Reliability Of Structural Components Research Articles

Exploring the Potential Application of an Innovative Post-Weld Finishing Method in Butt-Welded Joints of Stainless Steels and Aluminum Alloys.

The prerequisite of the weld bead finishing is intricately linked to the quality of the welded joint. It constitutes the final, yet pivotal, stage in its formation, significantly influencing the reliability of structural components and machines. This article delineates an innovative post-weld surface finishing method, distinguished by the movement of a specialized cutting tool along a butt weld. This method stands out due to its singular approach to machining allowance, wherein the weld bead height is considered and eradicated in a single pass of the cutting tool. Test samples were made of AISI 304L, AISI 316L stainless steels and EN AW-5058 H321, EN AW-7075 T651 aluminum alloys butt-welded with TIG methods. Following the welding process, the weld bead was finished in accordance with the innovative method to flush the bead and the base metal's surface. For the quality control of welded joints before and after the weld finishing, two non-destructive testing methods were chosen: Penetrant Testing (PT) and Radiographic Testing (RT). This article provides results from the examination of 2D profile parameters and 3D stereometric characteristics of surface roughness using the optical method. Additionally, metallographic results are presented to assess changes in the microstructure, the microhardness, and the degree of hardening within the surface layer induced by the application of the innovative post-weld finishing method.

FRACTURE ANALYSIS AND SHIELDING EFFECTS IN ADVANCED MATERIALS

Due to their ability to interconnect electrical and mechanical domains, piezoelectric materials are increasingly finding applications in advanced electromechanical systems. Notably, magneto-electric composites like BaTiO3-CoFe2O4 have emerged as vital materials for the next generation of devices. Exploring this realm is a complex and significant endeavor, demanding the attention of the scientific community and further research. Over recent decades, the scope of formulating and executing computational models for continuous media has substantially broadened, encompassing a diverse array of material properties and fields in computational models. This article centers on the utilization of asymptotic analysis as a mathematical tool for constructing approximate equations and assessing the relevance of various hypotheses. It delves into the utilization of the perturbation method, pioneered by Kagadiy T. S. and others, to tackle two-dimensional contact problems in electropelasticity, particularly in the context of materials with linear anisotropy. The extensive applicability of this asymptotic approach underscores its efficacy in simplifying intricate problems by breaking them down into a sequence of boundary problem resolutions grounded in the theory of potentials. The collaborative effort of the authors in this research underscores that employing the mentioned method opens up avenues for formulating pertinent boundary problems for the fundamental equations. This, in turn, allows for the representation of the initial electropelasticity problem as a superposition of more manageable boundary problems. While mechanical and electrical components can be treated separately, they still interact via boundary conditions. To conduct a numerical analysis, the article examines scenarios where one crack surface slides parallel to the crack front against another and selects relevant materials with known characteristics. Calculations reveal that, even in the absence of mechanical load, crack surfaces undergo relative sliding due to non-zero electrical or magnetic fields. The study of the shielding effect, which mitigates crack motion by altering magnetic field distribution, holds particular significance. This effect reduces the overall stress intensity factor and impedes crack propagation. Conducting such a comprehensive analysis is pivotal for comprehending and foretelling the strength and reliability of structural components composed of piezoelectric and piezomagnetic materials. It is imperative to conduct a thorough examination of the mechanisms governing their failure.

Influence of Delamination Size and Depth on the Compression Fatigue Behaviour of a Stiffened Aerospace Composite Panel.

Delamination in reinforced panels is one of the primary challenges facing the safety and reliability of aerospace structures. This article presents a sensitivity analysis of the fatigue behaviour during the compression of a composite aeronautical stiffened panel experiencing delamination. The main objective is to assess the impact of delamination size and depth on the lifecycle and structural integrity of the panel. Different dimensions and positions of delamination are considered to cover a comprehensive range of damage scenarios. The key feature of this sensitivity analysis is the adoption of a numerical procedure that is mesh- and load-step-independent, ensuring reliable results and providing valuable insight into the criticality of delamination and its impact on the fatigue behaviour during the compression of reinforced aeronautical panels. Sensitivity analyses are essential for enhancing the design process of aerospace structures, thereby contributing to the increased safety and reliability of structural components. In this regard, the use of robust and effective numerical procedures is of crucial significance. This may be seen as the real added value of this paper.

