Optimization Design and Nonlinear Bending of Bio-Inspired Helicoidal Composite Laminated Plates.

Inspired by the bionic Bouligand structure, helicoidal carbon fiber-reinforced polymer composite (CFRPC) laminates have been proven to own outstanding out-of-plane mechanical properties. This work aims to further explore the excellent bending characteristics of helicoidal CFRPC laminated plates and find out the optimal helicoidal layup patterns. The optimization design of laminated plates stacked with single-form and combination-form helicoidal layup sequences are carried out by using the finite element method (FEM) and adaptive simulated annealing (ASA) optimization algorithm on the Isight platform. Then, the nonlinear bending responses of optimal helicoidal CFRPC laminated plates are investigated via the FEM for the first time. The helicoidal CFRPC laminated plates under three different types of boundary conditions subjected to transverse uniformly distributed load are considered. The numerical results reveal that the combination-form helicoidal layup sequences can decrease the dimensionless bending deflection of laminated plates by more than 5% compared with the quasi-isotropic plate and enhance the out-of-plane bending characteristics of CFRPC laminated plates effectively. The boundary conditions can significantly influence the nonlinear bending responses of helicoidal CFRPC laminated plates.

Morphology of human ear canal and its effect on sound transmission.

The ear canal (EC) is essential for sound transfer and crucial for hearing. Some pathological conditions may modify its morphology, leading to EC sound pressure redistribution, and stapes footplate displacement (FPD) gain alteration. However, no consensus regarding pathological EC and its impact on sound transfer has yet been achieved. To address the effect of morphology of EC on sound pressure redistribution and FPD gain. Varied pathological EC finite element (FE) models were constructed and analyzed based on FE analysis. The results indicated that canal wall down mastoidectomy decreases the second resonance frequency of the EC. The canal wall down mastoidectomy, with conchaplasty increased the first resonance frequency, but decreased the second along with the interval sound pressure gain increased, following which the FPD gain was altered. Stenosis of the EC at the internal portion decreased the second resonance frequency with minimal effect to the first part. When the stenosis moved to the outer portion of the EC, the first resonance frequency decreased, and the second one increased, along with the interval sound pressure gain decreased and FPD gain. Finally, the simplified EC model exerted a minimal effect on sound transfer. The minimal change in EC, such as simplification, straightening, canal wall down mastoidectomy, or enlargement, moderately affects the sound transfer; however, the EC stenosis deteriorates the sound transfer remarkably.

Study of age-related changes in Middle ear transfer function.

Osteoporosis (OP) is common with advancing age. Several studies have shown a strong correlation between OP and otosclerosis. However, no studies have investigated OP of the malleus, incus or stapes in the human middle ear, its effect on middle ear transfer function. Here, we investigate whether these three ossicles develop OP, and how this affects middle ear transfer function. The effect of OP on middle ear transfer function was investigated in simulations based on a finite element (FE) method. First, the FE model used in our previous study was refined, and optimized by introducing viscoelastic properties to selected soft tissues of the middle ear. Then, the FE model was used to simulate OP of the three ossicles and assess its influence on middle ear transfer function. Other possible age-related changes, such as stiffness of the joints or ligaments in the middle ear, were also investigated. The results indicated that OP of the ossicles could increase the high frequency displacement of both the umbo and stapes footplate (FP). However, the stiffness of the middle ear soft tissue can lead to the decrease of middle ear gain at lower frequencies. Furthermore, loosening of these joints or ligaments could increase displacement of the umbo and stapes FP. In conclusion, although age-related hearing loss is most commonly conceived of as sensorineural hearing loss (SNHL), we found that age-related changes may also include OP and changes in joint stiffness, but these will have little effect on middle ear transfer function in elderly people.

Fatigue analysis of tympanic membrane after ossiculoplasty.

CONCLUSION: A tentative conclusion was made that the finite element method can be used to investigate the fatigue life of the tympanic membrane after ossiculoplasty; the main reason of the extrusion of the tympanic membrane may not be blamed to the fatigue mechanism under normal sound pressure. OBJECTIVE: This study was to investigate the extrusion of the prosthesis from the tympanic membrane at post-ossiculoplasty by finite element method. METHODS: A finite element model of the human middle ear has been constructed and used as the model of the constructed middle ear at post-ossiculoplasty. Then the fatigue life of the tympanic membrane was calculated under different sound pressure level using this model. RESULTS: The tympanic membrane would not be extruded under normal sound pressure level. The sound pressure level which caused the tympanic membrane to crack in less than 3 years was higher than 145.17 dB (362.5 Pa).