Determination of the Normal Contact Stiffness and Integration Time Step for the Finite Element Modeling of Bristle-Surface Interaction

In finite element modeling of impact,it is necessary to define appropriate values of the normal contact stiffness,Kn,and the Integration Time Step(ITS).Because impacts are usually of very short duration,very small ITSs are required.Moreover,the selection of a suitable value of Kn is a critical issue,as the impact behavior depends dramatically on this parameter.In this work,a number of experimental tests and finite element analyses have been performed in order to obtain an appropriate value of Kn for the interaction between a bristle of a gutter brush for road sweeping and a concrete surface.Furthermore,a suitable ITS is determined.The experiments consist of releasing a steel bristle that is placed vertically at a certain distance from a concrete surface and tracking the impact.Similarly,in the finite element analyses,a beam is modeled in free fall and impacting a surface;contact and target elements are attached to the beam and the surface,respectively.The results of the experiments and the modeling are integrated through the principle of conservation of energy,the principle of linear impulse and momentum,and Newton’s second law.The results demonstrate that,for the case studied,Kn and the impact time tend to be independent of the velocity just before impact and that Kn has a very large variation,as concrete is a composite material with a rough surface.Also,the ratio between the largest height of the bristle after impact and the initial height tends to be constant.

A Review on Fretting Wear Mechanisms,Models and Numerical Analyses

Fretting wear is a material damage in contact surfaces due to micro relative displacement between them.It causes some general problems in industrial applications,such as loosening of fasteners or sticking in components supposed to move relative to each other.Fretting wear is a complicated problem involving material properties of tribosystem and working conditions of them.Due to these various factors,researchers have studied the process of fretting wear by experiments and numerical modelling methods.This paper reviews recent literature on the numerical modelling method of fretting wear.After a briefly introduction on the mechanism of fretting wear,numerical models,which are critical issues for fretting wear modelling,are reviewed.The paper is concluded by highlighting possible research topics for future work.

Multi-Scale Analysis of Fretting Fatigue in Heterogeneous Materials Using Computational Homogenization

This paper deals with modeling of the phenomenon of fretting fatigue in heterogeneous materials using the multi-scale computational homogenization technique and finite element analysis(FEA).The heterogeneous material for the specimens consists of a single hole model(25% void/cell,16% void/cell and 10% void/cell)and a four-hole model(25%void/cell).Using a representative volume element(RVE),we try to produce the equivalent homogenized properties and work on a homogeneous specimen for the study of fretting fatigue.Next,the fretting fatigue contact problem is performed for 3 new cases of models that consist of a homogeneous and a heterogeneous part(single hole cell)in the contact area.The aim is to analyze the normal and shear stresses of these models and compare them with the results of the corresponding heterogeneous models based on the Direct Numerical Simulation(DNS)method.Finally,by comparing the computational time and%deviations,we draw conclusions about the reliability and effectiveness of the proposed method.

DIC Based Strain and Damage Analysis of Large Scale Steel to Composite Adhesive Joints Subjected to Tension and Compression Loading

This paper reports an experimental study of the mechanical response to tensile and compressive force of large scale steel to composite joints adhesively bonded with a thin layer of vinylester resin.In one specimen,the length of the reinforcing fibres in contact with the steel substrate has been reduced by saw cutting at both ends of the joint.This damaged specimen and four intact specimens were subjected to quasi-static tensile testing;six specimens were used for compression testing.The strain distribution at the composite surface and at the steel to hardwood connection of the specimen was monitored by digital image correlation(DIC).DIC allowed identifying the onset of damage in the tensile tested joints near the interface of the composite layer and the steel-hardwood connection.Both tensile and compression tested specimens failed due to significant peel strain concentration at the composite near the connection of steel and hardwood.The average strength of a specimen tested in compression was about 66%higher than the average strength of a specimen tested in tension.The strain concentration zone in the damaged specimen was away from the introduced saw cuts.As a result the damaged and intact tensile specimens showed the same failure strength and stiffness.All specimens failed by adhesive failure between the composite-hardwood interface.

