scholarly journals Surrogate Models for Estimating Failure in Brittle and Quasi-Brittle Materials

2019 ◽  
Vol 9 (13) ◽  
pp. 2706 ◽  
Author(s):  
Maruti Kumar Mudunuru ◽  
Nishant Panda ◽  
Satish Karra ◽  
Gowri Srinivasan ◽  
Viet T. Chau ◽  
...  

In brittle fracture applications, failure paths, regions where the failure occurs and damage statistics, are some of the key quantities of interest (QoI). High-fidelity models for brittle failure that accurately predict these QoI exist but are highly computationally intensive, making them infeasible to incorporate in upscaling and uncertainty quantification frameworks. The goal of this paper is to provide a fast heuristic to reasonably estimate quantities such as failure path and damage in the process of brittle failure. Towards this goal, we first present a method to predict failure paths under tensile loading conditions and low-strain rates. The method uses a k-nearest neighbors algorithm built on fracture process zone theory, and identifies the set of all possible pre-existing cracks that are likely to join early to form a large crack. The method then identifies zone of failure and failure paths using weighted graphs algorithms. We compare these failure paths to those computed with a high-fidelity fracture mechanics model called the Hybrid Optimization Software Simulation Suite (HOSS). A probabilistic evolution model for average damage in a system is also developed that is trained using 150 HOSS simulations and tested on 40 simulations. A non-parametric approach based on confidence intervals is used to determine the damage evolution over time along the dominant failure path. For upscaling, damage is the key QoI needed as an input by the continuum models. This needs to be informed accurately by the surrogate models for calculating effective moduli at continuum-scale. We show that for the proposed average damage evolution model, the prediction accuracy on the test data is more than 90%. In terms of the computational time, the proposed models are ≈ O ( 10 6 ) times faster compared to high-fidelity fracture simulations by HOSS. These aspects make the proposed surrogate model attractive for upscaling damage from micro-scale models to continuum models. We would like to emphasize that the surrogate models are not a replacement of physical understanding of fracture propagation. The proposed method in this paper is limited to tensile loading conditions at low-strain rates. This loading condition corresponds to a dominant fracture perpendicular to tensile direction. The proposed method is not applicable for in-plane shear, out-of-plane shear, and higher strain rate loading conditions.

2018 ◽  
Vol 183 ◽  
pp. 02037 ◽  
Author(s):  
Taamjeed Rahmaan ◽  
Ping Zhou ◽  
Cliff Butcher ◽  
Michael J. Worswick

Shear tests were performed at strain rates ranging from quasi-static (0.01 s-1) to 500 s-1 for AA7075-T6 sheet metal alloy at room temperature. A miniature sized shear specimen was used in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments. At maximum in-plane shear strains greater than 20%, the AA7075-T6 alloy demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the AA7075-T6 alloy showed mild positive rate sensitivity. The strain to localization (using the Zener-Holloman criterion), measured using the DIC technique, decreased with strain rate in shear loading. The strain at complete failure, however, exhibited an increase at the highest strain rate (500 s-1). The current work also focused on characterization of the thermal conditions occurring during high rate loading in shear with in situ high speed thermal imaging. Experimental results from the highest strain rate (500 s-1) tests showed a notable increase in temperature within the specimen gauge region as a result of the conversion of plastic deformation energy into heat.


2015 ◽  
Vol 10 (1) ◽  
pp. 155892501501000 ◽  
Author(s):  
Vasanthanathan Arunachalam ◽  
P. Nagaraj

In the present work, a generic experimental investigation procedure was developed on mechanical characterization and testing of carbon fabric/epoxy material under uniaxial tensile loading condition. In this study, using IR Thermographic NDT, the defects are identified by measuring changes in temperature online during testing and by taking temperature contour images on the surface of the composite samples. The unidirectional elastic properties such as tensile modulus, in-plane shear modulus, Poisson's ratio, and strength parameter like ultimate tensile strength, shear strength are reported. The estimated mechanical properties of carbon fabric/ epoxy composite were statistically analysed in this work using the Weibull distribution. In addition, emphasis on the microstructural investigation using Scanning Electron Microscope (SEM) is given, in order to study the fracture mechanism of the carbon fabric/epoxy composite under uniaxial tensile loading. The failure surfaces of the tensile tested carbon fabric/epoxy specimens were examined by SEM and the detailed fracture process such as matrix cracking, fiber pull outs and delamination are observed and discussed.


