Rotary Ultrasonic Machining Process Research Articles

3D FE cutting simulations of Nomex honeycomb composites in rotary ultrasonic machining process

3D FE cutting simulations of Nomex honeycomb composites in rotary ultrasonic machining process

3D FE cutting simulations of Nomex Honeycomb Composites in Rotary Ultrasonic Machining process

3D FE cutting simulations of Nomex Honeycomb Composites in Rotary Ultrasonic Machining process

Modeling and optimization of the magnetically coupled resonant wireless power transfer used in rotary ultrasonic machining process

Modeling and optimization of the magnetically coupled resonant wireless power transfer used in rotary ultrasonic machining process

The Precision Analysis of Cutting Edge Preparation on CBN Cutting Inserts Using Rotary Ultrasonic Machining.

This paper is focused on the issue of preparing the cutting edge microgeometry of cutting inserts made of cubic boron nitride (CBN). The aim of this research was to investigate the possibilities of rotary ultrasonic machining (RUM) for preparing asymmetric cutting edge microgeometries of various shapes (chamfers, circular, and elliptical rounding and their combinations) on a CBN cutting tool. In this article, a new type of advanced cutting edge preparation method is presented. CBN is relatively resistant to the most often used (abrasive) methods of cutting-edge preparation, due to its very high hardness (which is a prerequisite property for machining difficult-to-cut materials). Such hard materials could be processed using advanced manufacturing methods, and rotary ultrasonic machining (RUM) is one such method. Experiments have shown that RUM can be used for machining CBN. However, high hardness is not the only challenge here. For cutting edge preparation, it is necessary to achieve an adequate accuracy of size and dimensions. The presented paper analyzes the suitability of the RUM process for processing CBN inserts. The results of the experiment showed that this method can be used for preparing asymmetric cutting edge microgeometries with various shapes.

Effect of rotary ultrasonic machining parameters on surface integrity of advanced ceramics

The commercial use of advanced ceramics has been hampered by the lack of an efficient, low-cost machining process. Two of the most important requirements for making machining of ceramics economically viable are: i) obtaining high enough material removal rates and ii) developing a machining process that does not cause surface and subsurface damage to the ceramic component. Therefore, it is important to study, in-depth, machining processes that have the potential to machine advanced ceramics efficiently and reliably. In this study, two-level full factorial experiments were designed and run to determine the effect of rotary ultrasonic machining process parameters (grit size, vibration amplitude, and feed rate) on the process outputs (cutting force, surface roughness, and surface compressive residual stresses). The materials under investigation were sintered silicon nitride and sintered reaction-bonded silicon nitride. The experiments reveal the main effects as well as the interaction effects of the process parameters on the process outputs such as cutting force, surface roughness, and surface compressive residual stresses. Using a larger grit size has been found to decreases the tool axial force. Samples that had a rougher surface finish also showed the highest surface residual compressive stresses. Surface compressive residual stresses were present in all samples after rotary ultrasonic machining irrespective of the conditions used. The presence of surface residual compressive stresses was found to be independent of the direction of machining.

Behavior of Rotary Ultrasonic Machining of Ceramic Materials at a Wide Range of Cutting Speeds

The paper deals with the behavior of the rotary ultrasonic machining process at different cutting speeds of ceramic materials. This process is relatively new; therefore, there are gaps in information about its behavior at near-critical parameters. We adjusted cutting speeds 10 times lower and 10 times higher than the recommended one. The observed parameters were machine load, tool wear, and surface roughness. Alumina and zirconia ceramics were used as materials. The results will help with the optimization of the cutting parameters of the rotary ultrasonic machining process.

