Issue 78

Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Table of Contents

Experimental and numerical investigation of residual stresses in dissimilar butt weld joint made of cast iron and mild steel https://youtu.be/pmAJQHXV7t0 A. Bacco, A. Califano, A. Greco, R. Sepe ................................................................................ 1-18 Z. A. Betti, N. Betti https://youtu.be/qyeXfUEZUFY Heat treatment of steel using Carboxymethyl Cellulose (CMC) as a green quenching medium: effect of concentration on microstructure evolution and wear resistance ........................................... 19-30 K. Dileep, A. Srinath, N.R. Banapurmath, M. A. Umarfarooq, A. M. Sajjan https://youtu.be/jTY6fUJmC-A Mechanical and fracture response of epoxy nanocomposites reinforced with low concentration graphene and graphene–SiO ₂ hybrids ......................................................................................... 31-43 F. Veschi, F. Foiani, M. Palmieri, G. Morettini, F. Cianetti https://youtu.be/_2zebq-d9NY Fatigue damage assessment for Sine-on-Random: a comparative analysis of the predictive capability and application limits of spectral methods …................................................................ 44-73 N. Naboulsi, F. Ait Hmazi, F. Majid, F. Z. Karmil, N. Douiri, T. Hachimi https://youtu.be/2WfcFZHVI-M Effect of layer orientation and infill density on reliability and lifetime of FDM-printed conductive composites under tensile loading ………………………….…………………………….. 74-95 V. Pisarev, S. Eleonsky, A. Chernov, Y. Matvienko https://youtu.be/dyQ_lCdoC-w Influence of impact energy on residual stresses values inherent in damaged area of composite plate .. 96-117 C. Popa, L. Marsavina, C. Marsavina, C. Popa https://youtu.be/Jtvs5wzPFY0 Optimal shape determination of shear specimens using Machine Learning …............................... 118-128 N. Mohan, V. Bharathi, S. Harish, N. Santhosh, V. B. Hemadri, B. M. Ningegowda https://youtu.be/ayEwURnw-gM Comparative study on dry wear and tribocorrosion behavior of boronized martensitic stainless steels ……………..…………………………………………………………....…… 129-145

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

C. S. Karadumpa, M. Perumalla https://youtu.be/cfu64BY7kCA Development and performance evaluation of hybrid nano modified SCM-based concretes ………. 146-167 Manar Adel, Seleem S. E. Ahmad, Ahmed A. Elakhras https://youtu.be/LPjm_ljSyzo Investigating the effects of steel fibers and notch depth on the fracture behavior of reinforced concrete (RC) beams using both matrix-cracked and through-thickness cracked approaches ………….... 168-185 A. Sancak, A. Canda ş , S. Kurt, C. E. İ mrak https://youtu.be/wI6OEcBARDo Effects of seawater corrosion, notch timing, and test temperature on the impact toughness of AISI 1008 marine chain steel …………..………………………………………………….. 186-206 D.S. Lobanov, E.A. Chebotareva, K.I. Churin https://youtu.be/M51dSRvYcnY The effect of external service-induced defects on the mechanical properties of fibreglass-reinforced plastic under compression ……………………………………………………………... 207-219 V. I. Kolesnikov, O. A. Belyak, D. S. Bulgarevich, O. V. Kudryakov, S. V. Panin https://youtu.be/dG7nc5sNv18 Crystal plasticity modeling of perfectly bonded layered composites under combined normal/shear loading ....................................................................................................................................... 220-232 G. Palomba, D. D’Andrea, G. Risitano, P. Corigliano, D. D’Andrea https://youtu.be/UOGGU01i0ns Experimental and numerical modelling of AISI 316L Butt-welded joints under tensile stress using local material properties …………………………………………………………. 233-247 A. P. Soldatenkov, A. A. Shanyavskiy, E. V. Naydenkin, I P. Mishin, S. V. Panin, A. A. Bogdanov https://youtu.be/9lnp0J2r3Zs Effect of aging temperature on mechanical and fatigue properties of Ti-5Al-5V-5Mo-1Cr-1Fe alloy processed by radial-shear rolling ………………………..………………………… 248-259 A. Zakharov, V. Shlyannikov https://youtu.be/ihUlgUxVwHE Loading biaxiality and crack tip curvature effects on plastic stress intensity factor behaviour at small-scale and extensive plasticity ….……................................................................................ 260-274 T. Nasri, A. Hamdi, M. A. Borgi https://youtu.be/kfvXIAvlpKE Microstructure-explicit Chebyshev-enriched Paris law for short fatigue crack propagation in rolled AA2024-T351 ……............................................................................................................... 275-297 S. A. A. Mustafa, O. Shallah, M.A. Khafaga, M. Mashaal https://youtu.be/hBnjLSER1Oo Experimental evaluation of the cyclic behavior of implanted reinforced concrete shear walls …....... 298-314

