Thermo-Mechanical Forming Analysis and Mapping of Material Properties in Press Hardened Components with Tailored Material Properties

2014 ◽  
Vol 1063 ◽  
pp. 290-296
Author(s):  
Greger Bergman ◽  
Daniel Berglund ◽  
Kenneth Isaksson
Keyword(s):  
Axial Compression ◽  
Material Properties ◽  
Shear Fracture ◽  
Hot Stamping ◽  
Mesh Size ◽  
Material Model ◽  
Element Model ◽  
Viscoplastic Material ◽  
Size Dependent ◽  
Forming Analysis

A finite element model for failure prediction has been used for axial compression simulation of a front side member beam with tailored material properties. A corresponding experiment has been performed. The numerical simulation is divided into forming, mapping and axial compression. The coupled thermo-mechanical hot stamping simulation includes an austenite decomposition model that accounts for carbon segregation. In the mapping step, the phase composition is first mapped and then translated into global stress-strain curves and failure parameters using two different models. An elastic-viscoplastic material model including mesh size dependent localization and crack initiation with a ductile and shear fracture model is used in the axial compression simulation. The simulation shows acceptable agreement with the experimental results.

A Computer Simulation on Human Injury during the Aircrew/Seat Through-the-Canopy-Ejection

2011 ◽  
Vol 55-57 ◽  
pp. 179-182
Author(s):  
Zhi Qiang Li ◽  
Xiao Hu Yao ◽  
Long Mao Zhao
Keyword(s):  
Damage Mechanics ◽  
Human Head ◽  
Continuum Damage Mechanics ◽  
Material Model ◽  
Element Model ◽  
Continuum Damage ◽  
Viscoplastic Material ◽  
Simplified Finite Element Model ◽  
Design And Manufacture ◽  
Human Injury

For through-the-canopy-ejection-saving system with miniature detonation cord (MDC), screw/seat system has penetrated canopy to successfully escape after the strength of canopy weaken by MDC in the case of emergency. Injury of human head and spine is serious due to striking between aircrew/seat and canopy during the ejection. In the paper, considering MDC installed along all-around of canopy, the initial cut slot is used to model the damage of canopy impacted by detonation wave from MDC. Simplified finite element model of through-the-canopy-ejection-system has been established according to ergonomics. In FEM, canopy as PMMA employs elastic viscoplastic material model combined with continuum damage mechanics, crew is modeled as 50% deformable dummy. FEM is solved using nonlinear dynamics explicit code LS-DYNA3D. Head impact force and dynamic response index (DRI) of spine are obtained, and meet the requirement of nation army standard. Simulation results indicate that MDC installation way is avail to reduce physiology damage of airscrew. It also provides science foundation for safe design and manufacture of through-the-canopy-ejection-system.

A dynamic crash model for energy absorption in braided composite materials - Part II: Implementation and verification

2011 ◽  
Vol 45 (8) ◽  
pp. 867-882 ◽  
Author(s):  
Nathan D. Flesher ◽  
Fu-Kuo Chang ◽  
Nageswara R. Janapala ◽  
J. Michael Starbuck
Keyword(s):  
Composite Materials ◽  
Energy Absorption ◽  
Composite Structures ◽  
Material Model ◽  
Element Model ◽  
Failure Behavior ◽  
Viscoplastic Material ◽  
Braided Composite ◽  
Rate Dependent ◽  
Crash Model

A dynamic crash model is developed and implemented to model the failure behavior and energy absorption of braided composite structures. Part I describes the development and theoretical foundation of a viscoplastic material model that captures the rate-dependent behavior present in braided composite materials. Part II presents the implementation of the model into a finite element model program and the experimental results for tubes crushed from quasi-static to 4000 mm/s rates used to verify the model. Energy absorption decreases sharply with an increase in crush rate, which is reflected in this model. Design concepts are also introduced to increase energy absorption in braided composites.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Experimental Identification of Material Properties of Piezoelectric Patch Transducer

2013 ◽  
Vol 486 ◽  
pp. 205-210
Author(s):  
Zuzana Lašová ◽  
Robert Zemcik
Keyword(s):  
Health Monitoring ◽  
Material Properties ◽  
Element Model ◽  
Experimental Methods ◽  
Optical Microscope ◽  
Piezoelectric Patch ◽  
Experimental Identification ◽  
Substrate Structure ◽  
Significant Difference ◽  
Voltage Signal

This work is focused on identification of material properties of piezoelectric patch transducers used e.g. for structural health monitoring before attaching to the substrate structure. Two experimental methods were concerned. At first two piezoelectric patches were supplied with a pair of collocated strain gauge rosettes. Both transducers were actuated with the same periodical signal. Significant difference in the results for two transducers was found, however it was claimed to be within tolerance by the producer. As an alternative method a measurement in an optical microscope was chosen. The patch was clamped at one side and actuated by a voltage signal. The displacement of the free end was captured by the microscope and processed in a graphical editor. Finally, a finite element model of the transducer was created and its material data were obtained by calibration with experimental data.

