Joint Rotation Research Articles (Page 1)

ABSTRACT Seismic faulting can cause severe damage to buried ductile iron (DI) pipelines. Existing studies consider the scenarios of fault‐pipe crossing at a pipe joint or the middle of a pipe segment only. Moreover, there is a lack of analytical assessment methods for maximum joint rotation under normal faults. In this study, full‐scale experiments are conducted to analyse the influence of fault‐pipe crossing position on the behaviour of DI pipelines under 90° normal faulting. New tape optical fibres and linear potentiometers under an improved instrumentation scheme are employed to monitor the pipe strains and joint kinematics. The results indicate that as the fault‐pipe crossing position, rp , shifts from the joint ( rp = 0) to three‐quarters of the pipe barrel length ( rp = 0.75), the pipe‐soil interaction mechanism changes from the uplift capacity‐controlled mode to the bearing capacity‐controlled mode. In terms of joint kinematics (maximum joint rotation and axial displacement) and maximum bending strain, the most unfavourable fault‐pipe crossing positions are rp = 0∼0.25 and 0.75, respectively. The joint rotation near the fault trace should be prioritized to avoid the loss of DI pipe serviceability. An analytical model that enables safe evaluation of peak joint rotation under normal faulting is proposed.

Adhesively bonded joints between galvanized steel and carbon fiber-reinforced polymers (CFRPs) are critical in modern lightweight structures, but their performance is often limited by failure at the zinc–adhesive interface. This study presents a parametric analysis to investigate the influence of key geometric parameters on interfacial cracking in a single-lap joint (SLJ) configuration, employing a simplified analytical methodology based on Interface Fracture Mechanics (IFM). The model combines the Goland–Reissner approach for estimating crack-tip loads with highly simplified, constant shape functions to calculate the energy release rate (Gint) and phase angle (ψ). To provide a practical reference, experimental data from shear tests on S350 GD galvanized steel bonded to CFRP were used to estimate the range of interfacial fracture toughness for this material system. The parametric results demonstrate that, for a constant load, increasing the overlap length reduces the crack driving force (Gint), while increasing the adhesive thickness raises it. Crucially, the model indicates that a thicker adhesive layer shifts the fracture mode from shear- to opening-dominated, a trend consistent with the established mechanics of SLJs, where increased joint rotation amplifies peel stresses. The study concludes that while the use of constant shape functions limits the model’s quantitative accuracy, this simplified analytical framework effectively captures the qualitative influence of key geometric parameters on the joint’s fracture behavior. It serves as a valuable and resource-efficient tool for preliminary design explorations and for interpreting experimentally observed failure trends in galvanized steel–CFRP joints.

Study of torque transmission and clearance of a rotational flexible joint implemented in a planar mechanism

Knee contact force alone is insufficient to validate joint mechanics in musculoskeletal models.

A predictive method for estimating the glenohumeral joint center from palpable landmarks using multiple linear regression trained on CT data.

Cardan sequence selection influences subtalar and talonavicular joint kinematics.

This study systematically analyzes the dynamic behavior of bearing tilt-misalignment coupling faults in rotary joints and establishes a high-fidelity nonlinear dynamic model for a dual-support bearing–rotor system. By integrating Hertzian contact theory, the nonlinear contact forces induced by the tilt of the inner/outer rings and axial misalignment are considered, and expressions for bearing forces incorporating time-varying stiffness and radial clearance are derived. The system’s vibration response is solved using the Newmark-β numerical integration method. This study reveals the influence of tilt angle and misalignment magnitude on contact forces, vibration patterns, and fault characteristic frequencies, demonstrating that the system exhibits multi-frequency harmonic characteristics under misalignment conditions, with vibration amplitudes increasing nonlinearly with the degree of misalignment. Furthermore, dynamic models for single-point faults (inner/outer ring) and composite faults are constructed, and Gaussian filtering technology is employed to simulate defect surface roughness, analyzing the modulation effects of faults on spectral characteristics. Experimental validation confirms that the theoretical model effectively captures actual vibration features, providing a theoretical foundation for health monitoring and intelligent diagnosis of rotary joints.

