Frame Geometry Research Articles

The Notes on Slant Helices According to Equiform Frame on Symplectic Space

In this this paper, we have dealed with the properties of k-type. We express some characterizations for k-type slant helix according to equiform frame geometry in symplectic regular curves.

Development of a multibody model for go-karts considering frame flexibility

AbstractThis study focuses on the optimization dynamics of racing go-karts, which is heavily influenced by the frame's stiffness. Lacking suspensions and differentials, go-karts rely on the frame stiffness for wheel balancing and skid prevention by lifting the inner rear wheel during turns. Utilizing a rigid-flexible model in MSC Software ADAMS View, validated by frame deformation measurements, this research integrates finite element analysis with multibody techniques. The model, leverages computer aided design files for frame geometry and employs finite element analysis for frame validation. It facilitates evaluating go-kart dynamics through simulations, aiding in maneuver testing and design optimization. This approach provides a comprehensive framework for advancing go-kart designs.

Effects of scenery frame on visual depth perception in classical Chinese gardens: A case study of the Lvyin Pavilion in Lingering Garden

Visual depth (distance) perception is a fundamental aspect of environmental cognition, as it allows people to judge the spatial scale of their surroundings. However, estimating the depth of classical Chinese gardens is challenging, especially from static viewpoints that frame the scenery. Previous studies have examined how the internal components of the scenery frame affect depth perception. Still, the role of the frame and its peripheral information as environmental background have been largely overlooked. This study investigates how depth perception at viewpoints is influenced by viewing position displacement, frame geometry, and environmental context. The authors created nine stimulus materials in a cave virtual reality environment (three image treatments × three positions). Seventy-one participants were asked to evaluate depth perception using the magnitude estimation and adjustment methods. Their eye movement behavior was also recorded using an eye-movement instrument (SensoMotoric Instruments (SMI) eye-tracking glasses, 120 Hz). The results showed that participants could perceive spatial depth differences between viewing positions even when the internal viewpoint displacement was small; frame shape did not significantly affect depth perception and gaze behavior; and peripheral visual information of the frame enhanced depth perception significantly. Moreover, the form of the environmental background, especially the position of the scenery window, strongly guided the participants’ gaze. These findings suggest that ambient visual information significantly impacts environmental experience, which landscape designers should consider.

Incidence and predictors of continued ascending aortic dilatation after TAVI in patients with bicuspid aortic stenosis

Abstract Background Patients undergoing transcatheter aortic valve implantation (TAVI) for bicuspid aortic stenosis (AS) frequently present with ascending aortic (AAo) dilatation which is left untreated. The objective of this study was to study the natural progression and underlying mechanisms of AAo dilatation after TAVI for bicuspid AS. Methods Patients with a native bicuspid AS and a baseline AAo maximum diameter > 40 mm treated by TAVI and in whom post-TAVI computed tomography (CT) scans beyond 1 year were available were included. AAo dilatation was deemed to be either continuous (≥ 2 mm increase) or stable (< 2 mm increase or decrease). Uni- and multivariate logistic regression analysis was utilized in order to identify factors associated with continuous AAo dilatation post-TAVI. Results A total of 61 patients with a mean AAo maximum diameter of 45.6 ± 3.9 mm at baseline were evaluated. At a median follow-up of 2.9 years, AAo dimensions remained stable in 85% of patients. Continuous AAo dilatation was observed in 15% of patients at a rate of 1.4 mm/year. Factors associated with continuous AAo dilatation were raphe length/annulus mean diameter ratio (OR 4.09, 95% CI [1.40–16.7], p = 0.022), TAV eccentricity at the leaflet outflow level (OR 2.11, 95%CI [1.12–4.53], p = 0.031) and maximum transprosthetic gradient (OR 1.30, 95%CI [0.99–1.73], p = 0.058). Conclusions Ascending aortic dilatation in patients undergoing TAVI for bicuspid AS remains stable in the majority of patients. Factors influencing TAV stent frame geometry and function were identified to be associated with continuous AAo dilatation after TAVI; this should be confirmed in future larger cohort studies. Graphical Abstract

