Browsing by Author "Hall, Ian W."

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Alüminyum Oksit Uzun Fiber Destekli Mg Matris Kompozitlerin Statik ve Yüksek Hız Basma Davranışı
(Pamukkale Üniversitesi, 2004) Akil, Övünç; Güden, Mustafa; Çiftçioğlu, Muhsin; Hall, Ian W.; Taşdemirci, Alper; 03.02. Department of Chemical Engineering; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Bu çalışmada uzun alüminyum oksit (FP™) fiber destekli magnezyum matris kompozitlerin enine basma davranışının deformasyon hızına bağlı değişimi araştırılmıştır. Silindirik numuneler fiber doğrultusuna dik yönde değişik uzama oranlarında Split Hopkinson basınç çubuğu ve statik mekanik test cihazı kullanılarak test edilmiş uzama-gerilme ilişkileri incelenmiştir. Bunun yanında optik mikroskop ve SEM kullanılarak kırılma mekaniği belirlenmeye çalışılmıştır. Çalışma sonucunda malzemenin enine basma mukavemetinin deformasyon hızı ile arttığı tespit edilmiş olup mikro-yapı incelemesinde deformasyonun ikizlenme ve kayma ile gerçekleştiği belirlenmiştir.
Axial Compression of Aluminum Closed-Cell Foam Filled and Empty Aluminum Tubes
(Uludağ Üniversitesi, 2002) Toksoy, Ahmet Kaan; Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Aluminum closed-cell foam filled aluminum tubes with a polyester bonding layer between foam core and tube wall have been compression tested in ord er to detemiine specific energy absorption for the crash box applications. Aluminum foam, empty and foam filled tubes without bonding layer were also tested for comparison purposes, Preliminary results have shown that interaction effect has been found in foam filled tubes with polyester layer. In order to identify deforiDation mechanisms involving with tube deforination, deformed empty and foam filled tubes crosssections were microscopically analyzed and operative defoimationmechanisms were determined.
Citation - WoS: 123
Citation - Scopus: 135
Crushing of Aluminum Closed Cell Foams: Density and Strain Rate Effects
(Elsevier Ltd., 2000) Hall, Ian W.; Güden, Mustafa; Yu, C.-J; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The quasi-static and high strain rate compression behavior of an Al closed cell foam was examined in detail. The compression flow stress of the foam was a function of the relative density but exhibits little or no strain rate density. In addition to the flow stress, the energy absorption was also related to the foam density by a similar power law dependency. Metallographic observations of compressively deformed foam confirmed the general processes of progressive cell wall collapse.
Citation - WoS: 33
Citation - Scopus: 41
Development of Novel Multilayer Materials for Impact Applications: a Combined Numerical and Experimental Approach
(Elsevier Ltd., 2009-05) Taşdemirci, Alper; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
A well-verified and validated numerical model was used to investigate stress wave propagation in a multilayer material subjected to impact loading. The baseline material consisted of a ceramic faceplate and composite backing plate separated by a rubber or teflon foam interlayer: several variants were investigated in which the number, type, and total thicknesses of the interlayers were altered. Comparison of the variants showed that the use of multiple teflon foam interlayers could drastically reduce the average stress in the multilayer material. Based on the numerical results, further experimental work was undertaken upon one of the variants. Very large and unexpected tensile stress oscillations were observed in the ceramic layers, leading to a refinement of the numerical model which successfully reproduced the oscillations and also demonstrated that separation of the sample layers led to trapping of the stress wave within the layers. Use of the validated numerical model allowed detailed analysis of the processes of wave transmission and demonstrates the important synergy that can exist between experimental and modeling studies. The current study provides a valuable starting point for designing future multilayer materials with specific, controlled properties.
