Dimensional Finite Element Code Research Articles

Determination of tensile strength of concrete using a novel apparatus

This study presents a new and novel technique for the determination of the tensile strength of concrete specimens. A prismatic concrete specimen with a hole at its centre is placed in a new device, called seesaw, and with the use of a conventional loading machine in compression mode, a tensile stress is applied to the specimen for the determination of the indirect tensile strength. In this study, two types of concrete mixes were used for preparation of specimens. The mixes were made of gravel, sand, cement, water, polypropylene fibre, and admixtures. Concrete specimens were subjected to tensile loading using a new load convertor device and a universal loading machine was used for the application of the load to the specimen. The load was applied at the rate of 0.02 MPa/s. The two dimensional finite element code FRANC2D/L was used for numerical modelling of the specimens and the loading conditions to determine the stress concentrations around the hole as a function of the hole diameter and the specimen width. Based on the results of experiments and numerical modelling efforts, a new formula for determination of the tensile strength of concrete is proposed in this study. Concurrent with indirect tensile tests using this new device, splitting test were performed to confirm the observed tensile strength values for concrete specimens. Both experimental and numerical modelling results show that the tensile failure occurs around the sides of the hole along the horizontal axis.

An elasto-plastic damage constitutive model for jointed rock mass with an application

A forked tunnel, as a special complicated underground structure, is composed of big-arch tunnel, multi-arch tunnel, neighborhood tunnels and separate tunnels according to the different distances between two separate tunnels. Due to the complicated process of design and construction, surrounding jointed rock mass stability of the big-arch tunnel which belongs to the forked tunnel during excavation is a hot issue that needs special attentions. In this paper, an elasto-plastic damage constitutive model for jointed rock mass is proposed based on the coupling method considering elasto-plastic and damage theories, and the irreversible thermodynamics theory. Based on this elasto-plastic damage constitutive model, a three dimensional elasto-plastic damage finite element code (D-FEM) is implemented using Visual Fortran language, which can numerically simulate the whole excavation process of underground project and perform the structural stability of the surrounding rock mass. Comparing with a popular commercial computer code, three dimensional fast Lagrangian analysis of continua (FLAC3D), this D-FEM has advantages in terms of rapid computing process, element grouping function and providing more material models. After that, FLAC3D and D-FEM are simultaneously used to perform the structural stability analysis of the surrounding rock mass in the forked tunnel considering three different computing schemes. The final numerical results behave almost consistent using both FLAC3D and D-FEM. But from the point of numerically obtained damage softening areas, the numerical results obtained by D-FEM more closely approach the practical behaviors of in-situ surrounding rock mass.

Investigation into Bicycle Front Fork Forming Process of Simulation and Experiment

This study uses the three dimensional finite element code to examine the plastic deformation behavior of bicycle front fork forging. First the paper used Solid works 2010 3D graphics software to design the bicycle front fork die, and that used rigid-plastic model finite element analytical methods, and assuming mode to be rigid body. The front fork material is titanium alloy Ti-6Al-4V. A series of simulation analyses in which the variables depend on die temperature, billet temperature, forging speed, friction factors, die angle are reveal to effective stress, effective strain, die radial load distribution and damage value for bicycle front fork forming. The simulation combined Taguchi method to analysis optimization. The results of the analysis can be used to stabilize finite element software to forming front fork, and also confirm the suitability of bicycle front fork through experiment optimization.

An Investigation into the Shape Rolling of Sectioned Sheets with Internal Voids Using the Finite Element Method

This study uses the three dimensional finite element code to examine the plastic deformation behavior of internal void defects at the roll gap during the shape rolling of V-sectioned sheets. The finite element code incorporates the rigid-plastic model. The rolls are assumed to be rigid bodies and the temperature change induced during rolling is ignored. The analytical model is employed to conduct a systematic examination of the filling ratio at the roll gap, the spread ratio of the sheet, the rolling force, the principal strain, the mean stress, and the variation of the void dimension at the exit under rolling conditions characterized by different roll profile inclinations, roll radii, and thickness reductions, etc. The results of the analysis can be used to stabilize finite element software to form the shape rolling of sheets with internal void.

