Torsional Analysis Research Articles

Electrical Submersible Pumps: A System Modeling Approach for Power Quality Analysis With Variable Frequency Drives

This article proposes a high-level engineering guide to develop an integrated system model for power quality analysis in electrical submersible pump (ESP) applications with variable frequency drives (VFDs). Such analyses are troublesome in the industry due to the complexity of these systems. In this article, simple steps to perform system integration analyses of such arrangements, including torsional analysis, are developed. A simplified VFD-ESP model suitable for coupled electrical and mechanical analysis in steady state is proposed in all their configurations of practical interest. Such a model can be easily implemented in common simulation software, significantly reducing engineering efforts for implementation and analysis. The focus of the proposed model is the prediction of ESP failures that might result from a poor power quality caused by VFDs. Analytical expressions of different types of harmonics in these systems, as well as their accurate locations in the frequency domain, including their interharmonics and common-mode harmonics, are derived for this purpose. The effectiveness of the proposed model is verified through offline and real-time hybrid simulation results. Finally, a comparison between simulation results obtained using the proposed model and measurements collected on a down-scale laboratory prototype is carried out to demonstrate the accuracy of the suggested modeling approach.

Glass transition behavior of poly(methyl methacrylate) in compressed carbon dioxide revisited – New perspectives

Glass transition behavior of poly(methyl methacrylate) (PMMA) in compressed carbon dioxide has been investigated with a relatively new technique, High-Pressure Torsional Braid Analysis (HP-TBA), using two polymer samples of widely differing molecular weights, with Mw = 89,700 and 457,000 g/mol. For each sample, the glass transition temperature was determined along constant-temperature and constant-pressure pathways at 35, 70, and 90 °C and 30, 50, 75, 100, and 200 bar, respectively. The results show that the observed Tg behavior depends not only on the molecular weight but also on the rate of pressurization. Based on the present observations new interpretations are provided for the differences in the data reported in the literature along with new insights regarding the presence or absence of the retrograde Tg behavior. This study suggest that high molecular weight PMMA samples may not display classic retrograde Tg behavior.

Torsional vibration analysis of a powertrain with a power reflux hydraulic transmission system

World-wide constraints on the supply of fossil fuel resources exist in conjunction with stringent environmental constraints. Therefore, it is very important to develop advanced technologies to reduce fuel consumption. The transmission efficiency of an automatic vehicle is low because of the torque converter. Hence, in this study, a power reflux hydraulic transmission system (PRHTS) was proposed. It is important to avoid the phenomenon of resonance in a powertrain with a PRHTS, and thus it is necessary that the resonance point of a powertrain with a PRHTS does not exist in the resonance region of the engine. A dynamic and mathematical model of a powertrain with a PRHTS was developed to study the resonance characteristic of the powertrain. The amplitude-frequency characteristic curve of a powertrain for different speed ratios was obtained. The effect of torsional stiffness of the coupling and engine shock absorber on the amplitude-frequency characteristics of a powertrain with a PRHTS were examined. The simulation result indicated that it was necessary to exclude the resonance frequencies of the powertrain with a PRHTS from the operation range of the engine.

Size dependent coupled electromechanical torsional analysis of porous FG flexoelectric micro/nanotubes

In this paper, the governing equations of torsional porous flexoelectric microtubes made of functionally graded (FG) materials are investigated and obtained for the first time. First, the governing electromechanical coupling equations of the problem are extracted, and to achieve this goal, a modified non-classical flexoelectric theory has been used to derive these equations. The independent parameters of polarization in enthalpy relationships and the mechanical and electrical size effect are the important points in this theory. Noted that the independent parameter effects of polarization, mechanical and electrical size that is considered for the first time in this paper, are the capability of this theory, and the effect of these parameters is evaluated on direct and reverse flexoelectric. After that, the static analysis and free vibrations have been reviewed. And in the conclusion section interesting and valuable results have been obtained, that could help the torsional micro-sensors and torsional micro-actuators designers.

