bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Class of Distributed Photostrictive Orthogonal Actuators in Smart Curved Structures
Authors: Shih Hui-Ru , Tzou H. S.
Published: November 2021

In this study, active vibration control of a flexible smart structure using distributed opto-electromechanical photostrictive actuators is analytically investigated. This new class of distributed actuators is based on the photovoltaic, converse piezoelectric, and pyroelectric effects, and activated by high-energy light. A simply supported curved beam structure with a pair of surface bonded opto-electromechanical actuators is proposed. In order to prevent control spillover, the distributed actuators are spatially shaped to be orthogonal to the undesirable mode. The governing equations of motion are formulated. The mathematical model for estimating the actuator-induced force and moment, and actuation factor are presented. The effectiveness of active controls is evaluated with respect to different actuator thicknesses and curvature angles. The results obtained suggest that the potential of this new class of actuators as a viable means for controlling motion that related to structural deformation.
Fuzzy Logic Control Applications for Second Order Problems With Low Damping
Authors: Cohen Kelly , Weller Tanchum , Ben-Asher Joseph
Published: November 2021

A general methodology has been developed for the design of a robust control law for a family of lightly damped second order problems. In this research effort, the passivity approach has been extended to systems having non-collocated input/output pairs by introducing an observer that incorporates the nominal dynamical model of the plant. The developed passive observer-based control law emulates numerous dynamic vibration absorbers which are tuned to a targeted frequency using classical methods and the tuning ratios are time-invariant. However, the uniqueness of this approach is that the damping parameters of the emulated absorbers are continuously varied by means of a fuzzy logic control algorithm to provide near minimum-time suppression of vibration. The developed approach is applied to both several benchmarks in the field of structural dynamics as well as experiments using piezo-ceramic sensors and actuators. Results show that this methodology provides stability and performance robustness on the one hand as well as requiring relatively low amount of actuation authority for desired nominal plant close-loop behavior.
Vibration Reduction of Flexible Structures Using Extended Input Shaper and Smart Materials
Authors: Song G. , Kotejoshyer B. , Fei J.
Published: November 2021

This paper presents a new approach of integrating the method of command input shaping and the technique of active vibration suppression for vibration reduction of flexible structures during slew operations. The control object is a flexible composite beam driven by a high torque DC motor with the presence of nonlinearities such as backlash and stick-slip type of friction. Two piezoelectric patches are bonded on the surface of the flexible beam near its cantilevered end and are used as the smart actuator and the smart sensor respectively. In this new approach, the method of command input shaping is used to modify the existing command so that less vibration will be caused by the command itself. To overcome the nonlinearities associated with the DC motor, an extended shaper is designed. The technique of active vibration suppression using smart materials is used to actively control the vibration during and after the slew. With this pair of smart actuator and smart sensor, a strain rate feedback (SRF) controller is designed for active vibration suppression. With the extended Zero Vibration Derivative (ZVD) shaper and the SRF controller, the proposed new approach can effectively reduce the vibration of the flexible beam during slew operations.
Neural Network Tracking Control of a Shape Memory Alloy Wire Actuator Without a Position Sensor
Authors: Song G. , Chaudhry V. , Batur C.
Published: November 2021

Tracking control of shape memory alloy (SMA) actuators is essential in many applications such as vibration controls. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, open-loop control design has proven inadequate for tracking control of these actuators. Aimed at to eliminate the position sensor to reduce cost of an SMA actuator system, in this paper, a neural network open loop controller is proposed for tracking control of an SMA actuator. A test stand, including a titanium-nickel (TiNi, or Nitinol) SMA wire actuator, a position sensor, bias springs, and a programmable current amplifier, is used to generate training data and to verify the neural networks open loop controller. A digital data acquisition and real-time control system was used to record experimental data and to implement the control strategy. Based on the training data obtained from the test stand, two neural networks are used to respectively model the forward and inverse hysteresis relations between the applied voltage and the displacement of the SMA wire actuator. To control the SMA actuator without using a position sensor, the neural network inverse model is used as a feedforward controller. The experimental results demonstrate the effectiveness of the neural network open loop controller for tracking control of the SMA wire actuator.
Precision Position Control of a Shape Memory Alloy Wire Actuator With Forced Cooling
Authors: Barr T. A. , Penney N. , Song G.
Published: November 2021

The purpose of this paper is to study active position control of a shape memory alloy (SMA) wire actuator with forced cooling, particularly, in water. The TiNi, or Nitinol type shape memory alloy wire is selected as the actuating element for position control because of its high recovery stress (> 500 Mpa) and its high strain tolerance (up to 5%). However, SMAs exhibit hysteresis, a type of non-linearity, which causes adverse effects in the precision control of the actuator. To compensate for the non-linearity associated with the shape memory alloy, a control approach employing a robust compensator is used to actively regulate the position of the SMA wire actuator. To study methods to improve a SMA actuator’s response, water is used as the forced cooling liquid in this research. Experimental results show that the SMA actuator in water can be precisely controlled using the proposed control approach with a much faster response. Experimental data also show that the total energy consumption for the SMA actuator to perform back-and-forth tasks in water is similar to that in the air though holding a deformed shape in water consumes much more energy than that in the air for the SMA wire actuator.
Structural Modeling Considerations for Dynamic Optical Space Structure Simulations
Authors: Griffin Steven , Schrader Karl
Published: November 2021

