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41.
42.
Alexander Düster Leszek Demkowicz Ernst Rank 《International journal for numerical methods in engineering》2006,67(8):1094-1121
A discontinuous Galerkin approach for solving the discrete Boltzmann equation is presented, allowing to compute approximate solutions for fluid flow problems. Based on a two‐dimensional high‐order finite element and an explicit Euler time stepping scheme, the D2Q9 model is discretized and the results are compared to the exact solution of the Navier–Stokes equation. Four numerical examples are considered, including stationary and instationary problems with curved boundaries. It is demonstrated that the proposed method allows to obtain the desired, highly efficient exponential convergence. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Precipitation kinetics of Nb(C,N) in microalloyed steels is crucial for the achievement of favoured steel properties. Therefore, numerous experimental studies have been performed in the past and various theoretical models have been developed to describe Nb(C,N) precipitation. However, the experimental data is sometimes contradictory and even the thermodynamic data for NbC solubility in austenite have a large scatter. In this paper, experimental results on the Nb(C,N) and NbV(C,N) precipitation kinetics in deformed and undeformed austenite are reviewed. Based on these data and with the precipitation kinetics module of the software package MatCalc, computer simulations are performed. The predicted interfacial energy of precipitates is adjusted to match the observed kinetics. A comparison between experimental information and simulation, i.e. time ‐ temperature ‐ precipitation (TTP) diagrams, is drawn and discussed. The results of the computer simulations using modified interfacial energies are in good agreement with the experiments. 相似文献
45.
According to DIN-ISO 898-1 high tensile bolts of class 8.8 must have a quenched and tempered structure. Therefore either quenched and tempered wire rod is used for cold heading or the bolts are quenched and tempered after the bolt forming process. This paper presents a new wire rod, which offers the chance to get comparable or even better final properties and lower production costs: a low-carbon MnSi wire rod is used as basic material. The final tensile strength is produced by drawing and cold forming. The conventional final quenching and tempering is omitted and for many cases also baking can be avoided. An increased fatigue resistance and the elimination of final straightening of the bolts are additional advantages of the new process. 相似文献
46.
Yoon SH Huang Y Edgar JS Ting YS Heron SR Kao Y Li Y Masselon CD Ernst RK Goodlett DR 《Analytical chemistry》2012,84(15):6530-6537
Surface acoustic wave nebulization (SAWN) is a novel method to transfer nonvolatile analytes directly from the aqueous phase to the gas phase for mass spectrometric analysis. The lower ion energetics of SAWN and its planar nature make it appealing for analytically challenging lipid samples. This challenge is a result of their amphipathic nature, labile nature, and tendency to form aggregates, which readily precipitate clogging capillaries used for electrospray ionization (ESI). Here, we report the use of SAWN to characterize the complex glycolipid, lipid A, which serves as the membrane anchor component of lipopolysaccharide (LPS) and has a pronounced tendency to clog nano-ESI capillaries. We also show that unlike ESI SAWN is capable of ionizing labile phospholipids without fragmentation. Lastly, we compare the ease of use of SAWN to the more conventional infusion-based ESI methods and demonstrate the ability to generate higher order tandem mass spectral data of lipid A for automated structure assignment using our previously reported hierarchical tandem mass spectrometry (HiTMS) algorithm. The ease of generating SAWN-MS(n) data combined with HiTMS interpretation offers the potential for high throughput lipid A structure analysis. 相似文献
47.
Catalina Domínguez Ernst P. Stephan Matthias Maischak 《International journal for numerical methods in engineering》2012,89(3):299-322
In this paper, we developed an a posteriori error analysis of a coupling of finite elements and boundary elements for a fluid–structure interaction problem in two and three dimensions. This problem is governed by the acoustic and the elastodynamic equations in time‐harmonic vibration. Our methods combined integral equations for the exterior fluid and FEMs for the elastic structure. It is well‐known that because of the reduction of the boundary value problem to boundary integral equations, the solution is not unique in general. However, because of superposition of various potentials, we consider a boundary integral equation that is uniquely solvable and avoids the irregular frequencies of the negative Laplacian operator of the interior domain. In this paper, two stable procedures were considered; one is based on the nonsymmetric formulation and the other is based on a symmetric formulation. For both formulations, we derived reliable residual a posteriori error estimates. From the estimators we computed local error indicators that allowed us to develop an adaptive mesh refinement strategy. For the two‐dimensional case we performed an adaptive algorithm on triangles, and for the three‐dimensional case we used hanging nodes on hexahedrons. Numerical experiments underline our theoretical results. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
48.
K. Bobzin F. Ernst R. Nickel J. Rösing Dipl.‐Ing. Y. Rojas 《Materialwissenschaft und Werkstofftechnik》2007,38(7):533-537
Wear Protection of Titanium using Surface Brazing Titanium and titanium alloys possess high specific strengths up to a temperature of about 600 °C in addition to an extraordinary corrosion resistance [1]. The low wear resistance constitutes a crucial impediment for a much broader use. Titanium materials are especially susceptible to friction fatigue and erosion. Coating techniques have to be developed in order to counteract this technical constraint. Surface brazing presents a promising approach. Hard metals mixed with brazing filler metals on a silver and titanium basis were brazed in a vacuum furnace and subsequently characterized. Wear resistance was quantified and optimized using ball on disc measurements. 相似文献
49.
Ernst Schmidt 《Forschung im Ingenieurwesen》1949,16(1):19-29
Zusammenfassung Zur Berechnung von thermodynamischen Arbeitsprozessen von Verbrennungsgasen mit wechselndem Luftgehalt, wie sie besonders bei Gasturbinen in Fraye kommen, werden Diagramme vorgeschlagen, in denen die Enthalpie I und die Entropie & über dem Luftgehalt λ der Verbrennung aufgetragen sind mit Isothermen als Parameterlinien. Die Diagramme berücksichtigen ohne Vernachl?ssigung die ?nderungen der Gaszusammensetzung und die Temperaturabh?ngigkeit der spezifischen W?rme der Gase, sehen aber von deren Druckabh?ngigkeit sowie von Dissoziations-vorg?ngen ab, was bei den für Gasturbinen in Frage kommenden Drücken und Temperaturen ohne merklichen Fehler zul?ssig ist. Ein besonderer, das Zeichnen der Diagramme sehr erleichternder Vorteil ist, da? die Isothermen gerade Linien sind und nichtlineare Abh?ngigkeiten nur in den Randskalen für die Enthalpie und die Entropie auftreten. In den Diagrammen lassen sich auch Gasturbinenprozesse mit W?rmeaustauschern bequem darstellen. VDI 相似文献
50.