Delamination in rotary ultrasonic machining of CFRP composites: finite element analysis and experimental implementation

Delamination, an inter-ply debonding failure phenomenon, is considered as the most undesirable and challenging failure mode in hole making of carbon fiber-reinforced plastic (CFRP) composite laminates. The existence of delamination, even small ones, noticeably damages the strength and stability of the assembled products. It is reported that delamination is responsible for up to 60% of composite components’ rejection during assembling. In order to reduce delamination, rotary ultrasonic machining (RUM) has been studied and utilized in hole making of CFRP composites. Existing investigations on delamination of CFRP composites in RUM hole making are experimental studies, in which several methods (such as adjusting input variables and the use of supportive plate) to reduce delamination are reported. To understand delamination generation mechanisms and predict delamination initiation, theoretical investigations are needed. Cutting force models in RUM of CFRP composites have been developed, and it is well accepted that delamination is correlated to thrust force. However, there are no reported investigations to predict delamination initiation and study the impact of thrust force on the delamination of CFRP composites in the RUM hole-making process. Finite element analysis (FEA) could be an effective way to study the delamination in the RUM process. In this paper, FEA was conducted to predict delamination initiation and establish the relationship between the thrust force and delamination thickness in RUM, for the first time. In addition, experiments were conducted to validate the FEA model. The proposed model was proved to be effective in predicting delamination initiation, and the trends of the FEA results agreed well with those of the experimental results.

A mechanistic cutting force model based on ductile and brittle fracture material removal modes for edge surface grinding of CFRP composites using rotary ultrasonic machining

Rotary ultrasonic machining (RUM) has been proven to be an effective method for surface grinding of carbon fiber reinforced plastic (CFRP) composites. Cutting force is considered as the main criterion to evaluate the performance of RUM surface grinding process. The cutting force modeling is essential to better understand such a process. All reported cutting force models for RUM of CFRP are developed based on brittle fracture material removal mode (brittle mode). However, it is recently found that both ductile material removal mode (ductile mode) and brittle mode exist in RUM of CFRP. Among surface grinding processes, edge surface grinding is the mandatory and primary process to remove an amount of composite material from the workpiece edge to achieve the desired workpiece with high precision. In edge surface grinding process, cutting forces in both feeding direction and in depth-of-cut direction (being perpendicular to feeding direction) play important roles in material removal. In addition, the understandings of material removal mechanisms will greatly benefit the modeling development of cutting forces and improve the RUM process. In this study, a mechanistic model based on both ductile mode and brittle mode is developed to predict cutting forces in both feeding and depth-of-cut directions for RUM edge surface grinding of CFRP composites. A series of experiments are conducted to verify this mechanistic model. The model prediction agrees well with the experimental results under different groups of input variables.

Mechanistic prediction for cutting force in rotary ultrasonic machining of BK7 glass based on probability statistics

Material removal in rotary ultrasonic machining (RUM) of hard-brittle material is an abnormal complicated process, which involves the combination effects of the numerous abrasive grains with the random distributions in the dimensions and penetration depths. These stochastic characteristics result in the evident differences in the extrusion loading between the material and each individual grain, and their aggregate effects serve to significantly affect the cutting force of the diamond tool. However, few mechanistic prediction models of the cutting force have incorporated in the random distribution features of the abrasive grains, restricting the current optimization methods for the reduction of the cutting force during the formal RUM process. Giving consideration to the abrasive processing kinematics and their distribution features on the tool end-face, the number of the effective grains together with their penetration depths was calculated utilizing the probability statistics. Subsequently, the novel theoretical model of the cutting force was established by incorporating the gaussian distribution characteristics of the grain size and their penetration depths. Afterward, the confirmatory experiments were performed for the validation of the proposed cutting force model, revealing that the predicted results were accordant well with the experimental measurements. Furthermore, it was found that the number of the active abrasive grains accounted for 2.972% of the total number on the tool end-face at the specific processing parameters. Additionally, the mechanistic predictions of the developed model represented that the cutting force depicting an irregular decreasing trend with the grain dimension increasing, which was attributed to the coupling effects between the grain size and their number.