Boeing-SVS has developed an integrated modeling tool, Zelink, which effectively combines three commercial standard codes, Zemax, Simulink and Nastran, to predict the effect of quasistatic and dynamic disturbances on optical metrics of interest in optical space structures. Examples of optical metrics are time-varying wavefront error, point spread functions and predictions of image degradation. A simulation might involve specification of a slew angle and prediction of time-varying wavefront error. Different command shaping and attitude control techniques might be evaluated with respect to their ability to minimize wavefront error. Implementation of such simulations has shown significant dependence of simulation results on the structural modeling approach. In particular, one approach may introduce errors in the optical metric of interest, where another approach may avoid errors. The sensitivity of the optical metric is related to the necessity of maintaining the optical prescription when there is no structural deformation. A quasistatic rotation of the space structure should not significantly distort the optical prescription, since there is almost no structural deformation associated with this maneuver. This paper discusses structural modeling approaches and makes recommendations specific to optical space structure simulations.
Development and Integration of a Semi-Analytical PCB Thermal Design Technique With an Infrared Thermal Imaging System
Authors: Park Hyunjae , Nigro Nicholas , Gollhardt Neil , Lee Ping
Published: November 2021

Traditionally, analytical models are developed to predict the thermal behavior of Printed Circuit Boards (PCBs). The predicted results are then verified with other analytical or experimental results prior to using the models in design. This is a time intensive process and the results predicted using these models may include limitation due to idealization. In order to overcome this disadvantage, a semi-analytical model is proposed in this study. The semi-analytical model uses analytic theory in conjunction with results obtained from an Infrared-Radiation Thermal Imaging System (IRTIS). The model is verified and updated, allowing the results to be immediately incorporated into PCB thermal design. The parameters in the semi-analytical model are determined by employing a least squares temperature curve fit for the first upstream heating component in conjunction with a simple conduction model for the PCB wall. The model was tested with a natural convection cooled PCB with three inline heating components. Temperature data for the first upstream component was measured with an IRTIS and fit to the semi-analytical model. The model predicted temperature results for all three heating components with good agreement. The PCB thermal design technique enables the IRTIS to be employed as a preliminary design tool that significantly reduces design iterations through the use of the semi-analytical model.
Compact Air-Coupled and Hydronically Coupled Microchannel Heat Pumps
Authors: Jiang Yirong , Garimella Srinivas
Published: November 2021

Novel air-coupled and hydronically coupled heat pumps using microchannel components were investigated in this study. The air-coupled system uses microchannel tube, multilouver fin heat exchangers as the evaporator and condenser. In the hydronically coupled heat pump, refrigerant in the evaporator as well as the condenser transfers heat to an intermediate fluid such as an ethyleneglycol solution. The glycol loops are connected to the indoor/outdoor air through liquid-air heat exchangers. Models to simulate cycle thermodynamics, and single- and two-phase heat transfer in the components were developed to design these systems for cooling and heating mode operation. The components were optimized to develop the most compact systems that would satisfy system performance requirements. These systems were also compared with a conventional round-tube, plate-fin heat pump, which was designed using a commercially available simulation tool.

Results from this study show that indoor and outdoor units of air-coupled microchannel systems can be packaged in only one-half and one-third the space required for a conventional system. Even more compact refrigerant heat exchangers are required in the hydronically coupled system, because of the high heat transfer coefficients for these liquid-coupled heat exchangers, and the counterflow orientation. The hydronic coupling offers flexibility in system location, and is well suited for integrated space-conditioning and water heating systems. Both air-coupled and hydronically coupled systems result in significant reductions in refrigerant inventories compared to round-tube systems. The refrigerant charge of the microchannel air-coupled system is 20% less than that of the round-tube heat pump. For the hydronically coupled system, the refrigerant charge is only 10% of the charge in the round-tube heat pump.
Modeling of a Transcritical Carbon Dioxide Vapor Compression Cycle: Validation and the Effect of Refrigerant Pressure Drop on Cycle Performance
Authors: Robinson Douglas M. , Groll Eckhard A.
Published: November 2021

Due to world wide restrictions on the use of fluorocarbon based refrigerants, carbon dioxide has recently received attention as a possible replacement for those refrigerants in certain applications. In order to evaluate the potential performance of a transcritical vapor compression refrigeration cycle using carbon dioxide as the refrigerant, a cycle model has been developed which can simulate the operation of a carbon dioxide based air conditioner. This model is called ACCO2 and includes a detailed heat transfer analysis of the heat exchangers, accounting for the effect of both thermodynamic and thermophysical properties of carbon dioxide, as well as other component models.

