Surface Roughness Conditions Research Articles

Soil moisture estimation using RISAT-1 and SENTINEL-1 data using modified Dubois model in comparison with averaged NDVI

In past studies, several researchers took potential use of multi-temporal optical data and dual-polarized SAR data to assess drought by estimating soil moisture. In this study, Modified Dubois Model (MDM) semi-empirical model with Topp's model is used for retrieval of soil moisture. It involves retrieving the backscattering coefficient from RISAT-1 and SENTINEL-1 datasets to derive the surface roughness and soil moisture conditions. The estimated soil moisture retrieved from microwave SAR parameters is validated with field measurements provides soil moisture spatial variability over different land use classes and bare soil condition. The RISAT-1 derived soil moisture has R2 = 0.53, whereas SENTINEL-1 shows R2 = 0.84. It also confirms the possibility of two different polarization σ°HH and σ°VV backscatter involving MDM. It observes that SENTINEL-1 was found well correlated with ground-measured soil moisture. Also, the averaged NDVI sounds reliable with soil moisture ratio, which helps to understand the impact of agricultural drought monitoring.

Fatigue life analysis of aero-engine blades for abrasive belt grinding considering residual stress

Abrasive belt grinding technology is widely used in the processing of aero-engine blades. Residual stress is used as an indicator of grinding gauge integrity, which has a significant impact on the fatigue performance of aero-engine blades. In fatigue life research, experiments are mainly used to explore the influence of residual stress on fatigue life. Restricted by factors such as experimental efficiency and cost, it is necessary to simulate the influence of residual stress in the process of fatigue failure. Based on the theory of crack initiation and propagation, this paper proposes a life prediction algorithm considering residual stress; carries out a bending vibration fatigue experiment and simulation fatigue life analysis of aero-engine blade grinding with abrasive belt; compares the results of experiments and simulations and proposes a residual stress equivalent calibration method. Used theory, simulation, and experiment to verify the effectiveness of the method, and uses this equivalent calibration method to analyze the effect of residual stress on the fatigue life of aero-engine blades ground by abrasive belts. The experimental results show that the surface residual compressive stress will optimize the size and distribution of the surface stress during the service process of the aero-engine blade. Under the same external load and surface roughness conditions, a larger surface residual compressive stress will increase the aero-engine blade stiffness, reduce the aero-engine blade’s vibration amplitude, and reduce Surface stress, which in turn, has a beneficial effect on fatigue life. The proposed calibration method considering residual stress can accurately predict the fatigue life of aero-engine blades with a prediction accuracy up to 90%.

Optimization of surface integrity in face milling of AISI 52,100 alloy steel using Taguchi based grey relational analysis

The challenging demand to achieve high quality of the manufactured components, has resulted in development of precision machining processes, which serve as a good alternative to the grinding process. However, high-temperature generation is the major problem in the cutting areas during the machining of difficult-to-cut material; this temperature affects the surface integrity. Therefore, lubrication is required for the removal of heat due to temperature rise at the cutting zone. Because of the adverse effect of flood cooling on the worker's health and the environment, MQL is a suitable substitute to flood cooling. In this study, the effect of process parameters such as cutting speed, feed rate, Depth of cut, lubricant concentration, and flow rate on surface roughness and microhardness was studied during the face milling of AISI 52,100 alloy steel using MQL. Taguchi-based L-27 orthogonal array was used, and multi-response optimization was done using grey relational analysis (GRA). The Depth of cut was the highly influencing factor followed by feed rate, cutting speed, flow rate, and lubricant concentration. The optimum process parameters for the optimized condition for surface roughness and microhardness were cutting speed 150 m/min, feed rate 0.1 mm/rev, Depth of cut 0.3 mm, lubricant concentration 60%, and flow rate 100 ml/hr.

