steel fillet welded specimen to ease the way for subsequent Residual Stress Measurement using neutron diffraction and the contour method. We find that hydroblasting introduces compressive Residual Stress at the surface that will alter the surface Stress to be measured.
L. Bertini - One of the best experts on this subject based on the ideXlab platform.
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Recent advances in the hole drilling method for Residual Stress Measurement
Journal of Materials Engineering and Performance, 1998Co-Authors: M. Beghini, L. BertiniAbstract:The main activities in the hole drilling Residual Stress Measurement technique recently developed at the University of Pisa are reviewed and presented. Particular attention was paid to developing tools for increasing the limits indicated by the presently applied standard procedures for Residual Stress evaluation. For Residual Stresses that were assumed to be uniform through-thickness, the effect of plasticity was numerically analyzed and results formed the basis for a procedure that allows an increase in the maximum measurable Residual Stress up to 0.9 of the material yield strength. For nonuniform through-thickness Residual Stress, accurate analytical influence functions are proposed by which arbitrary interpolation of the influence coefficients is avoided and all the experimentally obtained strains, with no regard to their number, can be used as input for Residual Stress evaluation.
Edoardo Bemporad - One of the best experts on this subject based on the ideXlab platform.
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High resolution Residual Stress Measurement on amorphous and crystalline plasma-sprayed single-splats
Surface and Coatings Technology, 2012Co-Authors: Marco Sebastiani, Giovanni Bolelli, Luca Lusvarghi, Partha Pratim Bandyopadhyay, Edoardo BemporadAbstract:Abstract Residual Stress was measured on plasma sprayed crystalline Ni Al, Al2O3 and amorphous Al2O3 TiO2 ZrO2 CeO2 single splats, by using an incremental focused ion beam (FIB) micron-scale ring-core method (IμRCM). Tensile Residual Stress exists in polycrystalline Ni Al splats, where the quenching Stress is only partially relaxed by edge curling and through-thickness yielding. Significant compressive Stress was observed for the amorphous Al2O3 TiO2 ZrO2 CeO2 splats, where viscous flow above the glass transition temperature completely relaxed the quenching Stresses without micro-cracking. Comparatively lower compressive Stress was measured on crystalline Al2O3 splats, where, in spite of extensive micro-cracking, not all of the tensile quenching Stress was relaxed. Using Stress data and micro-crack geometry, the intrinsic shear adhesion strength of Al2O3 splats was calculated, giving insights into the role of (sub)micron-scale phenomena on adhesion/cohesion of thermally sprayed coatings. The proposed Stress build-up mechanisms and relaxation phenomena are supported by a TEM microstructural analysis of the splats. The experimental methodology developed provided a unique way for the study of the Residual Stress build-up mechanisms in amorphous and crystalline single splats obtained by plasma spraying, and gave further insights into the actual micro-scale phenomena that give rise to adhesion and nano-mechanical behavior of thermally sprayed coatings. The proposed approach is also expected to find a wide range of applications in materials science and engineering, as it allows for the Residual Stress Measurement even on amorphous materials with micrometer spatial resolution.
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A New Methodology For In-Situ Residual Stress Measurement In MEMS Structures
2010Co-Authors: Marco Sebastiani, Edoardo Bemporad, G Melone, L Rizzi, Alexander M. KorsunskyAbstract:In this paper, a new approach is presented for local Residual Stress Measurement in MEMS structures. The newly proposed approach involves incremental focused ion beam (FIB) milling of annular trenches at material surface, combined with high resolution SEM imaging and Digital Image Correlation (DIC) analysis for the Measurement of the strain relief over the surface of the remaining central pillar. The proposed technique allows investigating the average Residual Stress on suspended micro‐structures, with a spatial resolution lower than 1 μm. Results are presented for Residual Stress Measurement on double clamped micro‐beams, whose layers are obtained by DC‐sputtering (PVD) deposition. Residual Stresses were also independently measured by the conventional curvature method (Stoney’s equation) on a similar homogeneous coating obtained by the same deposition parameters and a comparison and discussion of obtained results is performed.
Michael Smith - One of the best experts on this subject based on the ideXlab platform.
