京都大学 / 新制・課程博士 / 博士(工学) / 甲第23478号 / 工博第4890号 / 新制||工||1764(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 川池 健司, 教授 藤田 正治, 准教授 米山 望 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In urban areas with limited space, deep borehole heat exchangers (DBHE) are coupled with ground source heat pump systems (GSHPS) to extract geothermal energy for building heating purposes. They can exploit more heat than common shallow systems. In this thesis, the open source software OpenGeoSys (OGS) has been utilized to analyse the long-term behavior and temperature evolution in and around single and multiple DBHEs. Moreover, an analysis to reduce the computation time has been applied. This way, the simulation time could be shortened by almost 75% by adjusting the tolerance of the non-linear solver and using an automatic time stepping in a first step. With larger element sizes, which still provide a sufficient result precision, the required duration could be shortened to less than 2% compared to the first method. Especially between the top and the bottom a layer size of 100 m is sufficient. The thickness around the top and bottom, however, should be small to avoid numerical inaccuracies. In the first years of operation most of the energy is extracted by the lower parts of the DBHE. Throughout the years, the contribution along the depth becomes more homogeneous and more soil is influenced. In summer, the top approximately 900 m are not contributing to the heat extraction but instead losing heat to the soil because of a low energy demand, which leads to high inflow temperatures. Considering the results of the in- and outflow temperature evolution, a single DBHE should be preferred over multiple systems. Nonetheless, those can multiply the extractable heat in a certain area and could be more economical.:List of Figures . . . v List of Tables . . . vii 1 Introduction . . . 1 2 Theoretical Background . . . 4 2.1 BHE equations . . . 5 2.2 Thermal Resistance . . . 6 2.3 Exchange Area . . . 10 2.4 Coefficient of Performance . . . 10 2.5 OpenGeoSys Pipe Network Feature . . . 12 3 Modeling Scenarios . . . 14 3.1 Model Setups . . . 15 3.2 Model Verification . . . 16 3.3 Model Environment . . . 20 3.4 Initial and Boundary Conditions . . . 22 3.5 Investigation on Computation Time Influences . . . 24 4 Results and Discussion . . . 30 4.1 In- and Outflow Temperature Evolution . . . 30 4.2 Energy Distribution . . . 34 4.3 Soil Heat Flux . . . 40 4.3.1 Winter in 2nd year . . . 41 4.3.2 Summer in 2nd year . . . 44 4.3.3 Winter in 30th year . . . 47 4.3.4 Summer in 30th year . . . 49 4.4 DBHE Heat Flux . . . 51 4.5 Soil Heat Flux in the Multiple DBHE Case . . . 55 4.5.1 Line Setup . . . 56 4.5.2 Square Setup . . . 61 4.6 Numerical Inaccuracies . . . 65 5 Conclusion . . . 68

The diploma thesis deals with the possibilities of using numerical simulation in investment casting technology. The first chapter of practical part deals with the use of simulations in the design of gating system for the shape-complex casting. At the same time, the practical part verified the accuracy of the simulation by test castings on which the X- ray inspection was performed. The results showed that the occurrence of internal defects predicted by simulation corresponded to the locations in the test casts. Next part of the thesis describes improvement of the use of liquid metal (so called “yield”) by numerical simulations. Two specific castings were chosen to perform simulation of current and newly designed variant of the gating system.

The aim of this thesis was to assess the degree of conformity between the mechanical properties evaluated by numerical simulation in software MAGMA5 and the measured values of hardness and ultimate tensile strength of lamellar graphite iron castings. The theoretical part of this thesis deals with the classification of cast iron, structural components of lamellar graphite iron, and the factors defining the resulting mechanical properties of the material. The practical part presents an attempt to find empirical dependencies between input parameters and results evaluated by simulation software. At the end, an analysis of the correlation between reality and simulation software is performed.

