2,312 results
Search Results
2. Experiment on Bending Bearing of Damaged Old Wooden Beams Strengthened with CFRP
- Author
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Xun Zhong Zhang, Yu Zhu, and Bin Jia
- Subjects
Materials science ,Bearing (mechanical) ,business.industry ,General Medicine ,Structural engineering ,Bending ,Compression (physics) ,law.invention ,Brittleness ,Flexural strength ,law ,Ultimate tensile strength ,Bearing capacity ,business ,Beam (structure) - Abstract
This paper completed a reinforced test of eight aging damaged old wooden beams of CFRP, studied the different layers of the CFRP reinforced rectangular failure pattern of the old wooden beams, the bending bearing capacity, load-deflection curve. The results show that reinforced aging old wooden beam repaired with CFRP not only improve the flexural bearing capacity and its failure mode changed from brittle tensile damage to compression of ductile damage.
- Published
- 2014
3. Rough Soft-EHL with Non-Newtonian Lubricant
- Author
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Panichakorn Jesda and Wongseedakeaw Khanittha
- Subjects
Materials science ,business.industry ,Young's modulus ,General Medicine ,Radius ,Compressible flow ,Non-Newtonian fluid ,Reynolds equation ,symbols.namesake ,Optics ,Lubrication ,symbols ,Surface roughness ,Composite material ,Lubricant ,business - Abstract
This paper presents the effect of surface roughness on soft elastohydrodynamic lubrication in circular contact with non-Newtonian lubricant. The time independent modified Reynolds equation, elastic equation and lubricant viscosity equation were formulated for compressible fluid. Perturbation method, Newton-Raphson method, finite different method and full adaptive multigrid method were implemented to obtain the film pressure, film thickness profiles and friction coefficient in the contact region at various the amplitude of surface roughness, surface speed of sphere, modulus of elasticity and radius of sphere. The simulation results showed that the film thickness in contact region depended on the profile of surface roughness. The minimum film thickness decreased but maximum film pressure and friction coefficient increase when the amplitude of surface roughness and modulus of elasticity increased. For increasing surface speeds, the minimum film thickness and friction coefficient increase but maximum film pressure decreases. When radius of sphere increases, the minimum film thickness increases but maximum film pressure and friction coefficient decrease.
- Published
- 2015
4. High Temperature Behaviour of Materials and Components under Creep Conditions
- Author
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Wei Sun and Thomas H. Hyde
- Subjects
Work (thermodynamics) ,Materials science ,Power station ,business.industry ,Constitutive equation ,Alloy ,Metallurgy ,General Medicine ,Structural engineering ,Welding ,engineering.material ,law.invention ,Stress (mechanics) ,Creep ,law ,engineering ,business ,Material properties - Abstract
This paper describes some recent work on the stress analyses and failure prediction of some typical pressurised high temperature components under creep conditions, including plain pipes, pipe bends, branch connections and welds etc, in the main steam pipework of power plant. The materials used are typically low alloy ferritic CrMoV steels. Experimental creep testing methods, and the procedures used for generating the material properties in creep and damage constitutive equations, are briefly described. Some typical numerical results are presented to illustrate the main characteristics of the behaviour of these components and to demonstrate the effects of geometry, material properties and loading modes on stress distributions and failure life predictions. The emphasis of the paper is on welded components.
- Published
- 2004
5. The Effect of Crack-Tip Interactions on the Curve-Fitting of Isopachics
- Author
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Janice M. Dulieu-Barton, Keith Worden, and A. B. Spencer
- Subjects
Stress field ,Stress (mechanics) ,Work (thermodynamics) ,Thermoelastic damping ,Materials science ,Cardioid ,business.industry ,Base (geometry) ,Curve fitting ,General Medicine ,Mechanics ,Structural engineering ,business - Abstract
Recent work by the authors has allowed the estimation of crack-tip SIFs by direct curvefitting of a cardioid form to measured isopachics from thermoelastic stress analysis. However, some of the curve-fits indicated that the cardioid form was inappropriate for the base model. One of the possible explanations for this is that the cardioid form is only suitable for an isolated crack-tip stress field. In the experimental data for the previous studies, a crack was placed centrally in a plate and there will therefore have been two (potentially) interacting crack-tips involved. The object of the current paper is to determine numerically, the stress field for such a crack system and to quantify the effect of any interactions on the curve-fitting procedure.
- Published
- 2004
6. Determination of Tensile and Compressive Stress Strain Curves from Bend Tests
- Author
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John Durodola, Guillermo Urriolagoitia-Sosa, and N.A. Fellows
- Subjects
Materials science ,Compressive strength ,business.industry ,Stress–strain curve ,Ultimate tensile strength ,Bauschinger effect ,General Medicine ,Structural engineering ,Compression (geology) ,Strain hardening exponent ,Deformation (engineering) ,business ,Stress intensity factor - Abstract
A new inverse method has been developed for the simultaneous derivation of tensile and compressive stress strain behaviour from bending tests only. This new procedure can be applied to materials having asymmetric tensile and compressive stress strain behaviour and also materials that have been previously strain hardened (Bauschinger Effect). This paper presents results obtained using the new method and compares them with experimentally obtained tensile and compressive stress strain curves. The agreement of the derived stress strain data in tension and compression is encouraging.
- Published
- 2004
7. Photoelastic Investigation of Friction and Residual Stress in Shrink-Fitted Shafts and Hubs
- Author
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Julian D Booker, I.A. Jones, and Christopher E Truman
- Subjects
Photoelasticity ,Materials science ,Shear (geology) ,Residual stress ,business.industry ,Forensic engineering ,General Medicine ,Slippage ,Structural engineering ,business - Abstract
This paper describes initial investigations into the use of frozen-stress photoelasticity to study the development of slippage within shrink-fitted shaft/hub pairs, with the aim of studying the residual stresses remaining after partial slippage has occurred. Results to date show the feasibility of measuring the shear stresses along the partially-slipping interface between shaft and hub.
- Published
- 2004
8. Elastic-Plastic Behaviour of a Plate with a Central Hole by Photoelastic Coating Method
- Author
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M. Ohira, S. Ohtaki, N. Matsumoto, and H. Kasayama
- Subjects
Materials science ,business.industry ,Tension (physics) ,Uniaxial tension ,chemistry.chemical_element ,Image processing ,General Medicine ,Elastic plastic ,Optics ,Circular hole ,chemistry ,Aluminium ,Photoelastic coating ,Composite material ,business ,Stress concentration - Abstract
An application of the elastic-plastic problem by the photoelastic coating method is presented in this paper. A general procedure of this experiment, such as image processing and separation of the difference of principal strain to obtaine stresses from isochromatic fringes is referred. The methodology to extract centre lines of coloured isochromatic fringes is explained. Experiments are conducted with cross-shaped aluminum specimens with a circular hole subjected to uniaxial tension and equi-biaxial tension. Results of image processing are shown, and the distribution of difference of principal strains and separated principal strain are shown in the case of equi-biaxial tension.
