scholarly journals Fragmentation model for tensile behavior of intermingled hybrid composites and optimal mixing ratio

2021 ◽  
Author(s):  
Juan David Vanegas- Jaramillo ◽  
Luis Javier Cruz-Riaño ◽  
Iván David Patiño-Arcila
Keyword(s):  
Mechanical Response ◽  
Hybrid Composites ◽  
Progressive Failure ◽  
Interfacial Strength ◽  
Fragmentation Model ◽  
Mixing Ratio ◽  
Strain Behavior ◽  
Damage Process ◽  
High Elongation ◽  
Fiber Breaks

A numerical fragmentation model is proposed to predict the mechanical response of intermingled, unidirectional hybrid composites under tensile loads. The model is based on a previously developed for unidirectional composites considering the critical number of fiber breaks and the correction of the fiber-matrix interfacial strength. Hybrids comprising two reinforcements are considered, and the energetic contribution of reinforcements is evaluated during the damage process. Additionally, the pseudo-ductile strain, yield strength, and the level of degradation of each reinforcement are estimated. The present model is compared with a progressive failure model and micromechanical finite element simulations, obtaining some similarities in the stress-strain behavior.  Results show that both low elongation and high elongation fiber sub-composite experience a linear tensile response where fibers remain intact (IF), and fragmentation (FM) where breaking appears. The sliding/separation phenomenon (SS) occurs in one of the sub-composites when crack saturation is obtained, and failure occurs when the other one undergoes the crack saturation. Results also show that the IF, FM, and SS phenomena are conditioned by the fiber mixing ratio, α. The model allows estimating the optimal value of α for which the highest pseudo-ductile strain and hybrid effect are reached.

Mechanical Response of Different Lattice Structures Fabricated Using the CLIP Technology

2016 ◽  
Author(s):  
Anil Saigal ◽  
John R. Tumbleston ◽  
Hendric Vogel
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Response ◽  
Elastic Response ◽  
Lattice Structures ◽  
Rhombic Dodecahedron ◽  
Structured Materials ◽  
Specific Strength ◽  
Strain Behavior ◽  
End Use ◽  
Continuous Liquid Interface Production

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral, octet, vertex centroid, dode, diamond, rhombi octahedron, rhombic dodecahedron and solid lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, plastic strain hardening to a peak in strength, followed by a drop in flow stress to a plateau region and finally rapid hardening associated with contact of the deformed struts with each other as part of densification. It was found that the elastic modulus and strength of the various lattice structured materials are proportional to each other. In addition, it was found that the octahedral, octet and diamond lattice structures are amongst the most efficient based on the measured specific stiffness and specific strength.

Continuum Description of the Time- and Strain-Dependent Poisson’s Ratio of Ligament Under Finite Deformation

2013 ◽  
Author(s):  
Aaron M. Swedberg ◽  
Shawn P. Reese ◽  
Steve A. Maas ◽  
Benjamin J. Ellis ◽  
Jeffrey A. Weiss
Keyword(s):  
Large Scale ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Large Strain ◽  
Fiber Direction ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Poisson's Ratios ◽  
Poisson’S Ratios ◽  
Strain Dependent

Ligament volumetric behavior controls fluid and thus nutrient movement as well as the mechanical response of the tissue to applied loads. The reported Poisson’s ratios for tendon and ligament subjected to tensile deformation loading along the fiber direction are large, ranging from 0.8 ± 0.3 in rat tail tendon fascicles [1] to 2.98 ± 2.59 in bovine flexor tendon [2]. These Poisson’s ratios are indicative of volume loss and thus fluid exudation [3,4]. We have developed micromechanical finite element models that can reproduce both the characteristic nonlinear stress-strain behavior and large, strain-dependent Poisson’s ratios seen in tendons and ligaments [5], but these models are computationally expensive and unfeasible for large scale, whole joint models. The objectives of this research were to develop an anisotropic, continuum based constitutive model for ligaments and tendons that can describe strain-dependent Poisson’s ratios much larger than the isotropic limit of 0.5. Further, we sought to demonstrate the ability of the model to describe experimental data, and to show that the model can be combined with biphasic theory to describe the rate- and time-dependent behavior of ligament and tendon.

scholarly journals Rock Failure Analysis Based on a Coupled Elastoplastic-Logarithmic Damage Model

2017 ◽  
Vol 62 (4) ◽  
pp. 753-774
Author(s):  
M. Abdia ◽  
H. Molladavoodi ◽  
H. Salarirad
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Mechanical Response ◽  
Damage Model ◽  
Yield Function ◽  
Irreversible Thermodynamics ◽  
Stiffness Degradation ◽  
Shear Stresses ◽  
Rock Materials ◽  
Damage Process