밸브 수압측정기의 구조해석

Existing hydraulic valve meter used in industrial fields precise pressure measurement gives inconvenience in precise measurement due to manually regulated pressures. In order to improve this inconvenience, the hydraulic valve meter was designed by using automatic design program CATIA and structural analysis of the designed hydraulic valve meter was conducted and internal water leaking, stress, strain and total deformation were obtained by applying three dimensional finite element code ANSYS. These results will be provided to develop new concepts of hydraulic valve meters as fundamental data.

Development of a Special Interface Element Between Brick and Plate Bending Elements

In this study a special three-dimensional interface element has been formulated for stress and displacement analyses in bonded joint between two adjacent plate bending and brick elements. Interface element has 16 nodes with 5 degrees of freedom in each node adjacent to plate bending element and 3 D.O.F in each node adjacent to brick elements. The interface element has ability to transfer three translations from each side of interface element and two more rotations in the side adjacent to the plate element. Stiffness matrix of this element was formulated and implemented in three dimensional finite element code. Using experimental and numerical work of strengthened RC concrete beams carried out by researchers, application of this element including variation of deflection, slip between plates and bricks, normal and shear stresses distributions in FRP plates have been verified. The results show, that this interface element is effective and can be used for structural components with this type of interface element.

A Coal Mine Dump Stability Analysis—A Case Study

The present paper mainly deals with a case study of failed dump slope in western coalfield limited, Nagpur, India. A huge mass of debris flow had happened during the routine the activity of mining. The failed dump had a height of 75 m with 43? slope angle which had slipped forward by 18m. Representative loose dump material samples were collected from the site and tested to determine the physico-mechanical properties of dump material. The dump material consisted of loose fragments and lumps of friable sandstone, shale, clay and carbonaceous shale. To evaluate the condition of failure, a well known, shear strength reduction tech-nique has been applied to achieve the desired factor of safety using two dimensional finite element code. Fi-nally, a economical, sustainable and stable dump angle and height has been suggested for smooth and safe disposal of the dump.

MYOGENIC RESPONSE IN ELASTIC ARTERIES: ELECTROMECHANICAL COUPLING

The myogenic response of an arterial vessel is referred to its pressure-dependent contraction, and was first proposed by [Bayliss 1902]. Myogenic response describes how a vessel adjusts its lumen diameter in response to the change of intravascular pressure. Arterial constriction is induced by pressure increase, while arterial dilation is due to a pressure decrease. However, this effects can also be induced by means of specific drugs. This mechanism starts within the smooth muscle cell present in blood vessels. Fundamental to the description of this active mechanism is the mathematical description of the contraction within the muscle cell. The smooth muscle cell developed by [Yang et al., 2003] and later modified by [Stalhand et al, 2007], has been incorporated in a finite strain three dimensional finite element code to study the myogenic response of anisotropic arteries. The model couples the electrophysiological activity occurring at cellular level with the mechanochemical mechanisms governing muscle contraction. The framework allows for studying the evolution of tissue properties, as well as a better understanding of the autoregulation of the vasculature.

Numerical Simulation of Bed Separation Development and Grout Injecting into Separations

In this paper, the Cosserat theory that has been incorporated into a three dimensional finite element code COSFLOW, is applied to analyze the development of bed separations in the layered overburden and grout injection into the bed separations. The mechanism of bed separation development during the longwall mining is investigated. A parametric study is carried out to investigate the effect of major factors including hard rock grade, panel height and panel weight on bed separation development. Based on the modeling, a conceptual model to describe the development process of bed separation is proposed. The effect of grout injecting into the bed separations on subsidence reduction is also studied and the conclusion agrees well with the common realization.

