bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Process Monitoring With MTConnect
Authors: Atluru Sri , Deshpande Amit
Published: July 2013

Statistical Process Control (SPC) techniques are used widely in the manufacturing industry. However, it is sometimes observed that a deviation that is within the acceptable range of inherent process variation does not necessarily conform to specifications. This is especially true in the case of low volume; high precision manufacturing that is customary in aerospace and defense industries.

In order to study the limitations posed by conventional SPC techniques in such manufacturing environments, a study was undertaken at TechSolve Inc., Cincinnati to develop a standalone SPC tool. The SPC tool so developed effectively communicates with an on-machine probe and analyzes the collected data to carry out a statistical analysis. MTConnect, a new-generation machine tool communications protocol, was used in developing the communication interfaces with the on-machine probe on a Computer Numerical Control (CNC) machine. The XML (eXtensible Markup Language) code used to extend the MTConnect schema to include the data obtained from the probing routines is also presented.

The statistical analysis was developed as a Graphical User Interface (GUI) in LabVIEW. The statistical analysis was carried out as a case study by producing a widget. Real machining was carried out to produce 48 of these widgets using a combination of end mills and face mills. The data obtained during the subsequent quality testing was used to carry out the statistical analysis.

The limitations of conventional SPC techniques during the developmental and analytical phases of the study are discussed. The presence of a chip during an on machine probing routine, the variations due to disparities in tool macro geometry, and the demand for conformance to requirements are studied in the view of a statistical process monitoring standpoint. Various alternatives are also discussed that aim to correct and improve the quality of machined parts in these scenarios.
Battery Prognostics: SoC and SoH Prediction
Authors: Lee Seungchul , Cui Harry , Rezvanizaniani Mohammad , Ni Jun
Published: July 2013

Battery applications (computer, cell phones or even in cars) have been extensively used in our daily life. The reasons for their success and extensive usage in the real world applications are their light weight, smaller sizes and greater energy densities. These unique characteristics render this class of battery an ideal candidate for powering electrical vehicles. However, due to lack of battery information, often time we will observe machine down time, operation malfunctioning, and even some catastrophic failure due to fast battery degradation and depletion. Thus, much of the attention has been focused on prognostics and health management of battery technologies for the stated purpose. In this paper, we will present two main algorithms that cannot only estimate a one-step-ahead prediction of the battery state but also can estimate the battery remaining useful life. The first method is the linear prediction error method. The second approach is the neural network algorithms. Both methods can predict the battery information accurately. However, particular algorithm specializes in different area of interest.
Thermal Response Characterization of Sheet Metals During Electrically-Assisted Forming (EAF)
Authors: Jones Joshua J. , Mears Laine
Published: July 2013

For the current practice of lightweight engineering in the automotive sector, it is common to introduce and use low density/high strength materials instead of costly engine/drivetrain technologies. With the introduction of these materials there are commonly many manufacturing difficulties which arise during their incorporation to the vehicle. As a result, new processes which improve the manufacturability of these materials are necessary. This work examines the manufacturing technique of Electrically-Assisted Forming (EAF) where an electrical current is applied to the workpiece during deformation. As a result of the applied current, Joule heating is present which increases the temperature of the material. In this work the thermal response of sheet metal for stationary and deformation tests using this process are explored and modeled. The results of the model show good agreement for the stationary tests while the deformation model predicts that all of the applied electrical current may not be transformed into Joule heating. Thus, this work suggests from the observed response that a portion of the applied current may be directly aiding in deformation (i.e. the Electroplastic Effect).
Robust Work Planning and Development of a Decision Support System for Work Distribution on a Mixed-Model Automotive Assembly Line
Authors: Antani Kavit , Madadi Alireza , Kurz Mary E. , Mears Laine , Funk Kilian , Mayorga Maria E.
Published: July 2013

Line balancing is a very resource-intensive and time consuming process which is highly reliant on the experience and expertise of a few employees. Line balancing is made even more complex due to the high level of option content in premium automobiles. The current phase of this study involves hands-on training on the automotive assembly line, precedence relationship mapping of all the tasks involved on a pilot assembly line, identification of constraints, and development of a strategy to manage option content and constraints. The second phase will include the generation of an optimal line balance through optimization on expected station utilization. The current line balancing process relies significantly on the experience level of the utility workers and team leaders. Although initially labor intensive, the precedence mapping exercise and option coding strategy will facilitate the development of a decision support system to aid the human decision-maker in making data-driven decisions about work distribution.
Fabrication of Aluminum Composites With Patterned Silicon Carbide Reinforcement Architecture by Semi-Solid Processing
Authors: Zhu Can , Wu Yufeng , Kim Gap-Yong
Published: July 2013

Semi-solid powder processing is a promising technology, combining the advantages of semi-solid forming and powder metallurgy. In this study, spray deposition process combined with semi-solid powder processing was used to synthesize an aluminum alloy composite and to control its microstructure. Silicon carbide (SiC) reinforced aluminum alloy composites were fabricated with and without microstructure pattern. The influence of different composite microstructure on mechanical properties was analyzed by microstructure analysis, bend test and fracture analysis. Bend test results showed that patterned microstructure has the potential to significantly improve composite strength with minimal sacrifice of ductility.
AFM-Based Nanoindentation Process: A Comparative Study
Authors: Promyoo Rapeepan , El-Mounayri Hazim , Varahramyan Kody
Published: July 2013

