Determination of the Actual Stress-Strain Diagram for Undermatching Welded Joint Using DIC and FEM.

This paper presents new methodology for determining the actual stress-strain diagram based on analytical equations, in combination with numerical and experimental data. The first step was to use the 3D digital image correlation (DIC) to estimate true stress-strain diagram by replacing common analytical expression for contraction with measured values. Next step was to estimate the stress concentration by using a new methodology, based on recently introduced analytical expressions and numerical verification by the finite element method (FEM), to obtain actual stress-strain diagrams, as named in this paper. The essence of new methodology is to introduce stress concentration factor into the procedure of actual stress evaluation. New methodology is then applied to determine actual stress-strain diagrams for two undermatched welded joints with different rectangular cross-section and groove shapes, made of martensitic steels X10 CrMoVNb 9-1 and Armox 500T. Results indicated that new methodology is a general one, since it is not dependent on welded joint material and geometry.

3D Digital Image Correlation Analysis of the Shrinkage Strain in Four Dual Cure Composite Cements.

The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on strain detected in all tested materials showing higher strain in samples with 2 mm thickness compared to 1 mm samples. Shrinkage strain values were the highest in Set PP samples indicated the possibility of undesirable de-bonding.

Laser-induced damages of different types of human gallbladder stones.

BACKGROUND/AIMS: Today, treatment of human calculi, and particularly those of gallbladder, is, to a large extent, less invasive procedure due to numerous non-invasive methods that have been developed. METHODOLOGY: CO2 laser of pulse (output 5W)(W-watt, SI unit system) and continual mode (output 15W) and diode laser (808 nm-nanometer, SI) were used for tests of fragmentation of gallbladder calculi in vitro. RESULTS: A total of 15 human gallbladder calculi of known size were examined, which had been collected during surgical interventions. Damages caused by laser were examined visually and by stereomicroscope (10 to 25 times magnification). During testing, the dependence of fragmentation on the type of laser effect, as well as the degree of fragmentation on the type of tested calculus was noted. Different types and dimensions of damage caused by various laser beams, as well as coloration changes of superficial layers in relation to the type of tested calculi was noticed. CONCLUSION: Accordingly, in this specific case, the priority for removal of gallbladder calculi by ablation will be given to diode laser.