Search results for: Frank Walther

Items from 1 to 20 out of 38 results

article

Shear Characterization of Additively Manufactured Short Carbon Fiber‐Reinforced Polymer

Patrick Striemann, Simon Bulach, Daniel Hülsbusch, Michael Niedermeier, more

Macromolecular Symposia > 395 > 1 > n/a - n/a

The additive manufacturing (AM) techniques Fused Deposition Modeling (FDM™) or Fused Filament Fabrication (FFF) are all based on material extrusion and are one of the most widely used AM methods. Serial production with this technology requires a deep understanding for the process and the effects of the process parameters on the mechanical properties. In literature tensile, compression, or flexural...

article

Innovationen zum optimalen Einsatz des wetterfesten Baustahls im Stahl‐ und Verbundbrückenbau

Dieter Ungermann, Peter Hatke, Marina Knyazeva, Frank Walther, more

Stahlbau > 90 > 2 > 106 - 115

Im Rahmen des gleichnamigen Forschungsprojekts „Innovationen zum optimalen Einsatz des wetterfesten Baustahls im Stahl‐ und Verbundbrückenbau“ wurden wesentliche Aspekte zur besseren Anwendung des wetterfesten Baustahls im Stahl‐ und Verbundbrückenbau untersucht. Neben aktuellen Analysen zur Bildung der korrosionshemmenden Deckschicht in der heutigen Atmosphäre erfolgte die Qualifizierung zweier geometrieunabhängiger...

article

Modeling gradient‐enhanced anisotropic ductile damage: Application to low cycle fatigue

Kai Langenfeld, Kerstin Möhring, Frank Walther, Jörn Mosler

PAMM > 20 > 1 > n/a - n/a

Low cycle fatigue is in general associated with large plastic strains accompanied by the formation and coalescence of pores. Considering continuum damage mechanics, many local constitutive models for ductile damage can be found in the literature. These local models however, that do not involve any length scale, lead to mesh dependent results. In order to regularize these local models, the micromorphic...

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Molecular phylogeny and trait evolution of Madeiran land snails: radiation of the Geomitrini (Stylommatophora: Helicoidea: Geomitridae)

Alissa Brozzo, Josef Harl, Willy De Mattia, Dinarte Teixeira, more

Cladistics > 36 > 6 > 594 - 616

The Geomitrini is the most species‐rich group of land snails in the Madeiran Archipelago. The phylogeny of the group is reconstructed based on mitochondrial and nuclear genetic markers. The timing of diversification, the colonisation history of the islands of the Madeiran Archipelago and the evolution of characters of the dart apparatus are studied. The results of the phylogenetic analyses confirm...

article

New insights into Southern Caucasian glacial–interglacial climate conditions inferred from Quaternary gastropod fauna

Christiane Richter, Daniel Wolf, Frank Walther, Stefan Meng, more

Journal of Quaternary Science > 35 > 5 > 634 - 649

In the present study, we performed gastropod analyses on loess–palaeosol sequences from northeast Armenia (Southern Caucasia) covering at least three glacial–interglacial cycles. The elaborated ecostratigraphy shows significant patterns of species composition related to the succession of pedocomplexes and loess, respectively. Pedocomplexes included species that can be associated with high‐grass to...

article

Patterns and processes in a non‐adaptive radiation: Alopia (Gastropoda, Clausiliidae) in the Bucegi Mountains

Eva L. Koch, Marco T. Neiber, Frank Walther, Bernhard Hausdorf

Zoologica Scripta > 49 > 3 > 280 - 294

We studied the door‐snail genus Alopia in the Southern Carpathians in Romania to better understand non‐adaptive radiations and the processes that determine their course. Alopia in the Bucegi Mountains offers the opportunity to study all stages of a radiation within a few kilometres. The species (as defined by the differential fitness species concept) in the most advanced stage of the radiation differs...

article

On the regularization for ductile damage models

Kai Langenfeld, Kerstin Möhring, Frank Walther, Jörn Mosler

PAMM > 19 > 1 > n/a - n/a

Modeling softening behavior often leads to ill‐posed boundary value problems. This, in turn, results in pathological mesh‐dependent computations as far as the finite‐element‐method is concerned. A by now widely used technique to eliminate these problems is the micromorphic approach by [1,2]. This regularization technique implicitly includes gradients of internal variables into the constitutive model...

article

Investigation of the anisotropic cyclic damage behavior of selective laser melted AISI 316L stainless steel

Felix Stern, Jan Kleinhorst, Jochen Tenkamp, Frank Walther

Fatigue & Fracture of Engineering Materials & Structures > 42 > 11 > 2422 - 2430

The additive manufacturing technique selective laser melting (SLM) is the most common process for metallic powders. The layer‐by‐layer process allows construction of components with high complex designs compared with conventional process routes. However, the orientation of parts related to the build platform and later to different loading conditions should be taken into account as the process‐induced...

