Soft Abrasive Flow Research Articles

Key technologies and development trends of the soft abrasive flow finishing method

Key technologies and development trends of the soft abrasive flow finishing method

Investigation on abrasive-wall collision mechanism and the universal design method for constraint module in soft abrasive flow polishing

Investigation on abrasive-wall collision mechanism and the universal design method for constraint module in soft abrasive flow polishing

Multi-physical Modeling and Adjusting for Ultrasonic Assisted Soft Abrasive Flow Processing

The polishing efficiency of the soft abrasive flow (SAF) method is low, which is not in line with the concept of carbon emission reduction in industrial production. To address the above issue, a two-phase fluid multi-physics modeling method for ultrasonic-assisted SAF processing is proposed. The acoustics-fluid coupling mechanic model based on the realizable k-ε model and Helmholtz equation is built to analyze the cavitation effect. The results show that the proposed modeling and solution method oriented to ultrasonic-assisted SAF processing have better revealed the flow field evolution mechanism. The turbulence kinetic energy at different ultrasonic frequencies and amplitudes is studied. Simulation results show that the ultrasonic vibration can induce a cavitation effect in the constrained flow channel and promote the turbulence intensity and uniformity of the abrasive flow. A set of comparative polishing experiments with or without ultrasonic vibration are conducted to explore the performance of the proposed method. It can be found that the ultrasonic-assisted SAF method can improve the machining efficiency and uniformity, to achieve the purpose of carbon emission reduction. The relevant result can offer a helpful reference for the SAF method.

Soft abrasive flow polishing method and optimization research on the constrained space

Soft abrasive flow polishing method and optimization research on the constrained space

Magnetic-assisted soft abrasive flow machining studied with smoothed particle hydrodynamics

In many microsystem applications, a nanometric surface quality is crucial to the performance of a device. Soft abrasive flow machining (SAFM) is capable of finishing surfaces at very fine scale with complex geometries since, unlike traditional flow machining processes, abrasive grains are carried by a very low viscosity fluid. Several empirical studies have been done to ensure final high quality surfaces by enhancing the performance of SAFM. However, the present study aims to propose a consistent numerical approach which can handle the fluid-structure interface problems as well as surface erosion to model SAFM and help to gain deeper understanding of the process. Moreover, the approach is employed to investigate the effect of an external magnetic field on the performance of the machining process. All phases, namely carrier fluid, abrasive grains and workpiece, and their interactions are fully resolved by using smoothed particle hydrodynamics. The abrasive grains are modeled by particles that are rigidly moved together. The approach is used to study the surface finishing of a Polymethyl Methacrylate-based microchannel under external magnetic fields. Results show that a magnetic field of suitable strength can considerably improve the material removal rate and hence enhance the performance of SAFM.

Erosion analysis and experimental research of gas-liquid-solid soft abrasive flow polishing based on cavitation effects

Traditional soft abrasive flow (SAF) polishing is limited by its low material removal rate and its applicability to large workpieces. To address this issue, an innovative technique of a cavitation-based gas-liquid-solid abrasive flow polishing (CGLSP) process is proposed. The energy generated from cavitation effects is employed to increase the kinetic energy of abrasive particles in the fluid flow and the random movement of abrasive particles near the surface. The CGLSP mechanism is first introduced, and then, the cavitation erosion characteristics and material removal mechanism of brittle-plastic materials during polishing are investigated using a coupling computational fluid dynamics model. The simulated results show that erosion of the workpiece surface mainly occurs in the spiral area of the polishing tool. Furthermore, the erosion rate and erosion depth increase with increasing cavitation intensity. Subsequently, polishing experiments are conducted to verify the validity of the CGLSP method. The polishing results are verified by scanning electron microscopy (SEM) images of the polished surface. After polishing with the CGLSP method, most of the surface irregularities, such as microcracks and massive structures, are removed. The experimental results demonstrate that controlled polishing with cavitation erosion and abrasion can achieve a much higher quality surface on a large workpiece.

Numerical and experimental study on the ultrasonic-assisted soft abrasive flow polishing characteristics

To resolve the low-polishing efficiency problem caused by the turbulent layer separation in soft abrasive flow (SAF) processing, an ultrasonic-assisted SAF (UA-SAF) method is proposed based on the vibration effect. The coupled computational fluid dynamics (CFD)-discrete element method (DEM) modeling method (CFD-DEM) and the dynamic mesh are used to represent the UA-SAF flow and the periodic moving boundary caused by ultrasonic vibration, while the particle-wall erosion is calculated by the Archard model. Through tracking the abrasive particle motion in the simulation, the particle-wall collision states and the particle cutting effect are revealed, which mainly includes the particle plowing and the particle impact erosion. It has been found from the simulation that the fluid turbulent motion and the fluid dynamic pressure which are the power source for the particles to obtain the anisotropic cutting kinetic energy can be strengthened obviously by the ultrasonic vibrating, which results in the increase of the probability of particle impacting the target surface, and then the particle-wall wear rate and the wear area can be improved. A set of comparative experiments, including the rough and precision polishing procedures, are then conducted to evaluate the polishing performance by using the SAF and UA-SAF, respectively. The variations of the surface roughness and the workpiece mass are obtained, and the surface morphologies are observed. The experimental results prove that the ultrasonic vibration can effectively improve the abrasive flow polishing efficiency and precision without producing cavitation erosion.

