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  • Online-Ressource  (12)
  • Cicero, Sergio  (12)
  • 1
    Online-Ressource
    Online-Ressource
    Fracture Behavior of Two Biopolymers Containing Notches: Effects of Notch Tip Plasticity
    MDPI AG ; 2020
    In:  Applied Sciences Vol. 10, No. 23 ( 2020-11-26), p. 8445-
    Details
    In: Applied Sciences, MDPI AG, Vol. 10, No. 23 ( 2020-11-26), p. 8445-
    Kurzfassung: This paper analyzes the notch effect on the fracture behavior of two biomaterials (a brittle bone cement and a ductile dental material) under mode I loading. U-notched Brazilian disk (UNBD) specimens of both materials were tested under remote compression, determining the corresponding fracture loads and load-displacement curves. Additionally, cracked rectangular and semicircular bend (SCB) specimens were tested under symmetric three-point bending in order to determine the fracture toughness of the two materials. Then, fracture loads were derived theoretically by applying the maximum tangential stress (MTS) and the mean stress (MS) criteria. Due to the brittle linear elastic behavior of the bone cement material, the MTS and MS criteria were directly applied to this material; however, given the significant nonlinear behavior of the dental material, the two fracture criteria were combined with the Equivalent Material Concept (EMC) for the fracture analyses of the dental material specimens. The results reveal a very good accuracy of both the MTS and the MS criteria for the fracture analysis of bone cement notched specimens. In the case of the dental material, very good results are also obtained when combining the MTS and the MS criteria with the EMC. The proposed approach can be useful for the fracture analysis of a wide range of biopolymers, from brittle to ductile behavior.
    Materialart: Online-Ressource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app10238445
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2020
    ZDB Id: 2704225-X
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  • 2
    Online-Ressource
    Online-Ressource
    Tensile-Tearing Fracture Analysis of U-Notched Spruce Samples
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 10 ( 2022-05-20), p. 3661-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 10 ( 2022-05-20), p. 3661-
    Kurzfassung: Spruce wood (Picea Mariana) is a highly orthotropic material whose fracture behavior in the presence of U-shaped notches and under combined tensile-tearing loading (so-called mixed-mode I/III loading) is analyzed in this work. Thus, several tests are carried out on U-notched samples with different notch tip radii (1 mm, 2 mm, and 4 mm) under various combinations of loading modes I and III (pure mode I, pure mode III, and three mixed-mode I/III loadings), from which both the experimental fracture loads and the fracture angles of the specimens are obtained. Because of the linear elastic behavior of the spruce wood, the point stress (PS) and mean stress (MS) methods, both being stress-based criteria, are used in combination with the Virtual Isotropic Material Concept (VIMC) for predicting the fracture loads and the fracture angles. By employing the VIMC, the spruce wood as an orthotropic material is modeled as a homogeneous and isotropic material with linear elastic behavior. The stress components required for calculating the experimental values of notch stress intensity factors are obtained by finite element (FE) analyses of the test configuration using commercial FE software from the fracture loads obtained experimentally. The discrepancies between the experimental and theoretical results of the critical notch stress intensity factors are obtained between −12.1% and −15% for the PS criterion and between −5.9% and −14.6% for the MS criterion, respectively. The discrepancies related to fracture initiation angle range from −1.0% to +12.1% for the PS criterion and from +1.5% to +12.2% for the MS criterion, respectively. Thus, both the PS and MS models have good accuracy when compared with the experimental data. It is also found that both failure criteria underestimate the fracture resistance of spruce wood under mixed-mode I/III loading.
    Materialart: Online-Ressource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15103661
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2022
    ZDB Id: 2487261-1
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    Online-Ressource
  • 3
    Online-Ressource
    Online-Ressource
    Critical Load Prediction in Notched E/Glass–Epoxy-Laminated Composites Using the Virtual Isotropic Material Concept Combined with the Average Strain Energy Density Criterion
    MDPI AG ; 2021
    In:  Polymers Vol. 13, No. 7 ( 2021-03-27), p. 1057-
    Details
    In: Polymers, MDPI AG, Vol. 13, No. 7 ( 2021-03-27), p. 1057-
    Kurzfassung: This paper attempts to validate the application of the Virtual Isotropic Material Concept (VIMC) in combination with the average strain energy density (ASED) criterion to predict the critical load in notched laminated composites. This methodology was applied to E/glass–epoxy-laminated composites containing U-notches. For this purpose, a series of fracture test data recently published in the literature on specimens with different notch tip radii, lay-up configurations, and a number of plies were employed. It was shown that the VIMC–ASED combined approach provided satisfactory predictions of the last-ply failure (LPF) loads (i.e., critical loads).
