Effect of temperature on the performance of a giant magnetostrictive ultrasonic transducer

The effect of temperature on the performance of a giant magnetostrictive ultrasonic transducer (GMUT) was investigated by measuring variations in the resonance frequency and mechanical quality factor of the GMUT at different temperatures. The equivalent circuit model of the GMUT was presented and the total electrical impedance equation was obtained. Curves of the impedance circle were obtained at different temperatures to determine the resonance frequency and mechanical quality factor. To verify the impedance-based results and obtain precise values of the resonance frequency and effective frequency bandwidth, the amplitude-frequency response within the same temperature range was examined experimentally. These results were consistent with those of the impedance analysis, which demonstrates the validity of the equivalent circuit model. Moreover, the resonance frequency and effective bandwidth of the GMUT were found to decrease with increasing temperature, which means that the vibration amplitude is more sensitive to variation in the resonance frequency at high temperature owing, for example, to static or dynamic system loading, changes in the material properties, or drive-signal variability. Accordingly, the temperature in the GMUT should be precisely controlled to improve the stability of vibration

Enhancing safety and efficiency in automated container terminals: Route planning for hazardous material AGV using LSTM neural network and Deep Q-Network

As the proliferation and development of automated container terminal continue, the issues of efficiency and safety become increasingly significant. The container yard is one of the most crucial cargo distribution centers in a terminal. Automated Guided Vehicles (AGVs) that carry materials of varying hazard levels through these yards without compromising on the safe transportation of hazardous materials, while also maximizing efficiency, is a complex challenge. This research introduces an algorithm that integrates Long Short-Term Memory (LSTM) neural network with reinforcement learning techniques, specifically Deep Q-Network (DQN), for routing an AGV carrying hazardous materials within a container yard. The objective is to ensure that the AGV carrying hazardous materials efficiently reaches its destination while effectively avoiding AGVs carrying non-hazardous materials. Utilizing real data from the Meishan Port in Ningbo, Zhejiang, China, the actual yard is first abstracted into an undirected graph. Since LSTM neural network can efficiently conveys and represents information in long time sequences and do not causes useful information before long time to be ignored, a two-layer LSTM neural network with 64 neurons per layer was constructed for predicting the motion trajectory of AGVs carrying non-hazardous materials, which are incorporated into the map as background AGVs. Subsequently, DQN is employed to plan the route for an AGV transporting hazardous materials, aiming to reach its destination swiftly while avoiding encounters with other AGVs. Experimental tests have shown that the route planning algorithm proposed in this study improves the level of avoidance of hazardous material AGV in relation to non-hazardous material AGVs. Compared to the method where hazardous material AGV follow the shortest path to their destination, the avoidance efficiency was enhanced by 3.11%. This improvement demonstrates potential strategies for balancing efficiency and safety in automated terminals. Additionally, it provides insights for designing avoidance schemes for autonomous driving AGVs, offering solutions for complex operational environments where safety and efficient navigation are paramount

Rotary ultrasonic machining of optical K9 glass using compressed air as coolant: a feasibility study

Optical K9 glass has been used in a variety of applications, including optics, electronics, thermodynamics, and fluidics. It has been regarded as a difficult-to-cut material because of its superior mechanical properties. Rotary ultrasonic machining (RUM) using cutting fluid has been used successfully to machine many different types of brittle materials, such as ceramics, sapphire, and optical K9 glass. Dry machining has been successfully employed in the machining of some materials. However, there are no reported investigations on the RUM of optical K9 glass using compressed air as a coolant. This paper, for the first time, investigates the RUM of optical K9 glass using compressed air as a coolant. The experimental investigations focus on the effects of the input variables (ultrasonic power, spindle speed, and feedrate) on the output variables (edge chipping size, cutting force, surface roughness, and ultrasonic power consumption)

