Purpose Finite Element Analysis Software Research Articles

Real-Time Hybrid Simulation Using Nonlinear Autoregressive with Exogenous Input Model through Data-Driven Arbitrary Polynomial Chaos Surrogate

The current practice of real-time hybrid simulation (RTHS) often requires specialized finite element programs for computational modeling of the analytical substructures. Considering the limited nonlinear modeling capacity or the increasing computation cost for complex modeling, surrogate models of the analytical substructure provide novel alternatives for RTHS to avoid finite element analysis with fast computation. This study explores the use of arbitrary polynomial chaos expansion (APC) and nonlinear autoregressive with exogenous input (NARX) model to emulate the dynamic behavior of analytical substructures in RTHS. The NARX model training can be conducted numerically in an off-line mode using existing general purpose finite element analysis software, and its implementation presents minimum computational demands on the RTHS equipment. RTHS of a single-degree-of-freedom structure with a self-centering viscous damper is conducted as proof of concept to experimentally demonstrate the effectiveness and superiority of the proposed APC-NARX-based approach. The APC is further compared with other metamodeling techniques including polynomial chaos expansion (PCE) and Kriging to surrogate NARX model coefficients to account for ground motion uncertainties in RTHS. It is demonstrated that APC-NARX modeling with optimal order enables better accuracy of RTHS results than those of Kriging- and PCE-NARX.

周期的な凹凸表面上を摺動するゴムの摩擦係数の解析

The friction coefficient between tire tread rubber and road surface is an important property for tire performances and the prediction of the friction coefficient is also important．In this study, the general purpose finite element analysis software “Abaqus” is used to obtain the hysteresis friction behavior between periodic rigid surfaces and rubber models in which hyperelastic and viscoelastic properties are taken into account．A multi-scale analysis is used to calculate the friction coefficients of each scale．The contact load between a road surface and a rubber model is determined by the average contact pressure calculated by a larger scale model analysis．As the model scale is smaller, the deformation of the rubber model and the friction coefficient become larger. The maximum friction coefficient is about 0.8 in λ = 1×10-4 mm scale model.

Analysis of 3D linear elastic masonry-like structures through the API of a finite element software

A new numerical procedure is presented to perform the analysis of three-dimensional linear elastic no-tension structures exploiting the application programming interface of a general purpose finite element analysis software. Masonry is replaced by an equivalent orthotropic material with spatially varying elastic properties and negligible stiffness in the case of cracking strain. A non-incremental algorithm is implemented to define the distribution of the equivalent material, minimizing the strain energy so as to achieve a compression-only state of stress for any given compatible load. Applications are shown for masonry-like solids of general shape visualizing load paths in walls subject to dead loads and out-of-plane live loads, circular domes under self-weight and a groin vault acted upon by both vertical and horizontal seismic loading.

Nonlinear buckling analysis of 2-D cold-formed steel simple cross-aisle storage rack frames

Industrial storage racks are among the most important structures made from cold-formed steel sections. They are widely used due to the increasing need for rational space utilization in warehouses, and other facilities used to store goods. Pallet rack is a material handling, storage aid system designed to store materials on pallets. Although there are many varieties of pallet racking, all types allow for the storage of palletized materials in horizontal rows with multiple levels. Rack systems are widely used in warehouses where they are loaded with valuable goods. The cold-formed steel columns usually have open cross-sections and are thin walled, making them vulnerable to torsional-flexural buckling and local buckling. The loss of goods may be greater than the total cost of the rack on which the goods are stored, which can indirectly affect the owner. Therefore, understanding the stability of rack structures is very important. This paper deals with numerical linear and nonlinear buckling analysis of 2-D cold-formed steel simple cross-aisle storage rack frames. The main focus of the study is to ascertain the stability of 2-D frames of a pallet racking system. With this objective, a pallet racking system with cold-formed steel sections is simulated by three-dimensional models using shell elements in ABAQUS, a general purpose finite element analysis software. Linear and nonlinear buckling analyses are carried out on these frames. Results are obtained from finite element analysis of frames with 12 types of column sections. Spacer bars and channel stiffeners are used to improve the torsional strength of original open cross sections. Results show that spacer bars and channel stiffeners are very effective in enhancing the strength of cold-formed steel pallet rack structures.

