Finite Element Model

Plant-based fibers have been selected as suitable reinforcements for composites due to their good mechanical performances and environmental advantages. This paper describes the development of a simulation procedure to predict the temperature profile and the curing behavior of the hemp fiber/thermoset composite during the molding process. The governing equations for the non-linear transient heat transfer and the resin cure kinetics were presented. A general purpose multiphysics finite element package was employed. The procedure was applied to simulate one-dimensional and three-dimensional models. Experiments were carried out to verify the simulated results. Experimental data shows that the simulation procedure is numerically valid and stable, and it can provide reasonably accurate predictions. The numerical simulation was performed for a three-dimensional complex geometry of an automotive part to predict the temperature distribution and the curing behavior of the composite during the molding process.

We present the development and use of a novel distributed geohazard modeling environment for the analysis and interpretation of large scale earthquake data sets. Our work demonstrates, for the first time, how earthquake-related surface deformation measured from satellite images using imageodesy algorithms is coupled with analysis and simulation using finite-element numerical models.

Objective: Human body finite element models (FE-HBMs) are available in standard occupant or pedestrian postures. There is a need to have FE-HBMs in the same posture as a crash victim or to be configured in varying postures. Developing FE models for all possible positions is not practically viable. The current work aims at obtaining a posture-specific human lower extremity model by reconfiguring an existing one. Methodology: A graphics-based technique was developed to reposition the lower extremity of an FE-HBM by specifying the flexion–extension angle. Elements of the model were segregated into rigid (bones) and deformable components (soft tissues). The bones were rotated about the flexion–extension axis followed by rotation about the longitudinal axis to capture the twisting of the tibia. The desired knee joint movement was thus achieved. Geometric heuristics were then used to reposition the skin. A mapping defined over the space between bones and the skin was used to regenerate the soft tissues. Mesh smoothing was then done to augment mesh quality. Results: The developed method permits control over the kinematics of the joint and maintains the initial mesh quality of the model. For some critical areas (in the joint vicinity) where element distortion is large, mesh smoothing is done to improve mesh quality. Conclusions: A method to reposition the knee joint of a human body FE model was developed. Repositions of a model from 9 degrees of flexion to 90 degrees of flexion in just a few seconds without subjective interventions was demonstrated. Because the mesh quality of the repositioned model was maintained to a predefined level (typically to the level of a well-made model in the initial configuration), the model was suitable for subsequent simulations.

This paper deals with the assessment of vibration control performance using enhanced smart constrained layer damping (ESCLD) treatment with edge elements. A beam finite element model has been developed based on Timoshenko beam theory with partially covered ESCLD. The edge elements are modeled as equivalent springs mounted at the boundaries of the piezoelectric layer. The Golla-Hughes-McTavish (GHM) method has been used to model the viscoelastic layer. The model is validated against published experimental results. Using linear quadratic regulator (LQR) optimal control, the effects of the ESCLD on vibration suppression performance and control effort requirements are investigated. Analysis shows that edge elements significantly improve the active action transmissibility of the SCLD treatment. Due to combined overall active and passive actions, the ESCLD treatment with sufficiently stiff edge elements could outperform both the SCLD treated system and the purely active system.

Adaptive thin-film nanocomposite coatings comprised of crystalline ductile phases of gold and molybdenum disulfide, and brittle phases of diamond like carbon (DLC) and ytrria stabilized zirconia (YSZ) have been investigated by specialized microstructurally based finite-element techniques. One of the major objectives is to determine optimal crystalline and amorphous compositions and behavior related to wear and durability over a wide range of thermo-mechanical conditions. The interrelated effects of microstructural characteristics such as grain shapes and sizes, local material behavior due to interfacial stresses and strains, varying amorphous and crystalline compositions, and transfer film adhesion on coating behavior have been studied. The computational predictions, consistent with experimental observations, indicate specific interfacial regions between DLC and ductile metal inclusions are critical regions of stress and strain accumulation that can be precursors to material failure and wear. It is shown by varying the composition, resulting in tradeoffs between lubrication, toughness, and strength, the effects of these critical stresses and strains can be controlled for desired behavior. A mechanistic model to account for experimentally observed transfer film adhesion modes was also developed, and based on these results, it was shown that transfer film bonding has a significant impact on stress and wear behavior.

