bluuebunny/crossref_metadata_2025 huggingface dataset:
Carpal Kinematics During Radial Ulnar Deviation
Authors: Patterson Rita M. , DaSilva Manuel F. , Viegas Steven F. , Goslings J. C.
Published: December 2021

This study investigates carpal kinematics during a wrist Radial/Ulnar deviation motion using high speed video data acquisition. A cadaver forearm was stabilized allowing unconstrained excursion of the wrist for passive range of motion.

Capitate/radius and 3rd metacarpal/radius angles were calculated to determine which measurement would be best for determining global wrist angle. The average difference in angle between the capitate and third metacarpal was 1.3 ± 1.3 degrees with a maximum difference of 5.0 degrees. Hence, the capitate-third metacarpal joint can be considered ridged.

The proximal wrist joint (R/L angle) contributed 15.1 degrees to global wrist radial ulnar deviation and the midcarpal joint (C/L angle) contributed 20.6 degrees to global wrist radial ulnar deviation (43.0% and 55.8%, respectively, of the 36.4° total wrist ROM). Radio-scaphoid angles averaged 16.8 degrees (46.5% of the 36.4° total wrist ROM). The radio-lunate joint and the capito-lunate joint contribute equally to global wrist radial ulnar deviation.

This new combination of motion analysis and 3D reconstructions of CT images affords a high speed, dynamic analysis of kinematics. It shows that normal carpal kinematics, during wrist radial/ulnar deviation, does not have an instantaneous screw axis (ISA) fixed in or limited to the capitate. In addition, the ISA data provides evidence that translational motion is a real and measurable component of normal carpal motion. This would change the understanding of carpal kinematics from previous studies, which suggested that the center of rotation was fixed in the capitate.
Finite Element Analysis of MOD Cavity Depth in a Restored Tooth
Authors: Lin Chun-Li , Chang Chih-Han , Wang Chau-Hsiang , Lee Huey-Er
Published: December 2021

Numerous studies have confirmed a correlation between the restored tooth fracture and the cavity design parameters. Improper geometric design of cavity could increase the unfavorable stresses of remaining tooth structure and cause fracture. However, the quantitative guideline for cavity preparation is unclear. This study developed an automatic mesh generation tool and employed finite element method to examine the stress distribution with different cavity depth designs in class II MOD restoration. The results indicated that for deeper cavity designs the unfavorable stress gradient was evident, therefore, the existence of a pulpal wall is essential.
Finite Element Analysis of Fiber Composite Dental Bridges: The Effect of Length / Depth Ratio and Load Application Method
Authors: Nowak Michael D. , Haser Kim , Goldberg A. Jon
Published: December 2021

Work is continuing in the evaluation of orthotropic fiber reinforce composites for use in the construction of dental bridges. Finite Element Analysis (FEA) models were constructed based upon mechanical testing of end clamped specimens center loaded with a metal indenter. Various length / depth specimens were evaluated in the elastic range, with a variety of load magnitudes.

Separate FEA models utilized single point loading, distributed loading, and the construction of a model indenter. Deflections at the loading point demonstrated that all models presented similar findings to those seen in mechanical testing. The similarity of results between the single loading point and the indenter FEA models suggest that either is reasonable for elastic range testing. The significantly shorter CPU run times for the single force models suggest that this may be the best means by which to model orthotropic fiber reinforced dental composites in the elastic range.
Undergraduate and Graduate Design Projects
Authors: Devey Gilbert B.
Published: December 2021

The National Science Foundation (MSF) was established in 1950 as an Independent Agency of the Federal Government with the broad mission to promote and advance scientific progress in the U.S. This is accomplished primarily by supporting research and education in all disciplines of the natural and social sciences, mathematics, and engineering. Support is provided principally in the form of grants awarded on a competitive basis under a rigorous peer review process; NSF does not conduct research itself. In 1992, NSF defined a project eligible for support as bioengineering research as one “...with diagnosis or treatment-related goals, that applies engineering principles to problems in biology and medicine while advancing engineering knowledge is eligible for support. Bioengineering research to aid persons with disabilities is also eligible”.1 Bioengineering at NSF has two defined programs: 1 - “Biochemical Engineering”, and 2 - a two-component activity “Biomedical Engineering” (BME) and “Research to Aid Persons with Disabilities” (RAPD). Undergraduate and Graduate Design Projects is part of the RAPD component of the program.
Injury Criteria of Child and Adult Dummies
Authors: Sances Anthony
Published: December 2021

Human injury tolerance is difficult because of physical differences between humans and animals, dummies and cadaver tissue. Human volunteer testing has been done but at sub injurious levels (Stapp, 1986 and Ewing, 1972). Considerable biomechanical engineering and tissue studies exist for the adult human cadaver however little is available for the pediatric population (Kumaresan, 1999). A number of dummies have recently been made available principally for airbag testing to bridge the gap between the 50 percentile hybrid III male dummy and the 95 percentile male dummy. (Kleinberger. 1998) The air bag dummies including the 12-month old CRABI dummy, 3-year old Hybrid III dummy, 6-year old Hybrid III dummy, the Hybrid III small female, Hybrid II mid-size male and 95 percentile large male are discussed.
Beyond Whiplash: Impact Evidence in Severe Spinal Injury
Authors: Syson Stephen R.
Published: December 2021

