Search Results (126)

In view of the key problems such as the weakened seismic performance and reduced safety caused by the expansion of openings at bottom floor of masonry structure to meet the functional requirements, a 1:4 scale model of a four-story brick-concrete masonry structure was designed and fabricated. Based on the principle of stiffness equivalence, the partial masonry walls on the side of the bottom floor with large openings were replaced by reinforced concrete walls, and then the pseudo static test was conducted on the model. Through the test, the seismic performance indexes such as the failure mode of each floor, the displacement, hysteresis curve, skeleton curve, and stiffness degradation were obtained. The results showed that the masonry structure can form a close connection with the reinforced concrete walls and then the whole structure exhibits the characteristic of ductility. There is no sudden change in bearing capacity during the loading and the hysteresis curves show that the structure retained a certain energy dissipation capacity during cyclic loading, without sudden loss of bearing capacity. The displacement of the second floor of the structure changes significantly, and its stiffness should thus be paid more attention to during the design process to avoid the formation of a weak floor. The torsional of the masonry structure with large openings at its bottom floor under earthquake can be avoided through the setting of reinforced concrete walls. Full article

Purpose—The flexspline of a harmonic drive constitutes a thin-walled structure with discontinuous gear rim and cylinder configuration, where cyclic stresses induce stress concentration, followed by crack initiation, propagation, and ultimately fatigue failure. This paper reviews advancements in understanding its mechanical properties and fatigue failure mechanisms, aiming to establish a foundation for enhancing operational longevity and guiding future research. Design/Methodology/Approach—The study integrates meshing theory, tooth shape parameters, cylinder stress influencers, and assembly/meshing stress considerations. Theoretical analysis, finite element simulations, and experimental methods are employed to examine stress patterns and fatigue dynamics. Structural parameters and tooth profiles are systematically analyzed for their impact on stress distribution and fatigue life. Findings—Flexspline fatigue failure arises from tooth root stress concentration and cylinder bending stress accumulation. The double-circular-arc tooth profile boosts load capacity by 35% relative to the involute profile, yet demands high-precision machining to preserve meshing performance. Increasing cylinder length mitigates stress concentration but reduces torsional stiffness, while optimized root fillet radii can lower the stress concentration coefficient by 28%. Assembly interference and meshing contact stress accelerate crack initiation, as validated by transient dynamics simulations. Surface strengthening processes (e.g., shot peening) enhance fatigue life by up to 66% through residual compressive stress regulation. Originality/Value—This paper synthesizes multi-scale research on flexspline design, structural optimization, and fatigue mechanisms, proposing novel approaches such as “manufacturability-oriented optimization” and digital twin-driven monitoring. By linking dynamic loads, material properties, and geometric parameters, it bridges theoretical gaps and provides actionable insights for high-precision harmonic drives in robotics and aerospace, advancing reliability in precision transmission systems. Full article

This study presents an experimental characterization and numerical assessment of Cu–Al–Be (CAB) shape memory alloys (SMAs) for potential applications in U-shaped flexural plate (UFP) seismic dampers. Six alloy compositions were evaluated through monotonic tensile tests, ASTM F2516 superelastic protocols, and increasing-amplitude cyclic loading to identify the material exhibiting stable superelastic behavior at room temperature. Among the tested materials, alloy CAB4.76-A showed the most favorable response, with high transformation stress, stable pseudoelastic behavior, and strain recovery exceeding 95% for strains up to 2.5%. A phenomenological finite element model based on the Auricchio constitutive formulation was calibrated using experimental data within the validated strain range (ε ≤ 0.025), showing good agreement in stiffness and stress prediction. The calibrated model was subsequently applied to simulate the response of a UFP device under orthogonal cyclic loading. The results indicate a strong dependence on loading orientation due to coupled bending–torsion effects, with the 90° direction exhibiting significantly higher strength and energy dissipation capacity. Comparison with analytical formulations originally developed for steel UFPs showed that these expressions provide approximate estimates when applied to SMA-based devices. The results suggest that Cu–Al–Be alloys are a promising alternative for UFP applications, while highlighting the importance of loading orientation and the need for future experimental validation at a device scale. Full article

