Publications by authors named "Bingbing An"

16 Publications

  • Page 1 of 1

Role of soft bi-layer coating on the protection of turtle carapace.

J Biomech 2021 Jul 9;126:110618. Epub 2021 Jul 9.

Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200444, China.

The turtle carapace is a biological armor exhibiting enhanced protection performance. Despite considerable efforts to characterize the structure-property relations of the turtle carapace, how the design of soft keratin-collagen bi-layer coating contributes to the protection of this biological armor remains largely unknown. In this study, calculations are carried out for fracture of the turtle carapace subjected to impact loading. The dynamic fracture of the bone layer, plastic deformation of the keratin-collagen bi-layer, and delamination at the keratin-collagen and collagen-bone interfaces are accounted for in the analyses. We reveal that plastic deformation and interfacial delamination within the soft bi-layer coating are two toughening mechanisms controlling the resistance to dynamic crack growth in the bone layer of the turtle carapace. The architecture of the keratin-collagen bi-layer coating enables large plastic deformation in the collagen layer and multiple delaminations within the bi-layer coating, preventing crack propagation in the bone layer. It is found that the dynamic fracture of bone layer in the turtle carapace depends on the stiffness mismatch and yield stress contrast between the keratin layer and the collagen layer. As the stiffness mismatch increases, small plastic deformation of the bi-layer coating occurs and the plastic deformation of collagen layer tends to emerge in the vicinity of the keratin-collagen interface, suppressing interfacial delamination and leading to weak resistance to fracture of the bone layer. The intermediate level of yield stress contrast can activate large plastic deformation and multiple delaminations within the bi-layer coating, mitigating fracture of the bone layer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jbiomech.2021.110618DOI Listing
July 2021

Enamel-inspired materials design achieving balance of high stiffness and large energy dissipation.

J Mech Behav Biomed Mater 2020 03 9;103:103587. Epub 2019 Dec 9.

Shanghai Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200050, China.

Owing to the unique non-self-similar hierarchical microstructure, enamel achieves the balance of high stiffness and toughness, and in turn provides important ideas for the bio-inspired materials design. In this study, a multiscale numerical study has been conducted to investigate whether the property of high stiffness and large energy dissipation could be duplicated in engineering materials through certain material design principles. Motivated by the structure of enamel, the bio-inspired materials consisting of hard and soft phases were considered, and the designing parameters including the cross-sectional shape, volume fraction, and inclination angle of the reinforcement, and other three parameters related to the waviness of the reinforcement were taken into account. It was found that by employing the non-self-similar hierarchical structure, the designed composites exhibited the balance between stiffness and toughness, which has not been achieved in many engineering materials yet. Furthermore, the influences of the aforementioned designing parameters on the mechanical performance of the composites have been elucidated. The findings of this study have provided a guideline for designing bio-inspired composites achieving the balance between stiffness and toughness.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2019.103587DOI Listing
March 2020

A theory of biological composites undergoing plastic deformations.

J Mech Behav Biomed Mater 2019 05 11;93:204-212. Epub 2019 Feb 11.

Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072, People's Republic of China.

Natural biological composites such as bone, dentin, nacre and enamel exhibit anisotropic microstructures, giving rise to orientation-dependent mechanical properties. Although the mechanical properties of these materials have been studied extensively, there is limited progress on modeling the common features associated with the orientation-dependent plastic deformation of biological composites. In this study, we develop a continuum theory for elastic-viscoplastic deformations of anisotropic biological composites. The pressure-sensitive and plastically dilatant plastic flow is incorporated into the theory, and the plastic spin related to the kinematics of the underlying substructure during macroscopic plastic deformation is explicitly taken into account. A special set of constitutive equations are implemented in a finite element program. Furthermore, the material parameters have been calibrated and numerical simulations of elastic-plastic deformation in bone are performed. It is found that the theory can capture the major features of plastic deformation of biological composites. The numerical simulations are in good agreement with experiments, demonstrating that the model is capable of predicting the complex plastic deformation of bone.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2019.02.008DOI Listing
May 2019

An analysis of crack growth in dentin at the microstructural scale.

J Mech Behav Biomed Mater 2018 05 26;81:149-160. Epub 2018 Feb 26.