- Published
- 2006
9. Thermoelastic Stress Analysis of Nitinol Self-Expanding Stents
- Author
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E. G. Little, James Eaton-Evans, I. A. Brown, and Janice M. Dulieu-Barton
- Subjects
Nitinol stent ,Stress (mechanics) ,Thermoelastic damping ,Materials science ,business.industry ,Uniaxial tension ,High resolution ,General Medicine ,Structural engineering ,Shape-memory alloy ,Composite material ,business ,Signal - Abstract
Self-expanding stents are small medical devices used to treat vascular disease and are typically fabricated from a super-elastic, shape memory alloy known as Nitinol and have a fine mesh structure. This paper describes preliminary work on the application of Thermoelastic Stress Analysis (TSA) to Nitinol stents. Uniaxial tensile tests were conducted on thin tubes of Nitinol to characterise the material mechanical properties. TSA calibration exercises were conducted, which showed that Nitinol exhibits a non-uniform thermoelastic response through its elastic region that corresponded to the superelastic behaviour. Initial TSA demonstrated that a viable thermoelastic signal could be obtained from the stents. In high resolution tests the effect of motion and noise were considerable but it was still possible to obtain a readable thermoelastic signal.
- Published
- 2006
10. A New Method of Measuring Young's Modulus for Flexible Thin Materials Using a Cantilever
- Author
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Atsumi Ohtsuki
- Subjects
Cantilever ,Materials science ,Optical fiber ,business.industry ,Modulus ,Young's modulus ,General Medicine ,Structural engineering ,Elasticity (physics) ,law.invention ,symbols.namesake ,law ,Cantilever method ,symbols ,Fiber ,Composite material ,business ,Elastic modulus - Abstract
This paper describes a development of a new method (: Cantilever Method) to measure Young’s modulus of flexible materials. The method is based on a nonlinear deformation theory that takes into account large deformation behaviors. A set of testing devices was designed and machined. Measurements were carried out on two kinds of flexible materials (PVC: a high-polymer material and SWPA: a steel material). The modulus measured by this method is “Secant modulus”. The results of my evaluation confirm that the new method is suitable for flexible thin plates or rods. Based on the assessments made the method can be further applied to thin sheet and fiber materials (e.g., steel belt, glass fiber, carbon fiber, optical fiber, etc.).
- Published
- 2006
11. Design of an Ultrasonic Blade for Cutting Bone
- Author
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Andrea Cardoni, Alan MacBeath, and Margaret Lucas
- Subjects
Artificial bone ,Materials science ,business.industry ,Drilling ,Thermal damage ,Ultrasonic sensor ,General Medicine ,Structural engineering ,Blade (archaeology) ,Edge (geometry) ,business ,Contact area ,Fatigue limit - Abstract
Damaging temperature effects observed during ultrasonic cutting operations are typically a result of friction between the vibrating blade and material, and combustion of debris. In order to prevent the high temperatures causing damage, the ultrasonic blade has to cut with a sufficient speed. This can be achieved either by applying a relatively high static load or by increasing the working vibration amplitude of the cutting edge, however, the result can be poor operational control and exceeding the fatigue limit of the blade, respectively. In this paper, the effect of blade tip profile is considered, particularly with reference to the influence of the cutting edge contact area on temperature under different static loading conditions. Titanium blades, with different cutting edge profiles are tested in a series of experiments that monitor cutting speed, static load, temperature around the cut site, and vibration amplitude at the cutting edge. The blades are tested cutting bovine femur and artificial bone material, and the cut surfaces are examined for signs of damage after each test. The experimental data reveal that blades with a small cutting edge contact area cut at a lower temperature, and that signs of thermal damage are less evident.
- Published
- 2006
12. FE Simulation of Laser Ultrasonic Surface Waves in a Biomaterial Model
- Author
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Zhihong Huang and A. L'Etang
- Subjects
Laser ultrasonics ,Materials science ,business.industry ,Energy flux ,General Medicine ,Mechanics ,Laser ,Finite element method ,law.invention ,Thermoelastic damping ,Optics ,Heat flux ,law ,Surface wave ,Ultrasonic sensor ,business - Abstract
This paper describes a study of laser generated ultrasonic waves in an 2-layer elastic, isotropic biomaterial model, in order to establish a modelling technique to simulate the thermoelastic response of high-power short pulse laser beams in human skin. The theory proposed in this paper takes into consideration the fundamental understanding of the laser/material interface. A finite element model using the commercial finite element code ANSYS is used to study the effects of laser pulse duration and energy flux contribution to the surface waves. The simulation comprises a set of boundary conditions that approximate a heat flux point source located on top of the surface of the material. Because of the time scale of interest, the elastic effects do not feed back into the thermal problems, so that a sequential coupled-field analysis was performed where the thermal and elastodynamic fields are uncoupled and treated separately. The initial finite element analysis involves a transient thermal analysis using a heat flux with Gaussian spatial variation to simulate the laser pulse heating. The results from the thermal analysis were read and applied to the structural analysis where the out-of-plane displacements histories are analyzed in the skin model with varying thicknesses
- Published
- 2006
13. Thermoelastic Stress Analysis of Composite Finger Joints
- Author
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Janice M. Dulieu-Barton, L. Rumsey, and Stephen Boyd
- Subjects
Stress (mechanics) ,Thermoelastic damping ,Materials science ,Pultrusion ,business.industry ,Shear stress ,Finger joint ,General Medicine ,Structural engineering ,Fibre-reinforced plastic ,business ,Joint (geology) ,Stress concentration - Abstract
The marine industry at present employs the use of aluminium extrusions in the construction of decks and superstructures that could be replaced with pultruded glass reinforced plastic (GRP) profiles. The length of the pultruded section is limited and therefore, efficient and economic jointing techniques must be developed that can withstand the loads applied to ship structures. This paper evaluates a novel means of adhesively bonded connection for GRP structures known as a finger joint. Various joint geometries are examined, load displacement behaviour is established and Thermoelastic Stress Analysis (TSA) is used to provide the full field stress distribution over the joint. The results of the TSA are compared with the load displacement behaviour. It is shown that by increasing fingertip angle there is a decrease in load carrying capacity, a decrease in shear stress and an increase in stress concentration factor at the finger joint tip.
- Published
- 2006
14. Determination of the Matrix of Rigidity of a Composite Material by the Combination of Speckle Interferometry and Ultrasonic Measurements
- Author
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B. Lorrain, Lofti Toubal, and Moussa Karama
- Subjects
Materials science ,business.industry ,Ultrasound ,Composite number ,General Medicine ,Speckle pattern ,Optics ,Rigidity (electromagnetism) ,Shearography ,Electronic speckle pattern interferometry ,Ultrasonic sensor ,Speckle imaging ,Composite material ,business - Abstract
The characterisation of composite plates used in structural work in the field of aeronautics is approached by associating ultrasound and speckle interferometry measurements. The reduced thickness of the specimens does not allow for gauge instrumentation to measure out-of plane deformation. A system was therefore used which makes it possible to obtain the cartography of the deformations in and out of-plane. This paper describes an application of electronic speckle interferometry in the measurement of through thickness deformation in composites.
- Published
- 2006
15. Load and Geometry Effect on Failure Mode Initiation of Composite Sandwich Beams
- Author
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Emmanuel E. Gdoutos and Maria S. Konsta-Gdoutos
- Subjects
Cantilever ,Materials science ,business.industry ,Composite number ,Geometry ,General Medicine ,Epoxy ,Structural engineering ,Honeycomb structure ,Shear (geology) ,Composite plate ,visual_art ,visual_art.visual_art_medium ,business ,Failure mode and effects analysis ,Beam (structure) - Abstract
Facing compressive failure, facing wrinkling and core shear failure are the most commonly encountered failure modes in sandwich beams with facings made of composite materials. The occurrence and sequence of these failure modes depends on the geometrical dimensions, the form of loading and type of support of the beam. In this paper the above three failure modes in sandwich beams with facings made of carbon/epoxy composites and cores made of aluminum honeycomb and two types of foam have been investigated. Two types of beams, the simply supported and the cantilever have been considered. Loading included concentrated and uniform. It was found that in beams with foam core facing wrinkling and core shear failure occur, whereas in beams with honeycomb core facing compressive failure and core shear crimping take place. Results were obtained for the dependence of failure mode on the geometry of the beam and the type of loading. The critical beam spans for failure mode transition from core shear to wrinkling failure were established. It was found that initiation of a particular failure mode depends on the properties of the facing and core materials, the geometrical configuration and loading of composite sandwich beams.
