Increase Of Ultrasonic Amplitude Research Articles

Study on Characteristics of Ultrasound-Assisted Fracture Splitting for AISI 1045 Quenched and Tempered Steel.

Ultrasonic vibration-assisted con-rod fracture splitting (UV-CFS) was used to carry out the fracture experiment of 1045 quenched and tempered steel. The effect of ultrasonic vibration on the fracture properties was studied, the fracture microstructure and the evolution of dislocations near the fracture were analyzed and the microscopic mechanism was analyzed. The results show that in the case of conventional fracture splitting without amplitude, the dimple and the fracture belong to ductile fracture. With the increase in ultrasonic amplitude, the plasticity and pore deformation of the con-rod samples decrease at first and then increase; when the amplitude reaches a certain point, the load required for cracking is reduced to a minimum and the ultrasonic hardening effect is dominant, resulting in a decrease in the plasticity of the sample, a cleavage fracture, a brittle fracture, the minimum pore deformation and high cracking quality. The research results also show that with the increase in ultrasonic amplitude, the fracture dislocation density decreases at first, then increases, and dislocation entanglement and grain breakage appear, then decrease, and multiple dislocation slip trajectories appear. The changes in the dislocation density and microstructure are consistent with the above results.

Numerical calculation and analysis of temperature field in ultrasonic welding of polypropylene dialyzer

Ultrasonic plastic welding is widely used in the bonding process of medical device accessories. In this paper, a thermo-force indirect coupling finite element analysis model was established in the ultrasonic plastic welding process between the blood cap and the shell of polypropylene (PP) dialyzer. The temperature field distribution between the blood cap and the shell was simulated and analyzed by using finite element analysis software, and the influence of welding process parameters on the temperature field was studied. The results show that: by changing the ultrasonic amplitude parameters, welding time parameters, initial pressure, etc., the longer the ultrasonic welding time, the temperature of the welding area will increase. In order to ensure the quality of the dialyzer, it should be controlled within 0.8-1 seconds. The increase of ultrasonic amplitude will make the welding temperature continue to rise, and in order to avoid poor welding, the amplitude should not exceed 120 ?m. The initial pressure has little effect on the temperature field.

Investigation on roller-type ultrasonic assisted magnetorheological finishing for biomedical small and complex surface of titanium alloy

Biomedical small workpieces made of titanium alloys are widely used in orthopedic implants. However, the poor abrasive resistance and the complex shape of the parts with small size could seriously reduce its finishing quality and efficiency. In this study, a roller-type ultrasonic assisted magnetorheological finishing (R-UMRF) for biomedical small and complex surface of titanium alloy was proposed. The R-UMRF principle was illustrated in detail. Then, the magnetic circuits of R-UMRF with three-pole electromagnet excitation device was designed and mathematical expressions of magnetic flux density in the MR fluid polishing region was further established. Moreover, simulation analysis of the designed magnetic circuit was performed as well. An experimental prototype was fabricated and tested to the feasibility of the developed MR polishing fluid and R-UMRF device. The results showed that the surface roughness decreases with the increase in spindle speed and roller speed, however, it first decreases and then increases with the increase in ultrasonic amplitude and the applied current. In addition, the surface roughness change rate increases with the increase in spindle speed and roller speed, however, it first increases and then decreases with the increase in ultrasonic amplitude and the applied current. The optimized process parameters for the titanium alloy screws are the MR polishing fluid of MRPF-2, the spindle speed of 240 r/min, the roller speed of 110 r/min, ultrasonic amplitude of 10 µm, and applied current of 4 A. The surface roughness Ra of 0.089 µm can be obtained after 140 min finishing under the optimized parameters. R-UMRF is an adaptable and efficient method for finishing small and complex surface of titanium alloy.

