Fracture and Damage Mechanics of Metals, Steels and Alloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Failure Analysis".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 12685

Special Issue Editor


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Guest Editor
University of Cassino and Southern Lazio, Dept. Of Civil and Mechanical Engineering, Via G. Di Biasio 42, 03043 Cassino, Italy
Interests: modeling materials behavior under extreme conditions (high strain rates, elevated temperature, pressure, large strain); fracture mechanics and damage mechanics; creep; experimental characterization; finite element simulation and computational mechanics; characterization and damage assessment of additively manufactured materials (metals and alloys)
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Special Issue Information

Dear Colleagues,

In recent years, modeling and simulation has increasingly become a primary tool to assess the structural integrity of mechanical components. To improve design-against-failure assessment routes, physically based models capable of accounting for different micromechanisms of damage and with clear material parameter identification procedures are needed. The present Special Issue invites papers to update the state-of-the-art of this relevant topic. Both review and original manuscripts are welcome. Special attention will be dedicated to the application to thermomechanical processes and in-service conditions characterized by extreme temperatures (low and high), large plastic deformation, high strain rates, and impact-related phenomena. Contributions demonstrating the applicability of damage models, where appropriate integrated with a more classical fracture mechanics approach, to practical application examples are also welcome.

Prof. Dr. Nicola Bonora
Guest Editor

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Keywords

  • Fracture (brittle, ductile, creep, fatigue, etc)
  • Damage mechanics
  • Extreme conditions (high strain rates, low-high temperature, large plastic deformation, etc.)
  • Procedures for material model parameter identification
  • Experimental testing

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Published Papers (4 papers)

