DSpace community: 機械工程研究所

Three-Dimensional Numerical Analysis of Thermal Field and Thermal Stress in β-????2??3 Crystal Growth Using the EFG Method

Fri, 06 Mar 2026 11:29:34 GMT

title: Three-Dimensional Numerical Analysis of Thermal Field and Thermal Stress in β-????2??3 Crystal Growth Using the EFG Method abstract: 在本論文中，建立了一個三維數值模型，用以分析採用邊界限定薄膜供料生長法（Edge-Defined Film-Fed Growth，EFG）生長 β-Ga?O? 晶體過程中的溫度場與熱誘發應力. 該模型是在穩態條件下建立, 並考慮了晶體沿 [010] 生長方向的各向異性熱導率, 同時假設結晶界面為平面. 透過電磁模擬獲得 EFG 系統內部的熱源分佈, 從而研究電磁加熱、溫度場以及晶體內熱應力形成之間的關係. 模擬結果顯示, 熱量主要在坩堝壁處產生, 並透過熱傳導與輻射傳遞至熔體與晶體, 進而形成軸向與徑向溫度梯度. 這些溫度梯度是熱應力產生的主要原因, 其中等效 von Mises 應力主要集中於靠近生長界面的晶體邊緣區域. 結果亦表明, 內部輻射對晶體內部的溫度分佈具有顯著影響, 而熔體流場對生長界面處的熱條件則未產生明顯影響. 此外, 本研究探討了在坩堝上方設置防護遮罩以改善熱傳條件並降低熱應力的效果. 結果顯示. 安裝遮罩可提高晶種區域的溫度, 減小軸向溫度梯度, 從而顯著降低熱應力. 進一步分析了晶體在生長過程中長度變化的影響, 結果顯示, 隨著晶體逐漸伸出高溫區, 溫度梯度與熱應力均呈現增加的趨勢. 總體而言, 本研究闡明了 EFG 法生長 β-Ga?O? 晶體過程中熱應力形成的機制, 並為優化系統設計與操作條件、降低熱應力及提升晶體品質提供了科學依據. ;In this thesis, a three-dimensional numerical model is developed to analyze the thermal field and thermally induced stress during the growth of β-Ga?O? crystals using the Edge-Defined Film-Fed Growth (EFG) method. The model is established under steady-state conditions and takes into account the anisotropic thermal conductivity of the crystal along the [010] growth direction, while the crystallization interface is assumed to be planar. The heat source distribution within the EFG system is obtained through electromagnetic simulations, allowing the relationship between electromagnetic heating, the thermal field, and thermal stress formation in the crystal to be examined. The simulation results show that heat is mainly generated at the crucible walls and transferred to the melt and the crystal through conduction and radiation, resulting in axial and radial temperature gradients. These temperature gradients are the primary cause of thermal stress, with the von Mises equivalent stress mainly concentrated near the crystal edges close to the growth interface. The results also indicate that internal radiation has a significant influence on the temperature distribution within the crystal, whereas the melt flow field has no noticeable effect on the thermal conditions at the growth interface. In addition, the effect of a protective shield placed above the crucible is investigated to improve heat transfer conditions and reduce thermal stress. The results demonstrate that the installation of the shield increases the temperature in the seed region, reduces the axial temperature gradient, and consequently leads to a significant reduction in thermal stress. Furthermore, the influence of crystal length during the growth process is examined, showing that as the crystal extends out of the hot zone, both temperature gradients and thermal stress tend to increase. Overall, this study provides insight into the mechanisms of thermal stress formation in β-Ga?O? crystals grown by the EFG method and offers a scientific basis for optimizing system design and operating conditions to reduce thermal stress and improve crystal quality.

應用實例分割與點雲配準於平面放置物件之機械手臂分揀系統開發;Development of a Robotic Arm Sorting System for Planar-Placed Objects by Applying Instance Segmentation and Point Cloud Registration

