Deformation and Failure Mechanism of Particulate Filled and Short Fiber Reinforced Thermoplastics: Detection and Analysis by Acoustic Emission Testing

Acoustic emission, the detection of signals during deformation, is a frequently used method for the study of local deformation processes occurring in heterogeneous polymer systems. Most of these processes result in the evolution of elastic waves which can be detected by appropriate sensors. The analysis of several parameters characterizing the waves offers valuable information about the possible deformation mechanism. The acoustic emission testing of composites may yield very different number of signals from a few hundred to more than 100,000. This latter was proved to be affected mainly by particle size, interfacial adhesion and composition, but other factors, such as matrix modulus and specimen size, also influence it. Local deformation processes are claimed to have a strong effect on macroscopic properties. Indeed, a close correlation was found between the initiation stress of the dominating particle related process derived from acoustic emission testing and the tensile strength in both polypropylene (PP) and poly(lactic acid) (PLA) composites. However, in polyamide (PA)-based heterogeneous polymer systems, deformations related to the matrix dominated composite properties. Besides forecasting failure, the method makes possible the determination of the inherent strength of lignocellulosic fibers being around 40 MPa as well as the quantitative estimation of adhesion strength for composites in which interactions are created by mechanisms other than secondary forces. The proposed approach based on acoustic emission testing proved that in PP/CaCO3 composites, the strength of adhesion can be increased by ten times from about 100 mJ/m2 to almost 1000 mJ/m2 in the presence of a functionalized polymer.

Characterization of acoustic emission signals under 3-point bending test

This paper summarizes a master’s thesis project which explored whether the characteristics of Acoustic Emission Testing (AET) signals can be used to detect yielding in steel samples undergoing a three-point bending test. A subset of existing data from a three-point bending test was exported and used as input. Data was processed by utilizing and developing tools to visualize and analyse the signal characteristics, primarily through a parameter-based approach. Signals were visualized, and parameters were optimized to identify and classify signal types. According to the obtained results, some limitations on classification were experienced due to the length of the hit data recorded. Though the work reported in this article lead to a reliable method for detecting yielding, the developed algorithms were not successful in identifying characteristics that could be used to detect yielding.

Comparison and research of acoustic emission testing standards for atmospheric storage tank

The acoustic emission testing standards ASTM E1930, BS EN 15856, JB/T 10764 and Q/SY GD 0211 for atmospheric storage tank are compared and analysed. Combined with production practice, the revision direction and reference suggestions of acoustic emission testing standards for atmospheric tank were proposed.

Acoustic Emission Testing and Ib-Value Analysis of Ultraviolet Light-Irradiated Fiber Composites

The failure behavior of composites under ultraviolet (UV) irradiation was investigated by acoustic emission (AE) testing and Ib-value analysis. AE signals were acquired from woven glass fiber/epoxy specimens tested under tensile load. Cracks initiated earlier in UV-irradiated specimens, with a higher crack growth rate in comparison to the pristine specimen. In the UV-degraded specimen, a serrated fracture surface appeared due to surface hardening and damaged interfaces. All specimens displayed a linearly decreasing trend in Ib-values with an increasing irradiation time, reaching the same value at final failure even when the starting values were different.

Monitoring of Elastoplastic Fracture Behavior of HSLA Steel Using Acoustic Emission Testing

The present study explores using acoustic emission testing (AE) to monitor the elastoplastic fracture toughness (JIC) of high-strength, low-alloy (HSLA) steel in two different orientations. Acoustic emission signals generated during the tests were found to be higher during bulk yielding upon initial loading, after which they decreased during intermediate loading before increasing again. The acoustic emission signals generated were used to correlate with the JIC values determined from unloading compliance tests. The point of crack initiation estimated by AE is lower than that determined by the unloading compliance tests. Beyond the point of crack initiation determined by AE, the acoustic emission signals generated increased rapidly, which is attributed to crack growth. The results of AE during crack initiation are supported by the peak amplitude of the acoustic emission signals. The possibility of using AE data to estimate fracture toughness values has also been explored for HSLA steel.

Кинетика процесса накопления повреждений и разрушения в зонах концентраторов при испытаниях образцов на разрыв

The paper considers the effect of various stress concentrators on processes of damage accumulation, initiation and propagation of crack in steel (steel 3) samples during uniaxial tensile. In the middle of the samples there was a transverse welded joint or a hole with a diameter of 5 mm. The acoustic-emission testing results showed that weight content of location impulses (Wi) in the clusters of low, middle and high energy level and criteria parameters value Wi at the stages of the samples destruction have similar pattern of change despite the various types of concentrators, stress-strain material diagrams, pattern of damage accumulation, number of registered acoustic emission (AE) events and its registration activity.