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Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Materials Characterization".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 24193

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Prof. Dr. Dražan Kozak

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Mechanical Engineering Faculty, University of Slavonski Brod, Slavonski Brod, Croatia
Interests: fatigue and fracture of welded joints; mechanical properties of AM components; structural integrity assessment; finite element analysis
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Nenad Gubeljak

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Faculty of Mechanical Engineering, University of Maribor, SI-2000 Maribor, Slovenia
Interests: welded joints; structural integrity assessment; fracture mechanics; finite element analysis, multi-scale modeling, fatigue
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Aleksandar Sedmak

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Innovation Centre, University of Belgrade, Belgrade, Serbia
Interests: welded joints; structural integrity assessment; fracture mechanics; finite element analysis; engineering materials
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Filler material used in welding should be the same class as base material, but welding codex often uses a filler with higher yield strength than the base material (f.i. by repair welding). Welded joints are also often the location of potential flaws, where flaw assessment assumes homogeneous material properties, but welds are heterogeneous. There is a compendium of yield load solutions for strength mis-matched fracture mechanics specimens developed to address the heterogeneity in the weld joint. However, solutions for the yield load at different combinations of the strength mismatch within the weld are missing, where mechanical testing and finite element simulations are necessary. In addition to more conventional approaches, a recently introduced multi-scale approach in the assessment of weld heterogeneity sounds very promising. It is an efficient tool to take into account residual stresses also, which can strongly affect the stresses distribution around the flaws in the heterogeneous weldments. The multi-scale methodology is computationally efficient and provides a possible means to bridge multiple length scales (from 10 nm in MD simulation to 10 mm in FE model). This could be a useful tool by considering an acceptable level of accuracy with respect to yield load in heterogeneous welds.

In this Special Issue, modern trends of heterogeneous welded joints testing and simulation, including the multi-scale approach, resulting in appropriate flaw assessment procedures, are highlighted and discussed.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Dr. Dražan Kozak
Prof. Dr. Nenad Gubeljak
Prof. Dr. Aleksandar Sedmak
Guest Editors

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Keywords

heterogeneous welded joints
fatigue and fracture of heterogeneous welded joints
mechanical testing
microstructure
multi-scale modeling
finite element analysis
structural integrity assessment
flaw assessment procedures for heterogeneous welds

Related Special Issue

Fatigue and Fracture Behaviour of Welded and Other Additive Manufactured Structures (Volume II) in Materials (9 articles)

Published Papers (11 papers)

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Research

18 pages, 10675 KiB

Open AccessArticle

The Effect of Material Heterogeneity and Temperature on Impact Toughness and Fracture Resistance of SA-387 Gr. 91 Welded Joints

by Milivoje Jovanović, Ivica Čamagić, Simon Sedmak, Aleksandar Sedmak and Zijah Burzić

Materials 2022, 15(5), 1854; https://doi.org/10.3390/ma15051854 - 02 Mar 2022

Cited by 8 | Viewed by 1608

Abstract

This paper presents the analysis of the behavior of welded joints made of 9–12% Cr-Mo steel SA-387 Gr. 91. The successful application of this steel depends not only on the base metal’s (BM) properties but even more on heat-affected-zone (HAZ) and weld metal (WM), both at room and at operating temperature. Impact testing of specimens with a notch in BM, HAZ, and WM was performed on a Charpy instrumented pendulum to enable the separation of the total energy in crack-initiation and crack-propagation energy. Fracture toughness was also determined for all three zones, applying standard procedure at both temperatures. Results are analyzed to obtain a deep insight into steel SA 387 Gr. 91’s crack resistance properties at room and operating temperatures. Results are also compared with results obtained previously for A-387 Gr. B to assess the effect of an increased content of Chromium. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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15 pages, 4924 KiB

Open AccessArticle

Cleavage Fracture of the Air Cooled Medium Carbon Microalloyed Forging Steels with Heterogeneous Microstructures

by Gvozden Jovanović, Dragomir Glišić, Stefan Dikić, Nenad Radović and Aleksandra Patarić

Materials 2022, 15(5), 1760; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15051760 - 25 Feb 2022

Cited by 5 | Viewed by 1677

Abstract

Cleavage fracture of the V and Ti-V microalloyed forging steels was investigated by the four-point bending testing of the notched specimens of Griffith-Owen’s type at −196 °C, in conjunction with the finite element analysis and the fractographic examination by scanning electron microscopy. To assess the mixed microstructure consisting mostly of the acicular ferrite, alongside proeutectoid ferrite grains and pearlite, the samples were held at 1250 °C for 30 min and subsequently cooled instill air. Cleavage fracture was initiated in the matrix under the high plastic strains near the notch root of the four-point bending specimens without the participation of the second phase particles in the process. Estimated values of the effective surface energy for the V and the Ti-V microalloyed steel of 37 Jm⁻² and 74 Jm⁻², respectively, and the related increase of local critical fracture stress were attributed to the increased content of the acicular ferrite. It was concluded that the observed increase of the local stress for cleavage crack propagation through the matrix was due to the increased number of the high angle boundaries, but also that the acicular ferrite affects the cleavage fracture mechanism by its characteristic stress–strain response with relatively low yield strength and considerable ductility at −196 °C. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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20 pages, 12759 KiB

