Scholarship & Research
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Item Development and characterization of a split Hopkinson pressure bar for testing high shock accelerometers(Montana State University - Bozeman, College of Engineering, 2022) Berg, Charlotte Katherine; Chairperson, Graduate Committee: David A. MillerExtreme environments pose significant challenges in the aerospace and defense fields. Prior to equipment deployment, dynamic testing is often conducted to identify potential failure points from high shock. Accelerometers are vital sensors for characterizing system response to transient inputs, such as impact and vibration, faced by atmospheric reentry vehicles or explosive protection equipment. However, accurate data collection is often inhibited by sensor damage or nonlinear response to dynamic inputs. A controlled experimental system capable of recreating extreme conditions is needed to assess sensor limitations and design options prior to full-scale structural testing. Conventionally built for high strain-rate material testing, a Split Hopkinson Pressure Bar uses colinear elastic bar impact to produce high energy, short-duration stress waves. Material samples are sandwiched between elastic bars and dynamic properties are derived from stress waves reflected by or transmitted through the sample. In this work, a modified Hopkinson Pressure Bar was developed to assess accelerometer response to high-energy, dynamic inputs. The modified system consists of a gas gun that propels a short steel striker into a longer steel incident bar, producing a nondispersive stress wave. A single-axis Endevco 7270 piezoresistive accelerometer is mounted on a fly-away structure aligned with the incident bar. The stress wave that reaches the accelerometer creates a shock impulse of similar magnitude and frequency as an explosive test. The Hopkinson Pressure Bar was characterized with a range of input configurations and produces acceleration pulses with amplitudes up to 100,000 g and durations of 0.2 ms. Strain signals were compared to accelerometer output in two mounting configurations over a range of shock levels. There was good agreement between strain-derived acceleration and peak accelerometer accelerations. Experimental system capabilities and limitations are presented alongside current challenges and directions for future research. The setup developed for this research increases sensor and material testing capabilities under extreme environmental conditions.Item In pursuit of value(Montana State University - Bozeman, College of Arts & Architecture, 2020) Gathje, Samuel Gehring; Chairperson, Graduate Committee: Jim ZimpelWhat follows is an exploration of the bounds of Material Intelligence in contemporary forms of making. While the physical work is autobiographical, and this research is broken up by anecdotal vignettes of my lived experience, the questions presented here are urgent and present. What is craft and where can it be most useful today? What objects hold stories, and how can we become more connected to these objects? In a world filled with the mass produced, I aim in this writing to showcase a different way of approaching material and making. A regard for old ways of seeing, and for a mindfulness when it comes to objects, stories, and spaces. This writing is my journey in pursuit of value. Through my own life, through various mentors, teachers, and lessons, I have learned to look to an object's origin to understand its value. Folk art (art of the people), the handmade, and traditional craft all ground us to place, time, experience or culture. I am not arguing that things must be done one way because it is tradition. Instead, I look at what these traditions provide beyond the object, which is often a communal experience of growth, appreciation, and learning. Craft can connect people across distance and time. To borrow a phrase from Glenn Adamson, I hope through this research to uncover a world of 'Fewer, Better Things'.Item A three dimensional finite element model of biofilm subjected to fluid flow and its application to predicting detachment potential(Montana State University - Bozeman, College of Engineering, 2006) Gammelgard, Peter Norman; Chairperson, Graduate Committee: Brett TowlerMicrobial biofouling of wetted surfaces can adversely impact the hydrodynamic performance of pressurized conduits. These impacts are due, in part, to the viscoelastic material properties of biofilm. Of particular interest is the response of biofilm to changing hydrodynamic conditions and its effect on potential for biofilm removal. The goal of this research was two fold; 1) to develop a three dimensional numerical model, incorporating the viscoelastic material description of biofilm, to simulate the response of biofilm to varying hydrodynamic conditions and 2) use this model to identify behavioral characteristics of said biofilm which provide insight into effective removal procedures. Using a viscoelastic Burger fluid material description for biofilm, a numerical fluid-structure interface model was developed.