Computation Model of Clamping Force for Jaw-Chucks

In dieser Arbeit wird ein analytisches Berechnungsmodell zur Ermittlung von Spannkräften bei Backenfuttern in Abhängigkeit von den Prozesskräften entwickelt. Bisherige bestehende Ansätze zur Ermittlung der erforderlichen Spannkraft führen aufgrund ihrer unzureichenden Modellbildung zu fehlerhaften und sehr unterschiedlichen und damit ungenauen Berechnungsergebnissen. Die Berechnung der optimalen Spannkraft ermöglicht neben der Erhöhung der Bearbeitungsgenauigkeit und der Prozesssicherheit, die Effektivität der Drehbearbeitung mit Backenfuttern, insbesondere mit modernen Spannsystemen für hohe Drehzahlen, zu erhöhen. Die notwendige Ausgangsspannkraft bei Außenspannung wird durch die zur Aufnahme der am Werkstück auftretenden Prozesskräfte erforderliche Mindestspannkraft und den dynamischen Spannkraftverlust infolge der Fliehkräfte beschrieben. Als Grundlage wird das Steifigkeitsverhalten von Spannmitteln mit Hilfe von experimentellen Untersuchungen und FEM-Analysen ermittelt. In dem Teilmodel zur Bestimmung des Spannkraftverlustes wird der Einfluss der Werkstück-, Spannfutter- und Spannbackensteifigkeit berücksichtigt. Die Fliehkräfte von verschiedenen Elementen haben unterschiedliche Auswirkungen auf den Spannkraftverlust, die durch verschiedene Kippeinflussfaktoren berücksichtigt werden. Zur Ermittlung der übertragbaren Kippmomente wird die Spannkraftverteilung in den Spannflächen mit Hilfe von FEM-Analysen untersucht und der Begriff der differentiellen Werkstücksteifigkeit eingeführt. Bei der Berechnung der erforderlichen Mindestspannkraft werden alle Belastungen der Werkstückspannung gleichzeitig berücksichtigt. Die Genauigkeit des neu entwickelten Spannkraftberechnungsmodells übersteigt die der bisherigen Berechnungsansätze deutlich. Das Modell besitzt sowohl für herkömmliche Spannfutter als auch für Spannfutter neuer Bauart, wie Keilflächenfutter mit Fliehkraftausgleich oder mit Backenschnellwechselsystem, Gültigkeit. Diese und der Grad der Genauigkeit des Berechnungsmodells werden anhand von experimentellen Untersuchungen und FEM-Analysen validiert. Die gewonnenen Erkenntnisse bilden die Grundlage zur Erstellung einer neuen VDI-Richtlinie, die bei der Ermittlung der zulässigen Drehzahl oder der notwendigen Ausgangsspannkraft von Backenfuttern in der Arbeitsvorbereitung Anwendung finden kann.In this thesis a comprehensive and optimized analytic computation model will be developed for the determination of clamping forces for jaw-chucks in dependence of process forces. Due to the inaccuracy of existing models the calculated required clamping forces are characterized by a significant deviation. The computation of optimized clamping forces enables the utilization of the potential of jaw-chucks for higher rotational speeds in order to increase the effectiveness of turning operations. Furthermore, the safety of process within of high speed turning as well as the machining accuracy are increased. The required initial clamping force for external clamping is determined by the required minimum clamping force for absorption of cutting forces, and the dynamic loss of clamping force due to the rotation of the used chuck. As basis for this model the stiffness behaviour of jaw-chucks is studied by means of experimental investigations and FEM analyses. In the sub model for the dynamic loss of clamping force the influence of the stiffnesses of the workpiece, chuck and top jaw on the dynamic clamping force is considered. The centrifugal forces of top jaws, base jaws, chuck body/piston and counterweights have different effects on the loss of clamping force, which are represented by different tilting-influence-factors. For the computation of the transmittable bending moment the distribution of pressure on the clamping surfaces is investigated by means of FEM analyses whereby the differential workpiece stiffness is defined as a new parameter. All loads of workpiece clamping like turning moment, bending moment, axial force and radial force are considered simultaneous while computing the required minimum clamping force. The accuracy of the new developed computation model of clamping force exceeds significant the accuracy of the existing models. This model is valid not only for conventional chucks but also for modern chucks, such as power operated wedge hook chuck with compensation of centrifugal force or with quick jaw change system. The validity and the accuracy of the new computation model are verified by means of numerous experimental investigations and FEM-computations. The obtained results in this thesis build the basis for the development of a new VDI-guideline, which can be applied to determine the allowed rotational speed or the required initial clamping force of jaw-chucks in manufacturing set up