The Influence of Structural Parameters on the Ultimate Strength Capacity of a Designed Vertical Axis Turbine Blade for Ocean Current Power Generators

An ocean current power generator is a power plant that uses kinetic energy from ocean currents to generate electricity. Considering that the blade is the component that receives the biggest load from seawater currents, its structural design should be strong enough to sustain the applied load. Therefore, this research seeks a suitable design and material for turbine blades using the finite element method (FEM). A NACA 0021 blade with a total length of 3600 mm is used for the base geometry. A parametric study was conducted by varying the spacing between the supports, the pitch angle, the material, and the frame model. Considering a high load, the suitable amount of space between the stiffeners was 2200 mm. It was found that a pitch angle variation between −20° and +20° did not significantly affect the strength of the blade structure. The frame geometry variation caused the rigidity and cross-section area of the blade to differ. Therefore, web-shaped or bar-shaped frames are preferable because they have optimal maximum load-to-weight ratios. The material variation analysis resulted in CFRP material being chosen because it had a high maximum load/weight ratio and a high maximum stress.

Compliant frame geometry for DEMES-based gripper and flapping wing actuators: A comprehensive design study

Dielectric elastomer minimum energy structures (DEMES) have attracted significant attention in the recent past because of their ability to switch between multiple equilibrium states. The DEMES is formed when a pre-stretched elastomer film adheres to an inextensible frame and is further allowed to attain an equilibrium configuration as a result of energy minimization. While several researchers have investigated; both theoretically and experimentally, the underlying mechanics of DEMES, a majority of them deploy simplistic boundary frames (square/rectangular/circular) to obtain the requisite minimum energy configuration. In this paper, we demonstrate that this seemingly restrictive choice of using simplistic frame geometries can be given away by designing more complex-shaped compliant frames capable of producing useful modes of deformation. To demonstrate this idea, two prototypes; namely, the four-arm gripper actuator and the flapping-wing actuator, are studied numerically and experimentally. In both cases, a single compliant frame is used to realize the respective configuration, thus circumventing the need to assemble multiple MES on a common platform. In tandem, we investigate the role of reinforcements in (a) controlling the warping in MES and (b) maximizing actuation in the desired mode of deformation. Finite element analysis are carried out using the ABAQUS to determine the equilibrium configuration of the actuators, and subsequently their electromechanical behavior. Experimental investigations involve the utilization of the commercially available VHB 4910 acrylic tape in conjunction with PET frames and 3D-printed reinforcements. Excellent qualitative agreement is achieved between the numerical predictions and the experimental observations. Finally, we allude to a few innovative frame architectures leading the MES of engineering interest.

Database of tall pre-Northridge steel moment frames for earthquake performance evaluations

This article describes a detailed database of tall steel moment frame buildings that are representative of the construction practices in San Francisco prior to the 1994 Northridge earthquake. The database contains design details that affect the structural performance of steel moment frames, including frame geometry, member cross-section sizes, and gravity system characteristics. This database also captures irregularities that might impact seismic response, such as podiums, setbacks, mass concentrations (mechanical, electrical, and plumbing (MEP) floors), interrupted column lines, and atriums. The database includes information on 89 moment frame buildings, 14 of which were built before 1960 and are constructed with riveted connections, while the remaining 75 have welded flange connections like those that suffered brittle fracture during the 1994 Northridge earthquake. The buildings are further distinguished between space frame, perimeter frame, and partial space frame systems. For about half (41/89) of the buildings in the database, section sizes of representative structural members were collected, which enabled the evaluation of the seismic design, elastic, and inelastic response using computational workflows. The design diagnostics indicate that most of the buildings meet the minimum seismic strength and strong-column weak-beam requirements of modern building codes, even though they were not necessarily designed with this intent. On the contrary, about one-third of the buildings do not meet the seismic design drift limit of current codes, and about half of them have weak beam-column panel zones. This database, associated structural analysis models, and processing scripts are published at DesignSafe https://doi.org/10.17603/ds2-wjad-r340 to facilitate collaboration and continued development of open-source data for high-resolution simulations to inform risk mitigation strategies on a regional scale.

Experimental Verification of Geometric Changes Caused by the Release of Residual Stresses for Large-Scale Welded Frames.

