Special Issue "Metal Plasticity and Fatigue at High Temperature"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (30 November 2019).

Special Issue Editors

Prof. Dr. Denis Benasciutti
E-Mail Website
Guest Editor
Department of Engineering, University of Ferrara, 44122 Ferrara, Italy
Interests: vibration fatigue; cyclic plasticity; multiaxial fatigue
Prof. Dr. Luciano Moro
E-Mail Website
Guest Editor
Politechnic Department of Engineering and Architecture (DPIA), University of Udine, 33100 Udine, Italy
Interests: multiphysics analysis, non-linear finite element simulations, failure analysis
Dr. Jelena Srnec Novak
E-Mail Website
Guest Editor
Politechnic Department of Engineering and Architecture (DPIA), University of Udine, 33100 Udine, Italy
Interests: cyclic plasticity; material characterization; thermo-mechanical fatigue

Special Issue Information

Dear Colleagues,

The situation in which a component is maintained at high temperature under the action of cyclic thermal and/or mechanical loading represents, perhaps, one of the most demanding engineering applications, if not in fact the most demanding. Examples can be found in many industrial fields, such as automotive (cylinder head, engine, disk brakes), steel-making (hot rolling), machining (milling, turning), aerospace (turbine blades), and fire protection systems (fire doors).

The presence of high temperatures usually induces some material plasticity in the most stressed region of the system, which, combined with cyclic loading variation, may lead to low-cycle fatigue failure.

In order to estimate the component fatigue life in such demanding operative conditions, a complete characterization of the high-temperature material behavior under cyclic loading (e.g. cyclic stress–strain response, cyclic plasticity, fatigue testing under isothermal and/or non-isothermal conditions) should be performed. Moreover, a reliable structural durability approach, which includes experimental results in numerical and/or predictive models (e.g. plasticity models, fatigue strength curves), needs to be developed as well.

The choice of the most appropriate material model to be used in simulations, or even calibrating the model to experimental data, often represents the most critical step in the whole design approach. Experimental techniques and modeling have to be properly managed to guarantee the reliability of the estimated fatigue life.

The purpose of this Special Issue is to collect papers aimed at providing state-of-the-art knowledge on the topic of metal plasticity and the fatigue strength of metals operating at high temperatures, with an emphasis on both experimental characterization and the numerical modeling of material behavior. Researchers are encouraged to submit their research papers on specific aspects of high-temperature material behavior and fatigue strength, or also to describe specific applications in which the above-mentioned topics are applied to relevant engineering case studies.

Prof. Dr. Denis Benasciutti
Prof. Dr. Luciano Moro
Dr. Jelena Srnec Novak
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Structural durability
  • Low-cycle fatigue
  • High temperature
  • Metal plasticity
  • Material characterization
  • Material numerical modelling
  • Finite element method
  • Failure analysis
  • Cyclic material behavior

Published Papers (11 papers)

