Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2025.12.288
C. Bellini , F. Berto , V. Di Cocco , P. Di Giamberardino , D. Iacoviello , S. Natali , D. Pilone , C. Schillaci
Electron Beam Melting (EBM) is an additive manufacturing process able to produce near-net-shape Ti6Al4V components, but the resulting anisotropic microstructure can lead to directionally dependent mechanical properties. This study investigates the influence of build orientation on the fatigue crack growth (FCG) behaviour of EBM-fabricated Ti6Al4V. Compact Tension specimens were manufactured in three distinct orientations relative to the build direction: horizontal (HH), vertical-horizontal (VH), and vertical-vertical (VV). FCG tests were conducted according to ASTM E647. The results revealed a strong FCG anisotropy. The VV configuration exhibited superior fatigue resistance, characterised by the lowest crack growth rates. Conversely, the HH orientation demonstrated the poorest performance, with significantly faster crack propagation. Fractographic analysis via SEM confirmed that the worst behaviour of the HH specimen was due to a low-energy, transgranular quasi-cleavage mechanism, exacerbated by process-induced porosity. These findings highlighted that building orientation is a critical design parameter that must be optimised to ensure the structural integrity and service life of fatigue-critical EBM components in demanding applications.
{"title":"Effects of growth direction on fatigue behaviour of EBMed Ti6Al4V specimens","authors":"C. Bellini , F. Berto , V. Di Cocco , P. Di Giamberardino , D. Iacoviello , S. Natali , D. Pilone , C. Schillaci","doi":"10.1016/j.prostr.2025.12.288","DOIUrl":"10.1016/j.prostr.2025.12.288","url":null,"abstract":"<div><div>Electron Beam Melting (EBM) is an additive manufacturing process able to produce near-net-shape Ti6Al4V components, but the resulting anisotropic microstructure can lead to directionally dependent mechanical properties. This study investigates the influence of build orientation on the fatigue crack growth (FCG) behaviour of EBM-fabricated Ti6Al4V. Compact Tension specimens were manufactured in three distinct orientations relative to the build direction: horizontal (HH), vertical-horizontal (VH), and vertical-vertical (VV). FCG tests were conducted according to ASTM E647. The results revealed a strong FCG anisotropy. The VV configuration exhibited superior fatigue resistance, characterised by the lowest crack growth rates. Conversely, the HH orientation demonstrated the poorest performance, with significantly faster crack propagation. Fractographic analysis via SEM confirmed that the worst behaviour of the HH specimen was due to a low-energy, transgranular quasi-cleavage mechanism, exacerbated by process-induced porosity. These findings highlighted that building orientation is a critical design parameter that must be optimised to ensure the structural integrity and service life of fatigue-critical EBM components in demanding applications.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"76 ","pages":"Pages 67-73"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2025.12.291
Mirco Daniel Chapetti
The increasing demand for reliability and safety in industrial mechanical components has heightened the focus on predictive methods in long-life fatigue analysis. Advances in fracture mechanics now enable accurate estimation of fatigue life and limits in components with small cracks or crack-like defects, often introduced during manufacturing. In processes like additive manufacturing, inherent defects may bypass the crack initiation phase, accelerating the fatigue process. Consequently, the damage mechanism primarily involves crack propagation from critical defects until component failure occurs.
However, the statistical variation in the size of inherent defects in certain materials or components results in significant dispersion in fatigue life under similar stress levels, making it difficult to identify and quantify the intrinsic strengths involved, and particularly challenging to compare different configurations.
This work advances the understanding of the essential structure of traditional S-N curves and the limitations they display in describing results. Proposed alternatives, as documented in the literature, are critically analyzed, and a new alternative is proposed, based on fracture mechanics methodologies that allow the entire propagation process to be quantified and the deficiencies of previous proposals to be explained.
