bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibratory weld conditioning: Treatment of specimens during cooling
Authors: Munsi A S M Y , Waddell A J , Walker C A
Published: April 2011

The aim of this study was to investigate the use of vibration to reduce the residual stress resulting from the welding process. Butt weld joints were subjected to vibration immediately after welding. While the specimens were cooling, vibration was applied to them over a specified range of temperatures. Three batches of specimens were processed in three temperature regions. The residual stresses were measured using an automated scanning X-ray diffractometer which provided detailed data over the area close to the weld and in the heat-affected zone. The residual stresses were found to be modified with an increase at some applied stress-temperature combinations and a decrease at others. With a suitable choice of vibratory treatment, welding stresses may be brought within desired design parameters.
Relationships between martensite transformation temperatures and compositions in Fe-Mn-Si-based shape memory alloys
Authors: Zhao C
Published: April 2011

The correlation between λ — ɛ martensite transformation temperatures ( Ms, As), the thermal hysteresis ( As - Ms) and the alloy compositions has been determined by using the multiple linear regression method based on existing experimental data for Fe-Mn-Si-based shape memory alloys. The empirical quantitative equations are: Ms (K) = 282 - 6.3Mn + 37.2Si - 8.1Cr - 6.3Ni; As (K) = 502 - 5.1Mn + 7.8Si - 4.3Cr - 9.2Ni; As - Ms (K) = 220 + 1.2Mn - 29.4Si + 3.8Cr - 2.9Ni (the alloy compositions are in weight per cent.) It has been demonstrated that the addition of Mn, Cr and Ni tends to lower the martensite transformation temperatures, but Si tends to increase them markedly. This agrees quite well with previous results which indicate that Mn, Cr and Ni increase the stacking fault energy of these alloys while Si decreases it. Moreover, the transformation thermal hysteresis decreases with increasing Si and Ni concentration but increases with increasing Cr and Mn content. The above-mentioned results are very useful for the composition design of this type of alloy.
Volume and density changes in polymer gels in seawater environments
Authors: Molloy P J , Cowling M J
Published: April 2011

Some polymer gels are capable of undergoing large volume changes and significant density changes under the influence of solvent composition and temperature. Such characteristics are of interest in the design of small underwater devices. Studies have been conducted on the effects of temperature on the density and volume of poly( N-isopropylacrylamide) (NIPA) gels. The gels were investigated in solutions of distilled water and solutions of natural seawater, which has an approximate salinity of 35 parts per thousand (ppt). For each solution, the effect of temperature from 5 to 50°C was investigated. Such gels contract significantly when heated above their phase transition temperatures. The transition temperature for gels in seawater, 26-28°C, was found to be lower than for gels in distilled water, 33-34°C. Gels in seawater become more dense at higher temperatures, whereas gels in distilled water decrease in density. Short-term tests reveal that such NIPA gels realize full contraction after 4-6 h, but re-swelling takes longer. Density values fluctuate greatly in the first few hours due to phase coexistence. Mechanical tests on the NIPA gels showed a marked increase in mechanical strength and elastic modulus as temperature was increased above the phase transition temperature.
The deformation of a dual-elastomer seal
Authors: Akisanya A R , Hitchcock G R , Thompson D S
Published: April 2011

The use of dual-elastomeric materials for minimizing the level of extrusion in a thick-section seal is examined. A thick-walled cylindrical seal made from a combination of conventional carbon-black-reinforced elastomer and a fibre-reinforced elastomer is considered. The deformation of the seal and the evolution of the contact pressure are determined by a combination of experimental test and detailed non-linear finite element analysis. The results show that the level of extrusion in the dual-elastomer seal is significantly less than that in conventional single-elastomer seals. The implications of the results for the design of packing elements used in the oil and gas industry are discussed.
Experimental verification of a constitutive model for concrete cracking
Authors: Winkler B , Hofstetter G , Niederwanger G
Published: April 2011

A constitutive model for concrete cracking, based on the smeared crack approach within the framework of the theory of plasticity, was verified by experiments on L-shaped structural members. The model is used for finite element ultimate load analyses of plain and reinforced concrete structures. The experimental investigations consisted of a series of L-shaped structural members, made of plain concrete and three series of reinforced L-shaped structural members with different layout of the reinforcement, which were loaded until failure. The comparison between experimental and computed results included the load at the initiation of cracking and the load-displacement curves in the pre- and post-peak regions. Additionally, the experimentally determined crack patterns were compared with the computed crack propagation and damage behaviour of the material.
The effect of vibratory stress on the welding microstructure and residual stress distribution
Authors: Munsi A S M Y , Waddell A J , Walker C A
Published: April 2011

