Failure Modes Research Articles

Post-buckling behavior and DSM design of cold-formed steel lipped channel columns experiencing local-distortional-global interaction

This paper describes experimental research investigating the structural behaviors, failure modes, and ultimate load-carrying capacities of fixed-ended cold-formed steel lipped channel columns eroded by local-distortional-global (L-D-G) buckling interaction under axial compression. Initially, a brief introduction on the selection of column geometry, which was based on the closeness between three elastic critical buckling stresses named elastic local, distortional, and global critical buckling stresses, was reported. In addition, detailed works involving measuring member geometries and initial geometrical imperfections, test set-up, and the arrangements of strain gauges and displacement transducers are described. Moreover, experimental investigation results of 33 cold-formed steel columns are discussed including deformed configurations, applied load vs. strains curves, applied load vs. displacement curves, failure modes, and ultimate load-carrying capacities. The tests demonstrated D-G interaction with no obvious local deformation observed even though the elastic critical loads of L, D, and G for the selected specimens are close. The results clearly demonstrate that the occurrence of D-G buckling interaction eroded the ultimate strengths of columns. Current DSM predictions are evaluated using experimental data of cold-formed steel columns related to the D-G buckling interaction. Furthermore, a design criterion based on DSM is proposed to identify cold-formed steel columns eroded by D-G buckling interaction and predict the ultimate strength, which is evaluated by all available experimental data collected from related literature.

Structural Behavior of Reinforced Concrete Columns Fully and Partially Reinforced with GFRP Bars Tested Under Concentric or Eccentric Compressive Loads

Concrete columns reinforced with glass fiber-reinforced polymer (GFRP) bars have been greatly interesting recently. The distinct properties of GFRP bars, such as high tensile strength and low modulus of elasticity compared to steel bars, as well as the linear stress-strain behavior, make the study of GFRP-reinforced concrete (FRP-RC) columns important. This paper investigates the structural behavior of column specimens reinforced by fully and partially GFRP bars subjected to concentric and eccentrically applied Compressive loads. 12 columns were reinforced by (36%, 64%, and 100%) of the GFRP bars ratio, and the control specimen was reinforced by conventional steel rebars; all specimens were tested under different eccentric ratios (e/h) 0, 0.66, and 1. The failure mode, the relation between the axial load and the average axial displacement, and a comparison between the experimental results and the theoretical interaction diagram for columns were presented and discussed. The results show that most of the failure in specimens occurs as a compressive failure, and it fails in the weakest region by crushing concrete, as well as kinking in GFRP bars. Using GFRP bars significantly increases the axial displacement values compared to the steel rebars in longitudinal reinforcement and decreases the failure load for specimens with an increase in the ratio of GFRP bars. The average axial displacement value for columns specimens tested under eccentric load at e/h equal to 0.66 and 1 decreases by 75% and 94.4% compared with the control specimen.

The Energy Absorption Characteristics and Structural Optimization of Titanium/UHMWPE Fiber Metal Laminates under High-Speed Impact

Fiber-metal laminates (FMLs), known for their lightweight and high strength, are widely used in structural protection in the fields of shipbuilding, military, and aerospace. Experiments were conducted using 12.7 mm hard spherical projectiles at speeds ranging from 915.7 to 1290.6 meters per second to study the high-speed impact on FMLs composed of titanium and Ultra-high Molecular Weight Polyethylene(UHMWPE). The primary failure modes of the fibers were tensile failure and compressive shear failure. With increasing impact velocity, the proportion of tensile failures in the fibers gradually decreased, transitioning to shear plug failure as the main failure mode, while the titanium alloy primarily experienced erosive perforation and petal-shaped tearing. At a speed of 1290.6 m/s, the titanium alloy began to exhibit significant adiabatic shear tearing in four directions. Further, a three-dimensional numerical model was established, which, through theoretical analysis and experimental validation, proved to be highly reliable. Using this theoretical model, a deeper analysis of the dynamic response and penetration mechanism of the structure was conducted, explaining the energy distribution mechanism and dynamic response mechanisms of various parts. Based on this model, improvements and optimizations were made to the laminar structure of the UHMWPE/titanium alloy FML. Placing metal at the back maximized energy absorption but led to more pronounced bulging.

