A Generalisation of the hill's quadratic yield function for planar plastic anisotropy to consider loading direction

In this work, a new generalised quadratic yield function for plane stress analysis that is able to describe the plastic anisotropy of metals and also the asymmetric behaviour in tension-compression typical of the Hexagonal Closed-Pack (HCP) materials, is developed. The new yield function has a quadratic form in the stress tensor and it simultaneously predicts the r-values and directional flow stresses, which is shown to agree very well with exper- imental results. It also accurately describes the biaxial symmetric stress state which is fundamental for the accurate modelling of aluminium alloys. The new quadratic yield function represents the non-symmetric biaxial stress state by performing a linear interpolation from pure uniaxial loading to a bi- axial symmetric stress state. The main advantages of this new yield function is that it can be used for the modelling of metals with any crystallographic structure (BCC, FCC or HCP), it only has ve anisotropic coeffcients and also that it is a simple quadratic yield criterion that is able to accurately reproduce the plastic anisotropy of metals whilst using an associated flow rule

On Contact Modelling in IsoGeometric Analysis

IsoGeometric Analysis (IGA) has proved to be a reliable numerical tool for the simulation of structural behaviour and uid mechanics. The main reasons for this popularity are essentially due to: i) the possibility of using higher order polynomials for the basis functions; ii) the high convergence rates possible to achieve; iii) the possibility to operate directly on CAD geometry without the need to resort to a mesh of elements. The major drawback of IGA is the non-interpolatory characteristic of the basis functions, which adds a di culty in handling essential boundary conditions and make it particularly challenging for contact analysis. In this work, the IGA is expanded to include frictionless contact procedures for sheet metal forming analyses. Non-Uniform Rational B-Splines (NURBS) are going to be used for the modelling of rigid tools as well as for the modelling of the deformable blank sheet. The contact methods developed are based on a two-step contact search scheme, where during the rst step a global search algorithm is used for the allocation of contact knots into potential contact faces and a second (local) contact search scheme where point inversion techniques are used for the calculation of the contact penetration gap. For completeness, elasto-plastic procedures are also included for a proper description of the entire IGA of sheet metal forming processes

STABILITY LOBES PREDICTION FOR CORNER RADIUS END MILL USING NONLINEAR CUTTING FORCE COEFFICIENTS

There are a vast number of different types of end mill tools used in the manufacturing industry, each type with a unique shape. These tool shapes have a direct influence on the cutting force it generates during machining. This article presents a more accurate approach to predicting the stability margin in machining by considering the cutting force coefficients and axial immersion angle as variables along the axial depth of cut. A numerical approach to obtaining a converged solution to the stability model is presented. The results obtained are validated using experimental results and a very good agreement is seen.Engineering and Physical Sciences Research Counci

Dynamic large deformation analysis of a cantilever beam

National Natural Science Foundation of Chin

A new damping modelling approach and its application in thin wall machining

In this paper, a new approach to modelling the damping parameters and its application in thin wall machining is presented. The approach to predicting the damping parameters proposed in this paper eliminates the need for experiments otherwise used to acquire these parameters. The damping model proposed was compared with available damping models and experimental results. A finite element analysis and Fourier transform approach has been used to obtain frequency response function (FRF) needed for stability lobes prediction. Several predicted stable regions using both experimental and numerical FRF’s for various examples gave a good comparison.Engineering and Physical Sciences Research Counci

Development of multiscale multiphysics-based modelling and simulations with the application to precision machining of aerofoil structures

This study aims to optimize the manufacturing process to improve the manufacturing quality, costs and delivering time with the help of multiscale multiphysics modelling and simulation. Multiscale multiphysics-based modelling and simulations are receiving more and more interest by research community and the industry particularly in the context of increasing demands for manufacturing high precision complex products and understanding the intrinsic complexity in associated manufacturing processes. Design/methodology/approach: In this paper, some modelling and analysis techniques using multiscale multiphysics modelling are presented and discussed. Findings: Furthermore, the possibility of adopting the multiscale multiphysics modelling and simulation to develop the virtual machining system is evaluated, and further supported with an industrial case study on abrasive flow machining (AFM) of integrally bladed rotors using the techniques and system developed. Originality/value: With the development of multiscale multiphysics-based modelling and simulation, it will enable effective and efficient optimisation of manufacturing processes and further improvement of manufacturing quality, costs, delivery time and the overall competitiveness.NATEP (Integrally Bladed Rotor - (IBR) - Abrasive Flow Machining

An improved prediction of stability lobes using nonlinear thin wall dynamics

With manufactured sections getting much thinner due to weight requirements, there is the vital need for more accurate prediction of stable cutting conditions in machining. The tools used in machining vary in shapes and design hence a more robust model is required to include these varieties. This paper first presents improvements to the well known stability model, by considering the nonlinearity of the cutting force coefficients, and axial immersion angle and their dependency on the axial depth of cut. Secondly, a finite element (FE) and Fourier transform approach to including the nonlinearity of the workpiece dynamics in thin wall machining when predicting stable region is presented. The model and approach are validated extensively using experimental results and a very good agreement has been achieved