Papers by Keyword: Finite Element Modeling

Abstract: During earthquakes, structures can collide with each other due to provision of very small or no gap between them. This collision can cause massive amount of damage and it can be a very critical issue for structures which get subjected to mainshock-aftershock sequence of significant magnitude. In the usual design practice of building structures, neither pounding nor aftershocks are considered. Therefore, in the current study, a detailed investigation of structures which can be commonly found in Karachi is performed when they are subjected to pounding under mainshock-aftershock sequences. To this end, a FEM model was developed and processed through nonlinear time-history analysis under natural and artificial mainshock-aftershock sequences. It was found that pounding under aftershocks can increase story shears up to 2.18 times and story drifts up to 1.46 times that in the absence of pounding. Results of this study also showed that during pounding under aftershock, structure is still subjected to similar amount of force as in mainshock, however it is already in a damaged state due to mainshock.

Abstract: The injection moulding industry is dynamically developing. The growing demand for more customizable products can be served by low or middle volume production using prototype moulds and inserts. The conventional material of prototype moulds is aluminum because of its excellent machinability, acceptable strength and stiffness and outstanding thermal conductivity. Prototype moulds are gaining ground in the injection moulding industry, yet their operational behavior (including exact mechanical and thermal process parameters) is largely unknown. We created a comprehensive state monitoring system that measures the operational strain, cavity pressure and temperature of different prototype injection moulds. This way, all important process parameters can be measured and the relations between the moulding parameters and the operational pressure loads, deformations and temperatures can be quantified and analysed.

Abstract: In this study, three-dimensional finite element modeling is utilized to simulate suction caisson foundations used for offshore wind turbines. The behavior of suction caissons in normally consolidated clayey soil subjected to lateral loading is investigated. A numerical model is calibrated and validated using experimental laboratory physical model. A parametric study is conducted to evaluate the effect of suction caisson diameter (D) and the ratio of skirt length (L) to caisson diameter (L/D) on the load-deflection response of a full-scale suction caisson. Several caisson diameters and length to diameter ratios were considered. The results of numerical analysis modeling demonstrated that the caisson ultimate load capacity and displacement are significantly affected by caisson geometry. Generally, increasing both the caisson diameter and length has substantially increased both caisson’s ultimate load capacity and displacement at failure. However, the increase in ultimate capacity and displacement reaches a threshold after which the increase in these values is less pronounced as D and L/D are further increased. Additionally, the effect of caisson geometry on relative stiffness is investigated. The relative stiffness of the suction caisson was found to increase proportionally with the increase of both diameter and length of the modeled caissons.

Abstract: This paper presented an analysis of the two-step of hot forging process are carried out to manufacture Upper Ball joint, which are including roughing and finishing operation. The part was made from SNCM8 alloy steel. The simulation has been done with application of QForm V10.1.6 software. The constitutive model based on Zener-Hollomon parameter was applied. As a result of simulations, metal flow lines, plastic strain, temperature distribution and effective stress for forgings were obtained. Finite element simulation by QForm V10.1.6. software is suggested as a valuable tool for predicting the hot deformation behavior of material during multi-stage of hot forging process which utilized to enhance the manufacturing process. In addition, the forming load and thickness during the forging process were analyzed. It was found that the deviation of forming load between simulation and experiment was raised to 10.71% and the maximum error of flank thickness was 5.137%. within specification. Therefore, the workpieces of the quality required by specification are obtained.

Abstract: In this study, 3D numerical simulations were performed to study the effect of Mn on the macrosegregation behaviors of carbon and chromium in a 40 MT steel ingot using Finite Element Modeling (FEM). Two Mn contents of 0 and 5 wt.% were investigated. Thermophysical properties such as specific heat, density and phase fractions were determined using thermodynamic software Thermo-Calc^®. Simulation results indicated that higher Mn content increases the carbon macrosegregation while it tends to lower the one of chromium. Moreover, it changes the solute poor band into rich one in the case of chromium and no bands were obtained for carbon. These results are analyzed in terms of the changes of thermophysical properties, interactions between alloying elements and the change in the primary solidification mode from δ-ferrite to austenite resulting from the increase of Mn concentration.

