Finite Element Contact Analysis Research Articles

In-Plane Combination of Micropillars with Distinct Aspect Ratios to Resist Overload-Induced Adhesion Failure.

Bioinspired micropillar adhesives have shown broad application prospects in space capture and docking, due to their strong adhesion, good environmental adaptability, and reusability. However, when performing space missions, unavoidable contact collision with target objects may cause large deformation of the micropillars, resulting in the loss of adhesion ability. This study reports a novel micropillar adhesive through the in-plane combination of micropillars (IPCM) with different aspect ratios, consisting of small pillars for retaining strong adhesion and large ones for resisting overload-induced adhesion failure. It is demonstrated that the IPCM array can still maintain 85% of the adhesion peak after static large deformation compared to a general micropillar array composed of the same pillars. The impact of element size and layout of the IPCM, as well as detachment velocity on adhesion performance under high preload is discussed. Furthermore, finite element contact analysis qualitatively reproduces the experimentally observed micropillar deformations and attributes the overload-induced adhesion failure to the redistribution of surface normal stress. Finally, the potential application of the IPCM in dynamic capture is demonstrated on different objects. The proposed IPCM opens up new design concepts for practical applications of bioinspired adhesives in space capture and docking.

Lightweight design of steel sprocket for roller chain drive using explicit dynamic simulation

Roller chain drives are frequently applied in a variety of machinery for mechanical motion and power transmission. The roller engagement location on the sprocket tooth contour and the resulted contact behavior is governed by the wear of components and pretension of the chain. Therefore, the influence of extension of chain resulted from wear and pretension of chain on contact behavior was investigated numerically using explicit dynamics module of ABAQUS software. The contact angles evaluated from the numerical simulation were assessed relative to those obtained from the basic rigid body analytical formulation. The chain elongation of 3% increased the maximum contact force up to 52% during engagement with the driver sprocket. The contact force raised to 400% when the pretension in the chain drive was increased from 200 to 1000 N, leaving the force distribution pattern unaltered. The optimal design of a steel sprocket is realized through equivalent static finite element contact analysis of a sprocket engaged with 3% extended roller chain. The dynamic finite element analysis in conjunction with topology optimization reduced the weight of the sprocket by 24%.

3D rolling contact finite element analysis of high-speed railway turnout considering ratchetting effect

The present work introduces a three-dimensional finite element model for the wheel-turnout-sleeper system, incorporating a cyclic constitutive model that accurately captures the nonlinear hardening behavior of rail steel under cyclic loadings. At the same time, a mixed implicit-explicit finite element method is employed to investigate the transient rolling contact behavior of wheel-turnout. Through dynamic analysis, the transient rolling contact status of the wheel-turnout, stress and strain responses of the turnout, and wheel-rail forces are investigated under varying crossing speeds and number of cycles. It is found that during the wheelset crossing, the contact stress remains relatively stable on the stock rail, and multi-point contact occurs at the wing rail and long point rail, and the contact stress on the surface of the long point rail is more significant. With an increase in crossing speed in the same cycle, there is a gradual rise in contact stress on the long point rail face. At the same crossing speed, with the increase in the number of cycles, the contact position between the wheelset and the long point rail gradually moves back, and the top width of the contact position gradually expands. Meanwhile, the fluctuation range of vertical displacement of the wheel center diminishes, and the wheel flange moves away from the long point rail. Additionally, a progressive accumulation of ratcheting strain is observed on the rail, and the ratcheting strain on the long point rail significantly exceeds that on the stock rail. The research results will help to provide a reference for the optimization and design of the critical cross-section profile of the long point rail and will have guiding significance for the maintenance and repair of turnouts.

