Yun-Lai Zhou

Damage detection using transmissibility compressed by principal component analysis enhanced with distance measure

Detecting structural damage in operational conditions still encounters some difficulties, especially in early-stage, as environmental varieties impose challenges in real engineering applications and may require large computational efforts in the structural health monitoring and potential maintenance. Unlike conventional strategies employing frequency response function or response data, a damage detection methodology is addressed in this study by employing transmissibility functions that retains a strong interrelation with structural damage or deterioration, in order to avoid the measurement of excitation, together with principal component analysis that leads to reduction in computational costs. In this procedure, transmissibility is extracted from the structural responses and main features are selected by principal component analysis for less computational costs. Then, via distance measures damage indicators are constructed for both intact and damaged states, and finally a numerical simulation with a clamped-clamped beam and a four-story benchmark are adopted to verify the applicability of the proposed procedure. The results demonstrate a good performance in structural damage detection.

Structural damage detection using transmissibility together with hierarchical clustering analysis and similarity measure

Maintenance and repairing in actual engineering for long-term used structures, such as pipelines and bridges, make structural damage detection indispensable, as an unanticipated damage may give rise to a disaster, leading to huge economic loss. A new approach for detecting structural damage using transmissibility together with hierarchical clustering and similarity analysis is proposed in this study. Transmissibility is derived from the structural dynamic responses characterizing the structural state. First, for damage detection analysis, hierarchical clustering analysis is adopted to discriminate the damaged scenarios from an unsupervised perspective, taking transmissibility as feature for discriminating damaged patterns from undamaged ones. This is unlike directly predicting the structural damage from the indicators manifestation, as sometimes this can be vague due to the small difference between damaged scenarios and the intact baseline. For comparison reasons, cosine similarity measure and distance measure are also adopted to draw out sensitive indicators, and correspondingly, these indicators will manifest in recognizing damaged patterns from the intact baseline. Finally, for verification purposes, simulated results on a 10-floor structure and experimental tests on a free-free beam are undertaken to check the suitability of the raised approach. The results of both studies are indicative of a good performance in detecting damage that might suggest potential application in actual engineering real life.

Damage Detection and Quantification Using Transmissibility Coherence Analysis

A new transmissibility-based damage detection and quantification approach is proposed. Based on the operational modal analysis, the transmissibility is extracted from system responses and transmissibility coherence is defined and analyzed. Afterwards, a sensitive-damage indicator is defined in order to detect and identify the severity of damage and compared with an indicator developed by other authors. The proposed approach is validated on data from a physics-based numerical model as well as experimental data from a three-story aluminum frame structure. For both numerical simulation and experiment the results of the new indicator reveal a better performance than coherence measure proposed in Rizos et al., 2008, Rizos et al., 2002, Fassois and Sakellariou, 2007, especially when nonlinearity occurs, which might be further used in real engineering. The main contribution of this study is the construction of the relation between transmissibility coherence and frequency response function coherence and the construction of an effective indicator based on the transmissibility modal assurance criteria for damage (especially for minor nonlinearity) detection as well as quantification.

Single side damage simulations and detection in beam-like structures

Beam-like structures are the most common components in real engineering, while single side damage is often encountered. In this study, a numerical analysis of single side damage in a free-free beam is analysed with three different finite element models; namely solid, shell and beam models for demonstrating their performance in simulating real structures. Similar to experiment, damage is introduced into one side of the beam, and natural frequencies are extracted from the simulations and compared with experimental and analytical results. Mode shapes are also analysed with modal assurance criterion. The results from simulations reveal a good performance of the three models in extracting natural frequencies, and solid model performs better than shell while shell model performs better than beam model under intact state. For damaged states, the natural frequencies captured from solid model show more sensitivity to damage severity than shell model and shell model performs similar to the beam model in distinguishing damage. The main contribution of this paper is to perform a comparison between three finite element models and experimental data as well as analytical solutions. The finite element results show a relatively well performance.

