An Elementary Plate Theory Prediction for Strain Energy Release Rate of the Constrained Blister Test

A technique based on elementary plate theory is proposed for estimating the strain energy release rate of the constrained blister specimen for the case of a relatively stiff blister adherend. The results of finite element analysis for an aluminum specimen confirm the applicability of the elementary plate theory approach for the constrained blister test. The paper also proposes an experimental scheme which could be automated to measure the necessary parameters to determine the strain energy release rate of the constrained blister specimen.     

An Elementary Plate Theory Prediction for Strain Energy Release Rate of the Constrained Blister Test

A technique based on elementary plate theory is proposed for estimating the strain energy release rate of the constrained blister specimen for the case of a relatively stiff blister adherend. The results of finite element analysis for an aluminum specimen confirm the applicability of the elementary plate theory approach for the constrained blister test. The paper also proposes an experimental scheme which could be automated to measure the necessary parameters to determine the strain energy release rate of the constrained blister specimen.     

A Simple Constant Strain Energy Release Rate Loading Method for Double Cantilever Beam Specimens

A simple loading arrangement is proposed to permit nearly constant strain energy release rate testing of double cantilever beam specimens. The inexpensive arrangement may be well suited to long term and environmental exposure testing of these specimens. An added advantage of the technique is that it also provides an attractive method to measure debond length. The geometrically nonlinear loading device provides constant strain energy release rate loading under idealized conditions. Analysis of the technique for realistic conditions reveals the appropriate test window for the device, and allows design guidelines to be developed. Experimental evaluation confirms the analytical predictions.     

The Constrained Blister—A Nearly Constant Strain Energy Release Rate Test for Adhesives

A modification of the blister test permits nearly constant strain energy release rate testing of adhesive bonds. By constraining the deformation of the blister, a promising device for automated evaluation of critical strain energy release rates can be obtained. The procedure is especially amenable to viscoelastic and environmentally-assisted debonding processes. Preliminary experimental evaluation of the time-dependent adhesive fracture toughness of a tape product is included.     

Determining Stability Constants Using the AKUFVE Technique

ABSTRACT

The AKUFVE techniques were developed by Rydberg and co-workers in the 1960s. The main aim was to be able to perform a series of liquid-liquid extraction data varying one or more parameters and at the same time achieve very pure phases. As such, this technique was later used for short-lived isotope studies in the SISAK system, but also as a standalone unit for a large number of thermodynamic studies of extraction systems both for fundamental understanding as well as more applied investigations. In this paper, the apparatus with modifications made over the decades is described. In addition, studies with stability constant determinations for the zirconium-water-acetylacetone system as well as lanthanide extraction using bromodecanoic acid are exemplified to demonstrate the potential use of the technique. The results shown clearly demonstrate the versatility and ability of the AKUFVE system.     

The Peninsula Blister Test: A High and Constant Strain Energy Release Rate Fracture Specimen for Adhesives

An extension of the island blister developed by Allen and Senturia to a peninsula-like geometry produces a fracture test which retains the very high strain energy release rates which are possible with the island blister, and also results in a constant strain energy release rate test for adhesive bonds. Analytical solutions are provided for predicting the strain energy release rates for this peninsula blister specimen when the blister adherend may be considered a plate, a pre-stressed membrane, and a simple membrane. Preliminary experimental results for a PSA tape are also presented. The analytical results suggest that the specimen may be extended to a variety of practical adhesive systems.     

Determination of Residual Stress Profile Using a Strain Gage Technique

A simple beam theory analysis is presented for the determination of residual stress patterns in beams or plates using a strain gage technique. The analysis is valid for a general stress distribution which need not be symmetric with respect to the neural axis. The experimental approach consists of attaching a strain gage on the surface of a beam or a plate and then grinding off the other side. The recorded strain vs thickness ground off data can be used to determine the corresponding stress profile.     

The Critical Energy Release Rate of Welded Joints Between Fiber-Reinforced Thermoplastics and Metals When Thermal Residual Stress is Considered

Thermal effects on welded joints between fiber-reinforced thermoplastics (FRTPs) and metals have been investigated theoretically and experimentally. Because FRTPs use thermoplastics as the matrix resin, they have advantages over fiber-reinforced thermoset plastics (FRPs or FRSPs), including the ability to be welded. When dissimilar materials are welded together, however, thermal stress occurs due to the different thermal expansions of the materials and affects the energy release rate of the joint. Therefore, a method for evaluating the true energy release rate, including the effect of thermal stress, is necessary for strength evaluation tests. Although several theories that compensate for the thermal stress and evaluate the true energy release rate have already been proposed, they require parameters that are difficult to measure. Therefore, it is difficult to apply them in experimental investigations. In this article, a theoretical method with easily measurable parameters is proposed to calculate the energy release rate of welded double cantilever beam (DCB) joints. The effect of the thermal stress on the critical energy release rate is discussed in terms of the experimental results of a welded DCB specimen composed of a FRTP and an aluminum alloy.     

