@article{SommerPfennigSammleretal., author = {Sommer, Konstantin and Pfennig, Anja and Sammler, Fiona and Abdelmoula, Mahmoud and Kamerer, Denis and Heiler, Roland}, title = {First Approach in Analysis of Tool Wear When Milling Additive Manufacturing (AM) Parts}, series = {Applied Sciences}, volume = {14}, journal = {Applied Sciences}, number = {14}, editor = {De Jesus, Ab{\´i}lio M. P.}, publisher = {MDPI}, issn = {2076-3417}, doi = {10.3390/app14146219}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-18866}, abstract = {Wire arc additive manufacturing (WAAM) and laser-based powder bed fusion (L-PBF) are additive manufacturing (AM) processes that allow the manufacturing of complex part geometries. The manufacturing of AM parts does not result in high-quality functional surfaces; therefore, postprocessing such as milling is usually required. For L-PBF parts, the support structures and, for WAAM parts, the undulating surface are usually removed after AM processes. These two application-related cases are investigated in this work, with the conclusion that support structure milling and the milling of the surface of WAAM parts lead to the dimensionally increased wear of milling tools in comparison to milling of solid material.}, subject = {Additive Manufacturing}, language = {en} } @article{NollerPfennigDahlmeyer, author = {Noller, Sebastian F. and Pfennig, Anja and Dahlmeyer, Matthias}, title = {Introduction of the Experimental Setup for the Investigation of the Novel Selective Melt Dispersion (SMD): A Directed Energy Deposition (DED) Process}, series = {Clean Technologies}, volume = {6}, journal = {Clean Technologies}, number = {2}, editor = {Luis Alconero, Patricia}, publisher = {MDPI}, issn = {2571-8797}, doi = {10.3390/cleantechnol6020030}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-18474}, pages = {572 -- 585}, abstract = {This study focuses on developing an experimental setup to investigate the Selective Melt Dispersion (SMD), a Directed Energy Deposition (DED) process. SMD as a means of in-process joining (IPJ) aims to integrate components and assemblies during additive manufacturing, combining the advantages of various processes for eco-friendly and economical resource utilization. The research initially analyzed DED systems and defined requirements for subsystems and the overall system. Critical subsystems, including the energy source, material feed, and others, were sequentially developed, and a proof of concept involved building 20 stacked welded tracks, validated through micrograph analysis. The study concludes by evaluating and discussing the fulfillment of the defined requirements. The system comprises a centrally arranged vibration-assisted powder feed; a laterally arranged laser incidence at a 45° angle; a kinematic structure where all axes are arranged on the workpiece, so the powder supply does not require movement; and a shield gas supply.}, subject = {Direct Energy Deposition}, language = {en} } @article{PfennigMohringWolf, author = {Pfennig, Anja and Mohring, Wencke and Wolf, Marcus}, title = {The Insignificant Improvement of Corrosion and Corrosion Fatigue Behavior in Geothermal Environment Applying Boehmit Coatings on High Alloyed Steels}, series = {Applied Sciences}, volume = {14}, journal = {Applied Sciences}, number = {4}, editor = {Wang, Kai and Wu, Jie and Deng, Yongjun and Chen, Lin}, publisher = {MDPI}, issn = {2076-3417}, doi = {10.3390/app14041575}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-18209}, abstract = {The efficacy of alumina-sol based coatings in a water-free atmosphere at high temperatures suggests a potential solution for enhancing the corrosion resistance of high-alloyed steels in Carbon Capture and Storage (CCS) environments. In this study, coupons of X20Cr13, designed for use as injection pipes with 13\% Chromium and 0.20\% Carbon (1.4021, AISI 420), were sol-gel coated with water and ethanol-based alumina. These coated coupons were then exposed to CO2-saturated saline aquifer water, simulating conditions in the Northern German Basin, for 1000 h at ambient pressure and 60 °C. Corrosion fatigue experiments were also conducted using specimens of X5CrNiMoCuNb16-4 (1.4542, AISI 630), a suitable candidate for geothermal applications, to assess the impact of the ethanol-based coating on the number of cycles to failure at different stress amplitudes. Unfortunately, the coating exhibited early spallation, resulting in corrosion kinetics and corrosion fatigue data identical to those of uncoated specimens. Consequently, the initially promising Boehmit coating is deemed unsuitable for CCS applications and further research therefore not advisable.