Structural Strength Evaluation Research Articles

Study on fracture of hyperelastic Kirchhoff-Love plates and shells by phase field method

Thin walled structures such as plates and shells are widely used in many engineering fields. To Predict its fracture behavior is of great significance for integrity design and strength evaluation of engineering structures. Numerical simulation of the fracture behavior of hyperelastic plates and shells is a challenge due to complex kinematic description, hyperelastic constitutive relationship, geometric nonlinearity and the degradation on elastic parameter caused by fracture damage. Combining Kirchhoff Love (K-L) shell theory with the fracture phase field method, and numerically discretizing the first and second order partial derivatives of displacement field and phase field by using T-splines and meeting the requirements of K-L plate and shell theory for the C1 continuity of the shape function, a model for the isogeometric analysis numerical formulation of the phase field fracture in hyperelastic K-L plates and shells is established. The fracture failure behavior of hyperelastic K-L plates and shells under the uniform load and displacement load is simulated, and the effect of the Gaussian curvature on the fracture behavior of hyperelastic K-L shells is studied. The simulation results show that the present numerical scheme can effectively capture the complex crack propagation path of plates and shells under the uniform load, and the displacement field can effectively reflect the crack distribution of materials. The thin shell with negative Gaussian curvature shows the excellent fracture performance under the internal pressure, and can withstand the greater internal pressure.

Strength Evaluation of the Flow Passage Stationary Structures of a Large Francis Turbine Unit

Abstract The multifield design and multifield coupling performance of the Francis turbine unit is a topic that needs to be studied deeply. In this paper, the strength evaluation of the stationary structures of the flow passage of a large Francis turbine unit under extreme conditions has been performed based on the fluid-structure coupling theory. The calculated stationary structures include the spiral casing, bottom ring, and head cover. The pressure load applied on the structures is 1.5 times the maximum head of the unit. The results show that there is stress concentration in the spiral casing, and the weld length with equivalent stress greater than 345 MPa reaches 800 mm; the maximum stress at the rib plate of the head cover reaches 357 MPa, which is greater than the yield limit 345MPa. Based on the evaluation results, the local and overall defects of the unit design can be found. The suggested strength evaluation methodology can provide references for the optimization of the unit and a theoretical basis for the operation of the unit.

Structural Behaviour and Strength Evaluation of a Venetian Church through Finite-Element Analysis

The evaluation of the structural behaviour of a masonry Venetian church with a pointed barrel vault is presented in this paper through an analysis following the necessary steps of a monument study. With a detailed geometric model and material estimation, the finite-element method is used to investigate the influence of specific structural parts of the structure, like masonry buttresses and wall connections, on the structural behaviour. The operational modal analysis is used to identify the structure dynamically. The comparison of the eigenfrequencies, which are estimated by in situ measurements and finite-element modal analysis, is used to perform a model identification. The response spectrum analysis, the static analysis after the subsistence of some parts following strengthening proposals, and the transient analysis of specific seismic excitations are used for the evaluation of the structural behaviour. The purpose of the work is to highlight the need for an interdisciplinary approach to the study of a monumental complex structure, regardless of its scale. The coexistence of structural elements of different stiffnesses, such as vaults, elongated walls, buttresses, transverse walls with pediment and belfry, as well as the concha, affects the mechanical behaviour and the pathology of the structure, which is difficult to study with simplifying models. From the analysis, it is concluded that subsidence problems, combined with seismic actions, lead to the cracking of the masonry, while the existence of buttresses limits the extension of the damage and contributes to the stabilization of the structure.

해양 시추선용 경량 수밀 공조 덕트의 구조해석 및 강도 평가

해양 시추선용 경량 수밀 공조 덕트의 구조해석 및 강도 평가

Orthopedic Scaffolds: Evaluation of Structural Strength and Permeability of Fluid Flow via an Open Cell Neovius Structure for Bone Tissue Engineering.

