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Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition)

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A Special Issue of Materials (ISSN 1996-1944) belonging to the section "Materials Simulation and Design".

Deadline for manuscript submissions: 20 October 2026 | Viewed by 13410

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Dr. Raul D. S. G. Campilho

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Department of Mechanical Engineering, ISEP-School of Engineering, Polytechnic of Porto, R. Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal
Interests: composite materials; joining processes; mechanical design; manufacturing processes; automation
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Dear Colleagues,

Nowadays, structural design is facing major challenges in the associated joining processes, such as material selection, different thermal coefficients and melting points, multi-material joining, the joining of thin-walled structures, traditional process effectiveness for new materials, cost efficiency and ecological issues. To provide a strong, reliable and lightweight solution for a given application, the designer should either consider hybrid joining or choose from a large variety of available processes, such as welding, brazing, riveting, mechanical fastening, adhesive bonding, clinching, friction stir welding, laser welding, diffusion welding, amongst others. These joining processes have evolved towards optimization and cost reduction in the early design stages in terms of their implementation and industrialization, destructive and non-destructive testing, and either analytical or numerical modeling. Numerical modeling is particularly effective for simulating complex geometries, different load scenarios and materials with plasticity or anisotropy. The finite element method, together with fracture mechanics techniques, is a powerful and common approach employed in the scientific community but is less applied for the study of complex loads, such as high strain rates, fatigue or impact, and it is seldom used in the industry. To develop state-of-the-art techniques and disseminate the recent advances in all types of joining, either experimental or numerical, the Third Edition of this Special Issue intends to follow the successful path of the first two Editions and bring together a significant number of high-quality contributions to this field of research through innovative and original works, subsequently promoting their dissemination via open access publishing.

Dr. Raul D. S. G. Campilho
Guest Editor

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Keywords

joining process
welding
brazing
riveting
mechanical fastening
adhesive bonding
clinching
friction stir welding
laser welding
diffusion welding
hybrid joining
experimental testing
numerical modeling
strength prediction
failure path prediction
finite element method
fracture mechanics
static load
dynamic load
impact load
fatigue load
residual stress
mechanical properties
thin-walled structures

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Published Papers (11 papers)

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Research

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34 pages, 19082 KB

Open AccessArticle

Experimental and Numerical Evaluation of Recycled Thermoplastic Composites for Structural Applications in Sustainable Construction

by Karla Parada-Rocha, Andrés Guzmán, Carlos Parada-Rocha and Nemesio Daza-Marquez

Materials 2026, 19(20), 4331; https://doi.org/10.3390/ma19204331 - 15 Oct 2026

Abstract

This study presents an experimental and numerical framework for evaluating recycled thermoplastic composites for structural applications in sustainable construction. The base material (BM), comprising recycled high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), was characterized in tension and compression; inverse mechanical identification yielded assigned domain fractions of 26%, 36%, and 38%, respectively. Numerical incorporation of acrylonitrile butadiene styrene (ABS) resulted in an optimized composite (CMo: 13% HDPE, 18% LDPE, 19% PP, and 50% ABS), increasing the predicted tensile elastic modulus from 871.36 MPa to 1670.4 MPa (91.7%). Thermal modeling illustrated the BM temperature distribution under prescribed boundary temperatures, while a preliminary structural assessment considered CMo beams, columns, and roof-support members for single-story housing and identified insufficient lateral stiffness under seismic loading. An inventory-based comparison yielded approximately 59% lower estimated CO₂-equivalent emissions for the CMo structural system than for the reinforced-concrete and steel reference, subject to the adopted emission factors and differing source boundaries. The framework supports formulation selection for further investigation, although experimental validation of the CMo, members, and connections remains necessary before structural suitability can be established. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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16 pages, 10455 KB

