Development of a Vibration Technique Based on Geometric Optimization for Fatigue Life Evaluation of Sandwich Composite Structures

A major obstacle to obtaining cost-effective experimental data on the fatigue life of sandwich panels is the prohibitive amount of time and cost required to carry out millions of cycles. On the other hand, vibration techniques applied to sandwich geometries fail to match the stress patterns that are obtained from standard flexural fatigue tests. To overcome such limitations, a vibration-based fatigue technique is proposed, which entails the use of sandwich specimens whose geometries are optimized to reproduce the stress distribution observed during three point bend loading while vibrating at the first resonant frequency. The proposed vibration technique was experimentally validated. The results, compared with the average number of cycles to failure at different stress ratios obtained via the Three-Point Bending test, showed high levels of accuracy. The proposed method is robust and time effective and indicates the possibility of attaining fatigue lifetime prediction of a wide class of composite elements, such as sandwich panels.

Analysing the Confinement Effect in Hollow Core Steel-Concrete Composite Columns under Axial Compression

Spun concrete technology allows manufacturing the reinforced concrete poles, piles, and columns with a circular hollow core. This concreting method ensures higher concrete density and strength than the traditional vibration technique and self-compacting concrete. This technology defines an attractive alternative for producing steel-concrete composite elements, allowing efficient utilisation of the materials due to the confinement effect. This study experimentally investigates the material behaviour of the composite columns subjected to axial compression. The experimental results support the above inference—the test outcomes demonstrate the 1.2–2.1 times increase of the compressive strength of the centrifugal concrete regarding the vibrated counterpart; the experimental resistance of the composite columns 1.25 times exceeds the theoretical load-bearing capacity. The proposed mechanical-geometrical parameter can help to quantify the composite efficiency. The parametric analysis employs the finite element model verified using the test results. It demonstrates a negligible bond model effect on the deformation prediction outcomes, indirectly indicating the steel shell confinement effect and confirming the literature results.

Induction Motor Bearing Faults Diagnosis Using Stator Current and Vibration Analysis

Several researches claim that the vibration technique, widely used in industry, is more efficient compared to the stator current analysis in the diagnosis of mechanical faults. On the other hand, researches show that the current technique is more advantageous especially in the diagnosis of electrical faults, in addition to the simplicity of the sensor positioning. The aim of this paper is to show that both diagnosis techniques can be complementary. For this, a comparative analysis of both diagnosis techniques performances is achieved. To this end, fault diagnosis of rolling element bearings used in induction motors is taken as an example, given the importance of bearings in energy transfer. Experimental results obtained show the complementarity of both techniques and their performances according to the faulty element of bearings.

DYNAMIC PERFORMANCE OF ADHESIVELY BONDED SINGLE LAP JOINTS WITH DIFFERENT FIBER ANGLE ORIENTATIONS OF ADHERENDS

This work aims to investigate the dynamic response of the adhesive bonding of Single Lap Joints (SLJs) using a free vibration technique. For this purpose, the joints with fixed-end conditions were subjected to the vibration test, and the results were compared with the numerical ones which were obtained from the Finite Element Method (FEM) via the ANSYS package program. The materials used in this study are an adhesive film, AF163 2K produced by 3M, and adherends, manufactured from a glass reinforced polymer matrix composite, produced by Hexcel. While four different adherends with different fiber orientations were used, the thickness of the adhesive layer in bonded region was kept constant, 0.2 mm. In doing so, the main concentration was given to the adherends as the energy dissipation was believed to come mainly from them. The main objective was to get high damping values without compromising any decrease in the structural performance of the joints. The experimental natural frequency, flexural rigidity and damping values of the joints were obtained as a parameter of the different adherend types. The results were also validated using numerical modal analysis.

Simulation and Analysis with Wavelet Transform Technique and the Vibration Characteristics for Early Revealing of Cracks in Structures

Implementation of improved instruments is used to detect damage in an accurate manner and fully analyze its characteristics. An aluminum beam has been used in this work to identify cracks by using a vibration technique. The simulation of frequency response feature was conducted using a finite element model to provide average measures of intensities of vibration. Two forms of wavelet packet transform (WPT) entropies Shannon and log energy were applied to identify the position, width, and size of the crack. The results showed that with an increase in crack depth, the amplitude also increased at certain crack sizes and for all crack positions. For two crack depths of 1.6 mm and 0.16 mm having the same crack size and position 12 mm and 60 mm, respectively, a 4.5% increase in amplitude was observed at a crack depth of 1.6 mm. Moreover, the amplitude varied inversely with the position. A 12.6% increase in amplitude was observed at a crack depth of 1.6 mm rather than 0.16 mm, while both depths occurred at the same crack position (75 mm) and size (20 mm). Experimental validation was performed on a cantilever beam with one crack. The maximum absolute error found was 7.5% for the crack position and 9.1% for the crack size. With the increase in crack depth, the obtained results decrease the stiffness of a beam in a single crack case.

Stiffness Optimization of Control Unit of Vehicle Using Vibration Technique

All modern automotive engines are controlled by an ECU. Engine efficiency, combustion, and emission characteristics are all affected by ECU tuning or tune-up. The electrical system in automobiles has evolved over time, and it now incorporates automatic machine control of automotive mechanics. In the beginning, a car’s electrical system consisted solely of primitive wiring technologies for supplying power to other parts of the vehicle. Engine management design specifications for the electronic control unit (ECU). Electronic systems are an unavoidable part of Engine management due to legislation requiring lower pollution, as well as the need for improved efficiency, fuel economy, and continuous diagnosis. The ECU of a TOYOTA Soluna car was used in this project for research and experimentation. ANSYS 19 software will be used to perform a modal and harmonic analysis of the current control unit. After that, different stiffener patterns will be added to improve the vibration characteristics of the ECU housing. We will finalize the stiffener pattern based on the FEA results. The FFT analyzer and the impact hammer test will be used to conduct experimental vibration testing.

Agitation Techniques to Enhance Drainage of Retained Hemothorax

Background. Retained hemothorax (RH) is a common problem in cardiothoracic and trauma surgery. We aimed to determine the optimum agitation technique to enhance thrombus dissolution and drainage and to apply the technique to a porcine-retained hemothorax. Methods. Three agitation techniques were tested: flush irrigation, ultrasound, and vibration. We used the techniques in a benchtop model with tissue plasminogen activator (tPA) and pig hemothorax with tPA. We used the most promising technique vibration in a pig hemothorax without tPA. Statistics. We used 2-sample t tests for each comparison and Cohen d tests to calculate effect size (ES). Results. In the benchtop model, mean drainages in the agitation group and control group and the ES were flush irrigation, 42%, 28%, and 2.91 ( P = .10); ultrasound, 35%, 27%, and .76 ( P = .30); and vibration, 28%, 19%, and 1.14 ( P = .04). In the pig hemothorax with tPA, mean drainages and the ES of each agitation technique compared with control (58%) were flush irrigation, 80% and 1.14 ( P = .37); ultrasound, 80% and 2.11 ( P = .17); and vibration, 95% and 3.98 ( P = .06). In the pig hemothorax model without tPA, mean drainages of the vibration technique and control group were 50% and 43% (ES = .29; P = .65). Discussion. In vitro studies suggested flush irrigation had the greatest effect, whereas only vibration was significantly different vs the respective controls. In vivo with tPA, vibration showed promising but not statistically significant results. Results of in vivo experiments without tPA were negative. Conclusion. Agitation techniques, in combination with tPA, may enhance drainage of hemothorax.