Failure Analysis Of Structures Research Articles

Elasto-plastic fine-scale damage failure analysis of metro structures based on coupled SBFEM-FEM

This paper presents a new high-performance, fine-scale damage analysis method using three techniques. Firstly, efficient and detailed mesh discretization is performed via octree, which can easily accomplish cross scale and thus significantly alleviate the burden of fine modelling using octant cubes. Secondly, the introduction of coupled scaled boundary finite element (SBFEs) into FEM can offer more generality, flexibility and conveniences. Thirdly, the parameter matrices (e.g. stiffness, mass, damping) of geometrically similar elements generated by octree are proportionable and can be pre-computed. Therefore, by leveraging the similarity among elements for elasto-plastic problems will significantly improve computational efficiency. In order to demonstrate the effectiveness of the new approach, a fine-scale damage evolution of DaiKai subway was comprehensively modelled using different mesh sizes. Plastic damage and generalized plasticity models for soil and interfaces were used. Results from the case study demonstrated that octree possesses the advantages of high robustness, ability for automation and capacity to work with fewer elements during mesh generation. The coupled SBFEM-FEM and the use of element similarity markedly improved the computation cost (50% computation time was reduced). The presented method bypasses the need for undesired compromise between simulation accuracy and solver efficiency.

Investigating causal factors of road damage: a case study

High rainfall leads to flood vulnerability and potentially leads to the failure of road pavement which affects the economic loss for the people. However, such road pavement failures need to be studied more deeply to be able to distinguish whether the failure is solely due to flood natural disaster or other factors, such as overloading and poor construction quality. This research is urgently needed because up to now there is no tool for assessing pavement failure as a tool of decision-making system that is able to distinguish road pavement failure causal factors into category of natural disaster or human negligence factors in accordance with the definition of building failure in Indonesia Law no. 2 year 2017. Assessment of the causal factor of failure is very important because it is closely related to the determination of the parties who must be legally responsible. This research intends to develop methods for assessing the damage and failure of pavement as a tool of rapid and accurate decision-making system to determine the factors of pavement failure. To obtain accurate results, a case study was taken on Kendal Timur road to enable a deep evaluation of the factors that causing failure on the road. The results showed that many factors involved in causing the failure of the road, such as un-functional drainage channel, uncontrolled overload due to the closing of weigh stations around the road, and also low quality of road maintenance work so that repeating similar road damages occurred in the not-too-distant future. Based on functional and structural failure analysis, as much as 71%, 10% and 19% of the road were in failed, critical and not-failed conditions, respectively.

Decomposed-Coordinated Framework With Enhanced Extremum Kriging for Multicomponent Dynamic Probabilistic Failure Analyses

For multicomponent structures enduring dynamic workloads coming from multi-physical fields, safety assessment is significant to guarantee the normal operation of entire structure system. In this paper, an enhanced extremum Kriging-based decomposed coordinated framework (E2K-DCF) is proposed to improve the dynamic probabilistic failure analyses of multicomponent structures. In this method, extremum Kriging model (EKM) is developed by introducing Kriging model into extremum response surface method (ERSM) to process the transient response problem and shorten computational burden in dynamic probabilistic failure analyses. Multiple population genetic algorithm (MPGA) is employed to solve maximum likelihood equation (MLE) and find the optimal hyperparameter $\boldsymbol \theta $ in the EKM, which is promising to enhance approximate accuracy; decomposed-coordinated (DC) strategy is used to handle the coordinated relationship of multiple analytical objectives. To validate the proposed E2K-DCF, the probabilistic failure analysis of turbine blisk radial deformation is conducted by comparing with different methods within time domain [0 s, 215 s], considering fluid-thermal-structural interaction. It is revealed that the failure probability of blisk radial deformation is only 0.0022 when the allowable value is $2.5702\times 10^{-3}$ m acquired from real world practice. Compared to the other approaches, this E2K-DCF has obvious advantages in fitting time and accuracy as well as simulation efficiency and accuracy. The results illustrate that the E2K-DCF is effective and applicable in dynamic probabilistic failure analysis. The efforts of this paper provide a novel viewpoint for the transient reliability evaluation of multicomponent structures, which is likely to enrich mechanical reliability theory.

