Swept Surface Research Articles

Surface reconstruction from FE mesh model

Abstract In the computer aided engineering process with finite element analysis, a CAD surface model is sometimes needed for various tasks such as remeshing, shape optimization or design modification. Occasionally, engineers who perform an analysis at the product design stage are given only finite element mesh models; corresponding CAD models can be unavailable. This paper presents a method to extract free-form B-spline surfaces and certain feature curves from a surface mesh model. First, using the k-means clustering method, our process segments given meshes into a number of regions according to principal curvature information; then, region operations are performed. Next, each region is converted to an approximately free-form B-spline surface. In the last step, feature curves to create loft or sweep surfaces are calculated by minimizing the distance error. Some practical examples are also presented to demonstrate the effectiveness and usefulness of our method. Highlights We propose a new method of creating CAD surfaces from given finite element mesh model. Feature curves are extracted for creating sweep or loft surfaces. By using the generated surfaces based on the feature curves, the shape modification can be easily performed in the designing process.

Development of 3D cartoon by using B-spline and sweep surface method

Development of 3D cartoon by using B-spline and sweep surface method

Real-time bone sawing interaction in orthopedic surgical simulation based on the volumetric object

Bone sawing is widely used for mandibular angle reduction. In this paper, we develop a surgical simulator for mandibular angle reduction with real-time collision detection, bone reconstruction and force haptic. A volume-based model was organized following the CT or MRI image sequence arrangement. The surgical instrument was simplified into two triangles in geometric model. Then, a new volume-based collision detection method was used to meet the real-time requirements of the simulator. Currently, most of the bone sawing operations regarded the swept surface as the real cut surface of bone. Due to the high-speed reciprocating of the bone saw operation, we innovatively used Marching Cubes Method for the real-time reconstruction of the bone internal sawing part and provided the users with a fine cutting surface. In addition, to obtain a well virtual effect, a simplified bone removal and reconstruction method is carried out to implement the real-time topological changing of the mandibular surface. This paper presents a mechanistic model for prediction of the force during bone sawing, and the simulated force is similar to the measured force in real surgery. Eventually, we realized the high quality visual rendering and tactile rendering, the refresh rate of the force reaches 1000 Hz, and visual refresh frequency up to 30 Hz. To validate the effectiveness of the system, some experiments of simulator evaluation based on the patient-specific data was constructed. Results shown that the virtual orthopedic surgical simulation system can provide inexperienced interns and students with a low-cost, repeatable surgical training platform.

Magnetization in narrow ribbons: curvature effects

A ribbon is a surface swept out by a line segment turning as it moves along a central curve. For narrow magnetic ribbons, for which the length of the line segment is much less than the length of the curve, the anisotropy induced by the magnetostatic interaction is biaxial, with a hard axis normal to the ribbon and an easy axis along the central curve. The micromagnetic energy of a narrow ribbon reduces to that of a one-dimensional ferromagnetic wire, but with curvature, torsion and local anisotropy modified by the rate of turning. These general results are applied to two examples, namely a helicoid ribbon, for which the central curve is a straight line, and a Möbius ribbon, for which the central curve is a circle about which the line segment executes a twist. In both examples, for large positive tangential anisotropy, the ground state magnetization lies tangent to the central curve. As the tangential anisotropy is decreased, the ground state magnetization undergoes a transition, acquiring an in-surface component perpendicular to the central curve. For the helicoid ribbon, the transition occurs at vanishing anisotropy, below which the ground state is uniformly perpendicular to the central curve. The transition for the Möbius ribbon is more subtle; it occurs at a positive critical value of the anisotropy, below which the ground state is nonuniform. For the helicoid ribbon, the dispersion law for spin wave excitations about the tangential state is found to exhibit an asymmetry determined by the geometric and magnetic chiralities.

Surface editing using swept surface 3D models

This paper presents a system for editing strip-like patches on the mesh using swept surface. The user first selects a rough cylinder-like region, the boundary of which is automatically refined. A swept surface approximation is automatically done, including extraction of the trajectory and the corresponding deforming 2D curves. The swept surface is described by a map from a real interval to both rigid body deformations and 2D curves. These 2D curves are analyzed and decomposed into many elements, which can be edited respectively, and a novel pattern analysis is also performed on these elements to extract curve patterns. These 2D curves serve as handles for controlling the geometry, and modifications to them can change the geometry directly. Thus, users can just edit the pattern or element curve to control the global geometry. We show the novelty and efficiency of our framework using varietal demonstrations.

