Mechanical 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 …