The ability of bone to regenerate itself through mechanobiological responses is its dynamic property. Mechanical cues from a neighboring environment produce the structural strain to promote blood flow and bone marrow mobility that in turn aids the bone regeneration process. Occurrences of these phenomena are crucial for the success of metallic scaffolds implanted in the host bone tissue. Thus, permeability and fluid flow-induced wall shear stress (WSS) are two parameters that directly influence cell bioactivities inside a scaffold and are crucial for effective bone tissue regeneration. Given that the scaffolds shall be implanted in the body, permeability assessment was carried out using non-Newtonian fluid. In this work, the triply periodic minimal surface scaffolds with Neovius architectures were fabricated by using selective laser melting technology. The estimation of fluid flow was carried out using computational fluid dynamics (CFD) analysis with a non-Newtonian blood fluid model. Further, the structural strength of various open cell Neovius lattices was evaluated using a static compression test, and in vitro cell culture using Alamar blue assay was evaluated. Results revealed that the values of intrinsic blood flow permeability of the three-dimensional (3D)-printed open cell porous scaffold with Neovius architecture were of the same order of magnitude as those of human bone, ranging from 0.0025 × 10-9 to 0.0152 × 10-9 m2. The structural elastic modulus and compressive strength of NOCL40, NOCL50, and NOCL60 lattices range from 3.27 to 3.71 GPa and 194 to 205 MPa, respectively. All of the values are comparable to the human bone, thus making these lattices a suitable alternative for orthopedic applications.

Rapid acquisition method for structural strength evaluation stresses of the ship digital twin model

The existing ship hull structure stress monitoring can only give the stress state of typical measuring points, but the monitoring point may not be the most dangerous location of the ship hull structure. To solve this problem, this paper carried out the research of ship strength digital twin. Concretely, to meet the real-time requirements for obtaining the structural stress state, this paper proposed a rapid acquisition method for structural strength evaluation stresses of the ship digital twin model, which realizes the rapid acquisition for structural yield strength evaluation stresses at the monitoring point and the non-monitoring point. To illustrate the specific application and application effect of the proposed method, the amidships three compartments section of a 21,000TEU ultra-large container ship was selected as the research object. And the case that this research object may suffer from the vertical wave bending moment and the horizontal wave bending moment simultaneously was considered. Related studies show that the proposed method can accurately recognize the load actually suffered by the ship monitoring structure. And the specific meaning of the ship monitoring structure referred to here is the ship hull structure that requires structural stress state monitoring. At the same time, related studies also show that the maximum error of the calculation results obtained by the proposed method does not exceed 0.0005% in obtaining the structural yield strength evaluation stress at the monitoring point, while the maximum calculation error does not exceed 0.032% in obtaining the structural yield strength evaluation stress at the non-monitoring point.

Structural Design of the Substructure of a 10 MW Floating Offshore Wind Turbine System Using Dominant Load Parameters

Fully coupled integrated load analyses (ILAs) to evaluate not only the load response but also the structural integrity are required to design a floating offshore wind turbine, since there has been no firmly established approach for obtaining the structural responses of a FOWT substructure in the time domain. This study aimed to explore if a direct strength analysis (DSA) technique that has been widely used for ships and offshore structures can adequately evaluate the FOWT substructure. In this study, acceleration and nacelle thrust were used for the dominant load parameters for DSA. The turbine thrust corresponding to the 50-year return period was taken from the literature. The acceleration response amplitude operator (RAO) was obtained through frequency response hydrodynamic analysis. The short-term sea states defined by the wave scatter diagram (WSD) of the expected installation area was represented by the JONSWAP wave spectrum. To account for the multi-directionality of the short-crested waves, the 0th order moments of the wave spectrum were corrected. The probabilities of each short-term sea state and each wave incidence angle were applied to derive the long-term acceleration for each return period. DSA cases were generated by combining the long-term acceleration and nacelle thrust to maximize the forces in the surge, sway, and heave directions. Linear spring elements were placed under the three outer columns of the substructure to provide soft constraints for hive, roll, and pitch motions. Nonlinear spring elements with initial tension were placed on the three fairlead chain stoppers (FCSs) to simulate the station-keeping ability of the mooring lines; they provided initial tension in the slacked position and an increased tension in the taut position. The structural strength evaluation of the coarse mesh finite element model with an element size same as the stiffener spacing showed that high stresses exceeding the permissible stresses occurred in the unstable members of the substructure. The high stress areas were re-evaluated using a fine mesh finite element model with an element size of 50 mm × 50 mm. The scope of structural reinforcement was identified from the fine mesh analyses. It was found that the DSA can be properly utilized for the substructure strength assessment of a FOWT.