Optimum pre-form dies in two-stage forging

Since 1980s the problem of manufacturing defect-free parts has been tackled with simulation tools. In this paper, a numerical method for shape optimisation of pre-form dies in a two-stage hot forging is presented. The object of optimisation is to eliminate work-piece defects that may arise during the forging process. A two dimensional finite element code has been developed for the simulation of the mechanical process and prediction of the defects. The material is incompressible and it follows the Norton–Hoff law. To deal with contact constraint, the velocity-projection algorithm is used. The optimisation method is based on a genetic algorithm supported by an elitist strategy. The developed scheme is used to design optimal pre-form dies for two axi-symmetric examples. The objective function is associated with the quality of the final product. Comparing the obtained optimal results with other articles justifies the proposed optimisation method.

Electromagnetic forces in the air gap of a permanent magnet linear generator at no load

The basis for the work is the slow speed energy conversion of ocean wave energy into electricity using a direct-drive three-phase permanent magnetized linear generator. One of several important issues is the normal forces in the air gap, which is critical when designing the support structure of the generator. The electromagnetic forces in the air gap have been analyzed using Maxwell stress tensor method implemented in a two- dimensional finite element code. Simplified analytic calculations are made in order to validate the results from the extensive computer calculations. The normal electromagnetic forces in the air gap, Fδ, are analyzed for a two-sided linear generator at no load. An unstable condition of the global force on the piston occurs due to the fast increasing normal force as the air gap width decreases. A horizontal displacement of the piston from a neutral position with 3mm air gap on both sides produces a resulting horizontal force on the piston, increasing with the displacement. A displacement of 1mm gives a resulting horizontal force on the piston of 5.5kN per pole and meter of core length, which is increased to 9kN per pole and meter of core length for a displacement of 1.5mm. Furthermore, the normal force varies due to cogging as the piston moves vertically. At a constant air gap width of 3mm the normal forces per pole are varying between 9.9 and 11.3kN∕m of core length as the piston is moving from one pole to the next.

Computational simulation of fatigue crack growth and demonstration of leak before break criterion

A thick plate with a semi-elliptical surface crack subjected to remote tension and tension fatigue loading is considered for the analysis. In the present study the material is assumed to have variable fracture toughness in the surface and thickness directions. Material with isotropic fracture toughness is also considered. The developed three dimensional finite element code which has the capability to handle singularity and evaluate fracture parameter based on force method is used to characterise the fatigue crack growth. Parametric study involving various initial crack sizes is carried out and Foreman’s equation is used to predict the crack growth. Various regions viz. break, leak before break are obtained.

First measurements of current distribution in moving fiber-armatures in railguns

Using miniaturized Rogowski coils developed at ISL, we are able to measure the currents flowing through moving metallic fiber-armatures in a railgun. The 15 mm square bore railgun is 0.5 m in length and is powered by a 150 kJ capacitor bank. The peak current is about 200 kA and typical launch velocities with this test bed reach 600 m/s. The armature consists of two fiber brushes made of the same metal (e.g. Cu-Cd) or two different metals (e.g. brass and Cu-Cd). The current distribution between the two brushes has been measured during the shot. A special voltage probe placed on one rail provides information about the rail resistance variation during projectile passage. A comparison between the experimental results and the current distribution calculated with a three dimensional finite element code, taking into account thermal effects, is presented.

CDM based finite element code for concrete in 3-D

This paper presents a three dimensional finite element code DAMAG3D for nonlinear analysis of concrete type materials modeled as elastic-damage. The CDM model adopted is the one as proposed by SUARIS W, OUYANG C, FERNANDO V. M. Damage model for cyclic loading of concrete. J Engng Mech, American Society of Civil Engineers 1990; 116(5): 1020–35. for monotonic and cyclic loading of concrete structures. Code DAMAG3D is applied to simulate response of concrete under monotonically increasing load paths of uniaxial compression, Brazilian test, strip loading and patch loading, with reasonable correlation established with experimental results and results from other nonlinear constitutive models.