A fluid mechanics approach to evaluating marine soft clay strength by a ball full-flow penetrometer

Ball full-flow penetrometer is widely used for testing the ultimate bearing pressure q of marine soil to evaluate the undrained shear strength su by the proposed bearing capacity factor N, and thus N is one of the primary concerns of marine geotechnical engineers. However, plastic constitutive model solutions of N resolved by using classical rigid-plastic materials described by the Tresca yield criterion are not suitable for evaluating the low-strength marine soft clays with viscous fluid characteristics. In this paper, the validated computational fluid dynamics (CFD) approach is used to simulate the interaction between the ball with smooth and rough surfaces and marine soft clays described by non-Newtonian fluids with shear thinning characteristics and rate effect. Based on this, the effects of the rate effect parameter λ, density and strength of the marine soft clay on N are systematically analyzed. Furthermore, during the ball's deep penetration, the equations of N considering different λ at rough and smooth ball surface conditions are established. Finally, the stress state of the marine soft clays around the ball and the mechanism of the rate effect leading to the variation of N are elucidated by the pressure distribution contours on the ball surface, the shear rate contours of the marine soft clay on the ball surface, and the velocity field contours of the marine soft clay around the ball, which provides a basis for the undrained shear strength su evaluation of low-strength marine soft clays.

Comparative investigations of cryo-treated and untreated inserts on machinability of AISI 1050 by using response surface methodology, ANOVA and Taguchi design

This study aims to focus on the machinability of the AISI 1050 workpieces with cutting inserts, treated under deep cryogenic heat (−146 °C), and with untreated ones, and to investigate the optimization of cutting parameters and heat treatment conditions for surface roughness and cutting force by using Taguchi mixed design and Response Surface Methodology (RSM). The machining experiment was performed on a CNC lathe with machining parameters such as three feed rates, three cutting speeds and a constant depth of cut under dry condition and with heat treatment condition. As is known, Taguchi design L18 (32 21) consists of three factors; cutting parameters with each one of three levels and heat treatment condition with two levels. The results of machining tests were evaluated considering surface roughness, vibrations and cutting force. Furthermore, chip morphology and wear led by cryo-treated and untreated inserts were detected with the aid of a scanning electron microscope. The results demonstrated that cryo-treated (CTI) insert had lower tool wear, vibration, and cutting force than untreated insert (UI) in all conditions. In aspect of chip morphology, untreated inserts had bigger and larger serrations than the treated inserts. In addition, according to Taguchi S/N ratio, optimal cutting parameters and heat treatment conditions were obtained from CHT1, V3, and f1 for the Fc and from CHT1, V1, and f1 for the Ra, respectively. Also, the most significant control factors on surface roughness and cutting force were feed rate depending on ANOVA results and RSM. Validation test results demonstrated that RSM and Taguchi mixed design calculated the cutting force (R2RSM (CTI and UI) = 99.99% and R2Tag. = 99.95%) and surface roughness (R2RSM (CTI) = 99.76%, R2RSM (UI) = 99.59% and R2Tag. = 99.12%). Therefore, RSM and Taguchi mixed design predicts highly well match experimental data with prediction data.

Dynamic Impact Factor Determination of an Existing Pre-stressed Concrete I-Girder Bridge Using Vehicle-Bridge Interaction Modelling

The dynamic Impact Factor (IM) of a bridge is influenced by many factors, including Vehicle-Bridge Interaction (VBI), vehicle speed and road roughness. This paper represents the dynamic effects of moving vehicles and the determination of IM of an existing Pre-stressed concrete I-girder bridge utilizing VBI modeling. Evaluation of the IM is expected to provide valuable information for condition assessment and management of the existing bridge. The interaction problem between the vehicle and the bridge includes a dynamic model for the bridge structure subsystem, a dynamic model for the vehicle subsystem, interaction constraints, road roughness modelling and numerical solution techniques for the dynamic systems. The Half-car model is utilized for modelling of the vehicle dynamics and the bridge dynamic model is idealized according to Finite Element Method (FEM). Then FEM along with the mode superposition method are utilized for determining the Equation of Motion (EOM) for the bridge subsystem. D’Alembert’s principle is used for developing EOM for the vehicle subsystem. The interaction between vehicle vibration and bridge vibration is established through the contact forces between the wheels and the bridge by employing the compatibility relationship between the contact points and by applying the static equilibrium condition. Lastly, Newmark’s-β method is used for solving the coupled mathematical model of the vehicle and bridge interaction problem to determine the responses of the two sub-systems. The whole procedure is then performed for different vehicle speeds and various bridge deck surface roughness conditions to determine the dynamic impact on the existing I-girder bridge named Teesta Bridge located in Bangladesh.