Turnout, a large external rotation of the lower limb joints, is a key element of jumps and of other postures in classical ballet technique. Correct transverse-plane alignment of body segments in turnout is critical to reduce technical errors and injury risk. Although many studies have examined turnout in static positions, there is a need for a deeper understanding of this element dynamically, particularly during uni- and bipodal jumps with body displacements in fifth position. Such insights could help improve the technique and the training protocols. This study investigated the external rotations of the hip, knee, and ankle in turnout during three phases (preparation, flight, and landing) of two jumps with displacement performed in the fifth position: one unipodal, the Sissone Ouvert, and one bipodal, the Assemblé Dessus. Twenty-eight pre-professional ballet dancers were analyzed with 10.9 ± 3.2 years of ballet practice, 12.4 ± 2.7 hours of weekly training and a passive hip external rotation (static turnout) of 53.9 ± 10.1 deg. The dancers were instrumented with 16 skin-markers according to the Plug-in-Gait protocol and an eight-camera motion analysis system recorded lower limb kinematics in the transverse plane of the self-selected leg. Temporal profiles of joint angles were time normalized and the external rotation peak of hip, ankle, and knee were compared across phases and joints by repeated measures analysis of variance (ANOVAs) and Newman–Keuls post hoc (p < 0.05). The external rotation peak of the ankle, knee, and hip differed across phases (p < 0.001) for both jumps. In the Assemblé, hip and knee rotation peaks exhibited a similar behavior between the preparation and flight, while the ankle reached its highest peak at landing (p = 0.022). In the Sissone’s preparation, knee and ankle peaks showed significantly greater rotation compared to hip (p < 0.001), whereas in the flight, the hip exhibited the highest rotation compared to the other joints (p < 0.001). The external rotation peak occurred in different instants in each phase and with respect to normalized jump duration (p < 0.001). In conclusion, the knee joint has little contribution to external rotations in the turnout; conversely, the ankle and the hip joints appear to be pivotal in maintaining the turnout respectively in the Assemblé and in the Sissone, the latter mainly during the flight phase.

To investigate effectiveness of arthroscopic superior capsular reconstruction using a "sandwich" patch combined with platelet-rich plasma (PRP) injection in treating massive irreparable rotator cuff tears. A clinical data of 15 patients (15 sides) with massive irreparable rotator cuff tears, who were admitted between September 2020 and March 2023 and met the selective criteria, was retrospectively analyzed. There were 8 males and 7 females with an average age of 62.1 years (range, 40-80 years). The rotator cuff tears were caused by trauma in 7 cases and other reasons in 8 cases. The disease duration ranged from 5 to 25 months, with an average of 17.7 months. According to the Hamada grading, the rotator cuff tears were rated as grade 1 in 2 cases, grade 2 in 8 cases, and grade 3 in 5 cases. All patients were underwent superior capsular reconstruction using the "sandwich" patches (autologous fascia lata+polypropylene patch+autologous fascia lata) combined with PRP injection on patches. The pre- and post-operative active range of motion (ROM) of the shoulder joint, American Shoulder and Elbow Surgeons (ASES) score, Constant-Murley score, University of California, Los Angeles Shoulder Rating Scale (UCLA) score, and visual analogue scale (VAS) score were recorded. The subacromial space was measured on the imaging and rotator cuff integrity was assessed based on Sugaya grading. All incisions healed by first intention after operation without any complications such as infection. All patients were followed up 12-18 months (mean, 14.4 months). At last follow-up, the active ROMs of flexion, abduction, external rotation, internal rotation of the shoulder joint, subacromial space, ASES score, Constant-Murley score, and UCLA score increased, and VAS score decreased, showing significant differences when compared with preoperative values ( P<0.05). There was no significant difference in the Sugaya grading between last follow-up and immediately after operation ( P>0.05). For massive irreparable rotator cuff tears, arthroscopic superior capsular reconstruction using the "sandwich" patches combined with PRP injection can restore stability of the shoulder joint, relieve pain, promote rotator cuff healing, and achieve good short-term effectiveness.

