Cavitation Impact Research Articles

The Use of Cavitation Peening to Increase the Fatigue Strength of Duralumin Plates Containing Fastener Holes

An effective method for improving the fatigue life of Duralumin plates with fastener holes, such as those used in the construction of aircraft, is to introduce a compressive residual stress around the fastener holes. Cavitation peening is a novel peening method that uses the cavitation impact produced when a high-speed water jet is injected into a water-filled chamber. In this paper, Duralumin plate specimens with holes were treated by cavitation peening under various conditions, and the fatigue strength of the specimens was determined using a plate bending fatigue test. It was revealed that a compressive residual stress was introduced not only on surfaces perpendicular to the axis of the cavitating jet but also on the walls of holes which were parallel to this. It was found that a 51% improvement in fatigue strength could be achieved by cavitation peening. Note that this is first report demonstrating an improvement in the fatigue life of Duralumin plates with fastener holes by cavitation peening.

Dynamic properties of the corrugated stainless steel membrane reinforced with the glass composite pressure resisting structure for LNG carriers

The primary barrier of cryogenic containment system (CCS) of liquefied natural gas (LNG) carriers is composed of corrugated stainless steel to reduce the thermal stress at the LNG temperature of −163°C under the pressure of 0.11MPa. The corrugation of the primary barrier not only buckles easily by the cavitation impact of LNG, but also produces large tumbling noise, which irritates the crews of LNG carriers.In this work, the corrugation of primary barrier was reinforced with the pressure resisting structure (PRS) of E-glass fiber epoxy composite to increase both the buckling resisting capability of the corrugation and to decrease the tumbling noise and vibration due to the cavitation impact of LNG. The natural frequency and damping ratio of the corrugation with and without PRS were measured, and various damping materials were wrapped around the PRS to determine an optimum vibration suppression structure. Also the impact load transmissibility of the primary barrier with PRS was investigated by the drop weight impact test, from which an optimum combination of PRS and the damping material has been suggested.

초음파 진동을 이용한 빙축열 시스템의 아이스 슬러리 생성 연구

아이스 슬러리는 유동성이 좋고 증발잠열이 커서 빙축열 시스템의 전열 유체로 선호되고 있다. 일반적으로 아이스 슬러리는 과냉각된 유체로부터 생성되는데, 동결이 과할 경우 배관을 막히게 하는 단점이 있다. 더욱이 아이스 슬러리 생성을 쉽게 하기 위해 과냉각온도를 낮출 경우 빙축열 시스템의 효율을 떨어뜨리기도 한다. 따라서 아이스 슬러리 생성을 효율적으로 제어할 수 있는 방법이 요구되고 있다. 본 논문에서는 초음파 진동에 의해 과냉각수에 캐비테이션 충격을 가하여 아이스 슬러리를 생성하는 새로운 방식의 빙축열 시스템에 관한 실험연구를 수행하여, 초음파 진동과 아이스 슬러리 생성과의 상관관계를 규명하고, 초음파 진동이 아이스 슬러리 생성을 성공적으로 촉진할 수 있음을 확인하였다. Ice slurry that is a mixture of fine ice crystals and liquid water is a widely used working fluid in the ice thermal energy storage system due to its flowability and large latent heat of fusion. Generally ice slurry is made from supercooled water. But the excessive supercooling causes the water to freeze even worse to block the pipe. Additionally large degree of supercooling of water degrades the efficiency of the ice thermal energy storage system. Therefore the effective method to control the phase change from supercooled water to ice slurry is needed. In this paper we experimentally studied a novel method to generate the ice slurry from the supercooled water using the ultrasonic vibration. It was found that the cavitation impact of supercooled water by ultrasonic vibration can help the generation of ice slurry.

Nanoscale Structuration of Semiconductor Surface Induced by Cavitation Impact

Papers in the Appendix were published in electronic format as Volume 1534

S133014 吸引キャビテーション援用砥粒加工法によるデバリング効果([S133]先進砥粒加工技術)

This paper deals with deburring of the needle tip by the cavitation aided machining using the micro abrasive. The novel method shows the machining ability by micro loose abrasives with the cavitation impact occurring in slurry. Slurry is sucked through the narrow gap between workpiece and the restrictor, and cavitation is occurred above workpiece surface downstream from the restrictor tip because of the sudden decompression. This study used a slurry flow made by a suction pump, because the suction flow can perform stable machining in comparison with a jet flow. The effect of cavitation-aided abrasive machining varies depend on restrictor shapes. So, an optimum condition means removing only burr generated by surface grinding machine make needle tip is showed by experimental and theoretical data in this paper. Deburring effect is determined by a setting direction of workpiece, machining time, abrasive size. In this paper, the optimum machining time for deburring is investigated.