Size dependent torsional electro-mechanical analysis of flexoelectric micro/nanotubes

The free vibration and static torsion of a coupling electromechanical flexoelectric micro/nanotube have been investigated, in the present study. Using the non-classical theory of continuum mechanics which is based on a strain gradient, the coupling governing equations of torsional flexoelectric micro/nanotubes have been developed. To derive the coupling governing equations the variational method has been used and the formulation with the classical and non-classical boundary conditions is generally derived for torsional flexoelectric micro/nanotubes. For the first time, the formulation of micro/nanotube torsional flexoelectric coupling with independent polarization effect is presented in this paper which can be used for specific applications. At last, the static analysis and free vibrations results are presented for specific mechanical and electrical boundary conditions. The parameter of mechanical and electrical size effect changes has a great effect on the results. However, the effect of the mechanical and electrical size effect parameter on direct flexoelectric torsion is also opposite, but the effect of mechanical and electrical size effect parameter on reverse flexoelectric torsion is similar. Polarization is also introduced as a new variable in the equations and its effect is investigated as an independent variable of the electric field in the results, in this paper. As a significant parameter, the results show that polarization plays an important role to simulate the torsional electromechanical structures.

Atomic Force Microscope Study of Friction at the Submicron-Scale During Tribotests With Self-Mated Steel

Abstract Friction at the microscale during reciprocal sliding tribotests was studied for the first time with self-mated steel (100Cr6/AISI 52100) taking advantage of an atomic force microscope (AFM). To this aim, microsized steel particles were glued to the AFM-cantilever and employed as colloidal tips to perform tribotests on a steel disc. The torsion of the cantilever, which correlates with the friction force, was measured during the tests. Due to the irregular shape of the test particles and their wear, it is not possible to calibrate the torsional response of the cantilever and absolute quantification of the friction force cannot be achieved. Nevertheless, the model system used in the presented measurements is more representative of the tribology of real mechanical tribo-elements than already studied systems, in which for example only one tribopartner is worn. Few tests with the same load did not yield any wear and show that the load and adhesion contributions to friction stay constant when the shape of the test particle does not change. Most of the presented tribotests engendered wear. For those tests, the increase of friction during the tribotests was detected and was attributed to the emerging plowing contribution. Furthermore, analysis of both torsion and local slope experienced by the cantilever during the tests gives information on the creation of wear particles and their influence on friction.

Influence of Cross-Section and Pitch on the Mechanical Response of NiTi Endodontic Files under Bending and Torsional Conditions-A Finite Element Analysis.

In this article, the effects of cross-section and pitch on the mechanical response of NiTi endodontic files is studied by means of finite element analyses. The study was conducted over a set of eight endodontic rotary files, whose geometry was obtained from combinations of two cross-sections (square and triangular) and four pitches. Each file was subjected to bending and torsional analyses, simulating the testing conditions indicated in the ISO 3630 Standard, in order to assess their stiffness and mechanical strength. The results indicate that endodontic files with a square cross-section have double the stiffness of those with triangular cross-sections, both in terms of bending and torsion. For both loading modes, endodontic files with a triangular cross-section can undergo larger deformations before overload failure than those with a square cross-section: up to more in bending and in torsion. Moreover, under equivalent boundary conditions, endodontic files with triangular cross-sections present a higher fatigue life than those with square cross-sections: up to more than higher for small pitches. The effect of pitch on the stiffness and strength of the file is smaller than that of the cross-section shape, but smaller pitches could be beneficial when using a triangular cross-section, as they increase the bending flexibility, fatigue life, and torsion stiffness. These results suggest a clinical recommendation for the use of files with a triangular-shaped cross-section and a small pitch in order to minimize ledging and maximize fatigue life. Finally, in this study, we reveal the sensitivity of the orientation of files with respect to the bending direction, which must be taken into account when designing, reporting, and interpreting test results under such loading conditions.

Torsional vibration analysis of shaft with multi inertias.

