Issue 49

Frattura ed Integrità Strutturale, 49 (2019); International Journal of the Italian Group of Fracture

Table of Contents

Y. Chang, L. Zheng, X. Pan, Y. Hong Further investigation on microstructure refinement of internal crack initiation region in VHCF regime of high-strength steels .……………………………………………………….... 1-11 E. Breitbarth, T. Strohmann, M. Besel, S. Reh Determination of Stress Intensity Factors and J integral based on Digital Image Correlation ….. 12-25 J. A. O. González, J. T. P. de Castro, G. L. G. Gonzáles, M. A. Meggiolaro, J. L. de França Freire Verification of the ΔK eff hypothesis along the fatigue crack path in thin and thick Al specimens 26-35 Yu. G. Matvienko Comparison of the constraint parameters in elastic-plastic fracture mechanics ………………... 36-43 G. Meneghetti, A. Campagnolo, F. Berto Averaged strain energy density estimated rapidly from the nodal stresses by FEM for cracks under mixed mode loadings including the T-stress contribution ……………………………. 53-64 L. Malíková, H. Šimonová, B. Kucharczyková, P. Miarka Multi-parameter fracture mechanics: crack path in a mixed-mode specimen ………………… 65-73 G. L. G. Gonzáles, J. A. O. González, J. T. P. de Castro, J. L. de França Freire Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip …………………………………………………………………………. 74-81 G. Meneghetti, M. Ricotta, G. Pitarresi On relation between J-integral and heat energy dissipation at the crack tip in stainless steel specimens ………………………………………………………………………..... 82-96 S. Seitl, P. Miarka, V. Růžička, L. Malíková, A. S. Cruces, P. Lopez-Crespo Approximation of the crack-tip field in fatigue cracks in bridge steel specimens: DIC analysis of different constraint levels …………………………………………………………..... T. Profant, J. Pokluda The ab-initio aided strain gradient elasticity theory: a new concept for fracture nanomechanics …. P. Trusov, E. Makarevich, N. Kondratev Multi-level model describing phase transformations of polycrystalline materials under thermo- mechanical impacts …………………………………………………………………

97-106

107-114

125-139

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Fracture and Structural Integrity, 49 (2019); ISSN 1971-9883

O. Y. Smetannikov, Y. A. Kashnikov, S. G. Ashikhmin, A. E. Kukhtinskiy Numerical model of fracture growth in hydraulic re-fracturing …………………..………… 140-155 M. Zhelnin, A. Kostina, O. Plekhov, I. Panteleev, L. Levin Numerical analysis of application limits of Vyalov’s formula for an ice-soil thickness ………… 156-166 M. Semin, L. Levin Numerical simulation of frozen wall formation in water-saturated rock mass by solving the Darcy-Stefan problem …………………………………………………....................... 167-176 V. P. Matveenko, N. A. Kosheleva, G. S. Serovaev, A. Yu. Fedorov Numerical analysis of the strain values obtained by FBG embedded in a composite material using assumptions about uniaxial stress state of the optical fiber and capillary on the Bragg grating …. 177-189 A. Zh. Akhmetov, I. Yu. Smolin, A. Yu. Peryshkin Numerical analysis of the state of stress and strain in the Yenisei Ridge based on the regional tectonic state in the Asian continent …...…………………………………………...…. 190-200 S. Smirnov, L. Zamaraev Comparative study of Shot creep of single-phase titanium alloys in air and neutral gas environment on the test temperature in range from 673 to 1323 K ………………………… 201-211 N. G. Burago, I. S. Nikitin, A. D. Nikitin, B. A. Stratula Algorithms for calculation damage processes ……...…………………………………….. 212-224 V. Matveenko, I. Shardakov, T. Korepanova Construction of analytical eigensolutions for isotropic conical bodies and their application for estimation of stresses singularity …........................................................................................... 225-242 Y. Bayandin, N. Saveleva, O. Naimark Steady plastic wave fronts and scale universality of strain localization in metals and ceramics ….. 243-256 A. Baryakh, S. Lobanov On one approach to the numerical modeling of the strain-stress state of layered rock mass ……… 257-266 N. S. Popova, E. M. Morozov, Y. G. Matvienko Predicting the crack path in a wedge under a concentrated tensile force by means of variational principle ………………………………………………………………………….. 267-271 O. Naimark Duality of singularities of multiscale damage localization and crack advance: length variety in Theory of Critical Distances ………………………………………………………… 272-281 M. Abbadeni, I. Zidane, H. Zahloul, Z. Madaoui Comparative study of conventional and hydromechanical deep drawing processes based on finite element analysis .....................……………………………………………………….. 282-290 S. Djaballah, K. Meftah, K. Khelil, M. Tedjini, L. Sedira Detection and diagnosis of fault bearing using wavelet packet transform and neural network …... 291-301

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Frattura ed Integrità Strutturale, 49 (2019); International Journal of the Italian Group of Fracture

