A multi-functional (sensing -actuating) greenhouse ventilation window heated/cooled naturally by convection was designed to overcome different industry challenges in terms of designing smart applications. This ventilation window design includes a three-pulley system to reduce the load on the NiTi actuator and enhance its long-life time. In addition, using the NiTi actuator allows energy saving due to natural phase transformation induction (i.e. convection) and high force generation compared to the small NiTi wire mass. Structural analysis was used to determine the force generated in the “C-shaped” NiTi wire after loading. Transient thermal and structural analysis also was used to investigate the strain rate effects on the shape memory response of “C shaped” NiTi alloy element under different thermomechanical loadings and boundary conditions. Two types of loading have been applied isothermally or at adiabatic conditions. The results showed a significant effect of the high loading rates on increasing the stress plateau which is caused by the corresponding shift in the transformation temperatures. As a result, it could be expected that the actuator life time could be reduced when a rapid, as opposed to a slow loading rate, is adopted. In addition, the dynamic loading of the NiTi leads to a decrease of the recoverable strain. Experimental work was done to validate the simulation model by testing a commercial NiTi sample dynamically and compare the macroscopic displacement during mechanical loading and the strain recovery process.

The Oseberg ship is known as one of the finest surviving artifacts from the Viking age, with origins dated back to the 800s. The ship has been displayed in the Viking ship museum in Oslo since 1926. The nearly 100 years on museum display along with the over 1000 years it was buried has weakened the structure of the ship. To slow down the deterioration, several research projects has been initiated, among them the project ''Saving Oseberg''. A part of ''Saving Oseberg'' is contributing to the planning of a new museum for the ship. As a basis for the planning, the ship has been monitored with photogrammetry. This is intended as a way to visualise the deformation and displacements of the ship due to seasonal changes in indoor temperature and humidity. In this thesis the photogrammetry data from the hull of the ship was used to make a finite element model, and through this model calculate the average strain on each element. The method was based on a previous research project conducted on the Swedish warship Vasa by a research group at the Division of Applied Mechanics at Uppsala University. The measurements of the ship was formed into a hull by Delaunay triangulation. The strain was approximated as a Green strain and evaluated using isoparametric mapping of the elements. Through the nodal displacements, the strain was evaluated by approximating the elements as tetrahedrons and calculating the average strain from these elements between the measurements. The result showed an oscillating behavior of the displacements, proving the proposal of seasonal depending displacements. The measured principal strains also matched to the corresponding relative humidity fluctuation during the year. The strain magnitude was relatively even throughout the ship, mostly varying between ±0.4% but certain areas were more subjected than others. A few elements on the starboard side showed very large strains through most of the measurements, this seemed very unusual and was probably the result of inaccuracies or errors in the data. Though the ship is subjected to relative small strains and permanent displacements after annual cycles, the mechano-sorptive strains may lead to accumulated deformation and eventually failure in the weak parts of the wood or at the high stress concentraion parts. In addition, the cyclic strain even in elastic range may cause fatigue failure in any material which could pose a large threat for the future conservation of the ship.