Analysis of causes of structural failures of buildings using TQC tools

This paper analyses structural failures of buildings over a period of ten years. Particular attention was paid to the analysis of structural failures caused by human mistakes. The analysis was performed according to two criteria: the stage of the building‘s life cycle and the type of works conducted in the area of the building site. The analysis was performed using a quality management tool (histogram and Pareto-Lorenza diagram), which allowed for identification of the causes responsible for the highest number of events. The analysis showed that three causes account for 64,61% of the structural failures that occurred.

Structural Failure Analysis of Earthquake Affected Buildings in Gorkha (Nepal) Earthquake 2015 in Kathmandu Valley

The major earthquake in April 25, 2015 of Mw 7.8 and aftershock of intensity Mw 7.3 on May 12, 2015 has caused not only a substantial death toll and huge economic losses, but also heavy damage to many buildings. This paper outlines the common observed damage patterns of different types of buildings in Kathmandu valley induced by the earthquake and their constructional deficiencies..We visited Department Of Urban Development and Building Construction (DUDBC) of Nepal Government, and Nepal Society for Earthquake Technology (NSET) and got various information regarding structural damages caused by Gorkha earthquake. After acquiring knowledge on this topic through internet and from NSET and DUDBC, the structural failure analysis of buildings affected during the earthquake in Kathmandu Valley was done by photo observation. Both unreinforced masonry buildings and reinforced masonry structures suffered low to heavy destruction. The construction and structural deficiencies were identified to be the major cause of failure, however local soil amplification, foundation problems, liquefaction associated damages and local settlement related damages were also significantly observed during this earthquake and reported in the paper. The Gorkha earthquake sequences delivered unprecedented opportunity to augment the understanding on seismic performance of the buildings. This paper is also motivated to point out the faintness in the past to current constructional practice of buildings, provide preventive measure and convey awareness to stake holders for future safer building construction practice.

A Deep Learning-Based Computational Algorithm for Identifying Damage Load Condition: An Artificial Intelligence Inverse Problem Solution for Failure Analysis

In this work, we have developed a novel machine (deep) learning computational framework to determine and identify damage loading parameters (conditions) for structures and materials based on the permanent or residual plastic deformation distribution or damage state of the structure. We have shown that the developed machine learning algorithm can accurately and (practically) uniquely identify both prior static as well as impact loading conditions in an inverse manner, based on the residual plastic strain and plastic deformation as forensic signatures. The paper presents the detailed machine learning algorithm, data acquisition and learning processes, and validation/verification examples. This development may have significant impact on forensic material analysis and structure failure analysis, and it provides a powerful tool for material and structure forensic diagnosis, determination, and identification of damage loading conditions in accidental failure events, such as car crashes and infrastructure or building structure collapses.

The thermal shock resistance prediction of porous ceramic sandwich structures with temperature-dependent material properties

A general numerical model to predict the thermal shock resistance of porous ceramic sandwich (PCS) structures with temperature-dependent material properties is developed. Knowledge of the temperature distribution and associated thermal stress in PCS panel is determined by the finite element method of coupled thermoelasticity. The present work considers the hot/cold shock induced center/edge cracks and measures the time-varied thermal stress intensity factors at the crack tip area. The roles of crack length, relative density of foam core, thermal shock load and geometric parameters of the PCS structures are examined. Moreover, fracture failure analysis of the whole PCS structures is carried out and crack propagation manners are detected. The thermal shock resistance curves of the structures are provided and the critical thermal shock temperatures are estimated for any selected characteristic materials. Results reveal that the thermal shock resistance of the PCS structures will be dramatically underestimated with the ignorance of temperature-dependent material properties. The analysis model of this paper provides a rapid prediction of thermal shock behavior of PCS structures at arbitrary temperatures.

Modeling of structural failure of Zircaloy claddings induced by multiple hydride cracks

Zirconium alloys have been serving as primary structural materials for nuclear fuel claddings. Structural failure analysis under extreme conditions is critical to the assessment of the performance and safety of nuclear fuel claddings. This work focuses on simulating structural failure of Zircaloy tubes with multiple hydride defects through modeling explicit crack propagation in ductile media. First, we developed an integrated cladding failure model by taking into account both crack initiation induced by hydride/matrix interface separation and ligament tearing-off between activated hydride cracks. Second, to accommodate the initiation, propagation, and coalescence of multiple cracks in finite plastic media we incorporated this structural failure model into a coupled continuous/discontinuous Galerkin (DG) based finite element code, a traditionally preferred implicit numerical framework. Third, to improve the adaptive placement of DG interface elements for crack propagation and to identify potential coalescence of cracks due to the interaction between adjacent hydride cracks, we defined a special failure index for the assessment of potential failure zones using both true plastic strain developed and predicted failure strain based on the Johnson–Cook material failure criterion. Finally, by calibrating the proposed material failure model using a cluster of Zircaloy material experimental tests, we successfully simulated a complete failure process of a fuel cladding tube with multiple hydride cracks.

