Structural Test Methods Research Articles

Hoop tensile properties and crack propagation investigation of 2D braided SiCf/SiC composite tubes: Experiments and simulations

SiCf/SiC composites are promising candidates for advanced pressurized water reactors (PWRs) fuel cladding materials due to their enhanced accident tolerance. Their mechanical properties are strongly influenced by the braided structure of continuous SiC fibers. This study fabricated SiCf/SiC composite tubes with braid angles ranging from 30° to 50°, evaluating their hoop tensile properties through expansion-due-to-compression (EDC) experiments and analyzing the damage process using finite element method simulation. Results indicate that variations in braid angles significantly affect structural density, thereby impacting mechanical strength under hoop tensile stress. Increased braid angles result in smaller pore units and higher pore density, leading to local stress concentrations and varied deflections at overlapping regions. The dynamic propagation behavior of cracks was investigated through acoustic and structural nondestructive testing methods. Finite element analysis of different braid configurations highlights the pivotal role of pore units in the initiation and propagation of hoop tensile cracks. This study enhances the understanding of toughening structures in 2D braided composites and provides a theoretical basis for future accident-tolerant fuel cladding design.

Expert CONsensus on Visual Evaluation in Retinal disease manaGEment: the CONVERGE study

Background/AimsRecent decades have seen significant advances in both structural and functional testing of retinal disease. However, the current clinical value of specific testing modalities, as well as future trends, need...

Gen Z buying patterns: comparing the influence of professional advising and social media engagement

PurposeThis paper aims to assess retail shopping avenues for young consumers based on the type of guidance and assistance they pursue (social media vs professional service provider) in purchasing situations judged to be important. Young consumers consider themselves pet parents and pets represent an extension of self. Thus, pet-related products, by their importance, represent an excellent area of analysis for this inquiry.Design/methodology/approachData collection was completed in a way that is contextually relevant and gives the results ecological validity with the assistance of a major supplier of pet food. A total of 470 Gen Z owners of small companion animals were obtained. The partial least squares structural equation modeling testing method is considered appropriate for the model analysis due to the structure and homogeneity of the sample and due to the precision of the method.FindingsResults indicate that, in accordance with social media engagement (SME) theory, high SME elevated social commerce purchase intentions while professional advice seekers reported increased brick-and-mortar shopping. Thus, context-dependent, young consumers may purchase from brick-and-mortar sites.Originality/valueThis paper draws on SME and Advice Response Theory and proposes an original model explaining channel selection preferences for young consumers based on the type of advice sought for important purchasing decisions. The model represents a steppingstone to investigate the mechanism that translates information search sources into buying through different channels.

Analysis of the Effects of the Economic Crises and Pandemic on Foreign Trade in 1994-2022 with RALS-LM Structural Break Unit Root Test Method: The Case of Türkiye

Türkiye commenced adopting export-led growth model by 1980. Via policies prioritizing the increase in export revenues, such as tax refunds, export credits, tax exemptions, and other subsidies, Türkiye targeted economic development by engaging in international trade and becoming a global economic agent. On the other hand, Türkiye gradually liberalized its financial markets starting in 1983 and completed the process of full liberalization of capital movements in 1989. However, adopting those liberal policies, Türkiye suffered many economic crises (1994, 2001, the 2008 global financial crises), paving the way to a sudden downturn in GDP, a decline in real income per capita, and employment. Also, the 2016 coup attempt, the 2018 Pastor Brunson crisis with the United States, and the COVID-19 pandemic in 2020, which created a severe global economic slowdown, negatively affected Türkiye’s economy. In this respect, within this paper, we aim to evaluate the impacts of those financial crises and the COVID-19 pandemic between the years 1994-2022 on Türkiye’s foreign trade and to find out if the effects of those crises on Türkiye’s foreign trade are temporary or permanent.
 For this reason, we utilized the RALS-LM Structural Break Unit Root Test Method. The results underline that the 2008 global financial crisis substantially affected Türkiye’s exports and imports. However, the results also underline that the effects of the 2008 global financial crisis on Türkiye’s foreign trade were temporary.