Department of Mechanics, Shanghai University, Shanghai 200444, People's Republic of China; Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai 200072, People's Republic of China.

Dentin is a biocomposite possessing complex hierarchical structure, which endows this hard tissue with excellent damage tolerance. In this study, crack growth in dentin at the microstructural scale is investigated and the synergistic effects of plastic deformation of intertubular dentin (ITD), elasticity and fracture properties of peritubular dentin (PTD), and fracture properties of PTD/ITD interface on the fracture of dentin are explored. A micromechanical model is developed, which captures the experimentally observed fracture process of dentin, i.e. occurrence of microcracking of PTD ahead of the main crack. It is found through numerical simulations that high relative stiffness and low cohesive strength of PTD increase the propensity of microcracking of PTD, whereas reduce the plastic dissipation and toughness of the microstructure of dentin. The microcracking of PTD can be also promoted by low toughness of PTD. The large friction angle and weak strain hardening of ITD could promote the microcracking of PTD, and simultaneously enhance the toughness of the microstructure of dentin. In addition, it is identified that the cohesive strength of the PTD/ITD interface plays a crucial role in dominating fracture mechanisms; low cohesive strength leads to fracture of interface and suppresses microcracking of PTD, which provides an explanation for the crack deflection along interface observed in experiments. Nevertheless, the toughness of interface has a negligible influence on the fracture of dentin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2018.02.029DOI Listing
May 2018

The effect of microcracking in the peritubular dentin on the fracture of dentin.

J Biomech 2017 Dec 25;65:125-130. Epub 2017 Oct 25.

Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.

Dentin is a biocomposite possessing elegant hierarchical structure, which allows it to resist fracture effectively. Despite the considerable efforts to unravel the peculiar fracture behavior of dentin, the effect of microstructural features on the fracture process is largely unknown. In this study, we explore the interaction between the primary crack with crack tip located in intertubular dentin (ITD) and microcracking of peritubular dentin (PTD) ahead of the primary crack. A micromechanical model accounting for the unique composite structure of dentin is developed, and computational simulations are performed. It is found that the microcracking of PTD located in the crack plane in front of the primary crack tip can promote the propagation of the primary crack, increasing the propensity of coalescence of primary crack and microcracks nucleating in PTD. We show that the two-layer microstructure of dentin enables reduction in driving force of primary crack, potentially enhancing fracture toughness. The high stiffness of PTD plays a critical role in reducing the driving force of primary crack and activating microcracking of PTD. It is further identified that the microcracking of PTD arranged parallel to the crack plane with an offset could contribute to the shielding of primary crack.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jbiomech.2017.10.022DOI Listing
December 2017

Protection mechanisms of the carapace of a box turtle.

J Mech Behav Biomed Mater 2017 07 24;71:54-67. Epub 2017 Feb 24.

Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.

In this study we explore the materials design principles of the carapace of a Terrapene Carolina box turtle, which possesses a sandwich-like structure consisting of a foam-like interior layer (FIL) enclosed by two dense exterior layers (DEL). A constitutive scheme accounting for the large deformation, plastic yielding and post-yield strain hardening caused by densification of the cells in the foam is developed to model the mechanical properties of the FIL, and a large deformation elastic-plastic model for the DEL is proposed. Computational simulations of the carapace subjected to indentation loading are performed and it is found that the layer sequence plays an essential role in the mechanical properties of the carapace. For the sandwich-like layering, the stiff DEL provides penetration resistance and the FIL contributes to the energy dissipation of the entire structure through plastic deformation, which enables reduction in back-deformations, enhanced penetration resistance and low stresses transmitted to the inner layer. For other layer sequential patterns, the contributions of the DEL and FIL are limited, leading to poorer mechanical performance. Based on these results, we propose that the sandwich-like structure of the carapace of the box turtle is designed to maintain sufficient resistance to penetration deformation, a defeating mechanism, and at the same time to significantly amplify energy dissipation, a defending mechanism. This double function could be used in the development of future human body armor.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2017.02.026DOI Listing
July 2017

Role of microstructure on fracture of dentin.

J Mech Behav Biomed Mater 2016 06 16;59:527-537. Epub 2016 Mar 16.

Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.

