Papers by Keyword: Finite Element

Abstract: There is a need for railway systems and upgrade their infrastructure to meet the future growing demand. This would expand the railway network by planning new track routes to increase the efficiency of railway transportation by running behavior of high train speeds between urban cities. The track/ballast; sleepers; and subgrade foundation system are important superstructure parts that need to be upgraded and improved to withstand high train speeds. A numerical finite element technique significantly benefits in simulating the impact of the dynamic response and predicting the deformation and stress distribution in the railway ballasted system. A three-dimensional finite element program PLAXIS ver. (20) have been utilized in this research to analyze the track of complex behavior under train loading. The vertical displacement of 3.8 mm was obtained at the rail/wheel contact point and greater than at the ballast embankment by about (19%) and (37%) for the subgrade foundation. Also, the maximum value of vertical displacement corresponds with the movement path of the train load is reduced laterally as the distance from the track centerline increases. The maximum vertical acceleration of 15.2 m/s² was obtained at surface points under track loading and decreased gradually with increased depth below the ballast embankment layer to reach a minimum value of 1.2 m/s². The vertical deformation was 1.3 mm, 2 mm, and 3.9 mm for 40 km/hr, 50 km/hr, and 60 km/hr respectively, and increased rapidly to 15 mm for train velocity greater than 70 km/hr due to the significant increase in train vibration level at higher speed. A critical train speed of 70 km/hr was observed that promoted the level of vibration and magnified the area of influence.

Abstract: Conventional finite element (FE) modelling, which employed structured mesh, is unable to simulate local damage evolution at microstructure level. This paper aims to investigate the creep rupture and damage behaviour of Grade 92 steel under a creep environment using microstructural-type FE mesh. The idealised microstructures of the material were generated based on the Voronoi tessellation technique. Three notched bar specimens with different notch acuities were modelled in Abaqus v6.13 software and a ductility exhaustion based damage model was employed to estimate the damage state. The influence of the notch constraint on the ductility is accounted for in the simulation. It is found that the results obtained from the proposed technique are in good agreement with the experimental data. All the prediction points fall within the scatter band of +/- factor of 2. The damage was predicted to initiate at a distance offset from the notch tip. As the acuity increases, the damage initiation site shifts further away from the notch.

Abstract: This paper presents the simulation of beef freezing process by using ANSYS software. On the basis of simulation results, factors affecting the freezing time including air velocity and freezing temperature were determined. Within the air velocity range ω = (5÷15) m.s^-1, an increase in the velocity by ω=1 m.s^-1 led to a decrease in the freezing time by τ =(6,5÷2,0) %. When the freezing temperature was reduced by t_e = 1 K, the freezing time was reduced by τ = (3,2÷2,5) % in the freezing temperature range t_e = (–35÷–45) °C.

Abstract: The main shaft of shot blasting machine mainly uses cylindrical roller bearing as the supporting part. The influence of stress, strain and temperature on bearing damage was studied by thermal structural coupling analysis of the bearing through finite element simulation. The causes and main damage forms of bearing surface were verified by super depth of field observation and finite element analysis. It is found that there exists pyramidal strain in the contact area between inner and outer raceway and roller, and its distribution form is continuous point distribution. The stress concentration is mainly distributed in the contact area between the roller face and the retaining edge, and the roller temperature is more concentrated in the area near the end face. The maximum length and depth of spalling pit on racetrack surface were 572.2μm and 14.15μm respectively. The maximum width and depth of the scratches on the roller surface are 386.7μm and 10.7μm, and the damage degree of the roller surface is not uniform. The thermo-structural coupling analysis is used to simulate the running state of bearings, which is of guiding significance to analyze the failure forms of bearings and improve the service life of bearings.

