扁平工件的最佳淬火

Heimsoth淬火激冷工艺的优化以及接触板由钢制改用铜制后的实验结果表明,低合金钢和合金钢工件淬火厚度可分别达20 mm和100 mm,而且均匀、优质、几乎不发生变形.本文介绍和讨论了钢号为1.7228和1.3343的工件淬火后的平面度试验结果.采用钢制淬火激冷夹具工艺后工件的平面度达到最小平面度偏差.通过比较铜激冷夹具和钢激冷夹具的试验结果检验了理论模型的正确性.随后采用铜激冷夹具也取得了初步的试验结果,并将根据待淬火工件情况在淬火激冷夹具领域内对其进一步优化.这种新工艺将来也可应用于C45和C75等低合金钢和非合金钢的淬火.     

Evolution strategies with cumulative step length adaptation on the noisy parabolic ridge

This paper presents an analysis of the performance of the (μ/μ,λ)-ES with isotropically distributed mutations and cumulative step length adaptation on the noisy parabolic ridge. Several forms of dependency of the noise strength on the distance from the ridge axis are considered. Closed form expressions are derived that describe the mutation strength and the progress rate of the strategy in high-dimensional search spaces. It is seen that as for the sphere model, larger levels of noise present lead to cumulative step length adaptation generating increasingly inadequate mutation strengths, and that the problem can be ameliorated to some degree by working with larger populations.     

Optimum tracking with evolution strategies

Evolutionary algorithms are frequently applied to dynamic optimization problems in which the objective varies with time. It is desirable to gain an improved understanding of the influence of different genetic operators and of the parameters of a strategy on its tracking performance. An approach that has proven useful in the past is to mathematically analyze the strategy's behavior in simple, idealized environments. The present paper investigates the performance of a multiparent evolution strategy that employs cumulative step length adaptation for an optimization task in which the target moves linearly with uniform speed. Scaling laws that quite accurately describe the behavior of the strategy and that greatly contribute to its understanding are derived. It is shown that in contrast to previously obtained results for a randomly moving target, cumulative step length adaptation fails to achieve optimal step lengths if the target moves in a linear fashion. Implications for the choice of population size parameters are discussed.     

The performance of a microchannel plate at cryogenic temperatures and in high magnetic fields, and the detection efficiency for low energy positive hydrogen ions

We have conducted a systematic study of the performance of a microchannel plate at cryogenic temperatures, and in a magnetic field perpendicular to the plate surface of up to 2.5 T. We observe no change in the characteristic pulse height distribution down to temperatures near 4 K if the count rate is kept sufficiently low. With increasing count rates the onset of saturation effects can be observed to be temperature dependent. For the specific plate used, this occurs around 1 kHz at the lowest temperature. This behavior is in good agreement with calculations based on a widely used model for the gain function of microchannel plates, if the plate resistance is allowed to be temperature dependent. Additionally we have studied the detection efficiency for low energy hydrogen ions of a chevron type microchannel plate under a variety of operating conditions at room temperature, and find the detection efficiency to level off around 60% at energies above 1 keV, if the plate is operated in a saturated gain mode.     

Untermodell für das Aufwallen von schäumenden Gemischen bei Druckentlastung

On the basis of standardised measurements in a small scale with low viscous, non foaming as well as weakly and intensively foaming systems in a so-called Industry Calorimeter exemplarily is shown that the integral foaming behaviour during an abrupt reactor top depressurisation can be classified according to the measured liquid level height for equal venting conditions and attributed to the models by DIERS, i.e., Churn turbulent flow with a distribution parameter of 1.5, resp., Bubbly flow with a parameter of 1.2 and 1.01. Such lab experiments are indispensable in case of unknown foaming behaviour under transient conditions. They allow, then, on the basis of the postulated worst credible design case for an adequate sizing of relief area, discharge piping system and foremost of the containment, reducing by this favourably the amount of discharged inventary.

