Damage Position Research Articles

Workability, Densification and Failure Characteristics of Selective Heated Sintered Powder Metallurgy Preforms during Upsetting

A study on workability, densification and failure characteristics of porous aluminum–titanium components has been performed by adopting a selective heating method under triaxial stress state condition. The required specimens were made using the powder metallurgy method with 90% of initial relative density and an aspect ratio of 1 through the appropriate compaction pressures. A sequence of upsetting has been executed on the powder metallurgical compacts using a hydraulic press for different titanium compositions (2-6%). In the upsetting process, the damage of the specimens mainly relies on the accumulation of stresses at the damage site. Hence, the damage site of the compacts was identified for various specimens using finite element simulation software. Once the damage position was identified, the compacts were heated at the damage sites (selective heating) for different temperatures, namely 100, 140, 195, 220 and 250 °C using a portable gas cartridge. As a result, the failure initiation is arrested thereby increasing the workability and densification. Selectively heating the damage zone of the components has relieved the accumulated stresses and has reduced the porosity (from 11.385 to 6.702% for Al-2%Ti, from 12.797 to 7.920% for Al-4%Ti and from 13.215 to 8.611% for Al-6%Ti) of the preforms. Thus, the damage limit of the components can be increased during upsetting by the selective heating process.

Empirical method for structural damage location using dynamic analysis

Abstract This paper presents the use of numerical model techniques for identification and damage location adopting the Modal Curvature Difference (MCD) method as reference for the analysis of a simply supported concrete structure. Then, an empirical formulation to detect damages in this structure is proposed. In this method, called Acceleration Summation Difference (ASD), the difference of acceleration amplitude between intact and damaged structures are calculated for concrete plates simply supported on rubber bearings. During the analyses, the finite element models were developed using SAP2000® software. The results obtained depicted that it is possible to determine the approximate position of one or more damages in the structure, with some restrictions, and the proposed ASD method presented good correlation to localize the position of single or multiple damages.

Stability Evaluation of Concrete Structure Considering the Local Damage Using Nondestructive Detection and Numerical Analysis

Shield tunneling is one of the most important technologies for building of underground engineering. Many grouting holes were prefabricated for the requirement of backfill grouting, which is easy to induce local damages and potential disasters, such as leakage and cracking. Accordingly, an integrated workflow for damage detection and stability evaluation was performed based on nondestructive testing (NDT) and numerical simulation. As a case study, this method was applied to an underwater shield tunnel. Firstly, Ground Penetrating Radar (GPR) was used to detect the conditions in grouting holes. Then, the infrared camera was used to determine the damaged positions induced by grouting holes. According to NDT results, the numerical models were developed to analyze the mechanical behaviors of structure. It indicated the geophysical inversion results are consistent with field conditions. The influence area increases with a significant value of water pressure, and stress magnitude would increase to 45KPa if the increment of water pressure reaches to 10KPa. As a promising application, structure stability was evaluated in the light of analytical results.

Fault Diagnosis of Rolling Bearing Based on GA-VMD and Improved WOA-LSSVM

To improve the fault identification accuracy of rolling bearings due to the problems of parameter optimization and low convergence accuracy, a novel fault diagnosis method for rolling bearings combining wavelet threshold de-noising, genetic algorithm optimization variational mode decomposition (GA-VMD) and the whale optimization algorithm based on the von Neumann topology optimization least squares support vector machine (VNWOA-LSSVM) is proposed in this manuscript. First, wavelet threshold de-noising is used to preprocess the vibration signal to reduce the noise and improve the signal-to-noise ratio (SNR). Second, a genetic algorithm (GA) is utilized to optimize the parameters of variational mode decomposition (VMD), and optimized VMD is adopted to extract the fault feature information. The VNWOA-LSSVM fault diagnosis model is built to train and identify the fault feature vectors. The proposed method is validated by experimental data. The results show that this method can not only effectively diagnose various damage positions and extents of rolling bearings but also has good identification accuracy.

