Instantaneous Area Research Articles

Instantaneous flow area calculation for modeling an axial piston pump: A point cloud-based technique

Instantaneous flow area calculation for modeling an axial piston pump: A point cloud-based technique

Exceptional load-bearing capability of Al FPCB/Cu FPCB lap joints using instantaneous laser-based large area facial soldering: Experimental and numerical investigations

This study introduces a novel method for integrating aluminum flexible printed circuit boards (FPCBs) and copper FPCBs into battery management systems (BMS) using and instantaneous large area facial laser source soldering. Achieving a robust bonding strength of 65 MPa involved applying 600 W of laser power for 2 s, enhancing atom diffusion and promoting intermetallic compound (IMC) growth. Finite Element Method (FEM) simulations revealed variations in heat transfer between Al and Cu, affecting IMC thickness at interfaces. Formation of the (Cu, Ni)3Sn4 phase within solder, and variations in laser output significantly influenced solder joint orientation and Al electrode nucleation. Excessive laser power (>800 W) caused critical damage, such as delamination at the Al-PI interface, altering fracture modes and bonding strength. Furthermore, with a detailed examination of the laser soldering phenomenon through both experimental and numerical investigations, this study provides a thorough understanding of the different soldering mechanisms in conventional reflow soldering compared to instantaneous uniform large-area heat source laser soldering. These insights provide new design and material considerations to replace the conventional wiring harness with Al/Cu FPCB lap joints which optimize the circuitry and reducing BMS volume.

Theoretical and experimental investigation of vibration-assisted scratching silicon

Interaction between tip and workpiece plays a crucial role in determining the scratching depth in Vibration-assisted Tip Based Nanofabrication (VTBN), which is more complicated than that of conventional scratching (without vibration-assisted). To establish the relationship between the scratching depth and machining parameters, a cubecorner indenter is employed to conduct VTBN procedure. The indenter is simplified as a cone to calculate the contact model in both 1D groove and 2D surface machining processes. An instantaneous normal load model is established based on the developed tip-workpiece contact model. Due to the variation of instantaneous contact area, effective contact area is put forward for the first time to predict the normal load. Effects of vibration frequency and amplitude on the normal load and surface quality are analyzed based on the proposed model. Experimental results show that higher frequency and larger amplitude will reduce the effective contact area. Vibration can increase the scratching depth and width without enlarging the cutting force. Furthermore, the inconsistency caused by scratching directions in conventional scratching is also overcome during VTBN.

High-speed train axle fretting fatigue scaling experiment research and damage analysis

This work presents the design of a scaled wheel axle fretting fatigue test equipment that takes into account the complicated load boundary conditions of high-speed train axles, which can realize the loading and monitoring of the axle weight load, wheel-rail contact vertical load and lateral load. The scaled wheel axle specimens are processed and assembled, and fretting fatigue tests are performed under varying stress conditions. The results show that the scaled axle's fretting fatigue limit is around 116 MPa under 1 × 107 rotational bending load cycles. The power spectral density of the wheel-rail contact load shows a tendency to decrease and then increase with increasing frequency. The crack initiation area, the crack propagation area, and the instantaneous fracture area are all marked by distinct crack propagation traces on the axle's fracture surface. There is noticeable reddish-brown oxidized abrasive debris on the axle interference fit contact edge, block material peeling and delamination on the contact surface, and a tiny amount of wear particles. The primary causes of damage to the axle contact edge area are fretting fatigue-induced delamination and fretting wear-induced material removal.

A Novel 1D Approach for Modelling Gas Bladder Suppressors on the Delivery Line of Positive Displacement Pumps

This paper concerns the utilisation of a gas bladder hydraulic suppressor to mitigate oscillations in the delivery flow rate of positive displacement machines. The research focuses on two primary objectives: first, the experimental validation of the potential of this solution and second, the formulation of a one-dimensional fluid dynamic model for the suppressor. The foundational framework of the fluid dynamic model is based on the equations governing fluid motion with a one-dimensional approach. To accurately depict the fluid dynamics within the suppressor, a unique approach for determining the speed of sound was incorporated, and it implemented the instantaneous cross-sectional area and the inertial effect of the bladder. This paper is a development of a previous work to also investigate the positioning along the delivery pipe of the suppressor with respect to the pump. The study presents the performance of the suppressor and points out the effects of its relative position with respect to the pump that becomes particularly relevant at high speeds.