- Published
- 2006
16. An Experimental and Finite Element Study of the Ductile Tearing Characteristics of High-Toughness Gas Pipeline Steel
- Author
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Ian C. Howard, J.R. Yates, S.S. Ayvar, and S.H. Hashemi
- Subjects
Toughness ,Materials science ,Bar (music) ,business.industry ,Damage mechanics ,Ultimate tensile strength ,Isotropy ,Fracture (geology) ,General Medicine ,Structural engineering ,Deformation (engineering) ,business ,Finite element method - Abstract
This paper reports recent results from a set of experimental and computational studies of ductile flat fracture in modern gas pipeline steel. Experimental data from plain and notched cylindrical tensile bars and standard C(T) specimens together with damage mechanics theories have been used to capture the flat fracture characteristics of a gas pipeline steel of grade X100. The modelling was via finite element analysis using the Gurson-Tvergaard modified model (GTN) of ductile damage development. The assumption of effective material damage isotropy was sufficiently accurate to allow the transfer of data from the notched bars to predict, in a 2D model, the crack growth behaviour of the C(T) specimen. This was in spite of the considerable ovalisation of the bars at the end of their deformation. However, it was not possible to obtain similar accuracy with a 3D model of the C(T)test, even after a large number of attempts to adjust the values of the GTN parameters. This, and the anisotropic shape change in the tensile bars, suggests very strongly that the damage behaviour is so anisotropic that conventional models are not good enough for a full engineering description of the flat fracture behaviour. Suitable averaging (of shape) in the modelling of the notched bar data, and the companion averaging associated with the 2D model of the C(T) data provide a relatively fast way of transferring engineering data in the tests. There is a discussion of potential ways in which to incorporate 3D effects into the modelling for those purposes where the considerable increase in computational time (due to the microstructurally-sized finite elements needed to capture the damage behaviour) is acceptable in order to include through-thickness effects.
- Published
- 2006
17. Design of a Multi-Axial Test Specimen for Fretting Fatigue in Splined Couplings
- Author
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I.R. McColl, P.M. Wavish, and Sean B. Leen
- Subjects
Coupling ,Spline (mathematics) ,Materials science ,business.industry ,Contact geometry ,Fretting ,General Medicine ,Structural engineering ,Multi axial ,business ,Rapid testing - Abstract
This paper describes the conceptual, embodiment and detailed design of a representative test specimen to mimic fretting variables in aero-engine splined couplings. A fretting bridge design was chosen for the multi-axial representative specimen from a set of four concepts evaluated. The test specimen was intended to facilitate more rapid testing for design against fretting fatigue and wear in the complex contact geometry of the spline coupling.
- Published
- 2006
18. An Inverse Procedure for Determining the Material Constants of Isotropic Square Plates by Impulse Excitation of Vibration
- Author
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Leonardo Pagnotta and Marco Alfano
- Subjects
Materials science ,business.industry ,Modal analysis ,Numerical analysis ,Mathematical analysis ,Isotropy ,Modulus ,Inverse ,General Medicine ,Structural engineering ,Impulse (physics) ,Vibration ,business ,Excitation - Abstract
The paper presents a procedure whereby the Poisson’s ratio and dynamic Young’s modulus of isotropic and homogeneous materials are determined using two of the first four frequencies of natural vibration in thin square plates. The procedure is based on suitable approximate relationships relating the resonant frequencies to the elastic constants of the material. These relations were derived from an extensive series of numerical analysis carried out by a finite element code. To measure the fundamental resonant frequencies, inexpensive computerized equipment is proposed. The procedure has been validated on Carbon Steel specimens.
- Published
- 2006
19. On the Stiffness and the Reinforcement Effect of Electrical Resistance Strain Gauges
- Author
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Leonardo D'Acquisto, Salvatore Fragapane, Bernardo Zuccarello, Augusto Ajovalasit, AJOVALASIT A, DACQUISTO L, FRAGAPANE S, and ZUCCARELLO B
- Subjects
Experimental mechanics ,Low modulus ,Materials science ,business.industry ,Stiffness ,General Medicine ,Structural engineering ,Gauge (firearms) ,Electrical resistance and conductance ,medicine ,medicine.symptom ,Reinforcement ,business ,Strain gauge - Abstract
The reinforcement effect of a strain gauge installed on low modulus materials can be significant. The increasing use of low modulus materials requires therefore the evaluation of such effect. This paper concerns the relationship between the local reinforcement effect and the strain gauge stiffness. The conclusion is that the gauge stiffness alone does not allow the user a thorough evaluation of the reinforcement effect.
- Published
- 2006
20. Plastic Response of Nested Systems under Static and Dynamic Loading Conditions Using FE and Experimental Techniques
- Author
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Edmund Morris, Abdul Ghani Olabi, and M.S.J. Hashmi
- Subjects
Ring (mathematics) ,Mandrel ,Materials science ,Dynamic loading ,business.industry ,Orientation (geometry) ,General Medicine ,Structural engineering ,Strain rate ,business ,Software package ,Finite element method - Abstract
This paper presents the study of nested rings crushed laterally between rigid platens at 2 different velocities. In this investigation two different types of nested ring configurations are analysed: (A) In-Plane; where three rings of varying diameter are placed within each other and their axes are parallel. (B) Out of-Plane; where the rings have a 90 degree orientation. Material used was cold finished, drawn over mandrel (DIN 2393 ST 37-2) and is referred throughout the paper as mild steel. The Cowper-Symonds relation was used to predict the dynamic yield stress of the rings and this was included in the FE material model. The results obtained from experiments were compared to that of finite element method using the software package Ansys. Discussion is made on the post – collapse behaviour of these systems. It was found that the Out of-Plane ring system exhibited a more desirable force-deflection response due to its 90 degree orientation.
- Published
- 2006
21. Effect of Contact Interaction on the Stress Intensity Factors for a Crack under Harmonic Loading
- Author
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Igor Guz and Oleksandr Menshykov
- Subjects
Materials science ,business.industry ,Crack tip opening displacement ,Allowance (engineering) ,Harmonic (mathematics) ,General Medicine ,Mechanics ,Structural engineering ,Crack growth resistance curve ,Crack closure ,Dynamic problem ,Fracture (geology) ,business ,Stress intensity factor - Abstract
This paper concerns fracture dynamic problems for elastic cracked solids with allowance for crack faces contact interaction. The contact problem for a penny-shaped crack with an initial opening under normally incident tension-compression wave is solved by the method of boundary integral equations. The solution is compared with those obtained without allowance for crack faces contact interaction for various values of the initial opening.