Composite panel structural health monitoring and failure analysis under compression using acoustic emission

This paper documents an application of the acoustic emission (AE) method for structural health monitoring (SHM) of an integrally stiffened composite panel. The panel consists of a skin and two T-stringers and represents a typical part of the wing or fuselage structure. Similar design is used in civil structure parts. Quasi-static loading under compression was carried out to determine the initiation of the buckling modes. Two pieces of integral panels were tested up to failure. Both panels were monitored using 9 AE sensors in the same configuration throughout the test. The final stage of the test was recorded with a high-speed camera to obtain a detailed view of failure development. The velocity of the propagated AE elastic waves was determined experimentally before the test based on the best match of the computed and real positions of the Hsu–Nielsen sources. The determined velocity was subsequently used for AE source localization during the compression test. Different failure mechanisms were directly linked to different sources of AE using cluster analysis. Visualization of the AE location clusters was performed via the Kernel density estimation. High-speed camera images confirmed that the location of failure corresponds with the localization of a specific cluster of AE events. The AE method demonstrated the detection capability of the critical spot at 87% of the panel strength in compression. In conclusion, AE is suitable as an SHM method for damage monitoring of aerospace composite structures as well as for applications in civil structures.

Equivalent static load method for hierarchical stiffened composite panel subjected to blast loading

Hierarchical anisogrid stiffened panel (HASP) consists of three parts: main stiffeners, sub-stiffeners, and panel. The basis of HASPs’ dynamic response calculation is equivalent to the orthotropic panel. There are mainly two methods to calculate the dynamic response of orthotropic panels. One is the modal superposition method, and this method is an accurate calculation; the other method is equivalent static load method, which is an approximate calculation of deflection. Equivalent static load method is equivalent to the structure as a single-degree-of-freedom (SDOF) system. Deflection and strain equivalent method were compared for structural failure analysis. On this basis, the dynamic amplification factor (Kd) was calculated and the effects of parameters on it were discussed. According to these two deflection calculation method, the pressure-impulse (P-I) curve was plotted and the variation of the P-I curve under different conditions was analyzed. These theories were applied to the composite HASP protective door, the deflection and P-I curve of the doors were obtained and verified by tests.

A dynamic ductile failure analysis of shell structures using a nonlocal XFEM method with experimental validation

This paper presents a finite element continuous-discontinuous approach for the dynamic ductile failure analysis of shell structures. The continuum damage model based on continuous displacements is used in the continuous stage to describe the diffuse micro-cracking in ductile failure of high-strength steel before a macro-crack is formed. In the context of a fully integrated shear deformable shell formulation, a nonlocal modeling procedure based on a projection of mid-plane reference surface is introduced to regularize the element-wise strain fields induced by the continuum damage model. In the discontinuous stage, an incorporation of velocity discontinuities in shell finite elements is pursued by XFEM method when the damage variable exceeds a critical value and the transition from a continuous to a discontinuous model is permitted. A phantom-node approach is employed in the XFEM method to simplify the numerical treatment of velocity discontinuities in the shell finite element formulation. Several numerical benchmarks are examined using the explicit dynamics analysis and the results are compared with the experimental data to demonstrate the effectiveness and accuracy of the proposed method.

Electrochemical corrosion failure analysis of large complex engineering structures by using micro-LPR sensors

This paper presents the effects of three major parameters; temperature, relative humidity and hygroscopic salts contaminants on the atmospheric corrosion of large steel structures. The effects of these three parameters have been analysed by using micro-sized LPR sensors to continuously monitor the corrosion rate of a degrading large structure under varying parameters. A long term, three years study was performed by deploying μ LPRs on strategically selected large military vehicles (main battlefield tanks), which are stationed in the Tank Museum at Bovington, UK. These vehicles are operational and are of historic significance with cultural biography, however structural deterioration through corrosion, corrosion fatigue, stress corrosion cracking and mechanical failures are a threat to these vehicles in terms of their conservation. A set of vehicles operational (uncontrolled environment) and non-operational (controlled environment) was selected for comparative analysis in context of corrosion rate. This research is founded on a novel real-time corrosion monitoring technique that enables to better understand the relationship between varying environmental parameters and corrosion rate of large steel-based mobile structures during operation. This research provides a synthesis of real time corrosion data, which has been accumulated over a period of three years. An overview of structural deterioration is presented and derived from a significantly large data, therefore it provides a more reliable and highly accurate assessment of failures due to corrosion.