Previous studies have suggested that weld microstructure may be modified by the presence of static stresses. In this investigation, vibratory stress was applied to mild steel specimens while they were being welded to observe its effect on the residual stress, microstructure and hardness of the material. Residual stresses were found to decrease in response to vibration whether it was applied during welding or after welding. It was found that the applied stress influenced the grain growth process in the weld. As a result of the treatment the hardness of the material was found to be increased by 25 per cent.
Elasticity solution for thick laminated circular cylindrical shallow and non-shallow panels under dynamic load
Authors: Alibiglu A , Shakeri M , Eslami M R
Published: April 2011

This paper studies the dynamic responses of axisymmetric cross-ply laminated deep and shallow panels subjected to asymmetric load based on three-dimensional elasticity equations. The shell panel is simply supported at four sides and has finite length. The highly coupled partial differential equations are reduced to ordinary differential equations with constant coefficients for the shallow-shell panel and variable coefficients for the deep panel by means of trigonometric function expansion in circumferential and axial directions. The resulting ordinary differential equations are solved by the Galerkin finite element method. Numerical examples are presented for (0/90), (0/90/0) and (90/0/90) laminations under dynamic loading, and the results for deep and shallow panels are compared.
Non-destructive testing—current capabilities and future directions
Authors: Cawley P
Published: April 2011

The non-destructive testing (NDT) industry is reviewed, the major techniques being described and current development directions and challenges identified. Visual inspection is probably the most widely used NDT technique but it does not generally involve the purchase of dedicated NDT instrumentation so it does not appear in market estimates. The NDT market is dominated by the ‘big five’ techniques: radiography, ultrasonics, eddy current, magnetic particle and penetrant testing. There is considerable research and development effort in other areas, particularly for niche markets. Nondestructive testing is a mature industry, the global market size for equipment being around $1 billion. However, the cost to users greatly exceeds this since much inspection is highly labour intensive, and extensive preparation for inspection is often required, particularly in-service. There is therefore a continuing drive to increase the speed of inspection, to reduce the preparation required and, if possible, to inspect without the need to shut down operation. With some notable exceptions, it is possible to find most types of defect. However, it is frequently not cost effective to do the inspection, so driving down overall inspection costs is a major research and development aim. The other significant research and development areas are in improving inspection reliability and in finding solutions in cases where there is currently no available inspection technique.
Cumulative static strength of tightened joints bonded with anaerobic adhesives
Authors: Dragoni E , Mauri P
Published: April 2011

This paper deals with the static strength of mechanically tightened joints augmented with anaerobic adhesives. Tests were performed on a variety of specimens distinguished by fairly homogeneous (annular butt joint) or realistically inhomogeneous (threaded, cylindrical and double lap joints) working conditions over the bondline. For each geometry, the strength of the dry (unbonded) joint was compared with the strength of the joint bonded with an assortment of anaerobics. The results indicate that the strength of all joints (bonded and unbonded) increases with the contact force. When strong adhesives (retainers) are used, the overall strength approximately equals the sum of friction and adhesive strengths, taken separately. When weak adhesives (threadlockers) are adopted, the superimposition of effects grossly overestimates the measured strength. A micromechanical model is proposed that explains the observed macroscopic behaviour.
Static and fatigue strength of a die-cast aluminium alloy under different feeding conditions
Authors: Avalle M , Belingardi G , Cavatorta M P , Doglione R
Published: April 2011

This paper reports investigations of the influence of porosity and casting defects on the static and constant-amplitude fatigue strength of a die-cast aluminium alloy. Three batches of specimens, differing in the sprue-runner design and consequently in content and types of defects, were tested in ‘as-cast’ conditions. Defects consisted of gas and shrinkage pores as well as cold fills, dross and alumina skins. Casting defects were observed to reduce significantly the static and fatigue properties of the material. Whereas for the static characteristics the decrease was progressive with the porosity range, for the fatigue strength the decrease was most significant from the lowest to the middle porosity range. The batches were classified with regard to the porosity level, as the metallurgical defects were not detectable through X-ray examination. The content and size of metallurgical defects were observed to increase together with the porosity level. Scanning electron microscopy (SEM) observation of the fracture surfaces demonstrated the important role played by dross, alumina skins and, above all, cold fills on the fatigue fracture.
High strain rate superplasticity in aluminium matrix composites
Authors: Ceschini L , Morri A , Orazi L
Published: April 2011

Recently, several studies have demonstrated that a variety of metallic materials, including aluminium-based composites, can exhibit superplasticity at relatively high strain rates (≤10−2s−1). High strain rate superplasticity (HSRS) is very attractive for commercial applications, mainly for materials difficult to shape or machine with conventional techniques, such as metal matrix composites. In this work, the possibility of achieving HSRS in a recently developed composite with an AA6013 matrix reinforced with about 20 vol % of SiC particles (AA6013/20/SiCp) was studied. Uniaxial tensile tests were carried out at high strain rates (1 × 10−1s−1 and 1 × 10−2s−1) and in a temperature range between 520 and 590°C. A maximum elongation-to-failure of 370 per cent was obtained at 560°C with a strain rate of 1 × 10−1s−1. This temperature is very close to the temperature at which melting of the composite starts. Scanning electron microscopy (SEM) analyses of fracture surfaces in the optimum superplastic condition showed the presence of filaments, the formation of which generally related to the presence of a liquid phase at the grain boundaries and/or at the interfaces.
Performance indices for arbitrarily scaled rectangular cross-sections in bending stiffness design
Authors: Pasini D , Burgess S C , Smith D J
Published: April 2011