Abstract The rock materials surrounding the underground excavations typically demonstrate nonlinear mechanical response and irreversible behavior in particular under high in-situ stress states. The dominant causes of irreversible behavior are plastic flow and damage process. The plastic flow is controlled by the presence of local shear stresses which cause the frictional sliding. During this process, the net number of bonds remains unchanged practically. The overall macroscopic consequence of plastic flow is that the elastic properties (e.g. the stiffness of the material) are insensitive to this type of irreversible change. The main cause of irreversible changes in quasi-brittle materials such as rock is the damage process occurring within the material. From a microscopic viewpoint, damage initiates with the nucleation and growth of microcracks. When the microcracks length reaches a critical value, the coalescence of them occurs and finally, the localized meso-cracks appear. The macroscopic and phenomenological consequence of damage process is stiffness degradation, dilatation and softening response. In this paper, a coupled elastoplastic-logarithmic damage model was used to simulate the irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution & plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening on post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Prager yield function was used to model plastic strains. Then, an algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model has been programmed in VC++ environment. Then, it was used as a separate and new constitutive model in DEM code (UDEC). Finally, the experimental Oolitic limestone rock behavior was simulated based on the developed model. The irreversible strains, softening and stiffness degradation were reproduced in the numerical results. Furthermore, the confinement pressure dependency of rock behavior was simulated in according to experimental observations.

Numerical Analysis of Faults on Deep-Buried Tunnel Surrounding Rock Damaged Zones

2011 ◽  
Vol 90-93 ◽  
pp. 74-78 ◽  
Author(s):  
Jun Hu ◽  
Ling Xu ◽  
Nu Wen Xu
Keyword(s):  
Numerical Analysis ◽  
Mechanical Response ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Factors Affecting ◽  
Rock Failure Process ◽  
Tunnel Instability

Fault is one of the most important factors affecting tunnel instability. As a significant and casual construction of Jinping II hydropower station, when the drain tunnel is excavated at depth of 1600 m, rockbursts and water inrush induced by several huge faults and zone of fracture have restricted the development of the whole construction. In this paper, a progressive failure progress numerical analysis code-RFPA (abbreviated from Rock Failure Process Analysis) is applied to investigate the influence of faults on tunnel instability and damaged zones. Numerical simulation is performed to analyze the stress distribution and wreck regions of the tunnel, and the results are consistent with the phenomena obtained from field observation. Moreover, the effects of fault characteristics and positions on the construction mechanical response are studied in details. Some distribution rules of surrounding rock stress of deep-buried tunnel are summarized to provide the reasonable references to TBM excavation and post-support of the drain tunnel, as well as the design and construction of similar engineering in future.

scholarly journals Subloading Surface Model and Experimental Study of Coal Failure under Cyclic Loading

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Si-fei Liu ◽  
Zhi-jun Wan ◽  
Jing-chao Wang ◽  
Shuai-feng Lu ◽  
Tong-huan Li
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Surface Model ◽  
Deformation Characteristics ◽  
Response Characteristics ◽  
Rock Structure ◽  
Specific Strain ◽  
Damage Process ◽  
The Stability ◽  
Number Of Cycles

The fatigue damage of rock is an important factor affecting the stability of rock structure. In this paper, the mechanical response of coal under cyclic loading was studied. In order to accurately describe the deformation characteristics of coal under cyclic loading, an elastic-plastic model of coal based on the theory of subloading surface was established and verified by experiments. The model can well reflect the Mancin effect and ratcheting effect of coal samples, which is basically consistent with the actual deformation characteristics of coal, and the theoretical value and experimental value are in good agreement. At the same time, the cyclic response characteristics of specimens under strain load disturbance were analyzed. The results show that the specific strain disturbance can only cause a certain damage to coal and the area of hysteresis loop decreases first, then stabilizes, and then increases as the number of cycles increases. In addition, the damage factor Dn in the model was analyzed in this paper. Dn, which can accurately describe the damage process of coal, accurately locate the time point of disturbance load change, and has greater sensitivity to coal failure, is helpful to improve the accuracy of the stability judgment of coal structure and ensure the safety of engineering. The above results are of great significance for strengthening the understanding of coal mass instability process and mode under cyclic loading.

scholarly journals Compressive Mechanical Properties of Porcine Brain: Experimentation and Modeling of the Tissue Hydration Effects

2019 ◽  
Vol 6 (2) ◽  
pp. 40 ◽  
Author(s):  
Raj K. Prabhu ◽  
Mark T. Begonia ◽  
Wilburn R. Whittington ◽  
Michael A. Murphy ◽  
Yuxiong Mao ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Water Content ◽  
Mechanical Response ◽  
High Strain ◽  
Peak Stress ◽  
Human Head ◽  
Element Analysis ◽  
Porcine Brain ◽  
Strain Behavior