Removal mechanism of NiTi alloy by ultrasonic assisted polishing based on molecular dynamics simulation

NiTi alloy has been widely used in mechanical and electronic, aerospace, energy and transportation, petrochemical industry and various biomedicine fields due to its unique super elasticity and shape memory effect. The traditional polishing method of NiTi alloy has the problems of poor consistency of polishing quality and low efficiency, especially for some NiTi alloy with complex shapes, the traditional mechanical contact method is difficult to polish its inner surface. For some NiTi alloys prepared by additive manufacturing, due to the existence of “step effect” and “spherodizing effect”, there are unmelted powder particles on the surface, and it also needs to be polished. However, it is necessary not to destroy the original structure shape and performance, but also to achieve high efficiency, high quality and consistent polishing, so it is a technical problem. Its polishing process is still unclear, and the polishing effect needs to be improved. Therefore, in this paper, molecular dynamics method was used to study the polishing process of ultrasonic vibration diamond abrasive particles on NiTi alloy. The influences of ultrasonic vibration frequency, ultrasonic amplitude and temperature on polishing force, average friction coefficient, surface morphology, structural evolution and dislocation distribution were studied, and the microscopic material removal mechanism was revealed. The results indicate that as the ultrasonic frequency increases, the number of normal force fluctuations increases, and the elastic and plastic deformation during the scratching process also increases. With the increase of ultrasonic amplitude, the average friction coefficient decreases, and the adoption of larger vibration amplitude is conducive to the scratching process, and the average friction coefficient will increase when the temperature increases, which is not conducive to the polishing process.

Multi-dimensional population balance modeling of sonocrystallization of pyrazinamide with systematic estimation of kinetic parameters based on uncertainty and sensitivity analyses

Application of ultrasound has several beneficial effects on both crystallization process and product crystal properties. This work focuses on experimental study and population balance modeling of ultrasound-assisted unseeded batch cooling crystallization of an important polymorphic pharmaceutical. The δ-polymorph of pyrazinamide, a drug for mycobacterium tuberculosis, exhibits plate-like morphology, and such crystals are best described by atleast two dimensions: length and width. A multi-dimensional population balance model for batch cooling sonocrystallization of pyrazinamide from its 1,4-dioxane solution is developed and validated. A series of experiments are performed with different ultrasound amplitudes (silent, 10%, and 50%) to study the effect of ultrasound on nucleation rate, crystal size, and polymorphism. The ultrasound is applied till the point of nucleation and an enhanced nucleation rate is introduced in the model in the presence of ultrasound irradiation. The various kinetic parameters are estimated following a systematic methodology based on uncertainty quantification and sensitivity analysis using experimental observations related to solute concentration and crystal size distribution. The Polynomial Chaos Expansion (PCE) is used to quantify the uncertainties in model prediction due to kinetic parameter uncertainties and sensitivity analysis is performed using total order Sobol’s sensitivity indices derived from PCE model. The kinetic parameters are estimated in two steps. First, a global search technique is used to simultaneously estimate all the kinetic parameters. Next, the less sensitive parameters are kept fixed and the more significant parameters are fine-tuned using a gradient-based local optimizer. Out of total nine kinetic parameters, only four parameters appeared to be significant for both silent and sonicated cases. The high-resolution finite volume scheme is used to solve the multi-dimensional population balance model and the simulation results agree very well with experimental data related to both concentration and crystal size distributions. The results revealed that compared to silent cases, sonication increased the nucleation rate by 102 times and 104 times for 10% and 50% amplitude, respectively. The growth rate was also enhanced significantly with increase in ultrasonic amplitude. All the experiments yielded the desired δ-polymorph of pyrazinamide.

Molecular dynamics study on surface effect in ultrasonic vibration assisted upsetting of monocrystalline copper

Ultrasonic vibration assisted plastic forming is a promising technology. However, the microscopic mechanism of ultrasonic vibration on interface friction behavior during the metal plastic forming process has not been fully understood yet. In this paper, based on the molecular dynamics method, the model for ultrasonic vibration assisted upsetting of monocrystalline copper was established, and the microscopic mechanism behind the surface effect of ultrasonic vibration was studied. The results show that the related data of interface friction can be directly extracted by the molecular dynamics method, and the plastic deformation behavior and interface friction behavior in the ultrasonic vibration assisted upsetting can be well reflected in the established model. The interface friction behavior of specimen is improved under the surface effect of ultrasonic vibration. On the one hand, ultrasonic vibration changes the relative position of the interface configurations, reduces the energy barrier ΔU, and helps the surface atoms to complete the potential well transitions on the periodic interface configuration, thereby reducing the energy dissipation in the sliding friction process. On the other hand, ultrasonic vibration induces the surface lattice mismatch or misalignment between the upper surface and the indenter plate, which avoids the structural interlocking phenomenon between different atomic interfaces, thereby promoting the change of interface friction from commensurability to incommensurability. With the increase of ultrasonic amplitude and ultrasonic frequency, the surface effect of ultrasonic vibration shows a trend of first decreasing and then flattening out. These findings play an essential role in revealing the microscopic mechanism of surface effect in ultrasonic vibration assisted plastic forming.