article

Engineering the residual stress state of the metastable austenitic stainless steel (MASS) disc springs by incremental sheet forming (ISF)

Fawad Maqbool, Ramin Hajavifard, Frank Walther, Markus Bambach

Production Engineering > 2019 > 13 > 2 > 139-148

The paper presents a novel methodology to form disc springs made of metastable austenitic stainless steel using incremental sheet forming (ISF), which is also used to generate compressive residual stresses. The research aims at replacing the shot peening process which has various disadvantages such as a change in disc spring geometry and replacing it with a method that allows a better control of spring...

article

Frequency‐dependent fatigue and corrosion fatigue assessment of brazed AISI 304L/BNi‐2 joints in air and synthetic exhaust gas condensate

Anke Schmiedt, Lukas Lücker, Matthias Manka, Wolfgang Tillmann, more

Fatigue & Fracture of Engineering Materials & Structures > 41 > 11 > 2338 - 2349

Since brazed components are often cyclically loaded in corrosive environments, the corrosion fatigue behaviour of the joints has to be investigated. Fatigue tests of brazed AISI 304L/BNi‐2 joints, relevant for exhaust gas heat exchangers, were performed with specimens in the as‐received condition and after pre‐corrosion according to VDA 230‐214. Additionally, the superimposed corrosion fatigue loading...

article

Mechanical characterization of friction drilled internal threads in AZ91 profiles

Philipp Wittke, Mirko Teschke, Frank Walther

The International Journal of Advanced Manufacturing Technology > 2018 > 99 > 9-12 > 3111-3122

In this study, the influence of friction drilling tool pre-heating on mechanical properties of chipless manufactured internal threads in thin-walled AZ91 magnesium casting alloy profiles is investigated. In this context, the influence of manufacturing processes on microstructure and the resulting fracture behavior during mechanical loading are in focus for the determination of failure mechanisms....

article

Development of biomimetic in vitro fatigue assessment for UHMWPE implant materials

Ronja Scholz, Marina Knyazeva, Dario Porchetta, Nils Wegner, more

Journal of the Mechanical Behavior of Biomedical Materials > 2018 > 85 > C > 94-101

An important research goal in the field of biomaterials lies in the progressive amendment of in vivo tests with suitable in vitro experiments. Such approaches are gaining more significance nowadays because of an increasing demand on life sciences and the ethical issues bound to the sacrifice of animals for the sake of scientific research. Another advantage of transferring the experiments to the in...

article

Polymorphism of a genital organ under sexual selection in Monacha kuznetsovi from the Caucasus (Gastropoda: Hygromiidae)

Marco T. Neiber, Frank Walther, Bernhard Hausdorf

Journal of Zoological Systematics and Evolutionary Research > 56 > 3 > 317 - 322

During mating the dart apparatus of the land snail group Helicoidea transfers an allohormone that increases paternity success. Thus, this organ is under sexual selection. Despite this selective advantage, the dart sac has independently been lost in many lineages in the Helicoidea, presumably because natural selection counteracts sexual selection. However, the selective pressures that result in the...

article

Dataset on the structural characterization of organosolv lignin obtained from ensiled Poaceae grass and load-dependent molecular weight changes during thermoplastic processing

Jörg Dörrstein, Ronja Scholz, Dominik Schwarz, Doris Schieder, more

Data in Brief > 2018 > 17 > C > 647-652

This article presents experimental data of organosolv lignin from Poacea grass and structural changes after compounding and injection molding as presented in the research article “Effects of high-lignin-loading on thermal, mechanical, and morphological properties of bioplastic composites” [1]. It supplements the article with morphological (SEM), spectroscopic (³¹P NMR, FT-IR) and chromatographic (GPC,...

article

On femtosecond laser shock peening of stainless steel AISI 316

Jan S. Hoppius, Lalit M. Kukreja, Marina Knyazeva, Fabian Pöhl, more

Applied Surface Science > 2018 > 435 > C > 1120-1124

In this paper we report on the competition in metal surface hardening between the femtosecond shock peening on the one hand, and formation of laser-induced periodic surface structures (LIPSS) and surface oxidation on the other hand. Peening of the stainless steel AISI 316 due to shock loading induced by femtosecond laser ablation was successfully demonstrated. However, for some range of processing...

article

Defect-correlated fatigue assessment of A356-T6 aluminum cast alloy using computed tomography based Kitagawa-Takahashi diagrams