Atomic force microscopy (AFM) has been widely used for nanomachining and fabrication of micro/nanodevices. This paper describes the development and validation of computational models for AFM-based nanomachining. Molecular Dynamics (MD) technique is used to model and simulate mechanical indentation at the nanoscale for different types of materials, including gold, copper, aluminum, and silicon. The simulation allows for the prediction of indentation forces at the interface between an indenter and a substrate. The effects of tip materials on machined surface are investigated. The material deformation and indentation geometry are extracted based on the final locations of the atoms, which have been displaced by the rigid tool. In addition to the modeling, an AFM was used to conduct actual indentation at the nanoscale, and provide measurements to which the MD simulation predictions can be compared. The MD simulation results show that surface and subsurface deformation found in the case of gold, copper and aluminum have the same pattern. However, aluminum has more surface deformation than other materials. Two different types of indenter tips including diamond and silicon tips were used in the model. More surface and subsurface deformation can be observed for the case of nanoindentation with diamond tip. The indentation forces at various depths of indentation were obtained. It can be concluded that indentation force increases as depth of indentation increases. Due to limitations on computational time, the quantitative values of the indentation force obtained from MD simulation are not comparable to the experimental results. However, the increasing trends of indentation force are the same for both simulation and experimental results.
Spiral Friction Stir Processing (SFSP) for the Extrusion of Lightweight Alloy Tubes
Authors: Abu-Farha Fadi
Published: July 2013

While friction stir processing (FSP) has been used to refine the grain structure in sheet metals, this work explores the potentials of refining the grain structure of bulk material using the friction stirring phenomenon via the novel concept of spiral friction stir processing (SFSP). With this concept, the rotating stirring tool is plunged into the material, rather than being traversed across it as in FSP; this imposes severe plastic deformation on the material while pushing it radially outwards in complex spiral paths. By confining the material within a closed cylindrical die, the processed material is microstructurally-refined while forming a tube via a special form of SFSP called “friction stir back extrusion” (FSBE). The hypothesised concept was investigated using samples from the AA6063-T52 aluminium alloy and the AZ31B-F magnesium alloy. The preliminary results presented here demonstrate the viability of SFSP, and the special form of FSBE, in producing tubular samples that are structurally sound, with no signs of voids or internal channels. Optical microscopy was performed at key locations within selected tube specimens, and the obtained micrographs clearly show the presence of a stir zone with a fine grain structure; grain size measurements demonstrate the effectiveness of the processing technique in refining the microstructure of the starting material.
Finite Element Analysis of Residual Stresses in High-Speed Dry Cutting of Biodegradable Magnesium-Calcium Alloy
Authors: Salahshoor M. , Guo Y. B.
Published: July 2013

Magnesium-Calcium (Mg-Ca) alloys have become attractive biodegradable orthopedic implant biomaterials recently. Residual stresses are proven to be very influential on degradation rate of these alloys in human anatomy. Due to time and cost inhibitive reasons, development of finite element models to predict residual stress profiles under various cutting regimes is highly desirable. In this context, a finite element model of orthogonal cutting without explicit chip formation is developed by adopting plowing depth approach in order to predict process induced residual stresses in high speed dry cutting of Mg-Ca0.8 (wt %) using diamond tools. Mechanical properties of Mg-Ca0.8 alloy at high strain rates and large strains are determined using split-Hopkinson pressure bar test. Internal state variable (ISV) plasticity model is implemented to model the material behavior under cutting regimes. The residual stress evolution process and effects of plowing speed and plowing depth on residual stress profiles are studied. Residual stress measurements are performed utilizing X-ray diffraction technique for validation purposes.
Characteristics of Cobalt Chromium Alloy Surfaces Finished Using Magnetic Abrasive Finishing
Authors: Graziano Arthur A. , Ganguly Vasishta , Bullard J. Whittaker , Yamaguchi Hitomi , Schmitz Tony
Published: July 2013

Freeform surfaces, including the femoral components of knee prosthetics, present a significant challenge in manufacturing. The finishing process is often performed manually, leading to high variation in quality. This study proposes using Magnetic Abrasive Finishing (MAF) to finish the cobalt chromium (Co-Cr) alloy femoral components of knee prosthetics and varying the surface pattern to alter surface wettability, which influences the tribological properties of the surfaces. As a first step, flat workpieces of the same material were used in this paper. To obtain an understanding of the relationship between surface pattern and wettability, two sets of finishing conditions were developed to yield two different surface patterns while maintaining roughness values (2–5 nm Ra). One surface consists of long cutting marks exhibiting strong directionality, while the other consists of short, intermittent cutting marks. The surface with strong directionality resulted in an increased contact angle between the workpiece and de-ionized water (from 90.0°±1.5° to 93.8°±2.5°), thus a decrease in wettability. The other surface showed a decreased contact angle (from 98.7°±5.3° to 93.3°±3.7°), thus an increase in wettability. This study experimentally demonstrates the feasibility of MAF to alter surface pattern—and to potentially alter the wettability—while maintaining initial surface roughness at a nanometer scale.
Calibration and Characterization of a Low-Cost Wireless Sensor for Applications in CNC End Milling
Authors: Harmon Andrew , Fussell Barry K. , Jerard Robert B.
Published: July 2013

