Special Issue "Fatigue and Fracture Behaviour of Additive Manufacturing Mechanical Components"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: 15 September 2019.

Special Issue Editors

Guest Editor
Prof. Dr. Roberto Citarella

Associate Professor, Department of Industrial Engineering, University of Salerno, Italy
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Interests: Fatigue, Fracture, BEM, Vibro-acoustics, Bioengineering
Guest Editor
Prof. Dr. Paulo M. S. T. De Castro

Department of Mechanical Engineering, Universidade do Porto, Porto, Portugal
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Interests: Fatigue; Fracture; Residual stresses; Structural connections; Structural integrity
Guest Editor
Prof. Dr. Angelo Maligno

Institute for Innovation in Sustainable Engineering, University of Derby, Derby, UK
Website | E-Mail
Interests: Linear and Non-linear FE Analysis; Computational and Experimental Damage and Fracture Mechanics; Computational and Experimental Stress Analysis; Computational Multi-physics Analysis and Fluid–Structure Interaction; Multiscale and Stochastic Modelling

Special Issue Information

Dear Colleagues,

The advent of additive manufacturing (AM) processes applied to the fabrication of structural components creates the need for design methodologies supporting structural optimization approaches that take into account the specific characteristics of the process. While AM processes give unprecedented geometrical design freedom, which can result in significant reductions of component weight (e.g., through part count reduction), on the other hand they have implications in the fatigue and fracture strength due to residual stresses and microstructural features. This is linked to stress concentration effects and anisotropy that still need research.This Special Issue of Applied Sciences aims at bringing together papers investigating features of AM processes with relevance to the mechanical behavior of AM structural components, particularly, but not exclusively, from the viewpoints of fatigue and fracture behavior. Although the focus of the issue is on AM problems related to fatigue and fracture, articles dealing with other manufacturing processes with related problems can also be included, in order to establish differences and potential similarities.The submission of papers on numerical simulation or reporting experimental work, or a combination of both, is welcome. The application of damage and fracture mechanics concepts, the appraisal of stress concentration effects, and the consideration of residual stresses and anisotropic behavior will be of particular interest for a range of AM structural applications that can be foreseen to go from biomedical engineering to aerospace components. 

Prof. Dr. Roberto Citarella
Prof. Dr. Paulo de Castro
Prof. Dr. Angelo Maligno
Guest Editors

Manuscript Submission Information

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Keywords

  • Fatigue
  • Fracture
  • Additive manufacturing
  • FEM

Published Papers (5 papers)