This paper presents geometric analyses of welded frames after free relaxing and vibratory stress relief (VSR). The tested frames were components of a prototype packaging machine. Two types of relaxation were carried out to remove stresses introduced as a result of the welding process. One of the frames was subjected to free relaxation, while the other one was subjected to accelerated vibration relaxation. Detection of the frame geometry changes was performed using a photogrammetric system. In addition, an evaluation of the geometry change was conducted for fifteen variants of a steel frame support. A comparative analysis of the geometric deviations of the frames after free and vibratory stress relief confirmed the assumption that the frame post vibration stress relief better reproduces the nominal dimensions. Nevertheless, it should be emphasized that after vibratory stress relief, the frame is not subject to further deformation, which is a desirable effect. In the case of free relaxing, the frame undergoes dimensional changes in a random manner. In summary, carrying out accelerated vibratory stress relief allows for control of spontaneous dimensional changes in the designed frame of a packaging machine resulting from spontaneous relaxation of stresses arising from the welding process. The shortening of the relaxation process of the welded frame is also an unquestionable advantage.

Understanding the mechanical behavior of intrauterine devices during simulated removal

ObjectiveTo evaluate differences based on intrauterine device (IUD) frame geometry in force, and stress, and strain at the stem/arms junction during simulated IUD removal. Study designWe manufactured injection-molded frame models for three Nova-T IUDs (Mirena [model M]; Liletta [model L]; Kyleena [model K]) and a Tatum-T IUD (Paragard [model P]) at two-times scaling. We created a custom fixture to simulate the uterus and used a screw-driven machine to pull models at various displacement rates through the 10 cm fixture cavity to measure force and strain and calculate stress at the IUD stem/arms junction. We tested models at 30 mm/min and higher displacement rates for exploratory analyses. We used Mann-Whitney U test for statistical testing. ResultsWe completed testing at 30 mm/min using five of each Nova-T model and nine model P samples. Resistance against the cavity walls created significantly more force on model P (11.83, interquartile range [IQR] 11.61–12.31) than any Nova-T model samples (p < 0.001). The smaller model K created slightly more median stress (MPa) than the larger model M (0.36 [IQR 0.33–0.38] and 0.79 [IQR 0.76–0.80], respectively, p = 0.008); model P samples generated significantly more median stress than other models (1.70 [IQR 1.67–1.77], p < 0.001). Strain plots demonstrated permanent deformation for some samples during IUD removal simulation. We tested 20 samples at various higher displacement rates up to 2500 mm/min, with stress notably increasing for model P samples with increasing rates. No fractures occurred. ConclusionsForce and stress at the stem/arms junction are higher with Tatum-T-shaped compared to Nova-T-shaped IUD models under the same testing conditions, and a higher speed of extraction causes more stress. ImplicationsSharp corners create vulnerability under static and fatigue loading in structural components due to increased local stresses. Our findings suggest that IUDs with Tatum-T frames should be removed slowly to minimize the stress at the stem/arms junction. Future studies can provide more information if performed with commercially available products.

The damping problem in non-linear viscoelastic frames under varying temperature

A theoretical consideration of the damping problem in frame engineering structures made of functionally graded materials with non-linear viscoelastic behaviour is carried-out. The frames studied are under external mechanical load and varying temperature. In particular, damping in a two-legged frame with supports on different levels is analyzed. The frame is subjected to a cyclic side load with simultaneous variation of the temperature. The material of the frame is functionally graded in the thickness direction. Thus, the material properties change smoothly along the thickness. Equilibrium equations are used for determining the curvature and the neutral axis coordinates in the members of the frame structure. The damping energy density is integrated in the volume of the frame members in order to find-out the damping energy in the whole frame structure. A parametric investigation is performed by using the solution of the damping energy in order to clarify the influence of various factors (the frame geometry, loading, etc.) on the damping phenomenon at different temperatures.

The Influence of Sagittal Pin Angulation on the Stiffness and Pull-Out Strength of a Monolateral Fixator Construct.