Design and validation of a novel knee biomechanical test method

A novel structural dynamics test method and device were designed to test the biomechanical effects of dynamic axial loading on knee cartilage and meniscus. Firstly, the maximum acceleration signal-to-noise ratio of the experimental device was calculated by applying axial dynamic load to the experimental device under unloaded condition with different force hammers. Then the experimental samples were divided into non-specimen group (no specimen loaded), sham specimen group (loaded with polypropylene samples) and bovine knee joint specimen group (loaded with bovine knee joint samples) for testing. The test results show that the experimental device and method can provide stable axial dynamic load, and the experimental results have good repeatability. The final results confirm that the dynamic characteristics of experimental samples can be distinguished effectively by this device. The experimental method proposed in this study provides a new way to further study the biomechanical mechanism of knee joint structural response under axial dynamic load.

On propagation characteristics of ultrasonic guided waves in helical strands

Steel strands have been widely used in industrial fields as a reliable load-bearing component. Under the influence of environmental erosion and fatigue stress, different types of damage, such as corrosion and fracture, will occur in the in-service steel strands, which will cause unpredictable loss of personnel and property. Ultrasonic nondestructive testing technology has become an ideal testing method for long-distance metal structures in recent years due to the advantages of long detection distance and high efficiency. The detection effect of ultrasonic nondestructive testing technology largely depends on the propagation characteristics of the selected guided wave modes. However, due to the influence of the helical structure of the steel strands and the contact between the wires, the propagation characteristics of the guided waves in the steel strands are very complicated. In this paper, a method for analyzing the dispersion characteristics of steel strands based on the Floquet boundary conditions (Floquet BCs) is proposed. The essence of this method is the mutual transformation principle of wave solution and vibration solution. To adapt to the helical structure of steel strands, this paper proposes a helical coordinate system and twisted coordinate system and deduces the corresponding wavenumber conversion formula. The results of Floquet BCs are consistent with the semi-analytical finite element method and sweep frequency finite element modeling method, which proves the correctness of the Floquet BC method from both theoretical and experimental perspectives. This paper provides a new idea for analyzing the dispersion characteristics of complex waveguides such as steel strands.

Coating thickness measurement of multilayer ferromagnetic samples based on pulsed eddy current testing technology

Pulsed eddy current (PEC) technology serves as a popular testing method for multilayer structures and is widely used in coating and substrate thickness measurement. However, in the coating thickness measurement of a multilayer structure, the substrate thickness effect is a disturbance that needs to be eliminated urgently. In order to reduce the substrate thickness effect, in this paper a twice difference normalisation method is proposed to obtain a signal feature independently of the substrate thickness effect for measuring the coating thickness of a multilayer ferromagnetic structure. The simulation and experimental results demonstrate that a fitting line of the peak value of twice difference normalisation signals can be obtained by using the twice difference normalisation method when only the coating thickness changes. The normalisation fitting line is immune to the substrate thickness effect and can be used to measure the coating thickness of a multilayer ferromagnetic structure, which means that the twice difference normalisation method is feasible for high-precision evaluation of the coating thickness of a multilayer ferromagnetic structure when the substrate thickness changes. This study will improve the coating thickness measurement accuracy of multilayer ferromagnetic structures when the substrate thickness changes in the PEC testing.

Deep learning-based damage estimation in concrete structures using acoustic emission data

Conventional structural testing methods assess damaged condition of the structures and they generally base on subjective visual inspection. To take necessary precautions before/during a disaster, real-time monitoring of damage progression is very important especially for critical structures such as bridges, viaducts, tunnels, dams and nuclear power plants. Acoustic emission (AE) has been proved to be a successful method for this purpose and it is used to locate even invisible micro-level cracks in the structures. The most important feature that makes this technique advantageous over other non-destructive testing methods is that it continuously monitors damages in structures subjected to load by sensors converting the waves emitted from the damage into electrical signals. By analyzing the parameters of the recorded signals, critical information such as the type, location, origination-time, size and direction of the damage can be obtained. In this study, it was aimed to estimate damage status of the concrete members exposed to loading by developing a deep learning-based damage detection model. This model was developed by monitoring AE activities of concrete and reinforced concrete specimens with different strength, size, properties and loading conditions. Afterwards, a relationship was established between the properties and load levels of the specimens with features of the AE signals. The developed model was tested on reinforced concrete elements under load. The results show that the model is successful at estimating the damage level.