Jochen Tenkamp, Alexander Koch, Stephan Knorre, Ulrich Krupp, more

International Journal of Fatigue > 2018 > 108 > C > 25-34

Modern aluminum cast alloys are promising candidates for highly loaded lightweight components due to their good strength-to-weight ratio. To enable a safe design of aluminum cast components, the microstructure characteristics, e.g. porosity, secondary dendrite arm spacing and Si eutectic morphology, have to be taken into account. This study deals with the influence of different porosity characteristics...

article

Influence of the deep hole drilling process and sulphur content on the fatigue strength of AISI 4140 steel components

Jan Nickel, Nikolas Baak, Dirk Biermann, Frank Walther

Procedia CIRP > 2018 > 71 > C > 209-214

When using quenched and tempered steels in the automotive industry or other industrial applications the fatigue behavior is of elementary importance. The surface and subsurface integrity of machined parts is known as one key factor related to the fatigue strength of components and is strongly influenced by the machining process. Especially for the deep hole single lip drilling, a large part of the...

article

Phylogeny and reclassification of the Caucasigenini radiation from the Caucasus region (Gastropoda, Hygromiidae)

Marco T. Neiber, Frank Walther, Bernhard Hausdorf

Zoologica Scripta > 47 > 1 > 54 - 62

The Caucasigenini is an endemic radiation of hygromiid land snails from the Caucasus region. A phylogenetic analysis of morphological characters of the genitalia and the shell showed that the morphological characters are insufficient for resolving the relationships within the Caucasigenini. Convergences of the few parsimony informative characters in other groups of the Hygromiidae demonstrate that...

article

In Situ Acoustic Monitoring of Thermal Spray Process Using High-Frequency Impulse Measurements

Wolfgang Tillmann, Frank Walther, Weifeng Luo, Matthias Haack, more

Journal of Thermal Spray Technology > 2018 > 27 > 1-2 > 50-58

In order to guarantee their protective function, thermal spray coatings must be free from cracks, which expose the substrate surface to, e.g., corrosive media. Cracks in thermal spray coatings are usually formed because of tensile residual stresses. Most commonly, the crack occurrence is determined after the thermal spraying process by examination of metallographic cross sections of the coating. Recent...

article

Corrosion fatigue assessment of creep-resistant magnesium alloys DieMag422 and AE42

Martin Klein, Gerrit Frieling, Frank Walther

Engineering Fracture Mechanics > 2017 > 185 > C > 33-45

Corrosion fatigue behaviors of creep-resistant magnesium alloys DieMag422 and AE42 were characterized by means of lifetime- and process-oriented approaches. Fatigue properties of both materials were assessed in constant amplitude tests at several adjusted corrosion rates. Deterioration and cracking mechanisms were identified and monitored by means of corrosion potential response analysis during constant...

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INFONA - science communication portal

Search results for: Frank Walther

Shear Characterization of Additively Manufactured Short Carbon Fiber‐Reinforced Polymer

Innovationen zum optimalen Einsatz des wetterfesten Baustahls im Stahl‐ und Verbundbrückenbau

Modeling gradient‐enhanced anisotropic ductile damage: Application to low cycle fatigue

Molecular phylogeny and trait evolution of Madeiran land snails: radiation of the Geomitrini (Stylommatophora: Helicoidea: Geomitridae)

New insights into Southern Caucasian glacial–interglacial climate conditions inferred from Quaternary gastropod fauna

Patterns and processes in a non‐adaptive radiation: Alopia (Gastropoda, Clausiliidae) in the Bucegi Mountains

On the regularization for ductile damage models

Investigation of the anisotropic cyclic damage behavior of selective laser melted AISI 316L stainless steel

Engineering the residual stress state of the metastable austenitic stainless steel (MASS) disc springs by incremental sheet forming (ISF)

Frequency‐dependent fatigue and corrosion fatigue assessment of brazed AISI 304L/BNi‐2 joints in air and synthetic exhaust gas condensate

Mechanical characterization of friction drilled internal threads in AZ91 profiles

Development of biomimetic in vitro fatigue assessment for UHMWPE implant materials

Polymorphism of a genital organ under sexual selection in Monacha kuznetsovi from the Caucasus (Gastropoda: Hygromiidae)

Dataset on the structural characterization of organosolv lignin obtained from ensiled Poaceae grass and load-dependent molecular weight changes during thermoplastic processing

On femtosecond laser shock peening of stainless steel AISI 316

Defect-correlated fatigue assessment of A356-T6 aluminum cast alloy using computed tomography based Kitagawa-Takahashi diagrams

Influence of the deep hole drilling process and sulphur content on the fatigue strength of AISI 4140 steel components

Phylogeny and reclassification of the Caucasigenini radiation from the Caucasus region (Gastropoda, Hygromiidae)

In Situ Acoustic Monitoring of Thermal Spray Process Using High-Frequency Impulse Measurements

Corrosion fatigue assessment of creep-resistant magnesium alloys DieMag422 and AE42

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