This paper describes recent research progress at the University of New Hampshire in the area of smart machining systems. Central to creating a smart machining system is the challenge of collecting detailed information about the milling process at the tool tip. This paper discusses the design, static calibration, dynamic characterization, and implementation of a low-cost wireless force sensor for end-milling. The sensor is observed to accurately measure force when most of the cutting power is band-limited below the sensor’s natural frequency. Sensor geometry constrains the milling application to a single tooth cutter; while this constraint is impractical for industrial applications, our sensor is shown to provide useful information in a laboratory setting.
Characteristics of Exfoliated Graphite Nanoplatelets-Polyamide12 Nanocomposites Processed by Extrusion Injection Molding
Authors: Karevan Mehdi , Kalaitzidou Kyriaki
Published: July 2013

Melt-mixing processes such as extrusion-injection molding induce shear mechanical forces to enhance the melt blend of nanofiller-polymer and have been considered as time and cost efficient in commercial processing of polymer nanocomposites (PNCs). Extensive research has been conducted so far to investigate the overall performance of melt-processed PNCs. However there is lack of systematic studies on the nanomaterial induced phenomena that dominate the properties of the end-use melt mixing processed parts leading to engineered high quality PNCs. Furthermore, studies for exploration of the structure-property relationships in the melt processed PNCs are also limited. In this work, nanocomposites of Polyamide-12 (PA12) reinforced with exfoliated graphite nanoplatelets (xGnP™) up to 15wt% were fabricated using two different compounding techniques: coating followed by melt mixing and direct melt mixing. Effects of the compounding methods on the reinforcing efficiency of xGnP within the PA12 matrix were investigated. To understand the reinforcing mechanisms contributing to alteration of the mechanical properties, rheological behavior of the PNCs were investigated in the linear viscoelastic region and correlated with the state of nanofiller-matrix interfacial interaction and the nanofiller dispersion. The results suggest that xGnP coating of the PA12 powder resulted in improved flexural strength of the PNCs with respect to that of the pure PA12 and of PNCs made by direct melt mixing. The rheological low-frequency measurements demonstrate that addition of xGnP resulted in a larger increase in the melt dynamic viscosity of the coated-melt mixed PNCs than the direct melt-mixed ones. This suggest stronger xGnP-PA12 interfacial interaction and better dispersion state of the nanofiller in the coated-melt mixed PNCs than the latter PNCs. Addition of xGnP content resulted in improved storage modulus for PNCs made by either compounding method. However, the results support the evidence of post-processing induced re-agglomeration or suppressed dispersing efficiency of the coating process at extreme xGnP content as was elucidated through the shear thinning behavior of the melt and the flexural modulus of the highly reinforced parts.
Integration of MTConnect and Standard-Based Sensor Networks for Manufacturing Equipment Monitoring
Authors: Lee Kang B. , Song Eugene Y. , Gu Peter S.
Published: July 2013

MTConnect is an open and extensible protocol designed for the exchange of data between shop floor devices and software applications. MTConnect allows manufacturers to facilitate retrieval of information and data from factory devices, such as machine tools, sensors, and controllers. Currently, MTConnect users read data from sensors through proprietary sensor interfaces using adaptors. The suite of Institute of Electrical and Electronics Engineers (IEEE) 1451 standards defines a set of open, common communication interfaces for sensor networks, including both sensor interfaces and network interfaces.

This paper proposes an integration architecture of MTConnect with IEEE 1451 standard-based sensor networks. In the architecture, MTConnect plays a network interface role in the IEEE 1451 standard-based sensor networks via an MTConnect Agent. An adaptor is used to provide the mapping between the MTConnect Agent and the IEEE 1451 sensor network. A prototype system integrating MTConnect with IEEE 1451.2-based sensor network has been developed. Two case studies are provided to illustrate the integration.
Mathematical Modeling of Cutting Forces in Micro-Drilling
Authors: Sambhav Kumar , Tandon Puneet , Kapoor Shiv G. , Dhande Sanjay G.
Published: July 2013

In drilling, the primary cutting lips and the secondary cutting lips of the drill shear the material while the central portion of the chisel edge indents the workpiece, making the cutting process complex to understand. As we go for micro-drilling, it exhibits an added complexity to the cutting mechanism when the edge radius gets comparable to chip thickness at low feeds. The presented work models the forces by the primary cutting lip of a micro-drill analytically using slip-line field that includes the changes in the effective rake angle and dead metal cap during cutting for cases of shearing as well as ploughing. To study the variation of forces experimentally, the primary cutting lip and chisel edge forces are separated out by drilling through pilot holes of diameter slightly above the drill-web thickness. Finally, the analytical and experimental results have been compared and the model has been calibrated.
Characterization of Joint Quality in Ultrasonic Welding of Battery Tabs
Authors: Lee S. Shawn , Kim Tae H. , Hu S. Jack , Cai Wayne W. , Li Jingjing , Abell Jeffrey A.
Published: July 2013

