Visualization Of Impact Damage Research Articles

Modeling of Tunnel Concrete Lining under Fire and Explosion Damage

This paper presents studies that focus on fire and explosion-induced damage of tunnel structures by employing the Discrete Element Method (DEM). By assuming a two-dimensional aggregate distribution and reconstructing the digital representation of the experimental concrete blocks, a numerical model of the tunnel lining concrete was established in the PFC2D program. The temperature distribution and the shock wave pressure at the surface of the tunnel lining were obtained by using Fluent and LS-Dyna separately; the final damage simulation of concrete section under different conditions was carried out in PFC2D. The results showed that PFC2D cooperatively provided more accurate and effective modeling and visualization of impact damage of concrete blocks. The visualizations of damage indicated the degree of damage more clearly and more intuitively. These findings also provide a potential method for further study of the damage assessment for entire tunnel lining structures.

Visualization of impact damage in annealed and chemically strengthened aluminosilicate glass

Abstract The damage propagation and fracture process of monolithic annealed and chemically strengthened aluminosilicate (ALS) glass plates are characterized using Edge-on impact (EOI) testing technique. The EOI experiments on two types of ALS glass plates at a medium impact velocity of ∼180 m/s with spherical and cylinders steel projectiles were completed using pneumatic gas-gun. The high-speed images in shadowgraph mode during the impact process were recorded at the framing rate of 1,000,000 frames per second (fps) to visualize the fracture and damage front in annealed and strengthened glass plates. The real-time captured shadowgraphs in case of annealed glass (AG) showed that the damage front initially starts to develop from the impact end and then after traveling some distance arrested in few microseconds and measured average front velocity against cylindrical and spherical projectile was 2658.91 m/s and 1710.0 m/s, respectively. The tensile wave reflection in AG impact case against both types of projectiles was observed. In a chemically strengthened glass (CSG), the damage front shape and propagation against both types of projectiles were quite different than the AG, front traveled in a self-sustained mode due to the release of elastic stored energy with the velocity of 1746.92 m/s and 1690.12 m/s, respectively. The damage evolution curves plotted from captured high-speed images show that damage traveled slower in case of the spherical projectile which suggests that the shape of the projectile has a great influence on the fracture process of annealed and strengthened glass. The damage front shape in CSG against cylindrical projectile impact was more dominant along the glass boundaries and the spallation effect was not observed in CSG against spherical projectile impact. Additionally, the damage-free zones and fracture surfaces were studied using a scan electron microscope (SEM) from collected post-test debris to discuss the fracture process.

Real-time visualization of impact damage in monolithic silicon carbide and fibrous silicon carbide ceramic composite

Impact resistance from foreign debris is a critical requirement for brittle ceramic and ceramic composite materials intended for use in the hot-section of gas turbine engines. A design to mitigate against such impact failures necessitates a detailed understanding of the driving failure mechanisms. The present study introduces a unique time-resolved experimental method which advances the latter effort. Specifically, a pulsed synchrotron X-ray source, in phase contrast imaging (PCI) configuration, is used as a medium, to visually characterize the evolution of damage inside the target materials during impact. As a proof of concept, two types of ceramic materials were tested: monolithic silicon carbide and fibrous silicon carbide composite. Impact was performed using a light-gas gun and 1.5 mm diameter spheres of partially stabilized zirconia (PSZ) and silicon nitride (Si3N4). The retrieved dynamic X-ray image sequences provided clear outlines of the damage features. In the case of the monolithic ceramic, the impact by a PSZ projectile initially produced a cone crack and complete failure resulted by extension of a median crack. By contrast, the fibrous composite deformed readily prior to cone crack formation. Nearly identical damage features were observed in the monolith for the Si3N4 projectile, with the exception of the added vertical tensile crack. For this same projectile, the fibrous ceramic showed very limited surface deformation and enhanced cone cracking and kinking of laminates along the crack path. The latter response is attributed to the change in projectile properties. Some of the target materials were recovered, and post-mortem analysis via scanning electron microscopy (SEM) showed correlation with observed X-ray damage profiles. Moreover, simple Hertzian contact was used to estimate damage for the elastic portion of impact. This approach was found to yield a reasonable match with experimental results for the surface displacement near the contact interface.

Impact damage visualization in a honeycomb composite panel through laser inspection using zero-lag cross-correlation imaging condition

A fully non-contact laser-based nondestructive inspection (NDI) system is developed to detect and visualize damage in structures. The study focuses on the size quantification and characterization of a barely visible impact damage (BVID) in a honeycomb composite panel. The hardware consists of a Q-switched Nd:YAG pulse laser that probes the panel by generating broadband guided waves via thermo-elastic expansion. The laser, in combination with a set of galvano-mirrors is used to raster scan over a two-dimensional surface covering the damaged region of an impacted quasi-isotropic [60/0/−60]s honeycomb composite panel. The out-of-plane velocities are measured at a fixed location normal to the surface by a laser Doppler vibrometer (LDV). An ultrasonic full wavefield assembled from the three-dimensional space-time data matrix in the interrogated area is first acquired and then processed for imaging the impacted damage area. A wavenumber filtering technique in terms of wave vectors is applied to distinguish the forward and backward wavefields in the wavenumber-frequency domain. A zero-lag cross correlation (ZLCC) imaging condition is then employed in the space-frequency domain for damage imaging. The ZLCC imaging condition consists of cross correlating the incident and reflected wavefields in the entire scanned region. The condition not only images the damage boundary between incident and reflected waves outside the damage region but also, for longer time windows, enables to capture the momentary standing waves formed within the damaged region. The ZLCC imaging condition imaged two delaminated region: a main delamination, which was a skewed elliptic with major and minor axis lengths roughly 17 mm and 10 mm respectively, and a secondary delamination region approximately 6 mm by 4 mm, however, which can only be shown at higher frequency range around 80–95 kHz. To conclude, the ZLCC results were in very good agreement with ultrasonic C-scan and X-ray computed tomographic (X-ray CT) scan results. Since the imaging condition is performed in the space-frequency domain, the imaging from ZLCC can also reveal resonance modes which are shown in the main delaminated area by windowing a narrow frequency band sequentially.