Performance indices are presented for the selection of optimal rectangular beams in bending stiffness design. Previous studies have developed performance indices for only three design cases: proportional scaling of width and height, constrained height and constrained width. This paper extends the methodology of the performance index to any arbitrary direction of scaling. The performance index has the form Eq/p, where q is a function only of the scaling vector between two cross-sectional envelopes of different materials. The paper also presents a graphical method for determining the performance of rectangular beams in stiffness design. The perormance index and the graphical method are applied to a design case study.
Probabilistic failure analysis of a fibre-reinforced plastic sandwich plate subjected to a lateral pressure load
Authors: Jeong H K , Shenoi R A
Published: April 2011

This paper deals with probabilistic failure analysis of a fibre-reinforced plastic (FRP) sandwich plate subjected to a lateral pressure load. Input parameters to the strength of the sandwich plate such as a lateral pressure load, elastic moduli and the geometric and ultimate strength values, are treated as basic design variables, and a specific probability distribution is applied to them to take into account their variability. Based on the selected basic design variables, simplified higher-order shear deformation theory (HSDT) is used to calculate the probabilistic structural response of the sandwich plate. The limit state equations are derived from polynomial failure criteria such as maximum stress, maximum strain, Tsai-Hill, Tsai-Wu and Hoffman criteria. The calculated probabilistic structural response of the sandwich plate and the basic design variables of the ultimate strength are then substituted into the derived limit state equations to define the failure or survival state of the sandwich plate. Results are interpreted in three categories such as probabilistic failures at the faces and the core, probabilistic strength distributions of the sandwich plate and sensitivity of each selected basic design variable to estimated probabilistic sandwich plate strength.
Analysis of preconditioned glass fibre reinforced composite sandwich I-beams in bending
Authors: Zhou G , Forbes A J , Foster N
Published: April 2011

The flexural mechanical behaviour of various composite sandwich I-beams has been investigated under quasi-static loading. Both intact and preconditioned I-beam specimens were examined. The intact I-beams had two different support spans. The preconditions included central voids and remote debonds, both embedded at the flange-web intersections, whereas remote, barely visible impact damage (BVID) was introduced on the flange surfaces. It was found that the behaviour of the present I-beams was nearly linear until ultimate failure approached, and that the load-bearing capability exceeded the design requirement, irrespective of the preconditions. The flexural rigidity of the intact I-beams calculated by using the lamination theory compared well with the experimental value. The analytical predictions for maximum deflections and maximum tensile strains were in reasonably good agreement with the respective experimental measurements. It was found that neither the central voids nor the remote debonds or BVID had a significant effect on the flexural behaviour. The process of structural failure was extremely complex and was affected to a greater extent by the relatively low mechanical properties of the polymethacrylimide (PMC) foam core. It was shown that foam compression and local web skin wrinkling were the major failure mechanisms, irrespective of the preconditions.
Experimental and numerical analysis of the deformation in mild steel wire during dieless drawing
Authors: Tiernan P , Hillery M T
Published: April 2011

Dieless wire drawing is the process of causing a reduction in a wire diameter without the use of conventional wire drawing dies. The wire, axially loaded with a force, is heated to an elevated temperature to initiate plastic deformation. The mechanics of this novel drawing process and a theoretical analysis of the deformation are discussed in this paper. The results of an experimental drawing programme carried out with mild steel wire at temperatures between 400 and 900°C are also presented. Mathematical models were developed and used to describe and predict the process deformation and both the stress and temperature distribution profile along the workpiece. A machine was designed and manufactured to facilitate an experimental programme of dieless drawing. The machine permitted continuous drawing of wire, while the reduction ratio, drawing load and temperature were automatically controlled using a personal computer. A finite element (FE) model of the wire was developed, and the results obtained from the FE analysis show good agreement with those obtained from both the experimental work and the mathematical modelling. Results obtained confirm that a complicated interdependence of the process parameters exists during the dieless drawing process.
Effects of particle size, particle volume fraction and matrix composition on the fatigue crack growth resistance of Al alloy/Al alloy + SiCp bimaterials
Authors: Milan M T , Bowen P
Published: April 2011