Fri, 06 Mar 2026 11:08:54 GMT

title: 應用實例分割與點雲配準於平面放置物件之機械手臂分揀系統開發;Development of a Robotic Arm Sorting System for Planar-Placed Objects by Applying Instance Segmentation and Point Cloud Registration abstract: 本研究針對醫療器械經清洗消毒後之回收處理流程，開發一套自動化分揀系統，旨在改善傳統人工作業仰賴人力判讀、易疲勞且效率受限之問題。在系統架構方面，硬體採用TM5-900協作型手臂搭配Ensenso N35立體相機，建立眼在手架構；針對扁平且金屬表面易滑動之器械特性，設計整合V型結構指夾與真空吸嘴的複合式末端執行器。軟體基於ROS2平台，整合YOLOv11實例分割與FastAPI後端介面，建構模組化的自動化控制系統。在技術方法上，提出「由粗至細」的配準策略。首先利用YOLOv11識別類別並生成遮罩以擷取目標點雲，接著利用FPFH(Fast Point Feature Histograms)特徵結合RANSAC(Random Sample Consensus)進行粗配準，最後透過點對平面ICP(Iterative Closest Point)演算法進行精細姿態修正，以計算器械在空間中的三維坐標。實驗結果顯示，針對高反光金屬器械，本系統之點雲配準平均適配度為0.969，均方根誤差控制在1.894 mm內。在隨機分類揀放實驗中，總共20個物件平均成功率為96.62%，平均處理耗時13.73秒。研究結果證實，本系統在定位準確度與作業效率上，已具備應用於醫療後勤自動化流程之可行性。 ;This study develops an automated pick-and-place system for the recycling process of medical instruments after cleaning and sterilization, aiming to address the efficiency limitations and fatigue issues associated with traditional manual sorting. Regarding the system architecture, the hardware integrates a TM5-900 collaborative robot with an Ensenso N35 stereo camera in an Eye-in-Hand configuration. A hybrid end-effector combining a V-shaped gripper and a vacuum nozzle was designed to handle flat instruments with slippery metal surfaces. The software is built on the ROS2 platform, integrating YOLOv11 instance segmentation and a FastAPI backend to establish a modular automated control system. For the technical methodology, a "Coarse-to-Fine" registration strategy is proposed. First, YOLOv11 is used to identify classes and generate masks to extract target point clouds. Then, FPFH(Fast Point Feature Histograms) features combined with RANSAC(Random Sample Consensus) are employed for coarse registration, followed by the Point-to-Plane ICP(Iterative Closest Point) algorithm for fine pose correction to calculate the 3D coordinates of the instruments. Experimental results indicate that for highly reflective metal instruments, the system achieved an average point cloud registration fitness of 0.969, with a Root Mean Square Error (RMSE) maintained within 1.894 mm. In random sorting and pick-and-place experiments involving 20 objects, the average success rate was 96.62%, with an average processing time of 13.73 seconds. These findings confirm that the system possesses the necessary positioning accuracy and operational efficiency for feasible application in automated medical logistics processes.

階梯型式微流道蒸發冷板流動沸騰性能研究

Fri, 06 Mar 2026 11:08:33 GMT

title: 階梯型式微流道蒸發冷板流動沸騰性能研究 abstract: 為了解決兩相蒸發冷卻技術應用於高發熱量電子元件散熱時所面臨的流動不穩定問題，並替代常用且具有高全球暖化潛勢（GWP = 1030）的冷媒 HFC-245fa，本研究提出了以階梯型式流道設計來改善微流道蒸發器之性能，並選用FMD-50為替代工作流體，其GWP值為7。相較於直線型流道，階梯型流道可有效降低冷板的壓降。其原因在於，當相同流量進入熱交換器時，流體於下游區域不再受限於狹窄的微流道空間，流道長度亦相對縮短，使流體不易受到幾何限制而產生過大的流動阻力，進而降低整體壓降。反觀直線型流道，由於流體受到流道幾何限制，導致其壓降相對較高。在階梯流道中，固定流道寬度為0.15mm，流道數量為80，並透過將鰭片高度為了解決兩相蒸發冷卻技術應用於高發熱量電子元件散熱時所面臨的流動不穩定問題，並替代常用且具有高全球暖化潛勢（GWP = 1030）的冷媒 HFC-245fa，本研究提出了以階梯型式流道設計來改善微流道蒸發器之性能，並選用FMD-50為替代工作流體，其GWP值為7。相較於直線型流道，階梯型流道可有效降低冷板的壓降。其原因在於，當相同流量進入熱交換器時，流體於下游區域不再受限於狹窄的微流道空間，流道長度亦相對縮短，使流體不易受到幾何限制而產生過大的流動阻力，進而降低整體壓降。反觀直線型流道，由於流體受到流道幾何限制，導致其壓降相對較高。在階梯流道中，固定流道寬度為0.15mm，流道數量為80，並透過將鰭片高度由3mm降低至1mm，以探討其對流動與熱傳特性的影響。以階梯型式流道來改善直線流道，在HFC-245fa中，可以將低13% 至68% 之壓降，然而其熱傳係數亦同時降低約 17% 至 20% 。在FMD-50中，無論階梯流道或是直線流道，其熱傳性能彼此間差異不大，但在壓降方面，只有在低流量中，直線流道之壓降高於階梯流道10% 至 70%，但在中、高流量中，兩者間的壓降差異不大。由3mm降低至1mm，以探討其對流動與熱傳特性的影響。以階梯型式流道來改善直線流道，在HFC-245fa中，可以將低13% 至68% 之壓降，然而其熱傳係數亦同時降低約 17% 至 20% 。在FMD-50中，無論階梯流道或是直線流道，其熱傳性能彼此間差異不大，但在壓降方面，只有在低流量中，直線流道之壓降高於階梯流道10% 至 70%，但在中、高流量中，兩者間的壓降差異不大。 ;To address the flow instability encountered in two-phase evaporative cooling applied to the thermal management of high–heat-flux electronic components, and to replace the commonly used refrigerant HFC-245fa with a high global warming potential (GWP = 1030), this study proposes a stepped-channel design to enhance the performance of microchannel evaporators and adopts FMD-50 as an alternative working fluid, with a global warming potential (GWP) value of 7. Compared with straight channels, the stepped-channel design effectively reduces the pressure drop of the cold plate. This improvement is attributed to the fact that, under the same inlet flow rate, the downstream region is no longer constrained by narrow microchannel geometry and the effective flow length is shortened. Consequently, the flow resistance induced by geometric confinement is alleviated, leading to a lower overall pressure drop. In contrast, straight channels impose continuous geometric constraints along the flow path, resulting in a relatively higher pressure drop. In the stepped-channel configuration, the channel width is fixed at 0.15 mm with a total of 80 channels, and the fin height is reduced from 3 mm to 1 mm to investigate its effects on flow and heat transfer characteristics.When HFC-245fa is used as the working fluid, the stepped-channel design reduces the pressure drop by approximately 13% to 68% compared with the straight-channel design; however, the heat transfer coefficient is simultaneously reduced by about 17% to 20%. For FMD-50, the heat transfer performance of the stepped and straight channels shows no significant difference. In terms of pressure drop, the straight-channel design exhibits a 10% to 70% higher pressure drop than the stepped-channel design under low flow rate conditions, whereas at medium and high flow rates, the pressure drop difference between the two configurations becomes negligible.

