varunr14/newsummary huggingface dataset:
In this paper a size dependent finite element model for Mindlin plate theory accounting for the position of the neutral plane for continuum incorporating surface energy effect is proposed to study the bending behavior of ultra thin functionally graded plates . The size dependent mechanical response is very important while the plate thickness reduces to micro nano scales . The classical finite element model is adopted to allow insertion of the surface energy into the total energy of the plate . Bulk stresses on the surfaces are required to satisfy the surface balance conditions involving surface stresses . Therefore unlike the classical continuum plate models the bulk transverse normal stress is preserved here . Moreover unlike most of previous studies in the literature the exact neutral plane position is pre determined and considered for FG plates . A series of continuum governing differential equations which include surface energy and neutral plane position effects are derived . A comparison between the continuum analysis of FG ultra thin plates with and without incorporating surface energy effects is presented . 


Highlights:
Investigating Mindlin bending behavior of ultra thin FG films. Accounting for the position of neutral plane and incorporating surface energy effects. Developing a finite element model to study the mechanical behavior of ultra thin FG films. Size dependent analysis of ultra thin FG films based on Gurtin and Murdoch surface conditions.
This paper presents an advanced analysis method for three dimensional semi rigid steel frames accounting for three main nonlinear sources . The second order effects are considered by the use of stability functions obtained from the solution of beam columns under axial force and bending moments at two ends . The spread of plasticity over the cross section and along the member length is captured by monitoring the uniaxial stress strain relation of each fiber on selected sections . The nonlinear semi rigid beam to column connection is simulated by a 3D multi spring element . The generalized displacement control method is applied to solve the nonlinear equilibrium equations in an incremental iterative scheme . The nonlinear load displacement responses and ultimate load results compare well with those of previous studies . It is concluded that using only one element per member with monitoring the end sections accurately likely predict the nonlinear responses of three dimensional semi rigid steel frames . 


Highlights:
An efficient analysis procedure of 3D semi rigid steel frames is proposed. A beam column element is developed for considering spread of plasticity effects. Stability functions are employed to predict second order effects accurately. Beam to column connections are modeled by 3D nonlinear spring elements. The proposed program can be developed for daily engineering design.
A computationally efficient C0 finite element model is developed for laminated composite and sandwich plates by implementing the inverse hyperbolic shear deformation theory recently developed by the authors . This model is used to determine responses of general laminates subjected to various combinations of boundary conditions . The present formulation has been generalized for all existing shear deformation theories involving shear strain function . An eight noded serendipity element with 56 degrees of freedom is used to discretize the plate domain . Influences of lamination sequence span to thickness ratio and boundary conditions are investigated for the flexural behavior of laminated composite and sandwich plates . Further the stability behavior of plates subjected to in plane loads is investigated for a variety of examples . Effects of boundary conditions and applied loads on the critical buckling loads and buckling mode shapes are also assessed for a class of laminates in order to show the efficacy of the present mathematical technique to predict the buckling mode shapes . 


Highlights:
A computationally efficient C0 finite element modeling in the framework of newly developed inverse hyperbolic shear deformation theory by the authors is developed. Flexural and stability behavior of laminated composite and sandwich plates is investigated. Influence of span to thickness ratio boundary conditions etc. on the structural behavior is investigated. Results are validated with the existing results and few new results are presented.
Condensation technique of degree of freedom is firstly proposed to improve the computational efficiency of meshfree method with Galerkin weak form . In present method scattered nodes without connectivity are divided into several subsets by cells with arbitrary shape . The local discrete equations are established over each cell by using moving kriging interpolation in which the nodes that located in the cell are used for approximation . Then the condensation technique can be introduced into the local discrete equations by transferring equations of inner nodes to equations of boundary nodes based on cell . In the scheme of present method the calculation of each cell is carried out by meshfree method with Galerkin weak form and local search is implemented in interpolation . Numerical examples show that the present method has high computational efficiency and convergence and good accuracy is also obtained . 


