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Weinong Chen
Purdue University

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Reference work
Published: 07 May 2021 in Handbook of Damage Mechanics
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High-speed X-ray phase contrast imaging enables in situ visualization of damage in optically opaque materials under high-rate loading conditions. This technique fits well in studying the impact damage mechanisms in geomaterials at the particle or meso-scale with observation window size in the order of millimeters. This chapter presents a series of experiments visualizing the impact damage process of various geomaterial particles. These experiments were performed with a synchronized system consisting of high-speed camera, full-field X-ray phase contrast imaging, and Kolsky compression bars. In these experiments, both single- and multiparticle configurations were examined. The X-ray phase contract images clearly demonstrated the evolution of damage within the particles, which were discussed for each configuration, revealing fundamental failure mechanisms in a particulate system under impact.

ACS Style

Junyu Wang; Niranjan Parab; Wayne Chen. High-Speed Real-Time X-Ray Visualization of Impact Damage Inside Geomaterials. Handbook of Damage Mechanics 2021, 1 -30.

AMA Style

Junyu Wang, Niranjan Parab, Wayne Chen. High-Speed Real-Time X-Ray Visualization of Impact Damage Inside Geomaterials. Handbook of Damage Mechanics. 2021; ():1-30.

Chicago/Turabian Style

Junyu Wang; Niranjan Parab; Wayne Chen. 2021. "High-Speed Real-Time X-Ray Visualization of Impact Damage Inside Geomaterials." Handbook of Damage Mechanics , no. : 1-30.

Research paper
Published: 04 May 2021 in Journal of Dynamic Behavior of Materials
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Perforation of aluminum alloy target plates by armor-piercing rounds have been shown to follow the cavity expansion scaling law, while fragment-simulating projectiles follow a shear-plugging scaling law. In both models, experimental compressive stress–strain data is needed to derive their respective material strength parameters, which are not always available. By comparison, modified Ludwik plasticity parameters are more widely available in existing literature for the aluminum alloys of interest in armor applications. We show that the maximum compressive strengths may be approximated using a fixed true strain value across 33 aluminum alloys. A simple linear relation is further established between the maximum compressive strength and the cavity expansion strength.

ACS Style

Zherui Guo; Weinong Chen. First-Order Approximations of Dynamic Material Strengths for the Ballistic Perforation of Aluminum Target Plates. Journal of Dynamic Behavior of Materials 2021, 1 -9.

AMA Style

Zherui Guo, Weinong Chen. First-Order Approximations of Dynamic Material Strengths for the Ballistic Perforation of Aluminum Target Plates. Journal of Dynamic Behavior of Materials. 2021; ():1-9.

Chicago/Turabian Style

Zherui Guo; Weinong Chen. 2021. "First-Order Approximations of Dynamic Material Strengths for the Ballistic Perforation of Aluminum Target Plates." Journal of Dynamic Behavior of Materials , no. : 1-9.

Journal article
Published: 28 April 2021 in Composites Science and Technology
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We integrated the high-speed synchrotron X-ray phase-contrast imaging (PCI) with a modified Kolsky compression bar loading platform to visualize the dynamic failure processes of cross-ply glass fiber reinforced composites (GFRCs). Four S-2 glass/SC-15 composite specimens were prepared, having similar thicknesses but different stacking sequences, namely as [012/9012], [9012/012], [08/908/08], and [908/08/908]. Three-dimensional synchrotron X-ray computed tomography and scanning electron microscopy (SEM) were employed to examine the microstructures and quantify the fiber volume fractions. Each specimen was notched and subjected to a dynamic three-point flexural loading. The onset of cracking close to the notch tip, crack propagation in 0° or 90° plies and their interface, crack opening, and ultimately failure of the specimen were captured by high-speed synchrotron X-ray PCI. Additional dynamic experiments were performed to determine the average time when the stress wave propagated through the specimen and correlate the X-ray images with the specimen's force-deflection response. Finally, the surface morphology of each specimen after the dynamic loading was imaged by SEM. Comparison between real-time X-ray images and post-fracture SEM images demonstrated the capability of the X-ray method to record damage evolution inside composites. Furthermore, the high spatial and temporal resolutions of the X-ray setup and edge enhancement by PCI enabled the identification of microscale damage features within 1 μs. Two damaging processes were identified, crack growth was quantified, and fracture toughness of the composites was evaluated. The method is deemed useful to reveal microscale damage mechanisms and track cracking behaviors inside cross-ply GFRCs under dynamic loading in real time.

ACS Style

Jinling Gao; Nesredin Kedir; Cody D. Kirk; Julio A. Hernandez; Junyu Wang; Shane Paulson; Xuedong Zhai; Todd Horn; Garam Kim; Kamel Fezzaa; Francesco De Carlo; Pavel D. Shevchenko; Tyler N. Tallman; Ronald Sterkenburg; Weinong Chen. High-speed synchrotron X-ray phase-contrast imaging for evaluating microscale damage mechanisms and tracking cracking behaviors inside cross-ply GFRCs. Composites Science and Technology 2021, 210, 108814 .

AMA Style

Jinling Gao, Nesredin Kedir, Cody D. Kirk, Julio A. Hernandez, Junyu Wang, Shane Paulson, Xuedong Zhai, Todd Horn, Garam Kim, Kamel Fezzaa, Francesco De Carlo, Pavel D. Shevchenko, Tyler N. Tallman, Ronald Sterkenburg, Weinong Chen. High-speed synchrotron X-ray phase-contrast imaging for evaluating microscale damage mechanisms and tracking cracking behaviors inside cross-ply GFRCs. Composites Science and Technology. 2021; 210 ():108814.

