scholarly journals Robust Identification of Strain Waves due to Low-Velocity Impact with Different Impactor Stiffness

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1283 ◽  
Author(s):  
Alessio Beligni ◽  
Claudio Sbarufatti ◽  
Andrea Gilioli ◽  
Francesco Cadini ◽  
Marco Giglio
Keyword(s):  
Sensor Networks ◽  
Low Velocity Impact ◽  
Time Of Arrival ◽  
Low Velocity ◽  
Metallic Structures ◽  
Robust Identification ◽  
Impact Monitoring ◽  
Multiple Impact ◽  
Processing Techniques ◽  
The Impact

Low-velocity impacts represent a major concern for aeronautical structures, sometimes producing barely detectable damage that could severely hamper the aircraft safety, even with regards to metallic structures. For this reason, the development of an automated impact monitoring system is desired. From a passive monitoring perspective, any impact generates a strain wave that can be acquired using sensor networks; signal processing techniques allow for extracting features useful for impact identification, possibly in an automatic way. However, impact wave characteristics are related to the impactor stiffness; this presents a problem for the evaluation of an impact-related feature and for the development of an automatic approach to impact identification. This work discusses the problem of reducing the influence of the impactor stiffness on one of the features typically characterizing the impact event, i.e., the time of arrival (TOA). Two passive sensor networks composed of accelerometers and piezoelectric sensors are installed on two metallic specimens, consisting of an aluminum skin and a sandwich panel, with aluminum skins and NOMEXTM honeycomb core. The effect of different impactor stiffnesses is investigated by resorting to an impact hammer, equipped with different tips. Subsequently, a method for data processing is defined to obtain a feature insensitive to the impactor stiffness, and this method is applied to multiple impact signals for feature uncertainty evaluation.

Time Dependent Low Velocity Impact Response of Turbomachinery Blade Made of Porous Exponential FGM

2019 ◽  
Author(s):  
Apurba Das ◽  
Gopal Agarwal ◽  
Kazuaki Inaba ◽  
Amit Karmakar
Keyword(s):  
Contact Force ◽  
Conical Shell ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Integration Scheme ◽  
Low Velocity ◽  
Conical Shells ◽  
Velocity Impact ◽  
Multiple Impact ◽  
The Impact

Abstract This study presents transient dynamic response of porous and non-porous exponential functionally graded (E-FGM) conical shells subjected to low velocity single and multiple impact. Hertzian contact law in modified form considering permanent indentation is used to calculate the impact response parameters. For finite element formulation eight-noded isoparametric shell element having five degrees of freedom per node is used. The dynamic equations for the low velocity impact problems are solved by Newmark’s time integration scheme. Parametric studies in terms of contact force, initial velocity of impactor, impactor displacement and shell displacement for Stainless Steel-Silicon Nitrite porous and non-porous conical shells (idealized as rotating turbo-machinery blade) under low velocity single and multiple impact are analyzed. Twist angle has significant effect on contact force but has marginal effect on contact duration. Contact force for perfect (porosity free) case is higher than that of porous one and the contact forces are found to decrease with higher porosity factor. Even porous FG conical shell is predicting lower contact force and higher shell displacement than that of uneven porous FG conical shell for a given porosity factor.

Sensor Networks for In-Situ Failure Identification in Woven Composites Throughout Impact

2007 ◽  
Author(s):  
Ryan Garrett ◽  
Kara Peters ◽  
Mohammed A. Zikry
Keyword(s):  
Sensor Networks ◽  
Optical Fibers ◽  
Matrix Material ◽  
Contact Forces ◽  
Low Velocity Impact ◽  
Woven Composites ◽  
Low Velocity ◽  
Cross Sectional ◽  
Fbg Sensors ◽  
The Impact

In this study, the development of embedded fiber Bragg grating (FBG) sensor networks within composite materials is investigated. Various densities of optical fibers were embedded within two-dimensional woven composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Cross sectional optical micrographs of the specimens were also used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Multiple FBG sensors were serially multiplexed together to create a single fiber sensing network capable of monitoring damage for each impact event. Residual strain information was gathered through strain distributions along the FBG sensors to map out the near-field and far-field regions with respect to the impact location. The resulting data will be used to better monitor and predict damage in the composite system when combined with global response data from the laminate itself.

