TY - JOUR A1 - Abbas, Karim A1 - Balc, Nicolae A1 - Bremen, Sebastian A1 - Skupin, Marco T1 - Crystallization and aging behavior of polyetheretherketone PEEK within rapid tooling and rubber molding JF - Journal of Manufacturing and Materials Processing N2 - In times of short product life cycles, additive manufacturing and rapid tooling are important methods to make tool development and manufacturing more efficient. High-performance polymers are the key to mold production for prototypes and small series. However, the high temperatures during vulcanization injection molding cause thermal aging and can impair service life. The extent to which the thermal stress over the entire process chain stresses the material and whether it leads to irreversible material aging is evaluated. To this end, a mold made of PEEK is fabricated using fused filament fabrication and examined for its potential application. The mold is heated to 200 ◦C, filled with rubber, and cured. A differential scanning calorimetry analysis of each process step illustrates the crystallization behavior and first indicates the material resistance. It shows distinct cold crystallization regions at a build chamber temperature of 90 ◦C. At an ambient temperature above Tg, crystallization of 30% is achieved, and cold crystallization no longer occurs. Additional tensile tests show a decrease in tensile strength after ten days of thermal aging. The steady decrease in recrystallization temperature indicates degradation of the additives. However, the tensile tests reveal steady embrittlement of the material due to increasing crosslinking. KW - additive manufacturing KW - fused filament fabrication KW - crystallization KW - polyetheretherketone KW - rapid tooling Y1 - 2022 U6 - http://dx.doi.org/10.3390/jmmp6050093 SN - 2504-4494 N1 - The article belongs to the Special Issue Advances in Injection Molding: Process, Materials and Applications VL - 6 IS - 5 SP - 1 EP - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - Abbas, Karim A1 - Hedwig, Lukas A1 - Balc, Nicolae A1 - Bremen, Sebastian T1 - Advanced FFF of PEEK: Infill strategies and material characteristics for rapid tooling JF - Polymers N2 - Traditional vulcanization mold manufacturing is complex, costly, and under pressure due to shorter product lifecycles and diverse variations. Additive manufacturing using Fused Filament Fabrication and high-performance polymers like PEEK offer a promising future in this industry. This study assesses the compressive strength of various infill structures (honeycomb, grid, triangle, cubic, and gyroid) when considering two distinct build directions (Z, XY) to enhance PEEK’s economic and resource efficiency in rapid tooling. A comparison with PETG samples shows the behavior of the infill strategies. Additionally, a proof of concept illustrates the application of a PEEK mold in vulcanization. A peak compressive strength of 135.6 MPa was attained in specimens that were 100% solid and subjected to thermal post-treatment. This corresponds to a 20% strength improvement in the Z direction. In terms of time and mechanical properties, the anisotropic grid and isotropic cubic infill have emerged for use in rapid tooling. Furthermore, the study highlights that reducing the layer thickness from 0.15 mm to 0.1 mm can result in a 15% strength increase. The study unveils the successful utilization of a room-temperature FFF-printed PEEK mold in vulcanization injection molding. The parameters and infill strategies identified in this research enable the resource-efficient FFF printing of PEEK without compromising its strength properties. Using PEEK in rapid tooling allows a cost reduction of up to 70% in tool production. KW - polyetheretherketone (PEEK) KW - rapid tooling KW - infill strategy KW - compression behavior KW - additive manufacturing KW - fused filament fabrication Y1 - 2023 U6 - http://dx.doi.org/10.3390/polym15214293 N1 - This article belongs to the Special Issue "Polymer Materials and Design Processes for Additively Manufactured Products" VL - 2023 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Abdel-Latif, Lotfie Ahmed A1 - Peeken, Heinz A1 - Benner, Joachim T1 - Thermohydrodynamic analysis of thrust-bearing with circular pads running on bubbly oil (BTHD-theory) JF - Journal of tribology Y1 - 1985 SN - 0742-4787 SN - 1528-8897 VL - 107 IS - 4 SP - 527 EP - 537 ER - TY - JOUR A1 - Abel, Alexander A1 - Kahmann, Stephanie Lucina A1 - Mellon, Stephen A1 - Staat, Manfred A1 - Jung, Alexander T1 - An open-source tool for the validation of finite element models using three-dimensional full-field measurements JF - Medical Engineering & Physics N2 - Three-dimensional (3D) full-field measurements provide a comprehensive and accurate validation of finite element (FE) models. For the validation, the result of the model and measurements are compared based on two respective point-sets and this requires the point-sets to be registered in one coordinate system. Point-set registration is a non-convex optimization problem that has widely been solved by the ordinary iterative closest point algorithm. However, this approach necessitates a good initialization without which it easily returns a local optimum, i.e. an erroneous registration. The globally optimal iterative closest point (Go-ICP) algorithm has overcome this drawback and forms the basis for the presented open-source tool that can be used for the validation of FE models using 3D full-field measurements. The