BackgroundThe transition in arthroscopic rotator cuff repair from single-row to double-row techniques has highlighted the efficacy of the suture-bridge configuration in providing enhanced biomechanical stability and coverage of the footprint. However, traditional methods often require multiple anchors and complex knot-tying procedures, resulting in prolonged surgical duration and increased costs. This study evaluated a customized suture-bridge approach incorporating a Simplified LassoLoop Suture, utilizing a single medial row anchor and a knotless lateral row anchor, to treat small to medium-sized rotator cuff tears.MethodsA retrospective review was conducted on 132 patients who received treatment at Jingzhou Hospital, Affiliated with Yangtze University, between June 2021 and June 2022. All patients underwent arthroscopic repair utilizing the specified technique. Clinical outcomes were evaluated preoperatively and at the final follow-up using the Visual Analogue Scale (VAS), University of California at Los Angeles (UCLA) shoulder rating scale, and Constant-Murley score.ResultsThe arthroscopic repair was conducted on 132 patients with small to medium Rotator cuff tears using simplified lassoloop suture technology. The procedure involved a single medium-row suture anchor and knotless lateral Row anchor for suture bridge fixation. Patients were followed up for 12–30 months (mean 23.9 ± 1.75 months) with no observed complications such as joint infection, anchor failure, or Rotator cuff re-tear. All surgical incisions healed without complications. Postoperative pain, assessed by the VAS score, decreased significantly from 7.6 ± 0.5 points preoperatively to 1.1 ± 0.3 points. Functional outcomes, evaluated using the UCLA shoulder rating score, improved considerably from 11.4 ± 1.0 before surgery to 33.0 ± 0.7 postoperatively. The constant-Murley score also significantly increased from 56.4 ± 2.4 before surgery to 94.9 ± 1.1 after surgery. Postoperative range of motion significantly improved compared to preoperative levels (p < 0.05).ConclusionsThe Simplified LassoLoop Suture Technique simplifies rotator cuff repair and yielded favorable short-term clinical outcomes for small-to-medium supraspinatus tears while maintaining a streamlined surgical workflow. Although the construct is conceptually intended to capture some features associated with dual-row fixation, our study did not test biomechanical performance, operative time, or cost; these hypotheses warrant validation in comparative and biomechanical studies.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13018-025-06274-1.

Morimoto, E, Matsui, M, Mori, S, Kumakura, T, Konishi, M, Michinobu, R, Fukuda, T, Takemura, M, and Kosaki, K. Comparison of brachial artery endothelial function in the dominant arm between male college baseball pitchers and fielders. J Strength Cond Res XX(X): 000-000, 2025-Although structural changes caused by exercise-induced vascular adaptation have been reported in baseball players, current evidence in the literature concerning vascular function remains limited. This cross-sectional study aimed to determine whether vascular endothelial function in the brachial artery of the dominant arm differed between university baseball pitchers vs. fielders. Ninety baseball players participated in this study. Brachial artery diameter and vasodilator function were measured in the supine position for each subject using an ultrasound imaging system. Shoulder joint range of motion and muscle strength were measured in supine and prone positions. Compared with the fielders, the pitchers had a decreased mean flow-mediated dilation (FMD) values (7.5% ± 2.5 vs. 10.6% ± 4.0%, p < 0.001) but significantly higher values for range of motion regarding external rotation (ER) of the shoulder joint (119.8 ± 8.5° vs. 115.7 ± 7.8°, p = 0.035), ER muscle strength (7.6 ± 2.2 N vs. 6.2 ± 2.0 N, p = 0.009), and baseline brachial artery diameter (4.2 ± 0.4 mm vs. 4.0 ± 0.4 mm, p = 0.010). Simple correlation analysis showed a negative correlation among FMD values, shoulder joint internal rotation strength, and ER range of motion. These findings indicate that functional exercise-induced vascular adaptations occur in the brachial artery of pitchers, indicating a possible role for position-specific demands in vascular remodeling.

