Small Tolerances Research Articles

Influence of Remote Laser Cutting on Magnetic Loss and Mechanical Properties in 0.2 mm Silicon Steel

Energy loss due to eddy current generation is a significant factor in reduced efficiency of electrical machines, therefore motor cores with thinner sheets are required due to their effect in reducing eddy currents. However, reducing the thickness of laminations is challenging due to the high tooling costs in blanking due to the small tolerances required, whilst other methods such as conventional laser cutting are too slow to be commercially viable. In this paper the influence of remote laser cutting on thin electrical steel sheets (Cogent/Tata Steel NO20 3.2% Si) has been investigated on the tensile strain to fracture, fatigue life, edge hardness, and energy loss in an AC magnetisation cycle for two laser power levels. The laser power has found to have no statistically significant influence on the bulk mechanical properties of the material, but significantly affects the measured specific loss. The latter was associated with the increased edge hardness at higher laser powers. Based on the parameters selected it is highly questionable whether RLC offers a viable method for lamination cutting, significant refinement of the laser parameters and/or the use an alternative laser such as an ultra-fast pulsed laser is required to be competitive with existing methods. Additionally, it is shown that energy loss increases linearly with respect to length of the cut edge - to the minimum cut spacing tested of 6 mm. These results can be used to optimise laser parameters to reduce the degradation of magnetic properties by decreasing laser power where possible.

The Impact of Velocity Update Frequency on Time Accuracy for Mantle Convection Particle Methods

AbstractComputing the velocity field is an expensive process for mantle convection codes. This has implications for particle methods used to model the advection of quantities such as temperature or composition. A common choice for the numerical treatment of particle trajectories is classical fourth‐order explicit Runge–Kutta (ERK4) integration, which involves a velocity computation at each of its four stages. To reduce the cost per time step, it is possible to evaluate the velocity for a subset of the four time integration stages. We explore two such alternative schemes, in which velocities are only computed for: (a) stage 1 on odd‐numbered time steps and stages 2–4 for even‐numbered time steps, and (b) stage 1 for all time steps. A theoretical analysis of stability and accuracy is presented for all schemes. It was found that the alternative schemes are first‐order accurate with stability regions different from that of ERK4. The efficiency and accuracy of the alternate schemes were compared against ERK4 in four test problems covering isothermal, thermal, and thermochemical flows. Exact solutions were used as reference solutions when available. In agreement with theory, the alternate schemes were observed to be first‐order accurate for all test problems. Accordingly, they may be used to efficiently compute solutions to within modest error tolerances. For small error tolerances, however, ERK4 was the most efficient.

An E band MMIC power amplifier design using 100 nm T‐Gate GaN HEMT on SiC

SummaryThe small signal modeling, design, fabrication, and measurement about monolithic millimeter‐wave integrated circuit (MMIC) using gallium nitride (GaN) power amplifier (PA) on silicon carbide (SiC) working at the E band are proposed in this paper. The two stage PA used customized 4 × 75 μm transistor with 100 nm T gate technology. The extraction and optimization of small signal model are based on single GaN high electron mobility transistor (HEMT)'s measurement. Balanced structure and new method are used by low impedance matching, which can simplify circuits prominently and benefit for die size reduction. Radial stub and LC stub are made the whole circuit in absolute stable status; the in‐series DC block metal–insulator–metal capacitor from the matching circuit ensure the process is within small tolerances. From the 61–66 GHz bandwidth, a peak 10.7 dB small signal gain is obtained from the designed MMIC GaN PA, and also, the maximum output power can reach 29.7 to 30.4 dBm from 61 to 66 GHz, with an associated the peak drain efficiency of 18.8%. The final die size without dicing slot is 3.0 × 1.74 mm2.