{"title":"Fracture mechanics approaches for material defect assessment and fatigue design","authors":"Mirco Daniel Chapetti","doi":"10.1016/j.prostr.2025.12.291","DOIUrl":"10.1016/j.prostr.2025.12.291","url":null,"abstract":"<div><div>The increasing demand for reliability and safety in industrial mechanical components has heightened the focus on predictive methods in long-life fatigue analysis. Advances in fracture mechanics now enable accurate estimation of fatigue life and limits in components with small cracks or crack-like defects, often introduced during manufacturing. In processes like additive manufacturing, inherent defects may bypass the crack initiation phase, accelerating the fatigue process. Consequently, the damage mechanism primarily involves crack propagation from critical defects until component failure occurs.</div><div>However, the statistical variation in the size of inherent defects in certain materials or components results in significant dispersion in fatigue life under similar stress levels, making it difficult to identify and quantify the intrinsic strengths involved, and particularly challenging to compare different configurations.</div><div>This work advances the understanding of the essential structure of traditional S-N curves and the limitations they display in describing results. Proposed alternatives, as documented in the literature, are critically analyzed, and a new alternative is proposed, based on fracture mechanics methodologies that allow the entire propagation process to be quantified and the deficiencies of previous proposals to be explained.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"76 ","pages":"Pages 89-98"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2025.12.284
Daniele Rigon , Eva Callegher , Filippo Mioli , Nicolò Bonato , Enrico Savio , Giovanni Meneghetti
This work presents a preliminary investigation into the estimation of fatigue limit in Ti6Al4V specimens produced via Laser Powder Bed Fusion of metals (PBF-LB/M) with surfaces in as-built conditions, by combining fracture mechanics with surface and volumetric defect characterization. Building upon a previously proposed approach that uses Extreme Value Statistics (EVS) to estimate the deepest micro-notch of PBF-LB/M as-built surfaces, this study presents a preliminary comparison between the estimated deepest notch from optical profilometry (OP), as a function of sample size, and the actual deepest surface notch measured across the entire outer surface of the gauge section of the specimen. In addition, internal and subsurface defects were characterized by X-ray computed tomography (CT) to provide a preliminary assessment of their relevance to fatigue behavior. The results show that EVS provides reliable estimates of the maximum depth, with less than 5% error for sufficiently large sample sizes. Finally, both surface roughness and subsurface defects led to similar effective crack sizes and fatigue threshold estimates, suggesting their comparable roles in early crack initiation for the considered material.
{"title":"Extreme value analysis of the equivalent flaw size for fatigue limit estimation in additively manufactured Ti6Al4V specimens with as-built surface condition","authors":"Daniele Rigon , Eva Callegher , Filippo Mioli , Nicolò Bonato , Enrico Savio , Giovanni Meneghetti","doi":"10.1016/j.prostr.2025.12.284","DOIUrl":"10.1016/j.prostr.2025.12.284","url":null,"abstract":"<div><div>This work presents a preliminary investigation into the estimation of fatigue limit in Ti6Al4V specimens produced via Laser Powder Bed Fusion of metals (PBF-LB/M) with surfaces in as-built conditions, by combining fracture mechanics with surface and volumetric defect characterization. Building upon a previously proposed approach that uses Extreme Value Statistics (EVS) to estimate the deepest micro-notch of PBF-LB/M as-built surfaces, this study presents a preliminary comparison between the estimated deepest notch from optical profilometry (OP), as a function of sample size, and the actual deepest surface notch measured across the entire outer surface of the gauge section of the specimen. In addition, internal and subsurface defects were characterized by X-ray computed tomography (CT) to provide a preliminary assessment of their relevance to fatigue behavior. The results show that EVS provides reliable estimates of the maximum depth, with less than 5% error for sufficiently large sample sizes. Finally, both surface roughness and subsurface defects led to similar effective crack sizes and fatigue threshold estimates, suggesting their comparable roles in early crack initiation for the considered material.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"76 ","pages":"Pages 35-42"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2026.01.076
Hugo Mesquita Vasconcelos , Pedro J.S.C.P. Sousa , António Silva , Susana Dias , J.P. Pinto , I.D. van Golde , Paulo J. Tavares , Pedro M.G.J. Moreira
Learning models based on hierarchical complexity reflect the way humans naturally acquire knowledge, and experimental evidence suggests they hold promise for improving the efficiency of model training in artificial intelligence (AI). This research presents an innovative approach to developing an AI model capable of classifying maritime acoustic signals, for ship identification or structural integrity assessment. Acoustic signal analysis is critical in maritime environments, as sound travels effectively underwater, offering potential for applications where above-water technologies are not possible. Nonetheless, decoding these acoustic signals is a complex task that presents significant computational challenges. This study applies the Model of Hierarchical Complexity (MHC) to maritime acoustic signal recognition. A domain-specific Order of Hierarchical Complexity was proposed, and three training configurations on a ResNet-18 backbone were evaluated under identical architecture and hyperparameters: traditional non-structured learning, two-stage (binary, multiclass), and full three-stage MHC-structured training. The dataset was strongly imbalanced across the 12 classes (11 vessel types and background), reflecting real maritime traffic; this realism introduced constraints on rare categories, lowering the model performance. The full MHC configuration achieved the best overall metrics (accuracy 0.82 and the highest macro-averaged precision, recall, and F1) with 1% better training time, comparable to the other tests. Improvements were concentrated in well-represented classes, indicating that MHC-structured training can organize learning without additional computational cost but does not, by itself, overcome class imbalance.
