Modern 3D printed components are finding applications in dynamic structures. These structures are often subject to dynamic loadings. To date, research has mostly focused on investigating the mechanical properties of these 3D printed structures with minimum attention paid to their modal analysis. This work is focused on performing experimental modal analysis of 3D printed structures. The results show that the adhesion type has the most significant impact on the vibration response and parameters obtained from the modal analysis. The average dynamic modulus, natural frequency, and damping coefficient increased by approximately 12.5%, 5.5%, and 36%, respectively, for the specimens printed using skirt adhesion compared to those printed using raft adhesion. SEM analysis suggests that the 3D printed specimens with skirt adhesion yielded flattened layers, while raft adhesion resulted in rounded layers. The flattened layers of the specimens with skirt adhesion are likely an indication of an enhanced heat transfer between the 3D printer bed and the specimen. The printed specimens with skirt adhesion are in direct contact with the printer bed during the printing process. This enhances the heat transfer between the specimen and the printer bed, causing the layers to flatten out. The enhanced heat transfer yields a better inter-layer diffusion, resulting in improved physical bonding at the layers’ interface. The improved bonding yields higher stiffnesses and natural frequencies. For the specimens with skirt adhesion, the improved heat transfer process is also likely responsible for the enhanced damping properties. The strengthened inter-layer bonding at the layer–layer interface provides better energy dissipation along the contact lines between the layers.
A project-based, freshman engineering course sequence has been developed and implemented for all new freshman engineering students with support from an NSF CCLI grant. The mission of the curriculum is to systematically instill the ten attributes of engineers outlined in the National Academy of Engineering report "The Engineer of 2020: Visions of Engineering in the New Century."The curriculum objectives are divided into seven threads that run concurrently throughout the freshman year: systems, electromechanical devices, fabrication and acquisition, software, fundamental engineering concepts, communication, and broadening activities. We have worked to structure the content timing and delivery so that the knowledge, skills and attitudes associated with each thread are built progressively. Curriculum objectives are directly tied to the ten attributes of "The Engineer of 2020."Instead of a textbook, students purchase a Parallax Boe-Bot kit that serves as a platform for laboratory and design projects, allowing students to quickly develop skills in programming and circuit prototyping. Students also purchase a set of tools for completing electromechanical projects and several software programs for facilitating engineering analysis and 3D modeling. A Freshman Projects Classroom was designed to promote team-based learning.The faculty and students are challenged by the new curriculum and are now more motivated and engaged in learning than with the prior curriculum. Assessments from this academic year suggest that the curriculum does accomplish our primary goal of preparing students to meet the attributes of "The Engineer of 2020."
This paper describes a model for high-school teacher professional development and student learning that can be readily adapted by other universities seeking meaningful partnerships with K-12 schools. In this program, university engineering and science faculty work collaboratively with high school teachers to present challenging engineering design projects to high school students.Our program consists of a series of Teacher Workshops for high school teachers, each followed by a Discovery Weekend with their students, and culminating in a challenge weekend. Each project includes a thorough integration of mathematics, science and engineering, thereby leading to a much deeper understanding of how the mathematics and science topics taught in high school are related to engineering design. This approach has led to increased confidence in the high school teachers, increased interest in STEM topics among the students, and a heightened awareness of the role engineering can play in meeting the challenges facing our society. The collaboration between university faculty and high school teachers maximizes the benefit to the students by having both their regular teachers and university faculty directly involved in their projects. It also effectively demonstrates to the students how diverse teams can often provide better solutions to problems.
As part of the freshmen engineering curriculum at Louisiana Tech University, students develop novel solutions to problems that "bug" them. During the spring quarter, students are asked to spend several weeks compiling bug lists -noting products or situations that they think could be improved. The students form teams and decide on which of their bugs they want to address. A creative problem solving approach is demonstrated to the students who generate and evaluate concepts for their solution. The teams then construct increasingly refined prototypes of their new product idea. Serving as the culmination of the experience, a Freshman Design Exposition is held in which the general public, other students, and judges view and provide feedback to the students' inventions. During the following academic year, the best projects are asked to enter their designs in an Idea Pitch competition which leads to the Top Dawg business plan competition where their ideas can be more formally explored.
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