- Published
- 2006
22. Stresses in Ultrasonically Assisted Turning
- Author
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Vadim V. Silberschmidt, A.V. Mitrofanov, Vladimir I. Babitsky, and Naseer Ahmed
- Subjects
Materials science ,Cutting tool ,business.industry ,Chip formation ,Acoustics ,General Medicine ,Surface finish ,Structural engineering ,Shear (sheet metal) ,Stress (mechanics) ,Vibration ,Sensitivity (control systems) ,business ,Quasistatic process - Abstract
Ultrasonically assisted turning (UAT) is a novel material-processing technology, where high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of applications. Compared to conventional turning (CT), this technique allows significant improvements in processing intractable materials, such as high-strength aerospace alloys, composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting forces, as well as a superior surface finish. A vibro-impact interaction between the tool and workpiece in UAT in the process of continuous chip formation leads to a dynamically changing stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a representative cycle of ultrasonic vibration. The dependence of various process parameters, such as shear stresses and cutting forces on vibration frequency and amplitude is also studied.
- Published
- 2006
23. Experimental Determination of Stress Concentrations in Composite Laminates and their Effects on Damage Evolution
- Author
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Costas Galiotis and Dionisios Katerelos
- Subjects
Stress (mechanics) ,Materials science ,business.industry ,Composite number ,Fail-safe ,General Medicine ,Structural engineering ,Composite laminates ,business ,Civil infrastructure ,Damage tolerance ,Structural element ,Stress concentration - Abstract
Composite laminates are used for the construction of a wide range of products; from civil infrastructure to aeronautical or space structures. Since all these structures cannot be built at once, but they are composed by several structural elements connected in various patterns, the problem of stress concentrations strikes importantly. Additionally, the structures are often designed in a “fail safe” manner, which bespeaks the damage tolerance of the material. This means that the structural element and the structure are called to operate in the presence of various forms of damage. Damage locations within a structural element or a structure cause stress rising. In the present paper experimental investigation of the stress concentration arising in composite laminates, (a) around a circular notch and (b) due to damage onset and growth during their lifetime, is presented. The experimental results are compared to analytical model predictions.
- Published
- 2006
24. A Finite Element Model for Ultrasonic Cutting of Toffee
- Author
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E. McCulloch, Margaret Lucas, and Alan MacBeath
- Subjects
Vibration ,Stress (mechanics) ,Materials science ,Cutting tool ,business.industry ,Heat generation ,Ultimate tensile strength ,Fracture mechanics ,Ultrasonic sensor ,General Medicine ,Structural engineering ,business ,Finite element method - Abstract
The performance of an ultrasonic cutting device critically relies on the interaction of the cutting tool and the material to be cut. A finite element (FE) model of ultrasonic cutting is developed to enable the design of the cutting blade to be influenced by the requirements of the toolmaterial interaction and to allow cutting parameters to be estimated as an integral part of designing the cutting blade. In this paper, an application in food processing is considered and FE models of cutting are demonstrated for toffee; a food product which is typically sticky, highly temperature dependent, and difficult to cut. Two different 2D coupled thermal stress FE models are considered, to simulate ultrasonic cutting. The first model utilises the debond option in ABAQUS standard and the second uses the element erosion model in ABAQUS explicit. Both models represent a single blade ultrasonic cutting device tuned to a longitudinal mode of vibration cutting a specimen of toffee. The model allows blade tip geometry, ultrasonic amplitude, cutting speed, frequency and cutting force to be adjusted, in particular to assess the effects of different cutting blade profiles. The validity of the model is highly dependent on the accuracy of the material data input and on the accuracy of the friction and temperature boundary condition at the blade-material interface. Uniaxial tensile tests are conducted on specimens of toffee for a range of temperatures. This provides temperature dependent stress-strain data, which characterises the material behaviour, to be included in the FE models. Due to the difficulty in gripping the tensile specimens in the test machine, special grips were manufactured to allow the material to be pulled without initiating cracks or causing the specimen to break at the grips. A Coulomb friction condition at the bladematerial interface is estimated from experiments, which study the change in the friction coefficient due to ultrasonic excitation of a surface, made from the same material as the blade, in contact with a specimen of toffee. A model of heat generation at the blade-toffee interface is also included to characterise contact during ultrasonic cutting. The failure criterion for the debond model assumes crack propagation will occur when the stress normal to the crack surface reaches the tensile failure stress of toffee and the element erosion model uses a shear failure criterion to initiate element removal. The validity of the models is discussed, providing some insights into the estimation of contact conditions and it is shown how these models can improve design of ultrasonic cutting devices.
- Published
- 2006
25. Improved Correlation of Measured and Predicted Hysteresis Loops in a Multiaxial Fretting Fatigue Test Rig for Spline Couplings
- Author
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E.J. Williams, Sean B. Leen, D. Houghton, and P.M. Wavish
- Subjects
Spline (mathematics) ,Materials science ,Amplitude ,business.industry ,Test rig ,Fretting ,General Medicine ,Slip (materials science) ,Structural engineering ,business ,Global model ,Finite element method - Abstract
This paper investigates the comparison of the measured and predicted force-displacement loops of a multiaxial representative fretting fatigue test rig for aeroengine spline couplings. A local finite element model of the fretting specimen and the fretting bridge is outlined. A more extensive model of the fretting test rig is then introduced. This global model also includes the loading structures. The model captures the compliance of the fretting test rig and improves the correlation of the observed hysteresis. This method allows the slip amplitude at the contacts to be quantified.
- Published
- 2007
26. Assessment and Minimization of the Residual Stress in Dissimilar Laser Welding
- Author
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J. H. Abboud, Abdul Ghani Olabi, and Khaled Y. Benyounis
- Subjects
Hole drilling method ,Materials science ,Mathematical model ,business.industry ,Laser beam welding ,General Medicine ,Welding ,Structural engineering ,Laser ,law.invention ,F-test ,law ,Residual stress ,Laser power scaling ,business - Abstract
Establishing the relationship between process parameters and the magnitude of residual stresses is essential to determine the life of welded components. It is the aim of this paper to develop mathematical models to assess residual stresses in the heat-affected zone of dissimilar butt jointed welds of AISI304 and AISI1016. These models determine the effect of process parameters on maximum residual stress. Laser power, travel speed and focal position are the process input parameters. Plates of 3 mm thick of both materials were laser welded using a 1.5 kW CW CO2 Rofin laser as a welding source. Hole-drilling method was used to compute the maximum principal stress in and around the HAZ of both sides of the joint. The experiment was designed based on a three factors five levels full central composite design (CCD). Twenty different welding runs were performed in a random order, 6 of them were centre point replicates and the maximum residual stresses were calculated for each sample. Design-expert software was used to fit the experiential data to a second order polynomial. Sequential F test and other adequacy measures were used to check the model’s performance. The results show that the developed models explain the residual stress successfully. Using the developed models, the main and interaction effect of the process input variables on the residual stresses at either side of the weld were investigated. It is found that all the investigated laser parameters are affecting the performance of the residual stress significantly.
