Strain最新文献

{"title":"Controlled single and repeated impact testing for material plastic behaviour characterisation under high strain rates","authors":"S. Breumier, Francis Trudeau‐Lalonde, T. Lafrance, É. Robert, A. Villani, G. Kermouche, M. Lévesque","doi":"10.1111/str.12399","DOIUrl":"https://doi.org/10.1111/str.12399","url":null,"abstract":"Instrumented single‐shot experiments provide crucial information of a material's response to impact events that can be used in shot‐peening modelling. However, no authors successfully used such test for constitutive model identification and validation as existing test rig generally cannot provide an accurate determination of the shot trajectory in three dimensions over a wide velocity range. In this work, a shot‐peening test rig that can propel single shot under the process conditions with a high aiming accuracy is presented. The test rig propels industrial shot by sudden pressurised gas release. A methodology to recover the propelled shot three‐dimensional trajectory within a 200‐μm accuracy using two high‐frequency cameras is developed in an open‐source in‐house code. The test rig can propel 0.5‐, 1.19‐ and 2.5‐mm‐diameter shot at velocity ranging from 0.8 to 143 m s−1 and can send several shots at the same position when using the largest shot diameter. Two potential applications of the set‐up are presented for (i) coefficient of restitution measurement with different shooting angles and velocities and (ii) crystal plasticity finite element model validation using the impact dent topology, the shot displacement curve and the crystal misorientation field under the dent.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12399","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49269091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identifying hyperelastic constitutive parameters with sensitivity‐based virtual fields","authors":"A. Tayeb, J. Le Cam, M. Grédiac, E. Toussaint, E. Robin, X. Balandraud, F. Canévet","doi":"10.1111/str.12397","DOIUrl":"https://doi.org/10.1111/str.12397","url":null,"abstract":"This work deals with the identification of hyperelastic constitutive parameters using the virtual fields method. The choice of the virtual displacement fields is a crucial aspect of the method, typically for reducing the sensitivity to the measurement noise. A first and simple option is to generate the virtual displacement fields randomly. Nevertheless, in case of hyperelastic models for which the stress is not a linear function of the constitutive parameters, improving the choice of the virtual displacement fields is not trivial and an alternative strategy has to be found. In the present study, the sensitivity‐based virtual fields approach is applied and compared with the randomly generated virtual displacement fields approach. Two material models were considered: the Mooney model, which describes quite well the behavior of hyperelastic materials for small and moderate strains, and the Ogden model, which accounts for the stress hardening phenomenon observed at higher strains. The full kinematic fields are measured by using the digital image correlation technique during an equibiaxial tensile test performed on a cruciform specimen. Identification results are discussed through their capability to predict the external force measured during the test. The sensitivity‐based virtual fields approach is found to improve significantly the prediction compared with the randomly generated virtual displacement fields approach.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42178560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Creep deformation measurement of ex‐service 12% Cr steel over nonuniform stress fields using digital image correlation","authors":"M. Rooyen, A. Forsey, S. Gungor, T. Becker","doi":"10.1111/str.12400","DOIUrl":"https://doi.org/10.1111/str.12400","url":null,"abstract":"Deterioration assessment of materials is essential to the continued effective operation of critical components in thermal power plants. Establishing the degree of creep exhaustion of power engineering alloys operating at high temperatures and stresses guides maintenance strategies to ensure reliable plant operation. Within progressive inspection philosophies, traditional laboratory‐based creep testing is often difficult to conduct on ex‐service steel due to the limited material availability from which to machine standard specimen geometries. This work investigates a technique for the measurement of creep strain curves at several stresses and at 600°C from a single test using a nontraditional specimen geometry together with full‐field strain measurement through digital image correlation (DIC). Of interest is ex‐service X20CrMoV12‐1 (X20) which is widely used in older, subcritical thermal power plants. The paper aims to show that multiple creep curves can be resolved over a spatially varying stress field using DIC whilst preserving material economy. Differences in creep behaviour between ex‐service X20 with varying levels of service exposure are evident from quantitative comparisons of the creep strain and rate curves through threshold stress computation which agrees with hardness measurements and microstructural observation of subgrains and precipitates using electron microscopy. These single‐specimen tests yield high densities of creep data which can be used in the calibration of creep damage models for characterisation of ex‐service X20.