Abstract Acoustic Emission Technique Research Articles

Acquisition of Acoustic Emission Signals from Rocks Using Directly Bonded PZT Patches

Acoustic emission (AE) technique is a proven effective technique for monitoring underground mines and caverns. With the advancement in the data acquisition technology, AE signals up to 2–5 MHz of frequency can be recorded successfully. However, this generates a lot of data to be analyzed and stored. This paper presents a concept of a simple and cost-effective, low-frequency AE technique for monitoring damages in the rocks. The tests were performed on Kota sandstone rock specimens in compression at three different displacement rates of 0.01, 0.05 and 0.1 mm/s. The AE signals were recorded successfully through thin square piezo-patches (used as the AE transducers) and a commercially available sound card for data logging. The proposed technique has been found to be easy and very much cost-effective in capturing low-frequency AE signals. The recorded data were processed for determining different AE parameters like cumulative AE count, relative energy of an event and event rate.

ASSESSMENT OF CRACK INITIATION AND PROPAGATION IN BONE USING ACOUSTIC EMISSION (AE) TECHNIQUES

Acoustic emission (AE) is a nondestructive testing (NDT) technique used for detecting damages, cracks, and leaks in different structures such as metals, composites, wood, fiberglass, ceramics, plastics, etc. In recent years, AE has gained popularity within the field of biomedical applications. The structure of bone is similar to composite materials, therefore, it is advantageous to use NDT technique. Thus, it can be used for monitoring the fracture behavior, crack initiation/propagation, and fatigue detection in bones. The goal of this study was to determine the usefulness of AE techniques in fracture detection phase of bones and to develop an NDT methodology for the monitoring of crack initiation and propagation in bones. This study describes AE activity during fracture of bone tissue under tensile loads. The experiments were carried out in vitro techniques using intact and fracture-simulated bovine tibias. The specimens were loaded to failure in tension using a mechanical testing machine. During the mechanical tests, AE signals were measured and recorded by using AE system processor equipped with two wideband piezoelectric sensors fixed to the surfaces of both ends of the test specimens. By superposing the load–time curve and the cumulative AE event–time curve, AE activities of crack initiation and propagation were identified. In all experiments, the cumulative AE number for each period of time rose up exponentially with the incremental tensile load. Load for AE initiation demonstrated a convincing linear interaction with AE event generation.

INVESTIGATION ON FRACTURE OF EPOXY-FILLED COMPOSITES BY ACOUSTIC EMISSION

Acoustic emission (AE) technique is widely used to monitor failure processes in composite materials includ-ing development of cracks and plastic deformations within the polymer matrix, fracture and debonding of inclusions, etc. In this study, the AE technique was applied investigating failure character of epoxy polymers with different content of nanofiller – fine polyethersulfone (PES) powder. Variation of material properties of the epoxy with 0, 5%, 7.5%, 10%, and 12.5% concentration (by weight) of the PES was assessed experimentally. Correlation between the PES content and the modulus of elasticity was found negligible. The same was characteristic for the tensile strength. Whereas, such a correlation was found significant for the fracture toughness that increased 1.5 times concerning the pure epoxy reference. Analysis of the cumulative AE counts indicated existence of three different stages of the damage accumulation process, which were unidentified using the load and the deformation diagrams. In the PES-modified composites, the damage ac-cumulation process was evidenced at the 10–20% of the ultimate load; whereas, in the pure epoxy, such a process was fairly slow until the 85% of the loading.

Amplitude Distribution of Emission Wave for Cracking Process

Acoustic emission technique is a method of assessment for structural health monitoring system. This technique is an effective tool for the evaluation of any system without destroying the material conditions. It enables early crack detections and has very high sensitivity to crack growth. The crack patterns in concrete beam have been identified according to the type of cracking process and the crack classifications using the AE data parameters are mainly based on the AE amplitude, rise time, and average frequency. These data parameters have been analysed using statistical methods of b-value analysis. This research paper will mainly focus on the utilization of statistical b-value analysis in evaluating the emission amplitude distribution of concrete beams. The beam specimens (150 × 250 × 1900) mm were prepared in the laboratory system and tested with the four point bending test using cyclic loading together with acoustic emission monitoring system. The results showed that this statistical analysis is promising in determining the cracking process in concrete beams.

Correlation of Acoustic Emission and Corrosion Resistance of Lacquer Coatings on Tin-Free Steel

Acoustic emission (AE) is a non-destructive technique which is well known for crack monitoring. Moreover, it has been widely used for corrosion and erosion damage on metallic structures. In this study, AE technique was applied for quick monitoring of corrosion resistance of lacquer coatings on tin free steel and laminated steel for food can-packaging. There were three types of coatings: (A) BPA-NI lacquer, (B) BPA-complied lacquer, and (C) PET lamination. These coatings were investigated in flat-sheet and in deformed sheet. Cathodic disbonding (CD) technique was carried out to cause separation between the coating and the metal substrate and initialize corrosion damage. AE signals was detected immediately with potential excitation, and showed good correlation with coating corrosion resistance during corrosion development. AE count signal matched with resulting current during CD, and proportional to corroded areas. In addition, coatings properties were measured before and after the CD process by electrochemical impedance spectroscopy (EIS). A combination of AE and CD techniques offers an in-situ non-destructive corrosion monitoring of coating quality before and during delamination development, and useful for can-packaging testing.