- Published
- 2007
27. Confidence of Detection of Fracture Signals Using Acoustic Emission
- Author
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Karen Margaret Holford, Samuel Lewin Evans, and Rhys Pullin
- Subjects
Matrix (mathematics) ,Materials science ,Acoustic emission ,business.industry ,Acoustics ,Cluster (physics) ,Cluster size ,Fracture (geology) ,General Medicine ,Structural engineering ,Gauge (firearms) ,business ,FOIL method - Abstract
This paper reports on a practical investigation into methodology confidence of detection (COD) in acoustic emission (AE) testing. The developed technique relies on a commercially available software technique called “source cluster analysis” that examines the number of detected signals over a specific area. Two factors that control cluster analysis are cluster size (the area that signals are detected within) and cluster threshold (the number of detected events required to trigger a cluster). A confidence of detection matrix was developed based on altering cluster size and cluster threshold which was then applied to a practical investigation of a four-point bend test monitored using AE. Fracture length in the specimen was monitored using a foil crack gauge. The varying sizes and thresholds of the confidence matrix were used in a cluster analysis of the recorded AE data, as the initial cluster formed in the fracture region a crack length could be identified (based on the foil crack gauge). Results showed that it was possible to detect a crack length of 0.55 mm with a very high level of confidence.
- Published
- 2007
28. Development of a Full-Field Displacement Measurement Technique at the Microscale and Application to the Study of Strain Fields in a Tensile Steel Specimen
- Author
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René Rotinat, Raphaël Moulart, Fabrice Pierron, Gilles Lerondel, Laboratoire de Nanotechnologie et d'Instrumentation Optique (LNIO), Institut Charles Delaunay (ICD), Université de Technologie de Troyes (UTT)-Centre National de la Recherche Scientifique (CNRS)-Université de Technologie de Troyes (UTT)-Centre National de la Recherche Scientifique (CNRS), and VU VAN, Jean-Baptiste
- Subjects
White light interferometry ,Materials science ,[SPI.OPTI] Engineering Sciences [physics]/Optics / Photonic ,Scale (ratio) ,business.industry ,Grid method multiplication ,Mechanical engineering ,02 engineering and technology ,General Medicine ,01 natural sciences ,Displacement (vector) ,law.invention ,010309 optics ,Interferometry ,020303 mechanical engineering & transports ,Optics ,0203 mechanical engineering ,law ,0103 physical sciences ,[SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic ,Photolithography ,business ,Lithography ,ComputingMilieux_MISCELLANEOUS ,Microscale chemistry - Abstract
This work deals with the development of a full-field extensometric method at a micrometric scale in order to precisely identify the local features of a metallic alloy at the scale of the grains. The full-field method that has been chosen is the grid method that applies a spatial phase-shifting algorithm to a periodic pattern. To mark the sample, direct interferometric photolithography was used. The paper presents the basic features of the technique and first mechanical test results are commented.
- Published
- 2007
29. Use of Micro Tensile Test Samples in Determining the Remnant Life of Pressure Vessel Steels
- Author
-
Mark Turski, Lyndon Edwards, W. Manaj, Mehmet E. Kartal, Zbigniew Pakiela, S. Hiller, Rafal M. Molak, S. Gungor, and Krzysztof J. Kurzydłowski
- Subjects
Digital image correlation ,Work (thermodynamics) ,Yield (engineering) ,Materials science ,business.industry ,Biaxial tensile test ,General Medicine ,Structural engineering ,Pressure vessel ,Ultimate tensile strength ,Composite material ,business ,Material properties ,Tensile testing - Abstract
The aim of this collaborative study was to measure mechanical properties of 14MoV67-3 steel taken from small sections of material machined in-situ from an operating high pressure collector pipe after different operating lifetimes (from 0h to 186 000h) at elevated temperatures (540°C). Conventional methods of measuring mechanical properties of materials, such as the uniaxial tensile test require relatively large test samples. This can create difficulties when the amount of material available for testing is limited. One way of measuring mechanical properties from small quantities of material is using micro tensile test samples. In this work, micro-samples with a total length of 7.22mm were used. Digital Image Correlation method (DIC) was employed for the strain measurements in a uniaxial tensile test. This paper shows that there is measurable difference in the yield, ultimate tensile strength and elongation to failure as a function of the plant operating conditions. This work demonstrates, therefore, a ‘semi-invasive’ method of determining uniaxial stress-strain behaviour from plant components.
- Published
- 2007
30. Collapse of Glass/Carbon Fibre Circular Cylinders under Uniform External Pressure
- Author
-
Carl T.F. Ross, Marcus Engelhardt, and Andrew P.F. Little
- Subjects
Materials science ,Buckling ,business.industry ,Hydrostatic pressure ,Isotropy ,von Mises yield criterion ,General Medicine ,Structural engineering ,Fibre-reinforced plastic ,business ,Orthotropic material ,Material properties ,Finite element method - Abstract
This paper describes an experimental and an analytical and numerical investigation into the buckling behaviour of cylindrical composite tubes under external hydrostatic pressure. The investigations concentrated on fibre reinforced plastic tube specimens made from a mixture of three carbon and two E-glass fibre layers. The lay-up was 0°/90°/0°/90°/0; the carbon fibres were laid lengthwise (0°) and the E-glass fibres circumferentially (90°). The theoretical investigations were carried out using a simple solution for isotropic materials, namely a well-known formula by “von Mises” and also by finite element analyses using ANSYS. The experimental investigations showed that the composite specimens behaved similarly to isotropic materials tested by various other researchers. The specimens failed by the common modes associated with this study, namely due to elastic buckling, inelastic buckling and axisymmetric yield failure. Furthermore it was discovered that the specimens failed at changes of the composite lay-up due to the manufacturing process of these specimens. These changes seem to be the weak points of the specimens. For the theoretical investigations two different types of material properties were used to analyse the composite. These were calculated properties derived from the properties of the single layers given by the manufacturer and experimentally obtained properties. Two different approaches were chosen for the investigation of the theoretical buckling pressure, a program called “MisesNP”, based on a well-known formula by von Mises for single layer isotropic materials, and two finite element analyses using the famous computer package called “ANSYS”. This latter analyses simulated the composite with a single layer orthotropic element (Shell93) and also with a multi layer element (Shell99). It was found out that the results obtained with ANSYS predicted questionable buckling pressures that could not be reproduced logically. Nevertheless this report provides Design Charts for all approaches and material types. These Design Charts allow the possibility of obtaining a ‘plastic knockdown factor’. The theoretical buckling pressures obtained using MisesNP or ANSYS can then be divided by the plastic knockdown factor, to give predicted buckling pressures. This method can be used for the design of full-scale vessels.
- Published
- 2007
31. Modelling the Uniaxial Impact Response of a Nonlinear Sandwich Structure with Interlaminar Buckling
- Author
-
Michael A Sek
- Subjects
Stress (mechanics) ,Acceleration ,Nonlinear system ,Materials science ,Buckling ,business.industry ,Shock response spectrum ,Exciter ,General Medicine ,Structural engineering ,business ,Compression (physics) ,Shock (mechanics) - Abstract
This paper describes the development of a software simulation tool of discrete elements which has been developed for the purpose of investigating the dynamic response of multilayer sandwich structures that incorporate highly nonlinear crumple (buckling) elements. These structures are to be optimised as cushions in order to minimise the transmission of shocks when exposed to transient excitation, such as in a free fall. Presented results are for multilayer corrugated paperboard. A single layer was modelled as a nonlinear 2-DOF system with an additional elastoplastic element to reflect contact conditions. Numerical models of the platen and the exciter with either acceleration or displacement control were developed and applied to perform numerical compression tests of the sandwich layer at various strain rates to validate the model of a single layer. Sandwich structures were then numerically assembled and subjected to simulated impacts. The model predicted inter- and intralaminar forces, displacements, velocities and accelerations. The shock attenuation characteristics were obtained and presented as the time-acceleration-static stress maps. A postprocessor was developed to produce animations to reveal complex dynamic interactions within modelled sandwich structures.
