Über die Eignung der Wechselbiegemaschine „WEBI”︁ zur Ermittlung von Ermüdungskennwerten

On Alternating Bending Machine WEBI's Suitability for Determination of Fatigue Characteristics Already in 1966, experimental investigations revealed that the flat bending torsion testing machine ?FLATO”? (Schenck, Darmstadt) doesn't keep constant its torsional moment amplitude in case of specimen's fatigue softening or hardening, respectively. Thus. conclusions concerning the material's fatigue characteristics drawn from such experimental results might therefore be seriously false. Furthermore, also the alternating bending testing machine ?WEBI”? (Schenck, Darmstadt) shows an equivalent behaviour concerning its bending moment amplitude. For this reason. the main findings of a comprehensive experimental study carried out on WEBI with an unalloyed steel C 45 (0.45 mass perccnl C) in different heat treatment conditions are reported in this paper.     

Benchmarking performance of machine and deep learning-based methodologies for Urdu text document classification

Neural Computing and Applications - In order to provide benchmark performance for Urdu text document classification, the contribution of this paper is manifold. First, it provides a publicly...     

Automatic classifier selection for non-experts

Choosing a suitable classifier for a given dataset is an important part of developing a pattern recognition system. Since a large variety of classification algorithms are proposed in literature, non-experts do not know which method should be used in order to obtain good classification results on their data. Meta-learning tries to address this problem by recommending promising classifiers based on meta-features computed from a given dataset. In this paper, we empirically evaluate five different categories of state-of-the-art meta-features for their suitability in predicting classification accuracies of several widely used classifiers (including Support Vector Machines, Neural Networks, Random Forests, Decision Trees, and Logistic Regression). Based on the evaluation results, we have developed the first open source meta-learning system that is capable of accurately predicting accuracies of target classifiers. The user provides a dataset as input and gets an automatically created high-performance ready-to-use pattern recognition system in a few simple steps. A user study of the system with non-experts showed that the users were able to develop more accurate pattern recognition systems in significantly less development time when using our system as compared to using a state-of-the-art data mining software.     

Meta-learning for evolutionary parameter optimization of classifiers

The performance of most of the classification algorithms on a particular dataset is highly dependent on the learning parameters used for training them. Different approaches like grid search or genetic algorithms are frequently employed to find suitable parameter values for a given dataset. Grid search has the advantage of finding more accurate solutions in general at the cost of higher computation time. Genetic algorithms, on the other hand, are able to find good solutions in less time, but the accuracy of these solutions is usually lower than those of grid search.     

Computer understanding of document structure

We describe a system which is capable of learning the presentation of document logical structure, exemplary as shown for business letters. Presenting a set of instances to the system, it clusters them into structural concepts and induces a concept hierarchy. This concept hierarchy is taken as a reference for classifying future input. The article introduces the sequence of learning steps and describes how the resulting concept hierarchy is applied to logical labeling, and reports the results. © 1996 John Wiley & Sons, Inc.     

Verbesserung des Schwingungsrißkorrosionsverhaltens von Stahlproben durch Beschichtung

Improvement of the corrosion fatigue behavior of steels by paint-coating Paint-coatings have been used extensively to prevent corrosion of steel. In order to investigate the influence of an anticorrosive paint on the corrosion fatigue strength of steel, specimens of SAE 4135 in a quenched and tempered state, and in salt bath nitrocarburized state, on the one hand, and specimens of the steel SAE 5115 in a salt bath carburized state, on the other hand, were subjected to comparative rotating bending fatigue tests in inert media and in aqueous 5 pct NaCl. The results demonstrate that the 5 pct NaCl environment is reducing fatigue life drastically, but the painting treatment, however, was found to improve significantly the corrosion fatigue life. Regarding the beneficial effect of the painting treatment on the corrosion fatigue behavior, a superiority of the nitrocarburized variant in contrast to the other variants was ascertained.     

Meßwertstreuung in Abhängigkeit von der Werkstoffhärte bei Kleinlasthärteprüfungen nach Vickers und Knoop

Dispersion of Vickers and Knoop diagonals as a function of workpiece-hardness at low load testing . A statistical analysis of low load hardness test results measured under industrial conditions by the comparative use of Vickers and Knoop indenters was carried out. Accordingly, recommendations can be given for the number of indentations necessary to ensure a constant shape of the distribution of sample means all over the investigated hardness area from approx. 150 up to 950 daN/mm₂.     

Wichtige Gesichtspunkte für die Härtemessung nach Vickers und nach Knoop im Bereich der Kleinlast- und Mikrohärte

Important aspects for low load testing of Vickers and Knoop hardness . There are various factors, which can affect the hardness number obtained in low load testing. Both, the Vickers and the Knoop indenter, are widespread applicated for hardness testing at low loads. Subsequently, in respect of these above mentioned hardness testing methods, it is given a summary concerning the most important factors, which, if they are not eliminated, can bring about serious errors in the test results.     

Lebensdauer- und Dauerfestigkeitsabschätzung von zugdruckwechsel- und zugschwellbeanspruchtem Stahl mittels Temperaturmessung

Estimation of the Endurance and the Fatigue Limit of Steel by Measuring Specimens′ Temperatures. Microplastic deformation processes are pre-requisites for fatigue crack formation within metallic materials. If the testing frequency of a specimen, cyclically stressed by a progressively-increasing load test, is not too low it is no great metrological problem to ascertain that special stress amplitude, σ_f,th (f ? fatigue limit, th ? thermometrical), at which specimen's temperature begins to rise due to the start of ‘remarkable’ microplastic deformations. Investigations of this kind, recently carried out by rotating bending showed a very good correspondence between σ_f,th and a statistically ascertained estimate of the fatigue limit, \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \sigma _{({\rm P} \simeq {\rm 0}\%{\rm)}} $\end{document} (P ? Probability of fracture), derived from comparatively performed Wöhler-tests. The purpose of this paper is to investigate the relationship between σ_f,th and \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \sigma _{({\rm P} \simeq {\rm 0}\%{\rm)}} $\end{document} for some carbon steels when cyclically stressed by push-pull and pulsating tensile loading, respectively. Both, unnotched and notched specimes were tested. Moreover, thermometrically monitored Wöhler-tests revealed that temperature measurements can provide a short-cut prediction of specimens′ lives. Above all it has to be mentioned that a reliable clue is gettable at a very early experimental stadium whether the cyclic stressed specimen will later become a ‘break’ or – normally much later – a ‘run-out’.