Longitudinal-torsional Vibration Research Articles

Cutting force prediction model considering tool-chip contact interface friction behavior in ULTVAM of Ti-6Al-4V

Ti-6Al-4V is widely used in the aviation industry because of its high strength, and good heat resistance. However, severe tool wear on the rake face occurs during the milling of Ti-6Al-4V, which is caused by intense friction between the tool rake face and the chips. To investigate tool wear in the milling of Ti-6Al-4V, ultrasonic vibration is introduced, and a cutting force prediction model that considers tool-chip contact interface friction behavior in Ultrasonic Longitudinal-Torsional Vibration-Assisted Milling (ULTVAM) is proposed in this paper. First, the tool tip motion trajectory and dynamic cutting thickness under ULTVAM were analyzed calculated, and compared with those in Common Milling (CM). Subsequently, the effects of ultrasonic vibration on the shear force under the ultrasonic softening effect, the friction force, and the friction reversal force on the tool-chip contact interface were investigated. A dynamic milling force model under ULTVAM was established before and after friction force reversal caused by ultrasonic longitudinal-torsional vibration. Finally, numerous experiments were conducted to validate the proposed model, and the experimental results indicated that the calculated dynamic milling forces agreed well with the measured values, with errors in the X and Y directions of 5.51% and 10.23%, respectively. In addition, the average roughness of the workpiece surface also decreased (1.08, 0.9, 0.6, 0.7 μm under ultrasonic amplitudes of 0, 1, 2, and 3 μm) and the tool wear state improved on the rake face under ULTVAM.

Longitudinal torsional vibrations of the chain drive system of mine scraper conveyor

To deeply analyse the dynamic characteristics of the scraper conveyor during operation, the mechanical characteristics of the coupled longitudinal and torsional vibrational modes under excitation by cargo loading are studied. Based on the Kelvin‒Voigt model and the point-by-point tension method, a model of the coupled longitudinal and torsional vibrations of the scraper chain drive system is established. Then the functional program is constructed and the numerical simulation is carried out. Finally, the correctness of the model is verified by comparison with experiments. The research results reveal the torsional vibration characteristics of the scraper chain drive system under two different working conditions, light load and medium load, and determine the influence area of the torsional vibration of the scraper. The results of this analysis provide a theoretical basis for the subsequent optimization of the scraper parameters, the prediction of scraper chain drive system failure, and the calculation to give an early warning before failure occurs.

Review on design of hybrid longitudinal-torsional ultrasonic vibration horn for rotary ultrasonic machining (RUM) processes

Longitudinal-torsional (L-T) vibration machining process in rotary ultrasonic machining (RUM) technologies has been considered one of the most promising method in order to cope the machining problems of various difficult-to-machine materials (composites, metallic alloys, abrasives, ceramics and glass). However, design complexity of the L-T machining systems keeps it limited for commercial applications. Hybrid L-T horn is the key component to achieve the efficient performance of RUM systems. Design of hybrid L-T horn is highly intricate due to slots geometry, position, and number of slots. At present, there is no study available in the literature specifically focused on the design and implementation of hybrid L-T horn. Therefore, this study systematically describes literature review on the design, simulations and implementation of hybrid L-T vibration horn in RUM applications of difficult-to-machine materials. Furthermore, the present research reveals the critical design parameters of hybrid L-T horn such as incident angle 47.6° gives better surface quality of the machined hole compared to 67.2° at designed resonant frequency 35 kHz.

Modeling and optimization of longitudinal-torsional vibration horn with the large tool head

There are problems such as large deviations in resonant frequency and difficulties in selecting the structural parameters of helical slot when designing longitudinal-torsional vibration horn with large tool head (HWLTD) using traditional design theory of horn. Therefore, in this paper, HWLTD was designed integrally, the model of HWLTD was established, longitudinal vibration frequency equation of HWLTD was derived and consequently, the resonant frequency was predicted and optimized. Then, the principle of vibration mode transformation (POVMT) of helical slots was derived. Combined with POVMT and ANSYS simulation analysis, resonant frequency and torsional-longitudinal ratio of longitudinal-torsional vibration of HWLTD were optimized, thereby improving the vibration characteristics of HWLTD. The resonant frequency and vibration effect of HWLTD were tested, and the measurements were agreed with the theoretical design and simulation analysis, which validates the HWLTD model and POVMT. The research provides a reference for the efficient and reliable design of HWLTD in the field of ultrasonic machining.

