This paper presents the dimensionless empirical equations and graph expressions of three flexure hinges for compliant mechanism designs. The in-plane and out-of-plane stiffnesses of the flexure hinges are developed. The rotational precision, denoted by the midpoint stiffness, is derived for the purpose of optimized geometric design. Based on the developed methodologies, the influences of the geometric parameters on the performance of the flexure hinges are investigated, and the performance comparisons among the flexure hinges are conducted to further understand the characteristics of these kinds of compliant mechanisms.

Three flexure hinges for compliant mechanism designs based on dimensionless graph analysis

This paper presents the closed-form compliance equations for the filleted V-shaped flexure hinges. The in-plane and out-of-plane compliances of the flexure hinges are developed based on the Castigliano's second theorem. The accuracy of motion, denoted by the midpoint compliance of the flexure hinges, is also derived for optimized geometric design. The influences of the geometric parameters on the characteristics of the flexure hinges are investigated. It is noted that the filleted V-shaped flexure hinges have diverse ranges of compliance corresponding to different filleted radius R and angle θ . These types of hinges can provide both higher and lower stiffnesses than circular flexure hinges. This makes filleted V-shaped flexure hinges very useful for wide potential applications with different requirements. The finite element analysis is used to verify the established closed-form compliance equations for these filleted V-shaped flexure hinges.

Closed-form compliance equations of filleted V-shaped flexure hinges for compliant mechanism design

\n Flexure-based compliant mechanisms are becoming increasingly promising in precision engineering, robotics, and other applications due to the excellent advantages of no friction, no backlash, no wear, and minimal requirement of assembly. Because compliant mechanisms have inherent coupling of kinematic-mechanical behaviors with large deflections and/or complex serial-parallel configurations, the kinetostatic and dynamic analyses are challenging in comparison to their rigid-body counterparts. To address these challenges, a variety of techniques have been reported in a growing stream of publications. This paper surveys and compares the conceptual ideas, key advances, and applicable scopes, and open problems of the state-of-the-art kinetostatic and dynamic modeling methods for compliant mechanisms in terms of small and large deflections. Future challenges are discussed and new opportunities for extended study are highlighted as well. The presented review provides a guide on how to select suitable modeling approaches for those engaged in the field of compliant mechanisms.

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Kinetostatic and Dynamic Modeling of Flexure-Based Compliant Mechanisms: A Survey

Elastic pivots are commonly used in precision machines and instruments as bearings for guiding small displacements or rotations. They provide accurate and frictionless motion with little hysteresis. Elastic pivots are frequently designed with either straight beams or notches shaped as conic sections with circular, elliptical, parabolic, or hyperbolic profiles. The compliance of a pivot is typically predicted by analytical expressions derived from implicit equations for the pivot’s profile. This article describes a more general geometric model suited to representing the entire family of conic section shapes using quadratic rational Bezier curves. This general representation of the geometry is suitable for computer aided design and analysis, especially with finite element methods that yield compliances and stress distributions. The utility of this formulation is demonstrated by optimizing an elastic pivot to meet compliance and stress requirements.

A unified geometric model for designing elastic pivots

This paper designs and analyzes a new kind of flexure hinge obtained by using a topology optimization approach, namely, a quasi-V-shaped flexure hinge (QVFH). Flexure hinges are formed by three segments: the left and right segments with convex shapes and the middle segment with straight line. According to the results of topology optimization, the curve equations of profiles of the flexure hinges are developed by numerical fitting. The in-plane dimensionless compliance equations of the flexure hinges are derived based on Castigliano’s second theorem. The accuracy of rotation, which is denoted by the compliance of the center of rotation that deviates from the midpoint, is derived. The equations for evaluating the maximum stresses are also provided. These dimensionless equations are verified by finite element analysis and experimentation. The analytical results are within 8% uncertainty compared to the finite element analysis results and within 9% uncertainty compared to the experimental measurement data. Compared with the filleted V-shaped flexure hinge, the QVFH has a higher accuracy of rotation and better ability of preserving the center of rotation position but smaller compliance.

Design and analysis of a high-accuracy flexure hinge

The paper formulates the closed-form stiffness equations that can be used to characterize the static, modal, and dynamic behavior of single-axis corner-filleted flexure hinges, which are incorporated into macro/microscale monolithic mechanisms. The derivation is based on Castiliagno’s first theorem and the resulting stiffness equations reflect sensitivity to direct- and cross-bending, axial loading, and torsion. Compared to previous analytical work, which assessed the stiffness of flexures by means of compliances, this paper directly gives the stiffness factors that completely define the elastic response of corner-filleted flexure hinges. The method is cost-effective as it requires considerably less calculation steps, compared to either finite element simulation or experimental characterization. Limit calculations demonstrate that the known engineering equations for a constant cross-section flexure are retrieved from those of a corner-filleted flexure hinge when the fillet radius becomes zero. The analytical model results are compared to experimental and finite element data and the errors are less than 8%. Further numerical simulation based on the analytical model highlights the influence of the geometric parameters on the stiffness properties of a corner-filleted flexure hinge.

Stiffness characterization of corner-filleted flexure hinges

Introduction-Aim: Pulmonary exacerbations increase the requirement of aminoglycoside (AG) antibiotics in patients with cystic fibrosis (CF). Some studies show that AGs have cumulative effect for ototoxicity. We aimed to investigate the relationship between&nbsp;AG exposure and hearing loss in patients with CF. Materials-Methods: The ongoing multicenter study included 55 patients with CF aged between 5-18 with a history of AG exposure.&nbsp;Standard pure tone audiometry, extended high frequency audiometry and DPOAE tests were perfomed. The patients were screened for m.1555A&gt;G mitochondrial mutation. Results: Mean age was 12 ±3.6 years and 56.4% (n=31) were male. 27.3% (n=15) of them had received parenteral AG more than 5 courses/lifetime.&nbsp;Hearing loss was detected in 7 ears in at least one frequency in standard audiometry. A decrease in high frequency audiometry thresholds was observed in 25 (24.2%) of 103 ears which were normal in standard audiometry. A decrease in high frequency hearing thresholds was detected in at least one ear in 14 patients (25.4%).&nbsp;While the rate of hearing loss was found to be 20% (n=8) in those who had a history of taking less than 5 courses of AG, it was 40% (n=6) in patients received more than 5 courses(p=0.12). No m1555A&gt;G mutation was detected in 28 patients whose mutation analysis were completed. Conclusion: As AG ototoxicity occurs primarily at high frequencies, extended high frequency audiometry is important in early detecting otoxicity.&nbsp;All CF patients with a history of AG exposure should be evaluated for hearing loss since hearing loss may only be noticed in late period by patients and caregivers.

Nicolae Bal

Papers

Stiffness characterization of corner-filleted flexure hinges

The association between the cumulative dose of aminoglycoside exposure and hearing loss in children with cystic fibrosis

P149 The association between the cumulative dose of aminoglycoside exposure and hearing loss in children with cystic fibrosis