Exploring the energy harvest of droplet flow over inducted film for the rainy-shiny solar panel application

An equivalent electrical circuit (EEC) based on transient pseudo-capacitive and electrostatic induction is established to understand the operating mechanism using voltage-time curve decomposition. All relative parameters including top electrode dimension and the instantaneous droplet area variation are used to demonstrate our droplet-base electricity generation (DEG) mechanism and illustrate the principle of the reverse voltage. Moreover, the Debye length concept is introduced to explain charge density at the interface between ionic droplet and the PTFE surface by various ion concentrations and valent number solutions. This work provides insightful and valuable perspective to explain the exponential decay of output voltage by instantaneous droplet area variation during leaving away from the PTFE surface. Moreover, the multi-functions of fluorinated ethylene propylene film coating on the solar panel by correct circuit design can improve 30% which is novel concept at rainy days alternated with dry ones.

Salt Effects on Caffeine across Concentration Regimes.

Salts affect the solvation thermodynamics of molecules of all sizes; the Hofmeister series is a prime example in which different ions lead to salting-in or salting-out of aqueous proteins. Early work of Tanford led to the discovery that the solvation of molecular surface motifs is proportional to the solvent accessible surface area (SASA), and later studies have shown that the proportionality constant varies with the salt concentration and type. Using multiscale computer simulations combined with vapor-pressure osmometry on caffeine-salt solutions, we reveal that this SASA description captures a rich set of molecular driving forces in tertiary solutions at changing solute and osmolyte concentrations. Central to the theoretical work is a new potential energy function that depends on the instantaneous surface area, salt type, and concentration. Used in, e.g., Monte Carlo simulations, this allows for a highly efficient exploration of many-body interactions and the resulting thermodynamics at elevated solute and salt concentrations.

Inversion Method for Instantaneous SSP Area Difference

Addressing the challenge of real-time estimation of instantaneous sound speed profiles (SSP for short). We proposes a SSP inversion method based on the travel time of vertically launched sound waves from seafloor stations to the sea surface. The basic principles of the inversion method are introduced, followed by an investigation into the calculation of instantaneous SSP area considering tidal and wave effects. The proposed method is validated by using semi-experimental data, the results indicate that the accuracy of predictions is poor if the correcting for the tidal and wave influences are not taken. However, after applying the correction equation proposed in this study to adjust for travel time, the relative error in the prediction of SSP area difference is less than 4%.

Study on scratch hardness in ultrasonic vibration-assisted scratching based on instantaneous contact analysis

The limited knowledge of scratch hardness in ultrasonic vibration-assisted scratch (UVAS) impedes a comprehensive understanding of the abrasive wear process with ultrasonic vibration. The main challenge is the complex kinematic-geometric characteristic of instantaneous contact induced by ultrasonic vibration and the abrasive particle. This paper proposed a novel method to describe the contact behavior exerted by ultrasonic vibration in multiple directions. The wear behavior of the indenter in the UVAS test was analyzed, and the indenter surface was measured to calculate the instantaneous contact area. Based on the developed model and the UVAS test, the effects of ultrasonic vibration on scratch hardness with varying scratch velocity and cutting depth are evaluated. It could be found that the scratch hardness for UVAS was reduced compared to that of common scratch owing to the changed contact states. This study provides an effective tool to capture the instantaneous contact state with a complex moving path and predicts the scratch hardness under ultrasonic vibration through common scratch tests.

Turbulent flow around a short rectangular cylinder in uniform flow at moderate Reynolds numbers