Open AccessArticle

Catastrophic Impact Loading Resilience of Welded Joints of High Strength Steel of Refineries’ Piping Systems

by Andrzej Klimpel, Anna Timofiejczuk, Jarosław Kaczmarczyk, Krzysztof Herbuś and Massimiliano Pedot

Materials 2022, 15(4), 1323; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15041323 - 11 Feb 2022

Viewed by 1725

Abstract

Refineries piping installation systems are designed, fabricated, and operated to assure very high levels of quality and structural integrity, to provide very high resilience to catastrophic events like earthquakes, explosions, or fires, which could induce catastrophic damage of piping systems due to collapse of nearby structures as towers, bridges, poles, walkways, vessels, etc. To evaluate the catastrophic impact loading resilience to failure of MMA (Manual Metal Arc Welding), GMA (Gas Metal Arc Welding), SSA (Self-shielded Arc Welding), and LASER+GMA of modern API 5L X80 pipes butt welded joints used for piping installation systems of refineries, the new, original technique of the quantitative and qualitative evaluation of impact loading resilience of butt welded joints of pipes was developed. The high-quality butt welded joints were impact loaded by the freely dropping 3000 kg mass hammer of the die forging hammer apparatus. The impact loading energy needed to exceed the yield strength of the extreme zone of welded joints and to induce catastrophic fracture of butt welded joints of API 5L X80 pipes was calculated using FEM (Finite Element Method) modeling of the impact loading process of tested butt welded joints of pipes. Results of the FEM modeling of impact loading technique of butt welded joints of piping systems indicate that it is a useful tool to provide valuable data for experimental impact loading tests of welded joints of pipes, decreasing the time and cost of the experiments. The developed impact loading technique of butt welded joints of pipes to simulate the catastrophic events in refinery piping systems and evaluate the resilience of the butt welded joints of pipes to catastrophic failure proved to be very efficient and accurate. Experiments of impact loading indicated that all specimens of butt welded joints API 5L X80 steel pipes are resilient to failure (cracks) in the extreme stressed/strained areas, above yield and tensile strength of the weld metals, no cracks or tears appeared in the extreme stressed/strained areas of the edges of the pipes, proving the very high quality of API 5L X80 steel pipes. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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24 pages, 7728 KiB

Open AccessArticle

Effects of Fixture Configurations and Weld Strength Mismatch on J-Integral Calculation Procedure for SE(B) Specimens

by Primož Štefane, Stijn Hertelé, Sameera Naib, Wim De Waele and Nenad Gubeljak

Materials 2022, 15(3), 962; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15030962 - 26 Jan 2022

Cited by 2 | Viewed by 1915

Abstract

This work presents the development of a J-integral estimation procedure for deep and shallow cracked bend specimens based upon plastic η_pl factors for a butt weld made in an S690 QL high strength low alloyed steel. Experimental procedures include the characterization of average material properties by tensile testing and evaluation of base and weld metal resistance to stable tearing by fracture testing of square SE(B) specimens containing a weld centerline notch. J-integral has been estimated from plastic work using a single specimen approach and the normalization data reduction technique. A comprehensive parametric finite element study has been conducted to calibrate plastic factor η_pl and geometry factor λ for various fixture and weld configurations, while a corresponding plastic factor γ_pl was computed on the basis of the former two. The modified η_pl and γ_pl factors were then incorporated in the J computation procedure given by the ASTM E1820 standard, for evaluation of the plastic component of J and its corresponding correction due to crack growth, respectively. Two kinds of J-R curves were computed on the basis of modified and standard η_pl and γ_pl factors, where the latter are given by ASTM E1820. A comparison of produced J-R curves for the base material revealed that variations in specimen fixtures can lead to ≈10% overestimation of computed fracture toughness J_Ic. Furthermore, a comparison of J-R curves for overmatched single-material idealized welds revealed that the application of standard η_pl and γ_pl factors can lead to the overestimation of computed fracture toughness J_Ic by more than 10%. Similar observations are made for undermatched single material idealized welds, where fracture toughness J_Ic is overestimated by ≈5%. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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11 pages, 3974 KiB

