Abrasive Waterjet Cutting Research Articles

Characterizing and modelling delamination of carbon-fiber epoxy laminates during abrasive waterjet cutting

Delamination is a common defect when abrasive waterjet (AWJ) cutting composite laminates. This paper presents experimental and numerical results used to characterize delamination when AWJ cutting a carbon-fiber/epoxy laminate. A fluid-structure interaction model was used to simulate the AWJ cutting. The structural domain used cohesive zone modeling to predict delamination along the ply interfaces. The numerical results showed that cutting delamination of the carbon-fiber/epoxy was primarily dependent on the normal interlaminar stress, with relatively large damage zones occurring ahead of the cutting front. This trend was also observed in X-ray micro-tomographs of an AWJ cut. To distinguish between side-wall and cutting-front forces, the loading generated by the jet was measured using a strain gage. This showed that the loads applied to the cutting front were larger than those generated on the side walls, and thus the likelihood of delamination was greater on the cutting front. The amount of delamination during AWJ cutting was measured using a moisture uptake methodology that was implemented with a six-factor (pressure, stand-off distance, abrasive flow rate, traverse speed, mixing-tube size, and fiber orientation) Taguchi experimental design. The trends evident in these data were consistent with the extent of delamination predicted by the numerical models, and show that traverse speed, abrasive flow rate, and mixing tube size had the most significant effect on delamination.

Preliminary study on occurrence of composite material delamination processed by abrasive water jet cutting

The paper presents a preliminary experimental study on processing composite materials (CFRP) using abrasive water jet cutting (AWJC) process, analysing the possibilities of occurrence of material delamination. AWJC is a proper solution for cutting CFRP because of reduced interface temperature, high flexibility, low mechanical loading and reduced cutting forces. Cutting CFRP using AWJC involves several challenges like material delamination due to the high velocity impact of the jet. To understand the delamination, three experimental tests were made: in the first test the cutting and the drilling was made with high water pressure (350 MPa), in the second test the cutting was made with high water pressure and for drilling was used low water pressure (200 MPa) and in last test a pre-drilled hole was used. Within those experiments was observed the CFRP delamination appears just during the drilling, not during the cutting. By decreasing the water jet pressure, the jet energy is decreased and in this way the delamination decrease.

Investigation on standoff distance influence on kerf characteristics in abrasive water jet cutting of composite materials

The paper presents an experimental study on processing composite materials using abrasive water jet cutting (AWJC) process, analysing one of the main process parameter, standoff distance (SOD). Carbon Fibre Reinforced Plastics (CFRP) are used in a wide range of industrial applications, like aerospace and automotive. Cutting CFRP using AWJC involves several challenges like high dimensional accuracy and good surface quality. To produce precise parts by using this process must be understand the influence of the process parameters on quality characteristics. On this study was investigated the standoff distance influence on kerf characteristics. The characteristics of the cut surface (kerf geometry, surface roughness and topography) were analyzed.

Analysis on abrasive waterjet cutting of glazed vitreous tiles using Taguchi-based RSM

The present work focussed on probing the effect of abrasive waterjet cutting (AWJC) process parameters (abrasive flow rate, jet traverse rate, nozzle diameter, water pressure and stand-off distance) on surface roughness and taper angle while handling glazed vitreous tiles. The quality characteristics (surface roughness and taper angle of cut) were observed during the cutting trials designed as per Taguchi's L18 orthogonal array. The field emission scanning electron microscope (FESEM) images and P-profile plots were also examined for the cut surfaces. An integrated approach of average signal-to-noise (S/N) ratio-based response surface methodology (ASN-RSM) was disclosed for parameter design. The confirmation test conducted with the near optimal setting had proved the effectiveness of the ASN-RSM approach in optimising the cutting characteristics of glazed vitreous tiles.

An Investigation in Abrasive Waterjet Cutting of Al6061/SiC/Al2O3 Composite Using Principal Component Based Response Surface Methodology

Abrasive waterjet was found effective in cutting materials like glass, steel and aluminium for various industrial applications. The effect of process parameters on abrasive waterjet cutting (AWJC) of Al6061/SiC/Al2O3 composite was disclosed in the present work. The cutting parameters taken for study were traverse speed, abrasive flow rate, water pressure and stand-off distance. Surface roughness, kerf width and bevel angle of cut were observed as the quality characteristics for various cutting trials. Experiments were designed using Taguchi's L18 orthogonal array and an integrated technique of principal component based response surface methodology (PC-RSM) was disclosed for designing the parameters. Significant improvements were observed in the quality characteristics obtained with optimal parameter setting identified by PC-RSM approach. Abrasive waterjet parameters like water pressure, stand-off distance and the interaction between abrasive flow rate and traverse speed were found to be influential on the quality characteristics.

