Geometric Influence Research Articles

Gear evaluation deviations-based crucial geometric error identification of five-axis CNC gear form grinding process

The gear form grinding accuracy is significantly affected by crucial geometric errors. The gear form grinding process is a special line contact forming method. There are exclusive evaluation standards for gear grinding accuracy. While the existing sensitivity analysis for spatial point errors cannot meet the final gear report requirements. Hence, a novel method for analysis of geometric error influence on the key gear evaluation deviations (GED) is proposed. First, the actual digital tooth surface considering geometric errors and gear form grinding mechanism was constructed according to the homogeneous transformation matrix (HTM) and multi-body system theory (MBS). Second, the GED of the digital tooth surface was gained according to the modified gear meshing equations. Third, the analytic mapping relationship between the GED and machine tool geometric errors was first established. Then, the crucial geometric errors affecting the GED were identified based on a proposed Morris method. Finally, the identification results were compared to the existing publications, and the compensation discussions of crucial errors were demonstrated to validate the advantages of the proposed method. It can be found that the compensation results of GED-oriented key errors are better than those of the traditional methods, which is beneficial to the improvement of evaluation reports.

Evaluation of Geometrical Influence on the Hydrodynamic Characteristics and Power Absorption of Vertical Axisymmetric Wave Energy Converters in Irregular Waves

Abstract To obtain the mechanical energy of waves from arbitrary directions, the vibration absorbers of wave energy converters (WEC) are usually vertically axisymmetric. In such case, the wave-body interaction hydrodynamics is an essential research topic to obtain high-efficiency wave energy. In this paper, a semi-analytical method of decomposing the complex axisymmetric boundary into several ring-shaped stepped surfaces based upon the boundary approximation method (BAM) is introduced and examined. The hydrodynamic loads and parameters, such as the wave excitation forces, added mass and radiation damping of the vertical axisymmetric oscillating buoys, can then be achieved by using the new boundary discretisation method. The calculations of the wave forces and hydrodynamic coefficients show good convergence with the number of discretisation increases. Comparison between the constringent results and the results of the conventional method also verifies the feasibility of the method. Then, simulations and comparisons of the hydrodynamic forces, motions and wave power conversions of the buoys with series draught and displacement ratios in regular and irregular waves are conducted. The calculation results show that the geometrical shape has a great effect on the hydrodynamic and wave power conversion performance of the absorber. In regular waves, though the concave buoy has the lowest wave conversion efficiency, it has the largest frequency bandwidth for a given draught ratio, while in irregular waves, for a given draught ratio, the truncated cylindrical buoy has the best wave power conversion, and for a given displacement of the buoy, the concave buoy shows the best wave power conversion ability.

Computational study of the geometrical influence of grain topography on short crack propagation in AA7XXX series alloys

Intergranular Environmentally-Assisted Cracking (EAC) has recently been reported to be an issue of concern in new-generation 7000 series aluminium alloys, such as AA7085, when exposed to humid air. The cracking process occurs in a highly brittle manner almost exclusively along grain boundaries (GB's) and has been attributed to hydrogen embrittlement, probably by GB decohesion within the stress field at the crack tip. Currently, how the highly heterogeneous grain structures found in these partially recrystallized materials impact the growth behaviour of microstructurally short cracks is poorly understood. In particular, there is expected to be a high sensitivity to the grain structure in the transition from initiation to sustained propagation, where the local mechanical driving force is very sensitive to the crack path. Volume Elements, VE's, with synthetic grain structures have been generated from real microstructure and texture data, so that the effects of important grain structure variables can be explored in crystal-plasticity simulations, to understand the extent to which typical grain-structural features affect the driving force for short-crack growth. Specifically, by considering the effect of different uncrystallised grain aspect ratios and embedding recrystallised grains in the model, the strain energy release rate has been calculated as a function of crack path. This has revealed large reductions and fluctuations in the driving force for short cracks in relation to the local grain structure encountered by the crack tip, which have been estimated by the model.

