Mechanical characterization of “blister” defects on optical oxide multilayers using nanoindentation

2012 ◽  
Vol 1454 ◽  
pp. 215-220 ◽  
Author(s):  
K. Mehrotra ◽  
H.P. Howard ◽  
S.D. Jacobs ◽  
J.C. Lambropoulos
Keyword(s):  
Mechanical Response ◽  
Mechanical Characterization ◽  
Site Specific ◽  
Acid Cleaning ◽  
Cleaning Procedures ◽  
Indentation Response ◽  
Multilayer Dielectric

ABSTRACTWe characterize “blisters”, defects observed in multilayer dielectric (MLD) coatings after exposure to acid cleaning procedures. Nanoindentation is used to make site-specific indentations across blisters to measure the mechanical response, especially their compliance under different conditions of loading. Two regions of statistically different mechanical response are identified within a blister defect and compared to the undisturbed regions of the MLD coating. The indentation response of blisters can vary across samples, and we suggest reasons for this variation.

scholarly journals Visco-Hyperelastic Characterization of the Equine Immature Zona Pellucida

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1223
Author(s):  
Elisa Ficarella ◽  
Mohammad Minooei ◽  
Lorenzo Santoro ◽  
Elisabetta Toma ◽  
Bartolomeo Trentadue ◽  
...  
Keyword(s):  
Zona Pellucida ◽  
Soft Matter ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Nonlinear Material ◽  
Prony Series ◽  
Critical Comparison ◽  
Highly Nonlinear ◽  
Good Agreement

This article presents a very detailed study on the mechanical characterization of a highly nonlinear material, the immature equine zona pellucida (ZP) membrane. The ZP is modeled as a visco-hyperelastic soft matter. The Arruda–Boyce constitutive equation and the two-term Prony series are identified as the most suitable models for describing the hyperelastic and viscous components, respectively, of the ZP’s mechanical response. Material properties are identified via inverse analysis based on nonlinear optimization which fits nanoindentation curves recorded at different rates. The suitability of the proposed approach is fully demonstrated by the very good agreement between AFM data and numerically reconstructed force–indentation curves. A critical comparison of mechanical behavior of two immature ZP membranes (i.e., equine and porcine ZPs) is also carried out considering the information on the structure of these materials available from electron microscopy investigations documented in the literature.

scholarly journals Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas

2022 ◽  
Vol 119 (3) ◽  
pp. e2117232119
Author(s):  
Giulio Franchini ◽  
Ivan D. Breslavsky ◽  
Francesco Giovanniello ◽  
Ali Kassab ◽  
Gerhard A. Holzapfel ◽  
...  
Keyword(s):  
Experimental Data ◽  
Smooth Muscle ◽  
Muscle Activation ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Viscoelastic Behavior ◽  
Material Model ◽  
Suitable Material ◽  
Dynamic Mechanical

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

scholarly journals Mechanical Characterization of Nanocomposite Joints Based on Biomedical Grade Polyethylene under Cyclical Loads

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2681
Author(s):  
Annamaria Visco ◽  
Cristina Scolaro ◽  
Antonino Quattrocchi ◽  
Roberto Montanini
Keyword(s):  
Titanium Dioxide ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Laser Light ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Weight Content ◽  
Percentage Weight ◽  
Static Mechanical

Polymeric joints, made of biomedical polyethylene (UHMWPE) nanocomposite sheets, were welded with a diode laser. Since polyethylene does not absorb laser light, nanocomposites were prepared containing different percentages by weight of titanium dioxide as it is a laser absorbent. The joints were first analyzed with static mechanical tests to establish the best percentage weight content of filler that had the best mechanical response. Then, the nanocomposites containing 1 wt% titanium dioxide were selected (white color) to be subjected to fatigue tests. The experimental results were also compared with those obtained on UMMWPE with a different laser light absorbent nano filler (carbon, with greater laser absorbing power, gray in color), already studied by our research team. The results showed that the two types of joints had an appreciable resistance to fatigue, depending on the various loads imposed. Therefore, they can be chosen in different applications of UHMWPE, depending on the stresses imposed during their use.

