Several studies on photovoltaic systems focused on how it operates and energy required in operating it. Little attention is paid on its configurations, modeling of mean time to system failure, availability, cost benefit and comparisons of parallel and series–parallel designs. In this research work, four system configurations were studied. Configuration I consists of two sub-components arranged in parallel with 24 V each, configuration II consists of four sub-components arranged logically in parallel with 12 V each, configuration III consists of four sub-components arranged in series–parallel with 8 V each, and configuration IV has six sub-components with 6 V each arranged in series–parallel. Comparative analysis was made using Chapman Kolmogorov’s method. The derivation for explicit expression of mean time to system failure, steady state availability and cost benefit analysis were performed, based on the comparison. Ranking method was used to determine the optimal configuration of the systems. The results of analytical and numerical solutions of system availability and mean time to system failure were determined and it was found that configuration I is the optimal configuration.

Scaling methods have been developed to describe the spatial variability of soils. Among them, physically based methods are more desirable in which the scaling factors can be estimated from the soil physical properties. Assuming that the pore size distribution of soils is lognormally distributed, Kosugi and Hopmans developed a physically based method to scale the water retention curve. However, similar to the previous methods, application of this method is limited to the similar soils. To alleviate this limitation, in this paper, a physically based method is proposed for Dissimilar soils. Using this method, data of a wide textural range of soils can be scaled without the similarity condition and can be represented by a unique exponential reference curve. This method was validated using 487 sets of soil retention curves taken from UNSODA database including all the textural classes from sand to clay. The results showed that the proposed method had a better performance in scaling the retention curves than that of Kosugi and Hopmans. The criteria defined here for scaling error was obtained equal to 0.074 and 0.105 for the proposed and Kosugi-Hopmans method, respectively. In addition, it was shown that, in contrast to the previous methods, the scaling error of the proposed method does not depend on the soil texture and all the soils have an equal chance for being scaled.

Mechanical properties of Dissimilar weld joints between GOST09ch16N4B (a martensitic stainless steel) and AISI 4130 thin sheets made by gas tungsten arc welding (GTAW) were studied using ER410NiMo and ER100S-G filler metals in post weld heat treated conditions. Heat treatment cycles consisted of austenitization at 900, 950 and 1000 oC for 1 h and this was followed by oil cooling and tempering at 400 and 500 oC for 1 h. Tensile tests and microhardness measurements were carried out to evaluate the mechanical properties. The base metals, heat affected zones (HAZs) and fusion zones were observed by optical microscope and scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS). Based on the results, it was found that the joints strength and microhardness profiles were almost independent of austenitization temperature, but they were affected by the tempering temperature. Increasing the tempering temperature led to the reduction in the hardness of AISI 4130 and the joints strength. Tensile samples were fractured in the base metals. Furthermore, the fracture was shifted from GOST09ch16N4B to AISI 4130 with increasing the tempering temperature. Crack initiation from delta-ferrite led to the fracture in GOST09ch16N4B. Strength and elongation obtained from different PWHTs indicated that tempering at 400 oC resulted in acceptable tensile properties for the weldments made with both filler metals.

Lap joints of commercially pure magnesium plates to aluminium plates (Magnesium plate on the top, and Aluminium plate, grade 1100, on the bottom side) were conducted by friction stir welding using various traveling and rotation speeds of the tool to investigate the effects of the welding parameters on the joint characteristics and strength. Defect-free lap joints were obtained in the welding traveling speed range of 40-80 mm/min, and rotational speed range of 1200-1600 rpm. The shear tensile strength of Mg/Al joints increased as a result of decreasing the welding speed from 120 to 40 mm/min at constant rotation speed of 1600 rpm. Defects such as surface grooves, excessive flash, tunnels, and voids were observed if the joints prepared out of the mentioned range. The effects of the welding parameters are discussed metallographically based on observations with optical and scanning electron microscopes.

