Assignment Of Material Properties Research Articles

Geometrical optimization and evaluation of the bridge safety guardrail

Abstract Lately, the rapid growth of traffic led to the construction of a new freeway bridge to ease the road congestion. This paper studied the crash behaviour of steel guardrails for semi-heavy traffic roads used on bridges. The guardrail structure is tested according to the SR EN 1317 standards at two velocity cases, corresponding to the TB 11 and TB 51 impact test description. To perform this evaluation study, the guardrail structure is first modelled in CAD environment software, respecting the commercial dimensions. The boundary conditions, the material properties assignment, and the load case creation are done by using dedicated FEA software. The obtained results are analysed and are proposed some design improvements to the base guardrail structure. The improved guardrail structure is tested under the same work conditions as the base structure. The conclusions of this research are presented in the last part of the paper.

Numerical Simulation Study on the Impact of Excavation on Existing Subway Stations Based on BIM-FEM Framework

Building information modeling (BIM) and finite element method (FEM) models have a wide range of applications in underground engineering design, construction, and operation and maintenance. This study employs a BIM-FEM framework to numerically simulate the impact of excavation on existing subway stations, using the Yanjiang New City Station TOD project as a case study. This framework simplifies the smooth integration of BIM and FEM models, automating functions such as assigning material properties, conducting construction simulations, and generating high-quality meshes. Simulation results reveal significant horizontal and vertical displacements in diaphragm walls, support structures, and subway station structures, with the greatest impacts occurring closest to the excavation site. The BIM-FEM framework is validated as an effective tool for designing foundation pit support structures, enhancing numerical modeling accuracy and efficiency in underground engineering. The findings contribute to a better understanding of the dynamic interactions between excavation and underground structures, informing the development of construction strategies and protective measures to ensure structural safety.

An in silico analysis of neuromodulation for pain relief: Determining the role of classical electrodynamics.

There has been ongoing debate about the efficacy and mechanism of action of neuromodulation devices in pain relief applications. It has recently been suggested that both issues may be resolved if electromagnetic theory is incorporated into the understanding and application of this technology, and we therefore undertook an in silico analysis to further explore this idea. We created a CAD replication of a standard neuromodulation electrode array with a generic linear 3/6 mm 8-contact lead, developed a parameterized algorithmic model for the pulse delivered by the device and assigned material properties to biologic media to accurately reflect their electromagnetic properties. We then created a physical simulation of the device's output both in air and in the biophysical environment. The simulations confirmed the presence of an electromagnetic field (EM field). Variations in programming of the device affected the strength of the EM field by orders of magnitude. The biologic media all absorbed the EM field, an effect which was particularly pronounced in cerebrospinal fluid and muscle. We discuss the implications of all these findings in relation to the literature. We suggest that knowledge of electromagnetic theory and its application within the biophysical space is required for the optimal use of neuromodulation devices in pain relief applications.

From tomographic imaging to numerical simulations: an open-source workflow for true morphology mesoscale FE meshes

Full-field techniques such as tomography are becoming progressively more central in the study of complex phenomena, in particular where spatiotemporal evolution is crucial, as in moisture transport or crack initiation in porous media. These techniques provide a unique insight in the local process whose quantification allows the improvement of our understanding and of the models describing them. Nevertheless, the model validation can be pushed further by attempting to explicitly represent the heterogeneities and simulate their role in the processes. Once validated, these models can be used to perform “virtual experiments”, and overcome the limitations of the experiments (e.g., sample size and number, fine control of the boundary and initial conditions). This study proposes a connection between tomography images and mesoscale models through a workflow that mainly employs open-source tools. This workflow is illustrated through the digitization of a Portland cement concrete sample, stemming from neutron tomographies and resulting in a numerical finite element mesh. The proposed workflow is flexible, allowing for the conversion of images from various sources, such as x-ray or neutron tomographies, to different numerical representations of the domain, such as finite element meshes or even a discrete domain required by discrete element methods, while preserving real morphologies with an accuracy proportionate to the specific need of the problem. Beside its generalizability, our method also offers automated labelling of the different domains and boundaries in both the volumetric and surface meshes, which is often necessary for assigning material properties and boundary conditions. Finally, the series of image, geometry and mesh processing steps described in this work are made available on a GitHub repository.