Aspects of Fretting Fatigue Finite Element Modelling

Fretting fatigue is a type of failure that may affect various mechanical components,such as bolted or dovetail joints,press-fitted shafts,couplings,and ropes.Due to its importance,many researchers have carried out experimental tests and analytical and numerical modelling,so that the phenomena that govern the failure process can be understood or appropriately modelled.Consequently,the performance of systems subjected to fretting fatigue can be predicted and improved.This paper discusses different aspects related to the finite element modelling of fretting fatigue.It presents common experimental configurations and the analytical solutions for cylindrical contact.Then,it discusses aspects of fretting fatigue crack initiation,such as crack location,orientation,and length,as well as stress averaging approaches.Then,it deals with the propagation stage;crack face interaction,orientation criteria,and crack growth rate are discussed.Lastly,additional aspects of recent research on fretting fatigue are reviewed:out-of-phase loading,cohesive zone modelling,wear effects,heterogeneity,and crystal orientation.Fretting fatigue is a phenomenon not well understood,and much more research is needed so that its understanding is increased and proper criteria and laws may be available for different cases.

Polygonal Finite Element for Two-Dimensional Lid-Driven Cavity Flow

This paper investigates a polygonal finite element(PFE)to solve a two-dimensional(2D)incompressible steady fluid problem in a cavity square.It is a well-known standard benchmark(i.e.,lid-driven cavity flow)-to evaluate the numerical methods in solving fluid problems controlled by the Navier-Stokes(N-S)equation system.The approximation solutions provided in this research are based on our developed equal-order mixed PFE,called Pe1Pe1.It is an exciting development based on constructing the mixed scheme method of two equal-order discretisation spaces for both fluid pressure and velocity fields of flows and our proposed stabilisation technique.In this research,to handle the nonlinear problem of N-S,the Picard iteration scheme is applied.Our proposed method’s performance and convergence are validated by several simulations coded by commercial software,i.e.,MATLAB.For this research,the benchmark is executed with variousReynolds numbers up to the maximum Re=1000.All results then numerously compared to available sources in the literature.

Improvement of Flat Surfaces Quality of Aluminum Alloy 6061-O By A Proposed Trajectory of Ball Burnishing Tool

Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool.In other words,burnishing paths should be multidirectional rather than monotonic,in order to cover uniformly the surface.Indeed,the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation,and that makes determining the optimum burnishing force an essential step of the burnishing process a success.Therefore,we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study.In this paper,we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns.Taking into consideration the optimum burnishing force,to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter(Rz).Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.

Numerical Analysis of Tilted Cutting and F128 Brushes

Road sweeping is an essential service that has to be conducted for public health,as well as aesthetic purposes.In many countries,sweeping vehicles are used for this activity.They usually comprise a gutter brush that sweeps the debris that is located in the road gutter.This work studies the performance of two kinds of gutter brushes:a cutting brush and a flicking(F128)brush.This is carried out by means of a 3-D dynamic,nonlinear Finite Element(FE)brush model developed by the authors.In this model,inertia forces are applied to the bristle,and its clamped end is fixed.Consequently,the surface(road)is rotated,translated,and raised.Bristle-road interaction is modelled as flexible-to-rigid contact.In particular,the aim of this article is to compare the performance of a conventional brush and a brush rotating at variable speed.As brushes normally work tilted,FE analyses are carried out for tilted cutting and F128 brushes,rotating at speeds that fluctuate at different frequencies.It is concluded that brush oscillations have a significant effect on bristle tip velocities and bristle-road forces.Also,at certain frequencies,oscillations seem to improve sweeping performance of the F128 brush.However,they do not appear to improve significantly the performance of the cutting brush.

Multiscale Analysis of the Effect of Debris on Fretting Wear Process Using a Semi-Concurrent Method

Fretting wear is a phenomenon,in which wear happens between two oscillatory moving contact surfaces in microscale amplitude.In this paper,the effect of debris between pad and specimen is analyzed by using a semi-concurrent multiscale method.Firstly,the macroscale fretting wear model is performed.Secondly,the part with the wear profile is imported from the macroscale model to a microscale model after running in stage.Thirdly,an effective pad’s radius is extracted by analyzing the contact pressure in order to take into account the effect of the debris.Finally,the effective radius is up-scaled from the microscale model to the macroscale model,which is used after running in stage.In this way,the effect of debris is considered by changing the radius of the pad in the macroscale model.Due to the smaller number of elements in the microscale model compared with the macroscale model containing the debris layer,the semi-concurrent method proposed in this paper is more computationally efficient.Moreover,the results of this semi-concurrent method show a better agreement with experimental data,compared to the results of the model ignoring the effect of debris.

The Effect of Surface Pit Treatment on Fretting Fatigue Crack Initiation

This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.

