Object Oriented Finite Research Articles

Characterization of Mechanical Performance of Composites Fabricated Using Innovative Carbon Fiber Wet Laid Process

Recent innovation in production of optimized nonwoven wet laid (WL) carbon fiber (CF) mats raised the question of optimal translation of the performance and isotropy into composites formed through these dry preforms. This work explores the mechanical behavior of composites produced from WL-CF mats in conjunction with the microstructure predicted through Object Oriented Finite Element Analysis (OOF). The mats used for the composites were prepared in two dispersion regimes using 25.4 mm long CF. The mixing regimes discussed in the author’s previous work, are identified as Method 1 for the traditional processing regime and Method 2 for the innovative regime that provided optimal nonwoven WL-CF mats. Composite panels from Method 2 mats showed a normalized tensile strength increase of 52% over those from Method 1 panels. Reproducibility analysis of composites made from Method 2 mats demonstrated a standard deviation of 2% in fiber weight content, 2% in tensile modulus and 9% in tensile strength, while composites made from Method 1 mats demonstrated a standard deviation of 5% in fiber weight content, 5% in tensile modulus and 17% in tensile strength. Systematic study of the microstructure and its analysis through OOF confirmed the isotropy translation of mats produced through method 2 to the composites. This study validated the hypothesis that optimal nonwoven mats lead to a well-balanced composite with optimal performance and that non-optimal nonwoven mats do not pack into a well-balanced composite.

Determining Stress-Strain Behavior of Zr<sub>60</sub>Cu<sub>10</sub>Al<sub>15</sub>Ni<sub>15</sub> Bulk Metallic Glass Using Object Oriented Finite Element Analysis

Determining mechanical properties of Bulk Metallic Glasses (BMGs) requires synthesizing of the alloys in bulk form. However obtaining metallic glass in bulk form is quite challenging due to its tendency towards crystallization. In such circumstances it is beneficial to determine the mechanical properties of materials using finite elemental analysis of microstructures. Thus, in the present investigation, using Object Oriented Finite Element Analysis (OOF2) software package, Stress-Strain analysis has been carried out on Zr60Cu10Al15Ni15 BMG to determine such mechanical properties. Specimen of Zr60Cu10Al15Ni15 BMG exhibiting three microstructurally distinct regions amorphous, partial crystalline and crystalline regions was used for this analysis. The Stress-Strain relationship have been estimated for each of the three distinct phases and the results are validated by determining the Modulus of Elasticity for all the phases and comparing it with the available experimental results from Nano-indentation test.

Characterization and methodology for calculating the mechanical properties of a TRIP-steel submitted to hot stamping and quenching and partitioning (Q&P)

Thermomechanical simulation of quenching, hot stamping, and quenching and partitioning processes of a high-strength TRIP-assisted steel were carried out in a Gleeble®3S50 thermo-mechanical simulator, coupled to the synchrotron X-ray diffraction line. The microstructures and mechanical properties were analyzed using Field Emission Gun Scanning Electron Microscopy (FEG-SEM), X-ray diffraction, and nanoindentation. The microstructures of thermomechanical treated specimens were modeled using the Object Oriented Finite Element (OOF) technique. The modeled microstructures were then fed into a finite element model to predict the mechanical behavior. By using a reverse algorithm method, the elasto-plastic mechanical properties of different microconstituents were determined. This was done through the analysis of instrumented nanoindentation loading-penetration curves. Tensile properties of the thermomechanical processed steels were measured by tensile testing of subsized specimens cut from samples processed on the Gleeble®3S50. The comparison between the experimental results and those of the reverse algorithm and the OOF modeled microstructure showed quite good agreement.