Citation - WoS: 23
Citation - Scopus: 25
Diatom Frustule-Filled Epoxy: Experimental and Numerical Study of the Quasi-Static and High Strain Rate Compression Behavior
(Elsevier Ltd., 2008) Taşdemirci, Alper; Yüksel, Sinan; Karsu, Deniz; Gültürk, Elif; Hall, Ian W.; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
In this study, centric type diatom frustules obtained from a diatomaceous earth filter material were used as filler in an epoxy resin with a weight percentage of 15% in order to assess the possible effects on the compressive behavior at quasi-static and high strain rates. The high strain rate testing of frustule-filled and neat epoxy samples was performed in a split-Hopkinson pressure bar (SHPB) set-up and modeled using the commercial explicit finite element code LS-DYNA 970. Result has shown that 15% frustule filling of epoxy increased both modulus and yield strength values at quasi-static and high strain rates without significantly reducing the failure strain. Microscopic observations revealed two main deformation modes: the debonding of the frustules from the epoxy and crushing/fracture of the frustules. The modeling results have further confirmed the attainment of stress equilibrium in the samples in SHPB testing following the initial elastic region and showed good agreement with the experimental stress–time response and deformation sequence of the samples in high strain rate testing.
Citation - WoS: 43
Dynamic Properties of Metal Matrix Composites: a Comparative Study
(Elsevier Ltd., 1998) Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Three distinctly different metal matrix composites have been tested at strain rates from quasi-static to ≈3000 s−1. It was found that the high strain rate response of each composite was determined primarily by (a) the response of the matrix in the absence of any reinforcement and (b) the damage formation and accumulation processes during deformation. High strain rate behavior of the short fiber composite was dominated by the matrix behavior at low strains but by fiber damage at high strains. The behavior of a whisker reinforced composite was dominated by the matrix properties at all strains. Re-loading tests produced increased fracture strains, indicating that adiabatic heating accelerates fracture of composites by permitting the development of local strain instabilities.
Citation - WoS: 190
Citation - Scopus: 222
Dynamics of Metal Foam Deformation During Taylor Cylinder–hopkinson Bar Impact Experiment
(Elsevier Ltd., 2003) Lopatnikov, Sergey L.; Gama, Bazle A.; Haque, Jahirul; Krauthauser, Carl; Gillespie, John W.; Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Analytical solutions for dynamic deformation of foam materials during the Taylor cylinder–Hopkinson bar impact experiment were obtained. It was shown that shock wave of foam collapse appears during the fast impact. The results of this experiment can be used in estimating the average material properties of the foam under dynamic loading conditions. Results show that the un-deformed and change in length of foam specimens are in good agreement between theory and experiment, as well as numerical analysis.
Citation - WoS: 28
Citation - Scopus: 29
Effect of Adhesive on the Strengthening of Aluminum Foam-Filled Circular Tubes
(Springer Verlag, 2004) Toksoy, Ahmet Kaan; Tanoğlu, Metin; Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Studies of the crushing behavior of closed-cell, aluminum foam-filled aluminum and steel tubes have shown an interaction effect between tubewall and foam filler [1, 2, 3]. The crushing loads of foam-filled tubes are, therefore, found to be higher than the sum of the crushing loads of foam (alone) and tube (alone) mainly due to this effect. Santosa et al. [1], based on FEM results, proposed the following equation for the average crushing load of foam-filled square tubes of length b,
Citation - WoS: 24
Citation - Scopus: 36
Effect of Strain Rate on the Compression Behaviour of a Woven Fabric S2-Glass Fiber Reinforced Vinyl Ester Composite
(Elsevier, 2003) Akil, Övünç; Yıldırım, Uygar; Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Quasi-static (~10−3s−1) and high strain rate (>500 s−1) compression behavior of an S2-glass woven fabric/vinyl ester composite plate was determined in the in-plane and through-thickness directions. In both directions, modulus and failure strength increased with increasing strain rate. A higher strain rate sensitive modulus was found in the through-thickness direction while a higher strain rate sensitive failure strength was found in the in-plane direction. In the in-plane direction, the failure mode was observed to change from splitting followed by “kink banding” (localized fiber buckling) to predominantly splitting at increasing strain rates, while it remained the same in the through-thickness direction.
