High-speed Water Jet Research Articles

Improving effects of cavitation peening, using a pulsed laser or a cavitating jet, and shot peening on the fatigue properties of additively manufactured titanium alloy Ti6Al4V

To demonstrate and compare the improving effects of cavitation peening and shot peening on the fatigue properties of additively manufactured metals, titanium alloy Ti6Al4V specimens prepared by direct metal laser sintering were treated by cavitation peening, using a pulsed laser or a submerged high-speed cavitating water jet, and shot peening and, subsequently, subjected to torsion fatigue tests. It was revealed that cavitation peening using a laser, shot peening, and cavitation peening using a cavitating jet prolong the fatigue life of AM Ti6Al4V at τa (applied stress) = 450 MPa by factors of 3.5, 3.2, and 1.4, respectively.

Airborne acoustic emission of an abrasive waterjet cutting system as means for monitoring the jet cutting capability

Abrasive waterjet cutting is a manufacturing technology making use of a high-speed waterjet with abrasive particles in suspension, for cutting materials with different mechanical properties. Product quality requirements are pushing towards an improvement of tracking and stabilization methods of the relevant process variables. Amongst those, the jet kinetic power defines the cutting capability and has a significant impact on the final cut features. This variable is subject to relevant fluctuations versus time. Besides, the current state of the art does not provide means for its in-line monitoring. The aim of this contribution is to monitor the airborne acoustic emission of an abrasive waterjet cutting head and investigate its correlation with the jet kinetic power. The investigation is carried out by means of factorial studies, in which the jet is fired at various water pressures and abrasive feed rates, providing different kinetic powers. The acoustic emission is synchronously monitored by means of a condenser microphone, installed on the cutting head. Data at frequencies above 40 kHz is found to constitute a robust and selective acoustic signature of the airborne jet. The acoustic signature is proven to be an effective in-line indicator of the jet kinetic power and its pressure-induced variations, whilst abrasive-induced variations remain undetected. A calibration procedure is presented, for translating the acoustic data into a jet kinetic power. The method is validated by means of further experiments that envisage its deployment in a real scenario. Overall, the presented method constitutes a robust tool for monitoring pressure-induced variations of the jet cutting capability.

Modeling of the cutting front profile in abrasive water jet machining based on the energy balance approach

High-speed abrasive water jet machining (AWJM) is a universal tool for manufacturing engineering materials. However, the application of AWJM is greatly limited due to the jet lag value caused by the cutting front profile. This paper proposes a new method to predict jet lag values at different cutting depths. The novelty is that a simplified mathematical model of the cutting front profile is developed based on the energy balance theory. Two groups of experiments were conducted to investigate the influences of process parameters on the jet lag value and the dissipated energy during cutting. The numerical regression method is adopted to obtain the energy dissipation function, which has taken the key parameters such as material property, cutting depth, traverse speed, and the initial water jet energy into consideration. The predicted curves are compared with experimental results under different operating situations with the least value of R2 = 0.9136 and the maximum deviation in percent of 16% at the jet exit point. The proposed method contributes to further research on product distortion in abrasive water jet cutting.

Numerical simulation of rock erosion performance of a high-speed water jet using an immersed-body method

Water jet drilling (WJD) is an effective technique for drilling micro-holes in the subsurface for reservoir stimulation . This study aims to investigate numerically the failure mechanism of rock during WJD and to assess the WJD performance before drilling. A 3D fluid-solid coupling model is developed for simulating WJD by coupling a mechanical solver based on the combined finite-discrete element method (FDEM) with a fluid solver using an immersed-body method. The new numerical model is capable of simulating crack initiation and propagation and fragment removal under the impact load of a high-speed water jet. The poroelastic effect is implemented via Biot's theory of poroelasticity . The numerical results show that: (1) rock failure is only observed in the Gildehaus sandstone with the lowest strengths among the three types of rock tested, (2) most of the cracks are tensile failures and pure shear cracks are rare, mixed mode cracks account for 15%∼40% of the total crack number depending on the mechanical boundary conditions , (3) increased water back pressure significantly suppresses jet erosion. The poroelastic effect on the rock failure is insignificant in the mesoscale simulations and will be further investigated using a microscale model in future.

Flow Field Simulation and Parametric Design of High-pressure Water Jet Cutting Leather Based on Fluent

This paper studies the flow field simulation process of high-speed water jet cutting leather. Based on the water jet impact model, Fluent is used to analyze different jet pressures, spray distances and nozzles diameter. The effect of the outlet diameter on the jet impact velocity and the impact area is studied. Through the study of three factors, it is found that the jet pressure has the greatest and most direct influence on the jet velocity. Therefore, adjusting the jet pressure is an important means to successfully complete the water jet cutting. The above research has a good guiding for cutting leather.