A methodology to consider local material properties in structural optimization

We propose a finite element methodology to consider local material properties for large cast iron components in shape optimization. We found that considering local strength instead of uniform strength within shape optimization brings to different results in terms of safety-cost balance for the same component. It is well known that local mechanical properties of large cast iron components are defined by their microstructure and defects, which locally affect the strength of the components. Considering or not local mechanical properties can dramatically change a component reliability evaluation during its design. Since a typical industrial aim for shape optimization is trying to get the optimal solution in terms of component quality and cost, considering local material properties is even more important than in traditional design process where no optimization techniques are used. We compute solidification process parameters via finite element solidification analysis, and then we exploit experimental correlation between these parameters and ultimate tensile strength to evaluate the local reliability of the finished component under its static loading conditions. We believe that this methodology represents an opportunity to better design casting components when mechanical properties are deeply affected by their production process as described in the provided examples. In these examples, we wanted to minimize casting cost constrained by a target reliability and we get component cost reduction by considering local material properties. Future research will address the problem of using dedicated casting simulation software instead of general purpose finite element analysis software to compute solidification analysis and then introducing fatigue analysis and correlation between fatigue material properties and casting process output variables.

Design optimization of spot welded structures to attain maximum strength

This study presents design optimization of spot welded structures to attain maximum strength by using the Nelder-Mead (Simplex) method. It is the main idea of the algorithm that the simulation run is executed several times to satisfy predefined convergence criteria and every run uses the starting points of the previous configurations. The material and size of the sheet plates are the pre-assigned parameters which do not change in the optimization cycle. Locations of the spot welds, on the other hand, are chosen to be design variables. In order to calculate the objective function, which is the maximum equivalent stress, ANSYS, general purpose finite element analysis software, is used. To obtain global optimum locations of spot welds a methodology is proposed by modifying the Nelder-Mead (Simplex) method. The procedure is applied to a number of representative problems to demonstrate the validity and effectiveness of the proposed method. It is shown that it is possible to obtain the global optimum values without stacking local minimum ones by using proposed methodology.

Nonlinear finite element analysis of masonry wall strengthened with CFRP strips

In many experimental studies, it has been proved that unreinforced masonry (URM) brick walls have high strength against lateral forces acting in plane. However, out-of-plane strength of URM brick walls against lateral forces has found to be quite low. According to the experiences that were obtained from the major earthquakes, the low out-of-plane performance of URM brick walls resulted in excessive loss of human lives during an earthquake, hence the strengthening of URM brick walls with CFRP strips has been appeared to be a very important subject. However, very limited literature has been found. Especially, the data obtained from experimental studies must be increased for the true understanding of the behavior of strengthened brick walls under out-of-plane lateral forces. However, in most cases, this procedure required large number of expensive experiments. At this stage, numerical analysis can be an appropriate choice, thus in this paper a finite element model is presented for modeling URM brick walls that are strengthened with CFRP strips. The numerical results are compared with the experimental ones and consistent results are obtained from the finite element model. General purpose finite element analysis software ANSYS is used throughout this study. Contact elements are used along the masonry wall–CFRP strip interfaces for the investigation of the stress distribution and load – strain behavior.

Natural vibration analysis of vertical rectangular plates and stiffened panels in contact with fluid on one side

This article presents a simple and efficient procedure for the natural vibration analysis of rectangular plates and stiffened panels in contact with fluid on one side. The assumed mode method is applied, where the natural frequencies and mode shapes are obtained by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange’s equation of motion. The Mindlin thick plate theory is applied for a plate, and in the case of stiffened panels, the effect of framing is taken into account by adding its strain and kinetic energies to the corresponding plate energies. Potential flow theory assumptions are adopted for the fluid, and free surface waves are ignored. The fluid velocity potential is derived from the boundary conditions for the fluid and structure and is utilized for the calculation of added mass using the assumed modes. The applicability and accuracy of the developed procedure are illustrated with several numerical examples using a developed in-house code. A comparison of the results with those obtained by general purpose finite element analysis software is provided, where very good agreement is achieved.