A. Kostina, M. Zhelnin, O. Plekhov Numerical analysis of a caprock integrity during oil production by steam-assisted gravity drainage method …………………………………………………………………………... A. Vedernikova, A. Iziumova, A. Vshivkov, O. Plekhov The approach to fracture diagnosis by means of experimental measurements of the stored energy . M. Hamdi, R. Zenasni, M.A. Khiat Critically evaluating mechanics of structure genome-based micromechanics approach ………… N. Kaddouri, K. Madani, M . A. Bellali, X. Feaugas Analysis of the presence of bonding defects on the fracture behavior of a damaged plate repaired by composite patch ……………………………………………………………...…. A. Guillal, N. Abdelbaki, M.E.A. Bensghier, B. Kopei Effect of shape factor on structural reliability analysis of a surface cracked pipeline-parametric study ……………………………………………………………………….……. A. Abdelhalim, G. Abdelmoumene, D. Lamia, D. Abderrazek ANNApproach to Predict the Flow Stress of CMn (Nb-Ti-V) Micro Alloyed Steel ……….. G. M. Dominguez Almaraz, L. M. Torres Duarte, C. J. Torres Pacheco Tension - torsion fatigue tests on the proton exchange membrane Nafion 115 (Perfluorosulfonic acid) …................................................................................................................................... A.V. Vakhrushev, A.Y. Fedotov Simulation of deformation and fracture processes in nanocomposites ……………………...… M. Bannikov, D. Bilalov, V. Oborin, O. Naimark Damage evolution in the AlMg6 alloy during high and very high cycle fatigue ……………… M. Tashkinov, D. Ershova, A. Shalimov Computational multi-scale analysis of simultaneous processes of delamination and damage accumulation in laminated composites ………………………………………………… S.A.G. Pereira, S.M.O. Tavares, P.M.S.T. de Castro Mixed mode fracture: numerical evaluation and experimental validation using PMMA specimens ……………………………………………………………………....…. L. Suchý, E. Leidich, A. Hasse, T. Gerstmann, B. Awiszus Fatigue strength of inner knurled interference fit joined by forming and cutting methods ……….. F.J.P. Moreira, R.D.S.G. Campilho Use of the XFEM for the design of adhesively-bonded T-joints …………………………… S. Pereira, A. Carvalho, L. Reis, M. Freitas, D. Montalvão Characterisation and evaluation of the mechanical behaviour of endodontic-grade NiTi wires … B. G. N., Muthanna, O., Bouledroua, M., Meriem-Benziane, M., Hadj Meliani, G., Pluvinage, R. K. Suleiman Numerical study of semi-elliptical cracks in the critical position of pipe elbow ………………

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Fracture and Structural Integrity, 49 (2019); ISSN 1971-9883

H. Araújo, M. Leite, A.M.R. Ribeiro, A.M. Deus, L. Reis, M.F. Vaz Investigating the contribution of geometry on the failure of cellular core structures obtained by additive manufacturing ……………………………………………………...……… M. J. Adinoyi, N. Merah, J. Albinmousa Analysis of Low-Cycle Fatigue Behavior of AW2099-T83 Al-Li Alloy …...…………….. D. Kumar, G. Jayaraman, M. Swamy, A. H. V. Pavan, Antony M. C. Harison, A. N. Sudhakar Optimization of Vanadium Content for Achieving Higher Wear Resistance and Hardness in High Cr-VWhite Cast Irons for Ball Tube Mill Liner Application ………………..…….. A. Kumar, Y.V. Nagaraja Bhat, B.K. Sreedhar, S.I. Sundar Raj, V.Prakash, P. Selvaraj Structural Integrity Assessment of Weld for Joining Waveguide to Annular Linear Induction Pump Subjected to Vibration ……………………………………………….………. R. Suresh Kumar, B.N. Rao, K. Velusamy, S. Jalaldeen Specimen Level and Component Level Simulations of Fatigue Crack Growth Behavior under Cyclic Bending .……..……………………………………………………………... R. V. Prakash, M. John Post- Impact Fatigue Damage Analysis of Quasi Isotropic CFRP Laminates through Infrared Thermography ………………………………………………………………...…... E.H, Besseghier, A, Djebli, M, Bendouba, A, Baltach, A, Aid A 3D analysis of crack-front shape of asymmetric repaired aluminum panels with composite patches ………………………………………………………………………….... C.Y. Liu, Y. Wang, X.P. Zhang, L.Z. Du Rock brittleness evaluation method based on the complete stress-strain curve ………………… R. Marat-Mendes, R. Martins, A. Garcia, L. Reis Flexural testing and analysis of full-strain-fields in sandwich composites ………………..…... Z. Rachid, A. K. Djafar, S. Abderahmane, M. Abdelmadjid, B. Smail Numerical simulation of a crack emanating from a micro-cavity in the orthopedic cement by technical sub modeling of total hip prosthesis …………………………….…………….... D. E. Belhadri, M. Belhamiani, W. N, Bouzitouna, W. Oudad Stress intensity factors analyses for external semi-elliptical crack for repaired gas-pipeline by composite overwrap under pressure ……………………………………………………. E.Y.L. Palechor, L.M. Bezerra, M. V. G. de Morais, R.S.Y.R.C. Silva, E.N. Barros, Damage identification in beams using additional rove mass and wavelet transform ………….... M. H. Miloud, I. Zidane, M. Mendas Coupled identification of the hardening behavior laws and Gurson–Tvergaard–Needleman damage parameters - Validation on tear test of 12NiCr6 CT specimen …………...................

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Frattura ed Integrità Strutturale, 49 (2019); International Journal of the Italian Group of Fracture