Numerical Design and Analysis of Advanced Roof Systems in Architecture with Environmentally Friendly Low-Carbon Materials

This research explores the viability of bamboo as a green replacement for timber in building practices. Bamboo’s advantages lie in its renewability, sustainability, and resilience to disasters, despite possessing mechanical properties similar to timber. The study proposes using Finite Element Analysis (FEA) simulations, a potent instrument for designing and analyzing intricate structures under varying loads. The research explicitly employs FEA simulations to examine the application of bamboo in complex rooftop systems, using two commercial 3D CAD software—Rhino7 and Strand7. Rhino7 is responsible for 3D model creation and the member’s division into minuscule elements, whereas Strand7 is used to assign material properties, establish boundary conditions, carry out simulations, and analyze the outcomes. This research includes case studies of bamboo grid-shell structures and implements the suggested methodology. The study’s objective is to augment the scarce engineering data and to analyze bamboo as a material and the impact it can have on construction. The study’s results underscore the potential of eco-friendly, low-carbon materials, such as bamboo, in the construction industry. It also illustrates the effectiveness of FEA simulation in analyzing elaborate structures.

An Attempt to Design of High-Rise Structures Using ETABS

Abstract: This paper aims to discuss about ETABS (i.e., Extended Three Dimensional Analysis of Building Systems) and its various stages of Design civil engineering structures. Designer will be able to specify the loads and perform the analysis all conveniently and quickly. It helps in understanding the overall behavior of the structure in terms of resulting bending moment, shear forces and deformations which can be viewed or plotted. Define the boundary conditions, assign material properties. Designer will be able to generate the geometry

Comparative numerical study to simulate masonry with bed joint reinforced repointing

Bed joint reinforced repointing is a retrofitting technique for unreinforced masonry structures that is commonly applied in the Netherlands to repair settlement-induced damage. Using this technique, the bed joints of masonry walls are reinforced with steel rebars that are embedded in a high strength repair mortar. Due to the increase of induced seismic events in the northern part of the Netherlands, an experimental study was carried out at Delft University of Technology to investigate the performance of this retrofitting technique for combined settlement and seismic loading. This paper aims to simulate the experimental results, with a focus on the comparison of different finite element modelling approaches for studying both un-strengthened and strengthened full-scale tested walls. To that end, three different models are investigated – comprising both macro (continuum) and simplified and detailed micro (brick-to-brick) modelling approaches. The bricks and mortar joints are modelled as one homogenous continuum in the macro model, whereas in the two brick-to-brick models these structural components are modelled separately, with the detailed model including interface elements to simulate the brick–mortar bonds. Nonlinear pushover analyses are subsequently carried out using all three modelling approaches, for both monotonic and cyclic loading cases. Based on these analyses, the detailed brick-to-brick model was found unsuitable to simulate the strengthened wall because cracks in the model mainly occur in the form of opening of the brick–mortar bond interfaces, while smeared cracking in the plane stress elements of the mortar joints is very limited. Similarly, the continuum damage model was found to be inaccurate when pre-existing damage in the experiment needed to be taken into account. The continuum damage model also showed lower axial stresses in the rebars, compared with the simplified brick-to-brick model, as the former does not allow for the direct assignment of material properties for the high strength repair mortar in the strengthened joints.

Effect of intramedullary nail stiffness on load-sharing in tibiotalocalcaneal arthrodesis: A patient-specific finite element study.

