A novel computer vision and point cloud-based approach for accurate structural analysis of a tall irregular timber structure

A reliable and accurate analytical model is desired for the printed circuit board (PCB) with IC package to predict the system response due to loadings such as shock and vibration simulation or even with thermal effect. This work addresses the procedure of model verification by the adoption of experimental modal analysis (EMA) to validate the finite element (FE) model constructed by FE commercial software. The PCB with one package adhered with the heating pad to emulate the heat effect is first considered for completely free boundary condition. The refined FE model of the PCB consists of detail components, such as the chip, substrate, compound and solder balls. The thermal effect on the PCB is simulated to conduct the temperature field analysis as well as the thermal stress. The modal analysis on the PCB with the heating in steady state is then performed to obtain the structural modal parameters, i.e. natural frequencies and mode shapes. The EMA is also carried out to determine the system modal properties that are used to update the analytical FE model. Through the comparison of frequency response functions and modal parameters between the analytical FE model and the real PCB structure, the refined FE model can be verified for material properties and thermal boundary conditions. The same procedure for model verification is then conducted via both EMA and FEA on the PCB in the fixed boundary that complies with the test fixture for the random vibration test of JEDEC specification. The verified equivalent FE model of the PCB can then be adopted to perform spectrum response analysis accordingly.

This study investigates the dynamic performance of a large‐span suspended steel space frame‐glass composite floor (SSSF‐GCF). Both the ambient vibration and the human‐induced vibration of the floor were experimentally measured to identify vertical dynamic characteristics and evaluate vibration serviceability of the floor. Although vertical dynamic characteristics of the floor based on the global simplified finite element (FE) model of the structure agree well with those identified via experimental modal analysis, the global simplified FE model significantly underestimates vertical vibration amplitudes of the floor due to the coupled effect between two layers. Accordingly, an equivalent local FE model of the floor system was proposed and updated via adjusting the vertical stiffness of the interstory hanging pillars. It is shown that the equivalent local FE model can well predict both the dynamic characteristics and human‐induced vibration response of the floor. Finally, the effect of the damping ratio on the acceleration response of the floor was numerically demonstrated with the verified local FE model.

As the rate of increase in areal density of the HDD has accelerated, dynamic characteristics of the HDD actuator need to be improved with respect to the performance of the tracking servo and shock transmission. Therefore, it is important to analyze the vibration characteristic of the HDD actuator that consists of the VCM part, E-block and pivot bearing. In this paper, vibration modes of the HDD actuator are investigated the using finite element and experimental modal analyses methods. To develop a detailed finite element model, finite element models of each components of the actuator assembly are constructed and tuned to the results of the EMA. The VCM coil is modeled as an equivalent finite element model that has an orthotropic material property using auto-model updating program. Auto-model updating program with improved sensitivity based iterative method is applied to build a detailed finite element model using the result of the EMA. A detailed finite element model of the HDD actuator is then constructed and analyzed.

The study aims to build an equivalent 2D model as an alternative to the 3D model of sandwich panel structures. This model enables for reducing model building time and calculation time in the design calculation of this sandwich structure. The research object in this study is corrugated core cardboard. First, the isotropic plasticity equivalent (IPE) model for the paper material is implemented in the Abaqus software, using the VUMAT user subroutine. Subsequently, the homogenization method is proposed as an equivalent elastic-plastic finite element model. This model is implemented in Abaqus using the UGENS subroutine. Finally, numerical simulations of different load cases between the 3D model and the equivalent 2D model are performed to confirm the accuracy of the proposed model. The comparison results indicate that the equivalent model ensures exceptional accuracy compared to the 3D model but significantly reduces model building time and CPU time.

Composite materials, particularly honeycomb composites, are widely utilized in various industries, including aerospace, due to their high energy absorption against the impact and exceptional strength-to-weight ratio. This study aims to leverage the plastic and elastic properties of these materials to develop a simplified numerical model that incorporates orthotropic properties for core modeling. By doing so, the need for detailed honeycomb structure modeling is eliminated, resulting in reduced computational costs and time. A comprehensive three-dimensional finite element model, accounting for structural intricacies, is presented based on experimental data from a reputable source (isotropic model) and its equivalent finite element model (orthotropic model). The model is validated by the experimental results, demonstrating good agreement. The study also investigates parameters such as energy absorption, the internal energy of the core and faces, maximum displacement, and maximum contact force under low-velocity impact scenarios with spherical and cylindrical projectiles. These findings highlight the effectiveness of the orthotropic model, particularly in showcasing greater energy absorption in the core of the sandwich panel when subjected to a cylindrical impactor.