H. Berrekia, D. Benzerga, A. Haddi Behavior and damage of a pipe in the presence of a corrosion defect depth of 10% of its thickness and highlighting the weaknesses of the ASME / B31G method ……………………..…… A. Bendada, D. Boutchicha, A. Chouiter, M. Miri Numerical-Experimental characterization of honeycomb sandwich panel and numerical modal analysis of implemented delamination ………………………………..………………... Y. Saadallah, S. Derfouf, B. Guerira A viscoelastic-viscoplastic model for a thermoplastic and sensitivity of its rheological parameters to the strain-rate …………………………………………………………………... L. Restuccia Fracture properties of green mortars with recycled sand …………………………………... E. Abdelouahed, H. Benzaama, M. Mokhtari, B. Aour Pipeline repair by composite patch under temperature and pressure loading ………………….. E. Abdelouahed, M. Mokhtari, H. Benzaama Finite Element Analysis of the thermo-Mechanical Behavior of composite Pipe Elbows under Bending and Pressure loading ………………………………………………………... Y. Liu, J. Ren, Z. Li, Q. Gao S. Zhao Carbonation Resistance of Reinforced Concrete under Bending Load ………………………. M. L. Puppio, L. Giresini Estimation of tensile mechanical parameters of existing masonry through the analysis of the collapse of Volterra’s urban walls ……………………………………………………. C. Bellini, V. Di Cocco, F. Iacoviello, L. Sorrentino Experimental analysis of aluminium/carbon epoxy hybrid laminates under flexural load …….. A. En-naji, N. Mouhib, H. Farid, M. El Ghorba Prediction of thermomechanical behavior of acrylonitrile butadiene styrene using a newly developed nonlinear damage-reliability model …………………………………………….……... H. Chbani, B. Saadouki, M. Boudlal, M. Barakat Determination of fracture toughness in plain concrete specimens by R curve ……………...…... A. Pola, D. Battini, M. Tocci, A. Avanzini, L. Girelli, C. Petrogalli, M. Gelfi Evaluation on the fatigue behavior of sand-blasted AlSi10Mg obtained by DMLS …………. C. Bellini, G. Giuliano, L. Sorrentino Friction influence on the AA6060 aluminium alloy formability …………………….……. D. A. Oshmarin, M. A. Iurlov, N. V. Sevodina, N. A. Iurlova Possibility of tuning shunt circuits for multimodal damping of vibrations of structure with piezoelectric element ................................................................................................................. S.A. Bochkarev, S.V. Lekomtsev, A.N. Senin Analysis of spatial vibrations of piezoceramic eccentric cylindrical shells interacting with an annular fluid layer …………………………………………………………………

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Fracture and Structural Integrity, 49 (2019); ISSN 1971-9883

H. Cao Analysis of mechanical properties of transition segment of road and bridge based on high-strength foam concrete ...........................................................................................................................

831-839

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Frattura ed Integrità Strutturale, 49 (2019); International Journal of the Italian Group of Fracture

Editorial Team

Editor-in-Chief Francesco Iacoviello

(Università di Cassino e del Lazio Meridionale, Italy)

Associate Editors Alfredo Navarro

(Escuela Superior de Ingenieros, Universidad de Sevilla, Spain)

Thierry Palin-Luc

(Arts et Metiers ParisTech, France) (University of Sheffield, UK) (University of Manchester, UK)

Luca Susmel John Yates

Guest Editors Valerii Matveenko

SI: Russian mechanics contributions for Structural Integrity (Institute of Continuous Media Mechanics Ural Branch of Russian Academy of Sciences, Russia) (Institute of Continuous Media Mechanics Ural Branch of Russian Academy of Sciences, Russia)

Oleg Plekhov

Guest Editors

SI: Fracture Mechanics versus Environment

Mohammed Hadj Meliani

(University of Chlef, Algeria) (University of Belgrade, Serbia ) (Lorraine University, Metz, France)

Ljubica Milovic Guy Pluvinage

Guest Editor

SI: Showcasing Structural Integrity Research in India

(Indian Institute of Technology Madras, India)

Raghu Vasu Prakash

SI: New Trends in Fatigue and Fracture

Guest Editors

Manuel Freitas

(University of Lisbon, Portugal ) (University of Lisbon, Portugal) (University of Lisbon, Portugal )

Luis Reis

Fatima Vaz

Guest Editors

SI: Crack Tip Fields (University of Sheffield, UK)

Luca Susmel

Michael Vormwald

(Technische Universität Darmstadt, Germany)

Advisory Editorial Board Harm Askes

(University of Sheffield, Italy) (Tel Aviv University, Israel) (Politecnico di Torino, Italy) (Università di Parma, Italy) (Politecnico di Torino, Italy)

Leslie Banks-Sills Alberto Carpinteri Andrea Carpinteri Emmanuel Gdoutos Youshi Hong M. Neil James Gary Marquis Ashok Saxena Darrell F. Socie Robert O. Ritchie Donato Firrao

(Democritus University of Thrace, Greece) (Chinese Academy of Sciences, China)

(University of Plymouth, UK)

(Helsinki University of Technology, Finland)

(University of California, USA)

(Galgotias University, Greater Noida, UP, India; University of Arkansas, USA)

(University of Illinois at Urbana-Champaign, USA)

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Fracture and Structural Integrity, 49 (2019); ISSN 1971-9883

Shouwen Yu

(Tsinghua University, China) (Fraunhofer LBF, Germany) (Texas A&M University, USA) (University of Dublin, Ireland)

Cetin Morris Sonsino

Ramesh Talreja David Taylor

Regional Editorial Board Nicola Bonora

(Università di Cassino e del Lazio Meridionale, Italy)

Raj Das

(RMIT University, Aerospace and Aviation department, Australia)

Dorota Kocańda Stavros Kourkoulis Carlo Mapelli Liviu Marsavina

(Military University of Technology, Poland) (National Technical University of Athens, Greece)

(Politecnico di Milano, Italy)

(University of Timisoara, Romania) (Tecnun Universidad de Navarra, Spain) (Instituto Superior Técnico, Portugal) (Università di Napoli "Federico II", Italy) (University of Belgrade, Serbia) (Tel-Aviv University, Tel-Aviv, Israel)

Antonio Martin-Meizoso

Raghu Prakash

(Indian Institute of Technology/Madras in Chennai, India)

Luis Reis Elio Sacco

Aleksandar Sedmak

Dov Sherman Karel Slámečka Petro Yasniy

(Brno University of Technology, Brno, Czech Republic) (Ternopil National Ivan Puluj Technical University, Ukraine)

Editorial Board Jafar Albinmousa Nagamani Jaya Balila

(King Fahd University of Petroleum & Minerals, Saudi Arabia)

