Elastic wave propagation in polycrystalline materials at different texture intensitiesGupta, Himanshu; Gopalakrishnan, S.; Suwas, S.
doi: 10.1117/12.3010117pmid: N/A
A 3-dimensional (3D) voxel-based synthetic Polycrystalline Volume Element (PVE) is generated at various texture intensities; subsequently, the structural-mechanics module of a commercially available finite element (FE) solver is used to simulate elastic wave propagation through the PVE. Keeping the grain size distribution unchanged, two extreme behaviour of wave velocities have been achieved at two texture condition(s), namely Cube texture {001}⟨100⟩ and Copper texture {112}⟨111⟩, where Cube texture corresponds to most compliance; in contrast to, Copper texture which corresponds to the stiffest direction of the crystals in the PVE. Results also show a significant suppression of wave dispersion with an increment in texture intensity.
Evaluating damage progress in prestressed anchor cables with artificial defects using acoustic emission technologyZhang, Lu; Su, Yongqi; Zeng, Jiajun; Zhu, Wanxu; Li, Hongyu; Zhang, Tonghao
doi: 10.1117/12.3009849pmid: N/A
For the purpose of lightweight and long span, the structural solution using cable is proposed, especially for the bridges and roofs design. Herein, one of the key members is the anchor cable, which plays decisive role in the cable structure. But the prestressed anchor cable is vulnerable to corrosion and fatigue damage due to various environmental activities. Failure due to accumulative defects or broken wires is inevitable, which seriously effects on the status of the cable-structure system. Therefore, it is essential to propose an efficient method which can realize the real-time evaluation and monitoring of the health status of the prestressed anchor cable. In this paper, the acoustic emission (AE) technique was proposed to quantify the damage progress in the prestressed anchor cable. In order to verify the proposed AE-based method, three prestressed anchor cables with different prescribed defects were tested to failure under the fatigue tensile. Different depths of scratches were preset at different positions of the steel wires in the cables. Aiming to the bundle of the anchor cable, the conventional 1-D AE localization and zonal localization method were combined to localize the micro-crack and rupture of cable. The relationship between AE signal signature and damage was established. The acoustic emission signatures were identified and characterized: (i) friction between cables; (ii) plastic deformation of cable; (iii) rupture. With the localization of AE and typical AE signature, the failure progress can be described. The massive AE signals of plastic deformation can provide the precursor of the cable rupture. AE shows good potential for predicting the healthy status of the prestressed anchor cable.
Pedestrian footstep localization using a deep convolutional network for time difference of arrival estimationAppelle, Aaron; Salvino, Liming; Lynch, Jerome P.
doi: 10.1117/12.3009826pmid: N/A
This paper presents a resource-constrained localization system that uses geophones to map pedestrian locations in outdoor spaces. It addresses the need to non-intrusively monitor the level of community utilization of social infrastructure, such as public parks and markets. The system measures the time differences of arrival (TDOA) of footstep ground vibration signals to localize people using hyperbolic positioning. However, signal noise and dispersion impair conventional approaches like cross-correlation to compute the TDOA. This paper introduces a 1D-convolutional neural network model to compute the TDOA based on training data collected at the deployment setting. The model takes short windows of synchronized geophone time-series as input and provides a real-time estimation of the time difference. Results from a validation study in an urban setting show that the TDOA model outperforms baseline methods by over 60%, achieving a localization accuracy of less than 1 meter for single pedestrians.
Real-time state estimation using recurrent neural network and topological data analysisRazmarashooli, Arman; Salazar Martinez, Daniel A.; Chua, Yang Kang; Laflamme, Simon; Hu, Chao
doi: 10.1117/12.3010900pmid: N/A
High-rate systems are defined as physical systems that undergo large perturbations, often exceeding 100 g’s, over very short durations, often less than 100 milliseconds. Examples include blast mitigation mechanisms and advanced weaponry. The use of control feedback to empower high-rate systems requires the capability to estimate system states of interest in the realm of microseconds. However, due to the dynamics of these high-rate systems being highly nonlinear and nonstationary, it is challenging to predict their behavior using conventional state estimation methods. To address this issue, we conduct a study that explores the integration of topological data analysis (TDA) and recurrent neural network (RNN) to improve predictive capabilities for high-rate systems. Here, TDA features are used as the input to a machine learning algorithm to determine the state of a high-rate system. We conduct practical evaluations using laboratory datasets from experiments in the dynamic reproduction of projectiles in ballistic environments for advanced research (DROPBEAR), focusing on localizing fast-changing boundary conditions on a cantilever beam. The study demonstrates the ability of the method to classify and predict a system’s fundamental frequencies. This approach helps understand the structure of the underlying high-rate dynamics, leading to improved accuracy and precision in state estimation and prediction.