ACCO2 simulates the operation of a carbon dioxide based air conditioner that uses air as the heat source and heat sink. An overview of component models and the methodology to combine them into an overall cycle model (ACCO2) is presented. ACCO2 was validated using experimental data and data from another validated air conditioner model. During validation, it was noted that the accuracy of refrigerant pressure drop prediction had a strong influence on the accuracy of the prediction of overall cycle performance. In addition, conclusions were drawn concerning the impact of refrigerant pressure drop in an actual carbon dioxide based air conditioner. Conclusions are also drawn concerning the validation and future uses for ACCO2.
Effect of Comfort Constraints on Cycle Efficiencies
Authors: Richter Matthew , Bullard Clark , Hrnjak Pega
Published: November 2021

The traditional ideal Evans-Perkins cycle analysis is extended to include the effects of the comfort of the conditioned space and finite airflow rates on cycle efficiency. Based on this, the performance of R410A and R744 for residential heating and cooling applications is compared. The effect on annual efficiency of the two refrigerants based on load requirements for three diverse climates is also discussed.
A Catalytically Sustained Microcombustor Burning Propane
Authors: Hatfield Jonathan M. , Peterson Richard B.
Published: November 2021

The performance of a catalytically sustained microcombustor was investigated. The reactants for combustion were air and propane, which were mixed together and delivered to the end of a bayonet-style, heat recirculating combustor having a reaction volume measuring approximately 0.25 mm3. Platinum wire in the shape of a coil was used as an active surface to catalyze the exothermic reactions. Measurements of temperature and reactant flow rate were made during the study. Results show that propane can be burned in a self-sustaining fashion in the microcombustor with heat release rates as low as 1.0 Watt.
The Characteristic Physical Parameter Approach to Modeling Chillers Suitable for Fault Detection, Diagnosis and Evaluation
Authors: Jia Yongzhong , Reddy T. Agami
Published: November 2021

Model-based fault detection and diagnosis approaches based on statistical models for fault-free performance concurrently require a fault classifier database for diagnosis. On the other hand, a model with physical parameters would directly provide such diagnostic ability. In this paper, we propose a generic model development approach suitable for large engineering systems that usually come equipped with a large number of sensors. Such a methodology, called the characteristic parameter approach, is proposed for large centrifugal chillers which are generally the single most expensive piece of equipment in HVAC&R systems.

The basis of the characteristic parameter approach is to quantify the performance of each and every primary component of the chiller (the electrical motor, the compressor, the condenser heat exchanger, the evaporator heat exchanger and the expansion device) by one or two performance parameters, the magnitude of which is indicative of the health of that component. A hybrid inverse model is set up based on the theoretical standard refrigeration cycle in conjunction with statistically identified component models that correct for non-standard behavior of the characteristic parameters of the particular chiller. Such an approach has the advantage of using few physically meaningful parameters (as against using the numerous sensor data directly) which simplifies the detection phase while directly providing the needed diagnostic ability. Another advantage to this generic approach is that the identification of the correction models is simple and robust since it requires regression rather than calibration. The entire methodology has been illustrated with actual monitored data from a centrifugal chiller. The sensitivity of this approach to sensor noise has also been investigated.
Rational Design of Vehicles: I — Multi-Objective Optimization
Authors: Paulus David M. , Gaggioli Richard A.
Published: November 2021

The customer for a vehicle typically has several desiderata, such as top speed, fuel economy, range, acceleration, .... Generally, these desiderata are conflicting. So, in order to deduce a single objective function, a means is needed for weighting (implicitly if not explicitly) the relative importance of these desiderata. That is, for weighting these “multiple objectives.” This paper presents a rational methodology for developing a single-objective function to be optimized during the design of a vehicle. The methodology does require answers from the customer(s) to a straightforward set of questions, referring to the desiderata. Based on the answers, the objective function follows, mathematically, in a straightforward manner. An application to a light, personal aircraft serves as a case study.
Energy Storage With Solid/Liquid Phase Change in Presence of Natural Convection
Authors: Pinelli M. , Piva S.
Published: November 2021

Solid/liquid phase change process has received great attention for its capability to obtain high energy storage efficiency. In order to analyse these systems, undergoing a solid/liquid phase change, in many situations the heat transfer process can be considered conduction-dominated. However, in the past years, it has been shown that natural convection in the liquid phase can significantly influence the phase change process in terms of temperature distributions, interface displacement and energy storage.