abstract: An orthotropic elasto-plastic damage material model (OEPDMM) suitable for impact analysis of composite materials has been developed through a joint research project funded by the Federal Aviation Administration (FAA) and the National Aeronautics and Space Administration (NASA). The developed material model has been implemented into LS-DYNA®, a commercial finite element program. The material model is modular comprising of deformation, damage and failure sub-models. The deformation sub-model captures the rate and/or temperature dependent elastic and inelastic behavior via a visco-elastic-plastic formulation. The damage sub-model predicts the reduction in the elastic stiffness of the material. The failure sub-model predicts when there is no more load carrying capacity in the finite element and erosion of the element from the finite element model. Most of the input parameters required to drive OEPDMM are in the form of tabulated data. The deformation sub-model is driven by a set of tabulated stress-strain data for a given strain-rate and temperature combination. The damage sub-model is driven by tabulated damage parameter-strain data. Two failure sub-models have been implemented – Puck Failure Model and Generalized Tabulated Failure Model. Puck Failure Model requires scalar parameters as input whereas, the Generalized Tabulated Failure Model is driven by a set of equivalent failure strain tabulated data. The work presented here focuses on the enhancements made to OEPDMM with emphasis on the background, development, and implementation of the failure sub-models. OEPDMM is verified and validated using a carbon/epoxy fiber reinforced composite. Two validation tests are used to evaluate the failure sub-model implementation - a stacked-ply test carried out at room temperature under quasi-static tensile and compressive loadings, and several high-speed impact tests where there is significant damage and material failure of the impacted panel. Results indicate that developed procedures provide the analyst with a reasonable and systematic approach to building predictive impact simulation models. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22431号 / 工博第4692号 / 新制||工||1732(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 大崎 純, 教授 西山 峰広, 准教授 聲高 裕治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In this study, parameters related to material properties, geometry, and external stimuli were examined individually to determine their influence on multi-story, partially grouted, perforated (openings), masonry shear walls using a finite element software FormWorks. The parameters studied were: the strength of grouted masonry prisms f'm,grouted; the strength of un-grouted (hollow) masonry prisms f'm,ungrouted; the ratio of mortar shear strength to masonry compressive strength; vertical and horizontal reinforcement ratios in terms of size and spacing of reinforcement; axial load; aspect ratio; and openings that were vertically and horizontally altered. To perform this study, finite element models were validated against the response of three experimental walls of two unique types that were built ½ scale and tested in a lab. The validated finite element models were designated as "base models" which accurately predicted the maximum strength of each wall within a tolerance of 5.9%, 3.3%, and 1.8%. Following validation, each parameter in question was varied individually to identify and quantify the sensitivity of the parameter and to observe the changes in shear capacity and deflection for this unique configuration of masonry shear walls. To capture the impact of these parameters, 38 different shear wall models were built and tested. The results were compared against the Masonry Standards Joint Committee (MSJC) (2013) code predictions using the applicable shear strength equations. Results of this study are specific to cantilever type masonry shear walls with large aspect ratios and openings in every story. Shear wall capacity was considered sensitive to the following parameters: compressive strength of grouted masonry; compressive strength of un-grouted masonry; joint strength ratio; vertical reinforcement ratio; axial stress; aspect ratio; and opening width. Shear wall capacity was considered not sensitive to the following parameters: horizontal reinforcement ratio; vertical reinforcement spacing; and horizontal reinforcement spacing. The sensitivity of shear wall capacity to opening height was determined inconclusive. The sensitivities were determined by fitting trend lines to the results of shear capacity vs. each parameter individually. Each MSJC (2013) code prediction un-conservatively over-predicted the shear wall capacity except one wall configuration that had a joint strength ratio of 0.045.

In this study, parameters related to material properties, geometry, and external stimuli were examined individually to determine their influence on multi-story, partially grouted, perforated (openings), masonry shear walls using a finite element software FormWorks. The parameters studied were: the strength of grouted masonry prisms f<&trade>m,grouted; the strength of un-grouted (hollow) masonry prisms f<&trade>m,ungrouted; the ratio of mortar shear strength to masonry compressive strength; vertical and horizontal reinforcement ratios in terms of size and spacing of reinforcement; axial load; aspect ratio; and openings that were vertically and horizontally altered. To perform this study, finite element models were validated against the response of three experimental walls of two unique types that were built ½ scale and tested in a lab. The validated finite element models were designated as œbase models which accurately predicted the maximum strength of each wall within a tolerance of 5.9%, 3.3%, and 1.8%. Following validation, each parameter in question was varied individually to identify and quantify the sensitivity of the parameter and to observe the changes in shear capacity and deflection for this unique configuration of masonry shear walls. To capture the impact of these parameters, 38 different shear wall models were built and tested. The results were compared against the Masonry Standards Joint Committee (MSJC) (2013) code predictions using the applicable shear strength equations. Results of this study are specific to cantilever type masonry shear walls with large aspect ratios and openings in every story. Shear wall capacity was considered sensitive to the following parameters: compressive strength of grouted masonry; compressive strength of un-grouted masonry; joint strength ratio; vertical reinforcement ratio; axial stress; aspect ratio; and opening width. Shear wall capacity was considered not sensitive to the following parameters: horizontal reinforcement ratio; vertical reinforcement spacing; and horizontal reinforcement spacing. The sensitivity of shear wall capacity to opening height was determined inconclusive. The sensitivities were determined by fitting trend lines to the results of shear capacity vs. each parameter individually. Each MSJC (2013) code prediction un-conservatively over-predicted the shear wall capacity except one wall configuration that had a joint strength ratio of 0.045.