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Digesh D. Joshi, Paresh V. Patel, Rinkesh V. Makawana https://youtu.be/WsV4bx6mzS8 Strengthening techniques for progressive collapse mitigation in RC and precast structures: a selective review and the potential of stainless-steel wire mesh ……................................................ 315-345 S. M. Khalil, A. A. Matloub, M. M. Fawzy, A. H. Yousef https://youtu.be/c7DtnvLy9dU Numerical investigation on web of steel I-beam with closed top flange under patch loading ............. 346-366 M. Bronovets, P. Bukovskiy, I. Goryacheva, A. Vshivkov, E. Gachegova, A. Iziumova, R. Sabirov, O. Plekhov https://youtu.be/DjbsD1Sk5Iw Increasing the wear resistance of rolling bearings by laser shock peening ….................................... 367-377 N. Nayak, H. N. Reddappa, N. C. Reddy, M. Ravikumar https://youtu.be/rxOluzz5GGU Study on multi-response optimization of mechanical, dielectric properties and fracture surface of alkali-treated sisal fibre reinforced polypropylene composites …..................................................... 378-392 M. S ł owik, A . Akram https://youtu.be/kN9LjqRgGyo The combined effect of cement matrix strength and aggregate type on the tensile behaviour of concrete ….................................................................................................................................. 393-408 M. Habashneh, M. M. Rad https://youtu.be/aa_vwzPDzfk Influence of mesh size, evolutionary rate, and filter radius on geometrically nonlinear topology optimization ….......................................................................................................................... 409-431 S. Vantadori, F. Iacoviello, C. Bellini, V. Di Cocco, C. Ronchei, D. Scorza, A. Zanichelli, R. Fiorillo https://youtu.be/xpksZGd8I88 Fatigue damage evolution in ZrO 2 -reinforced Al7075 metal matrix composites: from S-N curves to Paris multilinear regimes ….................................................................................................... 432-453 R. Shivashankar, R. Kiran, D. C. Savitha, V. Ravikumar, P. B. Asha, A. Anand, B. Suresha https://youtu.be/uawwt7NGI64 Synergistic effect of Silicon Nitride nanoparticles and Hemp/Basalt hybrid reinforcement on mechanical integrity and fracture resistance of epoxy composites …................................................ 454-473 A. A. Frantsuzov, A. Dong, K. S. Korobov, E. S. Statnik, A. I. Salimon, A. M. Korsunsky https://youtu.be/UpxeSVmehUM Comparative analysis of prior austenite grain size (PAGS) determination in high grade pipeline steels …...................................................................................................................................... 474-488

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

A. Gallo, E. Armentani, M. Ferraiuolo, M. Perrella https://youtu.be/fVdsnT3--h8 A second-order relaxed Newton framework for material parameters identification and stress constrained structural optimization …......................................................................................... 489-503 S. Majer, B. Budzi ń ski, P. Lehner, G. Szmechel https://youtu.be/mGdCTI8fgyw Design of pavements under extreme loads in challenging subsoil conditions in port areas – Case study of Szczecin and Ś winouj ś cie …........................................................................................... 504-518 C. Vendittozzi, A. Brindisi, A. Concilio, S. Ameduri, E. di Micco, F. Berto, S. Natali, D. Tittoni https://youtu.be/AM4NVIJjlsE Field FBG monitoring of helicopter landing gear: data integrity screening and time–frequency characterization of operational events …...................................................................................... 519-540

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Editorial Team

Editor-in-Chief Francesco Iacoviello Sabrina Vantadori

(Università di Cassino e del Lazio Meridionale, Italy)

(Università di Parma, Italy)

Co-Editor in Chief Filippo Berto

(Sapienza, Università di Roma, Italy)

Jianying He

(Norwegian University of Science and Technology (NTNU), Trondheim, Norway)

(National Technical University of Athens, Greece) (Perm Federal Research Center of the Ural, Perm, Russia)

Stavros Kourkoulis

Oleg Plekhov

Section Editors Sara Bagherifard Marco Boniardi Vittorio Di Cocco Ermioni Pasiou

(Politecnico di Milano, Italy) (Politecnico di Milano, Italy)

(Università di Cassino e del Lazio Meridionale, Italy) (National Technical University of Athens, Greece)

(Perm federal research center Ural Branch Russian Academy of Sciences, Russian Federation)

Oleg Plekhov

(Università di Parma, Italy)

Daniela Scorza

Advisory Editorial Board Harm Askes

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

Alberto Carpinteri Andrea Carpinteri Giuseppe Ferro Emmanuel Gdoutos Youshi Hong M. Neil James Gary Marquis Liviu Marsavina Thierry Palin-Luc 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 Politehnica Timisoara, Department of Mechanics and Strength of Materials, Romania) (Ecole Nationale Supérieure d'Arts et Métiers | ENSAM · Institute of Mechanics and Mechanical Engineering (I2M) – Bordeaux, France)

(University of California, USA)

Ashok Saxena

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

Aleksandar Sedmak

(University of Belgrade, Serbia)

