Energy Ratio Coefficient Research Articles

Rotating machinery fault diagnosis based on parameter-optimized variational mode decomposition

Variational Mode Decomposition (VMD) has been widely applied in rotating machinery fault diagnosis. However, VMD needs to solve two key problems in its application: parameter optimization and the selection of high-quality Intrinsic Mode Functions (IMFs). To address these issues, firstly, the Sparrow Search Algorithm (SSA) is employed to optimize VMD parameters, incorporating fitness functions based on the Hoyer measure and the square envelope spectrum negative entropy. Subsequently, by minimizing the fitness function, optimal parameters for VMD are obtained. Secondly, a novel IMF selection method is proposed, evaluating IMF quality through sample entropy, energy ratio, and Spearman rank correlation coefficient to identify IMFs sensitive to fault features. Finally, the proposed method is validated using gear and bearing datasets containing noise of varying intensities, demonstrating its outstanding capability for extracting sensitive information in different noise environments.

Plane wave reflection in micropolar hygro-thermoelastic half-space

The research problem aims to investigate the effect of heat and moisture on the propagation of plane waves in a micropolar hygro-thermoelastic medium. The governing equations of a hygro-thermoelastic micropolar medium are developed and solved to determine the velocity equation. The plane-wave solution reveals that the medium is propagated by two coupled transverse displacement waves, namely Coupled Transverse Micropolar wave (CTM-wave) and Coupled Transverse Displacement wave (CTD-wave). Additionally, three coupled longitudinal waves are observed: thermal diffusion TD-wave, longitudinal displacement P-wave, and moisture diffusion mD-wave. To assess the characteristics of these waves in the micropolar hygrothermal medium, the speed and distance of propagation are calculated for each wave type. This analysis provides information on how fast and how far the P-wave, TD-wave, mD-wave, CTM-wave, and CTD-wave can travel in the medium. Furthermore, the research problem determines the equations for the coefficient of reflection and energy ratio when a coupled plane wave is incident on the medium. These coefficients quantify the amount of reflected energy compared to the incident energy and provide insights into the wave behavior at the interface of the medium. Finally, the variations in energy ratio and reflection coefficient are depicted graphically, allowing for a visual representation of how these quantities change with different parameters or conditions. These graphs provide a comprehensive understanding of the wave behavior and the effects of heat and moisture on the propagation characteristics in the micropolar hygrothermal medium.

Vibration energy accumulation and absorption characteristics of pseudo acoustic black hole wedge

The Acoustic Black Hole (ABH) is an effective structure for harvesting and dissipating energy from flexural waves. It works by reducing the thickness of the ABH wedge in a power law relationship with m ≥ 2, which rapidly decreases the local phase velocity of flexural waves and leads to an energy convergence effect. However, the vibration performance may differ if the tapered wedge does not meet the requirements of a typical ABH. This article introduces and discusses two types of “pseudo-ABH” wedges: linear-degenerate ABH and step-degenerate ABH. These wedges do not follow the power-law and continuity conditions of typical ABH, respectively. To establish the dynamic models of pseudo-ABH wedges, the lumped-mass transfer matrix method (LTMM) and traveling wave analysis are introduced and validated using analytic solutions of the non-uniform one-dimensional Euler-Bernoulli beam and finite element method. Meanwhile, a good match between the results of the Timoshenko and Euler-Bernoulli beam theory also indicates the correctness of our model. The energy ratio and reflection coefficient are defined to characterize the energy accumulation effect and vibration absorption performance of the pseudo-ABH wedges. The vibration performance of the linear-degenerate ABH is closer to the typical ABH than the step-degenerate ABH. The step-degenerate ABH has more effective energy accumulation and reduction performance for individual frequencies. However, as the number of segments in the step-degenerate ABH increases, its dynamic performance becomes closer to that of the typical ABH. The novelty of this article is to study vibration energy accumulation and absorption characteristics of pseudo acoustic black hole wedges using LTMM model, disclose the differences of linear and step degenerate ABH for their performance, and recommend the step degenerate ABH in place of the typical ABH of a power law thickness relationship.

A Preliminary Fault Detection Methodology for Abnormal Distillation Column Operations Using Acoustic Signals

The fault detection of the chemical equipment operation process is an effective means to ensure safe production. In this study, an acoustic signal processing technique and a k-nearest neighbor (k-NN) classification algorithm were combined to identify the running states of the distillation columns. This method can accurately identify various fluid flow states in distillation columns, including normal and flooding states. First, the acoustic signals were collected under normal and abnormal states in an experimental distillation column. Then, the method of dual-domain feature extraction was used to extract the features such as the energy ratio and linear prediction coefficient (LPC). Moreover, the extracted feature parameters were analyzed and compared in a general way. Finally, the k-NN model was used to classify the acoustic signals. The results show that this method had high identification accuracy and provided an important reference for further research.

