Torsional Amplitude Research Articles

In situ torque transmissibility frequency response function measurements of a centrifugal pendulum vibration absorber in a torque converter clutch damper

This investigation details torsional testing and characterization of torque converter clutch (TCC) damper variants containing centrifugal pendulum absorbers (CPAs) utilized in light duty production vehicles. Data collected on a torque converter dynamometer test stand was used to correlate a nonlinear model of the combination TCC damper and CPA when locked with zero relative slip speed. The range of test torques and speeds are related to when driveline, chassis and body noise and vibration concerns are high and the damper-CPA combination are required to provide maximum isolation. To facilitate model correlation efforts, modified configurations of the same torque converter design were procured, enabling separation of damping effects from the CPA and damper springs. Under load, the locked TCC was torsionally excited to acquire torque transmissibility frequency response functions (TTFRFs). The anti-resonance of the CPA was measured, and the viscous damping coefficient estimated. A manual tuning and modified half-power bandwidth method were used to estimate the equivalent viscous damping of the CPA. Additional test cases included torsional excitation amplitude and oil temperature to ascertain differences in CPA response and tuning order. The objective of the investigation is to demonstrate the influence of damper spring and CPA integration, extraction of CPA damping from actual hardware and the utility of including representative damping in model-based design of future damper-CPA assemblies.

Torsional damper design for diesel engine: theory and application

Abstract Torsional vibration is the primary cause of engine crankshaft failure. Consequently, the reduction of engine vibration is of paramount importance for the enhancement of automotive safety and comfort. However, the lack of comprehensive insight into the damping mechanism of the torsional damper has impeded the effective control of engine torsional vibration. In order to gain insight into the vibration characteristics of the shaft system in an inline six-cylinder diesel engine, an analysis of the system’s behaviour during both free and forced vibration was conducted. A mathematical relationship was deduced between the dimensions, material, operational temperature and damping properties of the silicone oil damper. The objective was to determine the optimal damping and moment of inertia of the damper, with the aim of minimizing the torsional amplitude of the sixth harmonic. The results demonstrate a reduction in the six-harmonic torsional amplitude from 0.32° to 0.14° following the installation of the damper. The mean and relative deviations between the calculated and experimental results are 0.0018° and 0.83%, respectively. To facilitate the design of the silicone oil damper, a software program, Vibsim, was developed based on Visual Studio for the design and torsional vibration analysis of the silicone oil damper. This software is reliable in calculating results and is user-friendly.

Large amplitude and small size ultrasonic milling for BT40 tool holders

Abstract The current ultrasonic milling tool holders are relatively long in structure, and the tool is susceptible to generating detrimental radial vibrations during high-speed rotation. To achieve high-quality milling of difficult-to-machine materials, a longitudinal-torsional ultrasonic oscillator suitable for BT40 tool holders has been proposed, which can generate a large amplitude while maintaining a compact length. A longitudinal vibration ultrasonic transducer with an exponential front cover is designed using the analytical method. Based on the principle of acoustic wave reflection, four spiral grooves are introduced on the exponential variable cross-section bar to convert the longitudinal vibration into longitudinal-torsional composite vibration. The effects of groove width, groove depth, and spiral angle on the longitudinal-torsional resonance were analyzed using the single-factor method in finite element software, and the optimal spiral groove parameter combination was determined. The longitudinal-torsional ultrasonic transducer is assembled with the BT40 tool holder to construct a longitudinal-torsional ultrasonic tool holder model, and modal analysis was performed. The resonant frequency was determined to be 22, 845 Hz. An experimental platform was established to carry out impedance analysis and amplitude testing on the longitudinal-torsional ultrasonic tool holder. The results show that its resonant frequency is 22, 152 Hz, which is slightly different from the simulation value. The tool holder’s maximum longitudinal amplitude is 11.2 μm, and the maximum torsional amplitude is 4.3 μm, with a torsional-to-longitudinal ratio of 0.38. The performance of the longitudinal-torsional ultrasonic tool holder meets the processing requirements of most ultrasonic milling applications, and the correctness of the design method is verified.