Open AccessArticle

Yield Load Solutions for SE(B) Fracture Toughness Specimen with I-Shaped Heterogeneous Weld

by Pejo Konjatić, Marko Katinić, Dražan Kozak and Nenad Gubeljak

Materials 2022, 15(1), 214; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15010214 - 28 Dec 2021

Cited by 3 | Viewed by 1662

Abstract

The objective of this work was to investigate the fracture behavior of a heterogeneous I-shaped welded joint in the context of yield load solutions. The weld was divided into two equal parts, using the metal with the higher yield strength and the metal with the lower yield strength compared to base metal. For both configurations of the I-shaped weld, one with a crack in strength in the over-matched part of the weld and one for a crack in the under-matched part of the weld, a systematic study of fracture toughness SE(B) specimen was carried out in which the crack length, the width of the weld and the strength mismatch factor for both weld metals were varied, and the yield loads were determined. As a result of the study, two mathematical models for determination of yield loads are proposed. Both models were experimentally tested with one strength mismatch configuration, and the results showed good agreement and sufficiently conservative results compared to the experimental results. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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10 pages, 2251 KiB

Open AccessArticle

Estimation of C* Integral for Mismatched Welded Compact Tension Specimen

by Marko Katinić, Dorian Turk, Pejo Konjatić and Dražan Kozak

Materials 2021, 14(24), 7491; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14247491 - 07 Dec 2021

Cited by 2 | Viewed by 2315

Abstract

The C* integral for the compact tension (CT) specimen is calculated using the estimation equation in ASTM E1457-15. This equation was developed based on the assumption of material homogeneity and is not applicable to a welded CT specimen. In this paper, a modified equation for estimating the C* integral for a welded compact tension (CT) specimen under creep conditions is proposed. The proposed equation is defined on the basis of systematically conducted extensive finite element (FE) analyses using the ABAQUS program. A crack in the welded CT specimen is located in the center of the heat-affected zone (HAZ), because the most severe type IV cracks are located in the HAZ. The results obtained by the analysis show that the equation for estimating the C* integral in ASTM E1457-15 can underestimate the value of the C* integral for creep-soft HAZ and overestimate for creep-hard HAZ. Therefore, the proposed modified equation is suitable for describing the creep crack growth (CCG) of welded specimens. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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10 pages, 60510 KiB

Open AccessArticle

Contact Reactive Brazing of TC4 Alloy to Al7075 Alloy with Deposited Cu Interlayer

by Mengjuan Yang, Chaonan Niu, Shengpeng Hu, Xiaoguo Song, Yinyin Pei, Jian Zhao and Weimin Long

Materials 2021, 14(21), 6570; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14216570 - 01 Nov 2021

Viewed by 1750

Abstract

The brazing of Titanium alloy to Aluminum alloy is of great significance for lightweight application, but the stable surface oxide film limits it. In our work, the surface oxide film was removed by the ion bombardment, the deposited Cu layer by magnetron sputtering was selected as an interlayer, and then the contact reactive brazing of TC4 alloy to Al7075 alloy was realized. The microstructure and joining properties of TC4/Al7075 joints obtained under different parameters were observed and tested, respectively. The results revealed that the intermetallic compounds in the brazing seam reduced with the increased brazing parameters, while the reaction layer adjacent to TC4 alloy continuously thickened. The shear strength improved first and then decreased with the changing of brazing parameters, and the maximum shear strength of ~201.45 ± 4.40 MPa was obtained at 600 °C for 30 min. The fracture path of TC4/Al7075 joints changed from brittle fracture to transgranular fracture, and the intergranular fracture occurred when the brazing temperature was higher than 600 °C and the holding time exceeded 30 min. Our work provides theoretical and technological analyses for brazing TC4/Al7075 and shows potential applications for large-area brazing of titanium/aluminum. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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14 pages, 8977 KiB

Open AccessArticle

The Numerical Modelling Approach with a Random Distribution of Mechanical Properties for a Mismatched Weld

by Luka Starčevič, Nenad Gubeljak and Jožef Predan

Materials 2021, 14(19), 5896; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14195896 - 08 Oct 2021

Cited by 4 | Viewed by 1538

Abstract

The aim of this work was to include a local variation in material properties to simulate the fracture behaviour in a multi-pass mis-matched X-weld joint. The base material was welded with an over and under-match strength material. The local variation was represented in a finite element model with five material groups in the weld and three layers in the heat-affected zone. The groups were assigned randomly to the elements within a region. A three-point single edge notch bending (SENB) fracture mechanics specimen was analysed for two different configurations where either the initial crack is in the over or under-matched material side to simulate experimentally obtained results. The used modelling approach shows comparable crack propagation and stiffness behaviour, as well as the expected, scatter and instabilities of measured fracture behaviour in inhomogeneous welds. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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Graphical abstract