Wireless Communication With Flexible Reflector: Joint Placement and Rotation Optimization for Coverage Enhancement

Unlocking complex motion in one DoF higher pairs: Concept, constraint, and form closure for varying instantaneous center of rotation (VICR) joints

Excessive axial heat transfer through the shaft of high-speed rotary systems exposed to hot fluids can cause bearing overheating, lubricant degradation, thermal expansion-induced interference, and premature failure. This study introduces a passive thermal insulation strategy by incorporating an internal air gap within the shaft to disrupt the conduction path. Two rotary joint configurations—a conventional solid shaft and a modified shaft with an air gap—were evaluated under identical conditions using steady-state CFD simulations in ANSYS Fluent. The air-gap design lowered the peak bearing temperature by approximately 55%, a reduction attributed to increased thermal resistance and natural convection within the gap. A one-dimensional thermal resistance model further validated these findings, showing strong agreement with the CFD predictions. These results demonstrate that bearing overheating can be effectively mitigated without the need for surface coatings or external cooling systems, highlighting a simple yet robust design alternative for thermal management in next-generation high-temperature, high-speed rotary machinery.

ObjectiveWalking in a straight line is considered the simplest form of locomotion for healthy individuals. However, in daily life, the ability to walk along curved paths is essential for tasks such as avoiding obstacles and turning corners. Evaluating gait patterns that involve directional changes along curved trajectories offers a more ecologically valid assessment of functional mobility, thereby contributing to the development of rehabilitation strategies that are better aligned with daily living activities. The present study aimed to investigate differences in knee joint rotational angles between straight and curved walking in older adults, using the point cluster technique. Furthermore, the study sought to determine whether distinct knee rotational patterns exist between gentle and sharp curved walking, both categorized under curved walking.MethodsA total of 40 community-dwelling older adults participated in the study. Each participant performed one trial of straight walking, gentle curve walking (with a curvature radius of 2 meters), and sharp curve walking (with a curvature radius of 1 meter). During each walking condition, reflective markers attached to the body were recorded at a sampling frequency of 100 Hz. From the recorded trajectories of the reflective markers, knee joint angles for flexion-extension, abduction-adduction, and internal-external rotation were calculated.ResultsThe maximum flexion angle was 45.3 ± 10.1° during straight walking, 19.1±9.8° during gentle curve walking, and 23.5 ± 11.7° during sharp curve walking, with a significant difference observed by ANOVA (p < 0.01). Additionally, post hoc multiple comparisons showed significant differences between straight walking and gentle curve walking (p < 0.01), straight walking and sharp curve walking (p<0.01), and gentle curve walking and sharp curve walking (p < 0.05).The maximum external rotation angle was 8.4 ± 7.17° during straight walking, −2.3 ± 7.6° during gentle curve walking, and −5.8 ± 8.2° during sharp curve walking, with a difference observed by ANOVA (p < 0.05). Additionally, post hoc multiple comparisons showed significant differences between straight walking and gentle curve walking (p < 0.05).ConclusionDuring walking along a curved path, individuals adopt a gait strategy that involves internally rotating the knee joint prior to entering the curve. The internal rotation angle of the knee joint during the early stance phase was greater in sharp curve walking than in gentle curve walking, indicating that a smaller curvature radius requires a larger internal rotation angle. These findings suggest that curved walking demands a greater range of knee joint rotation compared to straight walking.

Calculation of a force effect from muscle action to a quaternion-based musculoskeletal model.

Ex vivo robotic measurement of the acute biomechanical impact of anterior cruciate ligament rupture in rats.

