Search

This paper presents a Computational Fluid Dynamics (CFD) simulation of the quenching process based on ISO 9950, focusing on the heat flux and heat transfer coefficient integrated over a metal specimen. The numerical method, which employs the two-fluid VOF method and frozen turbulence approach (Cukrov et al., Appl. Sci. 2023, 13, 9144), is used for the transient simulation. Since quenching processes involve complex boiling phenomena shifting from film boiling to nucleate boiling, a standard method based on VOF cannot be applied. The comparison of the simulation results with the ones obtained using correlation, and the data obtained using the Inverse Heat Transfer Analysis (IHTA) method have revealed that the proposed method can accurately predict the heat flux and heat transfer coefficient in the film boiling regime of the immersion quenching process. Note that the previous paper (Cukrov et al., Energies. 2023, 16, 7926.) presented the immersion process modeling and the temperature distribution, while the current paper examines the heat transfer characteristics of the immersion quenching process.

Skeleton curve-guided five-axis sweep scanning is an emerging surface inspection technique with marvelous inspection efficiency. The precondition of applying such a technique to a complex surface is to extract the skeleton curves of a two-manifold surface associated with partitioning the surface into compact surfaces. However, the work on extracting skeletons of two-manifold triangle mesh surfaces is scarce, as existing skeletonization methods mostly focus on either 2D planar shapes or 3D solid shapes. In this paper, we present a new approach to extract the skeletons on a two-manifold triangle mesh with boundaries. The skeletons are formed in the most intuitive manner of wave front propagation which is based on computing the initial value problem of geodesics on a triangle mesh. The step-length of wave front propagation is adaptively controlled to guarantee the appropriate density of skeleton points for having good connectivity. Experiments show that, as a direct application of the proposed skeleton generation and its associated surface partitioning result, the five-axis sweep scanning path of complex free-form surface can be generated conveniently. Experimental results also validate that the computation of our proposed approach is simpler and faster than the state-of-the-art geodesic Voronoi diagram (GVD) method when most of the two-manifold triangle mesh is nearly planar. Additionally, the augmented parameter used for tracing the wave front's geodesic propagation information is helpful for the skeleton-based surface partition, which is necessary for skeleton curve-guided five-axis sweep scanning. [ABSTRACT FROM AUTHOR]

As a new contacting surface inspection technology, five-axis continuous sweep scanning enables a much higher inspection efficiency compared with the traditional three-axis point-by-point inspection. However, currently how to plan an interference-free scanning path for an arbitrary free-form surface still heavily depends on human intervention and the scanning path thus obtained lacks severely in inspection efficiency since the unique kinematic characteristics of the five-axis inspection are ignored. Motivated by these deficiencies, this paper proposes a practical algorithm for automatically generating an interference-free and efficient five-axis continuous scanning path for an arbitrary free-form surface. The algorithm adopts the guiding-path + trajectory-curve paradigm for the generation of scanning curves while the collision-free constraint on the stylus is taken care of by considering the aggregate accessibility of the reference curves. A digraph is then constructed on the aggregated accessibility domains of the sample points of the guiding path and the stylus orientation along the guiding path is determined by finding the shortest path in this graph. A simple surface partitioning scheme is also introduced in case a surface cannot be scanned in a single pass and needs to be divided into suitable smaller patches. Preliminary experiments in both computer simulation and physical inspection of the proposed algorithm validate that, when compared with the two leading commercial solutions, the proposed algorithm not only is fully automatic without relying on human intervention but also achieves a much higher inspection efficiency. [ABSTRACT FROM AUTHOR]

The Finite Volume Particle Method (FVPM) is a meshless method for simulating fluid flows which includes many of the desirable features of mesh-based finite volume methods. In this paper, we develop a new 3-D FVPM formulation that features spherical kernel supports. The formulation is based on exact integration of interaction vectors constructed from top-hat kernels. The exact integration is obtained by an innovative surface partitioning algorithm as well as precise area computation of the sphere subsurfaces. Spherical-support FVPM improves the recently developed cubic-support version in two main aspects: spherical kernels have no directionality and result in smooth interactions between particles, leading to an improved method. We present three test cases that illustrate the improved accuracy and robustness brought by the spherical kernel. Although computations are 1.5 times slower on spherical support than cubic support, the cost is more than compensated by lower error with a higher convergence rate. [ABSTRACT FROM AUTHOR]

The present work is a continuation of the first part of the article and is devoted to the geometric calculation of shape parameters of the working surfaces of disk-shaver teeth for use in finishing cylindrical gears with an evolvent profile. A method has been proposed for determining the shape of the working surfaces in disk-shaver teeth during the recessed shaving of cylindrical gears with technologically modified teeth. In this case, the machined gear tooth surfaces are discretely specified, and consequently familiar analytical methods of tool profiling are unacceptable. [ABSTRACT FROM AUTHOR]

We present a theoretical study of a problem related to optimal free-form surface partitioning, which arises in surface machining in manufacturing. In particular, we consider partitioning a free-form surface in 3-D into two subsurfaces subject to a global objective function. As a key subroutine, we develop new algorithms for the geometric problem of processing an off-line sequence of insertions and deletions of convex polygons alternated with point membership/proximity queries on the common intersection of the polygons. We show how this subroutine can be used to solve surface 2-partitioning. Our algorithm for the 2-partitioning problem takes $\tilde O({m^2}n)$ time, where m is the number of polygons of size O(n) each. This improves the asymptotic time complexity of the previous best-known O(m2n2)-time algorithm. Our algorithms may be applicable to other accessibility and partition problems involving free-form surfaces in computer graphics and manufacturing. From the computational geometry point of view, our method combines nontrivial data structures, geometric observations, and algorithmic techniques that may be used to solve other geometric problems. For example, our algorithm can process O(n) insertions and deletions of convex polygons (of size O(n) each) and queries on their intersections in O(n2log log n) time, improving the "standard" O(n2log n) time solution. [ABSTRACT FROM AUTHOR]

