• A Computationally-Efficient Numerical Model to Characterize the Noise Behavior of Metal-Framed Walls

      Arjunan, Arun; Wang, Chang; English, Martin; Stanford, Mark; Lister, Paul (MDPI AG, Basel, Switzerland, 2015-08-07)
      Architects, designers, and engineers are making great efforts to design acoustically-efficient metal-framed walls, minimizing acoustic bridging. Therefore, efficient simulation models to predict the acoustic insulation complying with ISO 10140 are needed at a design stage. In order to achieve this, a numerical model consisting of two fluid-filled reverberation chambers, partitioned using a metal-framed wall, is to be simulated at one-third-octaves. This produces a large simulation model consisting of several millions of nodes and elements. Therefore, efficient meshing procedures are necessary to obtain better solution times and to effectively utilise computational resources. Such models should also demonstrate effective Fluid-Structure Interaction (FSI) along with acoustic-fluid coupling to simulate a realistic scenario. In this contribution, the development of a finite element frequency-dependent mesh model that can characterize the sound insulation of metal-framed walls is presented. Preliminary results on the application of the proposed model to study the geometric contribution of stud frames on the overall acoustic performance of metal-framed walls are also presented. It is considered that the presented numerical model can be used to effectively visualize the noise behaviour of advanced materials and multi-material structures.
    • A Fast New Numerical Tool for Designing Pre-stressed Dies for Backward Extrusion: Part 1: Die Behaviour

      Bonnavand, F.; Bramley, Alan N.; Mynors, Diane J. (Professional Engineering Publishing, 2001)
      Prestressed die inserts are often used in the forging of axisymmetric parts. Their use enhances overall tool economy and can enhance the quality of the finished forging. The design of tooling that incorporates prestressed die inserts is, however, complex. The complexity arises from the interrelated phenomena that occur within the dies during the forging process. As a result, it is not possible to obtain an analytical expression for critical parameters such as die stresses and deflections. This paper shows the limitations of currently used design methods, and identifies, for the backward extrusion process, which physical phenomena should be taken into account when designing prestressed tooling. (Professional Engineering Publishing)
    • A fast new numerical tool for designing prestressed dies for backward extrusion: Part 2: numerical analysis

      Bonnavand, F.; Bramley, Alan N.; Mynors, Diane J. (Professional Engineering Publishing, 2001)
      The economics of forging requires tools to be designed to ensure maximum service life. Ideally, this should be achieved by determining the maximum equivalent stress experienced by tools during service. However, the determination of the maximum equivalent stress in the dies through numerical simulations is very time consuming. For the case of a backward extrusion process, this paper proposes a method for its determination that is based on an analytical function of the process parameters. This function was obtained by generating a database that includes the maximum equivalent stress for a large range of process parameters. This database was then modelled by a function determined through statistical analysis. (Professional Engineering Publishing)
    • A Finite Element Analysis of the Stress Intensity Resulting from Single-Edge Pre-Cracked Beam Loading Conditions

      Kibble, Kevin A.; Turner, D. (ASTM International, 2001)
      The single-edge precracked-beam (SEPB) fracture toughness method has been investigated using finite element methods to analyze the stress intensity (K1) resulting from variations in bridge span, punch length, and virtual crack length. A two-dimensional half-plane, semi-infinite model was used to approximate the stress intensity from a fit of the nodal displacements of a crack face under SEPB loading conditions. The finite element method models the crack in situ, using six-node triangular elements specified around a singular point that simulates the crack tip. The analysis reveals that for increasing virtual crack length (), the stress intensity increases to a maximum where / = 0. With further increasing virtual crack length, the stress intensity decreases. The inflection point differs for varying span and fixed punch length, and for varying punch lengths with fixed span. The resulting stress intensities per new ton force loading are presented in tabular and graphical form. The presented series of graphs can be used to explore variations in precracking parameters. This finite element analysis provides useful data for those developing or adopting the SEPB fracture toughness measurement technique.
    • An Intelligent, Multi-Transducer Signal Conditioning Design for Manufacturing Applications

      Sillitoe, I; Button, M; Owhonda, E (Elsevier, 2017-01-24)
      This paper describes a flexible, intelligent, high bandwidth, signal conditioning reference design and implementation, which is suitable for a wide range of force and displacement transducers in manufacturing applications. The flexibility inherent in the design has allowed more than 10 specialised transducer conditioning boards to be replaced by this single design, in a range of bespoke mechanical test equipment manufactured by the authors. The board is able to automatically reconfigure itself for a wide range of transducers and calibrate and balance the transducer. The range of transducers includes LVDT, AC/DC strain gauge and inductive bridges, and a range of standard industrial voltage current interface transducers. Further, with a minor lowcost addition to the transducer connector, the board is able to recognise the type of transducer, reconfigure itself and store the calibration data within the transducer, thereafter allowing a plugand-play operation as transducers are changed. The paper provides an example of the operation in typical manufacturing test application and illustrates the stability and noise performance of the design.
    • Applications and Capabilities of Explosive Forming