This paper aims to develop and validate an ANSYS finite element model to predict both the cured shape and snap-through of unsymmetric bistable laminates actuated by piezoelectric macro fibre composites attached to the laminate. To fully describe piezoelectric actuation the three dimensional compliance [s ij ], piezoelectric [d ij ] and relative permittivity [ε ij ] matrices were formulated for the macro fibre actuator. The deflection of an actuated isotropic aluminium beam was then modelled and compared to experimental measurements to validate the data. The model was then extended to bistable laminates actuated using macro fibre composites. Model results were compared to experimental measurements of laminate profile (shape) and snap-through voltage. The modelling approach is an important intermediate step toward enabling design of shape-changing structures based on bistable laminates.

Physiological studies have shown that focal articular surface defects in the human knee may progress to degenerative arthritis. Although the risk of this evolutive process is multifactorial, defect size is one of the most important factors. In order to determine the influence of osteochondral defect size and location on the stress and strain concentrations around the defect rim, a finite element model of the human knee was developed. From our results, it became clear that the size and location of cartilage defects drastically affect to those variables. No stress concentration appeared around the rim of small defects, being the stress distribution mainly controlled by the meniscus contact. On the contrary, important rim stress concentration was found for large osteochondral defects. This alteration of the stress distribution has important clinical implications regarding the long-term integrity of the cartilage adjacent to osteochondral defects. ᭧ (E. Peña), bcalvo@unizar.es (B. Calvo), miguelam@unizar.es (M. Martínez), mdoblare@unizar.es (M. Doblaré). 0010-4825/$ -see front matter ᭧

We are investigating imaging techniques to study the tumor response to photodynamic therapy ͑PDT͒. Positron emission tomography ͑PET͒ can provide physiological and functional information. High-resolution magnetic resonance imaging ͑MRI͒ can provide anatomical and morphological changes. Image registration can combine MRI and PET images for improved tumor monitoring. In this study, we acquired high-resolution MRI and microPET 18 F-fluorodeoxyglucose ͑FDG͒ images from C3H mice with RIF-1 tumors that were treated with Pc 4-based PDT. We developed two registration methods for this application. For registration of the whole mouse body, we used an automatic three-dimensional, normalized mutual information algorithm. For tumor registration, we developed a finite element model ͑FEM͒-based deformable registration scheme. To assess the quality of whole body registration, we performed slice-by-slice review of both image volumes; manually segmented feature organs, such as the left and right kidneys and the bladder, in each slice; and computed the distance between corresponding centroids. Over 40 volume registration experiments were performed with MRI and microPET images. The distance between corresponding centroids of organs was 1.5± 0.4 mm which is about 2 pixels of microPET images. The mean volume overlap ratios for tumors were 94.7% and 86.3% for the deformable and rigid registration methods, respectively. Registration of high-resolution MRI and microPET images combines anatomical and functional information of the tumors and provides a useful tool for evaluating photodynamic therapy.

In the paper, parallelization of finite element modeling of solidification is considered. The core of this modeling is solving large sparse linear systems. The Aztec library is used for implementing the model problem on massively parallel computers. Now the complete parallel code is available. The performance results of numerical experiments carried out on the IBM SP2 parallel computer are presented.

Linearconstitutiveequationsofa thermopiezomagneticmedium involving mechanical, electrical, magnetic, and thermal e elds are presented with the aid of a thermodynamic potential. A thermopiezomagnetic medium can be formed by bonding together a piezoelectric and magnetostrictive composite. Two energy functionals are dee ned. It is shown via Hamilton’ s principle that these functionals yield the equations of motion for the mechanical e eld, Maxwell’ s equilibrium equations for the electrical and magnetic e elds, and the generalized heat equation for the thermal e eld. Finite element equations for the thermopiezomagnetic media are obtained by using the linear constitutive equations in Hamilton’ s principle together with the e nite element approximations. The e nite element equations are utilized on an example two-layer smartstructure, which consistsof a piezoceramic (barium titanate ) layer at the bottom and a magnetoceramic (cobalt ferrite ) layer at the top. An electrostatic e eld appl...

