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Measuring and modeling material properties during high loading rates - Material characterization of A36 steel under high loading rates using the Split Hopkinson Pressure Bar and numerical modeling

(2025) Krohn, Frida

This thesis aims to evaluate a method for analyzing the high strain rate behavior of A36 steel by combining experimental testing and numerical modeling. Experiments consisting of uniaxial compressive tests and Split Hopkinson Pressure bar tests were performed to cover low and high strain rates. The method’s ability to use low strain rate data to predict high strain rate behavior using the Johnson-Cook material model was evaluated. Numerical modeling and parameter optimization were performed in LS-DYNA and LS-OPT, respectively. The results showed reasonable agreement between the experiments and simulations for hydraulic compressive and Split Hopkinson Pressure Bar tests. Consistently, an explicit strain rate dependency is present throughout the tests, but fluctuations in the Split Hopkinson Pressure Bar data complicated the data analysis. The method has strengths and limitations. While the Johnson-Cook material model effectively models A36 steel at high strain rates, additional refinements in the numerical model and parameter optimization process are needed to obtain a reliable set of parameter values. Improving the reliability of the strain gauge data and introducing striker velocity measurements could elevate future method development. In this thesis, the method chosen to evaluate steel’s high strain rate behavior provides a foundation for further work. Refinements in experimental setup and numerical modeling are necessary to improve the reliability of the results before they can be applied effectively in future studies.

Measurement-Controlled Engines - Investigating the role of system-meter coupling time quantum information engines

(2025) Hagman, Rasmus

Nanoscale devices that transform energy into useful work are becoming ubiquitous. A critical task is to control energy transduction at the nanoscale. In this context, quantum measurement and the associated information acquisition can be leveraged to guide and enhance work output through feedback control. This thesis explores a quantum information engine as a prototype energy-transducing device controlled by measurement. This engine harnesses information transfer between a working medium, modelled as a two-level system, and a meter, modelled as a quantum harmonic oscillator. However, this information transfer is not instantaneous; it depends on the coupling time, which is the time required to correlate the system and the meter. This measurement time sets a lower bound on the cycle time of the quantum information engine, making information acquisition a crucial resource for the process. We investigate the cost of quantum measurement, in particular the energetic cost of coupling and decoupling the system and the meter in finite-time operations. Furthermore, we analyse possible schemes of extracting useful work: the ergotropy, or maximum work extraction under unitary transformations, and the excess work by stimulated emission. In both cases, the information about the system is exploited by conditioning the act of extracting work on the measurement outcome. Heat and work flows are analysed as functions of the system and meter temperatures to show that the quantum information engine can operate in different regimes: as a heat engine, a heat valve, a refrigerator and a “true” information engine by extracting work and cooling a colder bath. We show that the quantum information engine performance in terms of power output for very short measurement times, the Zeno limit, is small. To increase the power we need to increase the measurement time which, however, comes with a higher cost of measurement. We carefully analyse the work output-cost relation in different operating regimes of the quantum information engine to find optimal conditions for net work output and high engine performance.

Impedance measurement techniques for DC-biased systems

(2025) Henriksson

Abstract This thesis compiles information about six methods for impedance measurement of DC biased systems. It describes a physical interface for low-voltage Devices Under Test (DUTs) using the shunt-through method with DC-blocking capacitors. The interface is used to measure impedance versus frequency of three pouch cells of different dimensions and chemistries. In addition to the cell measurements, a separate set of measurements are carried out on inductors and capacitors with and without the use of the DC-blocking interface. The measurements show how parameters such as heat, conductor length and measurement setup affect the measured impedance. An interface model is presented that explains in what frequency and DUT impedance ranges each parasitic interface parameter affects the measurement results, and in what way. The conclusion of the thesis is that the used capacitor-based impedance measurement method was not accurate when measuring the low impedance of an electric vehicle battery cell. However, with the modification and improvements outlined in the thesis, the interface type could be used to measure devices with larger impedance, such as a complete high voltage electric vehicle battery consisting of the same cells.

The evaluation of sufficiency strategies in the building sector using life cycle assessment

(2025) Eriksson, Lina

The building sector has a monumental impact on the planet’s environmental state. Despite ongoing efforts, emissions are growing, partly due to increasing consumption, where resource improvements are consumed by expenditure. Efficiency and renewables through technology and sustainable resources cannot reduce the impact of growing demand without a decrease in overall consumption. In recent years, sufficiency has been highlighted as a mitigation strategy with great potential to reduce the environmental impact of the built environment. However, there are few clear examples of definite strategies in the building sector. Furthermore, many building sustainability frameworks include a life cycle assessment, but the result is typically presented as total impact per m2. This makes sufficiency problematic to evaluate, as the main strategies for the building sector are to reduce impact by reducing building and unit size, material demand, and energy consumption. There are currently few examples of sufficiency in LCA, and none are related to the building sector. For sufficiency to be successful in the building sector, the effect of the strategies needs to be quantifiable by LCA, as this is a prevalent method within sustainability and building performance analysis. This thesis explores how LCA can be applied to estimate the effect of sufficiency strategies within housing. The study implements the idea of Sufficiency LCA, using a sufficiency functional unit along with the conventional functional unit, evaluating possible measurements and the effect of strategies. Furthermore, the influence of functional units is studied by testing various units that could change the perception of the building’s impact and provide a more holistic assessment. The thesis concludes that a comparison to show the impact saved is required to evaluate sufficiency. One option is through an additional functional unit measuring the savings effect (a sufficiency functional unit), which is most effective for sufficiency strategies regarding unit sizes and functions. The second option is comparative analysis with other products, which works better for strategies concerning material use. Furthermore, including area per capita or capita as a functional unit would better present the function and size of a building, along with highlighting crucial sufficiency strategies, such as density and co-living. Moreover, multiple trade-offs can be seen between embodied and operational emissions and between production, maintenance, and end-of-life stages for materials.

Chalmershindret 2025

(2025) Anton, Emelie; Ekvall, Hanna; Jacobsson, Petter; Koningen, Ellen; Lindvall, Lina; Nilsson, Ida; Rapp, Johanna; Rosén, Victoria; Sjöblom, Alicia; Westberg, Ellen

Chalmershindret är ett årligt projekt i samarbete mellan Chalmers tekniska högskola och Göteborg Horse Show, där studenter utvecklar mätteknik för att analysera ekipagets prestation i hästhoppning. Årets projekt syftade till att mäta tiden över och mellan hinder med hjälp av geofoner som mäter markvibrationer. Utifrån vibrationsdata tränades en AI-modell för att identifiera avstamp och landning vid ett hinder. Projektgruppen delades in i en teknikgrupp samt en PR- och designgrupp. Teknikgruppen utvecklade mätutrustningen, medan PR- och designgruppen fokuserade på publikupplevelse, marknadsföring och hinderdesign. Projektet avslutades med mätningar och publikaktiviteter på Göteborg Horse Show 2025. Resultatet av mätningarna visade på vissa brister i AI-modellens tidsuppskattningar, och det kunde konstateras att mer träningsdata hade behövts för pålitligare resultat. Därför kompletterades mätningarna under Göteborg Horse Show med manuell tidtagning. Däremot visar vibrationsteknik potential för att i framtiden kunna bli ett användbart och effektivt analysverktyg för att mäta mellantider och tid i luften.