Engineering Commons^™

Differential Regulation Of Articular Cartilage Tensile Properties By Igf-1 And Tgf-Β1 During In Vitro Growth, M. E. Stender, N. T. Balcom, B. Berg-Johansen, K. J. Dills, D. Dyk, S. J. Hazelwood, A. C. Chen, R. L. Sah, S. M. Klisch

Mechanical Engineering

No abstract provided.

The Sources Of Heat Generation In Vibrothermography, Jeremy Renshaw, John Chen, Stephen Holland, R. Bruce Thompson

Mechanical Engineering

Vibrothermography, or sonic IR, is a nondestructive evaluation technique used to find surface and near surface defects—such as cracks and delaminations—through observations of vibration-induced heat generation. This method has significant interest as an industrial inspection method, however, a lack of understanding of the fundamental physics governing the heat generation process has limited its application despite extensive theoretical, numerical simulation, and experimental work. Significant theoretical and numerical simulation work has been performed, but has yet to be rigorously verified experimentally. This paper presents experimental verification of the sources of heat generation in vibrothermography; specifically friction, plasticity, and viscoelasticity. Specific experimental evidence …

Modeling The Collagen Fibril Network Of Biological Tissues As A Nonlinearly Elastic Material Using A Continuous Volume Fraction Distribution Function, Reza Shirazi, Pasquale Vena, Robert L. Sah, Stephen M. Klisch

Mechanical Engineering

Despite distinct mechanical functions, biological soft tissues have a common microstructure in which a ground matrix is reinforced by a collagen fibril network. The microstructural properties of the collagen network contribute to continuum mechanical tissue properties that are strongly anisotropic with tensile-compressive asymmetry. In this study, a novel approach based on a continuous distribution of collagen fibril volume fractions is developed to model fibril reinforced soft tissues as nonlinearly elastic and anisotropic material. Compared with other approaches that use a normalized number of fibrils for the definition of the distribution function, this representation is based on a distribution parameter (i.e. …

Contribution Of Proteoglycan Osmotic Swelling Pressure To The Compressive Properties Of Articular Cartilage, Eunhee Han, Silvia S. Chen, Stephen M. Klisch, Robert L. Sah

Mechanical Engineering

The negatively charged proteoglycans (PG) provide compressive resistance to articular cartilage by means of their fixed charge density (FCD) and high osmotic pressure (π_PG), and the collagen network (CN) provides the restraining forces to counterbalance π_PG. Our objectives in this work were to: 1), account for collagen intrafibrillar water when transforming biochemical measurements into a FCD-π_PG relationship; 2), compute π_PG and CN contributions to the compressive behavior of full-thickness cartilage during bovine growth (fetal, calf, and adult) and human adult aging (young and old); and 3), predict the effect of depth from the articular …

Vibroacoustic Study Of Circular Cylindrical Tubes In Roller Coaster Rails, Joshua I. Davis, Charles Birdsong, Harold M. Cota

Mechanical Engineering

Excessive noise generated by roller coasters during operation is a significant issue for amusement parks located near residential and business districts. Previous work showed that filling the rails with sand and pea gravel can provide noise reduction levels of up to 10 and 15 decibels. However, using damping materials may require additional support structures to accommodate the weight increase and, consequently, raise installation costs. This paper presents field results that characterize sound and vibration of roller coasters with different rail geometry and fill. Finite element modeling is used to compute the theoretical natural frequencies and mode shapes of a typical …

Refrigerant Mass Migration Modeling And Simulation For Air Conditioning Systems, Bin Li, Steffen Peuker, Predrag S. Hrnjak, Andrew G. Alleyne

Mechanical Engineering

Refrigerant mass migration and redistribution are regarded as key factors affecting the cycling performance of air conditioning and refrigeration systems. A dynamic model of an R134a automotive air conditioning system is presented as an example in this paper to capture the refrigerant migration during compressor shut-down and start-up operations. Model validation against experimental data demonstrates the capabilities of the modeling approach in predicting the refrigerant mass migration among the components during shut-down, and the resulting refrigerant redistribution behaviors during start-up. These results represent the first refrigerant mass migration prediction in a validated dynamic system model. In addition, the potential of …

An Industry-University Partnership Case Study, Peter Schuster

Mechanical Engineering

At many universities, senior undergraduate mechanical engineers work in teams on industry-sponsored capstone design projects. These projects provide an excellent opportunity for students to synthesize their courses, work with the more realistic deadlines and expectations of industry, and interact with company representatives. It also give industrial partners a chance to become educational partners with the university, preview potential new hires, and complete some noncritical projects at low cost.

