Non-invasive early detection of failure modes in total hip replacements (THR) via acoustic emission (AE)

Total hip replacements (THR) are becoming an common orthopedic surgucal procedure in the United States (332 K/year in 2017) to relieve pain and improve the mobility of those that are affected by osteoarthritis, ankylosing spondylitis, or injury. However, complications like tribocorrosion, or material degradation due to friction and corrosion, may result in THR failure. Unfortunately, few strategies to non-invasively diagnose early-stage complications are reported in literature, leading to implant complications being detected after irreversible damage. Therefore, the main objective of this study proposes the utilization of acoustic emission (AE) to continuously monitor implant materials, CoCrMo and Ti6Al4V, and identify degradations formed during cycles of sleeping, standing, and walking by correlating them to potential and friction coefficient behavior. AE activity detected from the study correlates with the friction coefficient and open-circuit potential observed during recreated in-vitro standing, walking, and sleeping cycles. It was found that the absolute energy level obtained from AE increased as the friction coefficient increased, potential decreased, and wear volume loss increased. Through the results, higher friction coefficient and AE activity were observed in Ti6Al4V alloys while there was also a significant drop in potential, indicating increased tribocorrosion activity. Therefore, AE can be utilized to predict material degradations as a non-invasive method based on the severity of abnormality of the absolute energy and hits emitted. The correlation between potential, friction coefficient, and AE activity was further confirmed through profilometry which showed more material degradation in Ti6Al4V than CoCrMo. Through these evaluations, it was demonstrated that AE could be utilized to identify the deformations and failure modes of implant materials caused by tribocorrosion.

Nonlinear Kalman Filtering for acoustic emission source localization in anisotropic panels

Nonlinear Kalman Filtering is an established field in applied probability and control systems, which plays an important role in many practical applications from target tracking to weather and climate prediction. However, its application for acoustic emission (AE) source localization has been very limited. In this paper, two well-known nonlinear Kalman Filtering algorithms are presented to estimate the location of AE sources in anisotropic panels: the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). These algorithms are applied to two cases: velocity profile known (CASE I) and velocity profile unknown (CASE II). The algorithms are compared with a more traditional nonlinear least squares method. Experimental tests are carried out on a carbon-fiber reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers to validate the proposed approaches. AE sources are simulated using an instrumented miniature impulse hammer. In order to evaluate the performance of the algorithms, two metrics are used: (1) accuracy of the AE source localization and (2) computational cost. Furthermore, it is shown that both EKF and UKF can provide a confidence interval of the estimated AE source location and can account for uncertainty in time of flight measurements.

Prediction of tribocorrosion processes in titanium-based dental implants using acoustic emission technique: Initial outcome

The use of dental implants is growing rapidly for the last few decades and Ti-based dental implants are a commonly used prosthetic structure in dentistry. Recently, the combined effect of corrosion and wear, called tribocorrosion, is considered as a major driving process in the early failure of dental implants. However, no previous study has reported the prediction of tribocorrosion processes in advance. Therefore, this study is a novel investigation on how the acoustic emission (AE) technique can predict tribocorrosion processes in commercially-pure titanium (cpTi) and titanium-zirconium (TiZr) alloys. In this study, tribocorrosion tests were performed under potentiostatic conditions and AE detection system associated with it captures AE data. Current evolution and friction coefficient data obtained from the potentiostatic evaluations were compared with AE absolute energy showcased the same data interpretation of tribocorrosion characteristics. Other AE data such as duration, count, and amplitude, matched more closely with other potentiostatic corrosion evaluations and delivered more promising results in the detection of tribocorrosion. Hence, AE can be consider as a tool for predicting tribocorrosion in dental implants. Experimental results also reveal Ti5Zr as one of the most appropriate dental implant materials while exposing Ti10Zr's lower effectiveness to withstand in the simulated oral environment.