Bending moment–curvature relations (M-χ) are useful in many beam modelling approaches. It allows describing in a simple way the mechanical behaviour at the cross-section scale and can be used to model continuous beams as single degree of freedom systems dedicated to perform stochastic analysis. This paper focused on tree mechanical charaterisation and presents an identification method for obtaining bending moment–curvature relationships up to failure from Digital Image Correlation (DIC) and experimental three points bending tests. Due to wood intrinsic variability, the proposed identification method has been validated from a Finite Element (FE) model which aims at simulating precisely the bending response of a cylindrical stem. The refined FE model has been developed based on the geometry and the boundary conditions of the experimentally tested stems. M-χ curves are derived from the FE model and used within a Single Degree Of Freedom (SDOF) approach. At the stem scale, the prediction of the SDOF model (Force-Displacement) is compared to the FE model and lead to a good agreement. Then the approach is used to characterise fresh European beech samples allowing deriving their mechanical properties (longitudinal Young modulus, modulus of elasticity and modulus of rupture).

Experimental and numerical study of T-shaped irregularly concrete-filled steel tube columns under combined axial loads and moments

In various applications it is important to determine dynamically equivalent spatial finite element (FE) model of complex structures. For instance, obtaining the FE model of an existing aerospace structure is a major requirement for reliable aeroelastic analysis. In such applications a reliable FE model may not be always available, and when this is so a dynamically equivalent FE model derived from modal test will be very useful. This paper presents a noble method to determine spatial FE model of a structure by using experimentally measured modal data along with the connectivity information of measurement points. The method is based on the mass and stiffness orthogonality equations written using experimentally determined mode shapes and natural frequencies. These equations are solved for geometric and material properties constituting global spatial mass and stiffness matrices of an initial FE model. Starting from this initial FE model, mass and stiffness orthogonality equations are updated iteratively employing experimentally obtained natural frequencies and corresponding eigenvectors from the FE model. Iterations are continued until eigensolution of the updated FE model closely correlates with experimentally measured modal data. A simulated case study on GARTEUR scaled aircraft model is presented in order to demonstrate the applicability of the method.

Welded joints in grid structures are susceptible to damage and destruction when exposed to random excitation. The complexity of the grid structure poses challenges for realizing the damage recognition of welded joints. In this study, a two-step method is proposed specifically for damage identification of welded joints in grid structures, combining wavelet analysis and fuzzy pattern recognition to accurately identify the location and extent of damage in welded joints. Firstly, the structure is divided based on the analysis of the influence range of joint damage. Key joints are selected within the sub-regions where sensors are installed, and the acceleration response of these key joints is measured. Wavelet analysis is then applied to identify the sub-regions where weld damage occurs. Secondly, an equivalent finite element model is established for joints with varying degrees of damage. The damage index, calculated as the ratio of the absolute value of the difference in the first-order element strain mode of the members, increases with the degree of damage during joint weld damage. By monitoring the changes in the damage index of sensitive members, which exhibit significant changes with varying weld damage degrees, a damage pattern database is constructed for each sub-region. The membership degree between joint damage and the patterns in the pattern database is then calculated to determine the location and degree of weld damage. To validate the effectiveness of the proposed method, an experiment was conducted using a grid structure model with replaceable members. Highly sensitive FBG sensors were designed to measure the acceleration response of the joints, resulting in accurate identification of damaged sub-regions solely through the measurement of key joint acceleration responses. Furthermore, within the damaged sub-regions, the fuzzy pattern recognition method precisely determined the location and degree of weld damage in the joints. The experimental results demonstrate that the proposed method effectively reduces the complexity of the structure by dividing the grid structure into sub-regions, and enables the two-step identification method to achieve successful damage identification for the joints in the grid structure with high efficiency and accuracy.

