464 Works

Temperature analysis of a pin-on-disc tribology test using experimental and numerical approaches

Oday Ibraheem Abdullah & Josef Schlattmann
The high thermal stresses generated at the interface between the contacting surfaces due to the sliding between parts of sliding system such as friction clutches and brakes. In this work, pin-on-disc test rig was built to find the temperature field during the sliding operation using experimental and numerical approaches. In the experimental approach, infrared camera was used to find the temperature distribution, while in the numerical approach a finite element technique has been used. Analysis...

Stabilization Columns for Embankment Support - Investigation, Verification and Further Development of Analytical Analyses

Holger Pankrath, Hatice Kaya & Ralf Thiele
As a technical and economical alternative to foundations on piles, but also to shallow foundations on improved soil, in recent decades a high number of soil improvement methods have been developed and established. Many of these methods use non-reinforced, cylindrical load bearing elements. A very common application of stabilizing columns is the improvement of a few meters thick soft soils below dams and embankments. But especially for this application, many failure cases are documented worldwide....

Analysis of the influence of burst-mode laser ablation by modern quality tools

Claus Emmelmann & Juan Pablo Calderón Urbina
The development of lasers in terms of pulse length and ablation quality has made wider the perspective of material processing. Ablation using picosecond lasers offers an almost "cold material removal", which causes minimal heat affected zones and enables sublimation without melt formation. Moreover, burst-mode intensifies these effects by the partition of pulses into groups of micro-pulses. Therefore, removal rate and surface quality are improved with an appropriate combination of burst-mode and other relevant process parameters....

Carbon nanoparticles’ impact on processability and physical properties of epoxy resins : a comprehensive study covering rheological, electrical, thermo-mechanical, and fracture properties (mode I and II)

Hauke Meeuw, Johann Körbelin, Valea Kim Wisniewski, Ali Shaygan Nia, Adrián Romaní Vázquez, Martin Rudolf Lohe, Xinliang Feng & Bodo Fiedler
A trade-off between enhancement of physical properties of the final part and the processability during manufacturing always exists for the application of nanocarbon materials in thermoset-based composites. For different epoxy resins, this study elaborates the impact of nanocarbon particle type, functionalization, and filler loading on the resulting properties, i.e., rheological, electrical, thermo-mechanical, as well as the fracture toughness in mode I and mode II loading. Therefore, a comprehensive set of carbon nanoparticles, consisting of carbon...

The influence of clamping pressure on joint formation and mechanical performance of Ti6Al4V/CF-PEEK friction-riveted joints

Natascha Zocoller Borba, Jorge F. dos Santos & Sergio T. Amancio-Filho
This work aims at investigating the influence of pre-set clamping pressure on the joint formation and mechanical strength of overlapping direct-friction-riveted joints. A pneumatic fixture device was developed for this work, with clamping pressure varying from 0.2 MPa to 0.6 MPa. A case study on overlapping joints using Ti6Al4V rivets and woven carbon fiber-reinforced polyether-ether-ketone (CF-PEEK) parts were produced. Digital image correlation and microscopy revealed the expected compressive behavior of the clamping system and the...

Analysis of refrigerant pipe pressure drop of a CO₂ air conditioning unit for vehicles

Christoph Subei & Gerhard Schmitz
This study investigates the pressure drop in refrigerant pipes of a CO₂ automotive air conditioning unit. A test rig to measure the pressure drop of arbitrarily shaped pipes is presented. As boundary conditions at the inlet of the test section, mass flow, pressure and enthalpy of the refrigerant are independently adjustable to values that cover the whole operating range of a CO₂ automotive air conditioning system for cars in the premium segment. Numerical analysis using...

A discussion on present theories of rubber friction, with particular reference to different possible choices of arbitrary roughness cutoff parameters

Andrea Genovese, Flavio Farroni, Antonio Papangelo & Michele Ciavarella
Since the early study by Grosch in 1963 it has been known that rubber friction shows generally two maxima with respect to speed - the first one attributed to adhesion, and another at higher velocities attributed to viscoelastic losses. The theory of Klüppel and Heinrich and that of Persson suggests that viscoelastic losses crucially depend on the “multiscale” aspect of roughness and in particular on truncation at fine scales. In this study, we comment a...

Fine bubble-based CO2 capture mediated by triethanolamine coupled to whole cell biotransformation

Daniel Ohde, Benjamin Thomas, Simon Matthes, Zeynep Percin, Claudia Engelmann, Paul Bubenheim, Koichi Terasaka, Michael Schlüter & Andreas Liese
Carbon capture technology can be set up in combination with biocatalysis to utilize the bound CO2 as substrate in the Kolbe-Schmitt like enzymatic reaction. The exemplary whole cell biotransformation of catechol to 2,3-dihydroxybenzoic acid in a triethanolamine-mediated multiphase system shows increased equilibrium conversion. Apart from the beneficial thermodynamics, the inherent fluid properties of triethanolamine is enabling easy application of CO2 fine bubbles as highly efficient gassing method to minimize the CO2 demand and CO2 emissions.

