Plain Waterjet Research Articles

An innovative method to perform maskless plain waterjet milling for pocket generation: a case study in Ti-based superalloys

This paper presents an innovative methodology/jet path on which plain waterjet (PWJ) can generate pockets of good dimensional/geometrical definition (minimised under/over-erosion) while the proposed method leads to the avoidance of grit embedment on the target workpiece and the elimination of extra cost and time related to the use of mask. The novelty of the paper relies on the proposal of jet-path strategy that minimises the variations in jet dwell time by providing “continuous” relative movement during the jet-part interaction (through minimisation of accelerations/decelerations of the machine head) and by removing a controlled amount of material in a series of layers using special techniques. The proposed method is powerful in its approach from which it ensures (quasi)equal exposure time for each zone of material over which the jet passes, so that the jet path is “totally contained” within the form to be generated; hence, no masking is necessary to define the contour/shape. This approach has been employed for generating pockets on two Ti-based superalloys commonly used in aerospace industries, followed by dimensional, geometrical and surface quality analysis. The results proved that this approach can produce milled surfaces of straightness of the pocket bottom (<200 μm), tolerance on depth of cut per layer (<20 μm), tolerance on the radii at the bottom of the pockets (<100 μm), surface roughness ( Ra=4–14 μm) and waviness ( Wa=10–13 μm) characteristics in conditions of high surface integrity (no cracks, contaminations, etc.).

AWJ Milling of Gamma Titanium Aluminide

A study was undertaken to determine the feasibility of the AWJ process for controlled depth milling of gamma Titanium Aluminide tiles. It was demonstrated that milling can be accomplished to 0.025-mm accuracy. To overcome undercutting near rib roots, the jet was clock-angled at about 15 deg to the vertical every set of passes. This allowed the milling to thin skins of about 0.5-mm. It was observed that as the material is milled, stresses were relieved, and either deformation or cracking may result. Accordingly, parts need to be annealed before milling. The milling to thin skins was successfully demonstrated on 150×300 mm2 parts without adverse effects. Also, the process of milling of the dual rib height was developed using the dual mask approach. Abrasive particle embedding on the milled surfaces was observed to be about 0.15% of the area, but cleaning with plain waterjets showed that all embedded particles can be removed. A detailed economic analysis confirmed that the AWJ milling process is relatively inexpensive and highly productive. The complete cost of milling including mask cutting, overhead, capital, and running cost is less than 300 USD/ft2.

1417 ウォータージェットを利用したセラミックス溶射皮膜のはく離除去 : 表面様相の変化に基づく分類(流体力学VI)

1417 ウォータージェットを利用したセラミックス溶射皮膜のはく離除去 : 表面様相の変化に基づく分類(流体力学VI)

Aspects of material removal mechanism in plain waterjet milling on gamma titanium aluminide

Due to providing reduced mechanical and thermal damages to workpiece surfaces, waterjet machining that is one of the most promising non-conventional processing methods found its niche application in cutting/shaping of materials with low machinability indexes. It can be even a more attracting technology if plain waterjet (PWJ) milling is employed due to reduced running costs (absence of abrasives) and the elimination of surface contaminations (grit embedment). The paper reports for the first time PWJ milling of a notoriously difficult-to-cut material, gamma titanium aluminide (γ-TiAl). Trials of different jet paths with varied milling parameters (e.g. water-hammer pressures, stepovers, number of passes) were conducted for understanding the removal mechanism of γ-TiAl in plain waterjet milling. The findings showed that the threshold water-hammer pressure for eroding the target material and for achieving uniform erosion were in the vicinity of 800 MPa and greater than 1 GPa, respectively. In addition, different fracture modes were observed on γ-TiAl when PWJ milling: (i) plastic deformation and crack initiation; (ii) stress wave propagation; (iii) micropits due to joint of crack lines; (iv) intergranular cracking/fracture, triple split and interlamellar/translamellar fracture. The stages (i)–(iii) occurred at lower water-hammer pressures and number of passes while the subsequent stage (iv) was only observed at higher water-hammer pressures or number of passes. The knowledge accumulated when studying the material removal mechanism and surface morphology enabled successful generation of 3D PWJ milled features (e.g. shallow pocket). To evaluate the capability of PWJ milling process, the geometrical accuracy and surface quality of the pocket has been examined. Finally, the advantages and drawbacks of the PWJ milling process are discussed to allow the definition where the technology is economically viable.