Darrell F. Socie

(University of Illinois at Urbana-Champaign, USA)

Cetin Morris Sonsino

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

Ramesh Talreja David Taylor

John Yates

(The Engineering Integrity Society; Sheffield Fracture Mechanics, UK)

Regional Editorial Board Nicola Bonora

(Università di Cassino e del Lazio Meridionale, Italy)

Raj Das

(RMIT University, Aerospace and Aviation department, Australia)

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Dorota Koca ń da 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)

Antonio Martin-Meizoso Mohammed Hadj Meliani

(LPTPM , Hassiba Benbouali University of Chlef. Algeria) (Indian Institute of Technology/Madras in Chennai, India)

Raghu Prakash

Luis Reis Elio Sacco

(Instituto Superior Técnico, Portugal) (Università di Napoli "Federico II", Italy) (University of Belgrade, Serbia) (Tel-Aviv University, Tel-Aviv, Israel)

Aleksandar Sedmak

Dov Sherman Karel Sláme č ka

(Brno University of Technology, Brno, Czech Republic) (Middle East Technical University (METU), Turkey)

Tuncay Yalcinkaya

Editorial Board Jafar Albinmousa Mohammad Azadi Nagamani Jaya Balila

(King Fahd University of Petroleum & Minerals, Saudi Arabia) (Faculty of Mechanical Engineering, Semnan University, Iran) (Indian Institute of Technology Bombay, India) (Università di Cassino e del Lazio Meridionale, Italy)

Costanzo Bellini Davide Berardi K. N. Bharath

(Sapienza, Università di Roma, Italy)

(GM Institute of Technology, Dept. Of Mechanical Engg., India)

Alfonso Fernández-Canteli

(University of Oviedo, Spain) (University of Mascara, Algeria)

Bahri Ould Chikh

Angélica Bordin Colpo

(Federal University of Rio Grande do Sul (UFRGS), Brazil)

Mauro Corrado

(Politecnico di Torino, Italy)

(University Politehnica of Bucharest, Romania)

Dan Mihai Constantinescu

Danilo D’Andrea Abílio de Jesus Umberto De Maio

(University of Messina, Italy) (University of Porto, Portugal) (Università della Calabria, Italy) (University of Belgrade, Serbia)

Milos Djukic

Andrei Dumitrescu

(Petroleum-Gas University of Ploiesti, Romania)

Devid Falliano

(Dipartimento di Ingegneria Strutturale, Edile e Geotecnica, Politecnico di Torino, Italy)

Leandro Ferreira Friedrich

(Federal University of Pampa (UNIPAMPA), Brazil)

Pietro Foti

(Sapienza, Università di Roma, Italy) (Universitat Politècnica de València, Spain)

Eugenio Giner Parsa Ghannadi

(Islamic Azad university, Iran)

P S Shivakumar Gouda Abdelmoumene Guedri

(Dayananda Sagar College of Engineering, Bengaluru, India)

(Université-MCM- Souk Ahras, Algeria) (Middle East Technical University, Turkey) (Hassiba Benbouali University of Chlef, Algeria)

Ercan Gürses

Abdelkader Hocine Daniela Iacoviello

(Sapienza, Università di Roma, Italy) (Bilkent University, Turkey) (Southeast University, China) (University of Piraeus, Greece) (Federal University of Pampa, Brazil)

Ali Javili

Cai Jingming

Dimitris Karalekas

Luis Eduardo Kosteski

Sergiy Kotrechko Grzegorz Lesiuk

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

(Wroclaw University of Science and Technology, Poland)

(Henan Polytechnic University, China)

Qingchao Li Paolo Lonetti

(Università della Calabria, Italy)

Tomasz Machniewicz

(AGH University of Science and Technology) (Università Politecnica delle Marche, Italy)

Erica Magagnini Carmine Maletta

(Università della Calabria, Italy)

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Sonia Marfia

(Università Roma Tre, Italy) (University of Porto, Portugal) (University of Porto, Portugal) (Università di Perugia, Italy) (University of Bristol, UK)

Lucas Filipe Martins da Silva

(Ternopil Ivan Puluj National Technical University, Ukraine)

Pavlo Maruschak Pedro Moreira Giulia Morettini Madeva Nagaral Vasile Nastasescu Stefano Natali Pavlos Nomikos Mahmoud Mostafavi Hryhoriy Nykyforchyn

(Aircraft Research and Design Centre, Hindustan Aeronautics Limited Bangalore, India) (Military Technical Academy, Bucharest; Technical Science Academy of Romania)

(Sapienza, Università di Roma, Italy)

(National Technical University of Athens, Greece)

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

Gianluca Parodo Arturo Pascuzzo

(Università di Cassino e del Lazio Meridionale, Italy)

(Università della Calabria, Italy)

Hiralal Patil

(GIDC Degree Engineering College, Abrama-Navsari, Gujarat, India)