Dynamic Failure Model of Thin Coal and Rock Mass under Uniform Impact Load

During the excavation of deep coal and rock mass, the radial stress of the free face changes from three-dimensional compression state to two-dimensional stress, bearing the combined action of dynamic disturbance and static load at the same time. With that, many mines suffer from dynamic disasters, such as coal and gas outburst, rock burst and rock caving during deep mining excavation, which is often accompanied by plate crack, spalling and other disasters, seriously affecting the stability of stope and roadway. Taking thin rectangular coal and rock mass as the research object, the dual equation of the free vibration was derived and the exact solution model of the free vibration was established with the use of Hamilton dual system. Based on the action characteristics of the uniform impact load, the effective mode of the forced vibration was obtained by using the Duhamel integral principle and the orthogonality of the mode function. Based on the third strength theory and the numerical simulation results, the dynamic damage process and development trend of coal and rock mass were analyzed under uniform impact load. It was concluded that the starting position of dynamic damage can be judged by the first order main mode, and the development direction and trend of the damage can be judged by the fifth and sixth order main modes. It was concluded that the vibration mode functions of coal and rock mass with four side fixed (C-C-C-C), the two sides fixed and simply supported on the other (S-C-S-C) are mainly composed of three modes that are the first order (dominant frequency), the fifth order and the sixth order, from which the dynamic damage mechanism is preliminarily studied.

Fatigue Damage Evaluation of Pile‐Supported Bridges under Stochastic Ice Loads

The Bohai Sea is the sea area with the worst ice condition in China, and the ice loads significantly threaten the safety of structures in the sea. The intense vibrations of the pile‐supported bridge under stochastic ice loads will increase the fatigue damage of a bridge structure and reduce the fatigue life of a bridge structure. In the present study, a comprehensive analysis model is presented to study fatigue damage for pile‐supported bridges under ice loads in Bohai Sea. On the basis of measured statistical data of ice parameters and stochastic ice loads spectrum of Bohai Sea, the time histories of the stochastic ice loads of Bohai Sea are simulated. Fatigue damage analysis is carried out in time domain utilizing the finite element method considering soil and bridge structure interaction. The effect of soil conditions and water depth on the cumulative fatigue damage of the pile‐supported bridges is studied. Numerical results indicate that in comparison with stiff soil conditions, pile‐supported bridges in soft oil conditions can increase the cumulative fatigue damage substantially; pile‐supported bridges in deep water also can increase the cumulative fatigue damage obviously. The study presented the first danger position of cumulative damage of the pile cross section under stochastic ice loads. The findings of this study can be used to fatigue damage evaluation and bridge construction in the ice‐covered sea area.

Influence of Internal Damage on the Vibration Behavior of Metallic Beam Structures

In structural engineering, detection of internal damage at the earliest possible stage of failure is one of the most significant factors for ensuring safety and reliability, and for limiting costs; this is critical to many practical applications. Several techniques to detect damage in engineering applications have been proposed in the literature; however, there is no consensus on which are the most effective. This study aimed to investigate the dynamic response of internal damage that occurs in an aluminum cantilever beam. This study describes a new technique to identify the internal damage within isotropic materials. Internal damage assessment of the beam was performed using a linear perturbation-free vibration study in ABAQUS (made by Finite Element software), to investigate the effectiveness of the damage detection technique. A damage detection scheme is evaluated for several scenarios varying by damage location and size, by relating fractional changes in modal energy to changes in natural frequency response parameters. The behavior of healthy and damaged beams are compared, and it is observed that the mode shape may be an effective method to detect damage.The intent of this work focuses on the best technique to identify the position of tiny damages within isotropic materials, and identifying the size of these damage points.

Damage Diagnosis of Top Tensioned Riser Based on Strain Response

Strain has a high sensitivity to structural damage and can be used for damage diagnosis of marine risers in engineering. Considering the structure and boundary conditions of the top tensioned riser, it can be simplified to the Euler-Bernoulli beam element, and the strain equation on the riser wall is derived. The element Root-Mean-Squared Strain(RMSS) difference is proposed as the damage index parameter of the riser. The finite element software ANSYS is used to simulate the element strain response of the 1000m length top tensioned riser in the South China Sea with different damage locations, damage degree and sea state parameters, and the RMSS difference curve is drawn. The results show that the RMSS difference has high sensitivity to the riser structure damage, and the damage position of the riser can be effectively identified in many different situations.