518 ウォータージェットの溶射皮膜はく離特性の評価(流体工学IV)

518 ウォータージェットの溶射皮膜はく離特性の評価(流体工学IV)

Response of titanium aluminide alloy to abrasive waterjet cutting: Geometrical accuracy and surface integrity issues versus process parameters

Due to their low thermal conductivity, high abrasion of cutting edges and a tendency to crack during machining, titanium aluminide (TiAl) alloys are notoriously difficult-to-cut materials when using conventional (e.g. turning, grinding, drilling, milling) cutting operations. Despite their low machinability TiAl alloys find niche application areas in the manufacture of complex shaped components for aerospace gas turbine engines. Abrasive waterjet (AWJ) machining is one of the most promising non-conventional machining processes for difficult-to-cut materials because of the reduced mechanical and thermal damage to workpiece surfaces produced using this technique. However, there is no information about the AWJ machining of TiAl alloys in the open literature. Based on a generic design of an aeroengine component, this paper investigates the response of a TiAl alloy to AWJ cutting process variables to enable generation of high-integrity surfaces. The effects of operating parameters (pump pressure, material removal rate, abrasive flow rate, and stand-off distance) on the output process quality measures have been investigated as follows: geometrical accuracy (kerf straightness); surface roughness homogeneity (measured along cutting direction on the cutting front surface to study the striation formation); workpiece surface integrity (grit embedment and possible recast micro-layers or material pull-out / micro-cracking after cutting). Advanced surface topography and metallurgical (e.g. SEM, EDX) analyses have been carried out to characterize the response of TiAl alloy to various AWJ conditions leading to the fulfilment of quality criteria of a group of targeted aeroengine components. It was found that the AWJ process has a very high capability (e.g. satisfactory geometrical accuracy, surface quality, minimum surface anomies) to cut TiAl alloy despite grit embedment. However, the authors have addressed this problem by plain waterjet cleaning know-how. In addition, a surprising phenomenon (bubble-like ‘TiO2-based spot’) caused by a strong exothermic reaction was found on the AWJ cut surfaces.

Cutting meat with bone using an ultrahigh pressure abrasive waterjet

An experimental study of abrasive waterjet (AWJ) cutting of beef, pork and lamb meat with and without bone is presented. Salt particles were used as the abrasives. It has been found that an AWJ could significantly increase the depth of cut with much improved cut quality in cutting pure meat as compared to plain (or pure) waterjet cutting, while a plain waterjet was incapable of cutting bone satisfactorily. The study shows that AWJ cutting produced a very narrow kerf of less than 1 mm and hence resulted in mush less meat loss than the traditional cutting processes, and meat can be cut at room temperature to eliminate the freezing or chilling costs. It is shown that a traverses speed of 20 mm/s can be used to cut through 44 mm thick beef rib bones with good cut quality. When slicing pure meat of 150 mm thickness, the traverse speed of 66.67 mm/s can yield very good cut quality. It is suggested that AWJ cutting is a viable technology for meat cutting. Plausible trends for the depth of cut, cutting rate and cut quality with respect to the process variables are discussed. Recommendations are finally made for the selection of the most appropriate process parameters for cutting meat of a given thickness.

308 ウォータージェットの流動構造と金属材料の加工特性に関する研究(機械材料・材料加工II)

308 ウォータージェットの流動構造と金属材料の加工特性に関する研究(機械材料・材料加工II)

P.094 Surgically assisted anterior segment distraction with tooth borne appliance (case report)

An experimental study of abrasive waterjet (AWJ) cutting of beef, pork and lamb meat with and without bone is presented. Salt particles were used as the abrasives. It has been found that an AWJ could significantly increase the depth of cut with much improved cut quality in cutting pure meat as compared to plain (or pure) waterjet cutting, while a plain waterjet was incapable of cutting bone satisfactorily. The study shows that AWJ cutting produced a very narrow kerf of less than 1 mm and hence resulted in mush less meat loss than the traditional cutting processes, and meat can be cut at room temperature to eliminate the freezing or chilling costs. It is shown that a traverses speed of 20 mm/s can be used to cut through 44 mm thick beef rib bones with good cut quality. When slicing pure meat of 150 mm thickness, the traverse speed of 66.67 mm/s can yield very good cut quality. It is suggested that AWJ cutting is a viable technology for meat cutting. Plausible trends for the depth of cut, cutting rate and cut quality with respect to the process variables are discussed. Recommendations are finally made for the selection of the most appropriate process parameters for cutting meat of a given thickness.

P.092 Evaluation of the efficiency of hyperbaric oxygen therapy on distraction osteogenesis applied in rabbits

An experimental study of abrasive waterjet (AWJ) cutting of beef, pork and lamb meat with and without bone is presented. Salt particles were used as the abrasives. It has been found that an AWJ could significantly increase the depth of cut with much improved cut quality in cutting pure meat as compared to plain (or pure) waterjet cutting, while a plain waterjet was incapable of cutting bone satisfactorily. The study shows that AWJ cutting produced a very narrow kerf of less than 1 mm and hence resulted in mush less meat loss than the traditional cutting processes, and meat can be cut at room temperature to eliminate the freezing or chilling costs. It is shown that a traverses speed of 20 mm/s can be used to cut through 44 mm thick beef rib bones with good cut quality. When slicing pure meat of 150 mm thickness, the traverse speed of 66.67 mm/s can yield very good cut quality. It is suggested that AWJ cutting is a viable technology for meat cutting. Plausible trends for the depth of cut, cutting rate and cut quality with respect to the process variables are discussed. Recommendations are finally made for the selection of the most appropriate process parameters for cutting meat of a given thickness.