Indentation-Damage Visualization in CFRP by Resistive Heating: Analytical Verification of The Inspection of Aircraft Using Its Lightning Protection Systems

Quick and automatic inspection of carbon fiber reinforced polymer (CFRP) aircraft after each flight would reduce the safety factor and allow for more flights. Visualization of impact damage was developed in an earlier study as an automatic self-monitoring method. The damaged area was visualized by selective and intense resistive heating based on its decreased through-thickness resistivity compared to undamaged areas. In the present study, the lightning protection system of a composite aircraft was used to apply a uniform electrical current distribution and electric heat to a large structure. Subsequent coupled thermal-electrical analyses showed that even small indentations (depth <0.15 mm) could be relatively easily detected in structures about 1 m in size.

Impact-damage visualization in CFRP by resistive heating: Development of a new detection method for indentations caused by impact loads

Rapid and automatic inspection of composite aircraft after every flight would reduce the safety factor and allow for more flights. Although, an electrical resistance change method (ERCM) has been proposed, there are many problems with its practical application. In this study, a new diagnostic method, impact-damage visualization, was developed. Indentation damage increases fiber–fiber contact at the interlaminar interface and electrical conductivity. Consequently, electrical current applied to the material will concentrate around the damaged area, and lead to selective and intense resistive heating. This temperature increase can be observed by thermography or detected as a change in electrical resistance caused by the temperature difference. The proposed method had sufficient reliability and sensitivity for practical application as a damage inspection method.

OS08-3-3 Impact damage visualization by resistive heating using lightning protection system for CFRP aircraft

OS08-3-3 Impact damage visualization by resistive heating using lightning protection system for CFRP aircraft

J044022 局所抵抗加熱を利用した複合材航空機構造の衝撃損傷診断([J04402]知的材料・構造システム(2))

If it is possible to inspect composite aircraft automatically and quickly after every flight, we can reduce the safety factor and allow for more flights. Although, an electrical resistance change method (ERCM) has been proposed as a self-monitoring method which can inspect rapidly even a large structure without expensive equipments, there are many problems with its practical application. In this study, a new diagnostic method, impact-damage visualization, was developed. Indentation damage increases fiber庸iber contact at the interlaminar interface and electrical conductivity. Consequently, electrical current applied to the material will concentrate around the damaged area, and lead to selective and intense resistive heating. This temperature increase can be observed by thermography or detected as a change in electrical resistance caused by the temperature difference. The lightning protection system of a composite aircraft was used to apply a uniform electrical current distribution and electric heat to a large structure. Subsequent coupled thermal-electrical analyses showed that even small indentations (depth <0.15 mm) could be relatively easily detected in structures >1 m in size.

OS08F028 Impact damage visualization by resistive heating using lightning protection system for CFRP aircraft

OS08F028 Impact damage visualization by resistive heating using lightning protection system for CFRP aircraft

Impact Damage Visualization of Heterogeneous Two-layer Materials Subjected to Low-speed Impact

A systematic experimental investigation of the generation and subsequent evolution of impact damage in heterogeneous two-layer materials is presented. Model layered specimens involving a compliant polymer layer bonded with a metal layer were designed and subjected to impact loading to simulate failure mechanisms in real time. High-speed photography and dynamic photoelasticity were utilized to visualize the nature and sequence of dynamic failure modes. A series of complex failure modes was documented. Interlayer crack growth (interfacial delamination) is the dominant dynamic failure mode. These cracks appear to be shear dominated and might proceed with intersonic speeds. Intralayer cracking always occurs in a local Mode I crack inside the weak layer. Both impact speed and interfacial bonding strength have significant influence on the impact failure. High-impact loading leads to high interlayer crack speeds. Specimens featuring ductile and weak bonds subjected to high-impact speeds are shown to feature intersonic cracks with clearly visible shear shock wave (Mach lines) emitted from the crack tips.

Visualization of Impact Damage in Ceramics Using the Edge‐On Impact Technique

Projectile impact generates severe fragmentation in ceramics which propagates at high velocities and precedes the penetration of the projectile. The high‐speed photographic technique of the Edge‐On Impact (EOI) has been developed at the Ernst‐Mach‐Institute (EMI) in order to visualize dynamic fracture in brittle materials. In a typical EOI test the projectile hits one edge of a specimen and fracture propagation is observed during the first 20 us after impact by means of a Cranz‐Schardin highspeed camera. EOI tests allow a characterization of different ceramics by the macroscopic fracture patterns, single crack velocities, and crack front velocities (damage velocities). The phenomenology of damage propagation in several ceramics and a ceramic‐metal composite is discussed. The EOI technique is useful for the evaluation of damage models for brittle materials because it enables a direct comparison of model predictions to experimental data obtained during the impact process.