Dynamic simulation of nozzle structure based on thermal-fluid-solid coupling analysis

Many engineering structures are subjected to the combined action of thermal field, flow field and vibration load during use. The mechanical analysis of this kind of structure has important theoretical significance and engineering practical value. However, due to the complexity of multi-field coupling, it is difficult to analyze dynamic response and dynamic strength. A method to simplify the thermal-fluid-solid coupling model for specific engineering issues was proposed aiming at modeling the actual situation in which the high temperature field of the engine nozzle structure is relatively stable. Heated grid reconstruction, thermal modal analysis technology, and fluid-structure coupling response calculation method based on modal superposition were taken to obtain the load distribution and dynamic response level of the engine nozzle structure under the condition of thermal-fluid-solid coupling, which created conditions for structural dynamic strength evaluation including the prediction of vibration fatigue life. The test structure of an engine nozzle was taken as an example to perform dynamic response calculation and fatigue life prediction under thermal fluid-solid coupling conditions. Then the location of weak parts of the structure was identified, and effective suggestions for design improvement was put forward. Compared with the actual test results, the feasibility and accuracy of the method are preliminarily verified.

Buckling and Post-buckling Analysis of Composite Hat Stiffened Panels under Axial Compression Loads

Owing to their unique material design-ability and excellent weight reduction properties of carbon fibre reinforced polymers(CFRP), commercial aircraft OEMs have been innovating design and manufacturing approaches to wider the application of advanced composites. In this paper, the bearing capacity of composite hat-stiffened panels is determined by an improved engineering calculation method and numerical analysis method. The effectiveness of both methods is verified by the test. The advantage of the engineering estimation method is simple and fast, which is suitable for the parametric analysis of the structure in the preliminary design phase. The finite element method can better simulate the test process and is suitable for the comprehensive evaluation of structural strength. The combination of the two methods has a high reference value for rapid design and selection.

Structural Analysis of the Governing Variables Affecting the Structural Strength Evaluation of the Lashing Bridges in Container Vessels

Structural Analysis of the Governing Variables Affecting the Structural Strength Evaluation of the Lashing Bridges in Container Vessels

Machine learning for strength evaluation of concrete structures – Critical review

Artificial intelligence (AI) in the form of machine learning enables the working framework to get more accurate at interpreting outcomes without being explicitly programmed. Machine learning is described as a collection of techniques and algorithms that are capable of extracting information from data and continually enhancing their capabilities through the process of learning from experience. In Machine learning, Artificial Neural Networks (ANN), Multiple linear regression, support vector machine, and linear regression are widely available. An outline of the benefits of machine learning (ML) in the domain of Civil Engineering is described in this article. The review focused more on the determination of the strength characteristics of concrete through machine learning. Rapid growth in the sophistication of these approaches has had a profound impact on Civil Engineering, particularly in the building and infrastructure industries. In the field of Civil Engineering, Machine Learning plays a significant role in forecasting strength, particularly compressive strength and the physical features of concrete, such as assessment of crack propagation, surface roughness, etc., as opposed to the references. The review shows that machine learning-based strength estimation yields reliable findings in comparison to experimental values. The review explores various machine learning models which are used to estimate concrete properties. The XGBoost produces the best accurate result (85%) with the lowest mean absolute error. The most significant shear strength and compressive strength features, according to an analysis of the relevance of the input parameters, are the ratio of shear span to effective depth, longitudinal reinforcement ratio, concrete strength, and volume percent of fiber. The analysis demonstrated that machine learning may be utilized successfully to determine the compressive and tensile properties of concrete.

