Search Results (195)

Shoulder-assisted heating friction plug welding (SAH-FPW) experiments were conducted to repair keyhole-like volumetric defects in 6082-T6 aluminum alloy, employing a novel concave backing hole technique on a flat backing plate. This approach yielded well-formed plug welded joints without significant macroscopic defects. Notably, the joints exhibited no thinning on the top surface while forming a reinforcing boss structure within the concave backing hole on the backside, resulting in a slight increase in the overall load-bearing thickness. The introduction of the concave backing hole led to distinct microstructural zones compared to joints welded without it. The resulting joint microstructure comprised five regions: the nugget zone, a recrystallized zone, a shoulder-affected zone, the thermo-mechanically affected zone, and the heat-affected zone. Significantly, this process eliminated the poorly consolidated ‘filling zone’ often associated with conventional plug repairs. The microhardness across the joints was generally slightly higher than that of the base metal (BM), with the concave backing hole technique having minimal influence on overall hardness values or their distribution. However, under identical welding parameters, joints produced using the concave backing hole consistently demonstrated higher tensile strength than those without. The joints displayed pronounced ductile fracture characteristics. A maximum ultimate tensile strength of 278.10 MPa, equivalent to 89.71% of the BM strength, was achieved with an elongation at fracture of 9.02%. Analysis of the grain structure revealed that adjacent grain misorientation angle distributions deviated from a random distribution, indicating dynamic recrystallization. The nugget zone (NZ) possessed a higher fraction of high-angle grain boundaries (HAGBs) compared to the RZ and TMAZ. These findings indicate that during the SAH-FPW process, the use of a concave backing hole ultimately enhances structural integrity and mechanical performance. Full article

The contact characteristics of radial tires are crucial for optimizing stress distribution, deformation, and wear. The non-uniform contact stress behavior induced by complex tread patterns remains under-explored in existing tire mechanics research. Taking the 205/50R17 radial tire as a representative case, a reverse modeling approach was employed to develop an accurate finite element model for tires incorporating intricate tread pattern features. The fidelity of the proposed tire simulation model was confirmed utilizing high-precision contour profiling techniques. The impact of diverse usage conditions and design parameters on the tire outer profile and ground contact characteristics under static and free-rolling states was analyzed. Experimental observations demonstrate that the increased inflation pressure leads to a proportional decrease in contact area. Under incremental vertical loading, the contact patch develops progressively into a saddle-shaped geometry featuring elevated shoulder regions and a recessed central zone. Increasing the belt angle compromises its hoop-stiffening function, thereby inducing elliptical contact patch geometry. Larger design diameters compromise contact length symmetry in shoulder regions. Variation in shoulder thickness at 85% of the tread width results in a significant difference in contact length between the left and right tread blocks in the rolling state. This work enables refinement strategies for both tread configurations and tire dimensional designs in industrial applications. Full article

Background: Ferrous metals are used extensively in the manufacturing of plates, pins, Kirschner wires (K-wires), and screws, and in the performance of partial and total joint replacement surgeries for the shoulder, elbow, and wrist joints. The primary surgical procedures commonly performed are hip and knee replacement surgeries. Metals possess a combination of high modulus, yield point, and ductility, rendering them well suited for load-bearing applications, as they can withstand significant loads without experiencing substantial deformations or permanent alterations in their dimensions. Application of metals and alloys is of prime importance in orthopedics as they lead the way to overcoming many issues encountered in implant use. In some instances, pure metals are used, but alloys consisting of two or more elements typically exhibit greater material characteristics, including corrosion resistance as well as toughness. The first item to address when selecting a metallic implant material is its biocompatibility. In this regard, three classes of materials are also commonly known as biomedical metals—316L stainless steel, pure titanium, and titanium alloys. Objective: The aim of this work is to create a model describing the material behavior and then simulate the metals under a load of 2300 N, which is equivalent to plastic loading. Methods: Under ten different case studies, a sub-routine was developed to combine the material characteristics of titanium and 316L stainless steel with the software. Results: The outcomes of the research were then investigated. A femur model was created using ANSYS software, and two materials, stainless steel and titanium, were used. The model was then exposed to a force of 2300 N. Full article