Corrosion inspection method of steam generator tubes using acoustic emission technique

Acoustic emission technique has been applied as the real-time and non-destructive inspection of corrosion on steam generator tubes. The corrosion signals gathered about steam generator tubes in service have been analysed. The detailed analysis reveals that the crack development of the heat transfer tubes has three stages. The results show that the accuracy of this method is comparable to the one of microscope examination.

The specific features of acoustic-emission testing of vessel equipment with a wall delamination of a technological origin

Acoustic-emission (AE) signals from the zones of delaminations in vessel walls of technological origin are analyzed via comparison to data that were obtained by the ultrasonic method and strength calculations. The boundaries of the detectability of a delamination-type flaw using the AE technique are established in accordance with the regulatory engineering documentation that is in force. A method for determining the dimensions, location depth, and opening width of a delamination using AE data and simple calculated dependences, which are applicable under testing conditions, is proposed.

An Approach to Acoustic Emission Technique Applications to Evaluate Damage Mechanisms in Composite Materials

Acoustic Emission technique is a versatile method for characterization in materials science. It is considered to be a “passive” non-destructive method since damage can be only evaluated when de defects are being developed during the test which, at the end of the day, it is considered an advantage because failure mechanisms and damage process can be monitored and identified during the load history. When a failure mechanism is activated due to a discontinuity in the material such as crack propagation, part of the total strain energy is dissipated as an elastic waves that propagate from the damage source through the medium. Therefore, this released energy can be detected by piezoelectric sensors that perceive the emitted signal from the damage notation site by the surface dynamic movement and convert it in an electrical response. Acoustic emission signals can be correlated with the onset of damage process occurring in the tested materials and also to de diverse failure mechanisms such as matrix cracking, interface damage, fiber fracture, etc. This paper proposes to discuss our information and results on acoustic emission materials characterization undertaken on different types of materials.

Extracting Acoustic Emission Signal Feature of Grinding Processing

Acoustic Emission (AE) may be defined as a transient elastic stress wave generated by the rapid release of strain energy in local area of material. To overcome the limitation of some traditional techniques, the AE technique, which provides high sensitivity and responding speed, were developed in the present paper. AE signature is usually difficult to be extracted and characterized in grinding process of 1Cr18Ni9Ti coatings due to their high hardness, great ductility, inhomogeneous structure and irregular surface with lots of hard points and pores. In this paper, AE signal of stationary grinding status before wheel-workpiece contact was characterized first, then AE signal of the grinding process was analyzed using root-mean-square (RMS) and power spectrum method. Results showed that before the contact occurred, the grinding signal is stable, with low amplitude and frequency ranging all frequency channels and no peak signal. However, when contact occurred, the RMS and spectrum of AE signal increased obviously and the bandwidth varied exquisitely between 100 KHz and 300 KHz. The real contact time between wheel and workpiece was about 0.5 to 1 ms.

On-line Monitoring of Engineering Components Using Acoustic Emission Technique

Acoustic emission technique (AET) has been used for on-line monitoring of pressure vessels with artificial defects in the laboratory and for monitoring structural integrity of storage vessels in heavy water plant. The laboratory studies are helpful for getting better insight into the deformation and fracture aspects in the vessels, towards better utilisation of AET for structural integrity of components. AE results generated during hydrotesting of the storage vessels were used to confirm the structural integrity of the vessels. AE was used to monitor compression loading of plain and fly ash concrete. This showed three stages due to crack closure/microcracking, steady crack propagation and unstable crack propagation. An attempt was made to compare the types of cracking in concrete using AE parameters.

Real-Time Monitoring of Degradation of Zirconia Ceramic by Acoustic Emission

Acoustic emission (AE) technique was employed to monitor the low temperature degradation (LTD) behavior of a zirconia ceramic, which was carried out in air at 200°C. AE signals, typical waveform of which exhibited as pulse-like type, were detected during LTD and increased with the duration time of LTD. The AE signal of accumulative counts number and amplitude in time domain exhibited a roughly sigmoid variation including three stages, which reflect approximately the evolution of LTD. The AE findings were supported by X-ray diffraction (XRD) examination. It was suggested that AE technique can be used to monitor the mechanism of LTD of zirconia ceramics.

The Application of Acoustic Emission Technology in Oil and Gas Storage and Transportation Equipment

Acoustic emission (AE) testing (AET) is an effective, nondestructive testing (NDT) method which is widely used throughout the petrochemical industry. It especially plays an important role in inspecting of atmospheric storage tank floor corrosion, oil and gas pipeline leakage and pressure vessel cracking. The AET methods and evaluation of storage tank, pipeline, sphere and other equipment in oil and gas storage and transportation system are reviewed in this paper, and the development trends of AE technique also be introduced. This technique has important significance in ensuring the security.