Open AccessArticle

Metallurgical and Mechanical Property Investigation of ETP Cu Similar Hybrid Friction Welds for Nuclear Fusion Applications

by Michail Dellepiane, Laurie da Silva and Athanasios Toumpis

Materials 2026, 19(19), 4066; https://doi.org/10.3390/ma19194066 - 23 Sep 2026

Viewed by 234

Abstract

The evolution of microstructure and mechanical properties in electrolytic tough-pitch (ETP) copper subjected to hybrid friction welding (HFW) was investigated. The effect of introducing a programmable brake on the flywheel’s rotation while maintaining constant friction and forging pressures was explored. The welded joints were examined through a series of investigations, including optical and scanning electron microscopy with electron backscatter diffraction, tensile and microhardness testing, followed by fractography. The optimised weld achieved the highest ultimate tensile strength (≈274 MPa), a 7.87% increase over the base material, and the greatest elongation (~22%), with ductile fractures and visible necking. The measured hardness distribution depicted higher values for the weld zone compared to the thermo-mechanically affected zone, both expressing a significant decrease from the heat-affected zone and base material due to pre-welding strain hardening existing within the copper alloy. EBSD analysis on the weld zone and thermo-mechanically affected zones revealed the presence of refined grains, with low grain orientation spread (GOS) and kernel average misorientation (KAM) values, which indicated the occurrence of dynamic recrystallisation (DRX) mechanisms during HFW. HFW was able to successfully produce ETP Cu-similar welds with 98.1% joint efficiency. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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19 pages, 11917 KB

Open AccessArticle

Influence of Specific Heat Input and Weld Configuration on Hardness and Residual Stress Distribution of S960MC Steel Welds

by Matus Murin, Libor Trsko, Frantisek Novy, Martin Fratrik, Michal Jambor and Vratislav Mares

Materials 2026, 19(10), 2062; https://doi.org/10.3390/ma19102062 - 14 May 2026

Cited by 1 | Viewed by 583

Abstract

This study investigates the influence of specific heat input and weld configuration on heat affected zone hardness and residual stress of S960MC high strength steel welds. In total, five types of weld samples were manufactured by Tungsten Inert Gas (TIG) autogenous welding and Metal Active Gas (MAG) butt welding to simulate the effect of increasing heat input and constraining the relative motion of welded parts during the heating and cooling phase. The obtained results show that the highest axial tensile residual stresses with magnitude above 900 MPa, combined with a hardness drop in a range from 13 up to 18%, occur mostly in the sub-critical heat affected zone, making it the critical zone of the weld. Increasing the heat input during welding does not have a simple correlation with generating more residual stresses and the trends obtained on the surface are different from results evaluated at a depth of 0.2 mm. Restraining the relative part motion during the welding affects mostly the tangential residual stresses, causing an increase in their tensile magnitude localized in the middle of the heat-affected zone while almost no influence on the axial residual stress component was recorded. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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15 pages, 1191 KB

Open AccessArticle

The Investigation of the Sensitivity of the Compliance to the Shape of the Spot in Welded Thermoplastic Single-Lap Shear (SLS) Joints

by Eva T. B. Smeets, Calvin D. Rans, René Alderliesten and Irene Fernandez Villegas

Materials 2026, 19(10), 2016; https://doi.org/10.3390/ma19102016 - 12 May 2026

Viewed by 526

Abstract

To ensure safety in structural design, a method to quantify the damage in thermoplastic ultrasonic single-spot-welded Single-Lap Shear (SLS) joints is needed. This paper investigates whether detailed knowledge regarding the shape of the weld is required when using the global compliance to quantify damage. A finite element model using cohesive zone elements is developed in Abaqus to simulate single-spot SLS specimens with varying weld areas, aspect ratios, and damage growth directions, covering damage levels from 0 to 90% of the initial weld area. For each configuration, the relationship between intact weld area and global compliance is evaluated, and the numerical trends are compared to previously published experimental data from similar joints. The results show that weld size and damage growth direction have negligible influence on the relationship between global compliance and weld area, and that weld shape is also insignificant as long as the aspect ratio remains within a practical range; only very elongated welds with an aspect ratio over 4.4, which are unlikely in production, deviate significantly. Global compliance can be used as a reliable indicator of damage in single-spot ultrasonic welds that is insensitive to weld shape. This enables simplified in situ damage monitoring and reduces the need for detailed geometric characterisation during mechanical testing. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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22 pages, 5562 KB

Open AccessArticle

Simulation of Static Ultrasonic Welding Based on Explicit Simulation and a More Accurate Representation of the Hammering Effect

by Filipp Köhler, Jan Yorrick Dietrich, Irene Fernandez Villegas, Clemens Dransfeld, David May and Axel Herrmann