      Mynors, Diane J.; Anderson, R.; Richardson, A.; Snape, R.G.; Standring, P.M. (Amsterdam: Elsevier, 2002)
      This paper examines the unique work being undertaken in the UK to ensure the continued competitiveness and advancement in capabilities of the companies that make up the UK metalforming industry. The work is a partnership between commercial metalforming simulation package vendors, universities and the industry through its main trade association the Confederation of British Metalforming. In examining the present activities, a case is made for a National Centre for Metalforming Simulation.
    • Burst Strength Analysis of Casing with Geometrical Imperfections

      Huang, Xiaoguang; Chen, Yanyun; Lin, Kai; Mihsein, Musa; Kibble, Kevin A.; Hall, Richard (ASME (American Society of Mechanical Engineers), 2007)
      Accurately predicting the burst strength is very important in the casing design for the oil and gas industry. In this paper, finite element analysis is performed for an infinitely long thick walled casing with geometrical imperfections subjected to internal pressure. A comparison with a series of full-scale experiments was conducted to verify the accuracy and reliability of the finite element analysis. Furthermore, three predictive equations were evaluated using the test data, and the Klever equation was concluded to give the most accurate prediction of burst strength. The finite element analysis was then extended to study the effects of major factors on the casing burst strength. Results showed that the initial eccentricity and material hardening parameter had important effects on the burst strength, while the effect of the initial ovality was small. (ASME)
    • Combination of finite element method and Drucker-Prager Cap material model for simulation of pharmaceutical tableting process

      Baroutaji, A.; Lenihan, S.; Bryan, K.; School of Mechanical, Electrical and Process Engineering, Cork Institute of Technology, T12 P928; BISHOPSTOWN, CORK IRELAND; School of Mechanical, Electrical and Process Engineering, Cork Institute of Technology, T12 P928; BISHOPSTOWN, CORK IRELAND; School of Mechanical, Electrical and Process Engineering, Cork Institute of Technology, T12 P928; BISHOPSTOWN, CORK IRELAND (Wiley, 2017-12-05)
      Density-dependent Drucker-Prager Cap (DPC) model is widely used for assessing the compaction behaviour of powders due to its capability of capturing the various phenomena associated with the powder compaction process such as work hardening, nonlinear densification, and frictional and compressible behaviour of the powder. This paper presents a full description of the Drucker-Prager Cap model for the compaction behaviour of microcrystalline cellulose (MCC) Avicel PH101 pharmaceutical powder. The experimental calibration process of Drucker-Prager Cap is detailed and all model parameters are calculated as a function of powder relative density. Also, the calibrated parameters are implemented in finite element code to perform a numerical simulation of a typical pharmaceutical tablet. The results showed that the finite element model (FEM) was able to accurately predict the compaction behaviour of the microcrystalline cellulose powder. Furthermore, the finite element predictions of stress and density distributions of the powders during the compaction were used to analyse the failure mechanisms associated with tableting.
    • Comparison of Sequentially and Fully Coupled Generalized Plane Strain FE Modelling of Multipass Welding

      Jiang, Wei; Yahiaoui, Kadda; Hall, Frank Richard; Laoui, Tahar (NAFEMS, 2005)
      The residual stress predictions from sequentially and fully coupled thermo-mechanical generalized plane strain models of thick multipass welded plate are shown to be in agreement with each other and experimental data. The research enabled the less computationally resource intensive sequential coupling method to be recommended when simulating this welding process.
    • Controlling the Cold Roll Forming Design Process

      Mynors, Diane J.; English, M.; Castellucci, M.; Bramley, Alan N. (Amsterdam: Elsevier, 2006)
      The cold roll forming process requires successive forming profiles to be determined and an appropriate number of profiled roll sets to be designed for the product to be rolled. This paper examines the design process and how one company has put in place a design-production control system that allows designs to be ranked in terms of quality and efficiency. In addition, consideration is given to the proportion of time given to each design task and how non-creative design activities can be automated.
    • Determination of the Relationship between Strength and Test Method for Glass Fibre Epoxy Composite Coupons using Weibull analysis

