Torsional Compliance Research Articles

Pneumatically Actuated Rehabilitation Equipment for the Sagittal and Frontal Plane Movements of the Neck Joint

The timely reintegration into their daily routine of patients suffering from work-related musculoskeletal disorders is a priority in medical rehabilitation. This can be accomplished by means of certain procedures and adequate medical rehabilitation equipment. Starting from these considerations this paper proposes an original constructive solution of a rehabilitation device designed for the passive mobilization of the neck joint in the sagittal and frontal plane. The constructive solution that is put forward uses a pneumatic muscle as the actuation element, ensuring the adaptability of the equipment to the particular pain tolerance of each patient. The construction and dimensioning calculations of the equipment are presented, followed by the determination of the torsional rigidity and compliance permitted by the system. Based on the results the paper concludes with recommendations for the optimum deployment of the rehabilitation equipment.

Design and analysis of three-dimensional chiral metamaterials for enhanced torsional compliance

Three-dimensional (3D) chiral structures are a subset of mechanical metamaterials known for their distinctive deformation characteristics, including the presence of auxetic and compression–torsion coupling behaviors. In this study, a novel 3D chiral metamaterial with high torsional compliance was designed. A gammadion-shaped chiral cell comprising inclined ligaments was incorporated into the chiral structure for enhanced torsional compliance. Finite element analyses (FEAs) were performed to demonstrate that the proposed chiral structure outperformed other chiral structures in terms of torsional compliance. Furthermore, FEAs were performed to investigate the influence of the slenderness ratio and ligament diameter of the chiral structure, on attaining a maximum torsional compliance of 18.6° N−1. These 3D chiral structures were fabricated using additive manufacturing techniques, and experimental validations were performed to observe and confirm the compression–torsion coupling behaviors. To further expand the utility of these 3D chiral structures, statistical analyses were conducted to establish regression models for effective density and torsional compliance, as functions of the slenderness ratio and ligament diameter. These regression models can enhance the applicability of the proposed chiral structures in the development of versatile functional components that require compression–torsion coupling behaviors.

Generalized model and performance analysis of two-axis flexure hinges based on quadratic rational Bézier curve

This article presents a generalized model of two-axis flexure hinges based on quadratic rational Bézier curve. The generalized closed-form compliance equations are derived based on the virtual work theory and the superposition relationship of the deformation. Then, how to determine the number of sensitive axes, the location of the primary and secondary sensitive axes, and the configuration of the notch profile are discussed. There are 20 types of notch profiles derived from single or mixed, symmetrical or asymmetrical curves. And, the correctness of the compliance equations is verified by finite-element analysis. The maximum relative error does not exceed 10%. Finally, the precision of rotation, the maximum stress, and the effect of structural parameters on the compliance are analyzed. The results show that for two-axis flexure hinges with a flush single curve notch profile, the proximity of the center of rotation to the load end does not significantly affect the axial compliance as well as the torsional compliance. For hybrid two-axis flexure hinges with symmetric structure, the ability to maintain the center of rotation under lateral forces is better than that under the same torque. The proposed generalized model provides a reference for the design of spatial compliant mechanisms.

Characterization of damping in 3D metal printed gear body using parameter optimization

With the rapid development of the global economy and the widespread use of high-speed machinery, vibration and noise pollution is becoming increasingly serious. The increased energy costs, environmental pollution, and carbon emissions have prioritized sustainable development for industry. As an important link of mechanical transmission, the gear transmission vibration and noise adversely affect the physical and mental health of operators and interfere with the normal use of machinery. This paper proposes a new metal 3D printing-made vibration-damping lightweight gear model. The solid gear web is replaced with a lightening hole structure that is expected to ensure rigidity and torsional compliance while controlling the damping effects of the gear web structure. Gears were manufactured from an additive manufacturing material using a metal 3D printing technique. This work advanced an experimental analysis of the dissipation properties of metal printed gear exploiting vibration tests. A gear frequency-sweeping excitation test bench was designed and developed to simulate in-plane excitation to produce a circumferential torsional mode of the specimen. Circumference damping estimates are guided by executing vibration exciter excitation on the setup. The half-power bandwidth and modal fitting methods were arranged and compared, relying on the measured frequency response function (FRF) single-degree-of-freedom (SDOF) approximation.