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Research

Open AccessFeature PaperArticle
Flow Stress of bcc Metals over a Wide Range of Temperature and Strain Rates
Metals 2020, 10(1), 120; https://doi.org/10.3390/met10010120 - 13 Jan 2020
Abstract
A physical-based model for the flow stress of bcc metals is presented. Here, thermally activated and viscous drag regimes are considered. For the thermally activated component of the flow stress, the diffusion-controlled regime at elevated temperature is also taken into account assuming the [...] Read more.
A physical-based model for the flow stress of bcc metals is presented. Here, thermally activated and viscous drag regimes are considered. For the thermally activated component of the flow stress, the diffusion-controlled regime at elevated temperature is also taken into account assuming the non-linear dependence of the activation volume on temperature. The model was applied to A508 (16MND5) steel showing the possibility to accurately describe the variation of the flow stress over the entire temperature range (from 0 K to Tm) and over a wide strain-rate range. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
Stress Relaxation Aging Behavior and Constitutive Modelling of AA7150-T7751 under Different Temperatures, Initial Stress Levels and Pre-Strains
Metals 2019, 9(11), 1215; https://doi.org/10.3390/met9111215 - 12 Nov 2019
Abstract
Age forming is an advanced manufacture technology for forming large aluminum panels. Temperature, initial stress level and pre-strains have a great effect on the formability and performance. The stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial stress levels and pre-strains was [...] Read more.
Age forming is an advanced manufacture technology for forming large aluminum panels. Temperature, initial stress level and pre-strains have a great effect on the formability and performance. The stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial stress levels and pre-strains was studied through stress relaxation tests, tensile tests and TEM observations. The results show that the formability can be improved with the increase of temperature, initial stress levels and pre-strains. Deformation mechanisms during stress relaxation of the material were analyzed on the basis of creep stress exponent and apparent activation energy. The aging precipitates of the studied alloy were not sensitive to the age forming conditions, but drastically coarsened at over aging temperature, which decreased the mechanical properties. In addition, the relationship between stress relaxation behavior and aging strengthening is discussed. Based on the dislocation theory and the modified Arrhenius equation, a stress relaxation constitutive equation considering the initial mobile dislocation density and temperature dependent activation energy was established. This model can predict very well the stress relaxation behavior under various temperature, stress level and pre-strain conditions, with an average error of 2%. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
Thermo-Mechanical Fatigue Lifetime Assessment of Spheroidal Cast Iron at Different Thermal Constraint Levels
Metals 2019, 9(10), 1068; https://doi.org/10.3390/met9101068 - 01 Oct 2019
Abstract
In previous work on the thermo-mechanical fatigue (TMF) of compacted graphite iron (CGI), lifetimes measured under total constraint were confirmed analytically by numerical integration of Paris’ crack-growth law. In current work, the results for CGI are further validated for spheroidal cast iron (SGI), [...] Read more.
In previous work on the thermo-mechanical fatigue (TMF) of compacted graphite iron (CGI), lifetimes measured under total constraint were confirmed analytically by numerical integration of Paris’ crack-growth law. In current work, the results for CGI are further validated for spheroidal cast iron (SGI), while TMF tests at different constraint levels were additionally performed. The Paris crack-growth law is found to require a different C P a r i s parameter value per distinct constraint level, indicating that Paris’ law does not capture all physical backgrounds of TMF crack growth, such as the effect of constraint level. An adapted version of Paris’ law is developed, designated as the local strain model. The new model considers cyclic plastic strains at the crack tip to control crack growth and is found to predict TMF lifetimes of SGI very well for all constraint levels with a single set of parameters. This includes not only full constraint but also over and partial constraint conditions, as encountered in diesel engine service conditions. The local strain model considers the crack tip to experience a distinct sharpening and blunting stage during each TMF cycle, with separate contributions to crack-tip plasticity, originating from cyclic bulk stresses in the sharpening stage and cyclic plastic bulk strains in the blunting stage. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
An Isotropic Model for Cyclic Plasticity Calibrated on the Whole Shape of Hardening/Softening Evolution Curve
Metals 2019, 9(9), 950; https://doi.org/10.3390/met9090950 - 30 Aug 2019
Abstract
This work presents a new isotropic model to describe the cyclic hardening/softening plasticity behavior of metals. The model requires three parameters to be evaluated experimentally. The physical behavior of each parameter is explained by sensitivity analysis. Compared to the Voce model, the proposed [...] Read more.
This work presents a new isotropic model to describe the cyclic hardening/softening plasticity behavior of metals. The model requires three parameters to be evaluated experimentally. The physical behavior of each parameter is explained by sensitivity analysis. Compared to the Voce model, the proposed isotropic model has one more parameter, which may provide a better fit to the experimental data. For the new model, the incremental plasticity equation is also derived; this allows the model to be implemented in finite element codes, and in combination with kinematic models (Armstrong and Frederick, Chaboche), if the material cyclic hardening/softening evolution needs to be described numerically. As an example, the proposed model is applied to the case of a cyclically loaded copper alloy. An error analysis confirms a significant improvement with respect to the usual Voce formulation. Finally, a numerical algorithm is developed to implement the proposed isotropic model, currently not available in finite element codes, and to make a comparison with other cyclic plasticity models in the case of uniaxial stress and strain-controlled loading. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessFeature PaperArticle
