Force Mode Research Articles

Progressive failure mechanism of existing-supplementary double-layer piles retaining excavation beneath existing underground space

The increasing degree of urbanization has resulted in traffic and space congestion. When there is no longer any aboveground space for development, the existing space underground is excavated, and the construction of underground buildings is expected to solve the above problems. In the excavation of an underground layer, it is necessary to drive supplementary and existing piles into the soil to form a double-layer pile-supported structure. Aiming at an existing–supplementary double-layer pile-supported structure and considering the pile spacing of the supplementary piles, use of crown beams, and other factors, this study performed a series of indoor model tests and an simulation analysis in combination with finite element analysis software to reveal the bearing characteristics of this structure. The results showed that the installation of supplementary piles could effectively inhibit soil slippage after pile driving, redistribute the soil pressure load of the existing piles, and reduce the number of soil cracks between the piles. With the increase in the supplementary pile spacing, the deformation of the existing–supplementary double-stacked piles gradually intensified, and the bending moment of the pile body and the horizontal displacement at the top of the piles increased. The installation of crown beams in the existing piles could strengthen the connection between the existing and supplementary piles, reduce the number of soil cracks between these piles, and change the force mode of the pile body. Considering the geological conditions and the influence of existing buildings, the deformation laws of the supporting structure and the soil around the foundation piles during the excavation of an underground layer of an L-shaped foundation pit were revealed. The research results are expected to provide a scientific and theoretical basis for the design and construction of downward additional support structures for existing buildings, along with socio-economic significance.

How do policies promote the sustainable development of older-adult care industry? A configuration analysis based on policy tools.

Under the background of population aging in China, the demand for older-adult care services and products is growing, and the older-adult care industry has great development prospects. A sound older-adult care policy system, that is, an effective policy tool mix, plays an important role in improving the sustainable development of older-adult care industry. Based on older-adult care policy documents from 31 Chinese provinces, this research extracts older-adult care policy tools via text mining. Then extracted policy tools are taken as conditional variables, and the development of older-adult care industry, which is manifested by the number of older-adult care companies across 31 regions is taken as the result variable. Through applying qualitative comparative analysis, the combined effect of different policy tools on the development of older-adult care industry is obtained. Results show that a single policy tool cannot constitute the necessary condition to facilitate the older-adult care industry. Hence, policy tools should be applied in combination. Five sustainable policy tool mixes which can promote the development of older-adult care industry are summarized, namely supporting policy-driven mode, fiscal and tax support mode led by supply-oriented policy tools, double-team mode driven by fiscal and tax support and the consumer market, multi-subject joint force mode, and technology compensation mode. The overall findings of this study imply that exploring the policy tool combinations is of vital importance to the sustainable development of older-adult care industry.

Bayesian Inference for the Calibration of Progressive Damage Model of Dovetail Specimens from Laminated Composite Fan Blade

Abstract Composite fan blades are the preferred alternative for the fan stage of most advanced high bypass ratio turbofan engines. The ability of the dovetail to safely bear this load is one of the key points of the multi-level “test pyramid” approach of compliance demonstration for special airworthiness regulation. Debonding between adjacent layers is the main damage mode of laminated composite fan blades. However, there is difficulty in measuring the as manufactured interlaminar mechanical properties used in finite element models. In this study, tensile loading was applied to simulate the interacting centrifugal force and capture mixed mode damage evolution. Structural responses and material damages were calibrated with measured tensile loads through Bayesian inversion. Posterior probability distributions of maximum interface tractions and contact stresses were solved using Markov chain Monte Carlo sampler. Results indicated the two bilinear cohesive material models had a capacity of predicting empirical means of longitudinal reaction forces as that in test considering additional discrepancy term (0.035 kN and 0.96 kN respectively), while they made an significant impact on the prediction of tensile load history especially when two delamination cracks initiated and propagated. Interface elements provided a higher matching quality in predicting loading history and capturing damage mechanism in association with in-plane progressive damage analysis. This calibrated parameter set could be functioned as benchmark in numerically determining the ultimate tensile load of dovetail elements and reducing the necessary number of physical tests at elemental length level.