The project deals with analysis and optimization of the geometry of the stamped part produced by the pillow hydroforming. The blank consists of two sheets of steel DC01, which is welded by laser beam. The forming process can cause excessive thinning and cracking of the part. By evaluation of mechanical tests is created material model, which is the basis for numerical simulation created in software PAM-STAMP. The outputs are analysis which provide information about critical points, failure pressure, limiting deformations and prediction of springback. Validity of the numerical simulation is verified by comparison with the experimentally obtained data. The comparative criterions are the failure pressure and the material thickness at various locations. Based on the results of the numerical simulation, the optimization of the geometry is created. The optimization uses different values of radius at the crack point.

The diploma thesis deals with the optimization of final position of overlaps on a forged cam. This part is manufactured in Šroubárna Kyjov, spol. s r.o. The cam is made from ČSN 14 109 (100Cr6) steel. The thesis is focused on the optimization of overlaps arising due to pressed burrs on the edges of the semifinished forging. Currently, the final position of these overlaps is very close to the edge of the pre-forged hole of the cam. Undesired chipping of material occurs during machining of the hole to the exact dimension. The final position of the overlaps is optimized by using the numerical simulation in Simufact Forming 15.0, including a verification simulation for optimal parameter settings. Various diameters of semifinished products, turned tools, and modification of shapes of the tools are tested in the thesis to prevent occurrence of the overlaps in undesired positions.

The aim of this work is to assess the possibilities of using numerical simulation tools in the process of laser welding of the guide rail of a car seat. In the diploma thesis, a description of the components and the problem, which consists in the deformation of the groove of the guide rail, was made. A description was made of the manufacturing operations that the components go through. The positives of selected welding methods were evaluated and the choice of those used in production was justified. A description of the issues of laser welding, deformation and the use of simulation tools was made. The influence of individual production operations was evaluated in terms of the size and nature of deformations. Using the Visual – Mesh, Visual – Weld and Visual – Assembly simulation tools, which are products of the French company ESI Group, the same state of the simulated and real process was achieved. Subsequently, a proposal for the elimination of deformations and its verification using a simulation tool could be approached. The use of a spacer wedge, which acts on the most deformed places of the groove, was proposed. By its application, the resulting deformations were eliminated or significantly reduced. In the last part of the work, a technical and economic evaluation was made, taking into account the current global crisis and the important role of the automotive industry.

The thesis presents an analysis and optimization of the manufacturing process of a part using the technology of parallel hydroforming. Two circular blanks made of DC01 steel with a thickness of 1 mm serve as a semi-manufactured part. In one of the blanks, the supply of the forming medium is constructed using Flowdrill technology. Subsequently, the two blanks are laser welded together and then formed. Numerical simulation using PAM-STAMP software was used to analyse the manufacturing process. This analysis provided information on wall thinning, deformation size, critical points on the product and springback. The numerical simulation was verified on the basis of comparison with an experiment. The criterion for verification was the course of the thickness of the part. Based on the results of the simulation, an optimization is performed in the thesis. It consists in determining the minimum required pressure of the forming medium for pressing the part, particularly for different distances between the two formed sheets.

One of the decisive factors of effective using of forward extrusion technology is lifetime of forming tools. Die is very loaded forming tool which loading and therewith related lifetime can be significantly affected by its construction. Construction also affected quality of extruded material. Finete element method allows to simulate this process and assess force which is needed to extrusion and state of stress in die and extruded material. Numerical simulation was realized in program ANSYS 11.0. Influence of reduction, angle of reduction, lenght of extruded material, rounding transition of die parts, extruded material and friction coefficient on die loading and emergence of cracks in extruded material was set in this diploma thesis. Results can be used to die construction optimalization.

This Master’s thesis deals with the influence of process parameters in forward extrusion on the initiation of chevron cracks in material by numerical simulation. Solution was executed by ANSYS 11 and the influence of fiction, angle of reduction, reduction and numbers of extrusion operations was solved for the 12 050.3 steel by the chosen conditions.