A wideband parallel‐plate waveguide design for FSS/FSR measurement

In this letter, a parallel-plate waveguide (PPW)-type transverse electromagnetic (TEM) transmission chamber covering 2–14 GHz is designed, analyzed, and fabricated, which consists of a feed structure and two metal cover plates. The feeding structure is made of a structure similar to a monoconical antenna, with a good impedance bandwidth. To reduce the edge radiation of the PPW structure, the TEM wave cell (TEM cell) is surrounded by absorbing foam. Moreover, to verify the testing effect of the designed TEM cell, a simple square frequency-selective surface was tested in the TEM cell. The test results are in good agreement with the simulation results. It has been shown that the designed TEM cell can be used as an effective supplement to the transmission reflection test method for periodic structures.

Multi-degree-of-freedom Hybrid Fire Testing of a Column in a Non-linear Environment

Hybrid fire testing is a testing method for structures on fire based on a substructuring method. A complete structure is divided in two substructures, one in a fire test laboratory (physical substructure), and one numerically simulated (numerical substructure). In fire engineering, some hybrid fire tests have been successfully performed in the last decades, but as the method is still in its infancy, these hybrid tests were limited to one-degree-of-freedom tests. The paper presents the first successful multi-degree-of-freedom hybrid test performed in fire engineering. The physical substructure is a steel column with an axial displacement and rotations at the ends controlled by electric jacks. The numerical substructure is a non-linear 2D plane frame structure modelled in SAFIR®. The equations of the algorithm, the experimental setup, the testing process, and the results are presented.

Attribute Implications and Reverberations of the Japanese Foreign Policy for Technology and Innovation Business in Thailand

Economic growth can be defined by real gross domestic value and international imports and exports supported by technology and innovation. Currently, there are concerns about the level of international technological policy investment, despite having the capability to be macroeconomically and business-valuable. The main objective of this research is to study the attributions in relationships and associations between the policy implications of technological business (PITB) and the effort of technology and innovation acceptance capacity (TIAC), which influence capacity development and foresight to ensure effective Japanese foreign policies. This research has been fully justified through business policy receiving technology and innovation, the potential for technology and innovation adoption (PTIA) and innovation for firm performance (IFP) of Japanese joint venture companies in Thailand was examined. Fifty-seven companies were subjected to the structural equation model testing method. Data collection was conducted by the questionnaire and an in-depth interview with validity and reliability checked under 4 main latent variables: PITB, TIAC, PTIA, and IFP. All processing was performed with the ADANCO 2.2.1 program. The research found that PITB had a positive correlation and directly influenced PTIA and IFP unless it had an inverse correlation to TIAC and the relationship between TIAC and PTIA. It can serve as a guide for how to correctly carry out the principle of creating a new Japan's foreign policy in the future. Doi: 10.28991/ESJ-2022-06-03-09 Full Text: PDF

A review of mode I dominant interfacial fracture toughness test methods of skin-core bonding for thermoplastic composite sandwich structures

Increased lightweight design via composite sandwich structures is a promising approach due to their exceptionally high weight-specific mechanical properties. The involved high cost when using sandwich composite structures has hindered applications in cost-sensitive markets up to now. However, full thermoplastic composite sandwich structures enable a cost reduction using novel processing routes based on fusion bonding of core and facesheet. In order to optimize such full thermoplastic composite sandwich structures and to ensure proper bonding of facesheet and core after manufacture, valid test methods for the quantification of skin-core interfacial bonding are required. This paper reviews existing test methods for the determination of Mode I dominant interfacial fracture toughness of sandwich structures. The main focus is set on cantilever beam tests as well as on peel tests. Based on a definition of requirements for suitable test methods, their applicability for full thermoplastic composite sandwich structures is evaluated. The Mandrel Peel Test results as most promising test method for thermoplastic sandwich structures, especially with thin facesheets.

