Arbitrary active constrained layer damping treatments on beams: Finite element modelling and experimental validation

This paper concerns the analytical formulation and finite element modelling of arbitrary active constrained layer damping (ACLD) treatments applied to beams. A partial layerwise theory is utilized to define the displacement field of beams with an arbitrary number of elastic, viscoelastic and piezoelectric layers attached to both surfaces, and a fully coupled electro-mechanical theory is considered for modelling the behavior of the piezoelectric layers. The damping of the viscoelastic layers is modelled by the complex modulus approach. The weak forms of the analytical formulation, governing the motion and electric charge equilibrium, are presented. Based on the weak forms, a one-dimensional finite element (FE) model is developed, with the nodal mechanical degrees of freedom being the axial displacement, transverse displacement and the rotation of the mid-plane of the host beam and the rotations of the individual layers, and the electrical elemental degrees of freedom being the electrical potential difference of each piezoelectric layer. Frequency response functions were measured experimentally and evaluated numerically for a freely suspended aluminium beam with an ACLD patch. In order to validate the FE model the results are presented and discussed.     

Numerical simulation of the stress peen forming process and experimental validation

Stress peening forming is widely used in the aeronautics industry to induce curvatures in wing skins. Most of the investigations of stress peen forming are empirical and experimental. In this paper, a three step numerical model that can simulate this process was developed. First, an implicit Finite Element Analysis (FEA) with ANSYS where a prebending moment along the spanwise direction of the component was performed. Then, an explicit FEA with LS-DYNA simulating shot impacts on the pre-stressed component was executed in order to obtain the resulting stresses inside the component. Finally, an implicit FEA with ANSYS was performed for calculating the arc heights and the curvature radii of the component in chordwise and spanwise directions. Numerical analysis of the process shows that the prebending moments have an influence not only on the residual stress profiles but also on the curvatures of the deformed component in chordwise and spanwise directions. This model was used to establish a relationship between the prebending moment and the resulting arc heights and residual stress profiles. The numerical strategies developed in this paper supply a useful tool for studying and optimizing the stress peening process.     

钢管弯制过程有限元仿真及断裂原因分析

针对某金属结构公司在钢管弯制过程中出现的个别钢管断裂现象进行研究,根据现场钢管弯制工艺和工序的情况描述,采用非线性有限元软件Marc对钢管的多工位弯制过程进行模拟仿真.以最恶劣的情况即曲率最大的胎具进行多工位弯制,仿真结果显示6个工位的连续弯制过程最大应力为552 MPa,没有达到材料的抗拉极限626 MPa,该弯制过程不会引起钢管强度失效.模拟钢管多种曲率胎具弯制下的应力应变分布情况和回弹后残余应力应变情况.仿真结果表明,弯制此种钢管最大曲率的圆弧时,钢管上的最大应力为542 MPa,小于材料的抗拉强度626 MPa;最大塑性应变为0.031,小于材料允许的最大伸长应变0.2.经过模拟仿真分析,该公司采用的弯制工艺不会引起材料强度失效断裂.引起钢管弯制断裂的原因为个别材料夹杂或气孔造成的小概率事件.     

Prediction of cutting temperature in orthogonal machining of AISI 316L using artificial neural network

In this study, an approach based on artificial neural network (ANN) was proposed to predict the experimental cutting temperatures generated in orthogonal turning of AISI 316L stainless steel. Experimental and numerical analyses of the cutting forces were carried out to numerically obtain the cutting temperature. For this purpose, cutting tests were conducted using coated (TiCN + Al₂O₃ + TiN and Al₂O₃) and uncoated cemented carbide inserts. The Deform-2D programme was used for numerical modelling and the Johnson–Cook (J–C) material model was used. The numerical cutting forces for the coated and uncoated tools were compared with the experimental results. On the other hand, the cutting temperature value for each cutting tool was numerically obtained. The artificial neural network model was used to predict numerical cutting temperatures by means of the numerical cutting forces. The best results in predicting the cutting temperature were obtained using the network architecture with a hidden layer which has seven neurons and LM learning algorithm. Finally, the experimental cutting temperatures were predicted by entering the experimental cutting forces into a formula obtained from the artificial neural networks. Statistical results (R², RMSE, MEP) were quite satisfactory. This demonstrates that the established ANN model is a powerful one for predicting the experimental cutting temperatures.     