Physically Guided Estimation of Vehicle Loading-Induced Low-Frequency Bridge Responses with BP-ANN

The intersectional relationship in bridge health monitoring refers to the mapping function that correlates bridge responses across different locations. This relationship is pivotal for estimating structural responses, which are then instrumental in assessing a bridge’s service status and identifying potential damage. The current research landscape is heavily focused on high-frequency responses, especially those associated with single-mode vibration. When it comes to low-frequency responses triggered by multi-mode vehicle loading, a prevalent strategy is to regard these low-frequency responses as “quasi-static” and subsequently apply time-series prediction techniques to simulate the intersectional relationship. However, these methods are contingent upon data regarding external loading, such as traffic conditions and air temperatures. This necessitates the collection of long-term monitoring data to account for fluctuations in traffic and temperature, a task that can be quite daunting in real-world engineering contexts. To address this challenge, our study shifts the analytical perspective from a static analysis to a dynamic analysis. By delving into the physical features of bridge responses of the vehicle–bridge interaction (VBI) system, we identify that the intersectional relationship should be inherently time-independent. The perceived time lag in quasi-static responses is, in essence, a result of low-frequency vibrations that are aligned with driving force modes. We specifically derive the intersectional relationship for low-frequency bridge responses within the VBI system and determine it to be a time-invariant transfer matrix associated with multiple mode shapes. Drawing on these physical insights, we adopt a time-independent machine learning method, the backpropagation–artificial neural network (BP-ANN), to simulate the intersectional relationship. To train the network, monitoring data from various cross-sections were input, with the responses at a particular section designated as the output. The trained network is now capable of estimating responses even in scenarios where time-related traffic conditions and temperatures deviate from those present in the training data set. To substantiate the time-independent nature of the derived intersectional relationship, finite element models were developed. The proposed method was further validated through the in-field monitoring of a continuous highway bridge. We anticipate that this method will be highly effective in estimating low-frequency responses under a variety of unknown traffic and air temperature conditions, offering significant convenience for practical engineering applications.

Triglobal resolvent-analysis-based control of separated flows around low-aspect-ratio wings

We perform direct numerical simulations of actively controlled laminar separated wakes around low-aspect-ratio wings with two primary goals: (i) reducing the size of the separation bubble and (ii) attenuating the wing tip vortex. Instead of preventing separation, we modify the three-dimensional (3-D) dynamics to exploit wake vortices for aerodynamic enhancements. A direct wake modification is considered using optimal harmonic forcing modes from triglobal resolvent analysis. For this study, we consider wings at angles of attack of $14^\circ$ and $22^\circ$ , taper ratios $0.27$ and $1$ , and leading edge sweep angles of $0^\circ$ and $30^\circ$ , at a mean-chord-based Reynolds number of $600$ . The wakes behind these wings exhibit 3-D reversed-flow bubble and large-scale vortical structures. For tapered swept wings, the diversity of wake vortices increases substantially, posing a challenge for flow control. To achieve the first control objective for an untapered unswept wing, root-based actuation at the shedding frequency is introduced to reduce the reversed-flow bubble size by taking advantage of the wake vortices to significantly enhance the aerodynamic performance of the wing. For both untapered and tapered swept wings, root-based actuation modifies the stalled flow, reduces the reversed-flow region and enhances aerodynamic performance by increasing the root contribution to lift. For the goal of controlling the tip vortex, we demonstrate the effectiveness of actuation with high-frequency perturbations near the tip. This study shows how insights from resolvent analysis for unsteady actuation can enable global modification of 3-D separated wakes and achieve improved aerodynamics of wings.

A sustainable floating dome biogas plants integrated with semi-transparent photovoltaic thermal collectors: Construction, production and economic analysis

The design and construction of a self-sustained solar photo-voltaic active thermal heating floating dome biogas plant (35 m3) offers an alternative solution for round year biogas production, managing food and agricultural waste, reducing greenhouse gas emissions and minimize pollution. Moreover, this proposed model addresses the challenge of achieving the desired operating temperature (35 ± 2 °C) specially during the cold climatic conditions, which often leads to low gas production and high hydraulic retention time in anaerobic digestion. The integration of solar modules with the biogas digester enables the utilization of thermal energy for slurry heating and electricity for force mode of operation, ultimately enhancing overall energy efficiency. However, to assess the performance of the system, proximate and ultimate analyses as well as a cost-benefit analysis were carried out, considering revenue, and costs associated with construction, operation, and maintenance. The plant produces a significant amount of gas (9–12 m3) and hot water (∼2000 L) replacing approximately one LPG cylinder/2 day as well as organic fertilizer. The economic analysis shows a positive net present value (19.5 lakhs), an internal rate of return (20%), and short discounted payback period (5.7 years). This highlights the economic feasibility of the proposed model and emphasizes the importance of considering economic factors in the design and implementation of sustainable energy solutions. Furthermore, this approach demonstrates the potential for sustainable development and the transition to cleaner and more efficient energy systems by integrating renewable energy generation, waste management, and cost reductions.