Three-dimensional printing has enabled the production of complex parts that are difficult to create with conventional manufacturing methods. Its additive nature has made it possible to create interconnected (assembled) parts in a single manufacturing step. This requires the development of new ways of designing, manufacturing, and testing mechanisms that do not require assembly after their creation, called non-assembly mechanisms. An approach is proposed for the design and experimental study of the properties of rotational joints created already assembled using FFF technology for 3D printing. The advantages and disadvantages of different 3D printing methods that can be used to obtain such assemblies are discussed. Basic principles for the design of assembled rotational joints, built without support structures, are introduced. Two examples of their application in creating functional robot models are presented. The features during production, and the advantages and disadvantages of the models are discussed. Models of directly assembled rotational joints with different clearances are studied, and an experiment is conducted based on measuring the magnitude of the current during the rotation of a link. This provides indirect results for the rolling resistance, on the basis of which the qualities of the joint are judged. The results from the experiments show that rotational joints with a diameter d = 10 [mm], created using FFF technology and PLA material, have the lowest resistance at a clearance in the range t = 0.15–0.25 [mm].

Integral abutment bridges (IABs) are increasingly adopted in transportation infrastructure due to their durability, reduced maintenance needs, and cost-effectiveness compared to conventional bridges. However, their reliable performance under live loads is strongly influenced by the nonlinear soil–structure interaction (SSI) at the pile–abutment joint, which remains challenging to quantify using conventional analysis methods. This study develops simplified spring-based models to capture the SSI behavior of pile–abutment joints in short-span IABs. Predictive equations for joint rotation, deflection, moment, and shear are formulated using Linear Regression (LR) and Response Surface Methodology (RSM). Unlike prior studies relying solely on FEM or traditional p–y curves, the novelty of this work lies in deriving regression-based spring constants calibrated against FEM analyses, which can be directly implemented in standard structural software. This approach significantly reduces computational demands while maintaining predictive accuracy, enabling efficient assessment of pile contributions and global bridge response. Validation against finite element method (FEM) results confirms the reliability of the simplified models, with RSM outperforming LR in representing nonlinear parameter interactions.

BackgroundThe ankle joint angle, typically measured between the tibia and metatarsus, shows only a small range of movement during the stance phase and remains relatively constant within species, but varies across taxa. This variation influences traits such as stride length, posture, and locomotor function. While joint angles are readily observable in living animals, they cannot be directly measured in extinct species, for which only skeletal remains are available. Therefore, estimating ankle joint posture from skeletal geometry is important for reconstructing locomotion in both extant and extinct mammals. In this study, we propose a mechanical model of the ankle extensor apparatus to estimate ankle joint angle from bones and test whether the muscle-lever system aligns consistently with skeletal features across taxa.MethodsWe developed a simplified mechanical model of the ankle extensor apparatus to calculate ankle extensor moment arm defined as the perpendicular distance from the ankle joint center to the muscle force line of action, which was assumed to be parallel to the tibia. To verify the Achilles tendon runs parallel to the tibia across taxa, dissections were performed on cadavers of 24 species in seven orders. We compared observed angle (θobs) from 26 species of zoo-kept terrestrial mammals, covering various body mass and locomotor modes, with estimated angle (θest) from skeletal specimens of the same species. θobswas the mean tibia–metatarsus angle during the stance phase, recorded laterally with a high-speed camera. θestwas measured on reassembled skeletal specimens as the ankle joint angle that maximized the extensor moment arm in the model. Phylogenetic comparative methods, including phylogenetic ANOVA and PGLS, were applied to analyze relationships among θobs, θest, body mass, and locomotor mode based on a time-calibrated phylogeny.ResultsDissections confirmed the Achilles tendon runs nearly parallel to the tibia across species. Stance phase ankle joint rotations were small. Therefore, θobs could be considered as representative for each species. Over 85% of the studied species maintained their ankle joint angle at which the mechanical advantage of the calcaneal lever was greater than 0.9. No significant differences in the mechanical advantage of the calcaneal lever were found among locomotor modes or taxonomic orders. A strong positive correlation was observed between θobs and θest (ρ = 0.70, p < 0.001).ConclusionOur mechanical model could estimate θest from skeletal morphology that closely match θobs during stance phase. Despite interspecific variation of θobs, the mechanical advantage of the calcaneal lever remains within a narrow range, suggesting mechanical optimization of the ankle extensor apparatus across terrestrial mammals. This model informs postural reconstruction in extinct species.