Size- and temperature-dependent Young's modulus and size-dependent thermal expansion coefficient of thin films

2016 ◽  
Vol 18 (31) ◽  
pp. 21508-21517 ◽  
Author(s):  
Xiao-Ye Zhou ◽  
Bao-Ling Huang ◽  
Tong-Yi Zhang
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Young’S Modulus ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Material Properties ◽  
Essential Role ◽  
Young's Modulus ◽  
Temperature Dependent ◽  
Size Dependent

Surfaces of nanomaterials play an essential role in size-dependent material properties.

Creep-Fatigue Interaction Effects On Pressure-Reducing Valve Under Cyclic Thermo-Mechanical Loadings Using Direct Cyclic Method

2021 ◽  
Author(s):  
Nak-Kyun Cho ◽  
Youngjae Choi ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Fatigue Failure ◽  
Material Properties ◽  
Structural Integrity ◽  
Direct Method ◽  
Element Model ◽  
Critical Loading ◽  
Creep Fatigue ◽  
Pressure Reducing Valve

Abstract Supercritical boiler system has been widely used to increase efficiency of electricity generation in power plant industries. However, the supercritical operating condition can seriously affect structural integrity of power plant components due to high temperature that causes degradation of material properties. Pressure reducing valve is an important component being employed within a main steam line of the supercritical boiler, which occasionally thermal-fatigue failure being reported. This research has investigated creep-cyclic plastic behaviour of the pressure reducing valve under combined thermo-mechanical loading using a numerical direct method known as extended Direct Steady Cyclic Analysis of the Linear Matching Method Framework (LMM eDSCA). Finite element model of the pressure-reducing valve is created based on a practical valve dimension and temperature-dependent material properties are applied for the numerical analysis. The simulation results demonstrate a critical loading component that attributes creep-fatigue failure of the valve. Parametric studies confirm the effects of magnitude of the critical loading component on creep deformation and total deformation per loading cycle. With these comprehensive numerical results, this research provides engineer with an insight into the failure mechanism of the pressure-reducing valve at high temperature.

FEBio finite element model of a pediatric cervical spine

2021 ◽  
pp. 1-7
Author(s):  
Sean M. Finley ◽  
J. Harley Astin ◽  
Evan Joyce ◽  
Andrew T. Dailey ◽  
Douglas L. Brockmeyer ◽  
...  
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Finite Element Model ◽  
Material Properties ◽  
Surgical Simulation ◽  
Element Model ◽  
Axial Stiffness ◽  
Published Data ◽  
Axial Tension ◽  
Flexion Extension

OBJECTIVE The underlying biomechanical differences between the pediatric and adult cervical spine are incompletely understood. Computational spine modeling can address that knowledge gap. Using a computational method known as finite element modeling, the authors describe the creation and evaluation of a complete pediatric cervical spine model. METHODS Using a thin-slice CT scan of the cervical spine from a 5-year-old boy, a 3D model was created for finite element analysis. The material properties and boundary and loading conditions were created and model analysis performed using open-source software. Because the precise material properties of the pediatric cervical spine are not known, a published parametric approach of scaling adult properties by 50%, 25%, and 10% was used. Each scaled finite element model (FEM) underwent two types of simulations for pediatric cadaver testing (axial tension and cardinal ranges of motion [ROMs]) to assess axial stiffness, ROM, and facet joint force (FJF). The authors evaluated the axial stiffness and flexion-extension ROM predicted by the model using previously published experimental measurements obtained from pediatric cadaveric tissues. RESULTS In the axial tension simulation, the model with 50% adult ligamentous and annulus material properties predicted an axial stiffness of 49 N/mm, which corresponded with previously published data from similarly aged cadavers (46.1 ± 9.6 N/mm). In the flexion-extension simulation, the same 50% model predicted an ROM that was within the range of the similarly aged cohort of cadavers. The subaxial FJFs predicted by the model in extension, lateral bending, and axial rotation were in the range of 1–4 N and, as expected, tended to increase as the ligament and disc material properties decreased. CONCLUSIONS A pediatric cervical spine FEM was created that accurately predicts axial tension and flexion-extension ROM when ligamentous and annulus material properties are reduced to 50% of published adult properties. This model shows promise for use in surgical simulation procedures and as a normal comparison for disease-specific FEMs.

Stress Effects in Drying Polymer Films

1994 ◽  
Vol 356 ◽  
Author(s):  
S. Y. Tam ◽  
L. E. Scriven ◽  
H. K. Stolarski
Keyword(s):  
Thin Films ◽  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Polymer Films ◽  
Material Properties ◽  
Film Surface ◽  
Viscoplastic Material ◽  
Stress Effects ◽  
Diffusion And Convection ◽  
Extra Stress

AbstractA model is developed to predict the magnitude and pattern of stress due to drying of polymer films. This model combines diffusion-and-convection equation with large deformation elasto-viscoplasticity, utilizing concentration dependent elastic and viscoplastic material properties to better represent the behavior of drying thin films.The results show that the highest stress occurs at film surface where the concentration depletion is the highest. The magnitude of this stress is induced by increasing mass transfer across the film surface but reduced by increasing diffusion coefficient. The edge effect is significant but local, limited to about four film thicknesses. Similarly, change in substrate induces extra stress.

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