Assessing Cracks in Reinforced Concrete Structure Using Acoustic Emission

Acoustic emission (AE) is an important nondestructive evaluation (NDE) technique used in the field of structural engineering. In this study AE technique with a new approach was employed to investigate the process of fracture formation in reinforced concrete structure. A number of reinforced concrete (RC) frames were tested under cyclic load and were simultaneously monitored using AE. The AE test data using intensity analysis method were analyzed. This is based on calculating two values called the historic index (HI) and severity (Sr). The results showed that HI and Sr increase with increasing of loading cycle and trend of HI and Sr showed that these parameters are able to indicate the levels of damage. Also, the results indicated that AE can be considered as a viable method to investigate the process of fracture formation in reinforced concrete structure.

Damage Source Identification of Welded Steel Beam Specimen Using Acoustic Emission

Acoustic emission (AE) method is a passive non-destructive technique is being used as the prime candidate in structural health and damage monitoring in civil structure for investigation process of damage in both case local and global monitoring. This technique was employed for investigation process of damage in steel beam specimens. Several-welded steel beam specimens were built and tested under loading cycle and were simultaneously monitored using AE. According the stages of failure of welded steel beams, The AE test data were analyzed by AE source location method. The results showed that source location of damage in steel structures could be identified using AE technique.

Fracture Formation Evaluation of Reinforced Concrete Beam Subjected to Cycle Loading Using Acoustic Emission Technique

Acoustic emission (AE) technique is one of the non-destructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. In present study, AE technique with a new approach was employed to investigate the process of fracture formation in reinforced concrete (RC) structure. Thirty RC beam specimens with continuous and non-continuous longitudinal rebar were prepared. The RC beams were tested under loading cycle and were simultaneously monitored using AE. The AE test data was analyzed using Relaxation, Load and Calm ratio. The trend of these methods during loading and unloading was compared with behaviour of each type of specimens. The trend of Relaxation ratio and Calm and Load ratio method during loading and unloading showed that these methods are strongly sensitive with cracks growth in RC beam specimens and were able to indicate the levels of damage. Also, results showed that AE can be considered as a viable method to predict the remaining service life of reinforced concrete. In addition, with respects to the results obtained from Relaxation, Load and Calm ratio indicated, a new chart is proposed.

Damage Evaluation Assessment of Reinforced Concrete Structure using b-value and Damage Parameter Analysis of Acoustic Emission Signals

Acoustic emission (AE) method is a passive non-destructive technique that can be applicable for structural health monitoring. This technique have been used in the field of reinforced concrete (RC) structure for investigation process of damage in both case local and global monitoring. In this study AE technique was employed to investigate the process of fracture formation in reinforced concrete (RC) structure. Five RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data using the b-value method and Damage parameter were analyzed. The the trend of Minimum b-value and Maximum Damage parameter in stages of failure showed that these method are able to indicate the levels of damage in RC frame. With respects to the results obtained, a new chart is proposed by cross plotting Load and b-value. Three levels (heavy, moderate and low) of damage in concrete structure can be identified using this chart.

Damage Source Identification of Reinforced Concrete Structure Using Acoustic Emission Technique

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures.

Uniaxial Compression with Acoustic Emission Experimental Study on Rock Damage Process

Acoustic emission technique is an important technique for monitoring crack propagation and failure process of rock, coal and concrete material. A uniaxial compression test with acoustic emission monitoring on coal and rock samples’ deformation and failure process were carried out. Failure precursor information of rock, coal and concrete material were studied through contrast analysis the experiment result include acoustic emission signals, strain, load correlation of sample inner crack propagation to failure process. The test provided necessary data to further understand on rock burst failure disaster. The test result provides a theoretical basis for further application of acoustic emission for prediction coal rock dynamic disaster, assessment rock and concrete structure stability and study rock concrete material failure process mechanism.

Experimental Study on Detecting the Building Damage Caused by Fire with Acoustic Emission Technique

Acoustic emission technique is a non-destructive detection method that can continuously and dynamically detect the damage evolution inside the structure. In this paper, a local fire experiment is conducted within an entity building to acquire and analyze acoustic emission parameters in the whole process of the experiment. Results show that the number of events is closely related to the crack development, the peak value of the energy rate occurs when a large number of cracks appear, signals with the amplitude less than 80db account for more than 90%, signal amplitudes produced by the building damage in different stages from fire development to fire attenuation are different, and most signals with the amplitude of 75db – 85db are produced in the stage of fire development.

Validity Evaluation of AE Technique on Damage Monitoring of Different Woven C/SiC Composites under Mechanical Loading

Acoustic emission (AE) technique was utilized for real-time monitoring the damage evolutions of 2-D and 3-D C/SiC ceramic matrix composites (CMC) under mechanical loading. AE signals for damage initiation and propagation were captured by AE equipment during the entire loading process. Different damage mechanisms of the two kinds of C/SiC composites were revealed on the basis of multi-parameter analysis. The experimental results validate the availability of AE technique on damage monitoring of C/SiC composites. And the AE technique can be used to distinguish the slight differences in damage mechanisms during damage evolution owing to different woven structures.