Formulation of non-local space-fractional plate model and validation for composite micro-plates

It is challenging to design nano/micro-devices because of their small size and tight engineering tolerances. Computer-aided design uses mathematical models of device parts, but contemporary models are not precise enough to capture all characteristics of the materials at the nano/micro-scale. In this work, we propose a novel mathematical model for composite nano/micro-plates in bending in the framework of a space-fractional continuum mechanics approach. This model yields closer mapping of experimental results compared to existing formulations. The developed theory is named the space-Fractional Kirchhoff–Love Plate (s-FKLP). We investigate how the parameters of the s-FKLP model, responsible for the scale effect description, affect the bending behavior of the micro-plates, considering different support conditions. In addition, we compare the results predicted by s-FKLP with the previously developed simpler (one-dimensional) space-Fractional Euler–Bernoulli Beam (s-FEBB) model to show that the choice of structural analysis strategy can influence design decisions. Despite its greater complexity, the s-FKLP is a more versatile approach to modeling micro-sized structures than the s-FEBB. The proposed s-FKLP model is empirically validated using real sandwich micro-plates. We conclude model alignment with the experimental data indicating that the model is suitable for representing sandwich micro-plates. We also find that the model’s length scale parameter corresponds to the microstructure’s grain size. The findings of this research may have implications for future work in the design and optimization of micro-sized devices.

Square Membrane Resonators Supporting Degenerate Modes of Vibration for High-Throughput Mass Spectrometry of Single Bacterial Cells.

In nanomechanical mass spectrometry, sensing devices are commonly placed in the vacuum environment and a stream of analytes is directed toward the sensor surface for measurement. Beam structures, such as double-clamped nanobeams and nanocantilevers, are commonly used due to their low inertial mass and the simplicity of the analytical models for mass extraction. The drawback of such structures is their low capture areas, compromising the capture efficiency and throughput of this technique. Bi-axisymmetric resonators, such as ultrathin square or circular membranes, arise as an optimal geometry to maximize capture efficiency while minimizing the device inertial mass. However, these structures present degenerate mechanical modes, whose frequency perturbations upon analyte adsorption are not well described by commonly used models. Furthermore, prior knowledge of the vibration mode shapes of the sensor is crucial for the correct calculation of the analyte's mass, and the mode shape of degenerate modes may change significantly after every adsorption event. In this work, we present an accurate analytical theory to describe the effect of mass adsorption on the degenerate modes of square membrane resonators and propose two different methods based on the new theory to update the vibration mode shapes after every adsorption event. Finally, we illustrate the problem experimentally obtaining the mass and adsorption position of individual Escherichia coli K-12 bacterial cells on commercial square silicon nitride membranes fabricated with very small tolerances.

TECHNICAL AND ECONOMIC ANALYSIS OF MANUFACTURING PROCESS FOR HIGH PRECISION CUSTOMIZED PART

This paper presents research results on optimum manufacturing process for prototyping high precision customized products parts and, therefore, products. The results would be applied to reduce research cost for development of new personalized devices used, for example, in prosthetics of missing limbs. These devices need high precision parts and, not the least, affordable costs. In order to obtain the prototype of these devices, several types of manufacturing processes have been analysed. As conclusion of the research results, we can state that the selection of the best manufacturing process type for obtaining high precision customized parts is a big challenge for engineers as they must get the best technique which ensures high precision (on one hand) and affordable costs (materials and equipment’s, on the other hand). When the prototyped parts are components of a special product, as example, an upper limb prosthesis, high attention should be also focused on the reliability of prototyped parts. 3D printing technologies have developed and extremely evolved lately but still there are cases when their performances are limited (especially when small dimensions and tight tolerances are required for parts’ geometry). Also, considering the component costs, an adequate analysis must be done in order to select the optimal variant of the production process. The research results presented in this paper are focused on the analysis of optimal cost for prototyping customized parts of personalized devices used for the upper limb prosthesis.