Monolateral pin-to-bar-clamp fixators are commonly used to stabilize acute extremity injuries. Certain rules regarding frame geometry have been established that affect construct stability. The influence of sagittal pin angulation on construct stiffness and strength has not been investigated. The purpose of this biomechanical study was to demonstrate the effect of a pin angulation in the monolateral fixator using a composite cylinder model. Three groups of composite cylinder models with a fracture gap were loaded with different mounting variants of monolateral pin-to-bar-clamp fixators. In the first group, the pins were set parallel to each other and perpendicular to the specimen. In the second group, both pins were set convergent each in an angle of 15° to the specimen. In the third group, the pins were set each 15° divergent. The strength of the constructions was tested using a mechanical testing machine. This was followed by a cyclic loading test to produce pin loosening. A pull-out test was then performed to evaluate the strength of each construct at the pin-bone interface. Initial stiffness analyses showed that the converging configuration was the stiffest, while the diverging configuration was the least stiff. The parallel mounting showed an intermediate stiffness. There was a significantly higher resistance to pull-out force in the diverging pin configuration compared to the converging pin configuration. There was no significant difference in the pull-out strength of the parallel pins compared to the angled pin pairs. Convergent mounting of pin pairs increases the stiffness of a monolateral fixator, whereas a divergent mounting weakens it. Regarding the strength of the pin-bone interface, the divergent pin configuration appears to provide greater resistance to pull-out force than the convergent one. The results of this pilot study should be important for the doctrine of fixator mounting as well as for fixator component design.

A Multidirectional Forearm Electromagnetic Generator Designed via Numerical Simulations

Harvesting biomechanical energy from daily human body motions provides a promising and sustainable power solution for wearable electronics, whose current power supplies, i.e., batteries, have unsatisfactory capacity and durability due to volume, shape, and flexibility constraints. Electromagnetic generators (EMGs) are favorable energy transducers because of their high energy-conversion efficiency, low dependence on frequencies, and long-term stability. However, an EMG that can effectively harvest energy from multi-directional arm motions at aperiodic low frequencies are yet to be created. Here, we introduce a unique EMG configuration by combining a linear and a helix frame into a monolithic unit (EMG-LH), enabling the EMG to scavenge energy from all kinds of arm motions up to 6 degrees of freedom (DOFs) (movement along XYZ axes and forearm rotations). The EMG frame geometry is designed and optimized according to numerical simulations. To clarify the working mechanism and maximize the power output, the copper coils’ winding pattern, the magnets’ velocity profiles, and the resulting voltage output are numerically simulated and then experimentally verified. Our EMG-LH outperforms linear EMGs (EMG-Ls) and helix EMGs (EMG-Hs) in harvesting energy from all arm motions. This work explicitly presents a forearm-wearable energy harvester as a sustainable power source for wearable electronics.

Applying a Combination of Cutting-Edge Industry 4.0 Processes towards Fabricating a Customized Component

3D scanning, 3D printing, and CAD design software are considered important tools in Industry 4.0 product development processes. Each one of them has seen widespread use in a variety of scientific and commercial fields. This work aims to depict the added value of their combined use in a proposed workflow where a customized product needs to be developed. More specifically, the geometry of an existing physical item’s geometry needs to be defined in order to fabricate and seamlessly integrate an additional component. In this instance, a 3D scanning technique was used to digitize an e-bike’s frame geometry. This was essential for creating a peripheral component (in this case, a rear rack) that would be integrated into the frame of the bicycle. In lieu of just developing a tail rack from scratch, a CAD generative design process was chosen in order to produce a design that favored both light weight and optimal mechanical behaviors. FDM 3D printing was utilized to build the final design using ABS-CF10 materials, which, although being a thermoplastic ABS-based material, was introduced as a metal replacement for lighter and more ergonomic component production. Consequently, the component was manufactured in this manner and successfully mounted onto the frame of the e-bike. The proposed process is not limited to the manufacturing of this component, but may be used in the future for the fabrication of additional peripheral components and tooling.

