bluuebunny/crossref_metadata_2025 huggingface dataset:
Damping Characteristics of Laminated Composite Beam With Multi-Separated Adhesive Cores
Authors: Dewa Hiromi , Sasaki Ryohko
Published: November 2021

The laminated composite steel sheets bonded by the structural adhesive are widely used as vibration damping structure members. These sheets are bonded in the full face in the usual application. The damping characteristics of these sheets are expected to improve, if the adhesive core are multi-separated, by increasing the strain energy dissipation at each edge of the core separated.

In this report, the damping characteristics of a five-layer composite beam with fixed end, in which adhesive core layers are separated equally, are evaluated by strain energy analysis. The results reveal that the damping characteristics of the beam with such treatment increase 50 ∼ 100% in comparison with the non-separated ones except for the adhesive with extremely small modulus of rigidity. We also show that there exist an effective number of separation. Furthermore, the damping characteristics of the beam which core layers are separated optimally are improved more than those with the cores separated equally. These analytical results are verified by means of an impact test.
Elasto-Plastic Finite Element Stress Analysis of Thermoplastic-Matrix Symmetric Cross-Ply Plates With Square Hole
Authors: Arslan Nurettin , Turgut Aydın , Sancaktar Erol
Published: November 2021

In this study, elasto-plastic stress analysis of symmetric cross-ply reinforced thermoplastic (PVC) matrix composite laminated plates with square hole is presented. A two-dimensional computer program is developed for elasto-plastic stress analysis of laminated plates by FEM. The thermoplastic matrix is reinforced using long stainless steel fibers. The composite plates are manufactured by using molds under the action of 2 MPa pressure, and heating up to 200 °C. The laminated plate with square hole consists of four reinforced layers bonded symmetrically in ([θ/-θ]2) cross-ply configuration. A first–order shear deformation theory, and nine node Lagrangian finite element method are used in analysis. The applied in-plane load, and the layer orientation angle are varied to obtain the corresponding variation of residual stresses, and the expansions of plastic regions for various cases.
Effect of Interface Damage on Fatigue Crack Growth for SiC Fiber-Reinforced Ti-15-3 Matrix Composite
Authors: Tanaka Yoshihisa , Liu Yu-Fu , Masuda Chitoshi
Published: November 2021

The fatigue crack growth behavior in SiC (SCS-6) fiber reinforced Ti-15-3 matrix alloy composite subjected to a constant tension-tension loading mode was studied using single edge specimen in 2 × 10−3 Pa vacuum at 293 and 823K, with a frequency of 2 Hz, and a stress ratio of R = 0.1. Direct measurement of the fatigue crack length, and the crack opening displacement along the crack wake during the test were carried out by scanning electron microscope (SEM). The increase in the test temperature was found to lead to a decrease in the fatigue crack growth rate. The degradation of bridging fibers in the crack wake was severe for T = 293K, and this behavior was dependent of the test temperature. Fine particle-like debris was found on the fracture surface in the region of crack propagation in specimens tested at T = 823K. This is thought to be caused by the interface wear behavior. The crack opening displacement along the crack wake tested at T = 823K decreased with increasing crack length, and this tendency is dependent on the applied stress range. The associated increase in the crack tip shielding is explained on the basis of the crack closure due to the matrix relaxation by fatigue creep and the interface wear behavior.
Strength Simulation of Woven Fabric Composite Materials With Material Nonlinearity Using Micromechanics Based Model
Authors: Tabiei A. , Song G. , Jiang Y.
Published: November 2021

The objective of the current investigation is to predict failure strength of woven composites, which considers the two-dimensional extent of woven fabric, based on micro-mechanics. The formulation has an interface with nonlinear finite element codes. At each load increment, global stresses and strains are communicated to the representative cell and subsequently distributed to each subcell. Once stresses and strains are associated to a subcell they can be distributed to each constituent of the subcell (i.e. fill, warp, and resin). Consequently micro-failure criteria (MFC) are defined for each constituents of a subcell and the proper stiffness degradation is modeled. Different stages of failure such as warp transverse failure, fill transverse failure, failure of pure matrix in longitudinal and shear, shear failure in fill and warp, and fiber in fill and warp in longitudinal tension are considered. Good correlation is observed between the predicted and the experimental results presented in the published literature. This material model is suitable for implicit failure analysis under static loads and is being modified for explicit finite element codes to deal with problems such as crashworthiness and impact.
Finite Element Analysis of a Test Specimen for Adhesion of Bone Cement to Steel Implants
Authors: Chhabra Nitin , Nicholson David W. , Chew Larry , Desai Vimal , Raab Simon
Published: November 2021