Dentin possesses unique hierarchical structure, which has a significant influence on the mechanical properties. Understanding the relationship between structure and mechanical properties of dentin is essential for preventing and curing oral diseases, as well as, potentially for developing man-made engineering materials with superior mechanical performance. In this study, the effect of the two-layered structure, where hard peritubular dentin (PTD) containing dentin tubules are embedded in soft intertubular dentin (ITD), on the fracture behavior of dentin is investigated. A numerical model is developed, in which PTD cracking, ITD cracking and the debonding of the interface between PTD and ITD are all taken into account. Numerical simulations reveal that PTD fracture and interface debonding are the major failure mechanisms, which are consistent with experimental observation. It is identified that the cohesive strength and critical separation of interface are the key parameters controlling which of the mechanisms is active. The low cohesive strength of interface and small critical separation of interface can lead to interface debonding, while the large cohesive strength and critical separation give rise to PTD fracture. In addition, it is found that large volume fraction of dentin tubules and small volume fraction of PTD can enhance the toughness of dentin, which provides a new insight into the degraded mechanical properties of old dentin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2016.03.008DOI Listing
June 2016

Bioinspired toughening mechanism: lesson from dentin.

Bioinspir Biomim 2015 Jul 9;10(4):046010. Epub 2015 Jul 9.

Department of Mechanics, Shanghai University, Shanghai 200444, People's Republic of China. Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai, 200072, People's Republic of China.

Inspired by the unique microstructure of dentin, in which the hard peritubular dentin surrounding the dentin tubules is embedded in the soft intertubular dentin, we explore the crack propagation in the bioinspired materials with fracture process zone possessing a dentin-like microstructure, i.e. the composite structure consisting of a soft matrix and hard reinforcements with cylindrical voids. A micromechanical model under small-scale yielding conditions is developed, and numerical simulations are performed, showing that the rising resistant curve (R-curve) is observed for crack propagation caused by the plastic collapse of the intervoid ligaments in the fracture process zone. The dentin-like microstructure in the fracture process zone exhibits enhanced fracture toughness, compared with the case of voids embedded in the homogeneous soft matrix. Further computational simulations show that the dentin-like microstructure can retard void growth, thereby promoting fracture toughness. The typical fracture mechanism of the bioinspired materials with fracture process zone possessing the dentin-like structure is void by void growth, while it is the multiple void interaction in the case of voids in the homogeneous matrix. Based on the results, we propose a bioinspired material design principle, which is that the combination of a hard inner material encompassing voids and a soft outer material in the fracture process zone can give rise to exceptional fracture toughness, achieving damage tolerance. It is expected that the proposed design principle could shed new light on the development of novel man-made engineering materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1748-3190/10/4/046010DOI Listing
July 2015

On the Mechanics of Fatigue and Fracture in Teeth.

Appl Mech Rev 2014 May 30;66(3):0308031-3080319. Epub 2014 Apr 30.

Department of Materials Science and Engineering, University of Washington , Seattle, WA 98195;

Tooth fracture is a major concern in the field of restorative dentistry. However, knowledge of the causes for tooth fracture has developed from contributions that are largely based within the field of mechanics. The present manuscript presents a technical review of advances in understanding the fracture of teeth and the fatigue and fracture behavior of their hard tissues (i.e., dentin and enamel). The importance of evaluating the fracture resistance of these materials, and the role of applied mechanics in developing this knowledge will be reviewed. In addition, the complex microstructures of tooth tissues, their roles in resisting tooth fracture, and the importance of hydration and aging on the fracture resistance of tooth tissues will be discussed. Studies in this area are essential for increasing the success of current treatments in dentistry, as well as in facilitating the development of novel bio-inspired restorative materials for the future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1115/1.4027431DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4240032PMC
May 2014

Damage mechanisms in uniaxial compression of single enamel rods.

J Mech Behav Biomed Mater 2015 Feb 4;42:1-9. Epub 2014 Nov 4.