capability of the tool is demonstrated using an application example from the field of biomechanics. Methodological problems that arise in real-world data and the respective implemented solution approaches are discussed. Y1 - 2020 U6 - http://dx.doi.org/10.1016/j.medengphy.2019.10.015 SN - 1350-4533 VL - 77 SP - 125 EP - 129 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Aboulnaga, E. A. A1 - Zou, H. A1 - Selmer, Thorsten A1 - Xian, M. T1 - Development of a plasmid-based, tunable, tolC-derived expression system for application in Cupriavidus necator H16 JF - Journal of Biotechnology N2 - Cupriavidus necator H16 gains increasing attention in microbial research and biotechnological application due to its diverse metabolic features. Here we present a tightly controlled gene expression system for C. necator including the pBBR1-vector that contains hybrid promoters originating from C. necator native tolC-promoter in combination with a synthetic tetO-operator. The expression of the reporter gene from these plasmids relies on the addition of the exogenous inducer doxycycline (dc). The novel expression system offers a combination of advantageous features as; (i) high and dose-dependent recombinant protein production, (ii) tight control with a high dynamic range (On/Off ratio), which makes it applicable for harmful pathways or for toxic protein production, (iii) comparable cheap inducer (doxycycline, dc), (iv) effective at low inducer concentration, that makes it useful for large scale application, (v) rapid, diffusion controlled induction, and (vi) the inducer does not interfere within the cell metabolism. As applications of the expression system in C. necator H16, the growth ability on glycerol was enhanced by constitutively expressing the E. coli glpk gene-encoding for glycerol kinase. Likewise, we used the system to overcome the expression toxicity of mevalonate pathway in C. necator H16. With this system, the mevalonate-genes were successfully introduced in the host and the recombinant strains could produce about 200 mg/l mevalonate. Y1 - 2018 U6 - http://dx.doi.org/10.1016/j.jbiotec.2018.03.007 SN - 0168-1656 VL - 274 SP - 15 EP - 27 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abouzar, Maryam H. A1 - Ingebrandt, S. A1 - Poghossian, Arshak A1 - Zhang, Y. A1 - Moritz, W. A1 - Schöning, Michael Josef T1 - Field-effect nanoplate capacitive pH sensor based on SOI structure JF - Semiconductor micro- and nanoelectronics : Proceedings of the Seventh International Conference , Tsakhcadzor, Armenia July 3-5 2009 Y1 - 2009 SP - 55 EP - 58 ER - TY - JOUR A1 - Abouzar, Maryam H. A1 - Ingebrandt, S. A1 - Poghossian, Arshak A1 - Zhang, Y. A1 - Vu, X. T. A1 - Moritz, W. A1 - Schöning, Michael Josef T1 - Nanoplate field-effect capacitive (bio-)chemical sensor array based on SOI structure JF - Procedia Chemistry. 1 (2009), H. 1 Y1 - 2009 SN - 1876-6196 N1 - Proceedings of the Eurosensors XXIII conference ; Eurosensors 23 SP - 670 EP - 673 ER - TY - JOUR A1 - Abouzar, Maryam H. A1 - Pedraza, A. M. A1 - Schöning, Michael Josef A1 - Poghossian, Arshak T1 - Label-free DNA hybridization and denaturation detection by means of field-effect nanoplate SOI capacitors functionalized with gold nanoparticles JF - Procedia Engineering. 5 (2010) Y1 - 2010 SN - 1877-7058 N1 - Proc. Eurosensors XXIV, September 5–8, 2010, Linz, Austria SP - 918 EP - 921 ER - TY - JOUR A1 - Abouzar, Maryam H. A1 - Poghossian, Arshak A1 - Cherstvy, Andrey G. A1 - Pedraza, Angela M. A1 - Ingebrandt, Sven A1 - Schöning, Michael Josef T1 - Label-free electrical detection of DNA by means of field-effect nanoplate capacitors: Experiments and modeling JF - Physica Status Solidi (a) N2 - Label-free electrical detection of consecutive deoxyribonucleic acid (DNA) hybridization/denaturation by means of an array of individually addressable field-effect-based nanoplate silicon-on-insulator (SOI) capacitors modified with gold nanoparticles (Au-NP) is investigated. The proposed device detects charge changes on Au-NP/DNA hybrids induced by the hybridization or denaturation event. DNA hybridization was performed in a high ionic-strength solution to provide a high hybridization efficiency. On the other hand, to reduce the screening of the DNA charge by counter ions and to achieve a high sensitivity, the sensor signal induced by the hybridization and denaturation events was measured in a low ionic-strength solution. High sensor signals of about 120, 90, and 80 mV were registered after the DNA hybridization, denaturation, and re-hybridization events, respectively. Fluorescence microscopy has been applied as reference method to verify the DNA immobilization, hybridization, and denaturation processes. An electrostatic charge-plane model for potential changes at the gate surface of a nanoplate field-effect sensor induced by the DNA hybridization has been developed taking into account both the Debye length and the distance of the DNA charge from the gate surface. Y1 - 2012 U6 - http://dx.doi.org/10.1002/pssa.201100710 SN - 1862-6319 VL - 209 SP - 925 EP - 934 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Abouzar, Maryam H. A1 - Poghossian, Arshak A1 - Pedraza, A. M. A1 - Gandhi, D. A1 - Ingebrandt, S. A1 - Moritz, W. A1 - Schöning, Michael Josef T1 - An array of field-effect nanoplate SOI capacitors for (bio-)chemical sensing JF - Biosensors and Bioelectronics. 26 (2011), H. 6 Y1 - 2011 SN - 0956-5663 SP - 3023 EP - 3028 PB - Elsevier CY - Amsterdam ER -