Tibiotalocalcaneal (TTC) arthrodesis is a procedure to treat severe ankle and subtalar arthropathy by providing pain free and stable fusion using IM nails. These nails can be manufactured with multiple materials and some feature the ability to dynamize the arthrodesis construct. However, the impact of IM nail material and nail dynamization on load-sharing and in the setting of bone resorption have not been quantified. This work utilized a patient-specific finite element analysis model of TTC arthrodesis to investigate IM nails with differing material moduli and the impact of nail dynamization on load-sharing and intersegmental compression in the setting of bone resorption. Each nail was virtually inserted into a patient-specific model of a hindfoot, which was segmented into the three bones of the TTC complex and assigned material properties based on the densitometry of the bone. Compression, amount of load-sharing, and stress distributions after simulated bone resorption were quantified and compared between the varying IM nails. Simulations revealed that bone segments were only subjected to 17% and 22% of dynamic gait forces in the titanium and carbon fiber nail constructs, whereas the pseudoelastic NiTi nail constructs allowed for 67% of the same. The titanium and carbon fiber nails lost all initial compression in less than 0.13mm of bone resorption, whereas the NiTi nail maintained compression through all simulated values of bone resorption. These data highlight the poor load-sharing of static nail TTC arthrodesis constructs and the ability of a pseudoelastic IM nail construct to maintain intersegmental compression when challenged with bone resorption.

Enhancing the mechanical stability of restored teeth with interfacial cracks: Finite element analysis

ObjectivesThis study aims to enhance the mechanical stability of restored molar teeth with class II occlusal-distal (OD) cavities. We seek to achieve this goal through a comprehensive investigation of three primary factors: (1) the choice of restoration material properties, (2) internal cavity geometries, and (3) the impact of double-layered restoration configurations. MethodsTo achieve our objectives, we initiated by creating two-dimensional (2D) models of restored teeth featuring class II OD cavities, utilizing scanned and segmented images of maxillary molar teeth. We drew 2D profiles of dentine and enamel, which were then imported into finite element analysis (FEA) software. To explore various cavity geometries, we implemented a total of thirteen different designs, encompassing straight, oblique, grooved, curved, and double-layered configurations. We utilized a semi-circular stone to simulate the application of contact load on the restored tooth. We applied identical boundary conditions and contact loading across all models. To assign material properties, we developed a Python code, enabling the automatic assignment of seven elastic moduli ranging from 2 GPa to 26 GPa to the restoration materials. Meanwhile, constant material properties were assigned to the enamel and dentine. In total, we conducted 133 FEA simulations to comprehensively analyse the effects of the aforementioned factors on the strength and performance of restored molar teeth. ResultsOur analysis revealed two key factors significantly influencing the mechanical resistance of treated teeth, particularly in the presence of a crack or debonding: (1) the marginal geometry of the OD cavity and (2) the elastic modulus of the restorative material. However, altering the internal cavity angle and implementing a double-layered restoration did not significantly influence the restored tooth's overall strength and performance in the face of crack or debonding situations. SignificanceThe findings of this study have substantial implications for designing and restoring class II OD cavities to enhance resistance to cracks or debonding. The use of curved marginal geometries in restoration design can significantly improve fracture resistance, with double-curved geometries reducing stress concentrations by approximately 43% compared to straight cavities. These results offer valuable guidance for strengthening the structural integrity of restored teeth, calling for further experimental investigations to explore practical applications and benefits.

STRESS ANALYSIS USING SOLIDWORKS SIMULATION

Stress analysis using SolidWorks Simulation is a powerful tool for predicting the behaviour of components and structures under various loading conditions. The methodology involves creating a 3D model of the component, assigning material properties, defining boundary conditions, meshing, setting up the analysis, and analysing the results. SolidWorks Simulation includes a wide range of analysis types, such as static, dynamic, and thermal, and provides a comprehensive suite of tools to visualize and analyse the results. The paper focusses on performing Solidworks simulation studies and hence comparing the results with the hand calculated results. The paper is prepared based on the second-year diploma project, in which the students were taught the basics of stress analysis and use of Solidworks 2021 software for performing stress analysis on bars and beams subjected to axial, bending, torsion and combined loads. However, in this paper only bending related problem has been discussed. The concept of stress analysis was also taught to the students and hence an example related to stress concentration has also been discussed. The results of the comparison reveal that the percentage variation between the hand calculated, and simulation results is less than 1%. KEYWORDS: Solidworks, Stress analysis, 3D modelling, Engineering design, Stress concentration, FEA

Comparative Biomechanical Analysis of Anterior Process Locking Plate Alone versus Combined with Percutaneous Cannulated Screw Fixation for Sanders Type II Calcaneal Fractures: A Finite Element Study.