(Indian Institute of Technology Bombay, India) (Indian Institute of Technology Kanpur, India)

Sumit Basu

Stefano Beretta Filippo Berto K. N. Bharath

(Politecnico di Milano, Italy)

(Norwegian University of Science and Technology, Norway) (GM Institute of Technology, Dept. Of Mechanical Engg., India)

Elisabeth Bowman

(University of Sheffield)

Alfonso Fernández-Canteli

(University of Oviedo, Spain) (Università di Parma, Italy)

Luca Collini

Antonio Corbo Esposito

(Università di Cassino e del Lazio Meridionale, Italy)

Mauro Corrado

(Politecnico di Torino, Italy) (University of Porto, Portugal)

José António Correia

Dan Mihai Constantinescu

University POLITEHNICA of Bucharest()

Manuel de Freitas Abílio de Jesus Vittorio Di Cocco Andrei Dumitrescu Giuseppe Ferro Riccardo Fincato Eugenio Giner Dimitris Karalekas Sergiy Kotrechko Grzegorz Lesiuk Paolo Lonetti Carmine Maletta Milos Djukic

(EDAM MIT, Portugal)

(University of Porto, Portugal)

(Università di Cassino e del Lazio Meridionale, Italy)

(University of Belgrade, Serbia)

(Petroleum-Gas University of Ploiesti)

(Politecnico di Torino, Italy) (Osaka University, Japan)

(Universitat Politecnica de Valencia, Spain)

(University of Piraeus, Greece)

(G.V. Kurdyumov Institute for Metal Physics, N.A.S. of Ukraine, Ukraine)

(Wroclaw University of Science and Technology, Poland)

(Università della Calabria, Italy) (Università della Calabria, Italy)

Sonia Marfia

(Università di Cassino e del Lazio Meridionale, Italy)

Lucas Filipe Martins da Silva

(University of Porto, Portugal)

Tomasz Machniewicz

(AGH University of Science and Technology)

Hisao Matsunaga

(Kyushu University, Japan)

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Frattura ed Integrità Strutturale, 49 (2019); International Journal of the Italian Group of Fracture

Milos Milosevic Pedro Moreira

(Innovation centre of Faculty of Mechanical Engineering in Belgrade, Serbia)

(University of Porto, Portugal) (University of Bristol, UK)

Mahmoud Mostafavi Vasile Nastasescu

(Military Technical Academy, Bucharest; Technical Science Academy of Romania)

Stefano Natali Andrzej Neimitz

(Università di Roma “La Sapienza”, Italy) (Kielce University of Technology, Poland)

(Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Ukraine)

Hryhoriy Nykyforchyn

Pavlos Nomikos

(National Technical University of Athens) (IMT Institute for Advanced Studies Lucca, Italy)

Marco Paggi Hiralal Patil Oleg Plekhov

(GIDC Degree Engineering College, Abrama-Navsari, Gujarat, India) (Russian Academy of Sciences, Ural Section, Moscow Russian Federation)

Alessandro Pirondi Dimitris Karalekas Luciana Restuccia Giacomo Risitano Mauro Ricotta Roberto Roberti

(Università di Parma, Italy) (University of Piraeus, Greece) (Politecnico di Torino, Italy) (Università di Messina, Italy) (Università di Padova, Italy) (Università di Brescia, Italy) (Università di Napoli "Federico II")

Elio Sacco

Hossam El-Din M. Sallam

(Jazan University, Kingdom of Saudi Arabia) (Università di Roma "Tor Vergata", Italy)

Pietro Salvini Mauro Sassu

(University of Cagliari, Italy) (Università di Parma, Italy)

Andrea Spagnoli Ilias Stavrakas

(University of West Attica, Greece) (Lublin University of Technology) (University of West Attica, Greece)

Marta Słowik Dimos Triantis Sabrina Vantadori Natalya D. Vaysfel'd Charles V. White

(Università di Parma, Italy)

(Odessa National Mechnikov University, Ukraine)

(Kettering University, Michigan,USA)

Shun-Peng Zhu

(University of Electronic Science and Technology of China, China)

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Fracture and Structural Integrity, 49 (2019); ISSN 1971-9883

Frattura ed Integrità Strutturale is an Open Access journal affiliated with ESIS

Sister Associations help the journal managing Australia: Australian Fracture Group – AFG

Czech Rep.: Asociace Strojních Inženýrů (Association of Mechanical Engineers) Greece: Greek Society of Experimental Mechanics of Materials - GSEMM India: Indian Structural Integrity Society - InSIS Israel: Israel Structural Integrity Group - ISIG Italy: Associazione Italiana di Metallurgia - AIM Italy: Associazione Italiana di Meccanica Teorica ed Applicata - AIMETA Italy: Società Scientifica Italiana di Progettazione Meccanica e Costruzione di Macchine - AIAS Poland: Group of Fatigue and Fracture Mechanics of Materials and Structures Portugal: Portuguese Structural Integrity Society - APFIE Romania: Asociatia Romana de Mecanica Ruperii - ARMR Serbia: Structural Integrity and Life Society "Prof. Stojan Sedmak" - DIVK Spain: Grupo Espanol de Fractura - Sociedad Espanola de Integridad Estructural – GEF Ukraine: Ukrainian Society on Fracture Mechanics of Materials (USFMM)

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Frattura ed Integrità Strutturale, 49 (2019); International Journal of the Italian Group of Fracture