Influence of microarc machining on resizing of aluminum parts

Problem. The change of the sizes of the processed samples (aluminum alloys) after oxidation in alkaline-silicate electrolyte at the anode-cathode mode is studied in the work. The two-layer structure of aluminum alloys after MAO processing is shown. The change in the size of the parts is determined by the phase composition of the coating. Goal. The goal is study of the changes in the size of the processed samples (aluminum alloys) after oxidation in alkaline-silicate electrolyte at the anode-cathode mode. The change of the sizes of the processed samples (aluminum alloys) after oxidation in alkaline-silicate electrolyte at the anode-cathode mode is studied in the work. Methodology. X-ray structural analysis (Dron - 3) in radiation Кα-Cu, microhardness measurement (PMT-3) with the load of 100 gr., measurement of coating thickness (vortex thickness gauge BT - 10NTs). Results. It is shown that in the case of predominant α- Al2O3 formation the δ / B ratio is 1.28, in the case of γ-Al2O3 formation, the δ / B ratio is 1.55 and in the case of mullite formation (3Al2O3 • 2SiO2) - 2.23. The calculation showed that the level of change in the size of the sample after MАO significantly depends on the phase composition of the coating. Experimental testing on different alloys and different electrolytes confirmed the different degree of change in size depending on the phase composition of the coating, which is determined by the modes of MAO and the composition of the electrolyte. Thus, the experimental value for alloy D16 subjected to MАO in different modes varies from 1.0 to 2.0; for B96 metal - 1.15-2.76; for AMg6 metal - 1.46-2.55. The results presented above relate to the total thickness of the formed coating. Given the two-layer structure of the coating and the fact that the thickness of the loose layer to be removed is 15 - 50% of the total thickness, the change in the size of the part after the final finishing of the friction surface should be insignificant. It has been experimentally established that from alloys D16, B96, AMg6 at optimal modes of MAO (thickness of wear-resistant coating 100 - 150 μm) the increase in the size of the part to the side is 5 - 10 μm. As for cast alloys (for example, Al9), the structure of the coating which contains a significant amount of mullite, the increase in the size of the part of such alloy after MАO and refining, more (compared to deformed alloys) and is 20 - 30 microns Al2O3. Originality. The calculation and research showed that the level of change in the size of the sample after MDO significantly depends on the phase composition of the coating itself. Considering the two-layer structure of the coating and the fact that the thickness of the loose layer to be removed is 15 - 50% of the total thickness, the change in the dimensions of the part after the final proofing of the surface should be insignificant. Practical value. Changes in the dimensions of the part must be taken into account when processing parts with small tolerances or eliminated by additional finishing by partially removing the main wear-resistant layer.

Characterization Techniques for Reconfigurable Reflectarray Unit Cells at 240 GHz

Reflectarrays and tunable surfaces receive increasing attention for wavefront engineering in the upper millimeter-wave range. As chip-based phase shifters can now be integrated with antenna elements, the performance verification at unit cell (UC) level is of great interest for a cost-efficient investigation of large-scale arrays. In this article, two UC designs with integrated phase shifter and on-chip antenna are evaluated experimentally at 240 GHz. For the first time, a single element is characterized above 100 GHz by applying the classic waveguide simulator technique. Since this method is mechanically problematic at high frequencies due to small dimensions and mechanical tolerances, an alternative approach involving a near-field probe is presented and investigated. The results for both measurement methods are compared and interpreted, assisted by full-wave simulations.

A Quantitative Parametric Study on Output Time Delays for Autonomous Underwater Cleaning Operations

Offshore pipelines and structures require regular marine growth removal and inspection to ensure structural integrity. These operations are typically carried out by Remotely Operated Vehicles (ROVs) and demand reliable and accurate feedback signals for operating the ROVs efficiently under harsh offshore conditions. This study investigates and quantifies how sensor delays impact the expected control performance without the need for defining the control parameters. Input-output (IO) controllability analysis of the open-loop system is applied to find the lower bound of the H-infinity peaks of the unspecified optimal closed-loop systems. The performance analyses have shown that near-structure operations, such as pipeline inspection or cleaning, in which small error tolerances are required, have a small threshold for the time delays. The IO controllability analysis indicates that off-structure navigation allow substantial larger time delays. Especially heading is vulnerable to time delay; however, fast-responding sensors usually measure this motion. Lastly, a sensor comparison is presented where available sensors are evaluated for each ROV motion’s respective sensor-induced time delays. It is concluded that even though off-structure navigation have larger time delay tolerance the corresponding sensors also introduce substantially larger time delays.