Citation - WoS: 26
Citation - Scopus: 40
Effect of Strain Rate on the Compression Behaviour of a Woven Glass Fiber/Sc-15 Composite
(Elsevier Ltd., 2004) Güden, Mustafa; Yıldırım, Uygar; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Strain rate dependent compression behavior of a plain-weave S-2 glass fabric SC-15 epoxy (rubber toughened resin) composite plate, currently studied as the backing plate for composite armor applications, was determined in the through-thickness direction (normal to the fiber plane) in the strain rate regime of 1×10−4 to 1.1×103 s−1. In the studied strain rate regime, the modulus and failure strength of the composite were found to be rate sensitive and increased with increasing strain rate. Microscopic observations showed that the composite failed by ductile failure, involving matrix cracks and, later, cracking through and between the fiber layers. Crack deflections at rubber particle/matrix interface and particle pull-out were observed in the failed samples, contributing to the toughness of the composite.
Citation - WoS: 11
Citation - Scopus: 11
The Effect of Strain Rate on the Compressive Deformation Behavior of a Sintered Ti6al4v Powder Compact
(Elsevier Ltd., 2008) Taşdemirci, Alper; Hızal, Alpay; Altındiş, Mustafa; Hall, Ian W.; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The high strain rate (220–550 s−1) and quasi-static (0.0016 s−1) compression deformation behavior of a sintered Ti6Al4V powder compact was investigated. The compact was prepared using atomized spherical particles (100–200 μm) and contained 38 ± 1% porosity. The deformation sequences of the tested samples were further recorded by high speed camera and analyzed as a function of strain. The failure of the compact, which was found to be similar in the studied high strain rate and quasi-static strain rate testing regimes, occurs through particle decohesion along the surface of the two cones in a ductile (dimpled) mode consisting of void initiation and growth and by void coalescence in the interparticle bond region. The effect of strain rate was to increase the flow stress and compressive strength of the compact while the critical strain corresponding to the maximum stress was shown to be strain rate independent.
Citation - WoS: 19
Citation - Scopus: 21
Effect of Strain Rate on the Compressive Mechanical Behavior of a Continuous Alumina Fiber Reinforced Ze41a Magnesium Alloy Based Composite
(Elsevier Ltd., 2006) Güden, Mustafa; Akil, Övünç; Taşdemirci, Alper; Çiftçioğlu, Muhsin; Hall, Ian W.; 03.02. Department of Chemical Engineering; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The compressive mechanical response of an FP™ continuous fiber (35 vol.%) Mg composite has been determined in the transverse and longitudinal directions at quasi-static and high strain rates. It was found that the composite in the transverse direction exhibited strain rate sensitivity of the flow stress and maximum stress within the studied strain-rate range of 1.3 × 10−4 to 1550 s−1. The failure strain in this direction, however, decreased with increasing strain rate. Microscopic observations on the failed samples have shown that the composite failed by shear banding along the diagonal axis, 45° to the loading axis. Twinning was observed in the deformed cross-sections of the samples particularly in and near the shear band region. The strain rate sensitivity of the fracture stress of the composite in transverse direction is attributed to the matrix strain rate sensitivity. In the longitudinal direction, the composite failed by kink formation at quasi-static strain rates, while kinking and splitting were observed at the high strain rates. The maximum stress in the longitudinal direction was, however, found to be strain rate insensitive within the strain rate regime of 1.3 × 10−4 to 500 s−1. In this direction, similar to transverse direction, twinning was observed in the highly deformed kink region. Several different reasons are proposed for the strain rate insensitive compressive strength in this direction.
