Substructure Model Research Articles

Dynamic Substructuring by the Craig–Bampton Method Applied to Frames

The Craig–Bampton method is a substructuring technique that reduces the number of internal degrees of freedom of substructures by approximations, using a set of truncated vibration modes. It is useful for structural designs with many degrees of freedom. This work aims to develop substructuring through the Craig–Bampton method for free vibration analysis on planar frames according to the frequency range of interest. The finite-element models of different substructures were assembled. Thus, the degrees of physical freedom were reduced according to the frequency range of interest. The reduced-order models were coupled. Thus, the physical response was obtained. Detailed calculation and the algorithm flowchart are provided. The study of frame dynamics using the present method in different frequency ranges of interest was presented and validated with the results of a commercial software. It was possible to clarify the coupling formulations of the component mode synthesis, as well as the amount of reduction of the number of equations provided by the method, reaching less than 4% of the complete model, for the considered cases.

Local wave propagation analysis in concrete-filled steel tubes with spectral element method using absorbing layers – Part II: Application in coupling system

In this paper, a two-dimensional (2D) time domain spectral element method (SEM) is developed for concrete-filled steel tube (CFST) and piezoelectric lead zirconate titanate (PZT) patches coupling system, where the piezoelectric and inverse piezoelectric effect of PZT actuator and sensor and their coupling effect with CFST are considered. The local wave field and the response of the embedded PZT sensor was numerically studied in a substructure of the CFST coupled with PZT patches and surrounded by absorbing layers with increasing damping (ALID) and the performance of the ALID in attenuating wave reflection at boundaries of the coupling substructure model is further investigated. Then, numerical simulation on the effect of interface debonding defect on local wave propagation within the coupling substructure model surrounded by the designed ALID was carried out. By comparing the displacement-based wave fields and the response of the embedded PZT sensor within the substructure, the effect of interface debonding defect on the wave propagation along the steel tube and in the concrete core, and the time history of the response voltage of the embedded PZT sensor is investigated in detail. Numerical results show that interface debonding defects in the substructure leads to changes in the wave propagation path, the local wave field, the time duration of wave travelling to the embedded PZT sensor from the PZT actuator mounted on the surface of the steel tube of CFST, as well as response voltage of the embedded PZT sensor. In addition, PZT sensor measurement is sensitive to the length of interface debonding defects but insensitive to their depth. SEM for the coupling substructure model with ALID instead of the model of whole cross section of CFST provides an efficient way to simulate the local elastic wave propagation for understanding the mechanism of the interface debonding defects detection approach based on wave measurement.

Influence of soil non-homogeneity on the base shear force of piled structures subjected to harmonic seismic waves

This paper aims at analyzing the effects of soil non-homogeneity on the dynamic behavior of piled structures. In order to fulfil this objective a procedure based on a substructuring model, which includes soil-structure interaction effects, is used to compute the dynamic response of slender and non-slender structures supported on several pile group configurations embedded in four different linear-elastic Gibson soil profiles. A numerical model based on the integral formulation of the elastodynamic problem and Green’s functions for the layered half space is used for the purpose of determining the foundation dynamic response in terms of impedances and kinematic interaction factors. The results obtained in terms of structural base shear force for each one of the variable-with-depth soil profiles are compared to those computed for an equivalent homogeneous soil. A significant influence of the soil profile on the structural harmonic response to seismic waves is observed in terms of maximum shear force at the base of the structure. The homogeneous assumption when modelling depth-varying soil profiles yields, in many cases, non-conservative results when predicting the structural dynamic behavior.

Method to estimate rotational stiffness: Trial masses, virtual masses, and virtual springs

This paper proposes a method to estimate the rotational stiffness at the coupled points of an assembled system. Conventional test-based rotational stiffness evaluation methods are sensitive to measurement errors and require a separate jig for testing. In contrast, as the proposed method uses the natural frequency shift phenomenon resulting from the addition of mass, the measurement error is relatively small, and accuracy is improved by excluding the interference of other modes. The proposed method also solves the complexity of the conventional method by changing the fixed condition of the system using frequency response function-based substructuring modeling; consequently, it does not require a dedicated jig for fixing. In this process, the concepts of trial mass, virtual mass, and virtual spring are introduced to systematically explain the proposed method and applied to the method using frequency shift. The results of experiments conducted on a vehicle shock absorber verify the utility of the proposed method.