Manufacturing of lithium-ion battery packs for electric or hybrid electric vehicles requires a significant amount of joining such as welding to meet desired power and capacity needs. However, conventional fusion welding processes such as resistance spot welding and laser welding face difficulties in joining multiple sheets of highly conductive, dissimilar materials with large weld areas. Ultrasonic metal welding overcomes these difficulties by using its inherent advantages derived from its solid-state process characteristics. Although ultrasonic metal welding is well-qualified for battery manufacturing, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. In order to establish such quality guidelines, this paper first identifies a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time. Samples of different weld quality were cross-sectioned and characterized with optical microscopy, scanning electronic microscopy (SEM), and hardness measurements in order to identify the relationship between physical weld attributes and weld performance. A novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization. The methodology provided in this paper links process parameters to weld performance through physical weld attributes.
Study of Size Effects on Deformation Behavior and Formability in Micro Metal Forming of Ti Foil
Authors: Xu Jie , Guo Bin , Shan Debin , Li Baishun
Published: July 2013

Micro forming technology becomes a promising approach to fabricate micro-parts due to its advantages of high productivity, low production cost, good product quality and mechanical properties, and near net or net shape characteristics. However, the deformation behaviors of material change and the so-called size effect occurs when the part dimension is decreased to micro-scale. To analyze the quality of micro-parts, the material flow stress, anisotropy, ductility and formability in micro-scale need to be considered. In the paper, micro tensile and micro deep drawing tests of Ti foils were used and the size effects on deformation behavior and formability of micro sheet metal forming were studied. The results show that the flow stress of Ti foils is related with foil thickness and grain size. The fracture behaviors also have been changed from shear dimple to slip separation with the decrease of foil thickness. The formability of micro deep drawing becomes worse with the decrease of micro cup dimension and the increase of grain size.
Engineering Cardiac Tissue Using Stem Cell Therapy to Mend the Broken Heart
Authors: Ivanov Zhanna A. , Scott Robert C. , Rosano Jenna , Krynska Barbara , Kiani Mohammad F.
Published: July 2013

Myocardial infarction (MI) is one of the most severe forms of coronary artery disease and is the leading cause of death in the United States [1]. Current treatments for an MI are either highly invasive, such as coronary artery bypass grafting and stent angioplasty, or might have undesirable long-term effects as is the case with pharmacological interventions. However, newly emerging methodologies, such as a less invasive stem cell therapy, aim to cure the disease rather than just alleviate its symptoms. This new tissue engineering technology has shown promise in restoring the homeostasis of the heart muscle after MI in preclinical and clinical studies [2]. However, controversies regarding inconsistent methodologies and a lack of mechanistic understanding of its actions have hampered progress in this field [3].
An Optimization Methodology for Cancer Growth Control Base on Breeder Genetic Algorithm-Finite Volume Coupling
Authors: Taheri Arash , Mohammadi-Amin Meisam , Habibpour-Ledari Ali
Published: July 2013

Cancer is a genetic disease caused by mutations in somatic cells. It appears to arise by a process in which an initial population of altered cells begins to proliferate abnormally. At each step, one cancerous cell acquires an additional mutation that gives it a selective advantage over its neighbors, such as more rapid growth, and the descendants of this cell become dominant within the cancer population. In culture, the proliferation of the most cancerous cells is not sensitive to density-dependent inhibition; therefore, cancerous cells usually continue growing to high cell densities.
Modeling and Analysis of Proximal Tibial Growth Plate Fractures in Adolescents
Authors: Basile Susan , Zhao Xiaopeng
Published: July 2013

Today, children and adolescents are participating heavily in organized athletics year-round. Each year, approximately one third of these children will experience a serious injury requiring a doctor’s or hospital visit. Physeal, or growth plate fractures, are one such type of overuse injury commonly seen in adolescents. At the knee joint, injuries in adolescents occur most often in the proximal region of the tibia as opposed to the middle or distal thirds of the tibia, or in the soft tissues of the joint, as seen in adults. While the exact reasons for this difference have not been directly and definitively quantified, several hypotheses have been suggested. They include differences in movement strategies, changes in limb inertial and material properties, and the timing of these changes in relation to one another. This work aims to compare the changes in and interaction of inertial properties of the lower leg and forces transmitted through the patellar tendon, along with tibiofemoral contact before, during, and after puberty. Forces were first determined using Kane’s method of dynamics in conjunction with an isometric knee extension study yielding separate adult and youth data. These results were then extended to a finite element analysis to load tibial models and investigate changes in stress and strain at the proximal tibia.
Real-Time FEM of Soft Tissues for Virtual Surgery
Authors: Willberg Christian , Berger Harald , Gabbert Ulrich
Published: July 2013