Journal description and aims Frattura ed Integrità Strutturale (Fracture and Structural Integrity) is the official Journal of the Italian Group of Fracture. It is an open-access Journal published on-line every three months (January, April, July, October). Frattura ed Integrità Strutturale encompasses the broad topic of structural integrity, which is based on the mechanics of fatigue and fracture and is concerned with the reliability and effectiveness of structural components. The aim of the Journal is to promote works and researches on fracture phenomena, as well as the development of new materials and new standards for structural integrity assessment. The Journal is interdisciplinary and accepts contributions from engineers, metallurgists, materials scientists, physicists, chemists, and mathematicians. Contributions Frattura ed Integrità Strutturale is a medium for rapid dissemination of original analytical, numerical and experimental contributions on fracture mechanics and structural integrity. Research works which provide improved understanding of the fracture behaviour of conventional and innovative engineering material systems are welcome. Technical notes, letters and review papers may also be accepted depending on their quality. Special issues containing full-length papers presented during selected conferences or symposia are also solicited by the Editorial Board. Manuscript submission Manuscripts have to be written using a standard word file without any specific format and submitted via e-mail to gruppofrattura@gmail.com. Papers should be written in English. A confirmation of reception will be sent within 48 hours. The review and the on-line publication process will be concluded within three months from the date of submission. Peer review process Frattura ed Integrità Strutturale adopts a single blind reviewing procedure. The Editor in Chief receives the manuscript and, considering the paper’s main topics, the paper is remitted to a panel of referees involved in those research areas. They can be either external or members of the Editorial Board. Each paper is reviewed by two referees. After evaluation, the referees produce reports about the paper, by which the paper can be: a) accepted without modifications; the Editor in Chief forwards to the corresponding author the result of the reviewing process and the paper is directly submitted to the publishing procedure; b) accepted with minor modifications or corrections (a second review process of the modified paper is not mandatory); the Editor in Chief returns the manuscript to the corresponding author, together with the referees’ reports and all the suggestions, recommendations and comments therein. c) accepted with major modifications or corrections (a second review process of the modified paper is mandatory); the Editor in Chief returns the manuscript to the corresponding author, together with the referees’ reports and all the suggestions, recommendations and comments therein. d) rejected. The final decision concerning the papers publication belongs to the Editor in Chief and to the Associate Editors. The reviewing process is usually completed within three months. The paper is published in the first issue that is available after the end of the reviewing process.

Publisher Gruppo Italiano Frattura (IGF) http://www.gruppofrattura.it ISSN 1971-8993 Reg. Trib. di Cassino n. 729/07, 30/07/2007

Frattura ed Integrità Strutturale (Fracture and Structural Integrity) is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0)

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Fracture and Structural Integrity, 49 (2019); ISSN 1971-9883

More than 1000 published papers!!!

D

ear friends, also this issue is really rich, with more than 60 published papers. Considering that in each issue we manage between 200 and 300 papers, it is evident the effort of the scientific community to support the journal: authors, reviewers, editorial boards members are warmly acknowledged for their efforts, their support and the time they spend on the journal! With this issue, a crucial number is obtained: more than 1000 (one thousand!!!) papers have been published in “Frattura ed Integrità Strutturale” since its first issue, in 2007. In the graph here below, you can see the cumulative published papers number, with the most important moments in the life of the journal.

In this issue, we have many “Special Sections” and we are grateful to the Guest Editors for their help in the reviewing process. Frankly speaking, without their help it would be impossible to publish issues like the present one. We warmly acknowledge Valerii Matveenko and Oleg Plekhov (SI: Russian mechanics contributions for Structural Integrity), Mohammed Hadj Meliani, Ljubica Milovic and Guy Pluvinage (SI: Fracture Mechanics versus Environment), Raghu Vasu Prakash (SI: Showcasing Structural Integrity Research in India), Manuel Freitas, Luis Reis, Fatima Vaz (SI: New Trends in Fatigue and Fracture) and, finally, Luca Susmel and Michael Vormwald (SI: Crack Tip Fields). In the last weeks, we activated in the journal three new plugins:

1) pdf embedded in the journal website structure: selecting a pdf, the file now is open inside the journal website; 2) papers statistics for each paper: you are able to visualize how many downloads and view were obtained for each paper, per year and per month. 3) “Online first”. As soon as the reviewing process is completed (... and the paper is accepted!), and the Publishing agreement and Visual Abstract is uploaded, the paper is immediately published in the “Online first” section, being immediately available! We hope that all these new plugins will be appreciated and, please, feel free to send us your suggestions to further improve the journal. Very best

Francesco Iacoviello Frattura ed Integrità Strutturale Editor in Chief

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

Focused on Crack Tip Fields

Further investigation on microstructure refinement of internal crack initiation region in VHCF regime of high-strength steels

Yukun Chang LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China School of Science, Harbin Institute of Technology, Shenzhen 518055, China yukunchang@foxmail.com Liang Zheng School of Science, Harbin Institute of Technology, Shenzhen 518055, China icon_lzheng@hit.edu.cn Xiangnan Pan, Youshi Hong* LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China panxiangnan@lnm.imech.ac.cn, hongys@imech.ac.cn A BSTRACT . The profile samples prepared by focused ion beam (FIB) in crack initiation region (CIR) and fish-eye (FiE) region of failed specimens subjected to rotary bending (RB) and ultrasonic axial (UL) fatigue testing with various stress ratios ( R ) were observed by transmission electron microscopy (TEM) with selected area electron diffraction (SAD) detection for two high-strength steels. The grain size and the thickness of nanograin layer along the crack growth path in CIR underneath fine-granular-area (FGA) were measured for the cases of R < 0, and a normalized quantity d * based on the detected SAD patterns was introduced to quantitatively demonstrate the variation of the grain size. The results showed that the nanograin size near the origin (an inclusion) of crack initiation is smaller than that away from the inclusion. Nevertheless, there was no evidence of grain refinement in CIR for the cases of R > 0 and the FiE region outside CIR for either negative or positive stress ratio cases, which suggests that the formation of nanograin layer in the FGA region is due to the numerous cyclic pressing (NCP) process and the plastic deformation ahead of the crack tip may cause certain extent of microstructure deformation but is insufficient to form nanograin layer on crack surfaces. K EYWORDS . Very-high-cycle fatigue; Nanograins; Microstructure refinement; Crack initiation; FGA; High-strength steels.