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Research

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Open AccessArticle
A Displacement Controlled Fatigue Test Method for Additively Manufactured Materials
Appl. Sci. 2019, 9(16), 3226; https://doi.org/10.3390/app9163226
Received: 6 July 2019 / Revised: 31 July 2019 / Accepted: 31 July 2019 / Published: 7 August 2019
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Abstract
A novel adaptive displacement-controlled test setup was developed for fatigue testing on mini specimens. In property characterization of additive manufacturing materials, mini specimens are preferred due to the specimen preparation, and manufacturing cost but mini specimens demonstrate higher fatigue strength than standard specimens [...] Read more.
A novel adaptive displacement-controlled test setup was developed for fatigue testing on mini specimens. In property characterization of additive manufacturing materials, mini specimens are preferred due to the specimen preparation, and manufacturing cost but mini specimens demonstrate higher fatigue strength than standard specimens due to the lower probability of material defects resulting in fatigue. In this study, a dual gauge section Krouse type mini specimen was designed to conduct fatigue tests on additively manufactured materials. The large surface area of the specimen with a constant stress distribution and increased control volume as the gauge section may capture all different types of surface and microstructural defects of the material. A fully reversed bending (R = −1) fatigue test was performed on simply supported specimens. In the displacement-controlled mechanism, the variation in the control signal during the test due to the stiffness variation of the specimen provides a unique insight into identifying the nucleation and propagation phase. The fatigue performance of the wrought 304 and additively manufactured 304L stainless steel was compared applying a control signal monitoring (CSM) method. The test results and analyses validate the design of the specimen and the effective implementation of the test bench in fatigue testing of additively manufactured materials. Full article
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Open AccessArticle
Fatigue Crack Growth under Non-Proportional Mixed Mode Loading in Rail and Wheel Steel Part 2: Sequential Mode I and Mode III Loading
Appl. Sci. 2019, 9(14), 2866; https://doi.org/10.3390/app9142866
Received: 3 June 2019 / Revised: 12 July 2019 / Accepted: 15 July 2019 / Published: 18 July 2019
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Abstract
Rolling contact fatigue cracks in rail and wheel undergo non-proportional mixed mode I/II/III loading. Fatigue tests were performed to determine the coplanar and branch crack growth rates on these materials. Sequential and overlapping mode I and III loading cycles were applied to single [...] Read more.
Rolling contact fatigue cracks in rail and wheel undergo non-proportional mixed mode I/II/III loading. Fatigue tests were performed to determine the coplanar and branch crack growth rates on these materials. Sequential and overlapping mode I and III loading cycles were applied to single cracks in round bar specimens. Experiments in which this is done have been rarely performed. The fracture surface observations and the finite element analysis results suggested that the growth of long (does not branch but grown stably and straight) coplanar cracks was driven mainly by mode III loading. The cracks tended to branch when increasing the material strength and/or the degree of overlap between the mode I and III loading cycles. The equivalent stress intensity factor range that can consider the crack face contact and successfully regressed the crack growth rate data is proposed for the branch crack. Based on the results obtained in this study, the mechanism of long coplanar shear-mode crack growth turned out to be the same regardless of whether the main driving force is in-plane shear or out-of-plane shear. Full article
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Open AccessArticle
Fracture Resistance of Monolithic Zirconia Crowns on Four Occlusal Convergent Abutments in Implant Prosthesis
Appl. Sci. 2019, 9(13), 2585; https://doi.org/10.3390/app9132585
Received: 28 April 2019 / Revised: 20 June 2019 / Accepted: 21 June 2019 / Published: 26 June 2019
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Abstract
Adjusting implant abutment for crown delivery is a common practice during implant installation. The purpose of this study was to compare the fracture resistance and stress distribution of zirconia specimens on four occlusal surface areas of implant abutment. Four implant abutment designs [occlusal [...] Read more.
Adjusting implant abutment for crown delivery is a common practice during implant installation. The purpose of this study was to compare the fracture resistance and stress distribution of zirconia specimens on four occlusal surface areas of implant abutment. Four implant abutment designs [occlusal surface area (SA) SA100, SA75, SA50, and SA25] with 15 zirconia prostheses over the molar area per group were prepared for cyclic loading with 5 Hz, 300 N in a servo-hydraulic testing machine until fracture or automatic stoppage after 30,000 counts. The minimum occlusal thickness of all specimens was 0.5 mm. Four finite element models were simulated under vertical or oblique 10-degree loading to analyze the stress distribution and peak value of zirconia specimens. Data were statistically analyzed, and fracture patterns were observed under a scanning electron microscope. Cyclic loading tests revealed that specimen breakage had moderately strong correlation with the abutment occlusal area (r = 0.475). Specimen breakage differed significantly among the four groups (P = 0.001). The lowest von Mises stress value was measured for prosthesis with a smallest abutment occlusal surface area (SA25) and the thickest zirconia crown. Thicker zirconia specimens (SA25) had higher fracture resistance and lowest stress values under 300 N loading. Full article
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Open AccessArticle
Fatigue Crack Growth under Non-Proportional Mixed Mode Loading in Rail and Wheel Steel Part 1: Sequential Mode I and Mode II Loading
Appl. Sci. 2019, 9(10), 2006; https://doi.org/10.3390/app9102006
Received: 29 March 2019 / Revised: 13 May 2019 / Accepted: 13 May 2019 / Published: 16 May 2019
Cited by 1 | PDF Full-text (11731 KB) | HTML Full-text | XML Full-text
Abstract
Fatigue tests were performed to estimate the coplanar and branch crack growth rates on rail and wheel steel under non-proportional mixed mode I/II loading cycles simulating the load on rolling contact fatigue cracks; sequential and overlapping mode I and II loadings were applied [...] Read more.
Fatigue tests were performed to estimate the coplanar and branch crack growth rates on rail and wheel steel under non-proportional mixed mode I/II loading cycles simulating the load on rolling contact fatigue cracks; sequential and overlapping mode I and II loadings were applied to single cracks in the specimens. Long coplanar cracks were produced under certain loading conditions. The fracture surfaces observed by scanning electron microscopy and the finite element analysis results suggested that the growth was driven mainly by in-plane shear mode (i.e., mode II) loading. Crack branching likely occurred when the degree of overlap between these mode cycles increased, indicating that such degree enhancement leads to a relative increase of the maximum tangential stress range, based on an elasto–plastic stress field along the branch direction, compared to the maximum shear stress. Moreover, the crack growth rate decreased when the material strength increased because this made the crack tip displacements smaller. The branch crack growth rates could not be represented by a single crack growth law since the plastic zone size ahead of the crack tip increased with the shear part of the loading due to the T-stress, resulting in higher growth rates. Full article
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Review

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Open AccessReview
Part Functionality Alterations Induced by Changes of Surface Integrity in Metal Milling Process: A Review
Appl. Sci. 2018, 8(12), 2550; https://doi.org/10.3390/app8122550
Received: 19 September 2018 / Revised: 4 November 2018 / Accepted: 14 November 2018 / Published: 9 December 2018
Cited by 2 | PDF Full-text (3452 KB) | HTML Full-text | XML Full-text
Abstract
It has been proved that surface integrity alteration induced by machining process has a profound influence on the performance of a component. As a widely used processing technology, milling technology can process parts of different quality grades according to the processing conditions. The [...] Read more.
It has been proved that surface integrity alteration induced by machining process has a profound influence on the performance of a component. As a widely used processing technology, milling technology can process parts of different quality grades according to the processing conditions. The different cutting conditions will directly affect the surface state of the machined parts (surface texture, surface morphology, surface residual stress, etc.) and affect the final performance of the workpiece. Therefore, it is of great significance to reveal the mapping relationship between working conditions, surface integrity, and parts performance in milling process for the rational selection of cutting conditions. The effects of cutting parameters such as cutting speed, feed speed, cutting depth, and tool wear on the machined surface integrity during milling are emphatically reviewed. At the same time, the relationship between the machined surface integrity and the performance of parts is also revealed. Furthermore, problems that exist in the study of surface integrity and workpiece performance in milling process are pointed out and we also suggest that more research should be conducted in this area in future. Full article
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