Impact damage of composite laminates with high-speed waterjet

Rain erosion may cause substantial damage to aircrafts during supersonic flight. Such event is investigated here via high-speed waterjet impact on composite laminates. An experimental setup is developed to produce waterjets with the speed up to 700m/s and a finite element model of the waterjet-composite impact event is established. The consistency of experiment and simulation results validates the adopted numerical methods. The distribution of the water-hammer pressure is non-uniform and the maximum pressure occurs near the contact periphery when the water is about to eject laterally. After a high-speed (300∼560m/s) waterjet impacts a composite laminate, the impacted surface depression is observed, and the typical surface damage presents a central region with no visible surface damage surrounded by a faded “failure ring” with resin removal, matrix cracking and minor fiber fracture. Delamination occurs at the interfaces of adjacent layers with unequal dimensions and longitudinal matrix cracking appears on the back surface. Both the velocity and the diameter of waterjets are crucial factors on CFRP damage extents. Water-hammer pressure, the stagnation pressure and propagation of stress waves are failure mechanisms for most matrix damage in CFRP impacted by waterjets.

An experimental measurement research on impact load of high speed water jet acting on a rigid target by a Hopkinson pressure bar

A high speed water jet generation device based on explosion in a cylindrical cavity is introduced, which can eject a well-characterized water jet with a velocity around 100 m/s. The evolution characteristics and impact phenomenon of water jet act on a rigid target are observed by a high speed camera and the impact load is measured by a Hopkinson pressure bar. The top shape of water jet develops from a convex spherical surface to a flat plane as the stand-off increases under the influence of air resistance. When the top of water jet contacts the target plate, a transient high-pressure zone appears at the liquid-solid interface. A horizontal annular splashing jet generates and the velocity of splashing jet is much higher than that of incident jet as the result of high-pressure zone. The impact load is measured by the Hopkinson pressure bar, including transient “water hummer” pressure and subsequent hydrodynamic load. The “water hummer” pressure of water jet with a flat top is twice that with a convex spherical top, while the subsequent hydrodynamic pressure is equivalent at a comparable transient impact velocity. The measurement results by a Hopkinson pressure bar are in good agreement with the theory formulas in terms of both “water hummer” pressure and hydrodynamic pressure. It is certified that the Hopkinson pressure bar has a credible measuring capacity for both transient and steady-state pressure. By controlling cavity depth, charge amount and stand-off distance, the different top shape and velocity of water jet can be obtained.

Natural rosin-grafted nanoparticles for extremely-robust and eco-friendly antifouling coating with controllable liquid transport

Owing to their highly efficient antifouling function, superhydrophobic coatings show great potential applications in both daily-life and industrial areas. Real-world applications, however, still encounter challenges, with the central concern being the mechanical robustness and eco-friendliness. Here, we developed a robust and eco-friendly superhydrophobic coating (RESC) by hybrid synergistic assembly between naturally-sourced raw material (rosin) and hydrophobic nanoparticles. The resulting product can reserve superhydrophobicity after tape-peeling, sandpaper abrasion, and even high-speed water jets up to 20 m/s. Additionally, the coating can prevent adhesion by water-based contaminants, and could repel solid contaminants upon washing with water. Intriguingly, when infused with silicone oil, the coating could easily repel low-surface-energy droplets covered with hot water, oil, and fouled oil, and these droplets could be transported controllably along a desired wetted path on the slippery surface. These results suggest that coatings with integrated functionalities can be potentially used under various harsh environments such as those encountered in chemical engineering, infrastructure, and biomedical applications.

Smart Piezo-bonded carbon fibre/epoxy composite structure: experiments and finite element simulation

Smart sensors patched to composite structures assist in the prediction of the mechanical behaviour of the structures. The present paper used finite element modelling and experimental procedures to conduct a detailed study on the response of composite laminate bonded with smart piezoelectric material. Fibre reinforced epoxy composite laminate was fabricated using the vacuum assisted resin transfer method. Test coupons in accordance with ASTM standards were prepared using high-speed and high-pressure abrasive water jet cutting. The mechanical properties of the composites were obtained through material characterization and the material properties were incorporated into the Finite element model. The layer-wise strain rate was computed with the ANSYS® Composite Prep Post module. A finite element model of a composite with piezoelectric sensor patch was created in ANSYS® APDL and harmonic analysis was conducted to determine the optimal frequency range for the applied load. An attempt was made to measure the strain by affixing lead zirconate titanate to a carbon fibre reinforced polymer laminate for cantilever configuration, and the LabVIEW® VI software module was integrated with the NI myDAQ system to detect the corresponding voltage for the excited frequency. The values of the generated voltage through numerical simulations were verified and validated using experimental counterparts.