Longitudinal-Torsional Frequency Coupling Design of Novel Ultrasonic Horns for Giant Magnetostrictive Transducers.

The use of advanced brittle composites in engineering systems has necessitated robotic rotary ultrasonic machining to attain high precision with minimal machining defects such as delamination, burrs, and cracks. Longitudinal-torsional coupled (LTC) vibrations are created by introducing helical slots to a horn's profile to enhance the quality of ultrasonic machining. In this investigative research, modified ultrasonic horns were designed for a giant magnetostrictive transducer by generating helical slots in catenoidal and cubic polynomial profiles to attain a high amplitude ratio (TA/LA) and low stress concentrations. Novel ultrasonic horns with a giant magnetostrictive transducer were modelled to compute impedances and harmonic excitation responses. A structural dynamic analysis was conducted to investigate the effect of the location, width, depth and angle of helical slots on the Eigenfrequencies, torsional vibration amplitude, longitudinal vibration amplitude, stresses and amplitude ratio in novel LTC ultrasonic horns for different materials using the finite element method (FEM) based on the block Lanczos and full-solution methods. The newly designed horns achieved a higher amplitude ratio and lower stresses in comparison to the Bezier and industrial stepped LTC horns with the same length, end diameters and operating conditions. The novel cubic polynomial LTC ultrasonic horn was found superior to its catenoidal counterpart as a result of an 8.45% higher amplitude ratio. However, the catenoidal LTC ultrasonic horn exhibited 1.87% lower stress levels. The position of the helical slots was found to have the most significant influence on the vibration characteristics of LTC ultrasonic horns followed by the width, depth and angle. This high amplitude ratio will contribute to the improved vibration characteristics that will help realize good surface morphology when machining advanced materials.

Conformational Landscapes of 2,3-, 2,4-, 2,5-, and 2,6-Difluorobenzaldehyde Unveiled by Rotational Spectroscopy.

We report the coexistence of anti-conformers and energetically unfavorable syn-conformers of 2,3-, 2,4-, 2,5-, and 2,6-difluorobenzaldehyde in the gas phase using broadband chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The rotational spectra of monosubstituted 13C isotopologues of the anti-conformers have also been assigned in natural abundance, which were used to derive their vibrationally averaged geometries and semi-experimental equilibrium structures. The energy differences between anti- and syn-conformations are estimated to be 10.9, 11.3, and 12.9 kJ/mol for 2,3-, 2,4-, and 2,5-difluorobenzaldehyde, respectively, at the theoretical level of DLPNO-CCSD(T)/def2-TZVP. Despite the steric repulsion caused by the close proximity between the oxygen atom of the aldehyde group and the ortho-substituted fluorine atom, our experimental results indicate the planarity of the syn-conformations. The frequencies of the large amplitude torsion between the phenyl and aldehyde groups have been estimated by experimental inertial defects, which agree with theoretical calculation results.

Nonlinear characteristics and radial-bending-torsional vibration of a blade with breathing crack

Rotor failures due to cracked blades are frequently observed in rotating machinery. The identification of cracking state of rotating blade based on vibration characteristics has garnered a lot of attention. However, nonlinear characteristics and vibration combining in radial, bending and torsional directions of a rotating blade induced by the crack breathing is yet not clear. This paper proposes a radial-bending-torsional dynamic model of rotating blade with breathing crack. A time-varying integration method is proposed for determining the crack state based on the strain energy release rate. The crack breathing behavior is described by Boolean operation and the numerical integration are applied to open or close the crack. The model is validated through modal analysis, vibration responses and contact state of crack surface. Frequency veering is changed between the 2nd flap and 1st edgewise frequency due to the existence of crack. Strong nonlinear behaviors are found in the radial and torsional vibrations because of the crack breathing. Nonlinearities are also found in the combined vibrations between the radial-bending and the bending-torsional directions. Radial and torsional vibration amplitude levels can be used as an indication of blade crack failure, but the applicability depends on the absolute response decided by the aerodynamic excitation and resonant vibration. These findings can serve as guidance in crack identification and cracking state monitoring of rotating blades.