{"title":"Hierarchical complexity-based AI model for efficient feature extraction in maritime acoustic signal recognition","authors":"Hugo Mesquita Vasconcelos , Pedro J.S.C.P. Sousa , António Silva , Susana Dias , J.P. Pinto , I.D. van Golde , Paulo J. Tavares , Pedro M.G.J. Moreira","doi":"10.1016/j.prostr.2026.01.076","DOIUrl":"10.1016/j.prostr.2026.01.076","url":null,"abstract":"<div><div>Learning models based on hierarchical complexity reflect the way humans naturally acquire knowledge, and experimental evidence suggests they hold promise for improving the efficiency of model training in artificial intelligence (AI). This research presents an innovative approach to developing an AI model capable of classifying maritime acoustic signals, for ship identification or structural integrity assessment. Acoustic signal analysis is critical in maritime environments, as sound travels effectively underwater, offering potential for applications where above-water technologies are not possible. Nonetheless, decoding these acoustic signals is a complex task that presents significant computational challenges. This study applies the Model of Hierarchical Complexity (MHC) to maritime acoustic signal recognition. A domain-specific Order of Hierarchical Complexity was proposed, and three training configurations on a ResNet-18 backbone were evaluated under identical architecture and hyperparameters: traditional non-structured learning, two-stage (binary, multiclass), and full three-stage MHC-structured training. The dataset was strongly imbalanced across the 12 classes (11 vessel types and background), reflecting real maritime traffic; this realism introduced constraints on rare categories, lowering the model performance. The full MHC configuration achieved the best overall metrics (accuracy 0.82 and the highest macro-averaged precision, recall, and F1) with 1% better training time, comparable to the other tests. Improvements were concentrated in well-represented classes, indicating that MHC-structured training can organize learning without additional computational cost but does not, by itself, overcome class imbalance.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"77 ","pages":"Pages 601-610"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2026.01.081
João Nuno Silva , Vítor M.G. Gomes , António Mourão , Pedro Montenegro , José A.F.O Correia , Abílio de Jesus
Railway vehicles operate under variable amplitude dynamic loads throughout their long service lives, making fatigue a critical design consideration for welded details. As a common structural material, steel exhibits an outstanding sensitivity to fatigue phenomena when subjected to cyclic loading. Despite this issue, the sector lacks a unified accepted reference standard for fatigue assessment. This paper provides a comparative analysis of the principal design references applied to steel railway components, namely ERRI B 12/RP60, EN 12663, DVS 1612, EN 17149-3, EN 1993-1-9, and the IIW Recommendations. The comparison addresses load scenarios, stress definitions (nominal, hot-spot, and notch approaches), reference survival probabilities, and verification philosophies. Four representative welded details from a freight wagon are assessed using numerical stress histories within each framework, with verification criteria being contrasted to evaluate practical implications. The results indicate that railway-specific design codes, particularly DVS 1612 and EN 17149-3 standard, provide more tailored and accurate fatigue verification than generic codes.