Kinematic modeling of a spatial three degrees-of-freedom compliant micro-motion parallel mechanism considering input coupling effect and bilateral restrained torsion

PurposeThis paper aims to improve the kinematic modeling accuracy of a spatial three-degrees-of-freedom compliant micro-motion parallel mechanism by proposing a modified modeling method based on the structural matrix method (SMM).Design/methodology/approachThis paper analyzes the problem that the torsional compliance equation of the circular notched hinge is no longer applicable because it is subject to bilateral restrained torsion. The torsional compliance equation is modified by introducing the relative length coefficient. The input coupling effect, which is often neglected, is considered in kinematic modeling. The symbolic expression of the input coupling matrix is obtained. Theory, simulation and experimentation are presented to show the validity of the proposed kinematic model.FindingsThe results show that the proposed kinematics model can improve the modeling accuracy by comparing the theoretical, finite element method (FEM) and experimental method.Originality/valueThis work provides a feasible scheme for CMPM kinematics modeling. It can be better applied to the optimization design based on the kinematic model in the future.

Threading holder based on axial metal cylinder pins to reduce tap risk during reversion instant

Internal thread profiles are used widely in manufacturing processes with the aim of assembling/disassembling different components during maintenance activities from the aeronautics sector until common industrial parts. The threading process is one of the last operations carried out to obtain those components, and consequently, it is an operation of high added value. Threading is a complex operation that must carefully synchronize the rotation with the feed movements to avoid tool breakage during the instant of tapping reversion stage. In order to avoid this risk, several toolholders were developed present in the literature but deficiencies in terms of stability and productivity. Therefore, in this work, a new toolholder is proposed in which the common springs used to mitigate the lack of perfect synchronization between rotation and feed movements are replaced by elastic metal pins achieving a torsional compliance toolholder. The results show that the use of the proposed toolholder implies not only a productivity increase but also a surface integrity improvement as well as a stress reduction that the cutting tap is subjected and thus, achieving a substantial improvement in the current tapping processes. In particular, the use of the proposed toolholder implied a 75% reduction of the maximum stress achieved in the reversal instant, improving 20% tool life with an increase of 30% cutting speed. Therefore, the use of the proposed toolholder implies a substantial improvement in the current tapping processes.

On Stretching, Bending, Shearing, and Twisting of Actin Filaments I: Variational Models.

Mechanochemical simulations of actomyosin networks are traditionally based on one-dimensional models of actin filaments having zero width. Here, and in the follow up paper (arXiv, DOI 10.48550/arXiv.2203.01284), approaches are presented for more efficient modeling that incorporates stretching, shearing, and twisting of actin filaments. Our modeling of a semiflexible filament with a small but finite width is based on the Cosserat theory of elastic rods, which allows for six degrees of freedom at every point on the filament's backbone. In the variational models presented in this paper, a small and discrete set of parameters is used to describe a smooth filament shape having all degrees of freedom allowed in the Cosserat theory. Two main approaches are introduced: one where polynomial spline functions describe the filament's configuration, and one in which geodesic curves in the space of the configurational degrees of freedom are used. We find that in the latter representation the strain energy function can be calculated without resorting to a small-angle expansion, so it can describe arbitrarily large filament deformations without systematic error. These approaches are validated by a dynamical model of a Cosserat filament, which can be further extended by using multiresolution methods to allow more detailed monomer-based resolution in certain parts of the actin filament, as introduced in the follow up paper. The presented framework is illustrated by showing how torsional compliance in a finite-width filament can induce broken chiral symmetry in the structure of a cross-linked bundle.

Экспериментальное определение крутильной податливости коленчатого вала двигателя 2Ч8,5/11

The article is devoted to the experimental determination of the torsional compliance of an incompletely supported crankshaft of a complex design. Comparison of the obtained compliance value with related to the significant formula (12.4%), the finite element method (4.98%). The obtained result will be used in calculating the torsional vibrations of the DGA-8.83 diesel generator set with the original rope coupling.

