Sine Sweep Test Research Articles

Data-driven modeling and analysis of nonlinear isolated mechanical system

This study aims to identify nonlinearities in the stiffness and damping characteristics of a passive pneumatic isolator connected to an ultra-precision manufacturing prototype in the uncoupled transverse and horizontal directions. Experimental data are collected using sine sweep tests and is used to plot nonlinear frequency response functions. The resulting analysis reveals a quadratic polynomial relationship between the equivalent stiffness and the system’s dynamic response, indicating a combination of quadratic and cubic nonlinearity. Similarly, the nonlinear damping characteristic is determined using the half-power bandwidth method, which exhibits a quadratic polynomial relationship between the equivalent damping and dynamic response. The linear stability analysis of the system for the identified nonlinear stiffness and damping characteristics reveals that the system remains linearly stable for the given range of frequency and excitation amplitudes. Furthermore, bifurcation analysis reveals the existence of complex solutions, such as period-2 and period-4 solutions, for higher excitation amplitudes.

Development of a Magnetic Levitation Wafer Handling Robot Transfer System with High-Accuracy and High-Cleanliness: Experimental Evaluation

Magnetic levitation can reduce particulate contamination that occurs during wafer transportation in the semiconductor manufacturing process. This technology radically eliminates contact between the wafer and the transport system, reducing friction, wear, and particle generation. Therefore, it is suitable for achieving high cleanliness in the ultra-fine line-width semiconductor production process and solving the need for particle removal in a vacuum environment. In this study, the roller and linear motion guide components of the wafer transfer system were replaced with a magnetic levitation module, and a robot arm was installed on top to transport a single wafer. A posture controller and a current controller were designed, and test equipment simulating the wafer transfer system was also manufactured and tested. Regarding mover and system identification, a sine sweep test was performed on the motion axis of the five degrees of freedom. Through the obtained system identification, it was possible to design the posture controller more precisely. Moreover, through levitation in standstill experiments and high-speed operation experiments, the wafer transport system can be used to verify dust-free high-speed transport and accurate positioning performance.

Passive Damping of Solar Array Vibrations Using Hyperelastic Shape Memory Alloy with Multilayered Viscous Lamina

A novel passive vibration-damping device is proposed and investigated for a large deployable solar array. One strategy for achieving high damping in a solar panel is using a yoke structure comprising a hyperelastic shape memory alloy and multiple viscous adhesive layers of acrylic tape. The effectiveness of the proposed system in achieving a high damping performance was demonstrated by conducting free vibration and low-level sine sweep tests using a solar array, and a 0.75-m-long flexible dummy structure was simulated. We also investigated the dependence of the damping performance of the proposed structure on the number of viscous lamina layers. Finally, the damping characteristics of the proposed system were assessed under predictable on-orbit temperature conditions.

Numerical investigation on suppression effect of movable part with spring system

Liquid sloshing in the tank not only affects the movement of the carrier, but also easily causes structural fatigue, or even structural damage. How to effectively suppress sloshing is one of the most important issues in naval architecture and ocean engineering. In this paper, an anti-sloshing method with a movable vertical part and spring system is presented. Based on CFD and FEM, sloshing states and displacements of the movable part at different spring stiffness are numerically studied, in order to investigate dynamic response characteristics of the fluid-structure coupling system formed by the tank-fluid-part. The results illustrate that the movable part with appropriate spring stiffness can suppress the sloshing more effectively than fixed part. By analysis of the relationship between sloshing liquid movement and the part displacement, phase difference between the part displacement and the wave elevation is found to be suitable to estimate the appropriate spring stiffness of the movable part under different conditions. In addition, numerical results of free decay tests and sine sweep tests illustrate that the movable part with appropriate spring stiffness can also shift the natural frequency of the tank-fluid-part system.

Experimental chatter process stability using end milling process on Al6061 alloy with multiple bearing span conditions

An end milling process's chatter stability analysis is complicated due to a lack of exact information of the spindle's geometrical design, the location of the bearings, and other spindle structural concerns. Self-excited chatter vibrations can only be studied with an exact transfer function in the most flexible area of the spindle tool structure, which an efficient spindle needs design. A new approach for assessing spindle vibration responses using sine sweep tests for a CNC end milling machine tool is the topic of this research. When the bearing span is considered as a design variable, the spindle's analytical model may be approximated. There are several trial runs until the model and experiment transfer functions agree. To obtain the process stability, the time varying forces are evaluated at the different cutting conditions.