Influence of Natural External Forcings on Interdecadal Variation of Global Land Monsoon over the Last Millennium in CESM-LME

Abstract Interdecadal variations of the global land monsoon have been previously attributed to internal fluctuations of the climate system, but the role of natural external forcings was underexplored. Here, we investigate this issue by using the Community Earth System Model ensemble simulations over the last millennium (LM) (AD 950–1850). Our analysis reveals that the surface temperature, with two dominant structures (global cooling/warming and longitudinal sea surface temperature gradient in the tropical Pacific, which affects the Walker circulation), predominantly shapes the leading forced mode of the global land monsoon. This mode, representing 19% of the total variance, manifests as consistent features across South Asia, the southern part of East Asia, North Australia, South America, and western South Africa, contrasting with other monsoon regions. Under global cooling conditions, the monsoon intensity is enhanced in the northern parts of the East Asian and eastern parts of the North and South African monsoons, but it decreases in the other monsoon regions. Under weak Walker circulation conditions, changes in atmospheric circulation in response to the sea surface temperature gradient in the tropical Pacific are associated with a substantial attenuation of almost all land monsoon regions. It was further shown that the global mean surface temperature and the tropical Pacific temperature gradient jointly account for 75% of the total variance in the leading mode of the global land monsoon, with 29% and 46% as their respective contributions. Furthermore, our results suggest that volcanic eruptions are the dominant external forcing for these variations. These findings provide valuable insights for future research on global monsoon dynamics. Significance Statement Our study using the Community Earth System Model reveals that surface temperature significantly impacts decadal global land monsoon (GLM) variations during the last millennium. Two key factors in relation to global-scale cooling/warming and changes in the tropical Pacific sea surface temperature gradient affect the GLM’s leading forced mode. The leading forced GLM features remain consistent across regions like South Asia, southern East Asia, North Australia, South America, and western South Africa. Under global cooling, monsoon intensities in most land monsoon regions are enhanced, while they are reduced in northern East Asian land monsoon regions. In contrast, weak tropical Pacific temperature gradient conditions cause a decrease in intensities in almost all land monsoon regions. Additionally, the global mean surface temperature and the tropical Pacific temperature gradient account for 75% of the total variance in the leading forced GLM variations, contributing 29% and 46%, respectively. Notably, volcanic eruptions emerge as the key external factor influencing these variations.

THREADED LUBRICANTS FOR DRILL PIPES BASED ON OIL PRODUCTION WASTE

The oil and gas industry occupies a leading position in the development of the country's fuel and energy complex, and the effectiveness of its activities largely depends on the technical and economic indicators of drilling. When performing well work and operating oil and gas wells, many material costs are associated with the operation of oil pipes, namely the reliability of threaded connections operating at high pressures and temperatures in aggressive environments. The need to develop deeper and deeper horizons, the use of forced drilling modes, the transition to later stages of operation of most oil and gas fields, the aging of existing funds and the increase in the volume of overhauls leads to an increase in tripping operations, and therefore the requirements for the reliability of the connection of oil-grade pipes are moving to a new level. Studies have shown that up to 87 % of all drill string accidents are related to poor thread condition. This unsatisfactory condition of the locking threaded joints forces us to look for ways to improve durability. Many foreign and domestic scientists have been studying and improving threaded joints in drill pipes. According to the authors, one of the most promising ways to increase the TEI of drilling is to develop and use more and more effective lubricants for locking joints of drilling tools. Studies have shown that conventional lubricants are not effective enough in modern realities, and sometimes lubricants are completely washed out of threaded joints. In addition, as the drilling depth increases, the friction force increases and the hydrodynamic load increases, and the increase in pressure in the threaded connection complicates the conditions due to the effect on the lubricant of chemically active and abrasive drilling muds and many other factors. The article discusses the obtained results of studies of lubricant bases for threaded connections of drill pipes used for the oil industry, the distinctive features of which are physical and chemical composition, including low molecular weight polyethylene, synthetic rubber, rubber softeners, powdered graphite, vegetable oils.The authors of the article selected the basis of lubricant from industrial rubber production waste, and also presented the advantages of the developed lubricants and materials. The practical significance of the obtained research results lies in the possibility of increasing the wear and sealing properties of threaded pipe joints used in drilling oil and gas wells.

