Influence Of Material Nonlinearity Research Articles

Static behavior of ribbed folded plate roof under vertical uniform load—Experimental study and meshfree method analysis

SummaryFolded plate roofs are widely used in building roofs due to their light weight and high stiffness. However, traditional folded plate roofs are often limited in application due to insufficient stiffness under the current trend of pursuing larger‐span roofs. Ribbed folded plate roofs can effectively solve this problem because ribs not only increase the stiffness of the roof and reduce stress concentration, but they are also easy to be formed into various shapes to meet different needs for buildings. Therefore, the detailed analysis was carried out on a reinforced concrete ribbed folded plate roof (RCRFR) under the vertical uniform load to investigate its static behavior. The bearing capacity, failure mode, load–displacement relationship, and strain variation were obtained through the test. Additionally, based on the finite element (FE) method, not only a comparison was conducted between RCRFR and reinforced concrete ribless folded plate roof (RCLFR), but the influence of material nonlinearity and geometric nonlinearity on the structure was also investigated. Moreover, the bending characteristics of RCRFR under design load were analyzed based on the reproducing kernel particle method. The experimental results showed that this structure had good mechanical properties within the design load. In the overload stage, the concrete on the underside of the structure was severely damaged. Furthermore, the yielding of the ribbed plate's reinforcing bars caused the increased vertical deformation difference between the ribbed plate and the top chord, and the ribbed plate and the central ridge beam. Eventually, the failure of the anchorage of the ribbed plate's reinforcing bars anchored in the central ridge beam and the top chord led to the loss of structural load‐bearing capacity. The FE analysis results demonstrated that ribs enhance the stiffness of the structure, with material nonlinearity having the primary impact and geometric nonlinearity exerting a secondary effect. The meshfree method analysis was in concordance with the experimental results as well as those of the FE analysis.

Research on ultimate Bearing Capacity of large Steel Box Girders under bending Moment

In order to study the ultimate bearing capacity of large welded box girder with initial imperfections, this paper considers the influence of material nonlinearity, geometric nonlinearity and initial imperfections, and uses the arc length increment method to modify Newton-Raphson formula to solve the problem. Through a large number of numerical simulation calculation, the calculation formula of stability ultimate bearing capacity of box girder under bending moment is summarized. The formula takes web height thickness ratio and flange width thickness ratio as parameters, which has a certain reference value for calculation and design of stability ultimate bearing capacity of welded box girder.

Wave propagation in a continuum phononic material with geomaterial-inspired nonlinearity

This presentation discusses the nonlinear wave propagation in a continuum phononic material with nonlinear mechanisms inspired by geomaterials. Geomaterials can exhibit nonlinear wave responses due to mechanisms such as material nonlinearity or lack of bonding between phases of material. We study the interaction of nonlinear and phononic behavior by introducing two geomaterial-inspired nonlinear mechanisms into a phononic material. The influence of material nonlinearity and nonlinearity due to delaminations between material phases are studied in a bilayer finite element model composed of alternating layers of stiff linear elastic material and soft hyperelastic material. To model delaminations, a binary contact condition is applied at the interface between layers. Measurements of the quasi-static nonlinear mechanical response of delaminations of different lengths are used as inputs into the finite element method simulations. The influence of the delamination nonlinearity plus material nonlinearity on the phononic material is studied in a full-scale time-domainfinite element model. This model is used to further probe the interaction between phononic band gaps and nonlinear wave response, as well as the dependence of delamination size and location on the nonlinear wave response.

Tests on stainless steel frames. Part II: Results and analysis

Austenitic stainless steels offer a suitable combination of high ductility, adequate toughness, considerable strain hardening and good fire resistance, making them excellent construction materials, especially for structures subjected to accidental loading such as seismic and/or fire events. With most of the research over the recent years devoted to the behaviour of single isolated stainless steel members, advances on structural systems are scarce, yet necessary, for the further development of design codes. Hence, an extensive experimental programme on EN 1.4301 austenitic stainless steel frames including tests at different structural levels –material, cross-section, member and frame levels– has been carried out at the Laboratory of Technology of Structures and Materials at Universitat Politècnica de Catalunya. The companion paper presents the tests carried out at cross-section and member level, and the knowledge gained from the planning of the experimental set-up for frame tests, including the adopted loading schemes, auxiliary elements and instrumentation. This paper presents the results of the four tests conducted on austenitic stainless steel frames under static vertical and horizontal loading. The analysis of the test results allowed to investigate the interaction of material and geometrical nonlinearities experimentally, as well as the assessment of the EN 1993-1-4 and EN 1993-1-1 provisions for the global analysis of stainless steel frames, where the influence of material nonlinearity on second order effects is evaluated, and which is currently limited to numerical studies only.