铁路车辆在其漫长的使用寿命中一直在变幅动载荷下运行，这使得疲劳成为焊接细节设计的关键考虑因素。作为一种常见的结构材料，钢在循环荷载作用下对疲劳现象表现出突出的敏感性。尽管存在这个问题，但该行业缺乏一个统一的公认的疲劳评估参考标准。本文对铁路钢构件的主要设计参考ERRI B 12/RP60、EN 12663、DVS 1612、EN 17149-3、EN 1993-1-9和IIW建议书进行了比较分析。比较涉及负载场景、应力定义（名义、热点和缺口方法）、参考生存概率和验证哲学。使用每个框架内的数值应力历史来评估货运货车的四个代表性焊接细节，并对比验证标准以评估实际意义。结果表明，铁路专用设计规范，特别是DVS 1612和EN 17149-3标准，提供了比通用规范更定制和准确的疲劳验证。
{"title":"A Standards-Based Comparison on Fatigue Design in Railway Steel Components","authors":"João Nuno Silva , Vítor M.G. Gomes , António Mourão , Pedro Montenegro , José A.F.O Correia , Abílio de Jesus","doi":"10.1016/j.prostr.2026.01.081","DOIUrl":"10.1016/j.prostr.2026.01.081","url":null,"abstract":"<div><div>Railway vehicles operate under variable amplitude dynamic loads throughout their long service lives, making fatigue a critical design consideration for welded details. As a common structural material, steel exhibits an outstanding sensitivity to fatigue phenomena when subjected to cyclic loading. Despite this issue, the sector lacks a unified accepted reference standard for fatigue assessment. This paper provides a comparative analysis of the principal design references applied to steel railway components, namely ERRI B 12/RP60, EN 12663, DVS 1612, EN 17149-3, EN 1993-1-9, and the IIW Recommendations. The comparison addresses load scenarios, stress definitions (nominal, hot-spot, and notch approaches), reference survival probabilities, and verification philosophies. Four representative welded details from a freight wagon are assessed using numerical stress histories within each framework, with verification criteria being contrasted to evaluate practical implications. The results indicate that railway-specific design codes, particularly DVS 1612 and EN 17149-3 standard, provide more tailored and accurate fatigue verification than generic codes.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"77 ","pages":"Pages 657-664"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2026.01.037
Valeria Lemkova , Florian Schaefer
High-pressure torsion (HPT), a method of severe plastic deformation, allows to alloy even immiscible phases to supersaturated nanocrystalline (nc) solid solutions and to produce bulk material of metal matrix composites (MMCs) with a nc matrix with out additional thermal load. With the aim of producing MMCs with functionalized ceramic particles (so-called intelligent or smart materials) a large variety of ceramic dispersoids was shown to be susceptible for the incorporation into a metallic matrix by HPT, independent of the mechanical contrast of the individual phases with a well engineered process route. The dispersoids are partially broken to a stabilized geometry and are finely dispersed. However, the microstructure evolution in the vicinity of these inclusions is strongly affected by the mechanical contrast between dispersoids and matrix material. For the material performance, especially in case of fatigue, a strong cohesion between matrix and particles is essential to avoid crack initiation. This interfacial cohesion was characterized by micro-beam bending fracture tests. The thermal stability of the microstructure was investigated by in situ heating in the SEM and examined regarding Zener pinning. The ceramic particles significantly influence the thermal stability compared to particle-free reference material.
{"title":"Metal Matrix Composites from Severe Plastic Deformation by the Example of High-Pressure Torsion as a Promising Tool to Manufacture Smart Materials","authors":"Valeria Lemkova , Florian Schaefer","doi":"10.1016/j.prostr.2026.01.037","DOIUrl":"10.1016/j.prostr.2026.01.037","url":null,"abstract":"<div><div>High-pressure torsion (HPT), a method of severe plastic deformation, allows to alloy even immiscible phases to supersaturated nanocrystalline (nc) solid solutions and to produce bulk material of metal matrix composites (MMCs) with a nc matrix with out additional thermal load. With the aim of producing MMCs with functionalized ceramic particles (so-called intelligent or smart materials) a large variety of ceramic dispersoids was shown to be susceptible for the incorporation into a metallic matrix by HPT, independent of the mechanical contrast of the individual phases with a well engineered process route. The dispersoids are partially broken to a stabilized geometry and are finely dispersed. However, the microstructure evolution in the vicinity of these inclusions is strongly affected by the mechanical contrast between dispersoids and matrix material. For the material performance, especially in case of fatigue, a strong cohesion between matrix and particles is essential to avoid crack initiation. This interfacial cohesion was characterized by micro-beam bending fracture tests. The thermal stability of the microstructure was investigated by in situ heating in the SEM and examined regarding Zener pinning. The ceramic particles significantly influence the thermal stability compared to particle-free reference material.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"77 ","pages":"Pages 279-291"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2026.01.020
Alexander Backa , Radovan Nosek , Nikola Čajová Kantová , Róbert Cibula
The structural integrity of small-scale biomass combustion chambers is significantly influenced by thermal stresses, particulate deposition, and material degradation. Particulate matter (PM) emissions from small-scale pellet boilers pose significant challenges in air quality management. The spatial distribution of PM and temperature within the combustion chamber, focusing on their relationship, is explored in this study. By employing a supplementary flue gas extraction system, PM dispersion in three central planes above a retort burner was characterized, and its correlation with thermal gradients was analyzed. PM concentrations and temperature values were measured at 25 distinct points per plane, allowing for a detailed analysis of their spatial relationship. Considerable variations in PM concentration across different regions of the combustion chamber were revealed by the results, with peak values exceeding 40 mg/m3, particularly in areas of high localized temperature gradients exceeding 800°C. The temperature-to-PM ratio, a novel parameter introduced in this study, was calculated with an average value of 25.45 and a standard error of 5.26, providing insight into combustion uniformity. The findings emphasize that uneven thermal loading can affect particulate matter formation, potentially leading to fouling and material deterioration within combustion systems. This has direct implications for design optimization, durability enhancement, and maintenance strategies in small-scale biomass boilers. These findings are crucial for design optimization and failure prevention in biomass combustion systems.
