Finite Element Analysis of Ceramic Coatings under Spherical Indentation with Metallic Interlayer： Part Ⅰ Uncracked Coatings

Spherical indentation of ceramic coatings with metallic interlayer was performed by means of axisymmetric finite element analysis （FEA）. Two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel were considered. Various combinations of indenter radius-coating thickness ratios and interlayer thickness-coating thickness ratios were used in the modeling. The effects of the interlayer, the coating and the substrate on the indentation behavior, such as the radial stress distribution along the coating surface as well as the coating interface, and the plastic deformation zone evolution in the substrate were investigated in connection with the above mentioned ratios. The coating cracking dominant modes were also discussed within the context of the peak tensile stresses on the coating surface and on the coating interface.     

Element Analysis of Ceramic Coatings under Spherical Indentation with Metallic Interlayer:Part Ⅱ Ring Crack

Spherical indentation of ceramic coatings with metallic interlayer was performed by means of axisymmetric finite element analysis(FEA). Two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel were considered. The fracture mechanics of the ceramic coatings mechanisms due to occurrence of surface ring cracks extending traverse the coating thickness under spherical indentation are investigated within the framework of linear fracture mechanics. The J-integral associated to such cracks was computed. The evolution of J-integral vs the crack length and the indentation depth was studied. The effects of the interlayer, the coating and the substrate on the J-integral evolution were discussed. The results show that a suitable metallic interlayer can improve the fracture resistance of the coating systems under the same indentation conditions through reducing the J-integral.     

Element Analysis of Ceramic Coatings under Spherical Indentation with Metallic Interlayer：Part Ⅱ Ring Crack

Spherical indentation of ceramic coatings with metallic interlayer was performed by means of axisymmetric finite element analysis （FEA）. Two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel were considered. The fracture mechanics of the ceramic coatings mechanisms due to occurrence of surface ring cracks extending traverse the coating thickness under spherical indentation are investigated within the framework of linear fracture mechanics. The J-integral associated to such cracks was computed. The evolution of J-integral vs the crack length and the indentation depth was studied. The effects of the interlayer, the coating and the substrate on the J-integral evolution were discussed. The results show that a suitable metallic interlayer can improve the fracture resistance of the coating systems under the same indentation conditions through reducing the J-integral.     

Finite Element Analysis of Mechanical Properties of 3D Four-directional Rectangular Braided Composites—Part 2: Validation of the 3D Finite Element Model

In the first part of the work, we have established a new parameterized three-dimensional (3D) finite element model (FEM) which precisely simulated the spatial configuration of the braiding yarns and considered the cross-section deformation as well as the surface contact relationship between the yarns. This paper presents a prediction of the effective elastic properties and the meso-scale mechanical response of 3D braided composites to verify the validation of the FEM. The effects of the braiding parameters on the mechanical properties are investigated in detail. By analyzing the deformation and stress nephogram of the model, a reasonable overall stress field is provided and the results well support the strength prediction. The results indicate it is convenient to predict all the elastic constants of 3D braided composites with different parameters simultaneously using the FEM. Moreover, the FEM can successfully predict the meso-scale mechanical response of 3D braided composites containing periodical structures.     

Nonlinear Finite Element Analysis of Paper Movement in Air

1IntroductionWitl1thedevelopInentofsciencetuldtechnology,officeequipment,suchascopiersal1dpril1ters,havebeenbecomingindispensablet()olsinthepeople'sdailylifC.Butcoonol1lyencounteredfaultinrunningofficcequipment,paPerjaIn,isbringingaboutmuchtroubletotheusersandthelnakersofofficeequiplnent.AnalyzingtheworkprocessofofficeequipInent,wecanfil1dtliatthepaperalwaysbetransportedalongacomPlexpath-Duringthetransportatiol1,thepaPerisloadedonmanydifferentpositionswitl1diffeentfeedingforces.Ifthepathco…     

Tailoring Sandwich Face/Core Interfaces for Improved Damage Tolerance—Part I: Finite Element Analysis

Various modifications of the face/core interface in foam core sandwich specimens are examined in a series of two papers. This paper constitutes part I and describes the finite element analysis of a sandwich test specimen, i.e. a DCB specimen loaded by uneven bending moments (DCB-UBM). Using this test almost any mode-mixity between pure mode I and mode II can be obtained. A cohesive zone model of the mixed mode fracture process involving large-scale bridging is developed. Results from the analysis are used in Part II, which describes methods and results of a series of experiments.     

