Finite Element Contact Analysis Research Articles

A global-local fretting analysis methodology and design study for the pressure armour layer of dynamic flexible marine risers

In this paper, a global-local fretting design methodology for the pressure armour layer of flexible marine risers is outlined. This includes global dynamic riser analysis, geometrical and analytical sub-models and local nub-groove contact finite element analysis. Furthermore, a fretting test rig is developed and utilised to quantify coefficient of friction and wear coefficient under representative nub-groove loading conditions. The combination of the global-local computational methodology and experimental characterisation of pressure armour wire material allows for the development of running condition fretting maps. This identifies design criteria for critical riser global curvatures that are associated with minimum number of cycles to failure. The design methodology presented in this paper is applied to a realistic riser design study, using extreme sea-state loading conditions. In this case study, the predicted pressure armour fretting fatigue lives are found to be in the same range as the plain fatigue lives of the tensile armour layer.

Evaluation of a structural epoxy adhesive for timber-glass bonds under shear loading and different environmental conditions

This article presents a study of timber-glass adhesive joints. It examines the shear specimen and shear tools preparation process and the evaluation of the results backed up with an overview of existing similar studies. The chosen adhesive was a cold-curing two-component structural bonding epoxy resin (Mapei Adesilex PG1). The shear tests were performed under different temperatures and the timber samples had different moisture contents. A simple shear test tool was designed and was clamped into a universal testing machine for the shear test. The force and crosshead displacement values from the universal testing machine were used for evaluating the results. The environmental conditions of 20 °C and 5% timber moisture content resulted in the highest average shear strength obtained from the shear tests of the analysed joints (9.89 MPa), whereas the environmental conditions of 50 °C and 20% timber moisture content resulted in the lowest average shear strength (3.42 MPa). It was found that the joint strength is dependent on the environmental temperature and timber moisture content. Moreover, the shear specimen load-displacement behaviour at the environmental temperature of 50 °C was linear and nonlinear – depending on the timber moisture content. The most frequent failure type was timber failure. Additionally, a nonlinear contact finite element analysis was performed to demonstrate the additional shear specimen rotation due to the clearance between the shear specimen and shear tools. This impact was evaluated regarding the stress distribution in the bond line. The evaluated epoxy resin adhesive was proved to be suitable for timber-glass bonds.

Tibio talar contact stress: An experimental and numerical study

AimsTibio-talar contact stress has been evaluated and successively compared by performing an ankle contact finite element (FE) analysis and an experimental test carried on an assembled simple synthetic model of ankle equipped with a high-resolution (Tekscan) pressure sensor. MethodsA numerical FEM analysis was carried out by simulating the ankle joint (foot, and tibia) in order to investigating the stress shielding on the contact surfaces. The foot was constrained at the base while a load of 980 N was applied on the top of the tibia. The same setup was experimentally reproduced by introducing a high-resolution (Tekscan) pressure sensor between tibia and foot. ResultsResults evidenced a good agreement between numerical and experimental data, a percentage difference of 15% was evaluated on the equivalent Von Mises contact stress. ConclusionThe obtained results reveal interesting consequences deriving by taking into account how the stress shielding can influence the integrity and resistance of bones. The methods used for this validation enable formal comparison of computational and experimental results, and open the way for objective statistical measures of regional correlation between FE-computed contact stress distributions from comparison articular joint surfaces.

Mesh stiffness analysis of beveloid gears for the rotating vector transmission

This paper investigates the meshing stiffness of beveloid gears in the beveloid rotate vector (BRV) transmission. It is a new kind of transmission evolved from rotate vector (RV) reducer. In the BRV transmission, the beveloid gear is a kind of involute gear with a bevel angle. The BRV transmission have high power density, large transmission ratio and high precision in geared coupled systems. However, there is rare systematic research conducted on the meshing stiffness analysis of the BRV transmission at present. Based on the loaded contact finite element analysis principle, a meshing stiffness analysis model for beveloid gears is established. The influence of different factors such as pitch cone angle, addendum coefficient, load and rim structure parameters of external gear on meshing stiffness are studied. The results show that the pitch cone angle and addendum coefficient have little effect on the shape of the meshing stiffness curve, but they have a significant influence on the amplitude of meshing stiffness. In contrast, the load can affect both the shape and the amplitude of the meshing stiffness curve obviously. Also, the size of scallop-hole and rim thickness have a great impact on the amplitude of the meshing stiffness. The prescribed piece of study can provide a better understanding for gear researchers in order to understand the influence of different parameters on dynamic characteristics analysis of the BRV transmission systems.

