Finite Element Wear Behaviour Modeling of AA7075 Coated with WS2/Cu Using ANSYS

Aluminium Alloys Are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. Aluminium alloys are widely used in engineering structures and components where light weight, or corrosion resistance is required. Alloys composed mostly of aluminium have been very important in aerospace manufacturing since the introduction of metal-skinned aircraft. Aluminium alloys are widely used in automotive engines, particularly in cylinder blocks and crankcases due to the weight savings that are possible. Manufacturing techniques and metallurgical advancements have also been instrumental for successful applications in automotive engines. The addition of elements to the aluminium gives the alloy improved strength, workability, corrosion resistance, electrical conductivity, and/or density, compared with the pure metallic element. (I.J Polmear 1995)

Experimental study and FEM simulation of wear performance of different composite materials and metals are one of the major research fields in tribology. Pin on disc is one of the main experimental set up for wear analysis and for FEM analysis different software packages like ANSYS and ABAQUS were used.The first attempt to develop wear model to predict the wear performance made by Archard [11] and this model was incorporated in wide range of wear studies and results obtained shows good agreement with experimental wear studies. Firaol et al. 2015 studied about the detailed analysis of wear measurement and wear analysis of overhead line contact wire using ANSYS workbench software [13].The simulation of contact wire is performed on pin on disc model, where the model is used for sliding contact analysis. Researchers proposed a method of calculation of wear through FEM analysis and further, wear analysis is based on Archards wear model[14]. A study was carried out to investigate the sliding wear and calculation of wear is based on the Lim and Ashbys wear map, Archards wear law and selected the ANSYS software was used for analysis [14]. Sullivan developed a mathematical model to relate the applied load and the wear which also includes other factors collectively can assumed as Archards wear coefficient[15]. Authors have conducted the experiment of FE analysis of sliding wear in metals. Model is formulated in legrangian frame work. Archard law is used for the wear calculation. Model is validated using rotation of brass pin in steel disc [16]. Veenhuizen et al. 2006 carried out study of wear in both FEA and pin on disc experimental methods for CVT belt. FE analysis of wear is done in ABAQUS software and wear fracture of belt was analyzed using FE methods and suggested remedies. Experimental determination of wear life has both cost and time effect [17]. The simulation of wear and life prediction can helps product developers in many manners such as designing better products, propose better maintenance plans to hold off failures and prevent financial losses. In this paper, recently published work (Davanageri et al.2017) on wear behaviour of AISI2507 Super Duplex Stainless Steel results were tested [22]. The finite element simulation of the wear test is carried out in ANSYS using Archards FEA model.

MATERIAL AND METHODOLOGY

AA7075 is an aluminium alloy containing zinc, magnesium, copper, zinc and other metals. One of the most commonly used aluminium alloys for structural applications is 7075 Al alloy due to its attractive comprehensive properties such as low density, high strength, ductility, toughness and resistance to fatigue. It has been extensively utilized in aircraft structural parts and other highly stressed structural applications.

Table 1. Chemical composition of 7075 Aluminium Alloy

1. 1. FEA wear simulation and Finite element theory

The main task of the finite element method (FEM) in the wear calculations is to compute the fields of contact stresses. The structure to be analysed is discretised with a number of elements, assembled at nodes. In FEM the function in question (displacement, temperature, etc.) is piecewise approximated by means of polynomials over every element and expressed in terms of nodal values. The elements of different type and shape with com plex loads and boundary conditions can be used simultaneously. In the structural analysis the degrees of freedom are defined as nodal displacements. The equations for every element are assembled into a set, expressed in the structural level as.

The flow-chart of the FE wear simulation procedure, consisting of a series of structural solution steps combined with additional calculations, The initial parameters given define the model geometry, loads, constraints and wear model parameters. Along with the element and material data. Special sub routines were developed for every configuration to generate the FE model and define the loads and constraints automatically. A good discretization must be found for every particular geometry and loading case. The areas with expected high stress gradients utilize a finer node mesh. More elements in the model are likely to provide more exact results but contribute to an increased computing time and use of disk space. After the FEA iterative stress solution was obtained, the contact region was located. The status of every contact element (closed or not) was determined. The contact node coordinates of closed contact elements define the contact are allocation. The nodal stresses of the nodes in the contact region determine the contact pressure distribution. The Euler method is used to integrate the wear law with respect to time. For each wear simulation step the system parameters are assumed to be constant and contribute to the wear depth at every node according to the following discretized wear model.