Martin Bache

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Antal Ürmös

Óbuda University

Sarang Degloorkar

University of Mumbai

Artem Shmelev

SUNY: Stony Brook University

Sze Li Siow

University Malaysia Sarawak

Maicon Sbardella

Universidade Federal de Mato Grosso (UFMT)

Vasileios Voutselas

UNIVERSITY OF THESSALY, GREECE

Dr Paulo Porto de Melo

Universidade Federal de São Paulo (UNIFESP)

ASTES Org

UMT

Alexa Magalhães Dias

ogunsanya abiodun

Bells University Of Technology, Ota, Ogun State.

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Papers by Martin Bache

CIEC17 – Community Editorial

Journal of the European Ceramic Society

High temperature corrosion-fatigue behavior of a shot peened nickel based superalloy

Corrosion Science

In-Situ Assessment of Fracture in SiCf/SiC Under Computed X-Ray Tomography

Volume 6: Ceramics; Controls, Diagnostics, and Instrumentation; Education; Manufacturing Materials and Metallurgy, 2018

The use of X-ray computed tomography (XCT) for detecting sub-critical damage and ultimate failure... more The use of X-ray computed tomography (XCT) for detecting sub-critical damage and ultimate failure mechanisms in a ceramic matrix composite is demonstrated. To this end, an initial XCT investigation of a CMC sample, using a commercially available in-situ mechanical loading rig, is presented. As an important step toward a better understanding of the mechanical behaviour of these materials, in-situ XCT inspection was performed on a macroscopic scaled test coupon, i.e. sampling a significant number of fibre bundles, whilst the material was subjected to monotonic tensile load. The observation of inherent processing artefacts, and the tracking of resultant damage in the structure of CMCs, was demonstrated, supported by post test inspections using optical and scanning electron microscopy. Further consideration is given to the requirements for developing XCT systems for in-situ inspection of CMC materials.

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Matrix Crack Networks in SiC/SiC Composites: In-Situ Characterisation and Metrics

Volume 6: Ceramics and Ceramic Composites; Coal, Biomass, Hydrogen, and Alternative Fuels; Microturbines, Turbochargers, and Small Turbomachines, 2021

Ceramic matrix composites can offer clear potential for a variety of engineering applications whe... more Ceramic matrix composites can offer clear potential for a variety of engineering applications where the temperature capabilities of conventional metals are exceeded. Continued mechanical characterisation is essential to gain an understanding of their associated damage and failure mechanisms across a wide range of representative temperatures. The present paper will report ongoing research to characterize the initiation of matrix cracking at room temperature under tensile stress and subsequent damage development under fatigue loading in a SiCf/SiC composite. Imaging and mechanical property data were obtained via in-situ loading within a scanning electron microscope. The temporal nature of damage development was also recorded through the selective employment of acoustic emission. Metrics to describe the spatial distribution of cracks, crack lengths and crack opening displacement under load will be presented. The inspections also provided detailed evidence of the associated crack closur...

Damage Development in SiCf/SiC Composites Through Mechanical Loading

Sophisticated mechanical characterisation is vital in support of a fundamental understanding of d... more Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states.Standard SiCf/SiC processing techniques inherently introduce porosity between the individual reinforcing fibres and between woven fibre bundles. Subsequent mechanical loading (static or cyclic) may initiate cracking from these stress concentrations in addition to fibre/matrix decohesion and delamination. The localised coalescence of such damage ultimately leads to rapid failure.Proven techniques for the monitoring of damage in structural metallics, i.e. optical microscopy, potential drop systems, acoustic emission (AE) and digital image correlation (DIC), have been adapted for the characterisation of CMC’s tested at room temperature. As processed SiCf/SiC panels were subjected to detailed X-ray computed tomography (XCT) inspection prior to specimen extraction and subsequent static and cyclic mechanical testing to verify their condition. DIC strain measurements, acoustic emission and resistance monitoring were performed and correlated to monitor the onset of damage during loading, followed by intermittent XCT inspections throughout the course of selected tests

Net shape hipping and the properties of hipped samples of Ti-6Al-4V

Biaxial Fatigue Testing of a High Strength Titanium Alloy

The near alpha titanium alloy, IMI685, has been the subject of much research interest because of ... more The near alpha titanium alloy, IMI685, has been the subject of much research interest because of a tendency to dwell sensitive fatigue at near ambient temperatures. Characteristic features of both cyclic and dwell response include the formation of subsurface cracks and the occurrence of quasi-cleavage facets at initiation sites. It has been suggested that these features are due to (a) plastic deformation, (b) the degree of stress triaxiality, (c) the presence of hydrogen. The current paper explores some of these issues.