Behaviour of square plate anchors under uplift load in reinforced clay has been studied using a three dimensional finite element displacement model with ANSYS software. Soil anchor System has been discretized with eight noded isoparametric brick elements for the soil and four noded isoparametric shell elements for the plate. Geotextile used as Reinforcing material has been modelled with two noded spar element activating tension only. Nonlinear soil behaviour has been considered with Drucker Prager model and the geometrical nonlinearity of geotextile has also been addressed in the analysis. Analysis has been carried out with embedment ratio up to four representing shallow anchor and the placement of geotextile has been varied from the top of the anchor plates. To validate the analysis model tests have also been carried out with 75mmX75mm and 50mmX50mm square plates. The results are presented with parametric variation and with normalized plots to obtain an estimate of pullout capacity.

With the deterioration of this nation's infrastructure comes the growing need for effective means of rehabilitating structures. Possibly one of the most challenging tasks is to upgrade the overall capacity of concrete structures. The utilization of composite materials in rehabilitating such structures represents an innovative use of new technology. Laboratory experiments have recently been conducted on a series of reinforced concrete T-beams to study the effectiveness of using externally applied composite fabrics as a method of increasing a beam's shear capacity. In the experiments, woven composite fabrics made of aramid, E-glass, and graphite fibers were bonded to the webs ofT-beams using a two-component epoxy. The beams were loaded in flexure and tested to failure. All beams failed in shear. The ultimate strengths of the externally reinforced beams were 60-150% higher than the strengths of beams without external reinforcement. This paper presents analyses of the externally reinforced concrete beams using finite element models. The quality of numerical simulations are assessed by comparing them with experimental results. To gain better insight into the behavior of externally reinforced concrete T-beams, several numerical parametric analyses were also performed. The significance of the results of these analyses with respect to potential retrofits of existing concrete beams in the civil infrastructure is addressed.

In this study, we present the first evidence and modeling efforts showing that surface severe plastic deformation (S 2 PD) can be more effective in producing metallic components with superior fatigue properties than shot peening (SP). With the aid of a wide battery of characterization techniques (i.e., X-ray diffractometry, optical microscopy, scanning electron microscopy, transmission electron microscopy, and 3-dimensional non-contact optical profilometry), micro-and nano-hardness testing, and finite element modeling, we have identified the underlying mechanism for the fatigue improvement. It is shown that the enhancement in the fatigue limit is derived from a nanocrystalline surface layer, a work-hardened surface region, and residual compressive stresses at the surface, all of which are introduced by S 2 PD and more substantial than that introduced by SP. (L.L. Shaw).

The application of a DC electric field down gradient to the contaminated zone in the subsurface can create an electrokinetic barrier. The electrical potential gradient causes the movement of ions which in turn imposes a viscous drag on the pore water. In clayey soils, this viscous drag can generate a high enough pore water pressure capable of counteracting the ground water gradient. This phenomenon can be used effectively as a barrier to prevent contaminant migration. A finite element model was developed to simulate the contaminant migration in soil under coupled hydraulic, electrical and chemical gradients. The model is also capable of predicting the associated changes in the soil like the pore water pressure, pH and voltage gradient as a function of time and distance from the electrode. This model was validated using the w experimental data presented by Yeung Yeung, A.T., 1990. Electro-kinetic barrier to contaminant x transport through compacted clay. PhD Thesis, University of California, Berkeley, 260 pp. . The results indicate very good agreement between the experimental and simulated results. The model predications show that when the anode is placed down gradient of the cathode, the cation migration could be completely arrested. However, the anions were found to move faster in the direction of the ground water flow and reduce the effectiveness of the barrier. This could be avoided by carefully designing the placement of the electrodes. If the contaminant of interest is either a cation or an anion, a simple double row of anode and cathode electrode arrangement could serve as an effective barrier. On the other hand, if the contaminant includes both anions and cations, then a triple-row configuration of electrodes need to be implemented. The model ) Corresponding author. 0169-7722r00r$ -see front matter q 2000 Elsevier Science B.V. All rights reserved.