Alessandro Pirondi Andrea Pranno Zoran Radakovi ć D. Mallikarjuna Reddy

(Università di Parma, Italy) (Università della Calabria)

(University of Belgrade, Faculty of Mechanical Engineering, Serbia) (School of Mechanical Engineering, Vellore Institute of Technology, India)

Luciana Restuccia

(Politecnico di Torino, Italy) (Università di Padova, Italy) (Università di Messina, Italy) (Università di Parma, Italy)

Mauro Ricotta

Giacomo Risitano Camilla Ronchei

Hossam El-Din M. Sallam

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

Pietro Salvini Mauro Sassu Raffaele Sepe

(Università di Cagliari, Italy) (Università di Salerno, Italy)

Abdul Aabid Shaikh

(Prince Sultan University, Saudi Arabia)

Dariusz Skibicki Marta S ł owik Luca Sorrentino Andrea Spagnoli Cihan Teko ğ lu Dimos Triantis Andrea Tridello

(UTP University of Science and Technology, Poland)

(Lublin University of Technology, Poland)

(Università di Cassino e del Lazio Meridionale, Italy)

(Università di Parma, Italy)

(TOBB University of Economics and Technology, Ankara, Turkey)

(University of West Attica, Greece) (Politecnico di Torino, Italy) (Università di Pisa, Italy) (Universidade de Brasília, Brasilia) (Kettering University, Michigan,USA)

Paolo Sebastiano Valvo Cristian Vendittozzi

Charles V. White Andrea Zanichelli Shun-Peng Zhu

(Università di Parma, Italy)

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

Special Issue

Russian mechanics contributions for Structural Integrity

(Mechanical Engineering Research Institute of the Russian Academy of Sciences, Russia) (Institute of Continuous Media Mechanics of the Ural Branch of Russian Academy of Science, Russia)

Valerii Pavlovich Matveenko

Oleg Plekhov

Special Issue Costanzo Bellini Camilla Ronchei Liviu Marsavina

Structural Integrity of Additively Manufactured Materials

(Università di Cassino e del Lazio Meridionale, Italy)

(Università di Parma, Italy)

(University of Timisoara, Romania)

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Special Issue

Modeling in Structural Integrity

Bartlomiej Blachowski

(IPPT PAN, Poland)

Martin Krejsa Petr Lehner

(VSB-Technical University of Ostrava, Czech Republic) (VSB-Technical University of Ostrava, Czech Republic)

Majid Movahedi Rad

(Széchenyi István University, Hungary) (California State University Fullerton, USA)

Ghosh Pratanu

Alexander Sedmak

(University of Belgrade, Serbia)

VIII

Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Fracture and Structural Integrity is an Open Access journal affiliated with ESIS

Sister Associations help the journal managing Algeria: Algerian Association on Fracture Mechanics and Energy -AGFME Australia: Australian Fracture Group – AFG Czech Rep.: Asociace Strojních Inženýr ů (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 Group of Fatigue and Fracture Mechanics of Materials and Structures

Poland: Portugal:

Portuguese Structural Integrity Society - APFIE Romania: Asociatia Romana de Mecanica Ruperii - ARMR Serbia:

Structural Integrity and Life Society "Prof. Stojan Sedmak" - DIVK Grupo Espanol de Fractura - Sociedad Espanola de Integridad Estructural – GEF

Spain: Turkey: Ukraine:

Turkish Solid Mechanics Group

Ukrainian Society on Fracture Mechanics of Materials (USFMM)

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Journal description and aims 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). Fracture and Structural Integrity 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 Fracture and Structural Integrity 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 must 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 Fracture and Structural Integrity 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.eu ISSN 1971-8993 Reg. Trib. di Cassino n. 729/07, 30/07/2007

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

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Fracture and Structural Integrity 78 (2026); International Journal of the Italian Group of Fracture

Celebrating our milestones and our dear friend, Leslie Banks-Sills

D

ear friends, the ECF25 ( 25 th European Conference on Fracture ) in Athens was a great success … and during this event, thanks to the help of the Greek Group of Fracture and of its President, our friend, Stavros Kourkoulis, it was possible to celebrate the 20 years of Fracture and Structural Integrity and the 2025 IF and CiteScore metrics.

During the conference we also celebrated the ESIS pillars, the colleagues that allowed us to live in the vibrant ESIS community, in a frame of friendship and collaboration. Among them, maybe the most important is Leslie Banks-Sills, the European Structural Integrity Society (ESIS) President (2010-2018) and a very good friend of the Italian Group of Fracture . Just a few days ago, we received the terrible and unexpected news that she passed away. I have no words to express the sadness for this terrible event. She was a great teacher, a great researcher, a great (the greatest!) ESIS President and a very good friend. We wish to remember her as in Favignana, in 2015, during the IGF23, when she was awarded with the IGF Honorary membership. To celebrate Leslie, her contribution to the research on fracture mechanics, her leadership in ESIS and her friendship with the Italian Group of Fracture , we decided to dedicate to her memory the IGF29 that will be held in 2027 in Vicenza. The new title of the event is: IGF29 – 29 th International Conference on Fracture and Structural Integrity In memoriam Leslie Banks-Sills, ESIS President (2010-2018)

In addition, IGF decided to establish a new 'IGF Bank-Sills Medal' to award researchers who have distinguished themselves in Theoretical Fracture Mechanics research. The winner will be selected through a selection process based on CV evaluation.