Performance Simulation for the Supporting Structure of Aero-Engine Rotor in Wide Frequency Domain

The inertia load of aero-engine indeterminate rotor support is calculated by the finite element method coupled with plane stress element and Fourier ring element. Without considering the dynamic characteristics of rotor’s supporting structure, the test results are error-prone and inefficient. A new method for testing the supporting structure performance of aero-engine rotor in wide frequency domain is proposed. On this basis, the structural model of the casing-support and the structural model of aero-engine rotor are constructed by substructure modelling method. Combining the two sub-models, the semi-physical simulation model of the vibration of the engine rotor’s supporting structure is obtained. By superimposing the additional dynamic stiffness matrix of the casing-supporting structure at the designated DOF position in the overall stiffness matrix of the finite element model of the rotor structure, the overall stiffness matrix of the aero-engine rotor supporting structure is obtained. The effective stiffness matrix can be used to calculate the structural dynamic characteristics of aero-engine rotor supporting structure. Experiments show that the average error of the proposed method is 0.0023 and the number of units is 7.98 e4. The calculation time and storage space are reduced by 310 minutes and 166 GB respectively compared with the performance test method of rotor support based on finite element analysis, which shows that the proposed method is more efficient and accurate.

Distributed active vibration cooperative control for flexible structure with multiple autonomous substructure model

The objective of this work was to suppress the vibration of flexible structures by using a distributed cooperative control scheme with decentralized sensors and actuators. For the application of the distributed cooperative control strategy, we first propose the multiple autonomous substructure models for flexible structures. Each autonomous substructure is equipped with its own sensor, actuator, and controller, and they all have computation and communication capabilities. The primary focus of this investigation was to illustrate the use of a distributed cooperative protocol to enable vibration control. Based on the proposed models, we design two novel active vibration control strategies, both of which are implemented in a distributed manner under a communication network. The distributed controllers can effectively suppress the vibration of flexible structures, and a certain degree of interaction cooperation will improve the performance of the vibration suppression. The stability of flexible systems is analyzed by the Lyapunov theory. Finally, numerical examples of a cantilever beam structure demonstrate the effectiveness of the proposed methods.

Coupled discrete-continuum approach for railway ballast track and subgrade macro-meso analysis

ABSTRACT This paper presents a multi-layer railway ballast track and substructure model, where a coupled discrete and continuous method is used for macro-meso dynamic behaviour analysis under moving wheel loads. In this coupled model, the discrete element method (DEM) is utilised to build the superstructure of the ballast track (i.e. rail, fastener, sleeper and ballast layer), which considers the complex ballast shape and particle size distribution from mesoscopic level. The finite difference method (FDM) is used to simulate the substructure (i.e. subgrade and foundation) with a consideration of computing cost. And then, the coupled model is achieved by satisfying displacement, velocity and contact force compatibility between the FLAC and the PFC. Finally, the dynamic analysis is carried out by applying the wheel-rail forces obtained from a vehicle-track dynamics model into the coupled model. The DEM parameters of ballast particles are calibrated based on the results of the ballast direct shear tests, and the dynamic behaviour of railway ballast track and subgrade system is validated with the field measurement. Through the numerical analysis, it is confirmed that the coupled DEM/FDM model can reliably reflect macro-meso dynamic behaviour and accurately reveal the contact characteristics between the ballast layer and subgrade.