The effect of different occlusal contact situations on peri-implant bone stress – A contact finite element analysis of indirect axial loading

Implant restoration is one of the basic treatments in dentistry today, yet implant loss from occlusal overload is still a problem. Complex biomechanical problems such as occlusal overload are often analyzed by means of the finite element method. This numerical method makes it possible to analyze in detail the influence that different loading situations have upon implants and tissues, which is a key element in optimizing these dental procedures.This study was designed to investigate the stress distribution in peri-implant bone of a single-tooth implant crown using the finite element method. The load was applied indirectly via an occluding tooth through a three and five contact setup into the implant crown. The friction coefficient values between the crown and antagonist were varied between 0.1 and 1.0. Additionally, three crowns with cusp inclinations of 20°, 30° and 40° were modeled. Non-linear contact computations indicated that an increase in friction changed the direction and magnitude of contact forces, which also led to reduced stresses in the bone. Furthermore, the stress magnitudes were higher when cusps of a greater inclination were used. The intensity of stress alterations was strongly dependent on the distribution and number of contacts, and the contact force vector. In maximum intercuspation, a resulting axial load due to well-distributed contacts prevented high stresses in bone even with high cusp inclinations and low friction. Therefore for long-term clinical success, particular attention should be paid to occlusal adjustment so as to prevent oblique loading onto dental implant restorations.

Geometric design and analysis of face-gear drive with involute helical pinion

Entire tooth surface precise modeling and systematic analysis method for face-gear drives with an involute helical pinion are investigated. A modified imaginary shaper is mathematically modeled as the geometric design tool. The entire tooth surface of the face gear is determined analytically as the envelope to the family of imaginary shaper tooth surface. A practical method to determine the minimum and maximum radii of the face gear is developed. Addendum modification of the face gear is implemented mathematically based on the modified imaginary shaper to improve face-gear tooth-top thickness. Conical modification of the pinion is proposed to avoid contact between face-gear tooth-root fillet and the pinion tooth. Transverse pressure angle modification of the pinion is also proposed to avoid edge contact arising at inner-end and outer-end edges of face-gear tooth. Finite element models with nine pairs of teeth are employed for 3D contact finite element analysis to investigate the basic characteristics of face-gear drives, including meshing and tooth contact analysis, contact and bending stress analysis, contact ratio, transmission error, mesh stiffness, and sensitivity test. The helical face-gear drive is sensitive to rotation direction and shaft angle error. The presented geometric design method is illustrated and validated by numerical examples and trial manufacture.

Elastic dynamics modelling and analysis for a valve train including oil film stiffness and dry contact stiffness

An elastic dynamics model for a valve train including combined stiffness of oil film and dry contact between a cam and a tappet, is proposed. Multi-directional elastic deformations of the valve train are solved by discretizing slender components into Rayleigh beam and bar elements. The oil film stiffness is determined by non-Newtonian elastohydrodynamic lubrication in the line contact, whereas the dry contact stiffness is achieved by using finite element contact analysis. A numerical solution for the dynamic model is developed and verified by conducting a dynamic stress experiment. The influences of rotation speed on the oil film stiffness and contact force between the cam and the tappet are discussed, and the combined effects of rotation speed and oil film stiffness on a dynamic transmission error of the valve train are analyzed. Results show that the oil film stiffness decreases when the cam rotation speed increases within a certain range, whereas the sharp increased contact force may enlarge the oil film stiffness when the speed exceeds a critical value. The oil film stiffness variation slight influences the contact force, but such variation significantly affects the dynamic transmission error.