This paper provides a brief overview of a multidisciplinary effort at the Naval Research Laboratory aimed at developing a computationally-based methodology to assist in the design of advanced Naval steels. This program uses multiple computational techniques ranging from the atomistic length scale to continuum response. First-principles electronic structure calculations using density functional theory were employed, semi-empirical angular dependent potentials were developed based on the embedded atom method, and these potentials were used as input into Monte-Carlo and molecular dynamics simulations. Experimental techniques have also been applied to a super-austenitic stainless steel (AL6XN) to provide experimental input, guidance, verification, and enhancements to the models. These experimental methods include optical microscopy, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, and serial sectioning in conjunction with computer-based three-dimensional reconstruction and quantitative analyses. The experimental results are also used as critical input into mesoscale finite element models of materials response.

A novel low-temperature Cu-Cu bonding approach called the insertion bonding technique has been developed. This technique hinges on the introduction of a tangential pressure at the metal-metal interface, which leads to a high localized plastic deformation that is essential for bond formation. Through finite element modeling studies, it is observed that the insertion bonding technique results in a significantly larger plastic deformation in comparison to the conventional bonding technique under the same bonding conditions. First experimental studies of the insertion bonding technique were performed and it is observed that an electrically yielding Cu-Cu joint is achieved at a low bonding temperature of 100°C. This shows that the insertion bonding technique holds much promise for low-temperature Cu-Cu bonding.

The first objective of this paper is to analyze the influence of mesh size and shape in finite element modeling of composite cutting. Also the influence of the level of energy needed to reach complete breakage of the element is considered. The statement of this level of energy is crucial to simulate the material behavior. On the other hand geometrical characteristics of the tool have significant influence on machining processes. The second objective of the present work is to advance in the knowledge concerning tool geometry and its effect in composite cutting.

After the 9-11 attack on the World Trade Center, interest in the design of structures for fire greatly increased. Some engineers have promoted the use of advanced analytical models to determine fire growth within a compartment and have used finite element models of structural components to determine temperatures within a component by heat transfer analysis. Following the calculation of temperatures, the mechanical properties at various times during the period of the fire must be determined. This paper provides structural engineers with a summary of the complex behavior of structures in fire and the simplified techniques which have been used successfully for many years to design concrete structures to resist the effects of severe fires.

A variety of parameters impact package reliability. One set of parameters that does not get much attention is the variations in package design that are assembly and vendor related. This study shows that solder pad size is important in solder joint reliability. Differences in solder pad size due to different vendors and processes can affect the reliability considerably. The impact of substrate thickness on package reliability has been shown in finite element stress analysis, moiré interferometry experiments, and reliability tests. However, in certain cases, the pad size effect can be so significant that it overrides the impact of substrate thickness. This work indicates that in order to obtain good correlation between predictive engineering results and reliability tests data, this factor should not be ignored. In this study, finite element simulation has been used to quantify the pad size effect on the BGA reliability in the PBGA package. Air-to-air thermal cycling test results were compared with FEM predictions. Optimized pad sizes are discussed and the impact on the solder joint reliability is predicted. Solder pad size effect was found to be a dominant feature in correlating test data with predictions.