Chicago/Turabian Style

Jinling Gao; Nesredin Kedir; Cody D. Kirk; Julio A. Hernandez; Junyu Wang; Shane Paulson; Xuedong Zhai; Todd Horn; Garam Kim; Kamel Fezzaa; Francesco De Carlo; Pavel D. Shevchenko; Tyler N. Tallman; Ronald Sterkenburg; Weinong Chen. 2021. "High-speed synchrotron X-ray phase-contrast imaging for evaluating microscale damage mechanisms and tracking cracking behaviors inside cross-ply GFRCs." Composites Science and Technology 210, no. : 108814.

Journal article
Published: 18 April 2021 in Composites Part A: Applied Science and Manufacturing
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This study aims to isolate interactions between plies and tows and reveal fundamental physics involved in transverse impact on fiber-reinforced composite (FRC) structures. Composite strips were sectioned from large panels and characterized by optical photography, three-dimensional synchrotron X-ray computed tomography, and scanning electron microscopy (SEM). Each strip was impacted perpendicularly by a right circular cylinder (RCC) projectile at a velocity ranging from ~ 150 to 600 m/s. The global strip behavior, as well as localized deformation and failure of the strip near the projectile corner, were both captured by high-speed optical imaging. S-Glass FRC strips were observed to fail in tension ahead of the RCC projectiles’ flat surfaces while Kevlar® FRC strips fractured at the projectile corners. The concept of critical velocity region previously used for impact on yarns was introduced to define different failure modes of each composite strip type. The strip damage extent was found to increase with the impact velocity and reach the maximum at the upper limit of the critical velocity region. Above the critical velocity region, the damage extent decreased with impact velocity. Wave propagations and load histories in the composite strips during impact were quantified and compared with Smith’s theory. Finally, critical velocities of single fibers, yarns, and composite strips and ballistic limits of single-ply and multi-ply composite panels were compared to provide insight into the design of impact-resistant fabrics and composites.

ACS Style

Jinling Gao; Zherui Guo.; Julio Andres Hernandez; Fengfeng Zhou; Yizhou Nie; Jian Gao; Boon Him Lim; Nesredin Kedir; Xuedong Zhai; Junyu Wang; Jung-Ting Tsai; Francesco De Carlo; Pavel D. Shevchenko; Tyler N. Tallman; Martin Byung-Guk Jun; Giuseppe R. Palmese; Weinong Chen. Transverse impact by RCCs on S-glass and Kevlar® FRC strips. Composites Part A: Applied Science and Manufacturing 2021, 146, 106425 .

AMA Style

Jinling Gao, Zherui Guo., Julio Andres Hernandez, Fengfeng Zhou, Yizhou Nie, Jian Gao, Boon Him Lim, Nesredin Kedir, Xuedong Zhai, Junyu Wang, Jung-Ting Tsai, Francesco De Carlo, Pavel D. Shevchenko, Tyler N. Tallman, Martin Byung-Guk Jun, Giuseppe R. Palmese, Weinong Chen. Transverse impact by RCCs on S-glass and Kevlar® FRC strips. Composites Part A: Applied Science and Manufacturing. 2021; 146 ():106425.

Chicago/Turabian Style

Jinling Gao; Zherui Guo.; Julio Andres Hernandez; Fengfeng Zhou; Yizhou Nie; Jian Gao; Boon Him Lim; Nesredin Kedir; Xuedong Zhai; Junyu Wang; Jung-Ting Tsai; Francesco De Carlo; Pavel D. Shevchenko; Tyler N. Tallman; Martin Byung-Guk Jun; Giuseppe R. Palmese; Weinong Chen. 2021. "Transverse impact by RCCs on S-glass and Kevlar® FRC strips." Composites Part A: Applied Science and Manufacturing 146, no. : 106425.

Journal article
Published: 11 March 2021 in Journal of Electrochemical Energy Conversion and Storage
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The safety of electrochemical energy storage system depends on the structural integrity of the call containment. Nominal values of cell case dimensions and material properties are the standard inputs for the mechanical analysis of prismatic lithium-ion batteries. However, such data usually do not account for any considerations on the influence of the manufacturing processes of the cell case. This study investigates the effects of the cell wall thickness and elastic modulus, resulting from deep-drawing process, on the cell and cell assembly response. It is found that the deep-drawing process degrades Young’s modulus relative to standard values and leads to a spatial variation in the wall thickness of the cell case. The use of actual cell case material properties and cell wall thickness values is required to obtain validated finite element models of the battery cell case. Using experiments on internal pressure loaded single battery cells and finite element computations, it is demonstrated that the use of nominal cell casing characteristics significantly underestimates the resistance provided by the cell case to counter swelling of the active battery components.

ACS Style

T. D. Nguyen; Jie Deng; Brian Robert; Weinong Chen; Thomas Siegmund. Deformation Behavior of Single Prismatic Battery Cell Cases and Cell Assemblies Loaded by Internal Pressure. Journal of Electrochemical Energy Conversion and Storage 2021, 18, 1 -16.

AMA Style

T. D. Nguyen, Jie Deng, Brian Robert, Weinong Chen, Thomas Siegmund. Deformation Behavior of Single Prismatic Battery Cell Cases and Cell Assemblies Loaded by Internal Pressure. Journal of Electrochemical Energy Conversion and Storage. 2021; 18 (4):1-16.