Verification of an independent dose calculation method for portal-specific QA of proton and carbon ion beams

ObjectiveTo verify the accuracy of an independent dose calculation method, as incorporated into an in-house developed treatment planning system (TPS), for performing quality assurance of dose distributions delivered to a water phantom planned by a clinical TPS. MethodsA Monte Carlo based track repeating algorithm was incorporated into an in-house treatment planning system for proton and carbon ion beams. Calculations were performed in a flat water phantom for both a traditional pencil beam algorithm and a new Monte Carlo algorithm, and then compared to measurements made at multiple depths with a 2D ionization array for 44 patient portals. The comparisons utilized a Gamma analysis. ResultsA total of 124 measurements were performed for proton and carbon ion patient portals. Using a small Gamma criteria of 2%/2 ​mm, an average of 93% and 97% of measurement points passed for each portal for pencil beam and Monte Carlo calculations, respectively. The passing rate was substantially higher for Monte Carlo calculations than for pencil beam calculations for portals that used a range shifter. ConclusionsThe implemented independent method has been verified against measurements. The high passing rate with small tolerances leads to the possibility of reducing the number of required quality assurance measurements.

Biogeography Meets Niche Modeling: Inferring the Role of Deep Time Climate Change When Data Is Limited

Geographic range shifts are one major organism response to climate change, especially if the rate of climate change is higher than that of species adaptation. Ecological niche models (ENM) and biogeographic inferences are often used in estimating the effects of climatic oscillations on species range dynamics. ENMs can be used to track climatic suitable areas over time, but have often been limited to shallow timescales; biogeographic inference can reach greater evolutionary depth, but often lacks spatial resolution. Here, we present a simple approach that treats them as independent and complementary sources of evidence, which, when used in partnership, can be employed to reconstruct geographic range shifts over deep evolutionary timescales. For testing this, we chose two extreme African disjunctions:Camptoloma(Scrophulariaceae) andCanarina(Campanulaceae), each comprising of three species disjunctly distributed in Macaronesia and eastern/southern Africa. Using inferred ancestral ranges in tandem with preindustrial and paleoclimate ENM hindcastings, we show that the disjunct pattern was the result of fragmentation and extinction events linked to Neogene aridification cycles. Our results highlight the importance of considering temporal resolution when building ENMs for rare endemics with small population sizes and restricted climatic tolerances such asCamptoloma, for which models built on averaged monthly variables were more informative than those based on annual bioclimatic variables. Additionally, we show that biogeographic information can be used as truncation threshold criteria for building ENMs in the distant past. Our approach is suitable when there is sparse sampling on species occurrences and associated patterns of genetic variation, such as in the case of ancient endemics with widely disjunct distributions as a result of climate change.

One-Step Enameling and Sintering of Low-Carbon Steels

Powder technology allows manufacturing complex components with small tolerances, saving material without subsequent machining. There is a growing trend in using sintered steel components in the automotive industry. Within 2020, about 2544 million US dollars was invested for manufacturing sintered components. Not only does this industry uses steel components, but the gas cooker industry also uses steel in its burners since they are robust and usually demanded by Americans, with forecasts of 1097 million gas cookers in 2020. Steel gas burners have a ceramic coating on their surface, which means that the burner is manufactured in two stages (casting and enameling). This work aims to manufacture the gas burners by powder metallurgy, enameling and sintering processes in a single step. To achieve this aim, the ASC100.29 iron powder has been characterized (flow rate, relative density and morphology); subsequently, the most suitable parameters for its compaction and an adequate sintering temperature were studied. Single-step sintering and enameling was achieved by compacting iron powder at 500 MPa and sintering at 850 °C for 5 min. The necessary porosity for mechanical anchoring of the coating to the substrate is achieved at this sintering temperature. Bending resistance tests, scratching, degradation under high temperature and basic solution and scanning electron microscopy were used to characterize and validate the obtained samples.