An analytical method is proposed to investigate the torsional vibration of the uniform circular shaft with multiple concentrated inertias. The governing equation is established based on the Hamiltonian principle and verified by the dynamical method. The theoretical solutions of frequencies and mode shapes under different boundary conditions are obtained using the separation variable method and integral transformation. The effectiveness of the proposed method is verified by comparison with existing literature. Considering the change of the magnitudes/positions/number of concentrated inertias, and different boundary conditions, the natural frequencies and mode shapes are discussed. Several general rules are obtained. Moreover, some interesting phenomena have been found and explained. The analytical method has applications in the design of shafting with multiple concentrated inertias and the reliability checking of the “approximate” solutions.

Torsional and longitudinal vibration analysis of a porous nanorod with arbitrary boundaries

In the present study, free torsional and axial vibrations of porous nanorods with torsional, axial elastic boundary conditions are presented via Eringen’s nonlocal elasticity theory. This theory takes into account the small size effect into the differential formulation due to dealing with nano-sized structures. Even though free axial and torsional vibrations based analysis of nanorod is a widely investigated topic, there are only few researches which exist in the scientific literature pertaining to the vibration analysis of porous nanostructures with nonrigid (deformable) boundary conditions. This study brings a contribution to the literature by presenting both porosity and small size effects with deformable boundary conditions. It is also planned to examine the effects of porosity and small size in detail. A model that allows to examine all of these effects within the framework is created within the scope of this study. To this end two torsional and axial springs are attached to the porous nanorod at both ends separately. Present model bridges the gap between deformable and non-deformable (rigid) boundary conditions. An eigen-value problem is constructed including torsional and axial coefficients by using Stoke transformation and the Fourier sine series. The novelty of this work is that it seeks to construct a general eigen value algorithm for the torsional and axial vibration frequencies of the porous nanorods subjected to the deformable and rigid boundary conditions for the first time. Moreover, the effects of some parameters such as porosity index, axial and torsional restraints on the free vibration frequencies are investigated and some conclusions are drawn.

Probing the competitive inhibitor efficacy of frog-skin alpha helical AMPs identified against ACE2 binding to SARS-CoV-2 S1 spike protein as therapeutic scaffold to prevent COVID-19.

In COVID-19 infection, the SARS-CoV-2 spike protein S1 interacts to the ACE2 receptor of human host, instigating the viral infection. To examine the competitive inhibitor efficacy of broad spectrum alpha helical AMPs extracted from frog skin, a comparative study of intermolecular interactions between viral S1 and AMPs was performed relative to S1-ACE2p interactions. The ACE2 binding region with S1 was extracted as ACE2p from the complex for ease of computation. Surprisingly, the Spike-Dermaseptin-S9 complex had more intermolecular interactions than the other peptide complexes and importantly, the S1-ACE2p complex. We observed how atomic displacements in docked complexes impacted structural integrity of a receptor-binding domain in S1 through conformational sampling analysis. Notably, this geometry-based sampling approach confers the robust interactions that endure in S1-Dermaseptin-S9 complex, demonstrating its conformational transition. Additionally, QM calculations revealed that the global hardness to resist chemical perturbations was found more in Dermaseptin-S9 compared to ACE2p. Moreover, the conventional MD through PCA and the torsional angle analyses indicated that Dermaseptin-S9 altered the conformations of S1 considerably. Our analysis further revealed the high structural stability of S1-Dermaseptin-S9 complex and particularly, the trajectory analysis of the secondary structural elements established the alpha helical conformations to be retained in S1-Dermaseptin-S9 complex, as substantiated by SMD results. In conclusion, the functional dynamics proved to be significant for viral Spike S1 and Dermaseptin-S9 peptide when compared to ACE2p complex. Hence, Dermaseptin-S9 peptide inhibitor could be a strong candidate for therapeutic scaffold to prevent infection of SARS-CoV-2.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00894-022-05117-8.