Chicago/Turabian Style

T. D. Nguyen; Jie Deng; Brian Robert; Weinong Chen; Thomas Siegmund. 2021. "Deformation Behavior of Single Prismatic Battery Cell Cases and Cell Assemblies Loaded by Internal Pressure." Journal of Electrochemical Energy Conversion and Storage 18, no. 4: 1-16.

Journal article
Published: 16 December 2020 in Composites Part B: Engineering
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We report the application of high-speed synchrotron X-ray phase contrast imaging (PCI) in real-time damage characterization for glass fiber reinforced composites (GFRCs) subjected to dynamic loading. Dynamic single-edge notched bending (DSENB) experiments on pre-notched S-2 GFRCs were performed on a modified Kolsky compression bar. During loading, the synchrotron X-ray beam penetrated through the composite specimen from the side to detect damage evolution inside the material. Entire dynamic events were recorded by a high-speed camera as image sequences.0° and 90° unidirectional and cross-ply composites were investigated. An optical imaging technique was also employed to capture similar dynamic events in comparison with the radiographic imaging. It is demonstrated that high-speed X-ray PCI had sufficient phase contrast to characterize a crack initiation at a 20-μm spatial resolution within 920 ns and track the crack geometry during propagation, thereby providing reliable data to quantify the dynamic damage resistance of GFRCs. Furthermore, being capable of recognizing microscopic damage-related features at a sub-10-μm resolution, high-speed X-ray PCI provided fundamental material failure mechanisms to reveal the essential of macroscale structural failure of composites. It can also track the damage evolution inside and between individual plies of laminated composites. However, current high-speed X-ray PCI technique only supports in-situ observation and the high timing and spatial resolutions are limited within a field of view of ~2.5 mm in square, preventing its application in the three-dimensional and larger-area damage detection for GFRC structures.

ACS Style

Jinling Gao; Nesredin Kedir; Cody D. Kirk; Julio Hernandez; Junyu Wang; Shane Paulson; Xuedong Zhai; Todd Horn; Garam Kim; Jian Gao; Kamel Fezzaa; Francesco De Carlo; Pavel Shevchenko; Tyler N. Tallman; Ronald Sterkenburg; Giuseppe R. Palmese; Weinong Chen. Real-time damage characterization for GFRCs using high-speed synchrotron X-ray phase contrast imaging. Composites Part B: Engineering 2020, 207, 108565 .

AMA Style

Jinling Gao, Nesredin Kedir, Cody D. Kirk, Julio Hernandez, Junyu Wang, Shane Paulson, Xuedong Zhai, Todd Horn, Garam Kim, Jian Gao, Kamel Fezzaa, Francesco De Carlo, Pavel Shevchenko, Tyler N. Tallman, Ronald Sterkenburg, Giuseppe R. Palmese, Weinong Chen. Real-time damage characterization for GFRCs using high-speed synchrotron X-ray phase contrast imaging. Composites Part B: Engineering. 2020; 207 ():108565.

Chicago/Turabian Style

Jinling Gao; Nesredin Kedir; Cody D. Kirk; Julio Hernandez; Junyu Wang; Shane Paulson; Xuedong Zhai; Todd Horn; Garam Kim; Jian Gao; Kamel Fezzaa; Francesco De Carlo; Pavel Shevchenko; Tyler N. Tallman; Ronald Sterkenburg; Giuseppe R. Palmese; Weinong Chen. 2020. "Real-time damage characterization for GFRCs using high-speed synchrotron X-ray phase contrast imaging." Composites Part B: Engineering 207, no. : 108565.

Journal article
Published: 08 December 2020 in Composites Science and Technology
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We propose a method to measure multiple dynamic material constitutive parameters of unidirectional fiber reinforced composites (FRCs) in a single experiment. Dynamic short-beam shear (DSBS) experiments were performed on a modified Kolsky compression bar, with integration of high-speed imaging and digital image correlation (DIC). The unidirectional FRCs investigated were S-2 glass fiber reinforced matrix of TGDDM-Jeffamine® D230 with monoamine functionalized partially reacted substructures (mPRS) and commercially available SC-15. Analytical solutions of normal and shear strains of a composite beam were derived based on Timoshenko beam theory, assuming material to be transversely isotropic and have different moduli in tension and compression in each principle material orientation. Tensile and compressive moduli were inversely computed through monitoring normal strain slope when specimen was constantly loaded at a speed of ~7.3 m/s within a small deflection. Non-linear shear stress-strain behavior of the composite was described via Ramberg–Osgood equation. Finite element (FE) analysis was conducted in ABAQUS, simultaneously defining via user subroutine UMAT the transverse isotropy of material, bi-modulus constitutive model, and non-linear shear stress-strain relation. The method proposed in this work was validated by comparing strain distributions computed by FE model and DIC measurements. Comparing with traditional dynamic tensile, compressive, and shear experiments on FRCs, this method significantly simplifies the specimen preparation and design of complicated gripping fixtures for multiple experiments. Furthermore, systematic errors resulting from variations of specimen geometry and dimension, loading direction, and instrumentation are reduced, thereby providing compatible data for numerical studies on impact behavior of composites.

ACS Style

Jinling Gao; Cody D. Kirk; Nesredin Kedir; Shane Paulson; Julio Hernandez; Jian Gao; Xuedong Zhai; Junyu Wang; Todd Horn; Garam Kim; Francesco De Carlo; Pavel Shevchenko; Tyler N. Tallman; Giuseppe R. Palmese; Ronald Sterkenburg; Weinong Chen. A method for characterization of multiple dynamic constitutive parameters of FRCs. Composites Science and Technology 2020, 203, 108607 .

