Influence Of Dimensional Parameters Research Articles

The influence of dimensional parameters on the kinetic range of four systems of deployable structures with hinged nodes and rigid rods

In several previous studies regarding foldable structures comprised of rods and knots, it has been usual to simplify their geometry to lines and points respectively. However, this study assumes that the dimensions that these elements necessarily acquire (due to their material condition) constitute an important issue in the folding and unfolding process. To test this hypothesis, the research first defines the concept of kinetic range and its various variants and studies how variations in the radius of the rods, the eccentricity of the knots and the opening angle influence this parameter. Furthermore, this study will demonstrate that this parameter is extensible to bar bundle systems and scissors systems and finally will verify that the results obtained by using algorithm-driven models are also verifiable by mathematical methods and experimentation using physical models. As a result, the methodology followed in this article allows the inclusion of a comparative table that classifies the performance of the structural systems studied in order to establish which is the optimum in relation to their kinetic range.

Static Modelling and Analysis of a Novel Movable Tooth Drive with Logarithmic Spiral Tooth Profiles

This paper presents a static model for a novel movable tooth drive with logarithmic spiral tooth profiles, to research contact force and load distribution during the meshing period. According to the geometric properties of the conjugate tooth profiles, their compatibility law considering the multi-tooth elastic meshing effect are investigated to reveal load distribution characteristic of the teeth. The static model of the mechanism is thus developed to systematically analyze variation in contact force during the rise travel. The results indicate that the contact force between the tooth and ring gear is proportional to the curvature radius of the contact point, and it increases exponentially and monotonically corresponding to the curvature radius of logarithmic spiral tooth profile; in the multi-tooth meshing condition, the load distribution of the teeth coincides with the ratio of the curvature radius of each contact point, and periodical pulsations of total contact force occur at the alternation of the teeth. Finally, the proposed model is validated by the FEM simulation of a prototype, and the influence of dimensional parameters is further discussed for the self-locking and force transmission characteristics of the tooth. The outcomes provide critical technical support for the static modelling and design of such transmission mechanism.

Effect of Dimensional Variables on the Behavior of Trees for Biomechanical Studies

The dimensional variables of trees play an important role in biomechanical studies that seek to estimate the risk of falls, since they influence their biomechanical behavior in relation to the forces to which they are subjected, and therefore, their safety factor. The aim of this research is to evaluate the effect of dimensional variables of trees on their mechanical behavior. A finite-element model was used to perform linear static analysis. The wood from the tree was considered clean, and the architectural model was based on dimensional variables of species commonly used in urban afforestation in São Paulo, Brazil. Different slenderness, tapering, height, and load level were used to analyze the tree mechanical behavior. The numerical-simulation model facilitates the evaluation of the influence of dimensional parameters of trees on deflections and stresses. The behavior of the deflections varies according to height, diameter, and loading level. Since the model considers the geometric variations of the section, the stresses show smooth variations along the trunk. The maximum module values of positive and negative stresses are not equal, and can undergo sudden variations in position along the trunk when local maximum stresses become global maximums.

Optical fiber sensing of small cracks in isotropic homogeneous materials

Monitoring of cracks and other damages is an integral part of ongoing research. Cracks and other damages may destroy the integrity of structures and even cause engineering accidents. Hence, it is of utmost importance to monitor the development of cracks in structures well in time to restrict the extent of overall damage. In this paper, a novel fiber optic sensor is discussed; this sensor is developed to monitor small cracks (crack openings between 0 and 0.8mm). The sensing principle of the sensor is first introduced and then the influence of dimensional parameters on the sensor is discussed through experimental investigations. The test results indicate that the sensor has a good initial perception capacity and a high sensitivity. Furthermore, the sensor is very effective in monitoring of small cracks.

Simulation of spin-torque diode microwave detectors

Spin-torque microwave detectors (STMD) provide a novel means of measuring the radio-frequency signals. We discuss the influence of dimensional parameters and direct current (DC) bias current on the performance of an STMD. We reveal that the performance of an STMD does not always improve with the current density. We also discuss the influence of the direction of the fixed-layer polarization. The results can be used for the optimization of an STMD.

Dimensional optimization of the Stewart platform based on inertia decoupling characteristic

SUMMARYInertia strongly influences the dynamic performance of parallel manipulators, and ignorance of inertia is apt to result in negative phenomena such as vibrations, overshoot, and slow response. This study analyzes the inertia-decoupling characteristic of Stewart platform. Because the inertia matrix of the Stewart platform is usually non-diagonal, inertia coupling occurs between its legs. Herein, decoupling to inertia is implemented, and independent control channels are determined. The influence of decoupled inertia on the control system is analyzed using the Adams simulation software, and the inertia index of the Stewart platform is proposed. Experiments are conducted on a prototype of the Stewart platform to verify the eigenvalue characteristic of decoupled inertia. The distribution of inertia index in the operational workspace is provided, and the influence of dimensional parameters on inertia index is discussed. Finally, dimensional optimization is realized with a set of optimized dimensions for good dynamic performance.

Analysis of Rotational Precision for an Isosceles-Trapezoidal Flexural Pivot

An isosceles-trapezoidal flexural pivot can be of great use for practical designs, especially in the cases that a pure rotation about a virtual pivot is required. The analysis of rotational precision for such a structure is important for the mechanical design in precise-required applications. For this purpose, a rigid isosceles-trapezoidal linkage model is first proposed to provide an accurate analytical result for its notch-type flexural counterpart. The influence of dimensional parameters on the center shift is discussed. In order to disclose the equivalence between leaf-type flexure structure and its pseudo-rigid-body model, a transitional model is introduced, from which an equivalent pseudo-rigid-body model for leaf-type isosceles-trapezoidal flexure structure is then derived. The results of both simulation and experiment verify that the equivalent rigid model is also accurate enough in the case of a larger deflection.