К безопасности труда при транспортировании гидросмесей по трубопроводу

The article describes the technology of pipeline transportation of hydraulic mixtures for stowing at underground mining. The relevance of optimization of the hydraulic mixture transportation processes is based on the fact that filling the excavated space during its abandonment is the main factor of injury prevention among workers and the integrity of industrial facilities. The aim of the study is to detail the hardening mixture transportation methods for increased distance compared to the reached distance. The maximum damage factor is a rockslide into the open excavated space; therefore, the delivery of stowing pulp to the location of use minimizes the hazard for miners. The advantages of the proposed solution are substantiated by the adopted study methods. The study results can be used for the development of a set of protective measures. The applied mixture transportation methods have been analyzed. The practices of hydraulic mixture transportation for the distance of 2.5 km, which exceeded the best global achievements, have been described. Models of the description of hydraulic mixture transportation have been provided including the models obtained by calculations and experimental pressure loss. The operation schedules in forced mode for pipeline transport have been provided. It has been demonstrated that the optimization of aspects of the issue is specifically relevant for the intensification of processes of metal deposit development. The outcomes of the experimental study can be used when involving accumulated washery refuse in the treatment. It is recommended to determine the parameters of efficient delivery of hydraulic mixtures in vibration-induced mode by modelling in accordance with the criteria of distance and reliability of transportation. The recommendations on the use of hydraulic mixture delivery technology in forced mode can be required when developing mineral deposits by open and underground methods and training highly qualified personnel.

Network- and CFD/CAA-modelling of the high frequency flame response in multi-jet combustors

Low order networks are widely used for linear stability analysis of combustors in the low frequency limit. High frequency stability analysis, however, is limited to cost-intensive numerical or experimental methods, since derivation of analytical solutions is either cumbersome or impossible. The article at hand provides a quasi-two-port network model for the effective modal acoustic pressure and axial velocity normalised with the transverse acoustic field for cylindrical combustors. This network modelling approach includes transfer matrices of acoustic area jumps, ducts for longitudinal, standing and spinning transverse and mixed mode wave propagation. The purely acoustic transfer matrices are validated with a generic non-reactive experiment. On the basis of phase-locked [Formula: see text] images of an engine-similar multi-jet combustor with a forced T1 mode, a locally distributed flame response model is derived, which is reduced to a global flame transfer matrix. A locally resolved convective flame response model is implemented in a numerical model in order to verify the provided theory by the comparison of the analytical and numerical flame transfer matrix for the high-frequency regime.

An invitation to resolvent analysis

AbstractResolvent analysis is a powerful tool that can reveal the linear amplification mechanisms between the forcing inputs and the response outputs about a base flow. These mechanisms can be revealed in terms of a pair of forcing and response modes and the associated energy gains (amplification magnitude) at a given frequency. The linear relationship that ties the forcing and the response is represented through the resolvent operator (transfer function), which is constructed through spatially discretizing the linearized Navier–Stokes operator. One of the unique strengths of resolvent analysis is its ability to analyze statistically stationary turbulent flows. In light of the increasing interest in using resolvent analysis to study a variety of flows, we offer this guide in hopes of removing the hurdle for students and researchers to initiate the development of a resolvent analysis code and its applications to their problems of interest. To achieve this goal, we discuss various aspects of resolvent analysis and its role in identifying dominant flow structures about the base flow. The discussion in this paper revolves around the compressible Navier–Stokes equations in the most general manner. We cover essential considerations ranging from selecting the base flow and appropriate energy norms to the intricacies of constructing the linear operator and performing eigenvalue and singular value decompositions. Throughout the paper, we offer details and know-how that may not be available to readers in a collective manner elsewhere. Towards the end of this paper, examples are offered to demonstrate the practical applicability of resolvent analysis, aiming to guide readers through its implementation and inspire further extensions. We invite readers to consider resolvent analysis as a companion for their research endeavors.