Softness abrasive flow polishing method using constrained boundary vibration

The polishing efficiency of the soft abrasive flow (SAF) method is low, especially for the hard-brittle materials. To resolve this problem, an abrasive flow polishing method using ultrasonic vibration is proposed. The polishing mechanism is first introduced, then the Euler multiphase model is used to build the fluid mechanical model of the proposed method. The turbulence kinetic energy (TKE) and particle dynamic pressure (PDP) at different vibration amplitudes and frequencies are studied. Simulation results show that the boundary vibration can promote the TKE and PDP, and hence, affecting the polishing efficiency and quality. A set of comparative polishing experiments with or without boundary vibration and different vibration amplitudes for K9 glass are then conducted to explore the performance of the proposed method. It can be found that this method can produce highly smooth surface for K9 glass and exhibits higher polishing efficiency as compared to the traditional SAF method.

Research on the incidence of soft abrasive flow to a wall and the machining characteristics

In this study, a calculation model was proposed to predict the motion locus of particles moving to a wall in boundary layers. The velocity of soft abrasive flow and the incident angle of the particles were obtained based on the results calculated by the mixture model and realizable k–ε model. After the model formed, the distributions of the dynamic pressure and the volume fraction of abrasive particles were analyzed and compared to experimental results. After analysis, it was found that the amount of removed material is positively correlated with the incident velocity and the volume fraction of abrasive particles, as well as the dynamic pressure on the surface of the workpiece. In addition, the comparison shows that the numerical simulation method is feasible to predict the flow field and effect of soft abrasive flow. In addition, it was found that the simulation results are consistent with the flow field distribution and machining effect. Therefore, this model can be used in design of constrained modules.

Cavitation-based soft abrasive flow processing method

To improve the processing efficiency and surface quality of soft abrasive flow (SAF) processing, we proposed a cavitation-based soft abrasive flow (CSAF) processing method and designed a CSAF processing tool, which uses the Venturi tube structure to create a cavitation effect. The microjet produced by cavitation accelerates the impact of abrasive particles on the workpiece and improves the processing efficiency of abrasive flow. Based on that, we designed the flow field profiles of the processing tool. We built a two-phase fluid dynamic model for CSAF to reveal the cavitation mechanism and evolution regularities based on the Schnerr-Sauer cavitation model and the mixture calculation method. The numerical results validated the feasibility of the proposed processing method, helped choosing the optimal structure sizes of flow passage. A particle image velocimetry (PIV)–based observation platform is established, the cavitation images with different flow parameters are obtained, and the validity of the simulation results is validated. The maximum flow velocity on the processing area in the SAF tool is 22.8 m/s, and the maximum flow velocity of the CSAF tool is increased to 46.2 m/s. With a developed CSAF processing experiment platform, the comparative experiment results with SAF showed that the proposed CSAF processing method achieves better surface quality and increases the material removal rate by 52%.

Study of soft abrasive flow field measurement based on particle image velocimetry

Soft abrasive flow (SAF) is a kind of solid-liquid flow used to grind complicated and tiny structures on moulds. In this study, soft abrasive flow field is simulated and then measured via the particle image velocimetry (PIV) to obtain its characteristics. Taking the structural surface of automobile mould as the research object, realizable k-e double-equation turbulent model is used to describe the soft abrasive flow field. The distributions of dynamic pressure, the velocity of the solid particles and the turbulent dissipation rate of the SAF field are obtained in simulation. The particle image velocimetry (PIV) measurement platform is established, and distributions of particle motion, velocity vector and vorticity of the flow field were obtained by PIV measurement platform. The measurement result of PIV is corresponding to that of the simulation, which shows that the soft abrasive flow field is turbulent. By using SAF, the roughness of the machined surface can be up to 27 μm.