{"title":"In-depth analysis of particulates and temperature within a small-scale pellet combustion chamber","authors":"Alexander Backa , Radovan Nosek , Nikola Čajová Kantová , Róbert Cibula","doi":"10.1016/j.prostr.2026.01.020","DOIUrl":"10.1016/j.prostr.2026.01.020","url":null,"abstract":"<div><div>The structural integrity of small-scale biomass combustion chambers is significantly influenced by thermal stresses, particulate deposition, and material degradation. Particulate matter (PM) emissions from small-scale pellet boilers pose significant challenges in air quality management. The spatial distribution of PM and temperature within the combustion chamber, focusing on their relationship, is explored in this study. By employing a supplementary flue gas extraction system, PM dispersion in three central planes above a retort burner was characterized, and its correlation with thermal gradients was analyzed. PM concentrations and temperature values were measured at 25 distinct points per plane, allowing for a detailed analysis of their spatial relationship. Considerable variations in PM concentration across different regions of the combustion chamber were revealed by the results, with peak values exceeding 40 mg/m<sup>3</sup>, particularly in areas of high localized temperature gradients exceeding 800°C. The temperature-to-PM ratio, a novel parameter introduced in this study, was calculated with an average value of 25.45 and a standard error of 5.26, providing insight into combustion uniformity. The findings emphasize that uneven thermal loading can affect particulate matter formation, potentially leading to fouling and material deterioration within combustion systems. This has direct implications for design optimization, durability enhancement, and maintenance strategies in small-scale biomass boilers. These findings are crucial for design optimization and failure prevention in biomass combustion systems.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"77 ","pages":"Pages 143-151"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2026.01.022
V. Kroužecký , M. Zetek , I. Zetková , S. Svozilová , L. Jeníček , J. Kec
The Selective Laser Melting (SLM) technique has become popular because it enables the manufacture of intricate metal components while maintaining high design freedom. The surface quality of downskin regions remains problematic when printing overhanging structures at an angle of less than 45°. These regions exhibit poor surface quality because insufficient heat dissipation produces excessive roughness and partially fused powder adhesion that leads to defect formation. Surface imperfections function as stress concentrators which reduce mechanical properties and fatigue resistance. In the energy industry, the issue takes on increased importance because component integrity and durability are fundamental requirements.
The research focuses on finding optimal process parameters to improve the surface quality of the down skin of SLM-produced 316L stainless steel parts. The parametric study systematically adjusted laser power and hatch spacing, along with other crucial parameters, to achieve reduced surface roughness and stable processing conditions. Researchers tested the optimized parameters’ impact on room-temperature mechanical properties like tensile strength.
The experimental results focus carefully on the relationship between reduced skin surface roughness, tensile strength, and fatigue life. They show how enhanced surface quality can delay the start of fatigue cracking and extend the life of components. This study advances SLM process optimization methods in structural applications where tensile strength and surface quality are critical design factors, particularly in the energy industry.