Application of Cavitation Aided Abrasive Machining to Manufacture of Micro Air Vents on Injection Molds

The purpose of this study is a practical application of the cavitation aided abrasive machining (CAAM). This study shows the machining effect of the precision abrasive machining on injection molds using the cavitation in a suction flow of slurry, which can easily finish to a fine surface by a simple apparatus. The cavitation occurred above the workpiece surface downstream of the restrictor tip because of the rapid decompression and then the abrasive grains in the water interfere with the workpiece surface by the cavitation impact. In this report, the possibility of application of the cavitation aided abrasive machining to the precision manufacturing of micro air vents on the rib of injection molds are generated by using masks of a certain thickness that are made on a special masking equipment, and the machining characteristics of micro air vents are investigated by analyzing the depth of micro grooves and the surface finish in machining of injection molds. When the depth of the micro grooves is approximately 1μm in the machining of 30 minutes, the manufacture of molding parts without burrs or residual voids is carried out by CAAM.

Controlled permeation of cell membrane by single bubble acoustic cavitation

Sonoporation is the membrane disruption generated by ultrasound and has been exploited as a non-viral strategy for drug and gene delivery. Acoustic cavitation of microbubbles has been recognized to play an important role in sonoporation. However, due to the lack of adequate techniques for precise control of cavitation activities and real-time assessment of the resulting sub-micron process of sonoporation, limited knowledge has been available regarding the detail processes and correlation of cavitation with membrane disruption at the single cell level. In the current study, we developed a combined approach including optical, acoustical, and electrophysiological techniques to enable synchronized manipulation, imaging, and measurement of cavitation of single bubbles and the resulting cell membrane disruption in real-time. Using a self-focused femtosecond laser and high frequency ultrasound (7.44 MHz) pulses, a single microbubble was generated and positioned at a desired distance from the membrane of a Xenopus oocyte. Cavitation of the bubble was achieved by applying a low frequency (1.5 MHz) ultrasound pulse (duration 13.3 or 40 μs) to induce bubble collapse. Disruption of the cell membrane was assessed by the increase in the transmembrane current (TMC) of the cell under voltage clamp. Simultaneous high-speed bright field imaging of cavitation and measurements of the TMC were obtained to correlate the ultrasound-generated bubble activities with the cell membrane poration. The change in membrane permeability was directly associated with the formation of a sub-micrometer pore from a local membrane rupture generated by bubble collapse or bubble compression depending on ultrasound amplitude and duration. The impact of the bubble collapse on membrane permeation decreased rapidly with increasing distance (D) between the bubble (diameter d) and the cell membrane. The effective range of cavitation impact on membrane poration was determined to be D/d = 0.75. The maximum mean radius of the pores was estimated from the measured TMC to be 0.106 ± 0.032 μm (n = 70) for acoustic pressure of 1.5 MPa (duration 13.3 μs), and increased to 0.171 ± 0.030 μm (n = 125) for acoustic pressure of 1.7 MPa and to 0.182 ± 0.052 μm (n = 112) for a pulse duration of 40 μs (1.5 MPa). These results from controlled cell membrane permeation by cavitation of single bubbles revealed insights and key factors affecting sonoporation at the single cell level.

Observation of Microstructural Deformation Behavior in Metals Caused by Cavitation Impact

To clarify the erosion mechanism of cavitation, we pay attention to the internal changes in grains caused by cavitation impact. The vibratory cavitation test based on ASTM G32 was carried out and the cross section of directly under the eroded surface of a specimen was observed using the electron backscattering diffraction (EBSD) technique. The situations of grain boundaries and the changes in the crystal orientations of grains in aluminum, copper, and steel were analyzed. As a result, the following observations were made. Cavitation impact causes grain refining of sub-micrometer order near the eroded surface. There exist small changes in crystal orientation in grains. In steel, grain boundaries were generated on the eroded surface and were growing inward in the grain. Finally, the mechanism of internal deformation of grains caused by cavitation impact was discussed.