Department of Mechanics, Shanghai University, Shanghai, 200444, PR China; Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai, 200072, China. Electronic address:

Enamel possesses a complex hierarchical structure, which bestows this tissue with unique mechanical properties. In this study, the mechanical behavior of single enamel rods was investigated under uniaxial compression. Numerical simulations were also performed using micromechanics models for individual enamel rods to identify the damage mechanisms contributing to the constitutive behavior. Experimental results showed that the single rods exhibited an elastic modulus ranging from 10~31 GPa, and that they undergo post-yield strain-hardening. The primary damage mode consisted of delamination within the assembly of mineral crystals. Results from numerical simulations suggest that strain localization within individual rods is responsible for the observed delamination, which is believed to arise from the non-uniform arrangement of mineral crystals. This mechanism was independent of mineral morphology and properties. The non-uniform crystal arrangement results in friction between crystals with different inclination angles and is believed to be responsible for the post-yield strain hardening behavior.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2014.10.014DOI Listing
February 2015

Fracture analysis for biological materials with an expanded cohesive zone model.

J Biomech 2014 Jul 14;47(10):2244-8. Epub 2014 May 14.

Department of Mechanics, Shanghai University, Shanghai 200444, China. Electronic address:

In this study, a theoretical framework for simulation of fracture of bone and bone-like materials is provided. An expanded cohesive zone model with thermodynamically consistent framework has been proposed and used to investigate the crack growth resistance of bone and bone-like materials. The reversible elastic deformation, irreversible plastic deformation caused by large deformation of soft protein matrix, and damage evidenced by the material separation and crack nucleation in the cohesive zone, were all taken into account in the model. Furthermore, the key mechanisms in deformation of biocomposites consisting of mineral platelets and protein interfacial layers were incorporated in the fracture process zone in this model, thereby overcoming the limitations of previous cohesive zone modeling of bone fracture. Finally, applications to fracture of cortical bone and human dentin were presented, which showed good agreement between numerical simulation and reported experiments and substantiated the effectiveness of the model in investigating the fracture behavior of bone-like materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jbiomech.2014.04.054DOI Listing
July 2014

On the mechanical behavior of bio-inspired materials with non-self-similar hierarchy.

J Mech Behav Biomed Mater 2014 Jun 29;34:8-17. Epub 2014 Jan 29.

Department of Mechanics, Shanghai University, 99 Shangda Road, Shanghai 200444, PR China; Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai 200072, PR China. Electronic address:

Biological materials exhibiting non-self-similar hierarchical structures possess desirable mechanical properties. Motivated by their penetration resistance and fracture toughness, the mechanical performance of model materials with non-self-similar hierarchical structures was explored and the distinct advantages were identified. A numerical model was developed, based on microscopic observation of enamel prisms. Computational simulations showed that the systems with non-self-similar hierarchy displayed lateral expansion when subjected to longitudinal tensile loading, which reflected negative Poisson׳s ratio and potential for greater volume strain energies when compared with conventional materials with positive Poisson׳s ratio. Employing the non-self-similar hierarchical design, the capability of resilience can be improved. Additionally, the non-self-similar hierarchical structure exhibited larger toughness, resulting from the large pull-out work of the reinforcements. The findings of this study not only elucidate the deformation mechanisms of biological materials with non-self-similar hierarchical structure, but also provide a new path for bio-inspired materials design.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2013.12.028DOI Listing
June 2014

[The effect of bleaching on fracture resistance in human dentin].

Hua Xi Kou Qiang Yi Xue Za Zhi 2012 Oct;30(5):530-4

Dept. of Stomatology, The Tenth People's Hospital Affiliated to Tongji University, Shanghai 200072, China.

Objective: To study the effect of bleaching on the mechanical properties of human dentin.

Methods: The finite element method (FEM) based the cohesive zone model had been employed to study the fracture resistance of human dentin. There types of dentin were considered, i.e. original dentin, dentin after direct-bleaching and indirect-bleaching.

Results: The bleaching treatments had large impact on the crack growth resistance of human dentin. The initiation toughness (1.48 MPa x square root of m), growth toughness (3.90 MPa x square root of m x mm(-1)) and plateau toughness (3.25 MPa x square root of m) of human dentin were reduced to 1.29 MPa x square root of m, 3.45 MPa x square root of m x mm(-1) and 2.71 MPa x square root of m respectively after indirect-bleaching. The worst case was the direct-bleaching which causes significant reductions in the growth toughness (0.14 MPa x square root of m x mm(-1)) and plateau toughness (1.63 MPa x square root of m) respectively, while the initiation toughness remained the same as that after indirect-bleaching.