Investigation of Low Velocity Impact Damage in Aluminum Alloys

2012 ◽  
Author(s):  
Benjamin Cooper ◽  
Andrei Zagrai
Keyword(s):  
Plastic Deformation ◽  
Impact Damage ◽  
Low Velocity Impact ◽  
Time Of Arrival ◽  
Low Velocity ◽  
Velocity Impact ◽  
Object A ◽  
Impact Detection ◽  
Aluminum Plates ◽  
The Impact

In structural health monitoring (SHM), impact detection and characterization techniques often focus on identifying parameters of impact such as the location and velocity of an impacting object. A distributed network of sensors is used to passively detect the mechanical wave created by the impact. Various techniques are used to analyze the signals based on time of arrival, amplitude and phase. A simpler architecture could be used to determine whether an impacting event was benign or caused damage and requires further evaluation. This research focuses on detecting attributes of impact-generated elastic wave signals that are indicative of local damage at the impact site. Waveforms deviate insignificantly for undamaged materials, however, when a material is stressed to plastic deformation or damaged the waveform of propagation through the material is noticeably affected. This change in wave speed may be detectable by SHM sensors, and can be used as an indicator of damage. Low velocity impact experiments were conducted on thin aluminum plates instrumented with piezoelectric and magneto-elastic sensors at various locations. The sensors acquired the initial passage of the impact wave signal before reflections off the boundaries became a significant element. By inspecting the signal for deviations induced by damage (such as plastic deformation), a routine for evaluating damage can be inferred. Further work may correlate features of the signal with damage severity providing an extra level of information in determining the next step in evaluating the damage. Using this approach, it may be possible to evaluate impact damage using limited numbers of passive sensors.

Response and failure modes of biaxial warp-knitted flexible composite subject to low-velocity impact

2021 ◽  
pp. 152808372110154
Author(s):  
Ziyu Zhao ◽  
Tianming Liu ◽  
Pibo Ma
Keyword(s):  
Impact Energy ◽  
Linear Density ◽  
Failure Modes ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Minor Effect ◽  
Low Velocity ◽  
Velocity Impact ◽  
Flexible Composites ◽  
The Impact

In this paper, biaxial warp-knitted fabrics were produced with different high tenacity polyester linear density and inserted yarns density. The low-velocity impact property of flexible composites made of polyurethane as matrix and biaxial warp-knitted fabric as reinforcement has been investigated. The effect of impactor shape and initial impact energy on the impact response of flexible composite is tested. The results show that the initial impact energy have minor effect on the impact response of the biaxial warp-knitted flexible composites. The impact resistance of flexible composite specimen increases with the increase of high tenacity polyester linear density and inserted yarns density. The damage morphology of flexible composite materials is completely different under different impactor shapes. The findings have theoretical and practical significance for the applications of biaxial warp-knitted flexible composite.

Energy absorbed ability and damage analysis for honeycomb sandwich material of bio-inspired micro aerial vehicle under low velocity impact

2020 ◽  
pp. 095440622097542
Author(s):  
Jianxun Du ◽  
Peng Hao ◽  
Mabao Liu ◽  
Rui Xue ◽  
Lin’an Li
Keyword(s):  
Honeycomb Structure ◽  
Low Velocity Impact ◽  
Parameter Study ◽  
Low Velocity ◽  
Micro Aerial Vehicle ◽  
Thin Walled Structures ◽  
Wide Range ◽  
Aerial Vehicle ◽  
Thin Walled ◽  
The Impact

Because of the advantages of light weight, small size, and good maneuverability, the bio-inspired micro aerial vehicle has a wide range of application prospects and development potential in military and civil areas, and has become one of the research hotspots in the future aviation field. The beetle’s elytra possess high strength and provide the protection of the abdomen while being functional to guarantee its flight performance. In this study, the internal microstructure of beetle’s elytra was observed by scanning electron microscope (SEM), and a variety of bionic thin-walled structures were proposed and modelled. The energy absorption characteristics and protective performance of different configurations of thin-walled structures with hollow columns under impact loading was analyzed by finite element method. The parameter study was carried out to show the influence of the velocity of impactor, the impact angle of the impactor and the wall thickness of honeycomb structure. This study provides an important inspiration for the design of the protective structure of the micro aerial vehicle.

Low Velocity Impact Resistance of CPVC Pipes Exposed to Natural Outdoor Weathering Conditions

2012 ◽  
Vol 445 ◽  
pp. 959-964
Author(s):  
Z. Khan ◽  
Necar Merah ◽  
A. Bazoune ◽  
S. Furquan
Keyword(s):  
Impact Resistance ◽  
Outdoor Exposure ◽  
Impact Testing ◽  
Low Velocity Impact ◽  
Pipe Material ◽  
Low Velocity ◽  
Impact Energies ◽  
The Impact ◽  
Impact Events ◽  
Outdoor Weathering

Low velocity drop weight impact testing of CPVC pipes was conducted on 160 mm long pipe sections obtained from 4-inch (100 mm) diameter schedule 80 pipes. Impact test were carried out for the base (as received) pipes and after their exposure to out door natural weathering conditions in Dhahran, Saudi Arabia. The results of the impact testing on the natural (outdoor exposure) broadly suggest that the natural outdoor exposures produce no change in the impact resistance of CPVC pipe material for the impact events carrying low incident energies of 10 and 20J. At the impact energies of 35 and 50J the natural outdoor exposures appear to cause appreciable degradation in the impact resistance of the CPVC pipe material. This degradation is noted only for the longer exposure periods of 12 and 18 months.

