scholarly journals Nonlinear analysis of isotropic slab bridges under extreme traffic loading

2015 ◽  
Vol 42 (10) ◽  
pp. 808-817
Author(s):  
Donya Hajializadeh ◽  
A. Salam Al-Sabah ◽  
Eugene J. OBrien ◽  
Debra F. Laefer ◽  
Bernard Enright
Keyword(s):  
Limit State ◽  
Element Model ◽  
Nonlinear Analyses ◽  
Traffic Loading ◽  
Linear Elastic ◽  
Isotropic Slab ◽  
Long Run ◽  
Load Effects ◽  
Linear And Nonlinear ◽  
First Time

Probabilistic analysis of traffic loading on a bridge traditionally involves an extrapolation from measured or simulated load effects to a characteristic maximum value. In recent years, long run simulations, whereby thousands of years of traffic are simulated, have allowed researchers to gain new insights into the nature of the traffic scenarios that govern at the limit state. For example, mobile cranes and low-loaders, sometimes accompanied by a common articulated truck, have been shown to govern in most cases. In this paper, the extreme loading scenarios identified in the long-run simulation are applied to a non-linear, two-dimensional (2D) plate finite element model. For the first time, the loading scenarios that govern in 2D nonlinear analyses are found and compared to those that govern for 2D linear and one-dimensional (1D) linear and nonlinear analyses. Results show that, for an isotropic slab, the governing loading scenarios are similar to those that govern in simple 1D (beam) models. Furthermore, there are only slight differences in the critical positions of the vehicles. It is also evident that the load effects causing failure in the 2D linear elastic plate models are significantly lower, i.e., 2D linear elastic analysis is more conservative than both 2D nonlinear and 1D linear and nonlinear analyses.

Finite element simulation of folding carton erection failure

2007 ◽  
Vol 221 (7) ◽  
pp. 753-767 ◽  
Author(s):  
D M Sirkett ◽  
B J Hicks ◽  
C Berry ◽  
G Mullineux ◽  
A J Medland
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
High Speed ◽  
Element Model ◽  
Machine Material ◽  
Linear Elastic ◽  
Element Simulation ◽  
Packaging Industry ◽  
First Time ◽  
The Eu

In response to recent European Union (EU) regulations on packaging waste, the packaging industry requires greater fundamental understanding of the machine-material interactions that take place during packaging operations. Such an understanding is necessary to handle thinner lighter-weight materials, specify the material properties required for successful processing and design right-first-time machinery. The folding carton industry, in particular, has been affected by the new legislation and needs to realize the potential of computational tools for simulating the behaviour of packaging materials and generating the necessary understanding. This paper describes the creation and validation of a detailed finite element model of a carton during a common packaging operation. The model is applied here to address the problem of carton buckling. The carton was modelled using a linear elastic material definition with non-linear crease behaviour. Air inrush suction, which is believed to cause buckling, was quantified experimentally and incorporated using contact damping interactions. The results of the simulation are validated against high-speed video of carton production. The model successfully predicts the pattern of deformation of the carton during buckling and its increasing magnitude with production rate. The model can be applied to study the effects of variation in material properties, pack properties and machine settings. Such studies will improve responsiveness to change and will ultimately allow end-users to use thinner, lighter-weight materials in accordance with the EU regulations.

scholarly journals Inclined convection in a porous Brinkman layer: linear instability and nonlinear stability

2019 ◽  
Vol 475 (2223) ◽  
pp. 20180614 ◽  
Author(s):  
Paolo Falsaperla ◽  
Andrea Giacobbe ◽  
Giuseppe Mulone
Keyword(s):  
Boundary Conditions ◽  
Nonlinear Stability ◽  
Three Dimensional ◽  
Linear Instability ◽  
Nonlinear Analyses ◽  
Rigid Boundary ◽  
Link Type ◽  
Linear And Nonlinear ◽  
First Time ◽  
Stress Free Boundary

In this article, we deal with thermal convection in an inclined porous layer modelled by the Brinkman Law . Inertial effects are taken into account, and the physically significant rigid boundary conditions are imposed. This model is an extension of the work by Rees & Bassom (Rees & Bassom 2000 Acta Mech. 144 , 103–118 ( doi:10.1007/BF01181831 )), where Darcy's Law is adopted, and only linear instability is investigated. It also completes the work of Falsaperla & Mulone (Falsaperla & Mulone 2018 Ric. Mat. 144 , 1–17 ( doi:10.1007/s11587-018-0371-2 )), where the case of stress-free boundary conditions is studied and the inertial terms are absent. In this model, the basic laminar solution for the velocity is a combination of hyperbolic and polynomial functions, which makes the linear and nonlinear analysis much more complex. The original features of the paper are the following: we study three-dimensional perturbations , providing critical surfaces for the linear and nonlinear analyses; we study nonlinear stability with the Lyapunov method and, for the first time in the case of inclined layers, we compute the critical nonlinear Rayleigh regions by solving the associated variational maximum problem ; we give some estimates of global nonlinear asymptotical stability; we study linear instability and nonlinear stability also with the presence of the inertial term , i.e. for a finite Va.

