finite elements method

Thick-walled cylindrical vessels are specially used in oil, chemical, nuclear and military industries in order to withstand internal pressure. The presence of the compressive residual stress in the walls increases the bursting pressure and fatigue life. Autofrettage processes and radial interference in multilayer cylinders are among the conventional methods of creating residual stresses in the pressure vessels. In order to achieve higher strength and fatigue life, the combination of these processes is also considered. J integral method is a suitable criterion for evaluating the crack parameters in elastic and elastoplastic strain fields. In this research, distribution of the J integral along the semi-elliptical crack front on the inner surface of the interferenced two-layered cylinder with closed end has been studied. Inner layer was autofrettaged. Burst pressure was determined based on the fracture toughness criterion (JΙC). Also, the effects of the autofrettage percent, radial interference; depth, angle and aspect ratio of the crack on the J integral and burst pressure variations have been investigated. The inner and outer layers of the cylinder were made of 7075-T6 aluminum alloy. The periodic nonlinear hardening behavior of this alloy has been predicted using Chabooche model. The validity of the results and their accuracy were examined

Nowadays, Inconel superalloys are often used in various industries due to their extraordinary properties. Some unique properties of Inconel, such as maintaining its yield strength at elevated temperatures, very low thermal conductivity, and high abrasion resistance, provide very difficult to cut conditions for machining this superalloy. This paper presents a method for simulating the direct aged Inconel 718 superalloy turning by using the power law equation based on the finite element method. One of the main objectives of this research is the correct determination of material properties based on power law equation such as strain hardening coefficients, strain rate sensitivity coefficient, thermal softening coefficients, and other coefficients required to simulate direct aged Inconel 718. The simulation results, such as shear plane angle, machining forces, chip temperature, and tool and chip shape, have been validated by reference [1]. This study, similar to [1], has been studied at three different undeformed chip thicknesses to examine the deformed chip thicknesses and other machining outputs such as machining forces using the power law equation. Third wave Systems-AdvantEdge software has been used for the current study. The output of this study has been investigated with the results of experimental research [1] and shows the high efficiency and accuracy of the present analysis.

The rolling industry is the most common and prosperous method of producing metal products. The first goal of the rolling process is to reduce the cross-sectional area or the thickness of the workpiece, this process is done in two ways, hot and cold rolling, the metal passes between two rollers to take the shape of the groove (calibre) of the roller, so the rolling rollers of the components They are essential in climbing factories. This research aims to analyze heat transfer in hot rolling conditions and find the heat distribution in rolling rollers using the finite element method. The simulation is non-linear and assumes that the roller is homogeneous, isotropic, and without cracks and thermal strain. And the ambient temperature is considered negligible. The heat distribution in the roller in this research has been obtained in two ways using the spray cooling system and without using this system, and then the results obtained from the finite element simulation have been verified with the extracted experiment data, The highest percentage of relative error in prediction was 08.334%, which indicated the matching of the results obtained from the numerical solution with the extracted data.

This study investigates the effect of using temperature-dependent and constant thermophysical properties on the precision of numerical simulation in the laser welding of titanium Ti60 alloy. A finite element model is made for 3 mm thick Ti60 alloy sheet piece and is affected by the laser beam using a three-dimensional moving heat source. For verification of the finite element model, the numerical results are compared with the results of experimental data. Also, the influence of the number of elements on the results is investigated. The results of the finite element modelling showed that the solidification starts from the bottom of the melt pool and progresses to the top of the sheet and along the weld seam. Also, the best results are obtained with all the thermophysical properties of density, thermal capacity and conductivity were temperature-dependent. The use of constant density reduces the maximum values of the temperature and dimensions of the weld pool, and the use of constant heat capacity increases these values. Still, these changes are such that (less than 2%), constant density and thermal capacity can be used to model the whole laser welding process. However, the use of constant thermal conductivity causes a large error in the maximum values of the temperature (about twice the value of this parameter), and the dimensions of the melt pool, and this parameter cannot be assumed constant in the simulation of laser welding.