Failure mode and load prediction of steel bridge girders through 3D laser scanning and machine learning methods

AbstractCorrosion poses a significant threat to the longevity of steel bridges, impacting overall structural integrity. To effectively assess the structural condition of corroded steel bridges, conventional methods rely on visual inspections or single point measurements. To enhance and modernize this approach, this study introduces a novel framework integrating laser scanning data, computational models, and convolutional neural networks (CNNs). The CNN models are trained on a data set consisting of more than 1400 artificial corrosion scenarios generated by parameterizing real scan data from naturally corroded girders. This innovative method predicts the residual capacity and failure mode of corroded beam ends, achieving a low error rate of up to 3.3%. Unlike established evaluation procedures, the proposed evaluation framework directly utilizes post‐processed laser scanner output, eliminating the need for feature extraction and calculations.

Analysis of tensile failure mechanism in intact, foliated, and cracked rocks using distinct element method: Influence of anisotropy

A thorough numerical analysis was conducted to understand the failure mechanisms and behaviour in intact rocks, foliated rocks and rocks with pre-existing cracks using the Brazilian tensile strength tests. The dominant anisotropy in rocks, especially foliated rocks like phyllites, slates and schists, as well as sedimentary rocks like sandstone, limestones and shale, leads to complex failure mechanism. The presence of cracks leads to anisotropy causing different mechanisms of failure and variation in tensile strengths of rock mass. Numerical simulations were conducted based on experimental studies of foliated phyllite and dolomitic limestone from the Tejam Group, Lesser Himalaya. The variations in failure behaviour and strength of foliated rocks were studied for samples at different foliation angle using the particle distinct element model. The simulation results show that with increase in foliation angle to the loading direction (from 0° to 90°), the peak tensile strength of rocks remains almost same for specimens with θ = 0° to 30° and then increases linearly till 90°. The influence of cracks as anisotropy was also studied by changing crack length (from 5 mm to 30 mm) and angle (from 0° to 90°). The development of failure patterns in rocks with pre-existing cracks leads to a better understanding of the failure modes and makes it possible to interpret failure behavior, pattern, and strength parameters. With increase in crack length, the tensile strength of rocks decreases. Overall, this study depicts the influence of anisotropy and microparameters on failure modes and behavior in Brazilian tensile strength tests on foliated and pre-cracked rocks.

S11-02 Frameworks for cardiotoxicity assessment: integrating key characteristics, AOPs and failure modes

S11-02 Frameworks for cardiotoxicity assessment: integrating key characteristics, AOPs and failure modes

Microstructural and mechanical properties of Al-5356 alloy structures fabricated using direct energy deposition (DED): In-pursuit to optimizing deposition parameters

Many industries including aerospace make extensive use of lightweight materials like aluminium alloys because of their extraordinary properties. Wire Arc Additive Manufacturing-Cold Metal Transfer (WAAM-CMT) as a part of modern direct energy deposition technique can be recommended for developing aerospace components of aluminium alloys. However, it is still necessary to investigate the impact of the combined change of developing parameters on some of the crucial qualities including metallurgical and mechanical properties. Therefore, in this part of research work, practically, various process parameters were tried for development of aluminium (Al-5356) alloy walls. Finaly, a specific set of parameters namely wire feed speed, scanning speed and inter layer temperature parameters with two levels of each were selected and with the assistance of these, four walls have been fabricated. Th preliminary analysis showed that low heat input accompanied by higher scanning speed of 60 cm/min and lower wire feed rate of 6 m/min was found to best suitable set of parameters for developing dimensionally stable Al wall with flaw less microstructure. The said set of parameters also showed higher hardness that also accompanied with finer grains, lower percentage towards high angle grain boundary and lower KAM. Even slight variation in these parameters that deal to high heat input can give rise of porosity and misalignment in the wall. Details of microhardness reported high hardness in the bottom part of the wall. However, in a single bead the hardness is higher in the top region, which may be owing to finer grains in the specified region. The above said set of parameters also able to deliver better tensile strength and toughness for Al-5356 alloy. The developed alloy showed improved strength in longitudinal orientation owing to intra layer failure with ductile mode of fracture in contrast to transverse orientation, where the failure mode was reported to mixed (ductile as well as brittle) owing to inter layer fracture.