Whiplash injuries often occur without noticeable damage to the interior of a vehicle, and only minor damage to the vehicle exterior. Severe spinal trauma is, however, almost always associated with a forceful head or torso contact. This paper is intended to help the investigator of a collision find and document physical evidence of a contact, in the event such a witness mark exists. A brief outline of a suggested investigation methodology includes the types of marks to look for, and how to hypothesize where to look.
Trends in the Design and Manufacture of Footwear
Authors: Thompson David E. , Dobson Gregory T. , Shaffer Howard , Cox Jordan J.
Published: December 2021

There are many new challenges facing the footwear industry as they seek to gain a technological advantage to offset the lower cost of production from the Pacific Rim. In fact, the use of technology in footwear is a very recent trend. There are many different approaches to the use of technology in footwear, and this panel seeks to highlight some of the issues involved and to raise the level of discourse in this important field. In addition to the manufacturing challenges within the industry, there are other critical new questions that are being discussed.
Low Velocity and Compression-After-Impact Response of Pin-Reinforced Sandwich Composites
Authors: Vaidya Uday K. , Kamath Mohan V. , Hosur Mahesh V. , Haque Anwarul , Jeelani Shaik
Published: December 2021

In the current work, sandwich composite structures with innovative constructions referred to as Z-pins, or truss core pins are investigated, in conjunction with traditional honeycomb and foam core sandwich constructions, such that they exhibit enhanced transverse stiffness, high damage resistance and furthermore, damage tolerance to impact. While the investigations pertaining to low velocity impact have appeared recently in Vaidya et al. 1999, the current paper deals with compression-after-impact studies conducted to evaluate the residual properties of sandwich composites “with” and “without” reinforced foam cores.

The resulting sandwich composites have been investigated for their low velocity (< 5 m/sec) impact loading response using instrumented impact testing at energy levels ranging from 5 J to 50 J impact energy. The transverse stiffness of the cores and their composites has also been evaluated through static compression studies. Compression-after-impact studies were then performed on the sandwich composites with traditional and pin-reinforcement cores. Supporting vibration studies have been conducted to assess the changes in stiffness of the samples as a result of the impact damage. The focus of this paper is on the compression-after-impact (CAI) response and vibration studies with accompanying discussion pertaining to the low velocity impact.
Evaluation of Heat Damage on B4C Particulate Reinforced Aluminum Alloy Matrix Composite Using Acoustic Emission Techniques
Authors: Shan D. , Nayeb-Hashemi H.
Published: December 2021

Aluminum alloys reinforced with B4C particle of average particle size of 10.5 μm and 20.9 μm were exposed to 535°C for various duration. The material degradation was evaluated by both mechanical and acoustic emission monitoring during tensile test. The micromechanisms of fracture changed from particle fracture and debonding, for as received specimens, to particle/matrix debonding after exposure to high temperature. The cumulative acoustic emission (AE) events during post heat exposure reduced with the increase of heal damage on the specimen. A Weibull probability distribution function that incorporates heat damage and relates to the cumulative events is developed. This model could be used to evaluate the extent of heat damage to a composite specimen.
Low Cycle Fatigue of Unidirectional Glass/Epoxy Composites
Authors: Harik V. M. , Klinger J. R. , Fink B. K. , Bogetti T. A. , Paesano A. , Gillespie J. W.
Published: December 2021

Low cycle fatigue (LCF) behavior of unidirectional polymer matrix composites (PMCs) reinforced with glass fibers is investigated. LCF conditions involve high loads reaching up to 90% of the material ultimate strength. LCF characterization of PMCs is carried out under tension-tension fatigue loading to identify the key physical phenomena occurring in PMCs under LCF conditions and to determine their unique characteristics. Analysis of experimental data indicates that finite strain rates, large strains and stress ratios may affect LCF behavior of PMC structures and the property degradation rates.
Mechanical Properties of Flat Braided Composites With a Circular Hole
Authors: Ohki Takeru , Ikegaki Shinya , Kurasiki Ken , Hamada Hiroyuki , Iwamoto Masaharu
Published: December 2021

In this study, fracture behavior and strength in the flat braided bar with a circular hole were investigated by static and fatigue test. Two type of specimens were prepared. They are a braided flat bar with an integrally-formed braided hole and a braided flat bar with a machined hole. Moreover, we also examined a specimen that had a metal pin inserted at the circular hole. This specimen was subjected to a static tensile test. The results of the tensile tests indicate that the strength of the flat bar with a braided hole was larger than that of the one with the machined hole. Furthermore, from the results of the fatigue tests, the flat bar with the braided hole showed higher fatigue property than that of the one with the machined hole.
Identification of In-Plane Elastic Constants of Composite Laminates Using Measured Strains
Authors: Kam T. Y. , Lin C. H. , Wang W. T.
Published: December 2021