Surface and volume effects in multimodal ultrasonic vibration assisted micro-extrusion forming: Experiments and modelling

Ultrasonic vibration (UV) has been widely used in microplastic forming with its advantage of improving the metal plasticity. However, the coupling mechanism of the surface and volume effects of UV is still unclear. In this study, the multimodal ultrasonic vibration (tool vibration (TV) and mold vibration (MV)) assisted micro-forward extrusion (MFE) and micro-backward extrusion (MBE) experiments of copper T2 were conducted. An analytical method for ultrasonic surface effect in multimodal UV assisted micro-extrusion forming process was proposed, and a decoupling analysis method of ultrasonic surface effects and volume effects was also presented. The results indicated that the extrusion stress reduction caused by surface effect and volume effect were increased with the increase of ultrasonic amplitude, and the extrusion stress reduction of MV was greater than that of TV. The surface quality of the sample was improved by UV, and the surface roughness with MV was lower than that with TV. In addition, the coupling mechanism of ultrasonic surface effect and volume effect was revealed, and a comprehensive analytical model was developed considering both ultrasonic surface effect and volume effect. The predicted results of the extrusion stress were well agreed with the experimental results, with a maximum error was only 3.2%. These results provide a theoretical basis for further studying the mechanism of UV assisted micro-forming.

Effect of ultrasonic vibration extrusion cutting on the corrosion resistance of ultra-fine grained strips

Ultrasonic vibration extrusion cutting (UVEC), a new processing method, is proposed to prepare ultra-fine grained materials with better corrosion resistance. The mathematical models, finite element simulations, and experiments are combined and validated against each other to investigate the mapping relationships and influence mechanisms among ultrasonic amplitude, stress field parameters, microstructure, and corrosion resistance. It is found that with the increase of ultrasonic amplitude, the equivalent strain, equivalent strain rate, grain refinement degree of strip and thickness of a nanocrystalline surface layer on the side of the strip in contact with a tool (front side) increase gradually. The immersion corrosion test shows that both sides of the strip have better corrosion resistance than original matrix, and the corrosion resistance of the strip front side is better than that of strip side in contact with the extrusion block (back side). The electrochemical corrosion test shows that with the increase of ultrasonic amplitude, the electrochemical parameters are improved. It is determined that the corrosion resistance of ultra-fine grained strips prepared by UVEC is significantly improved compared with the original matrix, and the overall corrosion resistance is best at 2 μm ultrasonic amplitude.

Study on the ultrasonic-assisted spinning of thin-walled cylindrical parts with longitudinal and transverse ribs

Current studies have shown that the application of composite energy fields in the plastic forming process can help reduce the forming load and promote material flow. In this paper, a new method of ultrasonic-assisted spinning integral forming for thin-walled cylindrical parts with outer ribs was proposed, which could not only improve the manufacturing efficiency of ribbed cylindrical parts, but also further improve the forming height of outer ribs. A simulation model of ultrasonic-assisted spinning for thin-walled cylindrical parts with longitudinal and transverse outer ribs was established, the influence of ultrasonic amplitude on the forming accuracy of longitudinal and transverse outer ribs was obtained, and the mechanism of ultrasonic vibration improving the forming accuracy of ribs was revealed. On this basis, ultrasonic-assisted spinning equipment was built to verify the feasibility of this process. The results showed that with the increase of ultrasonic amplitude, the forming height of longitudinal and transverse outer ribs gradually increases, and the effect of raising the forming height of transverse ribs is higher than that of longitudinal ribs. In addition, as the ultrasonic amplitude increases, the uniformity of the forming morphology of the outer rib is not obviously improved. The spinning of the outer rib is mainly realized by the material in the form of integral filling into the groove. The ultrasonic vibration improves the material flow properties, and promotes the filling of the material into the rib groove, thereby increasing the spinning forming height of the outer ribs. The forming height of the outer rib was measured with or without ultrasonic vibration. When the rolling reduction is 1 mm, the average forming height of the outer ribs is increased by 50% compared with that without ultrasound, which provides a new research idea for the integral forming of the spinning of thin-walled cylindrical parts with longitudinal and transverse ribs.