This paper presents a case study of a successful six-year partnership between the Automotive Bumper Project committee of the American Iron & Steel Institute (AISI) and a mechanical engineering department. The AISI …

A Simple Lab Project Integrating Theoretical, Numerical, And Experimental Stress Analysis, Peter Schuster

Mechanical Engineering

Learning is enhanced when students consider problems from different perspectives. Unfortunately, in stress analysis courses, the depth of the mathematical analysis and limited time and resources often restricts the focus to traditional closed-form solutions occasionally supplemented with simple demonstrations. In order to enhance student engagement and understanding, a lab mini-project was developed for teaching Castigliano’s method for structural analysis in a stress analysis course.

The mini-project consists of a design evaluation task which is investigated using three different methods: closed-form analysis, finite element analysis, and simple model build and test. The task is to select the better of two alternative …

Evaluation Of Transient Refrigerant Migration Modeling Approach On Automotive Air Conditioning Systems, Bin Li, Steffen Peuker, Pega Hrnjak, Andrew Alleyne

Mechanical Engineering

Automotive air conditioning systems are subject to constantly changing operation conditions and steady state simulations are not sufficient to describe the actual performance. The refrigerant mass migration during transient events such as clutch-cycling or start-up bas a direct impact on the transient performance. It is therefore necessary to develop simulation tools which can accurately predict the migration of the rerrigerant mass. To this end a dynamic model of an automotive air conditioning system is presented in this paper using a switched modeling framework. Model validation against experimental results demonstrates that the developed modeling approach is able to describe the transient …

An Advanced Numerical Model Of Gear Tooth Loading From Backlash And Profile Errors, Andrew Sommer, Jim Meagher, Xi Wu

Mechanical Engineering

This study demonstrates the early transient dynamic loading on teeth within a fixed-axis gear transmission arising from backlash and geometric manufacturing errors by utilizing a non-linear multi-body dynamics software model. Selection of the non-linear contact parameters such as the stiffness, force exponent, damping, and friction coefficients are presented for a practical transmission. Backlash between gear teeth which is essential to provide better lubrication on tooth surfaces and to eliminate interference is included as a defect and a necessary part of transmission design. Torsional vibration is shown to cause teeth separation and double-sided impacts in unloaded and lightly loaded gearing drives. …

A Differential Planetary Gear Model With Backlash And Teeth Damage, Xi Wu, Jim Meagher, Andrew Sommer

Mechanical Engineering

Planetary gear trains can be more compact and efficient as power transmissions than fixed axis gear trains but are also more complicated and less understood in terms of vibration health monitoring. A practical differential planetary gear train, which combines two inputs and one output, is studied using multi-body dynamics software. Backlash between the sun gear and planet gears are precisely specified to avoid teeth interference and undercut. In order to calculate accurate impact forces, an impact model is chosen. Tooth geometry errors are created on the sun gear. Constraints and contact forces to the model are applied as close as …

Work In Progress - Role Of Faculty In Promoting Lifelong Learning: Initial Findings, John Chen, Susan M. Lord, Katharyn Nottis, Michael Prince, Candice Stefanou, Jonathon Stolk

Mechanical Engineering

Calls for educational reform emphasize the need for student-centered learning approaches that foster lifelong learning. To be a lifelong learner includes characteristics consistent with those of self-directed learners, such as being curious, motivated, reflective, analytical, persistent, flexible, and independent. Instructor support of students’ self-directed learning (SDL) development relies on understanding and balancing these factors in the classroom. Engineering educators play a critical role in influencing outcomes related to SDL through their design of courses that support students’ transitions from controlled to autonomous learning behaviors. This study will examine a variety of engineering courses and pedagogical approaches. Each will be characterized …

