International Journal of Materials and Structural Integrity (14 papers in press)
Numerical investigation of the effect of fibre volume fraction on the stress distribution of aerospace grade Al-Li 8090 metal matrix composite
by Dineshsingh G. Thakur
Abstract: The response of the fibre-reinforced metal matrix composite under tensile loading during micromechanical study is the key significance for analysing the metal matrix composite material behaviour. The present study deals with the Representative Volume Element (RVE) of aerospace grade Al-Li (8090) matrix alloy reinforced with SiC fibres in order to assess the stress distribution around the SiC fibres of SiC/Al-Li 8090 metal matrix composite subjected to the load in transverse and longitudinal direction. Square and hexagonal arrays of RVE has been used for this study. The deformation of the RVE and stress distribution around the fibres has been examined for 5% to 25% volume fraction of SiC fibres. It is observed that, for constant transverse loading, stress transfer between matrix and fibre decreases with increment in fibre volume fraction for square array, whereas stress transfer between matrix and fibre is observed even with increment in fibre volume fraction for hexagonal array. In the radial direction of SiC fibres, 5% volume fraction of the SiC fibres shows the maximum longitudinal stress. Longitudinal stress decreases, as increment in the fibre volume fraction of SiC for square and hexagonal arrays of RVE.
Keywords: Al-Li (8090) alloy; SiC fibre; metal matrix composite; representative volume element; finite element method.
Effect of cryotreated electrodes on the machining efficiency of titanium alloy during electro discharge machining: a comparative study
by Munmun Unmun Bhaumik, Kalipada Maity
Abstract: Electro discharge machining (EDM) is one of the most promising non-conventional machining processes. It can machine any conductive material irrespective of its hardness because there is no direct contact between workpiece and tool. Cryotreatment is introduced in the machining field to boost the tool life as well as to lessen the production cost. In the present study, a comparison study has been performed on EDM of titanium grade 6 alloy using untreated and cryotreated double tempered brass, copper and zinc electrodes. The EDM efficiency has been measured by means of tool wear rate (TWR), surface roughness (Ra), radial overcut (ROC) and material removal rate (MRR); peak current, duty cycle, pulse on time, gap voltage are considered as control parameters. A metallographic study has been done for the untreated and cryotreated electrode surfaces. Lower MRR, TWR and better precision of machined surface can be achieved using cryotreated electrodes than that of untreated electrodes. The surface machined by cryotreated electrodes provides a better surface finish than the surface machined by untreated electrodes. A microstructural analysis has been performed for the electro discharge machined surfaces.
Keywords: cryotreatment; electro discharge machining; material removal rate; surface roughness; tool wear rate.
Shear surface wave propagation in stratified media with slip interfaces
by Karen Ghazaryan, Valentin Mozharovsky, Samvel Sarkisyan, Sergey Ohanyan
Abstract: The surface shear wave propagation is studied in elastic semi-spaces separated by an elastic layer with an imperfectly bonded interface between layer and semi-spaces. The dispersion equations are obtained analytically describing the surface wave phase speed. Based on the dispersion equation analysis it is shown that the interface imperfectness sufficiently decreases the phase speed and can also increase the number of shear wave modes.
Keywords: surface waves; shear waves; imperfect contact; slip model; dispersion.
Comparative study of the brittleductile transition between level ice and rafted ice based on uniaxial compression experiments
by Xiaodong Chen, Anliang Wang, Shunying Ji
Abstract: Driven by current and wind, rafted level ice is often deformed from level ice, which shows a brittle-ductile transition under compression. The rafted ice may induce significant loads on vessels and structures in the icy waters. To investigate the difference between level ice and rafted ice in the transition, a fieldwork of uniaxial compression tests was performed on both the level ice and artificial rafted ice in the Northeast of the Bohai Sea. In this area, the level ice has a typical h2 columnar structure and is later used to produce artificial rafted ice, which shows a 'sandwich' structure consisting of a strong upper part, a weak lower part and a freeze bonded in the middle. In the experiments, both types of ice were subjected to a compressive load parallel to the grain columns. Both of them failed in ductile mode at low strain rate and in brittle mode at high strain rate. In ductile mode, the wing cracks pileup dominates the failure process and the frictional crack sliding appeared in both the level ice and the weak part of rafted ice. Thus, the sandwich structure does not influence the compressive strength of rafted ice in the ductile mode. When the ice failed in brittle mode, the stress concentration took over and the ice failed in splitting. In this mode, the bonded layer of rafted ice plays an important role in the buckling after splitting. Compared with level ice, the rafted ice was highly weakened when it failed in brittle mode. From the strengthfailure mode relation, it seems that the two types of ice have similar strength in the ductile failure whereas the rafted ice is much weaker in the brittle failure. Moreover, the strengthstrain rate has a positive correlation in ductile failure mode and a negative correlation in brittle failure mode.