The Effect of Social Media Marketing, Word of Mouth, and Effectiveness of Advertising on Brand Awareness and Intention to Buy

The purpose of this research is to analyze the direct effect of social media marketing, word of mouth, and the effectiveness of advertising on brand awareness and its impact on intention to buy, either directly or indirectly. The data source of 50 respondents, obtained from the customers who only use transportation services in the area of Samarinda City. Models using path analysis programs and data are processed through SPSS version 23. This research states sub-structure model 1 is known as social media marketing and the effectiveness of advertising directly has a significant positive effect on brand awareness. From sub-structure 2, the effectiveness of advertising and brand awareness directly has a significant positive effect on the intention to buy. Finally, social media marketing and the effectiveness of advertising indirectly have a significant positive effect on intention to buy through brand awareness.
 Keywords: Social media marketing; Word of mouth; Effectiveness of advertising; Brand awareness; Intention to buy

Galaxy Cluster Mass Estimates in the Presence of Substructure

Abstract We develop and implement a model to analyze the internal kinematics of galaxy clusters that may contain subpopulations of galaxies that do not independently trace the cluster potential. The model allows for substructures within the cluster environment and disentangles cluster members from contaminating foreground and background galaxies. We estimate the cluster velocity dispersion and/or mass while marginalizing over uncertainties in all of the above complexities. Using mock observations from the MultiDark simulation, we compare the true substructures from the simulation with the substructures identified by our model, showing that 50% of the identified substructures have at least 79% of its members are also members of the same true substructure, which is on par with other substructure identification algorithms. Furthermore, we show a ∼35% decrease in scatter in the inferred velocity dispersion versus true cluster mass relationship when comparing a model that allows three substructures to a model that assumes no substructure. In a first application to our published data for A267, we identify up to four distinct galaxy subpopulations. We use these results to explore the sensitivity of inferred cluster properties to the treatment of substructure. Compared to a model that assumes no substructure, our substructure model reduces the dynamical mass of A267 by ∼22% and shifts the cluster mean velocity by ∼100 km s−1, approximately doubling the offset with respect to the velocity of A267's brightest cluster galaxy. Embedding the spherical Jeans equation within this framework, we infer for A267 a halo mass M 200 = (7.0 ± 1.3) × 1014 M ⊙ h −1 and concentration , consistent with the mass–concentration relation found in cosmological simulations.

Effect of repetitive firing on passive fit of metal substructure produced by the laser sintering in implant-supported fixed prosthesis.

PURPOSEThe aim of the present study was to investigate the passive fit of metal substructure after repetitive firing processes in implant-supposed prosthesis.MATERIALS AND METHODSFive implants (4 mm diameter and 10 mm length) were placed into the resin-based mandibular model and 1-piece of screw-retained metal substructure was produced with the direct metal laser sintering (DMSL) method using Co-Cr compound (n = 10). The distance between the marked points on the multiunit supports and the marginal end of the substructure was measured using a scanning electron microscope (SEM) at each stage (metal, opaque, dentin, and glaze). 15 measurements were taken from each prosthesis, and 150 measurements from 10 samples were obtained. In total, 600 measurements were carried out at 4 stages. One-way ANOVA test was used for statistical evaluation of the data.RESULTSWhen the obtained marginal range values were examined, differences between groups were found to be statistically significant (P<.001). The lowest values were found in the metal stage (172.4 ± 76.5 µm) and the highest values (238.03 ± 118.92 µm) were determined after glaze application. When the interval values for groups are compared with pairs, the differences between metal with dentin, metal with glaze, opaque with dentin, opaque with glaze, and dentin with glaze were found to be significant (P<.05), whereas the difference between opaque with metal was found to be insignificant (P=.992).CONCLUSIONPassive fit of 1-piece designed implant-retained fixed prosthesis that is supported by multiple implants is negatively affected by repetitive firing processes.

Dynamic characteristics of high-speed gasoline engine turbocharger based on thermo-elasto-hydrodynamic lubrication bearing model and flexible multibody dynamics method.

