bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Multi-Scale Sensing and Neural Network Data Fusion for Damage Identification
Authors: Studer Michel , Peters Kara
Published: May 2008

Multi-scale measurements, i.e. measurements of strain, strain gradient and integrated strain data, throughout a structural volume have demonstrated a great potential for improved damage identification. However, the large number of data and their different forms make fusion of the data difficult. To overcome this problem, a neural network data fusion approach is proposed. A simulation of damage identification in an isotropic cracked plate is presented. The crack position, angle and crack length are used as test parameters to be determined. A back-propagation neural network is trained to reproduce the crack angle and length as a function of all sensor responses. The improvement gained by using both multi-scale sensing and neural network data fusion for this specific case is significant. Testing of the sensitivity of the method to measurement errors or missing data demonstrated the robustness of the neural network to errors.
Finite Element Modeling of Repair Cartilage Beneath a Protective Layer
Authors: Owen John R. , Wayne Jennifer S.
Published: May 2008

Significant efforts are being devoted to the creation of replacement tissue for repair of defects in articular surfaces. Some success has been realized; yet, the normal zonal characterstics of articular cartilage throughout its thickness and normal material properties have not been reproduced in vitro in scaffolds nor in vivo in repairing defects. The fate of such transplanted scaffolds in vivo may be doomed mechanically from the outset if material properties of sufficient quality are not developed. The superficial tangential zone (STZ) has been shown to play a critical role in supporting axial loads and retaining fluids (Glazer and Putz, 2002, Torzilli, et al, 1983, Torzilli, 1993). Previous models have demonstrated excessive axial deformation of repair cartilage without the STZ (Smith, et al 2001, Wayne, et al, 1991) Additionally, modeling the STZ of normal cartilage as transversely isotropic has yielded better agreement with indentation experimental results than isotropic models (Korhonen, et al, 2002, Mow, et al, 2000, Cohen, et al, 1993). This study uses finite element analysis to model the STZ with a preferred direction parallel to the articulating surface, thereby simulating a “split-line” direction. The in-plane directions are modeled normal to the “split-line” direction and the articulating surface. Normal and repairing defects are modeled with the importance of the STZ emphasized.
The Studies of Mechanical Contribution of Pins of Wrist External Fixator Using Mechanical Model, Cadaver Model and In Vivo Patient Model
Authors: Chang Chih-Hao , Hou Sheng-Mou , Wang Jaw-Lin , Tsai Yuan-Quan
Published: May 2008

Wrist external fixator (WEF) is widely used in unstable distal radius fracture. The mechanical properties of WEF were thoroughly studied by many authors. The researches of external skeletal fixator include the stability of the frame structure, fatigue or failure model of pins, exploration of biomechanical characteristics of pin-bone interface, and the strength of pin clamps. The mechanical models [1–5] and cadaver bone [6] were frequently used to test the WEF. For most of the studies, the stiffness (or stability) of the construct was the criteria to evaluate the WEF. In these many studies, however, the mechanical contribution of pins was less studied. Due to the non-weight bearing property and prevention of injuries from the soft tissue of peri-wrist, the structure and elements of WEF are designed to be small and slender. It is hence important to find if all pins of WEF were necessary or proper designed. We tested the mechanical function of Traumafix WEF using the mechanical model, the cadaver model and in vivo patient model. The strains of the pins on the top surface were analyzed. The data showed that the load distribution of each pins were different from pins to pins, and from models. Our result suggests the distal pins of WEF can be smaller if the space of metacarpal bone is limited.
An Enterprise Decision Model for Optimal Vehicle Design and Technology Valuation
Authors: Cooper Adam B. , Papalambros Panos Y.
Published: May 2008

Design optimization traditionally has dealt with engineering design decisions. Yet it is well understood that optimal product decisions must be based on engineering as well as marketing and production considerations. An enterprise decision model attempts to link these aspects of the product development enterprise so that the value of the designed product to the enterprise can be assessed. The model also values new product technology in accordance with the enterprise’s current operations to increase the likelihood of commercialization success before committing to a new strategy. The valuation technique uses comprehensive engineering simulation to provide a preliminary understanding of the technology’s market and design potential. The model represents the enterprise in a mathematical formulation that simultaneously optimizes initial product design, product pricing, operating costs associated with capacity allocation and design decisions, and the value created by new products. The article demonstrates such a model for optimal vehicle design in a medium truck market experiencing hybrid penetration.
Design of Constrained Layer Damping Topologies
Authors: Lumsdaine Arnold , Pai Rohan
Published: May 2008