Output-Based Structural Damage Detection by Using Correlation Analysis Together with Transmissibility

Output-based structural damage detection is becoming increasingly appealing due to its potential in real engineering applications without any restriction regarding excitation measurements. A new transmissibility-based damage detection approach is presented in this study by combining transmissibility with correlation analysis in order to strengthen its performance in discriminating damaged from undamaged scenarios. From this perspective, damage detection strategies are hereafter established by constructing damage-sensitive indicators from a derived transmissibility. A cantilever beam is numerically analyzed to verify the feasibility of the proposed damage detection procedure, and an ASCE (American Society of Civil Engineers) benchmark is henceforth used in the validation for its application in engineering structures. The results of both studies reveal a good performance of the proposed methodology in identifying damaged states from intact states. The comparison between the proposed indicator and the existing indicator also affirms its applicability in damage detection, which might be adopted in further structural health monitoring systems as a discrimination criterion. This study contributed an alternative criterion for transmissibility-based damage detection in addition to the conventional ones.

The Rock Failure Behavior Analysis in Rock Cutting Using Finite Element Analysis

Rock cutting in various forms is used in mining and civil engineering area such as oil & gas drilling, tunneling etc. The dieted understand of the rock cutting mechanism is quite essential to the bit design and parameters selection. This study constructed the finite element model of rock cutting to investigate the crack initiation and propagation, chips formation and cutting force, and the effect of cutting depth on rock breaking mechanism is also analyzed. The results show that cutting depth plays an important role in the rock failure behavior, when the cutting depth is shallow, the ductile failure mode is dominated and brittle failure mode is dominated at the larger depth of cut. The cutting force increases linearly with the depth increase of cut when cutting depth is shallow; however, the nonlinearity of cutting force increase appeared when the depth of cut exceeds the threshold value. The magnitude of MSE tends to decrease with the depth increase of cut and tends to stabilize when the depth of cut reaches a certain value. The results obtained in this study can lead to an enhanced understanding of rock breaking mechanisms in rock cutting.

Investigation of Inclined Wellbore Stability Using Numerical Analysis

Wellbore instability problem is one of the key problems in drilling highly deviated, extended reach wells, particularly in high temperature, high-pressure formations (HPHT). However, many researches are focus on the vertical wellbore, and few studies have investigated on the three-dimensional inclined wellbore instability analysis which considering the influence of thermo-poroelastoplasticity. In this paper, a three-dimensional fully coupled thermo-poroelastoplasticity inclined wellbore stability model is presented by using finite element method, besides, this model can be used for the wells with any deviation angle and azimuth angle just by changing the far field stresses and boundary conditions. The distribution of pore pressure, wellbore stresses under the conditions of various deviation angle, consolidation times and temperatures have been analyzed. The research results show that, the stability problems are generally serious in deviated wells. The wellbore has more instability while the consolidation time increases and it has more instability in the heating cases than in cooling cases. The conclusions achieved in this paper will help the drilling engineers to understand the inclined wellbore instability problems correctly.

Structural system identification by utilizing transmissibility coherence from limited measured data

System identification performs as a core issue in structural dynamic analysis. In this study, transmissibility coherence is introduced for system identification with recalling the existing techniques based on transmissibility. Unlike previous approaches that require four-point measurement, the proposed methodology in this study only requires two-point measurement. The merit behind this approach is that the transmissibility coherence can be employed to estimate the subtraction of transmissibility between two reference points, by using auto- and cross-spectrum analysis. Verification using experimental data proves the feasibility of the proposed technique.

Review on structural damage assessment via transmissibility with vibration based measurements

In this study, transmissibility based damage assessment techniques with vibration measurement are reviewed with highlighting the recent advancements since damage might induce severe changes and cause huge economic losses in both civil and mechanical engineering structures. In recent years, transmissibility underwent booming and divergent application for damage assessment both in experimental model and engineering application, and this review provides a fundamental understanding for transmissibility based damage assessment by summarizing those research outputs, which can serve as useful reference for further