Modelling and indirect measurement of machine tool equivalent joint compliances

Machine tools require high geometric accuracy and stiffness. Both of these characteristics affect the radius of a radially loaded circular test. By using various loads, the machine's volumetric compliance can be studied as a function of position, orientation, and load. Further processing of the data using a kinematic and compliance model of the machine allows the equivalent joint compliances to be estimated. This model also allows to produce the characteristic patterns of loaded telescopic double ball bar readings associated with each compliance term. The compliance model contains numerous superfluous and confounded terms that are pruned from the model. The analytical model is then used to produce a numerical identification Jacobian that is further applied to estimate the compliances from test data gathered at various force levels. By using all force data at once global compliance values are estimated whereas using only adjacent force level data allows observing the change in compliance with force. The new nomenclature is introduced where each compliance term has three subscripts. The first subscript is the direction of the displacement, the second subscript is the applied force direction, and the third subscript is the relevant joint or axis. The dominant compliances are the X-axis on-axis compliance C XXX (confounded with the lateral compliance of the Y-axis C XXY ) and C YYY (confounded with C YYX ). It is observed that as the load increases from 76 to 706 N (by increments of 126 N), the dominant compliances increase by around 5%. Type A uncertainties of the calculated compliances are estimated from repeated measurements and are found to be relatively small. Some non-dominant compliances, such as the torsional compliance of the Y-axis C CCY account for deflection of less than 0.5% of that for the main compliances and has a negative value which is mechanically unexpected. It is explained in detail in the results and discussion section.

Influence of a static torque on plasticity and asperity-induced closure effects during fatigue crack growth in bainitic steel cylinders loaded in push-pull

Mode I fatigue crack growth with a superimposed static torque was investigated in bainitic steel. The torque had little effect on crack growth kinetics and path. However, the non-singular stress parallel to the crack front, and bending stresses due to eccentric crack growth triggered crack twisting, even in mode I. A progressive increase in crack sliding displacement was due to a rise in elastic torsional compliance, but also to plastic ratchetting at the crack tip, and to a progressive shearing of crack face asperities, which reduced the enhancement of roughness-induced closure by the torque, however shown to enhance plasticity-induced closure.

Parametric Study of a Composite Skin for a Twist-Morphing Wing

Although the benefits of morphing wings have been proven in many studies in the last few decades, the wing skin design remains one of the challenges to advancing and implementing the morphing technology. This is due to the conflicting design requirements of high out-of-plane stiffness to withstand aerodynamic loads and low in-plane stiffness to allow morphing with the available actuation forces. Advancements in the design of hybrid and flexible composites might allow for design solutions that feature this balance in stiffness required for this application. These composites offer new design parameters, such as the number of plies, the fiber-orientation angle of each ply in the skin laminate, and the spatial distribution of the plies on the skin surface. This paper presents a parametric study of a composite skin for a twist-morphing wing. The skin is made of periodic laminated composite sections, called “Twistkins”, integrated in an elastomeric outer skin. The twisting deformation is localized in the elastomeric sections between the Twistkins. The design parameters considered are the number of plies in the composite Twistkins, the fiber-orientation angle of the plies, the torsional rigidity of the elastomer, the width ratio, and the number of elastomeric sections. The computational analysis results showed that the torsional compliance can be increased by increasing the width ratio, decreasing the number of elastomeric sections, number of composite plies and the elastomer’s torsional rigidity. However, this would also lead to a decrease in the out-of-plane stiffness. The nonlinearity and rates at which these parameters affect the skin’s behavior are highlighted, including the effect of the fiber-orientation angle of the laminate plies. Hence, the study guides the design process of this twist-morphing skin.