Numerical simulations of coupled moisture and heat transfer in wood during kiln drying: Influence of material nonlinearity

Finite element simulations of coupled thermal and moisture fields in wood during kiln drying were observed with a focus on non-isothermal moisture transfer in three dimensional orthotropic models of wood with an initial moisture content below the fiber saturation point. Four different unsteady-state numerical models of the drying process were compared with the assumptions given by standards commonly used in wood kiln-drying processes. The first model describes linear simulation, and the other three models present nonlinear simulation using variable material coefficients dependent on temperature and moisture content, differing in settings of the Soret effect (thermodiffusion). A linear model was useful for predicting only the average moisture content during drying. Moreover, the nonlinear simulations were useful for computing the moisture content distribution. High differences (2.31% of moisture content) were found between the flow of moisture predicted by numerical models and standard requirements.

Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing

Abstract The thermo-elastic-plastic finite element method (FEM) is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas (TIG) arc-assisted laser welding-brazing (A-LWB) butt joint. The influence of material nonlinearity, geometrical nonlinearity and work hardening on the welding process is studied, and the differences in the welding temperature field, residual stress and welding distortion by A-LWB and by single laser welding-brazing (SLWB) are analyzed. The results show that the thermal cycle, residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments, which verifies the effectiveness of FEM. Compared with the SLWB, A-LWB can make the high-temperature distribution zone of weld in width direction wider, decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress. And the welding deformation also decreases to some extent.

Influence of material nonlinearity on the buckling resistance of stainless steel shells

One of the greatest challenges in the design of shell structures made of stainless steel compared to those made of carbon steel is the meaningful consideration of the nonlinear stress-strain behaviour of stainless steels which has a significant influence on the buckling behaviour of axially compressed shells in the medium slenderness range and lead to lower buckling strengths. A detailed description of the actual material behaviour of stainless steels is given by the material model developed by Arrayago, Real and Gardner on the basis of the by Rasmussen modified two stage Ramberg-Osgood material model. One of the parameters of which the model consists is the exponent n, which describes the nonlinear behaviour just before the 0.2% proof stress. This exponent is of great importance for the buckling behaviour of axially loaded shell structures of medium slenderness. For this reason, a thorough numerical parametric study has been conducted in order to evaluate the effect of the nonlinear material behaviour described by the exponent n on the buckling resistance of austenitic, duplex, and ferritic stainless steel shells. The numerical model has been validated by experimental results of axially compressed cylindrical shells conducted in the frame of the European RFCS-research project BiogaSS.

On the influence of material non-linearities in geometric modeling of kink band instabilities in unidirectional fiber composites

The axial compressive failure of aligned fiber composites triggered by kink band instabilities is the topic of investigation herein. Particular emphasis is put on the accurate prediction of the post-failure regime, where fiber composites are known to exhibit substantial post-failure strength. In this regard, a previous analytical model, based on geometric relationships and energy principles, is enhanced by consistently taking into account material non-linearities. Therefore, a non-linear constitutive law is introduced herein based on a newly developed exponential formulation. This non-linear constitutive law is subsequently implemented into the stress–strain response in interlaminar shearing as well as the compression response. The model enhancements are validated against published experimental data yielding excellent comparisons. Furthermore, the relevance of modeling non-linear material behavior in interlaminar dilation and bending is assessed using a bilinear constitutive law. However, implementing non-linear material behavior does not yield any improvements and can therefore be neglected.

Study on Finite Element Nonlinearity Calculation of Folding Rudder

This paper introduces material nonlinear finite element method and the establishment of finite element equation and realizes accurate modeling and calculation of folding rudder using material nonlinear finite element method. According to calculation and analysis, it is shown that the stress in contact part is relatively large due to stress concentration and material enters plastic deformation area. The influence of material nonlinearity on deformation calculation cannot be neglected. In this paper, deformation calculation results well coincide with experimental results.

Research on Overall Stability of Concrete-Filled Steel Tubular Bowstring Arch Bridge

Based on the finite element theory, the computational model, one through concrete filled steel tube tied-arch bridge was established under the considerations of both geometrical non-linearity and material non-linearity. And using the ANSYS software to study the bridge's arch rib construction process and the overall stability after the complete construction, the results show that the full-bridge’s stability coefficient are larger than other concrete-filled steel tube arch bridge; the in-plane stiffness is larger than the out-plane stiffness, and the influence of material non-linearity on the stability is notable. The results provide a good reference for the similar bridge's design and construction.