Analysis of the Damage of Cyclists in Electric Bicycle - Sedan Angle Collision

In order to study the vulnerable factors of the traffic accidents—the cyclist's injury factor at the moment of the accident—the computer simulation analysis method is used to restore the information collected by a real accident combined with the scene. From the established multi-rigid kinematics model, the corresponding injury situation of a body structure of a traffic accident rider is obtained, which involves the collision speed, the collision angle, the acceleration of each part of the human body and the force. The data is compared with ECE R44, FMVSS 213 and Euro NCAP 2009 regulations to analyze and restore various factors of bicycle injury in the collision. The results show that when the car and the non-motor vehicle have a low-angle collision, the cyclist's injury is mainly caused by the collision with the ground after the parabola movement, and the damage position of the human body depends on the order of contact with the ground.

Large Structural Shear Deformation and Failure Monitoring Using Bend Losses in Polymer Optical Fibre

Rapid identification of structural damage positions is essential to the post-disaster rehabilitation of structures and infrastructures. Large shear deformation, e.g., shear failure of bridge piers, shear-slip of slopes, and shear cracking of structural walls, is often the cause of structural instability. Distributed optical fibre sensing (DOFS) techniques have an advantage over point-based sensors in terms of spatial continuous structural condition monitoring. This paper presents the development of new measurement theory and algorithm to evaluate the structural shear deflection based on the large beam deflection and optical bend loss theories. The proposed technique adopted a photon-counting Optical Time Domain Reflectometer (ν-OTDR) with polymer optical fibres (POFs) which has a large deformation measurement range and high spatial resolution. In the experiment, shear deformation events can be successfully detected and evaluated from the proposed technique. When the normalised shear deformation is larger than 0.2, both the event locations and the magnitudes can be accurately determined. When normalised shear deformation is lesser than 0.2, the error in the magnitude evaluation increased, but the event location can be found with an absolute error <0.5 m. Multiple shear events can be treated as independent events when they are separated by more than 5 m. Various configurations of POFs attached to concrete beam specimens for rupture failure monitoring were also studied. The configuration that could maximise the POF curvature at the beam failure produced the largest ν-OTDR signals. In other configurations in which the POFs were only stretched at failure, the signals were less strong and were influenced by the POF-structure bonding strength.

Multi-sensor network for industrial metal plate structure monitoring via time reversal ultrasonic guided wave

Active ultrasonic guided wave is considered to be the most effective and important on-line damage monitoring method for industrial steel plates structure health monitoring. Aiming at the problem of poor practicability of extracting damage scattering signal from baseline signal, a baseline-free time reversal probabilistic imaging algorithm (BFTRPI algorithm) is proposed in this paper based on ultrasound guided waves time reversal theory and probability statistics principle. Firstly, the time reversal of signal and the adaptive focusing mechanism of wave source are used to eliminate the dispersion effect of Lamb wave by the multi-sensor network. Secondly, the energy characteristic difference coefficient between the reconstructed Lamb wave signal and the original excitation signal, is taken as the damage factor. Finally, the relative distance between the damage and the direct path of the sensor-actuator channel is used to adjust the weight distribution function. The weighted probabilistic values of each sensor path in the sensor network are mapped to the discrete coordinates in the detection area, and the probabilistic imaging of the damage appearing on these discrete coordinates is constructed for multiple damages imaging and location. Experiments on aluminium sheets show that the method can clearly separate the damage scattering signals without baseline signals, achieve the focus of the original excitation signal, and obtain the damage probability images of structure. Compared to traditional probability distribution function method, it has better imaging accuracy and imaging quality. The positioning accuracy of the BFTRPI algorithm is obviously higher than that of traditional algorithm. The estimated position by BFTRPI algorithm is more close to the actual damage position. The location area of damage and artifact for traditional algorithm are both higher than that of BFTRPI algorithm. This method can accurately identify and locate multiple damages in aluminium sheet, which verifies the validity of this method and has certain engineering application value.