Friction stir welding is an advanced welding process that is being investigated for use in many different industries. One area that has been investigated for its application is in healing critical nuclear reactor components that are developing cracks. However, friction stir welding is a complicated process and it is difficult to predict what the final properties of a set of welding parameters will be. This thesis sets forth a method using finite element analysis and a random forest model to accurately predict hardness in the welding nugget after processing. The finite element analysis code used and ALE formulation that enabled an Eulerian approach to modeling. Hardness is used as the property to estimate because of its relationship to tensile strength and grain size. The input parameters to the random forest model are temperature, cooling rate, strain rate, and RPM. Two welding parameter sets were used to train the model. The method was found to have a high level of accuracy as measured by R^2, but had greater difficulty in predicting the parameter set with higher RPM.

Osteoarthritis (OA) is a debilitating disease affecting roughly 31 million Americans. The incidence of OA is significantly higher for persons who have suffered a transtibial amputation. Abnormal cartilage stress can cause higher OA risk, however it is unknown if there is a connection between exercise type and cartilage stress. To help answer this, a tibiofemoral FEA model was created. Utilizing linear elastic isotropic materials and non-linear springs, the model was validated to experimental cadaveric data. In a previous study, 6 control and 6 amputee subjects underwent gait and cycling experiments. The resultant knee loads were analyzed to find the maximum compressive load and the respective shear forces and rotation moments for each trial, which were then applied to the model. Maximum tibial contact stress values were extracted for both the medial and lateral compartments. Only exercise choice in the lateral compartment was found to be a significant interaction (p<0.0001). No other interactions in either compartment were significant. This suggests that cycling reduces the risk for lateral OA regardless of amputation status and medial OA risk is unaffected. This study also developed a process for creating subject-specific FEA models.

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A parametric study of single-span integral abutment bridge (IAB) was conducted using finite element analysis to explore the effects of various load conditions, bridge geometries, and soil properties. This study investigated the difference between the live load distribution of traditional jointed bridges and integral abutment bridges (IABs) under HL-93 truck component load. The results showed that AASHTO live load distribution factors (LLDFs) were overly conservative by up to 50% to use for IABs. LLDFs for IABs proposed by Dicleli and Erhan (2008) matched well for interior girder moment, but they were unconservative for exterior girder moment by up to 20% for the bridges studied. The study further investigated the effects of various parameters on the IAB responses under dead, live, and thermal loads and load combinations specified by AASHTO. The results of this study are limited to short to moderate single-span straight bridges under dead, live, and thermal loads. Due to a fixity of superstructure and abutments in IABs, the bridge response to each loading is influenced by the relative stiffness of superstructure to substructure. Under combined loads, the amount of each load effect varied depending on superstructure and substructure stiffness, but the critical load combination for each bridge response was determined in this study. Yielding of piles seems unavoidable for IABs built on sand under combined loads even after the change of pile size or pile orientation, but replacing the soil around top 3m (10ft) of piles with softer material is effective to reduce the significant amount of pile moment for IABs built on sand foundation soil. This thesis includes some design recommendations based on the findings of this study.