Endoscopic techniques require small perforation holes only as entries for optical and surgical instruments; such enabling the treatment of injuries with a minimized damage of the surrounding health tissue. But the surgeon has to operate in a 3D domain by looking at a distorted 2D image at the screen. It is well known, that a good surgeon needs a continuous training to perform such operations reliable in a top quality. To overcome the high costs and tight ethical restrictions of animal based education and training has result in an increasing development and application of virtual surgery simulators [1]. One of the main issues of surgery simulators is to ensure simultaneously the real time performance of the device, the high-level image representation and an acceptable force-feedback behavior. The basics of such simulators are mathematical models of the involved soft tissues, which have to perform in a realistic physical manner, with dynamic nonlinear large deformations, including the interaction of the different constituents (instrument/organ, organ/organ, organ by itself, cutting, bleeding etc). In the paper the focus is on realistic organ models and the realization of a fast contact search and reaction algorithm.
Safe Device for a Theatrical Hanging
Authors: Ayer Harry B. , Grano Sarah K. , James Leah M. , Todd Beth A.
Published: July 2013

A low-cost hanging system was requested by the Theatre Department for the production of Henry V. Design constraints were developed with an emphasis on the actor’s safety. To that end, biomechanical literature related to head and neck injury was reviewed. During testing of the device, acceleration measurements were made for comparison with literature values. Finite element analysis was performed on the structural support to determine its effectiveness. The final design met all of the criteria and was tested extensively by the designers.
In Vitro DEXA-BMD Measurements Affected by Type of Soft Tissue Surrogate
Authors: Koch Kathleen , Tai Viva , Burch Shane , Mulligan Kathleen , Ames Christopher , McClellan Robert T. , Buckley Jenni M. , Matityahu Amir
Published: July 2013

Dual-energy x-ray absorptiometry (DEXA), the technique most widely used to assess skeletal integrity, is routinely performed on cadaveric tissue to ensure that the bone mineral densities (BMD) of the test specimens are representative of the target patient population for a particular orthopaedic device [1]. It is well established that DEXA-BMD measurements are sensitive to the amount of fat and other soft tissue present in the region of interest [2]. Recognizing that the removal of perivertebral soft tissue may affect DEXA-BMD readings of in vitro cadaveric specimens, biomechanics researchers have used various “torso surrogates” to simulate the removed tissue and x-ray attenuation. These include: 1) submersion of spinal sections in a physiological saline bath, 2) surrounding spinal sections with gel-filled packs, and 3) packing rice-filled bags around spinal sections and within the internal cavity of eviscerated torsos [3, 4]. It is unknown whether these inter-study differences in technique affect in vitro DEXA measurements. Given the prevalence of soft tissue artifacts in vivo, the goal of this study is to examine the sensitivity of in vitro DEXA-BMD to the quantity and composition of soft tissue surrogates. This work is the first step in a broader study to develop a set of best practices for DEXA scanning of cadaveric tissue.
Modeling the Efficiency of Movement: From Individual Muscles to Whole Organism
Authors: Umberger Brian R. , Gidley Alexis D.
Published: July 2013

In the context of human movement, efficiency is defined as the ratio of mechanical energy output (work) to metabolic energy input [1,2]. It is straightforward to determine whole-body efficiency in a task such as pedaling a bicycle ergometer. In this case, work is computed from the ergometer load and pedaling cadence, and metabolic energy is determined from pulmonary gas exchange. It is also relatively straightforward to determine the efficiency of contraction in isolated muscle preparations, where the work done is easily measured, and energy input can be inferred from heat production or oxygen consumption. However, our understanding of the efficiency of muscle function during locomotion, and how this contributes to organismal efficiency, is incomplete [1]. The ability to determine efficiency of individual muscles as they perform work in vivo would greatly enhance our understating in this area. Experimental measurement of both work and metabolic energy consumption in muscles during dynamic activities is currently limited to isolated applications in non-human animals [3]. Similar data could be obtained using computational modeling and simulation techniques, provided that estimates could be obtained for both muscle work and muscle metabolic energy consumption. This non-invasive approach would open the door to investigations in humans as well as other species. Therefore, the primary purpose of this study was to determine efficiency at both the organismal and muscular levels for bicycle pedaling, using a musculoskeletal modeling approach. A secondary purpose was to identify factors that account for between-muscle differences in efficiency.
Age Differences in Landing Phase Ankle Dynamics During a Balance-Restoring Step Response
Authors: Akula Chaitanya K. , King Gregory W.
Published: July 2013

Falls are a significant health concern among older adults. The rate of falls increases with age [1], and often leads to fall-related injuries such as fractures and head injuries. These lead to loss of independence, morbidity and fear of falling [2]. There are many strategies used to prevent falls, including those used to regain balance following a slip or trip. One such balance recovery maneuver is the step response, which involves respositioning the body’s base of support to recapture its moving center of mass [3]. Age-related performance declines in the step response may contribute to fall risk, especially during the step response landing phase where biomechanical strength requirements are largest [4]. Such age-related declines likely manifest themselves as alterations in lower extremity joint dynamics. While these effects are likely present in all lower extremity joints (hips, knees, and ankles), the purpose of this preliminary study was to investigate age effects in stepping leg ankle dynamics during a balance-restoring step response.
Quantification of Temporal Collagen and Microvessel Alignment Induced by Anchored Boundary Conditions During Angiogenesis
Authors: Underwood Clayton J. , Krishnan Laxminarayanan , Fung Allen , Reese Shawn , Hoying James B. , Weiss Jeffrey A.
Published: July 2013