Stable fixation of an orthopaedic implant to bone cement is critical to long term stability and durability in joint replacement. Poor interfacial bonding between metal and bone cement also leads to the formation of a nonadherent fibrous capsule in both soft and hard tissues, which can result in micromovement at the implant-tissue interface and ultimate failure of the implant. It is believed that some of the difficulties encountered by metallic implant devices can be reduced by the use of bioactive materials on the implant surface. In the current study MMA/HEMA coating, at a nominal thickness of 2mm, is present at the bone cement-metal interface. The MMA/HEMA coating is in the development stage. The goals of the present study are to assess the strength of the adhesive bond under loading and to assess its effectiveness with respect to increasing the osteoconductivity of the implant.
Modelling of Mechanically Regulated Tissue Formation Around Bone-Interfacing Implants
Authors: Simmons Craig A. , Meguid Shaker A. , Pilliar Robert M.
Published: November 2021

The clinical success of bone-interfacing orthopaedic and dental implants is dependent on adequate fixation of the implant by mechanical interlock with ingrown bone tissue (i.e., functional osseointegration). The rate and reliability with which osseointegration is achieved are influenced by a number of factors, including the surface geometry of the implant (Thomas and Cook, 1985; Simmons et al., 1999). However, the mechanisms by which implant surface geometry influences initial bone formation remain unresolved. Identifying the factors that allow bone-interfacing implants to osseointegrate more rapidly and reliably should lead to improvements in their use and design.
Core Technologies for the Enabling of Tissue Engineering
Authors: Nerem Robert M.
Published: November 2021

There is a new, emerging area of technology which has the potential to revolutionize the medical implant industry. This is tissue engineering or what I call the engineering of living tissues. The definition of this new, emerging area is the development of biological substitutes and/or the fostering of remodeling and regeneration, with the purpose being to replace, repair, maintain, and/or enhance tissue function.
Delivering a Safe and Effective Cellular Product
Authors: Schaeffer Susan
Published: November 2021

Apligraf® is a viable, bi-layered skin construct containing purified Type I bovine collagen and viable allogeneic human fibroblast and keratinocyte cells isolated from infant foreskin tissue. It is classified as a medical device in the United States and has been shown to be safe and effective in the treatment of venous stasis ulcers. Production of a living skin tissue presents unique challenges because of the number of diverse raw materials involved in its manufacture. Critical components such as collagen, cell banks, serum and media supplements are subjected to rigorous and costly testing to ensure that they are free of pathogens and impurities. Approaches to the quality challenges presented in the manufacture of Apligraf® will be discussed below.
Microstructural Factors in Neocartilage Function
Authors: Lewis Jack L.
Published: November 2021

Tissue engineering of cartilage and other connective tissues is a highly active area of research, motivated by the considerable medical need and commercial potential. Tissue with biological properties and biochemical composition similar to cartilage have been generated in laboratory cultures and animal models, and one method is being used in patients. Throughout the early development of regenerated cartilage, the focus has been on getting something to grow that is biochemically like cartilage and fills defects with tissue that visually looks like cartilage and holds up mechanically over the short term. The issues of cell source, culturing conditions, and scaffolds have also been addressed. However, all of the tissues generated have structure and microstructural organization that are not like natural cartilage. Although the clinical performance of the regenerated tissue appears promising, experience with prior regenerated tissue and the fact that the tissue is abnormal gives concern about the long term performance of the regenerated cartilage and the influence of activity level on this performance. Its long term mechanical properties are suspected to be inadequate. Future developments in this area will need to both enhance the mechanical characteristics of the regenerated tissue and develop methods and criteria for evaluating the tissue that is generated. Our work on matrix assembly by chondrocytes has been directed towards these ends. The goal has been to understand the microstructural basis for mechanical properties in tissue generated by chondrocytes in culture, develop methods to alter and control the microstructure, and build both experimental and theoretical models that allow evaluating the connection between microstructure and macroscopic properties. This is similar to a materials science approach which, we believe, will be one approach to the second generation of engineered tissues. The approach and results to date on tissue generated by chondrocytes will be described in this presentation. A specific question related to collagen network microstructure will be used to illustrate this approach.
Biocompatible Scaffolds for Engineered Arteries
Authors: Niklason L. E. , DuLaney T. V. , Moats A. K. , Mitchell S. , Prabhakar V.
Published: November 2021

Because of the tremendous clinical need for small caliber (< 6 mm diameter) arterial replacements, multiple approaches have been developed to culture biological arterial grafts both in vivo and in vitro. We have developed an approach that utilizes autologous smooth muscle and endothelial cells that are expanded in culture and then seeded onto rapidly degrading polyglycolic acid (PGA) scaffolds. The seeded tubular scaffolds are cultured under conditions of pulsatile radial stress to simulate the native hemodynamic environment. However, the effects of the type of culture scaffold on the phenotype and properties of tissue engineered vessels has not been investigated.
Materials Processing Technology for an Acellular Artificial Skin
Authors: Cahn Frederick
Published: November 2021

Artificial skin is a bilayer skin replacement system designed to regenerate dermal tissue. Prior to the commercial availability of artificial skin, surgically created wounds that cannot be closed by primary means (such as excising deep partial or full-thickness burns), had to be treated with autograft; a graft of the patient’s own skin harvested from a healthy donor site. This is because the dermal layer of skin cannot regenerate functional tissue spontaneously; instead, scar tissue forms. When applied surgically to a clean, excised wound bed, autograft becomes permanently engrafted, that is, it becomes permanently affixed to the underlying tissue and vascularized. However, autograft has serious drawbacks, including the creation of a donor wound, which has its own significant morbidity, and its unavailability in sufficient quantity in patients with large wounds.
Towards a Mechanism for Bioprosthetic Valve Failure
Authors: Vesely Ivan , Barber J. Edward , Mako W. John , Ratliff Norman B.
Published: November 2021

