High School Bridge Program: A Multidisciplinary STEM Research Program

A Science, Technology, Engineering and Math (STEM) summer Bridge Program was developed for high school students. The program was designed to encourage students to consider choosing an engineering major in college and to explore STEM as a future career. This was accomplished through a 10-week program involving multidisciplinary research activities. The participants in the program included 33 high school students. Among former participants in position to make a choice in terms of attending college, 100% had chosen to continue on in college, and 86% had chosen to major in a STEM area. The results indicated that that the program had enhanced their confidence in STEM and motivated them in choosing careers in STEM areas. Overall, the participants were very positive about the program and expressed appreciation for the opportunity

An Evaluation of a STEM Program for Middle School Students on Learning Disability Related IEPs

A year long Science, Technology, Engineering and Math (STEM) program was developed for middle schools students on Individualized Education Programs (IEPs) involving learning disabilities. The workshops were designed to encourage students both on IEPs and not on IEPs to explore STEM as a future career choice by building their knowledge and confidence. The participants in the workshops included 11 students on IEPs and 15 students not on IEPs. Parents also provided feedback regarding their attitudes toward the program. The results indicated that there were increases in student participant knowledge and career interest for both the students not on IEPs and the students on IEPs. Overall, reactions to the program from both students and parents were quite positive

Fatigue Behavior of Reinforced Welded Hand-Holes in Aluminum Light Poles with a Change in Detail Geometry

Welded aluminum light poles often contain hand-holes. These hand-holes are used to give access for electrical wiring installation and maintenance purposes. Wind load may cause light poles to be loaded in a cyclic manner. This cyclic loading can cause localized fatigue cracking around the hand-hole. Fatigue failure around hand-holes has been observed in the field, but studies surrounding the resistance of the hand-holes are few and far between. This study included four-point bending fatigue tests on welded aluminum poles containing hand-holes. Eight welded aluminum specimens, each with two hand-holes, were tested in fatigue. These 16 details were loaded at the same stress range. Each specimen had a slightly different geometry or treatment applied to the hand hole. These different details mimicked traditional reinforced hand holes, similar to those evaluated in previous studies. Changes in the treatment and/or geometry included milling the inside of hole, milling the inside of the hole as well as the cast insert prior to welding, and milling the cast insert itself prior to welding. Among the 16 details tested, 15 failed as a result of fatigue cracking. It was found that specimen failure would originated in the throat of the fillet weld and then proceeded to propagate into the reinforcement ring/casting. A finite element analysis was used in addition to the experimental study

Built-Up Closed-Rib Steel Orthotropic Bridge Decks

A new built-up closed-rib section is proposed that may improve the installation, performance, and durability of orthotropic steel bridge decks. The rib is composed of two partial or whole standard hot-rolled steel sections which are connected by a steel plate. The concept is used to design a built-up closed-rib replacement for the Benjamin Franklin Bridge deck. In addition, section performance was compared with the actual bulb section as well as a typical trapezoidal section through finite element simulations. The analyses indicate that the built-up section has smaller stress concentration values as compared with the other sections, and hence, improved fatigue resistance is expected. Finally, it is concluded that the built-up rib has potential to be considered in future orthotropic steel deck designs

Built-Up Closed-Rib Steel Orthotropic Bridge Decks

A new built-up closed-rib section is proposed that may improve the installation, performance, and durability of orthotropic steel bridge decks. The rib is composed of two partial or whole standard hot-rolled steel sections which are connected by a steel plate. The concept is used to design a built-up closed-rib replacement for the Benjamin Franklin Bridge deck. In addition, section performance was compared with the actual bulb section as well as a typical trapezoidal section through finite element simulations. The analyses indicate that the built-up section has smaller stress concentration values as compared with the other sections, and hence, improved fatigue resistance is expected. Finally, it is concluded that the built-up rib has potential to be considered in future orthotropic steel deck designs

The fracture behavior of an Al–Mg–Si alloy during cyclic fatigue

In this paper, is presented and discussed the cyclic fracture behavior of the Al–Mg–Si alloy 6063 that is a candidate used in luminaire light poles. The light poles were subject to fatigue deformation. Test sections were taken from the failed region of the light pole and carefully examined in a scanning electron microscope with the objective of rationalizing the macroscopic fracture mode and intrinsic micromechanisms governing fracture under cyclic loading. The fatigue fracture surface of the alloy revealed distinct regions of early microscopic crack growth, stable crack growth and unstable crack growth and overload. An array of fine striations was found covering the regions of early and stable crack growth. Both macroscopic and fine microscopic cracks were found in the region of unstable crack growth. Very few microscopic voids and shallow dimples were evident on the fatigue fracture surface indicative of the limited ductility of the alloy under cyclic loading conditions

A Study of Fatigue and Fracture Response of Cantilevered Luminaire Structures Made from Aluminum Alloy 6063

In the experimental results elegantly and exhaustively elaborated upon in this paper the local stresses, obtained from finite element analysis, was used to develop estimates of the stress intensity factor (SIF). In combination with crack growth data, the fatigue lives of both the through-plate and an integrally stiffened socket connection were estimated using software developed by the U.S. Air Force (and referred to as AFGROW). The fatigue life estimates correlated well with the test results provided the crack growth rate data was obtained under conditions of minimal closure at higher stress ratios (of the order R = 0.7). In an attempt to establish the fatigue lives in the high cycle regime, the measured residual stresses had to be included in the analysis. For identical stress ranges, the 25 mm thick through-plate socket connection exhibited noticeably lower fatigue lives when compared to the integrally stiffened shoe-base structure. Scanning electron microscopy observations revealed pockets of well-defined striations consistent with stable growth of the crack through the microstructure prior to the onset of unstable crack growth culminating in catastrophic fracture. In the slow growth region, the fracture surface revealed pockets of shallow, well-defined striations that were uniformly spaced indicative of the occurrence of localized microplastic deformation