유한요소 모델 변수의 역 추정법을 이용한 생체의 물성 규명

An inverse finite element (FE) model parameter estimation algorithm can be used to characterize mechanical properties of biological tissues. Using this algorithm, we can consider the influence of material nonlinearity, contact mechanics, complex boundary conditions, and geometrical constraints in the modeling. In this study, biomechanical experiments on macro and micro samples are conducted and characterized with the developed algorithm. Macro scale experiments were performed to measure the force response of porcine livers against mechanical loadings using one-dimensional indentation device. The force response of the human liver cancer cells was also measured by the atomic force microscope (AFM). The mechanical behavior of porcine livers (macro) and human liver cancer cells (micro) were characterized with the algorithm via hyperelastic and linear viscoelastic models. The developed models are suitable for computing accurate reaction force on tools and deformation of biomechanical tissues.

Numerical damage assessment of Haghia Sophia bell tower by nonlinear FE modeling

In the present paper, the numerical damage assessment of the masonry bell tower called “Haghia Sophia” in Trabzon, Turkey is performed by nonlinear 3D finite element modeling. The behavior of bell tower is determined under several different conditions: nonlinear static analysis containing dead and wind loads and nonlinear seismic analysis. In addition to, an assessment of the tower’s stability with respect to the tilt of the tower is carried out by means of a nonlinear analysis. In the nonlinear dynamic analysis, the east–west component of 1992 Erzincan earthquake is used. Cracking and crushing of the masonry have been taken into account, as well as the influence of material nonlinearity. The numerical analysis has given a valuable picture of possible damage evolution, providing useful hints for the prosecution of structural monitoring. The displacement and stress fields, as well as the distribution of cracking have been calculated and compared to the actual distribution of fractures in the tower. It is seen from the numerical results that there is a good agreement with present damages of the bell tower.

Nonlinear Stability Analysis on the Concrete Casting Step of Long-Span Concrete-Filled Steel Tube Arch Bridge

In recent years, concrete-filled steel tube (CFST) was developed and used extensively in civil engineering in China. In this paper, the method for stability analysis of long-span CFST arch bridge was introduced. Based on Jingyang River Bridge in Hubei province of China and finite element method, the spatial model was set up. Both linear and nonlinear stability of long-span CFST arch bridge in construction process were analyzed. The result indicated the influence of geometrical nonlinearity was small and the influence of material nonlinearity was evident. So, for analyzing the stability of long-span CFST arch bridge, the influence of geometrical nonlinearity and material nonlinearity must be considered at the same time. The results of paper were used to provide the basis for the construction control of the bridge.

Thermomechanics of Coupled Fields in Passive and Piezoactive Inelastic Bodies Under Harmonic Deformation

ABSTRACT The present article gives a brief overview of studies made at S. P. Timoshenko Institute of Mechanics of the National Academy of Sciences of Ukraine on thermomechanics of coupled fields in nonlinear inelastic passive and piezoactive materials and bodies under monoharmonic deformation. Our attention will be focused on the following subjects: (1) development of the nonlinear models of passive (without piezoeffect) and piezoactive (with piezoeffect) materials for monoharmonic vibrations with accounting for influence of such factors as material nonlinearity, dissipation, and temperature of dissipative heating; (2) development of the thermomechanical models of nonhomogeneous thin-walled inelastic elements under monoharmonic deformation; (3) development of numerical and analytical methods of the solution of coupled problems; (4) investigation of the influence of material nonlinearity, dissipation and temperature of dissipative heating on regularities of vibrations of the bodies with the passive and piezoactive materials, including influence of these factors on the efficiency of vibration control of elements with distributed sensors and actuators. Problem 1 is solved on the basis of concept of complex material characteristics. Accordingly the simplified nonlinear constitutive equations of passive and piezoactive materials are identical to the constitutive equations of linear theory of viscoelasticity, but the complex mechanical and electromechanical characteristics are temperature and field-dependent quantities. Averaged for period the rate of dissipation coincides with averaged electromechanical power. On the basis of these simplified constitutive equations the statement of coupled problems of thermomechanics in the passive and piezoactive inelastic spatial bodies are given. To solve Problem 2, the mechanical hypotheses of Kirchhoff–Love and similar hypotheses for electric field quantities and temperature are introduced. As a result the statement of coupled nonlinear problems of thermomechanics in the passive and piezoactive inelastic thin-walled elements are given. To solve Problem 3 one needs to use some iterative techniques such as method of step-by-step integration in time, method of variable characteristics and accelerating Steffensen-Eitken procedure. At each iteration, the linearized electromechanical and heat conductivity problems are solved by a method of discrete orthogonalization or by a finite element method. By the use of variational methods, the analytical solutions are also obtained. On the basis of the mentioned models, methods, and analytical and numerical solutions obtained, the influence of material nonlinearity, dissipation, and self-heating on the vibrations of nonhomogeneous spatial and thin-walled elements (in particular on the efficiency of active damping of vibrations of the elements) are investigated (Problem 4).