Effect of Heat Treatment on the Vibration Isolation Performance of Axially Symmetric NiTi Wire Mesh Damper

In this paper, superelastic (SE) NiTi wire is used to fabricate axially symmetric wire mesh dampers (WMDs) with the expectation of a higher damping capacity. However, the phase transformation damping of the NiTi WMD could be suppressed by the cold-work-induced dislocation. Therefore, the NiTi WMDs were heat-treated and then tested by a hydraulic universal testing machine. The NiTi WMD is found to achieve higher damping capacity when heat-treated at 200 °C. However, the WMD heat-treated at 250 °C suffers from a sharp decline in the loss factor in exchange for an improvement in the stiffness. The sine sweep test was then conducted to examine the dependency of the WMD’s vibration isolation performance upon the heat treatment temperature and the excitation acceleration. The NiTi WMD outperforms the 304 stainless steel (SS 304) WMD in damping capacity only when the excitation acceleration magnitude is less than 1.5 g. The stiffness of NiTi WMD can be improved without significantly compromising its damping capacity by heat treatment at 200 °C for 30 min. The present work carries out comprehensive measurements of the NiTi WMD’s response to dynamic mechanical test and sine sweep test and addresses how heat treatment influences the stiffness and damping capacity of the SE NiTi WMD.

Measuring nonlinearities of a cantilever beam using a low-cost efficient wireless intelligent sensor for strain (LEWIS-S)

In the context of experimental vibration data, strain gauges can obtain linear and nonlinear dynamic measurements. However, measuring strain can be disincentivizing and expensive due to the complexity of data acquisition systems, lack of portability, and high costs. This research introduces the use of a low-cost efficient wireless intelligent sensor for strain (LEWIS-S) that is based on a portable-sensor-design platform that streamlines strain sensing. The softening behavior of a cantilever beam with geometric and inertial nonlinearities is characterized by the LEWIS-S based on high force level inputs. Two experiments were performed on a nonlinear cantilever beam with measurements obtained by the LEWIS-S sensor and an accelerometer. First, a sine sweep test was performed through the fundamental resonance of the system, then a ring-down test was performed from a large initial static deformation. Good agreement was revealed in quantities of interest such as frequency response functions, the continuous wavelet transforms, and softening behavior in the backbone curves.

Nonlinear system identification framework of folding fins with freeplay using backbone curves

Due to wear and manufacturing tolerance, the freeplay is unavoidable in the hinges of folding fins, which exerts significant effects on the aerodynamic characteristics. This paper proposes a backbone-curve-based framework for the dynamical identification of folding fins containing the freeplay nonlinearity. With no need to measure the input force signal and the response signals of nonlinear related Degrees of Freedom (DOFs), the proposed method is more direct and elegant than most existing nonlinear identification approaches, and it contains three steps: Firstly, the underlying linear model of the folding fin structure is obtained through the modal test on its linear sub-parts, and then, the harmonic approximation solves the analytical expressions of the backbone curves of measurable DOFs. Secondly, response data measured from the sine-sweep test are used to extract the fitting points of backbone curves for these DOFs. Finally, the curve fitting approach is applied to identify the freeplay parameters. A series of numerical experiments verify the effectiveness of the proposed method. A real-life folding fin structure is also employed to illustrate how the method can be applied. These examples demonstrate that the identification framework can give an accurate dynamic model of the folding fin structure.

An experimental study on dynamic behaviour of a sandwich beam with 3D printed hexagonal honeycomb core filled with magnetorheological elastomer (MRE)

Sandwich beams with an aluminium face sheet and a magnetorheological elastomer (MRE) of varying proportions of elastomer and magnetic particles (weight to weight)% filled in a honeycomb core of Nylon and Resin8000 are manufactured and experimentally analysed in this study. To evaluate the dynamic properties of sandwich beams, manufactured structures subjected to sine sweep and classic shock tests and assessed both with and without magnetic field of varying intensities applied on the free end of the beam. The experimental results demonstrated good performance in vibration level attenuation, particularly in the structure’s primary vibration mode under consideration. The magnetic field applied was capable of lowering the first natural frequency of the proposed sandwich beam structures. Experiment results showed that an increase in an induced magnetic field shifted the natural frequencies, vibration amplitude, and damping ratio of sandwich panels with MRE honeycomb core.