Design and 3D printing of waveguide-based ultrasonic longitudinal-torsional transducers for medical needle insertion

This paper presents a new waveguide-based longitudinal-torsional (L&T) ultrasonic transducer. For synchronization of both the longitudinal and the torsional vibrations, a new circular array of helical structures was designed and developed. The array of helical structures is used as an effective waveguide to constrain the wave propagations to achieve harmonic longitudinal-torsional vibration. Analytical modeling of the new design is presented for synchronous L&T vibration conversion. A finite element (FE) analysis was used to optimize the geometric design of the new L&T transducer. The new design was fabricated using a selective laser melting (SLM) additive manufacturing (AM) process. Lab experiments were conducted to measure the impedance and vibration performance of the novel fabricated transducers and validate the L&T transducer design. The results show that the new waveguide-based transducer is promising to deliver synchronized L&T vibration with high vibrational power efficiency. The new L&T ultrasonic transducer can be developed for a vibratory needle insertion device, effectively reducing insertion force and bending.

Design and experimental investigation of stepped horn with a hollow part to allow individual design of amplitude amplification factors for longitudinal-torsional vibration source

In the ultrasonic vibration-assisted manufacturing method using complex vibration, the amplitude amplification factor of horn for each vibration is important. In this paper, we focus on longitudinal-torsional vibration as a complex vibration and propose a stepped horn with a hollow part as a horn that can design the amplification factors of these vibrations individually. The proposed equation for the amplification factor of the horn with a hollow part was derived from the equation of the conventional step horn without a hollow part, and the validity of the proposed equation was verified by the finite element method and experimental measurements. As a result, the validity of the equation was confirmed, and it was clarified that the proposed stepped horn with a hollow part can be individually designed for the amplitude amplification factors of longitudinal vibration and torsional vibration.

Theoretical and experimental investigations of ultrasonic vibration–assisted boring for titanium alloy

To effectively cope with the hard machinability challenges of hole caused by difficult-to-cut materials and high processing standards in aviation field, ultrasonic vibration–assisted boring (UB) methods with different modes are proposed. In this paper, the kinematics characteristics of UB were analyzed, the motion trajectory of tool was discussed. The comparison experiment of conventional boring and UB with longitudinal vibration and longitudinal-torsional vibration was performed to study the effect of ultrasonic field on the boring process, the influence of main parameters on boring force and surface roughness were investigated. The results show that UB can reduce boring force and surface roughness effectively, especially with the help of longitudinal-torsional vibration, compared with the conventional boring, the boring force could be reduced by 38.04–43.77%, and the surface roughness could be reduced by 25.48–41.47%. This study proves the feasibility of UB and provides theoretical and experimental reference for improving the surface quality of difficult-to-machine holes.

ТЕХНОЛОГИЯ УЛЬТРАЗВУКОВОГО ФОРМИРОВАНИЯ НЕПАЯНЫХ СОЕДИНЕНИЙ ЭЛЕКТРИЧЕСКИХ ПЛАТ С КОНТРОЛЕМ УСИЛИЯ ЗАПРЕССОВКИ

The paper discusses the issues of technology for the formation of non-soldered connections of electrical boards using ultrasonic vibrations. A developed and patented device for the formation of ultrasonic longitudinal torsional vibrations is described, which makes it possible to significantly reduce the pressing force, modify the properties of the surface layers of parts and control the pressing force of contact pins

Design and experimental study of longitudinal-torsional ultrasonic transducer with helical slots considering the stiffness variation

The ultrasonic transducer employing helical slots to generate longitudinal-torsional (L&T) ultrasonic vibration is popular in the field of hard and brittle material machining. However, the design approach for this type of L&T ultrasonic transducer is not well established. An improved design model combining equivalent circuit theory and material parameter equivalent method based on stiffness variation was proposed in this study. The structure parameters of the transducer can be obtained according to given resonance frequency and nodal position. The model can further predict electrical characteristics and mechanical responses under specific excitation. For the preliminary verification of this theoretical model and the optimization of the transducer, finite element analyses were carried out to investigate the influences of slot structure parameters on dynamic performances in terms of resonance frequency, frequency separation, and amplitude of L&T vibration. After that, a prototype was manufactured according to the design results, and the measurements of impedance curve and vibration amplitude were conducted. The experimental results indicate that this prototype resonates at 24,920 Hz with an effective electromechanical coupling coefficient of 0.19. Meanwhile, the vibration amplitude in longitudinal direction is 8.1 μm and that in tangential direction is 5.6 μm under 70-V sinusoidal voltage excitation, which are consistent with the theoretical design and simulation results. Furthermore, machining tests demonstrate that surface roughness reduction and surface quality improvement can be gained by adopting this L&T ultrasonic transducer, compared to using the longitudinal vibration transducer. The proposed design approach was validated and this study can provide guidelines for the design of L&T ultrasonic transducer for rotary ultrasonic machining (RUM).