Reliability analysis of low, mid and high-grade strength corroded pipes based on plastic flow theory using adaptive nonlinear conjugate map

Abstract Generally, the safety levels of corroded pipes are evaluated using the nonlinear probabilistic model thus, an accurate probabilistic model is the important step in the structural reliability analysis of corroded pipelines. In this paper, three novel probabilistic models are developed for describing the burst pressure in low, mid and high-strength grades steels. The developed probabilistic models for corroded pipelines include three terms as 1) model errors, 2) burst pressure of intact pipes based on stress criteria improved by the plastic flow theory and 3) different remaining corroded strength factors. The best models for each steel grades category of corroded pipeline are selected using the confidence index based on three burst experimental database tests of pipes. The best distributions of model error for different probabilistic burst corroded models are given based on Anderson-Darling statistic from the Normal, Lognormal, Frechet, Gumbel, and Weibull distribution functions. An adaptive conjugate map-based first order reliability method is developed to assess the structural failure analysis of corroded pipelines. Six corroded pipelines with different grades strength steels are selected to demonstrate the applicability of the proposed probabilistic models in structural reliability analysis. It conducted that the average shear stress yield criterion is the best plastic flow theory for modeling the burst pressure of intact pipes, where the Gumbel, Frechet and Lognormal are respectively the best distributions for model errors of low, mid and high-strength grade steels. The reliability results of corroded pipelines demonstrated that the depth of corrosion defects is a sensitive variable, which reduce the safety levels of all corroded pipe examples compared to the length of defect and operating pressure. The safety levels of corroded pipelines reduce about twice less than un-corroded pipes for corrosion defect depth to pipe thickness (d/t) in the range from 0.4–0.5 for almost pipes grades.

Multi-axis dynamic displacement measurement based on a strain shunt structure

Transient gap or crack width monitoring is essential for structural health monitoring and failure analysis of large civil structures. In this paper, an innovative multi-axis displacement sensor, which utilises metal foil strain gauges on a strain shunt structure, has been proposed. This displacement sensor has the advantages inherited from metal foil strain sensing, such as low cost, high precision, fast dynamic response and low power consumption, and can also measure displacement in two axes independently. The working principles and sensitivity are derived theoretically from key geometrical parameters of the shunt structure, and the linear response of strain values to the given displacement of two translational axes has been demonstrated experimentally. Furthermore, modal response, stress concentration, optimal gauges installation positions and bending deformation due to moment of the third axis are studied numerically.

Structural failure analysis of polycarbonate enclosures of electronic devices subjected to multiple ball impacts

The present study predicts the structural damage on polycarbonate enclosures of electronic devices in multiple ball impact tests, achieved through numerical simulation and experiments. A novel methodology in modelling repeated ball impacts was established and proven. It was found that the finite element model must be allowed to achieve static equilibrium at the end of each impact before the next impact. The ball impact was performed on the polycarbonate enclosures at different heights ranging from 20 to 70 cm. The results suggested that the maximum penetration depth from both finite element analysis (FEA) and experiment were in good agreement. The failure sites were also predicted with reasonable consistency.

Structural failure in large-span timber structures: A comprehensive analysis of 230 cases

This paper presents a comprehensive statistical analysis of structural failure in 230 large-span timber structures. The objective is to identify typical failures and their causes to enable structural engineers in charge of comparable structures to initiate necessary measures to avoid similar failures. The analysis shows the wide range of use of large-span timber structures such as buildings of public assembly, sports halls and storage facilities. More than two thirds of the structures were realized with glued-laminated timber. The most frequently observed failure is cracking along the grain (46%). The causes for such failure are low or frequently changing wood moisture content as well as systematic tensile stresses perpendicular to the grain resulting from the geometry of the structural elements. Almost half of the timber components featured low moisture contents of 10% or less. The majority of failures can be linked to planning errors. Timber products, manufactured and installed according to the state-of-the-art, are rarely the cause for failure. The same applies to high snow loads, which could partly be identified as the triggering event but not the cause for failure. Proposals to decrease errors and thereby the occurrence of failures are given.

