statement of the problem: one disadvantage of cement-retained crowns is the lack of predictable irretrievability. this problem can be overcome through designing a screw access hole in the metal substructure of cement-retained restoration and using porcelain stain to define this area. purpose: this study aimed to evaluate the influence of existence of screw access hole on porcelain fracture resi...

The paper discusses the experimental and finite element investigation into the failure mechanisms of uniply graphite-epoxy composite plates with circular holes loaded in uniaxial compression. The effect of hole size on the failure mode is established. Test specimens composed of a single layer of uniply graphite-epoxy sandwiched between two layers of transparent polyetherimide plastic were desig...

Phase contrast transmission electron microscopy is a powerful tool to enhance the image contrast of transparent materials such as ice-embedded biological specimens and polymer materials. In this method, a phase plate, which is placed at the back-focal plane of the objective lens, gives a phase shift for scattered electron waves, resulting in a significant enhancement contrast of specimens in im...

The translaminar fracture toughness of laminated composites can be determined experimentally assuming either linear elastic mechanics (LEFM) or cohesive zone model (CZM) hypotheses. Each theoretical frame is different in terms complexity and predictive capabilities. To clarify the latter point, we derived R(Δa) J(ω) curves from a set published results on over-height compact tension specimens si...

In this paper, the effect of interference fit on fatigue life of holed plate of mechanical joints was investigated experimentally. Fatigue tests were carried out on the holed specimens of Al-alloy 7075-T6 alloy. The interference fit process consists of force fitting a fastener into the hole with a negative clearance (diameter of the fastener is larger than of the hole) that produces beneficial ...

Hole drift mobilities have been measured using photocarrier time-of-l-light for several hydrogenated amorphous silicon-carbon alloy specimens. We find that, as the band gap increases, the hole drift mobility remains essentially constant. The temperature and dispersion properties were broadly consistent with hole multiple trapping in the valence bandtail. In conjunction with previous drift mobil...

in this research, the influence of bolt preload on the fatigue strength of 2024-t3 aluminium alloy double lap bolted joints has been studied experimentally and numerically. to do so, three sets of the specimens were prepared and each of them subjected to tightening torque of 1,2.5 and 5 n-m and then fatigue tests were conducted under various cyclic axial load levels. in the numerical method, th...