This study involves the determination of the mechanical and fracture properties of polyamide 6 reinforced with short glass fibres (35 wt. %) at five different moisture contents (0, 1, 2, 3, and 6 wt. %, respectively). The mechanical characterisation consisted of tensile tests on plane specimens to determine the influence of moisture content on the material's mechanical parameters. The study of fracture properties was carried out by performing single-edge notch bending tests on specimens with the levels of moisture mentioned above in order to obtain the critical stress intensity factor, K Ic . The experimental results showed that the material fracture behaviour cannot be properly described following this methodology; for this reason, a more ambitious scope was established, consisting of determining the J-integral during stable propagation by combining the experimental force vs. displacement curves with the results of a finite element numerical model. The analysis clearly demonstrates the improvement in the material's toughness as humidity increases. The subsequent fractographic study performed through scanning electron microscopy allowed the influence of moisture content on the fracture micro-mechanisms developed during fracture and propagation to be determined.

In this article, the Coefficient of Restitution (COR) and Energy Loss Percentage (ELP) of one-dimensional impacts are determined experimentally for different ball sizes using a drop test apparatus. Ball diameters range from 6 to 12 mm, made of steel and aluminum dropped on steel and aluminum sheets. Furthermore, effects of ball sizes on COR and contact time duration are studied numerically. In addition, time variation of displacement of the midpoint of sheet's top surface and vibration of the ball's center are investigated. This is done using a finite element model for elasto-plastic collisions. In this work, dynamic and explicit analyses have been carried out by using the LS-DYNA module of ANSYS. The numerical results are validated by the present experimental data. Moreover, the present results are compared with previous works. Results show that COR decreases as balls' diameters increase.

A technique is presented where actual experimental distributions, measured from a high strength carbon fibre composite, are considered in the development of a novel method to generate statistically equivalent fibre distributions for high volume fraction composites. The approach uses an adjusted measure of nearest neighbour distribution functions to define inter-fibre distances. The statistical distributions, characterising the resulting fibre arrangements, were found to be equivalent to those in the actual microstructure. Finite ...

A homogenization method is proposed for sandwich structures consisting of two plates interlaced with beams and shells in a periodic, lattice structure. The proposed method is a quasi-continuum approach where the constitutive response is obtained from the generalized forces of the interlacing elements. Buckling is studied as part of this model. Comparison of the homogenized model with fully discrete models show reasonable to very good agreement.

A significant number of existing reinforced-concrete bridges all over the world require maintenance and repair. Hence, the need for a rapid evaluation procedure for the diagnosis of existing bridges. This paper presents the application of a dynamic analysis methodology for structural evaluation of reinforced-concrete bridges. The methodology is based on the application of ambient vibrations non-destructive testing method and the identification of the structure total response using finite element method. A case study of a three span reinforced concrete bridge in a strong seismic activity area in the north of Algeria is analysed. The ambient vibration testing was carried out on the bridge, before and after its repair by the application of carbon fibre composites. The tests were conducted using an acquisition system made up of four accelerometers with three components placed at specific locations on the bridge. The finite element model gave comparable results to the experimental ambient vibrations tests. The modal parameters of the bridge before and after repair were identified by this in situ testing. The application of composite material to strengthen the structure increases the transverse rigidity of the structure and thus its modal frequency.

Finite element (FE) analysis is a valuable tool in musculoskeletal research. The demands associated with mesh development, however, often prove daunting. In an effort to facilitate anatomic FE model development we have developed an open source software toolkit (IA-FEMesh). IA-FEMesh employs a multiblock meshing scheme aimed at hexahedral mesh generation. An emphasis has been placed on making the tools interactive, in an effort to create a user friendly environment. The goal is to provide an efficient and reliable method for model development, visualization, and mesh quality evaluation. While these tools have been developed, initially, in the context of skeletal structures they can be applied to countless applications.

... mechanism, this paper presents a precise comparison between the results obtained by an analytical model for a simple geometrically non-linear cable-stayed beam [12] and those obtained by both finite element analysis and experiments on a physical model. ...

