A Data Fusion Method for Non-Destructive Testing by Means of Artificial Neural Networks

In the aeronautics sector, aircraft parts are inspected during manufacture, assembly and service, to detect defects eventually present. Defects can be of different types, sizes and orientations, appearing in materials presenting a complex structure. Among the different inspection techniques, Non Destructive Testing (NDT) presents several advantages as they are noninvasive and cost effective. Within the NDT methods, Ultrasonic (US) waves are widely used to detect and characterize defects. However, due the so-called blind zone, they cannot be easily employed for defects close to the surface being inspected. On the other hand, another NDT technique such Eddy Current (EC) can be used only for detecting flaws close to the surface, due to the presence of the EC skin effect. The work presented in this article aims to combine the use of these two NDT methods, exploiting their complementary advantages. To reach this goal, a data fusion method is developed, by using Machine Learning techniques such as Artificial Neural Networks (ANNs). A simulated training database involving simulations of US and EC signals propagating in an Aluminum block in the presence of Side Drill Holes (SDHs) has been implemented, to train the ANNs. Measurements have been then performed on an Aluminum block, presenting tree different SDHs at specific depths. The trained ANNs were used to characterize the different real SDHs, providing an experimental validation. Eventually, particular attention has been addressed to the estimation errors corresponding to each flaw. Experimental results will show that depths and radii estimations error were confined on average within a range of 4%, recording a peak of 11% for the second SDHs.

Study of Temperature Measurement Accuracy by Using Different Mounting Adhesives

Thermal compounds are adhesive used to improve heat conduction between two surfaces. It can be used to secure a thermocouple to a surface which the temperature is being measured. This paper studies the temperature accuracy when using different types of thermal adhesives to secure thermocouples to a metal surface. An aluminum block attached to heater resistors was heated up by supplying varying power levels to create different temperatures. The measured temperature is compared to a reference thermocouple in the aluminum block to check the accuracy of each thermocouple when it is secured with different adhesives. It was found using the Loctite 3873 to secure a thermocouple to a metal surface will produce the most accurate temperature reading with an error below 2.6°C. This enables researchers to use the appropriate adhesive to obtain the most accurate results and also to know what are the errors contributed by different adhesives.

Effect of Layering Techniques on Polymerization Shrinkage Stress of High- and Low-viscosity Bulk-fill Resins

Clinical Relevance The use of layering techniques is still advisable with many bulk-fill resins and should be the default unless a particular resin is known to not need it. SUMMARY Objective: The purpose of this study was to investigate how layering techniques affect polymerization shrinkage stresses of high-and low-viscosity bulk-fill resins. Method: Six high-viscosity and six low-viscosity bulk-fill resins were evaluated. Aluminum blocks with a mesial-occlusal-distal (MOD) cavity were machined and randomly divided into groups for different filling techniques (bulk-fill vs horizontal layering vs oblique layering) and further subdivided according to type of resin (high- vs low-viscosity). The cuspal deflection resulting from the polymerization of bulk-fill resin bonded to a MOD cavity within an aluminum block was measured with a digimatic micrometer. Scanning electron microscopy analyses of tested resins were also conducted. Results: In the high-viscosity bulk-fill resins, cuspal deflection of the MOD cavity ranged from 11.2 to 18.2 μm with the bulk-filling technique, from 10.7 to 15.5 μm with the horizontal layering technique, and from 10.9 to 15.2 μm with the oblique layering technique. In the low-viscosity bulk-fill resins, cuspal deflection of the material ranged from 9.2 to 19.8 μm with the bulk-filling technique, from 8.2 to 15.7 μm with the horizontal layering technique, and from 8.4 to 16.4 μm with the oblique layering technique. Conclusion: Cuspal deflections for some high-and low-viscosity bulk-fill resins were significantly reduced by using layering techniques, but the resultant improvement of layering techniques was not applicable to all the bulk-fill resins used in this study.

Evaluation of Linear Dimensional changes of Investment Material when Various Combinations of Dental Plaster and Dental Stone are used as an Investment Material

ABSTRACT Aims To evaluate dimensional stability when various combinations of dental plaster and dental stone are used as an investment material. Context Dental plaster is routinely used as an investing material to acrylize dentures with some acceptable linear dimensional changes in the finished acrylic denture. This study aimed to evaluate which combination of dental plaster and dental stone, when used as an investment, will produce fewer linear dimensional changes in acrylic dentures. Materials and methods An aluminum block is prepared with sharp margins. The block is invested with various combinations of dental plaster and dental stone. The linear dimensional changes are measured using a digital caliper. Statistical analysis The results obtained were subjected to statistical analysis using analysis of variance test. Results Investing with 100% dental stone and a combination of 70% dental stone and 30% dental plaster showed fewer dimensional changes. Conclusion A combination containing higher percentage of dental stone may be used for investing to produce a finished denture with fewer linear dimensional changes. How to cite this article Kumararama SS, Chowdhary R. Evaluation of Linear Dimensional changes of Investment Material when Various Combinations of Dental Plaster and Dental Stone are used as an Investment Material. Int J Prosthodont Restor Dent 2016;6(1):1-5.

Effect of the Metal Block on the Stress Distributed in the Adhesively Bonded Single Lap Steel Joint

The effect of 4 mm long metal block bonded to the end of the overlap zone on the stress distributed in adhesively bonded single lap steel joint was investigated using elasto-plastic finite element method (FEM). The results from the numerical simulation showed that the stress is varied a little when the joints with a couple of 4 mm long metal block adhered to both ends of the over lap or with a couple of adhesive fillet. Compared to the joint without the metal block, it is advantageous of reducing the peak stress in the adhesive layer near the ends of the lap zone in adhesively bonded single lap steel joints but its effect is less than that of the joint with a couple of adhesive fillet. There is no evidential difference in the effects between the steel and aluminum block.

Erosion Experimental Study on Organ-Pipe Nozzles in Air

Experiment of aluminum block erosion using organ-pipe nozzle was carried out in air. The erosion effects of water jet were used to evaluate the performance of organ-pipe nozzle. The experiment and corresponding data were used to analyze the effects of nozzle configuration, jet pressure, standoff distance. Results have shown that the organ-pipe water jets are much more effective in aluminum block erosion.