Parameter design for cut surface characteristics in abrasive waterjet cutting of Al/SiC/Al2O3 composite using grey theory based RSM

The abrasive mixed waterjet was successfully employed to cut many materials including austenitic steel, inconel and glass for a variety of industrial applications. The present work focusses on studying the surface roughness, striation zone and striation angle in Abrasive waterjet cutting (AWJC) of Al/SiC/Al2O3 composite. The water pressure, traverse speed, abrasive flow rate and stand-off distance were included as the dominant parameters in the study. The features of striation zone (length and angle) and surface roughness were observed as the responses for each of the cutting trials planned as per Taguchi’s L18 orthogonal array. Parameter design was performed using the grey theory based response surface methodology (g-RSM) by following the method of simultaneous optimization to forecast the optimal cutting condition. All the studied parameters and their interactions were found to have a substantial effect on the observed responses. Significant improvements were observed in the responses obtained with the optimal parameter setting predicted by the g-RSM approach. The Atomic force microscopy (AFM) images and P-profile plots were also studied to observe the texture of the cut surface.

Experimental Modelling and Analysis in Abrasive Waterjet Cutting of Ceramic Tiles Using Grey-Based Response Surface Methodology

The better machining capabilities of abrasive waterjet cutting (AWJC) characterized by the absence of thermal distortion make it highly competitive with other cutting processes employing plasma and lasers. The present report was oriented towards examining the effect of AWJC parameters like abrasive grain size, abrasive flow rate, nozzle–workpiece standoff, water pressure and jet traverse rate on the surface roughness and taper angle of cut produced with ceramic tiles. Taguchi’s L27 orthogonal array was used for conducting the cutting trials, and a combined technique of grey-based response surface methodology (g-RSM) was disclosed for obtaining the optimal level of AWJC parameters. The g-RSM method was supplemented with analysis of variance to identify the vital parameters affecting the quality characteristics. The optimal parameter setting was validated by conducting a confirmation test. The cut surfaces were also examined using field emission scanning electron microscope images, P-profile plots and atomic force microscope images.

Parametric analysis and optimisation on abrasive water jet cutting of silicon nitride ceramics

Abrasive water jet cutting (AWJC) is a rapidly developing technology that is used in industry for cutting of ceramic materials. Dense Si3N4, is one of the very hard ceramic materials, used for both room and high-temperature structural application, was machined by abrasive water jet machining technique. The selection of optimum values of important process parameters of AWJC processes such as water pressure, abrasive flow rate, traverse speed and standoff distance can be done based on parametric study and then optimisation of non-linear functions using Grey-Taguchi method has been introduced for determining optimal AWJC process parametric combinations.

Influence of Milling and Abrasive Waterjet Cutting on the Fatigue Behaviour of DP600 Steel Sheet

Theobservation of cracks in mechanical parts shows that cracks often initiate oncutting edges. A lot of effort has been done to developing theories to predictfatigue behaviour of welds. However for the cut-edges available data is veryscarce on the fatigue behaviour. Thispaper presents theresults obtained in fatigue tests on DP600 dual-phase steel sheet specimens, underthree types of cutting edges processes: milling with two cutting parameters andabrasive waterjet cutting. The tests were carried out using smooth specimens (Kt=1)and with a fatigue constant amplitude loading with R=0.1. Surface roughness andresidual stresses induced by these different cutting conditions were measuredand analysed. It was found that the fatigue strength of the abrasive waterjetcutting specimens was smaller than the predicted fatigue strength of themilling specimens and these may be attributed to the surface roughness inducedby the cutting process. Finally failure mechanisms were studied with the scanningelectron microscope (SEM) at fracture surfaces, including the identification ofthe fatigue crack initiation region. It was also observed that fatigue crackinitiation takes place on the cut-edges.

