Design of compliant mechanism lattice structures for impact energy absorption

Indiana University-Purdue University Indianapolis (IUPUI)Lattice structures have seen increasing use in several industries including automotive, aerospace, and construction. Lattice structures are lightweight and can achieve a wide range of mechanical behaviors through their inherent cellular design. Moreover, the unit cells of lattice structures can easily be meshed and conformed to a wide variety of volumes. Compliant mechanism make suitable micro-structures for units cells in lattice structures that are designed for impact energy absorption. The flexibility of compliant mechanisms allows for energy dissipation via straining of the members and also mitigates the effects of impact direction uncertainties. Density-based topology optimization methods can be used to synthesize compliant mechanisms. To aid with this task, a proposed optimization tool, coded in MATLAB, is created. The program is built on a modular structure and allows for the easy addition of new algorithms and objective functions beyond what is developed in this study. An adjacent investigation is also performed to determine the dependencies and trends of mechanical and geometric advantages of compliant mechanisms. The implications of such are discussed. The result of this study is a compliant mechanism lattice structure for impact energy absorption. The performance of this structure is analyzed through the application of it in a football helmet. Two types of unit cell compliant mechanisms are synthesized and assembled into three liner configurations. Helmet liners are further developed through a series of ballistic impact analysis simulations to determine the best lattice structure configuration and mechanism rubber hardness. The final liner is compared with a traditional expanded polypropylene foam liner to appraise the protection capabilities of the proposed lattice structure

Cellular Helmet Liner Design through Bio-inspired Structures and Topology Optimization of Compliant Mechanism Lattices

The continuous development of sport technologies constantly demands advancements in protective headgear to reduce the risk of head injuries. This article introduces new cellular helmet liner designs through two approaches. The first approach is the study of energy-absorbing biological materials. The second approach is the study of lattices comprised of force-diverting compliant mechanisms. On the one hand, bio-inspired liners are generated through the study of biological, hierarchical materials. An emphasis is given on structures in nature that serve similar concussion-reducing functions as a helmet liner. Inspiration is drawn from organic and skeletal structures. On the other hand, compliant mechanism lattice (CML)-based liners use topology optimization to synthesize rubber cellular unit cells with effective positive and negative Poisson's ratios. Three lattices are designed using different cellular unit cell arrangements, namely, all positive, all negative, and alternating effective Poisson's ratios. The proposed cellular (bio-inspired and CML-based) liners are embedded between two polycarbonate shells, thereby, replacing the traditional expanded polypropylene foam liner used in standard sport helmets. The cellular liners are analyzed through a series of 2D extruded ballistic impact simulations to determine the best performing liner topology and its corresponding rubber hardness. The cellular design with the best performance is compared against an expanded polypropylene foam liner in a 3D simulation to appraise its protection capabilities and verify that the 2D extruded design simulations scale to an effective 3D design

Structural Optimization of Thin-Walled Tubular Structures for Progressive Collapse Using Hybrid Cellular Automaton with a Prescribed Response Field

The design optimization of thin-walled tubular structures is of relevance in the automotive industry due to their low cost, ease of manufacturing and installation, and high-energy absorption efficiency. This study presents a methodology to design thin-walled tubular structures for crashworthiness applications. During an impact, thin-walled tubular structures may exhibit progressive collapse/buckling, global collapse/buckling, or mixed collapse/buckling. From a crashworthiness standpoint, the most desirable collapse mode is progressive collapse due to its high-energy absorption efficiency, stable deformation, and low peak crush force (PCF). In the automotive industry, thin-walled components have complex structural geometries. These complexities and the several loading conditions present in a crash reduce the possibility of progressive collapse. The Hybrid Cellular Automata (HCA) method has shown to be an efficient continuum-based approach in crashworthiness design. All the current implementations of the HCA method use a scalar set point to design structures with a uniform distribution of a field variable, e.g., stress, strain, internal energy density (IED), mutual potential energy. For example, using IED and mutual potential energy as the field variable result in high stiffness and progressive collapsing structures, respectively. This paper presents a modified version of the HCA method to design thin-walled structures that collapse progressively. In this methodology, the set point has two components, a prescribed response field, which promotes progressive collapse, and a variable offset value, which satisfies the mass constraint. The numerical examples show that this modified HCA method is capable of finding material distributions that exhibit progressive collapse, resulting in significant improvement in specific energy absorption (SEA) with relatively little change in the PCF

Thermomechanical Topology Optimization of Lattice Heat Transfer Structure Including Natural Convection and Design Dependent Heat Source

Lattice Heat Transfer (LHT) structures provide superior structural support while improving the heat transfer coefficient through their high surface-to-volume ratios. By using current Additive Manufacturing (AM) technologies, LHT with highly complex structures is possible. In this study, the design concept of LHT is further improved by implementing a thermomechanical topology optimization method. With utilization of design-dependent heat source, the method can be applied to generate stiffer LHT structures under mechanical and thermomechanical loads, without decreasing their thermal performance; relative to a design made of a uniform LHT having the same mass fraction. Two numerical examples are presented to illustrate how to use the proposed approach to design LHT sections. The results show that the mechanical performance can be improved more than 50% compared to a uniform LHT with the same mass fraction, without decreasing the thermal performance. The method does not require a fluid mechanics model, thus it is computational effective and particularly suitable for the conceptual design stage. The resulting optimized lattice is made possible by utilizing additive manufacturing technologies

Integration of Art Pedagogy in Engineering Graduate Education

The integration of STEM with the Arts, commonly referred to as STEAM, recognizes the need for human skill, creativity, and imagination in technological innovations and solutions of real-world technical problems. The STEAM paradigm changes the dominant “chalk and talk” lecture and “closed-ended” problem-solving orientation of traditional engineering pedagogy to a hands-on, studio-based, and open-ended creative learning approach, typical in art education. A growing body of literature has provided evidence of the favorable impact of situating STEAM in K-16 education. The long-term objective of this work is to promote creativity in engineering students by integrating learning methods and environments from the Arts into graduate STEM education. To this end, an integrating engineering, technology and art (ETA) educational model is developed and is currently being tested. This ETA educational model systematically merges technical instruction with studio-based pedagogy. The ETA model consists of three courses, which were piloted in the year 2017. In each course, engineering and art instructors and students collaborated for 15 weeks on design projects. These projects ranged from drones to architectural installations

Mechanizovaný způsob dobývání strmě uložených slojí s nebezpečím průtrže uhlí a plynů (PUP)

PrezenčníNeuvedenoNeuveden