- Published
- 2007
32. Numerical Study of the Effect of Welding Parameters on the Strength of Spot-Welded Joints
- Author
-
Glynn Rothwell, X. Kong, Xuejun Ren, R. English, B. Li, and Qing Xiang Yang
- Subjects
Materials science ,business.industry ,Automotive industry ,General Medicine ,Welding ,Structural engineering ,law.invention ,law ,visual_art ,Indentation ,visual_art.visual_art_medium ,Deformation (engineering) ,Material properties ,Sheet metal ,business ,Spot welding ,Test data - Abstract
Resistance spot welding (RSW) is widely employed in sheet metal fabrication, in particular in automotive bodies and structures. Manufacturers are increasingly demanding reduced design periods with improved safety requirements, which could potentially be achieved through computational simulations. This paper presents an integrated approach combining simulation of the welding process, materials characterisation and mechanical modelling to study the effect of welding parameters on the strength of spot-welded joints. The welding process was simulated and the dimensional attributes were used to build the mechanical models for strength analysis. The constitutive material properties of the base, nugget and the heat-affected-zone (HAZ) were determined by an inverse FE modelling approach using indentation test data. The predicted deformation of spot-welded joints of a typical automotive steel under tensile-shear load showed a good agreement with experimental results. The validated models were further used to predict effects of welding parameters on the strength and failure behaviour of weld joints. Potential uses of the approach in optimising welding parameters for strength were also discussed.
- Published
- 2007
33. Explicit Analysis on Temperature Field of 3D Laser Forming of Square Metal Sheet to Spherical Dome
- Author
-
Lijun Yang and Yang Wang
- Subjects
Materials science ,Field (physics) ,Laser scanning ,business.industry ,General Medicine ,Deformation (meteorology) ,Laser ,Curvature ,law.invention ,Temperature gradient ,Optics ,law ,visual_art ,visual_art.visual_art_medium ,Sheet metal ,business ,Thermal analysis - Abstract
Laser forming is a technique of using the energy from a laser beam to modify and adjust the curvature of sheet metals or hard materials. 2-dimention (2D) laser forming can reasonably accurately control bend angles with various materials. To advance this process further for realistic forming applications in a manufacturing industry, it is necessary to consider larger scale controlled 3-dimention (3D) laser forming. On the base of mechanism of 2D laser forming, the deformation mainly depends on the temperature gradient between upper and bottom surface of sheet metal. The work presented in this paper shows that the temperature field of using the spider scanning path to transform the thin square sheet to spherical dome by 3D laser forming. The explicit thermal analysis on 3D laser forming is shown in the article. This paper discusses the interaction between moving laser beam and sheet, the varied temperature field on the sheet during laser scanning. In order to give the verification on the results of simulation, the correlative experiment has progressed and the results of experiments are in accord with the simulation.
- Published
- 2007
34. Optimising Shot Peening Parameters Using Finite Element and Discrete Element Analysis
- Author
-
Ju Long Yuan, Tao Hong, and Dong Hui Wen
- Subjects
Element analysis ,Materials science ,business.industry ,Process (computing) ,Mechanical engineering ,Peening ,General Medicine ,Structural engineering ,Shot peening ,Finite element method ,Residual stress ,Shot (pellet) ,business ,Intensity (heat transfer) - Abstract
Shot peening is a cold-work process in which a stream of small spherical shot is blasted against a metallic component to generate a high compressive residual stress regime at the surface of the target. This paper presents a computational modelling of the shot peening process, in which the finite element (FE) method was employed to study the elastic-plastic dynamic process of the shot impact on a metallic target, and the discrete element (DE) method was used to study the multiple particles dynamics. Statistical analyses of the shot impact data reveal the relationships between peening process parameters and peening intensity, which can be used to optimise these process parameters to produce an improved outcome.
- Published
- 2007
35. A Finite Element Analysis of Micro/Meso-Scale Machining Considering the Cutting Edge Radius
- Author
-
Liang Li, Ning He, and Zi Yang Cao
- Subjects
Materials science ,business.industry ,General Medicine ,Radius ,Structural engineering ,Edge (geometry) ,Dissipation ,Finite element method ,Stress field ,Meso scale ,Rake angle ,Machining ,Composite material ,business - Abstract
In order to investigate the effects of cutting edge radius on micro/meso-scale cutting process, the current paper is concerned with a fundamental investigation of the contribution of cutting edge radius to cutting temperature, stress field and size effect by means of two-dimensional finite-element simulation for orthogonal cutting process. The results indicated that cutting edge radius has remarkable effects on cutting temperature and stress field, and the existence of cutting edge radius is one of the main reasons generating size effect. The cutting edge radius affects the micro/meso scale cutting process at smaller uncut chip thickness by altering the effective rake angle and enhancing the plowing effect, affecting the material deformation process, expanding and widening the plastic deformation zone, and causing higher energy dissipation due to increased tool-chip contact length.
- Published
- 2007
36. Detection Resolution of Acoustic Microscopy in Micro-Scale
- Author
-
Xiang Hui Guo, Kai Peng, Chunguang Xu, and Ding Guo Xiao
- Subjects
Materials science ,Optics ,Transducer ,business.industry ,Image quality ,Frequency domain ,Resolution (electron density) ,Calibration ,Acoustic microscopy ,Ultrasonic sensor ,General Medicine ,business ,Focus (optics) - Abstract
Scanning acoustic microscopy (SAM) is a powerful non-destructive testing tool used in the field of electronic package, micro-and nanomaterial and medication. The capability to distinct how minimum of defect is very important to detect the flaw in electronic packages. The detection resolution of SAM depends on the frequency of ultrasonic focus transducers. In this paper, the Multi-Gaussian Beam model to simulate the sound field of the focused transducers is discussed. Mainly the frequency domain imaging algorithm and 2D-Deconvolution method for better image quality and high resolution is analyzed. Finally, the calibration experiments for the detection resolution of 100MHZ transducer is carried out. In addition, the micro flaws with different dimensions are observed at different defocusing location. It is concluded that the detection resolution decreases with the deviating from focus plane, so the flaws should be sensitive on the focus area by precisely controlling the vertical position for better detection resolution.
- Published
- 2013
37. Wet-Etching Characteristics of ‹111› Orientated Silicon and its Application
- Author
-
Ming Qin and Hui Yang Yu
- Subjects
Microelectromechanical systems ,Materials science ,Cantilever ,Silicon ,Hybrid silicon laser ,business.industry ,chemistry.chemical_element ,General Medicine ,Microstructure ,Silicon on sapphire ,chemistry ,Etching (microfabrication) ,Optoelectronics ,Wafer ,business - Abstract
In this paper, a method of fabricating single crystal silicon microstructures on oriented silicon wafer is developed. The relationship of the (111) planes on silicon silicon wafer is analyzed based on the crystal lattice of the silicon, the method of judging these (111) planes is given. An anisotropy wet-etching experiment is done to verify the etching characteristics of silicon. The process of fabricating three dimension structures on silicon wafer is then given out and some basic MEMS structures such as cantilever beams, doubly-clamped beams are fabricated. With this method, it is easy to define the shape and thickness of the microstructure and the process is not complicate. Moreover, the structures made in this way have higher structural precision and mechanical strength.