화상 이미지 기반 FEM 해석을 이용한 기포제 혼입 시멘트 페이스트의 역학 성능 평가

콘크리트는 대표적인 불균질 재료이며 콘크리트의 역학적 특성은 다양한 요인들에 의해 영향을 받는다. 그 중 콘크리트 내부에 존재하는 공극은 콘크리트의 강도를 결정하는데 많은 영향을 주고 있기 때문에 공극의 분포 및 크기를 파악하는 연구는 매우 중요하며 그 방법으로 화상이미지를 이용한 연구가 대두되고 있다. 경량 기포 콘크리트는 현재 비구조용에 관한 연구만 진행되고 있기 때문에, 구조용으로 사용하기 위한 경량 기포 콘크리트의 역학적 특성을 평가하고 화상 이미지를 기반으로 FEM 해석을 이용한 검증에 관한 연구는 미비하다. 그러므로 기포제 혼입률에 따른 시멘트 페이스트를 제작하여 역학적 성능 평가를 실시하고 화상 이미지를 이용하여 FEM 해석을 실시하여 역학적 성능 비교 및 검증을 실시하였다. 본 연구에서 기포제 혼입률에 따른 공극 분포를 확인하기 위해 7수준으로 하였으며 추 후 구조용 경량 기포 콘크리트에 대한 연구를 진행하기 위해 물-결합재비를 20%로 하였다. 기포제 혼입률이 0.8%에서 단위 용적 질량이 최소가 되었으며 그 이상 혼입했을 시 기포 간의 상호 연결로 인한 깨짐 현상이 발생하여 단위 용적 질량이 증가하였다. 공극 분포에 따른 FEM 해석을 위해 화상분석기(HF-MA C01)를 이용하여 시멘트 페이스트 단면을 촬영하였고 이를 토대로 OOF(Object Oriented Finite elements)를 이용한 FEM 해석을 실시한 결과 실험 탄성계수와 해석 탄성계수가 일치하였다. Concrete is a representative heterogeneous material and mechanical properties of concrete are influenced by various factors. Due to the fact that pores in concrete affect determining compressive strength of concrete, studies which deal with distribution and magnitudes of pores are very important. That way, studies using picture imaging have been emerged. Studies on mechanical performance evaluation of structural lightweight foamed concrete and FEM analysis based on picture image are inadequate because lightweight foamed concrete has been researched for only non-structural. Therefore, in this study, cement paste with foaming agent to evaluate mechanical performance is made, FEM analysis with picture image is conducted and young's modulus of experiment and analysis are compared. In this study, dosage of foaming agent is determined 7 level to check pore distribution and water-binder ratio is determined 20% to progress research about structural light weight foamed concrete. Weight of unit volume is minimum at 0.8% of foaming agent dosage. However, weight of unit volume is increased over 0.8% of foaming agent dosage because of interconnection with independent pores. For FEM analysis, cement paste is photographed to use image analyzer(HF-MA C01). Consequently, the fact that Young's Modulus of experiment and FEM analysis are same is drawn by using OOF(Object Oriented Finite elements).

OOF3D: An image-based finite element solver for materials science

Recent advances in experimental techniques (micro-CT scans, automated serial sectioning, electron back-scatter diffraction, and synchrotron radiation X-rays) have made it possible to characterize the full, three-dimensional structure of real materials. Such new experimental techniques have created a need for software tools that can model the response of these materials under various kinds of loads. OOF (Object Oriented Finite Elements) is a desktop software application for studying the relationship between the microstructure of a material and its overall mechanical, dielectric, or thermal properties using finite element models based on real or simulated micrographs. OOF provides methods for segmenting images, creating meshes of complex geometries, solving PDE's using finite element models, and visualizing 3D results. We discuss the challenges involved in implementing OOF in 3D and create a finite element mesh of trabecular bone as an illustrative example.

Steel particles–porcelain stoneware composite tiles: An advanced experimental–computational approach

Innovative porcelain stoneware tiles with a surface layer containing 2.4 wt% of stainless-steel particles were produced by the Double Charge Technology. Considering this layer as a composite material, the effects of the metal particles on the mechanical behaviour of the ceramic matrix were extensively investigated in terms of Young's modulus, fracture toughness and flexural strength. With this aim, composite materials were prepared by using the same silicate-based ceramic matrix with increasing weight percentages of the same stainless-steel powder. The composites were accurately characterised. In particular, due to the high sintering temperature, possible changes at the interface between metal particles and ceramic matrix were thoroughly analysed by means of SEM and EDS microanalysis. To clarify the role of the observed chromium-rich interphase on the mechanical behaviour of the steel particles–stoneware composites, analytical equations were used and simulations were performed by using the Object Oriented Finite (OOF) element method.