The Cávado estuary inlet is situated in the coastal zone of Esposende (NW Portugal) where sandy beaches have migrated inland and thinned, and cliffs have retreated rapidly over the last years. The coastal zone of Esposende extends over 15 km from the Neiva River until Apúlia. The coastal segment of Esposende can be considered of mixed energy and wave-dominated type, according to DAVIS and HAYES (1984). The local tide is mesotidal and semidiurnal, with a maximum equinoctial spring tide high-water level of 3.9 m, a minimum low-water level of 0.2 m, and a mean spring tide of 3.49m (data from Instituto Hidrográfico da Marinha). The inlet is a natural feature of the Cávado estuary, subject to silting up, and enclosed between a breakwater on the northern side and the end of a migrant sandy spit on the southern side. Recently, it was suggested that the best option for decreasing silting-up and increasing navigability, would be to build two breakwaters and artificially manage the inlet. Thi...

An aero-structural design and analysis study of a telescopic wing with a conformal camber morphing capability is presented. An aerodynamic analysis of a telescoping wing, first with a high speed airfoil followed by an analysis with a low speed airfoil is performed. The data obtained from these analyses is used to determine the optimum polar curves for drag reduction at different speeds. This information in turn provided the background for devising an optimal morphing strategy for drag reduction assuming that the telescoping wing airfoil has the capability to step morph between the high and low speed airfoils.

The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

Finite element (FE) models of long bones are widely used to analyze implant designs. Experimental validation has been used to examine the accuracy of FE models of cadaveric femurs; however, although convergence tests have been carried out, no FE models of an intact and implanted human cadaveric tibia have been validated using a range of experimental loading conditions. The aim of the current study was to create FE models of a human cadaveric tibia, both intact and implanted with a unicompartmental knee replacement, and to validate the models against results obtained from a comprehensive set of experiments. Seventeen strain rosettes were attached to a human cadaveric tibia. Surface strains and displacements were measured under 17 loading conditions, which consisted of axial, torsional, and bending loads. The tibia was tested both before and after implantation of the knee replacement. FE models were created based on computed tomography (CT) scans of the cadaveric tibia. The models consisted of ten-node tetrahedral elements and used 600 material properties derived from the CT scans. The experiments were simulated on the models and the results compared to experimental results. Experimental strain measurements were highly repeatable and the measured stiffnesses compared well to published results. For the intact tibia under axial loading, the regression line through a plot of strains predicted by the FE model versus experimentally measured strains had a slope of 1.15, an intercept of 5.5 microstrain, and an R 2 value of 0.98. For the implanted tibia, the comparable regression line had a slope of 1.25, an intercept of 12.3 microstrain, and an R 2 value of 0.97. The root mean square errors were 6.0% and 8.8% for the intact and implanted models under axial loads, respectively. The model produced by the current study provides a tool for simulating mechanical test conditions on a human tibia. This has considerable value in reducing the costs of physical testing by pre-selecting the most appropriate test conditions or most favorable prosthetic designs for final mechanical testing. It can also be used to gain insight into the results of physical testing, by allowing the prediction of those variables difficult or impossible to measure directly.

This paper presents an industrial validation case to evaluate the efficiency of automated multi-level substructuring (AMLS). This relatively new technique allows analysis of large structures up to frequencies where conventional methods are too computationally expensive. The finite element model of an industrial-sized passenger vehicle will be subjected to the substructuring procedure of AMLS. The global response will then be presented in terms of synthesized frequency response functions (FRFs). It will be shown that the required computation times and disk space can be significantly reduced by using AMLS while maintaining a high accuracy of the synthesized FRFs. One of the main motivations for the work has been to find a tool for fast point mobility calculations to be used to estimate important SEA input parameters. It can be concluded that AMLS is well suited for calculating these point mobilities and that AMLS in combination with other solution schemes might speed up the calculations even further.