Ice breaking by a high-speed water jet impact

Ice breaking has become one of the main problems faced by ships and other equipment operating in an ice-covered water region. New methods are always being pursued and studied to improve ice-breaking capabilities and efficiencies. Based on the strong damage capability, a high-speed water jet impact is proposed to be used to break an ice plate in contact with water. A series of experiments of water jet impacting ice were performed in a transparent water tank, where the water jets at tens of metres per second were generated by a home-made device and circular ice plates of various thicknesses and scales were produced in a cold room. The entire evolution of the water jet and ice was recorded by two high-speed cameras from the top and front views simultaneously. The focus was the responses of the ice plate, such as crack development and breakup, under the high-speed water jet loads, which involved compressible pressure ${P_1}$ and incompressible pressure ${P_2}$ . According to the main cause and crack development sequence, it was found that the damage of the ice could be roughly divided into five patterns. On this basis, the effects of water jet strength, ice thickness, ice plate size and boundary conditions were also investigated. Experiments validated the ice-breaking capability of the high-speed water jet, which could be a new auxiliary ice-breaking method in the future.

Investigation of three-dimensional microstructural features of wood pulp-based wetlaid materials with/without hydroentanglement

Wood pulp-based wetlaid/spunlace (wetlace) material used for cleaning care has sufficient wet strength and disintegration after use. To obtain the effect of high-speed waterjet needle on the change of internal microstructural features of the material, wood pulp/Danufil wetlaid materials with/without hydroentanglement were prepared, and the microstructures of materials were reconstructed virtually by Micro-CT technology. The fault color images of materials along the thickness direction were received and statistical analysis was carried out by software. The results suggest that the pore diameter, fiber longitudinal arrangement and thickness of wetlaid web increases obviously after hydroentanglement. Meanwhile, the layer pore rate of each side of wetlaid and wetlace materials gradually both decreased from outside to inside, and are kept constant at 76% and 67% in the intermediate position, respectively. Furthermore, the longitudinal fiber content of each fault plane on both sides of the material is large, but the fiber arrangement is isotropic when it closes to the scanning center. Overall, hydroentanglement endows the wood pulp-based wetlaid material with special microstructural features and sufficient water absorption.

Life Cycle Environmental and Economic Comparison of Water Droplet Machining and Traditional Abrasive Waterjet Cutting

Abrasive waterjet (AWJ) cutting is a manufacturing technique, which uses a high-speed waterjet as the transport medium for abrasive particles to erode and cut through metal workpieces. The use of abrasives has significant environmental impacts and leads to the high operating costs of AWJ cutting. Therefore, it is important to investigate whether other metal cutting approaches can perform the same tasks with reduced environmental and economic impacts. One such manufacturing innovation is water droplet machining (WDM). In this process, the waterjet, which is immersed in a sub-atmospheric pressure environment, is discretized into a train of high velocity water droplets, which are able to erode and cut through the metal workpiece without abrasives. However, the cutting velocity of WDM is two orders of magnitude slower than AWJ. In this paper, a comparative life cycle and life cycle cost assessments were performed to determine which waterjet cutting technology is more beneficial to the environment and cost-efficient, considering their impacts from cradle to grave. The results show lower environmental and economic impacts for AWJ compared to WDM due to the AWJ’s ability to cut more metal over the service life than the WDM. Further sensitivity analyses give insight into how the change in abrasive rate is the most sensitive input for the AWJ, whereas the machine lifetime and electricity usage are the most sensitive inputs for the WDM. These results provide a valuable comparison between these alternative waterjet cutting technologies.

Analysis of the impeller's tip clearance size on the operating characteristics of the underwater vehicle with a new high-speed water jet propulsion pump

To make up for the lack of study on high-speed water jet propulsion pump tip clearances, a newly developed water jet pump system close to the critical specific speed nsc has been investigated. Based on the body of the underwater vehicle and the non-uniform flow, the pump system with different tip clearance sizes (0.1, 0.2, 0.4, 0.8 mm) is evaluated and validated via numerical simulations. Preliminary steady simulating results demonstrate that increasing the tip clearance size can reduce the overall performance of the head, the efficiency, pump thrust, and the consuming power. Following further unsteady simulations, we reveal the unsteady dynamic performance induced by the tip clearances, related to the similar distribution characteristics of the pressure intensities and the pressure pulsations around the underwater vehicle. Furthermore, the pressure intensity and pressure pulsations in the pump increase with the tip clearance. Quantitative and comparative analysis of the distribution characteristics indicates that the blade loading and scrapping effect of the shroud are key factors influencing the leakage flow. At last, the leakage flow's dynamic distributing law under different tip clearances have been clarified.