Uncertainty estimation using Gaussian error propagation in metal forming process simulation

AbstractThe ease of estimating the uncertainties of numerical simulations in metal forming is of particular interest. This uncertainty arises from, for example, material parameter identification, geometric dimensions, external loads, and contact conditions. In this paper, we aim to address this issue with the extension to geometric influences, and boundary as well as friction conditions. The uncertainty quantification from material parameter identification – here, in terms of sensitivities of the resulting simulations based on the confidence interval of the parameters – is transferred from the literature and the individual proportions are quantified and compared, respectively. For material parameter identification, experiments on steel and glass fiber reinforced plastic are used and the confidence intervals are determined. Particularly in the case of sequential determination of the parameters, the uncertainties are estimated with the aid of Gaussian error propagation. This concept can also be transferred to geometric dimensions or loads. The application of numerical differentiation for the sensitivities within the Gaussian error propagation leads to a concept where the finite element program can be treated as a black‐box. Here, all uncertainties of the simulation results are obtained, leading to the result that geometric influences in the deep drawing process used as well as the friction coefficient have the largest effect. This provides a very simple procedure for the uncertainty quantification of all individual influencing variables in any finite element simulation.

Определение участка нарезания мелкомодульных зубьев в эксцентриковых механизмах свободного хода

Normal forces use to transfer the load makes it possible to increase load capacity and reliability of the free running mechanisms. Normal forces in the eccentric free running mechanisms are realized in engagement of the fine-module teeth that are cut on the outer cage inner surface and the outer surface of the eccentric rings. To ensure correct operation of the mechanism in jamming and wedging, value of the fine-module teeth cutting section angle should be selected from the equality condition of the radial clearance between the outer cage teeth and the eccentric ring in the entire working section. To solve the problem, calculation scheme is proposed and mathematical model is obtained that describes relationship between the fine-module cutting section angle and the mechanism geometric parameters. The nature of the main geometric parameters influence (radius, eccentricity, radial clearance, module, etc.) on the value of the teeth cutting section angle was established. It is shown that eccentricity provides the greatest influence on the working area size, radial clearance and module influences are less pronounced.

A Finite Element Formulation to Three-Dimensionally Resolve Space-Charge Layers in Solid Electrolytes

All-solid-state batteries are seen as promising candidates to replace conventional batteries with liquid electrolytes in many applications. However, they are not yet feasible for many relevant applications. One particular question of interest is the identification of physical effects inside all-solid-state batteries and their quantitative influence on the performance of the entire battery cell. Simulation models can contribute to answering the aforementioned question by systematical studies, e.g. enabling or disabling certain physical effects. Especially the influence of space-charge layers (SCLs) is heavily discussed in the scientific community. So far, the different length scales of SCLs and the microstructure of a battery cell made a spatial discretization of realistic microstructures with resolved SCLs infeasible. However, thermodynamically consistent continuum models which are applied to simplified geometries are already established in the literature. In this work, we propose a model that enables the prediction of the spatial development of SCLs within geometrically resolved microstructures by exploiting that effects in SCLs are predominantly one-dimensional. With the proposed approach it is possible to quantify the geometric influence of realistic microstructures on the formation process of SCLs. SCLs in realistic microstructures remarkably differ from SCLs computed with simplified one-dimensional models which are already established in the literature.

Study of Bio-Fluid Dynamics in Carotid Artery System Using Numerical Methods

Computational Fluid Dynamics (CFD) has been largely used in understanding the haemodynamics of the carotid bifurcation system and to visualise the blood flow changes due to the carotid artery geometric variations. Such studies will be helpful in understanding the arterial blood flow behavior and atherosclerosis. The present study focuses on investigation of geometric variable patient-specific healthy carotid bifurcation system under physiological pressure conditions. Unsteady flow simulation is conducted in ANSYS Fluent under the rigid wall and non-Newtonian conditions. The haemodynamic parameters such as pressure, velocity, vorticity, helicity, and time-averaged wall shear stress (TAWSS) were evaluated to visualise and understand flow dynamics at critical zones of bifurcation system. Further, the importance of geometric influence on the bifurcation zone was also investigated, causing significant vortex formation zones. A considerable reduction in velocity and backflow formation was observed, which is responsible for reducing the shear stress. It is also demonstrated that low TAWSS regions surrounding the bifurcation zone are more prone to atherosclerosis development.

Geometric influence on the net magnetic moment in LaCoO3 thin films

The different magnetic behaviors of LaCoO_3 films grown on LaAlO_3 and SrTiO_3 substrates are related to the Co–O–Co bond angles and the constraints imposed on the Co–O bond lengths by the substrate geometries. The observed magnetic behavior is not consistent with ferromagnetism. Rather, long-range antiferromagnetic order occurs below T approx 90 K when the Co–O–Co bond angle is greater than 163^circ, consistent with the behavior of bulk and nanoparticles forms of LaCoO_3. A LaAlO_3 substrate prevents magnetic long-range order at low temperatures near the film–substrate interface and collinear antiferromagnetic sublattices away from the interface. At low temperatures, the antiferromagnetically ordered sublattices are non-collinear in films grown on SrTiO_3 substrates, leading to a significant net moment. The net moment is controlled by the geometry imposed by the substrate upon which the LaCO_3 film is grown.Graphical abstract