A Case Study for Using Engineering Judgement When Analyzing Finite Element Results

2020 ◽  
Author(s):  
Sean McGuffie ◽  
Nathan Barkley
Keyword(s):  
Finite Element ◽  
Static Load ◽  
Nonlinear Analyses ◽  
Static Test ◽  
Linear Elastic ◽  
Advantages And Disadvantages ◽  
Section Viii ◽  
Linear And Nonlinear ◽  
Division 2

Abstract The authors were tasked with designing and fabricating a thick walled (t > 4.5″) ASME Division 2 – Class 2 separator vessel. Due to its service requirements, the vessel is to be regularly hydrotested at 18.87 MPa (2,737 psig). Linear-elastic finite element (FE) evaluations of the vessel indicated that it passed all required Code checks, including the hydrotest check specified in Section VIII, Division 2, Paragraph 4.1.6.2. To develop a greater understanding of the advantages and disadvantages of each method, the FE analyst on the project routinely reanalyzes vessels that have been evaluated per the linear-elastic procedures of Part 5 of the ASME Section VIII, Division 2 Code with the nonlinear procedures also specified in Part 5. This practice allows for direct comparisons of the linear and nonlinear results and for identification of situations where nonlinear analyses could provide benefit. Such an analysis was performed on this vessel under the hydro-static test condition. However, this analysis failed due to solver failure / gross instability (plastic collapse) before the full hydro-static load was applied. The solver failure was confirmed and repeated in multiple FE packages. This presented a conundrum for the authors: should the linear-elastic results be accepted since the vessel passed the linear evaluations, or should they be invalidated since the nonlinear evaluations indicated that failure could occur during a hydrotest, which given the vessel’s operations, will occur frequently? This paper discusses the additional evaluations that were required to establish confidence that the vessel could be successfully hydrotested when fabricated. These included both the Code specified evaluations, and evaluations that allowed engineering judgement to be applied to the design.

Optimization of Solar Updraft Chimneys by Nonlinear Response Analysis

2013 ◽  
Vol 283 ◽  
pp. 25-34 ◽  
Author(s):  
Reinhard Harte ◽  
Martin Graffmann ◽  
Wilfried B. Krätzig
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Limit State ◽  
Internal Flow ◽  
Response Analysis ◽  
Nonlinear Analyses ◽  
Linear Elastic ◽  
Extreme Wind ◽  
High Investment ◽  
Internal Forces

Solar updraft chimneys (SUCs) form as engines of solar updraft power plants tower-like shell structures of extreme height with rather thin shell walls, similar to high chimneys comprising multiple flue gas ducts. The height of pre-designed SUCs presently reaches up to 1000 m. Thus they are exposed chiefly to extreme wind-loads and thermal actions from the internal flow of warm air. As first design attempt, the structural analysis of solar chimneys generally is carried out by linear elastic models. For optimization, the typical shell-like wind stresses have to be constraint towards a more beam-like response behavior, approaching as far as possible linear stresses over the entire chimney circumference. This requires rather strong ring stiffeners, either as spoke-wheels in the designs of sbp (Schlaich Bergermann and Partners) or as external stiffeners in the designs of K&P (Krätzig and Partners). Both alternatives require considerable construction efforts leading to high investment costs. There exists an interesting simplification of this stiffening, namely applying to the SUC shell relatively soft external rings, and admitting large-widths cracking in the limit state of failure. This cracking constraints and equalizes the meridional stresses over the chimney’s cross-section, saving large amounts of reinforcement steel in the SUC. The design requires materially nonlinear analyses to verify the internal forces under crack-formations. The manuscript will derive this concept and demonstrate the crack analysis by example of a 750 m high solar chimney.

scholarly journals Modified differential transform method for solving linear and nonlinear pantograph type of differential and Volterra integro-differential equations with proportional delays

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Seyyedeh Roodabeh Moosavi Noori ◽  
Nasir Taghizadeh
Keyword(s):  
Exact Solution ◽  
Differential Equations ◽  
Differential Transform Method ◽  
Hybrid Technique ◽  
Transform Method ◽  
Proportional Delays ◽  
Differential Transform ◽  
Computational Work ◽  
Linear And Nonlinear ◽  
First Time

AbstractIn this study, a hybrid technique for improving the differential transform method (DTM), namely the modified differential transform method (MDTM) expressed as a combination of the differential transform method, Laplace transforms, and the Padé approximant (LPDTM) is employed for the first time to ascertain exact solutions of linear and nonlinear pantograph type of differential and Volterra integro-differential equations (DEs and VIDEs) with proportional delays. The advantage of this method is its simple and trusty procedure, it solves the equations straightforward and directly without requiring large computational work, perturbations or linearization, and enlarges the domain of convergence, and leads to the exact solution. Also, to validate the reliability and efficiency of the method, some examples and numerical results are provided.