Highlights:
Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form. The local discrete equation is established by using moving kriging interpolation based on cells with arbitrary shape. Computational efficiency of present method is improved for nearly 22 times compared with the method proposed by Lei Gu in the numerical example. Numerical example also shows that the present method has good accuracy and convergence.
This research develops a new interpolation scheme a separable stress interpolation which allows stress based topology optimization with multiple materials . In common material interpolation function such as extended solid isotropic material with penalization for multiple materials Young s modulus is interpolated from those of several solids to a smaller value with respect to design variables whose number is same as the number of considered materials . When the same interpolated Young s modulus is used for stress evaluation it is found that the calculated stress norm becomes a small value when ones are assigned to the design variables of each element causing physically unacceptable layouts . In order to resolve this ill posed issue for STOMM we present the SSI scheme which computes the stress constraints of stacked elements separately . For a stable topology optimization process the computational issues of the p norm stress measure the number of stress evaluation points inside an element and the correction parameter for the approximated stress measure are addressed for STOMM . Furthermore we present a new regional constraint method based on the sorting algorithm . The applicability and limitations of the newly developed framework are discussed in the context of its application to several stress based topology optimizations with multiple materials . 


Highlights:
Stress based topology optimization with multiple materials is developed. A separable stress interpolation scheme should be used for the stress evaluation. Higher p norm stress values are obtained at more than one point per element. A new regional constraint method based on the sorting algorithm is developed.
The design of multi material compliant mechanisms by means of a multi Sequential Element Rejection and Admission method is presented in this work . The SERA procedure was successfully applied to the design of single material compliant mechanisms . The main feature is that the method allows material to flow between different material models . Separate criteria for the rejection and admission of elements allow material to redistribute between the predefined material models and efficiently achieve the optimum design . These features differentiate it to other bi directional discrete methods making the SERA method very suitable for the design of multi material compliant mechanisms . Numerous examples are presented to show the validity of the multi SERA procedure to design multi material compliant mechanisms . 


Highlights:
A generalized formulation to design multi material compliant mechanisms. The SERA method used for the optimization considers separate material models. Separate criteria to move material between the different material models are used to achieve the optimum topology. Numerous examples prove the validity of the proposed formation to design complex compliant mechanisms.
In the past structural model updating methods have been widely researched as a means to reconcile mathematical models because the key parameters in dynamic systems often change during their life cycle due to repair and replacement of parts or the environment . However there is very little literature that references model updating under the condition of complicated multi physics fields such as a high temperature environment . In this paper model updating in an HTE is proposed based on the hierarchical method and an iterative procedure is presented . With this method the temperature field updating of a structure is taken as the first stage and the multi objective optimization method and a surrogate model of radial basis functions are introduced to improve the robustness and efficiency of this stage respectively . Then the temperature distribution achieved from the former is imposed on the structure as a thermal load and the residuals of the modal characteristics are taken as objective functions to update the dynamic model of the structure in HTE . The proposed method is tested on an FE model of a wing model and the analysis of variance approach is employed to evaluate the parameter variability significance and to select the updating variable . The results of the study show that the developed hierarchical method is capable of identifying the input parameters of the temperature field and structure with good accuracy . 


Highlights:
Model updating in a high temperature environment is proposed based on the hierarchical method. Theoretical and numerical examples using the hierarchical method are presented. A method to improve the robustness and efficiency of the temperature field updating method was researched. The RBF with the difference basis function was evaluated by ANOVA. The analysis of variance method was used in dynamic structure model updating.
It has been a great challenge for many scientists and engineers to compute elastic plastic solutions for dynamically loaded cracked structures due to the fact that the solutions are much more complicated and computationally time consuming than corresponding static problems . The path independent integral originally developed for a two dimensional dynamically loaded stationary circular arc crack in a homogeneous and isotropic material is evaluated in the present study by taking elastic plastic material properties to quantify the crack problem . All the numerical results presented in this study were evaluated using general purpose finite element commercial software ANSYS together with the post processing program developed by the authors . Numerical results thus obtained are compared with good agreement within the limits of computational accuracy and the path invariant property of is well preserved over the integration contours . arbitrary region around the process zone body force vector physical component of body force vector Rice s path independent integral crack driving force for circular arc crack under multiple loads positive unit outward normal physical component of positive unit outward normal plane polar coordinate radius of the crack traction vector physical component of the traction vector displacement vector covariant derivative of with respect to physical component of mechanical strain energy density function contravariant stress tensor physical component of the stress tensor strain tensor covariant derivative of with respect to physical component of thermal strain tensor initial strain tensor arbitrary curve surrounding angle material density symbols not listed are defined as they appear in text . 