A flexible multibody dynamic calculation model based on thermo-elasto-hydrodynamic lubrication bearing model was established. This numerical simulation method provided a more realistic turbocharger calculation model and a more reliable theoretical support for studying the dynamic vibration characteristics of the floating ring bearing turbocharger system. In order to fully consider the dynamic characteristics of each component, the behavior of the floating ring bearing was described by generalized incompressible Reynolds equation in thermo-elasto-hydrodynamic lubrication model. The flexible body substructure models were established by the modal synthesis method. Based on this model, the direct mathematical model of the relationship between the eccentricity of the rotor and the oil film clearance on the turbocharger's surface vibration was established. The influence of eccentricity and oil film thickness on the surface vibration of the turbocharger body was calculated by transient dynamics method. The results showed that the eccentricity of the rotor and the vibration of turbocharger housing were monotonic functions, but the interaction between the whirl of internal and external oil films made the mechanism of the influence of the oil film thickness on the turbocharger body's vibration complicated. The research provided a new idea for the structural vibration and synchronous noise control of the supercharger.

All-On-Four Konseptine Göre Farkli Materyaller İle Üretilmiş Sabit Dental Protezlerin Stres Analizleri

Objective: The most important factor affecting the long-term success of implant supported systems is biomechanics after prosthesis delivery. The aim of this study was to investigate the prosthetic restorations designed by using different substructure materials on the implants placed according to All-On-4 technique in atrophic mandible with different stress analysis methods and compare the methods each other.Methods: For this purpose, a photo-elastic resin model, according to All-On-4 concept was prepared. After taking impression, fiber-reinforced resin, PEEK, zirconia and metal substructures were manufactured with Cad/Cam. Photo elastic stress analysis was performed. On the other hand 3D virtual models of the same substructures were formed with the .stl data of the CAD. Then finite element stres analysis was applied at the same circumstances.Results: In the photoelastic and finite element stres analysis, rigid substructures such as metal and zirconia showed lower stres values than elastic materials such as PEEK and fiber. As a facility of the finite element analysis internal stresses of the substructures were evaluated. Lower stresses were observed in fiber and PEEK infrastructures with low elastic modulus. Conclusion: İncreased modulus of elasticity of the infrastructure, reduced.stresses transmitted to the implants When the internal stresses of the materials were evaluated, lower stresses were seen in infrastructures such as fiber and PEEK with low elastic modulus .Photoelastic and finite element stress analyzes gave similar stress results to the implant and surrounding tissues. Therefore, the results supported each other.

Precise Seismic Substructural Model of the Eocene Chorgali Limestone in the Turkwal Oil Field, Central Potwar, Pakistan

The precise seismic substructural interpretation of the Turkwal oil field in the Central Potwar region of district Chakwal of Pakistan has been carried out. The research work was confined to the large fore‐thrust that serves as an anticlinal structural trap through ten 2D seismic lines. A precise seismic substructural model of the Eocene Chorgali Limestone with precise orientation of thrust and oblique slip faults shows the presence of a huge fracture, which made this deposit a good reservoir. The abrupt surface changes in dip azimuth for the Eocene Chorgali Limestone verifies the structural trends and also the presence of structural traps in the Turkwal field. The logs of three wells (Turkwal deep X‐2, Turkwal‐01 and Fimkassar‐01) were analyzed for petrophysical studies, well synthetic results and generation of an Amplitude Versus Offset (AVO) model for the area. The AVO model of Turkwal deep X‐2 shows abrupt changes in amplitude, which depicts the presence of hydrocarbon content. Well correlation technique was used to define the overall stratigraphic setting and the thickness of the reservoir formation in two wells, Turkwal‐01 and Turkwal deep X‐2. The Eocene Chorgali Limestone in Turkwal‐01 is an upward thrusted anticlinal structure and because of the close position of both wells to the faulted anticlinal structure, its lesser thickness differs compared to Turkwal deep X‐2. The overall results confirm that the Turkwal field is comparable to several similar thrust‐bound oil‐bearing structures in the Potwar basin.

