Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
97
result(s) for
"Pruitt, Lisa A"
Sort by:
Mechanics of biomaterials : fundamental principles for implant design
\"Teaching mechanical and structural biomaterials concepts for successful medical implant design, this self-contained text provides a complete grounding for students and newcomers to the field. Split into three sections: Materials, Mechanics and Case Studies, it begins with a review of sterilization, biocompatibility and foreign body response before presenting the fundamental structures of synthetic biomaterials and natural tissues. Mechanical behavior of materials is then discussed in depth, covering elastic deformation, viscoelasticity and time-dependent behavior, multiaxial loading and complex stress states, yielding and failure theories, and fracture mechanics. The final section on clinical aspects of medical devices provides crucial information on FDA regulatory issues and presents case studies in four key clinical areas: orthopedics, cardiovascular devices, dentistry and soft tissue implants. Each chapter ends with a list of topical questions, making this an ideal course textbook for senior undergraduate and graduate students, and also a self-study tool for engineers, scientists and clinicians\"-- Provided by publisher.
Book
Wear and Surface Cracking in Early Retrieved Highly Cross-linked Polyethylene Acetabular Liners
BACKGROUND:A higher degree of cross-linking has been shown to improve the tribological properties of ultra-high molecular weight polyethylene in laboratory studies; however, its effect on in vivo behavior has not been well established. We investigated in vivo wear mechanisms in retrieved highly cross-linked polyethylene acetabular liners in order to determine if early in vivo wear behavior is accurately predicted by hip-simulator studies.
METHODS:A total of twenty-four liners (twenty-one explanted and one unimplanted highly cross-linked liners and two explanted ethylene-oxide-sterilized non-cross-linked liners) were examined for this study. The average age of the patients was 59.9 years, and the average time in vivo was 10.1 months. Articular surface damage on the front and back sides of the liners was assessed with an optical scoring system. Surface quadrants were assigned a grade from 0 to 3 according to the observed wear mechanisms and the percentage of surface affected. The micromechanisms of liner damage were evaluated with use of scanning electron microscopy.
RESULTS:The average front and back-side explant damage scores were 11 (range, 2 to 26.5) and 6.7 (range, 3.7 to 13.3), respectively. There was consistent evidence of early surface deformation and cracking. All explants exhibited some form of surface change, including surface cracking, abrasion, pitting, or scratching. The original machining marks on the liner surface were observed to be either unaltered, drastically distorted, or absent.
CONCLUSIONS:Highly cross-linked ultra-high molecular weight polyethylene acetabular liners that were retrieved at an average of ten months after implantation exhibited signs of surface damage that had not been predicted by in vitro hip-simulator studies. These devices had not failed clinically as a result of wear. The discrepancy between in vitro and in vivo wear surfaces may be due to variability in terms of in vivo lubrication and cyclic loading or may represent early surface damage mechanisms that are not well demonstrated by long-term simulator studies.
Journal Article
Static mode fatigue crack propagation and generalized stress intensity correlation for fatigue–brittle polymers
Stable fatigue crack propagation is predominantly described by the Paris power law correlation of the crack growth rate with the amplitude cyclic stress intensity. The Paris relationship works well for most ductile materials but does not capture the response for fatigue–brittle materials lacking a cyclic damage mechanism, including ceramics and many polymers. Instead, crack growth rate of fatigue–brittle materials correlates to the peak cyclic stress intensity factor,
K
max
. This work shows that
K
max
correlation of fatigue crack growth is derived directly from static mode crack tip behavior with constant correlation coefficients, and that
Δ
K
correlations are not generally applicable for static mode crack propagation in fatigue–brittle polymers. This derivation predicts load ratio, frequency, and waveform effects, which are included in a general static mode fatigue crack propagation law. Fatigue crack propagation data of a known fatigue–brittle polymer are presented to demonstrate static mode crack propagation behavior correlation with
K
max
with constant parameters.