15 pages, 27383 KiB

Open AccessArticle

Numerical and Experimental Investigations of Fracture Behaviour of Welded Joints with Multiple Defects

by Mihajlo Aranđelović, Simon Sedmak, Radomir Jovičić, Srđa Perković, Zijah Burzić, Dorin Radu and Zoran Radaković

Materials 2021, 14(17), 4832; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14174832 - 25 Aug 2021

Cited by 14 | Viewed by 1951

Abstract

Current standards related to welded joint defects (EN ISO 5817) only consider individual cases (i.e., single defect in a welded joint). The question remains about the behaviour of a welded joint in the simultaneous presence of several different types of defects, so-called multiple defects, which is the topic of this research. The main focus is on defects most commonly encountered in practice, such as linear misalignments, undercuts, incomplete root penetration, and excess weld metal. The welding procedure used in this case was metal active gas welding, a common technique when it comes to welding low-alloy low-carbon steels, including those used for pressure equipment. Different combinations of these defects were deliberately made in welded plates and tested in a standard way on a tensile machine, along with numerical simulations using the finite element method (FEM), based on real geometries. The goal was to predict the behaviour in terms of stress concentrations caused by geometry and affected by multiple defects and material heterogeneity. Numerical and experimental results were in good agreement, but only after some modifications of numerical models. The obtained stress values in the models ranged from noticeably lower than the yield stress of the used materials to slightly higher than it, suggesting that some defect combinations resulted in plastic strain, whereas other models remained in the elastic area. The stress–strain diagram obtained for the first group (misalignment, undercut, and excess root penetration) shows significantly less plasticity. Its yield stress is very close to its ultimate tensile strength, which in turn is noticeably lower compared with the other three groups. This suggests that welded joints with misalignment and incomplete root penetration are indeed the weakest of the four groups either due to the combination of the present defects or perhaps because of an additional unseen internal defect. From the other three diagrams, it can be concluded that the test specimens show very similar behaviour with nearly identical ultimate tensile strengths and considerable plasticity. The diagrams shows the most prominent yielding, with an easily distinguishable difference between the elastic and plastic regions. The diagrams are the most similar, having the same strain of around 9% and with a less obvious yield stress limit. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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14 pages, 6284 KiB

Open AccessFeature PaperArticle

Determination of the Actual Stress–Strain Diagram for Undermatching Welded Joint Using DIC and FEM

by Nenad Zoran Milošević, Aleksandar Stojan Sedmak, Gordana Miodrag Bakić, Vukić Lazić, Miloš Milošević, Goran Mladenović and Aleksandar Maslarević

Materials 2021, 14(16), 4691; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14164691 - 20 Aug 2021

Cited by 12 | Viewed by 2347

Abstract

This paper presents new methodology for determining the actual stress–strain diagram based on analytical equations, in combination with numerical and experimental data. The first step was to use the 3D digital image correlation (DIC) to estimate true stress–strain diagram by replacing common analytical expression for contraction with measured values. Next step was to estimate the stress concentration by using a new methodology, based on recently introduced analytical expressions and numerical verification by the finite element method (FEM), to obtain actual stress–strain diagrams, as named in this paper. The essence of new methodology is to introduce stress concentration factor into the procedure of actual stress evaluation. New methodology is then applied to determine actual stress–strain diagrams for two undermatched welded joints with different rectangular cross-section and groove shapes, made of martensitic steels X10 CrMoVNb 9-1 and Armox 500T. Results indicated that new methodology is a general one, since it is not dependent on welded joint material and geometry. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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16 pages, 6225 KiB

Open AccessArticle

Prediction Model of the Resulting Dimensions of Welded Stamped Parts

by Milan Kadnár, Peter Káčer, Marta Harničárová, Jan Valíček, Mirek Gombár, Milena Kušnerová, František Tóth, Marian Boržan and Juraj Rusnák

Materials 2021, 14(11), 3062; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14113062 - 03 Jun 2021

Cited by 3 | Viewed by 2119

Abstract

The combination of stamping and subsequent welding of components is an important area of the automotive industry. Stamping inaccuracies affect the final size of the stamping and the welded part. In this article, we deal with a specific component that is produced by such a procedure and is also a common part of the geometry of a car. We focused on the possibility of using a negative phenomenon—deformation during welding—on the partial elimination of inaccuracies arising during stamping. Based on the planned experiment, we created a prediction model for the selected part and its production, with the help of which it is possible to determine suitable welding parameters for a specific dimension of the stamping and the required monitored dimension of the welded part. The article also includes the results of additional experimental measurements verifying the accuracy of the model and prediction maps for practice. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures)

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