Observation of Microstructural Deformation Behavior in Metals Caused by Cavitation Impact

Observation of Microstructural Deformation Behavior in Metals Caused by Cavitation Impact

Evaluation of the enhanced cavitation impact energy using a PVDF transducer with an acrylic resin backing

A transducer using a PVDF (Polyvinylidene Fluoride) film as a pressure sensitive material has been developed and applied to evaluate the cavitation impact energy. However, enhanced cavitation impact used for peening destroys the PVDF film, which is directly exposed to the cavitation impact through a polyimide tape. In the present paper, a newly developed PVDF transducer is proposed, in which a PVDF film with an acrylic resin, which attenuates the burst signal, is put on the backside of a metallic base, where the front surface of the metallic base is exposed to the cavitation impact.

Corrosion Behavior of Pressure Vessel Steel Exposed to Residual Bubbles After Cavitation Bubble Collapse

Abstract The corrosion potential of pressure vessel steel after exposure to residual bubbles and the open-circuit potential of Pt during cavitation were measured to investigate the corrosion behavior induced by residual bubbles after cavitation bubble collapse (as distinct from erosion caused by cavitation impact). The surfaces of the corrosion specimens were also investigated using x-ray photoelectron spectroscopy. It was shown that the residual bubbles shift the potential of a Pt electrode to a more anodic potential and that the oxide layer induced by the residual bubbles is different from that produced by normal water without residual bubbles.

Enhancing the Aggressive Strength of a Cavitating Jet and Its Practical Application

A cavitating jet is a useful tool for the practical application of cavitation. Cavitation impact arises when bubbles collapse and can be utilized to modify the surfaces of materials as an alternative to shot peening. Peening methods using cavitation impact are called “cavitation peening” or “cavitation shotless peening”, as shot is not required. In cavitation peening, cavitation is generated by injecting a high-speed water jet into water, i.e., a cavitating jet. In practical applications, it is very important to maximize the aggressive strength of the jet. In the present paper, in order to do this, the outlet geometry of the nozzle of a cavitating jet was optimized. High-speed observations were carried out to investigate any instability in the jet. The introduction of compressive residual stress into stainless steel was demonstrated to show the effect of cavitation peening. Scaling- and velocity-effects, i.e., the effect of the injection pressure, at the nozzle throat was also examined. It was shown that a large cavitating jet at low injection pressure was more aggressive than a small jet at high injection pressure, for the same power.

Suppression of Fatigue Crack Growth in Austenite Stainless Steel by Cavitation Peening

Cavitation normally causes severe damage in hydraulic machinery such as pumps and turbines by the impact produced by cavitation bubbles collapsing. Although cavitation is known as a factor of erosion, Soyama et al. succeeded in utilizing impacts of cavitation bubble collapsing for surface modification by controlling cavitating jet in the same way as shot peening. The local plastic deformation caused by cavitation impact enhances the fatigue strength of metallic materials, and the surface modification technique utilizing cavitation impact is called “cavitation peening (CP)”. It is well known that the peening improves fatigue strength by introducing compressive residual stress on the surface, but little attention has been paid to the behavior of fatigue crack growth of the material which was modified by CP. In the present study, the fatigue behavior of austenite stainless steel with and without CP was evaluated by a plate bending fatigue test, and the results revealed that the compressive residual stress introduced by CP suppresses fatigue crack growth rate by 70 % compared to that without CP.

Nitrogen incorporation into GaAs lattice as a result of the surface cavitation effect

Semi-insulating gallium arsenide was exposed to cavitation impact initiated by focusing a high-frequency acoustic wave into liquid nitrogen. Optical and atomic force microscopy methods were used for the analysis of surface morphology. Formation of microstructures as well as change in the chemical composition of the surface are observed. The morphology of the structures is highly dependent on the acoustic parameters. Raman spectroscopy data have confirmed the incorporation of nitrogen atoms into the GaAs lattice and Ga–N bond formation in the region of maximal structural change due to the cavitation impact.