Simulation and experimental study of ultrasonic vibration-assisted milling of GH4169 high-temperature alloy

GH4169 high-temperature alloy is widely used in aerospace and other fields because of its excellent fatigue, radiation, oxidation, and corrosion resistance. However, milling forces, high temperatures, and machining hardening can occur during milling processing. To explore the machining characteristics of GH4169 high-temperature alloy, an ultrasonic vibration-assisted milling model was established to study the effect of ultrasonic milling parameters on the milling process. The simulation results show that: the increase of ultrasonic amplitude can effectively reduce the machining stress, improve the chip-breaking effect and reduce the milling force; with the rise of milling speed, the separation characteristic is weakened, which is not conducive to chip breaking; the increase of radial cutting width will increase the machining stress and improve the milling force. Finally, by comparing the actual machining and simulation results, the error is within 10%, which verifies the feasibility of the simulation study and provides guidance for ultrasonic milling of GH4169 high-temperature alloy.

Large amplitude oscillatory shear (LAOS) and Fourier transform rheology of ultrasonically extruded epoxidized soybean oil colloids containing organically modified nanoclay

LAOS studies were carried out on untreated and ultrasonically treated ESO/nanoclay 30B colloids obtained by means of an ultrasonic twin-screw extruder at 100 and 400 rpm and ultrasonic amplitudes of 5, 10 and 13 μm. Obtained results were used to perform Fourier transform. Waveform, 3D stress response, elastic and viscous Lissajous curves show significant differences between the untreated colloids and colloids treated at 10 and 13 μm. G1′ and G1″ of colloids are increased with increase of ultrasonic amplitude, as a result of better nanoclay dispersion at higher ultrasonic amplitudes. A higher screw rotation speed also improved nanoclay dispersion for untreated colloid and colloid treated at 5 μm. However, for colloid treated at 10 and 13 μm, a lower screw rotation speed resulted in a better dispersion. This is due to less asymmetric bubble collapse and more jet flow in ultrasonic zone at lower screw speed, which promotes dispersion. Colloids treated at 10 and 13 μm showed yielding and then a non-linearity at a higher strain amplitude compared with untreated colloids. The values of GM′ and ηL′ of colloids calculated from intracycle data exhibited the densification and filler network breakup much more observable than those seen on values of G1′ and G1″. This means GM′ and ηL′ are more suitable for description of colloids with a two-step yielding behavior. Parameters S and T calculated based on intracycle data showed enormous differences in the strain hardening/softening and shear thickening/thinning behaviors between the untreated colloid and the colloids treated at 10 and 13 μm.

Plastic rod as a promising feed material for enhanced performance of ultrasonic plasticization microinjection molding: Plasticization rate, mechanical and thermal properties

A polymer plasticization rate measurement method is proposed for ultrasonic plasticization microinjection molding. The effect of ultrasonic amplitude on the plasticization rate of polypropylene (PP) rods was comprehensively investigated, and the mechanical and thermal properties of PP rods were studied using tensile tests, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results show that the plasticization rate of PP rods increased from 67.25 mg/s to 192.41 mg/s with increase of ultrasonic amplitude, an increase of 186%. The mechanical properties of the PP samples remained stable under different ultrasonic amplitudes, with tensile strength around 21 MPa and elongation at break about 21%. DSC and TGA results showed that PP samples exhibit improved thermal properties after ultrasonic plasticization compared with pure PP. The melting point of the PP sample decreased from 171.7 °C to 164.0 °C and the crystallinity increased from 26.1% to 38.7%. The temperatures corresponding to 1% and 5% weight loss of PP increased from 283.63 °C to 350.30 °C without ultrasonic amplitude to 393.70 °C and 420.13 °C, respectively. The studies have great significance to further understand the influence of ultrasonic plasticization process parameters on the plasticization rate and material properties of polymers.