Reactor Vessel Internals Segmentation Experience using Mechanical Cutting Tools

Abstract Some commercial nuclear power plants have been permanently shut down to date and decommissioned using dismantling methods. Other operating plants have decided to undergo an upgrade process that includes replacement of reactor internals. In both cases, there is a need to perform a segmentation of the reactor vessel internals with proven methods for long term waste disposal. Westinghouse has developed several concepts to dismantle reactor internals based on safe and reliable techniques, including plasma arc cutting (PAC), abrasive waterjet cutting (AWJC), metal disintegration machining (MDM), or mechanical cutting. Mechanical cutting has been used by Westinghouse since 1999 for both Pressurized Water Reactors (PWR’s) and Boiling Water Reactors (BWR’s) and its process has been continuously improved over the years. The complexity of the work requires well designed and reliable tools. Different band saws, disc saws, tube cutters and shearing tools have been developed to cut the reactor internals. All of those equipments are hydraulically driven which is very suitable for submerged applications. Westinghouse experience in mechanical cutting has demonstrated that it is an excellent technique for segmentation of internals. In summary, the purpose of this paper will be to provide an overview of the Westinghouse mechanical segmentation process, based on actual experience from the work that has been completed to date.

An investigation on use of colemanite powder as abrasive in abrasive waterjet cutting (AWJC)

In the present study, the cutting performance outputs (surface roughness, surface waviness and kerf taper angle) of colemanite powder as abrasive in abrasive waterjet cutting (AWJC) with varying traverse rate and abrasive flow rate were investigated experimentally. The performance outputs were compared to that of garnet which is in common use in industry as abrasive in AWJC industry. Al7075, marble, glass, Ti6Al4V and a composite material were selected as sample materials in the experiments. Furthermore, colemanite powder was mixed with garnet powder at certain proportions and the obtained surface characteristics were compared with those cut with pure garnet powder. It is found experimentally that in spite of higher amount of colemanite powder consumption with respect to garnet to perform the same cutting action, the colemanite powder could be an alternative powder for AWJC process.

INFLUENCE OF ABRASIVE WATERJET CUTTING CONDITIONS ON DEPTH OF CUT OF MILD STEEL

Abrasive waterjet cutting is superior to many other non-traditional machining processes in processing variety of materials, particularly difficult-to-cut materials and has found extensive applications in industry. This paper assesses the influence of process parameters on depth of cut which is an important cutting performance measure in abrasive waterjet cutting of mild steel. Experiments were conducted in varying water pressure, nozzle traverse speed, abrasive mass flow rate and standoff distance for cutting mild steel using abrasive waterjet cutting process. The effects of these parameters on depth of cut have been studied based on the experimental results. In order to correctly select the process parameters, an empirical model for the prediction of depth of cut in abrasive waterjet cutting of mild steel is developed using regression analysis. This developed model has been verified with the experimental results that reveal a high applicability of the model within the experimental range used.

Experimental and Statistical Evaluation of Cutting Methods in Relation to Specific Energy and Rock Properties

In a processing plant, natural stone can be cut by methods such as circular sawing (CS), frame sawing (FS), water jet cutting (WJC) and abrasive water jet cutting (AWJC). The efficiency of cutting systems can be compared using various parameters. In this study, the specific energy values were determined and compared to evaluate the efficiency of rock-cutting methods. Rock-cutting experiments were performed on 12 different types of rock samples using a circular sawing machine and an AWJC machine. The experimental results showed that the specific energy values in AWJC were generally higher than in CS. In addition, the relationships between specific energy values and rock properties were explained in this study. The Shore hardness and abrasion resistance were found to be strongly related to the specific energy values, and according to these parameters prediction charts of specific energy values were created.

A Cross-Sectional TEM Study of Abrasive Water Jet Cut Surface

Abrasive Water jet cutting (AWJ) is a process used to cut materials using a jet of pressurized water. These water jets are capable of cutting a variety of materials like superalloys, titanium alloys, stainless steel, tool steels, ceramics, armor tool and granite. In the present study an attempt has been made to investigate microstructural changes taking place in the sub-surface as a result of AWJ cutting using cross-sectional Transmission Electron Microscopy (TEM). TEM analysis shows that the sub-surface of the AWJ machined sample surface experienced severe deformations. The surface microstructure is observed to contain extremely fine sized grains, going down from sub-micrometer to nanometer range. The selected area diffraction pattern analysis also confirms the presence of extremely fine grained microstructure.

Characteristic Analysis of Metal Trough Faces Cut by Pre-Mixed Abrasive Waterjet

In order to improve the cutting efficiency of abrasive waterjet (AWJ), the relationship between pre-mixed AWJ cutting depth and pressure was experimentally studied. Then, through analysis of the cutting results, the topographic characteristics and formation mechanism of the cut trough faces were investigated. Moreover, through comparing the effects of different jet pressures on the topographic characteristics of AWJ cut trough faces and the SEM analysis of the cut trough faces at different pressures and depths, the effects of pre-mixed AWJ cutting mechanism on the characteristics of cut trough faces were investigated, and the characteristics of the trough faces of metals cut by pre-mixed AWJ were analyzed.