Hip implant performance prediction by acoustic emission techniques: a review

Nowadays, acoustic emission (AE) has its applications in various areas, including mechanical, civil, underwater acoustics, and biomedical engineering. It is a non-destructive evaluation (NDE) and a non-intrusive method to detect active damage mechanisms such as crack growth, delamination, and processes such as friction, continuous wear, etc. The application of AE in orthopedics, especially in hip implant monitoring, is an emerging research field. This article presents a thorough literature review associated with the implementation of acoustic emission as a diagnostic tool for total hip replacement (THR) implants. Structural health monitoring of an implant via acoustic emission and vibration analysis is an evolving research area in the field of biomedical engineering. A review of the literature reveals a lack of reliable, non-invasive, and non-traumatic early warning methods to evaluate implant loosening that can help to identify patients at risk for osteolysis prior to implant failure. Developing an intelligent acoustic emission technique with excellent condition monitoring capabilities will be an achievement of great importance that fills the gaps or drawbacks associated with osteolysis/implant failure. Graphical abstract.

Acoustic emission signals analysis to differentiate the damage mechanism in the drilling of Al-5%B4C metal matrix composite

Tool wear leads to dimensional inaccuracy and low surface quality in the workpiece, and unexpected sudden tool failure. Detection of tool wear is essential to enhance the quality of manufacturing components and extend tool life. The present work is aimed to investigate the various damage mechanisms involved in the cutting tool and workpiece during drilling of Al-5%B₄C composite using acoustic emission technique (AET). The dry drilling experiments were carried out at different spindle speeds and feed rates with high strength steel (HSS) tool. AE time-domain parameters such as count, energy, amplitude and root mean square (RMS) voltage were extracted from the signals and correlated with cutting parameters and tool damage. Fast Fourier transform (FFT) was applied to visualize the frequency components in the AE signals during the drilling process. The wavelet packet transform (WPT) approach was performed to the AE signals to identify and discriminate the various damage mechanism involved in the drilling. The differentiated damage mechanism and their corresponding wavelet energy content were studied. The wavelet energy ratio for decomposed components at different speeds was discussed. The vision measuring microscope was employed to measure the tool wear. The AE features, i.e., AE_RMS and wavelet coefficient increases with increasing tool wear. A scanning electron microscope was also utilized to characterize the microstructural damage present in the cutting tool and workpiece.

Comparative analysis of fracture characteristics between rock and rock-like materials

In order to investigate the characteristics of rock and rock-like materials during the fracture process, notched semi-circular bending (SCB) experiments of 3 rocks and 2 rock-like materials were conducted in this paper. The process of the crack mouth opening was measured with a clip gauge. Acoustic emission was used to analyze the damage and failure mode of the specimens. Meanwhile, the fracture process zone (FPZ) was analyzed with the digital image correlation (DIC). Finally, the differences in the fracture process between rocks and rock-like materials were observed with a polarized microscope, and the formation mechanism of FPZ was discussed. The results indicate that the sequence from brittleness to plasticity is gypsum, marble, granite, concrete and fine sandstone. The crack opening velocity of gypsum, marble, and granite reaches 0.02-0.025 mm/s, far exceeding that of sandstone and concrete at 0.003 mm/s and 0.005 mm/s. The stronger the brittleness of geomaterials, the less significant their acoustic emission effect. Only a few acoustic emissions occur during the fracture process of gypsum with 8 hits. Its fracture occurs instantaneously rather than through a process of damage to fracture and the failure mode is tensile failure. Sandstone has the strongest plasticity, with a large count of acoustic emissions before and after fracture, with a hit number of 5062, which is 630 times of pure gypsum. The fracture is a process of damage accumulation with 94% of sandstone, 89% of concrete, 80% of granite, and 60% of marble showing a tensile and shear failure mode except gypsum. In addition, the stronger the brittleness of geomaterials, the smaller their FPZ size. The FPZ of gypsum is only about 3 mm, which can be considered as lacking, while other materials are about 6-11 mm. The formation of FPZ depends on whether an interlocking structure can be formed inside the material, which is related to the base material and crystalline or aggregate particle size.

Failure evolution and instability prediction of fiber-reinforced polymer-confined cement mortar specimens under axial compression

In geotechnical engineering, a large number of pillars are often left in underground space to support the overlying strata and protect the surface environment. To enhance pillar stability and prevent instability, this study proposes an innovative technology for pillar reinforcement. Specifically, local confinement of the pillar is achieved through fiber-reinforced polymer (FRP) strips, resulting in the formation of a more stable composite structure. In order to validate the effectiveness of this structural approach, acoustic emission characteristics and surface strain field characteristics were monitored during failure processes, while mathematical models were employed to predict specimen instability. The test results revealed that increasing FRP strip confinement width led to heightened activity in acoustic emission events during failure processes, accompanied by a decrease in shear cracks but an increase in tensile cracks. Moreover, ductility was improved and deformation resistance capacity was enhanced within specimens. Notably, initial crack generation occurred within unconfined regions of specimens during failures; however, both length and width as well as overall numbers of cracks significantly decreased due to implementation of FRP strips. Consequently, specimen failure speed was slowed down accordingly. Finally, the instability of the partial FRP-confined cement mortar could be more accurately predicted based on the model of FRP-confined concrete. It was verified by the test results.