Abstract: The impact of initial mold temperatures on the formation of macrosegregated zone during the solidification process of large size steel ingots was numerically investigated. Three initial mold temperatures, representing the most commonly encountered industrial conditions, were examined. The flows induced by pouring jet, the thermo-solutal convection, and the thermomechanical deformation of the phases were all taken into consideration. The results indicated that a higher mold temperature increased the macrosegregation intensity in the upper section of the casting, along the centerline and in the mid-radius solute-enriched bands. The increase was associated with the increased temperature gradient in the casting, the advance predominance of thermal convection, and the delayed solidification process.

Abstract: Needle insertion in biological tissue has attracted considerable attention due to its application in minimally invasive procedures such as laparoscopy or transcutaneous biopsy. In this paper the force of the Veress needle insertion into the abdominal wall and the von Mises stress were studied, demonstrating the ability of finite element models to provide additional understanding of the processes taking place. Veress needle insertion force may cause complications during surgery, the most common being vascular lesions, thus affecting the precision and duration of surgery assisted by a portable abdominal insufflation device. This study was the first step in developing a force feedback for needle insertion into the abdominal wall assisted by a portable abdominal insufflation device. The CAD model of the prototype of a portable abdominal insufflation device was made. Then the prototype of a portable abdominal insufflation device was developed. For testing purposes an artificial silicone model was made. The paper also includes the experimental results obtained by measuring the maximum pressure inside the artificial silicone model after the penetration of the wall.

Abstract: The composite materials features and characteristic defects in the obtaining apertures by machining are considered. A new method for forming apertures in fibrous polymer composite materials is proposed. The optimal shape of a tool for piercing holes is determined. The profiles of the pointed part of the tool are compared using numerical modeling.

Abstract: Residual stress is one of the main reasons for failure of automotive cylinder blocks and engine heads. These failures are typically associated with in-service distortion or cracking occurring in engines during operation cycles. The problem becomes more pronounced for engines that are running at elevated operating pressures and temperatures, limiting R&D options in developing and implementing higher-efficiency engines. New aluminum alloys and manufacturing methods have been introduced with varying degree of success, in many cases affected by the stress magnitudes and stress distribution in the component. Therefore, active research is ongoing internationally on finding the most reliable methods of stress analysis as a basis for developing efficient methods for stress mitigation. The current study presents a comparison between two experimental strain measurements techniques: a destructive method that is based on application of strain gauge sensors, and a non-destructive method using neutron diffraction. The results indicate that although the strain gauge method provides an indication of the nature (i.e. compression or tension) of strain within a component, this method should primarily be used for surface measurements and qualitative analyses only. Neutron diffraction remains the superior technique for strain analysis, particularly for engineering components with complex geometries. The results from this study provide the transportation industry with a more comprehensive understanding of the efficacy of utilizing strain gauge sensors, neutron diffraction or finite element modelling for measuring the residual strain in cast components. The results will help manufacturers to develop the next generation of powertrain systems with increased efficiency and improved performance.

Abstract: A lot of interest to simulate piezocomposite actuators with finite element method has been increased recently. However, there are still open questions regarding the modeling methodology, accuracy, and computational time cost. In this work, a new technique for modeling macro fiber composite piezoelectric actuator by finite element analysis is proposed. The presented technique models the piezocomposite actuator as a simple monolithic piezoceramic material with just two electrodes along its longitudinal extremes instead of using the actual large number of electrodes which results in very fine finite element mesh with high computational time cost. The proposed technique is validated successfully by comparing its results with those of the actual detailed model as well as with the published experimental results and manufacturer’s data.