Citation: Chang Y.K., Pan X.N., Zheng L., Hong Y.S., Further investigation on microstructure refinement of internal crack initiation region in very-high-cycle fatigue regime of high strength steels, Frattura ed Integrità Strutturale, 49 (2019) 1-11.

Received: 08.04.2019 Accepted: 23.04.2019 Published: 01.07.2019

Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

I NTRODUCTION

F

atigue failure of engineering materials and structures bearing cyclic loading beyond 10 7 cycles, i.e. very-high-cycle fatigue (VHCF), may still happen in practical industrial applications [1-4]. VHCF behavior has attracted the attention of researchers in recent decades due to increasingly realistic requirements and scientific interests [5-9]. At present, it has been known that the typical morphology of the internal crack initiation region (CIR) for VHCF of high- strength steels is a fish-eye (FiE) containing a relatively rough region of fine-granular area (FGA), and it surrounds an inclusion which is considered as the origin of the crack initiation [10-13]. In general, FGA is regarded as the characteristic region of the internal crack initiation of VHCF due to its stable value of related stress intensity factor range and the consumption of the majority of total fatigue life [10,11,14]. As one of the most popular and challenging problems in VHCF, the formation mechanism of FGA has been investigated widely and deeply in last two decades [15-21]. Sakai et al. [18] examined the microstructure beneath the FGA by transmission electron microscopy (TEM). The TEM sample was prepared by focused ion beam (FIB) technique, and their results showed that the fine granular layer was observed in FGA region, whereas the fine polygonization was not observed in the location away from the FGA surface. Based on this observation, they proposed the model of “formation and debonding of fine granular layer” [22]. Similarly, an investigation by Grad et al. [15] reported that an average grain size of about 70 nm was observed in FGA for a high-strength steel and proposed an FGA formation mechanism called “local grain refinement at the crack tip”. This model was extended very recently by Spriestersbach and Kerscher [23]. The most recent investigations by Chai et al. [24,25] also believed that localized plastic deformation would promote the formation of FGA. It should be noted that only the fully reversed cyclic loading was considered in all above-mentioned investigations, meaning the stress ratio of R = ‒ 1. In order to investigate the formation mechanism of FGA more deeply and comprehensively, Hong et al. [16] first performed fatigue tests under different stress ratios via rotary bending (RB) and ultrasonic axial (UL) loading for two high-strength steels, then the profile samples were prepared by FIB at the characteristic region of crack initiation of failed specimens, and subsequently the microstructure of the samples were examined by TEM. Their observations revealed the existence of the thin nanograin layer of FGA under negative stress ratios, whereas the morphology of FGA was diminishing or even extinguishing under positive stress ratios without the evidence of nanograin feature. Based on such experimental results, a new model named “numerous cyclic pressing (NCP)” was proposed to describe the formation processes of FGA. Subsequently, some results obtained by our group on structural steels [26] and titanium alloys [27,28] have confirmed the NCP model. Most Recently, numerical and experimental results reported by Ritz et al. [29] also validated the NCP model. Despite the formation mechanism of FGA has been investigated widely by researchers, the effect of the plastic deformation ahead of the crack tip during crack initiation process on the microstructure refinement, and the more detailed characteristics of microstructure in CIR and FiE regions, are still not clear at the present time. Therefore, in this paper, further investigation was carried out on the microstructure features in the CIR and FiE regions for high-strength steels bearing fatigue loading up to very-high-cycle regime. Several profile samples prepared by FIB in CIR and FiE regions were examined by TEM with selected area electron diffraction (SAD) detection. The detailed observations indicate that the nanograin size near the origin of crack initiation is smaller than that away from the origin for the cases of R < 0, and higher compressive stress and longer loading cycles promote the microstructure refinement. Nevertheless, there was no evident grain refinement in CIR for the cases of R > 0 and the FiE region outside CIR for either negative or positive R cases, suggesting that the formation of nanograins in the FGA region is due to the NCP process and the plastic deformation ahead of crack tip may cause certain extent of microstructure deformation but is insufficient to form nanograin layer on crack surfaces. Test materials he test materials utilized in this research were two high-strength steels. For convenience, they were marked as material A and material B, respectively. The corresponding chemical compositions are listed in Tab. 1. Two heat- treatment processes were performed: austenization at 845 ℃ for 2 h in vacuum, oil-quenched then tempered for 2 h in vacuum at 180 ℃ for the specimens of material A, and austenization at 845 ℃ for 1 h in vacuum, oil-quenched then tempered for 2 h in vacuum at 180 ℃ for the specimens of material B. After such heat-treatment processes, identical T T EST MATERIALS AND EXPERIMENTAL PROCEDURE

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

microstructure of tempered martensite was obtained. Results of monotonic quasi-static tensile and micro-hardness tests exhibited their high strength and hardness with the ultimate tensile strength of 1849 MPa and the micro-hardness of 753 Hv (kgf/mm 2 ) for material A, and the ultimate tensile strength of 1896 MPa and the micro-hardness of 760 Hv (kgf/mm 2 ) for material B.

Material

C

Cr

Mn

Si

S

P

Fe

A B

1.06 1.04

1.04 1.51

0.88 0.29

0.34 0.24

0.005 0.003

0.027

Balance Balance

0.0058

Table 1 : Chemical compositions (wt. %) of two materials.