In this paper, finite element modeling of friction welding of two ASTM A106-B and AISI 4140 Dissimilar pipes is investigated. The effect of the friction welding parameters including rotation speed, friction pressure, friction time, forging pressure and forging time on the axial shortening are investigated using a fractional factorial design method. Because of the extreme material deformation, an innovative remeshing technique was scripted in Abaqus CAE to prevent the creation of distorted elements.27 models were solved and 3 validation experimental tests were carried out. Results showed that increasing the all parameters cause larger axial shortening. Friction pressure with 33.9% had the most effect on the axial shortening. Moreover, an increase in forging pressure and forging time has a limited effect on the axial shortening. After about 2 seconds from the beginning of the welding, the temperature of the interface becomes steady at about 1250oC. The validation tests revealed that the simulation error was about 5.6% which shows a good agreement between the finite element results and the experimental data.

Overlapped strips of titanium grade 2 and aluminum 3105-O alloy were welded together under an innovative spot-like pulse laser procedure. The tactile seam tracking on ring paths yielded reliable weld  t-up of 1 and 0. 5 mm thickness strips. Since the welding parameters of Ti-Al were narrow, three welding speeds of 4, 5, and 6. 67 mm. s-1 were chosen for the pretest conditions. The microstructural investigations showed that intermetallic compound Ti3Al formed in the Ti-rich fusion zone. Cracks formed in the Al-rich fusion zone as a result of TiAl3 precipitation. Dimple fracture occurred at 6. 67 mm. s-1 welding speed. Longer mixing time at Ti-Al interface occurred at lower welding speeds of 4 and 5 mm. s-1, which led to the formation of thicker intermetallic compounds and more massive crack generation. It also increased the hardness of the fusion zone and resulted in brittle fracture type during the tensile test. The highest strength was achieved with a welding speed of 4 mm. s-1, which was a result of more massive weld nugget and lower porosity.

The elimination of the FexAly type phases was considered the solution to low ductility presented in aluminum-steel welded joints. Recently, the researches do not seek the suppression but the control of the thickness of these compounds. In this work, Al-Fe joints were manufactured by solid state and fusion welding, looking for controlling the formation of intermetallic compounds. Temperature measurements were carried out during the welding. The joints interface was characterized using optical and scanning electronic microscopy, aided by chemical composition measures with X-EDS. The microstructural characterization at the interface of aluminum-steel joints, in solid state welded joints, demonstrated the absence of intermetallic compounds, which is attributed to the low temperature reached during the process-less than 300 ° C. In the case of fusion joints, it has observed the permanent formation of intermetallic compounds whose thickness varies significantly with the heat input.

Ultrasonic welding is gaining popularity for joining of thin and Dissimilar materials and foils in the fabrication of automotive Li-ion battery packs because of excellent efficiency, high production rate, high welding quality, etc. Precise control of the parameters of the welding process plays an important role in achieving good joint quality. Numerical simulation can greatly help control the main input parameters such as frequency, clamping pressure, friction coefficient, and vibration amplitude. In this present work, a three-dimensional thermo-mechanical Finite Element (FE) model is proposed using ABAQUS/EXPLICIT for the Dissimilar Al to Cu weld to predict the deformation and temperature as output parameters during welding process by varying input parameters. The simulation results showed that the clamping pressure, vibration frequency and friction coefficient have a great influence on heat production during the process which was critical to determine the final quality of the welded joint. Studies also showed that increased clamping force and welding frequency led to increased deformation.

This paper aims to investigate the likely effects of geogrid reinforcement configuration on footings bearing capacity. Using geogrids reinforcement layers with certain total areas in various uniform and non-uniform arrangements, the bearing capacities of footing models on reinforced sand beds were determined and compared. The first arrangement was the conventional uniform layout in which 3 geogrid layers of equal dimensions were considered. In the second group the same amount of geogrids were used in a trapezoidal profile in which smaller size geogrid were placed at upper layers and the geogrid dimensions increased with embedment depth. The third group consisted of arrangements in which the same amount of geogrids were used in an inverse trapezoidal layout i.e. the layer sizes decreased with embedment depth. The effect of soil density on the footing performance was also investigated. The tests results indicated that in all soil densities, the greatest bearing capacities were obtained for the sand beds reinforced with inverse trapezoidal reinforcement layouts while the least bearing capacities were determined for trapezoidal arrangements. The improvement ratio of bearing capacity due to geogrid reinforcement varied from 1.8 to 5.35 depending on the reinforcement layout and the sand bed density.