Complex Geometrical Conditions Research Articles

Surface integrity of gear shot peening considering complex geometric conditions: A sequential coupled DEM-FEM method

Shot peening is widely used in gear surface strengthening. Due to the complex 3D geometry of the gear target, the collision of shots occurs in the tooth space, resulting in the different shot dynamic and nonuniform features of surface integrity along the tooth profile. The existing models cannot accurately predict the surface integrity of gear shot peening, which hinders the process improvement. In this paper, a sequential coupled DEM-FEM method is proposed. The DEM model is used to represent the collision between shots and the final velocity distribution. Besides, with the determined shot kinematics, the FEM simulation for the gear shot peening process and its time optimization strategy are presented. The proposed method is validated by the gear shot peening tests. Based on the proposed method, the influence of gear geometry on shot impacts and uniformity of tooth surface integrity (surface roughness, surface topography, and compressive residual stress field) is investigated. This study provides an effective tool for optimizing gear shot peening technology and could be extended to other industrial parts with complex shapes.

Simulation and experimental research of tool path planning on profile and surface generation of aspherical-cylindrical lens array by ultra-precision envelope grinding

Profile accuracy and surface quality of microstructural array mold generated by ultra-precision machining are the premise of precision glass molding technology. Most optical applications of microstructural array mold need to obtain microstructures with sub-micron profile accuracy and nanoscale surface roughness. However, the structural characteristics of grinding wheel and array leads to the complexities of surface generation in envelope grinding. Experimental verification is time-consuming and laborious. In this paper, a multi-scale model is proposed to predict the surface topography of micro-aspherical-cylindrical structural array (MACSA) mold ground by different tool paths. Firstly, the ultrathin grinding wheel is reconstructed by considering the distribution characteristics of abrasive grains and the complex wheel profile. In this process, the grain distribution characteristics of the reconstructed grinding wheel are obtained by using the Johnson transformation the inverse Johnson transformation method. Then, a comprehensive model is established to understand the mechanism of the generation of the MACSA surface, which considers the wheel topography, the kinematics model of abrasive grains and the complex geometric conditions between tool and local surface profile in envelope grinding. The surface morphologies of MACSA obtained by simulation and experiment are coincident with each other very well. The simulation model is further verified by comparing the power spectral density (PSD) of the experimental and simulated surfaces. Based on the simulation and the experimental results, the effect of three tool path planning methods (constant step, constant arc length and constant scallop-height) on surface uniformity and profile accuracy is investigated to obtain a more uniform microstructural surface.

Application of New Triple Hook-Shaped Conformal Cooling Channels for Cores and Sliders in Injection Molding to Reduce Residual Stress and Warping in Complex Plastic Optical Parts.

The paper presents a new design of a triple hook-shaped conformal cooling channels for application in optical parts of great thickness, deep cores, and high dimensional and optical requirements. In these cases, the small dimensions of the core and the high requirements regarding warping and residual stresses prevent the use of traditional and standard conformal cooling channels. The research combines the use of a new triple hook-shaped conformal cooling system with the use of three independent conformal cooling sub-systems adapted to the complex geometric conditions of the sliders that completely surround the optical part under study. Finally, the new proposed conformal cooling design is complemented with a small insert manufactured with a new Fastcool material located in the internal area of the optical part beside the optical facets. A transient numerical analysis validates the set of improvements of the new proposed conformal cooling system presented. The results show an upgrade in thermal efficiency of 267.10% in comparison with the traditional solution. The increase in uniformity in the temperature gradient of the surface of the plastic part causes an enhancement in the field of displacement and in the map of residual stresses reducing the total maximum displacements by 36.343% and the Von—Mises maximum residual stress by 69.280% in comparison with the results obtained for the traditional cooling system. Additionally, the new design of cooling presented in this paper reduces the cycle time of the plastic part under study by 32.61%, compared to the traditional cooling geometry. This fact causes a very high economic and energy saving in line with the sustainability of a green mold. The improvement obtained in the technological parameters will make it possible to achieve the optical and functional requirements established for the correct operation of complex optical parts, where it is not possible to use traditional cooling channels or standard conformal cooling layouts.

Advanced Fabrication Techniques of Microengineered Physiological Systems.

