The leaf spring is one of the main components in an automobile which carries the weight of the vehicle and passenger as well as absorbs the vibration and shock produced due to road irregularities. The weight, natural frequency, stress developed, energy absorption, fatigue life, etc. are the key factors that need to be considered to design a leaf spring. Towards that, a novel design integrating a Negative Stiffness Honeycomb Structure (NSHS) in the leaf spring is proposed. The proposed design and the traditional leaf spring are analyzed using the commercially available Finite Element Method (FEM) software Abaqus. Both the traditional and NSHS models were created using Solidworks and modal, harmonic, structural, and transient analyses were performed. It is found that the natural frequency of the NSHS leaf spring is well above the frequency produced due to road irregularities although it is lower than the traditional spring. The total weight of the NSHS spring structure is reduced significantly by 30.73% compared to the traditional spring. Structural analysis shows a lower stress development and higher energy absorption capacity for the NSHS leaf spring. Transient analysis reveals lower mean stress in the proposed NSHS spring. The fatigue life is also found to be 82.78 % higher in the proposed design. The NSHS-incorporated novel leaf spring design may be an excellent alternative to the traditional leaf spring.

In this paper, the first and second stage compressor blades of a gas turbine were studied by the experimental and numerical modal analyses. At first, the geometric models of these blades were generated by the 3D scanner and then the mode shapes and the natural frequencies of each blade were extracted by a series of numerical modal analyses. The numerical results were compared with the data obtained from the experimental modal analysis and the validity and accuracy of the developed numerical models were confirmed. Unlike most studies that use fixed-free boundary condition for performing a modal analysis, this objective was pursued by applying a free-free boundary condition. This study also investigated the effect of using wax or glue for mounting the accelerometer on the blade by assessing the FRF curves obtained from the modal tests in the frequency range of 0-10000 Hz. The sensitivity of the test results to applying free-free boundary condition, the number of accelerometers and their positions were investigated by defining three modal test configurations. The results obtained by these test configurations were compared with the results of numerical analyses and finally, the best configuration for the modal test of the studied compressor blade was determined.