Failure Analysis of (± 55°)9 Filament-Wound GRE Pipes Using Explicit Finite Element Method: A Comparison with the Experimental Method

Journal of Failure Analysis and Prevention - In the present study, the progressive failure analysis of an industrial (± 55°)9 filament-wound glass fiber reinforced epoxy (GRE) pipe...     

Progressive damage and failure of mechanically fastened joints in CFRP laminates – Part I: Refined Finite Element modelling of single-fastener joints

This paper presents a refined Finite Element modelling for strength prediction, and especially bearing strength prediction, of mechanically fastened joints in CFRP laminates. Although the importance of delamination on the bearing strength of the joint is well established in the literature, only rarely has it been introduced into the models. In the present work, delamination onset and propagation are explicitly taken into account in the model by means of cohesive elements. The ply behaviour is described through a viscoelastic model combined with a progressive damage approach. A multi-model calculation strategy is developed to reduce the calculation costs. Prediction of the proposed model are compared to both bearing tests and open-hole tests results. For further validation, numerical predictions are also compared to filled-hole tensile tests and bearing/bypass interaction tests. Bearing, open-hole, and filled-hole tests are performed in this study. An original pin-bearing test configuration is proposed. Predicted strengths and experimental results turn out to be in good agreement. The obtained results are promising and demonstrate the capability of the proposed model to capture the material and stacking sequence effects on the joint behaviour and strength, as well as the influence of the geometrical dimensions of the joint.     

Analysis of Solidification in Spray Atomized and Codeposited Metal-matrix Composites Part Ⅰ: Atomization

Fluid mechanics, heat transfer and liquid-to-solid phase transformation are assessed in optimizing the spray atomization and codeposition process parameters for size refinement and microstructural uniformity of the deposited material. Atomization gas velocities, atomized droplets velocities, convective heat transfer coefficients, thermal histories of the solidifying droplets, freezing rates, fraction solid evolution and solid-liquid interface propagation velocity are calculated. The influence, on the deposit microstructural features, of process parameters like the atomization gas pressure, the pouring tube orifice diameter, the geometrical features of the atomization device,the potency of , pre-existing or injected as reinforcement, nucleation sites, the wetting angle between the liquid melt bnd impurity particles acting as preferred nucleation sites, the in-flight distance of the solidifying droplets in the atomization chamber, i5 evaluated. As a result of the evaluation, appropriate choice of the adjustable process parameters for the production of powders and/or deposits with desired grain size and microstructure, can be made.     

Failure Analysis and Finite Element Simulation of Above Ground Oil–Gas Pipeline Impacted by Rockfall

Pipeline is the most important transmission way of oil and gas. Rockfall impact is one of the factors that result in above ground oil–gas pipelines accidents. Deformation of oil–gas pipeline caused by rockfall impacts were investigated using finite element method. Pipeline deformation caused by spherical and cube rockfalls were discussed under radial impact, inclined impact, and eccentric impact. The results show that crater depth of spherical rockfall impact is bigger than the cube rockfall with the same volume. The smaller curvature radius of rockfall’s contact zone has a greater harm to oil–gas pipeline. Angle part impact of irregular rockfall is very harmful for oil–gas pipeline. Under inclined impact, the maximum plastic strain of spherical rockfall impact crater appears when incidence angle α is 45°. Pipeline is prone to rupture when α is small under cube rockfall impact. The plastic strain distribution of the impact crater is more uneven with the increasing of the incidence angle. Plastic strain zone of pipeline decreases with the increasing of eccentricity k under eccentric impact.     