Dynamic size optimization approach to support railway carbody lightweight design process

The transition to a globalised electrical power supply pushes rolling stock manufacturers to find structural solutions for reducing the power required by the vehicles. Within a market where details can make the difference in economic terms, the concept of design optimization is becoming established. However, current industrial procedure for the evaluation of carbody structural strength, in static field and according to EN 12663-1:2015 standard, does not include any optimization process. More in general, optimization processes, and especially dynamic optimization, are not widely used for designing of railway vehicles. In this framework, the present paper proposes a new dynamic optimization approach to support the design of railway vehicle carbodies subjected to static loads. Proposed methodology aims to minimize the mass of the metallic structure, working on the thicknesses of the optimized components, maintaining the baseline geometry. The constraint function was imposed on the first natural vibration frequency of the system. The optimization strategy is based on a dynamic size optimization process in conjunction with modal analysis techniques, applied on the single carbody shell. The procedure has involved the roof assembly of a single tram vehicle body. The proposed approach is resulted numerically efficient in terms of calculation times. Encouraging results have been achieved in terms of mass saving and mechanical behaviour of the carbody shell. Optimized components were 21% lighter than the original, that corresponds to 3% if evaluated on the total mass of the single carbody metallic structure. The methodology turns out to be a useful tool for supporting designers to reduce the mass of the carbody structures, reducing overdimensioning condition that could affect the carbody structure.

Practical estimation method for extreme value distribution of von Mises stress in ship structure

This study presents a practical method for estimating the extreme value distribution of von Mises stress for ship structural strength evaluations. The previous methods of calculating this distribution require somewhat complicated numerical calculations, such as multi-dimensional integration. In contrast, the proposed method is based on an asymptotic approximation and can be easily calculated in a similar way to the conventional linear statistical prediction. A closed expression was derived in the case of stress components which have non-zero mean value. The formula is derived under approximations that reflect realistic stress conditions when ships are under severe sea states. Through a structural analysis of a whole ship, it was comprehensively verified that the proposed method has sufficiently high accuracy for structural strength evaluation. Furthermore, a parametric analysis was conducted to clarify its limit of applicability.

INTERFACE DEVELOPMENT BETWEEN THE 3D CAD SOFTWARE AND THE STRUCTURAL STRENGTH ASSESSMENT SOFTWARE FOR EFFICIENT

As the ship design has been increasing complexity with the need to drive optimization and performance at the same time, the use of various computer-aided software during the ship design process is no longer an option for these days. However, most software basically supports their own proprietary file format which can only be used by their own software, and also requires to reiterate modeling the ship design which had already been used in other software. Often these repetitive works become a major hinder to streamline the design process due to the huge cost of time and effort and may have potential risk for human error. In this regard, interfaces to increase productivity between software for data reusability were developed, but the available data was limited in 2D CAD-based. However, as 3D CAD is adopted in the shipyards, it became possible to access and utilize the 3D modeling data containing various information of the ship design. We have developed the interface function that can carry out hull structural strength evaluation for classification approval very quickly and efficiently based on the 3D CAD model. In this paper, Korean Register (KR) present the interface between 3D CAD software, NAPA Designer, and classification’s structural strength assessment software, SeaTrust-HullScan [1], that can dramatically improve design productivity.