Smoothed Finite Element Analysis of Contact and Large Deformation Problems

Smoothed Finite Element Analysis of Contact and Large Deformation Problems

Finite element contact analysis of the hollow cylindrical roller bearings

Finite element contact analysis of the hollow cylindrical roller bearings

Constraining effect of load frames during full-scale rotor blade fatigue testing

In rotor blade fatigue tests used for the certification process, load frames are used to introduce the loads to the blade. These load frames have a constraining effect on the cross-sectional deformation. This work investigates these constraining effects using a finite element contact analysis on a current-generation commercial rotor blade. Two different load frame variants are considered: a conventional load frame covering most of the cross-section and a reduced load frame covering only the main spar caps. The interaction between blade and load frame is implemented via contact formulations, which allows pretensioning in combination with a flap and a lead-lag load case. Strains on the outer surface of the blade are evaluated and compared to an artificial reference loading. The area of influence of the load application through the load frame, in which the strains deviate significantly due to clamping effects, mostly corresponds to the 0.75 times the chord length assumed for the certification [1]. The strains in the trailing edge are significantly less affected by the reduced load frame variant than by the conventional one, thus potentially making it possible to consider the trailing edge at the position of the load frame as being properly tested for certification purposes.

A statistics view of contact pressure distribution for normal contact of fractal surfaces

Due to inherent nonlinear stiffness and damping characteristics, dry friction interfaces have a significant impact on the dynamics of jointed structures. When two surfaces are brought into purely normal contact, contact pressure distribution is of high concern. This work focused on the statistics of the contact pressure distribution between a rough surface and a smooth rigid plane, which provides new insight into the interface contact behaviour. First, the fractal rough surface is generated using the Weierstrass–Mandelbrot function with measured roughness parameters. With meshed rough surfaces, an elastic–plastic finite element contact analysis is performed to determine the contact pressure distribution. Then, the results of contact pressure are statistically analysed. The effects of roughness and contact load on contact area, contact stiffness and mean contact pressure are thoroughly investigated. The probability distribution of contact pressure is determined by fitting a continuous function using a twofold Weibull mixture model. The proposed probability distribution function is found to be capable of describing contact pressure. The contact pressure distribution is affected by the surface fractal characteristics and evolves with the contact load.

Contact analysis of heavy-duty apron feeder with clearance

The problem of clearance contact between the bearing plate and the supporting guide rail is studied when the heavy‐duty Apron Feeder is subjected to impact load. Based on the energy method, the impact force of the falling ore was calculated, and the nonlinear contact finite element analysis of the structure with clearance was performed using ANSYS Workbench. The results show that at the first moment of contact, the initial contact shape is an approximately linear contact, and then a deformation occurs near the contact line, which quickly evolves from a linear contact to a surface contact. The contact stress distribution is diffused outward along the initial contact boundary and gradually decreases, and the stress concentration occurs at the contact boundary. When the distance is different, the shape of the contact area is similar, but when the distance is large, the contact area is small and the stress distribution is more concentrated. The nonlinear contact calculation of the skirt feeder reveals the instantaneous contact process of the plate rail under the impact force and determines the influence of the distance size on the contact properties, which provides a theoretical basis for the selection of the distance value.

Vibration characteristics analysis of a type of turbine disk-blade assembly system in the civil aero-engine

The coupled vibration in the turbine disk-blade system (TDS) is one of the main bottlenecks that hinder the further development of high-performance engines. To analyze the vibration of the TDS, three types of contact conditions, involving bonded, frictionless, or frictional were used to simulate the contact between the turbine disk and the blades. Three finite element analysis (FEA) models of a typical TDS based on the tenon structure were developed. The experimental system was developed and experimental modal analysis (EMA) was performed. According to the comparison between FEA and EMA results, the most accurate model is the frictional contact FEA model. The average error of the frictional contact FEA model is 1.42%, and the root mean square error is 0.75%. The working modes of the TDS at different speeds were calculated using the frictional contact FEA model. Meanwhile, based on the newly developed FEA model, it is found that the weak links in the TDS are the blades. This work can provide a theoretical basis for the TDS structure optimization and promote the development of high-quality aero-engines.