scholarly journals Imaging the Human Thyroid Using Three-Dimensional Diffuse Optical Tomography: A Preliminary Study

2021 ◽  
Vol 11 (4) ◽  
pp. 1670
Author(s):  
Tetsuya Mimura ◽  
Shinpei Okawa ◽  
Hiroshi Kawaguchi ◽  
Yukari Tanikawa ◽  
Yoko Hoshi
Keyword(s):  
Optical Tomography ◽  
Tumor Hypoxia ◽  
Three Dimensional ◽  
Diffuse Optical Tomography ◽  
Element Model ◽  
Needle Aspiration ◽  
Human Thyroid ◽  
Tissue Oxygen Saturation ◽  
Preliminary Study ◽  
First Time

Thyroid cancer is usually diagnosed by ultrasound imaging and fine-needle aspiration biopsy. However, diagnosis of follicular thyroid carcinomas (FTC) is difficult because FTC lacks nuclear atypia and a consensus on histological interpretation. Diffuse optical tomography (DOT) offers the potential to diagnose FTC because it can measure tumor hypoxia, while image reconstruction of the thyroid is still challenging mainly due to the complex anatomical features of the neck. In this study, we attempted to solve this issue by creating a finite element model of the human neck excluding the trachea (a void region). By reconstruction of the absorption coefficients at three wavelengths, 3D tissue oxygen saturation maps of the human thyroid are obtained for the first time by DOT.

A New Reinforcement Measure Suited for Space Truss with No-Fire Operation

2014 ◽  
Vol 919-921 ◽  
pp. 401-405
Author(s):  
Zuo Yun Mei ◽  
Chuan Qing Liu ◽  
Xing Mi ◽  
Ping Wu
Keyword(s):  
Element Model ◽  
High Yield ◽  
Nonlinear Analyses ◽  
High Yield Strength ◽  
Shell Elements ◽  
Gas Stations ◽  
Space Truss ◽  
Reinforcement Measure ◽  
Space Trusses ◽  
Elastic Stage

A new reinforcement measure with no-fire operation is presented, which is very suitable for space trusses which are located in gas stations. A finite element model (FEM) is presented with shell elements and multipoint constraint elements. With this FEM, nonlinear analyses are carried out. Analytical results show that integral failure of reinforced pipe is caused by yielding of original pipe inside. So it is not necessary to reinforce original pipe using steel pipe bonded outside with high yield strength. With the increase of length of bonded pipe outside, loading according to elastic stage and ultimate bearing loading increase, it is clear that the length of bonded pipe outside is an important factor which influences the bearing capacity.

scholarly journals Exchange Rates and Monetary Fundamentals: What Do We Learn from Linear and Nonlinear Regressions?

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Guangfeng Zhang
Keyword(s):  
Exchange Rate ◽  
Exchange Rates ◽  
Correction Model ◽  
Exchange Rate Dynamics ◽  
Long Run ◽  
Exchange Rate Movements ◽  
Short Run ◽  
Us Dollar ◽  
Linear And Nonlinear ◽  
Japanese Yen

This paper revisits the association between exchange rates and monetary fundamentals with the focus on both linear and nonlinear approaches. With the monthly data of Euro/US dollar and Japanese yen/US dollar, our linear analysis demonstrates the monetary model is a long-run description of exchange rate movements, and our nonlinear modelling suggests the error correction model describes the short-run adjustment of deviations of exchange rates, and monetary fundamentals are capable of explaining exchange rate dynamics under an unrestricted framework.

Linear and nonlinear analyses of a wideband gyro-TWT

1989 ◽  
Vol 36 (4) ◽  
pp. 802-810 ◽  
Author(s):  
B.R. Cheo ◽  
A. Rekiouak
Keyword(s):  
Nonlinear Analyses ◽  
Linear And Nonlinear

scholarly journals Variation Simulation of Fixtured Assembly Processes for Compliant Structures Using Piecewise-Linear Analysis

2005 ◽  
Author(s):  
Michael L. Stewart ◽  
Kenneth W. Chase
Keyword(s):  
Piecewise Linear ◽  
Element Model ◽  
Linear Analysis ◽  
Elastic Analysis ◽  
Variation Analysis ◽  
Linear Elastic ◽  
Final Assembly ◽  
Compliant Part ◽  
Assembly Operations ◽  
Variation Simulation

While variation analysis methods for compliant assemblies are becoming established, there is still much to be done to model the effects of multi-step, fixtured assembly processes statistically. A new method is introduced for statistically analyzing compliant part assembly processes using fixtures. This method yields both a mean and a variant solution, which can characterize an entire population of assemblies. The method, called Piecewise-Linear Elastic Analysis, or PLEA, is developed for predicting the residual stress, deformation and springback variation resulting from fixtured assembly processes. A comprehensive, step-by-step analysis map is presented for introducing dimensional and surface variations into a finite element model, simulating assembly operations, and calculating the error in the final assembly. PLEA is validated on a simple, laboratory assembly and a more complex, production assembly. Significant modeling issues are resolved as well as the comparison of the analytical to physical results.

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