A Generic Multi-Axis Post-Processor Engine for Optimal CNC Data Creation and Intelligent Surface Machining

This paper focuses on the development of a multi-axis post-processor engine with a curvature-based feed adaptation module, capable of extracting generic CNC data for high precision machining. The motivation of this work stems from the drawback of standard and commercial post-processors to modify their internal source codes so as to be implemented to newly-developed functions which integrate modern CNC units. The multi-axis post-processor proposed in this work operates as a stand-alone function of an artificial intelligent module that optimizes machining parameters for standard swept cut multi-axis surface tool-paths. The post-processor developed receives APT source files previously been optimized by means of a genetic algorithm that handles cutting tool selection; radial cut engagement; maximum discretization step; lead and tilt angles. The algorithm optimizes the aforementioned machining parameters towards the minimization of the number of cutter locations found in a specific APT source file as well as the surface machining error as a combined effect of chordal deviation and scallop height. The final APT output is then properly handled by the post-processor engine so as to extract the final ISO code for a double-pivoted head 5-axis CNC machine and compute optimal values for feed rate in each NC block considering the interpolation error and curvature analysis given the surface properties. To simulate and verify our proposals, the MAZAK Vortex 1000 gantry-type 5-axis CNC machine tool equipped with a Fanuc 15i CNC unit has been selected as the manufacturing resource corresponding to the final CNC output that the proposed post-processor computes. A benchmark sculptured part is created and used for the virtual material removal simulation in CATIA® V5 R18. For that part, both the proposed post-processor engine and a commercially available post-processor were employed to extract G-code data whilst it was shown that identical outputs were obtained.

A Software Tool for Heart AVJ Motion Tracking Using Cine Cardiovascular Magnetic Resonance Images.

One important index to assess left ventricular diastolic function is the quantitative measurement of atrioventricular junction (AVJ) motion in one cardiac cycle including systole and diastole. The best way to perform the measurement is to use a software tool that can conduct AVJ motion tracking from cine cardiovascular magnetic resonance (CMR) images. In this paper, a software tool for this purpose is presented by using the insight segmentation and registration toolkit (ITK), the visualization toolkit (VTK), and Qt. We propose a surface area-based tracking approach in the software tool. In the tracking approach to obtain the surface area swept by six points being tracked, we manually select six points from four-, three- and two-chamber views of CMR images. After that, we reconstruct the 3-D coordinates of the six points from image acquisition parameters extracted from DICOM files. We perform interpolation by using parametric cubic curve fitting techniques. From the curve fitting results, we finally obtain the surface areas for all time points in one cardiac cycle. The software tool has been successfully implemented. The functionality include single point-based tracking, surface area-based tracking by using 6 tracked points, generation of displacement, sweep surface area and velocity, and generation of tracking movies. From the software engineering practice, it is concluded that ITK, VTK, and Qt are very handy software systems to implement automatic image analysis functions for CMR images, such as quantitative measure of motion by visual tracking. The software tool provides a convenient and efficient way to measure AVJ motion and extends the scope of methods for ventricular function assessment.

STEP-based feature recognition from solid models having non-planar surfaces

To enhance the interoperability of different CAD systems, 3D B-rep models should be represented in a neutral file format. Standard for exchange of product model data (STEP) is a neutral format that supports the representation of product model data from its geometrical and topological information to life cycle data. In this work, STEP-based feature recognition (FR) system is developed, which is capable of recognising the features having non-planar surfaces from solid models represented in STEP AP203 format. The considered non-planar surfaces are elementary (cylindrical, conical, spherical, toroidal) and advanced surfaces (i.e. B-spline and swept surfaces). The STEP AP203 file is accessed through Java Standard Data Access Interface (JSDAI). The recognition of considered non-uniform elementary and advanced surface features is performed by exploring the geometry and topological representation schema of the surfaces in STEP AP203 file in two phases. In the first phase, the surface and the edge-level geometrical and topological information of the considered object is extracted. In the second phase, the features with non-planar surfaces are recognised and presented as per the data needed for STEP AP224 format. Since the FR system uses STEP AP203 file as input, after recognising features, there is minimum chance of losing information from CAD model to feature representation. The developed FR system is demonstrated with a blow moulding die, which is having different non-planar elementary and advanced surfaces. The output information of the developed FR system is useful for downstream application such as automatic generation of STEP-NC programs.