Porcine bioprosthetic valves are commonly used to replace the native cardiac valves when they become diseased and dysfunctional. One class of bioprosthesis consists of whole pig aortic valves, tanned in glutaraldehyde and mounted on plastic or wire frames. These devices work very well in the short term (< 5 years) but eventually begin to fail gradually and typically do not last more than 15 years [1]. Many have tried to elucidate a mechanism of bioprosthetic valve failure, but little progress has been made, until recently. Historically, calcification has been thought to be the primary mechanism of bioprosthetic valve failure [2]. Recently, however, it has become recognized that mechanical damage to bioprosthetic valves can occur independently from calcification [3]. This shift in opinion has been supported by a number of observations. For example, Purinya et. al. [4] have shown that after four years of implantation, bioprosthetic valve explants have lower failure stresses and fail at greater strains than fresh porcine bioprostheses. Similar observations have been made in valves fatigued in vitro [5]. Others have shown that these mechanical changes are accompanied by biochemical changes in the collagen fibers [6]. We have shown previously in preliminary studies that glycosaminoglycans (GAGs) are lost from implanted bioprosthetic valves [7]. Since GAGs are responsible for maintaining tissue viscoelasticity, loss of GAGs would have detrimental effects on tissue mechanics. In separate studies, we have demonstrated that damage to elastin can also have detrimental effects on tissue mechanics, and on valve durability as a whole [8].
Large Displacement Flexural Properties of Tissue Engineered Heart Valve Scaffolds
Authors: Sacks Michael S. , Kaushal Sanjay , Mayer John E.
Published: November 2021

The need for improved heart valve prostheses is especially critical in pediatric applications, where growth and remodeling are essential. Tissue engineered heart valves (TEHV) have functioned in the pulmonary circulation of growing lambs for up to four months [1], and thus can potentially overcome limitations of current bioprosthetic heart valves. Despite these promising results, significant questions remain. In particular, the role of scaffold mechanical properties in optimal extra-cellular matrix development, as well as TEHV durability, are largely unexplored. We have previously demonstrated flexure testing as a sensitive and critical test for BHV tissue mechanical property evaluation [2]. The following study was conducted to determine the feasibility of using this technique to provide fundamental information required for optimizing TEHV scaffold designs.
Flow-Dependent Luminal Deposition of Microspheres in Porcine Carotid Arteries Ex Vivo
Authors: Enyinna Onyekachi C. , Chesler Naomi C.
Published: November 2021

Throughout the cardiovascular system, blood flow and pressure are unsteady and pulsatile, with oscillatory (zero-mean) flow in areas of bends and bifurcations (Ku 1997). Resulting hemodynamic forces have been proposed as a controlling factor for arterial wall permeability to atherogenic proteins such as low density lipoprotein (LDL). For example, Meyer et al. found that increased transmural pressure decreased LDL entrapment in the arterial media, and Lever and coworkers found that LDL entrapment was increased when stretching was prohibited by a restraining collar (Lever, et al. 1996; Meyer, et al. 1996).
A Device for Evaluating Laxity of the Thumb Carpometacarpal Joint
Authors: Soltz Michael A. , Koff Mathew F. , Balaguer Eric J. , Pawluk Robert J. , Strauch Robert J. , Rosenwasser Melvin P. , Ateshian Gerard A. , Mow Van C.
Published: November 2021

It has been proposed that ligamentous laxity promotes osteoarthritis of the thumb carpometacarpal joint. However, quantitative measurements of laxity for this joint have not been correlated with its incidence of osteoarthritis nor with other measures of degenerative changes such as joint congruence, surface remodeling, cartilage mechanical properties or biochemical composition. The goal of this study was to design and build a device for testing the laxity of the carpometacarpal joint, with the long-term aim of advancing our understanding of the etiology of osteoarthritis in this joint. This laxity tester has the ability to accurately measure the force-displacement response along the joint’s dorsal-volar, radial-ulnar, and distraction-reduction directions, as well as the torque-rotation response in pronation-supination. The compliance of the tester was evaluated and laxity curves were generated for a sample thumb carpometacarpal joint.
An Experimental Methodology to Evaluate the Rigidity of Penile Prostheses in Vitro
Authors: Wang Shyh-Jen
Published: November 2021