Airfoil lift calculation using wind tunnel wall pressures

An experimental method to calculate lift using static pressure ports on the wind tunnel walls and its associated limits has been explored in this article. While the wall-pressure measurement (WPM) technique for lift calculation has been implemented by other researchers, there is a lack of literature on the sensitivity of the WPM method to airfoil chord length, model thickness, surface roughness, and freestream conditions. Chord sensitivity studies showed that the airfoil chord to test section length ratio plays an important role in the accuracy of the measurements. Models need to be appropriately sized for optimum performance of the WPM method. Additionally, choosing the correct scaling ratio also ensures independence of lift measurements from freestream Reynolds number conditions. Finally, a combination of symmetric and cambered airfoils with thicknesses varying from 6 % − 21 % were tested and successfully validated against reference data for a freestream chord Reynolds number range of 100,000 to 550,000. The WPM method was found to be sensitive to varying surface flow conditions and airfoil thickness and has been shown to be a viable replacement to traditional lift measurement techniques using load balances or airfoils with surface pressure ports.

Experimental investigation of the effects of loading rate, contact roughness, and normal stress on the stick-slip behavior of faults

The tectonic movement rate, in situ stresses (e.g., normal stress) and fault roughness may change during the long evolutionary histories of seismogenic faults. To investigate the effects of these three factors on fault slip behaviors, we conducted direct shear tests by sequentially changing the shear loading rate and normal stress on small-scale granite specimens under three roughness conditions. We found that for a given fault system, the shear loading rate is a primary controlling parameter of the recurrence intervals of stick-slip events, and the correlation between them can be empirically expressed by a power law. Stick-slip recurrence intervals can influence the stress drops of stick-slip events via two different tendencies. The shear stress drops increase quasilinearly with the recurrence intervals at a given shear loading rate, while the combined data from all shear rate tests show that the shear stress drops increase with the logarithm of the recurrence time. In the investigated range of fault roughness, we observed that surface roughness conditions strikingly affect the sliding mode and recurrence frequency of stick-slip events. In detail, the two smooth fault systems slide with regular stick-slip events, and the roughest fault system exhibits bimodal behavior. Namely, at lower normal stresses, stick-slip events cannot be stably generated, a few were occasionally generated, and regular stick-slip events were interrupted by local stick-slip. When the applied normal stress is sufficiently high, the fault slides with continuous regular stick-slip events in the same way as those in the smoother fault systems. We further noticed that the recurrence frequency of stick-slip and friction drop are correlated at a fixed sliding distance, and this relationship can be described by an inverse proportional function. Our results suggest that all three factors, namely, shear loading rate, fault surface roughness and normal stress, can influence the behaviors of fault slip and hence are important for evaluating earthquake hazards.