Design of Open-Ended Structure Wideband PCB Rogowski Coil Based on New Winding Method

Compared with the traditional Rogowski coil, printed circuit board (PCB) Rogowski coil has the advantages of high measurement accuracy, simple manufacturing process and low cost. It has become an important device in current measurement. However, the existing PCB Rogowski coils are mostly closed, and the open-ended structure PCB Rogowski coils are susceptible to external magnetic field interference. This paper proposes an open-ended structure PCB Rogowski coil based on a new winding method, so that the two open-ended PCB Rogowski coils are evenly distributed when closed, while improving the coil’s immunity to external magnetic fields based on the winding method of equal area of the de-wired and loop. In addition, this paper uses the hybrid integration circuit and the back-end matching method to achieve the broadband measurement performance of the sensor. Finally, the experimental results show that the mutual inductance difference between the closed and open-ended structure PCB Rogowski coil is less than 0.5% under the same wiring mode. Under the equivalent current interference at 50 mm from the measured current, the maximum interference coefficient of the open-ended structure coil is 1.45%; in sine sweep and pulse current test conditions, the frequency band is 34 Hz–3.5 MHz.

Experimental investigation of dynamic vibration absorption to design an improved particle damper

We introduce a tuned particle damper (TPD) to improve the damping performance of the traditional particle damper by adding a dynamic vibration absorption structure. To better design a TPD as a dynamic vibration absorber (DVA), we changed the dynamics of a DVA system based on a primary cantilever system by introducing stainless steel balls and a carbon steel mass block. Using a series of sine-sweep tests on the primary cantilever system attached with a spring-mass system, we obtained frequency response function (FRF) curves under different conditions. Our experimental results show that the dynamic behavior of the primary cantilever system was more prominent on the resonance peak closer to the mass control area, whereas the dynamic behavior of the additional spring-mass system is more prominent on the resonance peak closer to the stiffness control area. Based on these results, we analyzed the abnormal but desirable dynamic characteristics of TPD presented in the discrete mass experiment, and the results indicates preliminary success with our design of a TPD.

A Nonlinear Model and Parameter Identification Method for Rubber Isolators under Shock Excitation in Underwater Vehicles

Rubber isolators are usually used to protect high-precision equipment of autonomous underwater vehicles (AUVs), avoiding damage from overlarge dynamic excitation. Considering the nonlinear properties of the rubber material, the nonlinear behavior of rubber isolators under shock exaltation is hard to be predict accurately without the available modal and accurate parameters. In view of this, the present study proposes a nonlinear model and parameter identification method of rubber isolators to present their transient responses under shock excitation. First, a nonlinear model of rubber isolators is introduced for simulating their amplitude and frequency-dependent deformation under shock excitation. A corresponding dynamic equation of the isolation system is proposed and analytically solved by the Newmark method and the Newton-arithmetic mean method. Secondly, a multilayer feed-forward neural network (MFFNN) is constructed with the current model to search the parameters, in which the differences between the estimated and tested responses are minimized. The sine-sweep and drop test are planned with MFFNN to build the parameter identification process of rubber isolators. Then, a T-shaped isolator composed of high-damping silicon rubber is selected as a sample, and its parameters were determined by the current identification process. The transient responses of the isolation system are reconstructed by the current mode with the identified parameter, which show good agreement with measured responses. The accuracy of the proposed model and parameter identification method is proved. Finally, the errors between the reconstructed responses and tested responses are analyzed, and the main mode of energy attenuation in the rubber isolator is discussed in order to provide an inside view of the current model.

Theoretical and experimental analysis of an electromagnetic seismic isolation system

A near-fault (NF) ground motion with a strong velocity pulse component can induce considerable base displacement and structural acceleration in a base-isolated structure. Conventional viscous dampers are typically used to reduce the excessive responses of a seismic base-isolated system. It is generally recognized that the manufacturing tolerance requirements and costs of a long-stroke damper are higher than those of a typical viscous damper due to the buckling criterion. Thus, to satisfy the large stroke and high damping requirements of isolation systems in NF regions, an electromagnetic seismic isolation system (EMSIS) were developed in this study. The rotational electromagnetic (EM) damper addresses the stroke limitation. The mathematical model and theoretical formulas of the EMSIS were first established. Next, a prototype EMSIS was manufactured and its performance was validated using a shaking table apparatus. The equivalent EM damping ratio of the EMSIS was calibrated using a series of sine sweep tests. The test results indicated that each EM damper could provide a damping force proportional to the relative velocity of its two ends. Thus, the EM damper behaved as a linear viscous damper, which is suitable for seismic isolation systems. Finally, the EMSIS was subjected to both NF and far-field (FF) ground motions. The theoretical results were in agreement with the experimental findings. The shaking table test results revealed that the EM damper can effectively mitigate the displacement and acceleration responses of the developed isolation system under NF ground motions.