A method for nondestructive evaluation of material constants of composite laminates is presented. An error function is established to measure the differences between the theoretically and experimentally predicted strains. The identification of the material constants is formulated as a constrained minimization problem in which the material constants are determined to make the error function a global minimum. A global minimization method together with a technique for normalizing the gradient of the objective function are used to solve the above minimization problem. The applications of the proposed method are demonstrated by means of several examples on the material constants identification of laminated composite cylindrical pressure vessels.
Modeling the Debonding Behavior of Step-Tapered Patches: Analytical Solutions and Numerical Analysis of Selected Structures
Authors: Karlsson A. M.
Published: December 2021

A common method to strengthening or stiffening a weak part of an airplane structure is to adhere a patch over the inferior surface. Typically, this is done in order to prevent a crack from initiating, or to prevent an already existing crack from growing. Evaluation of the efficiency of the patch has traditionally been done with respect to the extent of crack growth, (e.g. Park et al. 1992, and Paul and Jones, 1992), which of course is of crucial interest. However, the integrity of the patched system needs to be considered as well, since the failure of the composite system (formed by the patch and the base structure) may lead to a rapid growth of the preexisting crack in the base structure and may have overall catastrophic consequences. In this study we are therefore interested in investigating the initiation of debonding between the patch and the base structure, as well as the extent and stability of the debonding.

Early studies we conducted with respect to debonding suggested that relative long and relative compliant patches were preferred. Furthermore, an investigation regarding the effects of edge tapering on the debonding behavior showed that there are situations where a beveled edge may increase the propensity for debonding, requiring careful selection to achieve a suitable taper angle. In the present study, we investigate the integrity of the composite system for a base structure made from aluminum, and the patch made from aluminum or fiber reinforced epoxy, where both carbon and glass fiber are studied. In particular, we compare the materials selection in the patch, and for the case of a fiber-reinforced epoxy we also discuss the lay-up sequence.

To model the debonding behavior, an analytical model developed previous is extended to allow for the current materials properties. This model is fully self consistent and includes a Griffith type fracture criteria which yields the condition for the propagating bond zone boundary. The model also considers the unbonded part of the patch, which has earlier been shown to be in either of three configurations: (i) full sliding contact between the unbonded part of the patch and the base structure, (ii) only the edge of the patch remains in sliding contact with the base structure, or (iii) the patch has totally lifted of the base structure.

Results for both flat and curved structures are presented, as well as for a range of loading and boundary conditions. Among other results, it is seen that the degree of tapering is a more important parameter than the stacking sequence is with respect to the initiation and extent of debonding. Furthermore, a simplified testing method is discussed. In this method, the critical load for a case of simple boundary and loading conditions for a particular material system can be directly translated to the critical load for a more complicated structure.
A Hystersis Model for Piezoceramic Materials
Authors: Smith Ralph C. , Ounaies Zoubeida
Published: December 2021

This paper addresses the modeling of nonlinear constitutive relations and hysteresis inherent to piezoceramic materials at moderate to high drive levels. Such models are necessary to realize the full potential of the materials in high performance control applications, and a necessary prerequisite is the development of techniques which permit control implementation. The approach employed here is based on the quantification of reversible and irreversible domain wall motion in response to applied electric fields. A comparison with experimental data illustrates that because the resulting ODE model is physic-based, it can be employed for both characterization and prediction of polarization levels throughout the range of actuator operation. Finally, the ODE formulation is amenable to inversion with facilitates the development of an inverse compensator for linear control design.
Lagrangian and Lagrange Equation of Motion for Fractionally Damped Systems
Authors: Agrawal Om Prakash
Published: December 2021

Damping properties of various materials have recently been used as active and passive control parameters in smart structures. In these applications, the damping force is considered as proportional to velocity. In recent years, many investigators have demonstrated that the damping characteristics of a material can be modeled more accurately using a fractional derivative. Traditionally, Newton’s law is used to model such nonconservative systems, and when a Lagrangian, Hamiltonian, variational or other energy based approach is used, it is modified so that the resulting equations match with those obtained using Newtonian’s approach. In this paper we present a new Lagrangian containing derivatives of fractional orders, and a new Lagrange equation of motion for systems whose damping characteristics are described by a fractional derivative model. The method results in a state space type representation of the system. The method is applied to find the equations of motion of m/n order fractionally damped systems. Several examples are considered to show that the present scheme leads to a correct set of equations. It is hoped that this approach will help one to develop Hamiltonians, Jacobi theory, and other approaches in mechanics for systems containing fractional derivatives.
Modeling of the Electro-Mechanical (E/M) Impedance Response of a Damaged Composite Beam
Authors: Giurgiutiu Victor , Rogers Craig A.
Published: December 2021