Ultrasonic complex vibration source using two longitudinal vibration transducers and a uniform rod with diagonal slits

It has been reported that ultrasonic welding using planar vibrations results in higher weld strength and less damage to the work pieces compared with ultrasonic welding using linear vibrations. However, torsional vibration transducers are small and expensive, thus reducing flexibility in the use of the vibration source. Therefore, in this study, we developed an ultrasonic longitudinal-torsional vibration source using longitudinal vibration transducers and a uniform rod with diagonal slits. The proposed vibration source generates torsional vibration by using a uniform rod with diagonal slits instead of a conventional torsional vibration transducer. As a result, it is found that a planar vibration locus is obtained by inputting two resonance frequencies simultaneously.

Performance analysis of the longitudinal-torsional ultrasonic milling of Ti-6Al-4V

Titanium alloy is a typical difficult-to-cut material due to its high strength and high stiffness. To solve the problem of the low efficiency and poor surface quality in the milling of titanium alloy, this paper proposes a novel longitudinal-torsional ultrasonic vibration milling (LTUVM) process. An ultrasonic horn with spiral slots was designed to convert the longitudinal vibration into longitudinal-torsional vibration. The tooltip trajectory was modeled, and the finite elements analysis was used to analyze the cutting mechanism of LTUVM. The simulation results indicate a kind of separation cutting characteristics in every vibration cycle, which is beneficial to reduce the cutting force and improve the surface finish compared with the single longitudinal ultrasonic vibration milling (SLUVM). Then, cutting tests were conducted on Ti-6Al-4V to evaluate the performance of LTUVM. Experimental results demonstrated that the LTUVM could reduce the cutting force by 46–86% compared with the conventional milling (CM) and the SLUVM due to its separation cutting characteristics. Moreover, the surface morphology was analyzed, and a fractal dimension (FD) method was proposed to characterize the regularity and fragmental property of the machined surfaces. The surface morphology analysis results showed that the LTUVM can be used as a novel high-efficiency and high-quality surface texturing method for Ti-6Al-4V. The textured surface of the LTUVM has the superiority of high integrity and periodicity, which could be applied to effectively tune the tribological property of surface.

3Pa4-7 Study of longitudinal–torsional vibration source using stepped horn with hollow part

3Pa4-7 Study of longitudinal–torsional vibration source using stepped horn with hollow part

An Enhanced Hemostatic Ultrasonic Scalpel Based on the Longitudinal-Torsional Vibration Mode

This paper proposes an ultrasonic scalpel based on the longitudinal-torsional vibration mode to enhance the hemostatic ability. The concentrator of the proposed ultrasonic scalpel has been specially designed with spiral grooves to realize this vibration mode. The change of the working mode has enlarged the vertical motion component of the distal blade to efficiently radiate energy into the dissected tissues, supporting that the blood vessel can receive sufficient energy to be sealed. The electromechanical equivalent method has been employed in the initial design of the scalpel to obtain the desired resonance frequency. The structural optimization based on the finite element method (FEM) has been conducted to further improve the proposed design, as well as investigation of its dynamic performances. Both the conventional and presented ultrasonic scalpel prototypes were fabricated, and their important parameters such as, mechanical quality factor and resonance frequency, were tested and compared using an impedance analyzer. The ex-vivo experiments have been conducted to measure the vertical temperature distribution to investigate their transferring heat effects. The corresponding results indicated that the internal temperature values of tissues cut with the proposed hemostatic-enhanced ultrasonic scalpel are 24.0% higher on the 3mm layer, 16.5% higher on the 6mm layer, and 8.5% higher on the 9mm layer, respectively. The sealing capacity of the ultrasonic scalpels has been investigated through the coagulation dissection experiment on the chicken carotid and their burst pressure tests. The average burst pressure of the sealed vessels by the hemostatic-enhanced ultrasonic scalpel can achieve higher values than that of the conventional ultrasonic scalpel.