渦卷式壓縮機轉子之精密電化學加工製程研究;Research on Precision Electrochemical Machining Process of Scroll Compressor Rotor

Fri, 06 Mar 2026 11:08:15 GMT

title: 渦卷式壓縮機轉子之精密電化學加工製程研究;Research on Precision Electrochemical Machining Process of Scroll Compressor Rotor abstract: 本研究提出以精密電化學加工(Precision Electrochemical Machining, PECM)取代傳統CNC加工製造渦卷式壓縮機轉子，並建立完整之製程規劃。依轉子幾何外形與極間間隙設計工具電極，並採絕緣覆層消除加工時之雜散電流。為確保電解液於微小加工間隙中均勻更新，電極內部設置流道並施加低頻微振動，以加速反應產物排除、抑制氧化膜生成及避免短路。其次利用電腦模擬流場軟體Autodesk CFD 2024，對建立的多個動、靜渦卷加工流場模型進行分析以及調整電解液流場。本研究建立之流程與參數對於渦卷轉子製造提供可重複複製性，並可延伸應用至其他複雜曲面零件，如離心渦輪、燃油泵葉輪等。電化學加工方面，本研究探討了不同入口壓力以及進給速度對動渦卷及靜渦卷之齒型偏差量、壁面傾斜度與表面粗糙度。在動渦卷部分，以入口壓力8 bar、進給速度0.15 mm/min下，加工時間為92分鐘，齒型偏差量-0.255 mm ~ 0.352 mm，壁面傾斜度0.008° ~ 0.458°，側壁表面粗糙度Sa 0.217 μm。靜渦卷以入口壓力6 bar、進給速度0.1 mm/min，加工時間為138分鐘，齒型偏差量為 -0.034 mm ~ 0.684 mm，壁面傾斜度0.016°~0.262°，側壁表面粗糙度Sa 0.168 μm。 ;This study proposes replacing conventional CNC machining with Precision Electrochemical Machining (PECM) to manufacture scroll compressor rotors, and establishes a complete process plan. Based on the rotor geometry and the designed interelectrode gap, a dedicated tool electrode was developed, and an insulating coating was applied to eliminate stray currents during machining. To ensure uniform electrolyte renewal within the micro-scale machining gap, internal flow channels were integrated into the electrode and low-frequency micro-vibration was introduced to accelerate removal of reaction products, suppress oxide-film formation, and prevent short-circuiting. In addition, Autodesk CFD 2024 was used to analyze multiple flow-field models for machining both the orbiting and fixed scrolls, and to iteratively optimize the electrolyte flow distribution. The developed workflow and process parameters provide a repeatable and reproducible manufacturing route for scroll rotors, and can be extended to other complex freeform components such as centrifugal turbines and fuel-pump impellers. From the PECM experiments, this study investigated the effects of inlet pressure and feed rate on profile deviation, wall inclination, and surface roughness for both orbiting and fixed scrolls. For the orbiting scroll, under an inlet pressure of 8 bar and a feed rate of 0.15 mm/min, the machining time was 92 min; the profile deviation ranged from −0.255 mm to 0.352 mm, the wall inclination ranged from 0.008° to 0.458°, and the wall surface roughness is Sa 0.217 μm. For the fixed scroll, under an inlet pressure of 6 bar and a feed rate of 0.10 mm/min, the machining time was 138 min; the profile deviation ranged from −0.034 mm to 0.684 mm, the wall inclination ranged from 0.016° to 0.262°, and the wall surface roughness is Sa 0.168 μm.