Abrasive Water Jet Cutting

ICRACM, 2005, IT BHU, India

STATE-OF-THE-ART REVIEW OF RESEARCH AND DEVELOPMENT IN ABRASIVE WATERJET MACHINING OF COMPOSITES Pankaj Tambe and Mukul Shukla Mechanical Engineering Department, MNNIT Allahabad, 211004, India E-mail: [email protected] Abstract. Machining of composites by traditional methods like drilling, EDM, laser beam cutting etc. has many disadvantages. One of these is that almost all the traditional machining processes involve the dissipation of heat into the workpiece. This serious shortcoming has been overcome by jetting technologies. Hence there has been a great interest for improving the machining of composite materials particularly in the aerospace industry.

1. INTRODUCTION This paper presents a state-of-the-art review of the ongoing research and development in Abrasive waterjet machining (AWJM) of composites, with a critical review of the physics of the machining process, surface characterization and the newer applications complimentary to the basic research. Further challenges and scope of future development in AWJM are also projected. 2. PHYSICS OF AWJ MACHINING PROCESS The widely accepted explanation of the physics of the material removal process for ductile and homogenous materials is that of Hashish [1, 2] who investigated the AWJ cutting process using a high-speed camera to record the material removal process in a plexiglass sample. He found that the material removal process is a cyclic penetration process that consists of two cutting regimes. He termed these “cutting wear zone” and “deformation wear zone”, following Bittar’s erosive theory (Figure 1) [3]. The material removal process in brittle materials is viewed as a brittle fracture process. Zeng and Kim [4] used an energy approach for the derivation of their plastic elastic model for AWJ cutting of brittle materials. They assumed the total material removal of a single impact as the sum of the removal due to a plastic flow and brittle intergranular fracture. Investigation conducted into the material removal mechanism in refractory ceramics [5] indicated that in the smooth cutting region, material removal is by simultaneous cutting of the matrix and inclusion (transgranular), which could be due to the availability of higher specific jet energy at the top of the kerf, and in the rough cutting region the material removal process is by the removal of the binding matrix followed by the washing of the inclusion grain (intergranular) (Figure 2).

Figure 1. Wear cutting and deformation cutting mode

Figure 2. Intergranular network model

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ICRACM, 2005, IT BHU, India 3. SURFACE CHARACTERIZATION OF AWJ MACHINING The general characteristics of surface machined with abrasive waterjet are discussed in terms of surface texture and surface integrity [1]. These include: Surface Texture: Surface waviness (Figure 3), Kerf width and taper (Figure 4), Burr formation, Surface finish and Lay. Surface Integrity: Particle deposition, Delamination (Figure 5), Gouging, Microstructural transformation, Microcracking, Chipping, Hardness alteration, Heat affected zones and Residual stresses.

Figure 3. Surface waviness

Figure 4. Kerf taper

Figure 5. Delamination

3.1 Kerf characteristics Arola and Ramulu [6] determined the effect of cutting parameters on kerf characteristics and to develop empirical models for kerf profile and the features of the three distinct macroscopic regions. Gudimetla et al. [7] investigated the machinability and kerf formation characteristics associated with the abrasive waterjet cutting of industrial ceramics. 3.2 Striation formation In their study Chen et al. [8], proposed that striations are formed by the variation of the distribution of particle kinetic energy with respect to the cut surface. Chao and Geskin [9] used spectral analysis and found that the structure dynamics of the traverse system correlated with the cut surface striation, and machine vibration was the main cause of striation in AWJ cutting. 3.3 Surface roughness Lemma et al. [10] obtained improvements in surface quality as measured by Ra values, achieved using oscillation cutting of GFRP composites. Arola and Ramulu [11] found that the cutting parameters on the surface roughness change as a function of cutting depth. Wang [12] found that the surface roughness increases with an increase in water pressure and traverse speed. 3.4 Delamination Hashish [1] postulated that at a certain depth within a kerf, the abrasive waterjet deflects and will penetrate between the layers causing delamination when the jet pressure is sufficiently high. Capello et al. [13] proposed that excessive loading on the material owing to factors such as workpiece vibration causes failure in bonding or delamination in the lower region of the cutting. 4. OPERATIONS AND NEW APPLICATIONS OPERATION Drilling

DESCRIPTION 1. Rectangular shaped AWJ with rotating workpiece 2. Stationary workpiece with oscillating jet 3. Stationary workpiece with rotating jet

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ICRACM, 2005, IT BHU, India

Milling Turning Threading Three dimensional machining

1. 2. 1. 1.