Reaction rate ambiguities for perturbed spectroscopic data: Theory and implementation

The analysis of reaction systems and their kinetic modeling is important for both exploratory research and process design. Multivariate curve resolution (MCR) methods are state-of-the-art tools for the analysis of spectral series, but are also affected by an unavoidable solution ambiguity that impacts the obtained concentration profiles, spectra and model parameters. These uncertainties depend on the underlying model and the magnitude of the measurement perturbations.We present a general theoretical approach together with a computational method for the analysis of the solution ambiguity underlying arbitrary kinetic models. The main idea is to determine all those model parameters for which the corresponding pure component factorizations satisfy all given constraints within small error tolerances. This makes it possible to determine bands of concentration profiles and spectra that reflect the underlying ambiguity and circumscribes the potential reliability of MCR solutions. False conclusions on the uniqueness of a solution can be prevented. The procedure can be applied as a post-processing step to MCR methods as MCR-ALS, ReactLab or others. The Matlab program code is freely accessible and includes not only the proposed ambiguity analysis but also an MCR hard-modeling approach. Application studies are presented for two experimental data sets, namely for UV/Vis spectra on the relaxation of a photoexcited state of benzophenone and for Raman spectra on an aldehyde formation process.

A MULTI-FIDELITY NEURAL NETWORK SURROGATE SAMPLING METHOD FOR UNCERTAINTY QUANTIFICATION

We propose a multi-fidelity neural network surrogate sampling method for the uncertainty quantification of physical/biological systems described by ordinary or partial differential equations. We first generate a set of low/high-fidelity data by low/high-fidelity computational models, e.g. using coarser/finer discretizations of the governing differential equations. We then construct a two-level neural network, where a large set of low-fidelity data are utilized in order to accelerate the construction of a high-fidelity surrogate model with a small set of high-fidelity data. We then embed the constructed high-fidelity surrogate model in the framework of Monte Carlo sampling. The proposed algorithm combines the approximation power of neural networks with the advantages of Monte Carlo sampling within a multi-fidelity framework. We present two numerical examples to demonstrate the accuracy and efficiency of the proposed method. We show that dramatic savings in computational cost may be achieved when the output predictions are desired to be accurate within small tolerances.

Model-based design of areal material measures with component surfaces

The calibration and verification of areal surface topography measuring instruments is usually performed with artificial geometries that do not correspond to a practical measuring task like gratings or step height artefacts (ISO 25178-70:2014). While these processes have a sufficient process capability to meet the requirements of many industrial measurement applications, there are more and more applications that require small tolerances, which results in the necessity of a performance verification that is more closely related to the later performed measuring task. With a model-based design approach it is possible to design material measures based on component surfaces for an application-oriented performance verification. The initial point is a measured dataset, which is evaluated and virtually transformed in a way that on the one hand the target properties are met, but on the other hand also the functional properties of the surface that are relevant for the specific application are preserved. Based on the subsequent application of virtual manufacturing and measuring processes, also impacts from these processes can be considered in the design of the verification sample. In this study, we extend the basic approach that has been developed for the design of profile material measures e.g. with the manufacturing principle of ultra-precision turning (Seewig, Eifler, Schneider, Aurich Proc. CIRP 45 (2016), 259-262; Eifler, Schneider, Seewig, Kirsch, Aurich Eng. Sci. Technol. 4 (2016) 1993-2001. Seewig, Eifler, Schneider, Kirsch, Aurich Surf. Topog.: Met. Prop. 4 (2016) 024010. Eifler (2016)). to areal material measures and a corresponding manufacturing principle of micro-milling. With the model-based design approach, component surfaces are used to determine two different material measures that feature defined values of the surface texture parameters Sa, Sq, Sk, Svk, Spk as a case study. It will be shown that the areal surface texture parameters can be mapped to the designed material measures that enable a practical performance verification.