Determination of flow parameters of a water flow around an AUV body

Julian Hoth & Wojciech Kowalczyk
Autonomous underwater vehicles (AUVs) have changed the way marine environment is surveyed, monitored and mapped. Autonomous underwater vehicles have a wide range of applications in research, military, and commercial settings. AUVs not only perform a given task but also adapt to changes in the environment, e.g., sudden side currents, downdrafts, and other effects which are extremely unpredictable. To navigate properly and allow simultaneous localisation and mapping (SLAM) algorithms to be used, these effects need to...

Experimental investigation of a downwind coned wind turbine rotor under yawed conditions: preliminary results

Christian Schulz, Klaus Wieczorek, Stefan Netzband & Moustafa Abdel-Maksoud
The growing number of Floating Offshore Wind Turbine (FOWT) concepts that utilize a single point mooring and therefore rely on the self-alignment capabilities of the wind turbine (e.g. SCD nezzy or SelfAligner by CRUSE Offshore) demands an extension of the simulation methods used for their development. A crucial issue for these concepts is the accurate prediction of forces and moments, which contribute to the self-alignment. In contrast to the well-studied behaviour of torque and thrust,...

Data science based mg corrosion engineering

Tim Würger, Christian Feiler, Félix Musil, Gregor Feldbauer, Daniel Höche, Sviatlana V. Lamaka, Mikhail L. Zheludkevich & Robert Meißner
Magnesium exhibits a high potential for a variety of applications in areas such as transport, energy and medicine. However, untreated magnesium alloys are prone to corrosion, restricting their practical application. Therefore, it is necessary to develop new approaches that can prevent or control corrosion and degradation processes in order to adapt to the specific needs of the application. One potential solution is using corrosion inhibitors which are capable of drastically reducing the degradation rate as...

My smartphone tattles: considering popularity of messages in opportunistic data dissemination

Asanga Udugama, Jens Dede, Anna Förster, Vishnupriya Kuppusamy, Koojana Kuladinithi, Andreas Timm-Giel & Zeynep Vatandas
Opportunistic networks have recently seen increasing interest in the networking community. They can serve a range of application scenarios, most of them being destination-less, i.e., without a-priori knowledge of who is the final destination of a message. In this paper, we explore the usage of data popularity for improving the efficiency of data forwarding in opportunistic networks. Whether a message will become popular or not is not known before disseminating it to users. Thus, popularity...

Update on the impact of type 2 diabetes mellitus on bone metabolism and material properties

Ann-Kristin Picke, Graeme Michael Campbell, Nicola Napoli, Lorenz C. Hofbauer & Martina Rauner
The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide, especially as a result of our aging society, high caloric intake and sedentary lifestyle. Besides the well-known complications of T2DM on the cardiovascular system, the eyes, kidneys and nerves, bone strength is also impaired in diabetic patients. Patients with T2DM have a 40–70% increased risk for fractures, despite having a normal to increased bone mineral density, suggesting that other factors besides bone quantity must...

CRISPR/Cas9-facilitated engineering with growth-coupled and sensor-guided in vivo screening of enzyme variants for a more efficient chorismate pathway in E. coli

Minliang Chen, Lin Chen & An-Ping Zeng
Protein engineering plays an increasingly important role in developing new and optimizing existing metabolic pathways for biosynthesis. Conventional screening approach of libraries of gene and enzyme variants is often done using a host strain under conditions not relevant to the cultivation or intracellular conditions of the later production strain. This does not necessarily result in the identification of the best enzyme variant for in vivo use in the production strain. In this work, we propose...

Thinner and better: (Ultra-)low grammage bacterial cellulose nanopaper-reinforced polylactide composite laminates

Martin Hervy, Frederic Bock & Koon-Yang Lee
One of the rate-limiting steps in the large-scale production of cellulose nanopaper-reinforced polymer composites is the time consuming dewatering step to produce the reinforcing cellulose nanopapers. In this work, we show that the dewatering time of bacterial cellulose (BC)-in-water suspension can be reduced by reducing the grammage of BC nanopaper to be produced. The influence of BC nanopaper grammage on the tensile properties of BC nanopaper-reinforced polylactide (PLLA) composites is also investigated in this work....

Decision-makers’ underestimation of user innovation

Philip Bradonjic, Nikolaus Franke & Christian Lüthje
In the past few decades, much research has documented the importance of users as sources of innovations. Over the last 10 years, Research Policy alone has published 56 research articles investigating this phenomenon. We ask to what degree the findings of users as innovators have been absorbed by decision-makers responsible for new product development (managers) and by those who shape the contextual conditions for innovation (policy makers and public administration). A realistic perception of the...