We study cyclic codes over split two-branch finite local rings of the form $R_{\mathcal{l},m}={\mathbb{F}}_p[u,v]/⟨u^{\mathcal{l}},v^m,uv⟩,\mathcal{l},m\ge 2,$ whose radical filtration is governed by two independent nilpotent chains: $u\to u^2\to \cdots \to u^{\mathcal{l}-1}\to 0\mathrm{and}v\to v^2\to \cdots \to v^{m-1}\to 0.$ For the structural part, we develop a residue–torsion framework in which a cyclic code is described by one residue layer together with $\mathcal{l}-1$u-torsion layers and $m-1$v-torsion layers over ${\mathbb{F}}_p$. This yields divisibility constraints, a layered generator description, and an explicit cardinality formula in terms of the associated field cyclic codes. We then specialize to the split cube-zero ring $R=R_{3,3}={\mathbb{F}}_p[u,v]/⟨u^3,v^3,uv⟩,$ a non-chain local ring of type $(2,2)$ with basis $\{1,u,v,u^2,v^2\}$. For this ring, the general theory becomes a five-layer structure consisting of one residue layer, two first torsion layers, and two second torsion layers. Using an ${\mathbb{F}}_p$-linear Gray map adapted to this split radical filtration, we show that, when $gcd(n,p)=1$, the Gray image is linearly equivalent to a direct sum of five cyclic codes over ${\mathbb{F}}_p$, so the dimension is additive across the layers. The minimum distance, however, is not determined by this decomposition alone and requires separate analysis. When $n=p^s$, we derive exact distance formulas by reducing the problem to the five associated repeated-root cyclic codes over ${\mathbb{F}}_p$. For $p=3$ and $n=9$, we compute explicit examples whose Gray images are ternary codes of length 45, illustrating the theory and producing several optimal codes. These results give a structural and metric description of cyclic codes over the split local ring $R_{3,3}$ while placing its algebraic framework in the broader family $R_{\mathcal{l},m}$. Full article

Background: This study evaluated the effects of flattening the side of the bending resistance and torsional resistance of nickel–titanium files through finite element analysis of a novel flattened file and a standard nonflattened file. Methods: For torsion analysis, the tip of the file was fixed at 3 mm, generating a torque of 2.5 N·mm at the handle. For bending analysis of curved root canals (45° and 60°), the handle was kept fixed, a force of 1 N was applied at the tip, and the file was fixed at 3 mm. Results: The standard nonflattened file exhibited better torsional resistance. In contrast, the novel flattened file showed improved flexibility under 45° bending. Under this condition, lower maximum von Mises stress was observed in the flattened design compared with the standard file. At 60° bending, stress distribution varied with loading orientation, and higher stress concentrations were observed in the flattened file under specific bending directions, indicating reduced bending resistance under large deformation conditions. Conclusions: Since lateral flattening may reduce the cyclic resistance of files, caution should be exercised in the clinical use of such files. Full article

This article presents the results of research on electrically assisted forming (EAF) in the process of cyclic oscillatory torsion of CuZn30 brass. Experiments were conducted using pulsed electric current with varying parameters: pulse durations of 0.5, 2.5, and 5 ms, and pulse intervals ranging from 0.5 to 30 ms. Reference data for the electrically assisted torsion tests were obtained from conventional tests performed under identical conditions without current flow. A pronounced thermal effect was observed for specific current parameters. To accurately determine the impact of temperature rise on the deformability of CuZn30 brass during cyclic torsion, the authors conducted additional tests at elevated temperatures—corresponding to the average temperatures recorded during the EAF trials—without current application. In all investigated cases, EAF during cyclic oscillatory torsion led to a flow stress reduction ranging from nearly 8% to almost 25% compared to current-free trials. Furthermore, applying current parameters where the pulse interval exceeded the pulse duration resulted in a significant increase in strain to failure, ranging from nearly 25% up to 110% relative to the reference samples. The study also examined isophase current characteristics (where pulse duration equals pulse interval), which yielded results that clearly deviated from other configurations. The application of isophase pulses triggered a different material response, leading to a degradation of deformability by more than 21%. The presented research and findings may contribute to the further development of novel, energy-efficient, and advanced manufacturing processes in metal forming. Full article