Computational Methods for Inclined Cracks in Orthotropic Functionally Graded Materials Under Thermal Stresses

This article sets forth two different computational methods developed to evaluate fracture parameters for inclined cracks lying in orthotropic functionally graded materials, that are under the effect of thermal stresses. The first method is based on the J k -integral, whereas the second entails the use of the J 1-integral and the asymptotic displacement fields. The procedures introduced are implemented by means of the finite element method and integrated into a general purpose finite element analysis software. Numerical results are generated for an inclined edge crack in an orthotropic functionally graded layer subjected to steady-state thermal stresses. Comparisons of the mixed-mode stress intensity factors computed by the use of the proposed methods to those calculated by the displacement correlation technique point out that both approaches lead to numerical results of high accuracy. Further results are provided in order to illustrate the influences of inclination angle, material property gradation, and crack length upon the thermal fracture parameters.

Hygrothermal Fracture Analysis of Orthotropic Functionally Graded Materials UsingJk-Integral-Based Methods

This paper puts forward two differentJk-integral-based methods, which can be used to perform mixed-mode fracture analysis of orthotropic functionally graded materials subjected to hygrothermal stresses. The first method requires the evaluation of both components ofJk-integral, whereas the second method employs the first componentJ1and the asymptotic crack tip displacement fields. Plane orthotropic hygrothermoelasticity is the basic theory behind theJk-integral formulation, which is carried out by assuming that all material properties are functions of the spatial coordinates. Developed procedures are implemented by means of the finite element method and integrated into a general purpose finite element analysis software. Temperature and specific moisture concentration fields needed in the fracture analyses are also computed through finite element analysis. Each of the developed methods is utilized in conjunction with the superposition technique to calculate the hygrothermal fracture parameters. An inclined crack located in a hygrothermally loaded orthotropic functionally graded layer is examined in parametric analyses. Comparisons of the results generated by the proposed methods do indicate that both methods lead to numerical results of high accuracy and that the developed form of theJk-integral is domain independent. Further results are presented so as to illustrate the influences of crack inclination angle, crack length, and crack location upon the modes I and II stress intensity factors.

Study on Thermal and Structural Behavior of a Cable-Stayed Bridge under Potential Tanker Truck Fires

Bridges are important parts of traffic systems and need to provide the necessary safety for the traveling public. Fire is one of the most severe hazards that bridges may subject to during their lifetime. In recent years, due to rapid development of transportation systems, as well as increasing transport of hazardous materials, bridge fires have become a concern. Bridge fires caused by crashing of vehicles and burning of gasoline are much more severe than building fires and are characterized by a fast heating rate and a higher peak temperature which could lead to bridge collapse. Bridge failures during a fire can result in the disruption of commerce and services, and most importantly the loss of human life. It has become necessary to consider the potential exposure of bridges to flames from oil or liquefied petroleum gas fires. In this paper, potential fire scenarios relevant for a cable-stayed bridge crossing the Yangtze River are analyzed firstly, then the temperature distribution in key elements and the global structural behavior of the bridge under tanker truck fires is calculated by using general purpose finite element analysis software ANSYS. Numerical simulation results demonstrate that cable-stayed bridge may collapse under some specific fire scenarios and it is necessary to consider fire safety in bridge design.

Finite Element Analysis of Fire Behavior of Steel Girders in Bridges

Fire is one of the most severe hazards to which bridges may be subjected during their lifetime. In recent years, due to rapid development of transportation systems, as well as increasing transport of hazardous materials, bridge fires have become a concern. Bridge fires caused by crashing of vehicles and burning of gasoline are much more severe than building fires and are characterized by a fast heating rate and a higher peak temperature which could lead to bridge collapse. Bridge failures during a fire can result in the disruption of commerce and services, and most importantly the loss of human life. In this paper, thermal and structural behavior of a steel girder of highway bridge overpass in the East Bay’s MacArthur Maze in Oakland collapsed on April 29, 2007 is studied by using general purpose finite element analysis software ABAQUS. Finite element analysis results demonstrate that unprotected steel bridge may collapse untimely under some fire scenarios and it is necessary to consider fire safety in steel bridge design.

