Influence of cutting edge geometry and cutting edge radius on the stability of micromilling processes

The occurrence of tool vibrations in the micromilling process is undesirable because of its negative influence on the quality of microstructures. Due to the small dimensions of the undeformed chip parameter, the influence of the cutting edge on the chip formation and on the regenerative effect seems to be larger than in macrodimensions. Within this paper the results of an experimental investigation with micro end-milling cutters (d = 1 mm) are presented. Additionally, the influences of the cutting edge radius, the corner radius, and the feed per tooth on the tool vibration trajectories, the process forces, and chatter and its causes are discussed.     

Bitter-tasting monoglycerides from stored oat flour

Summary From stored ground oat grains with bitter taste a mixture containing 9-hydroxy-trans, cis-10,12-octadecadienoic-1-monoglyceride and 13-hydroxycis,trans-9,11-octadecadienoic-1-monoglyceride was isolated. To prove the structure both compounds were prepared. The threshold for bitter taste of the monoglycerides (1.1–2.2 mol/ml) is lower than that of the free 13-hydroxy-cis, trans-9,11-octadecadienoic acid (7.6–8.5 mol/ml). The corresponding 13-hydroperoxy linoleic acid is not bitter.

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Monoglyceride mit Bittergeschmack aus gelagertem Hafermehl

Zusammenfassung Aus gemahlenem Hafer, der bei der Lagerung bitter geworden war, wurde ein Gemisch bestehend aus dem 9-Hydroxy-trans, cis-10,12-octadecadien-1-monoglycerid und dem 13-Hydroxy-cis,trans-9,11-octadecadien-1-monoglycerid isoliert. Zum Beweis der Struktur wurden die Verbindungen synthetisiert. Die Schwelle für Bittergeschmack der Monoglyceride (1,1–2,2 mol/ml) ist niedriger als die der freien 13-Hydroxy-cis,trans-9,11-octadecadiensäure (7,6–8,5 mol/ml). Die entsprechende 13-Hydroperoxylinolsäure schmeckt nicht bitter.

     

Non-rigid isometric ICP: A practical registration method for the analysis and compensation of form errors in production engineering

The unprecedented success of the iterative closest point (ICP) method for registration in geometry processing and related fields can be attributed to its efficiency, robustness, and wide spectrum of applications. Its use is however quite limited as soon as the objects to be registered arise from each other by a transformation significantly different from a Euclidean motion. We present a novel variant of ICP, tailored for the specific needs of production engineering, which registers a triangle mesh with a second surface model of arbitrary digital representation. Our method inherits most of ICP’s practical advantages but is capable of detecting medium-strength bendings i.e. isometric deformations. Initially, the algorithm assigns to all vertices in the source their closest point on the target mesh and then iteratively establishes isometry, a process which, very similar to ICP, requires intermediate re-projections. A NURBS-based technique for applying the resulting deformation to arbitrary instances of the source geometry, other than the very mesh used for correspondence estimation, is described before we present numerical results on synthetic and real data to underline the viability of our approach in comparison with others.     

Thermomechanical Fatigue Behavior of the Intermetallic <Emphasis Type=Italic>γ</Emphasis>-TiAl Alloy TNB-V5 with Different Microstructures

The cyclic deformation and fatigue behavior of the γ-TiAl alloy TNB-V5 is evaluated under thermomechanical load for three different microstructures. For this purpose, strain-controlled thermomechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400 °C to 800 °C (673 K to 1073 K), and with two different strain ranges to set a fatigue-life relation. Cyclic deformation curves, stress-strain hysteresis loops, and fatigue lives of the tests are presented. The microstructures near-gamma (NG) and duplex (DP) show comparable fatigue lives under all test parameters. The microstructure fully-lamellar (FL) offers longer fatigue lives at the same loading conditions. For a general life prediction, the damage parameter of Smith, Watson, and Topper, P _SWT vs fatigue life, is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition (approximately 750 °C). In the completely brittle material behavior regime the quality of the lifetime prediction is unacceptable. The damage parameter P _HL by Haibach and Lehrke shows a comparable correlation to the fatigue life as P _SWT. The results are discussed with microstructural investigations.     