AMA Style

Jinling Gao, Cody D. Kirk, Nesredin Kedir, Shane Paulson, Julio Hernandez, Jian Gao, Xuedong Zhai, Junyu Wang, Todd Horn, Garam Kim, Francesco De Carlo, Pavel Shevchenko, Tyler N. Tallman, Giuseppe R. Palmese, Ronald Sterkenburg, Weinong Chen. A method for characterization of multiple dynamic constitutive parameters of FRCs. Composites Science and Technology. 2020; 203 ():108607.

Chicago/Turabian Style

Jinling Gao; Cody D. Kirk; Nesredin Kedir; Shane Paulson; Julio Hernandez; Jian Gao; Xuedong Zhai; Junyu Wang; Todd Horn; Garam Kim; Francesco De Carlo; Pavel Shevchenko; Tyler N. Tallman; Giuseppe R. Palmese; Ronald Sterkenburg; Weinong Chen. 2020. "A method for characterization of multiple dynamic constitutive parameters of FRCs." Composites Science and Technology 203, no. : 108607.

Journal article
Published: 08 July 2020 in International Journal of Impact Engineering
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We visualized, in real time, the deformation and failure of single fibers that were transversely cut at high loading rate. A reverse impact experimental technique was employed to introduce the dynamic cutting load onto the fiber. The failure process of the fiber was captured via an ultra-high-speed camera combined with an ultra-long working distance objective lens. Three failure modes were identified: partial penetration followed by tensile failure, complete incision and bending-induced brittle failure without penetration, corresponding to the KevlarⓇ KM2 Plus, DyneemaⓇ SK76 and S-2 Glass fiber, respectively. Such failure modes were found to be rate-independent but highly rely on the fiber nanostructure. It was found that all fibers had an increased energy absorption as the rate increased. Effects of fiber length and cut angle were also studied, potentially providing insight into the material design of cut-resistant textiles or composites.

ACS Style

Jinling Gao; Boon Him Lim; Xuedong Zhai; Yizhou Nie; Nesredin Kedir; Weinong Chen. Failure behaviors of single high-performance fibers under transverse dynamic cut. International Journal of Impact Engineering 2020, 144, 103660 .

AMA Style

Jinling Gao, Boon Him Lim, Xuedong Zhai, Yizhou Nie, Nesredin Kedir, Weinong Chen. Failure behaviors of single high-performance fibers under transverse dynamic cut. International Journal of Impact Engineering. 2020; 144 ():103660.

Chicago/Turabian Style

Jinling Gao; Boon Him Lim; Xuedong Zhai; Yizhou Nie; Nesredin Kedir; Weinong Chen. 2020. "Failure behaviors of single high-performance fibers under transverse dynamic cut." International Journal of Impact Engineering 144, no. : 103660.

Journal article
Published: 23 May 2020 in Journal of the Mechanics and Physics of Solids
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In this study, the dynamic cracking processes in porcine cortical bone were visualized in real-time using the high-speed synchrotron X-ray phase-contrast imaging (PCI) technique in three osteon orientations: in-plane transverse, out-of-plane transverse and in-plane longitudinal. The dynamic flexural loading applied on the pre-notched bone specimens was introduced by a modified Kolsky compression bar. High-speed X-ray images of the entire loading events were documented with a high-speed camera. Three-dimensional X-ray micro-computed tomography was conducted to examine the intact microstructures and obtain the basic material properties of the bone material used for mechanical characterizations. The onset location, where crack initiated, and the subsequent direction, along which the incipient crack propagated, were measured quantitatively using the high-speed X-ray images and the latter was found dependent on the osteon direction significantly. The crack propagation velocities were dependent on crack extension over the entire crack path significantly for all the three directions while the initial velocity for in-plane longitudinal direction was lower than the other two directions. Straight-through crack paths were observed for in-plane longitudinal specimens while the cracks were deflected and twisted in the in-plane transverse direction. For out-of-plane transverse direction, the cracks follow paths with tortuosity fall in between the other two directions, showing a mixed mode of fractures of the former two extreme cases. The toughening mechanisms, visualized by the high-speed X-ray images, and the corresponding fracture toughness, evaluated in terms of fracture initiation toughness and crack growth resistance curve (R-curve), were also found significantly different among the three osteon directions, suggesting an overall transition from brittle to ductile-like fracture behaviors at the dynamic displacement rate (5.4 m/s) as the osteon orientation varies from in-plane longitudinal to out-of-plane transverse, and to in-plane transverse eventually.

ACS Style

Xuedong Zhai; Yizhou Nie; Jinling Gao; Nesredin Kedir; Ben Claus; Tao Sun; Kamel Fezzaa; Weinong W. Chen. The effect of loading direction on the fracture behaviors of cortical bone at a dynamic loading rate. Journal of the Mechanics and Physics of Solids 2020, 142, 104015 .

AMA Style

Xuedong Zhai, Yizhou Nie, Jinling Gao, Nesredin Kedir, Ben Claus, Tao Sun, Kamel Fezzaa, Weinong W. Chen. The effect of loading direction on the fracture behaviors of cortical bone at a dynamic loading rate. Journal of the Mechanics and Physics of Solids. 2020; 142 ():104015.

Chicago/Turabian Style

Xuedong Zhai; Yizhou Nie; Jinling Gao; Nesredin Kedir; Ben Claus; Tao Sun; Kamel Fezzaa; Weinong W. Chen. 2020. "The effect of loading direction on the fracture behaviors of cortical bone at a dynamic loading rate." Journal of the Mechanics and Physics of Solids 142, no. : 104015.

