Analysis of crush-damaged carbon-fiber-reinforced-polymer (CFRP) composites with optimization-assisted post-peak-stress modeling

2020 ◽  
pp. 002199832095770
Author(s):  
Sheng Dong ◽  
Lars Gräning ◽  
Kelly Carney ◽  
Allen Sheldon
Keyword(s):  
Cross Sections ◽  
Peak Stress ◽  
Material Model ◽  
Material Behavior ◽  
Engineering Practice ◽  
Model Parameters ◽  
Optimization Strategy ◽  
Damage Models ◽  
Cfrp Composites ◽  
Force Time

In the presented effort, layered CFRP composites samples with differing thicknesses and cross-sections are manufactured and crushed under quasi-static loading conditions. Simulation of the crushes are conducted using traditional continuum mechanics damage models. Parameters are proposed to represent the post peak-stress material behavior including the residual strengths of the fiber and matrix, as well the ultimate strain for deletion of composite elements. This paper presents a systematic approach to identify optimal values for these post peak-stress parameters based on a methodology incorporating CAE models and numerical optimization. An adaptive meta-model based global optimization strategy, with the objective of matching the force-time characteristics of multiple crush experiments simultaneously, has been established to quantify the values of the CFRP’s post peak-stress degradation and erosion material model parameters through calibration. Using two separate test configurations for optimization, a set of values for those parameters are determined. This parameter set is shown to successfully predict the response of additional test cases, including matching of force-displacement curves and crushing modes. The resulting composite crush simulations show a good quantitative as well as qualitative agreement between simulations and experiments to a degree that is difficult to be achieved solely with previous engineering practice.

scholarly journals Assimilation of Dynamic Combined Finite Discrete Element Methods Using the Ensemble Kalman Filter

2021 ◽  
Vol 11 (7) ◽  
pp. 2898
Author(s):  
Humberto C. Godinez ◽  
Esteban Rougier
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Peak Stress ◽  
Discrete Element ◽  
Material Behavior ◽  
Model Parameters ◽  
Hopkinson Pressure Bar ◽  
Parameter Values

Simulation of fracture initiation, propagation, and arrest is a problem of interest for many applications in the scientific community. There are a number of numerical methods used for this purpose, and among the most widely accepted is the combined finite-discrete element method (FDEM). To model fracture with FDEM, material behavior is described by specifying a combination of elastic properties, strengths (in the normal and tangential directions), and energy dissipated in failure modes I and II, which are modeled by incorporating a parameterized softening curve defining a post-peak stress-displacement relationship unique to each material. In this work, we implement a data assimilation method to estimate key model parameter values with the objective of improving the calibration processes for FDEM fracture simulations. Specifically, we implement the ensemble Kalman filter assimilation method to the Hybrid Optimization Software Suite (HOSS), a FDEM-based code which was developed for the simulation of fracture and fragmentation behavior. We present a set of assimilation experiments to match the numerical results obtained for a Split Hopkinson Pressure Bar (SHPB) model with experimental observations for granite. We achieved this by calibrating a subset of model parameters. The results show a steady convergence of the assimilated parameter values towards observed time/stress curves from the SHPB observations. In particular, both tensile and shear strengths seem to be converging faster than the other parameters considered.

scholarly journals Numerical and experimental investigation of Johnson–Cook material models for aluminum (Al 6061-T6) alloy using orthogonal machining approach

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879779 ◽  
Author(s):  
Sohail Akram ◽  
Syed Husain Imran Jaffery ◽  
Mushtaq Khan ◽  
Muhammad Fahad ◽  
Aamir Mubashar ◽  
...  
Keyword(s):  
Coefficient Of Friction ◽  
Cutting Forces ◽  
High Speed ◽  
Material Model ◽  
Material Behavior ◽  
Experimental Results ◽  
Model Parameters ◽  
Al 6061 ◽  
Orthogonal Machining ◽  
Cutting Speeds

This research focuses on the study of the effects of processing conditions on the Johnson–Cook material model parameters for orthogonal machining of aluminum (Al 6061-T6) alloy. Two sets of parameters of Johnson–Cook material model describing material behavior of Al 6061-T6 were investigated by comparing cutting forces and chip morphology. A two-dimensional finite element model was developed and validated with the experimental results published literature. Cutting tests were conducted at low-, medium-, and high-speed cutting speeds. Chip formation and cutting forces were compared with the numerical model. A novel technique of cutting force measurement using power meter was also validated. It was found that the cutting forces decrease at higher cutting speeds as compared to the low and medium cutting speeds. The poor prediction of cutting forces by Johnson–Cook model at higher cutting speeds and feed rates showed the existence of a material behavior that does not exist at lower or medium cutting speeds. Two factors were considered responsible for the change in cutting forces at higher cutting speeds: change in coefficient of friction and thermal softening. The results obtained through numerical investigations after incorporated changes in coefficient of friction showed a good agreement with the experimental results.