Considerations for qualifying reliable eddy current array technique for detection of backwall cracksKoshti, Ajay M.
doi: 10.1117/12.3027030pmid: N/A
A reliable nondestructive evaluation (NDE) technique provides minimum 90% probability of detection (POD) with 95% confidence for detection of cracklike flaws of a qualified size. In this case, the flaws are on backside of metallic material. Eddy current array (ECA) probe or a single sensor eddy current probe in c-scanning mode is used for the flaw detection. Here, two geometries are considered for the test specimens. The two geometries are, a flat plate, and tube or pipe. The probe is assumed to be on outer diameter (OD) surface and the flaw is assumed to be at the inner diameter (ID) surface for tube inspection. The flaw and probe are on opposite side of wall thickness for inspection of plate material. The application may be used for acreage inspection or just for inspection of butt weld and heat affected zone (HAZ) in a tube, cylinder, or plate. The proposed approach is based on developing an instrument standardization or calibration procedure. Decision threshold of inspection procedure is determined using empirical qualification and noise data. The work explores essential parameters that are required to meet certain conditions to ensure reliable flaw detection. Physics-based simulation of eddy current array flaw detection is used to understand effect of essential parameters on signal response (amplitude and phase), and therefore flaw detectability. Simulation data is used to justify choice of calibration reference standard requirements and the qualification approach. Calibration reference standards use artificial flaws such as electro-discharged-machined (EDM) notches. An ECA technique qualification model is provided. Empirical study is proposed to estimate crack to artificial flaw signal response transfer ratio. The paper gives a brief description of tasks to be completed for qualifying ECA technique for reliable detection of the cracklike flaws.
Corrosion detection of steel-reinforced concrete specimens using synthetic aperture radarRaisi, Koosha; Abazarsa, Maryam; Yu, Tzuyang
doi: 10.1117/12.3010437pmid: N/A
Chloride-induced corrosion attack in steel-reinforced concrete highway bridges is a common and ongoing issue in New England. If left untreated, late-stage corrosion can result in steel rebar section loss, internal stress imbalance, and surface cracks. In recent years, nondestructive testing and evaluation (NDT/E) techniques have been emerging as alternative methods for structural health monitoring (SHM) of civil infrastructure. This paper aims to use synthetic aperture radar (SAR) for corrosion detection of steel-reinforced concrete (RC) panels that were subjected to chloride-induced rebar corrosion. For this purpose, three RC panels (30×30×12.7 cm2) were cast with a No.6 steel rebar (19 mm diameter) at their mid-height with one serving as baseline, and the other two were corroded by accelerated corrosion test (ACT). The RC panels were kept in a temperature-controlled environment (23 − 25 C) since 2017. The RC panels were scanned by a laboratory 10.5 GHz SAR with a 1.5 GHz bandwidth to develop SAR images with two scan ranges of 60 and 70 centimeters. The SAR images were analyzed in time domain and their amplitude parameters were used for corrosion detection. Furthermore, a half-cell potential device was used for verification and quantification in conjunction with out SAR parameters. Our results indicate that the progression of corrosion based on HCP, is correlated with SAR signal parameters such as maximum and integrated, and average SAR amplitudes.
Structural finite element modeling and static analysis of the bridge modular expansion joint under vehicle loadZhang, Haoyu; Chen, Lan; Zhou, Lin-Ren
doi: 10.1117/12.3010369pmid: N/A
Expansion joints are a crucial component of bridges, influencing not only the force state, service performance, and operational safety of the structures but also playing a substantial role in ensuring the comfort and safety of traffic on the bridge deck. This paper investigates the static mechanical responses of bridge modular expansion joints using a full-scale 3D solid finite element (FE) analysis method. Firstly, the working mechanism, force transmission path, and influencing factors of the modular expansion joint are analyzed. Secondly, a full-size 3D solid finite model of the modular expansion joint is established using ANSYS FE software and APDL parametric modeling. The model incorporates the actual structure, force transmission path, contact effects, and boundary conditions of the expansion joint. Then, the load size and action position of typical vehicles on the joint are analyzed to obtain adverse vehicle action. Finally, the force state of the modular expansion joint under vehicle load using the 3D solid FE model is calculated and discussed. This paper proposes a precise FE analysis method for the complex stress state calculation of bridge modular expansion joints, providing theoretical and technical support for damage identification, state evaluation, and safety assessment of such joints, and can also be learned and used for other types of bridge expansion joints.