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Research

22 pages, 9767 KiB  
Article
Inverse Identification of the Ductile Failure Law for Ti6Al4V Based on Orthogonal Cutting Experimental Outcomes
by Andrés Sela, Daniel Soler, Gorka Ortiz-de-Zarate, Guénaël Germain, François Ducobu and Pedro J. Arrazola
Metals 2021, 11(8), 1154; https://doi.org/10.3390/met11081154 - 21 Jul 2021
Cited by 5 | Viewed by 2394
Abstract
Despite the prevalence of machining, tools and cutting conditions are often chosen based on empirical databases, which are hard to be made, and they are only valid in the range of conditions tested to develop it. Predictive numerical models have thus emerged as [...] Read more.
Despite the prevalence of machining, tools and cutting conditions are often chosen based on empirical databases, which are hard to be made, and they are only valid in the range of conditions tested to develop it. Predictive numerical models have thus emerged as a promising approach. To function correctly, they require accurate data related to appropriate material properties (e.g., constitutive models, ductile failure law). Nevertheless, material characterization is usually carried out through thermomechanical tests, under conditions far different from those encountered in machining. In addition, segmented chips observed when cutting titanium alloys make it a challenge to develop an accurate model. At low cutting speeds, chip segmentation is assumed to be due to lack of ductility of the material. In this work, orthogonal cutting tests of Ti6Al4V alloy were carried out, varying the uncut chip thickness from 0.2 to 0.4 mm and the cutting speed from 2.5 to 7.5 m/min. The temperature in the shear zone was measured through infrared measurements with high resolution. It was observed experimentally, and in the FEM, that chip segmentation causes oscillations in the workpiece temperature, chip thickness and cutting forces. Moreover, workpiece temperature and cutting force signals were observed to be in counterphase, which was predicted by the ductile failure model. Oscillation frequency was employed in order to improve the ductile failure law by using inverse simulation, reducing the prediction error of segmentation frequency from more than 100% to an average error lower than 10%. Full article
(This article belongs to the Special Issue Fracture and Damage Mechanics of Metals, Steels and Alloys)
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15 pages, 1985 KiB  
Article
Gear Root Bending Strength: A New Multiaxial Approach to Translate the Results of Single Tooth Bending Fatigue Tests to Meshing Gears
by Franco Concli, Lorenzo Fraccaroli and Lorenzo Maccioni
Metals 2021, 11(6), 863; https://doi.org/10.3390/met11060863 - 25 May 2021
Cited by 21 | Viewed by 4439
Abstract
Developing accurate design data to enable the effective use of new materials is undoubtedly an essential goal in the gear industry. To speed up this process, Single Tooth Bending Fatigue (STBF) tests can be conducted. However, STBF tests tend to overestimate the material [...] Read more.
Developing accurate design data to enable the effective use of new materials is undoubtedly an essential goal in the gear industry. To speed up this process, Single Tooth Bending Fatigue (STBF) tests can be conducted. However, STBF tests tend to overestimate the material properties with respect to tests conducted on Running Gears (RG). Therefore, it is common practice to use a constant correction factor fkorr, of value 0.9 to exploit STBF results to design actual gears, e.g., through ISO 6336. In this paper, the assumption that this coefficient can be considered independent from the gear material, geometry, and loading condition was questioned, and through the combination of numerical simulations with a multiaxial fatigue criterion, a method for the calculation of fkorr was proposed. The implementation of this method using different gear geometries and material properties shows that fkorr varies with the gears geometrical characteristics, the material fatigue strength, and the load ratio (R) set in STBF tests. In particular, by applying the Findley criterion, it was found that, for the same gear geometry, fkorr depends on the material as well. Specifically, fkorr increases with the ratio between the bending and torsional fatigue limits. Moreover, through this method it was shown that the characteristics related to the material and the geometry have a relevant effect in determining the critical point (at the tooth root) where the fracture nucleates. Full article
(This article belongs to the Special Issue Fracture and Damage Mechanics of Metals, Steels and Alloys)
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14 pages, 3598 KiB  
Article
Process Condition Diagram Predicting Onset of Microdefects and Fracture in Cold Bar Drawing
by Yong-Hoon Roh, Donghyuk Cho, Hae-Chang Choi, Zhaorui Yang and Youngseog Lee
Metals 2021, 11(3), 479; https://doi.org/10.3390/met11030479 - 13 Mar 2021
Cited by 7 | Viewed by 2438
Abstract
This paper presents a process condition diagram (PCD) that not only identifies conditions under which materials fracture during bar drawing, but also infers the presence or absence of microdefects such as microvoids and microcracks in the drawn material as accumulative damage changes owing [...] Read more.
This paper presents a process condition diagram (PCD) that not only identifies conditions under which materials fracture during bar drawing, but also infers the presence or absence of microdefects such as microvoids and microcracks in the drawn material as accumulative damage changes owing to the die semi-angle and reduction ratio. The accumulative damage values were calculated by finite element (FE) analysis. The critical damage values were determined by performing a tensile test using a smooth round bar tensile specimen and performing FE analysis simulating the tensile test. High alloy steel with a 13 mm diameter was used for the draw bench testing in a wide range of drawing conditions. Scanning electron microscopy (SEM) analysis was performed to verify the usefulness of the PCD. SEM images showed that the accumulative damage roughly matched the size of microvoids around the non-metallic inclusions and the creation of microcracks, which eventually led to fractures of material being drawn. Hence, utilizing the proposed PCD, a process designer can design drawing conditions that minimize the occurrence of microdefects in the material being drawn while maximizing the reduction ratio. Full article
(This article belongs to the Special Issue Fracture and Damage Mechanics of Metals, Steels and Alloys)
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13 pages, 4502 KiB  
Article
Numerical Research of Fracture Toughness of Aged Ferritic-Martensitic Steel
by Remigijus Janulionis, Gintautas Dundulis and Albertas Grybėnas
Metals 2020, 10(12), 1686; https://doi.org/10.3390/met10121686 - 17 Dec 2020
Cited by 1 | Viewed by 2386
Abstract
Generally, material properties such as the modulus of elasticity, yield strength or fracture toughness are determined by conducting an experiment. Sometimes experimental determination cannot be done due to specific experimental conditions, lack of testing material and so on. Also, experiments are time consuming [...] Read more.
Generally, material properties such as the modulus of elasticity, yield strength or fracture toughness are determined by conducting an experiment. Sometimes experimental determination cannot be done due to specific experimental conditions, lack of testing material and so on. Also, experiments are time consuming and costly. Therefore, there arises the need for alternative determination methods. A numerical method for the fracture toughness determination of steel P91 is suggested in this paper. For this purpose, the universal finite element software ABAQUS was used. The numerical simulation of the C(T) specimen tension test was carried out using non-linear simulation for a conditional load PQ determination, and linear simulation for fracture toughness value KQ determination. The suggested method is validated by comparing numerical and experimental tests results. The secondary aim of the paper is the evaluation of the ageing effect on the fracture toughness of steel P91. Thermal ageing of the steel was carried out in an electric furnace at 650 °C up to 11,000 h. As the numerical results had a good coincidence with experimental data at room temperature, the prediction of fracture toughness at elevated temperature, i.e., 550 °C, using numerical method was carried out. Full article
(This article belongs to the Special Issue Fracture and Damage Mechanics of Metals, Steels and Alloys)
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