Friction Stir Welding (FSW) is widely used for high-strength aluminum alloys due to its solid-state bonding, which ensures superior weld quality and service stability. However, thermo-mechanical interactions during welding can induce complex residual stress distributions, compromising joint integrity. Previous studies have primarily focused on thermal load-driven stress evolution, often neglecting mechanical factors such as the shear force generated by the stirring pin. This study develops a three-dimensional thermo-mechanical coupled finite element model based on a moving heat source. The model incorporates axial pressure from the tool shoulder and torque-derived shear force from the stirring pin. A hybrid surface–volumetric heat source is applied to represent frictional heating, and realistic mechanical boundary conditions are introduced to reflect actual welding conditions. Simulations on AA6061-T6 aluminum alloy show that under stable welding, the peak temperature in the weld zone reaches approximately 453 °C. Residual stress analysis indicates a longitudinal tensile peak of ~170 MPa under thermal loading alone, which reduces to ~150 MPa when mechanical loads are included, forming a characteristic M-shaped distribution. Further comparison with a Coupled Eulerian–Lagrangian (CEL) model reveals stress asymmetry, with higher tensile stress on the advancing side. This is primarily attributed to the directional shear force, which promotes greater plastic deformation on the advancing side than on the retreating side. The consistency between the proposed model and CEL results confirms its validity. This study provides a reliable framework for residual stress prediction in FSW and supports process parameter optimization. Full article

Extreme rainfall events pose a growing threat to slab track subgrades by triggering mud pumping through fines migration and structural voids. This study introduces two innovations to enhance climate resilience in high-speed railway infrastructure: (i) the Rain Intensity Ponding (RIP) method, which links regional rainfall statistics with axle-pass thresholds to predict mud pumping potential; (ii) an optimized drainage retrofit using permeable shoulders and blind ditches. Physical model tests reveal that mud pumping occurs only when structural gaps, ponding, and cyclic loading coincide. The RIP method correctly identified a 71% exceedance in the critical ponding duration (52 min) on a representative high-speed line in Eastern China, explaining recurrent failures. Parametric analyses show that the proposed drainage retrofit—using shoulder fill with ka > 23 mm/s and blind ditches with kg > 23 mm/s—reduces ponding time by up to 90% under 1-year recurrence storms. This study establishes a physics-based, region-specific strategy for mud pumping mitigation, offering guidance for climate-adaptive slab track design and operation. Full article

Leonardite (LEO), a microbial derived product rich in humic and fulvic acids, has been tested, due to its beneficial properties for health and well-being, as a feed additive, mainly in non-ruminant species. Although there are some reports of LEO supplementation in ruminants fed with high-to medium-forage based diets, there is no information available of the potential effects of LEO in ruminants fed, under sub-tropical climate conditions, with high-energy diets during long-term fattening. For this reason, the objective of the present experiment was to evaluate the effects of LEO levels inclusion in diets for feedlot lambs finished over a long-term period. For this reason, 48 Pelibuey × Katahdin lambs (initial weight = 20.09 ± 3.55 kg) were fed with a high-energy diet (88:12 concentrate to forage ratio) supplemented with LEO (with a minimum of 75% total humic acids) for 130 days as follows: (1) diet without LEO, (2) diet supplemented with 0.20% LEO, (3) diet supplemented with 0.40% LEO, and (4) diet supplemented with 0.60% LEO. For each treatment, Leonardite was incorporated with the mineral premix. Lambs were blocked by weight and housed in 24 pens (2 lambs/pen). Treatment effects were contrasted by orthogonal polynomials. The average climatic conditions that occurred during the experimental period were 31.6 ± 2.4 °C ambient temperature and 42.2 ± 8.1% relative humidity (RH). Those values of ambient temperature and RH represent a temperature humidity index (THI) of 79.07; thus, lambs were finished under high heat load conditions. The inclusion of LEO in diet did not affect dry matter intake (p ≥ 0.25) and average daily gain (p ≥ 0.21); therefore, feed to gain ratio was not affected (p ≥ 0.18). The observed to expected dietary net energy averaged 0.96 and was not affected by LEO inclusion (p ≥ 0.26). The lower efficiency (−4%) of dietary energy utilization is an expected response given the climatic conditions of high ambient heat load presented during fattening. Lambs that were slaughtered at an average weight of 49.15 ± 6.00 kg did not show differences on the variables measured for carcass traits (p ≥ 0.16), shoulder tissue composition (p ≥ 0.59), nor in visceral mass (p ≥ 0.46) by inclusion of LEO. Under the climatic conditions in which this experiment was carried out, LEO supplementation up to 0.60% in diet (equivalent to 0.45% of humic substances) did not did not help to alleviate the extra-energy expenditure used to dissipate the excessive heat and did not change the gained tissue composition of the lambs that were fed with high-energy diets during long-term period under sub-tropical climate conditions. Full article