Mechanical Characterization of the Decellularized Porcine Small Intestinal Submucosa Extracellular Matrix

2013 ◽  
Author(s):  
Shijia Zhao ◽  
Linxia Gu ◽  
James M. Hammel ◽  
Haili Lang
Keyword(s):  
Mechanical Properties ◽  
Extracellular Matrix ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Small Intestinal Submucosa ◽  
Trade Name ◽  
Porcine Small Intestinal Submucosa ◽  
Small Intestinal ◽  
Intestinal Submucosa

In this work, the decellularized porcine small intestinal submucosa extracellular matrix (SIS-ECM), obtained from the commercial product under the trade name of CorMatrix, were tested in uniaxial tension. Preconditioning under cyclic loading of 2 N was conducted to stabilize the mechanical response of the tissue. The influence of rehydration time on the mechanical properties of the tissue was evaluated. Results suggested that the stiffness of SIS-ECM decreased with longer rehydration time. Considering the application of CorMatrix in pericardial closure, the native pericardium samples were also tested. The comparison indicated that the native pericardium is softer than rehydrated CorMatrix. This work can facilitate the surgeons to better choose the appropriate rehydration time when conducting the extracardiac implantations, such as pericardial reconstruction, pericardial closure, etc.

SITE SPECIFIC ELECTRO-MECHANICAL CHARACTERIZATION OF BOVINE KNEE ARTICULAR CARTILAGE

2012 ◽  
Vol 45 ◽  
pp. S162
Author(s):  
Reza Abedian ◽  
Mattias Reebmann ◽  
Christof Hurschler
Keyword(s):  
Articular Cartilage ◽  
Mechanical Characterization ◽  
Site Specific

scholarly journals Biomechanical Comparison of Glutaraldehyde-Crosslinked Gelatin Fibrinogen Electrospun Scaffolds to Porcine Coronary Arteries

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
E. Tamimi ◽  
D. C. Ardila ◽  
D. G. Haskett ◽  
T. Doetschman ◽  
M. J. Slepian ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Mechanical Characterization ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Vein Grafts ◽  
Electrospun Scaffolds ◽  
Response Data ◽  
Custom Made ◽  
Biomechanical Comparison

Cardiovascular disease (CVD) is the leading cause of death for Americans. As coronary artery bypass graft surgery (CABG) remains a mainstay of therapy for CVD and native vein grafts are limited by issues of supply and lifespan, an effective readily available tissue-engineered vascular graft (TEVG) for use in CABG would provide drastic improvements in patient care. Biomechanical mismatch between vascular grafts and native vasculature has been shown to be the major cause of graft failure, and therefore, there is need for compliance-matched biocompatible TEVGs for clinical implantation. The current study investigates the biaxial mechanical characterization of acellular electrospun glutaraldehyde (GLUT) vapor-crosslinked gelatin/fibrinogen cylindrical constructs, using a custom-made microbiaxial optomechanical device (MOD). Constructs crosslinked for 2, 8, and 24 hrs are compared to mechanically characterized porcine left anterior descending coronary (LADC) artery. The mechanical response data were used for constitutive modeling using a modified Fung strain energy equation. The results showed that constructs crosslinked for 2 and 8 hrs exhibited circumferential and axial tangential moduli (ATM) similar to that of the LADC. Furthermore, the 8-hrs experimental group was the only one to compliance-match the LADC, with compliance values of 0.0006±0.00018 mm Hg−1 and 0.00071±0.00027 mm Hg−1, respectively. The results of this study show the feasibility of meeting mechanical specifications expected of native arteries through manipulating GLUT vapor crosslinking time. The comprehensive mechanical characterization of cylindrical biopolymer constructs in this study is an important first step to successfully develop a biopolymer compliance-matched TEVG.

scholarly journals Materials Characterization of Cranial Simulants for Blast-Induced Traumatic Brain Injury