The electro-mechanical (E/M) impedance method has gained acceptance as an effective technique for structural health monitoring, damage detection, and failure prevention. In spite of extensive experimental validation of this novel method, very little work has been dedicated to its modeling. This paper develops a model of the E/M impedance response of a damaged composite beam interrogated by a PZT wafer active sensor. The electromechanical model for the interaction between the beam and the active sensor is developed from first principles. The effective axial force and bending moments induced by the PZT wafer into the beam are considered. Equations of motion for the flexural vibrations of a composite beam under moment excitation are developed. Solution in terms of normal modes with internal damping is obtained. The resulting response and the applied force are utilized to deduce general expressions for pointwise dynamic stiffness and pointwise dynamic compliance. Effective stiffness of the PZT wafer is also calculated, and the complex stiffness ratio for the PZT-structure interaction is determined. Hence, the complex electro-mechanical impedance and admittance are deduced.

A numerical example is given to illustrate the method and test its effectiveness. It is found that the real part of the effective pointwise dynamic stiffness interacts at par with the PZT stiffness at structural resonance frequencies. The imaginary part of the complex stiffness ratio directly reflects the pointwise structural resonances. Consequently, the real part of the electro-mechanical impedance directly reflects the pointwise structural resonances too. The same behavior is also found in the electro-mechanical admittance. Thus, the real part of the E/M impedance and the real part of the E/M admittance are found to be direct measures of the structural response, reflective of damage presence.
Impact Identification for Metallic Plate Using Distributed Smart Materials
Authors: Peelamedu Saravanan M. , Naganathan Nagi G.
Published: December 2021

In the design of automobiles, occupant safety during a crash is an important factor in consideration. The vehicle should identity impact, handle passenger safety through deployment of various safety restraint systems, and steer away the vehicle from impact. With this background, this work is to find the impact location, magnitude, and identify damage on a metallic structure.

The first phase through the use of experimental and FEA is to demonstrate the piezoceramic sensor effectiveness and its ability to handle different orientations. In the second phase, the dynamic plate equation for impact is developed using Mindlin plate model, Ritz energy approach, and Hamilton principle. In the third phase, different forward model case studies of static and dynamic compared with FEM and theoretical work. The final phase, is to find frequency of undamaged and damaged plate area of 0.1% and 1% for various locations, to help in damage or no damage identification scenario.
Biviscous Damping Behavior in Electrorheological Dampers
Authors: Wereley Norman M. , Lindler Jason
Published: December 2021

Electrorheological (ER) and magnetorheological (MR) flow mode dampers can exhibit biviscous damping behavior. Such behavior is characterized by a high damping preyield region for low velocities, with a transition to a relatively lower postyield damping, once the damper force exceeds the yield force of the damper. The biviscous damping behavior is a result of leakage, defined as a second path of Newtonian flow in addition to the Bingham plastic flow through the ER or MR valve. We experimentally demonstrate such bilinear damping behavior in a monotube ER shock absorber. The ER fluid is typically assumed to behave as a Bingham plastic fluid. Thus, two perspectives are examined to predict damping performance of the ER monotube shock absorber. First, the quasi-steady Bingham plastic analysis is coupled with a mechanical analysis of the leakage effects. Second, a biviscous constitutive perspective is described that allows for the leakage effects to be described as an apparent preyield viscosity of the ER fluid. Both perspectives prove to be useful in describing damping performance of the ER monotube shock absorber.
A Method for Measuring Short Crack R-Curve Behavior of Ferroelectric Ceramic
Authors: Chen Wei , Lynch Christopher S. , Lupascu Doru
Published: December 2021

This work describes a method for measurement of R-curve behavior in ferroelectric ceramics using four point bending specimens with a controlled surface crack. A short surface crack is produced by a Knoop indentation and the damage zone is polished away. The results are compared for two compositions of lead lanthanum zirconate titanate (PLZT), an elastio-plastic ferroelectric composition and a linear elastic electrostrictive composition. R-curves are measured in the crack length regime of 0.1 to 0.8 mm. The ferroelastic composition displays a toughness increase from 0.7 to 1.4 MPam. The linear elastic composition displays a constant toughness of between 0.6 and 0.7 MPa√m. The R-curve behavior of PLZT 8/65/35 is attributed to ferroelastic toughening.
Adaptive Shape Control for an SMA-Actuated Aerofoil Rib Structure
Authors: Webb Glenn V. , Lagoudas Dimitris C. , Kulkarni Mayur
Published: December 2021

This paper presents a methodology for shape control of a cantilevered beam with multiple SMA wire actuators. Previous research by the authors has centered on adaptive control of a single SMA actuator to elicit a desired structural response. The approach for a single SMA actuator is extended for multiple SMA actuators, which increases the complexity of actuator control. The effect of one actuator on the structural deformation is coupled with the effects of the other actuators. The cantilevered beam experiment is provided as a proof of concept for shape control strategies which can be applied to the more complicated aerofoil rib structure.
Modal Voltages of Linear and Nonlinear Structures Using Distributed Artificial Neurons
Authors: Howard R. V. , Chai W. K. , Tzou H. S.
Published: December 2021