Recycling-oriented design in soft robotics

Anh Minh Nguyen & Arthur Seibel
Soft robotics is a novel approach in the field of robotics. Soft robots or soft actuators are typically polymer-based and are characterized by their flexibility and adaptability, which brings new far-reaching applications. Soft robotics is currently at the peak of its research. One circumstance that is also present in this age is constant climate change; there is a demand for sustainability. This goes hand in hand with the design of products that are suitable for...

Transparency induced in opals via nanometer thick conformal coating

Guoliang Shang, Kaline P. Furlan, Robert Zierold, Robert Blick, Rolf Janßen, Alexander Petrov & Manfred Eich
Self-assembled periodic structures out of monodisperse spherical particles, so-called opals, are a versatile approach to obtain 3D photonic crystals. We show that a thin conformal coating of only several nanometers can completely alter the reflection properties of such an opal. Specifically, a coating with a refractive index larger than that of the spherical particles can eliminate the first photonic band gap of opals. To explain this non-intuitive effect, where a nm-scaled coating results in a...

Learning environmental field exploration with computationally constrained underwater robots : Gaussian processes meet stochastic optimal control

Daniel-André Dücker, Andreas René Geist, Edwin Kreuzer & Eugen Solowjow
Autonomous exploration of environmental fields is one of the most promising tasks to be performed by fleets of mobile underwater robots. The goal is to maximize the information gain during the exploration process by integrating an information-metric into the path-planning and control step. Therefore, the system maintains an internal belief representation of the environmental field which incorporates previously collected measurements from the real field. In contrast to surface robots, mobile underwater systems are forced to...

Desiccant-assisted air conditioning system relying on solar and geothermal energy during summer and winter

Peter Niemann, Finn Richter, Arne Speerforck & Gerhard Schmitz
At Hamburg University of Technology the combination of an open cycle desiccant-assisted air conditioning system and a geothermal system is investigated in the framework of different research projects for several years. The objective of this study is to investigate the energy efficiency of the overall system and to evaluate the geothermal system during summer and winter mode, based on data measured for a temperate climate region. Monitoring results of the performance for dehumidification and remoistening...

A review of the application of machine learning and data mining approaches in continuum materials mechanics

Frederic E. Bock, Roland C. Aydin, Christian J. Cyron, Norbert Huber, Surya R. Kalidindi & Benjamin Klusemann
Machine learning tools represent key enablers for empowering material scientists and engineers to accelerate the development of novel materials, processes and techniques. One of the aims of using such approaches in the field of materials science is to achieve high-throughput identification and quantification of essential features along the process-structure-property-performance chain. In this contribution, machine learning and statistical learning approaches are reviewed in terms of their successful application to specific problems in the field of continuum...

Nanoindentation-based study of the mechanical behavior of bulk supercrystalline ceramic-organic nanocomposites

Büsra Bor, Diletta Giuntini, Berta Domènech Garcia, Michael V. Swain & Gerold A. Schneider
Bulk poly-supercrystalline ceramic-organic nanocomposites were produced and characterized with a nanoindentation-based study. These nanocomposites were processed using two different routines, to compare their properties with and without crosslinking the organic ligands interfacing the ceramic nanoparticles. Together with the expected material strengthening induced by crosslinking, a distinct response emerges when using Berkovich and cube-corner indenters. The supercrystalline materials are prone to compaction, cracking and chipping phenomena that become more severe when a sharper tip is employed,...

Fail-safe optimization of beam structures

Julian Kajo Lüdeker & Benedikt Kriegesmann
In the current work, a fail-safe optimization of beam structures is carried out. This approach may provide an insight into the robustness of lattice structures. The use of beam elements allows a commonly used engineering approach for obtaining a fail-safe design to be applied. This consists of removing one beam element at a time and optimizing the remaining structure. At the end of the process, the maximum beam radii are used for the final design....

Dynamic simulation and investigation of the startup process of a postcombustion-capture plant

Thomas Marx-Schubach & Gerhard Schmitz
Carbon capture is an important possibility to reduce carbon dioxide emissions. To be able to study the startup process of such an amine-scrubbing process, a startup model of a postcombustion-capture plant (pcc-plant) was developed in the Modelica language and validated with measured data from a pilot plant in Heilbronn, Germany. Afterward, the process was scaled up in the model to handle the entire flue-gas flow of a 875 MW coal-fired power plant, resulting in three...

On notch and crack size effects in fatigue, Paris’ law and implications for Wöhler curves

Michele Ciavarella & Antonio Papangelo
As often done in design practice, the Wöhler curve of a specimen, in the absence of more direct information, can be crudely retrieved by interpolating with a power-law curve between static strength at a given conventional low number of cycles N0(of the order of 10-103), and the fatigue limit at a “infinite life”, also conventional, typically N∞=2·106or N∞=107cycles. These assumptions introduce some uncertainty, but otherwise both the static regime and the infinite life are relatively...

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  • 2019
    464

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