BACKGROUND Calcaneal fractures are the most common tarsal bone fractures, and account for 75% of intra-articular fractures. The purpose of this study was to compare the biomechanical stability of the anterior process locking plate combined with the percutaneous cannulated screw fixation (screw group) versus the anterior process locking plate fixation alone (plate group) for the treatment of Sanders type II calcaneal fractures using finite element analysis to provide a theoretical basis for clinical work. MATERIAL AND METHODS We established a 3D model of Sanders type II calcaneal fracture; assigned material properties to the internal fixation systems; applied loads; set up analysis criteria; analyzed the displacement of the fracture, relative displacement, stress state of bone tissue, and internal fixation; and compared mechanical stability. RESULTS For Sanders type II A, II B, and II C calcaneal fractures, the degree of displacement and relative displacement of the fracture in the screw group was less than that of the plate group. For all subtypes of Sanders type II calcaneal fractures, the screw group had better mechanical stability than the plate group. CONCLUSIONS Both fixation methods (screw and plate group) were within a reasonable range for restoring the levelling effect of the joint surface and maintaining the strength of fixation, and both had good mechanical stability. Finite element analysis is a relatively reliable method, and biomechanics and clinical studies must further verify the experimental results.

Credibility assessment of computational models according to ASME V&V40: Application to the Bologna Biomechanical Computed Tomography solution

Background and objectiveWhen a computational model aims to be adopted beyond research purposes, e.g. to inform a clinical or regulatory decision, trust must be placed in its predictive accuracy. This practically translates into the need to demonstrate its credibility. In fact, prior to its adoption for regulatory purposes, an in silico methodology should be proven credible enough for the scope. This has become especially relevant as, although evidence of the safety and efficacy of new medical products or interventions has been traditionally provided to the regulator experimentally, i.e., in vivo or ex vivo, recently the idea to inform a regulatory decision in silico has made its way in the regulatory scenario. While a harmonised technical standard is currently missing in the EU regulatory system, in 2018 the ASME issued V&V40–2018, where a risk-based framework to assess the credibility of a computational model through the performance of predefined credibility activities is provided. The credibility framework is here applied to Bologna Biomechanical Computed Tomography (BBCT) solution, which predicts the absolute risk of fracture at the femur for a subject. BBCT has recently been the object of a qualification advice request to the European Medicine Agency. MethodsThe full implementation of ASME V&V40–2018 framework on BBCT is shown. Starting from BBCT proposed context of use the whole credibility plan is presented and the credibility activities (Verification, Validation, Applicability) described together with the achieved credibility levels. ResultsBBCT risk is judged medium, and the credibility levels achieved considered acceptable. The uncertainties intrinsically present in the material properties assignment affected BBCT predictions to the highest extent. ConclusionsThis work provides the practical application of the ASME V&V40–2018 risk-based credibility assessment framework, which could be applied to demonstrate model credibility in any field and support future regulatory submissions and foster the adoption of In Silico Trials.

Statistical Shape and Bone Property Models of Clinical Populations as the Foundation for Biomechanical Surgical Planning: Application to Shoulder Arthroplasty.

