Alumina as a Computed Tomography Soft Material and Tissue Fiducial Marker
The use of 3D imaging is becoming increasingly common, so too is the use of fiducial markers to identify/track regions of interest and assess material deformation. While many different materials have been used as fiducials, they are often used in isolation, with little comparison to one another.
Multi-view digital image correlation systems for in vitro testing of arteries from mice to humans
Digital image correlation (DIC) methods are increasingly used for non-contact optical assessment of geometry and deformation in soft tissue biomechanics, thus providing the full-field strain estimates needed for robust inverse material characterization. Despite the well-known flexibility and ease of use of DIC, issues related to spatial resolution and depth-of-field remain challenging in studies of quasi-cylindrical biological samples such as arteries.
Microindentation of cartilage before and after articular loading in a bioreactor: assessment of length-scale dependency using two analysis methods
Microindentation is a technique with high sensitivity and spatial resolution, allowing for measurements at small-scale indentation depths. Various methods of indentation analysis to determine output properties exist.
Effect of macro-calcification on the failure mechanics of intracranial aneurysmal wall tissue
Calcification was recently found to be present in the majority of cerebral aneurysms, though how calcification and the presence or absence of co-localized lipid pools affect failure properties is still unknown.
The Association Between Curvature and Rupture in a Murine Model of Abdominal Aortic Aneurysm and Dissection
Mouse models of abdominal aortic aneurysm (AAA) and dissection have proven to be invaluable in the advancement of diagnostics and therapeutics by providing a platform to decipher response variables that are elusive in human populations. One such model involves systemic Angiotensin II (Ang-II) infusion into low density-lipoprotein receptor-deficient (LDLr-/-) mice leading to intramural thrombus formation, inflammation, matrix degradation, dilation, and dissection. Despite its effectiveness, considerable experimental variability has been observed in AAAs taken from our Ang-II infused LDLr-/- mice (n=12) with obvious dissection occurring in 3 samples, outer bulge radii ranging from 0.73 to 2.12 mm, burst pressures ranging from 155 to 540 mmHg, and rupture location occurring 0.05 to 2.53 mm from the peak bulge location.
Left ventricular geometry, tissue composition, and residual stress in High Fat Diet Dahl-Salt sensitive rats
Hypertension drives myocardial remodeling, leading to changes in structure, composition and mechanical behavior, including residual stress, which are linked to heart disease progression in a gender-specific manner. Emerging therapies are also targeting constituent-specific pathological features. All previous studies, however, have characterized remodeling in the intact tissue, rather than isolated tissue constituents, and did not include sex as a biological variable.
Radiofrequency ablation alters the microstructural organization of healthy and enzymatically digested porcine mitral valves
Myxomatous mitral valve degeneration is a common cause of mitral regurgitation and is often associated with mitral valve prolapse. With no known targets to pharmacologically treat mitral valve prolapse, surgery is often the only treatment option. Recently, radiofrequency ablation has been proposed as a percutaneous alternative to surgical resection for the reduction of mitral valve leaflet area.
Effects of Red Blood Cell Sickling on Right Ventricular Afterload
Hemolysis in sickle cell disease (SCD) releases cell free hemoglobin, which scavenges nitric oxide (NO), leading to pulmonary vascular vasoconstriction, increased pulmonary vascular resistance (PVR), and the development of PH. However, PVR is only one component of right ventricular (RV) afterload. Whether sickled red blood cells increase the total RV afterload, including compliance and wave reflections, is unclear.
Regional Mechanical Characterization of Porcine Pulmonary Arteries
Regional mechanical characterization of pulmonary arteries can be useful in the development of computational models of pulmonary arterial mechanics.
Adaptive Remodeling in the Elastase-induced Rabbit Aneurysms
Rupture of brain aneurysms is associated with high fatality and morbidity rates. Through remodeling of the collagen matrix, many aneurysms can remain unruptured for decades, despite an enlarging and evolving geometry.