Modeling of Depth of Cut in Abrasive Waterjet Cutting of Thick Kevlar-Epoxy Composites

Abrasive water jet cutting (AWJC) is one of the widely used non-conventional techniques for cutting difficult-to-cut materials like composites, super alloys and ceramics. However, while conducting initial trials the inability of the jet to cut through the workpiece is a major problem particularly in thicker materials. Therefore an accurate prediction of depth of cut (DOC) is absolutely necessary to achieve through cuts and more so to minimize delamination in polymer matrix composites. In this paper, a semi-empirical model is developed using non-linear regression analysis for prediction of DOC in AWJC of thick Kevlar-epoxy composites. Further, the model is verified by conducting experiments within the investigated range of process parameters and a good agreement is obtained between the two.

Predictive modelling of surface roughness and kerf widths in abrasive water jet cutting of Kevlar composites using neural network

Abrasive water jet cutting (AWJC) is one of the important non-traditional machining processes used for cutting of difficult-to-cut materials and intricate profiles. Cutting of Kevlar fibre reinforced polymer composites is a complex process, making it difficult to model, predict and improve the cut surface quality. This paper presents a detailed approach of the usage and effectiveness of a back-propagation neural network (NN) for modelling and prediction of three cut surface characteristics namely top kerf width, bottom kerf width and surface roughness (Ra) in AWJC of aerospace grade Kevlar-epoxy composites. Statistically designed full factorial experiments based on three process parameters [water jet pressure (WJP), abrasive flow rate (AFR) and quality level (QL)] at three levels each were conducted to generate the NN training database. The results demonstrate that the NN model was able to successfully model and predict the two kerf widths and surface roughness closely matching the experimental results.

Depth of cut models for multipass abrasive waterjet cutting of alumina ceramics

Predictive models for the depth of cut in multipass abrasive waterjet (AWJ) cutting of alumina ceramics are presented. Cutting operations both with and without nozzle oscillation are considered. The modelling process starts with the single pass cutting using a dimensional analysis technique and the particle erosion theories applied to alumina ceramics, before progressing to the development of the models for multipass cutting. The models are finally assessed both qualitatively and quantitatively when cutting an 87% alumina ceramic. It is shown that the model predictions are in good agreement with the experimental data with less than 1% of average errors.

Depth of cut models for multipass abrasive waterjet cutting of alumina ceramics with nozzle oscillation

An experimental study of the depth of cut in multipass abrasive waterjet (AWJ) cutting of alumina ceramics with controlled nozzle oscillation is presented. It is found that this cutting technique can significantly increase the depth of cut by an average of 50.8% as compared to single pass cutting without nozzle oscillation under the corresponding cutting conditions and within the same cutting time. Predictive models for the depth of cut are then developed. The modelling process starts with single pass cutting using a dimensional analysis technique and the particle erosion theories applied to alumina ceramics, before progressing to the development of the models for multipass cutting. The models are finally assessed both qualitatively and quantitatively with experimental data. It is shown that the model predictions are in good agreement with the experimental data with the average deviations of about 1%.

ENHANCING THE DEPTH OF CUT IN ABRASIVE WATERJET CUTTING OF ALUMINA CERAMICS BY USING MULTIPASS CUTTING WITH NOZZLE OSCILLATION

An experimental investigation is presented to increase the depth of cut in abrasive waterjet (AWJ) cutting of alumina ceramics by introducing a new cutting technique combining multipass operations with controlled nozzle oscillation. Plausible trends of the depth of cut per pass and total depth of cut with respect to the number of passes and the parameters in each pass are discussed. It shows that cutting with nozzle oscillation can significantly increase the depth of cut in the single-pass cutting mode, while further gains in the depth of cut can be made by using multipass cutting with nozzle oscillation. While multipass cutting can be used to increase the total depth of cut for machining thicker materials, it has been found that an average increase of 50.8% in the total depth of cut can be expected by using multipass cutting with nozzle oscillation as compared to single-pass cutting without nozzle oscillation within the same cutting time. Recommendations are finally made as a practical guide for the selection of process parameters in multipass AWJ cutting of alumina ceramics with controlled nozzle oscillation.