This work developed, validated, and compared statistical shape, statistical intensity, and statistical shape and intensity models (SSMs, SIMs, SSIMs) of scapulae from a clinical population. SSMs efficiently describe bone shape variation while SIMs describe bone material property variation, and SSIM's combine description of both variables. This work establishes these models' efficacy and whether they can be used in surgical planning. Models were developed using shoulder arthroplasty data of patients with bone erosion, which is challenging to treat and would benefit from improved surgical planning. Models were created using previously validated nonrigid registration and material property assignment processes that were optimized for scapula characteristics. The models were assessed using standard metrics, anatomical measurements, and correlation analyses. The SSM and SIM specificity and generalization error metrics were 3.4 mm and <1 mm and 184 HU and 156 HU, respectively. The SSIM did not achieve the same level of performance as the SSM and SIM in this study (e.g., shape generalization: SSIM-2.2 mm versus SSM-<1 mm). Anatomical correlation analysis showed that the SSM more effectively and efficiently described shape variation compared to the SSIM. The SSM and SIM modes of variation were not strongly correlated (e.g., rmax = 0.56 for modes explaining ≤2.1% of variance). The SSIM is outperformed by the SSM and SIM and the latter two are not strongly correlated; therefore, using the SSM and SIM in conjunction will generate synthetic bone models with realistic characteristics and thus can be used for biomechanical surgical planning applications.

Exploring the Integration of Architectural Design and Advanced Structural Analysis for Steel–Glass Structures: A Comparative Study of Different Case Scenarios

It is well known that finite element analysis (FEA) is a powerful tool when it comes to the design and analysis of complex structures for various load combinations, including light steel curve members. This abstract provides an overview of the FEA simulation process for designing such members (cure members), which involves constructing a 3D model, discretising the member into small elements, assigning material properties, defining boundary conditions, conducting the simulation, analysing the results, and making any necessary modifications to the design. FEA simulations can provide valuable insights into the behaviour of light steel curved members under different load combinations. This enables designers to optimise designs for strength, safety, and cost-effectiveness. This article proposes using two commercial 3D software programs, Rhino 7 and Strand7, to complete the FEA simulation of light steel curved members. The 3D model is created in Rhino 7, and the individual elements are discretised into more minor elements using Strand7 for assigning material properties, defining boundary conditions, running simulations, and analysing the results. The paper presents five case studies of steel–glass façades and applies the proposed methodology to each. Examples include Phoenix International Media Center in Beijing, Kazakhstan Pavilion and Science Museum in Astana, Moynihan Train Hall in New York City, Chadstone Shopping Centre in Melbourne, and the central light rail station in The Hague.

FINITE ELEMENT METHOD OF SEEPAGE AND STABILITY ANALYSIS OF SAURA-KEFFI EARTH DAM

Finite element method (FEM) based analysis using the SEEP/W and SLOPE/W sub-programme options of a GEOSTUDIO software was used to analyze Saura-Keffi earth dam in Nasarawa State, Nigeria with the view to analyze the dam seepage and its stability. The created dam geometry was assigned material properties and boundary conditions at reservoir water levels of: minimum (3 m), normal (6 m) and maximum (7 m). The analysis was conducted under the cases that the dam was without and with seepage measures (SCM). The results of the analyzed semi-permeable homogenous dam revealed a percentage reduction inseepage flux to 28.3% when the dam was considered with a central core and complete cut-off trench along the dam crest axis. see figure 7. The pore-water (PWP) revealed a decrease in value from (12 to 11.2) kPa at minimum water head with SCM. The PWP further increased by 18.9% as water rises from 6 m to 7m with SCM. The exit gradient showed an insignificant increase in value of 1.2% with the construction of SCM which indicates less flow at the exit end of the dam leading to increase in stability. The horizontal filter drain at the downstream lower and kept the phreatic line within the dam body to allow for adequate embankment and foundation drainage as shown in figure (5&amp;6). The F.S at the maximum water level revealed an increase in value from 1.27 to 1.52 when a horizontal filter was considered. The Morgenstern-priced method of slope stability was used to estimate an acceptable minimum F.S of 1.52 at 0.5 lambda value with the introduction of horizontal filter.