This work investigates the hardness and buckling force of penile prosthesis to further understand the rigidity of penile prosthesis before and after implantation. Evaluated herein are four prosthetic samples (inflatable 3, semi-rigid 1), five realities (inflatable 1, semi-rigid 4), and one after implantation of prosthesis. The hardness is measured with a hardness tester by pressing the tester’s indentor to the surface of the specimen. In addition, a patient after implantation is evaluated with respect to the hardness of penile versus various numbers of pumping. The buckling force of the prosthesis is also determined by a push-pull gauge and special designed sampling table. Results in this study demonstrate that although the inflatable prosthesis could only be pumped to a certain amount of hardness, hardness and buckling force correlate well with each other. After reaching the extreme hardness, prostheses can even be further pumped a few times. However, continuous pumping only puts more tension on the prosthetic material without increasing any hardness and could induce to mechanical failure of prosthesis. Results also indicate that the buckling force decreases with increasing length of the semi-rigid prostheses, and, then, enlarged when the prosthesis has a larger diameter. This in vitro non-invasive mechanical measurement of the rigidity in penile prosthesis can provide not only clinicians with further information about the penile prosthesis before implantation, but also the patients with more confidence in the prosthesis usage after implantation.
Stress-Dependent Effects of Platelet-Derived Growth Factor-BB on Fibroblast Migration and Traction Differ in Collagen and Fibrin
Authors: Shreiber David I. , Enever Paul A. J. , Tranquillo Robert T.
Published: November 2021

We used our novel assays of cell behavior in tissue equivalents to study the dose-response effects of PDGF-BB on RDF migration and traction in mechanically stressed and stress-free type I collagen and fibrin gels. PDGF-BB increased fibroblast migration significantly in all assays, but the effects on traction depended on the presence of stress and the nature of the ECM. PDGF-BB decreased fibroblast traction in stressed collagen gels, but increased traction in stress-free gels. No statistical conclusion could be inferred for stressed fibrin gels, and increasing PDGF-BB decreased traction in stress-free fibrin gels. These results demonstrate the complex response of fibroblasts to environmental cues, and point to opportunities to orchestrate cell behavior to affect the outcome of wound healing.
Fracture Patterns and Strain Information in Thoracolumbar Burst Fractures
Authors: Langrana Noshir A. , Harten Robert D. , Lin David C. , Reiter Mitchell F. , Lee Casey K.
Published: November 2021

A combined loading of axial compression and anterior shear on a spinal motion segment causes the severe form of burst fracture. Thoracolumbar motion segments were instrumented with a strain gage on the middle of the anterior wall and one near the base of the pedicles. Two samples were subjected to high-speed axial compression in the neutral position while two were tested in extension to maximize facet joint loading. The specimens tested in extension exhibited the more severe fracture pattern, indicated by failure of the middle column and an increase in interpedicular distance. Failure loads and ratio of strain at the base of the pedicles to strain at the anterior wall were higher in this group. The results suggest that the shear force transmitted through the facet joint and the pedicles to the posterior upper half of the vertebral body is an essential component of the injury mechanism.
Characterization of Porosity and Pore Size Distribution Changes in Human Compact Bone by Low-Field NMR
Authors: Ni Qingwen , King J. Derwin , Wang Xiaodu
Published: November 2021

Previous studies have shown that the overall porosity of bone has a significant effect on the mechanical strength of bone. In a comprehensive review on porosity of bone, Martin [1] described that small changes in porosity would lead to significant changes in the stiffness and strength of both compact and spongy bone. In a recently study, McCalden [2], reported that the porosity of bone has a significant effect to absorb energy during fracture. Since changes in numbers and sizes of these natural cavities are directly related to the remodeling processes and biomechanical properties of bone, a direct sensing technique to detect such changes in bone has been long wanted.
The Inspiratory and Expiratory Flow in Distensible Tracheostenosis Model
Authors: Sera Toshihiro , Satoh Sunao , Horinouchi Hirohisa , Kobayashi Kohichi , Tanishita Kazuo
Published: November 2021

To identify the possible mechanism of wheeze generation in the tracheostenosis, we measured the inspiratory and expiratory flow in the realistic model reconstructed based on CT data of patient. Trachea consists of tracheal cartilage rings and smooth muscle, which influence the localized variation of distensibility of model airway. The localized variation of distensibility was achieved by the varied thickness of silicone rubber based on the elastic modulus measured for the pig airway. The Reynolds number was 1100, and both inspiratory and expiratory flow were disturbed by the stenosis. The turbulence intensity for the distensible model is moderated compared the rigid model.
Development of Biomechanical Cervical Spine Physical Models
Authors: Milkowski Lisa M. , Crockett Robert S. , Kumaresan Srirangam
Published: November 2021

A methodology using rapid prototyping (RP) to produce discrete-region and continuous gradients in material mixtures to represent cervical spine vertebra is presented. Composites are created by using a RP lattice pattern as a host for filler materials. With additional process steps to replace the RP lattice epoxy, composites are also created with two different matrix materials creating differing local property regions. The internal structure thickness of the lattice pattern is varied in a continuous manner to produce composites ranging from the host material to the filler material. Results from initial samples are presented.
Three-Dimensional Woven Composite Materials for Impact Protection: Application to Soccer Shin Guards
Authors: Francisco Anthony C. , Leung Jeffrey C. , Moutos Franklin T. , Guilak Farshid
Published: November 2021