Study on the meshing evolving mechanism of a novel self-evolution hourglass worm drive

To satisfy the increasing unique characteristics of high precision and heavy-load performance in industrial equipment, a novel self-evolution hourglass worm drive is proposed in this paper. It is consisted of an involute helical beveloid (IHB) gear and an oblique planar enveloping (OPE) hourglass worm, and this worm drive gradually evolves from a local conjugate hourglass worm drive with point contact in the initial meshing state, and a middle meshing state (MES) hourglass worm drive with short-line contact with continuous operation and wear, as well as the finally evolves into a toroidal involute (TI) hourglass worm drive with line contact. According to the differential geometry theory and the spatial meshing principle, the mathematical models of this novel self-evolution hourglass worm drive are established in each evolution stage, the theory of backlash-adjustable is confirmed with introducing a pair of transition tooth surfaces, and the meshing contact area evolution mechanism was defined and elaborated. In addition, the meshing performance evolution of the contact area and the bearing capacity are simulated by numerical analysis including tooth contact analysis and finite element analysis. The analysis results show that with the continuous evolution, the contact area keeps increasing, and the bearing capacity also keeps improving. This study will provide a theoretical basis for the industrial application of this novel hourglass worm drive.

A novel bionic gripper based on the front tarsi of scutigers

A novel bionic gripper with bristles is designed based on the biological structure of the front tarsi of scutigers, and its simulation model is established. It was verified that the proposed bionic gripper not only achieved the expected gripping action but also completed the pinching motion with better grasping performance. Related parameters, such as displacement, velocity, acceleration, force, and torque, were also analyzed. Friction contact finite element analysis of the bionic gripper with bristle structure was performed using ABAQUS and compared with the control group. The finite element analysis results showed that the bristles could effectively improve the capture efficiency of the bionic gripper. The diameter and density of the bristles in the bionic gripper were optimized, and their influence on the gripping efficiency was analyzed. This study provides a reference for the structural design of bionic grippers and the practical application of bionic non-smooth surfaces.

Finite element analysis of contact between new-built structure and old subgrade in pile-plank structure

Under different working conditions of two vehicle load and four vehicle load, the changes of contact normal stress and friction normal stress between contact surfaces of pile-plank structure were systematically simulated by FEM respectively. The results show that the contact normal stress and friction normal stress are both maximum under the condition of four-vehicle load, and condition 23 is the most unfavorable overall stress situation in which the maximum contact normal stress reached 302.936kPa and the maximum friction normal stress reached 90.881kPa.

Modeling of multiwall carbon nanotubes reinforced natural rubber for soft robotic applications – A comprehensive presentation

Soft materials like rubbers, polymers and elastomers are non-linear hyper elastic materials or visco-elastic materials that show the large deformation under loading. One of the nonlinear material model is to be used in the simulation of soft mechanism. Mooney-Rivlin, Ogden, Polynomial, Arruda-Boyce, Yeoh, and Neo-Hookean and Extended Tube are some nonlinear hyperelastic material models existing in the practice. The objexctive of the current research is to present comprehensively the nonlinear material constants of the multiwall nanocarbon (MWCNT) reinforced natural rubber (NR) composites. NR/MWCNT composites with 5%, 10%, 20% and 30% weight fractions of MWCNTs are prepared through compression molding. The uniaxial tensile test was conducted on dumb bell specimens of ASTM D412-06a standard. The respective strain–stress data from uni-axial tensile tests are further curve fitted into existing popular nonlinear hyperelastic models. The nonlinear constants of respective model are comprehensively tabulated, which designers can use in the component design and analysis. Finite element contact analysis of a cylindrical soft finger pressed against a rigid plate is conducted and presented.