A novel material degradation model for unidirectional CFRP composites

Abstract A novel material degradation model (MDM), which is an essential component of progressive damage models for failure analysis of composite structures, is proposed based on the representative volume element (RVE) method. In this model, a material degradation rule accounting for seven failure modes in a modified Hashin-type failure criterion is proposed. This rule determines the mechanical parameters that are degraded when a failure occurs. The degradation factors of these parameters are calculated from the RVE models for perfect and damaged materials corresponding to the seven failure modes, which are based on the fundamental properties of transverse isotropic fibers and isotropic matrix. To verify the proposed method, the calculated MDMs are used in the progressive failure analyses of open-hole laminates made of three types of CFRP composites under tensile and compressive loadings. Furthermore, the failure analyses of four kinds of double-lap single-bolted joint structures with various layups and geometry dimensions are also conducted under tensile loading. The numerical predictions of failure loads, failure patterns and load-displacement curves are compared to the experimental results. Good agreement between the model predictions and the experimental results demonstrates the effectiveness of the proposed MDM for the progressive damage analyses of open-hole laminates and composite bolted joints.

Graphite-epoxy Composite Design for Aircrcaft Wing Spar Using Computational Techniques – Part I

This present work is on graphite-epoxy design for light weight high performance structure of an aircraft wing skin using computational technique. MATLAB MuPAD software was used to derive an analytical model for aircraft wing loads using symbolic computation to estimate the shear force acting on the wings while Autodesk Simulation Composite Design and ANSYS 14 Mechanical APDL (ANSYS Parametric Design Language) software were used to design and analyze the idealized composite structures of the wing skin. An idealized structure such as a flat plate which is a good approximation for the purposes of preliminary design and analysis was first developed using Autodesk Simulation Composite Design. After which, finite element analysis was also employed using ANSYS 14 Mechanical APDL to provide progressive failure analyses of the graphite-epoxy composite structures in order to determine the in-plane shear stress, displacement and other desired mechanical properties that would aid in material selection during fabrication and manufacturing. This investigation reveals that to withstand shear force of 3,000N for wing skin laminates designs, High Modulus (HM) and Ultra Modulus (UM) with [(+/-45)s] stacking sequence offers the best maximum shear stress output of 0.1991010 N/m2 prior to delamination. For failure prediction, Low Modulus (LM) and Ultra Modulus (UM) with [(+/-45)s] design has the best property prior to failure at 0.4991010 N/m2. HM and UM with [(+/-45/0/90)s] stacking sequence demonstrates the least compressive deformation of 0.004195m.

Independent cover meshless method for the simulation of multiple crack growth with arbitrary incremental steps and directions

The independent cover meshless method (ICMM) defines mesh irrelevant and node-based polynomial meshless interpolation functions over independent covers of discrete nodes and thus possesses the distinguished features of a simple formulation, low computational cost, the accurate numerical integration, and the convenient numerical implementation. By utilizing the unified continuous and discontinuous deformation analysis based on the ICMM interpolation theory, this paper systematically studies the simulation of complex crack propagation, the accurate calculation of mixed-mode stress intensity factors (SIFs) and the influence of crack growth increment and mesh density on the computational accuracy and stability. In the present computing framework, cracks are allowed to grow in arbitrary directions with arbitrary assigned incremental lengths. This technique provides a simple, convenient and efficient numerical method for fracture and failure analyses of brittle structures. Numerical examples for the calculation of stress intensity factors and the simulation of crack propagation demonstrate the accuracy, effectiveness and robustness of the present method.

A multiscale computational method with inheriting simulation of moving trans-scale boundary for damage-induced structural deterioration

PurposeThis paper aims to introduce a multiscale computational method for structural failure analysis with inheriting simulation of moving trans-scale boundary (MTB). This method is motivated from the error in domain bridging caused by cross-scale damage evolution, which is common in structural failure induced by damage accumulation.Design/methodology/approachWithin the method, vulnerable regions with high stress level are described by continuum damage mechanics, while elastic structural theory is sufficient for the rest, dividing the structural model into two scale domains. The two domains are bridged to generate mixed dimensional finite element equation of the whole system. Inheriting simulation is developed to make the computation of MTB sustainable.FindingsNumerical tests of a notched three-point bending beam and a steel frame show that this MTB method can improve efficiency and ensure accuracy while capturing the effect of material damage on deterioration of components and structure.Originality/valueThe proposed MTB method with inheriting simulation is an extension of multiscale simulation to structural failure analysis. Most importantly, it can deal with cross-scale damage evolution and improve computation efficiency significantly.