Mesoscale simulation method for preplaced aggregate concrete based on physics engine

Preplaced aggregate concrete (PAC) has up to 60% aggregate volume content, making mesoscale modelling difficult. A novel mesoscale simulation method based on physics engine was proposed in this study to accurately simulate the coarse aggregate skeleton of PAC. Unlike in conventional mesoscale simulations, point-to-point contacts between aggregates were formed due to virtual gravity in the physics engine. To verify this novel method, mechanical property and shrinkage behavior tests of PAC were conducted under different aggregate gradings and with different expansive agents. For the mechanical property test, the simulation results were compared with the test results in terms of the aggregate stacking state, failure mode, stress–strain curve, and mechanical property parameters. Repeatability and aggregate shape analyses were performed using finite element (FE) model. A similar comparison between the simulation and test results was also performed for the shrinkage behavior. A shrinkage coefficient reflecting the relationship between grout and PAC shrinkage was proposed. This novel mesoscale simulation method based on physics engine is particularly suitable for PAC. However, it is not limited to PAC and can be applied to the simulation of conventional concrete, thus solving the problem of traditional simulation methods that struggle to achieve a high aggregate fraction.

Design method for axially compressed H-sectional aluminium alloy slender column based on CSM

In this study, a section-limiting stress that considers the influence of cross-section slenderness on the load-carrying capacity proposed by the continuous strength method (CSM) is introduced for the first time in the design of axially compressed H-section aluminium alloy slender columns. Experimental and numerical simulation tests are conducted on these columns to understand their axial compression performance and failure modes, with subsequent validation of the numerical simulation methods. Using the CSM limiting stress, imperfection factor, and stability calculation factor, this study proposes a design method for the overall stability load-carrying capacity of axially compressed H-section aluminium alloy slender columns. The load-carrying capacity predictions of the proposed design method are compared with those of the European, American, Australian/New Zealand, and Chinese design standards using axial compression tests and numerical simulations. An evaluation of these design methods and standards is also presented. In addition, reliability analyses are conducted following the approaches proposed by the American Institute of Steel Construction and the European design standard to assess the reliability levels of the aforementioned design methods and standards. Finally, the study presents a calculation example of an aluminium alloy slender column using the proposed design method.

Reliability‐based Allowances of Corrosion Losses for Weathering Steel Bridges

AbstractLow demands on maintenance and 100% recyclability cause the growing popularity of weathering steel bridges worldwide. Recent experimental results made it possible to derive generic probabilistic models describing long‐term corrosion losses for various types of weathering steels and exposures. In the contribution, these probabilistic models are applied in reliability assessment. For representative structural members and failure modes, the material allowances for the loss of thickness are derived to achieve a specified target reliability in exposures corresponding to Corrosivity Categories C2 and C3. Numerical analysis reveals that the allowances recommended by the ECCS guideline are generally conservative. For larger sections exposed in C2, a “no allowance” strategy might even be considered. For C3, design allowance of about 0.5‐0.6 mm is then determined by the probabilistic approach.

Integrated optimization for X-bar control chart, preventive maintenance and production rate

There are close relationships among statistical process control, maintenance, and production that have not fully explored in existing studies. In this study, we propose an economic model for jointly optimizing the X-bar control chart, preventive maintenance, and production rate. Unlike conventional studies relying on known failure rate functions, we employ a Gamma process to describe the system's deterioration. This approach allows us to consider not only the relationship between the production rate and the deterioration rate but also a broad range of deterioration scenarios and failure modes in the integrated optimization. After calculating the failure probability at each time point, we propose a recursive method to derive the production revenue, process control costs, and quality losses. This approach explores the close inner relationship between the production rate, deterioration, process monitoring and maintenance. Subsequently, we establish an optimization model aimed at maximizing the profit rate within a renewal cycle. The decision variables of this model include the production rate, control chart coefficient, sample size, length of the first sampling interval, and number of sampling intervals. Finally, we use a case study to illustrate the effectiveness and validity of our proposed model by identifying and explaining the interactions between production rate, deterioration, process control and maintenance.