Multipass linear traverse cutting Rotating workpiece table and mask Workpiece rotated while the AWJ is traversed axially as well as radially

Workpiece is rotated while jet traverse axially

1. Usage of templates or masks 2. Controlling the exposure time through manipulation of traverse rate and the number of passes. Table 1. Different machining operations [14]

NEW APPLICATIONS Ice Jet Machining Abrasive Cryogenic Jet Machining

Abrasive Suspension Jet Machining Laser Microjet

MEDIA Ice particle Liquid nitrogen Water replaced by water based polymer Laser beam

Table 2. New applications [14]

5. CHALLENGES AND SCOPE OF FUTURE DEVELOPMENT 5.1 Development of an advanced controller The block diagram of the new generation of AWJ cutting system equipped with different levels of closed loop feedback control system is shown in Figure 6.

Figure 6. Block diagram of AWJ cutting control system hardware

5.2 Selection of optimal machining parameters The optimal parameters can be selected by using a Neural Network/Fuzzy Logic based system. 5.3 Consider each layer of composites Each layer of composite must be considered while determining the optimal machining parameters. For each layer the optimal machining parameters to be determined and control with

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ICRACM, 2005, IT BHU, India the help of an advanced controller as proposed in 5.1. 5.4 Dealing with newer class of composites Expert systems are to be developed, which can generate AWJ process parameters by taking the material properties and each layer’s detail as input data. 6. CONCLUSION The research oriented towards understanding the physics of the process has been very vital for the operations and system study. Development of combinations of the abrasive waterjet with other processes might lead to completely new possibilities. Towards the realization of an effective and optimum control of the AWJ process performance, the relationship between AWJ process parameters and process output needs to be understood in greater detail. References [1] Hashish M., Characteristics of surfaces machined with abrasive waterjets, J Eng Mater Technology, 113(1991), pp 354–362. [2] Hashish M., A modelling study of metal cutting with abrasive waterjets, J Eng Mater Technology, 106(1984), pp 88–100. [3] Bittar J., A study of erosion phenomena – Part I, II, Wear, 6(1963), pp 5–21 and pp 169–90. [4] Zeng J. and Kim J., Development of an abrasive waterjet kerf cutting model for brittle materials, Jet cutting technology, Kluwer Acad. Press, Dordrecht, (1992), pp 483-501. [5] Momber A., Kovacevic R. and Eusch I., Cutting refractory ceramics with abrasive waterjets A preliminary investigation, Proc. of 8th American waterjet conference, (1995), pp 229-244. [6] Ramulu M. and Arola R., A kerf characteristics in AWJ machining of graphite/epoxy composite, Transactions of the ASME, 118(1996), pp 320-332. [7] Gudimetla P., Wang J. and Wong W., Kerf formation analysis in the abrasive waterjet cutting of industrial ceramics, Journal of Materials Processing Technology, 128(2002), pp 123–129. [8] Chen F. L., Siores E., Morsi Y. and Yang W., A study of surface striation formation mechanisms applied to abrasive waterjet process, Proceedings of the CIRP, (1997), pp. 570– 575. [9] Chao, J. and Geskin E. S., Experimental study of the striation formation and spectral analysis of the abrasive water jet generated surfaces, J of Mat. Proc. Tech, 141 (2003), pp 213–218. [10] Lemma E., Chen F. L., Siores E. and Wang J., Study of cutting fiber-reinforced composites by using abrasive waterjet with cutting head oscillation, Compos. Struct, 57(2002), pp 297–303. [11] Arola D. and Ramulu M., The influence of abrasive waterjet cutting conditions on the surface quality of graphite/epoxy laminates, Int. J. Mach. Tools and Manufact, 34(1994), pp 295-313. [12] Wang J., A machinability study of polymer matrix composites using abrasive waterjet cutting technology, Journal of Materials Processing Technology, 94(1999), pp 30–35. [13] Capello E., Manno M. and Semeraro Q., Delamination in waterjet cutting of multilayer composite materials: A predictive model, Proceedings of 12th International conference on jet cutting technology, Rouen, France, (1994), pp 463-476. [14] Kovacevic R., Hasshish M., Mohan R., Ramulu M., Kim J. and Geskin S., State of the Art Research and Development in Abrasive Waterjet Machining, Transactions of ASME, 119(1997), pp 65-75.

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