Static and dynamic testing of 3D-printed beams for structural design and construction applicationRobinson, Tiana; Raisi, Koosha; Yu, Tzuyang
doi: 10.1117/12.3010173pmid: N/A
The development of 3D printing has revolutionized the construction industry, presenting a sustainable approach to creating complex structures. However, the use of 3D printing materials in structural applications requires a thorough examination of their strength and serviceability to ensure their safety for practical use. This study aims to investigate the mechanical properties of thirty-six 243.1 mm-long 3D printed W beams (flange thickness tf = 1.72 mm, web thickness tw = 2.11 mm, flange width bf = 17 mm for static testing, and bf = 12.31 mm dynamic testing, depth d = 13.1 mm, and fillet radius r = 2.19 mm) and ST beams (flange thickness tf = 1.77 mm, web thickness tw = 1.86 mm, flange width bf = 17 mm for static testing and bf = 14.6 mm dynamic testing, depth d = 12.2 mm, and fillet radius r = 1.87 mm) for structural design and construction applications through static and dynamic testing. Static testing assesses several parameters, including stress-strain curve, Young's modulus, deflection, Poisson's ratio, and shear modulus, while dynamic testing evaluates stiffness and damping under free vibration. Three filaments were used, including Acrylonitrile Butadiene Styrene (ABS), Polyethylene Terephthalate Glycol (PET-G) and Polylactic Acid (PLA). This research used strain gauges to develop stress-strain curves and a laser Doppler vibrometer (LDV) to measure stiffness and damping. Findings were developed on the mechanical properties of 3D printed W and ST beams to improve our understanding of 3D printing for structural design and construction applications. From our experimental result, we found that printing orientation can reduce the stiffness of specimens, even the material has a large value of Young's modulus. Printing orientation can also affect the damping of specimens
Off-axis digital image correlation using projected speckles for damage imaging with minimal surface preparationAbbott, T. Bryce; Yuan, Fuh-Gwo
doi: 10.1117/12.3010943pmid: N/A
This paper presents a feasibility study for the visualization of hidden damage in aluminum plates using the integration of a digital camera, projected speckles, and a baseline-free wavelet transform mode shape curvature (WT-MSC) damage index. To capture out-of-plane motion in the plates, off-axis 2D digital image correlation (DIC) is applied. With the camera at an angle with respect to the plate surface normal, a component of the higher-amplitude transverse displacements can be captured. Compared to 3D DIC, the system is less complex, there is no need for camera calibration, and the 2D DIC algorithm is more computationally efficient. A major limitation of DIC for practical applications is the need to apply a speckle pattern to the surface to introduce trackable features in the image for tracking displacement. Projected speckles replace the need for surface-applied speckle patterns. Thus, minimal surface preparation is required. Two geometrically identical 305-mm x 305-mm aluminum plates with thinning defects of different sizes and depths were used to demonstrate the system. Through the excitation of a 20 Hz to 1 kHz chirp signal in a single-edge-clamped plate, the first 12 transverse vibration modes of the plate were sensed. These mode shapes were recreated with the off-axis 2D DIC system, and a wavelet transform mode shape curvature (WT-MSC) damage index was applied for damage imaging. This index is sensitive to irregularities in the higher mode shapes caused by differences in geometry in the damaged regions. The system provided clear damage images with a clear correlation with actual damage geometry regardless of plate orientation. This system serves as a preliminary study for the eventual application of imaging barely visible impact damage in composite plates using projected speckles.
Investigating the mechanical failure mechanisms of a novel CFRP composite to inform computational modelsLostec, Guillaume; Corcoran, Louis; Chen, Hongxuan; Zhang, Wei; Long, Rong; Jin, Yinghua
doi: 10.1117/12.3012737pmid: N/A
Carbon fiber reinforced polymers (CFRP) are promising next-generation, lightweight materials for use in the automotive and aerospace industries. Unfortunately, the production cost of virgin carbon fiber is expensive, the manufacturing of CFRP parts is costly and wasteful, and the recycling of CFRP generally results in (1) the reduced mechanical properties of recycled carbon fibers (rCF) and (2) the incorporation of rCF into low-value composites. In efforts to improve upon these areas, we have recently developed malleable, healable, and recyclable vitrimer composites with milled rCF that have produced promising material and mechanical properties—this work aims to investigate and understand the damage/failure mechanisms of these materials. Herein, we utilize dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) to understand and observe the damage mechanisms that result in the mechanical failure of these materials. Further, we utilize this information to inform the development of a constitutive model. The model is based on a statistical description of the network structure. The principles of thermodynamics are then used to derive the constitutive behavior for CFRP.