Laminated or embedded distributed neurons on structural components serve as in-situ sensors monitoring structure’s dynamic state and health status. Thin film piezoelectric patches are perfect candidates for this purpose. A generic piezoelectric neuron concept is introduced first, followed by definitions of neural signals generated by an arbitrary neuron laminated on a generic nonlinear double-curvature elastic shell. This generic neuron theory can be applied to a large class of linear and nonlinear common geometries, e.g., spheres, cylindrical shells, plates, etc. To demonstrate the neuron concept, an Euler-Bernoulli beam laminated with segmented neurons is studied. Neural signals and modal voltages are presented. Theoretical results are compared with experimental data favorably.
Zero Gravity Validation of Smart Aperture Antennas
Authors: Yoon Hwan-Sik , Washington Gregory
Published: December 2021

In this study, a smart aperture antenna of spherical shape is modeled and experimentally verified. The antenna is modeled as a shallow spherical shell with a small hole at the apex for mounting. Starting from five governing equations of the shallow spherical shell, two governing equations are derived in terms of a stress function and the axial deflection using Reissner’s approach. As actuators, four PZT strip actuators are attached along the meridians separated by 90 degrees respectively. The forces developed by the actuators are considered as distributed pressure loads on the shell surface instead of being applied as boundary conditions like previous studies. This new way of applying the actuation force necessitates solving for the particular solutions in addition to the homogeneous solutions for the governing equations. The amount of deflections is evaluated from the calculated stress function and the axial deflection. In addition to the analytical model, a finite element model is developed to verify the analytical model on the various surface positions of the reflector. Finally, an actual working model of the reflector is built and tested in a zero gravity environment, and the results of the theoretical model are verified by comparing them to the experimental data.
Experimental Investigation of Nonlinear Vibration Absorbers
Authors: Agnes Gregory S.
Published: December 2021

An experimental investigation of the performance of nonlinear vibration absorbers on nonlinear systems was performed. The results verify the previous analytical findings of the authors. Initially, for low excitation, the nonlinear absorber gives better results than the nonlinear case. However as the forcing level is increased, the system response undergoes a series of Hopf bifurcations leading to chaotic behavior and poor absorption of the vibrations.
Viscothermal Damping in Thin Gas or Fluid Layers
Authors: Beltman W. M. , Basten T. G. H. , Tijdeman H.
Published: December 2021

This paper deals with viscothermal wave propagation, including acousto-elastic interaction. For wave propagation in thin gas or fluid layers, the effects of viscosity and thermal conductivity have to be accounted for. These effects can introduce a significant dissipation of energy. A model to describe viscothermal wave propagation was developed. It includes the effect of inertia, viscosity, compressibility and thermal conductivity. It was written in terms of dimensionless parameters. These parameters govern the validity of simplifications and they can be used to put models into perspective. The viscothermal model is validated with specially designed experiments. A numerical finite element model was developed that includes the full acousto-elastic coupling. This model was also validated with experiments. The influence of barriers in a thin layers was investigated experimentally. Finally, the new techniques were applied to a number of practical problems: the damping of double wall panels and the dynamical behaviour of a folded array of solar panels during launch.
Modified Extended Thermodynamic Model for Material Damping
Authors: Lu Xia , Hanagud S.
Published: December 2021

During the process of damping of a structure, the mechanical energy is converted to thermal energy. Yet, the most commonly used model for material damping is the linear viscous damping. There are many attempts to develop thermodynamic models for damping. To adequately describe damping, we need more variables than the classical state variables. A simple thermodynamic model that is based on the framework of extended non-equilibrium thermodynamics is presented. Heat flux, non-equilibrium stress field and the associated non-equilibrium internal energy are used as additional variables. Longitudinal vibrations of a uniform rod are studied to present the flexibility of thermodynamic modeling for material damping.
Mass Transfer Enhancement in an Intravenous Membrane Oxygenator Induced by a Pulsating Balloon
Authors: Guzmán Amador M. , Amon Cristina H.
Published: December 2021

The Intravenous Membrane Oxygentor (IMO) is a device that consists of hundreds of hollow fibers and an elastic, non-permeable, balloon that is positioned within the vena cava. The balloon inflates and deflates rhythmically to a given amplitude and frequency to generate cross flow, promote blood mixing, and enhance the gas exchange. The IMO has been designed to provide temporarily up to 50% of the O2 and CO2 exchange requirements to patients who suffer Acute Respiratory Distress Syndrome (ARDS) [1–4]. This illness affects approximately 150,000 people per year in the U.S. and is characterized by non-cardiogenic pulmonary edemas and a rapid and progressive malfunctioning of the lung [4]. The IMO device is an alternative therapy to conventional treatments such as mechanical ventilation and extracorporeal membrane oxygenation [5–7]. This paper reports the investigation of the flow and oxygen transfer characteristics of the IMO device shown in Fig. 1(a) and describes the numerically obtained flow patterns and the oxygen transfer characteristics for stationary and pulsating balloon regimes.
Analysis of Gender Based Thermal Regulation
Authors: Spieker Michael A. , Hayes Linda J. , Wissler Eugene H. , Colvin David P.
Published: December 2021