The feasibility of using the topology design method for structural damage identification is investigated for the first time. The finite element model of an undamaged structure and some point-frequency response functions of a damaged structure are assumed to be available. To carry out the feasibility study, the topology optimization formulation suitable for structural damage detection is newly set up, where both resonances and anti-resonances are used as the damage indication modal parameters. An idea to progressively reduce the candidate damaged elements is also developed to improve the accuracy and efficiency of the proposed method. Figure 3. The overview of the progressive design variable reduction (PR) strategy, especially for the small-sized damage identification. DAMAGE DETECTION BY THE TOPOLOGY DESIGN FORMULATION 1489 3. NUMERICAL CASE STUDIES

The biomechanics of skin and underlying tissues plays a fundamental role in the human sense of touch. It governs the mechanics of contact between the skin and an object, the transmission of the mechanical signals through the skin, and their transduction into neural signals by the mechanoreceptors. To better understand the mechanics of touch, it is necessary to establish quantitative relationships between the loads imposed on the skin by an object, the state of stresses/strains at mechanoreceptor locations, and the resulting neural response. Towards this goal, 3-D finite-element models of human and monkey fingertips with realistic external geometries were developed. By computing fingertip model deformations under line loads, it was shown that a multi-layered model was necessary to match previously obtained in vivo data on skin surface displacements. An optimal ratio of elastic moduli of the layers was determined through numerical experiments whose results were matched with empirical ...

Loss of coolant accident (LOCA) and loss of flow accident (LOFA) analysis is performed for ARIES-AT, an advanced fusion power plant design (1000 MWe). ARIES-AT employs a high performance, high temperature blanket system. It uses the high temperature SiC/SiC for structural material and LiPb for coolant-breeder. Due to the large difference between the time scale of plasma shutdown and the coolant or power loss, it is assumed that the plasma is immediately quenched at the onset of the LOCA/LOFA and the chamber components' temperature begins to rise due to the decay heat generated. A 2-D transient finite element model is established to examine the thermal behavior of the in-vessel components to determine the maximum temperature reached, the time, and duration of the peak. The model is axisymmetric in (r-z) around the reactor axis to show the details of temperature distribution in the vertical direction. The vacuum vessel is assumed adiabatic in the inboard side and radiates to the maintenance port located on the outboard side. The maximum temperature of steel in the reactor is about (600°C -700°C) after about 4 days from the onset of the accident. The highest temperature in the reactor is in the divertor region and it reaches ≈1050°C after about 2-3 hours. The analysis indicates that the reactor does not need any special scheme for decay heat removal.

Functional morphology of the calcareous test of Echinus esculentus was investigated by parametric finite element analysis, an engineering technique developed for numerical analysis of the behaviour of complex structures responding to external forces. Finite element models of the test were generated by methods of Computer Aided Geometric Design (CAGD) to calculate the mechanical responses to different types of loading. The load cases included vertical, concentrated load at the apex, vertical, distributed load on the upper third of the test, internal pressure and tensile forces as introduced into the test by tube feet activity. The objectives were the shape of the test, the distribution of material and the alternating zones of porous and non-porous plates within the test.-Echinoid tests resist external loading without showing any specific points of failure. The thickened margins of the periproct and peristome apertures account for load-bearing capacity as well as the thickened meridional structures which carry a greater portion of stress than the thinner parts of the test. Distribution of material is not a response to concentrated loads on the apex nor to self-weight. Taken strictly, echinoid tests are not thin (or membrane) shells. Under loading, bending moments occur which influence the stress state in the entire test. The pneu hypothesis could not be confirmed. Adaptation of the test shape or of the distribution of material as a response to internal pressure does not exist. Tests of regular echinoids are especially well adapted to the mechanical activity of the ambulacral tube feet, i.e. the shape of the test, its flattening towards the substrate, the outward bulge of the ambulacra and the differential distribution of material within the test.& b d y :

The surface nanocrystallization and hardening (SNH) is a relatively new process that has been developed to enhance fatigue and wear resistances. The SNH is similar to widely used shot peening (SP) in the sense that both processes entail repeated impacts of the work-piece surface with spheres. The difference between them lies in the sizes of spheres and the impact velocities used. Such a difference results in dramatic changes in kinetic energies and thus the thicknesses of the work-hardened layer and the nano-grained surface layer. In this study, finite element modeling is performed to provide quantitative description of these differences. The results show that the kinetic energy in the SNH process is typically 180 times larger than that in shot peening, and the deformation layer in the SNH process is about 10 times thicker than that generated in shot peening. Furthermore, the maximum plastic strain and the maximum residual compressive stresses in the SNH-processed work-piece are 100 and 10 times larger than those in the shot-peened work-piece, respectively. The implication of these differences on fatigue resistance has been discussed.