Warmest regards,

Francesco Iacoviello Fracture and Structural Integrity Editor in Chief

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A. Bacco et alii, Fracture and Structural Integrity, 78 (2026) 1-18; DOI: 10.3221/IGF-ESIS.78.01

Experimental and numerical investigation of residual stresses in dissimilar butt-weld joint made of cast iron and mild steel Arturo Bacco, America Califano, Alessandro Greco, Raffaele Sepe Dept. of Industrial Engineering, University of Salerno, 84084 Fisciano, Italy

arbacco@unisa.it, https://orcid.org/0009-0002-6689-0280 amcalifano@unisa.it, https://orcid.org/0000-0002-6344-8051 alegreco@unisa.it, https://orcid.org/0000-0002-5856-5704 rsepe@unisa.it, https://orcid.org/0000-0002-1089-4541

Citation: Bacco, A., Califano, A., Greco, A., Sepe, R., Experimental and numerical investigation of residual stresses in dissimilar butt-weld joint made of cast iron and mild steel, Fracture and Structural Integrity, 78 (2026) 1-18.

A BSTRACT . Dissimilar welded joints, formed by joining materials with different mechanical and chemical properties, present significant challenges in terms of design and manufacturing. This is mainly due to the different properties of the materials, which exhibit different behaviours when they are subjected to high thermal gradients. The joint consisted of dissimilar materials, spheroidal cast iron (GJS500-7) and structural steel (S355) welded using the Flux-Cored Arc Welding (FCAW) process. The research focuses on analysing the effects of thermal gradients, due to welding, on residual stresses and deformation on the welded joint. To this aim, Finite Element Method (FEM) was used to simulate the thermo-mechanical behaviour of the joint during the welding process to predict both the distortions and the residual stresses distribution. The numerical results are in accordance with the experimental ones, providing good confidence in the use of the model to predict residual stresses and distortions for this type of application. K EYWORDS . Residual stresses, Hybrid joint, Dissimilar materials, Cast Iron, Steel, FCAW.

Received: 28.05.2026 Accepted: 26.06.2026 Published: 12.07.2026 Issue: 10.2026

Copyright: © 2026 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.

I NTRODUCTION

elding currently represents the primary method for joining structural components within the vast family of metallic structures. This joining process is widely employed across various sectors, ranging from railways to aerospace and automotive industries. Consequently, recent scientific research has focused on analysing new types of welded joints and optimizing existing ones, aiming to increase efficiency and improve the mechanical performance of the W

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A. Bacco et alii, Fracture and Structural Integrity, 78 (2026) 1-18; DOI: 10.3221/IGF-ESIS.78.01