Journal article
Published: 20 February 2020 in Composite Structures
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The effects of stacking order on the ballistic performance may be detrimental if the order is improperly chosen. When the frontal material is constrained transversely by the rear material, it results in sub-optimal performance compared to the alternate configuration where both layers can freely deform. In this study, we examine the possibility of using the Cunniff velocity as a merit parameter in determining the optimal stacking order of heterogeneous diphasic soft armor systems by reviewing the results from previous studies. Experiments were performed on heterogeneous systems comprising ballistic-grade polyurea, Twaron® fabric, and Dyneema® UD laminate plies. Results show that the two constituent materials should be ordered such that the material with a higher Cunniff velocity is placed at the rear to minimize interference. The use of the merit parameter is then analyzed via existing models to examine the effects of changing various parameters. We further discuss the idea of “ballistically-thin” materials in relation to the concept of membrane strain energy dissipation efficiency of a soft armor target.

ACS Style

Zherui Guo; Weinong Chen. A merit parameter to determine the stacking order of heterogeneous diphasic soft armor systems. Composite Structures 2020, 241, 112086 .

AMA Style

Zherui Guo, Weinong Chen. A merit parameter to determine the stacking order of heterogeneous diphasic soft armor systems. Composite Structures. 2020; 241 ():112086.

Chicago/Turabian Style

Zherui Guo; Weinong Chen. 2020. "A merit parameter to determine the stacking order of heterogeneous diphasic soft armor systems." Composite Structures 241, no. : 112086.

Journal article
Published: 25 January 2020 in Composites Part A: Applied Science and Manufacturing
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Insight into the detailed fracture processes of single high-performance fibers improves understanding for the nature of their unique resistances to external loads. Here, we show the in-situ observation of entire fracture processes of an uncoated single Kevlar® KM2 Plus and Dyneema® SK76 fiber cut by a razor blade at various angles in a Scanning Electronic Microscope (SEM), including initial contact, deformation, crack initiation and propagation until final failure. The effects of gauge length, sputter coating of the platinum, fiber type and cutting angle on the fiber failure were investigated and discussed. The mass-efficient cutting resistance of a single fiber was evaluated by the specific energy. The diversity of the failure modes and cutting resistance were analyzed and attributed to the specific fiber nanostructure and different cutting angles.

ACS Style

Jinling Gao; Yizhou Nie; Boon Him Lim; Xuedong Zhai; Nesredin Kedir; Weinong Chen. In-situ observation of cutting-induced failure processes of single high-performance fibers inside a SEM. Composites Part A: Applied Science and Manufacturing 2020, 131, 105767 .

AMA Style

Jinling Gao, Yizhou Nie, Boon Him Lim, Xuedong Zhai, Nesredin Kedir, Weinong Chen. In-situ observation of cutting-induced failure processes of single high-performance fibers inside a SEM. Composites Part A: Applied Science and Manufacturing. 2020; 131 ():105767.

Chicago/Turabian Style

Jinling Gao; Yizhou Nie; Boon Him Lim; Xuedong Zhai; Nesredin Kedir; Weinong Chen. 2020. "In-situ observation of cutting-induced failure processes of single high-performance fibers inside a SEM." Composites Part A: Applied Science and Manufacturing 131, no. : 105767.

Journal article
Published: 17 December 2019 in Journal of the Mechanical Behavior of Biomedical Materials
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Most fatal human skull injuries occur under impact loading conditions, such as car collisions, where the strain rates fall in the range of intermediate (1/s−102/s) and high (102/s−103/s) rates. Therefore, knowledge of the mechanical behaviors of human cranial bone at higher strain rates, i.e., intermediate and high strain rates, may provide insight into the prevention of skull injuries and help the design of efficient head protection systems. In the present study, the compressive mechanical behaviors of human frontal skull bone along and perpendicular to its through-the-thickness direction were experimentally characterized at quasi-static (0.01/s), intermediate (30/s) and high (625/s) strain rates in this study. A total number of 75 specimens prepared from three male donors with ages of 70-74 were separated into three groups: quasi-static (N = 23), intermediate (N = 23), and high (N = 29) strain rates. Experiments at quasi-static and intermediate strain rates were performed using a hydraulically driven materials testing system (MTS), while a Kolsky compression bar was used to load the skull bone specimen at high strain rates. X-ray computed tomography was performed to obtain the structural parameters and visualize the microstructures of the skull bone. The in-situ failure processes of the specimens under high-rate loading were documented by a high-speed camera. The human skull exhibited a loading-direction dependent mechanical behavior, as higher ultimate strength and elastic modulus were found in the direction perpendicular to the thickness when compared with those along the thickness direction, exhibited an increasing ratio as high as 2 and 3 for strength and modulus, respectively. High-speed images revealed that the specimens loaded along the thickness direction generally failed due to the crushing in diploë (the trabecular bone tissue) whereas separation of the entire architecture was observed as the main failure mode when compressed in the perpendicular direction. The effect of loading rate was also evident: the skull specimens were increasingly brittle as strain rate increased from quasi-static to high rate for both the loading directions. The elastic modulus increased by a factor of 4 in radial direction and it increased by a factor of 2.5 in the tangential direction across the quasi-static, intermediate and high strain rates. Significant differences were also found in ultimate strength and work to failure as loading rate increased from quasi-static to high rates. The results also suggested that the strength in the radial direction was mainly depended on the diploë porosity while the diploë layer ratio played the predominant role in tangential direction.