The aim of this research is to determine the optimal topologies for viscoelastic lamina used for vibration damping. The optimization objective is to maximize the system loss factor for the first resonance frequency of a base structure. Previous optimal design studies examining viscoelastic lamina have been size or shape optimization studies, assuming a certain topology for the damping treatment. In this study, the topology is optimized to maximize vibration damping levels. The loss factor is computed using the Modal Strain Energy method in the optimization process. For the initial and optimal topologies, the loss factor results are validated by using the half-power bandwidth method, which requires obtaining the forced response of the structure. The ABAQUS finite element code is used to model the structure with two-dimensional, plane stress, continuum elements. The optimization code uses a Sequential Quadratic Programming algorithm. This study extends the results of a previous study by Lumsdaine (2002) by examining the effects of a number of parameters on the optimal damping levels and the optimal topologies. The parameters examined include the total elastic and viscoelastic material fractions and the base beam thickness. Results show that significant improvements in damping performance, over 300% in some cases, are obtained by optimizing the constrained damping layer topology.
Effects of Diabetes Mellitus on the Biomechanical Properties of the Female Rat Urethra in the Passive State
Authors: Prantil Rachelle L. , Jankowski Ronald J. , Torimoto Kazumasa , de Groat William C. , Chancellor Michael B. , Vorp David A.
Published: May 2008

Patients with diabetes mellitus (DM) suffer impaired lower urinary tract dysfunctions. The purpose of the current study was to evaluate the effects of DM on the passive biomechanical properties of the female rat urethra. DM was induced by injection of streptozotocin. Urethras were excised and mounted in an ex-vivo testing system. EDTA was added to the bath to inactivate smooth muscle. Continuous outer diameter measurements were made at proximal, middle, and distal portions of the urethra with a laser micrometer during stepwise increases of static, intraurethral pressure (0 to 20 mmHg). Compliance and beta stiffness were calculated from measured data. Healthy urethras served as controls. Statistical comparisons were made via ANOVA. The control tissue was most compliant proximally and decreased significantly along the length. This compliance gradient vanished with DM. A significant decrease in compliance and increase in beta stiffness was noted for 10 wk DM compared to controls. These findings suggest that DM has a large effect on the biomechanical properties of the urethra.
Spinal Posture Affects Whiplash Biomechanics
Authors: Stemper Brian D. , Yoganandan Narayan , Pintar Frank A.
Published: May 2008

The present study implemented the MADYMO 50th percentile male head-neck model to investigate effects of initial spinal posture on cervical spine kinematics in whiplash. The model was altered to three initial postures: lordosis, straight, kyphosis. The three models were exercised under 2.6 m/sec rear impact pulses. Segmental kinematics and ligament strains were investigated during cervical S-curvature and throughout the whiplash event. Anterior longitudinal ligament strains during S-curvature varied from 20 to 47% of maximum strains. Facet joint strains during S-curvature were 42 to 100% of maximum strains. This finding indicates that facet joint ligaments are more susceptible to whiplash injury during S-curvature, while anterior longitudinal ligament injury likely occurs during the extension phase. Kyphosis and straight postures increased anterior longitudinal ligament strains in the upper cervical spine from the lordosis posture. Lower cervical facet joint and anterior longitudinal ligament strains were greater in the lordosis posture. This study shows that spinal posture may affect injury mechanisms and render a specific population more susceptible to whiplash injury.
Modeling of Wheeled Mobile Robot on Rough Terrain
Authors: Tai Meihua
Published: May 2008

This paper presents kinematic and dynamic modeling of a wheeled mobile robotic platform for rough terrain operations. In the model, the body of the robot and each wheel set are considered as rigid bodies translating and rotating in space. For robots navigating on the ground, the external forces to the system are all coming from the road-tire interactions. In the kinematic model, it is assumed that the ground can provide whatever forces required to satisfy kinematic constraints at contact points, and in the dynamic model, the dynamic interactions between the tires and the terrain are considered.
Manufacturing and Active Control Testing of Active Composite Panels With Embedded Piezoelectric Sensors and Actuators: Wires Out by Cut-Holes and Embedding
Authors: Ghasemi Nejhad Mehrdad N. , Russ Richard
Published: May 2008

This work presents manufacturing and testing of active composite panels (ACPs) with embedded piezoelectric sensors and actuators. The composite material employed here is a plain weave carbon/epoxy prepreg fabric with about 0.3 mm ply thickness. A cross-ply type stacking sequence is employed for the ACPs. The piezoelectric flexible patches employed here are Active Fiber Composites with 0.33 mm thickness. Composite cut-out layers are used to fill the space around the embedded piezo patches to minimize the problems associated with ply drops in composites. The piezoelectric patches were embedded inside the composite laminate. High-temperature wires were soldered to the piezo leads, insulated from the carbon substructure by high-temperature materials, and were taken out of the composite laminates employing both cut-hole and embedding techniques. The laminated ACPs were co-cured inside an autoclave employing the cure cycle recommended by the composite material supplier. The Curie temperature of the embedded piezo patches should be well above the curing temperature of the composite materials as was the case here. The manufactured ACPs were trimmed and then tested for their functionality. Vibration suppression as well as simultaneous vibration suppression and precision positioning tests, using Hybrid Adaptive Control techniques were successfully conducted on the manufactured ACP beams and plates and their functionality were demonstrated. The advantages and disadvantages of ACPs manufactured by taking the wires out employing cut-holes and embedding techniques, in terms of manufacturing and performance, are presented.
Control-Oriented Modeling of Thermal Deformation of Machine Tools Based on Inverse Solution of Time-Variant Thermal Loads With Delayed Response
Authors: Fraser S. , Attia M. H. , Osman M. O. M.
Published: May 2008