The fatigue crack growth resistance of Al alloy/Al alloy + SiCp bimaterials for crack growth perpendicular to the interface is affected by thermal residual stresses, elastic mismatch, plastic mismatch and direction of crack approach to the interface. When the crack approaches the interface from the composite side, the crack growth resistance is mainly controlled by the compressive residual stress near to the interface. Conversely, when the crack grows from the aluminium side towards the composite, the crack is shielded primarily by the elastic/plastic mismatch. In this work, the effects of particle size, particle volume fraction and matrix composition on the fatigue crack growth resistance of Al alloy/Al alloy + SiCp bimaterials have been assessed. These parameters can affect both the thermal residual stress profile and the elastic/plastic mismatch, and hence the effective crack tip driving force for crack extension is also affected.
Optimization design of plates with holes by mimicking bones through nonaxisymmetric functionally graded material
Authors: Huang Jinhua , Rapoff A J
Published: April 2011

The larger natural holes in bone are not involved in failure because of the special material distribution in their vicinity. In this paper, a procedure was developed that designs the nonaxisymmetric functionally graded material distribution around a hole in a plate in an attempt to mimic bone for increased strength at small weight increase by minimizing a failure index (stress/strength ratio). Nonaxisymmetric graded material distributions were represented by a generic continuous function of eight design variables. The results show that the optimal nonaxisymmetric functionally graded plate with a hole has a material distribution pattern similar to that found in bone, and the load-carrying capability of the plate can be greatly increased at small hole weight ratio#.
A review of the cutting of composite materials
Authors: Gordon S , Hillery M T
Published: April 2011

The increased use of composite materials has led to an increase in demand for facilities to machine them. There are significant differences between the machining of metals and alloys and that of composite materials, because composites are anisotropic, inhomogeneous and are mostly prepared in laminate form before undergoing the machining process. In most cases, traditional metal cutting tools and techniques are still being used. While the process of metal cutting has been well researched over the years, relatively little research has been carried out on the cutting of composite materials. This paper presents a brief review of research on the cutting of fibre reinforced polymer (FRP) composites and medium-density fibreboard (MDF). Most of the research published is concentrated on the chip formation process and cutting force prediction with unidirectional FRP materials. A review of some recent research on the prediction of cutting forces for MDF is also presented.
Lap shear strength comparison between different random glass fibre reinforced thermoplastic matrix composites bonded by adhesives using variable-frequency microwave irradiation
Authors: Ku H S , Siores E , Ball J A R , Taube A , Siu F
Published: April 2011

This paper compares the lap shear strengths of three types of random glass fibre reinforced thermoplastic matrix composite joined by adhesives using microwave energy. Variable-frequency microwave (VFM) (2-18 GHz) facilities are used to join 33 wt % random glass fibre reinforced low-density polyethylene composite [LDPE/GF (33%)], 33 wt % random glass fibre reinforced polystyrene composite [PS/GF (33%)] and 33 wt % random glass fibre reinforced nylon 66 composite [nylon 66/GF (33%)]. With a given power level, the composites were exposed for various times to microwave irradiation. The primer or coupling agent used was a 5 min two-part adhesive.
Manufacture of diamond-coated cutting tools for micromachining applications
Authors: Jackson M J , Gill M D H , Sein H , Ahmed W
Published: April 2011

Micro- and nanomachining cutting tools are currently being developed in order to extend the range of manufacturing technologies available to the micro and nano engineer. Conventional diamond tools used for grinding operations have a number of problems associated with heterogeneity of the crystallites, decreased cutting efficiency and short life. Micromachining cutting tools are manufactured by imbedding diamond particles into the tip of the microtool using a suitable binder matrix material. The use of a diamond coating may offer an improvement in microtool technology. Chemical vapour deposition (CVD) of diamond coatings onto a cemented tungsten carbide (WC-Co) substrate is difficult. Generally, the adhesion of the diamond coating to cemented carbide substrates is poor. It is reported that binder materials such as cobalt can suppress diamond growth and enhance graphitic deposits, which cause poor adhesion and low diamond nucleation density. The effects of process parameters such as filament position, filament and substrate temperature and pretreated substrate material on the coating properties have been investigated using a number of experimental techniques.
Characterization of new structural core materials based on vinyl ester and hollow ceramic microspheres
Authors: Ayers S R , Van Erp G M
Published: April 2011

A new class of structural core material has been developed at the University of Southern Queensland for applications of composite materials in civil and structural engineering. These materials combine polymer resins with hollow ceramic microspheres to produce core materials with high structural capacity at low cost. A number of prototype structural elements using these materials have displayed significant potential for application in civil engineering structures. An ongoing research programme has been initiated to improve fundamental understanding of these materials and to provide the knowledge required for broad utilization. This current study has investigated the behaviour of core material formulations based on vinyl ester resins and hollow ceramic cenospheres. Investigations have focused on identifying key relationships between the constituent materials and resulting mechanical properties of the core material. A variety of matrix and filler characteristics have been examined. This work has shown that, at the type of filler levels considered feasible for structural engineering applications (vf > 30 per cent), the behaviour of the material is largely determined by the filler particles, with only minimal influence from the matrix material. Further investigations are continuing to quantify these effects and to develop predictive models for key relationships.
Fatigue performance of undamaged and repaired composite sandwich beams
Authors: Mahdi S , Kinloch A J , Matthews F L , Crisfield M A
Published: April 2011