Investigation of the optimal parameters for the surface finish of K9 optical glass using a soft abrasive rotary flow polishing process

A workpiece polished by soft abrasive flow polishing has the advantages of low damage and ultrasmoothness. However, due to the need to use a constrained flow path, the fluid dynamic pressure on the near wall surface of the workpiece has a gradient distribution, so achieving uniform polishing of workpieces of large size is difficult. To address this problem, this paper proposes a new method of soft abrasive rotary flow (SARF) polishing to achieve low damage, ultrasmooth, uniform polishing of a large-size K9 optical glass surface. A new SARF polishing system and a 6-outlet rotary polishing tool are designed. The SARF polishing principle is analyzed, and a polishing experiment is conducted on K9 glass. The experiment of surface roughness improvement of the K9 optical glass is designed by Taguchi method. Orthogonal arrays and the signal-to-noise ratio (S/N) are used to determine the optimal parameters for SARF polishing. Analysis of variance (ANOVA) is used to determine the effect of the main polishing parameters on the surface roughness of K9 glass. According to the results of the polishing experiment using a Taguchi L18 orthogonal array and S/N ratio analysis, the optimal parameters for K9 glass SARF polishing are revealed to be as follows: the abrasive material is CeO2, the polishing pressure is 0.35 MPa, the abrasive particle concentration is 5 wt.%, the average size of the abrasive particles is 0.7 μm, the polishing time is 1.5 h and the platform rotation speed is 10 rpm. After polishing the sample for 1.5 h under these parameters, the surface roughness decreases from the original value of Ra = 37.28 nm to Ra = 4.51 nm, and the surface roughness improves by 87.9 %.

An ultrasonic-assisted soft abrasive flow processing method for mold structured surfaces

As a fluid-based precise processing method, soft abrasive flow processing has been widely used in advanced electromechanical systems, complex mold manufacturing, and other engineering fields. Because of the low volume fraction of abrasive particles and micro-force/cutting removal characteristics, there exists a potential improvement in terms of processing efficiency and uniformity. In view of the above problems, this article presents an ultrasonic-assisted soft abrasive flow processing method. Based on the realizable k–ε turbulence model and the mixture flow model, an ultrasonic coupling enhancement dynamic model for soft abrasive flow is set up, and the kinetic energy transport equation of realizable k–ε turbulence model can be revised. Using particle image velocimetry technology, an on-line observation experimental platform for ultrasonic-assisted soft abrasive flow is developed to conduct the real-time acquisition of abrasive flow state and particle distribution in a constrained flow passage. An ultrasonic-assisted soft abrasive flow processing experimental platform is established to complete the processing experiment. The experimental results show that the ultrasonic excitation vibration can effectively enhance the turbulence intensity and distribution uniformity of the abrasive flow, the average processing time can be shortened by more than 6 h, and a better surface quality can be obtained.

Soft abrasive flow polishing based on the cavitation effect

The fluid medium used for soft abrasive flow (SAF) is of low viscosity and high flow velocity. The conventional SAF processing method is widely used due its ability to avoid damage and its adaptability of the workpiece surface. However, the current SAF method also suffers from limitations such as long polishing times and low processing efficiency. To address these issues, this paper proposes a method based on the cavitation effect to assist the soft abrasive flow polishing, termed CSAF. First, the working mechanism of CSAF is introduced through a schematic diagram. In addition, a CSAF fluid mechanic model is configured on the basis of the mixture multiphase model and cavitation model. Then, the distribution of key flow parameters, such as the velocity, dynamic pressure, and turbulent kinetic energy, is obtained and compared through computational fluid dynamic software. Numerical analysis results show that the flow field assisted by the cavitation effects shows better processing performance than SAF. Finally, particle imaging velocity (PIV) observation and experimental processing platforms are established, and extensive experiments are conducted. The processing comparison experiments showed that the abrasive flow assisted by the cavitation effect can lower the workpiece surface roughness to 3.46 nm with a satisfactory surface quality over a shorter time than the SAF method. The numerical analysis results are aligned with the PIV observation and the polishing experiment results. The SAF polishing method based on the cavitation effect significantly increases the polishing efficiency.

A gas-liquid-solid three-phase abrasive flow processing method based on bubble collapsing

Soft abrasive flow (SAF) processing presents advantages in avoiding surface damages and adapting complex workpiece shapes. However, the current SAF method exhibits low processing efficiency for materials. To solve this problem, a gas-liquid-solid three-phase abrasive flow processing method (GLSP) based on bubble collapsing is proposed. Through a surface constrained module, a multi-inlet constrained flow passage for silicon wafer processing is constructed, in which the bubbles are injected into the abrasive flow to strengthen the processing efficiency. On the basis of the Euler multi-phase model and population balance model (PBM), a GLSP fluid mechanic model is set up. Simulation results show that the bubble collapse region can be controlled by designing the flow passage structure and that the near-wall particle turbulent motion can be strengthened by decreasing the fluid viscosity. The observation and processing experiments show that the most violent bubble collapsing occurs in the initial constrained surface region. Bubble collapsing can result in an average particle velocity increase from 12.90 to 15.97 m/s. The proposed GLSP method can increase the processing efficiency by 50% compared with the SAF method, and the average surface roughness can reach 2.84 nm.

