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 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.     

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.     

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.     

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.     

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.     

Phosphogypsum Utilization Part Ⅱ: Preparation of Ammonium Sulphate

1.IntroductionIn0urprevi0usinvestigation,phosph0gypsum(PG)producedfromthediss0luti0nofsabyiaph0s-phateore(Sabyiaregion,Egypt)inH2SO4bythedihydrateprocess,wascharacterizedusingX-raydiffraction,chemicalanalysis,thermogravimetricandinfraredtechniquesI1].Theresultsofthischaracter-izationindicatedthatphosph0gypsumwasformedmainlyofgypsum,0.8%P2O5and185x1O-6rareearthelementsandfreefrombothradioactiveele-mentsandCdwhichfavouredtheutilization0fPGasarawmaterialf0rpreparati0n0fsomeusefulcom-pounds.…     

Analysis of Solidiflcation in Spray Atomized and Codeposited Metal-matrix Composites Part Ⅱ: Reinforcement Injection and Deposition

The influence of the injection of reinforcing particles (for the production of metal matrix composites and of the droplets-to-substrate heat transfer on the resulting microstructural uniformity of spray atomized and codeposited composite material is analyzed. The reinforcement particles injection velocity has to be limited between an upper and a lower critical values. in order to ensure entrapment into the matrix droplets in flight. The thermal history of the injected droplets during the deposition stage is calculated with the assumption that the in-flight solidifying droplets reach the substrate while containing still at least 20% liquid volume fraction, in order to avoid porosity of the deposited material. The substrate to pouring-tube orifice distance where that condition is achieved depends strongly on the atomization pressure and the convective heat transfer coefficient of the substrate. It is demonstrated that \"tailoring\" the microstructures and the reinforcement volume percent in the deposited material is feasible. The critical process parameters : the atomization pressure, the melt flow rate. the substrate to pouring-tube orifice distance, the reinforcement particles injection location and rate can all be adequately chosen in order to obtain any desired microstructure, grain size, reinforcement volume percent, with the additional benefit, if wanted, of rapid solidification processing     

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.     

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 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...     

Analysis of Heat Stresses of the Parts of the Cylinder–Piston Group with Heat‐Protective Coatings in an Internal‐Combustion Engine

The process of heat exchange in the cylinder of an internalcombustion engine has been investigated and the heat stresses of the working surfaces of the piston and the cylinder head have been analyzed. A method for calculating the heat resistance, the strength, and the thickness of heatprotective coatings has been developed. Results of thermalcycle testing of a piston with heatresistant coatings, the properties of which were calculated by the method proposed, are presented.     

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.     

Round-Robin test on chloride analysis in concrete—Part I: Analysis of total chloride content

The present paper gives part of the results of a Round Robin Test on chloride analysis in concrete, carried out by the Technical Committee TC 178-TMC. In this RRT, the analysis of total chloride, free chloride and the colourimetric determination of the front of chlorides in concrete have been tested. This paper reports the results corresponding to total chloride content. Water soluble chloride and colourimetric front are reported respectively in Parts II and III of the paper. A total of 30 laboratories around the world have participated in this RRT, and a total determination of 64 different analyses on triplicate specimens have been carried out. The procedure for the analysis of total chloride has been divided into two steps: extraction and analysis, discriminating the relability of the procedure followed in each of them. Two different methods of extraction of total chloride from the solid sample (A1 and A2) as well as six different forms of analysing the resulting liquids (C1 to C6) have been tested. It was also decided that other methods could also be used to the choice of each laboratory, as “other methods” (A3 and C7 for extraction and analysis respectively). (The complete recipes of these methods can be found in Annex 1 of the paper.) The statistical treatment of the data has been carried out according to the International Standard ISO 5725-1981 (F) for the determination of the reliability of testing methods: “Determination of the repeatability and reproducibility by Round Robin tests”. As a final result the methods of extraction and analysis recommended for total chlorides have been the following: C1-C1, A2-C4^*, A2-C7, A3-C4^* and A3-C7.     