The behaviour of undamaged (i.e. as-manufactured) and repaired carbon fibre reinforced plastic (CFRP) sandwich beams loaded in cyclic four-point bending is described. Three repair configurations (one overlap and two scarf) were tested in tension and compression, and two repair systems (high- and low-temperature cure) were employed. The repaired beams always showed an inferior performance compared with the as-manufactured beams. The lifetime was dependent on the repair configuration, with the overlap repairs performing surprisingly well when loaded in compression. The degradation of stiffness with cycling was also investigated and was related to the microscopic evolution of damage.
Titanium matrix reinforced composites produced by hot pressing of plasma-sprayed preforms
Authors: Valente T , Picchiotti S , Bartuli C , Testani C
Published: April 2011

The present work is focused on the fabrication of long fibre reinforced titanium composites by hot pressing of plasma-sprayed preforms. Thermal spraying of two different metallic matrices [Ti-6Al-2Sn-4Zr-2Mo-0.08Si (Ti6242S) and Ti-4.5Al-3V-2Mo-2Fe (SP700)] onto prearranged silicon carbide long fibres was performed using controlled-atmosphere plasma spraying equipment (CAPS), allowing deposition processes also in the high-pressure range. After optimization of the plasma spraying procedure, composite multilayers were fabricated by hot pressing at 1200 bar with different combinations of process parameters (temperature in the range 850-940 °C, and application time from 30 to 45 min). Consolidated samples were characterized by microstructural investigation and tensile testing at room and high temperature (up to 600 °C). Push-out and push-back tests were performed to investigate interfacial properties.
Ultimate loading evaluation of rubber springs used in engine suspension
Authors: Luo R K , Wu W X , Mortel W J
Published: April 2011

Rubber springs are widely used in industry as antivibration components giving many years of service. The Metacone range of mountings is well established as an antivibration mounting, suitable for engine suspension, where vertical and horizontal movement is controlled within the design. The Metacone mountings manufactured at Trelleborg-AVS are designed for maximum load capacity combined with a large deflection in an axial direction. An integrated design procedure (including material and prototype testing and finite element (FE) analysis) has been carried out to evaluate the component unit to meet customer requirements. The geometry data were imported from a computer aided design (CAD) system to a computer aided engineering (CAE) system. A solid three-dimensional model with appropriate mesh was generated for FE analysis. Detailed stress analysis was conducted, and conclusions from the FE results suggested that the assembly of the Metacone mounting unit is safe for prototype testing. The ultimate load test on the prototype unit was carried out in the present authors' laboratory, and the result has shown that the component has met customer requirements. Now the products have been manufactured and delivered.
Modelling of joint effects on refractory lining behaviour
Authors: Gasser A , Terny-Rebeyrotte K , Boisse P
Published: April 2011

Expansion joints play an important role in refractory linings as they reduce stresses during heating. It is therefore necessary to take them into account in a mechanical analysis. In the case where the lining is a masonry construction (made up of bricks), it would require an excessive number of elements to model each brick and joint. The proposed solution is to replace the masonry with a material that has the same behaviour (or very near) as masonry. Since it is difficult to perform experimental tests on a set of bricks (to identify the parameters of the equivalent material), these loads were simulated on an elementary cell using a model developed at a local scale (scale of the components, bricks and joints). At this scale, the joints are represented as contacts (with normal and tangential behaviour). The parameters of a simplified equivalent material were obtained by an inverse identification. This model was validated by a thermomechanical test on a real structure.
Improving through-thickness properties of fibre reinforced plastics using novel shaped fibres
Authors: Harris J , Bond I , Weaver P , Wisnom M R
Published: April 2011

Novel shaped fibres are introduced as a means of improving the through-thickness properties of composite materials. Twelve qualitative guidelines for the geometry of novel shaped reinforcing fibres are described, and the bounds they place on fibre designs are discussed. The paper concludes by proposing a fibre design that conforms to the majority of the guidelines. Manufacturing methods for experimental quantities of fibre and composite have been developed. Extensive development and testing are now under way to demonstrate the benefits of novel shaped fibres.
Finite element analysis of the design of an elastomeric foam seal for an automotive air filter
Authors: Azhikannickal E , Wild P M
Published: April 2011

A polyurethane foam sealing bead used in an automotive air filter is examined in this study. The sealing bead provides a seal between the air filter and the two components of the rigid split air filter housing. Tearing of the seal during service is a common mode of failure. Finite element analysis is used to identify the high strain regions in the seal at full closure of the housing that may result in tearing. Alternate sealing bead designs are developed and modelled in which failure is less likely to occur. Critical seal/housing design issues are identified, such as the maximum strains due to closure of the housing, closure forces and effects and manufacturing tolerances on seal performance. Key trade-offs between these design issues are also identified.
Laboratory assessment of the resistance to crack propagation in high-stiffness asphaltic materials
Authors: Collop A C , Sewell A J , Thom N H
Published: April 2011