Designing protective systems for the human head—and, hence, the brain—requires understanding the brain’s microstructural response to mechanical insults. We present the behavior of wet and dry porcine brain undergoing quasi-static and high strain rate mechanical deformations to unravel the effect of hydration on the brain’s biomechanics. Here, native ‘wet’ brain samples contained ~80% (mass/mass) water content and ‘dry’ brain samples contained ~0% (mass/mass) water content. First, the wet brain incurred a large initial peak stress that was not exhibited by the dry brain. Second, stress levels for the dry brain were greater than the wet brain. Third, the dry brain stress–strain behavior was characteristic of ductile materials with a yield point and work hardening; however, the wet brain showed a typical concave inflection that is often manifested by polymers. Finally, finite element analysis (FEA) of the brain’s high strain rate response for samples with various proportions of water and dry brain showed that water played a major role in the initial hardening trend. Therefore, hydration level plays a key role in brain tissue micromechanics, and the incorporation of this hydration effect on the brain’s mechanical response in simulated injury scenarios or virtual human-centric protective headgear design is essential.

On the Biaxial Mechanical Response of Porcine Tricuspid Valve Leaflets

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Keyvan Amini Khoiy ◽  
Rouzbeh Amini
Keyword(s):  
Tricuspid Valve ◽  
Computational Models ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Biaxial Stress ◽  
Strain Behavior ◽  
Highly Nonlinear ◽  
Rapid Transition ◽  
Biaxial Tensile Testing ◽  
The Right

Located on the right side of the heart, the tricuspid valve (TV) prevents blood backflow from the right ventricle to the right atrium. Similar to other cardiac valves, quantification of TV biaxial mechanical properties is essential in developing accurate computational models. In the current study, for the first time, the biaxial stress–strain behavior of porcine TV was measured ex vivo under different loading protocols using biaxial tensile testing equipment. The results showed a highly nonlinear response including a compliant region followed by a rapid transition to a stiff region for all of the TV leaflets both in the circumferential and in the radial directions. Based on the data analysis, all three leaflets were found to be anisotropic, and they were stiffer in the circumferential direction in comparison to the radial direction. It was also concluded that the posterior leaflet was the most anisotropic leaflet.

Evaluation of Mechanical Properties and Comprehensive Modeling of CMC with Stiff and Weak Matrices

2006 ◽  
Vol 45 ◽  
pp. 1435-1443 ◽  
Author(s):  
Dietmar Koch ◽  
Kamen Tushtev ◽  
Jürgen Horvath ◽  
Ralf Knoche ◽  
Georg Grathwohl
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Ceramic Matrix Composites ◽  
High Strength ◽  
Shear Mode ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Strain Behavior ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

The mechanical properties of ceramic matrix composites (CMC) depend on the individual properties of fibers and matrix, the fiber-matrix interface, the microstructure and the orientation of the fibers. The fiber-matrix interface of ceramics with stiff matrices (e.g. CVI-derived SiC/SiC) must be weak enough to allow crack deflection and debonding in order to achieve excellent strength and strain to failure (weak interface composites WIC). This micromechanical behavior has been intensively investigated during the last 20 years. With the development of CMC with weak matrices (weak matrix composites WMC) as e.g. oxide/oxide composites or polymer derived CMC the mechanical response can not be explained anymore by these models as other microstructural mechanisms occur. If the fibers are oriented in loading direction in a tensile test the WMC behave almost linear elastic up to failure and show a high strength. Under shear mode or if the fibers are oriented off axis a significant quasiplastic stress-strain behavior occurs with high strain to failure and low strength. This complex mechanical behavior of WMC will be explained using a finite element (FE) approach. The micromechanical as well as the FE models will be validated and attributed to the different manufacturing routes.

Force-Deflection Characteristics of SMA-Based Belleville Springs

2012 ◽  
Author(s):  
Franco Furgiuele ◽  
Carmine Maletta ◽  
Emanuele Sgambitterra
Keyword(s):  
Numerical Simulations ◽  
Mechanical Response ◽  
Nickel Titanium ◽  
Thermally Induced ◽  
Niti Alloys ◽  
Strain Behavior ◽  
Finite Element Software ◽  
Transition Mechanism ◽  
Functional Features ◽  
Software Code

The thermo-mechanical properties of Nickel-Titanium based Belleville washers have been analyzed by numerical simulations. In fact, these components exhibit unique mechanical and functional features due to the reversible stress-induced and/or thermally-induced phase transition mechanism of NiTi alloys. The numerical simulations have been carried out by using a commercial finite element software code and a special constitutive model for SMAs. The effects of the geometrical configuration of the washers as well as of the operating temperature, under fully austenitic conditions, have been analyzed. The results highlighted a marked hysteretic response, in terms of force-deflection curve, due to the hysteresis in the stress-strain behavior of NiTi alloys. In addition, a marked influence of the geometry, as well as of the temperature, has been observed on the thermo-mechanical response of the washer, i.e. in terms of both mechanical and functional properties.

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