In this paper, a procedure to analyse systems undergoing liquid/solid phase change in presence of natural convection in the liquid phase based on the utilisation of a commercial computer code (FLUENT), has been developed. This procedure is applied to a cylinder cavity heated from above and filled with a Phase Change Material. It was found that when the coupling with the environment, even if small, is considered, natural convection in the liquid phase occurs. The numerical results are then compared with available experimental data. The analysis shows that the agreement between numerical and experimental results is significantly improved when the results are obtained considering the presence of circulation in the liquid phase instead of considering the process only conduction-dominated. Furthermore, some interesting features of the flow field are presented and discussed.
Exergy Analysis of a Turbojet Engine Over a Complete Flight Cycle
Authors: Rosen Marc A.
Published: November 2021

Exergy analysis is used to evaluate the efficiency of a turbojet engine over an entire flight (including climb, cruise and descent), and to assess the sensitivity of these results to the selection of the reference environment. This study is an extension of previous work where the accuracy of an exergy analysis of a turbojet engine is evaluated for different reference environments on an instantaneous basis. The present work evaluates cumulative engine efficiencies. The results show that the use of a constant reference environment set at cruise altitude conditions yields cumulative exergy efficiencies that are within 0.01% of those found using a variable reference environment (equal to the operating environment conditions at all times) over a 3,500 km flight. This result is in contrast to the use of a constant sea-level reference environment where such are 3.7%. This significant cumulative efficiency difference with the choice of reference environment is not observed when using an instantaneous exergy analysis. Care must be exercised when using a constant reference environment, as for both constant sea-level and cruise-altitude reference environments cumulative rational efficiencies increase over the majority of the flight, whereas for a continuously varying reference environment these efficiencies decrease.
Introducing Thermal System Optimization in an Introductory Engineering Thermodynamics Course
Authors: Byerley Aaron R. , Newton Harry N. , Tuite John R.
Published: November 2021

This paper describes a thermal system analysis, design, and optimization project that has been successfully used for two years in an introductory engineering thermodynamics course. The project has provided the students with an opportunity to gain a first-order understanding of the optimization process through the use of spreadsheets and math applications packages. The assignment has been based on the modeling and optimization of a non-ideal gas turbine cycle for use in an Unlimited Class Hydroplane. Student teams are guided through the five steps of the engineering design process including 1.) “information gathering” using mostly web-based material; 2.) “problem definition and alternative generation” using the rules published by the Unlimited Class Hydroplane Racing Association; 3.) “evaluation” of the alternatives using a predictive model based upon thermodynamic principles; 4.) “decision making” using graphical and numerical results generated by spreadsheets and math applications packages; and 5.) “presentation” of the design recommendations in both oral and written reports. Compressor pressure ratio and isentropic efficiencies for the compressor and turbine were the three design variables. Penalty functions were assigned to each to account for component cost, weight, volume, and complexity. The objective function was defined as the ratio of “shaft power to total penalty units” and was maximized using surface plots generated in Excel 97. The optimal solution was also obtained using Mathcad 8.0, Mathematica 3.0, Solver (an add-in tool for Excel 97), and Ada 95, a general programming language. Animated surface plots clearly illustrated the underlying mathematical operations of optimizing a system of non-linear equations.
An Application of the Dynamic Balance Equation
Authors: Geskin Ernest S.
Published: November 2021

The Onsager formalism (generalized fluxes, sources and variables) is used to construct the dynamic balance equation. Previously this equation has been applied to the investigation of energy balance, which includes all interactions between a system and the environment. In this paper the work and non-work interactions are discussed separately. The corresponding forms of the generic balance equation are considered and the dynamic balances of the representative variables ( P V ¯ and enthalpy) are examined. It is shown that the equilibrium relations constitute particular cases of the constructed equations. At the same time the dynamic equations also reveal additional information about a system in question, for example, the developed equations determine the available work of a non-steady process. The paper demonstrates that the dynamic thermodynamic functions constitute an effective tool for systems description.
Design, Construction, Start-Up and First Experimental Trials of a Test Rig for Single Fuel Cells
Authors: Desideri Umberto , Lunghi Piero , Ubertini Stefano
Published: November 2021

The recent spreading of the interest for fuel cells brings, as a consequence, the need of intense effort for components and system development and testing. While the most resourceful cell developers have realized experimental set-ups for cell duration estimation, it is very rare to find test rigs for complete characterization of cell performance as a function of the numerous input parameters i.e. streams mass flow, composition, temperature and purity, fuel utilization factor, current density. In the present state of the art some modelling of the influence of these factors exists as well as some experimental results for cell potential evaluation at different current densities. What is not found in literature and is difficult to obtain is a complete experimental characterization of fuel cells in which the dependence of performances on a single factor is disaggregated from the others and clearly evaluated. This paper present a test rig for single cell designed to reach these targets and its first tests on a Molten Carbonate Fuel Cell. The experimental setup has revealed to be very flexible allowing the characterization of the system at different operating conditions.
Effects of Heat Accumulation on the Thermodynamic and Economic Performance of CHP
Authors: Portacha Jozef , Smyk Adam , Zielinska Alicja , Fiszdon Jerzy K.
Published: November 2021