Soccer shin guards have been shown to provide significant protection against minor injuries such as scrapes and contusions. However, several studies suggest that serious injuries such as tibia fractures may still occur despite the use of shin guards [1]. The majority (79%) of such fractures are minimally displaced, suggesting that the injuring impacts are slightly above the fracture tolerance of bone [1]. In this respect, shin guards with improved impact properties may be able to decrease the risk of serious injuries in soccer. Impact testing of shin guards has shown that some designs and materials provide better protection than others [2]. Generally, a shin guard reduces impact by using a stiff shell over which to distribute the impact and a compliant material that absorbs impact energy. Unfortunately, the protective physical characteristics of guards correlate best with increased weight and thickness, factors that conflict with players’ preferences for lighter, more comfortable guards.
Inverse Estimation of the In Vivo Mechanical Properties of the Human Cornea
Authors: Chang Shou-sung , Pinsky Peter M.
Published: November 2021

Various forms of refractive surgery for vision correction have come into clinical practice in which the corneal tissue is either incised, removed, added to, or redistributed. The outcomes of these procedures must be to a large extent determined by the intrinsic mechanical properties of the major structural layer of the cornea, the stroma1. If these mechanical properties, principally the Young’s modulus and shear modulus, are established for the human cornea, it will be possible to include them in a finite element model of the stroma that can help predict the outcome of keratorefractive procedures. In this study an opto-mechanical testing device was developed to measure the contour of a cornea deformed in situ by a mechanical probe. A nonlinear finite element model of the cornea was then constructed to simulate the experiment for use in inverse estimation of the in vivo Young’s and shear moduli of an individual eye.
Sensitivity to Pore Geometry of Virus Transmission Through Latex Channels: Experimental Analysis
Authors: Myers Matthew R. , Lytle C. David , Routson Licia B.
Published: November 2021

Previously published measurements of virus transmission through a channel comprised of two planar sheets of latex material displayed an unexpectedly high transmission rate for large virus residence times in the channel. Additional experiments demonstrated that the elevated transmission rate can be explained as a high sensitivity of virus transport to perturbations in channel geometry, for highly adsorptive viruses.
Contact Mechanics of Cell-Substrate Adhesion
Authors: Liu Kuo-Kang , Wan Kai-Tak
Published: November 2021

A thin-walled membranous capsule is adhered onto a rigid substrate by surface forces. In the presence of excessive osmotic pressure, the capsule will detach from the substrate due to membrane stretching. A simple energy balance is proposed to describe the adhesion mechanics.
Effect of Flow Rate on Properties of Resin Transfer Molded Disks
Authors: Olivero Kristian A. , Fuller Randal E. , Dhillon Inderbir S. , Altan M. Cengiz
Published: November 2021

The effect of flow rate on the mechanical properties of resin transfer molded disks is experimentally investigated. An experimental molding setup is constructed to fabricate fiber-reinforced, center-gated, disk-shaped composite parts. Disks are molded at different flow rates in order to observe the effect of this parameter on the mechanical properties of the final parts. Specimens are cut from different sections of the molded disks, and tested for strength and stiffness. Strength and stiffness are found to vary exponentially based on the maximum local fluid velocity during filling. Increased local velocity is found to reduce both the strength and stiffness of the molded parts due to increased voids induced by the faster moving fluid front.
Probabilistic Characterization of Fatigue Damage Data for Aerospace Materials
Authors: Orisamolu I. R. Wally
Published: November 2021

The development of stochastic models for representing the uncertainties present in a problem is a very important component of probabilistic reliability analysis. Stochastic modeling of engineering parameters require the determination of appropriate probability distribution functions and their associated statistical parameters. In cases that of practical interest, there are usually two or more random variables or processes involved, and hence it is further necessary to establish the correlations between the uncertain parameters or functions. The choice of stochastic models often influences the reliability values as well as the probabilistic sensitivity factors computed from analyses. This is especially so for probabilistic fracture mechanics and fatigue reliability calculations which constitute the cornerstone for durability and damage tolerance assessments.

The present paper reports the development of a methodology for probabilistic fatigue data characterization. The characterization utilizes raw fatigue damage (crack initiation or crack growth) data to determine the most appropriate probability distributions, statistical parameters and confidence bounds for the modeling parameters that are involved in fatigue damage initiation and propagation relations used in durability and damage tolerance prediction. Correlations between different parameters are also computed on the basis of well established deterministic models and standards (such as the ASTM E647-93 standard) that have been widely accepted in the industry. Statistical tests are implemented on the basis of Kolmogorov-Smirnov measures of model acceptability. The probabilistic models are determined using both the method of moments (MOM) and maximum likelihood estimators (MLE) and are packaged within the framework of a user-friendly computational tool (PRADAC). Illustrative practical examples are presented to demonstrate the utility of this probabilistic pre-processing computational tool and the important effects on fatigue reliability prediction of aerospace structural components.
Probabilistic Fatigue Damage Assessment for Small Crack Growth
Authors: Zhao Zhengwei Jack , Orisamolu Irewole Wally
Published: November 2021