As trees are planted in close proximity to properties and humans in a dense city like Singapore, uprooting of trees can pose safety concerns. Previous research studies have shown that soil properties are important factors that govern tree stability. Soil properties can be improved by mixing top soil (TS) with coarse-grained soil. The effects of soil improvement using coarse-grained soil on tree stability were investigated in this study. Granite chip was used as coarsegrained soil to improve the original top soil. Static analysis and finite element modeling were performed to study tree stability in an improved soil. Factors investigated include root geometry and soil shear strength parameter. Finite element results showed good agreement with static analysis in determining the maximum wind force needed to uproot the tree. Parametric study showed that the wind force needed to uproot the tree was influenced by the mode of failure and the magnitude was dependant on the root geometry and the soil properties. A mixture of 20% top soil and 80% granite chip by dry mass was the optimum mixture for withstanding the maximum wind force needed to uproot the tree.

This paper provides a summary overview of the current state-of-art in the radiocarbon dating of groundwater. While the use of natural14C measurements in applied hydrogeology still presents a difficult challenge, meaningful dates can be achieved if they are determined and interpreted in conjunction with the analyses of other isotopic species that occur in the natural environment. Although14C dating of groundwater can be, and often is, carried out as a matter of routine, any specific case study requires its own scientific design and effort. As is widely recognized, and discussed in considerable detail throughout the scientific literature, there are many hydrogeochemical reactions and/or physical processes that can alter the natural14C enrichment measured in environmental materials. Fortunately, for fresh groundwater resources such effects are in general well defined and therefore of limited significance. The primary challenge in applied groundwater dating is with the development of th...

In this work, the active vibration control of a uniform cantilever beam using piezoelectric materials subjected to transverse vibrations is studied. The equation of motion of a beam bonded with the piezoelectric actuator is realized based on the Euler Bernoulli beam theory and the Hamilton's principle. A linear time invariant state space model is derived. Numerical simulations of the equation of motion are performed. Moreover, a finite element model of the beam-piezo system is done using ANSYS APDL©. Two control algorithms were also implemented using ANSYS APDL code to reduce the flapwise bending vibrations of the beam. The two control techniques are: Linear quadratic regulator (LQR) and positive-position-feedback (PPF). Results of the PPF simulations were compared with that of the LQR control and the advantage of using PPF control over LQR control in the finite element simulations is presented.

Piezoelectric materials are widely used as distributed means for sensing and/or actuating a structure's response, by either bonding them to a structure's surfaces or embedding them into a laminate structure. Surface-mounted actuators are normally poled in thickness direction so that they work in the extension mode, while embedded actuators are more effective when poled in the longitudinal direction and thus working in the thickness-shear mode. It has been shown that embedded shear actuators may lead to less problems of actuators damage and debonding, minor dependence on actuators position and length and smaller stresses in the actuators. It has also been observed that surface-mounted extension actuators are generally more effective for very flexible host structures while embedded shear actuators are more effective for stiffer structures. These and other distinctive features of extension and shear actuators may be exploited to study their simultaneous use and to design a combined extension-shear actuated beam. Hence, this work presents the results of a numerical investigation of active vibration control using simultaneous extension and shear piezoelectric actuation for a clamped-clamped sandwich beam. The analysis is carried out using a laminate/sandwich beam finite element model combined to an optimal control with limited input. Results show that simultaneous use of extension and shear actuators is very promising since their actuation mechanisms are complimentary. In particular, a good damping performance was obtained over an increased frequency-range with very localized actuators.