Reinforcement Learning with Immediate Rewards and Linear Hypotheses

We consider the design and analysis of algorithms that learn from the consequences of their actions with the goal of maximizing their cumulative reward, when the consequence of a given action is felt immediately, and a linear function, which is unknown a priori, (approximately) relates a feature vector for each action/state pair to the (expected) associated reward. We focus on two cases, one in which a continuous-valued reward is (approximately) given by applying the unknown linear function, and another in which the probability of receiving the larger of binary-valued rewards is obtained. For these cases we provide bounds on the per-trial regret for our algorithms that go to zero as the number of trials approaches infinity. We also provide lower bounds that show that the rate of convergence is nearly optimal.     

Computer simulation of the initial rafting process of a nickel-base single-crystal superalloy

Rafting of the γ/γ′ morphology of nickel-base superalloys is a well-known phenomenon during high-temperature deformation. The initial stages of this type of directional coarsening were modeled two-dimensionally by the method of finite elements (FEs) using an energy-perturbation approach. In addition to the elastic energy density, the effect of the local difference of the hydrostatic stresses in γ and γ′ in combination with the different lattice parameters of the two phases was considered in the calculations as a further driving force. From the results of modeling, the deformation-induced internal stresses and strains were determined and used to evaluate the direction-dependent lattice parameters and lattice misfits of the two phases. The results agree well with experimentally determined values.     

A statistical model of fatigue damage evolution in particulate-reinforced metal-matrix-composites

A statistical model of fatigue damage evolution has been developed for particulate-reinforced metal-matrix-composites (MMCs) by taking into considerations both the initial damage distribution and the effect of particulate reinforcement on fatigue damage development. The growth of microscopically fatigue-damaged regions in particulate-reinforced MMCs is considered as a stochastic process, and both the non-equilibrium statistical method and minimum strength principle are used to establish the evolution equation of fatigue damage. The fatigue damage evolution equation developed in the present study characterizes not only the kinetic process of fatigue damage evolution but also sets up the relationship between the mechanism of fatigue damage growth of the microscopically damaged regions and the result of fatigue damage, i.e. degradation of mechanical properties of particulate-reinforced MMCs. A new expression for calculating the cumulative fatigue damage and a new formula for predicting the average fatigue strength of the particulate-reinforced MMCs are derived. Experimental data of 2080Al/SiC_p composites are analysed and compared with results obtained with the present model. It is shown that the experimental results can be described well by the calculations.     

Interlocking intramedullary nailing of pathological fractures of the shaft of the humerus

In previous experiments using the fat substitute sucrose polyester (SPE, or olestra), no compensatory response was observed on day 2 after experimental manipulations, which reduced the percentage of energy from fat to approximately equal to 30% from 40% on day 1. In the present study a more severe manipulation was made; the amount of energy from fat was reduced from 32% to 20% to determine whether such a reduction would provoke any physiologic or behavioral response. Subjects came to the unit for two, 2-d test sessions. Intake on day 1 was fixed: subjects were given meals containing either control fat (11319 kJ, 32% of energy as fat) or SPE (9561 kJ, 20% of energy as fat). On day 2, intake was ad libitum. On day 1 subjects rated themselves as more hungry while consuming the fat-substituted meals than when consuming the control meals and they disclosed greater hunger in the end-of-day questionnaires. The effect of the manipulation was carried over into day 2. By the end of day 2, subjects had compensated for 74% of the energy (fat) deficit caused by the previous day's manipulation. These results differ from those obtained when fat was reduced from 40% to 30% of energy; this more severe reduction reveals that a reduction in fat of this size can lead to a biobehavioral response. Together, these data suggest that people could change their diet to meet dietary guidelines; however, if a more severe reduction is attempted, adherence may be made more difficult by the strength of the compensatory response.