Rotary ultrasonic machining of carbon fiber–reinforced plastic composites: effects of ultrasonic frequency

Rotary ultrasonic machining (RUM) is effective and efficient in cutting carbon fiber–reinforced plastic (CFRP) composites. With ultrasonic vibration assistance, both machining efficiency and machining effectiveness can be improved. Ultrasonic vibration has two major variables (including ultrasonic amplitude and ultrasonic frequency), which play important roles in RUM processes. Other intermediate variables, such as ultrasonic power and indentation depth, are directly related to these two variables. Effects of ultrasonic vibration amplitude have been extensively investigated in RUM hole making and surface machining processes. However, the effects of ultrasonic frequency in RUM have not been reported. The effects of ultrasonic frequency under different combinations of tool rotation speed, feed rate, and depth of cut on output variables, including cutting forces, surface roughness, and machined surface characteristics, are investigated, for the first time, in this study. The critical frequency is analyzed for the RUM process. Three different levels of ultrasonic frequencies are generated and applied to the RUM process. The kinematic motions of abrasive grains in RUM with different frequencies are analyzed and discussed. The results show that RUM with higher frequency of ultrasonic vibration is a more effective machining process, leading to cutting force reduction and the machined surface quality improvement.

Effect of tool design parameters study in micro rotary ultrasonic machining process

Selection of tooling to perform specific operations like drilling and milling on ceramic materials using rotary ultrasonic machining process is an important aspect to meet stringent dimensions on workpiece as well as intended performance of tool. This phenomenon is more critical for micro rotary ultrasonic machining. In the present study, an effort was made to do micro drilling operation of O0.3 mm tool with varying geometry, having different wall thicknesses and abrasive grain sizes using design of experiments. The effect of tool-based parameters like grain size and wall thickness has been studied on axial cutting force, radial cutting force, tool wear, edge chipping area and taper. After examining axial and radial cutting forces, it has been concluded that lower wall thickness (80 μm) tool is good for drilling operation; and higher wall thickness (100 μm) tool is good for milling operation under same material removal rate conditions. It has been also investigated that lower wall thickness (80 μm) tool has less edge chipping area and less taper and can impart high drilling depth as compared to higher wall thickness (100 and 150 μm) tool. It is also concluded that lesser grain size (15 μm) tools are advantageous in terms of edge chipping area and cutting force for drilling and milling operations as compared to higher grain size (30, 35 and 45 μm) tool at constant material removal rate. Higher grain size tools have been broken at 1.13 mm3/h material removal rate conditions due to bad profile accuracy. But higher grain size tools have worked fairly well at less material removal rate condition. Higher grain size tools produced less wear. Tool wear was found minimum in higher wall thickness (100 μm) tool having higher abrasive grain size (30 μm). Using inferred results, O0.3 mm drilling experiments have been carried out on six aerospace ceramic materials. Also, groove of 0.5 mm size using O0.3 mm optimised tool has been successfully carried out in sintered SiC.

Rotary ultrasonic drilling of Ti6Al4V: Effects of machining parameters and tool diameter

This article presents the use of the rotary ultrasonic machining process for drilling holes in Ti6Al4V alloy which is regarded as a difficult-to-cut material due to its high-temperature strength and low thermal conductivity. This research presents an experimental investigation on the effect of the key rotary ultrasonic machining input parameters including ultrasonic power, spindle speed, feed rate, and the tool diameter on the main output responses including cutting force, hole cylindricity and overcut errors, and tool wear. No previous reports were found in literature to experimentally investigate the effect of the rotary ultrasonic machining parameters and the tool diameter on tool wear, surface integrity, and the accuracy of the drilled holes in Ti6Al4V alloy. The results showed that the rotary ultrasonic machining input parameters within the current ranges can significantly affect the quality of the drilled holes. Through proper selection of input parameters, holes could be drilled in Ti6Al4V alloy with smoothed surface morphology, low tool wear (0.7 mg) and very low cylindricity (2 µm) and overcut (120 µm) errors. Moreover, it was found that the selected level of any input parameter has the ability to significantly affect the influence of the other input parameters on the output responses.

A study on the effect of main process parameters of rotary ultrasonic machining for drilling BK7 glass

BK7 glass is an important engineering material with extensive applications in high-quality and precision transmissive optical components. However, BK7 glass is considered to be a difficult-to-cut material due to its high brittleness and nonconductivity. This article presents the use of rotary ultrasonic machining process for drilling holes in BK7 glass. No previous reports have been found in the literature to experimentally investigate the response of the BK7 glass to rotary ultrasonic drilling. The experimental investigations take into account the effect of the key rotary ultrasonic machining input parameters including the ultrasonic power, spindle speed and feed rate on the output responses of cutting force, exit chipping, surface roughness, hole cylindricity and overcut errors, and surface integrity. The results show that the input parameters within the current ranges can significantly affect the quality of the drilled holes. Moreover, the selected level of any input parameter has the ability to significantly affect the influence of the other input parameters on the output responses. Through proper selection of input parameters, holes could be drilled in BK7 glass with less fractured topography, low surface roughness (1.32 µm), low exit chipping size (0.85), and very low cylindricity (3 µm) and overcut (73.6 µm) errors.