Application of finite element analysis to predict the mechanical strength of ventilated corrugated paperboard packaging for handling fresh produce

The presence of vent holes in corrugated paperboard package causes material loss of the package, which compromises its strength and stability. To improve the structural design of fresh produce packages, it is important to understand the response of packages when subjected to various types and combinations of mechanical loads. This study aimed to develop a validated finite element analysis (FEA) model to study the structural behaviour of commonly used ventilated corrugated paperboard (VCP) package when subjected to compression load by considering the geometrical nonlinearities of the packages. Two package types were used: a control package without vent holes and standard vented packages. The FEA model accurately predicted the compression strength of the corrugated paperboard, control package and standard vent package. When compared with experimental results, the model predictions for the VCP package were within 10%. Compression strength of the standard vent packages were found to be linearly affected by paperboard liner thickness. Increasing and decreasing the baseline liner thickness of the standard vent package by 80% resulted in an increase and decrease in compression strength by about 15% and 19%, respectively. From the contact FEA model, maximum Von Mises stress was produced at the corners of the package. Von Mises stress was reduced by about 25% on changing the friction coefficient from 0 to 0.1. This study provides empirical evidence for package designers on how to improve the mechanical integrity of packages while at the same time aiming to maintain an optimum ventilation.

Influences of spline assembly methods on nonlinear characteristics of spline–gear system

As a connector, the spline is widely applied in gear transmission systems. In transmitting torque, the load and deformation of the spline are affected by the applied assembly method, and this effect leads a change in the time-varying meshing stiffness (TVMS) of the gear pair. Consequently, the nonlinear characteristics and vibration performance of the whole system can be affected. In this study, the TVMS of gear systems that use two different spline assembly methods, namely, the-side-fit and the-major-diameter-fit, is predicted by finite element contact analysis. Subsequently, the nonlinear dynamic model of the spline–gear system is established and its accuracy is verified through a vehicle vibration experiment. The numerical results reveal that the system assembled through the-side-fit and without spline exhibits a diverse range of periodic, sub-harmonic, and chaotic behaviours at high speed, whereas no bifurcation is observed through the-major-diameter-fit. As the magnitude of interference increases in the-major-diameter-fit, the dynamic transmission error decreases. Therefore, different assembly methods can affect the nonlinear characteristic. Moreover different magnitudes of interference in the-major-diameter-fit also have effects on the nonlinear characteristics and vibration performance of spline–gear systems.

Investigation on the dislocation evolution in nanoindentation with 2.5D discrete dislocation dynamics simulation and experiment

This study investigates the influence of materials' dislocation source density and initial dislocation density on dislocation evolution mechanism during nanoindentation process. On the basic of discrete dislocation dynamics (DDD) algorithm, a novel 2.5D nanoindentation numerical model was by proposed by coupling with finite element (FE) contact analysis. In particular, new reduced integration method and stress transmission mode were performed in this simulation scheme. Results showed that the dislocation multiplication and slip behavior were both significantly impacted by the initial dislocation source density. Meanwhile, the influence of initial dislocation density focused on the spatial arrangement of discrete dislocations. In addition, transmission electron microscope (TEM) analysis was used to reveal the dislocation configurations during nanoindentation process. Typical dislocation patterns including Shockley partial dislocation and Frank partial dislocation were found in extrusion region, which verifies the reasonable slipping conditions of DDD simulation. The results of this study can be useful in developing DDD model and predicting dislocation evolution rules in nanoindentation.

INFLUENCE OF MODELING METHODS FOR CARTILAGE LAYER ON SIMULATION OF PERIACETABULAR OSTEOTOMY USING FINITE ELEMENT CONTACT ANALYSIS

Finite element (FE) analysis has been used in the simulation of periacetabular osteotomy (PAO) to predict the improvement of contact pressure concentration in dysplastic hip joint. Since the cartilage layer is difficult to be segmented from CT or MRI images, most hip joint models were assumed to be a simple perfect ball and socket joint. However, the influence of different cartilage modeling methods on the reliability of the simulation has not been assessed. The objective of this study is to elucidate the influence of different cartilage modeling methods on predictions of cartilage layers’ contact pressure by FE contact analysis. In this study, the cartilage layer was generated by applying three typical kinds of modeling methods (spherical, uniform thickness, and midline-based). After comparisons with these cartilage modeling methods, the computational results demonstrate that the cartilage modeling methods have a dramatic influence on predictions of contact pressure in the PAO. The relatively continuous contact pressure distribution and lower peak contact pressure are observed in spherical cartilage modeling method. The discontinuous contact pressure distribution and higher peak contact pressure are obtained in uniform thickness and midline-based cartilage modeling methods. And the degree of discontinuous pressure distribution is even worse in the midline-based cartilage modeling method.