Sensitivity of step‐stress accelerated fatigue‐life tests on type I censored data—An engineering perspective

AbstractStep‐stress accelerated life testing is often used to estimate the fatigue life or reliability of structural components. Various methods exist for designing the optimal accelerated life test and estimating the parameters of the fatigue‐life or reliability models. Although they are based on rigorous mathematical formulations, they sometimes result in inappropriate estimates of the model parameters if the experimental data consists of censored data. This article presents a robust engineering procedure for estimating the parameters of the fatigue‐life curve and its scatter, which combines an inverse power law and the two‐parametric Weibull distribution. The presented methodology is tested on use cases that stem from the experimental fatigue‐life data. The results show that the proposed approach can yield a good estimate of the fatigue‐life model. Moreover, it can be further concluded that the sensitivity of the fatigue‐life model to the type I censored data strongly depends on the data scatter.

PDEM-based multi-component and global reliability evaluation framework for steel tubular transmission towers with semi-rigid connections

The conventional analysis and design of transmission towers usually ignore the effect of semi-rigid behaviors of bolted joints and simplify the joints as the rigid or pinned connection, which might overestimate or underestimate the structural response of transmission towers and the reliability of structural components and systems. To consider the effect of semi-rigid connections on the reliability of transmission towers in this paper, a stochastic dynamic finite element model of steel tubular transmission towers with semi-rigid connections (STTTs-SRCs) is established by deriving their stiffness matrix, where the uncertainties of dimensions, material and semi-rigid connections are considered and the wind loads are simulated as stochastic processes by the dimension-reduced probabilistic simulation approach. Then, based on the equivalent extreme-value event, the multi-component and global performance functions with stress and displacement failure modes for STTTs-SRCs are established, respectively. Further, a reliability evaluation framework for STTTs-SRCs is proposed based on the probability density evolution method (PDEM). Finally, a practical engineering transmission tower is regarded as an example to demonstrate the implementation process of the proposed reliability evaluation framework. Moreover, the reliability of steel tubular transmission towers with rigid and pinned connections is compared with that of STTTs-SRCs to investigate the effect of semi-rigid connections on the reliability of transmission towers. In general, the semi-rigid connections would mainly affect the value of the multi-component failure probability, however, it would not change the location where the maximum failure probability of components occurs. Additionally, the semi-rigid connection significantly affects the global failure probability of towers for the stress failure mode while slightly affects the global failure probability of towers for the displacement failure mode. Therefore, it may be more appropriate to consider the semi-rigid connections into the analysis and design of steel tubular transmission towers.

A novel very-high-cycle-fatigue life prediction model with interior microstructure induced cracking behavior of Inconel-713C superalloy at 25 °C, 750 °C and 1000 °C

Asymmetric load tests with stress ratio of 0.1 at 25 °C, 750 °C and 1000 °C were performed to investigate the high-cycle and very-high-cycle fatigue properties of Inconel-713C Ni-based superalloy. Results show that the life at 750 °C is longer than that at 25 °C, but shortens as temperature keeps rising to 1000 °C. Relevant crack initiation and growth belong to the mixed Modes I & Ⅱ cracking along the maximum shear stress. Moreover, due to the effects of temperature and vacuum environment, threshold values for small and long cracks, and the transition crack size decreases as the temperature increases. Moreover, further analysis of dislocation structures such as tangled dislocations, dislocation loops and finer stacking faults shows that the deformation mechanism with faceting cracking at 750 °C should be the interaction of bypassing and shearing mechanisms, especially under stress concentration effect of crack. Based on these, a crystallographic version of fatigue index parameter model for crack nucleation life is proposed and the predicted results are within a factor of two with respect to experimental data. The present model can be applied to predict the fatigue life based on the microstructure attributes and load conditions at different temperatures, which can effectively improve operational safety and reliability of structural components in reality.

