Acoustic-kinetic joint analysis: Synchronization and Evaluation of kinetic measurement data in AEA (Acoustic Emission Analysis) based diagnosis of arthritic knee joint defects

During a clinical study the AEA (Acoustic Emission Analysis) of arthritic defects in the knee joint was enhanced by the addition of kinetic measurement data. This enhanced AEA based method permits a non-invasive diagnosis and assessment of arthritic joint damage at an early stage. The diagnostic procedure includes three separate measurements that contribute in different ways to an extended diagnosis of the disease pattern [1, 2, 3]. During a series of three knee bends a force plate provides data of the ground force while a video-based gait analysis records the corresponding movement and the angles of hip-, knee-, and ankle joints. At the same time AEA detects the acoustic anomalies of damaged cartilage and the absolute angle of the system. The patterns of the kinetic data were analyzed to define the instants of time to correlate the data of the 3 measurement systems. The analysis of the force data yields a pattern with 8 phases. By means of the stance phase between the knee bends the instants of time are used to synchronize force and video based data. In the second step the synchronization of video based data was done by means of the absolute angle of the AEA system [4, 5]. The superposition of kinetic data and the acoustic emission permits a preliminary graphic representation and assessment of the measurement data. The procedure will be applied for the analysis of patients in a clinical study

The Assessment of the Condition of Knee Joint Surfaces with Acoustic Emission Analysis

The knee joint, being the largest joint in the human body, is responsible for a great percentage of leg movements. The diagnosis of the state of knee joints is usually based on X-ray scan, ultrasound imaging, computerized tomography (CT), magnetic resonance imaging (MRI), or arthroscopy. In this study, we aimed to create an inexpensive, portable device for recording the sound produced by the knee joint, and a dedicated application for its analysis. During the study, we examined fourteen volunteers of different ages, including those who had a knee injury. The device effectively enables the recording of the sounds produced by the knee joint, and the spectral analysis used in the application proved its reliability in evaluating the knee joint condition.

Determination of Fatigue Damage Initiation in Short Fiber-Reinforced Thermoplastic through Acoustic Emission Analysis

This study investigates the damage initiation in short glass fiber-reinforced polyamide 6.6 under fatigue loading using acoustic emission analysis. An optimized specimen geometry was developed to meet the specific requirements of this testing method, at the same time allowing further micromechanical studies. Specimens were preloaded with tensile–tensile fatigue loading, varying the maximum stress and the number of load cycles. Subsequently, the acoustic emission signals in residual strength tests were compared to those of undamaged specimens. The idea behind this approach is that only the damage that has not already occurred under fatigue load can be recorded in the residual strength tests. Using the analysis of acoustic energy, a stress threshold for damage initiation was identified. Furthermore, with tension–tension fatigue tests, the SN curve of the material was determined to estimate the lifetime for the identified stress threshold. The presented approach allows us to estimate a so-called endurance limit of short glass fiber-reinforced polyamide 6.6.

Influence of fiber alignment on pseudoductility and microcracking in a cementitious carbon fiber composite material

This research examines the effect of fiber alignment on the performance of an exceptionally tough 3D-printable short carbon fiber reinforced cementitious composite material, the flexural strength of which can exceed 100 N/mm2. The material shows pseudoductility caused by strain-hardening and microcracking. An extrusion-based manufacturing process allows accurate control over the spatial alignment of the fibers’ orientation, since extrusion through a tight nozzle leads to nearly unidirectional alignment of the fibers with respect to the directional movement of the nozzle. Specimens were investigated using mechanical tests (flexural and tensile load), augmented by non-destructive methods such as X-ray 3D computed tomography and acoustic emission analysis to gain insight into the microstructure. Additionally, digital image correlation is used to visualize the microcracking process. X-ray CT confirms that about 70% of fibers show less than 10° deviation from the extrusion direction. Systematic variations of the fiber alignment with respect to the direction of tensile load show that carbon fibers enhance the flexural strength of the test specimens as long as their alignment angle does not deviate by more than 20° from the direction of the acting tensile stress. Acoustic emission analysis is capable of evaluating the spatiotemporal degradation behavior during loading and shows consistent results with the microstructural damage observed in CT scans. The strong connection of fiber alignment and flexural strength ties into a change from ductile to brittle failure caused by degradation on a microstructural level, as seen by complementary results acquired from the aforementioned methods of investigation.