Integral finite element analysis of turntable bearing with flexible rings

This paper suggests a method to calculate the internal load distribution and contact stress of the thrust angular contact ball turntable bearing by FEA. The influence of the stiffness of the bearing structure and the plastic deformation of contact area on the internal load distribution and contact stress of the bearing is considered. In this method, the load-deformation relationship of the rolling elements is determined by the finite element contact analysis of a single rolling element and the raceway. Based on this, the nonlinear contact between the rolling elements and the inner and outer ring raceways is same as a nonlinear compression spring and bearing integral finite element analysis model including support structure was established. The effects of structural deformation and plastic deformation on the built-in stress distribution of slewing bearing are investigated on basis of comparing the consequences of load distribution, inner and outer ring stress, contact stress and other finite element analysis results with the traditional bearing theory, which has guiding function for improving the design of slewing bearing.

Numerical analysis of multiple friction contacts in bladed disks

The damping potential of multiple friction contacts in a bladed disk is investigated. Friction contacts at tip shrouds and strip dampers are considered. It is shown that friction damping effectiveness can be potentially increased by using multiple friction contact interfaces. Friction damping depends on many parameters such as rotational speed, engine excitation order and mode family and therefore it is not possible to damp all the critical resonances using a single kind of friction contact interface. For example, a strip damper is more effective for the low nodal diameters, where blade/disk coupling is strong. The equations of motion of the bladed disk with multiple friction contacts are derived in the frequency domain for a cyclic structure with rotating excitations. A highly accurate method is used to generate the frequency response function (FRF) matrix. Furthermore, a finite element contact analysis is performed to compute the normal contact load and the contact area of the shroud interface at operating rotational speed. The multiharmonic balance method is employed in combination with the alternate frequency time domain method to find the steady state periodic solution. A low-pressure turbine bladed disk is considered and the effect of the engine excitation level, strip mass, thickness and the accuracy of FRF matrix on the nonlinear response curve are investigated in detail.

Three Dimensional Finite Element Analysis of Rolling Contact between Wheel and Rail

The fatigue performance of the rails is affected by many factors, including service conditions, loading, mechanical properties, environment factors, and manufacturing processes. In this paper, the investigation on wheel-rail to identify the initial damages caused by Rolling Contact Fatigue (RCF) cracks and the location that experienced damages is presented. UIC 54kg rail (grade 900A) was used as the model in three dimensional (3D) finite element contact analysis. The fatigue crack growth on wheel-rail was carried out by considering the Hertz contact pressure. The finite element analysis results show that maximum stress concentration zone was between the wheel-rail surface (rail inside curve gauge corner) and it is above the yield stress limit for wheel-rail steel. Fatigue crack propagation within a depth affected stress concentration region was predicted. The stress intensity factors (SIF) for mode I, mode II and mode III fracture were plotted from ANSYS simulation. Three types of fracture modes were affected the UIC54kg rail Steel to fail or develop initial failure when the crack propagation exceeds 5 mm.

The effect of direct and indirect force transmission on peri-implant bone stress – a contact finite element analysis

In almost all finite element (FE) studies in dentistry, virtual forces are applied directly to dentures. The purpose of this study was to develop a FE model with non-linear contact simulation using an antagonist as force transmitter and to compare this with a similar model that uses direct force transmission. Furthermore, five contact situations were created in order to examine their influence on the peri-implant bone stresses, which are relevant to the survival rate of implants. It was found that the peri-implant bone stresses were strongly influenced by the kind of force transmission and contact number.