Conclusion: The cohesive zone modeling is an effective tool in characterizing the fracture behavior of human dentin. Bleaching treatments reduce the crack growth resistance of human dentin and increase the risk of fracture of teeth.
View Article and Find Full Text PDF

Download full-text PDF

Source
October 2012

Role of crystal arrangement on the mechanical performance of enamel.

Acta Biomater 2012 Oct 26;8(10):3784-93. Epub 2012 Jun 26.

Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072, People's Republic of China.

The superior mechanical properties of enamel, such as excellent penetration and crack resistance, are believed to be related to the unique microscopic structure. In this study, the effects of hydroxyapatite (HAP) crystallite orientation on the mechanical behavior of enamel have been investigated through a series of multiscale numerical simulations. A micromechanical model, which considers the HAP crystal arrangement in enamel prisms, the hierarchical structure of HAP crystals and the inelastic mechanical behavior of protein, has been developed. Numerical simulations revealed that, under compressive loading, plastic deformation progression took place in enamel prisms, which is responsible for the experimentally observed post-yield strain hardening. By comparing the mechanical responses for the uniform and non-uniform arrangement of HAP crystals within enamel prisms, it was found that the stiffness for the two cases was identical, while much greater energy dissipation was observed in the enamel with the non-uniform arrangement. Based on these results, we propose an important mechanism whereby the non-uniform arrangement of crystals in enamel rods enhances energy dissipation while maintaining sufficient stiffness to promote fracture toughness, mitigation of fracture and resistance to penetration deformation. Further simulations indicated that the non-uniform arrangement of the HAP crystals is a key factor responsible for the unique mechanical behavior of enamel, while the change in the nanostructure of nanocomposites could dictate the Young's modulus and yield strength of the biocomposite.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.actbio.2012.06.026DOI Listing
October 2012

The role of property gradients on the mechanical behavior of human enamel.

J Mech Behav Biomed Mater 2012 May 25;9:63-72. Epub 2012 Jan 25.

Shanghai Institute of Applied Mathematics and Mechanics, Shanghai, 200072, PR China.

In this study, the mechanical design principles of human enamel were evaluated using a hybrid experimental and computational approach. Nanoindentation was applied to evaluate the load-depth response of human enamel, and Vickers indentations were used to assess the damage behavior. An elastic-plastic numerical model was then developed to analyze the stress and strain distribution about the indentations, and to characterize energy dissipation about indents in three locations including inner, middle and outer enamel. Results confirm that enamel exhibits a gradient in its mechanical behavior. Outer enamel has a limited potential for energy dissipation by inelastic deformation, indicating that the ability of outer enamel to resist fracture is low. While inner enamel, the region close Dentin Enamel Junction (DEJ), possesses less resistance to penetration deformation, it has a much higher capacity to dissipate energy by inelastic deformation than outer enamel. The computational simulations identified that the gradients in mechanical properties of human enamel promote resistance to penetration, energy dissipation and mitigation of fracture, all critical performance requirements of human teeth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2012.01.009DOI Listing
May 2012

Fracture toughening mechanism of cortical bone: an experimental and numerical approach.

J Mech Behav Biomed Mater 2011 Oct 28;4(7):983-92. Epub 2011 Feb 28.

Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072, China.

In this investigation, the crack propagation mechanisms contributing to the toughness of cortical bone were studied using a combination of experimental and numerical approaches. Compact tension (CT) specimens were prepared from bovine cortical bones to achieve crack propagation in the longitudinal and transverse directions. Stable crack extension experiments were conducted to distinguish the crack growth resistance curves, and virtual multidimensional internal bond (VMIB) modeling was adopted to simulate the fracture responses. Results from experiments indicated that cortical bone exhibited rising resistance curves (R-curves) for crack extension parallel and perpendicular to the bone axis; the transverse fracture toughness was significantly larger, indicating that the fracture properties of cortical bone are substantially anisotropic. Microscopic observations showed that the toughening mechanisms in the longitudinal and transverse directions were different. When the crack grew in the transverse direction, the crack deflected significantly, and crack bifurcations were found at the crack wake, while, in the longitudinal direction, the crack was straight and uncracked ligaments were observed. Numerical simulations also revealed that the fracture resistance in the transverse direction was greater than that in the longitudinal direction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2011.02.012DOI Listing
October 2011
-->