Modeling of un-deformed chip thickness in RUM process and study of size effects in μ-RUM

Un-deformed chip thickness is a critical parameter in machining processes. Measuring un-deformed chip thickness experimentally is a complicated process, especially in micro machining and may not even be measured accurately. The un-deformed chip thickness has an influence on material removal rate, cutting forces, specific energy and surface finish etc. In ceramic machining, it is also an indication of material removal mode such as ductile or brittle fracture. In the present study, an effort is made to model undeformed chip thickness, cutting forces and specific cutting energy in rotary ultrasonic machining (RUM) applied to the side milling operation. RUM may be considered as super-imposition of ultrasonic vibrations on the grinding process. The kinematics of ultrasonic motion has been applied to the grinding for the development of the RUM process models. To validate the models, machining experiments have been performed on borosilicate glass in RUM and grinding modes. Percentage of ductile mode of fracture for the machined surfaces has been evaluated using SEM images. Surface roughness values have also been compared for the same material removal rate conditions to ascertain fracture mode. Developed models have been verified and found that ductile mode of fracture as well as surface finish were higher in RUM as compared to grinding process for same material removal rate. RUM process for six aerospace grade materials has also been tried using micro and macro tools and size effects studied.

Modeling of tool blockage condition in cutting tool design for rotary ultrasonic machining of composites

Although superior in properties, composite materials still have problems in machining, such as delamination, cracking, burning, tool blockage, and cost and efficiency issues. These problems can prevent wide application of extraordinary composite materials. As an effective method in composite machining, rotary ultrasonic machining (RUM) process has been paid much attention to recently. The current studies on RUM tool design are mostly based on experiments. However, the insufficiency of RUM tool design theory would generally result in the tool blockage, which subsequently leads to the sharp increase in cutting force and poor machining quality in the engineer application. Besides, few investigations are made to combine tool design parameters with machining conditions to avoid tool blockage during RUM process. In this work, based on the RUM material removal mechanism, two models for the chip space and the chip length are built. Thus, the tool blockage condition in RUM is linked with the tool design parameters and the cutting parameters. Experimental study is performed for theoretical verification. Due to the differences in the modalities of the chip, two typical types of composites, C/SiC and CFRP T700, are selected to obtain their tool blockage conditions. The test results show that to prevent the occurrence of blockage, the chip space should be greater than the chip length in C/SiC milling, while in T700 milling, the chip space should be at least over 8 times greater than the chip length.

Rotary Ultrasonic Machining of Sapphire: Feasibility Study and Designed Experiments

Sapphire, widely used in high-speed integrated-circuit chips, thin-film substrates, and various electronic components, is regarded as one of the most difficult to cut materials owing to its great hardness and low fracture toughness. Rotary ultrasonic machining (RUM) has been regarded as an effective processing method for hard and brittle materials. In this paper, RUM process is introduced into the drilling of sapphire for the first time. The feasibility to machine sapphire using RUM is studied. Moreover, results of a designed experimental study into RUM of sapphire are presented to discuss the main effects as well as interaction effects of process parameters (ultrasonic power, spindle speed, and feedrate) on outputs. The process outputs investigated include cutting force and edge chipping size.

Effects of High Frequency Vibration on the Surface Quality in Rotary Ultrasonic Machining of Glass BK7

Both rotary ultrasonic machining (RUM) and conventional grinding (CG) experiments were performed on the glass BK7 specimen to investigate the effects of high frequency vibration on the surface quality. The surface morphologies produced in the two machining processes were assessed and the associated material removal mechanisms were explored. Also, the influence of the spindle speed on the surface roughness was discussed. It was found that the mechanisms of the material removal involved in the RUM process were material pulverization and brittle fracture, while ductile flow and brittle fracture prevailed on the material removal in CG process. The increased spindle speed would reduce the lateral cutting depth of each abrasive, and promote the shielding effects of the lateral cracks generated by the previous abrasive, leading to the reduction of the surface roughness in both RUM and CG processes.