The influence of Reynolds number (Re) on the wake characteristics, Kelvin-Helmholtz instabilities and von-Kármán vortex shedding process around a short rectangular cylinder with length to height ratio of 0.5 was studied using particle image velocimetry. The Reynolds numbers based on cylinder height and free-stream velocity ranged from 3000 to 21000. The flow characteristics were analyzed using the instantaneous and mean velocity fields, as well as the Reynolds stresses, while the unsteady dynamics were elucidated using frequency spectra, proper orthogonal decomposition (POD) and reverse flow area. The results demonstrate that the size of the wake vortex reduced but the magnitudes of the Reynolds stresses increased with increasing Re, until Reynolds number independence is reached at Re = 10000. Regardless of Reynolds number, spectral analyses of the velocity fluctuations, POD mode coefficients and fluctuating reverse flow area showed dominant peaks at the same fundamental vortex shedding frequency. Meanwhile, instantaneous flow visualization showed that the structural coherency of the large-scale vortices increased with increasing Reynolds number. Cross-correlation analysis also revealed that the odd and even POD mode coefficients of the first two mode pairs, respectively, acted to contract and expand the instantaneous reverse flow area at the higher Reynolds numbers.

An analytic method for precisely determining the revisit time of SAR satellites and optimizing RGT orbit design

This paper addresses a particular analytic method for calculating the revisit time (RT) of Synthetic Aperture Radar (SAR) satellites in the circular repeating ground track orbit (RGTO) and its application to optimizing the orbital elements according to the payload characteristics. The most critical aspect of SAR payloads is sun-independent, allowing photos to be collected from ascending and descending phases (both-phase). Different from the traditional methods only considering single-phase, the proposed method is mapping every pass into its ascending and descending points on the Equator. A new concept of half-subcycle is presented in this paper to determine the distribution of the ascending and descending points. Through the combination of subcycle and half-subcycle, the both-phase ground track sequences can be fully obtained without resorting to complex computer programs. The minimum, maximum, and average RT, considered at the Equator, can be computed fast by establishing and analyzing the revisiting tracks in the both-side non-nadir instantaneous access area of the SAR payload. The step value of the RT can be a half-day instead of a full day as in previous researches. By studying both-phase acquisition and both-side non-nadir looking, the obtained results reflect better the actual characteristics of SAR payloads, comparing to traditional approaches. The method is also applied in studying SAR satellite’s orbital design process. With mission requirements and payload characteristics provided as inputs, the optimal orbit is rapidly determined.

Instantaneous Heat Transfer Coefficient of Droplets Impinged on Heated Surfaces

Droplet impingement is one of the phase change techniques used for equipment cooling because of the proper utilization of sensible and latent heat. This study analyzes droplet evaporation on aluminum and copper substrate. The instantaneous heat transfer coefficient (HTC) during evaporation of 100 µl de-ionized water is studied. The infrared camera is used to visualize and analyze the evaporation mechanism. The effect of substrate and fluid temperature on droplet evaporation is analyzed. The surface temperatures of both substrates are varied from 105 °C to 165 °C. The test fluid is maintained at temperatures of 30 °C, 50 °C, 75 °C, and 99.4 °C. The droplets exhibited Leidenfrost behavior for temperatures beyond 145 °C with copper and 150 °C with aluminum surface. It is observed that the evaporation rate is higher for copper than aluminum. A user-friendly interface is developed for determining the instantaneous surface area of an evaporating droplet. The apparent peak in the area in copper is higher than aluminum for all cases due to surface tension gradient and Marangoni flow. HTC increases with the temperature of droplet evaporating on a given substrate and is higher for copper. When substrate temperature increases for a given droplet temperature, the instantaneous HTC increases.

Inversion of reclaimed soil water content based on a combination of multi-attributes of ground penetrating radar signals

Rapid, accurate, and non-destructive acquisition of the distribution of reclaimed soil moisture information can provide data for the rapid monitoring of reclaimed soil in areas experiencing coal mining subsidence. However, the water content inversion methods based on ground penetrating radar (GPR) are mostly single-attribute analysis methods, which are easily affected by the soil structure. This paper proposes a multi-attribute joint analysis method, which can reduce the influence of complex soil structure on the prediction results. Surveys and soil sampling using GPR were performed on a subsided reclamation area in Huaibei City, Anhui Province, China. Correlation analysis of GPR attribute information and volumetric water content (VWC) showed that frequency peak (FP), average envelope amplitude (AEA), energy, instantaneous amplitude area, instantaneous frequency area, and average instantaneous frequency values were significantly related to the VWC of reclaimed soil. The applicability of different single-attribute analysis methods under the condition of reclaimed soil was compared. Results showed that the predictive effects of FP and AEA attributes were better than other attributes. Generally, the single-attribute analysis method was greatly affected by the structure of reclaimed soil, so the accuracy and reliability of this method need to be further optimized. The prediction results of the single- and multi-attribute joint analysis methods in the structure of reclaimed soil were compared and analyzed. This showed that the prediction accuracy and model reliability of the multi-attribute method are both higher than those of the single-attribute method. The multi-attribute method can overcome the problem of insufficient accuracy of water content detection of ground-seeking radar in soil with a complex structure. Finally, the multi-attribute method was used to obtain the water distribution information in the reclamation area. Results of this study provide new methods and ideas for the prediction of water content by GPR in soils with complex structure.