      Cattell, M. K.; Kibble, Kevin A. (Amsterdam: Elsevier, 2001)
      Glass fibre epoxy composite test coupons exhibit variability in their tensile strength data dependent on the test method used. The three common test standards are for tensile, three-point flexure and four-point flexure and it is accepted that flexure tests yield higher strengths than tensile tests. Tests were carried out on coupons of a woven E-glass epoxy composite for each type of test. The data for each test was found to fit a two-parameter Weibull distribution. The Weibull moduli for each of the test methods were approximately the same. This Weibull modulus is used to relate the strengths for different test methods using an equivalent volume method. It was found that the strength variability is dependent only on the equivalent volumes of test coupons and thus, a method is proposed for the prediction of tensile strengths from flexural strength tests and vice versa.
    • Development and Characterization of Phytosterol-Enriched Oil Microcapsules for Foodstuff Application

      Tolve, Roberta; Condelli, Nicola; Can, Aygül; Tchuenbou-Magaia, Fideline Laure (Springer Link, 2017-09-30)
      Phytosterols are lipophilic compounds contained in plants and have several biological activities. The use of phytosterols in food fortification is hampered due to their high melting temperature, chalky taste, and low solubility in an aqueous system. Also, phytosterols are easily oxidized and are poorly absorbed by the human body. Formulation engineering coupled with microencapsulation could be used to overcome these problems. The aim of this study was to investigate the feasibility of encapsulating soybean oil enriched with phytosterols by spray-drying using ternary mixtures of health-promoting ingredients, whey protein isolate (WPI), inulin, and chitosan as carrier agents. The effect of different formulations and spray-drying conditions on the microencapsules properties, encapsulation efficiency, surface oil content, and oxidation stability were studied. It was found that spherical WPI-inulin-chitosan phytosterol-enriched soybean oil microcapsules with an average size below 50 μm could be produced with good encapsulation efficiency (85%), acceptable level of surface oil (11%), and water activity (0.2–0.4) that meet industrial requirements. However, the microcapsules showed very low oxidation stability with peroxide values reaching 101.7 meq O2/kg of oil just after production, and further investigations and optimization are required before any industrial application of this encapsulated system.
    • Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

      Arjunan, A.; Wang, C.J.; Yahiaoui, K.; Mynors, D.J.; Morgan, T.; Nguyen, V.B.; English, M. (Elsevier, 2014-11)
      Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index Rw along with A-weighted pink noise C and A-weighted urban noise Ctr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid–structure interaction (FSI) to evaluate their acoustic insulation.
    • Energy Absorption Capacity of Prismatic Cellular Metals

      Kaaz, Michael; Hall, Frank Richard; Spence, J.; Bauer, H. (University of Wolverhampton, 2007)
      In this study the energy absorption capacity of prismatic cellular materials were examined using 2D Finite-Element (FE) simulations. The energy absorption capacity of many core topologies has been predicted under quasi-static compression. Subsequently, the dynamic impact behaviour of one of these structures, with good energy absorption characteristics, has been assessed for a range of impact velocities from 10 to 1000 m/s. As the impact speed increases, different deformation modes are noticed and the effects of stress wave propagation become more important. The importance of these studies is identified for the future development of lightweight, and impact-resistant, structured materials.
    • Evaluation of Limit Load Data for Cracked Pipe Bends under Opening Bending and Comparisons with Existing Solutions

      Yahiaoui, Kadda; Moreton, D. N.; Moffat, D. G. (Amsterdam: Elsevier, 2002)
      Most existing limit load solutions for cracked pipe bends under in-plane bending have been developed following the experimental work by Griffiths on bends with through-wall defects or by extrapolation of solutions developed for cracked straight pipes. No data exists for part-penetrating defects. This contribution summarises recently obtained experimental and finite element results from 13 tests on axially (at the crown) and circumferentially (at the intrados) cracked carbon steel pipe bends under opening bending loads. Comparisons with predictions by existing solutions for the cases investigated are reported. The solutions are shown to be excessively conservative and, on occasions, non-applicable to the cases for which they are intended. The presented data, together with results more recently made available in the open literature, could be used to form a working basis for revising the existing solutions. (Elsevier)
    • Ex-situ evaluation of PTFE coated metals in a proton exchange membrane fuel cell environment