Implications of Multi-asperity Contact for Shear Stress Distribution in the Viable Epidermis – An Image-based Finite Element Study

Understanding load transfer mechanisms from the surface of the skin to its deeper layers is crucial in gaining a fundamental insight into damage phenomena related to skin tears, blisters and superficial/deep tissue ulcers. It is unknown how shear stresses in the viable epidermis are conditioned by the skin surface topography and internal microstructure and to which extent their propagation is conditioned by the size of a contacting asperities.In this computational study, these questions were addressed by conducting a series of contact finite element analyses simulating normal indentation of an anatomically-based two-dimensional multi-layer model of the skin by rigid indenters of various sizes and sliding of these indenters over the skin surface. Indentation depths, local (i.e. microscopic) coefficients of friction and Young's modulus of the stratum corneum were also varied. For comparison purpose and for isolating effects arising purely from the skin microstructure, a geometrically-idealised equivalent multi-layer model of the skin was also considered.The multi-asperity contact induced by the skin topographic features in combination with a non-idealised geometry of the skin layers lead to levels of shear stresses much higher than those produced in the geometrically-idealised case. These effects are also modulated by other system parameters (e.g. local coefficient of friction, indenter radius).These findings have major implications for the design and analyses of finite element studies aiming at modelling the tribology of skin, particularly if the focus is on how surface shear stress leads to damage initiation which is a process known to occur across several length scales.

A Cartesian Slab Based Multiblocking Strategy for Irregular Cylindrical Surfaces

Cylindrical surfaces of many irregularities populate aerospace and automotive engine components. Many of these surfaces represent power transmitting shafts and rotary mating parts that require structured meshes to expedite contact and other finite element analyses with their mates. This poses a challenge to surface and volume mesh generators. In this paper a novel method of multiblocking based on 2D Cartesian slabs is proposed for the generation of predominantly structured meshes on irregular cylindrical surfaces. A seam generation technique comprises the first step, leading to the creation of an axial line of optimal length to split the 3D surface to facilitate 2D flattened or parametric space generation. The 2D parametric domain of the surface is next transformed to an axis-parallel local coordinate system for Cartesian slab generation. An intricate virtual face split operator is used to dissect the 2d parameter space into parallel rectangular slabs of uniform or varying thicknesses. A light-weight, mesher-native topology builder that uses virtual topological elements is proposed for constructing a virtual topology network of the slabs. Results demonstrate high quality, high fidelity transfinite-dominant meshes on a host of trimmed cylindrical surfaces.

Development of finite element contact analysis algorithm based on distance functions

Development of finite element contact analysis algorithm based on distance functions

Experimental and numerical analysis of semi-destructive device for in situ assessment of wood properties in compression parallel to grain

A reconstruction of historical timber structures requires precise diagnostics of mechanical properties of particular structural members, which would subsequently underlie a reliable plan of the reconstruction. Mechanical properties of wood are determined most exactly using destructive techniques, but often they cannot be used in historical constructions. This calls for using nondestructive or semi-destructive techniques that are still reasonably exact, not too invasive and can be profitably used in situ. This work examines a new nondestructive diagnostic tool that enables to determine strength and stiffness parameters of wood parallel to the grain in situ. The function of the instrument was verified using standard compression tests parallel to the grain that correlated with the instrument well (r = 0.92). Complicated stress state in the drilled hole was examined by contact finite element analysis and revealed high contribution of longitudinal elastic moduli in force measurement (r = 0.96).

Influence of solid solution strengthening on spalling behavior of railway wheel steel

The object of this paper is to investigate the influence of solid solution strengthening on the spalling behavior of railway wheel steel. White etching layer (WEL) was reproduced by twin-disc test and analyzed by phase transformation kinetic. Spalling of WEL was then evaluated by rolling contact fatigue (RCF) test and finite element analysis. The results show that solid solution strengthening improves the resistance to WEL formation for wheel steel through increasing the austenitization temperature. WEL remarkably reduces the RCF life of wheel steel. Whether containing WEL or not, solid solution strengthened steel exhibits a better rolling contact fatigue strength than the traditional wheel steel.