Analytical and Numerical Calculation of the Energy Release Rate for the Microbond-Test

The energy release rate for interface crack propagation for the Microbond-Test specimen is calculated by using several stress analysis methods. For the corresponding finite element calculation an axisymmetrical model (elliptical droplet) and linear elastic material properties are used. The analytical approximations use several stress analysis methods to obtain the energy release rate.

The resulting energy release rate curves suggest that the debonding process can be described at least partially as a stable crack propagation along the interface. Some experiments confirm this prediction. The matrix droplet contribution to the energy release rate can be considerable. Because of the very complex stress fields in the droplet a simple analytical approximation cannot be given. The qualitative dependences on the material properties and on the geometry can be explained from the presented analysis. The remaining correction factor can be obtained from a numerical calculation.     

Determination of the Elastic Modulus and Residual Stresses in Ceramic Coatings Using a Strain Gage

Formulas based on the beam theory are derived for calculating the in-plane elastic modulus and residual stresses in ceramic coatings. In addition to theoretical derivation, experimental data for SiC coating/graphite substrate composites are proposed. The results indicate that the modulus of SiC coatings is 359 GPa. The residual stresses are in compression and are functions of the ratio of substrate thickness to coating thickness.     

Rate Effects in Critical Loads for Radial Cracking in Ceramic Coatings

Rate effects in the Hertzian contact loading of model glass/polycarbonate and silicon/polycarbonate bilayers bonded by epoxy adhesive are examined. Glass is used because of its high susceptibility to slow crack growth, making this conventional contribution to the rate dependencies easy to distinguish. Silicon is used as a control material with effectively no slow crack growth. Abrasion damage is introduced into the undersurfaces of the brittle coating layers to provide controlled flaws for the initiation of radial cracks from flexural stresses introduced by the contact loading. Critical loads are measured as a function of loading rate. Comparative flexural strength tests on free-standing abraded specimens show a pronounced rate dependence in the glass but none in the silicon, entirely consistent with slow crack growth effects. The glass/polycarbonate bilayer critical load data show a similar trend, but with stronger loading-rate dependence, suggesting an extraneous contribution to the kinetics from the adhesive/substrate. The silicon/polycarbonate bilayer data also show a loading-rate dependence, albeit much smaller, confirming this last conclusion. Data from cyclic contact tests on the glass/polycarbonate bilayers coincide with the loading-rate data on lifetime plots, eliminating the likelihood of a mechanical component in the fatigue response. It is concluded that the adhesive/substrate contribution is viscoelastic in nature, from energy-dissipating (but noncumulative) anelastic deformation during the cyclic loading. Critical load tests on bilayers with different exposures to external water show no influence of external environment, suggesting that internal moisture is responsible for the slow crack growth in the glass-coating bilayers.     

防污涂料的环境风险评估与杀生剂释放率分析

介绍了有关防污涂料的环境风险评估的基本情况,以及目前采用的用于防污涂料中的杀生剂释放率的分析方法——旋转柱体实验方法与杀生剂物质恒定的计算方法,并将两种方法的特点进行了对比。结果表明,物质恒定的计算方法体现出对于环境风险评估的适用性。     

Phase Transformations of Plasma-Sprayed Zirconia–Ceria Thermal Barrier Coatings

Phase constituents and transformations of plasma-sprayed thermal barrier coatings (TBCs) with CeO₂-stabilized ZrO₂ (CSZ; 16–26 wt% CeO₂) have been investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The as-coated CSZ coatings with 16 and 18 wt% CeO₂ consisted only of the nonequilibrium tetragonal ( t ') phase. A mixture of the t ' and the nonequilibrium cubic ( c ') phases was observed for the as-coated CSZ coatings containing 20–26 wt% CeO₂. During 65 min cyclic oxidation at 1135°C (45 min hold time) in air, the t ' or the mixture of the t ' and the c ' phases decomposed to the equilibrium tetragonal ( t ) and the equilibrium cubic ( c ) phases. Some of the t phase transformed to the monoclinic ( m ) phase on cooling. More m phase was observed to develop in the CSZ coating containing 16 wt% CeO₂ than in the other coatings. More m phase was observed on the top surface than on the bottom surface of the CSZ coating. Spalling of the plasma-sprayed CSZ coating during thermal cycling occurred after 230 cycles for the CSZ coating containing 16 wt% CeO₂, whereas the lifetime of the CSZ coatings with 18–26 wt% CeO₂ ranged between 320 and 340 cycles.     