Keywords: sea ice; compression strength; brittle-ductile transition; rafted ice; strain rate.
Ultrasonically enhanced flow rate of polymer melt extrusion
by Matthew D. Moles, Anish Roy, Vadim Silberschmidt
Abstract: Currently, the innovation of thin-section polymeric parts formed by injection moulding is restricted by the economics and practicality of applying high levels of temperature and pressure during the manufacturing process. It is long recognised that subjecting non-Newtonian fluids to vibration can significantly enhance the flow rate and, hence, may be used to reduce pressure and thermal requirements in thin-section moulding. A new moulding process was developed using ultrasonic transducers to induce vibrations in the polymeric melt thereby enhancing the flow rate without degradation of the polymer. Generating ultrasound using piezoceramics mounted in close proximity to the extrusion die required a custom-designed heat-protected transducer stack. The device, with its extrusion die exposing the polymer melt to low-intensity vibrations, improved the flow rate of polypropylene by 33% in batch exposure mode.
Keywords: low-intensity vibration; ultrasound; polymer flow.
Concrete mix using tertiary treated wastewater and effect of ambient and elevated temperatures on its properties
by Jasem Alhumoud, Ammar Ben Nakhi
Abstract: The aim of this study is to investigate the effect of using tertiary treated wastewater (TTWW) on concrete mixes exposed to high temperatures (up to 800
Keywords: tertiary treated wastewater; potable water; concrete strength; flexural strength; elevated temperature.
Optimisation design of microstrip-line structure based on the response surface method and genetic algorithm
by Chunyue Huang, Chao Gao, Genxin Huang, Liangkun Lu
Abstract: A 3D electromagnetic simulation model of a microstrip-line was established, the signal integrity of the microstrip-line under high frequency was analysed, and the simulation results of its return loss S11 and insertion loss S21 were obtained at 5 GHz, respectively. The optimisation results of the simulation were verified through experiments. Plate thickness, microstrip-line width, microstrip-line thickness and dielectric constant were selected as the design variables, while return loss was selected as the objective function. A total of 29 sets of experimental simulations were designed, and the response surface method (RSM) and genetic algorithm (GA) were used to optimise the return loss. Furthermore, the optimisation results of simulation were verified through experiments. The results indicated that the optimised return loss S11 decreased to 1.2554 dB. Furthermore, they verified that the optimisation of the return loss was realised and the optimisation design of the microstrip-line structure based on RSM and GA was effective.
Keywords: microstrip-line; signal integrity; return loss; response surface methodology; genetic algorithm.
Thermodynamics of continua with complex rheology
by Evgenii V. Murashkin, Alexander V. Manzhirov
Abstract: The present study deals with the thermodynamic approach for modelling of the elastic-creep-plastic material behaviour. The proposed theory of finite elastic-creep-plastic deformations is based on the classical formalism of non-equilibrium thermodynamics. Reversible and irreversible components of total deformations are defined by the constitutive differential balance equations following from the multiple subdivision of metric tensor. The least action principle and the formalism of field theory are used for derivation of constitutive equation and conservation laws. The energy balance equation is specified for elastic-creep-plastic continuum. The constitutive stress-strain equations are obtained for isothermal isotropic non-linear elastic material. The specific form of elastic strain energy has been specified in terms of invariants of reversible strain tensor. The least action principle is generalised for dissipative behaviour of the materials. The specific features of dissipation function for creep and plastic materials are proposed and discussed. The boundary value problem on elastic-creep material is considered within the frameworks of the proposed model. Some results of the numerical simulation under axisymmetric conditions are discussed and graphically analysed.
Keywords: least action; dissipative potential; elasticity; plasticity; creep; yield criterion.
On the development of tribo-fatigue as the new section of mechanics
by Sergei Sherbakov, Cemal Basaran
Abstract: The paper presents a review of studies in the field of tribo-fatigue the science unifying fatigue, friction and wear.
Keywords: tribo-fatigue; friction; wear; mechanical fatigue; stress strain state; damage; entropy; mechanothermodynamics.
Experimental methods of investigation of contact-fatigue strength of wheel-rail system materials considering the action of electric current
by Leonid Novogrudskiy, Valeryi Kharchenko, Yuriy Skrypnyk, Mykola Opravkhata
Abstract: The paper illustrates the results of investigations into the influence of electric current pulses on the mechanical properties of rail steel in the initial rail state and after its operation within the electrified railway zone. It is shown that the degree and nature of the variation of strength and plasticity characteristics of M76 rail steel due to the action of the electric current pulses depends on the test temperature, the level of steel operating time, and the operating time of the surfaces of contact rail-wheel interaction. The action of the electric current pulses induces the variation in the stress-strain state of the material in the cross-section of the railhead within the rail-wheel zone. The test facilities developed at the G.S. Pisarenko Institute for Problems of Strength of the NAS of Ukraine are presented. These test facilities are applied for the investigations of contact wheel-rail interaction development considering both differential and integral actions of such operational factors as cyclic loading, rolling and sliding friction, ambient temperatures, electric current, and corrosion (stress and electric) with force parameters in the contact zone, which are consistent with the actual ones in railway transport operation.