Dwell and environmental aspects of fatigue in alpha/beta titanium alloys

Dwell sensitive fatigue in titanium alloys at near ambient temperatures was first recognized as a... more Dwell sensitive fatigue in titanium alloys at near ambient temperatures was first recognized as a consequence of aerospace component failures. Previous to this, extended periods of loading at peak or high mean stress were assumed to be benign to the accumulation of fatigue damage. Subsequent research has shown that quasi-cleavage facets are synonymous with dwell failures. Their formation is due to stress redistribution between weak and strong grains or regions within the bulk material and is therefore encouraged by inhomogeneous microstructures. Slip band models are discussed which account for the redistribution process. Although the dwell effect is mainly an initiation and small crack phenomenon subsequent crack propagation rates under dwell loading can be affected in the presence of selected corrosive species. The influence of oxidizing and reducing environments are assessed.

The effect of tension/torsion loading on low temperature dwell- sensitive fatigue in titanium alloys

Titanium Alloys: Processing and Properties

Metals, 2021

The invited review paper to accompany this special issue, authored by Williams and Boyer [...]

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Advances in Damage Monitoring Techniques for the Detection of Failure in SiCf/SiC Ceramic Matrix Composites

Ceramics, 2019

From a disruptive perspective, silicon carbide (SiC)-based ceramic matrix composites (CMCs) provi... more From a disruptive perspective, silicon carbide (SiC)-based ceramic matrix composites (CMCs) provide a considerable temperature and weight advantage over existing material systems and are increasingly finding application in aerospace, power generation and high-end automotive industries. The complex structural architecture and inherent processing artefacts within CMCs combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in CMCs. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. This is important if CMCs are to be utilised to their full potential within industrial applications. Bulk measurements of strain via extensometry or even localised strain gauging would fail to charac...

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Influence of surface layer on properties of hipped Ti–6Al–4V

Materials Science and Technology, 2006

ABSTRACT The nature of the surface region formed between Ti–6Al–4V and the mild steel tooling use... more ABSTRACT The nature of the surface region formed between Ti–6Al–4V and the mild steel tooling used to define the shape of net shape hot isostatically pressed (hipped) Ti–6Al–4V components has been evaluated. The surface topography has been assessed and analytical scanning electron microscopy (SEM) has been used to define the local changes in composition obtained under several hipping conditions. The tensile and fatigue properties of net shape hipped samples of Ti–6Al–4V have been compared with those obtained from samples produced by machining samples from larger hipped cylinders so that the surface layer is removed. The as hipped surface is irregular on the scale of the original powder particles and a 150 μm thick diffusion layer is produced under the standard hipping conditions. It has been found that the tensile properties of samples with the as hipped or machined surfaces are very similar. The fatigue limits of samples which were tested with the as hipped surface were significantly below those of samples which were machined to remove the as hipped surface. Electropolishing the as hipped samples to a depth of ∼150 μm leads to fatigue properties which are slightly higher than the properties of machined samples. These results are discussed in terms of the failure mechanisms during fatigue and issues in the production of net shape hipped products.

Hydrogen and fatigue behaviour in a near alpha titanium alloy

Scripta Metallurgica et Materialia, 1995

The beta processed near alpha titanium alloys were developed for high performance applications in... more The beta processed near alpha titanium alloys were developed for high performance applications in gas turbines. The principal requirement was an enhanced temperature capability coupled with competitive fatigue strength at lower temperatures. Paradoxically, these creep resistant alloys can give inferior fatigue performance at near ambient temperatures when the applied cycle has a dwell period at peak stress. This characteristic has obvious implications for components with operating envelopes that include long hold periods at relatively high static stress. Several factors have been implicated in the dwell sensitivity including plastic strain accumulation, biaxial and triaxial stress fields and microstructural condition. One particularly important consideration is hydrogen concentration. It has been argued that the life decrement is due to hydride formation at slip bands or crack tips. The fact that hydrogen diffusion is promoted by stress gradients can account for critical levels for hydride precipitation being reached in material with non-dangerous average concentration levels. The research was carried out on IMI685 (Ti-6Al-5Zr-0.5Mo-0.25Si), a typical representative of this class of material. The alloy was evaluated with an aligned alpha microstructure, since this is considered to be its most susceptible condition. Hydrogen concentrations were varied in the range 20--275 ppm. The research covered both tensionmore » and torsion loading modes but attention is given to the former only in this publication. The work clearly demonstrates specific regimes of behavior associated with the various hydrogen contents.« less

Novel low cost procedure for fabrication of diffusion bonds in Ti 6/4

Materials Science and Technology, 2009

Abstract A novel processing route has been developed with the aim of achieving low cost joining. ... more Abstract A novel processing route has been developed with the aim of achieving low cost joining. To this end, the fabrication of structurally sound bonds between a similar Ti 6/4 alloy couple has been facilitated by incorporating a copper based interlayer integral to the faying surface. A Gleeble thermomechanical simulator has been employed to optimise the key bonding parameters (i.e. pressure, time, temperature and environment) together with the quantity of copper required to produce high quality bonds with near parent properties. Metallographic sections, chemical composition and microhardness traverses across the bond line are all presented as evidence of joint form and integrity. The mechanical response of the bonds was assessed under monotonic tensile loading conditions. The suitability of this novel joining technique for the fabrication of engineering components and its implications are discussed.