joints. While the welding of homogeneous components (the same material for both parts being joined) is a consolidated process with predictable behaviour, the joining of dissimilar materials is generating significant interest within the scientific community [1–3]. This interest in hybrid structures is growing rapidly, as it enables the strategic use of different materials within the same component. This constitutes a major advantage in applications aimed at reducing structural weight or where specific material properties are required at targeted locations. A prime example is the coupling of the high mechanical strength of steel with the damping and anti-vibration properties typical of cast iron. The fabrication of such joints poses significant challenges, as joining dissimilar materials aims to create structural continuity between two components made of materials with different physicochemical properties. Exhibiting different thermal expansion coefficients, the two materials react differently to the welding process. The high localized thermal gradients generate strong non-linear temperature fields within the materials. Combined with the asymmetric thermal conductivity between the two materials, these can induce severe residual stresses and distortions during the heating and cooling cycles of the welding process, potentially compromising structural integrity [4]. To date, however, the experimental evaluation of these phenomena is often costly and limited to localized investigations. Therefore, numerical techniques, such as the finite element method (FEM), have increasingly become crucial for predicting the evolution of the stress-strain state during and after the welding process [5,6]. The accuracy of such models strictly depends on the correct implementation of process parameters (joint geometry, heat input, welding speed, number of passes) [7,8] and the thermal and mechanical properties of the utilized materials, which exhibit non-linear temperature dependence [9]. Despite the renewed scientific interest in dissimilar joints, evidenced by recent studies on complex configurations or high energy density processes [10], a literature review reveals a significant gap regarding the thermomechanical modelling of hybrid cast iron-steel structural joints. As a matter of fact, existing studies mainly fall into two categories that do not encompass the phenomenology investigated herein. On the one hand, for example, Pouranvari et al. [11] have clarified the experimental metallurgical aspects, demonstrating the effectiveness of nickel-based filler metals in preventing brittle phases in the fusion zone (FZ). However, these kinds of studies are often limited to post-mortem analyses (microstructure and hardness), lacking a predictive perspective on the evolution of residual stresses during the thermal cycle induced by the welding process. On the other hand, recent contributions to numerical modelling, such as the work by Farahani et al. [12], represent progress in cast iron simulation, yet they strictly focus on repair welding. In this configuration, the constraint is imposed by the cavity of the base material itself (cast iron only), a condition radically different from that of a butt joint, where the materials being joined are dissimilar and the plates are free to deform asymmetrically under the influence of different thermal expansion coefficients. Other studies on structural joints frequently refer to material combinations with more compatible characteristics, thereby limiting the transferability of their results to the hybrid cast iron-steel process. For instance, extensive research by Zhang et al. [13] has successfully characterized residual stresses in dissimilar steel joints (e.g., austenitic-ferritic). Although these works elucidate the mechanisms of asymmetric stress distribution, they deal with materials exhibiting relatively similar ductile behaviours, unlike the abrupt mismatch in physicochemical characteristics found between spheroidal cast iron and structural steel. Even when cast iron-steel coupling is addressed, as in Haihan [14], the analysis is often constrained to specific geometries like pipe-to-pipe connections. In such cases, the circumferential constraint dominates, masking the fundamental thermo mechanical evolution typical of linear butt welds. Quiang et al. [15], do effectively evaluate residual stresses in hybrid cast iron-steel joints, but they focus on high-thickness configurations. These require multiple welding passes, and the large thermal inertias of the involved components could mask the effects that welding processes might have on more commonly used thicknesses. A further reason explaining the scarcity of reference studies in the literature concerning residual stresses in cast iron-steel joints is related to the intrinsic complexity of welding cast iron. The operational criticalities associated with this material, primarily attributable to its high carbon content, are widely acknowledged within the scientific community [16,17]. Indeed, various types of defects can arise during the welding process: cold cracking due to shrinkage stresses near the fusion zone, porosity caused by the reaction between carbon and oxygen at high temperatures, and lack of fusion induced by the high presence of graphite, which hinders the proper melting of the base material. Furthermore, when cast iron is subjected to rapid cooling (typical of the post-welding phase), extremely hard and brittle heat-affected zones can form due to the inability of carbon to precipitate again as graphite, leading to the subsequent transformation of austenite into martensite. In this framework, the present work intends to bridge the scientific gap by proposing an advanced numerical model for the simulation of the welding of a cast iron-steel butt joint. The primary strength of this model lies in the geometric simplicity of the analysed configuration, featuring thicknesses typically utilized in industrial applications and a limited number of welding passes. This approach made it possible to derive

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residual stresses and deformations by isolating the fundamental thermo-mechanical phenomenology from scale and geometric effects (typical of large thicknesses) that could obscure the outcomes in other scenarios. The development of a welding process and the parallel fabrication of a cast iron-steel joint allowed for the implementation of real welding parameter values into the model, while simultaneously providing an experimental benchmark for the validation of the numerical model. The analysis conducted on the numerical model permitted, primarily, the evaluation of heat redistribution during welding and how it partitions differently between the two materials (via thermal analysis); then, the model allowed to carry out analyses of the residual stresses and deformations generated by the process (via mechanical analysis). Furthermore, having subjected the physical joint to non-destructive testing and hardness evaluations, the resulting joint also serves as a reference for other potential applications involving cast iron-steel welded joints. The work thus conducted aims to: provide a validated predictive tool capable of quantifying global thermomechanical effects in hybrid cast iron-steel joints as welding parameters vary and offer a reference for the attainable stress and deformation values, thereby serving as a foundation for the future structural design of complex hybrid cast iron-steel components.

M ATERIAL AND METHODS

T

he experimental campaign focused on a dissimilar butt joint characterized by a single 60° V-groove preparation. The specimen consists of an S355 structural steel plate joined to a GJS500-7 spheroidal graphite cast iron plate; the specific geometrical dimensions are detailed in Fig. 1. The chemical compositions and mechanical properties of the base materials are reported in Tabs. 1 and 2, respectively. The welding process employed was Flux-Cored Arc Welding (FCAW), utilizing a 1.2 mm diameter (Nickel-Iron based) filler wire with an Ar-CO2 shielding gas mixture. The joint was completed in two subsequent passes; the specific process parameters adopted are summarised in Tab. 3.

Materials:

C

Si

Mn

P

S

Cu

N

S355

0.14÷0.24 Max (0.55) Max (1.6) Max (0.035) Max (0.035) Max (0.55) Max (0.012)

GJS500-7

2.7÷3.7

0.8÷2.9

0.3÷0.7

Max (0.10) Max (0.020)

-

-

Table 1: Chemical composition (wt%).

R  [MPa] A ሺ % ሻ 470÷630 22

y  [MPa]

Materials

S355

>355 >320

GJS500-7 7 Table 2: Mechanical properties of the base materials at room temperature. 500÷675

Figure 1: Joint dimensions in [mm].