Modeling the effect of automated fiber placement induced gaps based on serial layer scanned point clouds

The gap is one of the most common defects during the AFP process, which has a nonnegligible impact on the mechanical properties of laminates. This paper proposes a novel three-dimension reconstructive gap model based on the in-process serial layer scanned point clouds, which can characterizes the gap features inside the laminate and pre-determine the mechanical performance before the subsequent procedures. The measured point cloud will be transformed into eligible and processible formats and then be used to generate a finite element grid using the element-based material property assignment method. The local material properties and fiber orientation are defined by previously assigned classes and grid geometries respectively. The effect of gap size on the in-plane tensile strength and damage evolution of laminates is investigated and both the experimental and simulation results find that the ultimate strength and stiffness show a significant decrease with the increase of gap size.

Modification to Mirels scoring system location component improves fracture prediction for metastatic disease of the proximal femur

BackgroundCorrectly identifying patients at risk of femoral fracture due to metastatic bone disease remains a clinical challenge. Mirels criteria remains the most widely referenced method with the advantage of being easily calculated but it suffers from poor specificity. The purpose of this study was to develop and evaluate a modified Mirels scoring system through scoring modification of the original Mirels location component within the proximal femur.MethodsComputational (finite element) experiments were performed to quantify strength reduction in the proximal femur caused by simulated lytic lesions at defined locations. Virtual spherical defects representing lytic lesions were placed at 32 defined locations based on axial (4 axial positions: neck, intertrochanteric, subtrochanteric or diaphyseal) and circumferential (8 circumferential: 45-degree intervals) positions. Finite element meshes were created, material property assignment was based on CT mineral density, and femoral head/greater trochanter loading consistent with stair ascent was applied. The strength of each femur with a simulated lesion divided by the strength of the intact femur was used to calculate the Location-Based Strength Fraction (LBSF). A modified Mirels location score was next defined for each of the 32 lesion locations with an assignment of 1 (LBSF > 75%), 2 (LBSF: 51–75%), and 3 (LBSF: 0–50%).To test the new scoring system, data from 48 patients with metastatic disease to the femur, previously enrolled in a Musculoskeletal Tumor Society (MSTS) cross-sectional study was used. The lesion location was identified for each case based on axial and circumferential location from the CT images and assigned an original (2 or 3) and modified (1,2, or 3) Mirels location score. The total score for each was then calculated. Eight patients had a fracture of the femur and 40 did not over a 4-month follow-up period. Logistic regression and decision curve analysis were used to explore relationships between clinical outcome (Fracture/No Fracture) and the two Mirels scoring methods.ResultsThe location-based strength fraction (LBSF) was lowest for lesions in the subtrochanteric and diaphyseal regions on the lateral side of the femur; lesions in these regions would be at greatest risk of fracture. Neck lesions located at the anterior and antero-medial positions were at the lowest risk of fracture. When grouped, neck lesions had the highest LBSF (83%), followed by intertrochanteric (72%), with subtrochanteric (50%) and diaphyseal lesions (49%) having the lowest LBSF. There was a significant difference (p < 0.0001) in LBSF between each axial location, except subtrochanteric and diaphyseal which were not different from each other (p = 0.96).The area under the receiver operator characteristic (ROC) curve using logistic regression was greatest for modified Mirels Score using site specific location of the lesion (Modified Mirels-ss, AUC = 0.950), followed by a modified Mirels Score using axial location of lesion (Modified Mirels-ax, AUC = 0.941). Both were an improvement over the original Mirels score (AUC = 0.853).Decision curve analysis was used to quantify the relative risks of identifying patients that would fracture (TP, true positives) and those erroneously predicted to fracture (FP, false positives) for the original and modified Mirels scoring systems. The net benefit of the scoring system weighed the benefits (TP) and harms (FP) on the same scale. At a threshold probability of fracture of 10%, use of the modified Mirels scoring reduced the number of false positives by 17–20% compared to Mirels scoring.ConclusionsA modified Mirels scoring system, informed by detailed analysis of the influence of lesion location, improved the ability to predict impending pathological fractures of the proximal femur for patients with metastatic bone disease. Decision curve analysis is a useful tool to weigh costs and benefits concerning fracture risk and could be combined with other patient/clinical factors that contribute to clinical decision making.