D-11 | Comparing Transcatheter Pulmonary Valve Frame Geometry at Implantation and Short-Term Function

D-11 | Comparing Transcatheter Pulmonary Valve Frame Geometry at Implantation and Short-Term Function

An automated topology optimization interpreter that generates space frames

This paper presents the methodology and theoretical foundation of topology optimization (TO) Results Spaceframe Interpreter, an automatic TO results interpreter that generates a closely associated space frame consisting of welded structural tubing or rectangular bars. TO is a computational technique that uses a finite element (FE) formulation to identify the most weight-efficient structure within a design domain. Density-based TO results in structures that take organic forms and is usually a tedious and cumbersome process to generate a computer-aided-design (CAD) model to manufacture through conventional techniques. The optimal topology frequently resembles a space frame, which is well-known as being a rigid, lightweight structure. The methodology of the TO results interpreter leverages several techniques from volumetric image processing and has four primary processes. First, the results are obtained from commercial FE/TO software and mapped into a cubic grid of voxels. Second, junction locations are extracted and member connectivity that represents a frame is identified. Third, a sizing optimization is incorporated to determine appropriate sectional dimensions of the circular or rectangular space frame members. Fourth, the optimized space frame geometry is imported into a CAD design tool to automatically create a design model. The logic and are implemented within the frame extraction processes. The automated TO interpreter is designed to interact with commercial FE analysis and CAD systems. The interpreter is demonstrated on various spatial examples including aerospace and automotive applications. In each case, the welded space frame closely resembles the TO result, with nearly equivalent stiffness and mass.

Economical Aspect of Truss Design Through Geometry Configuration

In engineering, truss structures are used extensively in bridge, tower, building, and numerous mechanical applications. Several studies have found that truss frames use the least steel weight when compared to other structural systems. The majority of truss frame design optimization research concentrated primarily on minimal weight design, and constructability, ease of fabrication, steel wastes, and the ideal geometric design parameter were not considered during the design optimization. Since the acceptable value range for factors like the span to depth ratio, truss frame typology, and diagonal angle is broad, there is no clear direction on how to determine the economical idea of truss frame geometry. To find the ideal geometry configuration for a truss frame, parametric studies were carried out, considering the truss frame span to depth ratio, truss frame typology, and diagonal angle. The study's conclusion offers a well-organized framework for choosing the best truss frame shape. According to the study's findings, there were no appreciable changes in the internal forces generated by the chords of the different truss typologies that may have resulted in substantial weight discrepancies. If constructability is a consideration, Warren trusses are a superior choice. When compared to proposals made by diverse sources, the projected truss span to depth ratio was significantly smaller. The study also showed that the member weight remains constant and does not significantly rise within a given range of the span to depth ratio.

A standard reference frame and geometry for nucleosomes.

The nucleosome is often described as a histone-DNA complex containing eight histones and 145-147 base pairs of DNA. The reality is more complex. Here we evaluate approximately 500 nucleosomes from the Research Collaboratory for Structural Biology with the goal of establishing a reference frame and standard geometry for describing the internal structure of mono-nucleosomes and the stacking of nucleosomes in arrays and clusters. Our reference frame places the center of mass of the nucleosome's octameric core at the origin. The positive x-axis aligns with the symmetry axis of the nucleosome and passes through the central base pair or base pair step associated with the octamer. The z-axis is defined by fitting a regular helix (constant pitch and radius) to the nucleosome. The positive direction is determined by the choice of reading strand. Two methods for defining this helix are explored. One fits a helix to the center line of the DNA, which is itself determined according to a standard reference geometry for DNA base pairs. The other fits a helix to the centers of mass obtained from the histones. The z-axes, so defined, are slightly askew. Over 100 nucleosomes are used to define a standard reference geometry for the histones and for super helices with 145, 146 and 147 base pairs. In all structures, the cumulative sum of Rise, Twist and arclength are linear functions of base pair index with R2 values in excess of 0.999. The standard geometry supports a rigorous definition of entry-exit angle and identification of structural anomalies. Select examples demonstrate how generalizations of the inter and intra base pair parameters can be utilized to analyze the internal structure of mono-nucleosomes, their stacking in arrays and clusters, and the ab initio assembly of atomic and coarse-grained structures.