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12400","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43046152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Material characterization of curved shells under finite deformation using the virtual fields method","authors":"Pieter Livens, S. Avril, J. Dirckx","doi":"10.1111/str.12398","DOIUrl":"https://doi.org/10.1111/str.12398","url":null,"abstract":"Although full‐field measurement techniques have been well established, material characterization from these data remains challenging. Often, no closed‐form solution exists between measured quantities and sought material parameters. In this paper, a novel approach to determine the stiffness of thin curved membranes is proposed, based on the virtual fields method (VFM). Utilizing Kirchhoff‐Love shell theory, we show that the displacements can be decomposed into an in‐plane displacement and a rotation of the mid‐surface of the shell. Consequently, the strain tensor at the outer surface of the shell can then be decomposed into a membrane and a bending part. This allows for the VFM to be applied based only on data of the outer surface and on surfaces of arbitrary curvature. The method is first applied to simulated data. It is shown that the elastic modulus can be identified with less than 5% error if the thickness and Poisson ratio are known accurately. A 5% uncertainty in either the Poisson ratio or the thickness changes the identified value by 5%. Then, the method is applied on experimental data acquired on rubber samples having a dome‐like shape. Tensile tests are performed on the same samples, which permits to assess the linearized Young's modulus of this material for moderate strains (0–2.1%). Using regression analysis, a Young's modulus of 1.21 ± 0.08 MPa is found. Next, we performed pressurization tests on eight dome‐like shapes with pressures up to 4 kPa. The average Young's modulus obtained with the novel virtual fields method is 1.20 ± 0.13 MPa. The results are in good agreement with the ones from the tensile test. Future applications could benefit from this method to analyse more complex shapes, for example those found in biological structures like arteries or eardrums.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12398","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46769287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extracting true stresses and strains from nominal stresses and strains in tensile testing","authors":"Rainer Schwab, Anton Harter","doi":"10.1111/str.12396","DOIUrl":"https://doi.org/10.1111/str.12396","url":null,"abstract":"Seemingly a simple task, the extraction of the flow curve (true stress vs. true plastic strain) from nominal stresses and strains in standard tensile testing still has its unsolved points. This study addresses two of them: (i) in materials without yield point phenomenon (or generally in the region of homogeneous plastic deformation), the true stress is typically calculated assuming constant volume, ignoring the elastic volume changes. Here, we derive a set of exact analytical solutions for true stresses and strains with remarkable simplicity and beauty that fully account for the elastic volume changes. This set of exact solutions is cross‐checked by finite element simulations as well as zeroth‐ and first‐order approximations; perfect agreement has been found. (ii) In materials with a pronounced yield point phenomenon, a complicated three‐dimensional stress state inevitably arises at the edge of the Lüders bands, which masks the real (or inherent) material behaviour. To determine the real material behaviour in the Lüders region, here we use a new macroscopic analytical approach characterised by a high true upper yield point, a typical strain hardening behaviour common for many materials, and the triaxiality of the stress state that inevitably develops at the edges of the Lüders bands and that determines the stress level at the observed lower yield point. This approach is verified by experiments (including video observations as well as digital image correlation (DIC) strain distribution measurements) and finite element simulations with very good agreement.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12396","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41376368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Information","authors":"","doi":"10.1111/str.12358","DOIUrl":"https://doi.org/10.1111/str.12358","url":null,"abstract":"No abstract is available for this article.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12358","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46604227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Information","authors":"","doi":"10.1111/str.12357","DOIUrl":"https://doi.org/10.1111/str.12357","url":null,"abstract":"No abstract is available for this article.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12357","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45864131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An experimental study of the feasibility of phase‐based video magnification for damage detection and localisation in operational deflection shapes","authors":"","doi":"10.1111/str.12380","DOIUrl":"https://doi.org/10.1111/str.12380","url":null,"abstract":"The below references in Civera et al. article[1] should be corrected as follows: [1] C. R. Farrar, K. Worden, Structural Health Monitoring: A Machine Learning Perspective, John Wiley & Sons 2012. ISBN 978-1-119-99433-6 [4] M. Civera, C. Surace, K. Worden, Detection of Cracks in Beams Using Treed Gaussian Processes, Structural Health Monitoring & Damage Detection, Vol. 7, Springer, Cham. 2017, pp. 85–97. [9] A. Rytter, Vibrational Based Inspection of Civil Engineering Structures. PhD dissertation, Aalborg Universitet 1993. ISSN 0902-7513 [15] M. Civera, L. Z. Fragonara, C. Surace, Video Processing Techniques for the Contactless Investigation of Large Oscillations. Journal of Physics: Conference Series, Vol. 1249, No. 1, IOP Publishing 2019, p. 012004. [23] E. Caetano, S. Silva, J. Bateira, Application of a vision system to the monitoring of cable structures, Seventh International Symposium on Cable Dynamics, 2007, pp. 225–236. [24] M. Q. Feng, Y. Fukuda, D. Feng, M. Mizuta, J. Bridge Eng. 2015, 20(12), 04015023. [30] C. Nonis, C. Niezrecki, T. Y. Yu, S. Ahmed, C. F. Su, T. Schmidt, Structural Health Monitoring of Bridges Using Digital Image Correlation, Health Monitoring of Structural and Biological Systems, Vol. 8695, International Society for Optics and Photonics 2013, p. 869507 [31] M. Malesa, D. Szczepanek, M. Kujawi nska, A. Świercz, P. Kołakowski, Monitoring of Civil Engineering Structures Using Digital Image Correlation Technique, EPJ Web of Conferences, Vol. 6, EDP Sciences 2010, p. 31014. [36] E. P. Simoncelli, W. T. Freeman, The Steerable Pyramid: A Flexible Architecture for Multi-scale Derivative Computation, Proceedings., International Conference on Image Processing, Vol. 3, IEEE 1995, pp. 444–447. [38] J. G. Chen, N. Wadhwa, Y. J. Cha, F. Durand, W. T. Freeman, O. Buyukozturk, J. Sound Vib. 2015, 345, 58–71. [40] H. Y. Wu, M. Rubinstein, E. Shih, J. Guttag, F. Durand, W. Freeman, ACM Trans. Graph. 