Highlights:
The numerical solutions presented in this paper provide attractive features of the integral The present results may be useful for future research in elastic plastic dynamic fracture. The integral has been found to maintain very nearly path independence. The present study recommends that the integral may be easily correlated to establish failure criteria.
The effect of various p method finite element model parameters on the prediction of planar crack front geometry in three dimensional structures is evaluated . An automatic crack growth method was developed using the commercial software StressCheck coupled with Microsoft Excel . The geometry of the evolving crack front was predicted using iterations of three dimensional finite element models to determine the stress intensity values at discrete points along the crack front and incrementing the crack length locally using the Paris growth law . Modeling parameters such as the global mesh size p level crack tip mesh size and the extraction radius used for determining the stress intensity factors were all considered . The effect of these parameters on the predicted shape of a growing elliptical crack front was evaluated through a series of simulations of a corner crack emanating from a centered hole in a plate . A single model of a through crack with a straight crack front was also used to compare the effects of the model parameters on a different geometric configuration . This study has shown that the corner crack geometry and the growth series are more sensitive to the number of elements along the crack front and the extraction radius than the through thickness crack . In addition convergence of the predicted crack front geometry does not guarantee convergence of the distribution of stress intensity factors along the crack front . It was also determined that for the models considered using a smaller overall mesh size is a more effective way of decreasing discretization error than increasing the p level . 


Highlights:
K is calculated more accurately at free surfaces using smaller extraction radii. Corner crack results are dependent on the number of elements along the crack front. Predicted crack front geometry depends on the shape of the K profile along the crack front. High p levels do not necessarily compensate for a coarse mesh. The energy norm should not be used as the sole indicator of solution convergence.
Wireless Mesh Sensor Networks have recently received a great deal of attention in the scientific and developers communities due to the significant advances of this technology in the wireless communication field . The main reason was that competing WMSN approaches that emerged in the last few years provide mesh capabilities to conventional WSN based applications encouraging researchers and end users to adopt new perspectives and solutions . Unfortunately each one of these approaches lacks some of the aforementioned mesh capabilities not assuring a priori the feasibility and especially the long term stability of WMSN applications . The IEEE 802.15.5 standard and in particular its Asynchronous Energy Saving mode was conceived to fill this gap since it integrates in a single solution most of these capabilities guaranteeing among other benefits a long network lifetime . However the ASES mode has no built in mechanisms to mitigate the negative effects of hidden terminals which sharply degrades the network performance . This fact leads us to conclude that any current WMSN approach is non exempt of some problem which prevents the definitive boost of this technology in the consumer market . Under these circumstances our contribution to the WMSN field in this paper is a twofold proposal addressed to alleviating the hidden terminal problems in a scenario running under the most relevant design premises of ASES mode . Therefore we first formulate a multi objective optimization and then solve it by using Goal Programming . Both mathematical techniques are applied to obtain the best solution that simultaneously minimizes the aggregate message collision time due to hidden terminals and maximizes the network lifetime . Secondly we propose the design of a MULti channel TIme scheduled algorithm for the HIdden Terminal problem avoidance which appropriately exploits the available bandwidth and accomplishes a straightforward coordination between any sender receiver pair . Finally the analysis and simulation experiments are presented and their results carefully discussed demonstrating the effectiveness of both proposals in the WMSN arena . 