Investigation of Surface Quality for Minor Scale Diameter of Biodegradable Magnesium Alloys during the Turning Process Using a Different Tool Nose Radius

The main objective of the study is to analyze the various cutting parameters to investigate the surface quality of the minor scale diameter of magnesium alloy in the dry turning process using a different tool nose radius (r). The surface roughness (Ra) was gauged, and micro-images produced by scanning electron microscopy (SEM) were reviewed to evaluate the machined surface topography. The analysis of variance (ANOVA), linear regression model and signal-to-noise (S/N) ratio were applied to investigate and optimize the experimental conditions for surface roughness. The study results imply that the feed rate and tool nose radius significantly affected the surface quality, but the spindle speed did not. The linear regression model is valid to forecast the surface roughness. The cutting parameters for optimum surface quality are a combination of a spindle speed of 710 rpm, a feed rate of 0.052 mm/rev and a tool nose radius of 1.2 mm. The machined surface topography contains the feed marks, micro-voids, material side and material debris, but they become smaller and decrease at a lower feed rate, larger tool nose radius and higher spindle speed. These results show the good surface quality of magnesium alloys in a dry turning process, which could be applied in implant, orthopedic and trauma surgery.

Probability law of turbulent kinetic energy in the atmospheric surface layer

We investigate the significance of turbulent kinetic energy (TKE, $k$) and its variability in the atmospheric surface layer (ASL), needed in many applications. The statistics of $k$ around its mean state is studied using the probability density function $p(k)$ for ASL flows with significant buoyancy forcing. A nonlinear Langevin equation that preserves $p(k)$ but allows linear relaxation of $k$ to its mean state is suggested and tested using multiple ASL data sets that span various stabilities and surface roughness conditions. Model parameters for the proposed Langevin equation are derived from similarity theory, reproducing measured $p(k)$ with minimal Kullback-Leibler divergence.

Research on the effect of SS316L electrode plate treatment on HHO gas production performance

The working principle of an internal combustion engine, in general, is to convert chemical energy from liquid fuels to mechanical energy. The type of fuel commonly used by internal combustion engines is fossil fuel, which until now has been increasing in use while its supply is running low. The presentstudy is to conduct research in the field of new and renewable energy as an alternative fuel to replace fossil fuels. Hydrogen is a new form of energy carrier that could be obtained through the process of water electrolysis and is a promising fuel supplement in the future. Hydrogen production through the electrolysis process continues to be develop to help use environmentally friendly fuels and can have a positive impact on engine performance and exhaust emissions. However, to produce consistent and quality HHO gas output, the current HHO gas generator still needs tobe improved especially for the production volume. The purpose of this research will be directed to the development of the effective electrode plate system in producing HHO gas. In order to improve the quality and volume of HHO gas production, it was found that the level of surface roughness and the contact angle of the material should be increased through grinding and polishing processes. In this research, various SS316L electrode plates with different surface roughness were made for the analysis of HHO gas production to match the expected volume of HHO gas production. Various conditions of surface roughness of the electrode plate are carrying out by grinding and polishing the surfaces of both sides of the electrode plate to a uniform roughness level.

An Investigation on Starvation Onset of Rough Surface Line Contacts

Abstract Utilizing a computational approach, this study quantifies the onset of lubrication starvation for line contacts of rough surfaces operating under typical ranges of automotive gearing applications. The response parameter is selected as the critical film thickness supply, at which starvation initiates. The potential influential parameters (predictors) considered include normal force density, rolling velocity, sliding, lubricant viscosity, and surface roughness amplitude. A non-Newtonian thermal mixed lubrication model is employed to determine the critical lubricant supply under various operating and surface roughness conditions. General linear regression is implemented to reach an easy-to-use equation (R-squared value higher than 97%), facilitating the quantification of starvation dependence on the predictors that are statistically significant.

Effect of Steel Surface Roughness and Expanded Graphite Condition on Sliding Layer Formation.

The aim of the research was to evaluate the influence of the initial roughness of a steel pin cooperating with a graphite ring—dry and wet—on the mechanism of sliding layer formation. A ring–pin friction pair was used for the study, where the rings were made of expanded graphite, while the pins were made of acid-resistant steel. In the first case, the steel pin interacted with a dry graphite ring, and in the second case, the graphite rings were moist. To determine the effect of initial surface roughness, the pins were divided into three roughness groups. To determine changes in surface geometry due to material transfer, the Ra and Rz parameters were measured. This project investigated how the initial roughness value of the steel surface pin cooperating with expanded graphite influences the formation of the sliding layer. Increasing the initial roughness of the steel surface interacting with the graphite contributes to faster layer formation and reduced roughness. The state of the expanded graphite—dry and wet—influences the formation of the sliding layer of graphite—a wet graphite component causes a faster smoothing of the steel surface. The running time of the wear apparatus has an effect on the resulting layer. The highest roughness group is the most favorable from the viewpoint of sliding layer formation.

