Verification of the elastic material characteristics of Norway spruce and European beech in the field of shear behaviour by means of digital image correlation (DIC) for finite element analysis (FEA)

Holzforschung ◽  
2017 ◽  
Vol 71 (5) ◽  
pp. 405-414 ◽  
Author(s):  
Jaromír Milch ◽  
Martin Brabec ◽  
Václav Sebera ◽  
Jan Tippner
Keyword(s):  
Finite Element Analysis ◽  
Elastic Material ◽  
Numerical Models ◽  
European Beech ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Data Sets ◽  
Element Analysis ◽  
Material Models ◽  
Material Characteristics

Abstract Norway spruce (Picea abies L. Karst.) and European beech (Fagus sylvatica L.) samples were loaded in shear mode aimed at testing their elastic material characteristics applicable in finite element analysis (FEA). More precisely, experimental and numerical analyses of uniaxial tensile test parallel to grain in longitudinal-radial (LR) or longitudinal-tangential (LT) shear of plane are described. The elastic material models in the FEA are based on own experimental data and those of the literature. The verification of material characteristics was performed by 3D numerical models with the same parameters as for the experimental tests. The fully orthotropic elastic material model was applied in the uniaxial tensile tests. The digital image correlation (DIC) method served for verification of the numerical models with proposed elastic material characteristics. Good correlation was found between numerically predicted and experimentally measured data. The minor differences between the two data sets could be mainly attributed to certain natural wood characteristics, which were neglected in the proposed models, i.e. especially variation of earlywood and latewood density. The proposed elastic material models offer general data sets for the evaluation of mechanical response of timber structures and especially in timber connexions.

Determination of the elasto-plastic material characteristics of Norway spruce and European beech wood by experimental and numerical analyses

Holzforschung ◽  
2016 ◽  
Vol 70 (11) ◽  
pp. 1081-1092 ◽  
Author(s):  
Jaromír Milch ◽  
Jan Tippner ◽  
Václav Sebera ◽  
Martin Brabec
Keyword(s):  
Norway Spruce ◽  
Plastic Material ◽  
Beech Wood ◽  
European Beech ◽  
Image Correlation ◽  
Numerical Analyses ◽  
Isotropic Hardening ◽  
Material Models ◽  
Material Characteristics ◽  
Non Linear

Abstract Experimental and numerical analyses are presented concerning of compression tests parallel and perpendicular to the grain, three-point bending, and double-shear joints in compliance with the relevant test standards (ASTM D2395, BS 373, EN 383 and EN 26891). Woods of Norway spruce (Picea abies L. Karst.) and European beech (Fagus sylvatica L.) were tested to describe their non-linear behavior. Elasto-plastic material models were the basis for the finite-element (FE) analyses with the input of own experimental data and those of the literature. The elasto-plastic material model with non-linear isotropic hardening was applied based on the Hill yield criterion in regions of uniaxial compression. The material characteristics were first optimized and validated by means of basic 3D FE models under the same conditions as applied for the experiments. Afterwards, the validated material models were implemented into the solver with more complex numerical analyses of wooden dowel joints. Concurrently, the digital image correlation (DIC) served for verification of the numerical wooden joint models. A good agreement (with a relative error up to 16%) was found between numerically predicted and experimentally measured data. The differences may be mainly attributed to some natural characteristics of wood which were not considered in the proposed material models. The proposed elasto-plastic material models are capable of predicting the wood’s ultimate strength, and therefore could contribute to a more reliable design of wood structures and their performance.

Comparison of Different Material Models to Simulate 3-D Breast Deformations Using Finite Element Analysis

2013 ◽  
Vol 42 (4) ◽  
pp. 843-857 ◽  
Author(s):  
Maximilian Eder ◽  
Stefan Raith ◽  
Jalil Jalali ◽  
Alexander Volf ◽  
Markus Settles ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Analysis ◽  
Material Models

scholarly journals On the Design of a Biodegradable POC-HA Polymeric Cardiovascular Stent

2012 ◽  
Author(s):  
Joonas Ponkala ◽  
Mohsin Rizwan ◽  
Panos S. Shiakolas
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Polymeric Composite ◽  
Coronary Stent ◽  
Element Analysis ◽  
Material Models ◽  
Solid Models ◽  
Biodegradable Stents