Materials 2026, 19(6), 1213; https://doi.org/10.3390/ma19061213 - 19 Mar 2026

Viewed by 973

Abstract

The utilisation of composite materials has the potential to play a vital role in the development of lightweight structures for future generations of aircraft, with the objective to reduce emissions. Ultrasonic welding is a process that has been proven to exhibit advantageous qualities, including the capacity to achieve welds with a comparatively short process time. Furthermore, its capacity to function as both a static and a continuous process makes it a viable candidate for facilitating the realisation of this objective. The present study investigates the potential of a novel explicit modelling approach for the static ultrasonic welding process to more accurately represent the welding process by incorporating a more precise representation of the hammering effect. The hammering effect describes the partial loss of contact between the sonotrode and the upper adherend. The model’s validation was achieved through a multifaceted approach that incorporates high-speed camera recording, encompassing digital image correlation, laser displacement sensor measurements, and static ultrasonic welding experiments. These experiments encompassed varying welding times, followed by fracture surface analysis. The findings showed that an explicit time-domain model can effectively represent the static welding process of unidirectional materials utilising a film energy director. The experimental validation demonstrated a high degree of correlation between the thermal behaviour of the welding interface and the simulation results. The study demonstrated that the neutral position of the sonotrode exhibited an increase during the initial phase of the welding process due to dynamic stresses. This phenomenon enables reduced constraint movement of the adherends and the energy director, which results in the disconnection of the sonotrode from both the upper adherend and the energy director, as well as the adherends and the anvil. The higher neutral position of the sonotrode was then implemented in an explicit simulation of the static ultrasonic welding process. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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23 pages, 8048 KB

Open AccessArticle

Fatigue Design of Tubular Carbon–Aluminium Bonded Joints Under Constant- and Variable-Amplitude Fatigue

by Mauro Ricotta, Gianmaria Bettio and Giovanni Meneghetti

Materials 2026, 19(4), 781; https://doi.org/10.3390/ma19040781 - 17 Feb 2026

Cited by 1 | Viewed by 838

Abstract

This study investigates the fatigue behaviour of carbon fibre–aluminium adhesively bonded tubular joints, representative of the suspension arm of a Formula SAE racing car, under both constant- and variable-amplitude fatigue loading. A linear elastic stress analysis was conducted using two-dimensional axisymmetric finite element models to determine the singular stress field parameters—specifically the Generalised Stress Intensity Factor (H₀) and the stress singularity exponent (s)—at critical adhesive–adherend interfaces. Experimental tests under quasi-static loading and constant amplitude, as well as variable-amplitude fatigue conditions, were performed. The constant-amplitude fatigue data were reanalysed in terms of both nominal maximum shear stress and H₀. The results show that the scatter index of the fatigue data was reduced by a factor of 1.46 when H₀ was used as the fatigue-driving parameter, indicating an improved correlation of the experimental results. Variable-amplitude fatigue tests were interpreted using Miner’s cumulative damage rule, confirming the suitability of H₀-based life estimation models even under realistic, variable-amplitude loading conditions. The results demonstrate that H₀ is an effective parameter for rationalising fatigue performance of tubular bonded joints and highlight its potential for fatigue design in composite–metal structural applications. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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17 pages, 2381 KB

Open AccessArticle

Experimental Assessment of Stress–Strain Response in Filament-Wound GFRP Pipes Under Internal Pressure Loading

by Costin Nicolae Ilincă, Ibrahim Naim Ramadan, Rami Doukeh, Adrian Neacsa, Alin Diniță, Eugen Victor Laudacescu, Marius Gabriel Petrescu, Marius Bădicioiu and Ștefan Alexandru Gavrilă