Creep and strength characteristics of cemented gangue backfill under coupling effect of load and acid corrosion

Cemented gangue backfill technology is beneficial to the reuse of solid waste and sustainable economic development. However, mine water has a great impact on the strength and deformation of cemented gangue backfill (CGB). In this study, the CGB specimens under load were placed in simulated acid mine water (H2SO4 solution). The changes in deformation, resistivity, and ultrasonic pulse velocity (UPV) of CGB were monitored. On the 360th day, the stress-strain curve and acoustic emission (AE) energy of the specimen during loading were recorded. The degradation mechanism of CGB was discussed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the deformation of CGB increased with time. The effect of H2SO4 solution concentration on the deformation was different in the early and late stages. Applying an 80% stress-strength ratio (SSR) reduced the strength and increased the deformation. The UPV and resistivity had different characteristics at different corrosion ages, which could be used for long-term stability monitoring of CGB. The CGB showed the strongest AE energy characteristics near the peak stress. The AE energy decreased with the increase of pH value in the pore compaction stage, and the AE activity of the CGB under 80% SSR was much greater than that of the CGB under 40% SSR. The erosion of the H2SO4 solution on the CGB was inhibited by applying a small load. Excessive load aggravated the erosion deterioration of CGB due to initial plastic damage. The research results can provide a reference for the durability design of CGB.

Experimental study on I/II/III mixed mode fracture characteristics of a combined rock mass under creep loading

I/II/III mixed mode fractures of intersecting joint fissures often occur in natural rock masses, and jointed rock masses are prone to rockbursts in deep underground engineering when subjected to long-term crustal stresses. However, most studies of the mechanical mechanisms of these intersected joints have been conducted by simplifying two-dimensional joint model tests. Furthermore, the fracture mechanisms of two-dimensional intersected joints under tension and compression are completely different from those of three-dimensional joints. This paper presents a novel prefabricated specimen with combinations of intersecting joints capable of detecting the failure behaviours of rock I/II/III mixed mode fractures under creep loading. Uniaxial compression and multistage creep tests are performed on prefabricated sandstone specimens with intersecting joints of 0°/0°, 0°/30°, 0°/60°, and 0°/90°. The experimental results show that with the increase in the number of prefabricated intersecting joints, the uniaxial compressive strength and elastic modulus values of the sandstone specimens gradually decrease. In addition, the sandstone specimens experience relatively few AE events and minor axial strain variations in the first creep stage and the second creep stage of the multistage creep test. The axial strain increases sharply due to the sharp increase in the number of AE events in the third creep stage. The 0°/60° sandstone specimen undergoes accelerated creep failure, resulting in mixed X-shaped tensile‒shear rupture. The RA value is high based on the quantification of the creeping cracks using the acoustic emission parameters of the rise angle (RA) and average frequency (AF). The AF values of the 0°/0°, 0°/30°, and 0°/90° sandstone specimens are high. The experimental results show that a larger joint intersection angle leads to greater mutual restraints and greater effects of prefabricated crack propagation in the rock specimens, thus increasing the final failure strength. Finally, based on the acoustic emission count, a characteristic variable D suitable for characterizing the creep damage evolution of a joint rock mass is established. The findings of this paper can facilitate an effective understanding of the creep effect of I/II/III mixed mode fracture and its micromechanism. The research results will have a certain reference value for the detection and risk mitigation of instantaneous and time-delayed rockbursts.