Damage identification research on beam structures by integrating multiple modal parameters

A new damage identification method with a fusion index to locate the damage position and identify the damage extent of beam structures is presented by integrating the modal strain energy and natural frequency sensitivity. The modal strain energy, which is with the limitation on obtaining the damage extent, is adopted to locate the damage position with avoiding the interference of structure itself. The natural frequency sensitivity, which is with false detection and interference happening when solely used, is adopted for identifying the damage extent. In order to further improve the precision of the damage quantification, additional masses are added on the beam structure to obtain more information about the natural frequency sensitivity. Then, the fusion index for damage identification is established through combining the modal strain energy and the natural frequency sensitivity before and after adding masses on beam structures. The results obtained by finite element analysis and experimental tests show that the presented method can locate and quantify damages on beam structures in an accurate and convenient way.

Guided wave SHM system for damage detection in complex composite structure

The paper deals with the development of a Finite Element (FE) model aimed to simulate the propagation mechanisms of guided waves in a complex composite structure, such as a blended Glass Fibre Reinforced Polymers (GFRP) winglet, for real-time damage detection and monitoring purposes. The reliability of the herein presented FE model has been assessed against an experimental tests campaign, involving the winglet under both reference/pristine configuration and impacted/damaged configuration, also changing the actuator location. Because of the good level of accuracy shown by the numerical-experimental comparisons, the FE model has been used also for numerically investigating new actuators and damage position configurations, not experimentally analysed. Damage Indexes (DI’s) have been calculated to quantify the variations of the signals’ amplitude caused by the induced damage. Moreover, the Probability Ellipse (PE) method, which estimates the probability of the presence of the damage in the monitored area starting from the knowledge of selected DI’s for each sensors-path, has been used in both older and newer damage position. The accuracy of the PE method in detecting the damage location is herein discussed.

An Aircraft Pallet Damage Monitoring Method Based on Damage Subarea Identification and Probability-Based Diagnostic Imaging

To improve the safety and economy of aircraft pallet use, an aircraft pallet damage monitoring method based on damage subarea identification and probability-based diagnostic imaging is proposed. In the proposed method, first, the large aircraft pallet monitoring area is divided into rectangular subareas, and a piezoelectric transducer sensor is pasted on each vertex of the rectangular subarea that is used to excitation and sensing the Lamb wave. Second, the damage subarea is identified according to the diagonal damage indexes. Third, the damage position in the damage subarea is calculated using the probability-based diagnostic imaging method and coordinate probability weighted algorithm. Finally, the aircraft pallet damage can be localized based on the damage subarea position. Frequency selection and damage simulation study results show that the Lamb wave is sensitive to aircraft pallet damage whose centre frequency ranges from 50 kHz to 150 kHz, and the damage index of a steel ball is less than that of all real aircraft pallet damage from 95 kHz to 125 kHz. The verification results show that the proposed method can locate aircraft pallet damage with an error of less than 2 cm.

Determining Structural Damage of Stone Curtain Walls by Dynamic Method

Dry hanging stone curtain wall is widely used in the building envelopes, but it was of ten deemed as a safety risk. The damage of the back anchorage structure may result in the urban disaster accident due to the falling down of the tone panel. There is no yet effective detection method because the damage part is hidden behind the panel. In this paper, a dynamic detection method is presented to monitor the damage degree of the anchorage structure on the back of the panel and to determine the damage location. Experiments indicate that the first three steps of natural frequency of the stone panel declined, with the increase of the damage degree of the anchorage structure. The degradation of the natural frequency can be used to identify the degree of back connection damage. In addition, the relationship between the damage position of the back connection and the modal parameters of the stone was investigated. It was found that the change of the damaged location significantly affected the modal vibration of the stone panel and the relative discriminant method is proposed to determine the damage position.