2020 ◽  
Vol 185 (Supplement_1) ◽  
pp. 205-213
Author(s):  
Anna Wermer ◽  
Joseph Kerwin ◽  
Kelsea Welsh ◽  
Ricardo Mejia-Alvarez ◽  
Michaelann Tartis ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
High Speed ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Shear Moduli ◽  
Trade Offs ◽  
Compressive Testing ◽  
Cadaver Studies

ABSTRACT Introduction The mechanical response of brain tissue to high-speed forces in the blast and blunt traumatic brain injury is poorly understood. Object-to-object variation and interspecies differences are current limitations in animal and cadaver studies conducted to study damage mechanisms. Biofidelic and transparent tissue simulants allow the use of high-speed optical diagnostics during a blast event, making it possible to observe deformations and damage patterns for comparison to observed injuries seen post-mortem in traumatic brain injury victims. Methods Material properties of several tissue simulants were quantified using standard mechanical characterization techniques, that is, shear rheometric, tensile, and compressive testing. Results Polyacrylamide simulants exhibited the best optical and mechanical property matching with the fewest trade-offs in the design of a cranial test object. Polyacrylamide gels yielded densities of ~1.04 g/cc and shear moduli ranging 1.3–14.55 kPa, allowing gray and white matter simulant tuning to a 30–35% difference in shear for biofidelity. Conclusions These materials are intended for use as layered cranial phantoms in a shock tube and open field blasts, with focus on observing phenomena occurring at the interfaces of adjacent tissue simulant types or material-fluid boundaries. Mechanistic findings from these studies may be used to inform the design of protective gear to mitigate blast injuries.

scholarly journals Production and Mechanical Characterization of Graphene Micro-Ribbons

2019 ◽  
Vol 3 (2) ◽  
pp. 42
Author(s):  
Maria Giovanna Pastore Carbone ◽  
Georgia Tsoukleri ◽  
Anastasios C. Manikas ◽  
Eleni Makarona ◽  
Christos Tsamis ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Mechanical Characterization ◽  
Chemical Vapor ◽  
Large Area ◽  
Mechanical Investigation ◽  
Raman Spectral ◽  
Compressive Tests

Patterning of graphene into micro- and nano-ribbons allows for tunability in emerging fields such as flexible electronic and optoelectronic devices, and is gaining interest for the production of more efficient reinforcement for composite materials. In this work we fabricate micro-ribbons from graphene synthesized via chemical vapor deposition (CVD) by combining ultraviolet (UV) photolithography and dry etching oxygen plasma treatments. We used Raman spectral imaging to confirm the effectiveness of the patterning procedure, which is suitable for large-area patterning of graphene on wafer-scale, and confirms that the quality of graphene remains unaltered. The produced micro-ribbons were finally transferred and embedded into a polymeric matrix and the mechanical response was investigated by in-situ mechanical investigation combining Raman spectroscopy and tensile/compressive tests.

Nanoindentation probing of high-aspect ratio pillar structures on optical multilayer dielectric diffraction gratings

2012 ◽  
Vol 1474 ◽  
Author(s):  
K. Mehrotra ◽  
H.P. Howard ◽  
S.D. Jacobs ◽  
J.C. Lambropoulos
Keyword(s):  
Aspect Ratio ◽  
Yield Stress ◽  
High Aspect Ratio ◽  
Mechanical Response ◽  
Diffraction Gratings ◽  
Material Hardness ◽  
Similar Dependence ◽  
Strain Model ◽  
Indentation Response ◽  
Multilayer Dielectric

ABSTRACTWe measure the mechanical response of optical multilayer dielectric (MLD) diffraction gratings, geometries which are constrained in only one transverse direction but free in the other, using nanoindentation. The results are explained using a stress-strain model, which reveals a uniaxial yield stress of 4.1- 4.6 GPa and predicts a similar dependence of yield stress on loads for both fully-elastic and fully-plastic solutions. Following R. Hill’s model of an expanding cavity under internal pressure, we show that the indentation response of the high-aspect ratio “pillar” geometry can be expressed in terms of uniaxial yield stress rather than material hardness.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

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