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Zusammenfassung Auf der Grundlage von Vergleichsmessungen im Kleinmaßstab mit niedrigviskosen, nicht schäumenden sowie schwach und heftig schäumenden Systemen in einem sog. Industrie Kalorimeter wird beispielhaft vorgeführt, daß sich das bei der plötzlichen kopfraumseitigen Druckentlastung dem Aufwallen überlagernde Schaumverhalten anhand der bei standardisierten Bedingungen gemessenen Aufwallhöhen einordnen und den von DIERS definierten Aufwallmodellen Churn turbulent flow mit einem Radialverteilungsparameter von 1,5 bzw. Bubbly flow mit einem Parameter von 1,2 und 1,01 zuordnen läßt. Derartige Laborversuche sind bei einem unter transienten Bedingungen nicht bekannten Schaumverhalten immer notwendig. Diese ermöglichen dann aber für den postulierten Pannenfall eine zutreffende Bemessung des Entlastungsquerschnittes, der Ableitung und insbesondere der Rückhalteeinrichtungen sowie damit einhergehend eine Verringerung des ausgetragenen Inventars.Submodel for level swell with superimposed foaming in case of reactor depressurisation

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Eingegangen: 12. Juli 2004Die Untersuchungen erfolgten im Rahmen des über die AiF von dem BMWA finanziell geförderten Vorhabens ,,Phasenseparationsmodell für die kontrollierte und die plötzliche Entspannung von Chemiereaktoren bei schäumenden Gemischen. Für die Unterstützung wird sehr gedankt.     

Qualms regarding the optimality of cumulative path length control in CSA/CMA-evolution strategies

Cumulative step-size adaptation (CSA) based on path length control is regarded as a robust alternative to the standard mutative self-adaptation technique in evolution strategies (ES), guaranteeing an almost optimal control of the mutation operator. This paper shows that the underlying basic assumption in CSA--the perpendicularity of expected consecutive steps--does not necessarily guarantee optimal progress performance for (mu/mu(I), lambda) intermediate recombinative ES.     

Mathematical Description of Experimentally Determined Charge Distributions of a Unipolar Diffusion Charger

The charge distributions of an improved opposed flow unipolar diffusion charger were measured using a tandem differential mobility analyzer (DMA) set up in a size range of approximately 20–400 nm. The charger is intended to be used in a portable aerosol sizer to measure particle size distributions. The determined charge distributions were represented by lognormal distributions, and a set of equations and coefficients was developed to calculate the charge distributions. These equations can be easily implemented in software for size distribution measurements. The agreement between the mathematically derived and measured charge distributions is very good, with regression coefficients R ² > 0.96. The investigations showed that approximately 55% of 20-nm particles remain uncharged, while up to 25 elementary charges need to be considered for multiple charge correction of 400-nm particles. Comparison with the Fuchs theory delivered satisfying agreement with the measured average charge levels, but charge distributions cannot be described by the Fuchs theory, likely caused by the charger geometry.

Copyright 2012 American Association for Aerosol Research     

An integrated approach for validating micro mechanical systems based on simulation and test

Miniaturization of macroscopic mechanical systems enables the opening of new areas of application for micro technological systems. Because of technological restrictions, especially when applying miniaturized conventional manufacturing techniques, shape and material deviations cannot be scaled down in the same dimension like micro parts. Thus, the long-term objective is to ensure the functioning by appropriate design measures. In doing so, determination of the transfer behavior by modeling and simulation is required. This work presents two ways for ensuring the required properties of micro gears and describes how the results do correlate. The experimental way uses the radial composite inspection as it is used in the macroscopic world. The simulative way deploys a rolling simulation by utilization of finite element analysis. The virtual prototypes are originated on measured real test gears. When comparing experiment and simulation of the rolling behavior, in some short and long wave areas deviations can be recognized. These can be ascribed to the reduction from three to two dimensions when modeling. Other deviations might be based on inaccuracies when mounting into the test rig. In other areas quite good correlations of test and simulation could be ascertained.     

Thermomechanische Behandlung von Manganhartstählen

Die durch Walzen oder Schmieden im Bereich von 700 bis 1050°C thermomechanisch behandelten Manganhartstähle X 120 Mn 12 und X 120 MnCrSiV 12 werden unter Einbeziehung einer anschließenden Haltedauer bei Umformtemperatur bzw. bei 440°C bezüglich ihres Gefüges und ihrer Eigenschaften vergleichend untersucht. Es zeigt sich, daß die Legierungszusätze an Chrom, Silicium und Vanadin eine höhere Umformtemperatur zur Erzielung einer gewünschten Verfestigung zulassen und damit die thermomechanische Behandlung erleichtern. Der Verschleißwiderstand wird nicht beeinträchtigt.