Scale effects on core design, fuel costs, and spent fuel volume of pressurized water reactors

The desire to improve the economic competitiveness and deployment pace of nuclear energy through modularization, manufacturing, and series production had led to the development of smaller size reactors. As the standard 17x17 fuel technology is mainly maintained in the pressurized water reactors (PWRs) category, this translates into a lower number of fuel assemblies in the core and sometimes a reduced fuel height. To assess the impact of such scale change in core design on fuel cycle cost and spent fuel volume, a scoping analysis tool is developed based on infinite lattice calculations, leakage, fuel management reduced models, and levelized unit cost of electricity (LCOE) estimate. As such, cost dynamics driven by fuel specific power, burnup, core leakage, feed, cycle length, fuel assembly height as well as uranium market data are captured with consistent set of assumptions and analysis methods. A selection of 5 reactor designs representative of leading PWR developers is assessed and compared. Pursuing higher specific powers and optimal burnups are highlighted as the main fuel cost reduction drivers, nevertheless, practical limitations and opportunities must be evaluated to establish the feasibility of such enhanced fuel operation. In consequence, a detailed core design is performed using SIMULATE3 code for 5 PWR variations including natural and forced coolant circulation modes, two reactor scales, power densities of 73, 112, and 123 kW/l and higher discharge burnups. Design and optimization are performed at the lattice level, for the reflector, and at the core loading level. Satisfactory steady-state operation including power distribution, coolant operating limits, and reactivity requirements are analyzed and reported in this paper. The fuel economics of the detailed core designs confirm the scoping analysis findings. Despite the unlocked power uprates in small PWRs, the achievable burnup for a given fuel specific power requires more enrichment and shorter fuel height results in higher fabrication costs per mass of fuel, which makes scaling down core size a more expensive endeavor on the fuel cycle front. Spent fuel volumes are reported for the PWRs designed in this paper. These volumes are driven by the core average discharge burnup regardless of the scale in consideration. Additional cost and core performance aspects related to heavy reflector gains, fuel-reflector substitution, and disposal cost policy in the U.S. are examined.

Ultra-sensitive tactile force/proximity sensor based on monolithically integrated microcantilever

This paper reports a monolithically integrated tactile force and proximity sensor composed of a piezoresistive microcantilever array and a signal processing circuit. Both the microcantilever array and the signal processing circuit were fabricated on a single-crystalline silicon device layer of a silicon-on-insulator (SOI) wafer with a partially depleted (PD) SOI CMOS (complementary metal oxide semiconductor) technology followed by three micromachining processes. A dual-detection sensor of tactile force and proximity was realized by packaging the microcantilever with a polydimethylsiloxane (PDMS) elastomer on a flexible printed circuit board. A force resolution of 68 μN, a force sensitivity of 14.6 mV/N and a minimum detectable displacement of 0.1 μm were obtained in force mode. A minimum detectable distance of 2.5 mm and 2.6 mm were achieved for objects and human proximity detections in photoelectric and thermomechanical modes, respectively. By using the ultra-sensitive force sensor, wrist radial artery pulse, fingertips pulse, breath and throat vibration of human body were collected accurately. These results prove that the integrated microcantilever can achieve both proximity and tactile sensing detections simultaneously with ultra-sensitivity.

Characterization of stability and support force of loess caves in northwest China

Numerous manually excavated loess caves are present within a cultural relic protection zone in the northwestern region of China. The collapse of these caves frequently leads to the cracking, tilting, and even collapse of ancient buildings above, posing a severe threat to the safety of cultural architectural relics. Investigating the stability and characteristics of deformation and failure in loess caves is essential for effectively reinforcing and protecting cultural relics. A two-dimensional model of a loess underground cavern was developed using OptumG2. The stability and modes of deformation and failure in the underground cavern were analyzed through the augmentation of soil gravity and the strength reduction method. This analysis determined the cavern's safety factor, force, deformation and damage mode, and the plastic zone's progression. Numerical simulations analyzed the force characteristics of the support structure under different stress release ratios. The findings revealed that, with the implementation of an anchor rod concrete lining support scheme, the most probable failure mode is a shear failure, initiating at the arch foot. The ground's stress release rate does not influence the safety factor of the cavern but rather the material, design, and strength of the support structure. However, the magnitude of the internal forces acting on the supporting structure by the soil in the cavern is related to the degree of ground stress release. When applied during significant stress release, support structures may experience reduced internal forces, albeit with more substantial stratum displacement; opting for an appropriate stress release when applying support structures is crucial for achieving optimal stratum displacement and lining internal forces.