The micromechanical stresses that arise within each phase (i.e., fiber, matrix, interphase) of a fiber-reinforced composite material under three-dimensional mechanical and hygrothermal loading are investigated analytically. An elasticity solution is developed for the case in which the fibers are arranged in a regular, periodic array. The model accounts for fiber-fiber interactions, multiple interphases, cylindrically-orthotropic and temperature- and moisture-dependent material properties. In addition to modeling micromechanical stress states, the model is used to calculate composite properties using knowledge of the stress variation in the individual phases present in the material system. The elasticity solutions developed herein are more accurate, more computationally efficient, and less numerically sensitive (in the modeling of thin interphases) than an equivalent finite element model. Results presented in this paper include the effect of interphase stiffness on the stress distribution in a composite lamina subjcted to tranverse loading. The study suggests that there is an “optimum” interphase stiffness which minimizes the stress concentration in the matrix region. Comparisons performed with a concentric cylinder model suggest that an appropriate interphase region can reduce the extreme stress variations caused by fiber-fiber interaction.

In this paper, a novel modeling method for hybrid excitation synchronous machines (HESMs) with radial/axial flux paths via magnetic equivalent circuit (MEC) is proposed. 3-D finite-element analysis (FEA) is essential when analyzing a machine with radial/axial flux paths due to the asymmetry in the axial direction. However, 3-D FEA is computationally expensive and time-consuming, especially during the preliminary design stage. The proposed modeling method is analyzed and validated based on an HESM with magnetic shunting rotor. The fundamental structure and working principle of the HESM with magnetic shunting rotor are introduced. On the basis of 3-D structure, an MEC considering saturation and leakage flux distribution is built and illustrated, as well as field analysis is performed. A 2-D equivalent finite-element model via MEC is built and illustrated. A prototype HESM with magnetic shunting rotor has been designed by the proposed modeling method and developed for experimental verification. With the proposed modeling method, the computational efficiency is significantly improved in the design stage. The proposed modeling method is verified by the good agreement between the predicted and measured results.

As a typical feature of traditional Chinese timber structures, columns with floating foot joints are prone to rocking under horizontal force. The column rocking behavior plays an important role in resisting lateral loads. This paper proposes modelling strategies for the rocking behavior of traditional timber columns. The proposed model can capture the contact state of the column foot via a series of distributed axial springs and the possible sliding via a horizontal spring. It has a lower computational cost than refined finite element (FE) models and is independent of numerical calibration compared to rotational spring models. The modelling strategies were validated against refined FE models and experimental data available in the literature. The principle behavior of the approach was carefully investigated including contact stiffness, distribution modes, spring numbers, column bending effects, and computational efficiency. Results show that the effective compression height of the column foot can take the value of the column radius to determine spring stiffness. Column bending needs to be considered in the mechanical analysis of column foot joints for slender columns. The case study on the lateral stiffness of traditional timber frames confirms the applicability of the proposed model in the structural analysis of ancient timber buildings.

Damage qualification is generally of concern in vibration-based damage assessment of bridges and structures, in which the model-based method, such as the finite-element (FE) model updating, is often a favorable choice in terms of efficacy and accuracy. However, the numerical problems to be solved are often ill-conditioned and sometimes even ill-posed, due to the limited number of the measurements and the large number of potential parameters to be updated in the FE model. Furthermore, in real-world applications, the effects of experimental and modeling errors. need to be accounted for From the practical point of view, there is often a trade-off between the cost of the vibration measurements and the precision of the experimental results, and another trade-off between the computational efficiency of the simplified FE model and the numerical fidelity of the refined FE model. The satisfactory solution of these problems is crucial to the success of the damage assessment in real-world applications, which remains scarce. In this paper, a multistage model updating approach is proposed for damage quantification of a prestressed concrete girder bridge by using the results of an extensive experimental campaign. Although severe corrosion damage had been found by visual inspection before the measurements, the vibration-based damage assessment was performed without a priori knowledge of the existence and location of damage. The appealing feature of this work is the scale and complexity of the studied structure. By updating a simplified orthotropic plate model, the damage was satisfactorily identified in terms of its extent and severity for both a simulated damage scenario and the real structure. A good balance between the accuracy and efficiency has been reached by the proposed multistage model updating approach. The developed methodology can be applied to similar multigirder bridges, which are common in the regional highway network.

Finite element modelling of concrete-filled steel stub columns under axial compression

A comprehensive finite-element model of a turbine-generator infinite-busbar system