Keywords: wheel-rail contact interaction; mechanical characteristics; operating time; electric current pulse; hardness; temperature; test facilities.
Brief introduction and recent development on the manufacture of aluminium alloy integral panels in aerospace applications
by Duanzhi Wang, Fen Xu, Lejian Yuan, Dong Zhang, Jiachen Liu, Yong Hu, Huifeng Kang, Qiusheng Ma, Yang Tong, Wenzhong Han
Abstract: With the worldwide rapid increase of demand for aerospace applications, such as aircraft, spaceflight missions, and construction of space stations, aluminium alloy integral panels were designed and manufactured to decrease the cost and improve their performance. This review article briefly introduces the applications, material selection, and development of manufacturing technologies of the aluminium alloy integral panels. The manufacturing technologies of the integral panels involve milling machining, press bending forming, extrusion, shot peening, creep age forming, and spin forming. Some developing shot peening and creep age forming technologies greatly supported a balance among cost, weight, and performance of the aluminium alloy integral panels, which avoided excessive manual labour, low material efficiency, and a mass of machining. The challenge of the combination of structural design, materials selection, manufacturing technology to improve the balance among cost, weight, and performance of the integral panels required further research and development.
Keywords: aluminium alloys; integral panels; manufacture; shot peening; creep age forming.
From fatigue and tribology to tribo-fatigue
by Leonid Sosnovskiy, Sergei Sherbakov, Michael Khonsari, Alexander Bogdanovich
Abstract: Friction is an amazing phenomenon of nature; wear is a crafty enemy of any system that moves or is deformed; fatigue is a stern scourge of modern machinery. Tribo-fatigue is the unifying science that treats friction, wear, and fatigue. In this paper, we present a brief review of some studies lying on the path from tribology to tribo-fatigue. Also presented are new developments in the field by means of entropic characterisation of materials.
Keywords: tribo-fatigue system; wear-fatigue damage; stress-strain state; limiting state; damage state; dangerous volume; interaction; irreversible damage.
Influence of shape of nano-Al2O3 in epoxy adhesive on the critical energy release rate of tapered double cantilever beam steel joints
by Sunil Kumar Gupta
Abstract: The critical energy release rate (GIC) in mode I of epoxy adhesive reinforced with alumina nanoparticles was determined using tapered double cantilever beam joints. Steel was used as adherend material. Spherical and cylindrical (rod) shapes of nano-Al2O3 were reinforced in adhesive by 0.5, 1.0, 1.5, and 2.0 wt.%. A significant improvement in the GIC of adhesive was obtained at 1.5 wt.% of spherical nano-Al2O3 and 1.0 wt.% of rod nano-Al2O3 over the neat epoxy adhesive. Reinforcement of rod shape of alumina nanoparticles offered a slightly better critical energy release rate of steel joints than the spherical shape of nanoparticles. The mechanisms for improvement in the GIC of adhesive containing spherical and rod alumina nanoparticles are discussed.
Keywords: epoxy adhesive; critical energy release rate; tapered double cantilever beam; alumina nanoparticles.
New cast iron MONICA loses its brittleness with increasing strength
by Leonid Sosnovskiy, Sergei Sherbakov
Abstract: Modern high-strength cast irons with spherical graphite have strength comparable with that of alloyed steel. However, the replacement of steel by cast iron when manufacturing critical duty products is restrained by the brittleness of cast iron: the higher is strength, the lower is plasticity. Now it is possible to overcome this law: a new material (cast iron) MONICA named after its alloying additives molybdenum (Mo), nickel (Ni) and copper (Cu) was created, which on the contrast loses its brittleness with increasing strength. A new (unexpected) regularity has been established: with the increase in strength of MONICA, its plasticity also increases. This was also confirmed by the results of tests on fracture toughness, rolling and mechanical fatigue. Specific mechanical and service properties of MONICA were analySed in comparison with traditional steels and known high-strength cast irons with spherical graphite (ADI). These properties were confirmed by operational tests of high-loaded full-scale parts: knives of cutting devices of high-performance forage harvesters, heavy railway rails, large gear wheels.
Keywords: HHgh-strength cast iron; tribo-fatigue; knife; rail; gear wheel; mechanothermodynamics.