Three-Dimensional Meshfree Analysis of Interlocking Concrete Blocks for Step Seawall Structure

This study adapts the flexible characteristic of meshfree method in analyzing three-dimensional(3D)complex geometry structures,which are the interlocking concrete blocks of step seawall.The elastostatic behavior of the block is analysed by solving the Galerkin weak form formulation over local support domain.The 3D moving least square(MLS)approximation is applied to build the interpolation functions of unknowns.The pre-defined number of nodes in an integration domain ranging from 10 to 60 nodes is also investigated for their effect on the studied results.The accuracy and efficiency of the studied method on 3D elastostatic responses are validated through the comparison with the solutions of standard finite element method(FEM)using linear shape functions on tetrahedral elements and the well-known commercial software,ANSYS.The results show that elastostatic responses of studied concrete block obtained by meshfree method converge faster and are more accurate than those of standard FEM.The studied meshfree method is effective in the analysis of static responses of complex geometry structures.The amount of discretised nodes within the integration domain used in building MLS shape functions should be in the range from 30 to 60 nodes and should not be less than 20 nodes.

Thermomechanical Behavior of Brake Drums Under Extreme Braking Conditions

Braking efficiency is characterized by reduced braking time and distance,and therefore passenger safety depends on the design of the braking system.During the braking of a vehicle,the braking system must dissipate the kinetic energy by transforming it into heat energy.A too high temperature can lead to an almost total loss of braking efficiency.An excessive rise in brake temperature can also cause surface cracks extending to the outside edge of the drum friction surface.Heat transfer and temperature gradient,not to forget the vehicle’s travel environment(high speed,heavy load,and steeply sloping road conditions),must thus be the essential criteria for any brake system design.The aim of the present investigation is to analyze the thermal behavior of different brake drum designs during the single emergency braking of a heavy-duty vehicle on a steeply sloping road.The calculation of the temperature field is performed in transient mode using a three-dimensional finite element model assuming a constant coefficient of friction.In this study,the influence of geometrical brake drum configurations on the thermal behavior of brake drums with two different materials in grey cast iron FG200 and aluminum alloy 356.0 reinforced with silicon carbide(SiC)particles is analyzed under extreme vehicle braking conditions.The numerical simulation results obtained using FE software ANSYS are qualitatively compared with the results already published in the literature.

Review on the Prediction of Residual Stress in Welded Steel Components

Residual stress after welding has negative effects on the service life of welded steel components or structures.This work reviews three most commonly used methods for predicting residual stress,namely,empirical,semi-empirical and process simulation methods.Basic principles adopted by these methods are introduced.The features and limitations of each method are discussed as well.The empirical method is the most practical but its accuracy relies heavily on experiments.Mechanical theories are employed in the semi-empirical method,while other aspects,such as temperature variation and phase transformation,are simply ignored.The process simulation method has been widely used due to its capability of handling with large and complex components.To improve its accuracy and efficiency,several improvements need to be done for each simulation aspect of this method.

Effect of fatigue load on the bending tribo-corrosion-fatigue behaviors between the main cable wires

The main cable bent around the saddle of the suspension bridge is subjected to the wind,the vehicle,the bridge’s own weight and the corrosive media.The coupling of the three loads and the environments causes the friction,the corrosion,and the fatigue(tribo-corrosion-fatigue)among the wires inside the main cable.In this paper,a wire bending tribo-corrosion-fatigue test rig was designed and developed.The effect of fatigue load on the bending friction behaviors between the cable wires in ultrapure water and 3.5%NaCl solution was explored.The tribological properties and electrochemical corrosion behaviors under different fatigue loading ranges were investigated.The tribo-corrosion-fatigue interaction between the cable wires was quantitatively characterized,and the mechanism of the interaction was analyzed.The results demonstrate that the increasing fatigue load exacerbates the coupling damage of the cable wires attributed to the enhanced interaction.The findings carry theoretical importance when assessing the main cable’s deterioration and the load-bearing safety of a suspension bridge.

Effect of wear debris on fretting fatigue crack initiation

Both wear and fatigue occur in fretting condition,and they interact with one another during the whole process.Fretting fatigue is commonly analysed without considering the effect of wear in partial slip regime,although wear affects the lifetime of crack initiation.This paper investigates,for the first time,the effect of wear debris on fretting fatigue crack initiation.To investigate the effect of debris,first fretting wear characteristics in partial slip regime are analysed for loading conditions.Then,the effect of wear on fretting fatigue crack initiation is investigated using Ruiz parameters and critical plane methods without considering the debris effect.Through the results,we can see that loading conditions affect the wear profiles in different ways.Moreover,wear has a significant effect on the fatigue in partial slip regime without considering debris especially on the crack initiation location.Finally,considering wear debris in the analysis,its effect on critical plane parameters is investigated.It is found that by considering the wear debris effect,the frtting fatigue crack initiation location is shifted towards the trailing edge.The predictions of both crack initiation location and lifetime show a good agreement with the experimental data.