Model updating of a scaled piping system and vibration attenuation via locally resonant bandgap formation

This study presents a Finite Element (FE) model updating methodology of a piping system and demonstrates vibration attenuation at its resonant frequencies using tuned local resonators distributed along its length. An experimental laboratory scaled version of a prototype piping system inspired from existing piping structures in the oil and gas industry is assembled to study its dynamic behavior under laboratory conditions. A dynamic structural similitude analysis is carried out to derive scaling factors for frequencies and mode shapes between the prototype and scaled piping systems. These scaling factors are verified with the aid of both detailed and reduced-order FE models. Experimental natural frequencies and mode shapes are obtained based on the impact hammer modal test and the forced vibration sine sweep test and then compared with numerical results. Discrepancies between measured and computed results due to uncertainties in the FE model necessitate the use of an FE model updating technique to minimize the error between the predicted and the measured response. This updating strategy is carried out by iteratively adjusting parameters associated with the assumed boundary conditions until a relatively faithful computational model that can replicate the actual behavior of the structure is obtained. The updated reduced order model is then used to investigate the creation of locally resonant bandgaps centered at the first three resonant frequencies of the structure by embedding tuned resonant cantilever beams with tip masses along the length of the piping system. Using a harmonic response analysis, it is shown that an attenuation is obtained at all considered target frequencies with distinct edge frequencies appearing in the frequency response for the third mode of vibration.

Constrained layer damping treatment of a model support sting

In transonic wind tunnel tests, the pulsating airflow is prone to induce the first order resonance of the sting support system. The resonance limits the wind tunnel test envelope, makes the test data inaccurate, and brings potential security risks. In this paper, a model support sting with constrained layer damping (CLD) treatment is proposed to reduce the first order resonance response. The CLD treatment mainly consists of material selection and geometric optimization processes. The damping performance of the optimized CLD sting is compared with an AISI 1045 steel sting with the identical diameter in laboratory. The frequency response curves of the CLD sting support system and the AISI 1045 steel sting support system are obtained by sine sweep tests. The test results show that the first order resonance response of the CLD sting support system is 37.3% of that of the AISI 1045 steel sting support system. The first order damping ratios are calculated from the frequency response curves by half power point method. It is found that the first order damping ratio of the CLD sting support system is approximately 2.6 times that of the AISI 1045 steel sting support system.

Design and Signal Delay Analysis of Spinning Missile Electric Rudder Control System

In order to meet the requirements of ultra-small special-purpose missiles for miniaturization, high dynamic characteristics and low signal delay of the missile-mounted rudder, and to reduce the working pressure of the navigation computer control system, a digital electric rudder control system based on MCU and H-bridge integrated power drive chip was designed and implemented. The system uses the Texas Instruments C2000 high-performance MCU as the core control unit to process the single-channel rudder position feedback signal. After the fuzzy position PID algorithm calculation, the control signal is output in the form of pulse width modulation (PWM) waveform, and the rudder control is completed by the DRV8872 power drive chip. Aiming at the problem of phase delay in missile attitude control system, the reason of delay is analyzed from the perspective of system composition. The phase delay formula is derived through theoretical calculation and sine sweep test. A method based on navigation computer deviation compensation is proposed. It has been proved by experiments that the rudder control system has good dynamic response capability and has good compensation effect on system signal delay.

Free and Forced Vibration Characteristics of a Flax Fibre Reinforced Composite Beam with Viscoelastic Core

Abstract In this study, free and forced vibration characteristics of a flax fibre reinforced composite beam with a viscoelastic core have been investigated using theoretical and experimental approaches. The theoretical approach involves finite element method incorporating layerwise modelling considering classical laminate theory for top and bottom composite face sheets. The transverse displacement field is assumed to be same for all the layers, whereas the axial displacement field for the viscoelastic core is linearly interpolated in terms of the displacements of the two face sheets. Natural Frequencies of the beam in cantilever configuration and transient response of the tip of the beam subjected to base harmonic excitation have been determined under the theoretical approach. The experimental approach involves sine sweep testing and base excitation testing for determination of natural frequencies and transient response of the tip respectively and the tests have been done using an electrodynamic shaker. The results obtained from both the approaches agree closely with each other and illustrate the effect of introduction of viscoelastic core in the natural fibre reinforced composite beam.