Differential Regulation Of Immature Articular Cartilage Compressive Moduli And Poisson’S Ratios By In Vitro Stimulation With Igf-1 And Tgf-Β1, Gregory M. Williams, Kristin J. Dills, Christian R. Flores, Michael E. Stender, Kevin M. Stewart, Lauren M. Nelson, Albert C. Chen, Koichi Masuda, Scott J. Hazelwood, Stephen M. Klisch, Robert L. Sah

Mechanical Engineering

Mechanisms of articular cartilage growth and maturation have been elucidated by studying composition-function dynamics during in vivo development and in vitro culture with stimuli such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta 1 (TGF-β1). This study tested the hypothesis that IGF-1 and TGF-β1 regulate immature cartilage compressive moduli and Poisson’s ratios in a manner consistent with known effects on tensile properties. Bovine calf articular cartilage from superficial-articular (S) and middle-growth (M) regions were analyzed fresh or following culture in medium with IGF-1 or TGF-β1. Mechanical properties in confined (CC) and unconfined (UCC) compression, cartilage matrix composition, and explant …

Role Of Faculty In Promoting Lifelong Learning: Characterizing Classroom Environments, Susan M. Lord, John Chen, Katharyn E. K. Nottis, Candice Stefanou, Michael J. Prince, Jonathon Stolk

Mechanical Engineering

Calls for educational reform emphasize the need for student-centered learning approaches that foster lifelong learning. To be a lifelong learner includes characteristics consistent with those of self-directed learners, such as being curious, motivated, reflective, analytical, persistent, flexible, and independent. Educational research has shown that the building of these aptitudes involves a complex interplay among nearly every aspect of human development. Instructor support of students’ self-directed learning (SDL) development relies on understanding and balancing these factors in the classroom. Engineering educators play a critical role in influencing outcomes related to SDL through their design of courses that support students’ transitions from …

Classes That Click: Fast, Rich Feedback To Enhance Student Learning And Satisfaction, John C. Chen, Dexter C. Whittinghill, Jennifer A. Kadlowec

Mechanical Engineering

No abstract provided.

Nitrous Oxide Cooling In Hybrid Rocket Nozzles, Patrick Lemieux

Mechanical Engineering

The Department of Mechanical Engineering at the California Polytechnic State University, San Luis Obispo, has developed an innovative program of experimental research and development on hybrid rocket motors (where the fuel and the oxidizer are in different phases prior to combustion). One project currently underway involves the development of aerospike nozzles for such motors. These nozzles, however, are even more susceptible to throat ablation than regular converging diverging nozzles, due the nature of their flow expansion mechanism. This paper presents the result of a recent development project focused on reducing throat ablation in hybrid rocket motor nozzles. Although the method …

Enhanced Vehicle Identification Utilizing Sensor Fusion And Statistical Algorithms, Stephane Roussel, Hemanth Porumamilla, Charles Birdsong, Peter Schuster, Christopher Clark

Mechanical Engineering

Several studies in the area of vehicle detection and identification involve the use of probabilistic analysis and sensor fusion. While several sensors utilized for identifying vehicle presence and proximity have been researched, their effectiveness in identifying vehicle types has remained inadequate. This study presents the utilization of an ultrasonic sensor coupled with a magnetic sensor and the development of statistical algorithms to overcome this limitation. Mathematical models of both the ultrasonic and magnetic sensors were constructed to first understand the intrinsic characteristics of the individual sensors and also to provide a means of simulating the performance of the combined sensor …

Work In Progress - Role Of Faculty In Promoting Lifelong Learning, Jonathon Stolk, Susan M. Lord, Candice Stefanou, John Chen, Katharyn E. K. Nottis, Michael J. Prince

Mechanical Engineering

Students’ development of self-directed and lifelong learning capacities is vital for their success in today’s engineering environment. Instructors play a critical role in influencing outcomes related to self-directed learning (SDL) through their design of courses that support students’ transitions from controlled to autonomous learning behaviors. Yet there is a critical lack of research examining how instructor choices promote self-directed (and eventually lifelong) learning development in undergraduate engineering students. In this work in progress, we introduce a project that explores how instructor choices affect a range of student outcomes related to their development as self-directed and lifelong learners. Drawing on existing …