Vibration and dynamics analysis of electric vehicle drivetrains

The importance of the vibration and dynamics of electric vehicle drivetrains has increased because of noise and durability concerns. In this study, the important dynamic responses of drivetrains, including the dynamic mesh force acting at the gear teeth, dynamic loads acting at the bearings, and torsional fluctuation of the tire or load under major vibration excitations, such as motor torque fluctuation excitation and spiral bevel gear mesh excitation, were investigated. The results demonstrate that at a lower motor speed, dynamic responses such as the dynamic mesh force, dynamic bearing loads, and dynamic torsional displacement of the tire or load under motor torque fluctuation are dominant. At a higher motor speed, however, the dynamic responses under the gear mesh excitation are dominant. In addition, increasing the pinion-motor torsional compliance is an effective approach for suppressing the dynamic responses of drivetrains under motor torque fluctuation.

CLOSED-FORM TORSIONAL COMPLIANCE OF TWO-AXIS FLEXURE HINGES

This paper focuses on closed-form equations of torsional compliance for two-axis flexure hinges with variable rectangular cross-section (VRC) which can serve as the alternatives of flexure spherical hinges in flexure-based spatial compliant mechanisms.

Mechanical comparison of two small interlocking nails in torsion using a feline bone surrogate.

To compare the torsional behavior of two small angle-stable interlocking nails (I-Loc and Targon) with that of locking compression plates (LCP). To evaluate the effect of implant removal on the torsional strength of feline bone surrogates. Experimental. Fracture gap constructs and intact explanted bone surrogates. Fracture gap constructs were stabilized with one of six implants (I-Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4) and then cyclically tested in torsion (n = 4/group). To simulate implant removal, intact surrogates with implant-specific pilot holes were then twisted to failure (n = 4/group). Torsional compliance (TC; °/Nm), angular deformation (AD; °), and failure torque (FT ; Nm) were statistically compared (P < .05). The I-Loc 4 had the smallest TC and AD of all constructs (P < .05). The largest TC (P < .05) was seen with the LCP 2.0. The Targon 2.5 had the largest AD (P < .05) secondary to locking interface slippage. Targon surrogates FT were the lowest of all groups (P < .05). Conversely, there was no difference between the FT of the I-Loc, LCP, and intact surrogates (P > .05). We showed that I-Loc nails provided greater torsional stability than size-matched Targon nails and LCPs. Conversely, Targon 2.5 locking interface slippage may jeopardize that construct's stability. Furthermore, the significantly reduced bone surrogate torsional strength provided evidence that the large Targon bolt holes increased the risk of postexplantation iatrogenic fracture. Our results provide evidence to conclude that the small I-Loc nails may be valid alternatives to other osteosynthesis options for feline fracture repair.

Determination of Torsional Compliance of Some Elements of Planetary Gears

The paper presents formulas for determining the torsional compliance of flat disks with a central hole and a torque measuring system, which are part of the planetary gears of drilling rigs.

Extreme contractility and torsional compliance of soft ribbons under high twist.

We investigate experimentally and model the mechanical response of a soft Hookean ribbon submitted to large twist η and longitudinal tension T, under clamped boundary conditions. We derive a formula for the torque M using the Föppl-von Kàrmànequations up to third order in twist, incorporating a twist-tension coupling. In the stable helicoid regime, quantitative agreement with experimental data is obtained. When twisted above a critical twist η_{L}(T), ribbons develop wrinkles and folds which modify qualitatively the mechanical behavior. We show a surprisingly large longitudinal contraction upon twist, reminiscent of a Poynting effect, and a much lower torsional stiffness. Far from threshold, we identify two regimes depending on the applied T. In a high-T regime, we find that the torque scales as ηT and the contraction as η^{2}, in agreement with a far from threshold analysis where compression and bending stresses are neglected. In a low-T regime, the contraction still scales as η^{2} but the torque appears T independent and linear with η. We argue that the large curvature of the folds now contributes significantly to the torque. This regime is discussed in the context of asymptotic isometry for very thin plates submitted to vanishing tension but large change of shape, as in crumpling.