Development of two-dimensional piezoelectric laser scanner with large steering angle and fast response characteristics.

We describe a two-dimensional piezoelectric laser scanner designed and tested to obtain a large steering angle of 1° and fast response characteristics of 200 Hz. To overcome the relatively small expansion capability of piezoelectric actuators, the displacement amplification mechanisms with two levers in series are employed to magnify the end tip of the lever which is connected to a 0.5-in. glass mirror. For fast response characteristics, the natural frequencies of the hinge mechanisms were calculated by using the finite element analysis technique. In order to evaluate the performance of the proposed scanner, the hinge mechanism has been manufactured of titanium alloy and the natural frequencies of the hinge mechanism have been measured by sine sweep test. Also, the actual machining test on the burning paper has been done by using a high power laser, and it is shown that the proposed laser scanner is capable of steering the laser beam 1° with a frequency of 200 Hz.

Full-Scale Experimental and Numerical Investigations on the Modal Parameters of a Single-Span Steel-Frame Footbridge

In this work, an examination on the modal properties of a single-span steel-frame footbridge is presented. The footbridge is situated in Jawornik (Lesser Poland). The footbridge is symmetrical since its main structure consists of two steel frames of the same shape. The boundary conditions for both frames are the same as well. The study was completed on the basis of numerical as well as experimental investigations. For finite element (FE) analysis, a 3-D model of the single-span steel-frame footbridge was created. For the experimental study, a research scheme for in situ tests was developed. Three kinds of excitation techniques were used during the in situ tests: shock excitation, operational vibration, and slow sine sweep testing. Different functions that estimate natural frequencies, i.e., the power spectral density function (PSD) and the frequency response function (FRF), were applied. The modal assurance criterion (MAC) was used as a mathematical tool for the verification of the mode shapes of natural vibrations obtained in experimental and numerical ways. Good compatibility was recognized between the results obtained for experimental and numerical procedures in terms of both the natural frequency and the mode of vibration. The identified and verified values of the five consecutive natural frequencies of the footbridge were smaller than 5 Hz, but they were recognized as being located outside the frequency range defined as having “maximum risk of resonance”. The numerical and experimental modal analysis revealed that all modes corresponding to the natural frequencies from the 0–5 Hz range have both a symmetrical and an anti-symmetrical nature. In particular, the first vertical mode, which can play a central role from the serviceability of the footbridge point of view has a symmetrical shape. The results of the research might be applicable to the dynamic study of the structure type considered in the analysis, i.e., for the dynamic assessment of a single-span steel-frame footbridge with a relatively large mass as well as stiffness. The investigation proved that ambient vibration modal experiments are enough for the experimental investigation of the modal properties of the structure.

Sine-Sweep qualification test for engine components: The choice of simulation technique

Most of mechanical components, especially those belonging to aerospace sector, vehicles and, in particular, the automotive sector need an experimental qualification phase aimed to determine both their functionalities and their structural strength. Regarding the structural strength, the tests most commonly required by regulatory standards and typically performed belong to two categories, so similar as different: Sine-Sweep test and Random test. The present work is part of a consolidated research topic aimed to develop design techniques making them as much simpler and faster as possible in order to reduce product development times up to the virtual verification of test conditions. In particular, the present work is aimed to propose a frequency domain methodology for dynamic simulation and evaluation of the fatigue behavior for Sine-Sweep test, comparing it with the time domain technique that is considered as reference. The activity carried out in collaboration with a well-known automotive industry (HPE-COXA S.p.A.) verified these methodologies on a test case proposed by the company itself, i.e. the qualification of a set of supplying pipe of a high performance engine. The comparison between the time domain approach and the proposed approach in frequency domain certifies the extreme reliability of the latter as well as the advantages it offers to the designer in terms of computational times that results to be extremely reduced. The activity then created the prerequisites for the development of future research activities aimed to reduce calculation times as much as possible making such calculation tools of easily accessible to the industrial community.