Effect of baffles on a partially filled cubic tank: Numerical simulation and experimental validation

In this paper, sloshing waves have been analyzed for baffled and un-baffled tanks. Numerical simulations were carried out based on volume of fluid (VOF) techniques with arbitrary-Lagrangian–Eulerian (ALE) formulation which adopts the displacement of solid, the pressure and displacement in the fluid as variables to model the coupled system. The response of the coupled system is obtained by using the well-known software ADINA, which offers efficient fully coupled fluid–structure interaction capabilities by finite element method. The results obtained are compared with the available experimental data to demonstrate the reduction of sloshing effects in fluid model.     

Finite element analysis and experimental validation of suppression of span in optical MEMS pressure sensors

Microsystem Technologies - An optical pressure sensor working on the principle of Fabry–Perot Interferometer (FPI) is designed for pressures range of 1 bar absolute. The sensor is...     

Finite element modelling of reinforcement with bond

This paper presents an efficient numerical model for simulating the bond between reinforcing bars and concrete. It is based on the one-dimensional geometry of reinforcing bars, and it considers interface surface properties. In spite of its relative simplicity, it allows the application of the same physical models as in the case of a full surface interface. An arbitrary bond-slip relationship can be implemented within the model. Four sample analyses are presented: reinforcement bar pull-out experiment, an example of a beam collapsing due to shear failure, an analysis of the shear strength of pre-stressed hollow core slabs and an assessment of serviceability of a pre-stressed concrete slab in the newly built ice hockey arena in Prague.     

Numerical simulation and experimental validation of novel hyperelastic micro-motion manipulator for water conserving device

Microsystem Technologies - The aim of this study was to evaluate a novel water-conserving micro-motion manipulator (manipulator) for application in the fluid flow rate regulator of a faucet through...     

Finite element and analytical modelling of a tractor-semitrailer vehicle

A tractor-semitrailer vehicle travelling over a random road surface is modelled using finite element and analytical methods. The vehicle's linear models are constructed in such a way as to describe the bounce and pitch modes of both the tractor and semitrailer, the bounce of each wheel-axle assembly, and also to account for the semitrailer beaming effect. The road surface irregularities are represented as stationary Gaussian random excitations. Spectral analysis technique is employed to analyze the dynamic response of the vehicle.

In this paper, the problem of the interaction of the vehicle with the road is discussed, the proposed mathematical models are presented, and the numerical results showing system eigenvalues, eigenvectors and power spectral densities of the vehicle stochastic response are given and analyzed. The finite element provides a powerful means for the prediction and assessment of the ride motion for this complex structure. The technique of spectral analysis is an effective tool for the analysis of road irregularities and the stochastic response of the road vehicles.     

Finite element analysis of steel rolling processes

The numerical simulation of rolling processes requires the coupling of several models that describe different physical phenomena such as the deformation of the work-piece together with its thermo-metallurgical evolution and the thermal evolution of the rolls together with its mechanical deformation. In this paper we develop the coupling between the purely mechanical model of the work-piece and the thermo-mechanical model of the rolls. We test the numerical formulation in the analysis of the hot rolling of steel coils and in the analysis of the hot mandrel rolling of seamless steel tubes.     

Finite element simulation of robotic origami folding

In this paper, we focus on some aspects of the finite element simulations of robotic paper folding and the reconstruction of models from the origami crease patterns by the robot arms. The paper highlights the simulation problems, which should be solved in developing our recent study in mechanical and geometrical design of the origami-performing robot. The basic premise underlying the study is that folding operations with the origami crease patterns are considered as the functions of the mechanical systems such as a robot. Manipulations with the foldable objects, such as a sheet of paper (the origami crease pattern), by the robot arms in the simulation environment lead to understanding the design of the origami-performing robot without testing physical prototypes at each design stage. In this case, dynamic and kinematic behavior of the robot arms in forming the 3D origami objects is modelled by using the finite element method (FEM) in LS-DYNA solver. For simulating, two forms of origami are considered: flexible, if bending is used for paper folding, and rigid, if origami patterns are considered as the kinematic systems. Results of the simulation are presented and provided by the illustrations.     