Coda Waves for Health Monitoring of Composites Under Low-Velocity Impact

2021 ◽  
Author(s):  
Subal Sharma ◽  
Vinay Dayal
Keyword(s):  
Ultrasonic Waves ◽  
Coda Waves ◽  
Low Velocity Impact ◽  
Coda Wave ◽  
Low Velocity ◽  
Fibrous Composite Material ◽  
Velocity Impact ◽  
Isotropic Composite ◽  
The Impact ◽  
Impact Damages

Abstract Coda waves have been shown to be sensitive to lab-controlled defects such as very small holes in fibrous composite material. In the real world, damages are subtler and more irregular. The main objective of this work is to investigate coda wave capability to detect low-velocity impact damages. The emphasis is to detect the presence of barely visible impact damages using ultrasonic waves. Detection of incipient damage state is important as it will grow over the life of the structure. Differential features, previously used in similar work, have been utilized to detect realistic impact damages on carbon fiber composites. Quasi-isotropic composite laminates were subjected to low-velocity impact energy ranging from 2J to 4.5J. Two differential features reported could be used detect the presence of damage. It is also observed that ply orientation can be a deterministic factor for indicating damages. The size and shape of the impact damage has been characterized using ultrasonic C-scans. Results indicate that coda waves can be used for the detection of damage due to low-velocity impact.

Low Velocity and Compression-After-Impact Response of Pin-Reinforced Sandwich Composites

1999 ◽  
Author(s):  
Uday K. Vaidya ◽  
Mohan V. Kamath ◽  
Mahesh V. Hosur ◽  
Anwarul Haque ◽  
Shaik Jeelani
Keyword(s):  
Impact Testing ◽  
Low Velocity Impact ◽  
Sandwich Composites ◽  
Low Velocity ◽  
Static Compression ◽  
Velocity Impact ◽  
Transverse Stiffness ◽  
Impact Studies ◽  
Compression After Impact ◽  
The Impact

Abstract In the current work, sandwich composite structures with innovative constructions referred to as Z-pins, or truss core pins are investigated, in conjunction with traditional honeycomb and foam core sandwich constructions, such that they exhibit enhanced transverse stiffness, high damage resistance and furthermore, damage tolerance to impact. While the investigations pertaining to low velocity impact have appeared recently in Vaidya et al. 1999, the current paper deals with compression-after-impact studies conducted to evaluate the residual properties of sandwich composites “with” and “without” reinforced foam cores. The resulting sandwich composites have been investigated for their low velocity (< 5 m/sec) impact loading response using instrumented impact testing at energy levels ranging from 5 J to 50 J impact energy. The transverse stiffness of the cores and their composites has also been evaluated through static compression studies. Compression-after-impact studies were then performed on the sandwich composites with traditional and pin-reinforcement cores. Supporting vibration studies have been conducted to assess the changes in stiffness of the samples as a result of the impact damage. The focus of this paper is on the compression-after-impact (CAI) response and vibration studies with accompanying discussion pertaining to the low velocity impact.

Experimental Investigation of Impacted and Non-Impacted Composite Laminates under Compressive Loading

2011 ◽  
Vol 284-286 ◽  
pp. 607-610
Author(s):  
Jiang Tao Ruan ◽  
Min Shen ◽  
Jing Wei Tong ◽  
Shi Bin Wang ◽  
Francesco Aymerich ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Optical Measurement ◽  
Speckle Pattern ◽  
Compressive Loading ◽  
Laminated Plates ◽  
Low Velocity Impact ◽  
Compressive Deformation ◽  
Electronic Speckle Pattern Interferometry ◽  
Low Velocity ◽  
The Impact

In this paper, the deformation measurements of impacted and non-impacted composite laminates under compressive loading are taken. [03/903]S orientated cross-ply laminated plates with impact delamination and without delamination are tested using an anti-buckling testing device in compression experiment. The delamination is induced by low-velocity impact test at the impact energy level of 3.105J. For both impacted and non-impacted specimens, the compressive deformation is measured by a carrier electronic speckle pattern interferometry (CESPI) optical measurement technique. It is found that the deformation behavior of the two specimens presents a mixed deformation mode. However, the delamination has significant effect on the compressive deformation of composite laminates.

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