A Review of the Structural Fire Performance Testing Methods for Beam-to-Column Connections

The structural fire performance tests for beam-to-column connections are critical in determining their fire performance at high temperatures. The current standard fire testing methods provide the procedures for establishing the fire resistance of each construction element exposed to a standard fire. However, these methods cannot verify the fire behaviour of the connections between building elements. Researchers have performed numerous fire tests on beam-to-column connections despite the lack of structural fire performance testing methods. This paper presents a comprehensive literature review of the structural fire performance testing methods for beam-to-column connections. The major areas in this review are travelling fires, development of travelling fires on beam-to-column connections, fire testing considerations, fire testing criteria, recent fire testing, and loading applications. This paper identifies the key issues and challenges of the structural fire performance testing methods for beam-to-column connections. Finally, this paper provides recommendations and discusses the way forward for structural fire performance tests on beam-to-column connections.

Stability Prediction for Real-Time Hybrid Simulation with Different Physical and Numerical Substructure Discretization Using Asynchronous Multirate Simulation

AbstractReal-time hybrid simulation (RTHS) is an emerging high-efficiency and low-cost structural test method. Stability analysis is a very important part of RTHS to ensure the stability of the exp...

Experimental Campaign to Verify the Suitability of Ultrasound Testing Method for Steel Fiber Reinforced Concrete Fortification Structures

Fortification structures, both military and civilian, are designed to resist a blast explosion to some extent. Their technical condition after a blast load must be assessed in a fast and reliable way to enable the users’ decision about the future use of the structure. Preferably, for the assessment of the protective structure, the non-destructive testing method should be used. To assess the suitability of ultrasound testing method for fortification structures built from steel fiber reinforced concrete, an investigation in a laboratory and in situ was conducted, together with numerical simulation and statistical evaluation. The numerical simulation of the blast load of a steel fiber reinforced concrete slab was conducted using multiphysics simulation software with the aim to verify basic parameters of the field experiment. During the field tests, several slabs were loaded by plastic explosive and changes in the structure of the slabs, before and after the blast load, were examined using the ultrasound pass-through method. After the field tests, the slabs were subjected to a destructive laboratory test to determine their residual strength. Subsequently, the data sets obtained from the measurements were tested using functional data analysis. The results from the ultrasound pulse method show that specimens after a dynamic blast load can in some cases increase the strength of their cement matrix.

Implementation of online model updating with ANN method in substructure pseudo-dynamic hybrid simulation

Substructure pseudo-dynamic hybrid simulation (SPDHS) is an advanced structural seismic testing method which combines physical experiment and numerical simulation. Generally, the key components which display nonlinearity first are taken as experimental substructures for actual test, and the remaining parts are modeled in simulation. Model updating techniques can be effectively applied to enhance the model precision of nonlinear numerical elements. Specifically, the constitutive model of the experimental substructure is identified online by the instantaneously-measured data, and the corresponding numerical elements with similar hysteretic behaviors are updated synchronously. Artificial neural network (ANN) can recognize the system which cannot be represented by definite numerical model, and thus avoids the structural response distortion caused by the inherent numerical model defects. In this study, a framework for online model updating in SPDHS with ANN method is expanded to implement actual test validation. Moreover, the effectiveness of ANN method is demonstrated by practical tests of a two-story frame model with bending dampers. Additionally, the unscented Kalman filter technique and offline ANN identification approach are both examined in the test validation. The experimental results show that, under the identical loading history, the online ANN method can significantly reduce the model errors and improve the accuracy of SPDHS.

Mechanical properties of laminated bamboo designed for curvature

Laminated bamboo is growing in potential as a novel construction material due to the need to lower the carbon impact of the built environment. The material utilises raw bamboo in an engineered composite to create a standardised prismatic section. The present study investigated the mechanical properties, as well as the performance under sustained load, of laminated bamboo sections which had undergone a secondary glue laminating process to facilitate the forming of curved profiles. Small and structural scale testing methods were used to evaluate the properties under varying service conditions representative of both internal and external environments. The results indicated that the material properties of the test pieces were generally consistent with previous studies. The long-term behaviour in bending was generally found to be consistent with or better than expectation based on the Eurocode 5 duration of load and creep factors applicable to solid or glued laminated timber, however, appear to be conservative when applied to laminated bamboo. In contrast, the Eurocode 5 torsional shear deformation factors appear to be unconservative for laminated bamboo. Further study is required to determine long-term performance in both bending and shear, in particular with respect to varying service class.