Design of step‐stress accelerated life tests for estimating the fatigue reliability of structural components based on a finite‐element approach

AbstractThis article describes how a step‐stress accelerated life test (SSALT) can be designed for testing the fatigue life and reliability of structural components with a dominant failure mode. With simple numerical simulations of the crack's propagation in the notched area of the structural part for different loading levels, the slope of the S–N curve for a structural component is initially estimated. Then, a very few fatigue–life experiments are carried out in the high‐cycle domain to determine the intercept of the structure's S–N curve. By considering the scatter from the material's P–S–N curve, different SSALT designs for the structural component can be composed and checked for their expected acceleration factor. The procedure is experimentally validated for the case of a notched specimen and two different SSALT designs. From the results it can be concluded that the predicted durations of the SSALT experiments correlate well with the real experiments.

Modeling of size, aspect ratio, and orientation of flattened precipitates in the context of Zr-H system under external stress

A model that simulates detailed morphology of flattened precipitates has been developed and applied for the Zr-H thermodynamic system as an example. The mathematical representation of the model is the system of six ordinary differential equations which are solved numerically. The model is based on the classical heterogeneous nucleation approximation to simulate the length, aspect ratio, and orientation of inclusions precipitated during cooling or dissolving during heating in the presence of external mechanical load. This model is directly appliable to the modeling of mechanical properties of zirconium alloys, which are widely used in the nuclear industry. In this practical case, hydrides, formed from hydrogen released during water corrosion, substantially affect the structural component reliability.

A Study on Technological Dynamics in Structural Health Monitoring Using Intelligent Fault Diagnosis Techniques: A Patent-Based Approach

The performance and reliability of structural components are greatly influenced by the presence of any abnormality in them. To this purpose, structural health monitoring (SHM) is recognized as a necessary tool to ensure the safety precautions and efficiency of both mechanical and civil infrastructures. Till now, most of the previous work has emphasized the functioning of several SHM techniques and systematic changes in SHM execution. However, there exist insufficient data in the literature regarding the patent-based technological developments in the SHM research domain which might be a useful source of detailed information for worldwide research institutes. To address this research gap, a method based on the Co-Operative Patent Classification (CPC) codes is proposed in the current study. The proposed method includes the patent analysis of SHM in terms of its global publication trend and technology-based applications. This analysis is performed using patent database search tools, namely, IncoPat and Espacenet. The period ranging from 2005 to 2019 is selected to retrieve the required patent documents. A new approach termed as Patents’ value is utilized to investigate the technological impact of a patent in the form of forward citations, technical stability, and scope of protection. The identification of emerging SHM techniques and forecasting of vacant technology is also part of current research work. The research results have revealed the increasing trend in the number of published patents each year related to various SHM technologies. In this regard, China, the United States, and South Korea are notified as to the major depositor countries, respectively. Hence, mapping of patent data in this research is an effort to illustrate the effectiveness of the proposed method to demonstrate the development trends and dynamic inventions over the time in SHM research domain to achieve the optimal damage inspections of various mechanical components.