ACS Style

Xuedong Zhai; Eric A. Nauman; Dana Moryl; Roy Lycke; Weinong W. Chen. The effects of loading-direction and strain-rate on the mechanical behaviors of human frontal skull bone. Journal of the Mechanical Behavior of Biomedical Materials 2019, 103, 103597 .

AMA Style

Xuedong Zhai, Eric A. Nauman, Dana Moryl, Roy Lycke, Weinong W. Chen. The effects of loading-direction and strain-rate on the mechanical behaviors of human frontal skull bone. Journal of the Mechanical Behavior of Biomedical Materials. 2019; 103 ():103597.

Chicago/Turabian Style

Xuedong Zhai; Eric A. Nauman; Dana Moryl; Roy Lycke; Weinong W. Chen. 2019. "The effects of loading-direction and strain-rate on the mechanical behaviors of human frontal skull bone." Journal of the Mechanical Behavior of Biomedical Materials 103, no. : 103597.

Journal article
Published: 17 July 2019 in Journal of the Mechanics and Physics of Solids
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We visualized, in real time, the dynamic fracture behaviors in porcine cortical bone from humerus and porcine trabecular bone from nasal bone at a high loading rate using high-speed synchrotron X-ray phase-contrast imaging (PCI). Dynamic three-point bending loading was applied on notched bone specimens by a modified Kolsky compression bar and images of the entire fracture events were recorded with an ultra-high-speed camera. Experiments at a quasi-static loading rate on material testing system (MTS) were also performed to identify the loading-rate effects on the fracture toughness of the two types of bone. Three-dimensional synchrotron X-ray computed tomography was conducted to examine the initial microstructures in the bone specimens before mechanical loading. At the dynamic loading rate, the onset locations of crack initiation were found to be independent from the bone types. The deleterious effect of dynamic loading rate on bone's fracture toughness was verified in this study and the crack was found to propagate at higher speeds in cortical bone than in trabecular bone. In a comparison of the observed more torturous crack paths at the quasi-static loading rate, cracks in dynamically loaded bone specimens generally followed the paths with less in-plane deflections and out-of-plane twists. However, our experimental results also indicated that, although the extent was diminished at dynamic loading rate, the crack deflections at osteon cement lines still played a role as a major toughening mechanism to dynamic fractures in transversely orientated cortical bone.

ACS Style

Xuedong Zhai; Jinling Gao; Yizhou Nie; Zherui Guo; Nesredin Kedir; Ben Claus; Tao Sun; Kamel Fezzaa; Xianghui Xiao; Weinong W. Chen. Real-time visualization of dynamic fractures in porcine bones and the loading-rate effect on their fracture toughness. Journal of the Mechanics and Physics of Solids 2019, 131, 358 -371.

AMA Style

Xuedong Zhai, Jinling Gao, Yizhou Nie, Zherui Guo, Nesredin Kedir, Ben Claus, Tao Sun, Kamel Fezzaa, Xianghui Xiao, Weinong W. Chen. Real-time visualization of dynamic fractures in porcine bones and the loading-rate effect on their fracture toughness. Journal of the Mechanics and Physics of Solids. 2019; 131 ():358-371.

Chicago/Turabian Style

Xuedong Zhai; Jinling Gao; Yizhou Nie; Zherui Guo; Nesredin Kedir; Ben Claus; Tao Sun; Kamel Fezzaa; Xianghui Xiao; Weinong W. Chen. 2019. "Real-time visualization of dynamic fractures in porcine bones and the loading-rate effect on their fracture toughness." Journal of the Mechanics and Physics of Solids 131, no. : 358-371.

Article
Published: 19 June 2019 in Journal of Dynamic Behavior of Materials
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Experiments with fragment-simulating projectiles (FSP) and aluminum plates are conducted to evaluate the performance of various aluminum alloys and plate thicknesses to resist perforation against fragments. Ballistic-limit velocity data for several aluminum alloys and plate thicknesses are presented in several US Army Research Laboratory (ARL) reports. In this study, we present additional ballistic-limit data for plates thinner than the plates reported by ARL. In addition, we present an equation that predicts the ballistic-limit velocity for fragment-simulating projectiles (FSP) that perforate aluminum armor plates. The ballistic-limit equation is presented in terms of dimensionless parameters so that the geometric and material problem scales are identified. Predictions and data from two different fragment-simulating projectiles and two different strength aluminum alloys show the range of plate thicknesses for reasonable model predictions.

ACS Style

Zherui Guo; Michael J. Forrestal; Stephenie Martinez-Morales; Weinong Chen. Perforation of Aluminum Armor Plates with Fragment-Simulating Projectiles. Journal of Dynamic Behavior of Materials 2019, 5, 409 -415.

AMA Style

Zherui Guo, Michael J. Forrestal, Stephenie Martinez-Morales, Weinong Chen. Perforation of Aluminum Armor Plates with Fragment-Simulating Projectiles. Journal of Dynamic Behavior of Materials. 2019; 5 (4):409-415.

Chicago/Turabian Style

Zherui Guo; Michael J. Forrestal; Stephenie Martinez-Morales; Weinong Chen. 2019. "Perforation of Aluminum Armor Plates with Fragment-Simulating Projectiles." Journal of Dynamic Behavior of Materials 5, no. 4: 409-415.