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Parameters

Values for 1st pass

Values for 2nd pass

Voltage V [V]

22

24.5

Current I [A]

160

175

Welding efficiency η [-]

0.8

0.8

Welding speed v [mm/s]

4.7

3.5

Depth [mm]

3.8

4.7

Table 3: Welding parameters.

Temperature acquisition To evaluate the thermal cycles and calibrate the numerical heat source, six K-type thermocouples were installed on the joint. The sensors were embedded at the mid-thickness of the plates (4.25 mm depth) through drilled blind holes, as detailed in Fig. 2. The thermocouples were arranged in a symmetrical configuration with respect to the Weld Centre Line (WCL): three on the S355 steel side and three on the GJS500-7 cast iron side. They were positioned at specific distances from the WCL (specifically at 23, 12.5, 8 mm) to evaluate the temperature distribution and cooling rates in both the Heat Affected Zone (HAZ) and the base material. Real-time temperature data acquisition was performed using a National Instruments PCI-6221 card interfaced with LabVIEW 8.5 software.

Figure 2: Position of thermocouples in [mm].

Joint defect detection and hardness Upon completion of the welding process, the joint underwent a post-process inspection to verify its structural integrity. Ensuring the absence of internal macro-defects (such as porosity, lack of fusion, or cracks) is a fundamental prerequisite for the validation phase, as the Finite Element (FE) model simulates an ideal continuum free from process-induced discontinuities. Non-Destructive Testing (NDT) was performed via Digital Radiography (RT). The inspection employed a Gilardoni XE-L industrial radioscopy and tomography system equipped with a 0.4 mm microfocus source, capable of detecting fine internal flaws. The specific acquisition parameters adopted for the radiographic test are detailed in Tab. 4. Following the non-destructive inspection, a transverse macro-section was extracted transversal to WCL for metallographic analysis and hardness testing. Standard sample preparation was performed: the specimen was hot mounted in thermosetting phenolic resin to ensure edge retention and planar polishing. The surface was ground and polished to a mirror finish, then chemically etched using a 5% Nital solution to reveal the macrostructural features and the distinct zones of the joint.

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The macrographic analysis served a dual purpose: it confirmed the absence of micro-defects undetected by radiography and, crucially, provided the experimental geometrical dimensions of the FZ and HAZ. These measurements were fundamental to calibrate the shape of the heat source in the numerical model.

Parameters Voltage [kV] Current [mA]

Values

181.0

2.5

Focus-Detector distance [mm] Focus-Object distance [mm]

1260.0

908.0

Pixel size [µm]

179

Gain [1pF]

2

Exposure [fps] 18 Table 4: Parameters of radiographic test.

Finally, a Vickers hardness profile (HV10) was measured across the joint cross-section. The indentations were spaced at 1 mm intervals along a line transverse to the welding direction, centred on the WCL, allowing for a detailed mapping of the mechanical property variations from the steel to the cast iron side.

FE MODEL

A

sequentially coupled thermal-mechanical analysis was adopted to predict the residual stress field. This approach assumes that the mechanical deformation has a negligible effect on the thermal history, significantly reducing computational cost without compromising accuracy. This methodology is consistent with previous numerical investigations conducted by the authors on similar joint configurations [18]. All simulations were performed using the commercial F code Abaqus/CAE 6.14-1. To ensure consistency between the thermal and mechanical solutions, an identical mesh topology was employed for both analyses, differing only in the element type: 8-node linear heat transfer brick elements (DC3D8) were used for the thermal solver, while 8-node linear brick elements (C3D8) were selected for the structural analysis. The mesh discretization was refined in the FZ and HAZ to capture the steep thermal gradients. To accurately simulate the thermo-mechanical behaviour of the joint, the physical and mechanical properties of the materials involved were modelled as temperature-dependent functions. Since experimental characterization at high weld temperatures was not performed in this study and since these are alloys widely used in industry (not special alloys), the non-linear material properties (both thermal and mechanical) were derived from consolidated literature data. Specifically, the thermo mechanical properties (conductivity, specific heat, density) (Fig. 3) for the S355 steel were adopted from the study by [19], while for the spheroidal cast iron, reference was made to the work of [12] on the influence of temperature on ductile iron. Regarding the elasto-plastic behaviour, temperature-dependent stress-strain curves were implemented based on experimental data reported by [20] for the steel component and by [12,21] for the nodular cast iron. As for the filler material, due to dilution with the base metals and the lack of specific data for the resulting alloy, the properties were assumed to be consistent with those of the spheroidal cast iron, a simplified approach successfully adopted in previous computational studies [12], in which the wire is simulated using the properties of the base material. This choice avoids steel because the massive carbon dilution from the cast iron makes the weld pool metallurgically closer to it. Furthermore, Ni-Fe fillers are engineered to match the thermal expansion of cast iron to minimize shrinkage stresses; modelling them this way avoids spurious stress peaks in the brittle cast iron HAZ, safely shifting the thermo-mechanical mismatch to the ductile and tough steel side. To simulate the progressive deposition of the filler material, the 'element birth and death' technique (Model Change option) was implemented. This modelling strategy, extensively tested by different research group to evaluate welding efficiency and distortions [22], involves discretizing the weld bead into multiple longitudinal sets, initially deactivated and progressively reactivated in synchronization with the moving heat source. The simulation steps replicated the experimental procedure: 1. deposition of the first pass;

2. inter-pass cooling time of 120 s; 3. deposition of the second pass; 4. final cooling to room temperature.