A three-dimensional finite element model for stress analysis of adhesive joints

This paper presents a new model for three-dimensional finite element analysis of adhesive joints. The model considers geometric and material nonlinearities and uses solid brick elements as well as specially developed interface elements. The interface elements allow the calculation of stresses at the adherend–adhesive interfaces. The application of the model to a single-lap joint is presented. The results of a linear elastic analysis highlight the three-dimensional nature of the stresses and stress concentrations at interfaces. The influence of material nonlinearities on the behavior of the joint is also discussed.

INTERNAL RESONANCES IN WHIRLING STRINGS INVOLVING LONGITUDINAL DYNAMICS AND MATERIAL NON-LINEARITIES

Internal resonance mechanisms between near-commensurate longitudinal and transverse modes of a taut spatial string are identified and studied using an asymptotic method, and the influence of material non-linearities on the resulting solutions is considered. Geometrical non-linearities couple longitudinal motions to in-plane and out-of-plane transverse motions, resulting in resonant and non-resonant interactions between linearly orthogonal string modes. Past studies have included only transverse modes in the description of string motions and have predicted periodic, quasi-periodic, and chaotic whirling motions arising from the geometrical non-linearities. This study considers further the inclusion of longitudinal motions and a non-linear material law, which are both appropriate for the study of rubber-like strings. An asymptotic analysis captures the aforementioned whirling motions, as well as a new class of whirling motions with significant longitudinal content. Periodic, quasi-periodic, and aperiodic (likely chaotic) responses are included among these motions. Their existence, hardening–softening characterization, and stability are found to be highly dependent on the magnitude of the material non-linearities.

Nonlinear Dynamics of a Taut String with Material Nonlinearities

A spatial string model incorporating a nonlinear (and nonconservative) material law is proposed using finite deformation continuum mechanics. The resulting model is shown to reduce to the classical nonlinear string when a linear material law is used. The influence of material nonlinearities on the string’s dynamic response to excitation near a transverse natural frequency is shown to be small due to their appearance at high orders only. Material nonlinearities appear at low order in the equations for excitation near a longitudinal natural frequency, and a solution for this case is developed by applying a second order multiple scales method directly to the partial differential equations. The material nonlinearities are found to influence both the degree of nonlinearity in the response and its softening or hardening nature.

Iterative strategies for solving systems of linear, algebraic equations arising in 3D BE-FE analyses of tunnel drivings

Simulations of excavations of tunnels can be performed by means of a coupling strategy using the boundary-element-method (BEM) and the finite-element-method (FEM). The BEM is employed for the discretization of the far-field of the tunnel, whereas the FEM is used for the interior of the tunnel and its vicinity. This strategy is based on the assumption that the influence of material non-linearities in the far-field can be neglected. The coefficient matrices of the resulting systems of linear, algebraic equations consist of a symmetric, banded, sparse part resulting from the FE subdomain and an unsymmetric, fully populated part obtained from the BE subdomain. Substantial reductions of the CPU time and the disk space required for the solution of the systems of linear, algebraic equations can be achieved by employing iterative solvers with preconditioning and using the computer hardware intelligently. In this paper, two strategies based on such solvers are proposed and explained in detail. The convergence behaviour of the implemented iterative solvers with regards to pure BE calculations is studied by means os solving selected numerical examples. The advantages of the two proposed methods relative to the original, direct solution strategy are demonstrated on the basis of coupled simulations. Additionally, some comments concerning the use of iterative solvers on a vector computer are given. © 1997 John Wiley & Sons, Ltd.

Influence of material non linearity in the articulated wood structures dynamics

This paper studies the effect of the non-linear behavior of the material in the movement of an articulate structure made of wooden bars, by means of an iterative of calculation method with lumped masses in the nodes.

Material Nonlinearity Effects in the Stress Analysis of Conical Disk Springs

The influence of material nonlinearity on the behavior of conical disk springs (Belleville springs) is investigated by means of finite element models. Both the load-deflection curve and the stress field of this kind of spring are shown to be significantly affected by the elastic-plastic behavior of the material. In particular, as far as the actual stress field is concerned, consideration of the material nonlinearity explains some apparent contradictions of well-known analytical formulations, such as the Almen-La´szlo´ theory, based on the usual assumption of linear elastic behavior of the material.