With the new emerging technologies of high performance machining and the increasing demand for improved machining accuracy in recent years, the problem of thermal deformation of machine tool structures is becoming more critical than ever. The major problem in implementing real-time control systems is the difficulty of measuring the relative thermal displacement between the tool and the workpiece during machining. Therefore, the design of a generic multi-axis control system requires the development of control-based models to estimate the transient thermal load and the thermal deformation of the structure in real-time. To satisfy the stringent accuracy and stability requirements of the control system, a new inverse heat conduction problem IHCP solver is developed. This solution is capable of including the inertia effect and the delay in the thermal response, in order to accommodate situations where the measured points cannot be located near the heat source, which may be buried into the structure. Experimental validation of these models showed their inherent stability even when the temperature measurement are contaminated with random errors. The excellent computational efficiency of the integrated system, which is well suited for real-time control applications involving multi-dimensional structures, was achieved by incorporating an inverse numerical Laplace transformation procedure. The result also showed that the thermal deformation transfer function behaves as low-pass filters, and as such it attenuates the high frequency noise associated with temperature measurement error.
Morphological and Elastic Properties of the Glenoid Region of the Shoulder
Authors: Lim D. , Seliktar R. , Wee J. , Nunes L. , Farrell E.
Published: May 2008

Researchers have tried to assess the morphological and mechanical characteristics of bone using various methods with a limited success (Mow and Hayes, 1997, and Cowin, 2001). This may be due to the complexity for documentation and characterization of architecture by the anisotropic and nonhomogeneous characteristic of the bone. The bones of the shoulder joint complex are particularly deprived of information on their mechanical and morphological properties. Very little is known for example on the mechanics and morphology of the glenoid of the shoulder. The present work presents an attempt to identify a proper method for the measurement and characterization of the morphology and mechanics of bone, particularly in the glenoid. Our results show that trabecular lines are directed at 82.15° ± 7.98° relative to the glenoid articular surface, young’s modulus obtained from CT scan was 230 ± 8 MP, and the elastic tensors obtained from cadaver were 326 ± 78 MPa for E2222, 144 ± 22 MPa for E1111=E3333, 49 ± 7 MPa for E3311, 59 ± 9 MPa for E1122=E2233, 51 ± 8 MPa for E1313, and 70 ± 10 MPa for E1212=E2323. These results were consistent with Wolf’s Law and were in agreement with results reported in literatures (Anglin et al., 1999, Frich et al., 1998, and Mansat et al., 1998).
An Engine-Starting Simulation With Friction Estimation: Background and Model Validation
Authors: Henry Rassem R.
Published: May 2008

This paper describes an engine-starting simulation that uses models of the electrical, engine dynamics and engine thermodynamics subsystems combining them with engine friction models. One of these friction models uses the physical parameters of the engine as basis for estimating the friction torque. This allows engine performance prediction, hence the ability to size the electrical starting system, without engine availability. The resultant simulation is developed using SIMULINK/MATLAB™ and it has been validated for two engines; the first is a 4-cylinder engine with a conventional valve train, and relatively high friction by today’s standards, and the second is a more recent 3-cylinder engine with lowfriction. Validation of the first engine was done based on matching its published starting tests with results obtained using this paper’s simulation. The validation of the second engine was carried out by comparing engine test results with simulation results. Tests in the first case were for engine starting including firing and in the second case were for cranking only conditions.
A Method for Mechanically Loading Joints During Dynamic Magnetic Resonance Imaging
Authors: Rausch Tracy L. , Wirick Beth A. , Stanhope Steven J. , Sheehan Frances T.
Published: May 2008