Implementation of Self-Help Housing Stimulant Assistance (BSPS) Program to Enhance the Tulang Bawang Community Prosperity

Every citizen has the right to live in prosperity both physically and mentally, with the fulfillment of physical, spiritual and social needs. To meet these needs the government has made a policy in the form of the Self-Help Housing Stimulant Assistance Program (BSPS), which aims to stimulate low-income communities to build / repair respective homes. The problem in this article is the urgency of housing policy through the BSPS Program in improving the welfare of the community in Tulang Bawang Regency? How is the implementation of housing policy through the BSPS Program in Tulang Bawang Regency? The research used a normative juridical and an empirical approach method. The data are primary and secondary. The result of the research shows that the urgency of housing policy through the BSPS Program is to meet the needs of the community in the form a decent house for habitation which is in line with the state's goals for the welfare of the people. One of them is the fulfillment of a house that is suitable for habitation and health, including building safety, reliability of structural components, improving the quality of non-structural component materials, health of lighting occupants, ventilation and sanitation as well as the minimum adequacy of building area. The BSPS policy in Tulang Bawang Regency is based on the PUPR Ministerial Regulation Number 07 of 2018 concerning BSPS, Perbup Tulang Bawang Number 36 of 2018 concerning Guidelines for Implementing Home Improvement Activities Sourced from the Regional Revenue and Expenditure Budget of Tulang Bawang Regency. The implementation of BSPS until 2019 has only been 7% (800) of 11,473 uninhabitable housing units (RTLH). In its implementation, BSPS has not been able to encourage public awareness of working together in building houses, according to the spirit of giving BSPS and giving BSPS there are still some that have not been on target. Judging from the benefits of the government housing policy, it can continue the policy for all low-income people (MBR), and future implementation can be carried out more selectively and on target.

Application of a Recurrent Neural Network and Simplified Semianalytical Method for Continuous Strain Histories Estimation

The durability and reliability of structural components are usually assessed based on fatigue loading under operating conditions. To obtain accurate fatigue loading in the form of continuous strain histories, a novel approach is proposed based on the combination of a recurrent neural network and simplified semianalytical method. The recurrent neural network named nonlinear autoregressive model with exogenous inputs (NLARX) is applied to determine the relationship between external loads and corresponding fatigue loading. Owing to the generalization ability of NLARX, semianalytical method, which is used to obtain sample database for NLARX model training and testing, is implemented with simplified multibody model. Durability tests of a torsion beam rear suspension are introduced to demonstrate the effectiveness of the proposed approach. The experimental results show that our proposed approach is able to achieve better estimation results, when compared with the conventional semianalytical method.

On-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures

Recently, some integrated structural identification/damage detection and reliability evaluation of structures with uncertainties have been proposed. However, these techniques are applicable for off-line synthesis of structural identification and reliability evaluation. In this paper, based on the recursive formulation of the extended Kalman filter, an on-line integration of structural identification/damage detection and reliability evaluation of stochastic building structures is investigated. Structural limit state is expanded by the Taylor series in terms of uncertain variables to obtain the probability density function (PDF). Both structural component reliability with only one limit state function and system reliability with multi-limit state functions are studied. Then, it is extended to adopt the recent extended Kalman filter with unknown input (EKF-UI) proposed by the authors for on-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures subject to unknown excitations. Numerical examples are used to demonstrate the proposed method. The evaluated results of structural component reliability and structural system reliability are compared with those by the Monte Carlo simulation to validate the performances of the proposed method.

Big data-enabled multiscale serviceability analysis for aging bridges☆

This work is dedicated to constructing a multi-scale structural health monitoring system to monitor and evaluate the serviceability of bridges based on the Hadoop Ecosystem (MS-SHM-Hadoop). By taking the advantages of the fault-tolerant distributed file system called the Hadoop Distributed File System (HDFS) and high-performance parallel data processing engine called MapReduce programming paradigm, MS-SHM-Hadoop features include high scalability and robustness in data ingestion, fusion, processing, retrieval, and analytics. MS-SHM-Hadoop is a multi-scale reliability analysis framework, which ranges from nationwide bridge-surveys, global structural integrity analysis, and structural component reliability analysis. This Nationwide bridge survey uses deep-learning techniques to evaluate the bridge serviceability according to real-time sensory data or archived bridge-related data such as traffic status, weather conditions and bridge structural configuration. The global structural integrity analysis of a targeted bridge is made by processing and analyzing the measured vibration signals incurred by external loads such as wind and traffic flow. Component-wise reliability analysis is also enabled by the deep learning technique, where the input data is derived from the measured structural load effects, hyper-spectral images, and moisture measurement of the structural components. As one of its major contributions, this work employs a Bayesian network to formulate the integral serviceability of a bridge according to its components serviceability and inter-component correlations. Here the inter-component correlations are jointly specified using a statistics-oriented machine learning method (e.g., association rule learning) or structural mechanics modeling and simulation.

