Experimental Study of Loaded Foams During Free Fall Investigation and Evaluation of Microstructure

We aim to maintain as much control as possible over the development of the microstructure during the manufacture of polyurethane foam with a certain density. As a result, the finished product may not contain the required characteristics for the shock absorber used. That is why polyurethane foam loaded with zinc oxide and silica must be able to sustain the cellular structure and strengthen it. Mechanical characterization was carried out utilizing a dynamic drop impact test conducted on locally developed and constructed equipment. Polyurethane foams' mechanical properties are highly reliant on their density, cell structure (size and shape), and the fraction of open or closed cells. Within the cell structure, the foam may be directed preferentially. Following that, Raman spectroscopy and SEM investigation were used to visualize the semi-opened cells of the cellular polymer. The cellular polymer appears to possess permanent, regular cellular structures with a high degree of reversibility in terms of overlap.

Development of a Weight-Drop Impact Testing Method for Dental Applications

For evaluating the impact strength of dental materials, the Izod test or Charpy test has been used, but specimen preparation for these tests is difficult due to the adjustment of a notch on them. By contrast, a weight-drop impact test does not require notched specimens. Therefore, it might be possible to measure the impact strength more accurately than conventional methods. This study aimed to establish appropriate conditions for applying the weight-drop impact test on small specimens of acrylic resin. To determine the most reliable impact fracture energy of acrylic resins, different diameters and thicknesses of PMMA resin specimens, diameters and weights of the striker, and diameters of the supporting jig were compared. For all specimen thicknesses, when the striker diameter was 6–10 mm, the impact fracture energy was constant when the inner diameter of the specimen-supporting jig was 8–10 mm. In addition, the measured E50% value was mostly equal to the median value of the impact fracture energy. Thus, for the weight-drop impact test, this method was effective for material testing of small specimens, by clearly specifying the test conditions, such as the thickness of disc-shaped specimens, the diameter of the striker, and the inner diameter of the specimen-supporting jig.

Analysis and Design of a Novel Concept Gasket to Improve the Reliability of the Balanced Armature Receiver Used in Earphones

Currently, balanced armature (BA) receivers are frequently used in earphones, owing to their small size and superior sound quality. However, the reliability of BA receiver earphones has become a considerable challenge, as they easily fail when subjected to external forces, especially during drop impacts. In addition, the original gasket cannot protect the BA receiver well. Therefore, this article focuses on improving the reliability of BA receiver earphones by designing a novel concept for the gasket. Based on a simplified model and analysis methods, the maximum von Mises stress on the armature with different drop directions and the maximum von Mises stress point must first be determined. The gasket was divided into two parts, one for linking and the other for shock absorption. This article focused on the design of the shock absorption structure. A novel concept gasket was proposed, and the analysis results showed that the gasket improved the shock absorption performance. For demonstrating the validity of the shock absorption performance of the novel concept gasket, three confirmatory experiments were performed: the drop impact test, X-ray photography, and sound performance, which included the sound pressure level and total harmonic distortion. The analysis results were experimentally verified.

The Evaluation of Absorption Performance of Magneto-Rheological (MR) Elastomer

This study examines the relation between the thickness of a specimen and the weight of an impactor for evaluating the shock absorption performance of magneto-rheological (MR) elastomers with and without a magnetic field. The shock absorption performance can be evaluated by calculating impact energy. The MR elastomer is a smart material and its mechanical properties change under the influence of a magnetic field. The drop impact test is performed to evaluate the amount of shock absorption of the MR elastomer for each test condition. Tests are also performed by varying the magnetic field during impact to improve the shock absorption performance of the MR elastomer, which is related to impact load. The results show a better shock absorption performance with a thicker MR elastomer, lighter impactor, and without a magnetic field. Also, the magnitude of impact and the time duration for stabilization are improved when the magnetic field is varied during the test.

Effective Mitigation of Shock Loads in Embedded Electronic Packaging Using Bilayered Potting Materials

Shock loads which are characterized by high intensity, short duration, and vibration at varied frequencies can lead to the failure of embedded electronics typically used to operate/control numerous devices. Failure of electronics renders these devices ineffective, since they cannot carry out their intended function. It is therefore the objective of this work to determine the behavior of a typical electronic board assembly subject to severe shock loads and the means to protect the electronics. Specifically, three aspects of the work were considered using 3D finite element (FE) simulations in supercomputer environment. The first was concerned with the dynamic behavior of selected electronic devices subject to shock loads. The second with the ability of different potting materials to attenuate the considered shock loads. The third was with the use of a new bilayer potting configurations to effectively attenuate the shock load and vibration of the electronic board. The shock loads were delivered to the Joint Electron Device Engineering Council (JEDEC) standard board using simulated drop impact test. The effectiveness of different protective potting designs to attenuate the effect of shock loads was determined by considering the two key factors of electronics reliability: the stress in the interconnection and deformation of the printed circuit board. Our results reveal the remarkable effectiveness of the bilayer potting approach over the commonly adopted single potting attenuation strategy.