Sridhar S. Condoor

Pitch and Longitudinal Fluting Effects on the Primary Stability of Miniscrew Implants

OBJECTIVE To test the hypotheses that pitch and fluting have no effect on the primary stability of miniscrew implants (MSIs). MATERIALS AND METHODS Maximum placement torque and pullout strength of experimental MSIs were compared with those of control MSIs with the use of synthetic and cadaver bone. MSIs with 1.00 mm pitch were compared with those with 1.25 mm and 0.75 mm pitch; MSIs with three longitudinal flutes were compared with the same MSIs without flutes. A total of 60 MSIs (15 of each design) were evaluated with synthetic bone; a split-mouth cadaver model was used to compare the three experimental designs against the 1 mm control MSIs (total of 90 MSIs). RESULTS The synthetic bone model showed higher placement torque and pullout strength for the 0.75 pitch than for the 1.0 mm and 1.25 mm pitch MSIs, but differences were significant (P < .05) only for pullout strength. The cadaver model showed no significant differences in placement torque or pullout strength associated with pitch. Both synthetic and cadaver bone models showed that MSIs with flutes had significantly (P < .05) higher placement torque and pullout strength. Spearman correlations between placement torque and pullout strength were statistically significant for both synthetic (r = .504) and cadaver (r = .502) bone. CONCLUSION Within limits, decreasing MSI pitch increases pullout strength, and fluting increases both placement torque and pullout strength.

Integrating design in engineering graphics courses using feature-based, parametric solid modeling

Several schools are introducing feature-based, parametric solid modeling as a part of the Engineering Graphics course in the freshmen year. This new technology made the traditional methods of teaching engineering graphics obsolete. In most cases, the traditional methods assume that there is one correct representation for a given part. On the other hand, in solid modeling, a part can be created using several approaches with the same- or different-set of primitives. Some of these approaches are superior to the others as they capture the real design intent accurately. Due to the strong relationship between the part modeling approach and the design intent, this technology provides an excellent opportunity for introducing design. The paper discusses the role of graphics in the design process. Then, it summarizes the changes in the design process due to solid modeling. For instance, the traditional wisdom of creating an assembly drawing before the part drawings is no longer practical. These changes require radical restructuring of our teaching methodology. To address the need, the paper presents a methodology for teaching engineering graphics with an emphasis on feature-based, parametric solid modeling. Students can use this methodology to: identify alternative approaches for creating the model; evaluate their ability to capture the real design intent accurately; and incorporate the design intent by defining an appropriate set of datum planes and following good dimensioning practices. This methodology provides a tight integration between design and engineering graphics.

Do New Wipe Materials Outperform Traditional Lead Dust Cleaning Methods

Government guidelines have traditionally recommended the use of wet mopping, sponging, or vacuuming for removal of lead-contaminated dust from hard surfaces in homes. The emergence of new technologies, such as the electrostatic dry cloth and wet disposable clothes used on mopheads, for removal of dust provides an opportunity to evaluate their ability to remove lead compared with more established methods. The purpose of this study was to determine if relative differences exist between two new and two older methods for removal of lead-contaminated dust (LCD) from three wood surfaces that were characterized by different roughness or texture. Standard leaded dust, <75 μm, was deposited by gravity onto the wood specimens. Specimens were cleaned using an automated device. Electrostatic dry cloths (dry Swiffer), wet Swiffer cloths, paper shop towels with non-ionic detergent, and vacuuming were used for cleaning LCD from the specimens. Lead analysis was by anodic stripping voltammetry. After the cleaning study was conducted, a study of the coefficient of friction was performed for each wipe material. Analysis of variance was used to evaluate the surface and cleaning methods. There were significant interactions between cleaning method and surface types, p = 0.007. Cleaning method was found be a significant factor in removal of lead, p <0.001, indicating that effectiveness of each cleaning methods is different. However, cleaning was not affected by types of surfaces. The coefficient of friction, significantly different among the three wipes, is likely to influence the cleaning action. Cleaning method appears to be more important than texture in LCD removal from hard surfaces. There are some small but important factors in cleaning LCD from hard surfaces, including the limits of a Swiffer mop to conform to curved surfaces and the efficiency of the wetted shop towel and vacuuming for cleaning all surface textures. The mean percentage reduction in lead dust achieved by the traditional methods (vacuuming and wet wiping) was greater and more consistent compared to the new methods (electrostatic dry cloth and wet Swiffer mop). Vacuuming and wet wiping achieved lead reductions of 92% ± 4% and 91%, ± 4%, respectively, while the electrostatic dry cloth and wet Swiffer mops achieved lead reductions of only 89 ± 8% and 81 ± 17%, respectively.

Parameter analysis for the application of the principle of direct and short transmission path: a valve-actuator design case study

Abstract Applying the principle of direct and short transmission path reduces the loads and deformations experienced by individual components. Due to its general applicability, this principle can aid the designer in synthesising and evaluating design configurations. However, the design process currently lacks methodologies for applying this principle (and others). This paper presents parameter analysis as a tool to create effective configurations incorporating fundamental design principles. It places a magnifying glass over a small portion of the design process of a valve-actuator system for a subsea oil-field application. The thought process is presented in a structured manner to effectively describe the approach. The paper elaborates on the parameter analysis cycles dealing with the principle of direct and short transmission path to illustrate the means for applying the principle during design. The benefits of design changes in each evaluation step are documented to demonstrate the value and impact of the principle of direct and short transmission path.