- Published
- 2012
38. Modelling of a Cervical Plate and Human Cervical Section C3 – C5 under Compression Loading Conditions Using the Finite Element Method
- Author
-
Luis Héctor Hernández-Gómez, E.A. Merchán-Cruz, Alejandro González-Rebatu, Guillermo Urriolagoitia-Sosa, Guillermo Urriolagoitia-Calderón, M. Dufoo-Olvera, Juan Alfonso Beltrán-Fernández, and R.G. Rodríguez-Cañizo
- Subjects
Section (fiber bundle) ,Stress (mechanics) ,Compression load ,Fixation (surgical) ,Materials science ,business.industry ,Head (vessel) ,General Medicine ,Structural engineering ,Implant ,business ,Compression (physics) ,Finite element method - Abstract
This paper presents the modelling of the effects due to load conditions on the cervical section defined between C3 and C5 after a cervical plate implant is used to transfer the compression loads from C3 to C5 as C4 is considered to be damaged as a result of a medical condition. For this study, three different scenarios which describe the common motion condition of the head-neck system are modelled. The first one refers to the effect of the head weight over the considered section. In the second case the average patient weight is supported by C3 and C5 vertebrae. The last case simulates extreme loading conditions as vertebrae lesions occur when these are compressed beyond its failure limit; the ultimate stress to compression load failure value is applied to C3. The stability and mechanical behaviour of cervical plates under compression loading conditions is evaluated using the Finite Element Method (FEM). Cervical plates are useful to restore stability of the spine by improving the inter-vertebral fusion, particularly when the cervical body has been damaged. The results show that the stresses on the plate and fixation screws, for the three cases, are within the elastic range. Conversely, it has to be considered that cortical and trabecular bone densities vary from one patient to another due to a number of factors, which can influence the fixation conditions of the screws. In the case of this analysis, healthy bone conditions were considered and the obtained results show that the risk of the integrity of the screwimplant- vertebrae system is not compromised.
- Published
- 2008
39. Local Effects during Indentation of Fully Supported Sandwich Panels with Micro Lattice Cores
- Author
-
S. Tsopanos, Robert Mines, Wesley J. Cantwell, Chris Sutcliffe, W. Brooks, Eva Shen, and S. McKown
- Subjects
Materials science ,business.industry ,Composite number ,chemistry.chemical_element ,General Medicine ,Penetration (firestop) ,Structural engineering ,Drop weight ,chemistry ,Aluminium ,Indentation ,Lattice (order) ,business ,Sandwich-structured composite - Abstract
This paper discusses the penetration behavior of fully supported sandwich panels with micro-lattice and foam cores, and composite skins. This behaviour is of importance during foreign object impact and perforation of sandwich structures. Experimental results are given for quasi-static penetration of micro-lattice and foam blocks, and it is shown that these two cellular materials are comparable. Experimental results are also given for drop weight penetration of fully supported skinned panels, and it is shown that skin failure and core penetration are also similar for the two core materials. It is concluded that there is scope for improving the performance of micro-lattice structure and so making such material superior to that of aluminium foam.
- Published
- 2008
40. Material Properties for Quantitative Thermoelastic Stress Analysis of Composite Structures
- Author
-
Janice M. Dulieu-Barton, Simon Quinn, S. Sambasivam, and R. K. Fruhmann
- Subjects
Stress (mechanics) ,Materials science ,Thermoelastic damping ,business.industry ,Composite number ,General Medicine ,Structural engineering ,Material properties ,business - Abstract
The sensitivity of the thermoelastic response to variations in the fibre volume fraction, resin material and manufacturing route is assessed. To quantify any effects a comprehensive materials testing programme has been conducted to obtain coefficients of thermal expansion, specific heat, density and the elastic properties, which is described in detail in the paper. The work is focused on attempting to ascertain if the source of the response is from the isotropic resin rich layer or from the orthotropic substrate. It is also demonstrated that small variations in material properties can have a significant effect on the calculated thermoelastic response.
- Published
- 2008
41. Real-Time Monitoring of Dynamic Stress Concentration by Mechanoluminescent Sensing Film
- Author
-
Chenshu Li, Chao-Nan Xu, Lin Zhang, Yusuke Imai, Hiroshi Yamada, and Wen Xue Wang
- Subjects
Materials science ,business.industry ,Alloy ,Uniaxial tension ,chemistry.chemical_element ,General Medicine ,Structural engineering ,engineering.material ,chemistry ,Aluminium ,engineering ,Composite material ,business ,Mechanoluminescence ,Dynamic stress ,Stress concentration - Abstract
In this paper, we demonstrate that a dynamic stress concentration around Lüders band can be directly displayed using mechanoluminescence (ML) sensing film of SrAl2O4:Eu (SAO) coated on the surface of metal. Uniaxial tensile test of an aluminum alloy (2.5% Mg) plate coated with the SAO sensing film was performed and the ML images were recorded using a high-speed camera. Captured ML images confirmed the formation and propagation of Lüders band clearly in real time.
- Published
- 2008
42. Tensile Strength of Fibers Extracted from the Leaves of the angustifolia Haw Agave in Function of their Length
- Author
-
I. López-Hernández, Luis Héctor Hernández-Gómez, Luis Silva-Santos, and Magdaleno Caballero-Caballero
- Subjects
Retting ,Materials science ,biology ,business.industry ,Young's modulus ,General Medicine ,Structural engineering ,Agave ,biology.organism_classification ,Viscoelasticity ,symbols.namesake ,Ultimate tensile strength ,symbols ,Relative humidity ,Fiber ,Composite material ,business ,Tensile testing - Abstract
This paper presents the results of the tensile strength evaluation of the fibers of the leaves of the agave species angustifolia Haw. The purpose of the study was to determine the mechanical behavior of the fibers under the following test conditions: (1) in fibers of the agave leave as a whole; (2) in three different longitudinal sections of the fiber: base, center and tip; (3) with a variable length and a constant test speed and (4) with a constant length and a variable test speed. The experiment began with the classification of the agave leaves by level; later the fibers were extracted through the process of retting; next the fibers were stabilized at a temperature of 20 ºc ± 2 ºc and at a relative humidity of 65 %; then the tensile tests were carried out. Finally, the Ultimate Tensile Strength (UTS), the Modulus of Elasticity (ME) and the Ultimate Strain (%) were evaluated. The results show that the fibers exhibit viscoelastic behavior and their characteristics are within the range of other similar vegetal fibers, which are currently being used by industry in the manufacture of new composites.
- Published
- 2009
43. Assessment of the Crack Compliance Method and the Introduction of Residual Stresses by Shot Peening Using the Finite Element Method
- Author
-
Guillermo Urriolagoitia-Sosa, E. Zaldivar-González, J. García-Lira, and J. M Sandoval Pineda
- Subjects
Compliance method ,Materials science ,Computer simulation ,Residual stress ,business.industry ,Ball (bearing) ,Peening ,General Medicine ,Structural engineering ,Shot peening ,business ,Mechanical components ,Finite element method - Abstract
The interest on the application of the shot peening process to arrest and/or delay crack growth is rising. The main effect of the shot peening technique is to introduce a residual stress field that increases the working life of mechanical components. In this paper, it is presented the numerical simulation (FEM) of the shot peening process and the effect of introducing a residual stress field. Besides, the consequence of changing the sizes of the impacting ball is analyzed. This work also used the Crack Compliance Method (CCM) for the determination of residual stresses in beams subjected to a numerical simulation of a shot peening process. The numerical results obtained provide a quantitative demonstration of the effect of shot peening on the introduction of residual stresses by using different sizes of impacting balls and assess the efficiency of the CCM.