This paper describes laboratory work undertaken to measure the resistance to crack propagation of bituminous materials comprising a range of binder grades from different sources. The compact tension (CT) test has been adapted for use with bituminous materials, and an image analysis technique, based on digital photographs of the specimen taken during testing, has been used to quantify crack length. Linear elastic fracture mechanics (LEFM) principles have been used to calculate the mode I stress intensity factor (SIF), and the Paris law has been used to quantify crack growth. Results show that the general trend is for the Paris law exponent n to decrease and for the multiplier A to increase with increasing temperature for each of the materials, indicating that, the harder the bitumen, the greater is the sensitivity to overloading. A good correlation was found between the values of A and n, and also between the values of A in the Paris law and the stiffness modulus of the asphaltic mixture. It was found that mixtures containing the nominal 15 penetration grade binders were least sensitive to variations in stiffness of the mixture, and mixtures containing the nominal 35 and 50 penetration grade binders were most sensitive to variations in stiffness of the mixture. The number of standard wheel loads required to cause a crack to propagate through the asphalt layer of a typical minor and major flexible pavement structure have been estimated using data from the CT testing. Results show that there is a good correlation between the stiffness modulus of the asphalt mixture and the predicted number of load applications to failure. The predicted number of load applications to failure increases as the stiffness modulus of the asphalt increases.
Dielectric and mechanical studies of the durability of adhesively bonded aluminium structures subjected to temperature cycling. Part 1: Examination of moisture absorption
Authors: Pethrick R A , Armstrong G S , Banks W M , Crane R L , Hayward D
Published: April 2011

Dielectric measurements and mechanical tests on adhesively bonded joints are reported for bonds having been aged by complete immersion in water at 50 and 65 °C and by changing between these temperatures. Such joints have direct application to aircraft structures and other important engineering areas. The dielectric frequency domain measurements at 3 MHz are used to monitor moisture ingress into the adhesive bond. Initially the rate of change in the permittivity follows pseudo-Fickian behaviour consistent with simple moisture diffusion. In all the cases studied, acceleration in the rate of increase in the permittivity was observed consistent with the moisture converting the interfacial oxide layer to hydroxide. Time domain reflectometry (TDR) measurements indicate that physical changes occur in the bond line. Shear and cleavage measurements were performed at regular intervals and indicate a loss of mechanical properties of the bond. Comparison of the TDR measurements with ultrasonic and optical images indicated that the dramatic loss of mechanical properties is coincident with the observation of defects having been created in the interfacial layer. A correlation between certain of the mechanical properties and the change in the dielectric permittivity is observed.
Feasibility study of producing alumina foam by plasma spraying
Authors: Devasenapathi A , Ng H W , Tan G H
Published: April 2011

Plasma spraying was utilized as a tool to produce alumina (AI2 O3) foam based on a new methodology. Blended powder of A12 O3 and calcium oxide (CaO) of different composition was plasma sprayed on predesigned moulds. The sprayed specimens were subsequently treated in water and glycerol in an ultrasonic cleaner at 80°C selectively to dissolve CaO and retain the A12 O3 matrix. Microstructural investigation showed a slight porosity similar to that observed in the plasma-sprayed coatings in the assprayed untreated specimens, which after treatment in water and glycerol exhibited a considerable increase in the extent of porosity. X-ray diffractometry (XRD) studies confirmed the dissolution of CaO, giving rise to porosity, as exhibited by the presence of peaks corresponding to CaO in the as-sprayed material and its absence after water and glycerol treatments.
Dielectric and mechanical studies of the durability of adhesively bonded CFRP structures subjected to aging in various solvents
Authors: Banks W M , Pethrick R A , Armstrong G S , Crane R L , Hayward D
Published: April 2011

Dielectric and mechanical tests of adhesively bonded carbon fibre reinforced plastic (CFRP) joints aged in a series of solvents are reported. The solvent systems include; deicing fluids (ethylene glycol), aviation fuel, moisture, brine and paint strippers and solvents (dichloromethane and butanone). These measurements indicated that the ingress of the solvent leads to swelling of the joints and plasticization of the adhesive with consequential changes in the mechanical properties. A study of the drying process after the joints have been aged indicated that in certain cases it was possible for the mechanical properties of the joints to be recovered to almost their original values. In other cases the recovery was limited and reflected changes occurring within the adhesive layer. It was difficult to establish an unambiguous correlation between the dielectric constant of the bond and the change in the mechanical strength although in the case of water and ethylene glycol a correlation does appear to exist. The paper discusses the usefulness of the dielectric method for monitoring the ageing of CFRP adhesively bonded joints.
Three-dimensional stresses in adhesively bonded lap joints with non-identical adherends
Authors: Narasimhan S , Shenoi R A , Jeong H K
Published: April 2011