Significant qualitative and quantitative data from the literature suggests that men and women differ in their response to extreme thermal environments. It is apparent that women sweat less (Morimoto et al., 1967; Wyndham et al., 1965), and have a thicker subcutaneous fat layer (Wells, 1991) relative to men. Men, on the other hand have higher resting and working metabolic rates relative to women, which tend to increase their core body temperatures at a faster rate. A whole body thermal regulation model (Wissler, 1985) designed by Gene Wissler is used to analyze the gender based thermal responses of men and women subjected to medium-high work levels in several thermal environments. This study has important application in estimating how gender differences affect the potential work performance of men and women in extreme thermal environments.
Motion of Microcarriers in Rotating-Wall Vessels
Authors: Gao Hongxia , Ayyaswamy Portonovo S. , Ducheyne Paul
Published: December 2021

It is now widely acknowledged that the simulated microgravity environment of NASA-designed rotating-wall vessels (RWVs) offers great advantages for three-dimensional growth of mammalian cells. In the rotating-wall vessel, the solid body rotation is accomplished by horizontally rotating a vessel, which consists of a cylinder or two concentric cylinders and is completely filled with culture medium, at a constant rotational speed. Mixing and shear forces in the RWV are due to the microcarriers’ motion in the fluid, and the contact that the microcarriers occasionally make with the wall and each other [1]. Therefore, the motion of microcarriers in the rotating flow is of interest and important in the design of the rotating-wall vessel bioreactors and in the guiding of RWV cell culture experiments under optimal operating conditions.

Predictions of a single microcarrier migration inside the RWV have been described in our previous study [2]. However, the particle-wall and the particle-particle interactions were not considered. In this study, we numerically investigate the motion of microcarriers with the effects of the collisions under consideration.
Mechanical Recovery of Cultured Axons After Dynamic Stretch: Correlation to Cytoskeletal Changes
Authors: Meaney David F. , Ewoterai Inifome , Wolf John A. , Lusardi Theresa G. , Smith Douglas H.
Published: December 2021

In this study, we used a novel device to stretch cultured CNS axons up to 77% of their initial length under mechanical conditions mimicking traumatic injury. The morphological response immediately following stretch was recorded using video microscopy techniques, and the cytoskeletal response to stretch was examined using immunocytochemistry techniques. Below the threshold for primary axotomy, axons maintained their overall position on the substrate but displayed periodic distortions at points along their length. These strain induced changes in axonal morphology were observed at all applied strains used in the current study. Moreover, a large fraction of the cultured axons showed a relatively uniform frequency of distensions along their length; only a small minority of the axons in the field showed a few or single larger distension along their length. Interestingly, all axons showing distensions gradually recovered to a straightened pre-stretch shape over a period of 45 min, with most of the relaxation occurring in the first 20 minutes. Phenomenological models developed for the observed mechanical recovery phenomena suggest a molecular-based recovery process (τave ∼ 24 minutes) that is consistent with previous towed growth experiments on neurites. Unlike previous towed growth experiments, though, permanent changes in the neurofilamentous cytoskeleton were observed at 2 hr. post-stretch. These data suggest there is an endogenous mechanism for axons to regain morphology after stretch despite permanent changes to parts of the cytoskeleton that occur after even a single mechanical stimulus.
Vitrification Fulfills its Promise as an Approach to Reducing Freeze-Induced Injury in a Multicellular Tissue
Authors: Taylor Michael J. , Song Ying C. , Kheirabadi Bijan S. , Lightfoot Fred G. , Brockbank Kelvin G. M.
Published: December 2021

The destructive effect of extracellular ice formation in organized multicellular tissues is known to be a principal reason why conventional techniques of cryopreservation fail to provide effective protection during freezing. Avoidance of ice during cooling can physically be achieved by vitrification, which is the amorphous solidification of a supercooled liquid by adjusting the solute composition and cooling rate such that nucleation and growth of ice crystals is prevented. In principal a biological system can be stabilized in the glassy (vitreous) state without the inherent problems associated with crystallization and so-called solution effects injury that arise from the increased concentration of solutes due to removal of water as ice.

This study was designed to evaluate a vitrification approach to storing a vascular tissue model (rabbit jugular vein) compared with a standard commercial method used clinically and employing slow cooling (l°C/min) with dimethylsulfoxide (DMSO) as the cryoprotective agent (CPA). A baseline vitrification medium (designated VS55) was used to replace at least 50% of the tissue water with a combination of CPAs. and vitrification was achieved using a relatively high cooling rate (> 40°C/min). After rewarming and removal of the CPAs. contractility of the blood vessel segments was evaluated in vitro using standard physiological response tests to a panel of reagents. The maximum contractions achieved in vitrified vessels were all greater than 80% of fresh matched controls with similar drug sensitivities. In contrast, frozen/thawed vessels exhibited maximal contractions below 25% of fresh matched controls with concomitant decreases in drug sensitivity.