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Figure 3: Thermo-mechanical properties for the S355 steel adopted from [19] and for the spheroidal cast iron from [12].

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Thermal analysis The thermal simulation of the welding process was carried out by solving the transient heat conduction problem, governed by Eqn. (1). This equation ensures energy conservation under nonlinear conditions, accounting for the temperature dependent material properties (density, specific heat, and thermal conductivity), along with an internal heat generation term representing the energy input supplied by the welding arc. To simulate the moving heat source, a volumetric heat flux was applied to the active elements of the FZ, calibrated to reproduce the experimental net heat input. This modelling approach aligns with methodologies successfully validated by the authors in previous investigations on butt and T-joints [23] The analysis also accounted for the effects of latent heat of fusion and solidification, which are essential for accurately predicting temperature peaks and the FZ size. Boundary conditions were defined by imposing heat losses due to natural convection and radiation on all free surfaces of the joint, adopting heat transfer coefficients consistent with literature and previous numerical calibrations [24] - T is the temperature distribution of the welded plate at time t ; - , C and k are the density, specific heat and thermal conductivity of the material, respectively; - q  is the rate of internal heat generation. where: the initial condition assumes a uniform ambient temperature 0 T Eqn. (2), while boundary conditions include heat exchange through convection and radiation Eqn. (3).   0 , , ; 0 T x y z t T   (2) y z x k T  k T  k T  T C q t    x x  y   y z z                              (1)

x k n k n k n x y z                x y y z z T T T



 , , ;

q x y z t 

(3)

n

- n q  is the heat flux at a generic boundary, with a local unit vector having components ( , , x y z n n n ) directed outwards; - 0 T is the initial temperature. Convective losses Eqn. (4) and radiative losses Eqn. (5) are combined into a single temperature-dependent film coefficient H Eqn. (6), simplifying the treatment of external heat dissipation,     0 , , ; nc c q h T x y z t T    (4)









, , ; r r q h T x y z t T    nr

(5)

c r H h h  

(6)

The heat supplied by the arc per unit length is calculated from process parameters such as voltage, current, welding speed, and arc efficiency Eqn. (7).



VI



Q

(7)

v

sensible Q sensible heat required to raise the material from ambient to

This energy is partitioned into three contributions:

latent Q latent heat associated with melting (where latent q is the latent heat for unit of mass, for

solidus temperature Eqn. (8),

steel equal to 277,000 J kg -1 and for cast iron 272,500 J kg -1 ) Eqn. (9),

body flux Q the remaining energy Eqn. (10). The elements

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are activated at the melting point, and for this reason the only heat that needs to be added is

body flux Q which is applied as a

volumetric source to the activated elements Eqn. (11),

T

T













s

s

sensible Q vol 

C dT m C dT  

(8)

seam

seam

T

T

0

0

latent seam latent Q m q 

(9)

real sensible Q Q Q   

* real seam Q Q L 

with

(10)

Q

body flux

latent

Q

body flux



Q

(11)

component

n

component

where: -

, seam seam L vol and seam m are the length, the volume and the mass of the seam, respectively; - s T is the solidus temperature; - component n is the number of components of the seam. To reproduce the progressive deposition of filler material, the weld bead is divided into discrete components. Each component receives heat input Eqn. (12) for a time interval corresponding to the torch travel speed Eqn. (13),

Q

body flux Q v

component





q 

(12)

vol

t

vol

L

component weld

seam component

L

component



t

(13)

weld

v

where component L is the length of components of the seam. Temperature-dependent thermal properties and phase-change effects are included, allowing accurate prediction of FZ and heat-affected zone geometry without requiring calibration of complex heat source models. This approach significantly reduces setup time while maintaining reliability in thermal field estimation. Mechanical analysis The mechanical analysis employs the nodal temperature history obtained from the thermal simulation as input to compute the stress–strain response of the welded joint. An elastoplastic material model was adopted, based on the von Mises yield criterion and isotropic hardening, accounting for temperature-dependent mechanical properties. This constitutive model, widely used for simulating steel [23,24], is expressed by the incremental form of the stress–strain law Eqn. (14), where the total stiffness matrix combines elastic and plastic contributions (15), incorporating thermal strains through the thermal stiffness term.

ep d D d C dT             th

(14)

    ep e p D D D      

(15)

where: -

ep D     is the total stiffness matrix; e D     is the elastic stiffness matrix;

-

8