Use of Scanning Electron Microscope and the Non-local Isotropic Damage Model to Investigate Fracture Process Zone in Notched Concrete Beams

In this study, a Scanning Electron Microscope (SEM) is used to understand the micro level aspect of the Fracture Process Zone (FPZ) in a concrete beam. It is mainly based on the preparation and analyzing samples which are considered as being a very important part of SEM (poor preparation techniques can lead to erroneous diagnosis of the concrete study). Numerically, the fracture of concrete requires the consideration of progressive damage, which is usually modeled by a constitutive law. This latest relies on numerical methods to obtain adequate solutions. It is shown herein that by using the Object Oriented Finite Element Method (OOFEM), obtained results agreed more or less with those of others researchers. On the other side, experimental results compromise those obtained by the use of the non-local isotropic damage model. It is finally proven throughout this study that the FPZ is defined by two parameters: the length and the width.

Finite Element Implementation of a Thermodynamic Description of Piezoelectric Microstructures

A model and numerical framework is developed for piezoelectric materials. The model treats the piezoelectric and electrostrictive effects by incorporating orientation‐dependent, single‐crystal properties. The method is implemented in Object Oriented Finite Element program, a public domain finite element code, so it can be applied to arbitrary two‐dimensional microstructures with crystallographic anisotropy. The model is validated against analytic solutions. Consistency of the method for known cases permits application of the technique to more complicated two‐dimensional systems. The piezoelectric and electrostrictive response is determined for a few simple device geometries and provides insight for design and convergence criteria.

Effects of pores and interfaces on effective properties of plasma sprayed zirconia coatings

It is difficult to establish structure–property relationships in plasma sprayed coatings because of their unique and intermingled splat microstructures incorporating networks of various intrinsic process-dependent microdefects. In this paper, these coatings are characterized using two distinctly different approaches, both based on novel experimental techniques and computational modeling tools. In each approach, detailed finite element models are illustrated to represent the porous coatings fabricated with four different types of zirconia feed powder. One approach is based on small-angle neutron scattering (SANS) studies carried out to quantify microstructure. In this approach, the pore morphology is idealized by artificially rebuilding, based on the collective microstructural information obtained in terms of component porosities of three pore systems, their opening dimensions and orientation. The other method relies on image analysis of real microstructural images obtained using scanning electron microscopy (SEM). The finite element mesh for the actual cross-sectional model, generated by thresholding the SEM images, is constructed with the object oriented finite (OOF) element method. Through these two approaches, the effective thermal conductivity and elastic modulus along the spray, as well as the transverse directions are estimated for thermally sprayed yttria-stabilized zirconia (PSZ) coatings. Our results show the effectiveness of these computational approaches for estimating material properties with each approach having its strength and weakness. However, in comparison with experimentally measured properties, there exist some limitations in both approaches. To further probe the source of discrepancy within the measurements, the coatings are thermal cycled to reduce the effect of splat boundaries on properties. Additional models are constructed for these coatings and their analysis is carried out. For the first time, the influence of the splat interfaces on the effective properties of sprayed coatings is quantified.

Development of the Object Oriented Finite Element Modeling System for 3-D Shell Structures

The biggest difficulty in the process of finite element (FE) analysis is the modeling of industorial products that have complex configulation. To overcome this, prototype of integrated finite element modeler, MODIFY (MODeling tool for Integrated Finite element analYsis) is developed by the authors [1]. MODIFY has three features : (1) FE modeling by the part object concept, (2) fully object-oriented data structure, (3) fully automated part by part mesh subdivision. In MODIFY, part objects consist of the geometry objects, the analytical condition objects and the relation objects, and the user only need to define and assemble them. The prototype system is applicable to FE modeling for 3-D plate structures.In this paper, MODIFY is extended for 3-D shell structures. Three enhncement was made. First, the shell object that is represented by B-rep model and rational B-spline surface is defined as a geometry object. Second, the mesh generator for 3-D curved surface is constructed. Finally, MODIFY is linked with external CAD syntem using IGES file, which is most widely used as a conversion in commercial CAD system.Several examples of finite element model generated by MODIFY are shown.