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.     

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.

     

Dynamic analysis of the micromilling process – influence of tool vibrations on the quality of microstructures

Micromilling is a suitable technique for the manufacturing of microstructured parts. The downscaling of the milling process leads to problems, which are caused by the low stability of microtools and their manufacturing. Tool vibrations and runout occur, resulting in poor surface qualities and undesirable surface location errors. The presented results of the experimental analysis include a stability diagram for the spindle speed range of n = 60,000–120,000 rpm and tool vibrations measured in the xy‐plane. Micrographs illustrate the influence of tool vibrations on the quality of the generated surface structures. In addition, the dynamic runout is characterized and its effects are discussed.     

Controlled Nitriding

A nitriding process is governed by the chemical potential of the saturating medium, the kinetics of mass transfer, and the composition and structure of the surface layer of parts. Controlled nitriding involves control of thermodynamic and kinetic parameters and of surface activation. The chemical potential of nitrogen, carbon, and oxygen in the saturating medium can be characterized by the parameters K _N, K _C, and K _O. In order to control the quality and obtain a nitrided layer with specified structure, they should be monitored and regulated. The values of K _N, K _C, and K _O are determined in an in-situ mode using gas analyzers based on solid electrolyte cells. The recently developed hydrogen sensors supplement the range of gas analyzers. In-situ control of a nitriding process with the help of analyzers makes it possible to meet the requirements on the surface layer, prevent disturbance of the equilibrium due to uncontrolled arrival of oxygen, and ensure the requisite proportion of the gas phases, thus optimizing the structure of the layer and its quality.     

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.     

会聚束电子衍射研究蠕变镍基高温合金中γ和γ^1相的局域应变分布

用高分辨率会聚束电子衍射方法（CBED）测量了单晶镍基高温合金CMSX-6在980℃蠕变后γ和γ^1两相中的弹性应变分布，测量表明在水平和垂直的γ通道中存在着弹性应变的差别，这种差别被认为是筏化的驱动力．在γ^1相中还观察到弹性应变的不均匀分布。     

Modelling, simulation and experimental investigation of chip formation in internal traverse grinding

We present recent developments in modelling and simulation of internal traverse grinding, a high speed machining process which enables both a large material removal rate and high surface quality. We invoke a hybrid modelling framework, including a process scale model, simulations on a mesoscale capturing the proximity of a single cBN grain and an analysis framework to investigate the grinding wheel topography. Moreover, we perform experiments to verify our simulations. Focus in this context is the influence of the cutting speed variation on the grain specific heat generation.     

On the formation of ridges and burnished debris along internal fatigue crack propagation in 42CrMo4 steel

A detailed microscopic analysis of fracture surfaces of 42CrMo4‐hardened steel after ultrasonic fatigue testing revealed globular and cylindrical particles located in ridges along the crack propagation direction. Observed particles could be easily taken for non‐metallic inclusions; however, chemical analysis showed that they are of the same composition as the steel matrix. The formation of such round‐shaped debris was found to be a result of cutting out the matrix fragments by ‘en passant’ cracks interaction and their subsequent fretting burnishing. Possible correlation of the parameters of ridges and debris with cyclic plastic zone width and martensite structure is discussed.     

A macroscopic approach towards the finite element simulation of tapping and thread milling of continuously reinforced extrusions

The Finite Element Analysis (FEA) is a suitable tool for the process design and the determination of technical failure. Within this paper, the FEA is used for simulating and analyzing the thread milling process and the tapping process for reinforced lightweight extrusion profiles. Two different finite element models are developed to simulate both processes. An elastic material behavior is implemented in the simulation. For the tapping process, the computed stresses during the process as well as the geometrical displacements are considerably higher than the stresses computed for the thread milling operation. This is caused by the lower mechanical loads occurring in the thread milling process. The results can be used to identify areas of high stresses which may cause material failure. Moreover, both processes can be analyzed with respect to their influence on the workpiece. The simulation results are compared to experiments.