Effects of axial and longitudinal-torsional vibration on fiber removal in ultrasonic vibration helical milling of CFRP composites

Abstract Helical milling (HM), axial ultrasonic vibration helical milling (A-UVHM) and longitudinal and torsional ultrasonic vibration helical milling (LT-UVHM) were developed for hole-making of Carbon Fiber Reinforced Plastic (CFRP) composites. Cutting trajectory, cutting speed, acceleration and effective rake angle of peripheral edge in HM and UVHM processes were modeled. Compared with HM, axial forces with UVHM processes were reduced by 9.0 %–35.7 %. The burrs at entrance and exit with UVHM were also reduced. In A-UVHM and LT-UVHM processes, an effect of shear with variable direction which is good to fracture fibers was presented, according to the relative movement of peripheral edge and fibers. Additionally, the variations of cutting speed and acceleration in A-UVHM and LT-UVHM are also helpful to fracture fibers, due to the wide range of speed and impact effect. Smooth surface with regular fiber fracture morphology and tiny fragments was generated in UVHM due to the effect of shear along variable direction. Compared with HM, the maximum effective rake angle of peripheral edge in UVHM was increased by 112.1 %–192.6 %, which is helpful to fracture fibers by sharper cutting edge.

Design and Experiment Study of Ultrasonic Longitudinal-Torsional Compound Consolidation Vibration System for Metal Foil

In order to realize the connection for metal foil, a longitudinal-torsional compound consolidation vibration system is proposed, and relative experiments are carried out. Firstly, the structure of longitudinal-torsional compound consolidation vibration system was designed, detailed structural design of the compound piezoelectric transducer and the compound horn in the vibration system was carried out, and torsional vibration analysis of the compound horn with spiral grooves was carried out based on mechanical principle. Secondly, modal calculation and harmonic response analysis of longitudinal-torsional compound consolidation vibration system were carried out, and corresponding vibration mode and harmonic frequency were obtained. The effect of structural parameters for the compound horn on the frequency of the consolidation vibration system was analysed, and structural parameters of the compound horn were optimized. Finally, the prototype was made, and the experimental platform was built to test the amplitude. When the frequency is near 20000 Hz, the resonance is achieved in three directions at the same time, and the resonance frequency is 19800 Hz. Through the frequency-scanning test, the maximum longitudinal amplitude of the consolidation vibration system is 16 μm, and the maximum torsional amplitudes of X and Y are 7.9 μm and 8.1 μm. The longitudinal-torsional compound consolidation vibration system can realize the connection of the same and different metal foils and has broad application prospects.

Experimental investigations on longitudinal-torsional vibration-assisted milling of Ti-6Al-4V

In vibration-assisted milling (VAM), an additional high-frequency oscillation is superimposed on the kinematics of a conventional machining process. This generates oscillations of the cutting edge in the range of a few micrometers, thereby causing a high-frequency change in the cutting speed and/or the feed. Consequently, a reduction of cutting forces, an increase of the tool life, and an improvement of the workpiece quality can be achieved. This paper shows and compares the effects of longitudinal and longitudinal-torsional (L-T) vibrations on the cutting force, the tool life, and the surface quality when milling Ti-6Al-4V. In comparison with the conventional milling process, the cutting forces are significantly reduced and the surface finish of the workpiece can be improved by introducing ultrasonic vibrations to the milling process. Longitudinal-torsional vibration assistance showed better overall process performance than the pure longitudinal vibration assistance.

A study ofthe surface microstructure and tool wear of titanium alloys after ultrasonic longitudinal-torsional milling

In order to obtain a better surface micro-morphology on the difficult-to-machine materials such as titanium alloys, the influence of ultrasonic parameters and cutting parameters on the tool path was analyzed theoretically under the ultrasonic longitudinal-torsional vibration. Ultrasonic longitudinal-torsional assisted milling (ULTAM) of titanium alloy was performed, based on a 20° slope. The effects of the ultrasonic parameters and cucuttintting parameters were studied on the surface morphology and surface roughness. The machined surface was examined using scanning electron microscopy (SEM) and white light interferometry. The characterization parameters of the three-dimensional surface micro-morphology including the arithmetic mean height (Sa), the surface skewness (Ssk), and the density of summits (Sds), were obtained under the corresponding cutting parameters. It was found that the ultrasonic amplitude exhibited a significant influence on the surface micro-morphology, followed by the spindle speed n, while the effect of the depth of cut (ap), and the feed amount per tooth (fz) was relatively less. Under the same cutting parameters for the surface, a comparative analysis for the friction and wear testing was performed between the ultrasonic milling and conventional milling (CM). The results showed that the ULTAM transformed the original ravines and anisotropic surface imperfections into an uniform and orderly scaly micro-texture, thus forming an isotropic surface texture in all directions. Furthermore, ULTAM transformed the surface into a fish-scale micro-texture, and thereby improved the surface quality. The fine and smooth surface morphology was conducive by shortening the running-in time, allowing the stable state of friction to be reached quickly, and thereby offering a higher stability in the friction process. `Compared to CM, the tool wear was reduced by 30%, due to the unique tool-work separation characteristics of the ultrasonic longitudinal-torsional assisted milling. Moreover, the unique intermittent cutting characteristics of the ultrasonic longitudinal and torsional milling not only reduced the cutting force and tool wear, but also inhibited the generation of the burr, thus improving the surface quality.