Warping torsion of FGM beams with spatially varying material properties

This contribution extends the author’s previous research results concerning effect of spatially varying material properties on warping torsion of beams with open cross-section made of Functionally Graded Material (FGM). The author’s FGM WT beam finite element is used in the calculations of the primary quantities. The secondary deformations due to the angle of twist is considered. The warping part of the first derivative of the twist angle, caused by the bimoment, is accounted as an additional degree of freedom at the beam nodes. The author’s Reference Beam Method, (RBM), is used for homogenization of the spatially varying material properties in the real beam onto effective constant or longitudinally varying stiffnesses for the homogenized beam. Enhanced equations for calculation of the normal and shear stresses with the influence of the deformation effect caused by the primary and secondary torsion moment are established. These equations also contain effect of the warping ordinate function and its gradients that depend on spatially varying material properties. The focus of the numerical investigation is on non-uniform torsional analysis of straight FGM cantilever beams with I- cross-section. An effect of the warping ordinate function and its gradients on the normal and shear stresses is evaluated and discussed. A significant effect of the spatial variability of material properties on the deformation as well as on the stress state in the FGM beams with I-cross-section, has been found. The real beams with spatially varying material properties are modelled with only a single FGM WT beam finite element. Obtained results for the primary and secondary variables are compared with the ones calculated by a very fine mesh of standard 3D-solid finite elements. A very good agreement of all the results has been achieved.

Analysis of torsionally loaded non-uniform circular piles in multi-layered non-homogeneous elastic soils

A new method for the torsional analysis of non-uniform circular piles partially or fully embedded in multi-layered elastic soils is developed. The mechanical response of non-uniform piles such as those with a linear variation in cross-section (i.e., tapered piles) or discontinuous variations (i.e., stepped piles), and reacting against a non-homogeneous elastic soil can be easily investigated with the proposed formulation. The non-homogeneity of the soil is incorporated by assuming a shear modulus distribution that fits a quadratic equation (i.e., G(z)=Go+sz+tz2). The governing differential equation (GDE) of a single non-uniform circular pile segment is derived and solved using the differential transformation method (DTM); then, the stiffness matrix of the segment is found by applying equilibrium and compatibility conditions at the ends of the element. The analysis of non-uniform piles in multi-layered soils is conducted by dividing the pile into multiple segments (i.e., each segment representing a change in soil properties or pile geometry) and then assembling them using classic matrix methods. The proposed matrix formulation is simple to implement, easy to incorporate into already available structural matrix analysis codes and provides accurate results when compared with more cumbersome analytical and numerical solutions. The simplicity, practicality and accuracy of the method is validated with five illustrative examples.

A Molecular Dynamics Study of Monomer Melt Properties of Cyanate Ester Monomer Melt Properties.

The objective of this work was to computationally predict the melting temperature and melt properties of thermosetting monomers used in aerospace applications. In this study, we applied an existing voids method by Solca. to examine four cyanate ester monomers with a wide range of melting temperatures. Voids were introduced into some simulations by removal of molecules from lattice positions to lower the free-energy barrier to melting to directly simulate the transition from a stable crystal to amorphous solid and capture the melting temperature. We validated model predictions by comparing melting temperature against previously reported literature values. Additionally, the torsion and orientational order parameters were used to examine the monomers’ freedom of motion to investigate structure–property relationships. Ultimately, the voids method provided reasonable estimates of melting temperature while the torsion and order parameter analysis provided insight into sources of the differing melt properties between the thermosetting monomers. As a whole, the results shed light on how freedom of molecular motions in the monomer melt state may affect melting temperature and can be utilized to inspire the development of thermosetting monomers with optimal monomer melt properties for demanding applications.

A softened membrane model for single-box multi-cell composite box-girders with corrugated steel webs under pure torsion

To analyze the nonlinear torsional behavior of single-box multi-cell prestressed concrete (PC) or reinforced concrete (RC) composite box-girders with corrugated steel webs (BGCSWs), a new theoretical model called unified softened membrane model for torsion (USMMT) is proposed in this study. It is developed from the softened membrane model for torsion which was formerly proposed for the torsional analysis of single-box single-cell PC/RC composite BGCSWs. This proposed model incorporates the different contributions of inner and outer corrugated steel webs (CSWs) in the multi-cell BGCSW to the torsional capacity by introducing a rational relationship of shear strains between inner CSWs and outer CSWs. The satisfactory accuracy of the proposed model is obtained when comparing with the experimental and the finite element analysis results, including the torque-twist curves and the smeared shear strains in concrete slabs and CSWs in the full-range torsional analysis. The comparison indicates that the proposed model is capable of predicting the overall torsional behavior of single-box multi-cell BGCSWs.