Materials 2026, 19(3), 639; https://doi.org/10.3390/ma19030639 - 6 Feb 2026

Cited by 2 | Viewed by 1441

Abstract

Fiber-reinforced polymer (FRP) pipes are increasingly used in pressure piping systems due to their corrosion resistance and favorable mechanical performance; however, the direct experimental validation of design assumptions adopted in international standards remains limited. The objective of this study is to experimentally validate the mechanical response and stress distribution of filament-wound GFRP pipes under representative loading conditions and to assess the consistency of the measured behavior with the allowable-stress design framework of ISO 14692 and complementary ASME and BS codes. In this study, the mechanical behavior of filament-wound glass fiber-reinforced polymer (GFRP) pipes is investigated through a combined experimental program including tensile, bending, and full-scale internal pressure tests. Electrical resistance strain gauges were applied in axial and circumferential directions to directly measure deformation under internal pressure up to 31 bar, allowing experimental stresses to be derived using orthotropic laminate relationships. The results demonstrate a predominantly linear elastic response within the service range, followed by progressive damage initiation at higher load levels, with circumferential stresses consistently exceeding axial stresses, confirming a hoop-dominated response. At the maximum applied pressure of 31 bar, axial and circumferential strains reached approximately ε_a ≈ 1.30 × 10⁻³ and ε_h ≈ 1.60 × 10⁻³, corresponding to experimentally derived stresses of σ_a^exp ≈ 15.3 MPa and σ_h^exp ≈ 18.8 MPa, without catastrophic failure. The novelty of this work lies in the direct integration of full-scale strain gauge measurements with standardized allowable-stress design assumptions, enabling an experimental validation of ISO 14692 that is rarely addressed in existing studies. The experimentally derived stress–strain data show good agreement with theoretical models and provide a direct link between measured behavior and the allowable stress philosophy and design equations defined in ISO 14692 and complementary ASME and BS design codes. The findings validate the applicability of standardized design approaches and provide experimentally grounded support for engineering design decisions in FRP piping systems. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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23 pages, 11658 KB

Open AccessArticle

Influence of Environmental Conditions on Tropical and Temperate Hardwood Species Bonded with Polyurethane Adhesives

by Marcin Małek, Magdalena Wasiak, Ewelina Kozikowska, Jakub Łuszczek and Cezary Strąk

Materials 2026, 19(3), 589; https://doi.org/10.3390/ma19030589 - 3 Feb 2026

Viewed by 1241

Abstract

This research presents a comprehensive evaluation of semi-elastic polyurethane adhesives used for bonding wooden flooring, with a particular focus on both domestic (oak) and exotic hardwood species (teak, iroko, wenge, merbau). Given the increasing interest in sustainable construction practices and the growing use of diverse wood species in flooring systems, this study aimed to assess the mechanical, morphological, and surface properties of adhesive joints under both standard laboratory and thermally aged conditions. Mechanical testing was conducted according to PN-EN ISO 17178 standards and included shear and tensile strength measurements on wood–wood and wood–concrete assemblies. Specimens were evaluated in multiple aging conditions, simulating real-world application environments. Shear strength increased post-aging, with the most notable improvement observed in wenge (21.2%). Tensile strength between wooden lamellas and concrete substrates remained stable or slightly decreased (up to 18.8% in wenge), yet all values stayed above the 1 MPa minimum requirement, confirming structural reliability. Surface properties of the wood species were characterized through contact angle measurements and 3D optical roughness analysis. Teak exhibited the highest contact angle (74.9°) and the greatest surface roughness, contributing to mechanical interlocking despite its low surface energy. Oak and iroko showed high wettability and balanced roughness, supporting strong adhesion. Scanning electron microscopy (SEM) revealed stable adhesive penetration across all species and aging conditions, with no signs of delamination or interfacial failure. The study confirms the suitability of polyurethane adhesives for durable, long-lasting bonding in engineered and solid wood flooring systems, even when using extractive-rich or dimensionally sensitive tropical species. The results emphasize the critical role of surface morphology, wood anatomy, and adhesive compatibility in achieving optimal bond performance. These findings contribute to improved material selection and application strategies in flooring technology. Future research should focus on bio-based adhesive alternatives, chemical surface modification techniques, and in-service performance under cyclic loading and humidity variations to support the development of eco-efficient and resilient flooring systems. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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20 pages, 9078 KB