The field of organs-on-chips (OOCs) has experienced tremendous growth over the last decade. However, the current main limiting factor for further growth lies in the fabrication techniques utilized to reproducibly create multiscale and multifunctional devices. Conventional methods of photolithography and etching remain less useful to complex geometric conditions with high precision needed to manufacture the devices, while laser-induced methods have become an alternative for higher precision engineering yet remain costly. Meanwhile, soft lithography has become the foundation upon which OOCs are fabricated and newer methods including 3D printing and injection molding show great promise to innovate the way OOCs are fabricated. This review is focused on the advantages and disadvantages associated with the commonly used fabrication techniques applied to these microengineered physiological systems (MPS) and the obstacles that remain in the way of further innovation in the field.

Thermal cloak with adaptive heat source to proactively manipulate temperature field in heat conduction process

Thermal cloaks can thermally hide an object without disturbing background thermal field. The coordinate transformation method for designing conventional thermal cloaks face some challenges that the physical properties of metamaterials are required to be anisotropic and inhomogeneous. Furthermore, the coordinate transformation is not applicable for complex geometrical conditions. In this study, a proactive thermal cloak is proposed. The cloak contains two concentric annular zones: one with high thermal conductivity and another with adaptive heat source. The cloaked zone is surrounded by the high thermal conductivity zone. The high thermal conductivity zone keeps the object in the cloaked zone from thermally being affected by outside zones. The heat source zone adjusts the background thermal field without any distortion. The thermal cloak with an analytical heat source distribution is presented for the 2D and 3D background thermal fields with uniform gradient. The adaptive heat source in the thermal cloak is designed by inverse problem theory of a numerical method for the 2D arbitrary background thermal field. This proactive thermal cloak can avoid the issue of anisotropic physical properties for the conventional thermal cloak designed with coordinate transformation method. The heat source thermal cloak with relatively easy implementation can manipulate temperature field proactively without contact. This thermal cloak is applicable for arbitrary background thermal fields and complex geometrical conditions by a numerical design approach. The proposed thermal cloak opens a new strategy to manipulate the thermal field with adaptive heat source.

A Novel Hybrid Kinect-Variety-Based High-Quality Multiview Rendering Scheme for Glass-Free 3D Displays

This paper presents a new hybrid Kinect-variety-based synthesis scheme that renders artifact-free multiple views for autostereoscopic/automultiscopic displays. The proposed approach does not explicitly require dense scene depth information for synthesizing novel views from arbitrary viewpoints. Instead, the integrated framework first constructs a consistent minimal image–space parameterization of the underlying 3D scene. The compact representation of scene structure is formed using only implicit sparse depth information of a few reference scene points extracted from raw RGB depth data. The views from arbitrary positions can be inferred by moving the novel camera in parameterized space by enforcing Euclidean constraints on reference scene images under a full-perspective projection model. Unlike the state-of-the-art depth image-based rendering (DIBR) methods, in which input depth map accuracy is crucial for high-quality output, our proposed algorithm does not depend on precise per-pixel geometry information. Therefore, it simply sidesteps to recover and refine the incomplete or noisy depth estimates with advanced filling or upscaling techniques. Our approach performs fairly well in unconstrained indoor/outdoor environments, where the performance of range sensors or dense depth-based algorithms could be seriously affected due to scene complex geometric conditions. We demonstrate that the proposed hybrid scheme provides guarantees on the completeness, optimality with respect to the inter-view consistency of the algorithm. In the experimental validation, we performed a quantitative evaluation as well as subjective assessment of the scene with complex geometric or surface properties. A comparison with the latest representative DIBR methods is additionally performed to demonstrate the superior performance of the proposed scheme.

Analytical Mobility Analysis of Bennett Linkage Using Geometric Algebra

It has been challenging to obtain an analytical or closed-form expression of the motion space of a Bennet linkage because it is over-constrained and has complex geometric conditions. This paper presents an analytical mobility analysis of the Bennet linkage using geometric algebra. Frist, the Bennet linkage is regarded as a 2-RR (R: revolute joint) parallel mechanism and the limb motion space is the join of two twists associated with the two revolute pairs. Then, the motion space of the output link of the Bennet linkage is obtained by using meet operator to calculate the intersection of the two limb motion space. Compared to the constrained screw-based method, the use of a meet operator results in fewer steps, thus simplifying the computation. This intersection presents an analytical or symbolic expression of the motion space of the Bennet linkage with straightforward geometric interpretations.