Fatigue and fracture are typical random phenomena due to various uncertainty sources, including material property, initial flaw and crack shape, structural configuration and geometry around crack tip, load fluctuation, and other environmental factors. As contrast to the most commonly used probabilistic fatigue growth models, which are built based on simplified fatigue crack growth law, a framework of probabilistic fracture mechanics based fatigue damage assessment methodology for small crack propagation is presented here. The proposed modeling is developed based on a comprehensive fatigue crack growth model, which accounts the effect of crack aspect ratio, stress ratio, and crack closure and retardation. Due to the complicated nature of the fatigue damage modeling adopted, a high non-linear limit state function with discontinuity resulted from physical domain jumping and overlapping are encountered. The advanced fast probability integration techniques in conjunction with response surface methodology and Monte Carlo simulation are used and the accuracy of the analysis is verified. The interface between probabilistic analysis package and the deterministic fracture mechanics analysis program is developed for the purpose of uncertainty propagation. The probability of failure of fatigue damage is computed first. The statistical characteristics of estimated fatigue life and critical crack size are obtained and presented through CDF/PDF curves. The sensitivity analysis is also performed, which provides an indication of the order of importance for the random variables considered. The results of the study have shown robustness and efficiency of the probabilistic analysis to deal with the real world challenge of uncertainty modelling, propagation, and quantification. Currently, possibility to combine the subject probabilistic damage assessment methodology with reliability updating techniques is under the investigation. The successfulness of the presented research activity will address an important issue of quantitative risk analysis for aging structures subjected to accumulative material damage.
Analysis of the Stem-Sleeve Interface in a Modular Titanium Alloy Femoral Component for Total Hip Replacement
Authors: Kurtz S. M. , Srivastav S. , Dwyer K. , Ochoa J. , Brown S.
Published: November 2021

Modular femoral components for total hip arthroplasty have been clinically available since the 1980s. Despite the widespread use of interlocking tapers in hip prostheses, researchers have raised concerns about fretting, which has been clinically observed at the tapered modular interface of retrieved femoral heads and the trunions, as well as at the stem-sleeve junctions of retrieved femoral stems. Fretting can lead to degradation of the modular interfaces by the mechanisms of fretting wear, fretting corrosion, and fretting fatigue, all of which have potentially negative consequences for a total hip arthroplasty.
Near Net-Shape Fabrication of Hydroxyapatite and HA-Alloy Composites
Authors: Litsky Alan S. , Sandhage Ken H. , Saw Eadan , Briggs Susahn , Gallagher Patrick K.
Published: November 2021

Near net-shaped bodies of hydroxyapatite (HA), Ca10(PO4)6(OH)2, have been fabricated by the oxidation of solid, metal-bearing precursors. High-energy mechanical alloying was used to produce an intimate powder mixture of metallic calcium and calcium pyrophosphate, β-Ca2P2O7, (4:3 ratio) that possessed an overall stoichiometry consistent with HA. The milled Ca-Ca2P2O7 mixtures were sufficiently malleable to allow for compaction, pressing, and machining into shaped green bodies with relatively high densities (80–86%). The green bodies were converted into phase-pure HA through heat treatments at 500–600° C in dry oxygen (for Ca oxidation), 850° C in moist oxygen or air (for HA formation), and 1100–1150° C in moist oxygen or air (for sintering). The offsetting volume changes associated with calcium oxidation (Vm[CaO] < Vm[Ca]) and subsequent HA formation (Vm[HA] > 4Vm[CaO] + 3Vm[Ca2P2O7]) resulted in HA bodies that retained the shapes and dimensions of the metal-bearing precursors to within a few percent. Current work is focused on the formation of interpenetrating composites of HA and implant grade cobalt-chromium alloy by similar methods.
Failure of Ceramic Coatings on Soft Substrates
Authors: Lawn Brian R.
Published: November 2021

A design concept for potentially hard damage-resistant ceramic coatings on relatively soft substrates is proposed. Such coating structures are of direct relevance to biomechanical structures, especially teeth and dental crowns. In this study failure modes in bilayers and trilayers with relatively hard, brittle coating outerlayers on soft, tough substrate underlayers are evaluated. Coating/substrate systems of interest include ceramic/ceramic, ceramic/metal, and ceramic/polymer. A key element of these structures is a well-bonded interface, to prevent delamination during stressing. The objective is to arrest intrusive coating cracks in a tough sublayer, rather than merely to deflect them along a weak interface.
Clinical Performance: A Reflection of Damage Accumulation
Authors: Rekow E. Dianne , Thompson Van P.
Published: November 2021

Clinical performance of an prosthesis is directly dependent on damage introduced during fabrication and during fatigue loading associated with function. The relation between shaping damage and fatigue damage on clinical performance of all-ceramic dental crowns was investigated. Materials used commercially for all-ceramic crowns and investigated in this study included a series of different microstructures of machinable glass ceramics (Corning), aluminas and porcelains (Vita Zahnfabrik), and zirconias (Norton).
The Tooth as a Basis for Biomimetic Design
Authors: Thompson Van P. , Kao Stephen , Kirkpatrick Ivory
Published: November 2021