Evaluation of structural and mechanical strength of symmetric tilt interface in W/Fe composite laminate using molecular dynamics

In this work, a tungsten (W)/iron (Fe) composite laminate is constructed by joining two constituents W and Fe according to the symmetric tilt interface relationship. The performance of the newly built W/Fe symmetric tilt interfaces is evaluated by interface energy, tensile stress–strain relationship, and strength and then compared with semi-coherent W/Fe boundaries and W and Fe symmetric tilt grain boundaries. The results show that even though most W/Fe symmetric tilt interfaces have very high interface energy, some have interface energy comparable to those of semi-coherent W/Fe boundaries and W and Fe symmetric tilt grain boundaries, and thus should be considered for W/Fe composites. The mechanical properties for tensile deformation parallel to the interface of these stable W/Fe symmetric tilt interfaces outperform the estimated values from composite theory and even those of semi-coherent W/Fe boundaries. Our findings suggest that the symmetric tilt interfaces not only play an important role in the interface strength of W/Fe composite laminate, but also should be incorporated into future designs of W/Fe or other composites to circumvent the lattice, thermal, and mechanical mismatches between heterogeneous constituents.

拘束効果を考慮した極低サイクル疲労下におけるき裂進展条件クライテリオンの提案

The strength evaluation of structures that requires high reliability, such as power generation facilities, is extremely important. It is necessary to ensure safety under extremely low cycle fatigue caused by earthquakes. However, a highly reliable evaluation method has not yet been developed because of variable fracture toughness due to the constraint effect with large deformation. The crack propagation criterion proposed in the previous study was confirmed validity under restrict condition. However, it is not considered constraint effect such as thickness and material properties. The objective of this study is confirmed whether the crack propagation criterion proposed in the previous study can apply changing of constraint effect. Furthermore, we propose the crack propagation criterion considered constraint effect under extremely low cycle fatigue.

Structural strength evaluation of injection production string in underground gas storage

Structural strength evaluation of injection production string in underground gas storage

Structural strength evaluation of injection production string in underground gas storage

In this paper, the mechanical analysis of multi cycle cyclic alternating load of injection production string is carried out. The theoretical analysis is carried out from two aspects: the analysis of pipe string pressure field and the analysis of pipe string temperature field during injection production. The effectiveness of the theory is verified by field examples.

クラッシュボックスの最大反力予測モデルの構築

The structural strength evaluation of crash boxes is predicted by machine learning in this study. The training data was obtained from the dynamic elastic plastic analysis of the crash box. The input physical quantities are barrier angle, box thickness, material properties and mass equivalent to vehicle weight. The output physical quantity is the reaction force. Buckling occurs in the analysis and different directions of corruptions are one of the most interesting phenomenon from a point of engineering view. Physically meaningful features that take into account physical laws, physical properties, shape, and so on were added. As a result, we showed that learning by CNN is possible with higher accuracy. In addition, data design and data augmentation that takes physical phenomena into account are necessary to deal with large outlier. We would like to propose an adaptive method for machine learning in structural evaluation that can be used for a wide range of structural evaluations.

Structural strength evaluation of a 3000 dwt river-barge, under oblique quasi-static design waves

The present study consists of the 3D-FEM global structural analysis of a typical open-top, double-hull, 3000 DWT inland navigation barge, having 90 m in length. The 3D-FEM model developed to perform the evaluation idealizes the barge structure with high accuracy, average element size being in the range of 50-75 mm. Two loading cases were analyzed, consisting of the ballast and full loading conditions. For the equilibrium floating condition in calm water and oblique design waves, an eigen iterative scheme has been used to generate the input parameters for the 3D-FEM analyzed cases. The push-barge finite element model has been subjected to oblique quasi-static design waves, headings ranging from 0 to 75 degrees. Wave heights considered in the analysis range from 0 to 1.2 m, step 0.3 m, corresponding to the Danube navigation conditions and freeboard limit imposed by the classification societies for inland navigation vessels. Numerical results following the FE analysis have been assessed by the yielding stress ratio, von Mises criterion, and the maximum deformation, thus indicating the structural areas that need to be improved in the design process.