Journal article
Published: 18 June 2019 in TURKISH JOURNAL OF MEDICAL SCIENCES
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To prepare a porcine model of obstructive sleep apnea-hypopnea syndrome (OSAHS) and observe the pathological and hemodynamic changes in the common carotid artery. Twelve male miniature pigs were randomly divided into the model and control group (n = 6). Pigs in the model group were kept in an air-flow negative pressure chamber at 0.96 ± 0.01 kPa, and the air oxygen content, temperature, and humidity were kept at normal culture conditions in both groups. After pigs in the model group presented symptoms of OSAHS, changes in the hemodynamics and morphology of the carotid artery were analyzed using color Doppler, and light and electron microscopy. An animal model of OSAHS was successfully created. The internal diameter of the carotid artery of pigs in the model group was decreased, while the intima thickness, peak-systolic mean velocity, and resistance index were increased when compared to the control group (P < 0.05). The results of the light and electron microscopy revealed an incomplete elastic plate, increased media thickness, irregular morphology of the smooth muscle cells, increased collagen fiber bundles, partially disordered elastic fibers, and smooth muscle layers. The quantitative analysis showed significantly increased elastic fibers in the media of the carotid artery in the model group (P < 0.01). Pathological changes in the tissue structure and hemodynamics in the negative pressure-induced pig OSAHS model were observed. We suggest that alterations in the upper airway pressure during OSAHS may lead to cardiovascular conditions through its pathological effects on the carotid artery.

ACS Style

Yongyi Liu; Lu Gao; Weinong Lv; Lin Lin; Yi Wang; Fan Jiang; Fan Feng; Lin Lın; Fan Fıang. Pathologic and hemodynamic changes of common carotid artery in obstructive sleep apnea hypopnea syndrome in a porcine model. TURKISH JOURNAL OF MEDICAL SCIENCES 2019, 49, 939 -944.

AMA Style

Yongyi Liu, Lu Gao, Weinong Lv, Lin Lin, Yi Wang, Fan Jiang, Fan Feng, Lin Lın, Fan Fıang. Pathologic and hemodynamic changes of common carotid artery in obstructive sleep apnea hypopnea syndrome in a porcine model. TURKISH JOURNAL OF MEDICAL SCIENCES. 2019; 49 (3):939-944.

Chicago/Turabian Style

Yongyi Liu; Lu Gao; Weinong Lv; Lin Lin; Yi Wang; Fan Jiang; Fan Feng; Lin Lın; Fan Fıang. 2019. "Pathologic and hemodynamic changes of common carotid artery in obstructive sleep apnea hypopnea syndrome in a porcine model." TURKISH JOURNAL OF MEDICAL SCIENCES 49, no. 3: 939-944.

Journal article
Published: 03 April 2019 in Fibers
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In this study, ballistic experiments were performed to determine the critical velocity of a Twaron® 2040 high-performance yarn transversely impacted by round projectiles. Four different round projectiles possessing a radius of curvature of 2 µm, 20 µm, 200 µm and 2 mm were used in this study. Load cells were mounted to the grips to measure the load history of the yarn upon impact. A high-speed camera was incorporated into the ballistic experimental setup to capture the failure process of the yarn upon impact. A scanning electron microscope was utilized to perform post-mortem failure analysis on the recovered specimens. The results showed that as the radius of curvature of the projectile increased, the critical velocity also increased. The critical velocities for all cases were bounded between those predicted from the Euler–Bernoulli beam and Smith models. Upon impact above the upper limit of the critical velocity, the axial loads revealed a demonstrative reduction. The failure surfaces changed from shear to fibrillation as the radius of curvature increased. For those specimens that failed in shear, Hertzian contact model was used to predict the critical velocity.

ACS Style

Boon Him Lim; Jou-Mei Chu; Jinling Gao; Benjamin Claus; Yizhou Nie; Wayne Chen. The Effect of Projectile Nose Shape on the Critical Velocity of High-Performance Yarn. Fibers 2019, 7, 29 .

AMA Style

Boon Him Lim, Jou-Mei Chu, Jinling Gao, Benjamin Claus, Yizhou Nie, Wayne Chen. The Effect of Projectile Nose Shape on the Critical Velocity of High-Performance Yarn. Fibers. 2019; 7 (4):29.

Chicago/Turabian Style

Boon Him Lim; Jou-Mei Chu; Jinling Gao; Benjamin Claus; Yizhou Nie; Wayne Chen. 2019. "The Effect of Projectile Nose Shape on the Critical Velocity of High-Performance Yarn." Fibers 7, no. 4: 29.

Journal article
Published: 05 March 2019 in Journal of Biomechanical Engineering
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We experimentally determined the tensile stress–strain response of human muscle along fiber direction and compressive stress–strain response transverse to fiber direction at intermediate strain rates (100–102/s). A hydraulically driven material testing system with a dynamic testing mode was used to perform the tensile and compressive experiments on human muscle tissue. Experiments at quasi-static strain rates (below 100/s) were also conducted to investigate the strain-rate effects over a wider range. The experimental results show that, at intermediate strain rates, both the human muscle's tensile and compressive stress–strain responses are nonlinear and strain-rate sensitive. Human muscle also exhibits a stiffer and stronger tensile mechanical behavior along fiber direction than its compressive mechanical behavior along the direction transverse to fiber direction. An Ogden model with two material constants was adopted to describe the nonlinear tensile and compressive behaviors of human muscle.

ACS Style

Xuedong Zhai; Eric A. Nauman; Yizhou Nie; Hangjie Liao; Roy J. Lycke; Weinong W. Chen. Mechanical Response of Human Muscle at Intermediate Strain Rates. Journal of Biomechanical Engineering 2019, 141, 1 .