This paper is concerned with the three-dimensional stress distributions in adhesively bonded joints with non-identical adherends and different geometrical dimensions and materials. The constitutive relations for the adhesive are developed using a modified pressure-dependent von Mises yield function and elasto-plastic idealization for the experimental stress-strain curve. The adherends and adhesive layers are both modelled using 20-noded solid elements. Observations have been made in particular on peel and shear stresses in the adhesive layer. Finite element results are found to match reasonably well with analytical solutions. Peel, shear and bending stresses in the lap joint address the three-dimensional behaviour prevailing in the single lap joint structure.
Development of a polymer alloy of polystyrene (PS) and polyamide (PA) for building functional part based on selective laser sintering (SLS)
Authors: Yusheng Shi , Zhichong Li , Haixiao Sun , Shuhuai Huang , Fandi Zeng
Published: April 2011

Polystyrene (PS) powder materials may be directly used for selective laser sintering (SLS). The part sintered with PS has high dimension precision, but its tensile strength is very low, only 5-6 MPa, and its solvent resistance capability is not good, which cannot meet the demands of the functional parts. The part sintered with polyamide (PA) has high mechanical properties and excellent resistance capability, so PA is suitable for building functional parts. However, the precision of the SLS part sintered with PA is low crystallinity. Also, PA's price is very high (relative to PS powder). Colligating the properties of the two materials, PS and PA, a polymer alloy of PS and PA for building functional parts is developped. Using this alloy as the sintering material, some parts are sintered successfully and the tensile strength of the parts increases to about 14 MPa, which can meet the demands of some functional parts.
Impact strength of vinyl ester composites cured by microwave irradiation: Preliminary results
Authors: Cheng Y M , Ku H , Snook C , Baddeley D
Published: April 2011

The shrinkage of vinyl ester particulate composites has been reduced by curing the resins under microwave conditions. The reduction in the shrinkage of the resins by microwaves will enable the manufacture of large vinyl ester composite items possible. This project is to investigate the difference in impact strength between microwave cured vinyl ester particulate composites and those cured under ambient conditions. Drop weight impact tests will be used to achieve the aim of the project. The results show that the difference in the impact strength is minimal.
Finite element analysis of residual stress in plasma-sprayed ceramic coatings
Authors: Valente T , Bartuli C , Sebastiani M , Casadei F
Published: April 2011

A numerical study was carried out by finite element analysis (FEA) for the calculation of absolute values and through-thickness variation of residual stress originating in thermal spray coatings. The investigated deposit was an air plasma sprayed alumina coating sprayed on a carbon steel substrate previously coated with Ni20Al bond coat. Results show compressive residual in-plane stresses with linear through-thickness variation and tensile normal and shear stresses having a peak at the coating-substrate interface. The influence of deposition temperature on residual stress was also investigated. The experimental validation of the FEA model was carried out using a high-speed hole drilling technique, suitably adapted for the analysis of a multimaterial structure through FEA calculation of the required calibration coefficients. A very good agreement between simulated and measured stresses was obtained, inspite of the adopted simplification hypothesis.
Contentious Hotspots: Ecotourism and the Restructuring of Place at the Biosphere Reserve Ria Celestun (Yucatan, Mexico)
Authors: Córdoba Azcárate Matilde
Published: April 2011

Tourism mobilities, conservation, and development planning are central social processes in the restructuring of places. This paper will argue that this is especially manifest in Biosphere Reserves where global agendas are spatially articulated through the creation of ‘contentious hotspots’ or ‘heated spots’, that is, sites within the local in which global mobilities are condensed and constantly at play through the performance of disruptive practices. The paper draws evidence from the ethnographical account of two disputes at the Biosphere Reserve Ria Celestun (Yucatan, Mexico) where tourism mobilities and conservation planning have established the ria and the beach as those contentious hotspots where mobilities are concentrated, space and resources are appropriated, and locals and institutions fight to stay still.
The optimum dimensioning of an underwater manipulator for weld inspection
Authors: Asokan T , Seet G , Angeles J
Published: April 2011

The optimum dimensioning of an underwater inspection manipulator is discussed in this paper. The inspection of a weld seam using an alternating current field measurement (ACFM) probe was identified as a five-dimensional Cartesian task. Due to the forward positioning of the required workspace, this manipulator requires two additional axes to locate its base with respect to the weld seam. This leads to a seven-axis manipulator, comprising a two-axis launching stage and a five-axis dexterous inspection stage. The optimization of the architecture of the latter five-axis inspection manipulator is the subject of this paper. In optimizing the architecture, various postures of the manipulator during the inspection process were considered, which thus allows identification of the limiting values of the joint angles for maximum dexterity. The optimum link lengths to ensure the highest dexterity were then determined from the results of the analysis. It is shown that the weld seam diameter and the manipulator condition number can be used as the deciding parameters for determining the relative link lengths of the five-axis inspection stage of the manipulator.
Crest height statistics of storm waves in deep water
Authors: Wolfram J , Venugopal V
Published: April 2011