A note on the nonlinear mechanical behavior of planar random network structures subjected to in-plane compression

2011 ◽  
Vol 45 (25) ◽  
pp. 2697-2703 ◽  
Author(s):  
Pär E. Åslund ◽  
Per Isaksson
Keyword(s):  
Mechanical Behavior ◽  
Elastic Material ◽  
Random Network ◽  
Material Model ◽  
Element Model ◽  
Material Behavior ◽  
Fiber Networks ◽  
Damage Models ◽  
Plane Compression ◽  
Random Fiber Networks

The microstructural effect on the mechanical behavior of idealized two-dimensional random fiber networks subjected to in-plane compression is studied. A finite element model utilizing nonlinear beam elements assuming a linearly elastic material is developed. On a macroscopic level, random fiber networks often display an asymmetric material behavior when loaded in tension and compression. In mechanical models, this nonlinearity is traditionally described using continuum elastic-inelastic and/or damage models even though using a continuum approach risks overlooking microstructural effects. It is found that even though a linear elastic material model is used for the individual fibers, the network gives a nonlinear response in compression. The nonlinearity is found to be caused by buckling of individual fibers. This reversible nonlinear mechanism is limited in tensile loading and hence offers an alternative explanation to the global asymmetry of random fibernetworks.

Machining Simulation of Ductile Iron and its Constituents: Part I — Estimation of Material Model Parameters and Their Validation

2001 ◽  
Author(s):  
L. Chuzhoy ◽  
R. E. DeVor ◽  
S. G. Kapoor ◽  
A. J. Beaudoin ◽  
D. J. Bammann
Keyword(s):  
Ductile Iron ◽  
Heterogeneous Materials ◽  
Material Model ◽  
Material Behavior ◽  
Model Parameters ◽  
Notched Specimens ◽  
Reverse Loading ◽  
Level Model ◽  
Validation Stage ◽  
Good Agreement

Abstract A microstructure-level simulation model was recently developed to characterize machining behavior of heterogeneous materials. During machining of heterogeneous materials such as cast iron, the material around the machining-affected zone undergoes reverse loading, which manifests itself in permanent material softening. In addition, cracks are formed below and ahead of the tool. To accurately simulate machining of heterogeneous materials the microstructure-level model has to reproduce the effect of material softening on reverse loading (MSRL effect) and material damage. This paper describes procedures used to calculate the material behavior parameters for the aforementioned phenomena. To calculate the parameters associated with the MSRL effect, uniaxial reverse loading experiments and simulations were conducted using individual constituents of ductile iron. The material model was validated with reverse loading experiments of ductile iron specimens. To determine the parameters associated with fracture of each constituent, experiments and simulation of notched specimens are performed. During the validation stage, response of simulated ductile iron was in good agreement with the experimental data.

Machining Simulation of Ductile Iron and Its Constituents, Part 1: Estimation of Material Model Parameters and Their Validation

2003 ◽  
Vol 125 (2) ◽  
pp. 181-191 ◽  
Author(s):  
L. Chuzhoy ◽  
R. E. DeVor ◽  
S. G. Kapoor ◽  
A. J. Beaudoin ◽  
D. J. Bammann
Keyword(s):  
Ductile Iron ◽  
Heterogeneous Materials ◽  
Material Model ◽  
Material Behavior ◽  
Model Parameters ◽  
Notched Specimens ◽  
Reverse Loading ◽  
Level Model ◽  
Validation Stage ◽  
Good Agreement

A microstructure-level simulation model was recently developed to characterize machining behavior of heterogeneous materials. During machining of heterogeneous materials such as cast iron, the material around the machining-affected zone undergoes reverse loading, which manifests itself in permanent material softening. In addition, cracks are formed below and ahead of the tool. To accurately simulate machining of heterogeneous materials the microstructure-level model has to reproduce the effect of material softening on reverse loading (MSRL effect) and material damage. This paper describes procedures used to calculate the material behavior parameters for the aforementioned phenomena. To calculate the parameters associated with the MSRL effect, uniaxial reverse loading experiments and simulations were conducted using individual constituents of ductile iron. The material model was validated with reverse loading experiments of ductile iron specimens. To determine the parameters associated with fracture of each constituent, experiments and simulation of notched specimens are performed. During the validation stage, response of simulated ductile iron was in good agreement with the experimental data.