Heat accumulation in cogenerating plants allows increased electricity production during highest demand period. It also causes change of the overall electricity production. Changes in cogeneration coefficient follow the same trend. This paper examines the effect on the average cogeneration factor caused by adding the heat accumulator to the existing CHP. Variation of this coefficient influences the plant economics, since electrical energy is most expensive during the peak hours. In the model presented the operating conditions vary due to variations in the surroundings temperature and due to cyclical operation of the heat accumulator. Assumptions made, the mathematical model, and numerical method used are also presented.
District Heating in the City of Tokyo: A Case Study Using a New Integrated Simulation Environment
Authors: Burer M. , Li H. , Favrat D. , Kraines S. , Wallace D.
Published: November 2021

This paper aims to illustrate a new holistic modeling environment through a case study implementing a district heating system to supply four groups of users identified in the city of Tokyo. The holistic modeling environment, called DOME (Distributed Object-based Modeling Environment) is being used by researchers in the Alliance for Global Sustainability (AGS) to develop a platform for assessing technologies and policies in order to significantly reduce CO2 emissions in large cities. DOME is used as an information based collaboration platform for supporting the decentralized integration of models built independently under various application tools and operating systems. It provides system engineers with the ability to access experts’ models over the Internet through user-friendly interfaces. The interfaces provide clearly identified input and output variables to support a facilitated integration. The DOME environment also provides tools for analyzing the resultant integrated system.

In this district heating simulation, a GIS (geographic information system) based land-use database manager, implemented as an object in DOME, is used to obtain the total ground area, the total building floor area, and the number and type of buildings in a specified region of Tokyo. Using the land use database manager, four groups of users are established. The heat demands of the users are derived using specific heat consumption data for the types of buildings considered. Users are either connected to the district heating system through direct heat exchangers on the supply or return line, or through local heat pumps which adapt the temperature to the needs locally, allowing a lower network temperature. Two different options are considered for the district heat supply: 1) a heat pump based superstructure comprising a gas turbine and a gas engine as cogeneration units, as well as an auxiliary boiler for peak load, and 2) a gas turbine / steam turbine combined cycle based superstructure with various options like steam injection and/or CO2 separation unit.

Physical and costing models for the two alternative production unit superstructures and for the district heating system are connected with the GIS database manager using DOME.

The environomic methodology, a simultaneous consideration of thermodynamic, economic and environmental criteria expressed as an aggregated cost, is used to assess the alternatives under different scenarios characterized by the cost of natural gas and the degree of pollution cost internalization.
The Use of Collaborative Learning in Biomedical Engineering Education
Authors: Gaver Donald P.
Published: November 2021

At Tulane University, we have developed a course that is intended to bridge the gap between traditional mathematics ‘tools-based’ courses taken by undergraduates and the application of these tools to model biological systems. This course, ‘Mathematical Modeling and Analysis of Biological Systems,’ was developed initially as a graduate-level course, and has migrated to become required of all Biomedical Engineering undergraduates.
A Matlab-Based Cardiac Mechanics Course: Exportable Tools for Graduate-Level Soft Tissue Biomechanics
Authors: Holmes Jeffrey W.
Published: November 2021

Graduate courses in finite elasticity and soft tissue biomechanics must deliver substantial theoretical content to prepare students for the complexities of soft tissue mechanics. In the laboratory students often discover that practical tasks such as calculating three-dimensional finite strain from marker data or reconstructing three-dimensional marker positions from two-dimensional views are not obvious despite mastery of the underlying theory. This course sought to replace as much didactic time as possible with hands-on MATLAB programming and simulations to illustrate basic theory and help students make the bridge to practical applications.
Tangential Stress in Cortical Bone Subjected to Dynamic Axial Loading
Authors: Choi J. H. , Dharan C. K. H.
Published: November 2021

Cortical bone is a complex hierarchical composite lamallae structure consisting, in general, of a mineral phase (calcium hydroxyapatite), an organic phase (collagen) and fluid [1]. In the analysis of bone, the liquid phase is usually neglected, an assumption that is reasonable for steady state or quasi-static loading. However, when cortical bone is loaded dynamically in the axial direction, the presence of the constrained fluid generates time-dependent stresses in the tangential direction. Since the tangential stress acts perpendicular to the weak transverse direction of the bone, it can create damage in this direction. Cyclic axial compressive loading will result in cyclic tensile loading in the tangential direction which can eventually result in fatigue damage. Such damage has actually been observed in studies conducted on heavily exercised race horses where damage was observed in the form of micro cracks oriented perpendicular to the tangential direction and whose fracture planes lie along the axial direction [2].