Effect of Temperature and Surface Roughness on the Tribological Behavior of Electric Motor Greases for Hybrid Bearing Materials

Greased bearings in electric motors (EMs) are subject to a wide range of operational requirements and corresponding micro-environments. Consequently, greases must function effectively in these conditions. Here, the tribological performance of four market-available EM greases was characterized by measuring friction and wear of silicon nitride sliding on hardened 52100 steel. The EM greases evaluated had similar viscosity grades but different combinations of polyurea or lithium thickener with mineral or synthetic base oil. Measurements were performed at a range of temperature and surface roughness conditions to capture behavior in multiple lubrication regimes. Results enabled direct comparison of market-available products across different application-relevant metrics, and the analysis methods developed can be used as a baseline for future studies of EM grease performance.

Rough Surface Scattering Model Comparisons for Radar Altimetry of Sea Ice

Currently, sea-ice thickness is often estimated using microwave radar altimetry. It is well known that radar measurements are highly dependent on the roughness characteristics of the observed scene and can have a profound effect on altimetry-based thickness estimates. This simulation-based study highlights the importance of sea-ice roughness parameterization in the context of radar altimetry. This work provides a new sea-ice roughness parameterization in the form of an elevation spectrum developed from field campaign data. The formulation of this elevation spectrum is partly based on the generalized power law. Simulations have been developed to predict electromagnetic scattering from surfaces described by the new spectrum, with a focus on the X-band (10 GHz) scattering with nadir incidence. In this work, both the analytical small slope approximation and numerically exact Method of Moments are applied to various sea-ice surface spectra, representing a wide range of surface roughness conditions. The results show that the normalized radar cross section of the sea-ice interface varies significantly depending on the surface elevation spectrum and the statistics of the rough interface. Comparisons with numerically exact methods show that analytical approximations to rough surface scattering work reasonably well for the cases considered here, except at large scattering angles.

Influence of Roughness and Curing Temperature on the Strength of Aluminum Adhesively Bonded Joints

This work presents a comprehensive experimental study on the effect of surface roughness and adhesive curing temperature on adhesively bonded joints of AA6082. The modification of surface morphology has been assessed by roughness measurements (contact and non-contact profilometry). In addition, mechanical changes in the resin properties due to different curing time have been probed through a series of instrumented indentation tests. Thus, adhesive bonded single lap joints were fabricated and tested to assess the changes in shear strength at varying surface roughness and curing conditions. The obtained results indicate the ability of the roughened surface to improve the joint strength together with the adequate combination of curing temperature and time among those suggested by the manufacturer.

Dynamics of interaction between an Euler-Bernoulli beam and a moving damped sprung mass: Effect of beam surface roughness

This work presents analytical expressions that identify the dynamics of the interaction between a simply supported Euler-Bernoulli beam and a moving sprung damped mass on the beam when the roughness on the beam surface is taken into consideration. The roughness load can have significant effects on the dynamics of the beam and its loading capacity, especially when the beam has poor surface conditions. Using the concept of perturbation, the solutions of the beam and mass are presented and validated by comparing the results with the finite element model. Because the determination of the roughness load requires the solution of an ill-posed inverse problem, the Tikhonov regularization and generalized cross validation methods are used to identify the moving load caused by the beam surface roughness. The performances of different regularization matrices (L matrices) under four noise levels (1%, 5%, 10%, and 20%) and three road classes are investigated in terms of their effectiveness in reducing errors in the prediction of the roughness load and mass motion. The results demonstrate that there is no optimal selection of regularization matrices (L matrices) crossing all the beam surface roughness conditions under the noisy disturbance. Under the lower noise levels (1% and 5%), the L1 matrix provided less error in the solution. However, when the noise level increased to 10% and 20%, the L0 matrix, the lower order regularization matrix, provided an acceptable solution. The results also indicated that beam surface roughness has an important impact on the roughness load identification and mass motion prediction.