Compliant flexural behaviour in laser sintered nylon structures: Experimental test and Finite Element Analysis – correlation

The aim of this paper is to present a simple and easily tuneable method of creating compact structures with gradient flexural properties using Selective Laser Sintering (SLS). The method makes use of a sine-wave ridged pattern commonly found in nature which produces a compliant bending pattern along various directions defined by the reference axes. These patterns have been adopted due to the ease with which it is possible to parametrically control the height, width, pitch and thickness of the designed structure. A series of 3-point bending tests and finite element analyses of flat and ridged specimens have been performed in order to obtain more appropriate material definition for the inclusion of such patterns into more complex structures.Results show that a parametrically defined ridged pattern has the ability to induce passive bending behaviour on structures. Differences in bending stiffness between 20% and 50% were observed for the directions parallel and perpendicular to the ridged pattern lines and a capacity to redistribute stresses across the bending specimen was highly dependent on the ridged pattern direction.     

The Melting Point of Palladium Using Miniature Fixed Points of Different Ceramic Materials: Part II—Analysis of Melting Curves and Long-Term Investigation

Fifteen miniature fixed-point cells made of three different ceramic crucible materials (\(\hbox {Al}_{2}\hbox {O}_{3}\), \(\hbox {ZrO}_{2}\), and \(\hbox {Al}_{2}\hbox {O}_{3}(86\,\%)+\hbox {ZrO}_{2}\)(14 %)) were filled with pure palladium and used to calibrate type B thermocouples (Pt30 %Rh/Pt6 %Rh). A critical point by using miniature fixed points with small amounts of fixed-point material is the analysis of the melting curves, which are characterized by significant slopes during the melting process compared to flat melting plateaus obtainable using conventional fixed-point cells. The method of the extrapolated starting point temperature using straight line approximation of the melting plateau was applied to analyze the melting curves. This method allowed an unambiguous determination of an electromotive force (emf) assignable as melting temperature. The strict consideration of two constraints resulted in a unique, repeatable and objective method to determine the emf at the melting temperature within an uncertainty of about \(0.1\,\upmu \hbox {V}\). The lifetime and long-term stability of the miniature fixed points was investigated by performing more than 100 melt/freeze cycles for each crucible of the different ceramic materials. No failure of the crucibles occurred indicating an excellent mechanical stability of the investigated miniature cells. The consequent limitation of heating rates to values below \({\pm }3.5\,\hbox {K}\,\hbox {min}^{-1}\) above \(1100\,{^{\circ }}\hbox {C}\) and the carefully and completely filled crucibles (the liquid palladium occupies the whole volume of the crucible) are the reasons for successfully preventing the crucibles from breaking. The thermal stability of the melting temperature of palladium was excellent when using the crucibles made of \(\hbox {Al}_{2}\hbox {O}_{3}(86\,\%)+\hbox {ZrO}_{2}(14\,\%)\) and \(\hbox {ZrO}_{2}\). Emf drifts over the total duration of the long-term investigation were below a temperature equivalent of about 0.1 K–0.2 K.     

Analysis of Hydrogen Diffusion in Metals with Trapping under Local Equilibrium Assumption

The assumption of the local equilibrium ofhydrogen distribution in metals[1]was used in themodel formerly developed[2]to describe the diffu-sion of hydrogen in metals.From the assumption adirect relationship between the hydrogen diffusivityand the hydrogen concentration in metals is estab-lished asD=D_o/{1+N_x(k/p)/[1+C(k/p)]}The comparison between the two results drawnfrom the assumption of equilibrium and the dynam-ics of hydrogen trapping[3]was also presented.Thecomputation results well explained the scatteringphenomenon existed in hydrogen diffusion data andsuggested that the experimental conditions shouldbe identical for the study of hydrogen permeation inmetals.     