가스하이드레이트 개발과정에서의 단층 재활성화 해석

본 논문에서는 해저 하이드레이트 퇴적층에서의 메탄가스 생산 과정에서 발생 가능한 생산정 주변 단층의 재활성화 가능성을 수치해석을 통해 평가하고 재활성화에 따른 미소지진 규모를 예측한 결과를 소개하였다. 가스 생산에 의한 하이드레이트 퇴적층의 유효응력 변화 및 역학적 변형은 TOUGH+Hydrate 코드와 FLAC3D 코드를 순차적으로 연계해석함으로써 시뮬레이션하였다. 단층면 재활성화 기준은 모어쿨롱(Mohr-Coulomb)법칙이 유효한 것으로 가정하였다. 30일간의 시험생산 해석 결과, 감압에 의한 공극압력 감소 및 유효응력의 증가가 주변 단층의 활성화를 일으킬 가능성은 크지 않은 것으로 나타났다. 초기응력 조건에 따른 활성화 가능성을 활동마찰각으로 평가한 결과로부터 수평응력에 비해 수직응력이 상대적으로 큰 정단층 응력조건(normal fault stress regime)에서 단층 재활성화 가능성이 상대적으로 큰 것으로 파악되었다. 또한, 정단층 응력조건에서 단층 재활성화에 기인한 유도지진 발생규모를 모멘트 크기(moment magnitude)로 추정할 경우, 모두 음(-)의 값을 보여 인간이 감지하지 어려운 수준의 미소지진에 해당하는 결과를 보였다. 다만, 본 해석은 하이드레이트 생산과정에서의 단층재활성화 가능성 평가를 목적으로 한 해석기법 구축 및 그 적용성을 소개할 목적으로 상당히 단순화된 지질구조 모델을 가정한 결과이므로, 향후 하이드레이트 시험 생산 및 상업 생산 지역에서의 상세 지질구조, 입력 물성 및 생산 설계조건을 반영한 해석에서는 상이한 결과를 보일 수 있을 것이다. In this paper, we perform a numerical analysis to evaluate the potential of fault reactivation during gas production from hydrate bearing sediments and the moment magnitude of induced seismicity. For the numerical analysis, sequential coupling of TOUGH+Hydrate and FLAC3D was used and the change in effective stress and consequent geomechanical deformation including fault reactivation was simulated by assuming that Mohr-Coulomb shear resistance criterion is valid. From the test production simulation of 30 days, we showed that pore pressure reduction as well as effective stress change hardly induces the fault reactivation in the vicinity of a production well. We also investigated the influence of stress state conditions to a fault reactivation, and showed that normal fault stress regime, where vertical stress is relatively greater than horizontal, may have the largest potential for the reactivation. We tested one simulation that earthquake can be induced during gas production and calculated the moment magnitude of the seismicity. Our calculation presented that all the magnitudes from the calculation were negative values, which indicates that induced earthquakes can be grouped into micro-seismic and as small as hardly perceived by human beings. However, it should be noted that the current simulation was carried out using the highly simplified geometric model and assumptions such that the further simulations for a scheduled test production and commercial scale production considering complex geometric conditions may produce different results.

On the Influence of Wire-lag on the WEDM of Low-radius Free-form Geometries

The wire electro-discharge machining (WEDM) is a widely-used machining process suitable to achieve the increasingly demanding precision requirements imposed by industry. Nevertheless, the use of conventional WEDM machines under some complex geometrical conditions makes sometimes difficult to fulfill these requirements, which is a topic of interest in the manufacturing of high-added aerospace components. Different effects overlap to damage precision when cutting these geometries. In this work a study on the causes of dimensional deviations in small-radius circles has been carried out. The study focuses on two effects: wire-lag and concavity shape on the workpiece produced by electrostatic and electromagnetic forces. At the sight of the results, a classification of radius is proposed taking into consideration the main cause of lack of accuracy. It has been found that wire-lag effect must only be considered when machining circles of radius smaller than a certain value that can be established by simulations. For the conditions of the tests of this study, this value is 3mm. It can also be stated that concavity effect is a function of machined radius.