    Materialart: Online-Ressource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym13071057
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2021
    ZDB Id: 2527146-5
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  • 4
    Online-Ressource
    Online-Ressource
    Determination of Translaminar Notch Fracture Toughness for Laminated Composites Using Brazilian Disk Test
    MDPI AG ; 2022
    In:  Polymers Vol. 14, No. 16 ( 2022-08-09), p. 3246-
    Details
    In: Polymers, MDPI AG, Vol. 14, No. 16 ( 2022-08-09), p. 3246-
    Kurzfassung: This paper evaluates the fracture of notched epoxy matrix composites using the Brazilian disk (BD) test from both numerical and experimental points of view. The study began with a comprehensive experimental program covering three different composite lay-ups (quasi-isotropic, unidirectional, and cross-ply) and various geometries of U and V notches. Specifically, the BD samples combined the three layouts, four different notch angles, and three notch radii with three specimens per combination, leading to an overall number of 108 fracture tests. The experiments showed the appropriateness of the BD test for the study of the fracture behavior of composite materials and provided a good pool of data for further investigations. Subsequently, the virtual isotropic material concept (VIMC) was applied in combination with two fracture criteria to theoretically predict the experimentally acquired fracture loads. This study demonstrated that using the VIMC approach can provide robust predictions while incurring much lower computational costs compared to the conventional approaches found in the literature.
    Materialart: Online-Ressource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym14163246
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2022
    ZDB Id: 2527146-5
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    Online-Ressource
  • 5
    Online-Ressource
    Online-Ressource
    Notch Fracture in Polymeric Specimens under Compressive Stresses: The Role of the Equivalent Material Concept in Estimating the Critical Stress of Polymers
    MDPI AG ; 2021
    In:  Applied Sciences Vol. 11, No. 5 ( 2021-02-27), p. 2104-
    Details
    In: Applied Sciences, MDPI AG, Vol. 11, No. 5 ( 2021-02-27), p. 2104-
    Kurzfassung: In this paper, the fracture of notched polymeric specimens under compressive stresses was investigated both experimentally and theoretically. In the experimental section, to determine the load-carrying capacity (LCC) of U-notched specimens made of general-purpose polystyrene (GPPS) and polymethyl-methacrylate (PMMA) polymers, tests were performed on notched square samples under compression, i.e., negative mode I loading. In the observation of the nonlinear behavior of the two polymers in the standard compressive tests, for the first time, the equivalent material concept (EMC) was used under compressive loading to theoretically estimate the critical stresses of the two polymers, which were shown to be significantly different from the ultimate strengths obtained from the standard compression tests. By linking the EMC to the maximum tangential stress (MTS) and mean stress (MS) criteria, the LCC of the notched specimens was predicted. The outcomes are twofold: First, MTS, MS, EMC–MTS, and EMC–MS criteria provide accurate predictions of the experimental critical loads observed in the U-notched polymeric specimens; second, the combination of the EMC with the MTS and MS criteria, allow such predictions to be obtained without any need for experimental calibration.
    Materialart: Online-Ressource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app11052104
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2021
    ZDB Id: 2704225-X
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  • 6
    Online-Ressource
    Online-Ressource
    Fracture Behavior of AA7075-AA6061 and AA7075-Cu Friction-Stir Welded Joints Containing Blunt V-Notches under Opening-Mode Loading
    MDPI AG ; 2023
    In:  Materials Vol. 16, No. 5 ( 2023-02-21), p. 1757-
    Details
    In: Materials, MDPI AG, Vol. 16, No. 5 ( 2023-02-21), p. 1757-
    Kurzfassung: The purpose of this study is to predict the load-bearing capacity (LBC) of fracture specimens containing V-notched friction-stir welded (FSWed) joints of AA7075-Cu and AA7075-AA6061 materials and subjected to mode I loading conditions. Due to the resulting elastic-plastic behavior and the corresponding development of significant plastic deformations, the fracture analysis of the FSWed alloys requires elastic-plastic fracture criteria, which are complex and time-consuming. Thus, in this study, the equivalent material concept (EMC) is applied, equating the actual AA7075-AA6061 and AA7075-Cu materials to equivalent virtual brittle materials. Then, two brittle fracture criteria, the maximum tangential stress (MTS) and mean stress (MS), are utilized to estimate the LBC of the V-notched FSWed parts. The comparison between the experimental results and the theoretical predictions reveals that both fracture criteria, in combination with EMC, can accurately predict the LBC in the analyzed components.
    Materialart: Online-Ressource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma16051757
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2023
    ZDB Id: 2487261-1
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    Online-Ressource
  • 7
    Online-Ressource
    Online-Ressource
    Using the Equivalent Material Concept and the Average Strain Energy Density to Analyse the Fracture Behaviour of Structural Materials
    MDPI AG ; 2020
    In:  Applied Sciences Vol. 10, No. 5 ( 2020-02-28), p. 1601-
    Details
    In: Applied Sciences, MDPI AG, Vol. 10, No. 5 ( 2020-02-28), p. 1601-
    Kurzfassung: This paper provides a complete overview of the applicability of the Equivalent Material Concept in conjunction with the Average Strain Energy Density criterion, to provide predictions of fracture loads in structural materials containing U-notches. The Average Strain Density Criterion (ASED) has a linear-elastic nature, so in principle, it does not provide satisfactory predictions of fracture loads in those materials with nonlinear behaviour. However, the Equivalent Material Concept (EMC) is able to transform a physically nonlinear material into an equivalent linear-elastic one and, therefore, the combination of the ASED criterion with the EMC (EMC–ASED criterion) should provide good predictions of fracture loads in physically nonlinear materials. The EMC–ASED criterion is here applied to different types of materials (polymers, composites and metals) with different grades of nonlinearity, showing the accuracy of the corresponding fracture load predictions and revealing qualitatively the limitations of the methodology. It is shown how the EMC–ASED criterion provides good predictions of fracture loads in nonlinear materials as long as the nonlinear behaviour is mainly limited to the tensile behaviour, and how the accuracy decreases when the nonlinear behaviour is extended to the material behaviour in the presence of defects.