Citation - WoS: 29
Citation - Scopus: 38
The Effects of Plastic Deformation on Stress Wave Propagation in Multi-Layer Materials
(Elsevier Ltd., 2007-11) Taşdemirci, Alper; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The behavior of a multi-layer material at high strain rate and the effect of plastic deformation on stress wave propagation were investigated by a combination of experimental and numerical techniques. Plastic deformation effects were studied in multi-layer materials consisting of ceramic, copper and aluminum subjected to large strains under high strain rate loading. First, stress wave propagation behavior for the monolithic metals was studied, and then extended to multilayer combinations of these metals with each other and with a ceramic layer. The axial stress distributions were found to be non-uniform in the elastic deformation range of the specimen. The degree of non-uniformity was much more pronounced in the multi-layer samples consisting of different materials. The presence of a ceramic layer increased the magnitudes of stress gradients at the interfaces. It was also found that a major effect of plastic deformation is a tendency to produce a more homogeneous stress distribution within the components. The implications of these observations for practical systems are discussed.
Citation - WoS: 11
Citation - Scopus: 18
Experimental and Numerical Investigation of High Strain Rate Mechanical Behavior of a [0/45 - 45] Quadriaxial E-glass/Polyester Composite
(Elsevier Ltd., 2011) Taşdemirci, Alper; Kara, Ali; Turan, Ali Kıvanç; Tunusoğlu, Gözde; Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Quasi-static (10−3–10−1 s−1) and high strain rate (∼900 s−1) compression behavior of an E-Glass fiber woven fabric reinforced Polyester matrix composites was investigated by using a Shimadzu AG-I testing machine and a Split Hopkinson Pressure Bar apparatus in the Dynamic Testing and Modeling Laboratory of Izmir Institute of Technology. During the experiments, a high speed camera was used to determine deformation behavior. In both directions, modulus and failure strength increased with increasing strain rate. Higher strain rate sensitivity for both elastic modulus and failure strength was observed in the in-plane direction. Based upon these experimental data, a numerical model was developed using the commercial explicit finite element code LS-DYNA to investigate compressive deformation and damage behavior of composites. Excellent agreement was demonstrated for the case of high strain rate loading. Also, the fracture geometries were successfully predicted with the numerical model.
Citation - WoS: 10
High Strain Rate Behavior of a Sic Particulate Reinforced Al2o3 Ceramic Matrix Composite
(Elsevier Ltd., 1998) Hall, Ian W.; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The high strain rate deformation behavior of composite materials is important for several reasons. First, knowledge of the mechanical properties of composites at high strain rates is needed for designing with these materials in applications where sudden changes in loading rates are likely to occur. Second, knowledge of both the dynamic and quasi-static mechanical responses can be used to establish the constitutive equations which are necessary to increase the confidence limits of these materials, particularly if they are to be used in critical structural applications. Moreover, dynamic studies and the knowledge gained form them are essential for the further development of new material systems for impact applications. In this study, the high strain rate compressive deformation behavior of a ceramic matrix composite (CMC) consisting of SiC particles and an Al{sub 2}O{sub 3} matrix was studied and compared with its quasi-static behavior. Microscopic observations were conducted to investigate the deformation and fracture mechanism of the composite.
Citation - WoS: 25
Citation - Scopus: 28
High Strain Rate Deformation Behavior of a Continuous Fiber Reinforced Aluminum Metal Matrix Composite
(Elsevier Ltd., 2000) Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
An aluminum metal matrix composite reinforced with continuous unidirectional α-Al2O3 fibers has been compression tested at quasi-static and dynamic strain rates. In the transverse direction, the composite showed increased flow stress and maximum stress within the studied strain rate regime, 10−3 to 3500 s−1. The strain rate sensitivity of the flow stress in this direction was found to be similar to that of a similar, but unreinforced, alloy determined from previous work. In the longitudinal direction, the maximum stress of the composite increased with increasing strain rate within the range 10−5 to 700 s−1. The strain rate dependent maximum stress in this direction was described by the strain rate dependent fiber buckling stress.