Understanding the abnormal effects of ultrasonic vibration on tool wear and surface generation in Zr-based bulk metallic glass cutting

Bulk metallic glasses (BMGs), which represent an emerging popular class of alloys, are regarded as difficult-to-cut materials. Ultrasonic vibration-assisted cutting (UVAC) has been reported as an effective method to improve the machinability of such materials. In UVAC, it is widely accepted that, the larger the ultrasonic amplitude, the better the processing outcome, i.e., lower cutting force, lower surface roughness and longer tool life. However, this study demonstrates that the cutting performance of BMGs can be enhanced only if the ultrasonic amplitude is within a carefully-determined window. Due to the high hardness, high elastic limit, and inhomogeneous deformation of BMGs, an excessive ultrasonic amplitude would violate the cutting performance of UVAC. On the one hand, the increase of ultrasonic amplitude can increase the cutting-in speed and actual cutting distance of the tool, which, due to the extreme hardness and elastic limit of BMGs, might lead to severe tool wear in the form of abrupt fracture and rapid flank abrasion, respectively. On the other hand, the increase of ultrasonic amplitude can increase the instantaneous maximum cutting speed of the tool, which, due to the inhomogeneous deformation of BMGs, might lead to local melting of the BMG. When the instantaneous cutting speed reaches a critical value, local material melting takes place on the newly generated surface, which will induce the deterioration of surface quality due to the formation of dimples and periodic micro-pools during UVAC. Based on the theoretical and experimental results, the process window of UVAC of BMGs has been identified. A process optimization strategy is proposed by synergistically considering the surface quality, tool life, and machining efficiency. Additional confirmatory experiments reveal that UVAC can effectively reduce the cutting force and surface roughness of BMGs if the process parameters are well-matched within the identified window. • UVAC improves the machinability of BMGs, unless an excessive vibration amplitude. • An analytical model of UVAC tool failure was established and verified by experiments. • The unique properties of BMGs induce the abnormal failure of UVAC tool. • Feathered dimples and micro-pools were found, the mechanism is revealed. • the process window and optimization strategy of UVAC of BMGs were proposed.

Tangential Ultrasonic-Vibration Assisted Forming Grinding Gear: An Experimental Study.

This study used a forming grinding wheel to machine an involute spur gear with ultrasonic vibration applied to the gear in order to improve the gear processing technology and enhance the gear processing effect. Conventional grinding and ultrasonic vibration-assisted forming grinding gear (TUVA-FGG) tests were carried out. The effects of grinding parameters, such as spindle speed, feed rate, radial grinding depth, and ultrasonic amplitude, on grinding force, grinding temperature, residual stress, surface roughness, and surface morphology were analyzed. The TUVA-FGG significantly improved processing efficiency. With the increase in spindle speed, the maximum reductions in the normal and tangential grinding forces, grinding temperature, and surface roughness reached 33.6, 24.5, 23.9, and 21.6%, respectively. With the increase in feed rate, the respective maximum reductions were 21.4, 19.7, 20.3, and 16.1%. With the increase in radial grinding depth, these values attained 24.6, 20.3, 21.5, and 17.6%, respectively. Finally, with the increase in ultrasonic amplitude, these reductions reached 21.4, 19.7, 21.5, and 19.4%. The maximum residual compressive stress grew by 30.3, 27.5, 30.9, and 27.5% with the increase of wheel rotation speed, feed speed, radial grinding depth, and ultrasonic amplitude, respectively. TUVA-FGG changed the conventional continuous cutting mechanism between the abrasive grain and workpiece into intermittent cutting, reducing grinding forces, grinding temperature, and surface roughness. Moreover, it increased residual compressive stress and improved the micromorphology of the tooth surface, thus enhancing gear machining efficiency.