Measuring the Drying Rate of Liquid Film Coatings Using Heat Flux Method

We propose a simple method of determining solvent drying rates from heat flux measurements across thin liquid films. The theory is based on quasi-steady conductive heat transport through coatings, combined with simultaneous heat and mass transfer in the gas phase. The measured evaporation rates well reproduce conventional gravimetric measurements with an uncertainty of less than 5%. Drying experiments also revealed that the proposed method is robust in systems with high levels of fluctuation and thus provides an alternative tool for monitoring drying kinetics in forced air flows.     

Effects of Plasma-Sprayed Ceramic Coatings on the Strength Distribution of Silicon Carbide Materials

Sintered α-silicon carbide and siliconized silicon carbide tubular materials were plasma-spray coated with various ceramic oxides using conventional air plasma-spraying technology. The strength distributions of the coated tubes were evaluated by fracturing samples at room temperature using a c-ring test configuration. Changes in strength are explained using statistical treatments of the data, including a Weibull approach. Failure origins are characterized using fractography via scanning electron microscopy. The stength of plasma-spray coated SiC was equivalent or superior to that of as-received material, despite a surface pretreatment which induced surface flaws in the SiC substrate.     

A Theoretical Study of Thin Film Delamination Using Clamped Punch-Loaded Blister Test: Energy Release Rate and Closed-Form Solution

Using an exact analytical solution of axisymmetric deformation of a circular membrane centrally connected to a rigid plate under the action of concentrated load at its center, we present an exact formula for the energy release rate applicable to ultrathin film–substrate systems without residual stresses or with small residual stresses. Also, a closed-form solution of axisymmetric deformation of circular membrane under the action of concentrated load at its center is presented.     

An End-Loaded Shear Joint (ELSJ) Specimen to Measure the Critical Energy Release Rate in Mode II of Tough,Structural Adhesive Joints

This paper introduces a newly developed specimen type, which is used to measure the critical energy release rate of tough, structural adhesives loaded in shear. This End-Loaded Shear Joint (ELSJ) specimen is loaded until a shear crack propagates through the adhesive layer. When the crack propagation is stopped, by unloading the specimen, the critical energy release rate in mode II, G _IIc, can be obtained by correlating the energy dissipated during the test and the measured crack area on the fracture surface of the specimen. The paper presents the dimensions of the ELSJ specimen, the corresponding test setup and the evaluation method used to obtain G _IIc. An overview of the advantages and the limitations of the new specimen type shows the need for its development and improvement when compared to some state of the art experiments. The first results of ELSJ tests are shown and discussed, using the crash-optimized structural adhesive — Henkel Terokal 5077. The experimental results presented, focus on thin adhesive layers and quasi-static test velocities.     

氟树脂防粘涂料的自分层性

利用俄歇电子能谱、红外光谱和电镜分析了研制的单层氟树脂防粘涂料的涂层内部变化,证实了涂层存在浓度梯度分布和自分层性。     

激光重熔等离子喷涂NiCr-Cr3C2涂层微观结构和性能研究

利用扫描电镜(SEM)、能谱仪(EDS)、显微硬度计及金相分析软件,对等离子喷涂NiCr-Cr3C2涂层激光重熔前后的显微组织结构、硬度和孔隙率变化进行研究,并探讨不同扫描速度对激光重熔效果的影响.结果表明:利用激光重熔NiCr-Cr3C2陶瓷涂层,能够有效提高涂层的硬度和致密度,减少孔隙率;研究条件下1.5m/min的扫描速度时激光重熔效果最好.     

Origin of Darkening in 8 wt% Yttria—Zirconia Plasma-Sprayed Thermal Barrier Coatings

The origins of darkening of 8 wt% Y₂O₃-ZrO₂ air plasmasprayed (APS) and low-pressure plasma-sprayed (LPPS) thermal barrier coatings (TBC) have been studied using X-ray photoelectron spectroscopy. The change of valence states of zirconium, due to the reduction of ZrO₂ to Zr₂O₃, was responsible for darkening of TBC. Quantification of Zr³⁺ oxide was related both to the black color of TBC and to the spraying technologies and parameters. Furthermore, impurity (Fe, Al, Si, and Na) segregation and exsolution phenomena were monitored as a function of the air thermal treatment (up to 1473 K) and it was demonstrated not to be the origin of darkening.