AMA Style

Xuedong Zhai, Eric A. Nauman, Yizhou Nie, Hangjie Liao, Roy J. Lycke, Weinong W. Chen. Mechanical Response of Human Muscle at Intermediate Strain Rates. Journal of Biomechanical Engineering. 2019; 141 (4):1.

Chicago/Turabian Style

Xuedong Zhai; Eric A. Nauman; Yizhou Nie; Hangjie Liao; Roy J. Lycke; Weinong W. Chen. 2019. "Mechanical Response of Human Muscle at Intermediate Strain Rates." Journal of Biomechanical Engineering 141, no. 4: 1.

Journal article
Published: 07 December 2018 in Fibers
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A ballistic parameter that influences the ballistic performances of a high-performance yarn is the critical velocity. The critical velocity is defined as the projectile striking velocity that causes instantaneous rupture of the yarn upon impact. In this study, we performed ballistic experiments to determine the critical velocity of a Twaron® yarn transversely impacted by a razor blade. A high-speed camera was integrated into the experimental apparatus to capture the in-situ deformation of the yarn. The experimental critical velocity demonstrated a reduction compared to the critical velocity predicted by the classical theory. The high-speed images revealed the yarn specimen failed from the projectile side toward the free end when impacted by the razor blade. To improve the prediction capability, the Euler–Bernoulli beam and Hertzian contact models were used to predict the critical velocity. For the Euler–Bernoulli beam model, the critical velocity was obtained by assuming the specimen ruptured instantaneously when the maximum flexural strain reached the ultimate tensile strain of the yarn upon impact. On the other hand, for the Hertzian contact model, the yarn was assumed to fail when the indentation depth was equivalent to the diameter of the yarn. The errors between the average critical velocities determined from experiments and the predicted critical velocities were around 19% and 48% for the Euler–Bernoulli beam model and Hertzian contact model, respectively.

ACS Style

Boon Him Lim; Jou-Mei Chu; Benjamin Claus; Yizhou Nie; Wayne Chen. Critical Velocity of High-Performance Yarn Transversely Impacted by Razor Blade. Fibers 2018, 6, 95 .

AMA Style

Boon Him Lim, Jou-Mei Chu, Benjamin Claus, Yizhou Nie, Wayne Chen. Critical Velocity of High-Performance Yarn Transversely Impacted by Razor Blade. Fibers. 2018; 6 (4):95.

Chicago/Turabian Style

Boon Him Lim; Jou-Mei Chu; Benjamin Claus; Yizhou Nie; Wayne Chen. 2018. "Critical Velocity of High-Performance Yarn Transversely Impacted by Razor Blade." Fibers 6, no. 4: 95.

Journal article
Published: 23 September 2018 in Fibers
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In this study, we performed off-axis transverse loading experiments to study the stress concentration developed in a high-performance yarn with different indenters. A universal testing machine was utilized to perform quasi-static transverse loading experiments on Twaron® yarns. Seven different round indenters possessing radius of curvature ranging from 0.20 to 4.50 mm were employed in the experiments. In addition, post-mortem failure analysis was performed on the recovered specimens via a scanning electron microscope. From the transverse loading experiments, the results showed that, as the radius of curvature of the indenters increased, the concentrated load decreased, causing the failure surfaces to change from a combination of kink band, snapped-back, and localized shear to only fibrillations. The concentrated stresses were predicted by a strain energy model when loaded by an indenter with a radius of curvature smaller than 1.59 mm. For indenters larger than 1.59 mm, the specimens failed in fibrillation, the concentrated stresses agreed well with the stresses predicted by quasi-static circular curved beam theory.

ACS Style

Boon Him Lim; Jou-Mei Chu; Wayne Chen. Mechanical Behavior of High-Performance Yarns Transversely Loaded by Different Indenters. Fibers 2018, 6, 69 .

AMA Style

Boon Him Lim, Jou-Mei Chu, Wayne Chen. Mechanical Behavior of High-Performance Yarns Transversely Loaded by Different Indenters. Fibers. 2018; 6 (4):69.

Chicago/Turabian Style

Boon Him Lim; Jou-Mei Chu; Wayne Chen. 2018. "Mechanical Behavior of High-Performance Yarns Transversely Loaded by Different Indenters." Fibers 6, no. 4: 69.

Article
Published: 20 September 2017 in Journal of Dynamic Behavior of Materials
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Kolsky bar data for viscoplastic materials are usually presented as true stress versus true strain curves at nearly constant values of engineering strain rates. However, constitutive models for numerical simulations require the true axial rate of deformation which is true strain rate. We present a procedure that uses existing data with constant engineering strain rate to obtain a constitutive equation in terms of true strain rate for 304 stainless steel and 4340 Rc 45 steel.

ACS Style

M. J. Forrestal; B. H. Lim; W. W. Chen. A Viscoplastic Constitutive Equation from Kolsky Bar Data for Two Steels. Journal of Dynamic Behavior of Materials 2017, 3, 534 -537.

AMA Style

M. J. Forrestal, B. H. Lim, W. W. Chen. A Viscoplastic Constitutive Equation from Kolsky Bar Data for Two Steels. Journal of Dynamic Behavior of Materials. 2017; 3 (4):534-537.

Chicago/Turabian Style

M. J. Forrestal; B. H. Lim; W. W. Chen. 2017. "A Viscoplastic Constitutive Equation from Kolsky Bar Data for Two Steels." Journal of Dynamic Behavior of Materials 3, no. 4: 534-537.