The current state of the art in coronary stent technology, tubular structures used to keep the lumen open, is mainly populated by metallic stents coated with certain drugs to increase biocompatibility, even though experimental biodegradable stents have appeared in the horizon. Biodegradable polymeric stent design necessitates accurate characterization of time dependent polymer material properties and mechanical behavior for analysis and optimization. This manuscript presents the process for evaluating material properties for biodegradable biocompatible polymeric composite poly(diol citrate) hydroxyapatite (POC-HA), approaches for identifying material models and three dimensional solid models for finite element analysis and fabrication of a stent. The developed material models were utilized in a nonlinear finite element analysis to evaluate the suitability of the POC-HA material for coronary stent application. In addition, the advantages of using femtosecond laser machining to fabricate the POC-HA stent are discussed showing a machined stent. The methodology presented with additional steps can be applied in the development of a biocompatible and biodegradable polymeric stents.

Computational Human Torso Model Validation for Frontal Blunt Trauma

2018 ◽  
Author(s):  
Carolyn E. Hampton ◽  
Michael Kleinberger
Keyword(s):  
Finite Element ◽  
Blunt Trauma ◽  
Energy Absorption ◽  
Elastic Material ◽  
Peak Force ◽  
Tissue Type ◽  
Absorption Data ◽  
Element Analysis ◽  
Material Models ◽  
Torso Model

Recent research on behind-armor blunt trauma (BABT) has focused on the personal protection offered by lightweight armor. A finite element analysis was performed to improve the biofidelity of the US Army Research Laboratory (ARL) human torso model to prepare for simulating blunt chest impacts and BABT. The overly stiff linear elastic material models for the torso were replaced with material characterizations drawn from current literature. FE torso biofidelity was determined by comparing peak force, force-compression, peak compression, and energy absorption data with cadaver responses to a 23.5 kg pendulum impacting at the sternum at 6.7 m/s. Nonlinear foam, viscous foam, soft rubbers, fibrous hyperelastic rubbers, and low moduli elastic material were considered as material models for the flesh, organs, and bones. Simulations modifying one tissue type revealed that the flesh characterization was most crucial for predicting compression and force, followed closely by the organs characterizations. Combining multiple tissue modifications allowed the FE torso to mimic the cadaveric torsos by reducing peak force and increasing chest compression and energy absorption. Limitations imposed by the Lagrangian finite element approach are discussed with potential workarounds described. Proposed future work is split between considering additional impact scenarios accounting for position and biomaterial variability.

scholarly journals Minimizing Residual Stress in Brazed Joints by Optimizing the Brazing Thermal Profile

2020 ◽  
Author(s):  
Ben Mann ◽  
Kurtis Ford ◽  
Mike Neilsen ◽  
Dan Kammler
Keyword(s):  
Elastic Material ◽  
Curie Point ◽  
Thermal Strain ◽  
Optimization Techniques ◽  
Filler Materials ◽  
Thermal Profile ◽  
Slow Cooling ◽  
Element Analysis ◽  
Material Models ◽  
Cooling Rates

Abstract Ceramic to metal brazing is a common bonding process used in many advanced systems such as automotive engines, aircraft engines, and electronics. In this study, we use optimization techniques and finite element analysis utilizing viscoplastic and thermo-elastic material models to find an optimum thermal profile for a Kovar® washer bonded to an alumina button that is typical of a tension pull test. Several active braze filler materials are included in this work. Cooling rates, annealing times, aging, and thermal profile shapes are related to specific material behaviors. Viscoplastic material models are used to represent the creep and plasticity behavior in the Kovar® and braze materials while a thermo-elastic material model is used on the alumina. The Kovar® is particularly interesting because it has a Curie point at 435°C that creates a nonlinearity in its thermal strain and stiffness profiles. This complex behavior incentivizes the optimizer to maximize the stress above the Curie point with a fast cooling rate and then favors slow cooling rates below the Curie point to anneal the material. It is assumed that if failure occurs in these joints, it will occur in the ceramic material. Consequently, the maximum principle stress of the ceramic is minimized in the objective function. Specific details of the stress state are considered and discussed.

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