This paper presents wave crest statistics for storm waves in deep water obtained from data collected over the last 7 years using wave altimeters mounted on the North Alwyn fixed oil and gas platform in the northern North Sea. The evolution of wave characteristics during the rise, peak and, decay of storms has been examined and it has been found that, as storms develop, there tends to be a focusing of the directional energy as the peak of the storm is approached followed by a directional defocusing as it decays. The effect of this upon the normalized crest elevations has been examined and sample distributions of crest heights taken from the start, peak and end of storms show some differences that are discussed. Three crest elevation probability distribution models based on second-order wave theory have been examined using these data and found to produce quite good predictions of observed crest heights except in the most extreme values.
Ships may encounter high wind loads—a statistical assessment
Authors: Blendermann W
Published: April 2011

The wind loads on ships are treated under long-term wind conditions. Probabilities of high forces and moments are given. A probabilistic criterion for wind heeling levers is proposed.
Design, manufacture and testing of stiffened panels for marine structures using adhesively bonded pultruded sections
Authors: Davies P , Choqueuse D , Bigourdan B , Gauthier C , Joannic R , Parneix P , L'Hostis J
Published: April 2011

This paper presents results from a programme designed to evaluate the use of bonded pultrusion sections to replace overlaminated stiffeners on composite sandwich panels for marine applications. First, the existing solution is described and results from uniform pressure loading tests of these panels are presented. Second, the design of bonded pultruded stiffeners is discussed, including results from preliminary tests to evaluate adhesives, and finite element calculations to optimize stiffener geometry. Finally, results from tests on two bonded stiffened panels are given and failure loads and mechanisms are compared to predictions.
Structural mechanical testing of a full-size adhesively bonded motorboat
Authors: Baur P , Roy A , Casari P , Choqueuse D , Davies P
Published: April 2011

This paper describes the tests performed on a full-size motorboat to demonstrate the potential for adhesive bonding to replace overlaminated connections. Adhesive bonding resulted in a significant reduction in assembly time for bulkhead connections compared with overlamination. Drop tests and sea trials were performed using specially adapted strain gauge instrumentation. These indicated low adhesive joint strain levels, even for severe test conditions. No damage was observed. The data obtained will be used to improve laboratory test procedures to simulate service loading of boat structures.
Lessons learnt from designing and producing adhesively bonded prototyping structures in a shipyard
Authors: Cantrill J , Kapadia A , Pugh D
Published: April 2011

As part of a joint European research programme, VT Shipbuilding carried out extensive structural adhesive bonding of a prototype aluminium ship superstructure. The work was part of the Bondship project, entitled, ‘Bonding of lightweight materials for cost-effective production of high-speed craft and passenger ships’. The project involved developing optimized production procedures by assembling adhesive joints in a realistic shipbuilding environment. Optimized procedures were developed for adhesive application and assembly techniques. It was found that the greatest difficulty in the build process was accounting for joint misalignments caused by poor dimensional control of modular units. Techniques including the insertion of aluminium flat bar into the joint and adhesive injection were used to overcome this. Valuable lessons were learnt regarding surface preparation, adhesive dispensing and the optimum operating temperature.
The designer's dilemma: How to deal with the uncertainty about the long-term performance of adhesively bonded joints
Authors: Weitzenböck J R , McGeorge D
Published: April 2011

This paper discusses a new approach to dealing with the dilemma that many designers of bonded joints face. They cannot demonstrate the required long-term performance of their bonded joints. At the same time there are no practical applications of bonded joints to build up in-service experience of load-carrying adhesively bonded joints in shipbuilding.
Development of Project Wings Home Visits, a Mental Health Intervention for Latino Families Using Community-Based Participatory Research
Authors: Garcia Carolyn , Hermann Denise , Bartels Anna , Matamoros Pablo , Dick-Olson Linda , Guerra de Patino Janeth
Published: April 2011

As the Latino population in the United States experiences rapid growth, the well-being of Latino adolescents is a growing concern because of their high rates of mental health problems. Latino adolescents have higher rates of mental health problems than their peers, including depressive symptoms, suicide attempts, and violence. Sophisticated, realistic health promotion efforts are needed to reduce these risk behaviors and enhance protective factors. Parents and schools can be key protective factors, or assets, in adolescents’ lives. This article details the steps undertaken to develop Project Wings Home Visits, a collaborative school-based, community-linked mental health promotion intervention for Latino adolescents and their families. Core to the intervention is the use of a community health worker model to provide home-based outreach and education to parents of Latino adolescents. The intervention was developed using a community-based participatory research approach that involved the cooperation of a community health care system, a public high school, and a university. Our process demonstrates the benefits, strengths, and challenges of using community-based participatory research in creating and implementing health promotion interventions.