Citation - WoS: 4
Citation - Scopus: 5
High Strain Rate Properties of an Sicw/2124-t6 Aluminum Composite at Elevated Temperatures
(Elsevier Ltd., 1998-07) Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Metal matrix composites, (MMC’s) provide several important advantages over unreinforced metals and alloys. Among these, higher moduli and yield stresses and enhanced thermo-mechanical properties are normally considered important in structural applications of MMC’s. It is also possible that MMC’s may be exposed to loading conditions involving high strain rates during service, for example, components of a car in collision with another or turbine blades hit by ingestion of foreign objects. In such situations of rapidly increasing loading conditions, the material property response may be considerably different from that which applies during slow loading of normal quasi-static testing and, consequently, dynamic mechanical properties are of increasing interest and importance.
High Strain Rate Reloading Compresson Testing of a Closed-Cell Alumnum Foam
(The European Association for Experimental Mechanics, 2007) Taşdemirci, Alper; Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Aluminum (Al) closed-cell foams are materials of increasing importance because they have good energy absorption capabilities combined with good thermal and acoustic properties. They can convert much of the impact energy into plastic energy and absorb more energy than bulk metals at relatively low stresses. When used as filling materials in tubes, they increase total energy absorption over the sum of the energy absorbed by foam alone and tube alone [1]. In designing with metallic foams as energy absorbing fillers, mechanical properties are needed for strain rates corresponding to those created by impact events. Quasi-static mechanical behavior of metallic foams has been fairly extensively studied, but data concerning high strain rate mechanical behavior of these materials are, however, rather sparse [2,3]. This study was initiated, therefore, to study and model the high strain rate mechanical behavior of an Al foam produced by foaming of powder compacts and to compare it with quasi-static behavior and, hence, determine any effect on energy absorbing capacity.
Citation - WoS: 5
Citation - Scopus: 7
High Strain Rate Testing of a Unidirectionally Reinforced Graphite Epoxy Composite
(Chapman & Hall, 2001-05) Hall, Ian W.; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Since accurate, reproducible methods of testing polymer composites are not very well developed or standardized, this research forms part of a program to gain a better understanding of the mechanical properties and failure mechanisms of polymer composites at high strain rates. Since failure modes differ markedly depending on fiber architecture, orientation, fiber/matrix combination and so forth, these initial tests were carried out using a simple unidirectionally reinforced composite. Beginning with testing in the longitudinal and transverse directions, reported here, future experiments are being carried out to determine how the high strain rate properties vary with angle of testing, and then move on to other simple fiber lay-ups, ±90◦, ±45◦, etc.
Citation - WoS: 36
High Strain-Rate Compression Testing of a Short-Fiber Reinforced Aluminum Composite
(Elsevier Ltd., 1997) Güden, Mustafa; Hall, Ian W.; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Compression behavior of 15–26 Vf% Saffil™ short-fiber reinforced Al-1.17wt.%Cu alloy metal matrix composites has been determined over a strain-rate range of approximately 10−4 to 2×103 s−1. The strain-rate sensitivity of composite samples at 4% strain, tested parallel and normal to the plane of reinforcement, was found to be higher than that of unreinforced alloy in the strain-rate range studied. Quantitative analysis of fiber fragment lengths from samples tested to different strain levels showed that, at small strains, high strain-rate testing induced a relatively shorter fiber fragment length distribution in the composite compared to quasi-static testing. At quasi-static strain rates, the fiber strengthening effect was found to increase with increasing Vf% and was higher in samples tested parallel to the planar random array. The observed anisotropy of the composite at quasi-static strain rates was also observed to continue into the high strain-rate regime. Microscopic observations on composite samples tested quasi-statically and dynamically to a range of strains showed that the major damage process involved during compression testing was fiber breakage followed by the microcracking of the matrix at relatively large strains. Fiber breakage modes were found to be mostly shearing and buckling.