Comprehensive tests of sintered carbides in the aspect of conical picks operational life

The span of an international tribunal’s local impact is not the same as its operational life, as Germany’s evolved relationship with Nuremberg highlights. Recognizing that the ICTY’s impact in Bosnia and Serbia will continue to evolve after the Tribunal ends its work, this chapter considers the Tribunal’s future impact, focusing in particular on its potential to stimulate a future reckoning with Serbia’s wartime past. While recognizing myriad differences between post-Milošević Serbia and postwar Germany, this chapter explores factors behind the latter’s eventual emergence as a “model penitent” long after German society rejected the moral message the Allies hoped Nuremberg would impart. It suggests that, after an extended period of “transitional denial,” Nuremberg may have contributed to Germany’s far-reaching reckoning with the past through a process of delayed norm diffusion.

Download Full-text

Self-healing materials for space applications: overview of present development and major limitations

CEAS Space Journal ◽

10.1007/s12567-021-00365-5 ◽

2021 ◽

Author(s):

Laura Pernigoni ◽

Ugo Lafont ◽

Antonio Mattia Grande

Keyword(s):

Orbital Debris ◽

Space Environment ◽

Technological Evolution ◽

Self Healing ◽

Space Systems ◽

Space Applications ◽

Structural Fatigue ◽

Operational Life ◽

Technological Limitations ◽

Human Exploration

AbstractIn the last decade, self-healing materials have become extremely appealing for the field of space applications, due to their technological evolution and the consequent possibility of designing space systems and structures able to repair autonomously after damage arising from impacts with micrometeoroids and orbital debris, from accidental contact with sharp objects, from structural fatigue or simply due to material aging. The integration of these novel materials in the design of spacecraft structures would result in increased reliability and safety leading to longer operational life and missions. Such concepts will bring a decisive boost enabling new mission scenario for the establishment of new orbital stations, settlement on the Moon and human exploration of Mars.The proposed review aims at presenting the newest and most promising self-healing materials and associated technologies for space application, along with the issues related to their current technological limitations in combination with the effect of the space environment. An introductory part about the outlooks and challenges of space exploration and the self-healing concept is followed by a brief description of the space environment and its possible effects on the performance of materials. Self-healing materials are then analysed in detail, moving from the general intrinsic and extrinsic categories down to the specific mechanisms.

Download Full-text

Effect of in-service burnout effect on the transonic leakage flows over cavity tip model

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/09576509211012113 ◽

2021 ◽

pp. 095765092110121

Author(s):

Zainab J Saleh ◽

Eldad J Avital ◽

Theodosios Korakianitis

Keyword(s):

Turbine Blades ◽

High Heat ◽

Navier Stokes ◽

Gas Temperature ◽

Flow Measurements ◽

Tip Leakage ◽

Leakage Flows ◽

Operational Life ◽

Flow Interactions ◽

Blade Tip

Increasing the gas temperature at the inlet to the high pressure turbine of gas turbine engines is known as a proven method to increase the efficiency of these engines. However, this will expose the blades’ surface to very high heat load and thermal damages. In the case of the un-shrouded turbine blades, the blade tip will be exposed to a significant thermal load due to the developed leakage flows in the tip gap, this leads to in-service burnout which degrades the blade tip and shortens its operational life. This paper studies the in-service burnout effect of the transonic tip flows over a cavity tip which is a configuration commonly used to reduce the tip leakage flows. This investigation is carried out experimentally within a transonic wind tunnel and computationally using steady and unsteady Reynolds Averaged Navier Stokes approaches. Various flow measurements are established and different flow behaviour including separation bubbles, shockwave development and distinct flow interactions are captured and discussed. It is found that when the tip is exposed to the in-service burnout, leakage flow behaves in a significantly different way. In addition, the effective tip gap becomes much larger and allows higher leakage mass flow rate in comparison to the sharp-edge tip (i.e. a tip at the beginning of its operational life). The tip leakage losses are found much higher for the round-edge cavity tip (i.e. a tip exposed to burn-out effect). Experimental and computational flow visualisations, surface pressure measurements and discharge coefficient variation are given and analysed for several pressure ratios across the tip gap.

Download Full-text

Structural Damage Identification of Composite Rotors Based on Fully Connected Neural Networks and Convolutional Neural Networks

Sensors ◽

10.3390/s21062005 ◽

2021 ◽

Vol 21 (6) ◽

pp. 2005

Author(s):

Veronika Scholz ◽

Peter Winkler ◽

Andreas Hornig ◽

Maik Gude ◽

Angelos Filippatos

Keyword(s):

Neural Networks ◽

Convolutional Neural Networks ◽

Composite Structures ◽

Damage Identification ◽

Vibration Response ◽

Damage Initiation ◽

Matrix Cracks ◽

Operational Life ◽

Multiple Data Sets ◽

Fully Connected

Damage identification of composite structures is a major ongoing challenge for a secure operational life-cycle due to the complex, gradual damage behaviour of composite materials. Especially for composite rotors in aero-engines and wind-turbines, a cost-intensive maintenance service has to be performed in order to avoid critical failure. A major advantage of composite structures is that they are able to safely operate after damage initiation and under ongoing damage propagation. Therefore, a robust, efficient diagnostic damage identification method would allow monitoring the damage process with intervention occurring only when necessary. This study investigates the structural vibration response of composite rotors by applying machine learning methods and the ability to identify, localise and quantify the present damage. To this end, multiple fully connected neural networks and convolutional neural networks were trained on vibration response spectra from damaged composite rotors with barely visible damage, mostly matrix cracks and local delaminations using dimensionality reduction and data augmentation. A databank containing 720 simulated test cases with different damage states is used as a basis for the generation of multiple data sets. The trained models are tested using k-fold cross validation and they are evaluated based on the sensitivity, specificity and accuracy. Convolutional neural networks perform slightly better providing a performance accuracy of up to 99.3% for the damage localisation and quantification.