Frequency coupling design of ultrasonic horn with spiral slots and performance analysis of longitudinal-torsional machining characteristics

Longitudinal-torsional (L-T) vibration in rotary ultrasonic machining (RUM) can further reduce the cutting force and improve the machining efficiency compared with the single longitudinal vibration in RUM. In this study, an ultrasonic step horn with spiral slots using the principle of mode conversion was designed to realize L-T vibration. The torsional amplitude to longitudinal amplitude (AT/AL) ratio is proposed to quantify the efficiency of mode conversion. Moreover, a simulation method was used to carry out the frequency coupling design of the ultrasonic horn with spiral slots. The influence of the step position and slot position with a spiral angle of 52° on the resonant frequency and amplitude of the ultrasonic horn were analyzed, respectively. Based on the simulation results, ultrasonic horns with different AT/AL were designed and fabricated. Finally, the results obtained through experiments with milling glass plane revealed that the cutting force was reduced by 48–73%, while the surface quality improved compared with single longitudinal vibration when the torsional vibration is coupled with the longitudinal vibration in RUM. The reasonable AT/AL ratio could effectively reduce the cutting force when the synthetic amplitude was the same. This indicates that the L-T vibration changes the trajectories of the diamond abrasives, which improves the machining performance.

Ultrasonic vibration-assisted grinding of blind holes and internal threads in cemented carbides

Cemented carbides are widely used in aerospace and mechanical processing industries due to their excellent physical and chemical properties. However, cemented carbide products processed by conventional methods have such deficiencies as poor surface integrity, high surface roughness, and high consumables. Given this, a method for machining blind holes and internal threads in cemented carbide by ultrasonic vibration-assisted grinding is introduced in this paper. The methodology combines ultrasonic-assisted grinding with helical mill-grinding to machine cemented carbide via a diamond form grinding wheel. Based on the characteristics of ultrasonic longitudinal-torsional vibration, the motion trajectories of individual abrasive particles under conventional grinding (Con-G) and ultrasonic longitudinal-torsional vibration-assisted grinding (ULTVAG) were analyzed. Tests were conducted to investigate the influence of machining parameters on the grinding force, hole surface quality, thread profile accuracy, and wear conditions of the two diamond form grinding wheels. The results obtained strongly indicate that ULTVAG can reduce the grinding force, while the grinding force is mostly controlled by the feed rate and is less affected by the spindle speed and ultrasonic vibration amplitude (UVA). With an increase in UVA, the hole surface roughness exhibits first decreasing and then rising. The optimal hole surface quality is observed at the longitudinal ultrasonic vibration amplitude A = 4 μm. At too high values of UVA, the hole surface quality becomes worse than that acquired via the conventional grinding. The first few threads machined by Con-G and ULTVAG are shown to meet the requirements of 6H precision of thread. As the number of processed threads increases, the wheel of Con-G becomes severely worn, resulting in insufficient machining precision. The number of threads machined by a single grinding wheel under ULTVAG is higher than that of Con-G. It is proved that ULTVAG with an appropriate UVA can reduce the wear of grinding wheel and prolong its service life, as well as improve the thread precision and qualified rate.

A semi-active control method for decreasing longitudinal torsional vibration of vehicle engine system: Theory and experiments

Due to diverse working conditions, the vehicle engine system may generate complicated nonlinear whole-body vibration with wide frequency band. Since conventional vibration control methods are usually designed in terms of the external excitations and implemented based on the linear models, their performance is difficult to improve. In this study, a new semi-active vibration absorption method that is both independent of external excitations and capable of dealing with nonlinear vibration problem is put forward to decrease the longitudinal torsional vibration of the vehicle engine system. It sufficiently utilizes nonlinear coupling and modal interaction to transfer and dissipate vibration energy, rather than relies on linear neutralization. A novel vibration absorber scheme with controllable frequency and controllable damping is proposed, which can be readily implemented by the control algorithms. Numerical simulations and virtual prototyping simulations have verified the correctness of theoretical research. Experimental investigations have been carried out to successfully examine the effectiveness and the feasibility of the proposed method.