Spatial sensitivity functions for rapid numerical simulation of borehole sonic measurements in vertical wells

Borehole sonic measurements are routinely used to measure dynamic elastic properties of rock formations surrounding a wellbore. However, shoulder-bed effects, mud-filtrate invasion, and near-wellbore damage often influence the measurements and bias the interpretations. Inversion-based methods can reduce the influence of complex geometric conditions in the estimation of formation properties from sonic logs, but they require fast-forward modeling algorithms. We have developed new spatial sensitivity functions for rapid modeling of borehole sonic measurements, which were equivalent to the Green’s functions of borehole modal wave measurements. An adaptive finite-element (FE) method was used to calculate 1D axial (vertical) and 2D (axial-radial) sensitivity functions, which combined the dependence of sonic logs on the wave mode, frequency, formation properties, and logging-instrument geometry. Semianalytical formulations were also used to calculate the sensitivity functions, which involved modeling the wave propagation through an effective layered medium. The 1D axial sensitivity functions were also extended to quantify propagation properties of nondispersive modes in a borehole. Calculated semianalytical sensitivity coefficients were efficient for rapid simulation of modal frequency dispersion in the presence of a logging tool. Simulated sonic logging measurements across synthetic thinly bedded and invaded formations were compared with numerical simulations obtained with the finite-element method. Our results confirmed the efficiency, reliability, and accuracy of the approximate sonic simulation method. The maximum relative error of the rapid simulation method was consistently less than 4%, with only 2% of the central processing unit time and 2% of the memory usage compared with FE simulations.

Rapid forward modeling of multidetector logging-while-drilling Sigma measurements

Multidetector logging-while-drilling (LWD) Sigma was introduced to the oil industry to measure neutron absorption cross section (Sigma) and radial length of invasion in shallow-invaded formations. Sigma quantifies the ability of a material to absorb thermal neutrons and is calculated from the late time portion of the time decay of thermal neutrons or gamma rays generated from thermal-neutron absorption. The assessment of invasion is made possible with the combination of a thermal-neutron detector and two gamma-ray detectors with different source-detector spacings. However, the interpretation of LWD Sigma logs is often affected by several environmental and/or geometric effects that can mask the formation response. A fast numerical simulation method embedded with inversion-based techniques can be used to estimate intrinsic formation Sigma from borehole measurements affected by shoulder-bed, invasion, and/or environmental effects. We developed a fast and accurate method to numerically simulate LWD multidetector thermal-neutron and gamma-ray time decays in realistic borehole environments. The method relies on Monte Carlo precalculated libraries of particle time decays and detector-specific flux sensitivity functions, while accounting for detector-specific borehole and diffusion effects. Simulations are benchmarked against test-pit measurements and Monte Carlo N-particle (MCNP) transport code calculations. Results indicate that multidetector time decays acquired under complex geometrical conditions can be numerically simulated in approximately 1e-5 the time required using MCNP, with average difference within two capture units. The simulation of time decays, rather than Sigma itself enables a direct relationship between actual rock Sigma and multidetector diffusion-affected time decays, thereby removing intermediate correction steps often used to convert apparent into intrinsic formation Sigma.

Generative geometric design

Boundary solid grammars use design rules that express complex geometric conditions and operations using a logical reasoning mechanism, allowing one to construct powerful rules and describe appropriate grammars for the generation of solid models for a variety of design domains. The formalism I present in this article is not sufficient for all engineering and architectural domains (e.g., polyhedral solids are not adequate geometric abstractions for mechanical design). The boundary solid grammar formalism is, however, well suited to extensions for the representation of nonlinear geometry and mixed-dimensional modeling. Design in these domains will require additional representations, such as electrical and hydraulic schematics, structural and aerodynamic meshes, kinematics, and assemblies. These representations and their analysis techniques will need to be integrated into a common framework to permit interdependent design analysis and generation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurements and characterization of high energy neutron fields

The application of the Monte Carlo code FLUKA in the simulation of the stray radiation field around high energy accelerators has been tested against experimental results obtained at the 250 GeV/ c hadron beam at CERN. The present paper demonstrates the validity of the code in predicting neutron spectra in very complex geometrical conditions with large attenuation factors involved. The same experimental data served as a confirmation of the behaviour of a modified Andersson-Braun rem counter with a response function extended up to hundreds of MeV (LINUS). The present results confirm previous experimental evidence of the much increased response of this monitor with respect to conventional instruments when used in radiation fields with a substantial high energy neutron component.

The angular and energy distributions of γ-irradiation scattered in water and iron

The angular and energy distributions of the γ-radiation from a 60Co source in water and iron has been measured in a semi-infinite geometry. Such measurements provide detailed information on multiple γ-ray scattering from which it is possible to calculate the γ-ray attenuation under complex geometrical conditions. The distributions obtained show that the maximum intensity occurs close to the energy corresponding to single scattering at minimum angle. The angular distributions have an exponential character with an exponent which varies linearly with the atomic number of the medium. The energy distributions are compared with the theoretical calculations of Goldstein and Wilkins (1).