The current study executes a fully coupled thermomechanical simulation of friction stir welding (FSW) process of aluminum 6061-T6 alloy T-joint type using finite element method. The analysis simulation accounts for the three steps of the FSW process which includes: plunging, dwelling, and moving stages. The temperature history, associated stresses and strains generated through the FSW phases, tool reaction force, and time-dependence of the energy dissipation were evaluated. To overcome the shortcomings of purely Lagrangian and Eulerian descriptions, Arbitrary Lagrangian Eulerian (ALE) formulation, adaptive meshing, and the mass scaling were used as techniques to improve sequence modeling of the friction stir welding process. Coulomb’s friction law with nonlinear friction coefficient was used to model contact between the tool and T-joint configuration. To verify the numerical results, an experimental setup was constructed to carry out the FSW of a T-joint. Meanwhile, embedded thermocouples were used in the advancing side to measure temperature close to the welding line. The results obtained throughout the simulation study showed that the temperature was symmetrically distributed across the T-joint width, and the temperature contour displayed a high gradient in the weld stirring zone with a V type shape after the plunge stage. Good correlation between numerical and experimental temperature results was obtained with a little shift in the peak value. The results of von-Mises value showed that the maximum stress has been moved from the skin part gradually into the stringer part with the advancement of the tool during plunging. The plastic strain value was higher on the advancing side in comparison with the retreating side. Moreover, the heat generation calculation showed that the frictional dissipation energy was responsible for generating most of the heat needed to obtain a successful FSW.
Joining tissue is a growing problem in surgery with the advancement of the technology and more precise and difficult surgeries are done. Tissue welding using laser is a promising technique that might help in more advancement of the surgical practice. Objectives: To study the ability of laser in joining tissues and the optimum parameters for yielding good welding of tissues. Methods: An in-vitro study, done at the Institute of Laser, Baghdad University during the period from October 2008 to February 2009. Diode and Nd-YAG lasers were applied, using different sessions, on sheep small intestine with or without solder to obtain welding of a 2-mm length full thickness incision. Different powers and energies were used to get maximum effect. Re
... Show MoreThe dynamic thermomechanical properties, sealing ability, and voids formation of an experimental obturation hydroxyapatite-reinforced polyethylene (HA/PE) composite/carrier system were investigated and compared with those of a commercial system [GuttaCore (GC)]. The HA/PE system was specifically designed using a melt-extrusion process. The viscoelastic properties of HA/PE were determined using a dynamic thermomechanical analyser. Human single-rooted teeth were endodontically instrumented and obturated using HA/PE or GC systems, and then sealing ability was assessed using a fluid filtration system. In addition, micro-computed tomography (μCT) was used to quantify apparent voids within the root-canal space. The data were statistically analys
... Show MoreA genetic algorithm model coupled with artificial neural network model was developed to find the optimal values of upstream, downstream cutoff lengths, length of floor and length of downstream protection required for a hydraulic structure. These were obtained for a given maximum difference head, depth of impervious layer and degree of anisotropy. The objective function to be minimized was the cost function with relative cost coefficients for the different dimensions obtained. Constraints used were those that satisfy a factor of safety of 2 against uplift pressure failure and 3 against piping failure.
Different cases reaching 1200 were modeled and analyzed using geo-studio modeling, with different values of input variables. The soil wa
Experimental results on harmonic distortions in 13.56 MHz RF Argon glow discharge using different grounded electrodes areas and electrodes spacing are presented. The experiment is carried out at four pressure values. RF power values used are between 20 and 90 watts. The results indicate significant increase in distortions at two specific values of the cone angle enclosing the two electrodes within its geometrical volume. The computation of the cone head angle gave the symmetry discharge or asymmetry as well as when the angle is small the condition is near symmetry discharge associated with decrease in the nonlinearity.
The aim of this study was to develop a sensor based on a carbon paste electrodes (CPEs) modified with used MIP for determination of organophosphorus pesticides (OPPs). The modified electrode exhibited a significantly increased sensitivity and selectivity of (OPPs). The MIP was prepared by thermo-polymerization method using N,N-diethylaminoethymethacrylate (NNDAA) as functional monomer, N,N-1,4-phenylenediacrylamide (NNPDA) as cross-linker, the acetonitrile used as solvent and (Opps) as the template molecule. The three OPPs (diazinon, quinalphos and chlorpyrifos) were chosen as the templates, which have been selected as base analytes which used widely in agriculture sector. The extraction efficiency of the imprinted polymers has been evaluat
... Show MoreAlthough the axial aptitude and pile load transfer under static loading have been extensively documented, the dynamic axial reaction, on the other hand, requires further investigation. During a seismic event, the pile load applied may increase, while the soil load carrying capacity may decrease due to the shaking, resulting in additional settlement. The researchers concentrated their efforts on determining the cause of extensive damage to the piles after the seismic event. Such failures were linked to discontinuities in the subsoil due to abrupt differences in soil stiffness, and so actions were called kinematic impact of the earthquake on piles depending on the outcomes of laboratory
This research examines the use of vibratory treatments to reduce residual stresses in small welded parts. In this experimental investigation, a post weld vibration treatment was applied to T- A106 steel pipe fitting specimens to study the effect of the treatment on the residual stress and the hardness of the material. The vibratory stress relief treatment was carried out at different vibration frequency. The results have demonstrated that post-weld vibratory stress relief of small size fittings is possible and residual stress may be relieved, and the treatment may be an alternative method for heat treatment especially when unchange in dimensions and material stability are required.
In this research, the effects of both current and argon gas pressure on the bending properties of welded joints were studied. Using the possible ranges of welding gas pressures and currents, Tungsten inert gas welding (TIG) of stainless steel (304) sheet was used to obtain their influence on the maximum bending force of the (TIG) welded joints. Design of experiment (DOE) ‘version 10' was used to determine the design matrix of experiments depending on the used levels of the input factors. Response surface methodology (RSM) technique was used to obtain an empirical mathematical model for the maximum bending force as a function of welding parameters (Current and Argon gas pressure). Also, the analysis of variance (ANOVA) was used to verif
... Show MoreThe aim of our study is to reveal the effect of steel reinforcement details,tensile steel reinforcement ratio, compressed reinforcing steel ratio,reinforcing steel size, corner joint shape on the strength of reinforcedconcrete Fc' and delve into it for the most accurate details and concreteconnections about the behavior and resistance of the corner joint ofreinforced concrete, Depending on the available studies and sources inaddition to our study, we concluded that each of these effects had a clearrole in the behavior and resistance of the corner joint of reinforced concreteunder the influence of the negative moment and yield stress. A studyof the types of faults that can be reinforced angle joints obtains detailsand conditions of c
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