A Nonlinear Constituent Based Viscoelastic Model For Articular Cartilage And Analysis Of Tissue Remodeling Due To Altered Glycosaminoglycan-Collagen Interactions, Gregory C. Thomas, Anna Asanbaeva, Pasquale Vena, Robert L. Sah, Stephen M. Klisch

Mechanical Engineering

A constituent based nonlinear viscoelastic (VE) model was modified from a previous study (Vena, et al., 2006, “A Constituent-Based Model for the Nonlinear Viscoelastic Behavior of Ligaments,” J. Biomech. Eng., 128, pp. 449–457) to incorporate a glycosaminoglycan (GAG)-collagen (COL) stress balance using compressible elastic stress constitutive equations specific to articular cartilage (AC). For uniaxial loading of a mixture of quasilinear VE constituents, time constant and relaxation ratio equations are derived to highlight how a mixture of constituents with distinct quasilinear VE properties is one mechanism that produces a nonlinear VE tissue. Uniaxial tension experiments were performed with newborn bovine AC …

Development Of A Reusable Aerospike Nozzle For Hybrid Rocket Motors, Patrick Lemieux

Mechanical Engineering

The Department of Mechanical Engineering at the California Polytechnic State University, San Luis Obispo, has developed an innovative program of experimental research and development on hybrid rocket motors (where the fuel and the oxidizer are in different phases prior to combustion). One project currently underway involves the development of aerospike nozzles for such motors. These nozzles, however, are even more susceptible to throat ablation than regular converging-diverging nozzles, due the nature of their flow expansion mechanism. This paper presents the result of a recent development project focused on reducing throat ablation in hybrid rocket motor nozzles. Although the method is …

Dynamics Simulation And Malfunction Diagnosis Of Heavy Machinery Using Msc Adams, Dewen Kong, Jim M. Meagher, Xi Wu

Mechanical Engineering

No abstract provided.

Integrating Adams Software Into An Upper Division Mechanical Design And Analysis Course, Xi Wu, Dewen Kong, Jim Meagher

Mechanical Engineering

No abstract provided.

Simulating The Growth Of Articular Cartilage Explants In A Permeation Bioreactor To Aid In Experimental Protocol Design, Timothy P. Ficklin, Andrew Davol, Stephen M. Klisch

Mechanical Engineering

Recently a cartilage growth finite element model (CGFEM) was developed to solve nonhomogeneous and time-dependent growth boundary-value problems (Davol et al., 2008, “A Nonlinear Finite Element Model of Cartilage Growth,” Biomech. Model. Mechanobiol., 7, pp. 295–307). The CGFEM allows distinct stress constitutive equations and growth laws for the major components of the solid matrix, collagens and proteoglycans. The objective of the current work was to simulate in vitro growth of articular cartilage explants in a steady-state permeation bioreactor in order to obtain results that aid experimental design. The steady-state permeation protocol induces different types of mechanical stimuli. When the specimen …

Use Of Ultrasonic Sensors In The Development Of An Electronic Travel Aid, Chris Gearhart, Alex Herold, Brian Self, Charles Birdsong, Lynne Slivovsky

Mechanical Engineering

Ultrasonic sensors present one of the most cost-effective digital distance measurement systems available for mobile applications. Their effectiveness is limited, however, in applications involving complex environments and when information on sensor position is unavailable. This paper focuses on the implementation and limitations of ultrasonic sensors and system design considerations during development of an Electronic Travel Aid [ETA] for the visually impaired utilizing ultrasonic sensors and vibrotactile feedback. Our work with sensors included signal filtering and triangulation to improve performance characteristics of ultrasonic-based measurements. Additionally, we describe the use of computer modeling to aid in the design of ultrasonic sensor systems.