Teeth are uniquely capable of withstanding high forces (>200 N) with small contact area (< 0.5 mm2) and a high number of fatigue cycles (> 107) with little evidence of damage. Yet the tooth is comprised of an outer very brittle, anisotropic, highly crystalline enamel layer supported by an inner soft, but tough dentin. These structures are joined by a small (appoximately 30 microns wide) transition zone called the dento-enamel junction (DEJ). The DEJ plays a critical role in transfer of stress across the layers of the tooth. How the enamel-dentin complex (EDC) comprised of these layers and the DEJ is able to withstand the high contact loads and high cycle fatigue is not well understood. An understanding of the interplay of the various components would serve as the basis for design of dental ceramic or resin based composite crowns capable of service lives approaching those on natural teeth. Current all ceramic crowns have high failure rates (1–5% per yr) on molar teeth and improved performance is required before CAD-CAM restorations can be successful.
Deformation and Failure in Stochastic Fibrous Networks: Scale, Dimension and Application
Authors: Sastry A. M. , Wang C. W. , Berhan L.
Published: November 2021

Simulating local deformation and failure in stochastic fibrous materials is of interest in a number of key materials technologies, including papers and filters, electrochemical substrates, and biomaterials. The local initiators of both deformation and damage are of key technological interest as they govern the properties of networks, and allow rational design of networks once variance in global properties is reasonable predicted.

Here, we examine several key microphenomena associated with failure of these networks, and further, map loading and environmental conditions under which each dominate. These mechanisms include tensile and bending failures, failures due to stress risers resulting from the way in which particles are bonded, and failures due to morphological changes (such as corrosion processes in batteries).

We also describe stochastic approaches for particle/fiber network generation, including the tracking of key geometric features. We show that single-parameter distribution functions rarely capture the real morphological variability seen in engineered microstructures, and suggest a methodology for more robust descriptions. We also present results of both large and small scale simulations of failure progression, and describe the importance of scale effect in numerical methods.
Advances in Probabilistic Methods
Authors: Cruse Thomas A.
Published: November 2021

Advances in probabilistic methods to support the design of mechanical systems is now moving to the engineering desktop. Basic modeling strategies are understood and in use in many applications. There are still issues to be resolved in the application of these methods to reliability critical applications. Some of these issues will be highlighted. At the same time, the design of complex aerospace systems requires more than just probabilistic methods as we know them now. The presentation will review a recent study by its author on the development and application of non-traditional and non-deterministic methods new methods to the life cycle design and analysis of extremely complex aerospace systems. Not only “traditional” mathematical analysis methodologies (such as mathematical optimization, Bayesian methods, or robust statistical design) are reviewed, but also “soft” or “non-traditional” methods (such as neural networks, fuzzy logic or genetic algorithms). In particular, emphasis will be given to the synthesis of many of these elements into the design systems of the future.
An Investigation of Fatigue in Polymer/Metal Composites
Authors: Kung E. , Mercer C. , Allameh S. , Popoola O. , Soboyejo W. O.
Published: November 2021

The fatigue behavior of Fe-Ni-base metal/polymer composites is discussed in this paper. These are proposed as self lubricating surfaces with the potential to replace conventionally lubricated pistons in automotive engines. Following a description of composite microstructure and basic mechanical properties, the paper examines the effects of polymer volume fraction on long fatigue crack growth. The effects of temperature on fatigue crack growth are then elucidated before presenting some initial fracture mechanics concepts for the prediction of fatigue life. The implications of the results are assessed for the design of durable surfaces.
Probabilistic Approaches to the Prediction of the Effects of Multiple Parameters on the Mechanical Properties of Gamma-Based Titanium Aluminides
Authors: Soboyejo A. B. O. , Ni Y. , Mercer C. , Soboyejo W. O.
Published: November 2021

Multiple parameter expressions of the form, Y = αoXiαi (where αo and ai are empirically-derived exponents), are presented for the prediction of the effects of multiple parameters, Xi, on the mechanical properties, Y, of gamma-based titanium aluminides. The multiparameter expressions, obtained via multiple linear regression techniques, provide single functions for the prediction of the combined effects of composition, microstructure and temperature on basic mechanical properties such as yield/ultimate tensile strength, plastic strain to failure and fracture toughness. Approximate exponential reliability functions are also presented for the prediction of the probabilities of failure/survival at various possible stress/strain/stress intensity factor levels. The use of Bayes theorem is proposed for the improvement of the exponential reliability functions as more data becomes available. Simplified analytical methods are presented for the prediction of the combined errors of prediction. The paper highlights the need for multiparameter probabilistic mechanics approaches to the prediction of basic mechanical properties.
30 Blood-based glycoprotein signatures in advanced non-small-cell lung carcinoma (NSCLC) receiving first-line immune checkpoint blockade
Authors: Lindpaintner Klaus , Cheng Michael , Prendergast Jillian , Normington Karl , Wong Maurice , Xu Gege , Cong Xini , Rice Rachel , Lawrence Marissa , Michael Kesi , Serie Daniel
Published: November 2021

Background

Immune checkpoint blockade is an integral component of first-line therapy for most patients with ad-vanced non-small cell lung cancer (NSCLC), however individual patient outcomes are highly variable and improved biomarkers are needed. Protein glycosylation is an emerging mechanism of immune evasion in cancer. We examined blood-based glycopeptide signatures in a cohort of advanced NSCLC patients treated with first-line immune checkpoint blockade.