MatDEM-based study of disc cutter force model in open TBM tunnels: Incorporating installation radius and synergistic effects

The prediction of rock cutting force is critical for tunnel boring machine performance and cutterhead design. This paper presents a novel model for rock cutting force prediction based on the Colorado School of Mines (CSM) model, which incorporates the installation position of disc cutters by introducing installation radius and synergistic effect factors. Linear cutting tests in the laboratory and large-scale rotary cutting simulations in MatDEM software were conducted to examine the impact of these factors. Results indicate that the normal and rolling forces increase and stabilize as the installation radius increases. The synergistic effect produces three force modes in a cutting circle, with mode α having the largest cutting force, mode β having a smaller force, and mode γ having the smallest force. The impact of installation radius and synergistic effect varies with rock-cutter parameters. Multiple regression analysis was used to determine the introduced factors. The proposed model was validated with rock strength and operation data from the Irtysh River conveyance project. The results demonstrate that the proposed model outperforms the CSM model in predicting cutting force in field conditions.

Experimental ginger drying by a novel mixed-mode vertical solar dryer under partial and fully loaded conditions

An innovative and compact mixed-mode vertical solar dryer (MVSD) with a circular solar collector is developed and tested for ginger slices drying under partial and fully loaded conditions. Ginger slices samples of 4, 5 and 6 mm thick were used for natural convective drying in MVSD under partially loaded condition. The thickness of the ginger slices was observed to affect the performance of the MVSD. The drying rate and thermal efficiency were observed to be highest for 5 mm thick ginger slices sample under partially loaded condition. The MVSD was further tested with full loading capacity for 5 mm thick ginger slices drying under natural and forced convection modes (NC and FC modes). The drying behavior of ginger slices was well described by Midilli-Kucuk model. Heat transfer coefficients and efficiency (thermal and exergy) were observed to be higher under forced convection mode. Embodied energy and energy payback time were observed as 554.44 and 585.53 kWh; and 2.85 and 2.99 years under NC and FC modes, respectively. The values of annualized capital cost and payback period were observed as INR 389.41 and 408.17; and 1.85 and 6.86 years under NC and FC modes, respectively. The quality of the ginger dried under FC mode was found comparatively better than that of under NC mode.

Research on puncture classification method of seed implantation robot based on force/image model

This article focuses on the use of a puncture classification method for prostate cancer seed implantation robots. To address the limitations of seed implantation surgery, different tissues in the human body are punctured and classified to improve the precision and success rate of seed implantation. This paper discusses an information fusion sensing technique that can be used in seed implantation surgery, which senses the real-time state of the puncture needle by fusing force and image modes and dramatically improves puncture accuracy and surgical tolerance. In addition, considering the multiscale feature problem of the image recognition process, this paper improves the YOLOv8 model by adding a global attention mechanism (GAM_Attention) to the backbone of the model, which significantly improves the image recognition success rate. Then, datasets of the puncture force and real-time puncture images were produced through puncture experiments. Preliminary puncture experiments with different models were completed, and the experimental results showed that the classification method improved the classification accuracy. The accuracy of seed implantation is improved by this method, which may provide a new idea for deep learning in seed implantation modality perception.