Torsional vibration analysis and fuzzy adaptive PID control optimization of underwater vector propulsion shaft systems

To examine the torsional vibration of vector propulsion shaft system (VPSS), a four-degree-of-freedom vibration model of the VPSS is established by concentrated mass approach, and the torsional vibration differential equation of the VPSS is deduced based on the Lagrange approach. The vibration differential equations is addressed numerically applying the Runge-Kutta algorithm to investigate the effect of various working shaft angles β on the free and forced vibration of the VPSS under the excitation conditions. To further reduce the torsional vibration amplitude and avoid fatigue damage of the system, and considering the nonlinear relationship within the system, this study develops a fuzzy adaptive PID approach to control the VPSS. The results show that the maximum torsional vibration amplitude of the VPSS is reduced by more than 70% and the transient response time is shortened by more than 90% with this control approach, which effectively reduces the torsional vibration amplitude of the VPSS and thereby significantly improves the safety performance of the underwater vehicle. This may provide technical references for the vibration control theory of the VPSS as well as engineering applications.

Self-excited force characteristics and flow mechanisms of a 5:1 rectangular cylinder in torsional vortex-induced vibration and flutter

In this paper, the self-excited force characteristics, flow rules and vibration mechanisms of a 5:1 rectangular cylinder in torsional vortex-induced vibration (VIV) and flutter were investigated through wind tunnel tests and numerical simulations. The nonlinearity of the self-excited lifting moment is not monotonous but exhibits a peak within a specific reduced wind speed and amplitude range. The amplitude-dependent characteristics of dimensionless work and aerodynamic damping are the primary reasons for non-divergent vibration, which is mainly influenced by the amplitude-dependent phase difference. The reduced wind speed significantly affects the formation zone length and convection speed of the leading-edge vortex, thereby determining the distribution of surface pressure phase difference and dimensionless work. As the reduced wind speed increases, there is a positive and negative alternation in dimensionless work, leading to the occurrence of torsional VIV and flutter. While the torsional amplitude does not affect the distribution of phase difference, it merely influences the formation zone length, resulting in amplitude-dependent dimensionless work and accounting for the non-divergent vibration. The characteristics of vortex convection, pressure phase variation and dimensionless work of the 5:1 rectangular cylinder in torsional VIV and flutter follow similar rules, indicating that the two vibration forms share the same inherent essence.

Optimized design of silicone oil torsional damper for diesel generator

Abstract Due to the high cylinder pressure and high-performance requirements, the silicone oil damper of an inline six-cylinder diesel generator needs to be optimized to reduce the crankshaft stress. The centralized mass method was used to simplify the crankshaft system. A multi-body dynamic model was established, and the crankshaft stress and torsional vibration amplitude were simulated. The results show that the excessive shear stress at generator crank pin 5 is due to the resonance between the first-order intrinsic frequency of the shaft system and the 3rd harmonic torsional vibration. The shear stress was analyzed for different damper thicknesses and stiffnesses, and it was found that the shear stress at crank pin 5 was minimized when the damper thickness was 60 mm and the torsional stiffness was 250,000 N·m/rad. The torsional amplitudes at different speeds and frequencies were measured in the bench test, and the results were consistent with the calculations. The designed silicone oil torsional damper meets the requirements of the 2000-hour bench test.

Study on heat dissipation of torsional vibration damper for engine crankshaft

Abstract High temperatures in torsional vibration dampers can cause silicone oil to fail, increasing crankshaft vibration and shortening component fatigue life. Accurate prediction of the damper temperature field is key to the manufacture of highly reliable torsional vibration dampers. This study establishes the relationship between temperature, torsional vibration amplitude, silicone oil viscosity, rotational speed, housing and inertia ring clearance, and heat generation power based on Comsol. A bench test was carried out on a 6-cylinder inline diesel engine. The simulated temperature profile matched the tested result in terms of trend and relative value, and the established model could accurately predict the temperature field of the engine crankshaft torsional vibration damper.