Experimental procedure Rotary bending and ultrasonic axial loading are commonly used in the VHCF tests of materials. In the previous research developed in our group, material A was tested on a rotary bending machine with R = ‒ 1, and material B was tested on an ultrasonic machine (equipped with a tensile facility to superimpose required mean stress) running at the resonant frequency of 20 kHz with the stress ratios of R = ‒ 1, ‒ 0.5, 0.1 and 0.3. More detailed information concerning the fatigue tests was described in [16]. Then the morphology of the fracture surface was observed by scanning electron microscopy (SEM), and it was noticed that the failure of every specimen was due to internal cracking originated from an inclusion [16]. In addition, for the purpose of investigating the characteristics of microstructure for FGA and FiE on the fracture surface, several specimens under various loading conditions were cut by FIB to obtain the profile samples, and their relevant data were listed in Tab. 2. Subsequently these samples were carefully examined by TEM, especially near the fracture surfaces, and the microstructure details were detected by SAD with an aperture diameter of 200 nm.

Loading condition

Sampling location

σ a

σ max

σ min

N f

Sample

/MPa

/MPa

/MPa

/cycles

RB, R = ‒ 1 RB, R = ‒ 1 UL, R = ‒ 1 UL, R = ‒ 0.5 UL, R = 0.1 UL, R = 0.3 UL, R = 0.3

‒ 775 ‒ 750 ‒ 989 ‒ 422

A1 A2 B1 B2 B3 B4 B5

775 750 989 633 534 430 430

775 750 989 844

2.40×10 7 5.08×10 7 1.11×10 8 4.81×10 8 1.84×10 7 8.70×10 8 8.70×10 8

CIR FiE CIR CIR CIR CIR FiE

1187 1229 1229

119 368 368

Table 2: Loading conditions and sampling locations of several failed specimens.

R ESULTS AND D ISCUSSION

Microstructural features in CIR for negative stress ratio cases t can be seen from Tab. 2 that A1, B1 and B2 samples were cut from CIR of the failed specimens bearing fatigue loading with negative stress ratios in VHCF regime. Fig. 1 illustrates the microstructural features of sample A1. It is seen from Fig. 1a that the crack initiated from a spherical inclusion then to form an FGA region. The small dashed yellow rectangle in Fig. 1a represents the sampling location in the FGA region, and Fig. 1b illustrates the bright field imaging (BFI) of sample A1. Figs. 1c and 1d show the SAD patterns at the locations just underneath the FGA surface with discontinuous diffraction rings of polycrystals, which suggests that there are several grains within the diffraction area of 200 nm in diameter. Figs. 1e and 1f are dark field images (DFI) of the left and right dashed green boxes marked in Fig. 1b, and the fine granular layer can be clearly observed in both figures. Fig. 2 illustrates the microstructural features of sample B1. Similar to the above situation of sample A1, in the failed specimen associated with sample B1, the crack also originated from an inclusion to form an FGA region. BFI and DFI of the sample, displayed as a small dashed yellow rectangle in Fig. 2a, are presented in Figs. 2b and 2c, respectively. Both BFI I

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

and DFI showed that there are many fine grains near the fracture surface. SAD patterns of the left, middle and right dashed yellow circles marked in Fig. 2b are illustrated in Figs. 2d-f. All of these three patterns are discontinuous diffraction circles, suggesting several grains existing at these different locations. Similar results were obtained for sample B2 (as shown in Fig. 3).

Figure 1: Microstructural features of sample A1 (RB, R = ‒ 1, σ a = 2.40 ╳ 10 7 ), (a) SEM image of CIR showing the sampling location by a marked dashed yellow rectangle; (b) BFI; (c,d) SAD patterns of the left and right dashed yellow circles in (b); (e,f) DFI of the left and right dashed green boxes in (b). = 775 MPa, N f

Figure 2: Microstructural features of sample B1 (UL, R = ‒ 1 , σ a

= 989 MPa, N f

= 1.11 ╳ 10 8 ), (a) Origin of crack initiation showing

clear FGA feature; (b) BFI; (c) DFI; (d-f) SAD patterns of the left, middle and right dashed yellow circles in (b).

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

Figure 3: Microstructural features of sample B2 (UL, R = ‒ 0.5 , σ a = 4.81 ╳ 10 8 ), (a) SEM image showing crack origin; (b) BFI; (c,d) DFI of the left and right dashed green boxes in (b); (e-g) SAD patterns of the left, middle and right dashed yellow circles in (b). The above experimental results indicate the existence of nanograins in CIR underneath FGA surface for the cases of R = ‒ 1 and ‒ 0.5 under RB and UL loading conditions, confirming that the nature of FGA is a nanograin layer [16]. For the detail investigation of the relationship between the grain size and loading conditions, the distribution of grain size in CIR underneath FGA surface for samples A1, B1 and B2 was measured and the results are illustrated in Fig. 4. It is seen from Fig. 4 that the grain size ranges from 20 nm to 130 nm, and the average equivalent diameters are 54 nm, 48 nm and 73 nm for A1, B1 and B2, respectively. Similarly, the distribution of thickness for these nanograin layers along the crack growth path was shown in Fig. 5, indicating that the average values of thickness are 315 nm, 435 nm and 386 nm for A1, B1 and B2, respectively. Note that the data in Figs. 4 and 5 are largely discrete, which suggests that the grain size and the thickness of nanograin layer are affected by cyclic loading condition and the microstructure of the material. As an effective method for analyzing the microstructure of materials, SAD technique can be utilized to reveal the essential characteristics of the microstructure more objectively. According to the diffraction principle [30], SAD patterns will appear as a series of rings if it contains many grains with different orientations within the selected area, and with the increase of the number of grains, namely more fine grains, diffraction rings will become more continuous. Therefore, for the purpose of quantitatively describing the distribution of grain size under different loading conditions, a normalized quantity d* is introduced and expressed as: = 633 MPa, N f

 0 * l d l

(1)

where l 0 presents the perimeter of a completely continuous diffraction ring associated with a given crystal plane family, and l presents total lengths of the ring measured in experiments. For this purpose, a number of discontinuous diffraction rings associated with {110} planes for samples A1, B1 and B2 were measured, and the results described by d* are illustrated in Fig. 6. The value of d* notably decreases along the crack growth path, implying that the size of nanograins gradually increases with the propagation of the crack, which may be due to gradually-reduced pressing actions. Moreover, the datum points of B1 are evidently higher than those of A1 and B2, suggesting that the greater compressive stress and the longer loading cycles may promote the grain refinement.