In Vivo Image-Based 4D Modeling of Competent and Regurgitant Mitral Valve Dynamics
In vivo characterization of mitral valve dynamics relies on image analysis algorithms that accurately reconstruct valve morphology and motion from clinical images. The goal of such algorithms is to provide patient-specific descriptions of both competent and regurgitant mitral valves, which can be used as input to biomechanical analyses and provide insights into the pathophysiology of diseases like ischemic mitral regurgitation (IMR).
MicroCT Imaging of Heart Valve Tissue in Fluid
Heart valve computational models require high quality geometric input data, commonly obtained using micro-computed tomography. Whether in the open or closed configuration, most studies utilize dry valves, which poses significant challenges including gravitational and surface tension effects along with desiccation induced mechanical changes.
4D Porosity Evolution in Additively Manufactured 316L Stainless Steel through Tensile Testing and X-Ray Computed Tomography
Many aspects of ductile failure through microvoid coalescence remain elusive due to the challenging spatial and temporal scales it operates on. Experimentally resolving all aspects of the process remains a significant goal of researchers. Much of the current understanding has been derived from post-mortem metallography, leaving key aspects of its evolution undocumented.
An Corrosion Small Punch Test for Developing Stress Corrosion Cracking in Stainless Steel
Spent AGR (advanced gas-cooled reactor) fuel cladding may suffer from stress corrosion cracking (SCC) during the interim storage period in cooling ponds and compromise the structural integrity of fuel storage.
Influence of Temperature, Strain Rate, and Condition on the Mechanical Response of an AlSi-PES Abradable
To improve the efficiency and operational stability of aero-engine compressors, abradable liners are used to facilitate reduced clearances between the blade tips and the surrounding casing. However, their properties are highly variable due to sensitivities in the plasma spraying process and complex in-service phenomena such as blade-casing interactions and thermal ageing. The abradable variability makes it difficult to model blade-casing interactions accurately, leading to suboptimal blade geometries and clearances.
An Experimental Method for Fatigue Testing Cast Iron Water Pipes Using Combined Internal Water Pressure and Bending Loads
Investigations into the fatigue failures mechanism of Grey Cast Iron (GCI) water pipes are inhibited by the lack of a lab-based method to conduct extensive high-cycle biaxial fatigue test programmes.
Why Is It So Challenging to Measure Residual Stresses ?
Residual stresses have a "hidden" character because they exist in a material without the presence of any external loads. They cannot easily be added or subtracted in a quantified manner, as is done when measuring applied stresses, and so are much more challenging to measure.
Estimation of the Deformation Gradient Tensor by Particle Tracking Near a Free Boundary with Quantified Error
Obtaining accurate displacement measurements for large material deformation and/or rotation presents a distinct challenge to digital image correlation (DIC) due to cumulative and decorrelation errors, particularly near material boundaries.
Split-Hopkinson Pressure Bar Testing of Water with Partial Lateral Confinement
For the first time, the high-strain-rate behaviour of water is investigated experimentally and validated to LS-DYNA numerical simulations, using Smooth Particle Hydrodynamics (SPH).
Evaluation of Recyclable Multilayer Packaging Designs Utilising Controlled Interlayer Adhesion
The packaging industry is utilising increased levels of bio-based or recycled plastics and virgin plastic-based packaging is irreplaceable in more demanding applications such as food and pharmaceutical storage where different types of functional plastics are combined in a laminate form to produce multilayered packaging (MLP). Even though MLP are very effective in packaging applications, the typical multilayer format is a barrier to effective recycling, limiting the value and market for the use of recovered materials.
A Comparative Study of the Modal Response of Additively and Subtractively Manufactured Thin Plates After Thermal Loading
Additively-manufactured parts contain residual stresses induced by manufacturing. These residual stresses can be relaxed or redistributed by thermal loading. The presence of internal stress influences the dynamic response of parts, and this is of particular interest in thin plates subject to thermoacoustic loading in hypersonic vehicles and fusion reactors.