A multiple rolling-point loading method for low-stress equal-radial-depth cropping

A multiple rolling-point loading method for low-stress equal-radial-depth cropping is proposed considering the eccentricity of transient fracture areas of metal bars. The crack propagation criterion under single rolling-point loading is provided. The extended finite element method (XFEM) is used to simulate the longest contiguous propagation of crack fragment and polycyclic propagation of annular crack under multiple rolling-point loading. The bar can then transiently fracture with high-quality section. The cropping experiments of multiple rolling-point loading curves obtained in this paper reveals that the instantaneous fracture area can be reduced by up to 65% and the eccentricity of bars can be avoided.

Investigation of heat and mass transfer characteristics during the flame propagation of biomass straw from an initial linear fire source

Biomass straw has gradually received attention as a new energy that is easily accessible. The deep understanding of burning characteristics is critical to the efficient and safe utilization of biomass straw as a new energy, and further benefit to estimate the hazard of straw fire disasters. In the present study, the straw stacked into a rectangle with a length of 1 m, and widths from 0.1 m to 0.6 m was ignited from in a width with a linear-source fire. The heat and mass transfer characteristics during the flame propagation were investigated. The results showed that the flame front shape evolved from concave to convex as the straw width widened. Specifically, the critical transition range of straw width was from 0.3 m to 0.4 m due to the change of the dominant heat transfer factors. The residual mass of straw decreased linearly because of the uniform flame spreading process, indicating a constant MLR. The MLR was determined by the function of the aspect ratio of the instantaneous combustion area, which is shown as n+1/n. The flame temperature above the center position of the rectangular straw increased first and then dropped gradually. The peak dimensionless temperature presented a piecewise function with (z−z0)m˙−2/5.

A numerical method to compute flexible vertical responses of containerships in regular waves

In this paper, a series of simulations of hydroelastic problems of containerships are conducted by a nonlinear 3D panel method which is based on the generalized Taylor Expansion Boundary Element Method (TEBEM). In the structure part, the Transfer Matrix Method is selected to perform a modal analysis which provides key parameters of hydroelastic calculation. In the hydrodynamic part, the nonlinearities arising from the variations of instantaneous wetted surface area are considered in the solutions of hydrostatic restoring forces as well as 1st order incident wave forces. Meanwhile, an extended Modified Logvinovich Model (MLM) is presented to predict the slamming forces due to the large-amplitude incident waves. The numerical predictions of the hydroelastic responses of a 6750-TEU containership and S175 in regular waves are presented. The effects of wave steepness and sailing speed as well as the variation characteristics of load components against with wave direction are studied. The numerical and experimental results are in acceptable agreement which proves the accuracy of the proposed method.

Real-time instantaneous wide-area ocean acoustic monitoring in the shallow Great South Channel and deep ocean south of Rhode Island with Northeastern University coherent hydrophone array

A large-aperture 160-element coherent hydrophone array system, developed in-house at Northeastern University, was deployed and tested at sea in shallow water Great South Channel and deep ocean south of Rhode Island during September 2021. The system implements the passive ocean acoustic waveguide remote sensing technology for real-time instantaneous wide area ocean monitoring. The array data sampled at 100 kHz per element were processed in real-time at sea to provide beamformed spectrogram imagery in multiple frequency subbands from 10 Hz to 50 kHz and spanning 360 degree horizontal azimuths about the receiver array. A wide variety of acoustic detections were made in real time, including marine mammal vocalizations and motion-related signals, fish grunts and other fish-generated signals, tonal and broadband signals from distant ships and own tow ship. Real-time detections of marine mammal vocalizations include fin whale 20 Hz pulses, humpback whale songs and social sounds, minke whale buzz sequences, sperm whale echolocation and social clicks, dolphin whistles and echolocation clicks, as well as calls from unidentified baleen and toothed whale species. A database of automatically detected signals with bearing-time information along with extracted time-frequency characteristics was generated in real-time at sea.