The mechanical characterization of elastomers requires particular attention to multiaxial deformation states, as their service behavior is rarely governed by simple loads. Instead, performance and failure mechanisms are strongly influenced by complex, combined stress states. The present work introduces a compact electromechanical tension–torsion testing machine capable of applying axial and torsional loads both independently and synchronized for multiaxial testing. The system also enables torsional cyclic tests over a wide range of frequencies with efficient stress reversal through a “zero-backlash” actuation solution, while allowing free axial expansion and contraction of the specimen to achieve pure torsion across the full deformation range. The device integrates industrial-grade components within a modular architecture, ensuring reliability, maintainability, and scalability. FE analyses were carried out to optimize the frame design and verify its stiffness under critical load cases. The resulting system provides a versatile and cost-effective solution for complete multiaxial testing and mechanical characterization of elastomers, as well as other materials, expanding current experimental capabilities for academic and industrial research needs. Full article

This study investigates the fatigue behavior of 3D-printed ABS subjected to cyclic torsional loads, with a focus on the effects of infill density and raster angle on torsional fatigue performance. A total of 50 test specimens representing 25 unique combinations of infill density (20%, 40%, 60%, 80%, 100%) and raster angle (25°/−65°, 45°/−45°, 75°/−15°, 0°/90°) were fabricated and tested using the cyclic torsion system. Fatigue failure was defined as a 75% reduction in torsional strength, recorded through cycle-by-cycle torque monitoring. The twist angle was cyclically varied between ±10° at a frequency of 5 Hz until failure occurred. The results indicate that increasing infill density significantly improves fatigue life by reducing internal porosity and enhancing load transfer, with the greatest gains observed at high infill levels (≥80%). Raster angle has a minimal effect at low infill densities but becomes critical at higher densities, where optimized filament orientations substantially extend fatigue life. Intermediate raster angles, particularly 25° and 75°, outperform orthogonal layouts by enabling better stress redistribution and inter-layer load sharing, while a 90° orientation leads to premature failure due to stress concentration and inter-layer debonding. When normalized by mass, specimens with 100% infill and intermediate raster angles achieve the highest fatigue endurance, highlighting the synergistic role of infill density and raster orientation in optimizing the durability and mass efficiency of 3D-printed components under cyclic torsional loading. Full article

Objectives: To provide a mechanism-oriented integration of clinical and biomechanical evidence regarding fixation failure in fifth metatarsal fractures, with particular emphasis on Jones and diaphyseal stress fractures, and to clarify the mechanical determinants that influence construct performance under physiologic gait-related loading. Methods: A narrative, concept-driven review was conducted focusing on experimental biomechanical investigations and clinically relevant outcome studies addressing cyclic shear, bending, torsion, interfragmentary gap behavior, and loading direction. Special attention was given to studies employing advanced experimental models, including three-dimensional printed anatomical constructs combined with digital image correlation (DIC), to evaluate fixation strategies under simulated gait-phase loading conditions. Literature selection was guided by thematic relevance to construct mechanics and clinical fixation outcomes rather than systematic retrieval criteria. Results: Available evidence indicates that fixation constructs relying predominantly on interfragmentary compression demonstrate increased sensitivity to imperfect reduction, interfragmentary gaps, and multidirectional cyclic shear forces, particularly during midstance loading. Experimental models suggest that loading angle and gap size significantly influence stress concentration and failure patterns. Plate-based and hybrid constructs may provide improved resistance to cyclic bending and shear in specific experimental conditions, maintain stability in the presence of small fracture gaps, and distribute mechanical loads more uniformly across the fracture site. These biomechanical characteristics may help explain reported clinical patterns of delayed union, refracture, and hardware failure in high-demand patients or in cases with cortical compromise. Conclusions: Fixation failure in fifth metatarsal fractures appears to result from the interaction between fracture morphology, patient-specific loading demands, and construct biomechanics. Mechanism-based integration of biomechanical findings with clinical context may support individualized surgical decision-making. However, given the heterogeneity of available clinical data and the inherent limitations of experimental models, biomechanical insights should be interpreted as hypothesis-generating and complementary to clinical judgment rather than prescriptive guidance. Full article