Multi-spindle drilling of Al2024 alloy and the effect of TiAlN and TiSiN-coated carbide drills for productivity improvement

High precision drilling is required to ensure the structural integrity of the aircraft. Therefore, strict quality controls are required to ensure optimum hole quality since hundreds of thousands of holes are drilled into different aircraft structures. The large number of holes required for riveting means that their installation must be carried out in a fast and precise manner. This can be achieved using multi-head drilling tools that can drill several holes simultaneously. The current study investigated the use of a multi-spindle drill head that can produce three holes simultaneously. Uncoated carbide and TiAlN-coated and TiSiN-coated carbide drills were used to assess cutting forces, hole surface roughness, burr formations and tool condition when machining Al2024 aerospace alloy under dry machining conditions. Analysis of variance was employed for estimating the relationships between the input parameters (spindle speed, feed and tool coating) and the studied hole quality metrics. Furthermore, a regression model was developed with a regression coefficient (R2) of more than 90% for the prediction of measured responses. Interestingly, better results in lower thrust force and surface roughness were obtained using the uncoated carbide drills compared with TiAlN and TiSiN, while the performance of TiAlN was found to be better than those obtained from TiSiN.

Experimental and Theoretical Study of the Effect of Hull Roughness on Ship Resistance

Hull roughness increases ship frictional resistance and, thus, results in economic and environmental penalties. Its effect has been prevalently predicted using the similarity law scaling procedure. However, this method has not yet been validated with experimental data using a model ship. This study presents an experimental investigation into the effect of roughness on ship resistance and provides a validation of the similarity law scaling, by using tank testing of a flat plate and a model ship. Both the plate and the ship were tested in smooth and rough surface conditions, respectively. For the rough surface conditions, sand grit (aluminum oxide abrasive powder) was applied on the surfaces of the flat plate and the ship model. The roughness functions of the rough surface were derived by using the results obtained from the flat plate tests. Using the roughness function and the flat plate towing test, frictional resistance was extrapolated to the length of the model ship following the similarity law scaling procedure. The total resistance of the rough ship model was first predicted using the extrapolated frictional resistance and the result of the smooth ship model, and then compared with the results from the rough ship model. The predicted total resistance coefficients for the rough ship model showed a good agreement with the measured total resistance coefficient of the rough ship model, thus proving the validity of using Granville’s similarity law scaling to extrapolate the roughness effect on ship resistance.

Lattice Boltzmann simulation of water flow through rough nanopores

Water transport at the nanoscale is a significant phenomenon related to unconventional hydrocarbon production. This study develops a new model of the lattice Boltzmann method to simulate the nanoconfined water transport through a rough pore. The proposed model considers the interface viscosity and the slip length according to the surface wettability. Water flow simulations are conducted to analyze the flow characteristics and the transport capacity under various wettability and surface roughness conditions. Results show that the fluid velocity and pressure distributions along the flow direction are profoundly affected by the rough surface. As the contact angle increases, the transport capacity has a minor increase in the hydrophilic condition, but a significant rise in the hydrophobic state. Also, with the increase of relative surface roughness, the transport capacity for the hydrophobic rough nanopore is greatly enhanced, while for the hydrophilic pores, only a minor variation is observed. The dimensionless liquid permeability gradually decreases as the relative surface roughness increases irrespective of the wettability. However, the fractal dimension of the rough surface rarely affects both the transport ability and the dimensionless permeability. Finally, this study presents an empirical permeability estimation model for rough nanopores.