Download Full-text

Deployment requirements for deorbiting electrodynamic tether technology

CEAS Space Journal ◽

10.1007/s12567-021-00349-5 ◽

2021 ◽

Cited By ~ 1

Author(s):

Giulia Sarego ◽

Lorenzo Olivieri ◽

Andrea Valmorbida ◽

Alice Brunello ◽

Enrico C. Lorenzini ◽

...

Keyword(s):

Lorentz Force ◽

Electrodynamic Tether ◽

Operational Life ◽

Electrodynamic Tethers

AbstractIn the last decades, green deorbiting technologies have begun to be investigated and have raised a great interest in the space community. Among the others, electrodynamic tethers appear to be a promising option. By interacting with the surrounding ionosphere, electrodynamic tethers generate a drag Lorentz force to decrease the orbit altitude of the satellite, causing its re-entry in the atmosphere without using propellant. In this work, the requirements that drive the design of the deployment mechanism proposed for the H2020 Project E.T.PACK—Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit—are presented and discussed. Additionally, this work presents the synthesis of the reference profiles used by the motor of the deployer to make the tethered system reach the desired final conditions. The result is a strategy for deploying electrodynamic tape-shaped tethers used for deorbiting satellites at the end of their operational life.

Download Full-text

Mechanisms of High Efficiency and Stabilization of Baffled Constructed Wetland in Treatment of Domestic Sewage

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.1057 ◽

2013 ◽

Vol 295-298 ◽

pp. 1057-1061 ◽

Cited By ~ 1

Author(s):

Chang Bing Ye ◽

Zhi Ming Zhou ◽

Ke Zhao ◽

Qin Liu

Keyword(s):

Constructed Wetland ◽

Removal Rate ◽

Short Circuit ◽

Domestic Sewage ◽

Wetland Plants ◽

Stable Operation ◽

Removal Rates ◽

Operational Life ◽

High Efficient ◽

Hydraulic Load

To solve the problem of short-circuit of individual current constructed wetland, a baffled constructed wetland was designed and applied to treat domestic sewage by our research group. The wetland plants were composed of Eichhormia crassipes, Oenanthe javanica, Cyperusalternifolius, Phragmites communis and Aquatic. The results of 18 month indicated that the optimal hydraulic load of baffled constructed wetland was 2.0~2.2 m3/(m2•d). At the hydraulic load of 2.0m3/(m2•d), the COD, TN and TP removal rates of baffled constructed wetland could be over 76.40%, 76.12%, 65.37%, respectively, at 24°C. When the temperature decreased to 12°C, the COD, TN, TP removal rates of system decreased to 67.56%、62.75% and 61.33%, respectively; The SS removal rate of the first 6 compartments was about 79.5% and that of system could maintain 87.18% during the operation of system. Based on the results of trial, the mechanisms of extending the baffled constructed wetland's operational life was owed to high efficient SS removal rate of the first 6 compartments which was used as constructed wetland and anaerobic baffled reactor (ABR). As a result, the long-term stable operation of system in treatment of domestic sewage was explained with extending about 5 times service life than that of individual current constructed wetland. The mechanisms of higher efficiency of baffled constructed wetland in treatment of domestic sewage were owed to the longer flow line of system and the up-down flow of domestic sewage makes pollutant more intimate contact with roots of wetland plants.

Download Full-text

Reclamation of National Energy Board Regulated Pipeline Rights of Way: A Life Cycle Approach

4th International Pipeline Conference, Parts A and B ◽

10.1115/ipc2002-27305 ◽

2002 ◽

Author(s):

Kent Lien

Keyword(s):

Life Cycle ◽

Environmental Assessment ◽

Life Cycle Approach ◽

Application Process ◽

Operational Life ◽

Construction Operation

As part of its mandate, the National Energy Board (NEB) regulates the construction, operation, and abandonment of interprovincial and international pipelines. The primary legislation which directly and indirectly addresses reclamation of NEB lines are the National Energy Board Act and the associated Onshore Pipeline Regulations, 1999, and the Canadian Environmental Assessment Act. The NEB uses a life cycle approach to pursue appropriate reclamation of disturbed rights of way. Initially, reclamation related issues are addressed at the application stage. Subsequent to the application process, the actual implementation of reclamation measures occurs during construction of the line. Success of reclamation is monitored during the operational life of a line through inspection and auditing procedures, with additional measures being implemented as necessary.

Download Full-text