Finite element analysis (FEA) modelling and experimental verification to optimise flexible electronic packaging for e-textiles

Microsystem Technologies - In this paper a three-dimensional model of a novel electronic package has been developed using Finite element analysis to evaluate the shear load, tensile, bending and...     

Finite element modelling of compartment masonry walls in fire

A finite element model called MasSET has been developed which is capable of predicting the structural behaviour of single leaf masonry walls subject to elevated temperatures. The analysis models a slice through the wall as a column strip in plane stress, and also includes material with geometric non-linearity. The model has been previously validated by comparison with experimental results [1] and is used in this paper to conduct a parametric study investigating the effects of slenderness ratio, load eccentricity and boundary conditions. The results of the investigation are presented by way of failure temperatures for each condition, and show conclusive findings to the effects of each parameter investigated.     

Finite element modelling of cable networks with flexible supports

The objective of the paper is to present a mathematical model for analysis of prestressed cable structures with flexible contour beam. The proposed numerical procedures are based on a discrete scheme according to the finite element method. A reliable model of the interaction of the flexible contour beam with the cable network enables the achievement of more efficient solutions in the design analysis. Geometrical nonlinearity is accounted for in the cable net substructure and the contour beam is modelled by linear beam elements. Equations are solved by iterative methods and explicit time integration. The described numerical technique has been employed to model prestressing, static and dynamic behaviour. Theoretical results have been compared to experimental data and used in practical applications.     

海船撞击跨海大桥的有限元模拟与海上建筑物的防御

为预测某海湾大桥受船舶撞击后的响应,建立该大桥和万吨级海船的有限元模型,利用ANSYS和LS-DYNA模拟海船在8 m/s的正常航速下,船首以90°正向撞击主桥墩承台部位的过程. 通过分析各构件的损伤变形情况,给出桥体应力分布,输出碰撞构件的位移曲线和撞力曲线. 结合实验结果提出对大桥桥墩承台结构优化及海上建筑物防护的建议. 该方法可为桥梁的抗撞击优化设计提供参考.     

Micro-milling performance of AISI 304 stainless steel using Taguchi method and fuzzy logic modelling

In this study, micro-milling of AISI 304 stainless steel with ball nose end mill was conducted using Taguchi method. The influences of spindle speed, feed rate and depth of cut on tool wear, cutting forces and surface roughness were examined. Taguchi’s signal to noise ratio was utilized to optimize the output responses. The influence of control parameters on output responses was determined by analysis of variance. In this study, the models describing the relationship between the independent variables and the dependent variables were also established by using regression and fuzzy logic. Efficiency of both models was determined by analyzing correlation coefficients and by comparing with experimental values. The results showed that both regression and fuzzy logic modelling could be efficiently utilized for the prediction of tool wear, cutting forces and surface roughness in micro-milling of AISI 304 stainless steel.     

Finite element simulation of dynamic strain-localization: A multi-scale problem

A Finite Element procedure for the post-localization analysis of elasto-plastic solids is developed. To ensure unique solutions, the Duvaut-Lions visco-plastic regularization procedure [1] is implemented. A bifurcation analysis of the underlying backbone elasto-plastic material is performed to locate the shear band and to define its orientation. The width of the shear band is assumed to be much smaller than the characteristic element size h. To capture the structure of the shear band, the kinematics is enriched by incorporating additional degrees of freedom in a patch within the element and overlying the shear band. Within each localized element, compatibility is ensured between the strain fields inside and outside the patch. A Petrov-Galerkin type procedure to account for the narrow width of the patch is implemented. The results indicate formation of mesh and patch invariant shear bands. Finally, the effects of varying material parameters are studied. The results are found to be consistent with known localization characteristics.     

Uncertainty-based loads analysis for spacecraft: Finite element model validation and dynamic responses

The stochastic correlation and validation of spacecraft structural dynamic models and the stochastic launcher-satellite coupled loads analysis present several points of interest and involve novel aspects. This paper describes the main objectives of two studies in progress under the technical management of the European Space Agency and performed by consortia of European industries and university. The paper presents an overview of the major aspects related to the implementation of the approach, the identified methods and tools and the future developments.