This study clearly demonstrates a significant benefit of vitrification compared with conventional freezing and thawing for preserving smooth muscle contractile function of preserved blood vessels. Vitrification may prove to be an effective way to minimize the deleterious effects of freezing and thawing in cryopreserved tissues, or engineered tissue constructs.
Three-Dimensional Microstructure of Muscle Tissues During Freezing and Thawing
Authors: Ishiguro Hiroshi , Horimizu Takashi
Published: December 2021

Three-dimensional behavior of ice crystals and cells during the freezing and thawing of biological tissues was investigated microscopically in real time by using a confocal laser scanning microscope (CLSM) and a fluorescent dye, acridine orange (AO). Fresh tender meat (2nd pectoral muscles) of chicken was stained with the AO in physiological saline, and then frozen and thawed in a uniform temperature under two different thermal protocols: a) slow-cooling and rapid-warming and b) rapid-cooling and rapid-warming. The CLSM noninvasively produced tomograms of the tissues to clarify the pattern of freezing, morphology of ice crystals in the tissues, and the interaction between ice crystals and cells.
Heat Transfer in Laminar Tube Flow of a Suspension Containing Microencapsulated Phase-Change Material
Authors: Mulligan J. C. , Boyer D. K.
Published: December 2021

A numerical formulation of the energy equation is developed for the laminar flow of a MEPCM fluid in a tube at a constant velocity and subjected to a constant and uniform wall heat flux. MEPCM fluids are phase-change fluids that are suspensions comprised of particles of microencapsulated phase-change material (MEPCM) in a carrier fluid. The thermodynamic behavior of MEPCM fluids is modeled for both melting and crystallization and included in an enthalpy formulation of the energy exchanges. A particular phase-change case involving a microPCM fluid is then solved for conditions that produce melting and crystallization of the phase-change material. Heat transfer results are presented which show that the MEPCM phase-change characteristics, along with system parameters, have significant effects on the potential of MEPCM fluids to improve heat transfer and facilitate enhanced temperature control in pumped loops.
Use of MicroPCMs in Agricultural Applications
Authors: Cartwright D. Kelly , Bryant Yvonne G. , Colvin David P.
Published: December 2021

Microencapsulated phase change materials were tested in several agricultural systems, including mycoherbicide development, alleviation of heat stress in agronomic crops and frost prevention. The primary constraint to development of mycoherbicides is the lack of free moisture for weed infection and excessively high temperatures. Using microencapsulated water, the time of free moisture exposure necessary for infection by Colletotrichum capsici (mycoherbicide) on pitted morningglory was reduced by 56%, while use of a customized microPCM to regulate temperature increased effectiveness as much as 70%. A combination of the microencapsulated water and microPCM also improved disease severity significantly. The technology also improved control by C. malvarum on prickly sida. Although variable, microPCMs reduced the severity of frost damage on tomatoes and impatiens with temperature decline inside specific plant parts treated with a variety of microPCMs slowed dramatically. Research on the use of microPCMs to protect plants from heat stress is currently ongoing. The potential for microPCM use in agricultural is high.
Test Geometries for Bondline Cracked Photoelastic Models; Preliminary Results
Authors: Smith C. W. , Gloss K. T. , Liu C. T.
Published: December 2021

By interrogating polyurethane specimens containing bondlines with cracks photoelastically, the authors are conducting a study of the effect of fixed ends upon the stress intensity factor (SIF) for double edge cracked specimens for test specimens of relatively short height. Preliminary results suggest that, while the presence of the bondline increases the SIF with increasing crack length, reducing the specimen height will reduce the SIF level for all crack lengths.
Numerical Study for Global Detection of Cracks Embedded in Beams
Authors: Lipsey S. A. , Kwon Y. W.
Published: December 2021

Damage reduces the flexural stiffness of a structure, thereby altering its dynamic response, specifically the natural frequency, damping values, and the mode shapes associated with each natural frequency. Considerable effort has been put into obtaining a correlation between the changes in these parameters and the location and amount of the damage in beam structures. Most numerical research employed elements with reduced beam dimensions or material properties such as modulus of elasticity to simulate damage in the beam. This approach to damage simulation neglects the non-linear effect that a crack has on the different modes of vibration and their corresponding natural frequencies. In this paper, finite element modeling techniques are utilized to directly represent an embedded crack. The results of the dynamic analysis are then compared to the results of the dynamic analysis of the reduced modulus finite element model. Different modal parameters including both mode shape displacement and mode shape curvature are investigated to determine the most sensitive indicator of damage and its location.
An Accurate Explicit Direct Time Integration Method for Computational Structural Dynamics
Authors: Tchamwa Bertrand , Conway Ted , Wielgosz Christian
Published: December 2021

The purpose of this paper is to introduce a new simple explicit single step time integration method with controllable high-frequency dissipation. As opposed to the methods generally used in structural dynamics, with a consistency experimentally chosen of second order, the new method is only first-order-consistent but yields smaller numerical errors in low frequencies and is therefore very efficient for structural dynamic analysis.