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the net task group 4 Residual Stress Measurement and analysis round robin on a three pass slot welded plate specimen
International Journal of Pressure Vessels and Piping, 2017Co-Authors: Michael Smith, Ann C Smith, Carsten Ohms, Robert C WimporyAbstract:Abstract Accurate prediction and Measurement of Residual Stresses in welds is an important part of assuring their short and long-term structural performance in high value, safety critical engineering components and structures. However, both Measurements and predictions of weld Residual Stresses often exhibit high levels of variability that are not widely appreciated. The mission of the European Network on Neutron Techniques Standardization for Structural Integrity (NeT) is to develop experimental and numerical techniques and standards for the reliable characterisation of Residual Stresses in structural welds. The NeT Task Group 4 project examined Residual Stresses in a three-pass slot-welded plate specimen fabricated from AISI 316L(N) austenitic stainless steel plate. Several nominally identical specimens were fabricated under closely controlled conditions, with detailed records kept of the manufacturing history, weld process parameters, transient temperatures during welding, and the resulting geometric distortions. Comprehensive Stress-strain material property characterisation was then undertaken, extending to the isothermal cyclic tests necessary to calibrate the mixed isotropic-kinematic material hardening models required for accurate weld Residual Stress prediction. Parallel Residual Stress Measurement and simulation round robins were performed by a large number of participants from around the world. Residual Stresses were measured using neutron and high energy synchrotron diffraction, surface X-ray diffraction, surface and deep hole drilling, the contour method, and ultrasonics. Neutron diffraction Measurements were made at eight different instruments. The diffraction Measurements database alone is large enough to generate reliable mean profiles, to identify clear outliers, and to establish that there is no statistically significant difference in the Residual Stress field in the specimens used for the non-destructive Measurements. NeT Task Group 4 gives a unique insight into the real-world variability of diffraction-based Residual Stress Measurements, and forms a reliable foundation against which to benchmark other Measurement methods. NeT Task Group 4 is also a unique test bed for the development and validation of weld Residual Stress simulation techniques in austenitic stainless steel. Its combination of extensive materials characterisation, accurately characterized welding temperature transients, and reliable Residual Stress and distortion Measurements is currently unrivalled. About thirty finite element simulations were submitted to the network over the course of the project, giving insights into the required accuracy of welding thermal solutions, the mechanical solution accuracy achievable using optimized material constitutive models, and the level of acceptable error in finite element Residual Stress simulation results for use in structural integrity assessments of high integrity engineering components.
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The NeT Task Group 6 Weld Residual Stress Measurement and Simulation Round Robin in Alloy 600/82
Volume 6B: Materials and Fabrication, 2016Co-Authors: Michael Smith, Ondrej Muránsky, Vasileios Akrivos, Jean AnglesAbstract:The mission of the NeT European collaborative network is to develop experimental and numerical techniques and standards for the reliable characterisation of Residual Stresses in structural welds. NeT achieves this by conducting parallel Measurement and prediction round robins on closely controlled and well characterised benchmark weldments. NeT TG6 follows on from the successful TG1 and TG4 benchmarks, which both examined welds in AISI 316L material. NeT TG6 examines an Alloy 600 plate containing a three pass “slot” weld made with Alloy 82 consumables. This paper describes the NeT TG6 project as a whole, and presents preliminary materials characterisation, Residual Stress Measurement, and Residual Stress modelling results.
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the net Residual Stress Measurement and modelling round robin on a single weld bead on plate specimen
International Journal of Pressure Vessels and Piping, 2009Co-Authors: Christopher E Truman, Michael SmithAbstract:The mission of the European Network on Neutron Techniques Standardization for Structural Integrity (NeT) is to develop experimental and numerical techniques and standards for the reliable characterisation of Residual Stresses in structural welds. NeT was established in 2002 by the European Union Joint Research Centre, and over 35 organisations from Europe and beyond are involved in the network. NeT operates on a contribution in kind basis from industrial, academic, and research facility partners. Each problem examined by NeT is tackled by creating a dedicated Task Group which undertakes Measurement and modelling studies and the interpretation of the results. Task Group 1 (TG1) was formed to examine the benchmark problem of a single weld bead laid down on the top surface of an austenitic steel plate. This weld geometry produces a strongly three-dimensional Residual Stress distribution, with similar characteristics to a weld repair, in a compact, portable specimen, which is amenable to Residual Stress Measurement using diverse methods. The single weld pass is relatively straightforward to model using finite element methods, and allows full moving heat source Residual Stress simulations to be performed in practical time scales. However, because the weld bead is laid onto a relatively thin plate, the predicted Stresses are very sensitive to key modelling assumptions such as total heat input and the thermal transient time history, making the bead-on-plate a challenging benchmark problem. Two parallel round robin activities were performed as part of TG1, covering Residual Stress Measurement and Residual Stress prediction. Four nominally identical bead-on-plate specimens were manufactured under closely controlled and documented conditions, and appropriate materials' characterisation testing was performed on both plate and weld material. Two protocol documents were written to define and control the experimental Residual Stress Measurement and finite element simulation round robins, respectively. The bead-on-plate specimens were then circulated to TG1 Measurement round robin participants to perform Residual Stress Measurements. In parallel, the finite element simulation protocol was circulated to TG1 simulation round robin participants to allow them to predict the transient welding temperature history and the weld Residual Stresses in advance of Measurements being available. The results from this initial round robin are referred to as Phase 1 results and form the basis of the technical papers contained within this special issue. It is noted that prior to the Phase 1 round robin, the weld fusion boundary profile was measured in test beads deposited at the same time and using the same welding conditions as the benchmark bead-on-plate specimens. The weld efficiency, , was not specified during the Phase 1 round robin. Analysts were expected to deduce the efficiency by matching both the fusion boundary position and transient temperatures during welding. However, after completion of Phase 1, two of the bead-on-plate specimens were destructively examined to confirm the weld fusion boundary geometry, and a number of finite element sensitivity analyses performed to confirm the importance of selected finite element solution variables. The insights gained from the round robin activities were then incorporated into a Phase 2 finite element simulation protocol. This reduced the number of free solution variables available to participants, and was focussed on examining those aspects of the problem not fully understood after completion of the first round robin. In particular, an efficiency of 75% was specified in the final Phase 2 version of the protocol. The Phase 2 simulation round robin is currently under way.