Previously we have found that in addition to mechanical strain, an anchored boundary condition alone can alter the organization of microvessel outgrowth during in vitro angiogenesis [1]. Microvessels were found to align parallel to the long axis of the anchored gel construct after 6 days in vitro. However, unanchored cultures did not show alignment of microvessels. This ability to control the direction of angiogenesis has immense implications for engineering prevascularized grafts and tissues in vitro, therefore an understanding of this process is important. The goal of this study was to first determine whether or not the underlying collagen matrix aligns similar to microvessels, and second to determine the timing of this alignment.
Immediate and Long-Term Response of Engineered Cartilage After Mechanical Injury
Authors: Tan Andrea R. , Rajan Vikram , Ateshian Gerard A. , Hung Clark T.
Published: July 2013

Regenerative strategies for engineering cartilage have recently shown promise, as they have been capable of producing tissues comparable in Young’s modulus and glycosaminoglycan (GAG) content to native cartilage [1]. The response of engineered cartilage, when implanted, relies on its ability to withstand the harsh chemical and mechanical environment of the implantation site. Mechanical stimuli, in particular, have been identified as important regulators of chondrocyte function and can induce inflammatory responses or the release of proteoglycans from cartilage explants [2–4]. The downstream effects of these responses can induce chondrocyte death as soon as a few hours after and up to 7 days post injury [5]. In cartilage explants, injury to the tissue can produce structural damage and osteoarthritic-like changes including a loss of mechanical properties, increased collagen degradation, and reduced proteoglycan synthesis [2,6]. Injurious loads have been identified as one potential mechanism leading to apoptosis and necrosis [8].
Investigation of Wall Shear Stress Over an Early Atherosclerotic Plaque in the Left Coronary Artery of a Patient by Intravascular Ultrasound and Computational Fluid Dynamics
Authors: Suo Jin , McDaniel Michael , Dhawan Saurabh , Samady Habib , Giddens Don
Published: July 2013

A small isolated region with mild atherosclerotic thickening in the left anterior descending (LAD) coronary artery was identified in a relatively young patient using invasive coronary angiography. The left main (LM) coronary artery and LAD were reconstructed based on biplanar angiography images and intravascular ultrasound (IVUS). The flow field in the lumen was simulated by computational fluid dynamics (CFD) with Doppler-measured flow boundary conditions. The results offer insight into the local flow environment in the neighborhood of an early atherosclerotic plaque in a specific human subject under in vivo conditions. The investigation is continuing with other patients who have mild plaques in the left coronary artery in an effort to elucidate in vivo atherogenesis.
MRI Analysis of Femoral Cartilage Thickness in Early Osteoarthritis Knee Patients for Uni-Condylar Knee Potential
Authors: Yildirim Gokce , Arno Sally , Khmelnitska Ekaterina , Walker Peter S.
Published: July 2013

Over the past several decades, Magnetic Resonance Imagining has become a standard in cartilage thickness analysis (Gray 2008, Potter 2006). However, MRI analysis has not been used to indicate patients with early osteoarthritic (OA) cartilage changes for early intervention procedures (EIP) such as grafts or minimally-invasive unicondylar knee replacements. The objective of this study is to examine the viability of using MRI to identify early osteoarthritis of articular cartilage and identify the affected areas in a clinical setting. Based on the results of studies previously conducted in this lab, along with the fact that the majority of axial loading in the knee occurs during the impact phase of walking, we expect to find the majority of lesions to be localized to the distal femur, with the posterior condyles remaining largely intact.
The Bulge Inflation Response of Bovine Sclera
Authors: Myers Kristin M. , Nguyen Thao D.
Published: July 2013

Glaucoma is one of the leading causes of blindness in the United States and in the world [1]. It is caused by damage to the retinal ganglion cells (RGC), a type of neuron that transmits visual information to the brain. Despite therapeutic efforts to reduce the rate of vision loss in glaucoma patients, the rate of blindness remains high [2]. There is evidence that elevated intraocular pressure (IOP) plays an important role in the damage to RGCs [3–5], but the relationship between the mechanical properties of the connective tissue and how it affects the cellular function is not understood. The load-bearing eye wall consists of the cornea and the sclera. Both tissues are collagen rich structures with preferentially aligned collagen lamellae dictating its mechanical response. Previous studies have shown that the viscoelastic material response of the eye wall differs between normal and glaucoma animal tissues [6]. However, these previous studies relied on strip testing of tissue samples.
Combined Effect of Tibiofemoral Alignment and Meniscectomy on the Contact Stresses at the Knee: A FEA Investigation
Authors: Yang N. H. , Canavan P. K. , N.-Hashemi H.
Published: July 2013