Vibration-based structural health monitoring using symbiotic organism search based on an improved objective function

Vibration-based structural health monitoring (VSHM) relying on model updating methods has been developed greatly and nowadays, not only serves as a major subset of SHM, but also shapes a special class of optimization problems. The historical course of evolution of this field via different research groups and with different goals and objectives, has resulted in the emergence of multiple objective functions, each appropriate only for certain damage scenarios and incapable of reasonably addressing others. The natural frequency residual (NFR) is an objective function sensitive to the damage intensity, which in the meantime, fails to predict the damage location in the symmetric structures. The total modal assurance criterion (TMAC) is another objective function which is sensitive to the damage position, but fails to estimate of the damage severity in the uniformly damaged structures. The present work successfully provides an innovative solution to unify both aforementioned objectives in a holistic objective function (HOF), through a particular combination of NFR and TMAC. Additionally, the competency of the above HOF for solving the VSHM problems has been investigated and demonstrated using a symbiotic organism search (SOS) optimization algorithm. The robustness and efficiency of the proposed VSHM method are verified through assessment of two un-damped benchmark structures. The obtained results indicate that in all damage scenarios, the HOF predicts with a high precision the damage location and succeeds in the high accuracy estimation of the damage extent. Consequently, the combination of the proposed HOF criterion and the SOS optimization algorithm is recommended as a reliable technique for VSHM.

Experimental and numerical analyses of stiffened composite panels with delamination under a compressive load

L-shaped stiffened composite panels provide an efficient structure for engineering applications. However, they often produce delamination in the preparation and service process due to a series of factors. To study the effect of different types of delamination on the compressive strength of stiffened composite panels, ABAQUS finite element software was used in combine with the progressive damage subroutine user-defined field variable (USDFLD), and the finite element model was established based on cohesive theory to realize the prediction of the progressive failure process and strength of the stiffened composite panels. The results showed that the delamination of a stringer had a greater impact on the strength of the stiffened composite panels than did the debonding between the skin panel and a stringer and the delamination of the skin panel. The debonding delamination and delamination of a stringer exhibited delamination growth near the damage position during static compression, but delamination of the skin panel exhibited no delamination growth. The experimental results were in good agreement with the finite element simulation results, which verified the validity of the finite element model.

Calibrating static measurement data from distributed fiber optics by the integration of limited FBG sensors based on the extended kernel regression method

Thanks to the rapid development of fiber optic sensors, the arrival of distributed sensors makes continuous and dense measurement possible for real structures. The distributed fiber optic sensors could provide a very high number of sensors along one single fiber, which is of great significance for structural health monitoring, especially for the detection of the damage position. However, the accuracy of data measured from fiber optic distributed sensors, such as strain and displacement etc., are sometimes not as accurate as those obtained from traditional fiber optic sensors such as fiber Bragg gratings (FBGs) and strain gauges. In this paper, to enhance the accuracy of static strain data measured from distributed fiber optic sensors, an extended kernel regression (EKR) method is applied to combine the distributed sensor measurement with those from four FBG sensors. These provide quite accurate static strain data; the strain values at locations where the FBGs are absent can therefore be predicted by the EKR method, which uses the data from distributed fiber optics as a biased model. The static experimental activities have been carried out in a laboratory, using a cantilever beam structure under different static loads.

Analytical study on damage detection method using displacement influence lines of road bridge slab

Structural health monitoring has garnered attention as a method to quantitatively evaluate damage to road bridges, and various dynamic and static damage detection methods have been proposed recently. However, few damage detection methods focus on the displacement shapes of road bridge decks. In this study, a damage detection approach is proposed using Displacement-Based Index (DBI) and Grey Relational Coefficient (GRC), in which displacement influence lines of deck slabs are used as inputs in the evaluation procedures. Parametric studies were performed by changing the damaged positions and boundary conditions of a full-scale bridge model to examine their possible effects on the performance of the proposed method. The results indicated that either approach could properly detect damage in the simulation model. In addition, because the proposed method was insensitive to damage away from the measurement position, it was clarified that damage detection could be performed accurately by installing multiple displacement meters at appropriate intervals.

Wear-out evolution analysis of multiple-bond-wires power modules based on thermo-electro-mechanical FEM simulation

In this paper, an electro-thermo-mechanical finite-element method (FEM) simulation approach is proposed to analyse the wear-out evolution of multiple-bond-wires chips in power electronic modules. Cracks are introduced along the simulation, based on the sensitive damage position at each simulation step, in order to emulate the realistic wear-out sequence occurring in real cases. This process has been made semi-automatically, by running many simulations, each time with updated crack geometry using the previous step results. The proposed method has been successfully used to interpret the typical on-state voltage degradation curve of accelerated life tests.