MASS FLOW RATE AND VELOCITY MEASUREMENTS FOR PLAIN AND ABRASIVE HIGH SPEED WATER JETS

Mass flow rate measurements for plain and AWJ are performed at different pressures and mathematical models are derived to predict mass flow rate, density and velocity. A high-pressure container is used to collect the water/slurry over a given period of time. The results show consistency with the machine manual at the maximum pressure. Mass flow rates for AWJ are higher than plain water jets, but the difference does not seem to be highly dependent on pressure. The difference in these flow rates is attributed to the abrasive added in the AWJ case. The momentum transfer ratio is computed by measuring the ratio of abrasive to plain water jet impacting forces using piezoelectric transducers. The relationship between jet velocity and pressure is observed to be linear, and the corresponding mathematical models are generated. These models will subsequently be used to determine the kinetic energy of the jet as it exits the orifice and hits the target material. When the exit velocity of the jet is measured (through direct force measurements) it becomes possible to obtain an expression for the energy dissipation function as a function of pressure, target material and feed rate.

LASER OBSERVATION ON THE INNER FLOW STRUCTURE OF WATER JETS(Water Jet)

To make clear the structure of the straight-water jets (STWJ, or plain-water jets), the axial and radial distributions of the STWJ were measured by using a laser-doppler-velocimeter (LDV). Abrasive-water suspension jets (AWSJ) velocity was also examined experimentally and compared with the STWJ velocity. Experimental data showed that the average AWSJ velocity exceeded the average STWJ velocity in the range of the diffused flow region far from the nozzle.

Control of chip flow direction in high-pressure water jet-assisted orthogonal tube turning

This paper shows the possibility of controlling the chip side-flow direction in water jet-assisted turning using flat-faced inserts without any chip formers. The experiments were performed under orthogonal cutting conditions of an end of a pipe with plain water jet assistance with a pressure up to 80 MPa and a flow up to 81/min. The jet was directed perpendicular to the cutting edge into the tool/chip interface. Experimental results show that the chip side-curl radius can be successfully controlled. A correlation between the jet momentum, jet diameter and side-curl radius is presented and widely discussed.

Chip control in tube turning using a high-pressure water jet

A stable chip control using inserts with integrated chip formers is difficult, especially if the feed rate or cutting depth is not within the range recommended for the insert. This paper shows the possibility of controlling the chip upcurl radius in turning by using flat inserts without any chip formers. An experimental study was made of the skew cutting of an end of a pipe using a plain water jet with a pressure of up to 80 MPa and a flow of up to 8 l/min. The jet was directed perpendicularly to the cutting edge into the tool/chip interface. Investigations show that the chip upcurl radius can be successfully controlled. A correlation between water jet power, jet momentum and upcurl radius is presented and discussed. An empirical model of the above-mentioned correlation is also suggested.

Investigations into decoating and recycling of pipeline elements using the on-site high-pressure water jet technique

The paper describes investigations into the application of the high-pressure water jet technique for the recycling of coated pipeline elements. The paper starts with the introduction and definition of the process parameter 'selectivity'. After this, a review about the general principles of jet cutting technology, including tools, is given. Finally, the author reports on the decoating and demolition of covered steel pipes by plain and abrasive water jets. High-pressure water jets are versatile tools for the complete and partial decoating of steel pipes. Abrasive water jets can be used successfully to cut steel pipes including different coating systems.

On the behaviour of concrete under water jet impingement

It is important from the economics point of view to understand the behaviour of concrete under loading due to plain water jets. Investigations which are based on mass removal measurements, grain size analysis, and mercury intrusion show that the performance of failure can be described using fracture mechanics methods. The reactions of hardened cement paste and concrete differ widely from each other because of the influence of interfaces between the cement paste and the aggregate.

Comparison of the performance of high-speed abrasive-entrained, cavitating and plain water jets for selective mining applications : Vijay, M M Int J Surf MinV6, N1, 1992, P1–9

Comparison of the performance of high-speed abrasive-entrained, cavitating and plain water jets for selective mining applications : Vijay, M M Int J Surf MinV6, N1, 1992, P1–9

Comparison of the performance of high-speed abrasive-entrained, cavitating and plain water jets for selective mining applications

ABSTRACT This Investigation was concerned with the potential of the high-speed abrasive-entrained, cavitating and plain water Jets for selective mining of metal-bearing rock minerals, by slotting along the seams or fragmentation within the ore zone. Limited number of tests were conducted in the laboratory on slotting of metal-bearing and non-metal-bearing (muck or waste) rock samples supplied by the mines in Northern Ontario, Canada. The range of independent variables investigated were as follows: Tests with cavitating jets, issuing from a simple conical entry and from a centre-body nozzle, were conducted under submerged conditions. The nozzle diameter was held constant at 1·20 nun for all the tests. The conclusion from this preliminary and limited investigation was that all three types of high-speed water jets have a good potential for selective mining of netal bearing rock material, although more work Is required to optimize the nozzle systems. Within the range of variables investigated, the jets had vi...