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

60

A1, d = 54 nm B1, d = 48 nm B2, d = 73 nm

50

40

30

20

Frequency, %

10

0 20 40 60 80 100 120 140 160 0

Grain Size, nm

Figure 4: Distribution of grain size underneath FGA surface for samples A1, B1 and B2.

1000

A1, t = 315 nm B1, t = 435 nm B2, t = 386 nm

800

600

400

200

Thickness of Nanograin Layer, nm

0

0

2

4

6

8

10

Distance along Crack Growth Path, μm

Figure 5: Thickness of nanograin layer along crack growth path underneath FGA surface for samples A1, B1 and B2.

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

A1, RB, R =  1 B1, UL, R =  1 B2, UL, R =  0.5

d* , Normalized Quantity

4

6

8

10

12

14

16

Distance along Crack Growth Path, μm

Figure 6: Distribution of normalized quantity d * versus crack growth path for samples A1, B1 and B2.

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

Microstructural features in CIR for positive stress ratio cases The above results indicate that the features of nanograins clearly prevailed underneath the fracture surface in the FGA region for the cases with negative stress ratios, whereas the microstructural features were not clear for the cases with positive stress ratios. It is well known that the plastic deformation occurs at crack tip. Based on the equation proposed by Murakami et al. [31]:     1/2 max max = K c area (2) and the plastic zone size ( r p ) at crack tip under plane strain condition [32]: the value of K max and crack size, causing the expansion of the plastic zone near the crack tip. In order to investigate the effect of the plastic deformation at the crack tip on the microstructure of high-strength steels, two profile samples cut in CIR (B3 and B4) with positive stress ratios and two samples cut in FiE (A2 and B5) were prepared. The results of the samples cut in CIR are presented in this section, and the results of samples cut in FiE will be presented in next section. Fig. 7 illustrates the microstructural features of sample B3 ( R = 0.1), and the sampling location is denoted by a small dashed yellow rectangle shown in Fig. 7a, from which a cluster of inclusions as the origin of crack initiation and the diminishing FGA feature can be clearly observed. Fig. 7b presents the whole BFI of sample B3, and the DFI of its local location (dashed green box) is illustrated in Fig. 7c, showing that any position on the profile is original martensite microstructure, meaning no sign of grain refinement. Fig. 7d shows the SAD pattern of slightly elongated diffraction spots, which is the result of localized plastic deformation. Fig. 7e shows the SAD pattern with typical isolated spots, which are the normal diffraction of a single crystal, i.e., the original coarse martensite microstructure. Similar observations of sample B4 ( R = 0.3) are obtained as shown in Fig. 8. increases with the raise of σ max   y        2 max p 1 6 K r (3)

Figure 7: Microstructural features of sample B3 (UL, R = 0.1, σ a

= 534 MPa, N f

= 1.84 ╳ 10 7 ), (a) SEM image showing crack origin; (b)

BFI; (c) DFI of the dashed green box in (b); (d,e) SAD patterns of the left and right dashed yellow circles in (b).

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Y. Chang et alii, Frattura ed Integrità Strutturale, 49 (2019) 1-11; DOI: 10.3221/IGF-ESIS.49.01

Figure 8: Microstructural features of sample B4 (UL, R = 0.3, σ a BFI; (c) DFI; (d,e) SAD patterns of the left and right dashed yellow circles in (b). = 989 MPa, N f

= 8.70 ╳ 10 8 ), (a) SEM image showing crack origin; (b)

Microstructural features in FiE Fish-eye is a typical morphology of VHCF for metallic materials, but the microstructural features in the FiE region were not very clear so far. For the purpose of further examination for the microstructure features in FiE, two profile samples (A2 and B5) were prepared by FIB cut from the FiE region of failed specimens in VHCF regime under R = ‒ 1 and 0.3. The loading conditions of these two specimens are also listed in Tab. 2. Fig. 9 illustrates the microstructural features of sample A2, for which the sampling location (quadrate rabbet) is close to the outer boundary of the FiE (Fig. 9a). Fig. 9b presents the whole BFI of A2 and Fig. 9c illustrates the DFI of its local field, showing any position on the profile is original martensite microstructure. Fig. 9d shows the SAD pattern with slightly elongated spots, which is the result of localized plastic deformation. Fig. 9e shows isolated spot pattern indicating only one grain within the diffraction area of 200 nm in diameter. In brief, the result of Fig. 9 shows that the microstructure underneath the fracture surface in the FiE region does not undergo grain refinement, which may be related to insufficient pressing during cycling because of the relatively faster crack growth rate in the FiE region. Fig. 10 illustrates the microstructural features of sample B5 (also cut from FiE region), similar to the results shown in Fig. 9. There is no evidence of microstructure refinement in spite of the high maximum stress ( σ max ), suggesting that plastic deformation ahead of crack tip cannot cause the formation of nanograins.

C ONCLUSIONS

n this paper, a series of profile samples from two high-strength steels were prepared by FIB in CIR and FiE regions of failed specimens subjected to rotary bending and ultrasonic axial cycling up to VHCF regime with various stress ratios. Then such samples were observed by TEM with SAD detection. Based on the experimental investigations, the following conclusions were obtained: I

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