Fabrication and hydrogen permeation through novel BaZr0.9Y0.1O3−δ – Cu composite ceramic-metallic membranes

This study is the first report of a dense BaZr0.9Y0.1O3−δ – Cu (BZY–Cu) ceramic-metallic (cermet) composite membrane for high-temperature hydrogen separation. BZY serves as a proton conductor, while Cu provides electronic conductivity for charge compensation. A novel molten-copper infiltration technique is used to form a dense cermet membrane by infiltrating a porous BZY substrate. A porous BZY “skeleton” is fabricated from a spray-dried powder provided by CoorsTek, consisting of the pre-cursor oxides BaSO4, ZrO2, and Y2O3. The powder is dry pressed into pellets. These pellets then undergo solid-state reaction and sintering in one step at 1650 °C for 10 h to form the porous ceramic skeleton. Cu and CuO powders are mixed to form a powder containing 8 at.% O. This powder is uniaxially pressed into a pellet, that is placed on top of the BZY skeleton. The skeleton and Cu–CuO pellet are placed into a controlled-atmosphere furnace, and heated to 1200 °C in a 330 ppm oxygen environment (balance argon). Under these conditions, the liquid Cu–O spontaneously infiltrates the BZY skeleton. While dwelling at 1200 °C, the gas environment is changed to a 10 mol.% hydrogen environment (balance argon) for 12 h. Then the sample is cooled to 450 °C and annealed for 24 h to reduce residual stresses within the membrane. Electron micrographs of the resulting membranes reveal that the cermet is nearly fully dense.Hydrogen permeation through a 1.90 mm thick BZY–Cu membrane was measured as a function of temperature and hydrogen partial pressure gradient. A maximum flux of 2.42 × 10−3 mLSTP cm−2 min−1 was observed at 882 °C with a 1.0 atm hydrogen partial pressure gradient. The contribution of hydrogen evolution due to water-splitting at the sweep surface was examined by varying the humidification of the feed and sweep gas streams. Degradation of performance was not observed over the course of 30 days of testing; rather, a slight increase was seen. Electron micrographs of the BZY–Cu membrane after testing do not reveal porosity or cracking through the bulk thickness of the membrane. However morphological changes were observed at the surfaces. On the feed surface (highly reducing environment), Cu has left the BZY skeleton and formed Cu spheres on the surface. On the sweep surface, this de-wetting is more pronounced. Copper has also left the BZY skeleton and formed a nearly dense, non-hermetic layer of pure Cu. These changes effectively reduce the membrane thickness while also increasing surface roughness and the area of the gas–solid interface. This may explain the apparent increase in performance over time.

Determination of cutter-head geometry for the face-milling of hypoid gears

Special-purpose multi-axis CNC machines are used for the face-milling of hypoid gears. These machines are equipped with specially design cutter-head, consisting of inside and outside blades, to machine the convex and concave sides of the gear teeth. In this research, CAD model of a face-milling cutter-head is developed, in which side cutting edges of inside and outside blades of the cutter system are built on the rake face. Since the side cutting edges are not on the axial plane of the cutter, the sweep surface formed by the cutting edges are hyperboloids, rather than the cylindrical surfaces as assumed in the other researches. Due to the hyperboloid sweep surfaces of the cutter, the gear teeth formed by the face-milling have not only curvature along the length of the teeth but also have curvature along the flank-wise direction. It leads towards the result that the blade angles are not equal to the flank angles of the gear teeth at the mean point. Therefore, a CAD-based cutter geometry determination model is built, to calculate the geometry parameter of the cutter-head, such as blade angles and the average cutter radius, for the given parameters of the gear teeth at the mean point.

Kodama-Schwarzschild versus Gaussian Normal Coordinates Picture of Thin Shells

Geometry of the spacetime with a spherical shell embedded in it is studied in two coordinate systems: Kodama-Schwarzschild coordinates and Gaussian normal coordinates. We find explicit coordinate transformation between the Kodama-Schwarzschild and Gaussian normal coordinate systems. We show that projections of the metrics on the surface swept by the shell in the 4D spacetime in both cases are identical. In the general case of time-dependent metrics we calculate extrinsic curvatures of the shell in both coordinate systems and show that the results are identical. Applications to the Israel junction conditions are discussed.