In order to take advantage of the opportunities that dynamic Magnetic Resonance Imaging (d-MRI) offers to the study of in vivo joint mechanics, d-MRI compatible devices capable of producing joint loads replicating dynamic physiological activities are needed (Sheehan et al., 1999). The purpose of this research effort was to design, model and test a device for the expressed purpose of using d-MRI to study precise ankle joint dynamics during loaded pseudo-functional movements. The device adjusts to subject specific anthropometric measurements, allowing for the device’s axis of rotation to approximate the ankle’s transverse axis. By combining imaging data and the model of the device, the magnitude, direction and point of application of the force applied to the foot were calculated throughout the motion cycle, with an average error of .7 Nm. This allows for comparisons between the externally applied load and internal ankle joint kinematics to be made, which are essential determinants for in vivo estimates of forces within tendon and ligament. The next phase of this work will be to combine this device with fast-Phase Contrast MRI (fast-pc), a previously developed d-MRI technique for the quantification of 3D musculoskeletal motion, in order to create a complete tool for the noninvasive in vivo measurement of joint kinematics during a loaded dynamic functional task in both healthy and impaired ankles.
Repeatable Dynamic Rollover Roof Test Fixture
Authors: Friedman Donald , Jordan Acen , Nash Carl , Bish Jack , Honikman Terence , Sigel Jason
Published: May 2008

Experimental rollover tests have been criticized for their poor emulation of actual rollovers and for their lack of repeatability. We have designed and built a test fixture that overcomes both of these criticisms. The fixture holds a passenger compartment, weighted to match the inertia characteristics of a complete vehicle, or a complete vehicle at the appropriate pitch and yaw. The compartment is then rotated about its principal (longitudinal) axis through an arc that mimics the rolling motion of an entire vehicle. At the appropriate roll angle and falling velocity, the roof strikes a moving patch of concrete. The compartment is controlled throughout the sequence and is suspended after the impact, so that a sequence of impacts can be individually studied in separate tests. Initial tests have shown that we can achieve repeatable impacts. Test variables include pitch, yaw, roll rate and vehicle center of gravity motion (both lateral and vertical velocity). This test device addresses the various shortcomings of previous rollover tests, fixtures and the various static and drop tests of vehicles conducted to determine rollover performance.
Decomposition-Based Assembly Synthesis of Multiple Structures for Minimum Production Cost
Authors: Cetin Onur L. , Saitou Kazuhiro
Published: May 2008

An extension of decomposition-based assembly synthesis for structural modularity is presented where the early identification of shareable components within multiple structures is posed as an outcome of the minimization of estimated production costs. The manufacturing costs of components are estimated under given production volumes considering the economies of scale. Multiple structures are simultaneously decomposed and the types of welded joints at component interfaces are selected from a given library, in order to minimize the overall production cost and the reduction of structural strength due to the introduction of joints. A multiobjective genetic algorithm is utilized to allow effective examination of trade-offs between manufacturing cost and structural strength. A new joint-oriented representation of structures combined with a “direct” crossover is introduced to enhance the efficiency of the search. A case study with two aluminum space frame automotive bodies is presented to demonstrate that not all types of component sharing are economically justifiable under a certain production scenario.
Finite Element Modeling of Knee Joint Contact Pressures and Comparison to Magnetic Resonance Imaging of the Loaded Knee
Authors: Yao Jiang , Salo Art D. , Barbu-McInnis Monica , Lerner Amy L.
Published: May 2008

A finite element model of the knee joint could be helpful in providing insight on mechanisms of injury, effects of treatment, and the role of mechanical factors in degenerative conditions. However, preparation of such a model involves many geometric simplifications and input of material properties, some of which are poorly understood. Therefore, a method to compare model predictions to actual behaviors under controlled conditions could provide confidence in the model before exploration of other loading scenarios. Our laboratory has developed a method to apply axial loads to the in vivo human knee during magnetic resonance imaging, resembling weightbearing conditions. Image processing algorithms may then be used to assess the three-dimensional kinematics of the tibia and femur during loading. A three-dimensional model of the tibio-menisco-femoral contact has been generated and the image-based kinematic boundary conditions were applied to investigate the distribution of stresses and strains in the articular cartilage and menisci throughout the loading period. In this study, our goal is to investigate the contact patterns during long term loading of up to twenty minutes in the healthy knee. Specifically, we assess the use of both elastic and poroelastic material properties in the cartilage, and compare model predictions to known loading conditions and images of tissue deformations.
Failure Mechanisms of Thermal Barrier Coatings at High Temperature
Authors: Chen Xi
Published: May 2008

Thermal barrier coatings (TBCs) are widely used in turbine engines. They are regarded as one of the most successful innovations and applications of coatings in industry. Thermal barrier system comprise thermally insulating materials having sufficient thickness and durability that they can sustain an appreciable temperature difference between the load bearing alloy and the coating surface. TBC exhibit multiple failure modes. Among them, the Foreign Object Damage (FOD) and mechanical erosion are the most prevalent failure modes of TBC at high temperature. In this study, based on a new scaling analysis of impact mechanics, FOD and erosion of TBCs are analyzed by using the finite element method. Impact and material variables are grouped into the smallest possible parameter set to provide explicit results. Microstructural effects are factored into the approach. Three different domains have been explored governed by particle size, velocity, temperature and TBC composition. Numerical simulations show that crack initiation is activated by transient stresses and delamination is governed by residual stresses. The transient stresses occurring near the free surface lead to crack initiation and material removal. Failure criterions are derived which provide useful insights on how to improve FOD and erosion resistances.
Fuzzy Logic Control of a Laboratory Magnetic Levitation System
Authors: Mohan Parimi V. Ram , Jain Piyush , Garg Devendra P.
Published: May 2008