Development of a large-aperture 160-element coherent hydrophone array system for instantaneous wide area ocean acoustic sensing

A large-aperture coherent hydrophone array and processing system has been developed in-house at Northeastern University (NU). The overall acoustic aperture length is 194 m with 160-elements nested into four sub-apertures each with 64 hydrophones and spacing corresponding to half-wavelength at design frequencies in Hertz of 250, 500, 1000, and 2000. Hydrophones with integrated broadband preamplifiers designed with a linear frequency response from 10 to 50 kHz sending differential pair amplified and filtered analog signals to 24-bit, 32-channel Analog to Digital Converters (ADC) with sampling rate programmable up to 100 kHz per channel. Array internals are designed using field replaceable pressure tolerant components including hydrophones, preamplifiers, power modules, telemetry units, and ADC verified by testing in an in-house assembled pressure chamber. Forward and aft modules are equipped with non-acoustic sensor elements to provide depth, heading, pitch, roll, and temperature measurements. The NU array was made without specialized facilities by utilizing modular interchangeable array interconnects allowing for conventional array populating and filling methods. The system implements real-time array data acquisition and processing including beamforming, beamformed spectrogram generation and signal detections. The NU array has been sea tested in 2021 in both shallow and deep water environments of the US Northeast coast.

Surface profile and milling force prediction for milling thin-walled workpiece based on equivalent 3D undeformed chip thickness model

With the development of the aviation manufacturing industry, the application range of thin-walled parts is rapidly increasing. Accurate machining process and surface topography prediction are the keys to ensuring machining quality. This article is based on the relative geometric relationship between the real motion trajectory of the milling cutter and the workpiece; the undeformed chip thickness equation and the two-dimensional surface contour feature algorithm are established. By introducing the parameters of milling cutter critical height, milling cutter helix angle, and lag angle parameters, the three-dimensional surface profile prediction model and the equivalent three-dimensional model considering the chip formation process are derived. And the calculation equations of the instantaneous chip cross-sectional area and the blade-workpiece contact length of the three phases of chip formation are established, respectively. The multiple linear regression method was used to fit the orthogonal test results of titanium alloy Ti-6Al-4 V, so as to complete the dynamic milling force identification, and finally establish the milling force prediction model. The accuracy of the prediction model was verified by the single factor method, and the influence of different parameters on the milling process of thin-walled parts was observed. The results show that the established model has high accuracy in predicting the surface profile and milling force of thin-walled parts. This study provides guidance for efficient prediction of the milling process of thin-walled parts.

Modeling of interfacial area for single deformed bubble based on VOF method

Bubble geometric shape and hydrodynamic behavior affect directly mass, momentum and heat transfer at the interfacial area in the bubbly flow regime. A numerical model is developed to calculate instantaneous bubble interfacial area based on the VOF method. After data fitting, a new correlation is developed to associate the normalized bubble interfacial area with Eötvös and Galilei numbers. Considering the variation in liquid viscosity and surface tension of different gas–liquid systems, the influence of interface sharpening schemes on bubble hydrodynamics is illustrated comprehensively. With a moving reference frame, long-term bubble behavior is investigated in the air–water system and the temporal evolution of bubble hydrodynamics is analyzed in detail. Simulation results are validated by experimental data in terms of bubble rising velocity, aspect ratio and bubble deformation factor. The results indicated that the interface sharpening scheme affects the calculation of bubble interfacial area significantly. Both liquid viscosity and surface tension contribute to the formation of a stable terminal bubble interface. In the given range, the evolution of terminal interfacial area is found to agree well with the predicted correlation. Regarding long-term bubble behavior, three stages for instantaneous rising velocity and bubble interfacial area are observed, which are the damped oscillatory stage, the transition stage and the quasi-stable stage. Bubble deflection direction may be opposite to internal gas jet direction due to vortex shedding. In general, the numerical models applied in this study are proven to be feasible for bubble interfacial area calculation.