Shear bond strengths of six different porcelain laminate veneer materials cemented to enamel with two different MDP-containing resin cements

Purpose: To compare the shear bond strengths of six different porcelain laminate veneer (PLV) materials cemented to enamel with two different MDP-containing resin cements. Materials and methods: Totally 120 disc specimens were fabricated with In-Ceram alumina (ICA), Turkom-Cera^TM (TCR), IPS Empress (IPS), IPS Empress-II (IPS2), Finesse (FNS), and Ceramco-3 (CER) ceramic systems (n = 20). Sixty specimens were cemented with self-adhesive resin cement (Clearfil SA), and 60 specimens were cemented with self-etch resin cement (Panavia F2.0) to enamel. Thus, 120 PLV–enamel specimens were assigned to 12 experimental groups (ICA/Pv, ICA/Cf, TCR/Pv, TCR/Cf, IPS/Pv, IPS/Cf, IPS2/Pv, IPS2/Cf, CER/Pv, CER/Cf). Shear force was applied on PLV–enamel interfaces until failure. Obtained data were statistically analyzed with ANOVA and t-tests. Results: Obtained shear bond strength values (SBSV) ranged as follows, respectively; TCR/Cf (7.70 MPa), FNS/Cf (7.57 MPa), TCR/Pv (6.91 MPa), ICA/Pv (5.05 MPa), CER/Pv (4.75 MPa), IPS2/Cf (4.66 MPa), FNS/Pv (4.43 MPa), IPS2/Pv (3.97 MPa), CER/Cf (3.82 MPa), IPS/Pv (3.62 MPa), ICA/Cf (3.59 MPa), IPS/Cf (3.11 MPa). Highest SBSV were obtained in TCR groups (7.70 MPa for TCR/Cf and 6.91 MPa for TCR/Pv) and lowest SBSV were obtained in IPS groups (3.11 MPa for IPS/Cf and 3.62 MPa for IPS/Pv) in both resin cements. No significant bond strength difference was found between two resin cements. Conclusions: TCR groups showed highest SBSV; lowest SBSV were obtained with both IPS PLVs. The resin cement type did not significantly affect the bond strength value of a ceramic type, except for the Finesse system.     

Application of an asymmetrical four point bend shear test to solder joints

The asymmetrical four-point bend shear (AFPB) test method was used to measure the shear strength and creep properties through the stress relaxation experiments using three different Pb-free solder joint compositions in an assolidified condition. Since it was difficult to shear the uniform specimens and the local bending usually occurs at the inner loading points, the notches were introduced at the joint line to preferentially weaken this region. The stress analysis by finite element modeling showed that the straight notches transform the parabolic shear stress distribution in the uniform specimen into a relatively uniform shear distribution along the bond line in the notched specimens. Therefore, the shear strength results from the notched specimens are expected to be much more accurate. Experiments showed that both the Sn-3.6Ag-1Cu (wt.%) and Sn-3.6Ag-1Cu-0.45Co joints have superior strength and creep properties as compared to the Sn-3.5Ag joint. However, there was no statistical difference between the shear strength of the Sn-3.6Ag-1Cu and Sn-3.6Ag-1Cu-0.45 Co joints. Moreover, the difference between the creep resistance of these two types of joints was small.     

Pearlite spheroidization

The static spheroidization of a silicon-containing steel was studied employing quantitative metallography and hardness measurements. Specimens with interlamellar spacings of 0.57 and 0.26m were annealed at temperatures of 600, 650 and 700° C to obtain the spheroidization of Fe₃C. The results of quantitative metallography and hardness measurements indicate that the rate of spheroidization is controlled by the diffusion of iron at the Fe-Fe₃C interface. The increase in the rate of spheroidization due to a reduction in the interlamellar spacing is thought to be caused by an increase in the defect density in the Fe₃C plates when pearlite has a smaller interlamellar spacing.     

On the dual spherical motions—ISur les mouvements spheriques duaux (lére partie)

In this paper it is shown that if the axes of curvature of the ruled surfaces $\text{U}{}_1\text{(t)}$ in the moving and fixed spaces intersect each other perpendicularly then the dralls (or distribution parameter) of the ruled surfaces, which are generated by the geodesic trihedron U₁, U₂, U₃s of a dual curve $\text{U}{}_1\text{(t)}$, satify the A. Mannheim and R. Hamilton's formulae. Furthermore, the “explicit characterization” of the spherical curve of striction is given in terms of U₃-surface and the skewness of distribution of the generator of U₁-surface.     