Real‐time hybrid simulation of a space substructure based on high‐strength steel composite Y‐eccentrically braced frames

Real-time hybrid simulation (RTHS) is a novel structural seismic test method that has good application prospects. The applicability of RTHS for large-scale space frame structures is further investigated in this study based on high-strength steel composite Y-eccentrically braced frames (Y-HSS-EBFs). First, an RTHS system was established, which included OpenSees, OpenFresco, an xPC-Target, and an electrohydraulic servo control system. An adaptive feedforward delay compensator based on displacement prediction was introduced. Then, a shaking table test model of a three-story Y-HSS-EBF was taken as the prototype, the third-story frame with the strongest nonlinear performance was taken as the experimental substructure, and the remaining two stories were taken as the numerical substructure in order to perform the RTHS. The results of the RTHS were compared with those obtained in a purely numerical model and a shaking table test, and the stability of the RTHS system was analyzed. The results indicate that the RTHS results are in good agreement with the numerical simulation results and that RTHS can be used to obtain results similar to the ones obtained using the shaking table. In the typical seismic testing frequencies and the mass distribution ranges of the substructures, the RTHS system displayed good stability and reliability and was able to effectively evaluate the seismic performance of large-scale space frame structures.

Mitigation of environmental problems using brick kiln rice husk ash in geopolymer composites for sustainable development

Brick kilns uses assorted amount of rice husk as fuel to fire the stacks of soil bricks. In India, the rice husk ash (RHA) created during the burning process of bricks has yet to be properly exploited. The main focus of this study is to enhance the structural properties of geopolymer composites using brick kiln incinerated rice husk ash waste. The Physico-chemical analysis of brick kiln rice husk ash indicates the presence of high silica (88%) content with the evidence of XRD and FTIR analysis, SEM images shows high porous structure and PSD analysis gives a bonding nature of particle size as binding ingredient. The geopolymer mixes were made manually with different percentage of RHA 0%, 10%, 20% and 30% replaced partially in Siliceous Flyash. To identify suitability of the mixture for geopolymer concrete production, properties like workability and fresh density of the mixture was investigated using manually casted cubes having a size of 100 ​mm and keeping for oven drying at 40° ±2 ​°C upto 24 ​h. Compressive strength as destructive structural test method was investigated at the respective duration of curing. The findings led to the conclusion that increasing the percentages of RHA in the combination improves the mixture for geopolymer concrete composites with the increase of curing time. At 10% RHA addition, the optimal compressive strength of 42.19 ​N/mm2 was achieved. The compressive strength of the RHA was found to decrease by 0.8% at 10% addition, which is negligible when compared to the control geopolymer mix (i.e., mix with 0% RHA), implying that the RHA from brick kilns can be employed to improve the structural qualities of geopolymer concrete composites.

INCREASING THE VISITS AND RETAINING E-LOYALTY TOWARDS WEBSITE

The growth of users and transactions through e-commerce create its own phenomenon of fluctuating visits on website. Its was valuation regarding how often the website being visited or attracts that attention from visitors. This could be measured by examining those influences from customer interface quality, customer satisfaction and switching cost towards E- loyalty on the use of e-commerce website. Research data obtained through a questionnaire that distributed to 150 respondents by Structural Equation Modeling test method of IBM SPSS AMOS 22. All Results show that Customer Interface Quality has capable to provide positive and significant impact towards e-loyalty, as well as Customer Satisfaction which partially or as a mediate variable for Quality Customer Interface that also signs positive and significant influence over it. From these result tells that Switching Cost does not had significant influence or either partially as a mediator to e-loyalty. Customer Satisfaction is most influential variable to e-loyalty on website visits.