This paper deals with the Fuzzy Logic control of a Magnetic Levitation system [1] available in the Robotics and Control Laboratory at Duke University. The laboratory Magnetic Levitation system primarily consists of a metallic ball, an electromagnet and an infrared optical sensor. The objective of the control experiment is to balance the metallic ball in a magnetic field at a desired position against gravity. The dynamics and control complexity of the system makes it an ideal control laboratory experiment. The student can design their own control schemes and/or change the parameters on the existing control modes supplied with the Magnetic Levitation system, and evaluate and compare their performances. In the process, they overcome challenges such as designing various control techniques, choose which specific control strategy to use, and learn how to optimize it. A Fuzzy Logic control scheme was designed and implemented to control the Magnetic Levitation system. Position and rate of change of position were the inputs to Fuzzy Logic Controller. Experiments were performed on the existing Magnetic Levitation system. Results from these experiments and digital simulation are presented in the paper.
Optimal Placement of PZT Transducers for Passive Vibration Control of Planar Composite Structures
Authors: Venna Suresh V. , Lin Y. J.
Published: May 2008

In this paper, an attempt is made to determine the electric potential that would be generated in the piezoelectric vibration absorber using finite element piezoelectric analysis to determine optimal location for damping of first mode. Optimal placement of piezoelectric vibration absorber for passive vibration control of a cantilever composite plate is investigated. Finite element piezoelectric modal analysis is performed. Models based on placing piezoelectric vibration absorbers at five different locations on the surface of the plate and incorporating piezoelectric properties are built. Modal analysis is used to find the electric potential developed in the piezoelectric vibration absorber. The location that yields the highest amount of electric potential would be the best location for the vibration absorber. First bending mode of the cantilever composite plate is aimed for damping. Results of the analysis are verified with an experimental testing of the composite plate with piezoelectric vibration absorber firmly attached to the plate. A good agreement is found between the analytical and experimental results. Further, a resistive shunt circuit is designed for the passive damping of the first mode and attached to the vibration absorber in which the electric potential developed would be dissipated as heat to obtain passive vibration compensation. The experiment also demonstrates that a damping of 6 percent is obtained in the first mode and a great amount of damping is achieved in the second and third modes too.
Three Dimensional Doctor-Patient Contact Forces During Chiropractic Spinal Treatments
Authors: Gudavalli Maruti R. , Rowell Robert M.
Published: May 2008

This paper reports on the three-dimensional loads measured during chiropractic treatments delivered during low back spinal procedures. A three dimensional force transducer was placed between the doctors hand and the patient while delivering the treatment. Two doctors have delivered treatments to a total of five subjects on two consecutive days. A laptop computer was used to collect data using labview software and Keithly instruments PCMCIA card. The data was analyzed using Mathcad software to determine the magnitudes of the forces delivered. The results show three-dimensional loads are applied by the doctor at the doctor’s hand-patient interface. The compressive forces reached as high as 450 Newtons, and the shear forces have reached as high as 150 Newtons. The moments have reached as high as 4Nm. This information is valuable in further understanding the effects of these loads on the spine.
Lagging Motion of Forced Nonlinear Oscillators
Authors: Karng Sand Woo , Kim Ki Young , Kwak Ho-Young
Published: May 2008

The lagging motion of nonlinear oscillators with respect to the externally driven field was treated analytically and the calculation results were compared with observed results. Such lagging problem may occur in nonlinear systems whose behavior crucially depends on the frequency of the applied force. The lagging motion of the nonlinear oscillator with respect to the harmonically driven field made the oscillator respond in a way that reduced the effect of the applied field. The calculation considering the lagging motion yielded proper results in the expansion ratio of the bubble under ultrasound and trajectories in phase plane, the frequency spectrum for a forced inverted pendulum, and the amplitude response of the Duffing oscillator.
Application of Frequency Domain ARX Models and Extreme Value Statistics to Impedance-Based Damage Detection
Authors: Fasel Timothy R. , Sohn Hoon , Park Gyuhae , Farrar Charles R.
Published: May 2008