Modification of NiCoCrAlY with Pt: Part Ⅰ. Effect of Pt depositing location and cyclic oxidation performance

Pt layers of 5 μm in thickness were electroplated before or after depositing NiCoCrAlY coating by arc ion plating(AIP) aiming for identifying the effect of Pt enriching position on microstructure and cyclic oxidation behavior of Pt modified NiCoCrAlY coatings. Al-rich zones formed at the same position of Ptrich zones for both modified coatings due to uphill diffusion of Al driven by Pt. Cyclic oxidation tests at 1000 and 1100?C indicated that oxidation resistance of NiCoCrAlY was improved by Pt modification via different mechanisms: at surface, Pt-rich zone promoted selective oxidation of Al to form α-Al_2O_3,whilst at coating/substrate interface Pt-rich zone acted as effective diffusion barrier for titanium. Roles of Pt played in enhancing the oxidation performance of various Pt-modified NiCoCrAlY coating were investigated.     

Size effects in concrete fracture – Part II: Analysis of test results

This paper presents an analysis of the extensive experimental program aimed at assessing the influence of maximum aggregate size and specimen size on the fracture properties of concrete. Concrete specimens used were prepared with varying aggregate sizes of 4.75, 9.5, 19, 38, and 76mm. Approximately 250 specimens varying in dimension and maximum aggregate size were tested to accomplish the objectives of the study. Every specimen was subjected to the quasi-static cyclic loading at a rate of 0.125mm/min (0.005in./min) leading to a controlled crack growth. The test results were presented in the form of load-crack mouth opening displacement curves, compliance data, surface measured crack length and crack trajectories as well as calculated crack length, critical energy release rate, and fracture toughness (G ₁). There is a well pronounced general trend observed: G ₁ increases with crack length (R-curve behavior). For geometrically similar specimens, where the shape and all dimensionless parameters are the same, the R-curve for the larger specimens is noticeably higher than that for the smaller ones. For a fixed specimen size, G ₁ increases with an increase in the aggregate size (fracture surface roughness). For the same maximum aggregate size specimens, the apparent toughness increases with specimen size. It was clear that the rate of increase in G ₁, with respect to an increase of the dimensionless crack length (the crack length normalized by the specimen width), increases with both specimen size and maximum aggregate size increase. The crack trajectory deviates from the rectilinear path more in the specimens with larger aggregate sizes. Fracture surfaces in concrete with larger aggregate size exhibit higher roughness than that for smaller aggregate sizes. For completely similar specimens, the crack tortuosity is greater for the larger size specimens. The crack path is random, i.e., there are no two identical specimens that exhibit the same fracture path, however, there are distinct and well reproducible statistical features of crack trajectories in similar specimens. Bridging and other forms of crack face interactions that are the most probable causes of high toughness, were more pronounced in the specimens with larger maximum size aggregates.     

The Melting Point of Palladium Using Miniature Fixed Points of Different Ceramic Materials: Part I—Principles and Performances

Fifteen miniature fixed-point cells made of three different ceramic crucible materials (\(\hbox {Al}_{2}\hbox {O}_{3},\, \hbox {ZrO}_{2}\), and \(\hbox {Al}_{2}\hbox {O}_{3} (86\,\%)+\hbox {ZrO}_{2}\) (14 %)) were filled with pure palladium and used for the calibration of type B thermocouples (Pt30%Rh/Pt6%Rh). The melting behavior of the palladium was investigated by using different high-temperature furnaces usable in horizontal and vertical positions. It was found that the electromotive forces measured at the melting temperature of palladium are consistent with a temperature equivalent of ±0.25 K when using a furnace with an adequate temperature homogeneity (±1 K over a length of 12 cm), independent of the ceramic crucible materials. The emfs measured in the one-zone furnaces with larger temperature gradients along the crucibles are sensitive related to the position of the crucibles in the temperature gradient of these furnaces. This is caused by higher parasitic heat flux effects which can cause measurement errors up to about \(\text {-}\)(1\(\text {-}\)2) K, depending on the thermal conductivity of the ceramic material. It was found that the emfs measured by using crucibles with lower thermal conductivity \((\hbox {ZrO}_{2})\) were less dependent on parasitic heat flux effects than crucibles made of material of higher thermal conductivity \((\hbox {Al}_{2}\hbox {O}_{3})\). The investigated miniature fixed points are suitable for the repeatable realization of the melting point of palladium to calibrate noble metal thermocouples without the disadvantages of the wire-bridge method or the wire-coil method.