Acoustic resolvent analysis of turbulent jets

Abstract We perform a resolvent analysis of a compressible turbulent jet, where the optimisation domain of the response modes is located in the acoustic field, excluding the hydrodynamic region, in order to promote acoustically efficient modes. We examine the properties of the acoustic resolvent and assess its potential for jet-noise modelling, focusing on the subsonic regime. Resolvent forcing modes, consistent with previous studies, are found to contain supersonic waves associated with Mach wave radiation in the response modes. This differs from the standard resolvent in which hydrodynamic instabilities dominate. We compare resolvent modes with SPOD modes educed from LES data. Acoustic resolvent response modes generally have better alignment with acoustic SPOD modes than standard resolvent response modes. For the optimal mode, the angle of the acoustic beam is close to that found in SPOD modes for moderate frequencies. However, there is no significant separation between the singular values of the leading and sub-optimal modes. Some suboptimal modes are furthermore shown to contain irrelevant structure for jet noise. Thus, even though it contains essential acoustic features absent from the standard resolvent approach, the SVD of the acoustic resolvent alone is insufficient to educe a low-rank model for jet noise. But because it identifies the prevailing mechanisms of jet noise, it provides valuable guidelines in the search of a forcing model (Karban et al. in J Fluid Mech 965:18, 2023). Graphical abstract

Atomic wetting of oil droplets into hexagons and stripes

HypothesisPrevious studies showed that liquid droplets can be spherical caps or polygonal shapes on patterned surfaces. We hypothesize that these phenomena can be narrowed down to nanoscale and affecting liquid molecular wetting. We anticipate observing preferential wetting on the underlying substrate with atomic crystalline lattice. ExperimentsThis study explores the wetting behavior of oil nanodroplets deposited on highly ordered pyrolytic graphite (HOPG) with atomic force microscope (AFM). Oil droplets were scanned with hydrophobic and hydrophilic AFM tips in water in peak force mode AFM, carefully controlling the scanning force. Simple modeling was carried out using Surface Evolver to simulate how oil droplets wet on HOPG with molecular lattice. FindingsThe results showed two distinct wetting behaviors: the hexagonal nanodroplets and stripe nanometric films. In both cases, the droplets appear to wet preferentially along preferred orientations which reflect the atomic periodicity of the underlying substrate. This preferential wetting occurs because the atomic roughness is significant at the length scale of the nanodroplets, while the eventual outcome of the wetting (i.e. whether the droplet settles to a finite contact angle, or wets completely into a nanometric film) is dependent on the spreading parameter of the droplet-substrate system, independent of scanning direction.

Analysis of the technology of manufacturing a semi-finished part for a hollow part of a complex geometric form using the technology of hot volume stamping

Abstract. Background. Today, the actual issues in the production of metal products are the saving of materials and the productivity of production, as this has a significant impact on the cost of finished products. This especially applies to hollow products with a complex geometric shape. Such products include parts or semi-finished products that have hollow cavities and additional elements in the design in the form of flanges, or variable wall thickness along the height of the product. Such parts are widely distributed in mechanical engineering, aircraft construction and in the production of special purpose products, in particular in the field of ammunition production. Therefore, the manufacturing technology of such parts should ensure mass production and have an economic effect. Goal. By calculation, using the finite element method (FEM) in the DEFORM software environment, determine the option of stamping, from blanks of different diameters, a semi-finished product of a hollow part of a complex geometric shape using the technology of hot three-dimensional stamping, and analyze the proposed technological process of obtaining a semi-finished product. Methodology of implementation. Using MSE in the DEFORM software environment, simulation of hot three-dimensional stamping of a semi-finished product was carried out for a hollow part of a complex geometric shape made of blanks of different diameters. In this way, the option of obtaining a semi-finished product with a minimum number of transitions and a guaranteed possibility of implementing the technological process of mold formation was chosen. For the selected option, an analysis of the force modes of forming, normal stresses on the contact surfaces of the workpiece with the tool, and the stress-strain state of the deformed metal was performed. The results. A semi-finished product manufacturing technology for a hollow part of a complex geometric shape using hot three-dimensional stamping technology is proposed. This technology will be implemented in the production of the adapter housing part, which is used in the design of the 120 mm mine. By calculation, with the help of MSE in the DEFORM software environment, the variant of semi-finished product molding for the "Body-adapter" part was determined using the technology of hot three-dimensional stamping, and an analysis of the technological operation of semi-finished product molding was carried out. The temperature regime of the process, technological efforts, parameters of the stress-strain state of the deformed material, the distribution of normal stresses on the deforming tool are determined. The results of the conducted computer modeling make it possible to take into account the design features and select the necessary technological equipment for mass production. Conclusions. The technology for serial production of semi-finished products by hot volumetric stamping has been developed and substantiated. This technology made it possible to increase the rate of material utilization by two times compared to the technology of obtaining a part by mechanical processing from graded rolled steel.