In this paper, the applicability of an auto-regressive model with exogenous inputs (ARX) in the frequency domain to structural health monitoring (SHM) is established. Damage sensitive features that explicitly consider nonlinear system input/output relationships are extracted from the ARX model. Furthermore, because of the non-Gaussian nature of the extracted features, Extreme Value Statistics (EVS) is employed to develop a robust damage classifier. EVS provides superior performance to standard statistical methods because the data of interest are in the tails (extremes) of the damage sensitive feature distribution. The suitability of the ARX model, combined with EVS, to nonlinear damage detection is demonstrated with an impedance-based method that uses piezoelectric (PZT) material as both actuators and sensors. The analyzed data is obtained from a laboratory experiment of a three-story building model.
Comparison of Non-Nominal Geometry Models Represented in Physical Versus Virtual Environments
Authors: Wickman Casper G. , So¨derberg Rikard
Published: May 2008

In the automotive industry today, virtual geometry verification activities are conducted with nominal models in the early design phases. Later in the design process when the first physical test series are made, are concepts verified in a non-nominal manner. Errors detected at this stage can result in expensive post-conceptual changes. By combining Computer Aided Tolerance (CAT) simulation tools with Virtual Reality (VR) tools, virtual environments for non-nominal geometry verification can be utilized. This paper presents the results from a study, conducted at Volvo Cars, that investigates the perceptional aspects that are related to verification of quality appearance, using non-nominal virtual models. Although a realistic non-nominal model is created, the interpretation, i.e. how the model is perceived, must be clarified. This would represent a validation of the model from a perceptional point of view. Since the effect of geometric variation is a specific application, with high demands on realistic and detailed representation, perceptional studies are needed to ensure that VR and other virtual representations can be used for this kind of application. The question is whether it is possible to evaluate aspects like flush, gap and see-through in virtual environments. In this paper, two environments are compared, one physical and one corresponding virtual environment. Three adjusted physical vehicles are mapped to the virtual environment and compared using non-immersive desktop VR in a visualization clinic with test subjects from the automotive industry. The study indicates that virtual objects are judged as less good looking compared with physical objects. There is also a higher degree of uncertainness when judging virtual objects.
Organic Working Fluids for a Combined Power and Cooling Cycle
Authors: Vijayaraghavan Sanjay , Goswami D. Y.
Published: May 2008

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling as useful outputs. Initial studies were performed with an ammonia-water mixture as the working fluid in the cycle. This work extends the application of the cycle to working fluids consisting of organic fluid mixtures. Organic working fluids have been used successfully in geothermal power plants, as working fluids in Rankine cycles. An advantage of using organic working fluids is that the industry has experience with building turbines for these fluids. A commercially available optimization program has been used to maximize the thermodynamic performance of the cycle. The advantages and disadvantages of using organic fluid mixtures as opposed to an ammonia-water mixture are discussed. It is found that thermodynamic efficiencies achievable with organic fluid mixtures, under optimum conditions, are lower than those obtained with ammonia-water mixtures. Further, the refrigeration temperatures achievable using organic fluid mixtures are higher than those using ammonia-water mixtures.
A Two-Phase Fluid Model for Simulation of Cavitation Phenomena in Pipe-Line Hydraulic Systems
Authors: Negri Claudio
Published: May 2008

This paper presents the details of a new fluid mathematical model developed for the numerical simulation of hydraulic systems that can work in cavitating conditions. The proposed fluid model allows you to obtain physical properties, i.e. density, bulk modulus, enthalpy, entropy, void fraction and sound speed, of a liquid-vapor-gas mixture so that the mixture itself can be treated as a homogeneous fluid (homogeneous two-phase fluid model). The model was applied in the numerical analysis of pipe-line test cases. in particular, both travelling cavitation, followed by a shock-wave, and fixed cavitation due to the superposition of depression waves, are examined and numerically simulated. Besides, relevant results are shown about sound speed variations in the zones of cavitation. The author is then interested in evaluating the approximation affecting the results obtainable by using an isothermal approach, by comparing them to the results obtainable by solving the full set of conservation equations (including the energy conservation law). An analysis on the entropy production due to the propagation of shock waves is proposed, along with an estimation of the inaccuracies occurring if an isentropic or isothermal evolution is assumed.
Influence of Martensitic Transformation on the Durability of TBC Systems (Invited)
Authors: Chen M. W. , Glynn M. L. , Pan D. , Ramesh K. T. , Hemker K. J. , Ott R. T. , Hufnagel T. C.
Published: May 2008

Microstructural evolution of bond coat with thermal cycling was characterized with transmission electron microscopy (TEM) and high temperature X-ray diffraction (HT-XRD) analysis. Before thermal cycling, the structure of asfabricated bond coat was confirmed to be a long-range ordered B2 β-phase. After thermal cycling to ∼28% of the cyclic life, the bond coat was found to transform into a Nirich L10 martensite (M) from its original B2 structure. The transformations, M ↔ B2, were demonstrated to be reversible and to occur on heating and cooling in each cycle. Quantitative high temperature XRD measurements verified the phase transformations produce about 0.7 % transformation strain. Finite element calculations incorporating the transformation strain indicate that the mertensitic transformation significantly influences the development of stresses and strains in TBC systems.
Sliding Mode Control of Vibration in a Flexible Structure Using Output Feedback Method
Authors: Pai M. C. , Sinha A.
Published: May 2008