Boss Tower and Baseplate Flange Optimization

The swaging process is commonly used in head stack assembly, which is a process that is undertaken to either reduce or increase the diameter of tubes or rods. In the head stack assembly process, a swage boss engages with an arm hole of E-Block. Current hard disk drives have very small tolerances, requiring the swage effect of new hard disk drives to be reduced to as little as possible. In this study, finite element analysis (FEA) was used to reduce the swage effect. At present, FEA and investigative tests indicate that a significant portion of gram changing through swaging is caused by E-block tip deformation due to swaging. Deformation of the E-block tip is the result of unbalanced swage forces between the tension and compression suspension. Achieving optimization concepts leads to a new swage plate design to reduce the gramload change of the target and to equalize the swage forces. The FEA results found that gramload change of the target decreased by 35% on the tension side, and by 65% on the compression side through swage by boss tower. The HGA torque out was not different. The suspension flange was also studied. Subsequently, suspension manufacturing is able to bias the suspension as incoming HGA. The flange deformation might be closer to zero after the swaging process.

Temperature influence on involute gear measurements

Involute gears are high-stress components used in a variety of drivetrain applications. Small manufacturing tolerances require low measurement uncertainties in production metrology. A well-established traceability chain from industrial facilities to national gear measurement standards is essential for reliable quality control. Especially for large parts, the ambient and workpiece temperatures contribute to the measurement uncertainty considerably. However, measurements on the shop floor can rarely be performed at exactly 20 °C, which is the international reference temperature for dimensional metrology. In this paper, the influence of thermal expansion on gear deviations is discussed. Theoretical considerations are compared to results obtained via finite element analysis (FEA) as well as to experimental data. This also includes measurements of PTB’s large gear measurement standards under different temperature conditions. The outcome of this study can be used either to estimate measurement uncertainty contributors in industrial applications or to compensate thermally induced errors in gear measurements.

Humankind Engineering and Management: Robotic Track

Assembly processes in aircraft production are particularly difficult to automate due to a variety of technical challenges including, small batch sizes, large product dimensions, small tolerances, and limited work space. Fully automated systems are expensive and require a large amount of servicing effort during their life time. The developed solution is therefore a semi-automated approach based on Human-Robot-Collaboration (HRC).

Effect of solvent lamination on roll-to-roll hot-embossed PMMA microchannels evaluated by optical coherence tomography

Manufacturing of microfluidic based diagnostic devices requires small tolerances and uniform quality to guarantee reliable and repeatable test results. This work describes characterization of morphological changes that occur to a hot embossed PMMA microfluidic channel after solvent lamination with a PMMA lid. A non-contact cross-sectional analysis of the lidded microfluidic device was performed by optical coherence tomography (OCT). The solvent induced morphology change led to a porous structure in bottom corners of hot-embossed channels, which allowed a fluid to absorb in the material. The measurements of solvent diffusion showed faster diffusion rate at the corners of the channel, in which the accumulated stress during the embossing process was the highest. The stress profile was verified by simulation of von Mises stresses during a molding phase of a hot embossing process. The porous structure with increased fluid diffusion has an unwanted effect on bioassay result, e.g. when detection molecules leak into the substrate thus leading to unspecific signal on chip. OCT was found to be a valuable, non-destructive imaging method to monitor solvent diffusion process and lamination process quality.

Eccentric loading of a 25-m long composite column subjected to a combination of axial compression and transverse gravity loading using a horizontal test method

This article presents a feasibility study where fibre-reinforced structural elements are assembled into long slender columns using adhesive bonding. The columns are intended to be part of an externally guyed high-voltage transmission tower where they are subjected to a combination of compressive and transverse loads. The article has shown that 25-m long poles can be made with small tolerances in both angularity and concentricity. Previous published scientific work on buckling of composite columns was applied to predict the behaviour of the pole as it was being loaded in compression to 1200 kN or within 5% of its critical load in a bespoke horizontal test jig. The confidence in the material, the structural elements, the analysis method and the quality of the test equipment has shown that there is a potential in further optimization of the structure that will ultimately be a part of a high-voltage composite tower.