Study on the delamination damage prediction of wind turbine blade spar cap based on morphology feature recognition

In order to study the degradation of local mechanical properties caused by delamination defects of wind turbine blades, a progressive damage prediction method of blade spar cap based on quantitative identification of delamination morphology features by infrared thermal image was proposed in this paper. Firstly, based on the thermal conduction theory of laminate plates, infrared thermal imaging technology was used to realize quantitatively identify delamination morphology features. Then, based on the cohesive zone model (CZM) and the classical laminate theory (CLT), a numerical analysis model of unidirectional laminate with delamination defects was established, and the accuracy of the numerical model was verified by comparison with the experimental results of axial tensile and compressive displacement loads. Finally, a 2 MW-45.3 blade spar cap with maximum chord cross-section was used as a prediction model, and the effect of different delamination sizes and depths on the failure mode, failure strength and damage evolution of the blade spar cap was successfully predicted by using the equivalent fatigue load. The research shows that the delamination depth has a more profound influence on the damage of spar cap compared with the delamination size. With the increase of delamination depth, the delamination failure modes undergo the evolution process of non-buckling, local buckling, delamination expansion and strength failure. Shallow delamination causes local buckling and strength failure of blade spar cap. When the delamination depth reaches half of the spar cap thickness, the delamination extends to intralaminar and interlaminar, the local failure changes to global failure.

Mechanical performance and reinforcing mechanisms of foamed concrete strengthened by carbon fibers

Foamed concrete (FC) is a lightweight and environmentally friendly building material that offers versatile applications in civil engineering. However, FC is inherently weak in withstanding tensile and compressive loads. While incorporating fibers into FC has been shown to resist crack propagation and enhance its mechanical properties, the specific mechanisms through which carbon fibers affect FC’s tensile and compressive behaviors remain unclear. This study aims to address this gap by incorporating short-cut carbon fibers into FC to achieve a micro-reinforcement effect and enhance its compressive and tensile performance. The mechanical properties, failure modes, and microstructure evolution of carbon fiber-reinforced FC at different density levels, carbon fiber lengths, and contents were comprehensively explored. Digital Image Correlation (DIC) was utilized to analyze crack propagation, and an optimal mix ratio experiment was conducted. The results demonstrate that incorporating carbon fibers effectively enhances the mechanical performance of FC, with a more significant impact on specimens with a density of 500 . Furthermore, the maximum improvements in tensile and compressive strengths reached 250% and 88.5%, respectively. This study suggests that optimal reinforcement ratio can be achieved through mix ratio adjustments and curve fitting formulas, thereby optimizing the tensile and compressive performance of the specimens.

Characterization of load-bearing and failure properties of fractured rock masses reinforced by negative pressure grouting

Grouting injection is a vital technique for addressing the challenges of high stress and significant deformation in the surrounding rock during deep mining operations, playing a crucial role in promoting green and low-carbon extraction methodologies. In this study, grouting reinforcement processes were examined by conducting grouting experiments on a fractured rock with varying negative pressures (0-100 kPa), followed by uniaxial compression testing of the grout-reinforced bodies. This investigation explored the diffusion patterns of grout under negative pressure and established a constitutive model of damage-bearing capacity for bodies reinforced by negative pressure grouting. It further studied the enhancement effect of negative pressure on the load-bearing capacity of the reinforced bodies and analyzed the instability mechanism of damage and failure in these bodies. The results indicated that the diffusion of grout under negative pressure is influenced by four types of forces, which alter the extent of grout diffusion within the fractured rock mass. Introducing a damage constitutive model that serially connects pore and framework elements characterizes the damage and failure behavior of grout-reinforced bodies under different negative pressures. As the negative pressure increases, changes in porosity, water-to-cement ratio, and admixture quantity occur in the grout-reinforced specimens, with the strength mean curve showing a trend of first increasing and then decreasing, reaching a threshold at a negative pressure of 60 kPa. With increasing negative pressure, the negative pressure damage variable decreases and then increases, and the stronger the interfacial microelement connections caused by the negative pressure, the greater the bearing capacity, ultimately manifesting in different failure modes.

Interplay of Tunnel Geometry and Shallow Foundation Stability in Rock: Comparative Insights into Failure Modes

Interplay of Tunnel Geometry and Shallow Foundation Stability in Rock: Comparative Insights into Failure Modes

Behavior prediction of reinforced concrete beams shear strengthened with CFRP

This work presents the computational modeling of reinforced concrete beams, strengthened to shear with carbon fiber-reinforced polymers (CFRP), using the finite element method (FEM) and the customized ANSYS software, version 19.2. It is important to emphasize that contact elements and bilinear cohesive zone models provided by ANSYS were used to model the concrete-reinforcement interface. These models were used to identify the modes of premature failure caused by the debonding of the reinforcement, which causes poor use of the CFRP's resistance properties. The structural elements used in this analysis were twelve simply supported reinforced concrete beams, without and with shear reinforcement using CFRP, which were experimentally tested by Khalifa (1999). From the analysis of the results, it was observed that the developed numerical models were able to accurately predict the behavior of the simulated beams, both in terms of load-displacement, as well as the load and rupture mode of the beams.