МЕТОДИЧЕСКИЕ РЕКОМЕНДАЦИИ ПО ТОПОЛОГИЧЕСКОЙ ОПТИМИЗАЦИИ СИЛОВЫХ КОНСТРУКЦИЙ С ПРИМЕНЕНИЕМ СРЕДСТВ ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Methodological recommendations are proposed for the development of the process of topological optimization of load carrying structures adapted for the use of additive technologies. The stage of postprocessing of the polygonal geometry of the part generated as a result of optimization is considered in detail. The validation stage is included in the process of topological optimization by comparing the calculated and experimental data to assess the operability (strength) of the optimized structure. For the option of manufacturing load carrying structures by 3D printing, it is planned to conduct studies of the mechanical properties of the material obtained on a 3D printer, taking into account the printing settings and the orientation of the material layers relative to the applied load during testing. An example of approbation of the proposed methodological recommendations is given on the example of a load carrying hook included in the design of a wheeled transport anti-ram device. The optimization was performed in the SolidThinking Inspire software environment (Altair Engineering, USA). The results of the calculated and experimental determination of the destructive load are presented for the initial and optimized hook design. For the experiment, the hooks were made of ABS plastic using FDM technology. Finite element models of hooks were developed in the ANSYS Workbench software package (ANSYS, USA). Assignment of material properties, boundary conditions and applied load is performed in the LS-PrePost application, calculation in the LS-DYNA solver (ANSYS, USA). The calculated and experimental efficiency estimates were 44.4 and 57.8 %, i.e. their difference is within 13.4 %. The zones and the nature of the destruction identified by calculation and experimentally completely coincide. The results obtained confirm the correctness of the proposed methodological recommendations, the selected modeling approaches and the determination of the properties of the material of the structure manufactured by 3D printing.

31EMF Intubatable 3D Printed Airway Manikin: A Feasibility Study for Replicating Real Patient Anatomy

31EMF Intubatable 3D Printed Airway Manikin: A Feasibility Study for Replicating Real Patient Anatomy

A comprehensive 2 Dimensional and 3 Dimensional FEM study of scarf repair for a variety of common composite laminates under in-plane uniaxial and equibiaxial loadings

Due to their potential to recover strength and stiffness with a minimum impact on aerodynamic performance of a damaged structure, scarf repairs are boosted as a viable repair option for primary aero-structures. So far, most of the experimental and numerical studies have been limited to joint specimens and their equivalent 2 Dimensional models and a few number of studies attempted to examine the results using real scarf repair geometry. Suggestions previously made to justify the difference between scarf joint and scarf repair strength and possible solution to diminish the difference are challenged in current work. Here, it is tried to investigate the strengths and shortcomings of 2D scarf joint modelling and their influence on the associated results by promoting 3 Dimensional Finite Element Modelling of complete geometry of the scarf repair. A method to assign material properties to a planar geometry of composite material has been developed that provides the possibility of plane strain, plane stress, and generalized plane strain modelling options of a scarf repair cross section under uniaxial load. Besides, accuracy of scarf joint specimen as a representative to scarf repair to predict load carrying capacity of a circular scarf repair is investigated. The study mainly focuses on 2D and 3D FEM simulation results discrepancies considering the effect of angle ply, cross ply and various stacking sequences of quasi-isotropic laminate under uniaxial and equi-biaxial loads. Results show that the laminate lay-up angles and stacking sequence substantially affect the 2D and 3D simulations agreement. Also, the observed discrepancies in scarf repair and scarf joint results are not limited to the effects of plastic deformation of the adhesive, but it seems the modelling shortcomings greatly affect the results. In overall, the current work demonstrates that for a particular laminate, joint specimen does not represent reasonably a scarf repair. In fact, the load carrying capacity estimated based on joint specimen data can mislead decision making procedure in a way that results in rejection of an eligible repair. To avoid inaccurate strength estimation, a 3D simulation of a scarf repair especially for a load other than uniaxial tension or compression is strongly recommended.