Nonlinear Dynamic Analysis of the Wind–Train–Bridge System of a Long-Span Railway Suspension Truss Bridge

In order to study the coupling vibration between a bridge and a train under the action of crosswind loads, a dynamic interaction model of the wind–train–bridge system is established considering the geometric nonlinear factors of a long-span suspension bridge. A calculation frame is composed, and a corresponding computer program is written. A long-span highway–railway suspension bridge scheme is studied as an example. The linear and nonlinear vibration responses of the bridge under the simultaneous action of both train loads and wind loads are compared using the self-written program, and the influence of wind velocity and train speed on the dynamic responses of the bridge is studied. The results show that the large displacement nonlinearity of the structure does not influence the changing tendency of bridge displacement and acceleration time histories, but reduces the maximum values of the responses. The geometric nonlinear influence on the bridge accelerations is more obvious than that on the displacements. The natural frequencies of this long-span suspension bridge are very low and it is sensitive to wind action. The changes in train speed and average wind velocity have a great influence on the maximum value of bridge displacement, especially when the lateral deformation and acceleration increase sharply with the wind velocity, and the coupling vibration between wind, train, and the bridge can easily occur. The research results can provide references for the safe operation and maintenance of long-span bridges.

Surface Modification with Phosphate and Hydroxyapatite of Porous Magnesium Scaffolds Fabricated by Binder Jet Additive Manufacturing

The presence of porosity within magnesium-based orthopaedic implants is known to be beneficial, promoting cell proliferation and vascularisation. However, the presence of porosity increases the surface area available for corrosion, compounding the issue of high corrosion rates which has long been plaguing magnesium-based materials. This work looks at the influence of hydroxyapatite and phosphate conversion coatings on the corrosion performance of conventionally cast, dense Mg-Zn-Zr alloys and binder jet additive manufactured porous Mg-Zn-Zr scaffolds. The performance of coating on dense Mg-Zn-Zr was found to be more effective than the coating on the porous Mg-Zn-Zr scaffold, with the discrepancies attributed to both the microstructure and geometric influence of the binder jet additive manufactured, porous Mg-Zn-Zr scaffold, which not only increases the rate of hydrogen evolution but also reduces the ability of the hydrogen gas generated within the pore channels to escape to the sample’s surface. This restricts the effectiveness of coating application for porous Mg scaffold. Furthermore, the limited diffusion within the pore channels can also result in differing localized corrosion environments, causing discrepancies between the localised corrosion environment within the pore channels and that at the bulk electrolyte.

Analytical analysis of nonlinear internal resonance bandgap of pendulum-type metamaterial

In this paper, a pendulum-type metamaterial (PTM) is designed with a pendulum bob hinged at the primary mass. Considering the effect of geometric nonlinearity, the nonlinear dynamic equations of PTM unit cell are presented with the aid of the Bloch theorem. The analytical formula of dispersion equation is deduced to discuss the nonlinear internal resonance bandgap using the harmonic balance method. The obtained bandgap of the metamaterial is in good agreement with the numerical simulation result. The nonlinear geometric influence of pendulum on PTM bandwidth is significant. The bandgaps under different internal resonances are substantially different from each other due to the nonlinear effects. The upper boundaries of the frequency bandgap under 1:1/2 and 1:1/3 internal resonance rise nonlinearly to higher than those under linear and 1:1 internal resonance conditions. It shows that the impact of 1:1/2 and 1:1/3 internal resonance on the bandgap could be more obvious as the strong nonlinearity is taken into consideration.

1972: Una formulación sudamericana del concepto de interfaz.

From the educational Chilean national design school reform in 1928 under Vkhutemas, Poland and vernacular indigenous geometric art influence, with an abrupt interruption in 1929, up to Gui Bonsiepe’s design development for the Production Development Corporation (CORFO), interrupted in September 1973, we can distinguish a period in both Chilean and Latin American history, where different design definitions emerged as the main axis for a possible and effective self-determination.
 This meant that various public policies, with greater or lesser continuity, were gradually consolidating development through added value. Symbolically at least, public policies focused on reversing the process of dependence on small economies, countering the endogenous system of exclusive production of raw materials with little added value.
 Within this period we witness two conjunctures that come together as exceptional situations that go beyond the adoption of an external productive system: the consolidation of these objectives took place in the formulation of the interface interaction design concept in 1972, at the same time as the 3rd United Nations Conference to Trade and Development (UNCTAD III) was being held in Chile, a great interface that would articulate a decentralized development model on a global scale.
 The interaction design at that time, even more than before, became a strategic tool to materialize the aspirations of own technological development, linked to other areas of the country’s economy and culture, particularly in the project of decentralized administration of the state companies, which included the hitherto unprecedented transmission of information in real time, the Cybersynor Synco project.