An accurate approach to determine the cutting system for the face milling of hypoid gears

In this research, mathematical model of an accurate cutting system for the face milling of hypoid gear is developed. For the machining of hypoid gear, a conventional cutter system is considered, which contains the groups of inside and outside blades. These blade models are called accurate due to the consideration of rake, hook, relief and pressure angles in the design. Mathematical representation of the tooth cutting edges of the blades is developed. By assembling the blade models in the cutting system and revolving it around the cutter rotation axis, swept surface and profiles of inside and outside blades are generated. Using the local synthesis method, determination of cutting system geometry is performed for the given parameters of the gear. In cutting system parameters, average cutter radius and pressure angles of the tooth cutting edges are the variables in this algorithm, whereas the hook, rake and relief angles are assumed to be given. Sensitivity analysis is performed, to analyse the sensitivity of the cutting surface, with respect the blade’s rake and hook angle. Finally, an application is presented for a standard gear geometry. A cutter system is determined for the gear and it is virtually face milled, and the geometric parameters are validated against the given parameters of the gear.

Interactive tree modeling and deformation with collision detection and avoidance

AbstractWe present an interactive tree modeling and deformation system that supports an efficient collision detection and avoidance using a bounding volume hierarchy of sweep surfaces. Starting with conventional tree models (given as meshes), we convert them into sweep surfaces and deform their branches interactively while detecting and avoiding collisions with many other branches. Multiple tree models (sharing the same topology) can be generated with great ease using this sweep‐based approach, and they can serve as a basis for the generation of a multiparameter family of trees. We demonstrate the effectiveness of our approach in an automatic generation of similar trees, the colonization of trees to form a forest, and the tree growth, aging, and withering simulations. Copyright © 2015 John Wiley & Sons, Ltd.

Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions at extreme temperatures (>800°C). This is especially true when fuels are present at the permeate surface. For both inert and reactive (fuels) operations, solid-state oxygen surface vacancies (δ) are ultimately responsible for driving the oxygen flux, JO2. In the inert case, the value of δ at either surface is a function of the local PO2 and temperature, whilst the magnitude of δ dictates both the JO2 and the inherent stability of the material. In this study values of δ are presented based on experimental measurements under inert (CO2) sweep: using a permeation flux model and local PO2 measurements, collected by means of a local gas-sampling probe in our large-scale reactor, we can determine δ directly. The ITM assessed was La0.9Ca0.1FeO3−δ (LCF); the relative resistances to JO2 were quantified using the pre-defined permeation flux model and local PO2 values. Across a temperature range from 825°C to 1056°C, δ was found to vary from 0.007 to 0.029 (<1%), safely within material stability limits, whilst the permeate surface exchange resistance dominates. An inert JO2 limit was identified owing to a maximum sweep surface δ, δmaxinert. The physical presence of δmaxinert is attributed to a rate limiting step shift from desorption to associative electron transfer steps on the sweep surface as PO2 is reduced. Permeate surface exchange limitations under non-reactive conditions suggest that reactive (fuel) operation is necessary to accelerate surface chemistry for future work, to reduce flux resistance and push δpast δmaxinert in a stable manner.

Comparison of the Goryachkin Theory to Soil Flow on a Sweep

The Goryachkin trihedral wedge theories describe soil flow over a surface resembling the wing of a sweep. The current study tested the Goryachkin crushing and lifting theories’ prediction of soil flow across a sweep by comparing with measurements from observed soil flow. Treatments included sweeps with three different rake angles (13.5, 16, and 44°) operated at three speeds (5, 7, and 9 km/h) and at two depths (50 and 100 mm). Flow direction was determined from scratch marks on the sweep surface.