Sustainable surface modification using cavitation impact for enhancing fatigue strength demonstrated by a power circulating-type gear tester

In order to enable the manufacture of lightweight materials for transportation equipment, such as cars and aircraft, an improvement in the fatigue strength of materials is required, as these forms of transport are designed taking fatigue fracture into consideration. Surface treatment procedures, such as shot peening, are generally employed to improve fatigue strength. Shot peening deforms metallic materials to produce work hardening and introduce compressive residual stress, leading to improved fatigue strength. Although shot peening is an effective and reliable method against fatigue fracture, the shot eventually becomes dust and industrial waste. Recently, a peening method without the use of shot using cavitation impact has been developed. This is called ‘cavitation peening’. In the present paper, gears, which are typical machine components, were examined in order to demonstrate the improvement in fatigue strength by cavitation peening. Gears made of carburised chromium molybdenum steel were treated by cavitation peening and shot peening. The fatigue strength was evaluated using a power circulating-type gear test machine. Under the conditions employed, the gear lifetime was limited by fracture at the root of the tooth. The improvement in the fatigue strength of gears treated by cavitation peening was 24% and in those treated by shot peening it was 12% compared with non-peened gears. It was demonstrated that cavitation peening can improve the fatigue strength of gears without the use of shot.

2P-43 Observation of the internal change of grains in metals caused by cavitation impact(Poster Session)

2P-43 Observation of the internal change of grains in metals caused by cavitation impact(Poster Session)

Study on Cavitation Aided Abrasive Machining on Glass

The purpose of this study is to develop the cavitation aided abrasive machining which makes effective use of cavitation occurring in suction flow of slurry for fine machining. In this paper, a fundamental machining phenomenon of glass using the cavitation suction flow is clarified and machining characteristics are experimentally investigated by the observation of machined surface and surface roughness, stock removal and cavitation impact. Abrasive grains impinge on a workpiece surface to physically remove work material and generate fine surface in the machining. Then it can finish the polished glass surface of 9.3nmRz down to about 5.0nmRz by using abrasives of WA 4000.

混相流研究の進展 ４ ノズル出口形状によるキャビテーション噴流まわりの衝撃力の強力化

Impact force around a cavitating jet can be utilized for surface modification to improve fatigue strength of metallic materials. A peening method by cavitation impacts is called cavitation shotless peening (CSP), as shots are not required. For making practical use of CSP, enhancement of capability of the cavitating jet is required. In the present paper, an optimum nozzle outlet geometry that the mass loss shows the maximum was found by changing the nozzle outlet geometry through erosion test. In addition, the discharge frequency of cavitation clouds, Strouhal number and cavitation impacts by changing with nozzle outlet geometry were measured. It was revealed that nozzle outlet geometry affected the capability of the cavitating jet, the frequency of impacts, Strouhal number and the maximum value of cavitation impact force.

G0301-3-3 キャビテーションピーニングによる駆動モータ用電磁鋼板の降伏応力向上(材料力学部門一般(3))

Electrical steel sheet is using for interior permanent magnet (IPM) motor of hybrid electric vehicle (HEV) and electric vehicle (EV). In order to raise allowance rotating speed of IPM motor to realize high efficiency, it is necessary to improve yield stress of the electrical steel sheet by partially strengthening method such as peening, as the high-strength electrical steel sheet enhanced by rolling has low conversion efficiency because of high iron loss. A peening method using cavitation impact named as "cavitation peening (CP)" can improve the fatigue strength of metallic materials by introducing compressive residual stress. CP can peen the surface even through deep narrow region, as the bubbles can reach these parts and collapse where peening is required such as stress concentration area. In the present paper, the electrical steel sheet was peened by CP and the tensile test was conducted in order to demonstrate that improvement of yield stress of the electrical steel sheet for IPM motor by CP.

Fundamental Study on the Precision Abrasive Machining Using a Cavitation in Reversing Suction Flow

The purpose of this study is to make clear the machining effect of the precision abrasive machining using the cavitation in reversing suction flow, which can easily finish to a fine surface by a simple apparatus. The machining fluid including loose micro abrasive grains is sucked by a pump, and the cavitation occurs ahead of the nozzle fixed in the suction chamber because of the rapid decrease of pressure of machining fluid. We use the cavitation impact to make the abrasive grains to interfere with the workpiece surface. In this report, the possibility of application of the new abrasive machining to the precision manufacturing is investigated by analyzing the behavior of machining fluid, the stock removal and the surface finish in machining of glass. The cavitation impact is strongest under the nozzle clearance of 20mm and restriction nozzle diameter of 4mm. Glass surface is finished up to several nanometers in Ry with slight stock removal by the proposed abrasive machining.