AI_deation: A Creative Knowledge Mining Method for Design Exploration

Ideation is a core activity in the design process which begins with a design brief and results in a range of design concepts. However, due to its exploratory nature it is challenging to formalise computationally. Here, we report a creative knowledge mining method that combines design theory with a machine learning approach. This study begins by introducing a graphic design style classification model that acts as a model for the aesthetic evaluation of images. A Grad-CAM technique is used to visualise where our model is looking at in order to detect and interpret visual syntax, such as geometric influences and color gradients, to determine the most influential visual semiotics. Our comparative analysis on two Nordic design referents suggests that our approach can be efficiently used to support and motivate design exploration. Based on these findings, we discuss the prospects of machine vision aided design systems to envisage concepts and possible design paths, but also to support educational objectives.

The Methodological and Experimental Research on the Identification and Localization of Turbomachinery Rotating Sound Source

The localization and quantification of turbomachinery rotating sound sources is an important challenge in the field of aeroacoustics. In order to compensate the motion of a rotating sound source, a rotating beamforming technique is developed and applied in a flow duct, which uses a wall-mounted microphone array placed circularly parallel to the fan, to detect the broadband noise source of the aeroengine fan. A simulation of three discrete rotating sound sources with a non-constant rotational speed is pursued to verify the effectiveness in reconstruction of the correct source positions and quantitative prediction of the source amplitudes. The technique is ulteriorly experimentally implemented at an axial low-speed fan test rig facility. The fan test rig has 19 rotor blades and 18 stator vanes, with a design speed up to 3000 rpm. The method can accurately identify the radial and circumferential positions of the three rotating sound sources in the simulation case, large side-lobes appear near the main-lobe of the sound source due to the geometric influence of the microphone array. A noticeable feature of beamforming images for axial flow fan is that the sound sources appear to be concentrated in the tip region rather than distributed along the span.

Compressor geometric uncertainty quantification under conditions from near choke to near stall

Geometric and working condition uncertainties are inevitable in a compressor, deviating the compressor performance from the design value. It’s necessary to explore the influence of geometric uncertainty on performance deviation under different working conditions. In this paper, the geometric uncertainty influences at near stall, peak efficiency, and near choke conditions under design speed and low speed are investigated. Firstly, manufacturing geometric uncertainties are analyzed. Next, correlation models between geometry and performance under different working conditions are constructed based on a neural network. Then the Shapley additive explanations (SHAP) method is introduced to explain the output of the neural network. Results show that under real manufacturing uncertainty, the efficiency deviation range is small under the near stall and peak efficiency conditions. However, under the near choke conditions, efficiency is highly sensitive to flow capacity changes caused by geometric uncertainty, leading to a significant increase in the efficiency deviation amplitude, up to a magnitude of −3.6%. Moreover, the tip leading-edge radius and tip thickness are two main factors affecting efficiency deviation. Therefore, to reduce efficiency uncertainty, a compressor should be avoided working near the choke condition, and the tolerances of the tip leading-edge radius and tip thickness should be strictly controlled.

Magnet-Actuated Piezoelectric Harvester for Energy Harvesting from Fluids

Energy harvesting has been at the forefront of research due to the significant interest in green energy sources, especially for powering remote sensors in structural health monitoring of coastal and offshore facilities. This work reports the magnet-actuated piezoelectric harvesters (M-APH) that use magnetic coupling to actuate piezoelectric film-embedded silicon rubber strips for energy harvesting from fluids. The piezo-silicon strips are deflected by the tip-magnets in the actuation system, such that the M-APH can effectively be triggered to generate electrical energy from vibration. The M-APH prototypes are printed using 3D printing technology, and the experiments are conducted to determine the output electrical voltage using a rectifier. Strip properties are varied to study the geometric influence (i.e., thickness and shape) on the energy performance. The electrical performance was evaluated for each curved piezoelectric strip and straight strips according to the piezoelectric material used. The reported M-APH can be applied to various fluids for energy harvesting.

