International Journal of Advanced Design and Manufacturing Technology
Volume:17 Issue: 2, Jun 2024

Hemodynamic forces are felt by the biomechanical receptors of the arterial wall to give an appropriate response to maintain homeostasis. On the other hand, baroreceptors are a type of biomechanical receptors that are sensitive to abnormal stretch sizes. It is very important to predict the distribution of stress and strain caused by the hemodynamic field to the vessel wall in pressure-sensitive areas to evaluate the function of these receptors. In the present study, a three-dimensional (3-D) model of the aortic arch is presented. The geometry was reconstructed based on the CT images. Also, numerical analysis was performed using the fluid-structure interaction method. First, the hemodynamic field containing the pressure and velocity distribution in the blood area was obtained. Then, the deformation and stress fields in the solid domain were analyzed. The results show that the highest vertical stress occurs in the posterior supra aorta. So, the amount of this maximum vertical stress increases up to 5 kPa in some places; these points have higher tensions, and they can be susceptible to rupture and aneurysm diseases. Higher normal stress happened at the aortic root and the supra-aortic branches and reached approximately 200 kPa at Peak Systole. Also, the highest amount of strain occurs in the posterior supra aorta, reaching 0.001.

A variety of parameters influence the performance of piezoelectric sensors and actuators, such as support and concentrated mass. This paper presents a finite element formulation for piezoelectric structures and studies the effect of parameters on them. This method was developed based on the Bernoulli-Euler beam and the model is considered for use as a beam structure using the Variation Principle. The model was used for static and vibration analysis. The effects of support on the deflection of the piezoelectric beam were studied. Modal analysis was also carried out for the electromechanical coupling and uncoupling beams, and the effect of the concentrated mass was deduced. The finite element model was developed with FORTRAN programming Language and was implemented with MATLAB software. A comparison of the results between the analytical method, engineering software, and this program, showed acceptable accuracy.

In this paper, the nonlinear phenomenon including hump and chaos analysis along with chaos control of an active suspension in vehicles has been studied. The unstable periodic orbits of the system are stabilized using the novel developed delay feedback control algorithm based on the fuzzy sliding mode system. The chaotic Equations of motions are derived via Newton-Euler relations then, the nonlinear phenomenon such as jump and chaos in the vehicle dynamics has been confirmed using forcing frequency method. The results of the forcing frequency demonstrate the changes in system behaviour from the periodic to the irregular chaotic responses. In order to eliminate the chaotic responses in the vertical dynamics of the vehicle, a new fuzzy sliding delay feedback control algorithm is designed on the active suspension. The controller gain of the sliding feedback control is online estimated via fuzzy logic causing to rejection of the chattering phenomenon in the sliding mode algorithm besides the improvement in the responses of the feedback system. Simulation results of the control system depict a reduction of settling time and energy consumption along with eliminating the overshoots and chaotic vibrations.

In sensitive mechanisms, achieving the required accuracy of the final parts at the most suitable price is a complex process. The tolerance design process is essential in design and manufacturing to achieve a quality and low-cost product. Allocation of appropriate tolerances is always time-consuming and challenging, especially for complex products, as it involves many aspects of design, manufacturing, and quality issues. In this research, a program has been written in MATLAB, in which by only one geometry model, all possible interferences of assembled parts for all tolerances and nominal sizes in different production modes have been investigated. By using this program, it is possible to add or reduce applied tolerances to nominal sizes and check the interference of parts for all tolerances. Also, temperature effects must be considered when designing a product that operates in a wide temperature range. This approach could ensure that the values of the output parameters of the mechanism remain stable with various temperature changes. The considered case study is particular clock whose structural parameter tolerances often significantly affect the accuracy of the timing output of the entire movement of the mechanism in the program; the tolerance of the parts of the delay clock mechanism has been studied. By analysing the tolerance of geometric non-interference and considering the strain of the parts due to the operating temperature of the mechanism, 24% of the examined sizes should be reduced to avoid interference and the tolerance of the axis position of the clock should be reduced to ±0.01.

The disordered fibrous networks provide load-bearing and main structural to different biological materials such as soft tissues. These networks display a highly nonlinear stress-strain relationship behavior when subjected to mechanical loads. This nonlinear strain-stiffening behavior is dependent on the network microstructure and properties of constituting fiber. We conduct a comprehensive computational study to characterize the importance of material properties of individual fibers as well as the local connectivity or coordination number and bending rigidity in the overall nonlinear mechanical response of a 3D random fiber network. The presented model shows the nonlinear stiffening with increasing applied shear strain more than critical shear strain. We determine the amount of strain-stiffening as a function of network microstructure parameters and the amount of nonlinearity of the fibers. The results show that the constitutive behavior of fibers displays much more strain-stiffening than networks made up of linear fibers. We find that the importance of the nonlinear reaction of individual fiber materials in the general mechanical behavior of networks becomes more important with increasing network connectivity. Furthermore, the amount of stress created in the network under shear increases with the enhanced connectivity of the network due to an increase in the network stiffness. Our model points to the important role of the mechanical response of individual fiber as well as the microstructure of the network in determining the overall mechanical properties of the 3D random network, which could be used to design and better understand the complex biomimetic network systems such as biological tissues and artificial engineering networks.

Second-order corrugated cores are one type of hierarchical cores that use the common corrugated cores as constituent elements for the main core. This paper attempts to identify and optimize the bending properties of composite sandwich panels with second-order corrugated core. To this end, both first- and second-order corrugated cores are constructed and force-displacement diagrams are extracted in three-point bending tests. Finite element models are created and the deflection results are validated by experiments. Based on the Taguchi method, various finite element models with different geometrical parameters are modeled and reaction force and stiffness are determined. Stiffness formulas for first- and second-order corrugated cores are determined by using regression analysis. The constrained-optimization results are determined to optimize the stiffness of sandwich panels with first- and second-order corrugated cores, separately. The global optimization problem is implemented to compare the first- and second-order configurations.

In the present study, a numerical model is developed to predict time-dependent temperature variations inside a solar greenhouse by solving the continuity, Navier-Stokes, and energy Equations using ANSYS Fluent. This paper considers all heat transfer mechanisms into and out of the greenhouse, including convection, radiation, and conduction. The surface-to-surface model and SIMPLE method are employed to analyse thermal radiation between surfaces within the greenhouse and to couple pressure and velocity in solving the flow-field Equations numerically, respectively. This study specifically investigates the unsteady temperature distribution within a solar greenhouse located in Makran, Iran (latitude: 25.3054°N, longitude: 60.6411°E). The numerical method of this study is validated by comparing its results with experimental data. The high accuracy demonstrated by this approach supports the conclusion that the model can effectively study the flow field and thermal behaviour inside solar greenhouses. It is demonstrated that fluctuating boundary conditions cause the thermal conditions inside the greenhouse to vary dynamically over time. The results depict the spatial variation of temperature distribution at different levels from the soil surface at 13:00 on the first and second days of modelling in Makran. These insights are expected to play a crucial role in improving greenhouse design and management practices in agriculture.