Optimization of Flexible Hose for Reducing Flow Maldistribution in Manifolds

Coolant Distribution Systems (CDS) are required to be optimally designed to ensure predefined mass flow rate in all parallel channels between exit and collecting manifolds, while maintaining low-pressure drop across them. Even small change in the pressure drop at component level will result in maldistribution of flow rate and increase in overall pressure drop of CDS. Numerical and experimental study had been carried out in the work proposed for change in pressure drop due to deformation of end connector’s bend cross section, in a flexible hose. The methodology for optimum modelling of the problem on CFD tool using sub-structuring method is also suggested. In sub-structuring method a part of complete hose (henceforth referred as sub-structured model), has been used instead of complete model of flexible hose. Results of sub-structuring model were compared with that of a complete model of a flexible hose. Numerical values obtained from simulation were validated with experimental results. Optimum bend cross section for avoiding maldistribution in parallel channels and increase in pressure drop of CDS were calculated. Substantial reduction in computation cost was achieved with negligible loss of accuracy in pressure drop values.

Discovery prospects of dwarf spheroidal galaxies for indirect dark matter searches

We study the prospects for the Large Synoptic Survey Telescope (LSST) to find new dwarf spheroidal galaxies in the Milky Way. Adopting models of Milky-Way halo substructure and phenomenological prescriptions connecting subhalos and satellite galaxies, we obtain surface brightness distributions of V-band magnitude that lead us to predict that LSST will discover tens to hundreds of dwarf spheroidal galaxies above its sensitivity. The soon-to-be-discovered dwarfs will be interesting targets for indirect searches of dark matter annihilation yields. We forecast the distribution function of gamma-ray emission from dark matter annihilation in these objects, and discuss the detectability of these signals at both Fermi Large Area Telescope (LAT) and Cherenkov Telescope Array (CTA). By combining information from the predicted dwarf galaxies, we obtain an expected sensitivity to the annihilation cross section ⟨ σ v ⟩ of 10−26 cm3 s−1 (for dark matter particles of mass 10 GeV with Fermi-LAT) and 5× 10−24 cm3 s−1 (for dark matter particles of mass 500 GeV with CTA). We find that the current uncertainties in the mass measurement of the Milky-Way halo are relatively minor compared with the Poisson errors associated to drawing the most promising dwarfs from the underlying flux distribution.

Study on heavy-duty journal bearing lubrication based on Elasto-hydrodynamic lubrication method

Main bearing wear failure to become one of the main factors affecting the service-life of the engine, so it is necessary to form the effective analysis of the main bearing lubrication method, which is used in the design of main bearing lubrication and friction. In this paper, the model of substructure of V8 diesel engine is built based on flexible multi-body dynamics, the various nonlinear factors in the process of engine working process are considered, and the EHD of main bearings is analysed by the EXCITE software. On the basis of the V8 engine model, the bearing load and lubrication performances of different poly- condensation of main bearing are compared. The main bearing lubrication properties of the analysis results can be used for the engine lubrication system design and optimization.

Numerical modeling of high-strength steel composite K-eccentrically braced frames and spatial substructure hybrid simulation tests

Substructure hybrid simulation test (SHST) is a novel seismic experimental method for analyzing structures, which usually divides the global structure into two components: the experimental substructure and the numerical substructure. An SHST system based on the OpenFresco platform was established. To ensure the high accuracy of the numerical substructure in SHST, a finite element model that corresponded to a quasi-static experimental investigation on high-strength steel composite K-shaped eccentrically braced frame (K-HSS-EBF) was established and analyzed using OpenSees. A three-story and five-span spatial K-HSS-EBF was used as the prototype and the three-story steel frame with a K-eccentric brace on the left second span was taken as the experimental substructure. The remaining four-span was modeled as a numerical substructure in OpenSees. SHST was performed with a half-scale hybrid simulation model. According to the test results, the displacement loading precision of the experimental substructure was analyzed. In addition, the shear link rotations of the experimental and numerical substructures were compared. The time curve of the displacement and the base shear of the hybrid simulation model were also compared with the simulation results of the global numerical model. The results revealed that the seismic response characteristics of the K-HSS-EBF were successfully recaptured using the numerical substructure model established in OpenSees and the spatial SHST system based on OpenFresco.