Author(s):  
Kian Sing Tan ◽  
Young W. Kwon

Strain rate affects the behaviors of engineering structural materials, such as metals and composites, in terms of their stiffness and strength. In particular, yield and failure strengths and strains depend on the strain rate applied to the materials. When a structural material is subjected to a typical dynamic loading, the material usually undergoes various strain rate loading conditions. Then, the main question is whether the material is going to fail or not. To the authors’ best knowledge, there has been no failure criterion proposed for a varying strain rate loading condition. This paper presents a failure criterion under non-uniform strain rate conditions. Experiments were also conducted to support the proposed failure criterion using aluminum alloy AA3003-H14. This study also investigated the failure envelopes in terms of strain rates and the normalized failure strengths. Furthermore, evaluations of various stressstrain relations under different strain rate loading conditions were also undertaken.


Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3021
Author(s):  
Nicolas Candau ◽  
Oguzhan Oguz ◽  
Edith Peuvrel-Disdier ◽  
Jean-Luc Bouvard ◽  
María Lluïsa Maspoch ◽  
...  

The effect of the strain rate on damage in carbon black filled Ethylene Propylene Diene Monomer rubber (EPDM)stretched during single and multiple uniaxial loading is investigated. This has been performed by analyzing the stress–strain response, the evolution of damage by Digital Image Correlation (DIC), the associated dissipative heat source by InfraRed thermography (IR), and the chains network damage by swelling. The strain rates were selected to cover the transition from quasi-static to medium strain rate conditions. In single loading conditions, the increase of the strain rate yields in a preferential damage of the filler network while the rubber network is preserved. Such damage is accompanied by a stress softening and an adiabatic heat source rise. Conversely, increasing the strain rate in cyclic loading conditions yields in a filler network accommodation and a high self-heating whose combined effect is proposed as a possible cause of the ability of filled EPDM to limit damage by reducing cavities opening during loading, and favoring cavities closing upon unloading.


2019 ◽  
Vol 6 (6) ◽  
pp. 066548
Author(s):  
Xiaofeng Wang ◽  
Tongya Shi ◽  
Hebin Wang ◽  
Songze Zhou ◽  
Chao Xie ◽  
...  

2006 ◽  
Vol 129 (4) ◽  
pp. 664-669
Author(s):  
J. Pan ◽  
P.-C. Lin

In this paper, governing equations and solutions for asymptotic singular and nonsingular crack-tip sectors in perfectly plastic materials are first summarized under combined in-plane and out-of-plane shear loading conditions. The crack-tip fields under mixed mode II/III loading conditions are then investigated. An assembly of crack-tip sectors is adopted with stress discontinuities along the border of the two constant stress sectors. The solutions of the crack-tip fields under pure mode II, mixed mode II/III, and nearly pure mode III loading conditions are presented. The trends of the angular variations of the mixed mode II/III crack-tip stresses agree with those of the available computational analysis and the asymptotic analysis for low strain hardening materials. The pure mode II crack-tip stresses are similar to those of Hutchinson, and the nearly pure mode III stresses are similar to those of the pure mode III crack-tip field of Rice.


Author(s):  
Danika Hayman ◽  
Christie Bergerson ◽  
Samantha Miller ◽  
Michael Moreno ◽  
James E. Moore

PLLA is a commonly used biodegradable polymer in stent designs because it is non-toxic and easily eliminated from the body. However, very little is known about the effect of loading conditions on the degradation rate. Rajagopal and Wineman developed a model of polymer degradation which is driven by load applied to the fiber [1]. Soares et. al. further developed this model for use with PLLA stent fibers under tensile loading conditions [2]. In this model the degradation rate is linearly related to deformation through the radius in the (IB, IIB) plane. Both models predict that greater deformation will induce a higher degree of degradation.


2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Huiyang Luo ◽  
Chenkai Dai ◽  
Rong Z. Gan ◽  
Hongbing Lu

The mechanical behavior of human tympanic membrane (TM) has been investigated extensively under quasistatic loading conditions in the past. The results, however, are sparse for the mechanical properties (e.g., Young's modulus) of the TM at high strain rates, which are critical input for modeling the mechanical response under blast wave. The property data at high strain rates can also potentially be converted into complex modulus in frequency domain to model acoustic transmission in the human ear. In this study, we developed a new miniature split Hopkinson tension bar to investigate the mechanical behavior of human TM at high strain rates so that a force of up to half of a newton can be measured accurately under dynamic loading conditions. Young’s modulus of a normal human TM is reported as 45.2–58.9 MPa in the radial direction, and 34.1–56.8 MPa in the circumferential direction at strain rates 300–2000 s−1. The results indicate that Young’s modulus has a strong dependence on strain rate at these high strain rates.


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