The Digital Image Correlation technique applied to the deformation behavior of welded sheet joints

The existence of a welded zone generally influences the local strain and stress distribution especially in case of welding defects. A method able to measure the local deformability can hence give many important information about the real stress and strain fields useful to improve the welded structure design. In this experimental work, some new generation automotive steels have been considered, because of the well known welding problems due to their unstable microstructural condition. Such materials, known as Q&P steels and available only as thin sheets, require a suitable quenching process able to give high mechanical resistance and satisfying deformability. Some sheet samples were welded by electron beam technique, because it is able to reduce the width of the heat affected zone where the main microstructural changes are concentrated. From such samples, tensile specimens were machined. During the tensile tests, the deformations were measured both by a traditional extensometer and by a 3D Digital Image Correlation (3D DIC) technique. A preliminary investigation of the melted and the heat affected zones resulted in small dimensions (about 10 mm) and hence the measuring setup has been optimized in order maximize the achievable measuring resolution minimizing the resulting uncertainty. This result can be achieved by a pattern generated by a suitable software and by an accurate preparation of the surface where the pattern will be deposited on

070-I * TRIBECA STUDY: (TRI)FECTA (B)IOPROSTHESES (E)VALUATION VERSUS (C)ARPENTIER MAGNA-EASE IN (A)ORTIC POSITION

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Tropospheric Ozone In A Mountain Forest Area: Spatial Distribution And Its Relation With Meteorology And Emission Sources

Biological injuries to forest ecosystems in two lateral valleys of Valtellina (Italy) have been studied. The selected areas are characterized by different forest novel decline symptoms and ozone concentration levels. Analyses of meteorological and air quality data collected by fixed and mobile stations located in the two valleys are presented. Ozone concentration has been measured both by passive samplers and continues analyzers and the ozone vertical gradient in one valley has been determined. In order to investigate the relation between emission sources, ambient ozone levels and plant biological injuries, a modeling research project has been started. As preliminary results the wind field obtained by the application of two diagnostic meteorological models, MINERVE and CALMET, and the computation of the biogenic emissions are presented. Some examples of spatial distribution and temporal trend of the most important pollutants emitted by plants are discussed

Experimental analysis about the evaluation of tungsten carbide-bur, piezoelectric and laser osteotomies.

Aim: Osteotomies are performed in oral surgery with five kinds of cutting instruments: 1) burs (Tungsten carbide cylindric burs), 2-3) ultrasound Piezosurgery (type I and II), 4-5) and lasers (Er:YAG; Er,Cr:YSGG). This study compares the quality of cutting of every single instruments, evaluating accuracy (length, thickness, depth and morphology), velocity (number of passages and time) and entity of damage. Methods: In vitro experiments with ten osteotomies were performed on one-hundred of cow ribs with each instrument. In vivo surgery was performed on New Zealand white rabbit: two osteotomies are made with all instruments on the mandible and on the shinbone, totalizing four osteotomies for each instrument. Samples are processed to be evaluated through histological exam at stereomicroscopy Discussion: Results show a statistically significant variability on "thickness" (p value=0.001), "time" (p value=0.001), "depth" and penetration speed (p-value=0.001; p-value=0.001) and the "number of passages" (p-value=0.001). No differences have been observed in "length" (p-value=0.078). Histological analysis reveals that osteotomy performed with laser and Piezosurgery II generates major damage to osteocytes near cutting surfaces. Conclusion: Currently, purchase and management elevated costs, minor versatility of use, and long training times for equipments such as Piezosurgery and laser limit their general use, but remain advantageous in case of risky interventions near noble structures. Choice of device depends on experience maturated by operator in time, characteristics of operation and patient's clinical conditions

Transapical off-pump echo-guided mitral valve repair with neochordae implantation mid-term outcomes

Background: The NeoChord echo-guided transapical beating heart repair is a promising early-stage minimally invasive surgical procedure for degenerative mitral valve (MV) regurgitation (DMR) correction. The technique has been improved since its inception following procedure standardization, patient selection optimization, and learning curve stabilization. We hereby present the mid-term clinical results through three years of our large single center experience. Methods: All consecutive patients with severe symptomatic DMR due to prolapse or flail of one or both mitral leaflets that underwent the NeoChord procedure between November 2013 and June 2019 were included. Patients were categorized according to MV anatomy; Type A isolated central posterior leaflet prolapse and/or flail, Type B posterior multi-segment prolapse and/or flail, Type C anterior and/or bi-leaflet prolapse or flail, Type D paracommissural prolapse and/or flail and/or significant leaflet and/or annular calcifications. Patients underwent clinical and echocardiographic follow-up at one, three, six, twelve months and yearly thereafter. Clinical outcomes and the composite primary endpoint (patient success) were defined according to Mitral Valve Academic Research Consortium (MVARC) criteria. Mitral regurgitation (MR) severity was graded as absent, mild, moderate and severe according to American Society of Echocardiography (ASE) and European Society of Cardiology (ESC) guidelines. Results: Two hundred and three patients were included; median follow-up was 24 months [interquartile range (IQR), 9–36]. Median age was 64 years (IQR, 54–74 years), median Society of Thoracic Surgeons (STS) Predicted Risk of Mortality (PROM) was 0.60% (IQR, 0.32–1.44%). There were 106 Type A patients (52.2%), 68 Type B (33.5%), 16 Type C (7.9%), and 13 Type D (6.4%). Kaplan-Meier estimate of survival was 99.0%±0.7% at one and two years and 94.0%±2.9% at three years. At one-year follow-up patient success was 91.2%±2.0% and 111 patients (74%) presented a residual MR mild or less (1+). At three-year follow-up patient success was 81.2%±3.8% and 32 patients (64%) had a residual MR mild or less (1+). Patient success was significantly different according to anatomical type (P=0.001). Echocardiographic analysis showed a significant acute left ventricle and left atrial reverse remodeling that was maintained up to three years. Conclusions: The NeoChord echo-guided transapical beating heart repair procedure demonstrated good clinical outcomes and echocardiographic results up to three-year follow-up

Reduction of precocious peri-implant resorption cone

Aim: After implant-insertion, bone tissue, newly-formed on peri-implant crest, undergoes to a mild marginal osseous readjustment due to build-up of inflammatory cell tissue (ICT). The present study verifies the possibility to limit bone resorption by placing implant fixtures 0.5 mm outside cortical bone edge. Methods: A clinically-controlled randomized study on 100 implants has been performed to compare early resorption process of implant fixtures placed 0.5 mm outside cortical bone edge with implant-fixtures inserted according to juxtacortical bone conventional protocols. Results: After 6 months, bone implant level was higher with emersion approach (-1.01\ub10.54 mm, mean\ub1SD) than with submerged treatment (-1.56\ub10.5 mm) (P<0.001). Conclusion: Factors to achieve an excellent result at mean-long term seem to be very good, even though the latter have to be confirmed by follow-up

Relation between toughness, infinite fatigue life and microstructure in large blooms for automotive plastic molds.

Presentazione orale al European Congress on Advanced Material and Processes (Euromat 2005), Praga (R. Ceca), 5/10/2005 - 8/10/200