Numerical study on contact force of paralleled beveloid gears using minimum potential energy theory

Using minimum potential energy theory and slicing method, a computational approach to calculate the magnitude and distribution of contact force for paralleled beveloid gear pair was proposed in this article. The theoretical tooth contact model was built based on spatial gearing theory to calculate the mesh parameters including the coordinates, normal vectors, and equivalent radius for meshing points. Then, the analytical contact force model of paralleled beveloid gear pair was derived based on minimum potential energy theory. Finite element contact analysis was conducted to verify the proposed model. Finally, the influences of macro-geometry design parameters on the contact force distribution were investigated. Results show that the pressure angle has a limited influence on the contact force distribution. The increase in helix and cone angles will observably increase the asymmetry of contact force distribution as well as the fluctuation of contact force distribution for a single tooth. A good correlation was obtained between the proposed analytical model and the finite element model for the distribution and magnitudes of contact force.

Face-gear drive: Assessment of load sharing, transmission characteristics and root stress based on a quasi-static analysis

The present manuscript expands on a procedure developed to calculate load sharing, transmission characteristics, tooth root stress and the flank contact pressure in face-gear drives. On the one hand the procedure uses the analytical determination of the contact path for meshing of rigid gears including the dimensions, and directions of the contact ellipses based on Hertzian theory of elastic contact. On the other hand it uses the determination of the load-dependant compliance of a pair of teeth by finite element analysis. The combination of these two calculation methods / approaches renders the finite element contact analysis unnecessary thus significantly shortening the required computation time. The exact geometric representation of the tooth flanks for the finite element analysis is also not required. This not only avoids a greater preprocessing effort but also enables an efficient automation of the procedure. All steps of this procedure are described in depth in this manuscript. The accuracy of the proposed semi-analytical approach is validated through a direct comparison with an FEM contact analysis carried out as an example for a face-gear drive.

Adaptive control of normal load at the friction interface of bladed disks using giant magnetostrictive material

A novel application of magnetostrictive actuators in underplatform dampers of bladed disks is proposed for adaptive control of the normal load at the friction interface to achieve the desired friction damping in the structure. Friction damping in a bladed disk depends on operating parameters, such as rotational speed, engine excitation order, nodal diameter normal contact load, and contact interface parameters, such as contact stiffness and friction coefficient. The operating parameters have a fixed value, whereas the contact interface parameters vary in an unpredictable way at an operating point. However, the ability to vary some of these parameters such as the normal contact load in a controlled manner is desirable to attain an optimum damping in the bladed disk at different operating conditions. Under the influence of an external magnetic field, magnetostrictive materials develop an internal strain that can be exploited to vary the normal contact load at the friction interface, which makes them a potentially good candidate for this application. A commercially available magnetostrictive alloy, Terfenol-D is considered in this analysis that is capable of providing magnetostrain up to 2 × 10-3 under prestress and a blocked force over 1500 N. A linearized model of the magnetostrictive material, which is accurate enough for a direct current application, is employed to compute the output force of the actuator. A nonlinear finite element contact analysis is performed to compute the normal contact load between the blade platform and the underplatform damper as a result of magnetostrictive actuation. The nonlinear contact analysis is performed for different actuator mounting configurations and the obtained results are discussed. The proposed solution is potentially applicable to adaptively control vibratory stresses in bladed disks and consequently to reduce failure due to high-cycle fatigue. Finally, the practical challenges in employing magnetostrictive actuators in underplatform dampers are discussed.

Optimization design of a novel X-type six-high rolling mill based on maximum roll system stiffness.

The present investigation devices a novel X-type six-high (X-6h) mill. In addition, parametric models of different roll layouts such as the four-high (4-h), I-type six-high (I-6h), and X-6h mills are established. Three-dimensional (3D) finite element (FE) contact analysis for a strip rolling process is conducted when the mills are subjected to a constant vertical load of 65 kN. Through comparative analysis of von Mises stress, contact stress and elastic deformation displacement in three roll layouts, the rigidity characteristic of each is obtained, and it is found that the proposed X-6h mill has the largest roll gap stiffness. The influence of different roll diameter ratios on the roll gap stiffness of the roll system is investigated, based on which an optimization design model is built. Further, by taking into account the roll gap stiffness of the roll system as the optimization objective, the optimum diameter ratios of backup roll (BUR) to work roll (WR) of the X-6h rolling mill is achieved via the genetic algorithm (GA) optimization method, obtaining the optimum structural parameters of BUR and WR as well. The reliability of the proposed design is verified by manufacturing a prototype mill which produced magnesium alloy and aluminum alloy strips of high quality.