Tensile Behavior of 82/182 Filler, Butter and Heat-Affected-Zones in a 508 LAS - 316 SS Dissimilar Weld: Tensile Test, Material Model and Finite Element Model Validation

2019 ◽  
Author(s):  
Subhasish Mohanty ◽  
Joseph Listwan ◽  
Saurindranath Majumdar ◽  
Krishnamurti Natesan
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Low Cycle Fatigue ◽  
Material Model ◽  
Material Behavior ◽  
Test Material ◽  
Model Parameters ◽  
Fe Model ◽  
Component Level ◽  
Dissimilar Weld

Abstract In this paper we present the room temperature tensile test results for 82/182 Filler, Butter Weld and Heat-Affected-Zone in a 508 LAS − 316 SS Dissimilar Weld (DW). Also we present the associated tensile properties and material hardening model parameters; those can be used for future component level stress analysis modes. In addition, we present the finite element (FE) model of the uniaxial DW tensile-test specimens to validate the accuracy of the estimated material model parameters. Through the FE model results, we also explain the importance of various offset strain yield stress in capturing the material behavior in a mechanistic (using FE) modeling approach particularly while modeling the plasticity driven low-strain-amplitude low-cycle-fatigue damage of a structural component.

Prediction of Process-Induce Distortions and Residual Stresses of Ancomposite Suspension Blade

2015 ◽  
Vol 362 ◽  
pp. 224-243 ◽  
Author(s):  
Robert Hein ◽  
Tobias Wille ◽  
Khalil Gabtni ◽  
Jean Paul Dias
Keyword(s):  
Residual Stresses ◽  
Automobile Industry ◽  
Material Model ◽  
Contact Angle Measurement ◽  
Reaction Model ◽  
Angle Measurement ◽  
Material Behavior ◽  
Model Parameters ◽  
Degree Of Cure ◽  
Simulation Strategy

This paper deals with a universal simulation strategy for the calculation of process-induceddistortions and residual stresses of a composite part. The mechanical material behavior is describedby a viscoelastic material model depending on temperature and degree of cure . The required materialparameters are derived by dynamic mechanical analyses. For the description of the reaction kinetic aphenomenological based model considering chemical and diffusion-controlled reactions is introduced.The reaction model parameters are fitted to isothermal and dynamic DSC measurements via globaland local optimization. The thermal expansion and chemical shrinkage are characterized by thermalmechanical analysis and using the contact angle measurement method. The simulation strategy isdemonstrated for a GFRP suspension blade for the automobile industry. Based on a sequential coupledtemperature-displacement analysis thermal hot spots, temperature and degree of cure distributions aswell as the final corresponding process-induced distortions and residual stresses are calculated andanalyzed. The development of the stiffness and the correlated stress during the curing process arediscussed in more detail. Furthermore, the effect of a degree of cure dependent stiffness on the stressesis investigated.

Ramberg–Osgood material behavior expression and large deflections of Euler beams

2020 ◽  
pp. 108128652093236
Author(s):  
Ronald J Giardina ◽  
Dongming Wei
Keyword(s):  
Cross Sections ◽  
Nonlinear Behavior ◽  
Material Model ◽  
Material Behavior ◽  
Combined Loading ◽  
Elastic Behavior ◽  
Large Deflections ◽  
Euler Beam ◽  
Special Cases ◽  
Material Behaviors