Strain-Based Condition Assessment of a Suspension Bridge Instrumented with Structural Health Monitoring System

Strain provides information about local behavior of structural components, and is one of the most concerned parameters in the structural health monitoring (SHM) of civil structures. It plays an important role in the condition assessment of bridges in terms of fatigue or yielding of the structural material, safety reserve or reliability of structural components, etc. The Wind And Structural Health Monitoring System (WASHMS) deployed on the suspension Tsing Ma Bridge (TMB) in Hong Kong has hitherto operated continuously for 17 years. As part of the WASHMS, 110 strain gauges were installed on the bridge to measure the dynamic strain response of the TMB. Based on the strain measurement data acquired in 2012, the structural condition of the TMB is evaluated by addressing the following issues: (1) Evaluation of the characteristics of stress responses in structural members on different deck cross-sections and comparison with the results obtained in 1999. (2) Statistical analysis of daily maximum stresses in different members and comparison with the design values (designated stresses) due to live loads at both serviceability limit state (SLS) and ultimate limit state (ULS). (3) Evaluation of the inner forces of monitored structural members and the corresponding strength utilization factors (SUFs). The assessment results obtained in the present study can be used as a reference or guideline for scheduling the bridge inspection and maintenance activities.

Mode III fracture toughness of the Zr61Ti2Cu25Al12 bulk metallic glass

The intrinsic mode III fracture initiation toughness is measured for the Zr61Ti2Cu25Al12 (ZT1) bulk metallic glass (BMG), which is known to have a high mode I fracture toughness (KIC). The plastic strain intensity factor ΓIII was used as a measure of the fracture resistance under elastic–plastic conditions. The intrinsic mode III fracture initiation toughness of ZT1 BMG, ΓIIIC, is found to be 29 μm, equivalent to a KIIIC of 51 MPa√m. The corresponding fracture energy release rate is similar to or higher than that of conventional engineering metals such as high-strength aluminum alloys and some steels. The subcritical crack growth in ZT1 prior to catastrophic fracture is characterized by an extension of a microscopically zig–zag crack front. ZT1 exhibits a relatively low ratio of KIIIC/KIC of ∼0.39, indicating that the material is more susceptible to mode III fracture. In engineering design with BMGs, the mode III fracture toughness is thus a useful baseline to ensure the reliability of structural components.

Predicting laser weld reliability with stochastic reduced‐order models

SummaryLaser welds are prevalent in complex engineering systems and they frequently govern failure. The weld process often results in partial penetration of the base metals, leaving sharp crack‐like features with a high degree of variability in the geometry and material properties of the welded structure. Accurate finite element predictions of the structural reliability of components containing laser welds requires the analysis of a large number of finite element meshes with very fine spatial resolution, where each mesh has different geometry and/or material properties in the welded region to address variability. Traditional modeling approaches cannot be efficiently employed. To this end, a method is presented for constructing a surrogate model, based on stochastic reduced‐order models, and is proposed to represent the laser welds within the component. Here, the uncertainty in weld microstructure and geometry is captured by calibrating plasticity parameters to experimental observations of necking as, because of the ductility of the welds, necking – and thus peak load – plays the pivotal role in structural failure. The proposed method is exercised for a simplified verification problem and compared with the traditional Monte Carlo simulation with rather remarkable results. Copyright © 2015 John Wiley & Sons, Ltd.