EXPERIMENTAL INVESTIGATIONS ON SUBSURFACE DAMAGE IN ROTARY ULTRASONIC MACHINING OF GLASS BK7

The present study aimed to establish an exact comprehension of the subsurface damage patterns generated during rotary ultrasonic machining (RUM) of glass BK7 process. First, the subsurface damage of the specimens produced with and without ultrasonic using three different diamond tools was compared and characterized by means of the bonded interface sectioning technique. Then, the RUM scratching tests were conducted on the polished specimen surfaces with two diamond tools to investigate the subsurface damage formation mechanisms involved in formal RUM process. The damage characteristics of the RUM scratches were investigated with respect to the kinematics principles of the abrasives and the dynamic fracture theory of the brittle material. As a result, three types of RUM-induced subsurface damage were identified: pulverization, chipping and cracking. The pulverization layer characterized by finer debris was just populated near the top surface of the RUM specimen without extending into the interior material. The finer debris should emerge simultaneously, resulting from the increased strain rate and the decreased dynamic fracture toughness of the material, both of which were aroused by the inertia loading of the abrasive when reaching the vertex of its sinusoidal trajectory.

Experimental Investigation on Surface/Subsurface Damage in Rotary Ultrasonic Machining of Glass BK7

Experiments were carried out to study the effect of ultrasonic vibration on the surface roughness and subsurface damage (SSD) in rotary ultrasonic machining (RUM) of glass BK7. As a comparison, some conventional grinding (CG) experiments were also performed under the same process parameters with there of the RUM ones. The surface roughness of the RUM/CG samples was measured with a surface profilometer. The SSD of these specimens was assessed and characterized by a measuring microscope with the help of the taper polishing method. Also, the influence of process parameters (cutting depth, feed speed, and spindle speed) on the surface/subsurface quality was discussed. As a result, both the surface roughness and the SSD depth of the RUM/CG specimens were reduced with the increased spindle speed, while increased with the increasing of feed speed and cutting depth of the diamond tool. Compared with the CG process, the introduction of ultrasonic vibration resulted in the higher surface roughness and SSD depth, due to the fact that the max cutting depth of the abrasive in the RUM process increased by an amplitude compared with that in the CG process.

Influences of vibration on surface formation in rotary ultrasonic machining of glass BK7

Abstract This paper presented a fundamental investigation of the surface formation mechanisms involved in rotary ultrasonic machining (RUM) of glass BK7 process. Comparative observations of the scratches, generated in the scratching tests with and without ultrasonic, were performed using optical microscopy, white-light interferometer, and scanning electron microscopy (SEM). Giving consideration to the scratch morphologies and the abrasive process kinematics, the mechanisms of surface formation provoked by the ultrasonic superposition were investigated. Additionally, the formal machining tests with and without ultrasonic were also conducted to validate these surface formation mechanisms. As a result, a nondimensional parameter K was proposed to quantitatively describe the ultrasonic effects of the abrasives as well as to correlate these effects with the machining conditions. Due to the periodic variation in the effective work angle of the abrasive, the material accumulated slightly at the RUM groove entrance, whereas serious material accumulation appeared at the exit. The stress imbalance on the specimen surface induced by the dramatic fluctuation of the abrasive inertia load caused plenty of tortuous cracks in 0.2 μm-sized length emerge on the RUM grooves generated in the ductile material removal stage. A novel theoretical model of the surface formation mechanisms involved in formal RUM process was established by incorporating the ultrasonic effects, such as the lower dynamic fracture toughness of material, cyclical variation in the effective work angle of the abrasive, and the larger abrasive inertia force. Experimental results obtained in formal machining tests revealed that superimposing an ultrasonic vibration could distinctly reduce the cutting force of the diamond tool without seriously worsening the surface quality of the specimens.