This paper presents a new approach for the robust control of vibration in a flexible structure in the presence of uncertain parameters and the effect of observation spillover. The development of the technique which is based on the sliding mode control algorithm and direct output feedback is presented. The uncertainty matrix need not satisfy the invariance or matching conditions. The small gain theorem / μ analysis is applied to analyze the asymptotic behavior of the closed-loop system with parametric uncertainties inside boundary layers. Using a flexible tetrahedral truss structure, numerical examples are presented to verify the theoretical analysis.
Nano Science and Engineering in Mechanics and Materials
Authors: Chong Ken P.
Published: May 2008

The transcendent technologies include nanotechnology, microelectronics, information technology and biotechnology as well as the enabling and supporting civil infrastructure systems and materials. These technologies are the primary drivers of the twenty first century and the new economy. Mechanics and materials are essential elements in all of the transcendent technologies. Research opportunities, education and challenges in mechanics and materials, including nanomechanics, carbon nano-tubes, bio-inspired materials, coatings, fire-resistant materials as well as improved engineering and design of materials are presented and discussed in this paper.
Structural Analysis of Nonlinear Control Systems Using Singular Value Decomposition: Part I — Approach
Authors: Gwak Kwan-Woong , Masada Glenn Y.
Published: May 2008

Structural information of a system/controller allows a designer to diagnose performance characteristics in advance and to make better choices of solution methods. Singular value decomposition (SVD) is a powerful structural analysis tool that has been applied to linear systems and controller designs, but it has not been used for nonlinear systems. In this paper, SVD is use to structurally analyze and to optimally design nonlinear control systems using the linear algebraic equivalence of the nonlinear controller. Specifically, SVD is used to identify control input/output mode shapes, and the control input/output distribution patterns are analyzed with the mode shapes. Optimizing control effort and performance is achieved by truncating some mode shapes in the linear mode shape combinations.
Single Cell Mechanics
Authors: Micoulet Alexandre , Spatz Joachim P.
Published: May 2008

In tissues or blood vessels properties and functionalities of cells are influenced substantially by frequent mechanical perturbations. We describe a cantilever-based technique which allows to precisely manipulate a single cell in model experiments in vitro that mimic mechanical situations in vivo. Cell mechanical responses are evaluated under physiological conditions by separating between two basic mechanical perturbations that are constant mechanical stress or constant cell shape deformation. The essential requirements for these investigations are the development of an automated cell force and deformation detection by fiber optics, a feedback loop, and sufficient mechanical stability of the setup under thermal gradients caused by its local heating apart from room temperature to 37°C. Thus, we can discriminate between elastic behavior of a cell, viscoelastic flow at constant strain and active cell responses at both, constant strain or stress. Such quantitative stress-strain data are applied to test physical models that describe cellular responses to mechanical stimuli. Parallel to mechanical characterization, the cell is visualized by optical microscopy which allows concurrent observations of cell shape and intracellular morphological changes.
Mechanical Damage to the Intervertebral Disc Annulus Fibrosus Subjected to Cyclic Tensile Loading
Authors: Ryan David A. , MacLean Jeffrey J. , Iatridis James C.
Published: May 2008

Damage progression in the circumferential direction of the disc annulus is likely to occur in vivo in response to cyclic loading with associated degradation in tensile material properties, yet this information is not available in the literature. We hypothesize that damage of the annulus will be increased by the number of cycles and magnitude of strain applied to the tissue. Therefore, the objective of this study is to obtain a quantitative relationship between number of cycles and magnitude of tensile strain and damage on the annulus fibrosus. Damage to the annulus is assessed through measurement of permanent deformation (% elongation) and peak stress in the tissue under cyclic loading conditions.
Distributed Mechanical System Simulation Based on a General “Gluing Algorithm”
Authors: Wang Jinzhong , Ma Zheng-Dong , Hulbert Gregory M.
Published: May 2008

Three key concepts are presented in this paper, which comprise the foundation of a distributed simulation platform for design and virtual prototyping of general mechanical systems that have their subsystems distributed amongst dispersed development units in multi-layered supply chains. First, a new gluing algorithm, denoted as the T-T method, is developed, which enables distributed simulations (both the component model and simulation of the component) to be coupled while maintaining the independence of the separate component simulations. Second, a general and efficient model description for simulation is defined using XML. Each model is described with an XML file and stored in model database. A complete model then can be assembled based on these model descriptions. Simulation of a model is started simply by sending the model description to a simulation server. Third, a logical distributed architecture is laid out that can be implemented with one of the existing technologies for distributed computing. Interfaces between different network components have been standardized to enable extensibility of the architecture. These concepts have been incorporated into a prototype distributed simulation system that demonstrates the potential of the new techniques for solving real engineering design problems.
Mechanical Characterization of Human Skin From In-Vivo Tests and Simulation of Reconstructive Surgery
Authors: Gambarotta Luigi , Massabo Roberta , Morbiducci Renata
Published: May 2008

