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 …

A Study Of Solder Joint Failure Criteria, Jianbiao Pan, Julie Silk

Industrial and Manufacturing Engineering

One of the challenges in an experimental study of solder joint reliability is to determine when cracks occur in a solder joint or when a solder joint fails. Cracks in a real solder joint are difficult to identify using an X-Ray system. Cross-sectioning and scanning electron microscopy (SEM) is a destructive method. A common non-destructive test method is to monitor resistance increase in a solder joint or a daisy-chain. However, no scientific research has been done in establishing the relationship between the crack area of an interconnection and the change in resistance of the interconnection. This paper proposes a method …

Effect Of Gold Content On The Reliability Of Snagcu Solder Joints, Jianbiao Pan, J. Silk, M. Powers, P. Hyland

Industrial and Manufacturing Engineering

Electroplated Ni/Au over Cu is a popular metallization for printed circuit board finish as well as for component leads, especially wire-bondable high-frequency packages, where the gold thickness requirement for wire bonding is high. The general understanding is that less than 3 wt% of Au is acceptable in SnPb solder joints. However, little is known about the effect of Au content on the reliability of SnAgCu solder joints. The purpose of this paper is to determine the acceptable level of Au in SAC305 solder joints. Three different package platforms with different Au thicknesses were assembled on boards with two different Au …

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 …

Updating Purchasing Specifications For Energy-Efficient Commercial Boilers For The Federal Energy Management Program, Arturo Avila, James Lutz

STAR Program Research Presentations

The Federal Energy Management Program (FEMP) and the Environmental Energy Technology Division (EETD) at Lawrence Berkeley National Laboratory (LBNL) are conducting a research project that aims to update the current purchasing specification for energy-efficient commercial boilers. Data available on the internet was used to document the efficiencies, prices and other relevant data on commercial boilers. Boiler models were classified according to their fuel use (gas or oil) and if they produced hot water or steam. Boilers were ranked from highest to lowest thermal efficiency. Scatter plots were used to assess the ranges of efficiencies over a range of boiler capacities …

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 …

Evolving A Summer Engineering Camp Through Assessment, Katherine Chen, Lizabeth Schlemer, Heather Scott Smith, Teana Fredeen

Industrial and Manufacturing Engineering

EPIC (Engineering Possibilities in College) is a one-week summer program for high school students (entering 9th-12th grades) to learn about engineering and experience hands-on labs in a university atmosphere. It's an opportunity for students to explore the different types of engineering available at many universities. The aim of EPIC is to expand the College of Engineering mission to K-12 students: "To educate students for careers of service, leadership and distinction in engineering or other fields by using a participatory, learn by doing, ‘hands-on’ approach".

The Inside-Out Classroom: A Win-Win Strategy For Teaching With Technology, Daniel J. Waldorf, Lizabeth Schlemer

Industrial and Manufacturing Engineering

As costs of higher education soar and many universities face uncertain funding models, institutional pressures have increased to improve instructor efficiency. At the same time, U.S. industry leaders and leading educators have called for improvements in engineering education based on more interactive, hands-on student learning experiences. Although many efforts have been made to take advantage of technology to either improve student learning or to maintain student learning while increasing instructor efficiency, few approaches have been shown to improve both learning and efficiency. A teaching method is proposed to improve student learning and increase student satisfaction while also addressing the instructors’ …

Design Projects With Out-Of-Town Companies, Lizabeth Schlemer

Industrial and Manufacturing Engineering

The capstone design class in the industrial engineering department at California Polytechnic State University, San Luis Obispo (Cal Poly) includes projects with companies. The projects are large ambiguous facilities design problems that allow students to incorporate many aspects of the IE curriculum. For the past 15 years students have been participating in these projects with local companies. Over the past several years, companies from out of town (200 miles to the north in Mountain View or 200 miles to the south in Oxnard) have participated. These out of town companies have presented certain logistical issues, but they have proven to …

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 …

Effect Of Gold Content On The Reliability Of Snagcu Solder Joints, Jianbiao Pan, Julie Silk, Mike Powers, Patrick Hyland

Industrial and Manufacturing Engineering

Electroplated Ni/Au over Cu is a popular metallization for PCB finish as well as for component leads, especially wire-bondable high frequency packages, where the gold thickness requirement for wirebonding is high. The general understanding is that less than 3 wt% of Au is acceptable in SnPb solder joints. However, little is known about the effect of Au content on the reliability of SnAgCu solder joints. The purpose of this study is to determine the acceptable level of Au in SAC305 solder joints. Three different package platforms with different Au thicknesses were assembled on boards with two different Au thicknesses using …

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 …