Parametric studies and optimal design of the exponents collocation of a segmented acoustic black hole beam

Acoustic black hole (ABH) is a promising way to deal with the flexural vibration of different structures. By utilizing power-law profiles in extremities of structures, ABH could gradually reduce the phase velocity of the propagating flexural waves and realize the capture of waves in the ABH portion. However, it is difficult to manufacture an efficient ABH extremity in practical implementations, and the existence of truncation always leads to greatly reduction of ABH effect at the range of desired frequencies. In this paper, parametric studies of segmented ABH beams have been carried out to investigate how different ABH portions’ exponents affect the vibration attenuation performance of the segmented ABH beam, thus further optimizing the exponents collocation design to get the better ABH effect around the desired frequencies. The detailed meshing scheme has been first studied to guarantee the accuracy of the numerical simulation model. Then, the mobility of different segmented ABH beams with varying exponents collocations are compared to show the influence of power-law exponent changes of the first and second ABH portions on their vibration attenuation performance. Additionally, the energy ratio and reflection coefficient have also been calculated to reveal the underlying physical mechanism. Furthermore, the radial basis function based neural network and simulated annealing method are used to establish the surrogate model and optimize exponents collocation. The optimized segmented ABH beam exhibits more perfect vibration attenuation performance because of possessing lower reflection coefficient. Finally, an experiment has been completed to validate the optimization result.

Three-dimensional numerical investigation of mixed-mode debonding of FRP-concrete interface using a cohesive zone model

• A 3D mixed-mode cohesive zone model of the FRP-concrete interface is proposed. • The mixed-mode damage factor based on the exponential softening relationship is clearly expressed. • The friction in the interface is considered independently by considering the interface sliding. • The simulation results fit well with the experimental ones in different validation cases. • The shear-peeling debonding behavior of the interface with different peeling angles is analyzed particularly. As a low-cost high-performance method for concrete structural reinforcement and repair, the external bonding (EB) of fiber-reinforced polymer (FRP) laminates has gradually become popular. But these FRP-reinforced structures usually fail prematurely due to the interfacial debonding. Thus, the mixed-mode debonding behavior of the FRP-concrete interface by a 3D cohesive zone model (CZM) will be analyzed in this study. The 3D CZM provided a detailed description of interfacial damage propagation and friction-sliding evolution during the whole debonding process. Based on the program coding which implements the proposed CZM, numerical models will be built according to the previous experiments. By comparison, the numerical and experimental results showed a good agreement. Besides, the key parameters, which include peeling angle, strength ratio, energy ratio, and friction coefficient, will also be investigated to assess their effect on the interfacial bond capacity.

Reflection of hygrothermal waves in a Nonlocal Theory of coupled thermo-elasticity

The investigation of the reflection issue in a hygrothermal medium in nonlocal elasticity is the focus of the current research project. The velocity equation is created by formulating and solving the governing equations of a hygro-thermoelastic material. The solution for plane waves predicts three incorporated plane waves, including longitudinal displacement, P-wave, thermal diffusion TD-wave and moisture diffusion mD-wave and shear vertical SV wave propagate in the medium. The velocity of P, TD, mD and SV waves are computed for the hygrothermal medium. Expressions for the energy ratio and reflection coefficient are developed for the incidence of a hygrothermal plane wave. The effect of hygrothermal parameters and nonlocal parameter on velocity, the reflection coefficient and energy ratio are displayed on a graph.

Grindability of titanium alloy using cryogenic nanolubricant minimum quantity lubrication