Thermomechanical Fatigue of Lost Foam Cast Al–Si Cylinder Heads—Assessment of Crack Origin Based on the Evaluation of Pore Distribution
Metals 2019, 9(8), 821; https://doi.org/10.3390/met9080821 - 26 Jul 2019
Abstract
In automotive cylinder heads, thermomechanical fatigue (TMF) leads to crack initiation within the critical loaded sections. This effect becomes even more relevant in lost foam cast cylinder heads since its system-dependent porosity shows a significant influence on the lifetime under TMF loading. This [...] Read more.
In automotive cylinder heads, thermomechanical fatigue (TMF) leads to crack initiation within the critical loaded sections. This effect becomes even more relevant in lost foam cast cylinder heads since its system-dependent porosity shows a significant influence on the lifetime under TMF loading. This work covers the identification of a criterion for crack initiation in order to provide the basis for an effective quality control with improved statistical safety by nondestructive testing. Specimens extracted from lost foam cylinder heads were investigated by uniaxial TMF tests, X-ray micro computer tomography (μCT), and scanning electron microscopy (SEM). Due to pore analyses on a global and local scale, it is concluded that pore networks are crucial for crack initiation. Thus, a tool for computation of pore accumulations from μCT data containing interaction criteria by Murakami was developed in order to assess the crack origin. The consideration of pore accumulations significantly improves the predictive accuracy compared to the consideration of single pores. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessFeature PaperArticle
Probabilistic Modeling of Slip System-Based Shear Stresses and Fatigue Behavior of Coarse-Grained Ni-Base Superalloy Considering Local Grain Anisotropy and Grain Orientation
Metals 2019, 9(8), 813; https://doi.org/10.3390/met9080813 - 24 Jul 2019
Abstract
New probabilistic lifetime approaches for coarse grained Ni-base superalloys supplement current deterministic gas turbine component design philosophies; in order to reduce safety factors and push design limits. The models are based on statistical distributions of parameters, which determine the fatigue behavior under high [...] Read more.
New probabilistic lifetime approaches for coarse grained Ni-base superalloys supplement current deterministic gas turbine component design philosophies; in order to reduce safety factors and push design limits. The models are based on statistical distributions of parameters, which determine the fatigue behavior under high temperature conditions. In the following paper, Low Cycle Fatigue (LCF) test data of several material batches of polycrystalline Ni-base superalloy René80 with different grain sizes and orientation distribution (random and textured) is presented and evaluated. The textured batch, i.e., with preferential grain orientation, showed higher LCF life. Three approaches to probabilistic crack initiation life modeling are presented. One is based on Weibull distributed crack initiation life while the other two approaches are based on probabilistic Schmid factors. In order to create a realistic Schmid factor distribution, polycrystalline finite element models of the specimens were generated using Voronoi tessellations and the local mechanical behavior investigated in dependence of different grain sizes and statistically distributed grain orientations. All models were first calibrated with test data of the material with random grain orientation and then used to predict the LCF life of the material with preferential grain orientation. By considering the local multiaxiality and resulting inhomogeneous shear stress distributions, as well as grain interaction through polycrystalline Finite Element Analysis (FEA) simulation, the best consistencies between predicted and observed crack initiation lives could be achieved. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
Some Recent Advances on Thermal–mechanical Fatigue Design and Upcoming Challenges for the Automotive Industry
Metals 2019, 9(7), 794; https://doi.org/10.3390/met9070794 - 17 Jul 2019
Abstract
Automotive industry faces numerous evolutions regarding environment regulations and parts reliability. Through the specific case of a cylinder head, actual and forthcoming challenges for low-cycle and thermal–mechanical fatigue design in an industrial context are presented. With a description of current design approaches and [...] Read more.
Automotive industry faces numerous evolutions regarding environment regulations and parts reliability. Through the specific case of a cylinder head, actual and forthcoming challenges for low-cycle and thermal–mechanical fatigue design in an industrial context are presented. With a description of current design approaches and highlighting limitations, this work focuses on variable loadings, constitutive models and their interaction with the environment, fatigue criteria, and structure validations, the four major steps to meet a reliable design. The need to carry out extended experimental databases for different complexity levels is emphasized to provide a better understanding of loadings and their impact on the strength of materials and structures, as well as the production of more physically-based models that are easier to identify and lead to higher levels of reliability in the thermal–mechanical design process. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessFeature PaperArticle
Transient Effects in Creep of Sanicro 25 Austenitic Steel and Their Modelling
Metals 2019, 9(2), 245; https://doi.org/10.3390/met9020245 - 19 Feb 2019
Abstract
Transient effects upon stress changes during creep of the new Sanicro 25 steel were investigated experimentally using the helicoid spring specimen technique. The creep behaviour was found to be qualitatively the same as that observed earlier with the creep-resistant 9% Cr ferritic-martensitic P-91 [...] Read more.
Transient effects upon stress changes during creep of the new Sanicro 25 steel were investigated experimentally using the helicoid spring specimen technique. The creep behaviour was found to be qualitatively the same as that observed earlier with the creep-resistant 9% Cr ferritic-martensitic P-91 steel, but the transient strains are considerably smaller. Negative creep rate, which is strain running against the applied stress, was observed with any stress decrease. Parameters for the complex creep model were estimated and model results were compared to the creep rates measured experimentally. The model can be used for the finite element method modelling of the creep and stress relaxation effects in the components made from the Sanicro 25 steel. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