Dopamine hydrochloride and carboxymethyl chitosan coatings for multifilament surgical suture and their influence on friction during sliding contact with skin substitute

In order to reduce the damage to tissue and fill the interstices between fibers,multifilament sutures are frequently treated with certain coating materials.The objective of this study was to create and characterize dopamine hydrochloride(DA)and carboxymethyl chitosan(CMCS)coatings on surgical sutures and investigate their effects on the frictional performance of the surgical sutures during sliding through a skin substitute.The effects of the treatment on the physical and chemical characteristics of the surgical sutures were evaluated.The friction force of the surgical sutures during sliding through the skin substitute was experimentally determined using a penetration friction apparatus.The coefficient of friction(COF)was calculated using a linear elastic model and was used to estimate the frictional behavior of the surgical suture‐skin interactions.The results showed that the DA coating could evenly deposit on the surface of the etched multifilament surgical suture surfaces in a weakly alkaline buffer solution.The CMCS coating material could form a uniform film on the surface of the sutures.Minor changes in the surface roughness of the multifilament surgical sutures with different treatments occurred in this study.The friction force and the COF of the multifilament surgical sutures with DA and CMCS coating showed little change when compared with untreated multifilament surgical sutures.

Damage detection in steel plates using feed-forward neural network coupled with hybrid particle swarm optimization and gravitational search algorithm

Over recent decades,the artificial neural networks(ANNs)have been applied as an effective approach for detecting damage in construction materials.However,to achieve a superior result of defect identification,they have to overcome some shortcomings,for instance slow convergence or stagnancy in local minima.Therefore,optimization algorithms with a global search ability are used to enhance ANNs,i.e.to increase the rate of convergence and to reach a global minimum.This paper introduces a two-stage approach for failure identification in a steel beam.In the first step,the presence of defects and their positions are identified by modal indices.In the second step,a feedforward neural network,improved by a hybrid particle swarm optimization and gravitational search algorithm,namely FNN-PSOGSA,is used to quantify the severity of damage.Finite element(FE)models of the beam for two damage scenarios are used to certify the accuracy and reliability of the proposed method.For comparison,a traditional ANN is also used to estimate the severity of the damage.The obtained results prove that the proposed approach can be used effectively for damage detection and quantification.

Fatigue crack propagation across grain boundary of Al-Cu-Mg bicrystal based on crystal plasticity XFEM and cohesive zone model

In this paper,a methodology integrating crystal plasticity(CP),the eXtended finite element method(XFEM)and the cohesive zone model(CZM)is developed for an Al-Cu-Mg alloy to predict fatigue crack propagation(FCP)across grain boundary(GB)of Al-Cu-Mg alloy during stageІІ.One GB model is incor-porated into FCP constitutive law to describe grain interaction at GB.A bicrystal containing GB is built up to simulate FCP behavior through L participated GBs.Modelling features including GB characteristic,cumulative plastic strain(CPS)distribution and crystal slipping evidence can be identified.The numer-ical results are compared with published experimental data to check the accuracy of model.This work demonstrates that the combination of CP containing GB constitutive laws,XFEM and CZM is a promising methodology in predicting twist angle-controlled crack deflection through GBs.

A data-assisted physics-informed neural network(DA-PINN)for fretting fatigue lifetime prediction

In this study,we present for the first time the application of physics-informed neural network(PINN)to fretting fatigue problems.Although PINN has recently been applied to pure fatigue lifetime prediction,it has not yet been explored in the case of fretting fatigue.We propose a data-assisted PINN(DA-PINN)for predicting fretting fatigue crack initiation lifetime.Unlike traditional PINN that solves partial differential equations for specific problems,DA-PINN combines experimental or numerical data with physics equations as part of the loss function to enhance prediction accuracy.The DA-PINN method,employed in this study,consists of two main steps.First,damage parameters are obtained from the finite element method by using critical plane method,which generates a data set used to train an artificial neural network(ANN)for predicting damage parameters in other cases.Second,the predicted damage parameters are combined with the experimental parameters to form the input data set for the DA-PINN models,which predict fretting fatigue lifetime.The results demonstrate that DA-PINN outperforms ANN in terms of prediction accuracy and eliminates the need for high computational costs once the damage parameter data set is constructed.Additionally,the choice of loss-function methods in DA-PINN models plays a crucial role in determining its performance.