The defect suppression of titanium alloy disturbed by low thermal conductivity is an urgent problem in grinding. The existing green manufacturing processes such as Nanolubricant minimum quantity lubrication (NMQL) and cryogenic air cooling are unsatisfactory due to insufficient cooling or lubrication performance. Cryogenic NMQL (CNMQL) is a new approach that utilizes the heat transfer capacity of cryogenic air and antiwear/antifriction performance of nanolubricant. However, the lack of grindability analysis and in-depth mechanism explanation limits the optimization and application of CNMQL. In this research, the calculation formulas for the Energy ratio coefficient of the cooling medium (Rm) and Defect ratio (Dr) of workpiece surface were established to evaluate Ti-6Al-4V grindability based on other common parameters, including force, temperature, surface roughness, workpiece and debris morphology. Results show that the lowest grinding force (tangential force is 46.8 N, normal force is 61.4 N), grinding peak temperature (151.2 °C), and surface roughness value (Ra = 0.468 μm) are obtained by CNMQL, compared with NMQL and cryogenic air cooling. The Rm in CNMQL is 36.4 %, which is 68.5 % higher than that of NMQL. The Dr value under CNMQL is 2.67 %, which is 84.5 % lower than cryogenic air cooling and 69.2 % lower than NMQL. Cryogenic nanolubricant displays excellent grinding performance due to its higher viscosity and shows significant improvement of convective heat transfer capacity. The critical cutting depth and plastic accumulation are significantly reduced therefore resulting in fewer surface defects.

Experimental study on the performance of an improved dehumidification system integrated with precooling and recirculated regenerative rotary desiccant wheel

High temperature and humidity conditions in enclosed cabins pose a threat to the safety of staff and equipment, and will result in intensive energy consumption by conventional air conditioning dehumidification systems. Therefore, an improved dehumidification system integrated with precooling and recirculated regenerative rotary desiccant wheel was proposed. The effects of the process air parameters (temperature and humidity), precooling temperature and regeneration air parameters (temperature and flow ratio) were experimentally investigated. Key performance indicators were analyzed, including the moisture removal capacity (MRC), thermal coefficient of performance (COPth), sensible energy ratio (Es) and dehumidification coefficient of performance (DCOP). The MRCtot was found to be improved by 29.7% at most compared with that of a conventional chilled water cooling system. In particular, the optimal MRC was obtained by an appropriate ratio between the regeneration and process airflows. The optimal ratio was determined between 8% and 20%. The DCOP and Es of the rotary desiccant wheel decreased with increasing regeneration airflow ratio. Moreover, COPth ranged from 0.33 to 1.17, and was improved with increasing process air temperature/humidity and decreasing precooling temperature. Overall, the feasibility of the system was verified and dehumidification characteristics under various working conditions were demonstrated to prompt its application.

Numerical investigation of a new type tube for shell-and-tube moving packed bed heat exchanger

An elliptical-like combined tube (ELCT) is proposed for the shell-and-tube moving packed bed heat exchanger. The heat transfer of particle flow around the ELCT is numerical studied. The kinetic energy ratio, contact number, contact time and heat transfer coefficient are analyzed. It is found that, the heat transfer performance of the ELCT is similar to that of the elliptical tube (ET) and better than the circular tube (CT). Compared with the CT, the ELCT significantly reduces the stagnation zone and the cavity zone, and improves the heat transfer at the top and the bottom of the tube (average increase of 42% and 53%). Furthermore, compared with the ET and the CT, the ELCT has better inside-tube heat transfer performance (average increase of 5% and 29%), various inside-tube heat transfer enhancement techniques (same with the CT) and better flexural capacity (average increase of 8% and 36% under same mass).

能量配比系数对铝合金激光-MIG复合焊接气孔的影响

能量配比系数对铝合金激光-MIG复合焊接气孔的影响

Scattering of plane-wave through fluid medium of finite width between self-reinforced and triclinic half spaces

The appearance of scattering (reflection and transmission phenomena) in three-dimensional plane-waves incident at a triclinic half space superimposed by the fluid layer underneath a self- reinforced half space is discussed thoroughly. The techniques of Christoffel equation and Cardon's method are applied to analyze the theoretical and numerical results. Closed form solution for reflection and refraction coefficient of plane waves is accomplished. Reflection and refraction curves are sketched for plane-waves by adjusting some significant values. The concepts of energy ratio, critical angle and conservation of energy are introduced. A closed form solution for velocity profile and reflection/refraction coefficients of all reflected and refracted waves is obtained along with numerical simulation. The effect of incidence angle on reflection/transmission angle is discussed thoroughly. The graphs of energy ratio, velocity profile, reflection and refraction coefficient for a plane-wave is determined.