Thermomechanical transformation fatigue of TiNiCu SMA actuators under a corrosive environment – Part I: Experimental results

In this two-part paper, the thermomechanical fatigue of TiNiCu shape memory alloy (SMA) wire actuators undergoing thermally induced martensitic phase transformation in a corrosive environment is investigated. The main objective of this work is to evaluate the cyclic response and fatigue behavior of TiNiCu SMA wire under corrosive conditions and to compare it to results obtained for fatigue testing in a corrosion-free environment. Part I focuses on the various experimental aspects of this work, including the presentation of fatigue results as a function of various testing parameters. The variable test parameters are five applied stress levels from about 50 MPa to about 250 MPa, and two different actuation strains, one corresponding to full actuation or complete transformation and the other to partial transformation. The results from fatigue testing in a corrosive environment show a consistent reduction of the fatigue life compared to corrosion-free fatigue results, in both complete and partial transformation conditions. It is also observed that corrosion-assisted fatigue leads to more scattered fatigue data and this spread is mostly attributed to enhanced and accelerated damage mechanisms due to corrosion. From these conclusions, a microstructure evaluation is performed to understand the damage that contributes to lower fatigue limits under corrosion and is presented in Part II of this work. Fracture surfaces, development of fatigue cracks and effect of corrosion are presented and discussed. The conclusion from the microstructure analysis has led to the formulation of a damage accumulation model accounting for a cyclic corrosion mechanism. This modeling approach allows for determining the fatigue life reduction of SMA wire actuators in a corrosive environment. All results of the microstructure analysis and fatigue life modeling are presented in Part II.     

Performance of steel beams strengthened with CFRP laminate – Part 1: Laboratory tests

Research on the behaviour of beams strengthened with different configurations of carbon-fibre-reinforced-polymer (CFRP) laminates, in both the serviceability and ultimate limit state, has been conducted at Chalmers University of Technology. Additionally, the failure modes and the interfacial shear stresses in the bond line have been studied. The methods used in the research work were laboratory tests and simplified analytical solutions and the work took the form of parametric studies on the strengthened steel beams. CFRP laminates and epoxies with different material properties were attached to the tension flange of steel beams with I cross-sections. The strengthened beams were tested in four-point bending where the deflection of the beams and the strains, in both the steel beams and the laminates, were measured. The results show that it is possible to increase the moment capacity of a steel beam with CFRP bonded to its tension flange. Additionally, it is possible to predict the degree of increase in capacity by using simplified analytical solutions.     

Performance of steel beams strengthened with CFRP laminate – Part 2: FE analyses

A new method for repairing and strengthening steel is under development and consists of using CFRP (carbon-fibre-reinforced-polymer) laminates bonded to the steel substrate. Research on this method has been conducted by a few research groups in recent years. The idea is to let the CFRP laminate carry a large part of the stresses and thereby reduce the load on the steel, which may have had its capacity lowered due to deterioration or fatigue. The present paper presents the results of FE analyses of steel beams strengthened with bonded CFRP laminates. The interfacial shear and peeling stresses that appear in the bond line between the steel and CFRP laminate are studied in both the elastic and plastic phase of the steel beam. Comparisons with the results obtained from laboratory tests conducted on steel beams strengthened with bonded CFRP laminates show that the behaviour of the strengthened beams can be captured using FE analyses. The distribution of the shear and peeling stresses near the end of the bond line were obtained from the FE analyses, together with the interfacial stresses that develop near beam mid-span due to the yielding of the steel. These stresses may exceed the capacity of the adhesive and cause debonding in this region.     

Round-robin test on chloride analysis in concrete — Part II: Analysis of water soluble chloride content

In Part I of this paper, general trends in the realisation of this Round Robin Test on chloride analysis in concrete (carried out as part of the work developed by the Technical Committee TC 178-TMC), as well as the results corresponding to total chlorides were given. The present paper reports the results corresponding to the extraction of water soluble chlorides. Results concerning the determination of the penetration front of chlorides by colourimetric techniques will be given in Part III. A total of 30 different laboratories around the world have participated in this Round Robin Test. All of them have performed analyses of total chlorides, having performed 64 different determinations of total chlorides in triplicate specimens. Among them, 20 laboratories have analysed water soluble chlorides. The total number of different determination of free chlorides, in triplicate specimens, has been of 37. Concerning the colourimetric method, 7 laboratories have taken part in the determinations, being the total number of different determinations of the colourimetric front, of 10. Two different methods of extraction from the solid sample (B1 and B2) have been tested. It was also decided that other methods could also be used to the choice of each laboratory, as “other methods” (B3). (The complete recipes of these methods can be found in Annex 1. The statistical treatment of the data has been carried out according to the International Standard ISO 5725-1981 (F) for the determination of the reliability of testing methods: “Determination of the repeatability and reproducibility by Round Robin tests”. Finally, it has been concluded that both methods, B1 and B2, are reliable enough to extract water soluble chlorides from concrete. However the method that each laboratory currently uses (other methods) is not recommendable.