Several assumptions are commonly made throughout the literature with regard to the mechanical expression of material behavior under a Ramberg–Osgood material model; specifically, the negligible effects of nonlinearity on the elastic behavior of the material. These assumptions do not reflect the complicated nonlinearity implied by the Ramberg–Osgood expression, which can lead to significant differences in the member model response from the true material behavior curve. With the proposed approach, new explicit results for Ramberg–Osgood materials are achieved without relying on these assumptions of material and model expression. The only assumptions present within the proposed model are the standard mechanical assumptions of an Euler beam. A general nonlinear moment–curvature relationship for monotone material behaviors is constructed. Large deflections of cantilever Euler beams with rectangular cross-sections under a combined loading are modeled. Numerical validation of this new method against results already given in the literature for the special cases of linear and power-law material behaviors are provided. An analysis is presented for three common material behavior relationships, with a focus on how these relationships are expressed through the deflection of members under the application of force within the model; this analysis clearly demonstrates that the sub-yield nonlinear behavior of the Ramberg–Osgood expression can be significant. The distinctions between material behavior expression demonstrated in this analysis have been long overlooked within the literature. This work addresses a gap between the modeling of Ramberg–Osgood material behaviors and the implementation of that model in mechanics.

Imperfection Insensitivity of Thin Wavy Cylindrical Shells Under Axial Compression or Bending

2020 ◽  
Vol 87 (4) ◽  
Author(s):  
Kshitij Kumar Yadav ◽  
Simos Gerasimidis
Keyword(s):  
Axial Compression ◽  
Cross Sections ◽  
Cylindrical Shells ◽  
Decisive Role ◽  
High Sensitivity ◽  
Material Model ◽  
Material Behavior ◽  
Imperfection Sensitivity ◽  
Wave Parameters ◽  
Bending Load

Abstract The presence of imperfections significantly reduces the load carrying capacity of thin cylindrical shells due to the high sensitivity of thin shells to imperfections. To nullify this unfavorable characteristic, thin cylindrical shells are designed using a conservative knockdown factor method, which was developed by NASA in the late 1960s. Almost all the design codes, explicitly or implicitly, follow this approach. Recently, a new approach has emerged to significantly reduce the sensitivity of thin cylindrical shells. In this approach, wavy cross sections are used instead of circular cross sections for creating thin cylinders. Past studies have demonstrated the effectiveness of wavy cylinders to reduce imperfection sensitivity of thin cylinders under axial compression assuming linear elastic material behavior. These studies used eigenmode imperfections which do not represent realistic imperfections found in cylinders. In this paper, using a realistic dimple-like imperfection, new insights are presented into the response of wavy cylinders under uniform axial compression and bending. Furthermore, the effectiveness of the wavy cylinders to reduce imperfection sensitivity under bending load is investigated assuming a plastic Ramberg–Osgood material model. The effect of wave parameters, e.g., the amplitude and the number of waves, is also explored. This study reveals that wavy thin cylinders are insensitive to imperfections under bending in the inelastic range of the material. It is also found that the wave parameters play a decisive role in the response of thin wavy cylinders to imperfections under bending.

scholarly journals Variation of Passive Biomechanical Properties of the Small Intestine along Its Length: Microstructure-Based Characterization

2021 ◽  
Vol 8 (3) ◽  
pp. 32
Author(s):  
Dimitrios P. Sokolis
Keyword(s):  
Small Intestine ◽  
Orientation Angle ◽  
Axial Direction ◽  
Material Model ◽  
Biomechanical Properties ◽  
Intestinal Wall ◽  
Model Parameters ◽  
Material Models ◽  
Hyper Elastic ◽  
Rat Tissue

Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine and test whether there was a significant variation in the passive biomechanical properties along the length of the organ. Rat tissue was cut into eight segments that underwent inflation/extension testing, and their nonlinearly hyper-elastic and anisotropic response was characterized by a fiber-reinforced model. Extensive parametric analysis showed a non-significant contribution to the model of the isotropic matrix and circumferential-fiber family, leading also to severe over-parameterization. Such issues were not apparent with the reduced neo-Hookean and (axial and diagonal)-fiber family model, that provided equally accurate fitting results. Absence from the model of either the axial or diagonal-fiber families led to ill representations of the force- and pressure-diameter data, respectively. The primary direction of anisotropy, designated by the estimated orientation angle of diagonal-fiber families, was about 35° to the axial direction, corroborating prior microscopic observations of submucosal collagen-fiber orientation. The estimated model parameters varied across and within the duodenum, jejunum, and ileum, corroborating histologically assessed segmental differences in layer thicknesses.

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