Investigation of Objective Parameters of Vehicle Door Closing Transient Sound Quality Based on Complex Analytic Wavelet Method

In view of the deficiency of psychoacoustic objective parameters in prediction of nonstationary vehicle sound quality, we propose an innovative method to extract the transient acoustic time‐frequency characteristic parameters as objective parameters to evaluate the quality of vehicle door closing sound based on complex analytic wavelet. The signal is decomposed by empirical mode decomposition (EMD) and the decomposed intrinsic mode function (IMF) components are analyzed by the spectrum analysis. On the basis of human auditory frequency range, some IMF components are eliminated and the main frequency bands of the effective IMF components are extracted as the analytical frequency bands of the complex analytic wavelet. The center frequencies of the complex analytic wavelet analysis are extracted according to the critical bands, thereby determining wavelet parameters (band width, center frequency, scale factor, etc.,). To highlight the influence of high‐frequency components and balance the data discrepancy, we extract the energy ratio coefficient as the objective parameter after weighting the time‐frequency components. By comparing with the extracted objective parameters of traditional psychoacoustics, the correlation between the subjective evaluation results and the energy ratio coefficients is analyzed. The results demonstrate that the energy ratio coefficients extracted based on the complex analytic wavelet transform have a greater correlation with subjective evaluation results than the traditional psychoacoustic objective parameters. In addition, the frequency components of 1720 Hz∼3150 Hz have a strong negative correlation with the vehicle door closing sound quality.

Effect of Gas Pressure on Rock Burst Proneness Indexes and Energy Dissipation of Coal Samples

To investigate the influence of gas pressure on rock burst proneness of coal, the rock burst proneness tests were conducted under different gas pressures. Based on the energy method, the rock burst proneness and energy accumulation law are analyzed. The following conclusions can be drawn: (1) The change laws of impact energy index, the effective impact energy index and the residual energy index are consistent, reducing with the increase of gas pressure. (2) Before the coal failure, the total energy, the elastic energy, and the dissipated energy of coal specimens increase with the increase of the stress. The increase speed of total energy is the fastest, the elastic energy takes the second place, and the dissipated energy is the slowest. (3) The failure energy ratio and stress drop coefficient defined by energy can be used to describe the rock burst proneness. (4) The failure modes of coal samples transform from brittle failure into ductile shear failure with the increase of gas pressure. (5) In the coal seam which has typical dynamic hazards, there is a critical value of gas pressure. When the gas pressure is higher than the critical value, gas outburst is the main disaster. When the gas pressure is lower than the critical value, the rock burst is the main disaster.

Grinding temperature and energy ratio coefficient in MQL grinding of high-temperature nickel-base alloy by using different vegetable oils as base oil

Vegetable oil can be used as a base oil in minimal quantity of lubrication (MQL). This study compared the performances of MQL grinding by using castor oil, soybean oil, rapeseed oil, corn oil, sunflower oil, peanut oil, and palm oil as base oils. A K-P36 numerical-control precision surface grinder was used to perform plain grinding on a workpiece material with a high-temperature nickel base alloy. A YDM–III 99 three-dimensional dynamometer was used to measure grinding force, and a clip-type thermocouple was used to determine grinding temperature. The grinding force, grinding temperature, and energy ratio coefficient of MQL grinding were compared among the seven vegetable oil types. Results revealed that (1) castor oil-based MQL grinding yields the lowest grinding force but exhibits the highest grinding temperature and energy ratio coefficient; (2) palm oil-based MQL grinding generates the second lowest grinding force but shows the lowest grinding temperature and energy ratio coefficient; (3) MQL grinding based on the five other vegetable oils produces similar grinding forces, grinding temperatures, and energy ratio coefficients, with values ranging between those of castor oil and palm oil; (4) viscosity significantly influences grinding force and grinding temperature to a greater extent than fatty acid varieties and contents in vegetable oils; (5) although more viscous vegetable oil exhibits greater lubrication and significantly lower grinding force than less viscous vegetable oil, high viscosity reduces the heat exchange capability of vegetable oil and thus yields a high grinding temperature; (6) saturated fatty acid is a more efficient lubricant than unsaturated fatty acid; and (7) a short carbon chain transfers heat more effectively than a long carbon chain. Palm oil is the optimum base oil of MQL grinding, and this base oil yields 26.98N tangential grinding force, 87.10N normal grinding force, 119.6°C grinding temperature, and 42.7% energy ratio coefficient.