Abstract: The Cowper-Symonds relationship is the most common empirical equation used to model the influence of strain rates in steel structures subjected to blast loads. The simplicity of this relationship makes it as the preferred choice due to the minimum number of coefficients used in the equation. However, different coefficients were reported from experimental results where it was found that the coefficients could be influenced by the thickness of the specimens, types of materials and method of testing. Even so, the actual coefficients even for the same type of material such as for mild steel could be differ. It is known that strain rates effect increases the yield strength of steel, and this could reduce the maximum displacement of steel structures such as steel plates subjected to blast loads. This influence could be more significant if the steel plate was stiffened. Therefore, this study investigated the influence of Cowper-Symonds coefficients for steel plates with stiffeners subjected to close-in blast loads. The numerical investigations were performed using finite element software, Abaqus. The target plate was a 0.4 m x 0.4 m plate with 0.002 m of thickness subjected to a 0.012 kg of Plastic Explosive No. 4 (PE4) at 0.04 m stand-off distance. The influenced of stiffeners were investigate first where five stiffeners’ configurations were used and, in each configuration, the stiffeners come with different geometry ratios. Two best stiffened steel plates have been chosen to study the influence of different Cowper-Symonds coefficients. Different coefficient values of dominator, D and hardening coefficients, q was used. The results shows that any possible coefficient combinations of Cowper-Symonds relation are possible to use in predicting response of steel plates subjected to blast loads. From this study, the most ideal stiffened square steel plates for offshore platform could be identified.

Abstract: The energy performance of buildings represents a major challenge in terms of sustainable development. The buildings and buildings construction sectors combined are responsible for over one-third of global final energy consumption and nearly 40% of total direct and indirect CO₂ emissions. In order to reduce the energy consumption of buildings and their harmful impact on the environment, special attention has been paid in recent years to the use of bio-based materials. Several works have been carried out in the last decades in order to model the coupled heat, air and moisture transfers in the building envelope but the difficulties lies in the identification of numerous parameters that the HAM proposed models use. In the present paper, a sensitivity study regarding the HAM parameters is implemented in order to apprehend the most determining parameters during the transfer processes. A reduced model based on these parameters is then determined.

Abstract: The energy performance of buildings represents a major challenge in terms of sustainable development. The buildings and buildings construction sectors combined are responsible for over one-third of global final energy consumption and nearly 40% of total direct and indirect CO₂ emissions. In order to reduce the energy consumption of buildings and their harmful impact on the environment, special attention has been paid in recent years to the use of bio-based materials. In the present paper, a model of heat and moisture transfer hollow hemp concrete wall is proposed using finite element method. The energy and mass balances are expressed using measurable transfer drivers as temperature water content and vapor pressure and coefficients related explicitly to the macroscopic properties of material as thermal conductivity, specific heat, and water vapor permeability. The proposed model is implemented in MATLAB code and validated through experimental measurements.

Abstract: Aiming at the reliability of thin-film thermocouples applied to turbine blades at high temperatures, combined with high-temperature tests and finite element analysis, this paper studies its failure mechanism and thermal stress under thermal load. Multi-layer thin-film thermocouple samples were prepared on ceramic substrate, and high-temperature tests were carried out under different temperature loads, and the phenomenon of film shedding and cracking was observed using electron microscope. This paper analyzes the failure mechanism of the film sensor based on the function and structure, and uses ANSYS to analyze the thermal stress distribution of the film under high temperature load. Combining several existing theoretical models, this paper analyzes the factors affecting the thermal stress of the film and conducts simulation verification.

Abstract: This paper explores the ultimate strength of the composite floor system of structural steel concrete. ABAQUS, used to research non-linear competencies and ultimate load-carrying capability of such floor systems, developed the Finite Element Model (FEM) in 3-D. A comparison of computed values with experimental results has validated the proposed finite element model. The measured and experimental findings show a good match with an average variation of 10%. In parametric study effects of different sizes of shear studs on the ultimate strength of the floor system have been explored on full size specimens. Results show that an increase in height of the shear stud with the same diameter increases the ultimate strength of the floor system. An Increase in the diameter of the shear stud also increases the ultimate capacity of the floor system.

Abstract: The Miss stress, Max.principal strain and Magnitude displacement have important influence on the fatigue life of the Ni-based single crystal super-alloy turbine blades. This work investigated The Miss stress, Max.principal strain and Magnitude displacement of Ni-based single crystal super-alloy specimen with single hole along dangerous path under different working conditions by Abacus. The results show that the initial crack length and loading stresses are larger, the crack growth on the specimen is faster, and then, the fatigue life is the shorter. Moreover, for the different stress ratios, smaller stress ratio can lead to lower fatigue life. The result is significant to design turbine of Ni-based single crystal super-alloy of high accuracy, high reliability and high strength.