In this work, cortical bone is modeled as a biphasic material consisting of a permeable composite material filled with fluid. The geometry considered is that of a hollow cylinder made up of multiple concentric permeable lamellae filled with fluid (Fig. 1). When this structure is loaded axially in compression, a tensile tangential stress is developed which decays with time. The decay rate is a function of permeability and radial position. The greater the permeability, the faster the decay rate. The tangential stress peaks at the inner radius and decreases with radial position (Fig. 2). The tangential stress also peaks earlier at the inner radius. The rate of decay is slower at the outside surface where the bone is subjected to the tangential stress for a much longer time than at the inner surface (Fig. 2).

This view of bone as a biphasic structure subjected to dynamic loading may provide a rationale for some of the damage modes observed in vivo in bones subjected to cyclic and impact loading.
Effects of Anterior Spinal Instrumentation on Single-Level Cervical Graft Mechanics
Authors: DiAngelo Denis J. , Liu Weiqiang , Kelly Brian P. , Foley Kevin T.
Published: November 2021

Anterior cervical discectomy with or without graft fusion is an acceptable surgical method for the treatment of cervical spondylosis or other spinal disc diseases. A graft-alone or graft with supplemental spinal instrumentation may be used to immobilize the operated/injured region to promote bony fusion. Graft fusion with instrumentation is intended to restore the mechanical integrity of the operated spine and decrease graft complications. Although the surgical procedure should restore the mechanical integrity of the operated spine, little is known of the load-sharing mechanics of single-level grafted constructs. We have previously shown that anterior instrumentation reverses the loading mechanics of a multi-level cervical strut-graft tested under physiologic flexion and extension conditions (DiAngelo et al., 2000). We hypothesize that a single-level anterior cervical plate will function in a similar manner. That is, a single-level anterior cervical plate will reverse the loads on the graft by loading the graft in extension and unloading the graft in flexion. We also hypothesize that a graft-alone construct does not provide adequate stabilization comparable to that of the graft-plated condition tested in flexion and extension. The objective of the study was to determine the biomechanical stability of four different spine conditions tested under physiologic flexion and extension conditions. They included the harvested, discectomized, graft-alone, and graft with single-level anterior cervical plate.
Finite Element Modelling of a Biocomposite Intervertebral Disc
Authors: Khoang Voon S. , Lim Chwee T. , Ramakrishna Seeram
Published: November 2021

Previous research on artificial intervertebral disc had concentrated on the use of metallic materials like Ti or Co-Cr-Mo alloys for the harder endplates [1], and polymeric materials like Polyurethane for the softer inner core [2,3]. The protocols from these had yielded various degrees of success. In recent years, the use of composite as a biomaterial has attracted much attention due to their highly tailorable material properties. This generates a motivation to use composite materials as a substitute.
In-Vitro Measurements of Microgravity Induced Kinematics Changes on Spine
Authors: Reiter David , Sarigul-Klijn Nesrin , Gupta Munish , Fathallah Fadi
Published: November 2021

It has been observed that astronauts gain height up to 7 cm during space flight due to microgravity effects. This is due partly to the swelling of inter vertabral Dics (IVD). As a result of this most astronauts experiences low back pain. The mechanisms of pain are not well understood yet. The physiological changes that occur from microgravity environment are simulated via bed rest studies on earth. These studies verify the height change and are good simulations of the microgravity of Space Flight. There has not been any studies showing how the fluid shift effects the kinematics of the spine. In our study we designed a ground based in-vitro experiment to measure the kinematics changes induced by microgravity on spine.
Effects of Cortical Shell Concavity on Vertebral Body Compressive Properties
Authors: Liebschner Michael A. K. , Keaveny Tony M. , Rosenberg William S.
Published: November 2021

Quantification of the structural role of the vertebral shell and trabecular centrum is essential to determine if the shell should be given equal consideration when predicting the fracture strength. The contribution of the cortical shell and endplate to the stiffness and strength of the vertebral body is not well understood and the literature remains controversial [1–5]. The uncertainty of the mechanistic support of the cortical shell and the role of its geometry is due in part to the difficulty in obtaining physical information about the shell[5]. A study on sheep vertebrae performed by Kasra and Grynpas [6] suggested a negative correlation between failure load and the tangent of the cortical shell curvature measured in the AP and lateral plane. Nevertheless, the structural role of the vertebral shell may be different in human vertebrae due to altered loading situations and different geometry. Another study by Edmonston et al. [7] implied a strong correlation between vertebral bone density and thoracic curvature. No study reported in the literature investigated the effect of the cortical shell concavity of human vertebral bodies on their mechanical properties.
Development of a Rate-Dependent Material Model for UHMWPE Joint Replacement Components
Authors: Houchaime W. , Petrella A. , Dietz T. , Halloran J. , Rullkoetter P.
Published: November 2021