Outcomes of Self-Expanding Transcatheter Pulmonary Valves: Extended Follow-Up of a Prospective Trial

<b>Background:</b> The Venus-P valve was the first self-expanding valve used world-wide for transcatheter pulmonary valve replacement (TPVR) in patients with severe pulmonary regurgitation (PR). We intended to report the extended follow-up results from the prospective trial (No. NCT02590679). <b>Methods:</b> A total of 38 patients with severe PR (mean age 24.2 ± 13.2) were included. Follow-up data were obtained after implanted at 1, 6, and 12 months and yearly after. The frame geometry was assessed on post-implant computer tomography (CT) scanning by calculating the non-circularity [circularity ratio (minimum diameter/maximum diameter) < 0.9] and under-expansion [expansion ratio (derived external valve area/nominal external valve area) < 0.9). Adverse events (all-cause mortality, reintervention, valve dysfunction, stent fracture and endocarditis) were recorded. <b>Results:</b> All valves were implanted successfully with normal function at discharge. Geometric CT analysis showed under-expanded valve was detected in 22 patients (63%) and non-circular valve was seen in 16 patients (46%). During a median follow-up of 4.8 years (range 0.3–8.1), there were 1 death and 1 surgical explant, both resulting from endocarditis. Five-year freedom from valve dysfunction and stent fracture were 84.8% (95%CI 74.8–94.7) and 83.5% (95%CI 73.8–93.2). Endocarditis occurred in 3 patients at a median time of 7 months. Stent fracture was more common in patients with non-circularity stents. <b>Conclusion:</b> TPVR using Venus-P valve is associated with favorable outcomes at 5 years. Non-circular shapes in the valve level may have a higher risk of stent fracture.

On Structural Design of Steel Roof Truss Geometry Used in Factory Shed

Use of steel is steadily increasing all over the world in civil engineering related fields due to its superior material properties like high strength and durability, high ductility, light weight etc. Various types of steel structures become more popular because of their high aesthetic appearance. Among these steel structures, roof trusses are widely used to cover large column free open areas like shopping malls, auditoriums, car parking lots, stadiums as well as factory sheds etc. Design of steel truss members is an important aspect to the practicing civil engineers. Hence this paper aims to study the design and analysis of different types of truss geometries used in a factory shed using commercial well-established software package STAAD Pro V8i. Various types of truss geometries like Pratt truss, Howe truss, Fink truss are considered in the present investigations with different aspect ratios. Besides these truss geometries, portal frame geometry is also taken up here to examine the best suitable geometries which are to be used as roofing units in industrial purposes. The results obtained from the present numerical experimentations are studied meticulously to extract a set of meaningful conclusions regarding the design and optimum choice of steel truss geometry which is used as roofing units in industrial sheds. The practical design guidelines along with the best choice of roof trusses are highlighted in the results and discussions section of this paper.

Impact of nickel–titanium super-elastic material properties on the mechanical performance of self-expandable transcatheter aortic valves

Self-expandable transcatheter aortic valves (TAVs) elastically resume their initial shape when implanted without the need for balloon inflation by virtue of the nickel–titanium (NiTi) frame super-elastic properties. Experimental findings suggest that NiTi mechanical properties can vary markedly because of a strong dependence on the chemical composition and processing operations. In this context, this study presents a computational framework to investigate the impact of the NiTi super-elastic material properties on the TAV mechanical performance. Finite element (FE) analyses of TAV implantation were performed considering two different TAV frames and three idealized aortic root anatomies, evaluating the device mechanical response in terms of pullout force magnitude exerted by the TAV frame and peak maximum principal stress within the aortic root. The widely adopted NiTi constitute model by Auricchio and Taylor (1997) was used. A multi-parametric sensitivity analysis and a multi-objective optimization of the TAV mechanical performance were conducted in relation to the parameters of the NiTi constitutive model. The results highlighted that: five NiTi material model parameters (EA, σtLS, σtUS, σtUE and σcLS) are significantly correlated with the FE outputs; the TAV frame geometry and aortic root anatomy have a marginal effect on the level of influence of each NiTi material parameter; NiTi alloy candidates with pareto-optimal characteristics in terms of TAV mechanical performance can be successfully identified. In conclusion, the proposed computational framework supports the TAV design phase, providing information on the relationship between the super-elastic behavior of the supplied NiTi alloys and the device mechanical response.