Steel girders with corrugated webs are increasingly used in bridge and building structures subjected to cyclic variable loads, where the geometry of the corrugation plays an important role in fatigue performance. This paper investigates the fatigue behaviour and failure mechanisms of full-scale steel girders with sinusoidal corrugated webs subjected to static and cyclic four-point bending. Five simply supported girders were tested: one reference beam under monotonic static loading, two beams under long-term cyclic loading with different load ranges ΔF and numbers of cycles N, and two beams subjected to cyclic loading followed by a static test to failure. The experimental programme focused on the influence of the load range ΔF and the number of cycles N on damage development, stiffness degradation and residual load-bearing capacity, as well as on the interaction between local web instability and global lateral–torsional buckling. The test results show that two main failure mechanisms may occur: (I) local buckling of the corrugated web combined with yielding of the flanges, and (II) a combined mechanism involving local web buckling and lateral–torsional buckling of the girder. For the investigated configurations and within the range of load ranges and numbers of cycles considered, the load range ΔF was found to be the dominant parameter governing fatigue damage, whereas the number of cycles had a secondary influence. The global stiffness of the girders in the elastic range remained almost unchanged until the late stages of loading, and even after pre-fatigue loading, the girders were able to carry a significant portion of their original ultimate load. The results provide experimental data and insight that are relevant for the fatigue assessment and design of steel girders with sinusoidal corrugated webs in bridge and building applications. Full article

Scrap tire-derived geomaterial has been gaining attention recently as an alternative material for improving the ground. This paper presents a fundamental experimental investigation into sand–rubber mixtures using hollow cylinder torsional shear apparatus, with the aim of enhancing our understanding of the integrated effects of rubber content and cyclic stress ratio (CSR) on the liquefaction characteristics of the mixtures. The results show that the incorporation of granular rubber into sand not only reduces excess pore water pressure during cyclic loading but also alters the generation mode of pore water pressure. The liquefaction resistance of the sand–rubber mixture increases significantly when the rubber gravimetric proportion exceeds 10%. The energy dissipation per loading cycle decreases with increasing rubber content, whereas the cumulative dissipative energy exhibits an opposite trend, showing a positive correlation with rubber content. In addition, this rubber-enhanced effect shows CSR dependence; the cumulative energy dissipation significantly diminishes at a high CSR. Therefore, the effect of granular rubber addition to sand on pore water pressure tends to become more pronounced at higher rubber contents. Full article

As a key component in robots, the harmonic drive directly impacts the reliability and lifespan of the whole system. Due to the cyclic inertial loading and installation errors, the harmonic drive possesses unique but complicated vibration features. This study proposes a novel dynamic modeling method for the harmonic drive to unravel its coupled vibration mechanism and frequency distribution characteristics. To represent the gear meshing force between flexspline and circular spline, as well as the contact roller forces of the thin-wall bearing, two contact mechanics models are developed. Actual excitations are modeled by considering installation errors and cyclic inertial loading. A dynamic model considering translational and torsional directions is then established to unravel the coupled vibration of the primary components in the harmonic drive. Through theoretical and simulation analyses, the vibration features of the harmonic drive exhibit almost no meshing frequency components. Experiments under different transmission ratios and input speeds confirm the effectiveness of the proposed dynamic model. The verified theoretical interpretation of vibration features has provided fundamental insights into the dynamic behavior of harmonic drive. Full article