Open AccessArticle

Investigating the Effects of Iron Dilution on the Corrosion Resistance of Inconel 625 Welding Overlay on Carbon Steel

by Alexandre Borghi Cunha, Jan Vatavuk and Carlos Roberto Camello Lima

Materials 2025, 18(24), 5574; https://doi.org/10.3390/ma18245574 - 11 Dec 2025

Cited by 8 | Viewed by 1728

Abstract

This study investigates the influence of iron dilution on the microstructure and corrosion behavior of Inconel 625 weld overlays deposited on carbon steel. Different deposition strategies were employed to control dilution and to evaluate its effect on elemental segregation. The overlays were characterized in terms of microstructural evolution, chemical distribution, and corrosion performance under standardized testing conditions. The results show that increasing iron dilution enhances chemical segregation within the dendritic structure, which governs the initiation of localized corrosion. A critical dilution condition associated with the onset of pitting was identified. These findings advance the understanding of dilution-controlled corrosion mechanisms in nickel-based alloy overlays. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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21 pages, 7939 KB

Open AccessArticle

Femtosecond Laser Single-Spot Welding of Sapphire/Invar Alloy

by Yuyang Chen, Yinzhi Fu, Xianshi Jia, Kai Li and Cong Wang

Materials 2025, 18(16), 3839; https://doi.org/10.3390/ma18163839 - 15 Aug 2025

Cited by 5 | Viewed by 1631

Abstract

Ultrafast laser welding of glass/metal heterostructures has found extensive applications in sensors, medical devices, and optical systems. However, achieving high-stability, high-quality welds under non-optical contact conditions remains challenging due to severe internal damage within glass materials. This study addresses thermal management through synergistic control of thermal accumulation effects and material ablation thresholds. Using the sapphire/Invar alloy system as a model for glass/metal welding, we investigated thermal accumulation effects during ultrafast laser ablation of Invar alloy through theoretical simulations. Under a repetition rate of 1 MHz, the femtosecond laser raised the lattice equilibrium temperature by 700 K within 10 microseconds, demonstrating that high repetition rate femtosecond lasers can induce effective heat accumulation in Invar alloy. Furthermore, ablation thresholds for both materials were determined across varying repetition rates via the D² method, with corresponding threshold curves systematically constructed. Finally, based on the simulation and ablation threshold calculation results, laser parameters were selected for ultrafast laser single point welding of sapphire and Invar alloy. The experimental results demonstrate effective thermal effect mitigation, achieving a maximum shear strength of 63.37 MPa. Comparative analysis against traditional scan welding further validates the superiority of our approach in thermal management. This work provides foundational theoretical and methodological guidance for ultrafast laser welding of glass/metal heterostructures. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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Review

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36 pages, 4882 KB

Open AccessReview

Emerging Trends in Ultrasonic and Friction Stir Spot Welding of Polymers and Metal-Polymer Hybrids: A Review of Process Mechanics, Microstructure, and Joint Performance

by Kanchan Kumari, Swastik Pradhan, Chitrasen Samantra, Manisha Priyadarshini, Abhishek Barua and Debabrata Dhupal

Materials 2026, 19(8), 1602; https://doi.org/10.3390/ma19081602 - 16 Apr 2026

Viewed by 1178

Abstract

The growing need for lightweight, multifunctional, and high-performance structures in the automotive, aerospace, electronics, and medical industries has driven the development of advanced joining technologies for polymers and metal-polymer combinations. Among these, ultrasonic welding (USW) and friction stir spot welding (FSSW) have emerged as promising solid-state techniques capable of producing reliable joints with minimal thermal degradation and enhanced interfacial bonding. This review focuses on recent developments in USW and FSSW of thermoplastics, fiber-reinforced composites, and hybrid metal–polymer systems, with a particular emphasis on process mechanics, microstructural evolution, and joint performance. The mechanisms of heat generation, material flow behavior, and consolidation are discussed in relation to key process parameters, including applied pressure, rotational speed, vibration amplitude, plunge depth, and dwell time. Microstructural transformations such as polymer chain orientation, recrystallization, interfacial diffusion, and defect formation are analyzed to establish process–structure–property relationships. Mechanical performance metrics, including lap shear strength, fatigue resistance, impact behavior, and environmental durability, are critically compared across different materials and welding methods. Furthermore, recent advances in numerical and thermo-mechanical modeling, in situ process monitoring, and data-driven optimization are discussed to highlight pathways toward predictive and scalable manufacturing. Current industrial applications and existing limitations such as challenges in automation, thickness constraints, and hybrid material compatibility are also evaluated. Finally, key research gaps and future directions are identified to improve joint reliability, sustainability, and broader industrial adoption of advanced solid-state welding technologies. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Third Edition))

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