Finite Element Implementation of the Microplane Theory for Simulating a Rigid Concrete Pavement-Vehicle Interaction*

This paper presents an approach for modeling concrete pavement, based on the constitutive implementation of Bazant's microplane theory, for the purpose of predicting pavement response due to complex loading by vehicles. This includes implementation of the microplane theory in a three dimensional finite element code and verification of its numerical accuracy. The analytical method is then verified. The program's accuracy under simple static loading is verified by comparison with two of the most widely used pavement design codes. Experimental data from the literature are used to verify the approach developed for both cyclic response and prediction of material softening, a critical feature of the Portland Cement Concrete (PCC) concrete material used in pavement. The analysis is also verified against experimental influence function data for a single axle, Finally, the analytically predicted pavement response is verified for dynamic multi-axle truck loading. Based on agreement with experimental data, the model developed captures the essential characteristics of concrete pavement subjected to complex

A Numerical Study of the Buckling and Failure Characteristics of Laminated Composites with Elliptical Holes

An investigation of the buckling and failure characteristics of laminated composites with elliptical holes has been conducted. To predict critical buckling load and first ply failure load, we performed a three-dimensional finite element analysis. The critical buckling load and corresponding buckling modes were predicted by solving an eigen-value problem. After the buckling modes were calculated, the failure analysis was performed to estimate the first ply failure load as a post buckling response. To predict the first ply failure load, we used Tsai-Hill's failure criterion. All these numerical analyses were performed using the three dimensional finite element code “CompAna3D” developed in this research. Using CompAna3D, the effects of hole size, hole aspect ratio, and hole distance on the buckling and failure responses were evaluated numerically in thin laminated plates under compressive loading

A Numerical Study of the Buckling and Failure Characteristics of Laminated Composites with Elliptical Holes

An investigation of the buckling and failure characteristics of laminated composites with elliptical holes has been conducted. To predict critical buckling load and first ply failure load, we performed a three-dimensional finite element analysis. The critical buckling load and corresponding buckling modes were predicted by solving an eigen-value problem. After the buckling modes were calculated, the failure analysis was performed to estimate the first ply failure load as a post buckling response. To predict the first ply failure load, we used Tsai-Hill's failure criterion. All these numerical analyses were performed using the three dimensional finite element code “CompAna3D” developed in this research. Using CompAna3D, the effects of hole size, hole aspect ratio, and hole distance on the buckling and failure responses were evaluated numerically in thin laminated plates under compressive loading

Process simulation in sheet metal forming

The finite element simulation is now widely used in the design of stamping tools. That is, the trial and error procedure is replaced by simulation in which defects of sheet forming processes are predicted and evaluated. The theoretical background and numerical implementation of a three dimensional finite element code ITAS-3D, developed with support of The Sheet Metal Forming Simulation Research Group in Japan are discussed. Structure of an integrated stamping tool design CAE software system under development is also presented.

Power losses and magnetic forces analysis in large dipole magnets cryostat

The magnetic analyses performed in the design process of the cryostat of a superconducting dipole magnet, with on axis magnetic flux density of 5 T and overall length about 4 m are presented. The high values of magnetic flux and stored energy require an accurate evaluation of the eddy currents induced on the cryostat structure during a discharge of the magnet. This evaluation is needed both to design the mechanical structure of the cryostat and to estimate the heating of the conducting parts. A comparative study of the structure, using different materials and evaluating time effects of electrical disconnections in the metallic parts, has been performed by means of a three dimensional finite element code. The efficiency of the different solutions is compared and discussed. >

Impact analysis of fiber reinforced metal. 1st Report. Two dimensional impact analysis code.

Two dimensional finite element code was developed. It can analyze the deformation of fiber reinforced metal matrix composites under lateral impulsive loading. Two types of rectangular isoparametric element were used. Using this code, elastic-plastic large displacement problems with anisotropy can be treated. The varidity of the code was demonstrated by calculating four different types of problems and carefully examining their results. Problems delt were elastic large displacement dynamic analysis of cantilever beam, anisotropic analysis of rigid punch indentation, elastic-plastic large displacement dynamic analysis of clamped beam and elastic analysis of plate with finite strain. Dynamic tensile tests of boron/aluminum composites were analyzed by this code. Fair agreement was obtained between the experimental and numerical results, though it is difficult to compare these results exactly because of some scatter in the experimental data.