Damage prevention analysis of heavy-duty gear body based on finite element neural network

The method of damage prevention analysis of heavy-duty gear body based on finite element neural network is proposed to improve the effectiveness of damage prevention analysis of heavy-duty gear body. Firstly, a design platform for gearbox gears of caterpillar tractors is developed based on finite element theory, the three-dimensional model of the gear is designed on this platform, and the bending and contact finite element analysis of the gear teeth is carried out, the bending stress and contact stress of the gears are obtained, which provides a basis for the parameter design and reliability of the gears. Secondly, a neural network algorithm is introduced to predict and analyse the impact of damage data of heavy-duty gear body. Finally, the effectiveness of the proposed algorithm is verified by simulation experiments.

Predicting stress and creep life in Inconel 718 blade-disk attachments

Due to several physical and computational difficulties in Finite Element (FE) analysis of contact in fir-tree blade-disk attachments of gas turbines, there has always been a great demand for stress, fatigue and creep life assessment of fir-tree joints without modeling physical contact. However, reliability of these models is not trivial. To meet these challenges, in the current paper, three different analysis methodologies were examined for creep life assessment in a turbine engine disk. This is a significant problem for designers and operators of gas turbines. Two simple models were developed with removal of the blade from the FE domain as well as a detailed 3D model containing a blade and it’s contact details. Numerical results were compared with available experimental stress measurement. Creep material behavior models were also developed and parameters for the Liu-Murakami damage model together with the Norton creep law were determined for Inconel 718 at 620 °C. A creep subroutine was written and creep analyses of these joints were performed for typical service temperature of 620 °C and the maximum time period of 100,000 h. FE results were compared with fracture mode of service induced cracks. For the different load cases ranging from 3000 rpm to 9000 rpm, it is demonstrated that methodology based on simple models are very efficient. The equivalent pressure model always underestimates the value of peak stress whereas the virtual link model provided more realistic results. The results are discussed according to the different failure criteria for the fir-tree joints life assessment. Results presented in the paper are valuable for failure analysis of these critical components. Moreover, the stress distribution obtained from the simple realistic model can be used for the life assessment codes applicable to other types of failure mechanism.

Reversible adhesion to rough surfaces both in and out of water, inspired by the clingfish suction disc

Adhesion is difficult to achieve on rough surfaces both in air and underwater. In nature, the northern clingfish (Gobiesox maeandricus) has evolved the impressive ability to adhere onto substrates of various shapes and roughnesses, while subject to strong intertidal surges. The suction disc of the clingfish relies on suction and friction to achieve and maintain adhesion. Inspired by this mechanism of attachment, we designed an artificial suction disc and evaluated its adhesive stress on rough surfaces and non-planar geometries. The artificial suction disc achieved adhesion strengths of 10.1 ± 0.3 kPa in air on surfaces of moderate roughness (grain size, 68 µm), and 14.3 ± 1.5 kPa underwater on coarse surfaces (grain size, 269 µm). By comparison, a commercially available suction cup failed to exhibit any significant adhesion in both scenarios. The roughly 2 g heavy clingfish-inspired suction discs gripped concave surfaces with small radii of curvature (12.5 mm) and supported payloads up to 0.7 kg. We correlated the effect of key bioinspired features (i.e. slits, a soft outer layer, and body geometry) to adhesion performance using contact visualization techniques and finite element analysis (FEA). The suction discs were then tested on a remotely operated vehicle (ROV) to demonstrate their utility in the soft manipulation of fragile objects.