The vertebral arteries supply blood to the upper spinal cord, brainstem, cerebellum, and posterior part of the brain. These arteries are susceptible to deformation from external factors such as muscular, ligamentous, or bony structures, and any interruption of blood flow may result in vertebrobasilar insufficiency. Among the osseous variants of the cervical spine with potential pathological significance, variations in the number, shape, and size of the foramen transversarium, as well as the presence of bony bridges in the first cervical vertebra, may suggest a predisposition to vertebrobasilar insufficiency. A skeletal sample from the post-Classical cemetery of Corfinio (12th–15th centuries CE; L’Aquila, Italy) was examined. Regarding the morphology of the foramen transversarium, shape variations were identified in 32 of the 108 vertebrae analysed (a prevalence of 29.6%). Particularly noteworthy are three findings in the atlas: (i) a high prevalence of foramen transversarium variants (35.7% for hypoplastic and double foramina), (ii) a coefficient of roundness consistent with a brachymorphic shape, and (iii) a high prevalence of bony bridges —especially ponticulus posticus (52.9%) and retrotransverse foramen (64.7%). All of these findings may indicate a predisposition to vertebrobasilar insufficiency in the individuals studied. It is hypothesised that external mechanical factors, such as carrying heavy loads on the head, neck, and shoulders due to work activities, along with possible genetic influences related to kinship, may have contributed to the high prevalence of these osseous variants. Full article

This study investigated kinetic and physiological load characteristics of Self-Manual Resistance Training (SMRT) lat pulldown. SMRT lat pulldown is a training method in which practitioner generates resistance manually using their own muscular force by gripping a towel with both hands and pulling it outward in a horizontal direction. We analyzed shoulder and elbow joint moments in frontal plane (2D) and muscle activity levels of latissimus dorsi (LD), posterior deltoid (PD), biceps brachii (BB), and triceps brachii (TB) during 10 maximal-effort repetitions of SMRT lat pulldown in 11 resistance-trained men. For comparison, we also measured muscle activity levels during a machine lat pulldown for 10 reps at 75% 1 RM load in same participants. Peak shoulder adduction and elbow extension moments during SMRT lat pulldown were both approximately 70% MVC. Mean rectified EMG of LD was significantly greater during machine lat pulldown than SMRT lat pulldown, whereas that of PD was significantly greater during SMRT than machine version. Mean rectified EMG of TB was high during SMRT, and that of BB was high in machine version. SMRT lat pulldown appears to produce relatively large shoulder adduction and elbow extension moments, increasing PD and TB activation and limiting LD activation. Full article

Background/Objectives: Shoulder injuries are common in overhead sports like tennis due to repetitive unilateral movements that can lead to muscle imbalances. This study aimed to compare muscle recruitment and asymmetry during bilateral shoulder injury prevention exercises (performed with both arms simultaneously) in tennis players versus non-tennis athletes. Methods: Thirty-nine athletes (sixteen tennis players, twenty-three non-tennis athletes) performed two bilateral scapular retraction exercises at 45° and 90° shoulder abduction. Surface electromyography (sEMG) recorded the activation of the middle and lower trapezius. Root Mean Square (RMS), peak RMS and muscle symmetry indices were analyzed. Results: Tennis players showed significantly lower trapezius activation, especially during prone retraction at 90°. Muscle symmetry was slightly higher in tennis players at 90°, but asymmetry increased at 45°, suggesting angle-specific adaptations. Conclusions: Repetitive asymmetric loading in tennis may reduce the activation of scapular stabilizers and contribute to muscular imbalances. Including targeted bilateral exercises in training may help improve scapular muscle function and reduce injury risk in overhead athletes. Full article