{"title":"Optimization of process parameters for support-free inclined wall printing and their effect on the mechanical properties of 316L parts produced by slm","authors":"V. Kroužecký , M. Zetek , I. Zetková , S. Svozilová , L. Jeníček , J. Kec","doi":"10.1016/j.prostr.2026.01.022","DOIUrl":"10.1016/j.prostr.2026.01.022","url":null,"abstract":"<div><div>The Selective Laser Melting (SLM) technique has become popular because it enables the manufacture of intricate metal components while maintaining high design freedom. The surface quality of downskin regions remains problematic when printing overhanging structures at an angle of less than 45°. These regions exhibit poor surface quality because insufficient heat dissipation produces excessive roughness and partially fused powder adhesion that leads to defect formation. Surface imperfections function as stress concentrators which reduce mechanical properties and fatigue resistance. In the energy industry, the issue takes on increased importance because component integrity and durability are fundamental requirements.</div><div>The research focuses on finding optimal process parameters to improve the surface quality of the down skin of SLM-produced 316L stainless steel parts. The parametric study systematically adjusted laser power and hatch spacing, along with other crucial parameters, to achieve reduced surface roughness and stable processing conditions. Researchers tested the optimized parameters’ impact on room-temperature mechanical properties like tensile strength.</div><div>The experimental results focus carefully on the relationship between reduced skin surface roughness, tensile strength, and fatigue life. They show how enhanced surface quality can delay the start of fatigue cracking and extend the life of components. This study advances SLM process optimization methods in structural applications where tensile strength and surface quality are critical design factors, particularly in the energy industry.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"77 ","pages":"Pages 161-169"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2025.12.283
Jürgen Bär , Naveen K. Kanna , Larissa Duarte , Mauro Madia
The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the models is necessary. However, the standardized staircase method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks.
Rectangular notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows a rapid production of very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a Direct Current Potential Drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with low experimental effort and time consumption. The tests have shown that in case of the normalized steel none of the models describes the determined values for the fatigue limit. For the hardened steel, the plot of the fatigue limit as a function of the Murakami parameter √area in combination with the El Haddad model allows a satisfactory description of the measured values.
{"title":"Determination of the Kitagawa-Takahashi Diagram using DC Potential Drop Measurements","authors":"Jürgen Bär , Naveen K. Kanna , Larissa Duarte , Mauro Madia","doi":"10.1016/j.prostr.2025.12.283","DOIUrl":"10.1016/j.prostr.2025.12.283","url":null,"abstract":"<div><div>The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the models is necessary. However, the standardized staircase method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks.</div><div>Rectangular notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows a rapid production of very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a Direct Current Potential Drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with low experimental effort and time consumption. The tests have shown that in case of the normalized steel none of the models describes the determined values for the fatigue limit. For the hardened steel, the plot of the fatigue limit as a function of the Murakami parameter √area in combination with the El Haddad model allows a satisfactory description of the measured values.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"76 ","pages":"Pages 27-34"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.prostr.2026.01.005
L.A. Lingnau , J. Heermant , L.M. Sauer , J.L. Otto , F. Walther
Forming-induced ductile damage, such as the formation and growth of voids, has been largely ignored in commercial component design, resulting in the potential for lightweighting not being fully exploited. Forming-induced ductile damage has also been shown to have a significant impact on the fatigue properties and therefore performance of components. The evolution of damage under mechanical stress and its impact on fatigue performance is therefore essential for optimizing component design and maximizing the economic potential of lightweight construction. In this paper, microstructural changes are analyzed in-situ under a scanning electron microscope (SEM) using a tension-compression module. The focus is on the interaction between different load paths, forming-induced ductile damage and microstructural features such as voids or manganese sulfides. Quantitative damage analysis based on image data and AI-image segmentation allows precise quantification of the load path-dependent damage accumulation. The insights gained provide a deeper understanding of the impact of forming-induced ductile damage on load path-dependent damage mechanisms in both forming processes and fatigue testing.
{"title":"Quantification of the load path-dependent damage development in case hardening steel 16MnCrS5","authors":"L.A. Lingnau , J. Heermant , L.M. Sauer , J.L. Otto , F. Walther","doi":"10.1016/j.prostr.2026.01.005","DOIUrl":"10.1016/j.prostr.2026.01.005","url":null,"abstract":"<div><div>Forming-induced ductile damage, such as the formation and growth of voids, has been largely ignored in commercial component design, resulting in the potential for lightweighting not being fully exploited. Forming-induced ductile damage has also been shown to have a significant impact on the fatigue properties and therefore performance of components. The evolution of damage under mechanical stress and its impact on fatigue performance is therefore essential for optimizing component design and maximizing the economic potential of lightweight construction. In this paper, microstructural changes are analyzed in-situ under a scanning electron microscope (SEM) using a tension-compression module. The focus is on the interaction between different load paths, forming-induced ductile damage and microstructural features such as voids or manganese sulfides. Quantitative damage analysis based on image data and AI-image segmentation allows precise quantification of the load path-dependent damage accumulation. The insights gained provide a deeper understanding of the impact of forming-induced ductile damage on load path-dependent damage mechanisms in both forming processes and fatigue testing.</div></div>","PeriodicalId":20518,"journal":{"name":"Procedia Structural Integrity","volume":"77 ","pages":"Pages 26-33"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146102508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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