2012, 31(4), 1–8. [43] O. Christensen, Azerbaijan J. Math. 2014, 4, 25. ISSN 2218-6816 [51] T. H. Oh, R. Jaroensri, C. Kim, M. Elgharib, F. E. Durand, W. T. Freeman, W. Matusik, Learning-based video motion magnification. in Proc. Eur. Conf. Comput. Vision, (ECCV), 2018, 633-648. SpringerLink: https://link.springer. com/conference/eccv [52] E. H. Yunus, U. Gulan, M. Holzner, E. Chatzi, Sensors 2019, 19(5), 1229. [53] A. Sarrafi, P. Poozesh, C. Niezrecki, Z. Mao, Mode Extraction on Wind Turbine Blades via Phase-based Video Motion Estimation, Smart Materials and Nondestructive Evaluation for Energy Systems, Vol. 10171, International Society for Optics and Photonics 2017, p. 101710E, April. DOI: 10.1117/12.2260406 [56] Z. I. Praisach, P. F. Minda, G. R. Gillich, A. A. Minda, Proc. 4th WSEAS Int. Conf. Finite Differences-Finite Elements-Finite Volumes-Boundary Elements, Vol. 201(1), Paris 2011, pp. 82-87, ISBN: 978-960-474-298-1","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12380","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48143028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Speckle pattern creation methods for two‐dimensional digital image correlation strain measurements applied to mechanical tensile tests up to 700°C","authors":"Phuong Luong, R. Bonnaire, J. Perie, Q. Sirvin, L. Penazzi","doi":"10.1111/str.12388","DOIUrl":"https://doi.org/10.1111/str.12388","url":null,"abstract":"The purpose of this study is to develop novel speckle pattern techniques for digital image correlation (DIC) kinematic measurements of mechanical tests at high temperatures, typically from 400 to 700°C. In this context, the speckle pattern should not only meet morphological criteria (size, density, distance) in order to improve spatial resolution, but it should also present a high contrast and resist high temperature and strain levels. To find a speckle pattern matching these specifications, a comparison was performed on six types of speckle made using different techniques. First, a computer‐generated speckle pattern that meets DIC criteria was numerically designed to produce six types of speckle pattern. Next, the speckle patterns produced using these six techniques were compared in terms of speckle morphology, image quality and adherence to titanium alloy TA6V material at high temperatures. From 25 to 600°C, the speckle pattern made by the technique combining anodisation and laser engraving named M5 technique gave the best contrast (highest value of mean intensity gradient [MIG] and Shannon entropy value) and the adherence of 200% of strain measurements to the TA6V material. At 700°C, speckle image quality is considerably reduced due to oxidation of the titanium alloy, and this may not be suitable for DIC measurements. Only the speckles produced by painting in which the paint plays a protective role provide with a better speckle contrast compared with other techniques. However, these speckle patterns enable only a strain measurement of 22% by the DIC method. This article concludes with guidelines for producing a speckle pattern suitable for high‐temperature mechanical tests.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12388","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44418723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metrological assessment of multi‐sensor camera technology for spatially‐resolved ultra‐high‐speed imaging of transient high strain‐rate deformation processes","authors":"Adrien Vinel, R. Seghir, J. Berthe, G. Portemont, J. Réthoré","doi":"10.1111/str.12381","DOIUrl":"https://doi.org/10.1111/str.12381","url":null,"abstract":"The present work proposes a metrological route for capturing spatially‐resolved ultra‐high‐speed kinematic full‐field data from high strain‐rate experiments and multi‐sensor camera technology. This paper focuses, from an application point of view, on highly resolved rotating mirror cameras, such as the Cordin‐580. This camera allows 78 frames of 8 megapixels to be recorded at up to 4 million frames per second (fps). The optical apparatus induces distortions that need to be taken into consideration. Distortions are modelled with Zernike polynomials and recovered using Digital Image Correlation (DIC) with a tailored synthetic speckle pattern. Effective displacements can then be quantitatively obtained with subpixel precision. After an assessment of the calibrated camera performance, this methodology is used to record, at 480,000 fps, the fracture of a pre‐notched sample subjected to an inertial impact test. The kinematic fields obtained quantitatively captured the events occurring during the test, such as the compression wave and the induced Poisson effect, the Mode‐I crack initiation and the shear strain concentration at the notch tip. The achievement of a DIC displacement and strain random error of, respectively, 5 μm (0.15 pixels) and 2 mm m−1, combined with a high spatio‐temporal sampling, provides a promising way for quantitatively analysing very fast transient and heterogeneous phenomena.","PeriodicalId":51176,"journal":{"name":"Strain","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2021-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/str.12381","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47762493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}