Acoustic emission monitoring of damage modes in reinforced concrete beams by using narrow partial power bands

This work presents an acoustic emission (AE) based method, named a series of narrow partial power bands (SN2PB), to monitor the damage mechanisms within reinforced concrete beams during quasi-static bending tests. Unlike conventional time-domain methods, which give a global view of the involved cracking modes, SN2PB has the advantage of obtaining information on cracking modes within each AE hit in reduced frequency bands. SN2PB is applied by dividing the frequency content of each AE signal into narrow bands. Results show that the same AE signal can contain shear and tension cracking signatures at the lower and upper frequency bands, respectively. This work shows also the presence of a transitional domain between the two distinct bands. Changes and fluctuations corresponding to the involved mechanisms during the entire mechanical tests are therefore followed and visualized in the form of a heatmap. Moreover, the densities of the shear and tensile mechanisms at an instant are also determined using a Gaussian Mixture Model. Results show that the separation obtained using the SN2PB method is more advantageous than that of the conventional method based on the average frequency and the RA parameter.

Artificial intelligence and machine learning as a viable solution for hip implant failure diagnosis-Review of literature and in vitro case study

The digital health industry is experiencing fast-paced research which can provide digital care programs and technologies to enhance the competence of healthcare delivery. Orthopedic literature also confirms the applicability of artificial intelligence (AI) and machine learning (ML) models to medical diagnosis and clinical decision-making. However, implant monitoring after primary surgery often happens with a wellness visit or when a patient complains about it. Neglecting implant design and other technical errors in this scenario, unmonitored circumstances, and lack of post-surgery monitoring may ultimately lead to the implant system's failure and leave us with the only option of high-risk revision surgery. Preventive maintenance seems to be a good choice to identify the onset of an irreversible prosthesis failure. Considering all these aspects for hip implant monitoring, this paper explores existing studies linking ML models and intelligent systems for hip implant diagnosis. This paper explores the feasibility of an alternative continuous monitoring technique for post-surgery implant monitoring backed by an in vitro ML case study. Tribocorrosion and acoustic emission (AE) data are considered based on their efficacy in determining irreversible alteration of implant material to prevent total failures. This study also facilitates the relevance of developing an artificially intelligent implant monitoring methodology that can function with daily patient activities and how it can influence the digital orthopedic diagnosis. AI-based non-invasive hip implant monitoring system enabling point-of-care testing.

The study of mechanical properties and fracture evolution of coal-rock masses under hard roof-soft floor conditions

As the depth of coal mining in China continues to increase, the fracturing of coal rock masses has an increasingly complex impact on the surrounding rock roadways. The majority of the mine's roadways run through coal rock masses with hard roofs and soft bottoms, which typically exhibit complex dynamic behaviour. To further research the mechanical behaviour and fracture evolution of coal rock masses under hard-roof and soft-floor conditions, the study is based on the majority of working faces in a mine, which have hard roofs and soft floors. Uniaxial compression tests were utilized to study the mechanical properties of coal rock masses under hard-roof and soft-floor circumstances, using acoustic emission monitoring, whole-process imaging technologies, and fractal dimension analysis. The experimental results are as follows: The uniaxial compressive strength of the coal rock mass is significantly higher than that of its weakest component. The results of the experiment are as follows: The uniaxial compressive strength of coal rock mass is significantly higher than that of its weakest component. Samples with different soft rock strengths exhibited dissipated energy greater than the accumulated energy before the stress maximum, accompanied by volume expansion and the formation of shear surfaces. Samples with higher soft rock strengths tend to exhibit brittle failure, while weaker samples show stress-softening behaviour. Internal fracture complexity varies amongst samples with varying soft rock strengths. A fractal study of the acoustic emission parameters was carried out utilizing MATLAB programming. The fractal analysis results show that acoustic emission ringing counts and energy time series of coal rock masses under hard-roof and soft-floor settings have good fractal properties. The fractal analysis results show that acoustic emission ringing counts and energy time series of coal rock masses under hard-roof and soft-floor settings have good fractal characteristics. Acoustic emission ringing counts tend to have a larger correlation dimension than acoustic emission energy. However, while the sample is fracturing on a vast scale, the ringing count correlation dimension fluctuates very little. The correlation dimension distribution of samples with lower strength is more concentrated after the stress maximum, implying that the deformation and fracturing of the floor rock in highways under hard-roof and soft-floor circumstances are more complex. Both the correlation dimension D of acoustic emission ringing counts and energy indicate a continuous fall before peak stress, which can be used to anticipate coal rock mass fracture. This study, based on the mechanical behaviour and fracture evolution of coal rock masses under hard-roof and soft-floor conditions, provides a foundation for disaster avoidance by controlling the stability and structural deformation of floor rock in hard-roof and soft-floor highways.