TiC-reinforced cast Cr steels

A new class of materials, namely TiC-reinforced cast chromium (Cr) steels, was developed for applications requiring high abrasion resistance and good fracture toughness. The research approach was to modify the carbide structure of commercial AISI 440C steel for better fracture resistance while maintaining the already high abrasion resistance. The new alloys contained 12Cr, 2.5–4.5Ti, and 1–1.5C (wt.%) and were melted in a vacuum induction furnace. Their microstructure was composed primarily of a martensitic matrix with a dispersion of TiC precipitates. Modification of TiC morphology was accomplished through changing the cooling rate during solidification. Wear rates of the TiC-reinforced Cr steels were comparable to that of AISI 440C steel, but the impact resistance was much improved.     

Fatigue life determination of plasma nitrided medical grade CoCrMo alloy

In this paper, the fatigue behaviour of plasma nitrided medical grade forged CoCrMo alloy was studied. Since metallic biomaterials are used for implant applications where high and/or cyclic stresses along with corrosive effects of human body are of concern, enhancing mechanical and surface properties of implant alloys is crucial. Plasma nitriding was implemented at three different temperatures as 600, 700 and 800 °C for time intervals of 1 and 4 h. S–N curves of untreated and nitrided specimens were obtained via axial tension compression fatigue tests. It was found that plasma nitriding treatment reduces the fatigue resistance of forged CoCrMo alloy by the ratios of 7–23% depending on the surface roughness, phase structure and hardness of the modified layer which are determined by the treatment parameters.     

Fabrication of a New Hybrid Coronene/n-Si Structure by Using Spin Coating Technique and its Photoresponse and Admittance Spectroscopy Studies

Silicon - Coronene/n-Si Schottky structure has been fabricated by Coronene thin film deposited on n-Si substrate using the spin coating technique. The current-voltage (I-V) characteristics of the...     

Influence of shallow and deep cryogenic treatment on the corrosion behavior of Ti6Al4V alloy in isotonic solution

This study investigated the corrosion behavior of cryogenically treated Ti6Al4V alloys in an isotonic solution. Samples were subjected to shallow or deep cryogenic treatment, and some samples then underwent an aging procedure. They were characterized by microstructural analysis, an open circuit potential test, an electrochemical impedance method, and a potentiodynamic test. The polarization tests demonstrated that the deep cryogenic treatment shifted the corrosion potential to more anodic values compared to the untreated sample. For all treated samples, it was found that the corrosion current densities were lower than those in the untreated sample, and the lowest current densities were registered for the sample subjected to deep cryogenic treatment for 36 hr. The shallow cryogenic treated samples and the sample aged without cryogenic treatment showed semicapacitive loops with poor corrosion impedance compared to the untreated sample, whereas deep cryogenic treatment produced Warburg impedance with diffusion in the solid phase.     

Monotonic and low cycle fatigue behaviour of 2024‐T3 aluminium alloy between room temperature and 300 °C for designing VAWT components

In the present study, the results of the monotonic tension tests and low cycle fatigue tests performed on aluminium alloy EN AW‐2024‐T3 under various operating temperatures are presented in order to assess the fatigue behaviour of the aluminium alloy under evaluated temperatures. Monotonic tests were performed to determine the influence of temperature on mechanical properties of the material. The aim of cyclic tests was to acquire the parameters required for Manson–Coffin equation in order to plot strain–fatigue life curves. Moreover, stress–strain behaviour of the alloy and the cyclic hardening behaviour were evaluated using Ramberg–Osgood equation. Finally, P_SWT‐damage parameters for each temperature have been calculated for further investigation of the effects of the temperature on fatigue life using acquired data while taking the account of mean stress effect into calculations. Variations in the experimental data due to various test temperatures are presented for both monotonic and cyclic tests.     

Effect of FeB additions on sintering characteristics of injection moulded 17-4PH stainless steel powder

High density sintering of precipitation hardening stainless steel such as 17-4 PH involves a combination of relatively high temperature (>1350°C) and extended sintering time. In this study, the effect of addition of FeB on sintering characteristics of 17-4 PH stainless steel was investigated. Addition of boron is promoted to get highly dense sintered steels. The amount of boron plays a role in determining the sintered microstructure and properties. With the increased amount of FeB sintered density and tensile strength increase while sintering time and temperature decrease.