Statics Analysis on Workbenches of Three Kinds of Electromaglev Linear Feed Unit

Based on the disciplines theory such as the mechanics and electromagnetics, this paper presents three kinds of electromaglev linear feed unit, with the help of the 3D modeling software Solidworks and large general purpose finite element analysis software ANSYS. The statics analysis on workbenches of the three kinds of electromaglev linear feed unit are made by using of ANSYS, then the results are analyzed and compared. It can be identified as the conclusion that, the structural stiffness on workbenches of the three kinds of magnetic linear feed unit can basically meets the requirement, and all of them can be selected as the needed structural design. But the four-L separately suspended and oriented type electromaglev linear feed unit has the better structure stiffness, and take the weight, cost, load capacity and dynamic characteristics and other factors into account, we preferred to choose the workbench design of the four-L-pillar separately suspended and oriented type electromaglev linear feed unit.

Análisis térmico de soldadura GTAW sobre placa de acero AISI 316L empleando el método de elementos finitos

En el presente trabajo se realiza la modelación térmica de soldadura GTAW sobre placa de acero inoxidable AISI 316L. Se analizan los aspectos teóricos más relevantes a considerar durante la ejecución de un análisis de este tipo. En la simulación se emplea un software de análisis por elementos finitos de uso general y se enriquece una metodología, previamente desarrollada, para la modelación en 3D no lineal transitoria del proceso de soldeo. En dicha metodología se implementa una subrutina en lenguaje APDL, programada con el modelo volumétrico de fuente calor de doble elipsoide, en un sistema de coordenadas cartesiano. Se analiza la influencia del paso de tiempo seleccionado sobre los resultados de la simulación. Finalmente se valida la metodología enriquecida, en base a la correlación de los resultados del modelo respecto a los resultados experimentales.

Simulation of wear and contact pressure distribution at the pad-to-rotor interface in a disc brake using general purpose finite element analysis software

Passenger car disc brakes are safety-critical components whose performance depends strongly on contact conditions at the pad-to-rotor interface. The interface can be classified as a conformal dry sliding contact. During braking both brake pad and rotor surfaces are worn, affecting the useful life of the brake as well as its behavior. This paper discusses how wear of the pad-to-rotor interface can be predicted using general purpose finite element analysis software. A three-dimensional finite element model of the brake pad and the rotor is developed to calculate the pressure distribution in the pad-to-rotor contact. A wear simulation procedure based on a generalized form of Archard's wear law and explicit Euler integration is used to simulate the wear of the brake pad under steady-state drag conditions.

A Comparison of Methods for Predicting Residual Stresses in Strain-Hardening, Autofrettaged Thick Cylinders, Including the Bauschinger Effect

High-pressure vessels, such as gun barrels, are autofrettaged in order to increase their operating pressure and fatigue life. Autofrettage causes plastic expansion of the inner section of the cylinder, setting up residual compressive stresses at the bore after relaxation. Subsequent application of pressure has to overcome these compressive stresses before tensile stresses can be developed, thereby increasing its fatigue lifetime and safe working pressure. This paper presents the results from a series of finite element models that have been developed to predict the magnitude of these stresses for a range of end conditions: plane stress and several plane-strain states (open and closed ended, plus true plane strain). The material model is currently bilinear and allows consideration of strain hardening and the Bauschinger effect. Results are compared to an alternative numerical model and a recent analytical model (developed by Huang), and show close agreement. This demonstrates that general purpose finite element analysis software may be used to simulate high-pressure vessels, justifying further refining of the models.

A beam segment element for dynamic analysis of large aqueducts

Large aqueduct structure is a complex structure that is commonly used in hydraulic engineering, especially in large-scale water conveying projects. The analysis of dynamic response for an aqueduct structure is necessary if the aqueduct is built in an earthquake area. Traditional 3D finite element analysis is time consuming and the existing simplified response method cannot take into account all the effects, such as the bending-torsion coupling effect and the constrained torsion, of the deformations of the thin wall structure of the aqueduct body. For this special structure, a simple and yet accurate model for dynamic analysis is needed. In this paper, a beam segment element is developed and used for the calculation of dynamic response for aqueduct structures. With the frame of the aqueduct being modeled using beam element, the proposed model can calculate the dynamic response of the whole aqueduct structures. Results are compared with that of a general purpose finite element analysis software using 3D finite element model. Good agreement is achieved between the two models. However, the proposed model needs less elements and much less computing time.