Structural analysis of W7-X: Overview

The Wendelstein 7-X (W7-X) modular stellarator is in the assembly phase at the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald, Germany. The goal of the project is to demonstrate that this type of machine is a viable option for a fusion power-plant. The “pentagonal” magnet system of the machine encompasses 50 non-planar and 20 planar superconducting coils with sophisticated support structure. Structural reliability of components as well as resulting deformations and displacements during various modes of operation have to be considered not only for the magnet system but also throughout the whole cryostat whose main components are the plasma vessel, outer vessel, ports, and thermal insulation. A reliable prediction of the W7-X structural behaviour is only possible by employing complex finite element (FE) simulations with a hierarchical set of FE models. A special strategy has been developed and implemented for the task. The design is basically completed, main parameters are defined, and most of the W7-X components are manufactured. Therefore, the focus in the analysis is being shifted to the creation of parametric FE models which allow performing fast analyses of possible non-conformities, changes in the assembly procedure, and future exploration of operational limits. This paper gives an overview of the implemented analysis strategy, the applied safety margins, and focuses on the most remarkable results.

Reliability analysis of diesel engine crankshaft based on 2D stress strength interference model

A 2D stress strength interference model (2D-SSIM) considering that the fatigue reliability of engineering structural components has close relationship to load asymmetric ratio and its variability to some extent is put forward. The principle, geometric schematic and limit state equation of this model are presented. Reliability evaluation for a kind of diesel engine crankshaft was made based on this theory, in which multi-axial loading fatigue criteria was employed. Because more important factors, i.e. stress asymmetric ratio and its variability, are considered, it theoretically can make more accurate evaluation for structural component reliability than the traditional interference model. Correspondingly, a Monte-Carlo Method simulation solution is also given. The computation suggests that this model can yield satisfactory reliability evaluation.

Fatigue reliability of structural components

The paper is concerned with reliability assessment of structural and mechanical components subjected to cyclic variable amplitude service load. Due to relatively easy simulation and simple computational procedure, computer simulations based on the Monte Carlo method are often used for reliability assessments of engineering objects. The only disadvantage of such a method is a large number of repetitions of the fatigue-life assessment procedure required for attaining good accuracy in the range of high levels of reliability. Useful tips enabling the decrease of the number of samplings in the simulation procedure and preserving required reliability levels are the subjects of the discussion presented below. The rules for dimensioning structures and mechanical components using the deterministic and probabilistic input data have been formulated, and the relation between the safety factor and the fatigue-failure probability of structural components has been analysed as well.

室温および高温下における２．２５Ｃｒ‐１Ｍｏ鋼の超高サイクル疲労寿命特性

An ultrasonic fatigue testing machine was developed to obtain the very high cycle fatigue life at elevated temperature for safety and reliability of structural components in the faster breeder reactor (FBR). This testing machine consists of an amplifier, booster, horn and equipments such as a system controller and data acquisition. The test specimen is attached at the end of the horn. The electric power generated in the amplifier is transformed into the mechanical vibration in the converter and is magnified in the booster and horn. The developed ultrasonic fatigue testing machine enables to carry out the fatigue test at 20kHz so that it can perform the very high cycle fatigue test within a very shorter time as compared with the regular fatigue testing machines such as a hydraulic fatigue testing machine. This study carried out very high cycle fatigue tests using type STBA 24, the steel for tube in boiler and heat exchanger, at room and elevated (673K) temperatures by the developed testing and conventional hydraulic testing machines, and obtained the fatigue lives. This paper also described the cracks observed on specimen surface of fatigued specimen and discussed the very high cycle fatigue strength properties. It was confirmed that the fatigue data obtained by the ultrasonic fatigue testing machine are continuous and compatible with the results obtained by the hydraulic tension-compression testing machine. Fatigue lives more than 106cycles at room and high temperatures can be predicted conservatively by the best fit design curve employed in the nuclear power plant design.