A Flexible shaft-driven Remote and Torsionally Compliant Actuator (RTCA) for wearable robots

This paper presents the conceptual development and validation tests of a novel actuation paradigm for wearable robots, the flexible shaft-driven Remote and Torsionally Compliant Actuator. The RTCA exploits both the torsional compliance and bending properties of a commercial flexible shaft to provide simultaneously the advantages of remote actuation systems: improved weight distribution and reduced inertia on the distal joints, together with the advantages of compliant systems. The flexible shaft can be modelled following the proposed methodology as a torsionally compliant element that can be bent, so that the RTCA's output transmitted torque can be estimated based on the flexible shaft's torsional deflection angle and spatial configuration, allowing accurate torque control at the distal joint following a remote actuation approach based only on position sensors. Torque control and transparency tests were used to validate the proposed torque estimation and control approach. Finally, we presented a realistic implementation approach of the RTCA concept into a test bench resembling a lower limb exoskeleton as a case study for wearable robots. Results confirmed the capabilities of the proposed approach and supported the envisioned advantages of this novel actuation paradigm, constituting a promising solution for future developments in this field.

Analysis and Computation Method of Torsional Compliance of Worm Gear

Analysis and Computation Method of Torsional Compliance of Worm Gear

A 3D study of the relationship between leaf vein structure and mechanical function

We investigate the structures and mechanical properties of leaf midribs of Ficus microcarpa and Prunus dulcis, which deposit calcium oxalate crystals, and of Olea europaea midribs which contain no mineral deposits, but do contain lignified fibers. The midrib mechanical performance contributes to the leaf’s ability to maintain a flat conformation for light harvesting and to efficiently reconfigure to reduce wind drag. We use a novel approach involving 3D visualization of the vein structure during mechanical load. This involves the use of customized mechanical loading devices that fit inside a microCT chamber. We show that the elastic, compression and torsional moduli of the midribs of leaves from the 3 species examined vary significantly. We also observed different modes of fracture and buckling of the leaves during compression. We assess the contributions of the calcium oxalate crystals to the mechanical and fracture properties. In F. microcarpa midrib linear arrays of calcium oxalate crystals contribute to resisting the bending, in contrast to P. dulcis leaves, where the calcium oxalate crystals do not resist bending. In both F. microcarpa and P. dulcis isolated calcium oxalate crystals enable high torsional compliance. The integrated microCT – mechanical testing approach could be used to investigate the structure-mechanics relationships in other complex biological samples. Statement of significanceLeaves need to maintain a flat conformation for light harvesting, but they also need to efficiently reconfigure to reduce wind drag. The leaf central vein (midrib) is a key structural component for leaf mechanicss. 3D visualization of the vein structure under mechanical loads showed that veins can be stiffened by reinforcement units composed of calcium oxalates crystals and lignin. The stiffening units can influence the bending and fracture properties of the midribs, and can contribute to determine if buckling will occur during folding. Mineral stiffening elements could be a widespread strategy to reinforce leaf veins and other biological structures. This structural-mechanical approach could be used to study other complex biological samples.

Characterization of the torsional structural properties of feline femurs and surrogate bone models for mechanical testing of orthopedic implants.

To characterize the torsional structural properties of the feline femur and design a bone model surrogate for mechanical testing of feline orthopedic implants. Experimental. Paired feline femurs (n = 30) and bone models (8 materials, n = 4/group). Femurs were cyclically tested nondestructively in torsion and then loaded to failure. A generic femoral model was then designed from native femur dimensions and tested similarly by using 1 of 8 materials that were 3-dimensionally printed or machined. Outcome measures consisting of torsional compliance, angular deformation (AD), and torque to failure were compared by using Student's t test (P < .05). Failure modes are reported as descriptive statistics. Torsional compliance (1.6 ± 0.3°/Nm, 2.0 ± 0.1°/Nm), AD (3.1 ± 0.6°, 3.8 ± 0.2°) and torque to failure (7.8 ±1.2 Nm, 8.1 ± 1.3 Nm) did not differ between feline femurs and short-fiber epoxy (SFE) models. Conversely, most printed materials displayed excessive TC and failed by plastic deformation (AD > 15-fold that of native femurs) rather than by fracture. Feline bone and SFE both failed by spiral fractures. None of the outcome measures differed between the 4th generation SFE model and cadaveric femurs, but differences were identified between feline bone and printed materials. Machined SFE can be used to create a surrogate bone model with torsional structural properties similar to those of feline femurs. In contrast, common printable materials appear unsuitable to produce a realistic feline bone surrogate.