      Baroutaji, A.; Carton, J.G.; Oladoye, A.M.; Stokes, J.; Twomey, B.; Olabi, A.G. (Elsevier, 2017-08)
      Metallic-based bipolar plates exhibit several advantages over graphite-based plates, including higher strength, lower manufacturing cost and better electrical conductivity. However, poor corrosion resistance and high interfacial contact resistance (ICR) are major challenges for metallic bipolar plates used in proton exchange membrane (PEM) fuel cells. Corrosion of metallic parts in PEM fuel cells not only increases the interfacial contact resistance but it can also decrease the proton conductivity of the Membrane Electrode Assembly (MEA), due to catalyst poisoning phenomena caused by corrosive products. In this paper, a composite coating of polytetrafluoroethylene (PTFE) was deposited on stainless steel alloys (SS304, SS316L) and Titanium (G-T2) via a CoBlast™ process. Corrosion resistance of the coated and uncoated metals in a simulated PEM fuel cell environment of 0.5 M H2SO4 + 2 ppm HF at 70 °C was evaluated using potentiodynamic polarisation. ICR between the selected metals and carbon paper was measured and used as an indicator of surface conductivity. Scanning Electron Microscopy (SEM), 3D microscopy, Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and contact angle measurements were used to characterise the samples. The results showed that the PTFE coating improved the hydrophobicity and corrosion resistance but increased the ICR of the coated metals due to the unconductive nature of such coating. Thus, it was concluded that it is not fully feasible to use the PTFE alone for coating metals for fuel cell applications and a hybrid coating consisting of PTFE and a conductive material is needed to improve surface conductivity.
    • Experimental Investigation on the Sound Reduction Performance of Frequency Controlled Acoustic Interference Cavities

      Arjunan, Arun; Stanford, Mark; Rackley, Jonathan (German Acoustical Society (DEGA), 2016-08)
      The European directives on noise reduction associated with rail, road and aviation clearly depicts the need for high efficiency sound attenuating structures for targeted noise reduction. Consequently, this paper presents key observations from Phase 1 of the UK Department of Transport (DfT) funded research project to investigate the targeted creation of acoustic interference to develop high-efficiency noise abatement structures. Geometrical cavity inspired from existing theories around Herschel-Quincke concept is experimentally investigated for the creation of frequency dependent acoustic interference. The interference cavity within a global structure was digitally conceived and prototyped using the Selective Laser Sintering (SLS) process in a Nylon 12 material. A modified impedance tube method was then used to measure the frequency dependent Sound Reduction Index (R) for a frequency range of 250 to 1600 Hz. The results showed that depending on the frequency of interest acoustic interference can be recreated by controlling the cavity length. In addition R values of 72.47 dB were observed at 900 Hz confirming the potential of the technology for high efficiency noise barriers. The observation presented in this paper establishes a new viewpoint for the use of acoustic interference for targeted noise abatement.
    • Finite Element Modelling of Multipass Fusion Welding with Application to Complex Geometries

      Jiang, Wei; Yahiaoui, Kadda (Professional Engineering Publishing, 2007)
      The current paper presents recently completed work in the development of advanced multi-pass weld modelling procedures, with the ultimate objective of predicting weld residual stress distributions in thick-walled complex geometries. The modelling technique was first developed using simple three-dimensional geometries, for which experimental data was available for validation purposes. All the non-linearities associated with welding, including geometry, material, and boundary non-linearities, as well as heat source movement were taken into account. The element removal/reactivate technique was employed to simulate the deposition of filler material. Combined with a newly developed meshing technique, the model was then applied to predict residual stress distributions for a relatively thick stainless steel piping branch junction. Finally, a parametric study was conducted to assess the effects of various manufacture-related welding parameters on the final residual stress fields. The interpass temperature and cooling rate were found to be the two most sensitive parameters affecting resultant residual stresses. The residual stress profiles can be optimized relatively easily by adjusting these parameters. This research demonstrated that the developed modelling technique has potential in multi-pass welding process optimization and wide industrial applications including weld repairs.(Professional Engineering Publishing)
    • Finite Element Prediction of Residual Stress Distributions in a Multipass Welded Piping Branch Junction

      Jiang, Wei; Yahiaoui, Kadda (ASME (American Society of Mechanical Engineers), 2007)
      Piping branch junctions and nozzle attachments to main pressure vessels are common engineering components used in the power, oil and gas, and shipbuilding industries amongst others. These components are usually fabricated by multipass welding. The latter process is known to induce residual stresses at the fabrication stage, which can have severe adverse effects on the in-service behavior of such critical components. It is thus desirable if the distributions of residual stresses can be predicted well in advance of welding execution. This paper presents a comprehensive study of three dimensional residual stress distributions in a stainless steel tee branch junction during a multipass welding process. A full three dimensional thermomechanical finite element model has been developed for this purpose. A newly developed meshing technique has been used to model the complex intersection areas of the welded junction with all hexahedral elements. Element removal/reactivate technique has been employed to simulate the deposition of filler material. Material, geometry, and boundary nonlinearities associated with welding were all taken into account. The analysis results are presented in the form of stress distributions circumferentially along the weld line on both run and branch pipes as well as at the run and branch cross sections. In general, this computational model is capable of predicting three dimensional through-thickness welding residual stress, which can be valuable for structural integrity assessments of complex welded geometries. (ASME)
    • Finite Element Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction

      Jiang, Wei; Yahiaoui, Kadda; Hall, Frank Richard (American Society of Mechanical Engineers (ASME), 2005)
      This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of three-dimensional temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.