    Materialart: Online-Ressource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app10051601
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2020
    ZDB Id: 2704225-X
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  • 8
    Online-Ressource
    Online-Ressource
    A Methodology to Determine the Effective Plastic Zone Size Around Blunt V-Notches under Mixed Mode I/II Loading and Plane-Stress Conditions
    MDPI AG ; 2021
    In:  Metals Vol. 11, No. 7 ( 2021-06-29), p. 1042-
    Details
    In: Metals, MDPI AG, Vol. 11, No. 7 ( 2021-06-29), p. 1042-
    Kurzfassung: The determination of the ductile failure behavior in engineering components weakened by cracks and notches is greatly dependent on the estimation of the plastic zone size (PZS) and, particularly, the effective plastic zone size (EPZS). Usually, time-consuming complex elastic–plastic analyses are required for the determination of the EPZS. Such demanding procedures can be avoided by employing analytical methods and by taking advantage of linear elastic analyses. In this sense, this work proposed a methodology for determining the PZS around the tip of blunt V-notches subjected to mixed mode I/II loading and plane-stress conditions. With this aim, firstly, existing approximate mathematical expressions for the elastic stress field near round-tip V-notches reported in the literature are presented. Next, Irwin’s approach (fundamentally proposed for sharp cracks) and a yield criterion (von Mises or Tresca) were applied and are presented. With the aim of verifying the proposed methodology, elastic–plastic finite element analyses were performed on virtual AISI 304 steel V-notched specimens. It was shown that the analytical formulations presented cannot estimate the complete shape of the plastic zone. However, the EPZS, which is crucial for predicting the type of ductile failure in notched members, can be successfully estimated.
    Materialart: Online-Ressource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met11071042
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2021
    ZDB Id: 2662252-X
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    Online-Ressource
  • 9
    Online-Ressource
    Online-Ressource
    Mixed Mode Fracture Investigation of Rock Specimens Containing Sharp V-Notches
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 24 ( 2022-12-08), p. 8779-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 24 ( 2022-12-08), p. 8779-
    Kurzfassung: This work aims to assess both experimentally and analytically the fracture behavior of rock specimens containing sharp V-notches (SV-notches) subjected to mixed mode I/II loading. To this end, firstly, several mixed mode fracture tests were conducted on Brazilian disk specimens weakened by an SV-notch (SVNBD sample), performed in their corresponding center and with various notch opening angles. Secondly, the fracture resistance of the tested samples was predicted using a criterion named MTS-FEM. This approach is based on the maximum tangential stress (MTS) criterion, in which the tangential stress is determined from the finite element method (FEM). Additionally, in the present research, the required critical distance is calculated directly from finite element analyses performed on cracked samples. Comparing the experimental results and the analytical predictions, it is shown that the fracture curves obtained from the MTS-FEM criterion are in agreement with the experimental results. These results are achieved without the need for the calculation of stress series expansion coefficients, as an additional advantage of the proposed approach.
    Materialart: Online-Ressource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15248779
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2022
    ZDB Id: 2487261-1
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 10
    Online-Ressource
    Online-Ressource
    Extension of the Equivalent Material Concept to Compressive Loading: Combination with LEFM Criteria for Fracture Prediction of Keyhole Notched Polymeric Samples
    MDPI AG ; 2021
    In:  Applied Sciences Vol. 11, No. 9 ( 2021-04-30), p. 4138-
    Details
    In: Applied Sciences, MDPI AG, Vol. 11, No. 9 ( 2021-04-30), p. 4138-
    Kurzfassung: This work analyzes, both theoretically and experimentally, the fracture process of square specimens weakened by keyhole notches and subjected to compressive stresses. Two materials are covered: general-purpose polystyrene (GPPS) and poly(methyl methacrylate) (PMMA). Firstly, the load-carrying capacity (LCC) of the specimens is determined experimentally. Then, by using the equivalent material concept (EMC) for compressive conditions coupled with the maximum tangential stress (MTS) and the mean stress (MS) criteria, the LCC of the notched specimens is predicted. The results show that by using the approach proposed in the present investigation, not only can the critical loads in the keyhole notched polymeric specimens be precisely predicted, but also the corresponding compressive critical stress of the two mentioned polymers can be successfully estimated.
    Materialart: Online-Ressource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app11094138
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2021
    ZDB Id: 2704225-X
    Standort Signatur Einschränkungen Verfügbarkeit
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