The present work is devoted to the geometric calculation of shape parameters of the working surfaces of disk-shaver teeth for use in finishing cylindrical gears with an evolvent profile. These are primarily gears for the transmissions of cars and light trucks, which must meet strict noise requirements. This imposes corresponding requirements on their machining precision. [ABSTRACT FROM AUTHOR]

This paper describes a simple but effective method for partitioning free-form surfaces. Here, based on the surface curvatures, a free-form surface can be successfully partitioned into convex, concave and saddle regions. The chain code technique in the image processing field is applied to determine the boundaries of each region. These regions can be separately machined by different kinds and sizes of cutting tool. Therefore, the machining time can be reduced significantly. A B-spline surface is given as an example to demonstrate the proposed method including partitioning and machining. A Matlab® program was developed to perform the surface partitioning task and to get the coordinates of all points on the boundaries. Pro/Engineer® Wildfire 2.0 was used to create the computer-aided design (CAD) model of the free-form surface and generate the tool path for each region for illustration purposes. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a systematic scheme for developing feasible tool-paths for machining a sculptured surface on a multi-axis NC machine. In our previous paper (in CAD journal), a simplified problem of CT-dependent partitioning of a sculptured surface is solved with application of the focal surfaces. The derived solution to the problem is convenient for particular cases when the angle of the surfaces and local relative orientation is identical to zero (). In general case of sculptured surface machining on multi-axis NC machine, the identity often doesn’t observe. Here this problem is enhanced up to cases when the actual value of the angle could be of arbitrary value. The reported approach is based on application of the characteristic surfaces of novel kind. The characteristic surfaces of the newly discovered kind are referred to as the characteristic -surfaces. The reported solution to the problem is based on implementation of the DG/K-method of surface generation. The methodology presented here is a general one. It combines the activities of exploration of topology of a given sculptured surface, of the generating surfaces of the cutting tool, of the cutting tool configuration and of the cutting tool motion that it performs in the machining operation relative to the work, thus making the production process flexible, automatic and controllable. The approach is the CAD/CAM orientated one. The effectiveness of the proposed approach is verified from numerical simulation. Perfect correlation of the reported results with those previously published by the author, as well as by other researchers, is observed. [Copyright &y& Elsevier]

Abstract: Topic of the paper is in the area of sculptured surface machining (SSM). The objectives of the paper are as follow. Firstly, to develop an approach that enables one detecting regions of sculptured surface those are not accessible for a cutting tool of a given design (i.e. regions, which cutter cannot reach without being obstructed by another portion of the part). Secondly, if we observe any not-machinable regions, the approach to be developed has enable one to subdivide the sculptured surface P onto the cutter-accessible and onto the cutter-not-accessible regions. To resolve the problem of sculptured surface partitioning, focal surfaces for the surfaces P and T were applied. Based on implementation of focal surfaces, cutting-tool-dependent characteristic surfaces are introduced. This enables derivation of equation for boundary curve, and enhancing the developed approach for locally extremal kinds of tangency of the surfaces P and T. The effectiveness of the proposed approach is verified from numerical simulation with the simple and clear examples. The main advantage of the developed approach over existing methods is that it incorporates topology not only of sculptured surface to be machined but also topology of the machining surface of a tool to be applied. This makes obtained results more fitted for engineering application. Taken as a whole, the topic covered in this paper enables one to develop reliable software for machining the sculptured surface on multi-axis CNC machine. [Copyright &y& Elsevier]

A novel method for laser processing freeform surfaces is proposed and demonstrated in this article. The method employs empirical data on the 3D limitations of a given laser process, namely the negative effects of focal offset and angle of incidence on the process performance, to partition a freeform surface into triangular laser processing fields. In this way, processing efficiency can be maximized by minimizing part repositioning while fully utilizing the capabilities of high dynamics galvo scanners. In this proof of concept, the surface of 3D printed Ti–6Al–4V spherical shells was improved by more than 90% and subsequently textured, using the proposed method. Conclusions were made about the advantages of this new approach for processing freeform surfaces consistently and efficiently. Image 1 • A novel and efficient method for laser processing freeform surfaces is proposed and demonstrated. • Common tessellation algorithms were utilized to generate the largest possible laser patches while maintaining process performance. • The surface roughness of additively manufactured Ti–6Al–4V was reduced by up to 96% using ns laser polishing. • LIPSS were successfully produced on rough additively manufactured 3D parts after laser polishing them. [ABSTRACT FROM AUTHOR]

Surface properties of aqueous solutions are important for environments as diverse as atmospheric aerosols and biocellular membranes. Previously, we developed a surface tension model for both electrolyte and nonelectrolyte aqueous solutions across the entire solute concentration range (Wexler and Dutcher, J. Phys. Chem. Lett. 2013, 4, 1723-1726). The model differentiated between adsorption of solute molecules in the bulk and surface of solution using the statistical mechanics of multilayer sorption solution model of Dutcher et al. (J. Phys. Chem. A 2013, 117, 3198-3213). The parameters in the model had physicochemical interpretations, but remained largely empirical. In the current work, these parameters are related to solute molecular properties in aqueous solutions. For nonelectrolytes, sorption tendencies suggest a strong relation with molecular size and functional group spacing. For electrolytes, surface adsorption of ions follows ion surface-bulk partitioning calculations by Pegram and Record (J. Phys. Chem. B 2007, 111, 5411-5417).