Highlights:
WMSN approaches offer new perspectives to conventional WSN based applications. Among WMSN proposals the ASES mode guarantees the most relevant mesh capabilities. ASES has no mechanisms to mitigate the negative effects of hidden terminals HT . Under ASES rules we propose an optimization model and a multi channel time slotted algorithm to alleviate the HT problem. An intensive performance evaluation study is discussed to validate our proposals.
In order to enhance the crash characteristics and geometrical accuracy components hot formed in a fully martensitic state have gained in the last few years more and more importance . However the very high strength exhibited by these components makes subsequent operations such as cutting difficult due to the high process forces and associated high wear of the cutting tools . Moreover for some applications such as B pillars and other automotive components that may undergo impact loading it may be desirable to create regions of the part with softer and more ductile microstructures . The novel process called the tailored tempering process allows doing this by suppressing the martensitic transformation in those zones of the sheet located under heated parts of the tools . In the paper a numerical model of the tailored tempering process was developed accurately calibrated and validated through a laboratory scale hot forming process . Using the commercial FE code Forge a fully coupled thermo mechanical metallurgical model of the process was set up . The influence of the phase transformation kinetics was taken into account by implementing in the model phase transformation data namely the shift of the TTT curves due to the applied stress and the transformation plasticity coefficients gained from an extensive dilatometric experimental campaign and analysis . A laboratory scale hot formed U channel was produced using segmented tools with heated and cooled zones so that the cooling rate of the blank can be locally controlled during the hot forming process . The part Vickers hardness distribution and microstructural evolution predicted by FORGE were then compared with the experimental results proving the validation of the numerical model by taking into account the influence of the transformation plasticity and deformation history on the phase transformation kinetics . 


Highlights:
Influence of the phase transformation kinetics was taken into account by implementing in the FEM model phase transformation data. Segmented tools with heated and cooled zones were used to locally control the cooling rate of the blank. Numerical model validation by considering the influence of the transformation plasticity and deformation history on phase transformation kinetics.
This study proposes a nonlocal finite element technique that is based on the super convergent patch second derivative recovery methods . The SCP second derivative recovery methods are proven effective in evaluating the Laplacian of the equivalent strains at C0 linear elements . The element based patches and their construction criteria are defined . Other patch based techniques either are limited to structured meshes or only utilize nodal based patches for first derivative recoveries . The SCP technique has not previously been used to recover higher order strain derivatives . The proposed technique can deal with unstructured meshes with various element types and the patches are constructed in a fashion that greatly accelerates the evaluation of Hessian matrices . A numerical example of a strain gradient damage mechanics problem is given at the end . The results show that the proposed technique is capable of evaluating the Laplacian of the equivalent strains and has the potential for even higher order derivative recovery . 


Highlights:
A nonlocal finite element technique is proposed that is based on the superconvergent second derivative recovery methods. A way to construct element based patches is proposed that is suitable for unstructured meshes. The proposed technique is implemented with a simplified Hessian matrix computation process. The proposed technique is verified by the recovery of the equivalent strains in a nonlocal damage mechanics model.
This paper is concerned with the development and application of high order full integrated tetrahedral finite elements to large deformable elastoplastic homogeneous solids . This strategy differs from usual ones adopted in literature that use low order and sub integration methods to solve this kind of problems . The motivation is to find a more precise stress distribution inside solids that develops large strains in elastoplastic situations . In order to do so two elastoplastic formulations are developed and implemented . The first called hyperelastoplastic is based on the multiplicative decomposition of the deformation gradient the intermediate configuration and the elastic Mandel stress tensor and it is devoted to large strain evolution . The second called Green Naghdi elastoplastic is based on the additive decomposition of the Green Lagrange strain tensor and the second Piola Kirchhoff stress tensor and it is devoted to small strain and is used as a reference to the second development . In both cases the three dimensional von Mises yield criterion the associative plastic flow rule and mixed hardening are used . Some structural problems have been numerically simulated and convergence analysis is carried out . The results for the force versus displacement and the distributions of the plastic parameters are provided . The numerical results show that as expected the analysis error can be controlled by mesh refinement . The presented hyperelastoplastic formulation can model both finite elastic and finite plastic strains . 


Highlights:
Analysis of homogeneous elastoplastic materials under static isothermal and large deformation conditions. Parallel processing enables the use of high order fully integrated solid tetrahedral finite elements. These elements present locking free behavior and reliable stress fields for mechanical problems.