An innovated theory and closed form solutions for the elastic lateral torsional buckling analysis of steel beams/columns strengthened with symmetrically balanced GFRP laminates

An innovated theory based on the principle of total stationary buckling energy is successfully developed for the elastic lateral torsional buckling analysis of steel beams/columns strengthened with symmetrically balanced GFRP laminates. Two closed form solutions and four eigenvalue solutions of the buckling resistances are then developed based on the theory and based on postulated buckling displacement functions. The present theory captures the partial interaction between the steel member and the GFRP laminates, stacking sequences and orthotropic properties of GFRP laminae, shear deformations in the GFRP laminates, and local and global warping deformations. The elastic buckling resistances predicted by the present solutions are well validated against those of three dimensional finite element analyses, as presented in three examples and two parametric studies of the present study. The present solutions are fast and convenient to predict the elastic buckling resistances of GFRP-strengthened beams/columns. Based on the parametric studies conducted, it is observed that the effects of GFRP lamina stacking sequences (with different fiber orientation angles), GFRP laminate thicknesses, GFRP moduli of elasticity, GFRP shear moduli, and adhesive shear moduli on the elastic buckling resistances are significant.

Method for Adjusting Torsional Natural Frequencies of Powertrains with Novel Coupling Design

Torsional vibrations are inherently present in every rotating powertrain. In resonant conditions, torsional vibrations can be significantly amplified. A typical method to reduce the torsional vibration particularly at resonance is to modify the torsional natural frequencies with the component design. Commonly, a straightforward method for the modification is the adjustment of the torsional stiffness of a coupling. This study presents a method to modify the torsional natural frequencies using a coupling design with continuously adjustable torsional stiffness. The presented coupling design is investigated with torsional analysis and experimental measurements. Torsional analysis was utilized to predict the effects of varying the coupling stiffness to the torsional natural frequencies of a powertrain. The experimental measurements were conducted by attaching the adjustable stiffness coupling to the powertrain and measuring the change in the torsional natural frequencies while the torsional stiffness of the coupling was adjusted. The torsional natural frequencies were determined from the measurements by identifying the resonance induced torsional vibrations from the vibration response of the powertrain. The torsional vibrations were excited to the system by a load motor. The measurements showed that the first torsional natural frequency of the powertrain changed from 15.6 Hz to 43.0 Hz as the torsional stiffness of the coupling was adjusted. The results of the torsional analysis and the experimental measurements were compared to determine the performance of the realized coupling. The results indicated that the torsional natural frequencies determined by torsional analysis agree well with the experimentally measured results. The prediction errors were generally below ±5%, which is typically considered as a margin for accurate torsional analysis.

Nonlinear torsional primary resonance analysis of suspension bridge with generalized configuration using mathematical model

Torsional vibration of long span suspension bridge can be commonly induced by various sources, and detailed investigation is required from both design and safety point of view. This study proposes a continuum model of the generalized suspension bridge using the Hamilton principle. This model can consider any inclination angle of main cables. The horizontal and vertical motions of main cables, and torsional motion of deck are considered individually in this model. The proposed model is verified by comparing its modal properties with those from a finite element model. The nonlinear primary resonances of the two lowest torsional modes are studied through multiple-scale method (MSM) under harmonic excitation. The effects of system parameters, such as inclination angle of hangers, sag-to-span ratio, tensile stiffness of main cable and torsional stiffness of deck, on the resonance responses are investigated in this study. Results show that, increasing inclination angle of main cable and torsional stiffness of deck can intensify the softening feature of the system. In contrast, increasing the sag-to-span ratio and tensile stiffness of main cable can strengthen the hardening feature.

Exact Solutions for Torsion and Warping of Axial-Loaded Beam-Columns Based on Matrix Stiffness Method.