Surgical removal of meniscal tissue alters the kinematics and load distribution of the knee and decreases the contact area causing greater magnitude of compressive stress and shear stress. These changes may result in damage to the knee cartilage and lead to subsequent osteoarthritis (OA) (1). Allen et al. (2) found a significant increase in knee OA after meniscectomy with pre-existing abnormal frontal plane tibiofemoral alignment. Tibiofemoral alignment affects the varus/valgus moment during ambulation and during single-leg stance, Fig. 1A. The varus moment, or adduction moment, is the primary factor in the distribution of the force to the medial compartment of the knee joint during normal gait (4). Previous finite element analysis (FEA) studies investigating partial and total meniscectomies applied only axial loads and do not take into account the varus moment that occurs during single-leg support (4, 5). The present 3-D FEA investigation utilizes subject specific loading conditions (including the varus knee moment) to study the combined effect of tibiofemoral knee alignment and partial and total meniscectomies on the stresses at the knee cartilage.
Image-Based CFD Modelling of Hemodynamic Factors in Aneurysm Formation Using a Novel Approach for Digital Removal of Saccular Aneurysms
Authors: Ford Matthew D. , Hoi Yiemeng , Piccinelli Marina , Antiga Luca , Steinman David A.
Published: July 2013

Although local hemodynamic forces are widely believed to play a role in aneurysm pathogenesis, the hemodynamic mechanisms have not been confirmed in a prospective manner. Ideally, one would identify the patient-specific vessel that is prone to aneurysm formation and follow it longitudinally to investigate the associated aneurysm formation factors or mechanisms. However, such studies are not practical in humans, and so the knowledge to predict aneurysm formation at a specific location, a priori, is not available.
Repeated Dynamic Loading Modulates Cartilage Gene Expression but Does Not Improve Mechanical Properties of MSC-Laden Hydrogels
Authors: Huang Alice H. , Mauck Robert L.
Published: July 2013

Mesenchymal stem cells (MSCs) are a multi-potential cell type that can differentiate toward a variety of tissue-specific phenotypes, including cartilage. Given their chondrogenic potential, MSCs are a promising cell source for cartilage tissue engineering (TE). However, while MSCs readily undergo chondrogenesis in 3D culture and deposit a cartilage-like matrix, the mechanical properties of MSC-seeded constructs are greatly inferior to chondrocyte-seeded constructs similarly maintained [1]. To date, optimization strategies for enhancing functional MSC chondrogenesis, including increasing seeding density and transient application of growth factor, have shown limited success [3]. Using microarray analysis, we have recently demonstrated that mis-expression of certain genes, including lubricin, chondromodulin and RGD-CAP, a collagen associated protein, may underlie this disparity in mechanical function [2]. In this study, we examined dynamic compression as an alternative method to enhance MSC differentiation. Previous work using chondrocyte-based constructs have demonstrated that matrix biosynthesis and mechanical properties were improved with the application of cyclic compression [4]. Furthermore, upregulation of lubricin was observed when surface motion was applied to chondrocyte-seeded porous scaffolds [5]. While significant effort has gone toward optimizing loading parameters to direct tissue growth of chondrocyte-based constructs, few studies have examined the effects of mechanical stimulation on MSC-based constructs. Some have demonstrated positive effects on MSC chondrogenesis with application of compressive loading [6, 7], while others have shown that long-term loading may adversely affect the developing mechanical properties of MSC-seeded constructs [8]. In this study, we examined the effects of repeated dynamic compressive loading on MSC chondrogenesis and showed that mechanical properties and gene expression were modulated by this loading modality.
Developmental Cardiovascular Remodeling Associated With Reduced Elastin Levels in Mice Occurs After Embryonic Day 18
Authors: Wagenseil Jessica E. , Ciliberto Chris H. , Knutsen Russel H. , Levy Marilyn A. , Kovacs Attila , Mecham Robert P.
Published: July 2013

Elastin provides reversible extensibility and stores energy during the cardiac cycle in large blood vessels. It is only present in vertebrate animals with a closed circulatory system and high, pulsatile blood pressures. Elastin is crucial for proper cardiac function in vertebrates, as mice lacking elastin (eln-/-) die soon after birth with cardiovascular abnormalities including long, tortuous, stenotic, stiff arteries and high left ventricular (LV) pressure with low cardiac output [1, 2].
Examining Adaptive Extracellular Responses of Living Cells Under Mechanical Stimulation Through Probing Fibronectin Response
Authors: Steward Robert L. , Cheng Chao-Min , LeDuc Philip R.
Published: July 2013

The extracellular matrix (ECM) has been shown to be an important cellular component due to the structural support it provides. This extracellular component has been linked to wound healing, cell adhesion, blood coagulation, cell differentiation and migration, maintenance of the cellular cytoskeleton, and tumor metastasis. Many studies have investigated the effects of the ECM protein, fibronectin, and its assembly and structural organization through chemical stimulation, but few have probed its link to mechanics. As cells alter their extracellular environment through fibronectin modulation and secretion, we examined this link to examine how cells alter their extracellular environment in response to applied mechanical stress. These results indicate the importance of mechanics in fibronectin organization and have implications in a variety of fields including mechanotransduction, biophysics and bioengineering.
A Nonlinear Biphasic Model for Fluid Transport and Tissue Deformation During Constant Flow Rate Infusion Into Brain Tissue
Authors: Smith Joshua H. , García Jose Jaime
Published: July 2013