Importance of teaching the history of technology

In most engineering courses, students learn concepts, methods and tools. The education community seldom focused its attention on teaching the historical aspects of engineering and technology. As a result, students know very little about famous engineers, case histories, evolution of engineering science and technology, and influence of engineering activity on the society. The reading of engineering case histories emphasize the role of human error/failure in engineering design, the practice of engineering as an art form, and the difference between engineering and scientific activities. Due to the synergy between the product evolution and the product design, case histories can improve student learning in the capstone design courses. The paper presents a unique teaching approach, which backs away from the engineering achievements to the products and people behind the achievements, and then to the thought processes involved in the product design. This teaching approach exposes students to a few key engineering concepts and ties them with case histories. The paper illustrates the teaching paradigm using the case history of typewriters.

Work in progress: Weekly innovation challenge: Changing the mindset one step at a time every week

While the value of the entrepreneurial mindset in engineering is now well recognized, faculty members are still struggling to find curricular and extracurricular activities to instill this mindset. This paper presents weekly innovation challenges as a relatively easy to implement set of activities that can be incorporated into: i) Existing courses as impromptu competitions and icebreakers that require no major curricular overhaul ii) Extracurricular activities to effectively engage students and faculty, and iii) Outreach activities to promote STEM and entrepreneurship through summer camps, engineers week competitions, K-12 outreach, and open-house events. The goal of the weekly innovation challenges is to instill the entrepreneurial mindset and foster interdisciplinary team to address a need under tight time constraints. In the long-term, the challenges have the potential to change the eco-system of the entire school. This paper provides insights into the organization of such challenges and logistics in conducting them.

Reformulating the Statics Course: A Design-Based Approach

Statics is a pivotal course, whose concepts serve as the building blocks for future courses in engineering. From the experience of teaching the follow-on courses to statics, we found several systemic problems present in most statics textbooks. These problems manifest themselves as lower-than-expected abilities in the students when applying the concepts to design/analyze real systems in subsequent courses. The resulting disappointment in engineering educators is common and well documented. The pedagogy outlined in this paper is based on the premise that students learn more effectively when the relevance of the concepts to real world problems and a systematic improvement in their skill set is tactilely, emotionally, and rationally understood. To this end, the pedagogy brings design theory into the course content. The paper discusses rationale behind the pedagogy and its possible implementation scheme with examples. The pedagogy is flexible and can be integrated into an existing learning approach.© 2008 ASME

Mold Management of Wetted Carpet

This study evaluated the growth and removal of fungi on wetted carpet using newly designed technologies that rely on physical principles of steam, heat, and fluid flow. Sixty samples of carpet were embedded with heat-treated house dust, followed by embedding, wearing with a hexapod, and wetting. Samples were inoculated using a liquid suspension of Cladosporium sphaerospermum prior to placement over a water-saturated foam pad. Incubation times were 24 hr, 7 days, and 30 days. Cleaning was performed using three methods; high-flow hot water extraction, hot water and detergent, and steam. Fungal loading increased from approximately 1500 colony forming units per area (CFU/cm2) in 24 hr to a maximum of approximately 10,200 CFU/cm2 after 7 days with a slight decline to 9700 CFU/cm2 after 30 days incubation. Statistically significant differences were found among all three methods for removal of fungi for all three time periods (p < 0.05). Steam-vapor was significantly better than the alternative methods (p <0.001) with over 99% efficiency in mold spore decline from wetted carpet after 24 hr and 30 days, and over 92% efficiency after 7 days. The alternative methods exhibited lower efficiencies with a decline over time, from a maximum of 82% and 81% at 24 hr down to 60% and 43% at 30 days for detergent-hot water and high-flow, hot water extraction, respectively. The net effect of the mold management study demonstrates that while steam has a consistent fungal removal rate, the detergent and high-flow, hot water methods decline in efficiency with increasing incubation time.

Numerical Analysis of Tool Performance in Up Milling of Ti-6Al-4V Alloy

Ti-6Al-4V is widely used in industry because of its high strength-to-weight ratio at elevated temperatures, its excellent resistance to fracture and corrosion, and biological properties. However, Ti-6Al-4V is classified as hard-to-cut material because of its high chemical reactivity with most tool materials and its low thermal conductivity that causes high temperature on the tool face. Consequently, prediction of the tool temperature distribution has great significance in predicting tool wear pattern. In this research, Finite Element Method (FEM) is employed to conduct numerical investigation of the effects of cutting conditions (cutting speed, feed/tooth, and axial depth of cut) in corner up milling on temperature of the tool rake face. The tool material used is general carbide and the behavior of the workpiece Ti-6Al-4V is described by using Johnson-Cook plastic model. Because of the computational expense, a separate heat transfer model is built to analyze the heat transfer process after the tooth disengages the workpiece and before it engages the workpiece again to predict change of temperature distribution during this cooling process. This research provides helpful guidance for selecting tool cooling strategies in up milling Ti-6Al-4V alloy.Copyright

PRO/MECHANICA-based structural and random vibration analysis of picosatellite structure

This paper focuses on the structural and vibration analysis of a low-cost picosatellite structure to the launch load environment. This picosatellite complies with the CubeSat program design specifications, where the satellite is less than one kilogram in mass with a dimension of 10 cm3. The satellite structure is treated as a combination of beams and thin plate elements. A detailed finite element model is developed to observe its responses to the quasi-static accelerations induced by the launch vehicle. The natural frequencies of the prototype were computed numerically through finite element based methods and compared with the natural frequencies induced by the launch vehicle. It was also found that the maximum stress experienced by the structure during launch was well within the stress limits of the material.