Regarding to the vast application of composite materials in the modern and advanced industries, accurately predicting the fracture and damage behavior of these materials is very important. Carrying out less and simple experiments leads to reducing the cost and time, therefore, designing and analyzing of the above mentioned materials need to find and applying the fracture and damage criteria. In the Iran country, these materials are more used for manufacturing the aircraft and for this reason, in this research airfoil piece is selected and simulated. For this aim, The Puck, Tsai-Wu, and Sun damage and fracture criteria are implemented into the ABAQUS commercial software, employing an implicit subroutine. After the simulation of the airfoil, the damaged zones and critical points of the airfoil are predicted by the three mentioned criteria, results of the numerical simulations are compared with the experimental results and validated. Comparison of the numerical and experimental results reveals that the predicted results of the Puck's damage criterion is closer to the practical results and is more reliable for predicting the damage in the airfoil loading test.

Creating melt joints in aluminum is an obstacle in introducing this metal into structures. This is due to the fact that fusion welding methods of aluminum leaves mechanical and metallurgical defects in the final produced parts. Friction stir welding is a non-melting replacement fabrication method, which creates welded joints from a semi-solid material state. In this paper, friction stir lap welding of 7075 aluminum alloy is studied both numerically and experimentally with the aim of investigating the shear strength of the welded joint. The shear strength which is calculated by the simulation is maximum 14 to 15 % lower to the acquired experimental results, which shows that the simulation process can appropriately be utilized to predict the shear strength of the welded joints for different cases. In addition, the results show that the maximum shear strength is equal to 165 Mpa which is obtained for a case in which the rotational speed is 1250 rpm, the linear speed is 50 mm/min and the tilt angle is set to 3˚.

Ultrasonic Phased Arrays are an emerging technology in nondestructive testing and evaluation. Some important factors affecting on the performance of these probes include, positioning elements in probe, number of elements, distance between two elements, elements length, and time delays to excite probe elements. The type of linear phased array probes is a prevailing type in which elements placed side by side and longitudinally. In this paper based on analyzing the existent laws in design and performance of the phased array probes related to the propagation of ultrasonic waves, an improved dimensional design for ultrasonic linear phased array probes, as well as improvement of the sequence of time delays to excite the probe elements are done. In order to evaluate the performance of the probe with improved design in comparison with a similar ordinary probe, an ultrasonic phased array test is simulated using FEM-based ABAQUS software. By numerical simulations, the performance of the probe with improved design versus the ordinary probe for propagating the guided waves in a thin square aluminum plate is compared. In first part, the attenuation coefficient of the received signals of reflected wave is evaluated, and in second part, the performance of the probes for radial scanning is compared. Results of both simulations confirm that the performance of the probe with improved design is much better than the similar ordinary one. Specially, the probe with improved design propagates the ultrasonic waves with the maximum head wave energy, and steers them with higher accuracy towards a determined direction.

Because of their wide application in industries requiring high pressure and temperature, manufacturing square and rectangular pipes have attracted more attention than ever before. There are various methods such as extrusion, tensile and stress for manufacturing square pipes. Another method on which studies have focused in recent years is the re-forming of round pipes in order to turn them into square or rectangular ones. The methods suggested in these researches are all applicable for the manufacture of square pipes without the possibility of manufacturing rectangular pipes. The method introduced in this paper consists of filling the pipe with bismuth and rolling it in three successive stages. In this research, first, the intended process is simulated in Abaqus software, and then a real sample is manufactured by an experimental test. The manufactured sample is checked with regard to its dimensions and is compared with the results obtained from the simulation. The results of the study show that the method of filling the pipe with bismuth and moving it through three rollers is an appropriate method for the manufacture of thin-walled pipes with rectangular cross-section.

In this paper, experimental results of a deep drawing process to produce a cylinder of high strength steel with a spherical head were compared with it’s simulation results and three proposal design types. Meanwhile, the amount of limiting draw ratio in some stages was determined. Accuracy and precision of the results of a finite element software to predicting the multi stage deep drawing process of high-strength thin steel sheets was measured. ABAQUS version 6-9-3 was used to simulate the process. In this research, the raw material was a circular blank of annealed steel AISI-4130 with 2 mm thickness that in experimental test, subjected to one drawing stages, three redrawing stage and two heat treatment stages. The uni-axial tensile test was performed to determine the mechanical properties of the steel sheet. Numerical thickness distribution was compared with the experimental results in different stages of deep drawing and the accuracy was good (about 2.55%). Base on this results the proposal designs were simulated to introduce the properties of the most suitable design types.