This paper is concerned with the finite element Analysis and Modal testing of an industrial radial flow impeller. The goal is to determine and verify the vibration characteristics of the impeller using both experimental and analytical techniques.The finite element model of the impeller with tapered blades was built using a 3D solid element. The convergence properties of the FE model was then verified by mesh refinement and mass distribution methods. Next, a pre-test plan was performed before conducting a Modal test in order to select the proper suspension points, driving point(s) and response points on the  impeller.Impact testing using hammer excitation and laser Doppler vibrometer (LDV) response measuring techniques were used to measure the vibration properties of the impeller. Using a scanning laser Doppler vibrometer enabled the backplate modes to be described in terms of their nodal diameter components. The nodal diameters versus natural frequencies graph was then compared with the same results obtained from FE and hammer testing and showed good agreement. Finally, a parametric study was conducted on disc thickness, blade thickness, blade trailing, leading edge profiles and blade mistuning. It was found that the effect of varying disc thickness on the lower modes of the impeller was not significant. However, significant natural frequency shifts were observed for the higher modes. It was also concluded that varying the blade leading edge position had a marked effect on the natural frequencies while the lower modes were somehow insensitive to the variation of trailing edge position.

Experimental and numerical studies are implemented in this work to investigate the Modal characteristics of three-layered viscoelastic sandwich beams and plates with a natural rubber core and distinct isotropic face layers. In this study, the material of face layers in both beams and plates is varied with uniform face thickness by keeping the core constant to maintain the constant volume. Through the use of the Impact Hammer Modal Testing technique, experimental Modal Analysis is carried out with SAMURAI and ME' Scope software. The beams and plates are subjected to numerical Analysis using ANSYS 19.2 Mechanical APDL Software, a finite element Analysis (FEA) tool to evaluate the Modal characteristics. The Modal characteristics including natural frequencies and mode shapes of both beams and plates are evaluated under various boundary conditions, such as Clamped-Free (C–F), Simply-Supported (S–S), Clamped–Simply Supported (C–S), and Clamped-Clamped (C–C) for beams. Other plate boundary conditions that are taken into consideration for plates in this inquiry include C-F-F-F (Cantilever), S-S-S-S (All edges simply-supported), C-F-C-F (opposite edges clamped and other edges free), and C-C-C-C (All edges clamped). Ultimately, an excellent agreement is established when the outcomes of the experimental Modal Analysis are compared to those from ANSYS. The research also investigates how varying face layer material densities and end conditions affect natural frequencies at constant volume.

Given the inherently time-consuming nature of Incremental Dynamic Analysis (IDA), which requires extensive computational resources to simulate multiple ground motions and assess various structural responses, it is essential to explore more efficient methodologies that maintain accuracy while reducing Analysis time. The MPA-based IDA algorithm (MIDA) is being developed for various structures to address the limitations of IDA. In this study, six individual masonry structures were examined, including three walls with varying perforation dimensions and three three-dimensional buildings subjected to two retrofitting conditions. These structures were analyzed using 30 ground motion accelerations. The masonry structures, reinforced with either a shotcrete layer or a coating application, were evaluated as homogeneous and anisotropic materials using a finite element-based macro-modeling approach. Additionally, IDA was performed, and the maximum displacement of the masonry structures was compared to that of the MIDA. The results indicate that, except under high surcharge conditions, the MIDA procedure not only significantly reduces computational time but also provides reasonable accuracy compared to the IDA precision algorithm. Therefore, it can be concluded that the difference between the IDA and MIDA methods is influenced by the lateral stiffness of the masonry structures being analyzed

The central issue of this paper is the semantics of the Modal propositions, with emphasis on the necessary and permanent propositions. First, the writer offers a short explanation of the Modal propositions according to the traditional logic, then describes their temporal Analysis, and finally, criticizes such an interpretation. However, the whole perspective of the paper is not merely negative, and the writer tries to reread and recognize the traditional views and comments on the semantics of the Modal propositions.