Study on Compressive Strength of Bamboo (Guadua amplexifolia J. Presl) in San Jorge River Basin, Colombia

Bamboo is a fast-growing plant commonly used to produce handicrafts, baskets, furniture, and other goods. Guadua amplexifolia J. Presl, a native woody bamboo species of Colombia, has been the subject of limited scientific research. This study conducted in the San Jorge River basin in Montelíbano (Córdoba) evaluated Guadua amplexifolia J. Presl's compressive strength to find its potential applications. Samples from four- and five-year-old bamboo culms were collected for analysis. The findings showed a positive correlation between the modulus of rupture and density. In contrast, the modulus of elasticity showed a weak positive correlation. It was seen that the predominant mode of compressive strength failure was type A (accounted for 66.7%) in the samples tested. The mean value for the modulus of rupture was 43.1 x10-3 MPa, and the mean modulus of elasticity value was 1075.5 x10-3 MPa. Earlier studies reported lower calculated values for modulus of rupture and modulus of elasticity for G. amplexifolia J. Presl bamboo than other bamboo species.

Comprehensive Insight into the Failure Mechanisms, Modes, and Material Selection of Steam Turbine Blades

Addressing the critical issue of turbine blade failures, particularly in steam turbine systems, this comprehensive review delves into examining and analyzing various failure mechanisms associated with steam turbine blades. The discussion extends to the mode utilized in investigating these failures, with a specific focus on the crucial role of steam turbines in power generation. The review synthesizes various studies that have explored suitable blade materials for optimized performance and reduced failure risks. Findings reveal common failures such as thermal stress, mechanical stress, corrosion, erosion, fatigue, and creep in turbine blades and hubs. Consequently, the review serves as a valuable resource, providing insights into failure mechanisms and advocating for the implementation of suitable materials to enhance the reliability and performance of steam turbine blades.

Using physics-informed neural networks to predict the lifetime of laser powder bed fusion processed 316L stainless steel under multiaxial low-cycle fatigue loading

Axial-torsional Low-Cycle Fatigue (LCF) tests were conducted under strain control on Additively Manufactured (AM) 316L stainless steel using laser powder bed fusion. The tests covered various strain amplitudes under tension-compression, proportional, and pure shear loading paths. The AM 316L stainless steel exhibited cyclic softening and transgranular cracking under all the investigated loading conditions. The presence of deposition defects, predominantly the lack of fusion type, was identified as the main factor influencing the crack initiation and propagation, as well as the scatter in the fatigue lifetime. Therefore, to account for the damaging effects of these deposition related defects on fatigue lifetime, a novel physics-informed neural network was proposed. Subsequently, this neural network was combined with the critical plane approach, based on the tensile mode of failure, in order to predict the lifetime of AM 316L stainless steel. The predicted data exhibited a good correlation with the experimental results.

Reliability assessment of an aircraft locking mechanism considering tribocorrosion and correlated failure modes in a marine environment

Landing gear door locking mechanisms are critical for aircraft safety, as their failure can lead to severe accidents. Therefore, these mechanisms must meet stringent reliability requirements. This study introduces a reliability evaluation method for a locking mechanism operating in a marine environment, which integrates dynamic simulation with a tribocorrosion experiment of the joints. Initially, a multibody dynamic model of the locking mechanism was developed to establish the boundary conditions for the joints. Subsequently, an accelerated tribocorrosion experiment was performed to assess the tribocorrosion behavior of these joints. Based on the experimental outcomes, the motion torque and output of the locking mechanism were determined. Considering the correlation between failures due to insufficient accuracy and jamming, an improved response surface methodology utilizing cross-utilization of experimental points was developed. Reliability of the locking mechanism was subsequently confirmed. The present findings indicated that the maximum wear depth in the corrosive environment increased by 25.28 μm (37.15 %) compared to a non-corrosive, dry friction environment. Similarly, the maximum friction coefficient in the corrosive environment increased by 0.0818, which corresponds to an increase of approximately 11.76 %. Furthermore, the proposed reliability evaluation method proved to be 33 % more efficient than the traditional response surface method.