Methods

Pretreatment blood samples were obtained from 46 advanced NSCLC patients treated with first line pembrolizumab or pembrolizumab + carboplatin + pemetrexed. All patients provided written in-formed consent to the institutional review board–approved protocols (#02–180 and 13–367) at the Da-na-Farber/Harvard Cancer Center (Boston, MA), and the study was conducted in accordance with the Declaration of Helsinki. Samples were analyzed using an advanced glycoproteomics platform (Inter-Venn Biosciences) that combines ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry with a proprietary neural-network-based data processing engine. 409 individual glycopeptide (GP) signatures derived from 67 abundant serum proteins were analyzed and correlated with overall survival (OS) and other clinical outcomes.

Results

We identified 30 GPs with abundance differences using a False Discovery Rate (FDR) threshold of 0.05. Using the 5 most predictive GP markers, we created a multivariable model for OS by generating leave-one-out cross-validation (LOOCV) scores and determining an optimized cutoff value of -0.83 (range: -2.2 - 3.4) for these scores using Harrell’s concordance index. The median overall survival was 2.8 years for patients (n=14) whose GP classifier value was above the cutoff and 0.8 years for patients (n=32) whose GP classifier value was below the cutoff (HR 7.4, 95% CI 1.7–32.1, p=0.007) The model’s perfor-mance was not affected by sex, age, or treatment regimen.

Conclusions

Blood-based glycopeptide signatures may represent novel, non-invasive biomarkers of clinical out-come to first-line immune checkpoint blockade in advanced NSCLC. Additional research is needed to validate these findings in larger cohorts and to explore potential applications relevant to clinical decision-making.

Ethics Approval

The study obtained ethics approval from the institutional review board (approved protocol #02–180 and 13–367) at the Dana-Farber/Harvard Cancer Center (Boston, MA), and the study was conducted in accordance with the Declaration of Helsinki.

Consent

All patients provided written informed consent to the institutional review board–approved protocols (#02–180 and 13–367) at the Dana-Farber/Harvard Cancer Center (Boston, MA), and the study was conducted in accordance with the Declaration of Helsinki.
53 Unique insights into PDAC development revealed by both InSituPlex® and imaging mass cytometry
Authors: Quong Andrew , Rees Mark , Maclean Kirsteen , Manesse Mael , Nieto Jordan , Esch Amanda , Fleury Devan , Wharton Keith , Chatterjee Gourab
Published: November 2021

Background

Pancreatic cancer remains a deadly disease due to difficulties hindering its early diagnosis, giving way to metastasis of the tumor and resulting in poor prognosis. While there are many neoplasms of the pancreas, pancreatic invasive ductal adenocarcinoma (PDAC) is the most common and treatment options are few, with poor overall survival. Aggressive surgeries such as the Whipple procedure coupled to systemic chemotherapy is one of the few treatment options. Recently, several publications have demonstrated improved outcomes with the inclusion of immunotherapy to cytotoxic drug combinations in some patients, however optimally selecting patients as candidates for immunotherapy-chemotherapy combinations remains a critical challenge. The complexities of the tumor microenvironment have been implicated in the failure of chemotherapy, radiation therapy, and immunotherapy. The tumor microenvironment of PDAC is especially rich with multiple interactions between pancreatic epithelial/cancer cells, stromal cells, immune cells and the extracellular matrix (ECM). PDACs are characterized by a complex ECM of desmoplastic reaction consisting of an extensive and dense fibrotic stroma that surrounds and infiltrates clusters of malignant epithelial cells, together with the loss of basement membrane integrity and an abnormal vasculature.

Methods

In the present study we demonstrate a tissue phenotyping workflow combining three complementary methods that can unravel novel insights in the complex tumor microenvironment. This novel translational workflow delivers tissue morphology information, spatial phenotyping of immune cell population on whole slides, and high dimensional imaging in selected regions of interest (ROI), by combining H&E, multiplex immunofluorescence (mIF), and Imaging Mass Cytometry (IMC™).

Results

The use of the InSituPlex® UltiMapper® I/O PD-L1 kit enabled the streamlined combination and alignment of H&E and mIF data, leading to the strategic selection of relevant ROIs, while utility of IMC technology enabled downstream imaging of 35 protein markers associated with the ECM in the selected ROIs to provide a deeper understanding of the tumor microenvironment.

Conclusions

The incorporation of advanced multiplex imaging platforms such as mIF and IMC with routine H&E workflow in tumor biology can deliver some of the much-needed insight into tumor morphology, cellular composition, cellular functions, and cell-cell interactions and paves the way for potentially improved clinical prognosis and efficacy prediction in patients with cancer.