Research into the Disintegration of Abrasive Materials in the Abrasive Water Jet Machining Process.

The size and distribution of abrasive particles have a significant influence on the effectiveness of the cutting process by the high-speed abrasive water jet (AWJ). This paper deals with the disintegration intensity of abrasive materials in AWJ cutting during the creation of the abrasive jet. An evaluation of the abrasive materials was performed after forming in the cutting head was carried out and grain distribution was evaluated using the geometric and logarithmic Folk and Ward method. The influence of the abrasive concentration of abrasive materials such as alluvial garnet, recycled garnet, corundum, and olivine on grain distribution was studied. A recovery analysis was also carried out and the recycling coefficient was determined for each abrasive material tested.

Characteristics of cavity collapse behind a high-speed projectile entering the water

We investigate cavity collapse regimes behind high-speed projectiles entering the water. Using numerical simulations, we confirmed two different collapse phenomena: deep pinch-off and consecutive collapse. We performed a theoretical analysis to develop the relationship between projectile motion and cavity evolution. We found that projectile acceleration is the most significant factor determining the initial cavity collapse. There is a critical acceleration determining the direction of cavity collapse at the location of deep pinch-off. The pressure field is obviously affected by the collapse. The increase in pressure induced by surface pinch-off accelerates the collapse at the cavity tail. Because of the impact of surface pinch-off, consecutive collapse can be seen if a projectile reaches critical acceleration near a free surface. Otherwise, the cavity will pinch off at a distance from the surface of the water and form a deep pinch-off. Particular attention is paid to the impact of consecutive collapse on the projectile. Numerical calculations show that cavity collapse and a high-speed water jet have an obvious impact on the stability of the projectile. The jet exerts great pressure on the projectile, and the accompanying splash droplets contaminate the cavity wall. Cavity pulsation and the asymmetric geometry of the projectile-cavity system aggravate attitude deflection.

Influence of External Jet on Hydraulic Performance and Flow Field Characteristics of Water Jet Propulsion Pump Device

Water jet propulsion technology has broad application prospects in the field of ships, and water jet technology is a kind of high and new technology that is booming and has a wide range of applications. However, there are a few studies on the effect of the external jet on the performance of the water jet propulsion pump, and it is urgent to carry out this research. In this paper, the standard k-ε turbulence model is used to carry out the numerical simulation study of the influence of the external jet on the hydraulic performance and flow field characteristics of the water jet propulsion pump device. This paper discusses the selection of calculation models, the division of grids and the setting of turbulence models, and an in-depth analysis of the calculation results. The research results show that when a high-speed water jet enters a moving water body, it will cause turbulence in the moving water body. With the increase of jet flow, the turbulence phenomenon will be improved. The average velocity of the outlet section of the nozzle is consistent with the change of the total pressure. The average vortex gradually decreases, the turbulent kinetic energy changes little, the turbulence dissipation first decreases and then increases, and the nozzle axial force changes more and more. The axial force and thrust of the device will obviously increase when the two water streams merge and spray, and they will increase with the increase of the jet flow rate. By revealing the influence mechanism of the external jet on the water jet propulsion pump device, it can provide a theoretical basis and guiding direction for further optimizing the hydraulic performance of the entire device.

Comparison of the disintegration abilities of modulated and continuous water jets

This study investigated the erosion phenomena of a high-speed modulated water jet (MWJ) and a continuous water jet (CWJ) during jet–material interaction. The disintegration abilities of self-excited and continuous water jets were compared. The erosion abilities of the MWJ and CWJ for two levels of hydraulic powers (26 and 72 kW) on the aluminum alloy EN AW-6060 were tested. The CWJ was generated using a StoneAge 0.069″ nozzle with a circular orifice having a diameter of 1.75 mm, and the MWJ was generated by a nozzle with a rectangular orifice having dimensions of 1.5 mm × 1.5 mm. Owing to the asymmetrical MWJ profile, two different alignments of jet position (0° and 90°) with respect to the direction of nozzle travel were examined. A six-axis industrial robot equipped with both nozzles ensured the movement of the particular trajectory with a traverse speed of 1 mm/s. An optimal standoff distance was observed for all tested pressures of the given hydraulic powers with respect to the nozzle and material position. High-pressure flow diagnostic sensors were used to accurately adjust the hydraulic power of the tested operating conditions. A total of 29 samples with dimensions of 100 mm × 50 mm × 20 mm were investigated during experimental testing. Each erosion test was repeated three times. Subsequently, the eroded groove profiles were studied using a MicroProf FRT optical profilometer. Basic parameters such as average material groove depth, groove width, and material removal rate were statistically analyzed. The irregularities and specific surface characteristics of the eroded grooves were examined using scanning electron microscopy. It was observed that using MWJ, a four-times higher erosion rate of material removal can be achieved compared with standard CWJ using the same technological conditions. The details of the experiments are presented in this paper.