Koopman mode analysis on discovering distributed energy transfer of post-transient flutter of a bluff body

The flutter response of a rectangular cylinder model with an aspect ratio of 5 is investigated by direct numerical simulation for various Reynolds numbers (Re) and flow angles of attack (α). The results show that the lower α and Re, the larger the torsional amplitude at the critical reduced flow velocity (Ur) corresponding to the occurrence of flutter. High-order Koopman mode analysis method (HOKM) was developed to synchronously capture the inherent flow and structural modes. The element-mode-based energy transfer between cylinders and flow modes was used to reveal the underlying mechanism. HOKM analysis shows that only odd-order modes contribute to the occurrence of flutter, with an augmentation in Ur enhancing this phenomenon. By analyzing the work done in odd-order modes, it is found that the primary mode always occupies the main contribution to the work done. The leading-edge endpoint portion is always where the maximum work is done. An escalation in Re and α notably influences both the spatially relevant part (WΦ) and the temporally relevant part (Wc), while an increase in Ur predominantly impacts WΦ. This study offers universal guidance on the safety and protection of ocean engineering structures and flow control strategies.

Cutting Performance of a Longitudinal and Torsional Ultrasonic Vibration Tool in Milling of Inconel 718

Inconel 718 has excellent thermal and chemical properties and is widely used in the manufacture of aerospace parts; however, there are some problems in the machining of Inconel 718, such as a large milling force, serious tool wear, and poor surface quality. In this research, a type of longitudinal–torsional ultrasonic milling (LTUM) tool is designed based on theoretical computations and FEM simulation analysis. To verify the design rationality of the developed LTUM tool, milling experiments are performed. It is verified that the LTUM tool can realize an elliptical vibration path at the tool tip. The resonance frequency of the tool is 21.32 kHz, the longitudinal amplitude is 6.8 µm, and the torsional amplitude is 1.4 µm. In the milling of Inconel 718, the experimental data of LTUM are compared with those of conventional milling (CM). The comparative experiments show that the LTUM tool can effectively lessen the milling force and tool wear in the milling of Inconel 718, improve the surface quality, inhibit the generation of burrs, and improve the chip breaking ability. The application potential of the LTUM tool in high-performance milling of Inconel 718 parts is proven.

Experimental study of wind-field characteristics and torsional vortex-induced vibrations for a split three-box deck sitting above water waves

The wind-field characteristics of a split three-box deck sitting above water waves and its torsional vortex-induced vibrations (VIVs) were experimentally investigated using wind-tunnel and wave-flume tests. The wind field was measured using turbulent flow instrumentation (TFI) Cobra probe. To test the VIVs of the split three-box deck, a test system that could elastically suspend the deck sectional model by eight springs and guarantee free oscillation of the deck sectional model only in the heaving and torsional directions was constructed. The test results indicated that the regular wave height (H) and regular wave period (T) mainly promoted the overall turbulence-intensity (Iuvw) and turbulence-intensity component (Iw). These contributions were further strengthened by an increase in H and a decrease in T, respectively. In general, the variations in Iuvw and Iw, particularly the latter, should be regarded as the major cause of the change in the maximum torsional VIV amplitudes of the deck sectional model with a scale ratio of 1:60 when compared to the mean local wind speed (U) and wind-speed component (w). The differences in these amplitudes under different cases in the first lock-in regions were not evident, whereas those in the second lock-in regions were significant. In the second regions, the smaller the relative bridge clearance (a/H), the smaller the maximum torsional VIV amplitudes, and the maximum torsional VIV amplitudes increased with T, which were all smaller than those in the corresponding wind-only case. Moreover, the larger the bridge clearance (a), the larger the maximum torsional VIV amplitudes in the wind-only cases (a = 0.30, 0.42, 0.50, and 0.58 m). Evidently, the presence of water waves is conducive to the suppression of torsional VIVs of the split three-box deck when VIVs occur.