Reproductive biology of NW Mediterranean tonguefish Symphurus nigrescens and Symphurus ligulatus

The population structure and reproductive biology of deep-water continental margin Cynoglossidae is poorly known. Here, we focused on two highly abundant species of the upper slope of the NW Mediterranean Sea, Symphurus nigrescens and S. ligulatus. Megafaunal sampling of 37 hauls was conducted between April 2003 and May 2004 in the Blanes canyon and the adjacent open slope between 300–1500 m depth. The differential bathymetric distribution between the two species was surveyed by standardizing catch data per unit of swept surface and by pooling resulting densities by 100 m depth interval. Females of both species were classified into a five-stage maturity scale according to their external appearance and their gonads dissected for histological analysis. The analysis of the species' bathymetric distribution revealed a differential and only partial overlap. In both species, an increase in size with depth was observed coinciding with the dominance of females in deeper depth strata. The shallower species, S. nigrescens showed a marked spawning period with a peak in summer. In contrast, the deeper-living species, S. ligulatus, presented a longer spawning period ranging from spring to autumn. Moreover, histological examination demonstrated that the ovaries of both species had an asynchronous organization. Present results on spatial-temporal size frequency distribution, spawning temporality and oocyte size are discussed assuming interspecific competition and the different environmental conditions related to their bathymetric distribution.

Modeling of cutting forces in orthogonal turn-milling with round insert cutters

Accurate prediction of cutting force plays an important role in simulation and application of orthogonal turn-milling operation. However, the existing cutting force models for this operation are limited to the case with flat-end cutters, which is not enough in practice. The objective of this paper is to extend the simulation of cutting forces in orthogonal turn-milling into the case with round insert cutters. To achieve this goal, the basic kinematic relationship between the tool and the part is discussed firstly in detail. Then, the approaches to determine two vital factors, namely undeformed chip thickness and the tool-part engagement region are presented. With the real swept surface of the cutting edge replaced by the geometry envelop of the tool, the analytical formulation of the undeformed chip thickness is derived. The engagement region is determined by judging the positions of discretized cutting edge elements and the in-process workpiece surface, which is described by the mapped grids. Using the cutting coefficients calibrated through experiments, cutting forces are calculated. Validation experiments under different conditions were conducted on a turn-mill machine tool with rotating cutting force dynamometer used. The results prove that the proposed model is capable of predicting cutting forces accurately both in shape and magnitude.

Surfaces for modeling arteries in virtual reality simulators

We propose a surface model that can be used as part of an internet based educational medical simulator to train physicians in cardiovascular interventions. This is the first step towards building a real device which can be placed in a remote laboratory and operated upon by physicians from the comfort of their homes. The model assembles arteries and has planar segmentation to increase efficiency of the collision-detection algorithm. It is based on Sweep Surfaces and can be extended to T- and Y-like bifurcations with small mesh deformations. We also describe a continuous force vector field, representing the interaction between the catheter and the surface. The computation time is almost unaffected when the resolution of the artery is increased, and the algorithm allows real-time executions which are very important for remote learning.

The Construction of Sweep Surface Based on Precision Control

Sweep is useful in CAD modeling process. But its precision is hard to control when we use discrete modeling method. In this paper, the sweep surface is constructed by projected-based approach. Vector and distance methods are proposed to detect the local self-intersection of sweep surface. Beside these, it gives the precision control methods in the corner of sweep surface to improve the precision. Finally, we discuss the factors that influence the precision of sweep surface.

Measuring the oxygen profile and permeation flux across an ion transport [formula omitted] membrane and the development and validation of a multistep surface exchange model

A novel ion transport membrane laboratory reactor is introduced which can sample gases at the La0.9Ca0.1FeO3−δ membrane surface at high temperature flux conditions. Experimental data (spatial profiles and operating condition sensitivity) is presented and used to validate detailed 1D and 2D numerical models under inert (CO2 sweep) operating conditions; the numerical models account for mass transfer resistances to the membrane surface. Bypassing the mass transfer resistances experimentally allows for direct parameterization of a three resistance oxygen flux model; a unique solution method based on bespoke experimental datasets to find surface exchange reaction rate constants is demonstrated. Membrane operating regimes and oxygen off-stoichiometric coefficients can thus be determined highlighting the importance of surface exchange studies and the obvious requirement to reduce sweep surface PO2 through oxyfuel reaction integration and/or flow field adjustments. A more complex first-order flux model is also proposed and tested incorporating the surface oxygen ion concentrations in the surface exchange reactions; this is found to give similar material parameters to the simpler zero-order model studied in the literature for this particular case.