A comprehensive experimental/numerical procedure is presented for the in vivo characterization of the mechanical properties of human skin and the simulation of reconstructive surgery. The procedure uses in vivo experimental tests, which can be performed during surgery, a numerical model formulated within the framework of nonlinear finite strain elasticity and a nonlinear parameter identification technique for the calibration of the model. The skin is treated as a time independent and hyperelastic membrane and the problem is solved through a finite element discretization. The procedure is applied to characterize the scalp skin tested by Raposio and Nordstro¨m, 1998, and to simulate a simple surgical procedure of excision and closure. The application highlights the validity of the proposed approach.
Laser Repair Process Yields for MEMS Devices Adhered During Release or Operation
Authors: Koppaka Sai B. , Phinney Leslie M.
Published: May 2008

Undesirable adhesion in microelectromechanical systems (MEMS) is referred to as stiction and is a principal failure mechanism in surface-micromachined MEMS devices. Adhesive failures can occur in a number of ways. The adhesive failures that occur during the release stage, which includes the etching of sacrificial layers, the subsequent chemical treatments, and the drying processes, are referred to as release-related stiction and failures that occur while the device is in operation are referred to as in-use stiction. A method of repairing these stiction-failed structures released from isopropyl alcohol (IPA) by Nd:YAG laser irradiation is described by Rogers et al. [1]. The current paper reports the effectiveness of the laser repair process and the corresponding thermomechanical model predictions for microcantilevers that have failed due to release from water, octadecyltrichlorosilane (OTS) and supercritical CO2 drying, along with IPA released structures. The paper also discusses the efficiency of the model and the laser repair process for devices that have failed due to in-use stiction. The results show that the laser repair process is very effective for both failure modes and that the model predicts the laser repair of cantilevers that have failed due to release-related stiction much better than for in-use stiction failed cantilevers.
CBGA Solder Joint Thermal Fatigue Life Estimation by a Simple Method
Authors: Wong T. E. , Lau C. Y. , Fenger H. S.
Published: May 2008

A simple analysis method was developed to determine the fatigue life of a ceramic ball grid array (CBGA) solder joint when exposed to thermal environments. The solder joint consists of a 90Pb/10Sn solder ball with eutectic solder on both top and bottom of the ball. Failure of the solder joint occurs at the eutectic solder. A closed-form solution with the equilibrium of displacements of electronic package assembly was first developed to calculate the solder joint strains during the temperature cycling. In the calculation, an iteration technique was used to obtain a convergent solution in the solder strains, and the elastic material properties were used for all the electronic package assembly components except for the solder materials, which used elastic-plastic properties. A fatigue life prediction model, evolved from an empirically derived formula based upon a modified Coffin-Manson fatigue theory, was then established. CBGA test results, obtained from Motorola, combined with the derived solder strains were used to calibrate the proposed life prediction model. In the model calibration process, the 255- and 304-pin CBGA test results, which were cycled between 0°C and 100°C or −40°C and 125°C, were reasonably well correlated to the calculated values of solder strains. In addition, this calibrated model is remarkably simple compared to the model used in an evaluation by finite element analysis. Therefore, this model could be used and is recommended to serve as an effective tool to preliminarily estimate the CBGA solder joint thermal fatigue life.
An LMI Optimization Approach to the Design of Structured Linear Controllers Using a Linearization Algorithm
Authors: Han Jeongheon , Skelton Robert E.
Published: May 2008

This paper presents a new algorithm for the design of linear controllers with special constraints imposed on the control gain matrix. This so called SLC (Structured Linear Control) problem can be formulated with linear matrix inequalities (LMI’s) with a nonconvex equality constraint. This class of prolems includes fixed order output feedback control, multi-objective controller design, decentralized controller design, joint plant and controller design, and other interesting control problems. Our approach includes two main contributions. One is that many design specifications such as H∞ performance, generalized H2 performance including H2 performance, l∞ performance, and upper covariance bounding controllers are described by a similar matrix inequality. A new matrix variable is introduced to give more freedom to design the controller. Indeed this new variable helps to find the optimal fixed-order output feedback controller. The second contribution uses a linearization algorithm to search for a solution to the nonconvex SLC problems. This has the effect of adding a certain potential function to the nonconvex constraints to make them convex. Although the constraints are added to make functions convex, those modified matrix inequalities will not bring significant conservatism because they will ultimately go to zero, guaranteeing the feasibility of the original nonconvex problem. Numerical examples demonstrate the performance of the proposed algorithms and provide a comparison with some of the existing methods.