Background: Bone elasticity is one of the most important biomechanical parameters of the skeleton. It varies markedly with age, anatomical zone, bone type (cortical or trabecular) and bone marrow status. Methods: This review presents the result of a systematic review and analysis of 495 experimental and analytical papers on the elastic properties of bone tissue. The bone characteristics of hip, shoulder, skull, vertebrae as a function of the factors of age (young and old), sex (male and female), presence/absence of bone marrow and different test methods are examined. The Bayesian neural network (BNN) was used to estimate the uncertainty in some skeletal parameters (age, sex, and body mass index) in predicting bone elastic modulus. Results: It was found that the modulus of elasticity of cortical bone in young people is in the range of 10–30 GPa (depending on the type of bone), and with increasing age, this slightly decreases to 10–25 GPa, while trabecular tissue varies from 0.2 to 5 GPa and reacts more acutely to osteoporosis. Bone marrow, according to several studies, is able to partially increase stiffness under impact loading, but its contribution is minimal under slow deformations. Conclusions: BNN confirmed high variability, supplementing the predictions with confidence intervals and allowed the formation of equations for the calculation of bone tissue elastic modulus for the subsequent selection of the recommended elastic modulus of the finished implant, taking into account the biomechanical characteristics of bone tissue depending on age (young and old), sex (men and women) and anatomical zones of the human skeleton. Full article

Background/Objectives: High-intensity functional training (HIFT) combines multijoint aerobic and resistance exercises. Despite its popularity, limited research has investigated dietary or supplementation strategies to enhance adaptations to HIFT. Hence, this study aimed to examine the effects of egg white and whey protein supplementation during HIFT on physical performance in trained individuals. Methods: Thirty recreationally trained volunteers (20 males, 10 females), aged 23–55, underwent 6 weeks of HIFT (three times/week) while receiving 0.6 g/kg/day of egg white protein, whey protein, or maltodextrin (placebo) in a researcher-blinded, randomized, triple-crossover, and counterbalanced design, with 2 weeks of washout between supplements. Participants followed isoenergetic diets providing 1.0 g/kg/day of protein. Before and after each intervention, VO₂max, the maximal strength (1 RM) and force–velocity relationship of shoulder press, the peak torque and strength endurance of knee extensors and flexors, and the strength endurance of core muscles were measured. The training session load was monitored during each intervention period’s first and last weeks. Data were analyzed by three-way ANOVA (supplement × time × sex), with repeated measures on supplement and time. Results: The duration, energy expenditure, training load score, and cardio load of each training session increased from the beginning to the end of each training period by 2–11% (p < 0.05). The 1 RM of shoulder press and strength endurance of core muscles increased by 3–6% (p < 0.001). Protein supplementation did not affect any of these outcomes. Conclusions: Short-term HIFT improved exercise capacity, upper-body strength, and core endurance. However, increasing protein intake from 1.0 to 1.6 g/kg/day did not further enhance performance. Full article

Anteroinferior shoulder dislocations require surgical intervention when related to critical glenoid bone loss. Scapular spine bone blocks have emerged as a promising alternative to traditional bone augmentation techniques. However, limited data exist on their biomechanical stability when using different suture-based fixation techniques. This study aimed to evaluate primary stability and micromotion after glenoid augmentation using a scapular spine bone block. A total of 31 fresh-frozen human shoulder specimens underwent bone block augmentation. The specimens were randomized into three groups: double-screw fixation (DSF), single-suture bone block cerclage (SSBBC), and double-suture bone block cerclage (DSBBC). Biomechanical testing was conducted using cyclic loading (5000 cycles at 1 Hz) and micromotion was analyzed using an optical 3D measurement system. Statistical analysis showed that medial irreversible displacement was significantly greater in the SSBBC group compared to DSF (p = 0.0386), and no significant differences were found in anterior or inferior irreversible displacements. A significant difference was noted in posterior reversible displacement (p = 0.0035), while no differences were found in inferior or medial reversible displacements. Between DSF and DSBBC, no significant differences were found in irreversible or reversible displacements in any direction. DSBBC provided stability comparable to DSF while offering a viable metal-free alternative. In contrast, SSBBC displayed inferior biomechanical properties, raising concerns about its clinical reliability. Full article