The aim of this study is to investigate the integration of Shape Memory Alloy (SMA) torque tubes into SmallSats’ thermal management systems to passively deploy radiator panels in an autonomous manner. Specific aspects of the investigation are related to material production, thermomechanical characterization, structural integration, and assessment of overall prototype functionalities. Implementation feasibility was evaluated through a 12U CubeSat test case. Starting with NiTi tubes ($50.8\%$ at Ni.) intended for pseudoelastic applications, a combined aging and shape-setting heat treatment process was selected to achieve both SME characteristics and an S-shaped geometric configuration. Comprehensive material characterization was conducted using differential scanning calorimetry (DSC) and mechanical testing to evaluate post-treatment phase transformation temperatures (PTTs) and torsional load response. Experimental results demonstrated the actuator’s capacity to fully recover imposed rotations exceeding $90$° against resisting torques up to 0.1 Nm. Material cyclic stability analysis revealed rapid stabilization after four cycles, with maintained performance through 80 cycles. The experimental validation culminated in benchtop prototype testing, which achieved an $85$° deployment rotation, evidencing the viability of the proposed mechanism. Full article

This paper provides advances in the study of principal $\mathrm{SO}\left(3\right)$-bundles over smooth projective real curves, with applications to robot manipulation orientation. The work introduces a novel specific classification of these bundles, establishing a bijection between isomorphism classes and specific direct sums of cyclic groups. The explicit computation of the cohomology ring $H^{*}(P,\mathbb{Z})$ for a principal $\mathrm{SO}\left(3\right)$-bundle P over a real curve X, revealing its complete structure and torsion subgroups, is a major contribution of the paper. This paper further demonstrates that the equivariant cohomology $H_{\mathrm{SO}\left(3\right)}^{*}(P,\mathbb{Z})$ is isomorphic to $H^{*}(X,\mathbb{Z})\otimes H^{*}(B\mathrm{SO}\left(3\right),\mathbb{Z})$, with implications for connections and curvature. These results are then applied to robotics, showing that for manipulators with revolute joints, a principal $\mathrm{SO}\left(3\right)$-bundle encoding end-effector orientation whose second Stiefel–Whitney class characterizes the obstruction to continuous orientation control exists. For robots with spherical wrists, the configuration space factors as a product, allowing for the decomposition of connections with control implications. Finally, a mechanical connection is constructed that minimizes kinetic energy, with its curvature identifying configurations where small perturbations cause large orientation changes. Full article

Utilizing a novel approach that concomitantly assessed cyclic fatigue and torsional overloading, we aimed to establish the maximum number of artificial canals that can be prepared by Hyflex EDM and NeoNiTi A1 operated at two different speeds until their separation. Forty-eight files were equally divided into four groups: (A) Hyflex EDM operated at 300 rotations per minute (RPM) and (B) at 500 RPM, and (C) NeoNiTi A1 at 300 RPM and (D) at 500 RPM. Files were used to completely shape 10 sequential artificial canals unless file separation occurred. Maximum number of canals prepared was noted and averaged. Fractography was conducted to determine the mechanism of file separation. Hyflex EDM prepared significantly more canals compared to NeoNiTi A1 (p = 0.008). When operated at 300 RPM, Hyflex EDM prepared significantly more canals compared to NeoNiTi A1 (p = 0.028), whereas no significant difference was observed when they were operated at 500 RPM (p = 0.116). One NeoNiTi file broke due to cyclic fatigue while another one separated due to torsional overloading. Hyflex EDM files showed signs of both mechanisms. Within the limitations of this study, one file safely prepared four to five canals before its fracture. There was a trend towards fewer prepared canals as the RPM increased. Full article