Influence of Strain Rate and Waveshape on Environmentally-Assisted Cracking during Low-Cycle Fatigue of a 304L Austenitic Stainless Steel in a PWR Water Environment
Metals 2019, 9(2), 197; https://doi.org/10.3390/met9020197 - 08 Feb 2019
Abstract
In this paper, the low cycle fatigue resistance of a 304L austenitic stainless steel in a simulated pressurized water reactor (PWR) primary water environment has been investigated by paying a special attention to the interplay between environmentally-assisted cracking mechanisms, strain rate, and loading [...] Read more.
In this paper, the low cycle fatigue resistance of a 304L austenitic stainless steel in a simulated pressurized water reactor (PWR) primary water environment has been investigated by paying a special attention to the interplay between environmentally-assisted cracking mechanisms, strain rate, and loading waveshape. More precisely, one of the prime interests of this research work is related to the consideration of complex waveshape signals that are more representative of solicitations encountered by real components. A detailed analysis of stress-strain relation, surface damage, and crack growth provides a preliminary ranking of the severity of complex, variable strain rate signals with respect to triangular, constant strain-rate signals associated with environmental effects in air or in PWR water. Furthermore, as the fatigue lives in PWR water environment are mainly controlled by crack propagation, the crack growth rates derived from striation spacing measurement and estimated from interrupted tests have been carefully examined and analyzed using the strain intensity factor range ΔKε. It is confirmed that the most severe signal with regards to fatigue life also induces the highest crack growth enhancement. Additionally two characteristic parameters, namely a threshold strain εth* and a time T*, corresponding to the duration of the effective exposure of the open cracks to PWR environment have been introduced. It is shown that the T* parameter properly accounts for the differences in environmentally-assisted growth rates as a function of waveshape. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
Application of a area -Approach for Fatigue Assessment of Cast Aluminum Alloys at Elevated Temperature
Metals 2018, 8(12), 1033; https://doi.org/10.3390/met8121033 - 06 Dec 2018
Cited by 5
Abstract
This paper contributes to the effect of elevated temperature on the fatigue strength of common aluminum cast alloys EN AC-46200 and EN AC-45500. The examination covers both static as well as cyclic fatigue investigations to study the damage mechanism of the as-cast and [...] Read more.
This paper contributes to the effect of elevated temperature on the fatigue strength of common aluminum cast alloys EN AC-46200 and EN AC-45500. The examination covers both static as well as cyclic fatigue investigations to study the damage mechanism of the as-cast and post-heat-treated alloys. The investigated fracture surfaces suggest a change in crack origin at elevated temperature of 150 C. At room temperature, most fatigue tests reveal shrinkage-based micro pores as their crack initiation, whereas large slipping areas occur at elevated temperature. Finally, a modified a r e a -based fatigue strength model for elevated temperatures is proposed. The original a r e a model was developed by Murakami and uses the square root of the projected area of fatigue fracture-initiating defects to correlate with the fatigue strength at room temperature. The adopted concept reveals a proper fit for the fatigue assessment of cast Al-Si materials at elevated temperatures; in detail, the slope of the original model according to Murakami should be decreased at higher temperatures as the spatial extent of casting imperfections becomes less dominant at elevated temperatures. This goes along with the increased long crack threshold at higher operating temperature conditions. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Open AccessArticle
An Explicit Creep-Fatigue Model for Engineering Design Purposes
Metals 2018, 8(10), 853; https://doi.org/10.3390/met8100853 - 19 Oct 2018
Cited by 1
Abstract
Background: Creep-fatigue phenomena are complex and difficult to model in ways that are useful from an engineering design perspective. Existing empirical-based models can be difficult to apply in practice, have poor accuracy, and lack economy. Need: There is a need to improve on [...] Read more.
Background: Creep-fatigue phenomena are complex and difficult to model in ways that are useful from an engineering design perspective. Existing empirical-based models can be difficult to apply in practice, have poor accuracy, and lack economy. Need: There is a need to improve on the ability to predict creep-fatigue life, and do so in a way that is applicable to engineering design. Method: The present work modified the unified creep-fatigue model of Liu and Pons by introducing the parameters of temperature and cyclic time into the exponent component. The relationships between them were extracted by investigating creep behavior, and then a reference condition was introduced. Outcomes: The modified formulation was successfully validated on the materials of 63Sn37Pb solder and stainless steel 316. It was also compared against several other models. The results indicate that the explicit model presents better ability to predict fatigue life for both the creep fatigue and pure fatigue situations. Originality: The explicit model has the following beneficial attributes: Integration—it provides one formulation that covers the full range of conditions from pure fatigue, to creep fatigue, then to pure creep; Unified—it accommodates multiple temperatures, multiple cyclic times, and multiple metallic materials; Natural origin—it provides some physical basis for the structure of the formulation, in its consistency with diffusion-creep behavior, the plastic zone around the crack tip, and fatigue capacity; Economy—although two more coefficients were introduced into the explicit model, the economy is not significantly impacted; Applicability—the explicit model is applicable to engineering design for both manual engineering calculations and finite element analysis. The overall contribution is that the explicit model provides improved ability to predict fatigue life for both the creep-fatigue and pure-fatigue conditions for engineering design. Full article
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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