Polyethylene wear has been implicated in osteolysis and can lead eventually to implant loosening. Abrasive/adhesive wear and delamination or pitting damage in ultra-high molecular weight polyethylene (UHMWPE) joint replacement components has been in part attributed to high joint contact stresses. The propensity of total joint replacement systems for these types of wear is often assessed by evaluating the joint contact stresses and contact areas and these often serve as a basis for differentiation of systems. The rate-dependency of polyethylene can have a significant effect on these contact characteristics of joint replacement components. Previously, researchers have used experimental and analytical methods to determine joint contact characteristics. Most of the analytical studies, however, have not included the important time-dependent behavior of UHWMPE.
Indentation of Articular Cartilage: Effects of Specimen Radius on Determined Properties
Authors: Spoon Corrie E. , Wayne Jennifer S.
Published: November 2021

The indentation test is a commonly used experimental setup to determine properties of articular cartilage, both in the laboratory and as a clinical tool, as it is a test that can be performed in situ. Behavior of normal cartilage and tissue generated in reparative studies have been thus obtained [1, 2, 3]. It has been shown from a finite element study [4] that the behavior of cartilage in indentation stress relaxation can be affected by the tissue width relative to the radius of the indenter. Another finite element study of the indentation of osteochondral defects showed that this ratio also affected specifications of boundary conditions [5]. This investigation sought to evaluate the effect of changing geometric parameters (e.g. tissue width and indenter radius) on the properties determined from creep indentation experiments.
Depth-Dependent Material Property Inhomogeneities Affect the Deformation and Electric Fields in the Chondrocytes and Extracellular Matrix During Compression
Authors: Sun D. D. , Mow V. C. , Lai W. M. , Guo X. E.
Published: November 2021

The biosynthetic activities of chondrocytes are regulated by the mechanical and electrochemical (MEC) environments around cells in the extracellular matrix (ECM) such as matrix deformation, stress/strain, fluid and osmotic pressures and electrical potential [e.g., 1–3]. These MEC parameters are the signals that chondrocytes sense and respond to under mechanical or chemical loading. Therefore, detailed quantification of these MEC signals is a key step toward the understanding the mechano-signal transduction mechanism in cartilage. Since microscopic measurements of MEC environments around cells is generally not possible experimentally, theoretical cell-ECM interaction models have attracted research interests in efforts to predict the MEC fields around and within the chondrocytes encased in the ECM [e.g., 4–6]. These models show that during mechanical compression the responses of the chondrocytes and ECM are intrinsically coupled, influenced by their material properties, and are strongly time and depth dependent [4–6]. For example, the chondrocytes and ECM at the surface zone of the articular cartilage undergo significantly larger axial compression, shear, osmotic pressure and electrical potential than those at the deeper zones [5,6].
Potential Roles for Collagen and Decorin in Strain Rate Sensitive Tendon Fascicle Mechanical Properties
Authors: Robinson Paul S. , Lin Tony W. , Reynolds Paul R. , Derwin Kathleen A. , Iozzo Renato V. , Soslowsky Louis J.
Published: November 2021

Little is known about the contributions of specific extracellular matrix components of tendon to the tissue’s mechanical properties. Type I collagen, given its abundance and association into long fibrils, is thought to dominate the elastic properties of tendon. Proteoglycans (PGs) are believed to provide elasticity through their potential role in transferring stress between discontinuous fibrils, as well as viscoelasticity via their interaction with water. Previous studies suggest relationships between collagen or PGs and tissue mechanics [1,2]. However, no study to date has isolated the contributions that distinct tendon components make to the elastic and viscoelastic properties of tendon. Recently, transgenic mice with prescribed mutations or deletions of various genes for specific tendon constituents have become available. In this study, we use transgenic mice as a tool to investigate the contributions of tendon components to tendon function based on a previously described approach [3]. In particular, we compare the strain rate sensitivity among fascicles from the tails of mice described in Table 1. We hypothesize that (a) fascicles with alterations in type I collagen (C1TJ8 and C1M8) will have different elastic properties but no difference in strain rate sensitivity than age-matched controls (CTL8), and (b) fascicles with alterations in proteoglycan (DKO8 and CTL3 [4]) will have different elastic properties and different strain rate sensitivity than CTL8 fascicles.
Comparison of Two Calcaneal Osteotomies in a Flatfoot Model
Authors: Otis James C. , Sung Il-Hoon , Lee Sam , Hubbard Christopher , Deland Jonathan T.
Published: November 2021

Posterior tibial tendon dysfunction (PTTD) often leads to adult acquired flatfoot deformity. Loss of the tendon’s invertor function results in a progressively lower medial longitudinal arch, hindfoot valgus and forefoot abduction. Treatment varies based on surgeon preference, but typically consists of a medial slide calcaneal osteotomy (slide) and a flexor digitorum longus (FDL) tendon transfer. The concept of a medial displacement calcaneal osteotomy with a posterior distraction (distraction) has been introduced, and demonstrated to significantly reduce the inversion force requirement for heel rise compared to the slide[l]. This finding is significant as it suggests that the distraction is more efficacious than the slide in correcting deformity. However, it has not been validated on a flatfoot model.
Simulation and Control of a Robotic/UFS Testing System With Application to Lumbar Spine Biomechanics
Authors: Doehring Todd C. , Gilbertson Lars G. , Kang James D.
Published: November 2021