The delivery of therapeutic agents into the brain is impeded by the blood-brain barrier, preventing adequate treatment of diseases of the central nervous system. Convection enhanced delivery was developed as a means to deliver therapeutic agents directly into brain tissue and to transport the drugs in the extracellular space using convective flow. Poroelastic or biphasic models have been used to study the concomitant fluid transport and tissue deformation that occurs during infusion, however previous studies have been limited by the assumption of linear elasticity of the solid phase [1].
In Vitro Study of Pulsatile Flow Through a Motionless Diode Valve in the Pulmonary Position
Authors: Camp Tiffany A. , Figliola Richard , Beasley Donald , Conover Timothy , McQuinn Tim , Hsia T.-Y.
Published: July 2013

Pulmonary circulation shows a tolerance for mild regurgitation and pressure gradient. [1]. Given these tolerances, we have explored using a fluid diode as a pulmonary valve. Camp et al showed that diode valves are able to regulate flow in the pulmonary position with promising results and could be tolerated using a pig model [2, 3]. Flow and shear stress patterns are two other hemodynamic concerns that must be considered during heart valve design. Elevated bulk flow shear stresses, wall shear stresses, and turbulent stresses within bioprostheses and mechanical valve flow fields are recognized as a cause of cell and platelet damage, initiating platelet activation and triggers for thrombogenesis [4–7]. In this study, we conduct in vitro flow field analysis of the flow downstream of a proposed prototype diode valve in order to observe the flow and shear stress patterns.
Enhancement in Treatment Planning for Magnetic Nanoparticle Hyperthermia: Optimization of the Heat Absorption Pattern
Authors: Salloum Maher , Ma Ronghui , Zhu Liang
Published: July 2013

Magnetic nanoparticle hyperthermia has potential to achieve optimal therapeutic results due to its ability to deliver adequate heating power to irregular and/or deep-seated tumor at low magnetic field frequency and amplitude [1]. The heat generated by the particles under the application of an external alternating magnetic field is mainly due to the Néel relaxation mechanism and/or Brownian motion of the particles [2]. In clinical applications, it is very important to ensure a maximum damage to the tumor while protecting the normal tissue. The resulted heating pattern by the nanoparticle distribution in tumor is closely related to the injection parameters [3, 4].
Contactless Investigation of Nuclear Mechanics of Normal and Lamin Mutant Cells Using a 3D Image- and Model-Based Framework
Authors: González Paula , Reichenzeller Michaela , Eils Roland , Gladilin Evgeny
Published: July 2013

Apart from storing most of the DNA in eukaryotic cells, the cell nucleus provides mechanical protection through its nuclear envelope to ensure the integrity of the genome. The nuclear lamina is known to play an important role in this respect by supplying a structural framework for the nucleus [1]. The severe diseases arising from mutations in the LMNA gene confirm the importance of the lamin proteins for normal cell functionality [2]. Most experimental techniques for investigation of the cell mechanics are based on the application of external forces onto the cell boundary [3]. Thus, the quantitative determination of the mechanical properties of intracellular structures in situ, still represents a challenging task. In our previous works, we proposed a 3D image- and model-based framework for analysis of intracellular mechanics [4]. In this work, we extend this approach to a fully contactless investigation of nuclear mechanics of normal and LMNA–/– mutant cells. Differently from previous approaches, cellular deformation was induced by chemical agents, i.e., without any mechanical contact with the cell boundary. In particular, we focus on (i) comparative analysis of 3D structural response of nuclear matter with respect to external forces in normal and pathological cell, as well as (ii) determination of the scarcely-investigated nuclear compressibility (i.e. the Poisson’s ratio).
Altered Shear Stress Stimulates Upregulation of Endothelial VCAM-1 and ICAM-1 in a BMP-4- and TGF-β1-Dependent Pathway
Authors: Sucosky Philippe , Balachandran Kartik , Jo Hanjoong , Yoganathan Ajit P.
Published: July 2013

Inflammation and calcification are common features of aortic valve (AV) diseases [1]. AV diseases preferentially occur in the aortic side of the valvular leaflets where they are exposed to complex and unstable hemodynamic conditions [2]. The reasons for this side-specific response, potentially associated with the local shear stress environment, are not completely understood. In addition, while it has been shown that exposure of vascular endothelial cells to oscillatory shear stress induces inflammatory responses by bone morphogenic protein (BMP)-4-dependent mechanisms [3], it is not clear whether BMP plays a role in the inflammation of AV leaflet exposed to altered mechanical environment. In the present study, we hypothesized that AV inflammation occurs preferentially in the aortic surface of AV leaflets in a BMP and TGF-β1-dependent manner due to the local hemodynamic loading conditions. This hypothesis was tested via three sets of experiments focused on the biological response of porcine AV leaflets using either a standard or pro-osteogenic medium.