Journal Article
Determination of strain energy function for arterial elastin: Experiments using histology and mechanical tests
The long-range reversible deformation of vertebrate arteries is primarily mediated by elastin networks that endure several million deformation cycles without appreciable fatigue. To determine how elastin contributes to the composite arterial properties, we studied the three-dimensional microstructure and biomechanics of isolated elastin. We initially estimated the sensitivity of these studies by comparing two elastin isolation protocols, autoclaving and alkali-extraction, and measured their effect on isolated elastin using uniaxial tests and histology. These studies show that autoclaved tissues have
(1) a trend for higher modulus
(
900.79
±
678.02
kPa
)
than alkali-extracted samples
(
417.74
±
162.23
kPa
)
albeit with higher collagen–proteoglycan impurities, and (2) greater optical density
(
78.6
±
9.1
%
)
than alkali-extracted groups
(
46.2
±
5.9
%
)
, suggesting that autoclaving is superior to alkali-extraction for biomechanical tests on elastin. Using these data we show that an isotopic Mooney–Rivlin model cannot adequately represent arterial elastin. The neo-Hookean model, with coefficient 162.57
(
±
115.44
)
kPa
for autoclaved and 76.94
(
±
27.76
)
kPa
for alkali-extracted samples, fits the uniaxial data better. Autoclaved elastins also show linear stress–strain response and equal stiffness in circumferential and axial directions suggesting equal number of layers in these directions and that elastin may help distribute tensile stresses during vessel inflation. Histology of autoclaved and control porcine arteries reveals axial elastin fibers in intimal and adventitial layers but circumferential medial fibers. We propose an orthotropic material symmetry for arterial elastin with two orthogonally oriented and symmetrically placed mechanically equivalent fibers. An exact form of the constitutive equation will be obtained in a future study.
Journal Article
Microscale wear behavior and crosslinking of PEG-like coatings for total hip replacements
The predominant cause of late-state failure of total hip replacements is wear-mediated osteolysis caused by wear particles that originate from the ultrahigh molecular weight polyethylene (UHMWPE) acetabular cup surface. One strategy for reducing wear particle formation from UHMWPE is to modify the surface with a hydrophilic coating to increase lubrication from synovial fluid. This study focuses on the wear behavior of hydrophilic coatings similar to poly(ethylene glycol) (PEG). The coatings were produced by plasma-polymerizing tetraglyme on UHMWPE in a chamber heated to 40°C or 50°C. Both temperatures yielded coatings with PEG-like chemistry and increased hydrophilicity relative to uncoated UHMWPE; however, the 40°C coatings were significantly more resistant to damage induced by atomic force microscopy nanoscratching. The 40°C coatings exhibited only one damage mode (delamination) and often showed no signs of damage after repeated scratching. In contrast, the 50°C coatings exhibited three damage modes (roughening, thinning, and delamination), and always showed visible signs of damage after no more than two scratches. The greater wear resistance of the 40°C coatings could not be explained by coating chemistry or hydrophilicity, but it corresponded to an approximately 26–32% greater degree of crosslinking relative to the 50°C surfaces, suggesting that crosslinking should be a significant design consideration for hydrophilic coatings used for total hip replacements and other wear-dependent applications.
Journal Article
Viscoelastic properties of plasma-treated low-density polyethylene surfaces determined by nanoscale dynamic mechanical analysis
Nanoscale dynamic mechanical analysis (nanoDMA) was used to determine changes in surface viscoelastic properties of low-density polyethylene (LDPE) due to Ar plasma treatment. The experimental results show that the exposure of LDPE to high-power plasma produces a more solid-like response compared to low-power plasma. In addition, high-power plasma treatment results in permanent modification of the near-surface microstructure of LDPE, while low-power plasma treatment yields a microstructure that exhibits time-dependent viscoelastic properties. The results of this study show that nanoDMA is an effective method for evaluating changes in surface viscoelastic properties of polymers due to modification of the near-surface microstructure by inert plasma treatment.
Journal Article
Introduction to Engineering Design for Freshman: Implementation of Leadership and Service Learning for Broadening Engineering Ingenuity
Engineering Design and Analysis is a course that provides first year students an
Conference Proceeding
Viscoelastic properties of plasma-treated low-density polyethylene surfaces determined by nanoscale dynamic mechanical analysis
Nanoscale dynamic mechanical analysis (nanoDMA) was used to determine changes in surface viscoelastic properties of low-density polyethylene (LDPE) due to Ar plasma treatment. The experimental results show that the exposure of LDPE to high-power plasma produces a more solid-like response compared to low-power plasma. In addition, high-power plasma treatment results in permanent modification of the near-surface microstructure of LDPE, while low-power plasma treatment yields a microstructure that exhibits time-dependent viscoelastic properties. The results of this study show that nanoDMA is an effective method for evaluating changes in surface viscoelastic properties of polymers due to modification of the near-surface microstructure by inert plasma treatment.
This investigation shows that inert plasma treatment can significantly modify the surface properties of polymers and that nanoDMA can differentiate between viscoelastic behaviors of untreated and plasma-treated polymer surfaces.
Report