Undergraduate Engineers Develop Hydraulic Servo Control Systems Using Model-Based Design With Simulink, Charles Birdsong

Mechanical Engineering

In the past, control engineering was the exclusive province of computer and electrical engineers with advanced degrees and years of experience in low-level programming languages. Today, engineers and students alike can use Model-Based Design to rapidly design and implement real-time control systems without having to learn low-level programming. Used throughout the automotive and aerospace industries, Model-Based Design places a high-level system model at the center of development. This approach helps engineering students understand not only the basic physics of system components, but also the interaction between components and the behavior of the overall system.

The Effectiveness Of Asynchronous Podcasting Of Classes, John Chen

Mechanical Engineering

In this study we examine in some detail the effectiveness of enhanced podcasting compared with traditional face-to-face class meeting. Enhanced podcasting goes beyond simply recording the audio portion of a lecture. It may include the video footage from the class meeting or, as in our case, the presented material (including each written pen stroke) exactly as seen by students sitting in the classroom with the instructor. The course we studied is Applied Thermodynamics, a junior-level course for mechanical engineering students. For this study we had access to three sections of the course, all taught by the same faculty member. For …

Transient Refrigerant Migration And Oil Distribution Of An R134a Automotive A/C System, Steffen Peuker, P. S. Hrnjak

Mechanical Engineering

Automotive fixed orifice tube (FOT) systems are especially prone to cycling losses due to their clutch cycling operation. Therefore, it is important to better understand the dynamics of the refrigerant and oil migration during transient events such as cycling and start-up. To measure the refrigerant mass and oil distribution of an automotive R134a FOT breadboard system, two ball valves around each component are added. By simultaneously closing the valves, the refrigerant and oil is trapped in different sections of the system and can be measured. The transient refrigerant migration during a stop-start transient as well as the refrigerant mass distribution …

Numerical Simulation Of Thermo-Elasticity, Inelasticity And Rupture Inmembrane Theory, Michael Taylor

Mechanical Engineering

Two distinct two-dimensional theories for the modeling of thin elastic bodies are developed. These are demonstrated through numerical simulation of various types of membrane deformation. The work includes a continuum thermomechanics-based theory for wrinkled thin films. The theory takes into account single-layer sheets as well as composite membranes made of multiple lamina. The resulting model is applied to the study of entropic elastic elastomers as well as Mylar/aluminum composite films. The latter has direct application in the area of solar sails. Several equilibrium deformations are illustrated numerically by applying the theory of dynamic relaxation to a finite difference discretization based …

A Nonlinear Finite Element Model Of Cartilage Growth, Andrew Davol, Michael S. Bingham, Robert L. Sah, Stephen M. Klisch

Mechanical Engineering

The long range objective of this work is to develop a cartilage growth finite element model (CGFEM), based on the theories of growing mixtures that has the capability to depict the evolution of the anisotropic and inhomogeneous mechanical properties, residual stresses, and nonhomogeneities that are attained by native adult cartilage. The CGFEM developed here simulates isotropic in vitro growth of cartilage with and without mechanical stimulation. To accomplish this analysis a commercial finite element code (ABAQUS) is combined with an external program (MATLAB) to solve an incremental equilibrium boundary value problem representing one increment of growth. This procedure is repeated …

Regulation Of Immature Cartilage Growth By Igf-I, Tgf- Β 1, Bmp-7, And Pdgf-Ab: Role Of Metabolic Balance Between Fixed Charge And Collagen Network, Anna Asanbaeva, Koichi Masuda, Eugene J-M.A. Thonar, Stephen M. Klisch, Robert L. Sah

Mechanical Engineering

Cartilage growth may involve alterations in the balance between the swelling tendency of proteoglycans and the restraining function of the collagen network. Growth factors, including IGF-I, TGF-β1, BMP-7, and PDGF-AB, regulate chondrocyte metabolism and, consequently, may regulate cartilage growth. Immature bovine articular cartilage explants from the superficial and middle zones were incubated for 13 days in basal medium or medium supplemented with serum, IGF-I, TGF-β1, BMP-7, or PDGF-AB. Variations in tissue size, accumulation of proteoglycan and collagen, and tensile properties were assessed. The inclusion of serum, IGF-I, or BMP-7 resulted in expansive tissue growth, stimulation of proteoglycan deposition but not …