Nonlinear noise of hydrofoil cavitation considering sound velocity variation and phase transitions

Cavitation noise is an important part of underwater radiated noise (URN). It not only reduces the concealment and comfort of ships, but also affects marine life. In this paper, a detailed study of cavitation noise is carried out for NACA0012 hydrofoil and a wavy-leading-edge hydrofoil. The nonlinear sound pressure is computed by direct volume integration in FW-H formulation, considering the sound velocity change caused by the phase transition and the spherical sound source caused by the cavity volume change. By comparing with the experiment, the acoustic prediction method proposed in this paper is verified. The acoustic study is conducted from the perspectives of streamwise distribution, spanwise distribution, far-field directivity, influence of cavitation number and geometric influence. Three components and the sound source distributions are analyzed. The results show that, for cavitation state, nonlinear sound pressure is larger than the linear one and dominates in the near field. At further distances, the spherical component dominates. The cavitation noise of the modified hydrofoil is enhanced, and the source intensity is increased by 1–2 orders of magnitude.

On the Transferability of Fatigue and Cyclic Deformation Data to 100 µm Thin Structures

The fatigue properties and cyclic deformation behaviour of materials are usually determined using cylindrical specimens (e.g., Ø7.5 mm). Since the transferability to very small dimensions has not been comprehensively considered so far, this study investigates the transferability of specimen data from high-strength steel X5CrNiCuNb16-4 to real structures characterised by a wall thickness of 100 µm. Regarding fatigue, extensive calculations demonstrate that for notched specimens and thin structures, both the material-mechanical support factor concept according to the FKM guideline and the point method of the Theory of Critical Distance (TCD) make correct predictions of the local fatigue strength, with a maximum deviation from experimental values of less than 5%. However, the study points out that the TCD is only conditionally applicable for thin-walled structures, as the material parameter a0 must be significantly smaller than the wall thickness. Regarding the deformation behaviour, the material reveals special flow characteristics in the first hysteresis. Nevertheless, a combined hardening approach is suitable for modelling. The validation of the model by a plastic deformation of the structure seems plausible, although geometric influences prove to be dominant. In conclusion, even 100 µm thin structures can be evaluated using conventional specimen tests and established assessment or modelling methods.

Investigation of the Influence by Size Effects on the Material Characterization of the Uniaxial Compression Stress State

For the evaluation of final component properties under consideration of production-induced material characteristics, it is necessary to determine the mechanical parameters of parts and structures. Thus, there is a need of new test methods for the material characterization and quality control of produced goods. The miniaturization of the test specimens offers the potential for the local testing of the material properties at almost any position on the component. However, due to the reduction in size of the test specimens, size effects can occur which may affect the material behavior. For this reason, this contribution analyses the influence of size effects on the derived material parameters in dependence of the specimen size and material by using upsetting tests according to DIN 50106:2016 standard. The materials Cu-OFE (copper), X5CrNi18-10 (stainless steel) and AA7075-T6 (aluminum) are investigated to ensure a broad transferability of the findings. The specimens are cut from a bar stock by using a high precision 3D micro electrical discharge milling machining. Due to the small size, every specimen is measured with an optical 3D coordinate measuring system to determine the exact size. Through these investigations, the reproducibility and scatter in the determination of material properties for scaled cylindrical upsetting specimens are evaluated. Furthermore, limits of geometric dimensions at constant aspect ratios are derived. The results of this investigation enable an estimation of the geometrical influence of the specimen size in regard to the mechanical properties.

Diffraction of shock waves through a non-quiescent medium

An investigation of shock diffraction through a non-quiescent background medium is presented using both experimental and numerical techniques. Unlike diffracting shocks in quiescent media, a spatial distortion of the shock front occurs, producing a region of constant shock angle. An example of this process arises in the exhaust from a pulse-detonation combustor. As the background velocity is increased, such as through the inclusion of a converging nozzle at the exhaust, the spatial distortion becomes more apparent. Numerical simulations using a compressible Euler solver demonstrate that the distortion is not due to the geometrical influence of the nozzle, but rather is a function of the magnitude of the background flow velocity. The distortion is studied using a modified geometrical shock dynamics formulation which includes the background flow and is validated against experiments. A simple model is presented to predict the shock distortion angle in the weak-shock limit. Finally, the axial decay behaviour of the shock is investigated and it is shown that the advection of the shock by the background flow delays the arrival of the head and tail of the expansion characteristic at the centreline. This leads to an increase in the rate of decay of the shock Mach number as the background flow velocity is increased.