Optimization of Profile and Material of Abrasive Water Jet Nozzle

The objective of this work is to study the behaviour of the abrasive water jet nozzle with different profiles and materials. Taguchi-Grey relational analysis optimization technique is used to optimize the value with different material and different profiles. Initially the 3D models of the nozzle are modelled with different profiles by changing the tapered inlet angle of the nozzle. The different profile models are analysed with different materials and the results are optimized. The optimized results would give the better result taking wear and machining behaviour of the nozzle.


INTRODUCTION
Abrasive water jet machining is the process of cutting materials with good finish on the machined surface unconventionally. This process can be implemented in broad range of industries where both hard and brittle materials can be machined effectively using this process [2]. The problem associated with these high speed jet nozzles are wear along the nozzle walls [11]. The wear at the wall of the nozzle is mainly due to the complex function of particle impact and wall properties [3]. Also these complex phenomenons include the geometry of the nozzle and other operating parameters [4]. Jukti et al [5] has done major experiment on this abrasive water jet machining process and said that experiments in future had to be done with various ceramic materials.
The main objective of the work is to study the wear in the nozzle walls with different profile and materials. Junkar et al [6]  Element Analysis can be used for understanding the influences of process parameters on it.
The nozzle materials vary differently which depends on the operating pressure and nozzle design [7] and hence there are not large materials available for selection of nozzle material.
Ye et al [8] in his paper had concluded that the internal shape of nozzle which is critical to the acceleration of abrasive particles and to the wear of the nozzle. The work also states that the optimized inlet angle can lead to less erosion along the walls. Deepak et al [9] has experimented on abrasive water jet machining technique and concluded that increasing the inlet pressure makes an increase in skin friction coefficient.
By taking these aspects into consideration to improve wear resistance and machining process, nozzle geometry and nozzle materials are taken as parameters. The optimized result gives the perfect result to improve the wear and machining behaviour of the nozzle.

EXPERIMENTS AND METHODS
The 3D model of the nozzle is modelled using the Catia V5 R20 software. The basic dimensions taken for modelling the nozzle are

Diameter -1mm
Length -20mm Cylindrical Tube Length -6mm Four models of the nozzle is modelled using four different inlet angles respectively.
The four different inlet angles used are 50 0 , 60 0 , 70 0 , 80 0 . proper idea to the perfect results and helps to save cost and valuable time.
The constant load that is used in this project work is 3.5E5 Pa pressure which is assumed to be acting along the cylindrical tube of the abrasive water jet nozzle.
For the four different materials and four different inlet angles the orthogonal array will be 2 4 , which is total number of 16 experiments.
The analysis is done and the total deformation and the stress values are noted in the experimental design tabulation for further optimization process.    The optimization process to be used is the Taguchi-Grey relational method as there is more than one response in the experimental design.
The S/N ratio for the observed results are found out using the formula Yij = −10log ( 2 ) which is the formula for smaller the better Since the deformation and stress values have to be minimised, the approach that is used in this particular experiment is smaller the better for both the responses.  After calculating the grey relational coefficients, the grey relational grade value is calculated by calculating the average value of the grey relational coefficient of both the responses. Grey relational grade gives the relational degree between the sequences.