Study on surface morphology of titanium alloy curved thin-walled parts by longitudinal-torsional composite ultrasonic assisted milling

In order to obtain titanium alloy curved thin-walled parts with better surface quality, longitudinal-torsional composite ultrasonic assisted milling (LTCUAM) was studied. The tool tip trajectory model and the surface roughness model of LTCUAM were established. It was found that LTCUAM could obtain lower surface roughness than common milling (CM) through analyzing the theoretical model. Finally, the effects of milling parameters and acoustic parameters on surface morphology were studied by orthogonal test and single factor test. The experimental results indicated that the surface roughness Ra and the surface arithmetic average height Sa value decreased in different degrees after LTCUAM. However, various milling parameters and acoustic parameters had different effects on the reduction of Sa and Ra. With the increase of ultrasonic amplitude, both Sa and Ra displayed a trend of decreasing first and then increasing. With the increase of spindle speed, both Sa and Ra decreased first, then increased and then decreased. With the increase of the feed per tooth, both Sa and Ra basically showed an increasing trend. The results demonstrated that better surface texture and surface quality can be obtained with lower feed per tooth, medium ultrasonic amplitude and spindle speed.

On the material removal mechanism in rotary ultrasonic milling of ultralow-density silica aerogel composites

Silica aerogel composite with ultralow density is a kind of highly porous solid with excellent property of thermal conductivity. It is widely used for thermal insulation in aerospace, national defense and military industries. However, silica aerogel composites are difficult to process, due to the poor mechanical properties, low strength and high brittleness. Therefore, it is necessary to investigate the processing characteristics and material removal mechanism of silica aerogel composites. In this article, a cutting model of silica aerogel composites is established firstly and the fracture mechanism of fiber was analyzed. Then the ultrasonic milling and conventional milling experiments were performed respectively to obtain the features of machined surface. Macro morphology and surface roughness of machined surfaces in different process conditions are compared to investigate the influence of different process conditions on the processing quality. Scanning electron microscope (SEM) was used to obtain the micro morphology of processed surfaces. By comparing and analyzing the micro morphology of processed surfaces, the influence of process conditions on removal mechanism was investigated. The theoretical cutting force and experiment cutting force is compared to verify the cutting model. The results show that the burrs and pits decrease with the ultrasonic vibration amplitude, and increase with the tool diameter. Processing quality of up-milling is better than down-milling. It is indicated that shearing and pulling off are the main removal mechanism of silica aerogel composites. When the silica aerogel composites are processed by rotary ultrasonic milling and up milling, the fibers will be mainly removed by shearing mechanism and the proportion of fibers removed by shearing facture mechanism will be improved with the increase of ultrasonic amplitude.

Cavitation Effect in Ultrasonic-Assisted Electrolytic In-Process Dressing Grinding of Nanocomposite Ceramics.

Ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding is a promising technology that uses a metal-bonded diamond grinding wheel to achieve a mirror surface finish on hard and brittle materials. In this paper, the UA-ELID grinding was applied to nanocomposite ceramic for investigating the cavitation effect on the processing performance. Firstly, the ultrasonic cavitation theory was utilized to define the cavitation threshold, collapse of cavitation bubbles, and variation of their radii. Next, the online monitoring system was designed to observe the ultrasonic cavitation under different ultrasonic amplitude for the actual UA-ELID grinding test. A strong effect of ultrasonic cavitation on the grinding wheel surface and the formed oxide film was experimentally proved. Besides, under the action of ultrasonic vibration, the dressing effect of the grinding wheel was improved, and the sharpness of grain increased by 43.2%, and the grain distribution was dramatically changed with the increase of ultrasonic amplitude. Compared with the conventional ELID (C-ELID) grinding, the average protrusion height increased by 14.2%, while the average grain spacing dropped by 21.2%. The UA-ELID grinding reduced the workpiece surface roughness Rz and Ra by 54.2% and 46.5%, respectively, and increased the surface residual compressive stress by 44.5%. The surface morphology observation revealed a change in the material removal mechanism and improvement of the surface quality by ultrasonic cavitation effect. These findings are considered instrumental in theoretical and experimental substantiation of the optimal UA-ELID grinding parameters for the processing of nanocomposite ceramics.