Full-Scale Observations for the Combined Wind-Induced Responses of a Cylindrical Tower

This paper presents full-scale observations of wind-induced vibrations on a 140[Formula: see text]m high cylindrical reinforced concrete tower under non-stationary and strong wind conditions. The vibration responses of the tower in two planar orthogonal axes and rotation, in conjunction with wind speed and direction data, have been utilized to extract the response characteristics. The primary focus is on discussing the correlation of wind-induced responses in three components: Along-wind, across-wind, and torsion. Throughout the varying levels of oscillation, the tower’s responses clearly exhibit correlations among these components. The correlation coefficients between along-wind and across-wind responses, as well as along-wind and torsional responses, remain negligible across the entire dataset. In contrast, during intense oscillations, there is a near-perfect correlation between the across-wind and torsional responses. Furthermore, the probability density functions (PDFs) of the response components under strong wind conditions significantly deviate from the Gaussian distribution and closely resemble the Cauchy distribution. The joint PDFs also indicate that the along-wind response is statistically independent of the other response components, while the across-wind response correlates well with the torsion, as indicated by the non-Gaussian distribution. This paper also includes distinct observations regarding dominant oscillating frequencies, torsional amplitudes, and vertical vibration amplitudes. The importance of this research lies in its examination of the relationship between different response components, a crucial aspect in understanding how structures behave under wind loading. By emphasizing the need for full-scale measurements, this study aims to provide valuable validation for previous theoretical and experimental research findings.

The strain ratio-dependent multiaxial low cycle fatigue behaviour and life prediction of 316L stainless steel based on critical plane at elevated temperature

The study mainly investigates the effect of strain ratio on the multiaxial low cycle fatigue behaviour of 316L at 550 °C. The evolution of both axial and torsional stress amplitude is observed to go through three stages: cyclic hardening, softening and fracture. What's different is that the torsional loading experiences fewer cyclic hardening cycles compared to the axial loading. Regarding the interaction between axial and torsional stresses, it is observed that as the torsional strain increases, the axial deformation response presents a lower peak stress and a higher softening rate, while the torsional peak stress and softening rate hardly changes with the increase of axial strain amplitude. The fracture pattern is obtained through three-dimensional (3D) depth-of-field observation. It is discovered that as the strain ratio increases, the fracture pattern transits from tensile failure mode to shear failure mode. Furthermore, the orientation angle of the fracture surface increases and lies between the critical plane angle of maximum shear strain and maximum normal strain, indicating a mixed failure mode. Additionally, a comparison of nine representative critical plane models reveals that the energy-based models can better predict the multiaxial fatigue life influenced by the strain ratio. Finally, based on the analysis of deformation and failure mechanisms, a normal damage parameter weakening factor (NDWF) is introduced into the KBM-R model, and an improved normal stress component (INSC) is introduced into the Wu-R model. The two modified models well capture the impact of strain ratio and accurately predict the multiaxial fatigue life of both 316L and P92 steel.

Ultrasonic complex vibration source equipped with a step horn with a welding tip and its welding characteristics

We have developed a different type of ultrasonic complex vibration source that can generate planar vibrations. The ultrasonic complex vibration source is equipped with a step horn with a hollow part that incorporates a welding chip to improve practicality for industrial applications. The hollow portion in the step horn attached to the ultrasonic complex vibration source enables the adjustment of the longitudinal and torsional vibration amplitude. In this work, we performed finite element method analysis to develop the ultrasonic complex vibration source equipped with a step horn containing a hollow part and a welding tip. The ultrasonic complex vibration source was manufactured and the vibration characteristics and welding properties were measured. The same welding strength was obtained under similar experimental conditions to conventional ultrasonic complex vibration sources. Our results demonstrate that ultrasonic complex vibration sources can be miniaturized and are practically useful.