This study aimed to develop new parameters for electromyography (EMG)-based muscle fatigue assessments. First, various combinations of frequency band parameters, including the high-frequency band (HFB: >95 Hz), medium-frequency band (MFB: 46–95 Hz), and low-frequency band (LFB: 15–45 Hz), were assessed to evaluate the fatigue detection performance of individual parameters during isometric muscle contractions. The experimental design involved applying three force levels (30%, 40%, and 50% of the maximum voluntary contraction) and targeting three muscles (upper trapezius, mid-deltoid, and pectoralis major) due to their relevance in shoulder load postures associated with musculoskeletal disorders. A total of 15 participants were involved in this study. The effectiveness of each parameter was assessed through response sensitivity evaluations. Through these evaluations, we confirmed that the previously mentioned individual frequency bands, along with the proposed H/(M + L) frequency band, exhibited high statistical significance and sensitivity under various experimental conditions. Specifically, our findings demonstrated that the H/(M + L) frequency band effectively assessed fatigue levels with high sensitivity and accuracy at low force levels during static isometric contractions. Overall, these results are expected to improve the accuracy of evaluations of individual shoulder muscle fatigue, thereby reducing the risk of shoulder injuries. Full article

Background: The overhead squat movement involves various bodily structures, but the interaction with three-dimensional elastic resistance along the kinetic chain approach requires further understanding. Objectives: We aim to describe and compare scapular and trunk kinematics during an overhead squat under different external resistance conditions. Methods: The three-dimensional shoulder and trunk kinematics of 19 male participants were captured at 15-degree intervals, from 30 to 120 degrees, during the overhead squat movement and analyzed by phase. Results: Scapular posterior tilt was significantly affected by resistance during the UNLOAD phase (p = 0.005, η²ₚ = 0.26). Significant resistance-by-arm elevation interactions were found for scapular upward rotation during the LOAD phase (p = 0.003, η²ₚ = 0.19) and UNLOAD phase (p < 0.001, η²ₚ = 0.24); for scapular internal rotation during both the LOAD (p < 0.001, η²ₚ = 0.37) and UNLOAD phases (p = 0.006, η² = 0.19); and for scapular posterior tilt during both the LOAD (p = 0.003, η²ₚ = 0.26) and the UNLOAD phases (p = 0.006, η²ₚ = 0.21). Trunk flexion/extension showed a significant effect on resistance during the LOAD phase (p = 0.008, η²ₚ = 0.24). Conclusions: Increasing resistance through elastic resistance significantly improves scapular kinematics via the trunk during arm elevation. This underscores the potential of the overhead squat movement as a valuable tool for assessing and treating scapular and trunk dysfunction. Full article

Background/Objectives: The repetitive overhead throwing of baseball stresses the posterior shoulder, including the rotator cuff and capsule, causing stiffness, tissue thickening, and dysfunction. Previous studies on collegiate baseball players have linked these changes to glenohumeral internal rotation deficits, pain, and injuries. However, these studies primarily used acoustic radiation force impulse-based shear wave elastography (SWE), which has limitations, including tissue heating and lack of portability. The acute effects of pitching on infraspinatus (ISP) muscle elasticity in high school pitchers remain unclear. Therefore, this study aimed to evaluate the acute impact of pitching on ISP muscle elasticity in high school baseball pitchers using continuous SWE (C-SWE), which is a safer and more portable method. The relationship between ISP muscle elasticity and pitching load was also examined. Methods: ISP muscle shear wave velocity (SWV), shoulder range of motion, and strength were evaluated in high school baseball pitchers. The participants were categorized into pitching and non-pitching groups based on whether they pitched with full effort on the day of their medical checkup. C-SWE was used to assess ISP muscle elasticity. Results: The pitching group had considerably higher ISP muscle SWV on the dominant side than the non-pitching group (p = 0.008). A significant positive correlation was observed between pitch and ISP muscle SWV (r = 0.467, p = 0.003). Conclusions: Repetitive pitching acutely increases ISP muscle stiffness in high school pitchers, contributing to posterior shoulder tightness. C-SWE is a safe and practical method for assessing tissue elasticity and developing injury prevention strategies. Full article