Browsing by Author "Hosseinzadeh, F"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- ItemThe incremental contour method using asymmetric stiffness cuts(Elsevier, 2021-01-01) Achouri, A; Hosseinzadeh, F; Bouchard, PJ; Paddea, S; Muránsky, OAn incremental Contour Method (iCM) of residual stress measurement is proposed where residual stresses in the body of interest are sequentially reduced by successive contour cuts and the risk of stress re-distribution plasticity is mitigated or eliminated. The cutting-induced plasticity is known to cause significant inaccuracies when trying to measure the near-yield residual stresses using a conventional single cut contour method. The iCM procedure implements a new displacement data processing approach for the general case of sectioning at an arbitrary plane where the cut parts do not possess mirror-symmetric elastic stiffness. The basis for the new asymmetric stiffness data analysis approach is presented and the accuracy of the new method demonstrated using both numerical and experimental case studies. © 2020 The Authors. Published by Elsevier Ltd.
- ItemInvestigating optimal cutting configurations for the contour method of weld residual stress measurement(Elsevier, 2018-07) Muránsky, O; Hosseinzadeh, F; Hamelin, CJ; Traore, Y; Bendeich, PJThe present work examines optimal cutting configurations for the measurement of weld residual stresses (WRS) using the contour method. The accuracy of a conventional, single-cut configuration that employs rigid clamping is compared with novel, double-embedded cutting configurations that rely on specimen self-constraint during cutting. Numerical analyses examine the redistribution of WRS and the development of cutting-induced plasticity (CIP) in a three-pass austenitic slot weld (NeT TG4) during the cutting procedure for each configuration. Stress intensity factor (SIF) analyses are first used as a screening tool; these analyses characterise lower stress intensities near the cutting surface when double-embedded cutting configurations are used, relative to SIF profiles from a single-cut process. The lower stress intensities indicate the development of CIP – which will ultimately affect back-calculated WRS – is less likely to occur when using an embedded configuration. The improvements observed for embedded cutting approaches are confirmed using three-dimensional finite element (FE) cutting simulations. The simulations reveal significant localised plasticity that forms in the material ligaments located between the pilot holes and the outer edges of the specimen. This plasticity is caused by WRS redistribution during the cutting process. The compressive plasticity in these material ligaments is shown to reduce the overall tensile WRS near the weld region before this region is sectioned, thereby significantly reducing the amount of CIP when cutting through the weld region at a later stage of the cutting procedure. Further improvements to the embedded cutting configuration are observed when the equilibrating compressive stresses in material ligaments are removed entirely (via sectioning) prior to sectioning of the high WRS region in the vicinity of the weld. All numerical results are validated against a series of WRS measurements performed using the contour method on a set of NeT TG4 benchmark weld specimens. © 2017 Elsevier Ltd.
- ItemMitigating cutting-induced plasticity in the contour method, part 1: experimental(Elsevier B.V., 2016-09-01) Hosseinzadeh, F; Traore, Y; Bouchard, PJ; Muránsky, OApplication of the contour method for the measurement of weld residual stresses (WRS) is prone to inaccuracy due to plastic deformation resulting from the redistribution of typically high (close to yield) WRS during the cutting process. The current work, seeks ways to mitigate cutting-induced plasticity by controlling stress redistribution through optimisation of the contour cutting configuration. The idea of using a stress-informed fracture mechanics approach to find the optimal cutting configuration is introduced. The level of plasticity associated with different cutting configurations is then assessed, allowing control of the location and magnitude of cutting-induced plasticity to occur during the cutting process. A conventional edge-crack cutting configuration is compared with a proposed double-embedded cutting configuration by measuring the longitudinal WRS in two three-pass slot weld specimens (NeT TG4) produced using identical weld procedures. The experimental results show that a novel double-embedded cutting configuration leads to greater accuracy in WRS measurements relative to conventional edge-crack cutting configurations at the expense of higher levels of plasticity being introduced local to small ligaments. © 2016 Published by Elsevier Ltd.
- ItemMitigating cutting-induced plasticity in the contour method. Part 2: Numerical analysis(Elsevier, 2016-09-01) Muránsky, O; Hamelin, CJ; Hosseinzadeh, F; Prime, MBCutting-induced plasticity can have a significant effect on the measurement accuracy of the contour method. The present study examines the benefit of a double-embedded cutting configuration that relies on self-restraint of the specimen, relative to conventional edge-crack cutting configurations. A series of finite element analyses are used to simulate the planar sectioning performed during double-embedded and conventional edge-crack contour cutting configurations. The results of numerical analyses are first compared to measured results to validate the cutting simulations. The simulations are then used to compare the efficacy of different cutting configurations by predicting the deviation of the residual stress profile from an original (pre-cutting) reference stress field, and the extent of cutting-induced plasticity. Comparisons reveal that while the double-embedded cutting configuration produces the most accurate residual stress measurements, the highest levels of plastic flow are generated in this process. This cutting-induced plastic deformation is, however, largely confined to small ligaments formed as a consequence of the sample sectioning process, and as such it does not significantly affect the back-calculated residual stress field. © 2016 Elsevier Ltd.
- ItemNumerical analysis of retained residual stresses in C(T) specimen extracted from a multi-pass austenitic weld and their effect on crack growth(Elsevier, 2014-08) Muránsky, O; Smith, MC; Bendeich, PJ; Hosseinzadeh, F; Edwards, LSmall scale fracture mechanics test specimens of austenitic stainless steel weld and heat affected zone material are often extracted from non-heat-treated weldments, which contain significant weld residual stresses. Although these stresses are substantially relaxed by the process of specimen extraction, they may still reach levels that can affect subsequent testing if the applied loads are low and deformation is elastic. Long-term creep crack growth testing is one such case, where failure to take account of retained residual stresses could result in unrealistically high measurements of creep crack growth at applied load levels equivalent to those in operating plant. This paper describes a research programme to predict the start-of-creep-test levels of retained residual stress and residual stress intensity factor in compact tension C(T) specimen blanks extracted from non-post heat-treated AISI 316 weldments. The simulations were validated using neutron diffraction and slitting residual stress measurements and stress intensity factor measurement. A pass-by-pass finite element simulation of the original weldment is performed first, and followed by extraction of the C(T) specimen blank. The predicted retained residual stresses in the specimen are compared with residual stress measurements made on similar blank using neutron diffraction, and slitting techniques. The elastic stress intensity factor due to residual stress is then evaluated on the crack plane of the C(T) specimen and compared with experimental measurements made using the slitting method. Good agreement is achieved between measurement and simulation, providing validated basis for future modelling of long term creep crack growth tests. © 2014, Elsevier Ltd.