}, subject = {Stahl}, language = {en} } @article{NollerPfennigHeiler, author = {Noller, Sebastian Friedrich and Pfennig, Anja and Heiler, Roland}, title = {High-speed tensile testing of extruded PC based polymers for cable ducts}, series = {Journal of Physics: Conference Series}, volume = {1425}, journal = {Journal of Physics: Conference Series}, number = {1}, publisher = {IOP Publishing}, issn = {1742-6588}, doi = {10.1088/1742-6596/1425/1/012195}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-15684}, pages = {1 -- 8}, abstract = {Previous tensile tests at 50, 100 and 400 mm/min using standard polycarbonate/acrylonitrile butadiene styrene (PC/ABS) material qualities have led to the suspicion that strain at break decreases with increasing test speed. Here, the plastic deformation component is regarded as the main burr cause. Thus, higher process speeds during punching would lead to less burr formation. This thesis was proven by high-speed tensile tests with a self-developed test rig operating at a test speed of 36.000 mm/min. Both, pure standard materials, provided by a polymer granules supplier, and customized materials were investigated. The customized materials contain unknown additives generally used in industry, e.g. fillers. All samples were taken laterally from in-situ cable ducts. The remaining plastic strain was introduced as material parameter to compare the results of high-speed and conventional tensile tests. The investigations show that the remaining plastic strain which is understood as the major burr cause decreases with increasing test speed. Furthermore, the mean values of the remaining plastic strain of the individual materials converge when exposed to higher test speeds. This leads to the thesis that one tool configuration can be used for different polycarbonate (PC) based materials presumed the process speed is adjusted correctly.}, subject = {ABS-Kunststoffe}, language = {en} } @article{PfennigWolfKranzmann, author = {Pfennig, Anja and Wolf, Marcus and Kranzmann, Axel}, title = {Corrosion and Corrosion Fatigue of Steels in Downhole CCS Environment — A Summary}, series = {Processes}, volume = {9}, journal = {Processes}, number = {4}, publisher = {MDPI}, issn = {2227-9717}, doi = {10.3390/pr9040594}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-14680}, pages = {33}, abstract = {Static immersion tests of potential injection pipe steels 42CrMo4, X20Cr13, X46Cr13, X35CrMo4, and X5CrNiCuNb16-4 at T = 60°C and ambient pressure, as well as p = 100 bar were performed for 700-8000 h in a CO2-saturated synthetic aquifer environment similar to CCS sites in the Northern German Basin (NGB). Corrosion rates at 100 bar are generally lower than at ambient pressure. The main corrosion products are FeCO3 and FeOOH with surface and local corrosion phenomena directly related to the alloy composition and microstructure. The appropriate heat treatment enhances corrosion resistance. The lifetime reduction of X46Cr13, X5CrNiCuNb16-4, and duplex stainless steel X2CrNiMoN22-5-3 in a CCS environment is demonstrated in the in situ corrosion fatigue CF experiments (axial push-pull and rotation bending load, 60°C, brine: Stuttgart Aquifer and NGB, flowing CO2: 30 L/h, +/- applied potential). Insulating the test setup is necessary to gain reliable data. S-N plots, micrographic-, phase-, fractographic-, and surface analysis prove that the life expectancy of X2CrNiMoN22-5-3 in the axial cyclic load to failure is clearly related to the surface finish, applied stress amplitude, and stress mode. The horizontal grain attack within corrosion pit cavities, multiple fatigue cracks, and preferable deterioration of austenitic phase mainly cause fatigue failure. The CF life range increases significantly when a protective potential is applied.}, language = {en} } @article{PfennigKranzmann, author = {Pfennig, Anja and Kranzmann, Axel}, title = {Understanding the Anomalous Corrosion Behaviour of 17\% Chromium Martensitic Stainless Steel in Laboratory CCS-Environment—A Descriptive Approach}, series = {Clean Technologies}, volume = {4}, journal = {Clean Technologies}, number = {2}, editor = {Das, Diganta B.