The new method remains explicit for any structural dynamics problem, even when a non-diagonal damping matrix is used in linear structural dynamics problem or when the non-linear internal force vector is a function of velocities. Convergence and spectral properties of the new algorithm are discussed and compared to those of some well-known algorithms. Furthermore, the validity and efficiency of the new algorithm are shown in a non-linear dynamic example by comparison of phase portraits.
Quantification of Corrosion in 7075-T6 Aluminum Alloy
Authors: Obert B. , Ngo K. , Hashemi J. , Ekwaro-Osire S. , Sivam T. P.
Published: December 2021

In aging aircraft the synergetic interaction between corrosion and fatigue has been shown to impact the life expectancy of aluminum alloys. The objective of this study was to quantify the effects of corrosion, in terms of mass loss, on the static strength and fatigue life of 7075-T6-aluminum alloy. This was an experimental study conducted on samples with laboratory-controlled corrosion of varying mass loss levels at their mid-surface on one side. The specimens were covered with special masking material to allow corrosion only in the desired area. Both fatigue life and the ultimate tensile strength of the specimens were observed to drop significantly with small amounts of mass loss (less than 5%). After the initial decrease the UTS was observed to decrease linearly with additional mass-loss. The fatigue life of the specimens decreased significantly with additional mass loss. The topology of the pits, and the related subsurface damage hinted at existence of areas of high stress concentration resulting in the immediate reduction of UTS and fatigue life of the specimens.
Stress Concentration of Shape Memory Alloy Fiber Reinforced Composites in Elastic Axisymmetric Deformations
Authors: Tsai Hungyu , Fan Xinjian
Published: December 2021

In an effort to investigate the mechanical properties of shape memory alloy (SMA) fiber reinforced composites, the stress distribution due to the phase change in the fiber is examined. We study a simple model involving a single infinite fiber embedded in an infinite elastic matrix. A portion of the fiber is allowed to undergo uniform phase transformations along the axial direction while the matrix remains linearly elastic. Under perfect bonding condition, the deformation of the fiber forces the matrix to deform in the elastic regime in order to accommodate the transformation strain. To simplify the analysis, the elasticity of the fiber is ignored. The problem is formulated as axisymmetric deformations for the matrix with a piecewise linear boundary condition at the interface with the fiber as a result of the phase transformation in the fiber. The exact elasticity solution (in integral form) to this problem is found using Love’s stress function and Fourier transform. The normalized forms of the solution are presented. The asymptotic behaviors of the stress distributions near the phase boundary are analyzed in details. The characteristics of the singularities near the phase boundary are obtained for this model. Numerical evaluations are also performed to obtain the distributions of the displacements, the strains, and the stresses in the matrix. In particular, the shear load transfer profiles along the interface are obtained for various aspect ratios of the transformed region.
Elasto-Plastic Analysis of Thermal Stress Development During VAR of Ingots
Authors: Alam M. K. , Wong K. K. , Semiatin S. L.
Published: December 2021

The vacuum arc remelting (VAR) process has been developed to melt and cast high quality aerospace materials such as titanium alloys. VAR comprises the continuous remelting of a consumable electrode by means of a dc arc under vacuum or a low partial pressure of argon. The molten metal solidifies in a water-cooled copper crucible leading to high cooling rates that often results in large thermal stresses. The development of temperature gradients and the resulting thermal stresses during the VAR processes was investigated using an elasto-plastic material model with temperature dependent thermomechanical properties. Detailed solutions were obtained by using the commercial finite element code ABAQUS.
Promoting the Study of Science, Mathematics, Engineering and Technology in Urban School Districts via Video Programming
Authors: Mackie Calvin
Published: December 2021

This paper describes methods and theories used to alter the attitudes and motivation of the 83,000 students of the New Orleans Public School system. The project attempts to affect systemic change in the study of science, mathematics, engineering and technology via development of a motivational and informational video series from live presentations at target schools. The city of New Orleans and the New Orleans Public School system are demographically 75% and 85% African-American, respectively, and there is an overwhelming need to expose the students to role models beyond athletes and entertainers. The author has developed a comprehensive program to assist the New Orleans Public School system in developing motivation and fostering positive attitudes toward education, in general, and the study of science, math, engineering and technology, in particular.

The program’s goal and vision are to convince students that they can be whatever they choose with math, science, engineering and technology as possible alternatives, presenting career opportunities well into the next century by developing the whole individual into a motivated, critical thinking human being with the ability to make life-sustaining decisions. The videos are based on successful theories and presentations the author has developed and presented. Students at target schools are pre- and post-tested to determine the presentations’ effectiveness.

The videos are aired continuously on community and educational access channels across the city, reaching over 300,000 homes. Furthermore, a presently functional web site whereby students receive additional information and resources in the all areas of education including science, math and engineering complements the video series.