Gas compensation-based abrasive flow processing method for complex titanium alloy surfaces

To resolve the problems of uniformity and efficiency of soft abrasive flow (SAF) processing for complex titanium alloy surfaces, a gas compensation-based abrasive flow (GCAF) processing method is proposed. By the constrained modules, an enclosed flow passage covering the titanium alloy surface is built up, in which the gas phase is injected to enhance the turbulence intensity of abrasive flow. Taking the constrained flow passage as the objective, a three-phase fluid mechanic model for GCAF is set up based on the realizable k-e model and the mixture model. The profiles of velocity and dynamical pressure of abrasive flow field in the constrained flow passage are obtained, and the turbulence variation regulars caused by gas compensation are revealed. Numerical results show that the proposed method can strengthen the turbulence intensity of abrasive and improve the distribution uniformity of dynamical pressure. A GCAF processing experimental platform is developed, and the experiments are performed. The results prove that the proposed method can obtain better processing efficiency and uniformity, the average surface roughness is less than Ra 0.3, and the surface topograph of micro-peak and micro-valley can reach less than 50 and 10 μm, respectively.

Improved Soft Abrasive Flow Finishing Method Based on Turbulent Kinetic Energy Enhancing

Soft abrasive flow(SAF) finishing can process the irregular geometric surfaces, but with the matter of low processing efficiency. To address the issue, an improved SAF finishing method based on turbulent kinetic energy enhancing is proposed. A constrained flow passage with serration cross-section is constructed to increase the turbulence intensity. Taking the constrained flow passage as the objective, a two-phase fluid dynamic model is set up by using particle trajectory model and standard k-e turbulence model, and the flow field characteristics of the flow passage are acquired. The numerical results show that the serration flow passage can enhance the turbulence intensity, uniform the particles distribution, and increase the particle concentration near the bottom wall. The observation results by particle image velocimetry(PIV) show that the internal vortex structures are formed in flow passage, and the abrasive flow takes on turbulence concentrating phenomenon in near-wall region. The finishing experiments prove that the proposed method can obtain better surface uniformity, and the processing efficiency can be improved more 35%. This research provides an abrasive flow modeling method to reveal the particle motion regulars, and can offer references to the technical optimization of fluid-based precision processing.

An improved soft abrasive flow finishing method based on fluid collision theory

Soft abrasive flow (SAF) finishing has advantages in precise processing for the workpieces with tiny scale or irregular geometric surfaces. However, current SAF finishing methods have surface quality problem caused by uneven flow field profile. To resolve the problem, a novel double-inlet SAF finishing method is proposed based on the fluid collision theory. Taking two constrained processing apparatuses (single-inlet and double-inlet) as the objectives, in combination with the shear stress transport (SST) k-ω turbulence model, the fluid mechanic models for the two apparatuses are set up, and the preliminary abrasive flow field characteristics are acquired. Referring to the collision conservation principles, the profiles of dynamical pressure and turbulence intensity in double-inlet constrained passage are obtained. The simulated results show that the flow field distribution of single-inlet passage is in a steady state and non-uniform, a periodic oscillation phenomenon appears in double-inlet passage, and it can enhance the turbulence intensity and movement randomness of abrasive flow. The processing experiments show that the proposed SAF finishing method can make the roughness on parallel flowing direction less than 50 nm and can improve the finishing uniformity and efficiency.

Pattern Recognition of the Soft Abrasive Flow Based on Wavelet Packet

A Pattern Recognition method based on wavelet packet and artificial neural is proposed for solid-liquid two-phase flow characteristic parameters and the non-linear relationship between flow pattern. This method firstly established the physical and dynamic model, then set a monitoring point. To get the optimum wavelet tree and its information entropy, six floors of wavelet packet was used to decompose the collected velocity fluctuation signal. Transported the proper vector which is component by information entropy into Back Propagation neural network to train and identify. The recognition results show that this method can effectively overcome the subjectivity of traditional identification methods. It has good recognition effect, thus provide an effective choice for solid-liquid two-phase flow pattern recognition.

Soft Abrasive Flow Machining

Soft Abrasive Flow Machining (SAFM) was presented as a new finishing process about the existing problems that the irregular surface of plastic mould was polishing difficultly. The paper first introduced the working principle and feature of SAMF. Secondly, the main influences of SAFM were analyzed. The problem of technology and theory urgent to settle was discussed. At the last, the technology development of SAFM was expected.