}, publisher = {MDPI}, issn = {2571-8797}, doi = {10.3390/cleantechnol4020014}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-15986}, pages = {239 -- 257}, abstract = {To mitigate carbon dioxide emissions CO2 is compressed and sequestrated into deep geological layers (Carbon Capture and Storage CCS). The corrosion of injection pipe steels is induced when the metal is in contact with CO2 and at the same time the geological saline formation water. Stainless steels X35CrMo17 and X5CrNiCuNb16-4 with approximately 17\% Cr show potential as injection pipes to engineer the Northern German Basin geological onshore CCS-site. Static laboratory experiments (T = 60 °C, p = 100 bar, 700-8000 h exposure time, aquifer water, CO2-flow rate of 9 L/h) were conducted to evaluate corrosion kinetics. The anomalous surface corrosion phenomena were found to be independent of heat treatment prior to exposure. The corrosion process is described as a function of the atmosphere and diffusion process of ionic species to explain the precipitation mechanism and better estimate the reliability of these particular steels in a downhole CCS environment.}, subject = {Korrosion Stahl}, language = {en} } @article{HutterPfennig, author = {Hutter, Florina G. and Pfennig, Anja}, title = {Reduction in Ground Times in Passenger Air Transport: A First Approach to Evaluate Mechanisms and Challenges}, series = {Applied Sciences}, volume = {13}, journal = {Applied Sciences}, number = {3}, editor = {Li, Jiangchen and Liu, Peiqing}, publisher = {MDPI}, issn = {2076-3417}, doi = {10.3390/app13031380}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-16688}, pages = {1 -- 17}, abstract = {Rising air travel demand, airport capacity issues, and schedule disruptions form part of the challenges that aviation stakeholders have to face in the upcoming decades. Minimizing ground times is one of their recent objectives as extended ground times induce operational, economic, and environmental risks. The flow of ground operations has a high impact on the overall air transportation system. Therefore, the impact and risks of extended ground times in passenger air transport were thoroughly compared, weighed, and compared based on pre-selected individual literature sources. Several studies deliver solution approaches to reduce ground times. The turnaround especially is a key element of any flight operation and impacts the competitive advantage of airlines and airports. Next to infrastructural changes, technological advancements, and operational performance improvements, the cooperation of stakeholders is a measure to shorten ground times. Special focus lies on the improvement of boarding procedures. They are essential for passenger air transport and reducing ground times.}, subject = {Luftverkehr}, language = {en} } @article{PfennigSimkin, author = {Pfennig, Anja and Simkin, Roman}, title = {Identifying the Initial Corrosion Fatigue Failure Based on Dropping Electrochemical Potential}, series = {Applied Sciences}, volume = {15}, journal = {Applied Sciences}, number = {1}, editor = {Miotello, Antonio}, publisher = {MDPI}, issn = {2076-3417}, doi = {10.3390/app15010403}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-19926}, abstract = {The corrosion fatigue of duplex stainless-steel X2CrNiMoN22-5-3 can be determined by purely alternating axial cyclic load to failure using hour-glass shaped specimens. The experimental setup comprises a corrosion chamber allowing for the circulation of an aquifer electrolyte heated to 369 K simulating a carbon capture and storage as well as geothermal power plant environment. During engineering of a carbon storage site or geothermal power plant, it may be crucial to determine the failure onset of a component beforehand. Therefore, an algorithm with 93.3\% reliability was established based on splitting the measured potential values into ten time series with a capacity of ten values. The failure of corrosion fatigue specimens in a geothermal environment correlates to the drop of the curves of the electrochemical potential which is measured simultaneously within the corrosion chamber. Crack initiation was, therefore, successfully derived from the electrochemical potential.}, subject = {corrosion fatigue}, language = {en} }