The typically-used element torsional stiffness GJ/L (where G is the shear modulus, J the St. Venant torsion constant, and L the element length) may severely underestimate the torsional stiffness of thin-walled nanostructural members, due to neglecting element warping deformations. In order to investigate the exact element torsional stiffness considering warping deformations, this paper presents a matrix stiffness method for the torsion and warping analysis of beam-columns. The equilibrium analysis of an axial-loaded torsion member is conducted, and the torsion-warping problem is solved based on a general solution of the established governing differential equation for the angle of twist. A dimensionless factor is defined to consider the effect of axial force and St. Venant torsion. The exact element stiffness matrix governing the relationship between the element-end torsion/warping deformations (angle and rate of twist) and the corresponding stress resultants (torque and bimoment) is derived based on a matrix formulation. Based on the matrix stiffness method, the exact element torsional stiffness considering the interaction of torsion and warping is derived for three typical element-end warping conditions. Then, the exact element second-order stiffness matrix of three-dimensional beam-columns is further assembled. Some classical torsion-warping problems are analyzed to demonstrate the established matrix stiffness method.

Torsional Deformation Analysis of Large Miter Gate under Different Operating Conditions

As an important part of the navigation facilities for water conservancy and electricity in Gezhouba, the operation safety of herringbone gates is critical. Due to the minor torsional stiffness of the gate, it is easy to produce torsional deformation during operating under the water pressure, wind load, and gravity, which may lead to fatigue damage. In this study, a gate model with a combination of plate unit and the solid unit was developed, taking a ship lock herringbone gate as an example. According to the gate load under different working conditions, such as self-weight, surge, etc., in this research, we used the finite element analysis software ANSYS to analyze and calculate the stress and strain of the gate, with and without a back tie, and obtained the characteristics of the gate torsional deformation under various working conditions. The results show that the gate’s deformation degree and the direction under different working conditions vary greatly. The maximum deformation point mostly appears in the upper or lower corners of the oblique joint column. The gate deformation can be significantly reduced by adding the back tie. The research results provide a theoretical basis for further optimizing the design of the gate and installation of the back tie to reduce the fatigue damage of the miter gate.

The Systolic and Diastolic Cardiac Function of Patients With Type 2 Diabetes Mellitus: An Evaluation of Left Ventricular Strain and Torsion Using Conventional and Speckle Tracking Echocardiography.

Objectives: This study aimed to quantify left ventricular (LV) myocardial strain and torsion in patients with type 2 diabetes mellitus (T2DM) and evaluate their systolic and diastolic function using conventional and speckle tracking echocardiography.Methods: Forty-seven patients with T2DM were divided into a group without microvascular complications (the DM A group) and a group with microvascular complications (the DM B group), while another 27 healthy participants acted as the control group. All the participants had had an echocardiography examination. All the original data were imported into EchoPAC workstation for the analysis and quantification of LV strain and torsion.Results: Compared with the control group, the LV end-diastolic volume, end-systolic volume, and ejection fraction of the DM A and DM B groups showed no significant differences, but the global longitudinal strain and the global circular strain were reduced in the DM B group. There were significant differences in the left ventricular relative wall thickness (RWT), left ventricular mass index (LVMI), the early mitral valvular blood flow velocity peak/left ventricular sidewall mitral annulus late peak velocity, left ventricular sidewall mitral annulus early peak velocity/left ventricular sidewall mitral annulus late peak velocity, isovolumic relaxation time, peak twisting, peak untwisting velocity (PUV), untwisting rate (UntwR), time peak twisting velocity (TPTV), and time peak untwisting velocity (TPUV) between the DM A, DM B, and control groups. While the peak twisting velocity (PTV) was slower in the DM B group compared with the control group, the RWT, PTV, PUV, UntwR, TPTV, and TPUV in the DM B group were significantly different from the DM A group.Conclusion: The cardiac function of patients with T2DM in its early stages, when there are no microvascular complications, could be monitored with the analysis of two-dimensional strain and torsion.