An augmented free-interface-based modal substructuring for nonlinear structural dynamics including interface reduction

This work proposes two novel aspects for modal substructuring of geometrical nonlinear structural dynamics. Firstly, we present a non-intrusive model order reduction technique for substructures using an augmented free-interface method with residual flexibility attachment modes. Non-intrusive model reduction methods are beneficial, because they do not require to access substructures' closed form equations of motion while building nonlinear reduced models. Therefore, they can be easily combined with commercial finite element packages. Generally, the interface of substructures can contain many degrees-of-freedom leading to reduced order models, which are still computationally expensive. As a second novel point, the nonlinear reduced models of substructures are developed when the augmented free-interface-based method is combined with three interface reduction techniques (one system-level and two local-level), which so far have only been used with the fixed-interface method of Hurty/Craig-Bampton. The proposed methods are compared in terms of accuracy and computational efficiency with the two existing non-intrusive-based modal substructuring methods: nonlinear free-interface and nonlinear Hurty/Craig-Bampton methods. The performance of the improved free-interface method is examined on two different geometrically nonlinear structures by applying random pressure on them and comparing displacement spectral densities. The dynamic results show a remarkable improvement of accuracy compared to the nonlinear free-interface method and a slightly improved accuracy compared to the nonlinear Hurty/Craig-Bampton method. This improvement is achieved while the online computational costs are not increased significantly.

Accuracy and Efficiency of Updated FRF Coupling for the Dynamic Behaviour Investigation of an Assembled Structure

The frequency based substructuring (FBS) method allows the combination between the experimental and analytical frequency response function (FRF). The combined FRF is then used for calculation of the dynamic behaviour of an assembled structure which usually consists of a large number structural components or substructures. However, the accuracy of the dynamic behaviour calculated using the FBS method relies heavily on the quality of experimental FRF data of the interfaces on which, in practice, it is very problematic to be attained. Furthermore, in most cases, some parts of rotational FRF data are not included in the FBS method due to the complex measurement process. The exclusion of the rotational FRF data will usually lead to numerous errors in the combined FRF data. Therefore, this paper proposes a new frequency response function (FRF) coupling of the FBS method that may uniquely address the difficulties and improve the quality of predicted results of the FBS method. The proposed coupling was formulated based on the finite element method, model updating method and FRF synthesize method. The finite element model of the physical test substructure was developed and reconciled based on the mode shapes obtained from experimental modal analysis. The FRF synthesize method was performed on the updated finite element model to obtain a complete matrix with a full degree of freedom FRF data containing all the translational and rotational FRF data required. It was found that the proposed coupling has allowed generating full translational and rotational FRF data. The generation has improved significantly the FRF coupling process and the quality of the predicted dynamic behaviour of the FBS method.

Nonradical transformation of sulfamethoxazole by carbon nanotube activated peroxydisulfate: Kinetics, mechanism and product toxicity

In this work, the transformation of sulfamethoxazole (SMX) by peroxydisulfate (PDS) activated with one multi-walled carbon nanotube (CNT) via a nonradical pathway was examined, and the underlying reaction mechanism was explicated. The nonradical PDS/CNT process exhibited considerable reactivity toward SMX, and the oxidation of SMX was enhanced by the decrease of solution pH. The addition of background inorganic ions (i.e., bicarbonate and chloride ion) showed ignorable impacts on SMX transformation, while natural organic matter resulted in the decrease of SMX oxidation rate. The stoichiometric efficiency of SMX degraded vs PDS consumed in the presence of CNT was obviously higher compared to that obtained in the case of zero-valent iron (a common heterogeneous metal activator for PDS). The oxidation of sub-structural model compounds in the PDS/CNT process unveiled that the main reactive functional group of SMX molecule for attack by nonradical reactive species was aniline moiety, while the isoxazole moiety could also be slowly oxidized. A total of six oxidation products were identified during SMX treatment by the PDS/CNT process, and their generation pathways mainly included hydroxylation, isoxazole ring opening, and sulfonamide NS bond cleavage. Ecotoxicity analysis by ECOSAR showed that the toxicity of these products was generally lower than parent SMX. Consequently, this work demonstrate that the emerging PDS/CNT oxidation technology is likely a prospective candidate for destruction of SMX in water and wastewaters.