Surface Roughness, Areal Topographic Measurement, and Correlation to LCF Behavior in a Nickel-Based Superalloy

Journal of Materials Engineering and Performance, 2014

Surface roughness often determines fatigue performance of advanced engineering components making ... more Surface roughness often determines fatigue performance of advanced engineering components making definition of this parameter essential subsequent to manufacture. Traditionally, topography measurements employ an average amplitude parameter, R a , obtained from a two-dimensional contact measurement. This parameter, however, is highly localised making it relatively unreliable. This study attempts to correlate areal (3D) topographic, measurements with the low cycle fatigue (LCF) performance defined for a nickelbased superalloy (Waspaloy). Three different surface finishes, namely longitudinal polished, circumferential ground, and longitudinal ground were applied to fatigue specimens. The height and orientation of the topographic features with respect to the loading axis were found to affect LCF performance. Results indicate a close correlation between cycles to failure and the maximum height (S z) and ten-point height (S 5z) parameters. A power fit to account for the topographic effect was generated based on the experimental data.

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High temperature fatigue behaviour in an advanced nickel based superalloy: The effects of oxidation and stress relaxation at notches

Theoretical and Applied Fracture Mechanics, 2016

The low cycle fatigue performance of the nickel based superalloy RR1000 was investigated under a ... more The low cycle fatigue performance of the nickel based superalloy RR1000 was investigated under a variety of load waveforms at high temperature, employing a double edge notch geometry under load control. Experiments on a plain cylindrical specimen design under strain control were later performed to simulate the constrained conditions at the root of the notch in order to characterise the interaction between surface constituents and the environment. A significant fatigue debit was demonstrated under both load/ strain scenarios when superimposing a dwell period at the minimum point of the cycle. This debit was attributed to a reduction in fatigue crack initiation life resulting from oxidation damage which subsequently cracks under cyclic tension together with a modification to the mean stress through cyclic stabilisation. The same dwell period superimposed at the peak of the cycle was essentially benign for excursions under strain control loading.

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Fatigue Crack Growth in Flow Formed INCONEL 718

Materials Science Forum, 2016

Fatigue crack propagation has been measured in flow formed Inconel 718 (IN718). Test pieces were ... more Fatigue crack propagation has been measured in flow formed Inconel 718 (IN718). Test pieces were extracted from a flow formed tubular structure in the longitudinal direction, retaining the tube curvature across their width. Crack growth rates (da/dN) were measured at 20, 300, and 400oC. For comparison, tests were repeated on specimens with an identical geometry but machined from conventionally forged IN718. Detailed metallurgy of the flow formed material is presented.

Microstructural characterisation of a nickel alloy processed via blown powder direct laser deposition (DLD)

Materials & Design, 2017

A three dimensional structure of varying wall thickness has been manufactured from an alloy simil... more A three dimensional structure of varying wall thickness has been manufactured from an alloy similar to 718 and subjected to metallographic characterisation. The technique is evaluated as a process capable of generating complex geometries. This can be used to add features or as a free form fabrication method. However, in order to allow for comparison to structures developed through more traditional techniques, detailed microstructural characterisation has been undertaken to attempt to understand the potential effect of variation on resultant mechanical properties. Samples were extracted from six locations with different wall thicknesses, intricate features and intersecting ligament geometry. A ʺ linearly arrayed structure within a  matrix was consistent throughout the component. Micro-porosity was restricted to isolated, spherical pores less than 1 m in diameter. Electron back-scatter diffraction and X-ray computed microtomography quantitative microstructural analysis techniques have been utilized to assess the influence of layering upon microporosity, patternation and grain structure. A detailed comparison is also made between blown powder Direct Layer Deposition (DLD) and a similar deposition technique, shaped metal deposition (SMD). Blown powder DLD produces a smaller weld pool and results in a more consistent microstructure than SMD, with less evidence of unfavourable phases brought about by prolonged exposure to high temperatures. The improved microstructure, however,

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Creep deformation mechanisms in a γ titanium aluminide

Materials Science and Engineering: A, 2016

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

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Method of Forming a Component Joint

CIEC17 – Community Editorial

Journal of the European Ceramic Society

High temperature corrosion-fatigue behavior of a shot peened nickel based superalloy

Corrosion Science

In-Situ Assessment of Fracture in SiCf/SiC Under Computed X-Ray Tomography

Volume 6: Ceramics; Controls, Diagnostics, and Instrumentation; Education; Manufacturing Materials and Metallurgy, 2018

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Matrix Crack Networks in SiC/SiC Composites: In-Situ Characterisation and Metrics

Volume 6: Ceramics and Ceramic Composites; Coal, Biomass, Hydrogen, and Alternative Fuels; Microturbines, Turbochargers, and Small Turbomachines, 2021