Experimental investigation of stone drilling using water jet generated by electromagnetic actuator

This paper aims to experimentally investigate the performance of a high-speed water jet generated by an electromagnetic actuator to drill the stone's surface. The electromagnetic actuator was designed and built by following the impact driven method (IDM). The experiment confirmed that the maximum jet velocity of 239.57 m/s and maximum impact pressure of 133.27 MPa are obtained at the traveling distance of 30 mm, the liquid volume of 0.1 mL, voltage capacity of 500 V, and the nozzle's orifice diameter of 0.5 mm. The performance characteristics, e.g., jet velocity and impact pressure of the water jet generator, have the potential for applying to many medical and engineering applications. The application of a high-speed water jet for stone drilling is investigated as a preliminary study. The water jet was then applied to drill the sandstones. The effects of numbers of a jet pulse to the jet drilling's depth in sandstones were reported, and the failure mechanisms of sandstone are also discussed. Finally, it is concluded that the high-speed water jet generated by the electromagnetic actuator has the potential to apply to stone drilling application.

Superhydrophobic surface with excellent mechanical robustness, water impact resistance and hydrostatic pressure resistance by two-step spray-coating technique

Superhydrophobic surfaces (SHSs) exhibit outstanding liquid-repellent properties, attracting numerous attentions from both academia and industry. However, their weak mechanical robustness and poor water impact resistance still limit their practical applications. Herein, SHSs were fabricated by a simple and scalable two-step spray-coating technique, i.e., spray-coating micro-particles as bottom layer, followed by spray-coating nanoparticles onto the micro-particles as top layer; both micro- and nano-features were firmly affixed by low-surface-energy polymer binder. By carefully tuning the micro-particle ratio in bottom layer and mixed solvent ratio in top layer, we obtained the optimized micro/nano- hierarchical structures, which offered the SHSs super-repellence to various liquids (e.g., water, blood and honey) and excellent mechanical robustness to cloth wipe, eraser rub, multi-cycled sandpaper abrasion and tape peel-off. The SHSs withstood high-speed droplet impact and water jet impact with water impact speed of up to ~9.5 m/s (corresponding to ~3760 of Weber value). In addition, they maintained the superhydrophobicity under a hydrostatic pressure of 0.1 MPa for more than one month, or 3 MPa for more than 12 h, which is the highest record ever reported.

SPH-FEM simulation of concrete breaking process due to impact of high-speed water jet

The process of concrete breaking by a high-speed water jet was simulated in this study based on the coupled method of smoothed particle hydrodynamics and the finite element method. The Riedel–Hiermaier–Thoma constitutive model was adopted to describe the mechanical characteristics of the concrete material. Various impact velocities (250–800 m/s) and jet diameters (1.0–3.0 mm) were simulated to investigate the effect of incident parameters on the dynamic responses and damage behaviors of the concrete material. The simulation results were also verified by water-jet impact experiments. The results show that the model can reproduce the nonlinear behaviors of concrete due to the impact of the water jet, including crack propagation, large deformation of the crushing crater, and penetration. For the constant jet diameter, a critical velocity of water-jet flow is identified. Lateral cracks can be generated inside concrete when the impact velocity exceeds the critical velocity, which can enhance the water-jet capability significantly to damage the concrete. The evolution process of the concrete crushing crater is also obtained. The initial shape of the crushing crater is “ω-shaped” and then gradually transforms into “V-shaped” until being penetrated by the water jet. The section shape of the concrete crushing hole is trapezoidal after penetration. For impact velocity v ranging from 250 to 500 m/s, the size of the concrete crushing hole increases with the increase in v, and the section shape tends to be rectangular. If v exceeds 500 m/s, the size and section shape no longer change significantly. It was also found that the greater the diameter of the water jet, the more the sensitivity of crushing hole size on water-jet velocity.