Control of biomechanical experiments, especially those involving musculoskeletal joints such as the knee or spine, is a complicated problem because of the highly nonlinear kinematic, structural, and material properties of the tissue. Historically, materials testing machines with one or two degrees of freedom (DOF) (e.g. biaxial Instron, MTS) have been used. However, these devices, originally designed for testing of “standardized” engineering materials, are limited in two critical areas: 1) The number of DOF, and 2) The control system, which restricts the experiment to either “force control” or “displacement control” methods.
Anisotropic Nonlinear Friction at Biomaterial Interfaces: Theory and Application
Authors: Mesfar W. , Shirazi-Adl A. , Dammak M.
Published: November 2021

The interface friction exists in natural and artificial joints as well as many engineering systems in which different bodies articulate. It often plays an important role in mechanics of the system. In the cementless arthroplasty, the friction between the prosthesis (including stems and screws) and the host bone is exploited to increase the stability of the operation. Our previous experimental studies have shown that the interface between bone and various porous coated surfaces exhibit a nonlinear friction that remains nearly the same in different directions; a nonlinear isotropic friction [1,2]. More recent bidirectional friction tests between cancellous bone or polyurethane cubes and a metallic porous coated plate have demonstrated that the interface load-displacement curve is highly nonlinear with significant coupling between two perpendicular directions [3]. Model studies incorporating measured nonlinear response have demonstrated the importance of proper simulation of nonlinear response as compared with Coulomb friction and of the coupling between orthogonal directions [3–5]. In this study, we aim to extend the earlier model studies to incorporate nonlinear direction-dependent anisotropic friction between two surfaces. Our objectives are set to: (a) develop constitutive equations to present interfaces with nonlinear anisotropic friction properties; and (b) implement and apply in a finite element study of a cube resting on a block subjected to normal and shear loads.
A General Adhesive Wear Simulation for Total Joint Replacements: Application to the Patellofemoral Joint
Authors: Petrella Anthony J. , Miller Mark C.
Published: November 2021

Advances in design, materials, and fixation have increased the longevity of total joint replacements and significantly reduced the incidence of mechanical failure or loosening of implant components. Wear of the ultra-high molecular weight polyethylene (UHMWPE) bearing material used in most implants is now among the most important problems in total joint replacement. Wear tests in joint simulators are the gold standard for evaluation of wear resistance and are performed on a routine basis in many research laboratories. Physical wear testing, however, is labor intensive and time consuming. Numerical wear simulations have been developed and applied to the hip joint to evaluate adhesive wear of polyethylene liners [1,2]. The purpose of this project was to develop a general adhesive wear simulation applicable to any articulating joint with arbitrary geometry and subject to arbitrary relative motion. Validation of the model was established through application to the patellofemoral joint of a total knee replacement.
The Wear of UHMWPE in Total Knee Replacements: Experimental and Finite Element Analysis of Contact Behaviour
Authors: Murphy Dorothy M. , Kavanagh Alan , McGloughlin Tim M.
Published: November 2021

Upon examination of failed total knee replacements, it has been concluded that it is the performance of the ultra high molecular weight polyethylene (UHMWPE) tibial component that governs the useful lifespan of such a joint. Severe wear of UHMWPE is associated more with tibial components of the knee than with the acetabular cups of total hip replacements. This is due to a notable lack of congruity between the articulating surfaces which leads to the presence of significant localised stresses in the femoro-tibial interface.
A Direct Comparision of Patient and Simulator Total Knee Replacement Kinematics
Authors: DesJardins John D. , Banks Scott A. , Benson Lisa C. , LaBerge Martine
Published: November 2021

The need to critically evaluate the efficacy of current total knee replacement (TKR) wear testing methodologies is great. Proposed international standards for TKR wear simulation have been drafted, yet their validity continues to be debated. The “gold standard” to which all wear testing methodologies should be compared is the measured in vivo TKR performance of the patient population. With the exception of retrieval analyses, few detailed comparisons of in-vitro vs. in-vivo TKR performance have been performed to date. The current study compares simulator TKR wear testing kinematics to measured in vivo TKR kinematics to evaluate the validity of the proposed ISO force-controlled wear testing methodology.
Comparison of Upper and Lower Hybrid III Dummy Neck Compression Forces Under Vertical Loading
Authors: Friedman Keith
Published: November 2021

The determination of the relationship of the upper and lower Hybrid III dummy neck transducer loads during vertical drop test loading was of interest in the present study. The anthropometric test device is a tool used in crash analysis. It is typically used for frontal or side crash analysis. It has however been used for vertical drop or rollover studies (1).