Wave reflection and refraction in rotating and initially-stressed piezoelectric crystals

The purpose of this paper is to address the wave reflection and refraction in the rotating piezoelectric crystals subjected to a biaxial, homogeneous stress field. Besides, utilizing the inhomogeneous wave theory enables additional reflected and refracted surface waves to solve the problem of discrepancy between independent wave modes and boundary equations. A set of homogeneous equations in displacements and electric potential is derived within the rotatory coordinate system in the presence of the Coriolis and centrifugal acceleration. The performed plane example shows that there is a critical point when angular velocity equals the wave frequency, at which no quasi-longitudinal wave can be generated, reflected or refracted, and close to which the characteristics of the quasi-longitudinal wave change sharply. In addition, the presence of the Coriolis and centrifugal accelerations demonstrates noticeable influence upon the wave propagation and reflection/refraction, namely the wave velocities and attenuations, the angles of the reflected/refracted bulk waves, the reflection/refraction amplitudes and energy ratio coefficients. The analysis results also indicate that the reflected and refracted waves can transform into the type of surface wave at some incident angles. Finally, compared with the rotation effects, the waves are not sensitive to the initial stresses.

Experimental research on the energy ratio coefficient and specific grinding energy in nanoparticle jet MQL grinding

Nanoparticles are solid nanoscale particles with features such as antiwear, antifriction, and high load-carrying capacity. This research applied nanoparticles in the cooling lubrication of grinding and theoretically analyzed the impact of cooling lubrication on the grinding surface through the energy ratio coefficient and specific grinding energy. First, the workpiece surface temperature was measured using a thermal infrared imager. A three-dimensional dynamometer was used to identify the tangential grinding force during grinding. Results showed that, with different cooling lubrication approaches, the grinding surface was distributed to workpiece, grinding wheel, grinding fluid, and abrasive debris according to different energy ratio coefficients. The calculation demonstrated that the energy ratio coefficient of dry grinding reached 64.3 %. However, the energy ratio coefficient of flood lubrication, minimal quantities of lubricant (MQL), and nanoparticle jet MQL was 36.8, 52.1, and 41.4 %, respectively. These findings indicated that nanoparticle jet MQL realized a cooling effect close to that of flood lubrication. The specific grinding energy of nanoparticle jet MQL was 35 J/mm3, which was close to that of flood lubrication at 29.8 J/mm3. This finding indicated that the lubrication effects of nanoparticle jet MQL were also similar to those of flood lubrication. Moreover, molybdenum disulfide, carbon nanotube (CNT), and zirconium oxide nanoparticles were added in the grinding fluid to conduct the grinding experiment with nanoparticle jet MQL. The comparison of energy ratio coefficients showed that the cooling performance of CNT nanoparticles was satisfactory. CNT nanoparticles were subsequently added into the grinding fluid at the volume concentrations of 1, 2, and 3 % for the grinding experiment. The results showed that the best cooling effects occurred under the 2 % volume concentration of CNT nanoparticles. Through rounds of selections and optimizations, our research acquired the nanoparticle types and volume concentration that had satisfactory cooling effects and should therefore be added in the grinding fluid.

Inhomogeneous wave reflection in a rotating piezoelectric body

The purpose of this paper is to address the wave reflection over the rotating piezoelectric boundary surface in the framework of inhomogeneous wave theory which can introduce an additional reflected surface wave over the boundary surface to solve the problem of discrepancy between independent wave modes and boundary equations. A set of homogeneous equations in displacements and electric potential is derived within the rotatory coordinate system in the presence of the Coriolis and centrifugal acceleration presenting noticeable influence upon the wave propagation and reflection. Other than the transverse wave, the performed plane example shows that there is a critical point of when angular velocity equals the wave frequency for the quasi-longitudinal wave. The results also reveal that the angular velocity is accompanied by the modification of reflected waves especially in the case of reflected surface mode as well as the reflection angles, the amplitudes, and energy ratio coefficients.

Research on Extracting Cyclostionary Statistics of Amplitude-Modulated Signals Based on Cumulant

Regarding the cyclostationary of of amplitude-modulated signals, a method for extracting cyclostionary statistics of amplitude-modulated signals based on Cumulant is proposed. An index, energy ratio coefficient is defined to assess signals modulated degree. Theoretical data and Simulation data are analyzed, and it is found that the energy ratio coefficient increases with the increasing modulated degree.

Absorbing boundary conditions for dynamic analysis of fluid-saturated porous media

Based on Biot's two-phase mixture theory and the paraxial approximation, the absorbing boundary conditions in the time domain for u-w, u-U and u-p formulations are presented for the dynamic analysis of fluid-saturated porous media. These absorbing boundaries are equivalent to the viscous boundaries in the fundamental mode. The expressions for the energy ratio and reflection coefficient between the reflected and incident waves along the absorbing boundary are given. The numerical results show that the proposed absorbing boundaries can greatly suppress the spuriously reflected wave and model the far field of the system. These results also dynamic analysis of infinite fluid-saturated porous media. for the transient dynamic analysis of infinite fluid-saturated porous media.