P-061. Successful vaginal delivery in pregnant women with preeclampsia undergoing labor induction with Prostaglandin

Silica aerogel composite with ultralow density is a kind of highly porous solid with excellent property of thermal conductivity. It is widely used for thermal insulation in aerospace, national defense and military industries. However, silica aerogel composites are difficult to process, due to the poor mechanical properties, low strength and high brittleness. Therefore, it is necessary to investigate the processing characteristics and material removal mechanism of silica aerogel composites. In this article, a cutting model of silica aerogel composites is established firstly and the fracture mechanism of fiber was analyzed. Then the ultrasonic milling and conventional milling experiments were performed respectively to obtain the features of machined surface. Macro morphology and surface roughness of machined surfaces in different process conditions are compared to investigate the influence of different process conditions on the processing quality. Scanning electron microscope (SEM) was used to obtain the micro morphology of processed surfaces. By comparing and analyzing the micro morphology of processed surfaces, the influence of process conditions on removal mechanism was investigated. The theoretical cutting force and experiment cutting force is compared to verify the cutting model. The results show that the burrs and pits decrease with the ultrasonic vibration amplitude, and increase with the tool diameter. Processing quality of up-milling is better than down-milling. It is indicated that shearing and pulling off are the main removal mechanism of silica aerogel composites. When the silica aerogel composites are processed by rotary ultrasonic milling and up milling, the fibers will be mainly removed by shearing mechanism and the proportion of fibers removed by shearing facture mechanism will be improved with the increase of ultrasonic amplitude.

SY5-2. Simplified prediction criteria and management of preeclampsia for LMIC

Silica aerogel composite with ultralow density is a kind of highly porous solid with excellent property of thermal conductivity. It is widely used for thermal insulation in aerospace, national defense and military industries. However, silica aerogel composites are difficult to process, due to the poor mechanical properties, low strength and high brittleness. Therefore, it is necessary to investigate the processing characteristics and material removal mechanism of silica aerogel composites. In this article, a cutting model of silica aerogel composites is established firstly and the fracture mechanism of fiber was analyzed. Then the ultrasonic milling and conventional milling experiments were performed respectively to obtain the features of machined surface. Macro morphology and surface roughness of machined surfaces in different process conditions are compared to investigate the influence of different process conditions on the processing quality. Scanning electron microscope (SEM) was used to obtain the micro morphology of processed surfaces. By comparing and analyzing the micro morphology of processed surfaces, the influence of process conditions on removal mechanism was investigated. The theoretical cutting force and experiment cutting force is compared to verify the cutting model. The results show that the burrs and pits decrease with the ultrasonic vibration amplitude, and increase with the tool diameter. Processing quality of up-milling is better than down-milling. It is indicated that shearing and pulling off are the main removal mechanism of silica aerogel composites. When the silica aerogel composites are processed by rotary ultrasonic milling and up milling, the fibers will be mainly removed by shearing mechanism and the proportion of fibers removed by shearing facture mechanism will be improved with the increase of ultrasonic amplitude.

P-057. Preeclampsia prediction based on urine peptidome study

Silica aerogel composite with ultralow density is a kind of highly porous solid with excellent property of thermal conductivity. It is widely used for thermal insulation in aerospace, national defense and military industries. However, silica aerogel composites are difficult to process, due to the poor mechanical properties, low strength and high brittleness. Therefore, it is necessary to investigate the processing characteristics and material removal mechanism of silica aerogel composites. In this article, a cutting model of silica aerogel composites is established firstly and the fracture mechanism of fiber was analyzed. Then the ultrasonic milling and conventional milling experiments were performed respectively to obtain the features of machined surface. Macro morphology and surface roughness of machined surfaces in different process conditions are compared to investigate the influence of different process conditions on the processing quality. Scanning electron microscope (SEM) was used to obtain the micro morphology of processed surfaces. By comparing and analyzing the micro morphology of processed surfaces, the influence of process conditions on removal mechanism was investigated. The theoretical cutting force and experiment cutting force is compared to verify the cutting model. The results show that the burrs and pits decrease with the ultrasonic vibration amplitude, and increase with the tool diameter. Processing quality of up-milling is better than down-milling. It is indicated that shearing and pulling off are the main removal mechanism of silica aerogel composites. When the silica aerogel composites are processed by rotary ultrasonic milling and up milling, the fibers will be mainly removed by shearing mechanism and the proportion of fibers removed by shearing facture mechanism will be improved with the increase of ultrasonic amplitude.