Study on the Vortex‐Induced Vibration Performance of the LSOB Girder of a Valley‐Crossing Suspensions Bridge

The lower semi‐open box (LSOB) girder is widely used in large‐span bridges due to its favorable stress performance and cost‐effectiveness. The vortex‐induced vibration (VIV) of the LSOB girder was studied by using a 1:55 section model wind tunnel test. The test results show that there are obvious vertical and torsional VIV intervals with significant amplitudes at each angle of attack with the damping ratios of about 0.35%. The CFD numerical simulations indicate that VIVs of LSOB girders are mainly induced by two types of vortices: one at the inclined webs of leeward wind nozzles and another at the upstream upper surfaces of the deck. Conventional aerodynamic vibration suppression measures, such as the lower central stabilizing plate and the guide vane at the gantry rail, demonstrate that the lower central stabilizing plate can reduce the VIV response at all wind angles of attack, decreasing vertical amplitude by 40%–50% and torsional amplitude by 10%–25%. Although adding a guide vane further optimizes the VIV performance, its effect is limited. Installing the lower central stabilizing plate helps redistribute vortices below the girder, transforming large vortices into smaller ones, most of which do not detach, thereby reducing vortex shedding intensity in the wake area. The bilateral guide vanes at the maintenance car track further weaken the wake vortices at the diagonal webs on the leeward side.

Multi-band Torsional Vibration Amplitude Demodulation for Planetary Gearbox Fault Diagnosis under Time–varying Speed Conditions

Multi-band Torsional Vibration Amplitude Demodulation for Planetary Gearbox Fault Diagnosis under Time–varying Speed Conditions

Investigation on carbon fiber fracture mechanism of honeycomb composites in longitudinal‐torsional ultrasonic‐assisted milling processes

AbstractA multi‐edge micro‐tooth longitudinal‐torsional ultrasonic‐assisted milling (LTUAM) model was established based on the hard brittle characteristics of carbon fiber honeycomb composites and the weak strength characteristics of the hole wall interface. The study analyzed the effects of ultrasonic characterization parameters on the cutting force, honeycomb wall width, and surface morphology. The results indicate that using LTUAM significantly reduced the cutting force and decreased the length and height of the burrs at an appropriate ultrasound amplitude. The spindle speed had the least impact on the width of the honeycomb wall, but increased with the longitudinal‐torsional ultrasonic amplitude and feed rate. The maximum error between the simulated and experimental cutting force values was approximately 19%. The longitudinal amplitude and torsional amplitude were 3 and 5 μm, respectively, the length of burrs decreased by 52.7%, and there was less delamination and tearing damage. LTUAM proved to be beneficial in improving cutting performance. Compared with conventional milling (CM), LTUAM resulted in regular fiber fracture morphology and smaller fragments on the honeycomb surface. In addition, the high‐frequency ultrasonic vibration promoted carbon fiber fracture and the surface roughness value under LTUAM was approximately 36.72% smaller than that of CM.Highlights Ultrasonic milling mechanism of carbon honeycomb is studied. Kinematic simulation of the tool of carbon honeycomb was studied during LTUAM. LTUAM promotes the fracture of carbon fibers. A multi‐edge micro‐tooth LTUAM model was established of carbon honeycomb. Deformation of the cell wall can be avoided by ultrasonic vibration of the cutter.

Adaptation of the Facchinetti, de Langre and Biolley model for the hydroelastic vortex-induced vibrations of a cantilevered flat plate

This paper examines the ability of coupled system models, derived from the Facchinetti, de Langre and Biolley model, to fit the vortex-induced vibrations observed on a cantilevered rectangular flat plate, with zero angle of attack, in a hydrodynamic tunnel. Two VIV areas have been scrutinized. The first one for 0.6×105≤Re≤105 and the second one for 4.5×105≤Re≤7×105 where two distinct hydrodynamic excitation mechanisms, characterized by two Strouhal numbers, successively lock the first bending and first torsional mode of the plate respectively. For the bending VIV, exhibiting weak fluid–structure coupling, good results were obtained using a hybrid model for which a structure oscillator forced at ωv1=2πSt1U/D is coupled with a wake oscillator associated to the second Strouhal number. Regarding the torsional VIV, amplitude response and successive frequency lock-in have been satisfactorily reproduced using a structure oscillator (in rotation) coupled with two distinct wake oscillators.