- Published
- 2009
44. Study on Vibration Friction Mechanism and Vibration Response Analysis Based on Vibration Compaction System
- Author
-
Yun Nan Teng, Bang Chun Wen, Xiao Peng Li, and Hui Ma
- Subjects
Vibration ,Mechanism (engineering) ,Nonlinear system ,Materials science ,business.industry ,Active vibration control ,Stick-slip phenomenon ,General Medicine ,Structural engineering ,business ,Intensity (heat transfer) ,Friction torque ,Abrasion (geology) - Abstract
Friction of two objects or inner friction of loose materials in vibration case can present different characteristics that are different from conventional conditions. The practice shows that vibration can reduce friction coefficient and friction force between two objects, lighten abrasion of objects, reduce energy consumption and increase greatly working efficiency. The mechanism of friction in vibration case was revealed in this paper. The Curve of vibration intensity to internal friction of soil was given. The investigation indicated that friction converts from static to sliding in vibration case. The internal friction is reduced with frequency increasing and there exists the optimal vibration intensity to make internal friction least. At last, nonlinear dynamic model of vibration friction system about compaction equipment was established and its resonance response was obtained.
- Published
- 2009
45. Numerical Analysis on Starved Elastohydrodynamic Lubrication Characteristics of Spiral Bevel Gears
- Author
-
Qiang Yang, Yu Tao Yan, Yan Zhong Wang, and Zhi Li Sun
- Subjects
business.product_category ,Materials science ,Spiral bevel gear ,business.industry ,Numerical analysis ,General Medicine ,Mechanics ,Film pressure ,Midpoint ,Optics ,Lubrication ,Bevel gear ,Point (geometry) ,business ,Spiral - Abstract
The spiral bevel gears of attack helicopter transmission systems are taken as an object in this paper. The numerical analysis model for starved elastohydrodynamic lubrication (SEHL) of spiral bevel gears is established on the basis of the analysis of load tooth contacts analysis and SEHL in elliptical contacts. The SEHL characteristics of spiral bevel gears are also analyzed. The results are as follows: during the course of a gear-tooth meshing cycle of the spiral bevel gear, the extremum of minimal film thickness and maximal film pressure occurs near midpoint of the path of contact, and leans to dedendum. The minimal value of the minimal film thickness is 0.39 um, and the maximal value of the maximal film pressure is 0.69 GPa. The value of minimal film thickness gradually increases with the increasing of meshing point velocity. When the velocity of meshing point exceeds 110 m/s, the increase became tardiness. As the load of meshing point increases, the value of minimal film thickness gently diminishes.
- Published
- 2009
46. Finite Element Analysis of the Effect of the Compressive Loading on Fatigue Crack Growth under Different Loading
- Author
-
Jia Zhen Zhang, Xin Song, Hui Tang, and Yu Sha
- Subjects
Stress (mechanics) ,Crack closure ,Materials science ,business.industry ,Crack tip opening displacement ,General Medicine ,Structural engineering ,Compression (geology) ,Paris' law ,business ,Crack growth resistance curve ,Stress intensity factor ,Stress concentration - Abstract
In this paper, elastic-plastic finite element analysis has been performed in order to obtain the fatigue crack tip parameters under tension-compression loading. Two centre-cracked high-strength aluminum alloy with a crack length of 2mm under different tension-compression loading are analyzed. The analysis shows that the compressive loading has a significant contribution towards the crack tip plasticity and the crack tip stress. In a tension-compression loading the crack tip displacement increases with the increase of the compressive stress and the crack tip compress stress increases with the increase of the compressive stress. The maximum stress intensity Kmax in the tension part of the stress cycle and the maximum compressive stress in the compression part of the stress cycle are the main factors controlling the near crack tip parameters.
- Published
- 2009
47. Study on Kinematics of Shape-Adaptive Tool for Free-Form Surfaces Compliantly Polishing
- Author
-
Jian Ming Zhan, Ming Ming Wu, and Jian Bo Zhang
- Subjects
Surface (mathematics) ,Materials science ,Optics ,business.industry ,Process (computing) ,Polishing ,Mechanical engineering ,Free form ,General Medicine ,Kinematics ,Curvature ,business - Abstract
A new free-form surfaces shape-adaptive polishing tool is introduced in this paper, which can change its pose with the surface of workpiece. The simulation of this tool system’s polishing process is taken using ADAMS, and the kinematics of the shape-adaptive tool on the curvature varying surfaces of the workpiece is investigated. The simulating results indicate that the tool system can fit the varying curvature and slope of the workpiece’s surface very well.
- Published
- 2009
48. Stiffness Analysis of 3-RPR Planar Parallel Mechanism to the Stiffness Control
- Author
-
Clément Gosselin and Shu Jun Li
- Subjects
Materials science ,business.industry ,Stiffness ,General Medicine ,Structural engineering ,Mechanism (engineering) ,Planar ,Transformation (function) ,Bending stiffness ,medicine ,Tangent stiffness matrix ,Direct stiffness method ,medicine.symptom ,business ,Stiffness matrix - Abstract
The analytical stiffness equations of the 3-RPR planar parallel mechanism are derived in this paper based on the Conservative Congruence Transformation (CCT) stiffness matrix proposed in [1-3]. Stiffness maps of the 3-RPR mechanism are plotted in order to show the behaviour of the stiffness with and without external forces. The stiffness characteristics of the mechanism are analyzed and discussed in details. Numerical examples show that the stiffness in x and in y are well balanced, while the stiffness in tends to be lower.
- Published
- 2009
49. Research of Displacement Measuring System Based on Capacitive Grating Sensor
- Author
-
Shan Hui Wang, Ying Gang Zhou, and Guang Ping Yu
- Subjects
Observational error ,Optics ,Materials science ,business.industry ,System of measurement ,Capacitive sensing ,Measure (physics) ,General Medicine ,Capacitive displacement sensor ,Grating ,business ,Capacitance ,Displacement (vector) - Abstract
Capacitive grating sensor can be used to measure the length, as its capacitance changes with the shift difference. There are several measuring systems consisting of capacitive sensor, but all their basic principles are capacitive differential sensing. The structure, principles and characteristics of capacitive sensors are introduced in this paper. Especially, we designed a high-resolution electronic length measuring system based on Capacitive Grating Sensor. And the measurement error of the system and the reason are analysed. For this system, the measuring range is from 0 to 500mm, the resolution is 1um, the indication error is 5um, the measuring speed is 1m/s. Accurate measurement on account of large displacement is achieved with the system.
- Published
- 2010
50. A Novel Temperature Sensor Based on Gold Interdigital Electrodes and Nano ZnO Particles
- Author
-
Guo Hua Hui
- Subjects
Materials science ,business.industry ,Precipitation (chemistry) ,Semiconductor materials ,Electrode ,Nano ,Electronic engineering ,Optoelectronics ,General Medicine ,Sensitivity (control systems) ,business - Abstract
Nano ZnO is an important kind of semiconductor materials, and it has been widely used in various single detection fields. In this paper, we prepared nano ZnO powder through direct precipitation method. We fabricated temperature sensor utilizing the interdigitated Au electrodes drop-deposited by nano ZnO powder. The response of the sensor to temperature was studied by CHI660 electrical chemical workstation. The results proved that the temperature sensor based on nano ZnO material presented sensitivity and repeatibility
- Published
- 2010
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