Fatigue Strength Research Articles

Effects of Pediatric Endurance and Limb Strengthening (PEDALS) Program Versus Lower Limb Strength Training in Diplegic Cerebral Palsy

Objective: To evaluate the comparative effects of pediatric endurance and limb strengthening (PEDALS) program versus lower limb strength training in diplegic cerebral palsy(CP). Methodology: It was a Randomized clinical trial and a sample of 24 cerebral palsy (CP) patients was drawn through a consecutive sampling technique. One group of 12 patients received the PEDALS program and other group B of 12 patients received lower limb strength training. Group A PEDALS program was applied for 30 minutes, 3 days/week for 12 weeks, total 36 session and Group B lower limb strength training was applied 6-8rep, 1-3sets for3 days/week for 12 weeks, total 36 session. Outcome was measured with GMFM-88, Six-minute walk test and goniometer pre and post treatment. Results: Mean age for both group were 9.95±2.21. Mean value for total GMFM score for Group A was 64.916±8.129 and mean value for Group B was 65.33±9.92 with p-value > 0.05. Mean value for six minute test for Group A was 199.58±13.55 and for Group B was 195.50±15.71 with p-value >0.05 and ROM for Group Aand Group B p-value>0.05. Conclusion: Result shows that PEDALS program as well as lower limb strength training is effective in improving endurance, gross motor function and ROM in diplegic CP. Keywords: Cerebral palsy, endurance, pediatric, strength, training.

Dynamic behavior of piled jacket offshore wind turbines based on integrated aero-servo-hydro-SSI-OWT model

Jacket foundation is typically the preferred choice for Offshore Wind Turbines (OWTs) erected in water depth varying from 40 m to 80 m. In this paper, an integrated dynamic analysis model is designed to study the coupling between aerodynamics, servodynamics, hydrodynamics, soil-structure interaction for piled jacket OWTs. The performances of the AeroDyn and ServoDyn modules are verified by FAST, showcasing their applicability under deterministic and stochastic environmental conditions. The OWT dynamic responses, especially for t-z modeling, stress-transfer mechanism and structural fatigue damage, are subsequently studied. The overall deformation of the jacket calculated by the nonlinear elastic t-z curve in the API guideline, is overwhelmed by the t-z curve formulated using bounding surface plasticity framework, due to the ignorance of the loading history effect. Accompanied by a “compressed-released-recompressed” stress-transfer process, the downwind tube would experience high stress level, hence necessitating more attention in the ultimate limit state design of piled jacket structure. Otherwise, the upwind tube seems to be more decisive to the fatigue limit state design of piled jacket structure, owing to severe fluctuation in structural stress caused by a “tensed-released-re-tensed” stress-transfer tendency.

LIMITATIONS IN FATIGUE STRENGTH EVALUATION OF THE WEB-FLANGE CONNECTION OF STEEL RUNWAY BEAMS - А REVIEW

This study reviews the current state of research and limitations on the fatigue strength of web-flange connections in steel runway beams for overhead cranes. It evaluates key factors influencing fatigue strength, including stress-strain behavior, notch classifications, and various web-flange configurations (welded, rolled, combined). The research stresses the need for accurate fatigue life assessments, particularly for both new and older structures built with simplified standards. Key findings show the impact of notch classifications and stress interactions due to bending, tensile, and compressive forces. The study aims to improve calculation methods, offering recommendations for refining fatigue verification techniques, and assesses connection configurations' effectiveness in achieving desired fatigue life. The practical implications point to increased steel crane runway beams' durability through better fatigue life prediction and localized stress analysis.

Evaluating the effects of exercise protocols in hospitalized onco-hematological patients: a systematic review.

Physical activity is associated with improved functionality, independence and quality of life in cancer patients undergoing active treatment. Exercises can be prescribed to improve patient outcomes. Evaluate the effects of applied exercise protocols on functional capacity, quality of life, fatigue and muscle strength in hospitalized onco-hematological patients compared to conventional treatment. Systematic literature review carried out in PUBMED, EMBASE and Scopus databases with the following descriptors: Hematological neoplasms AND Exercise Therapy AND Hospitalization, in November 2023. Studies with adult inpatients with hematological neoplasms who performed an exercise protocol in the intervention group were included. After applying the eligibility criteria, 9 articles were included in the review, 7 of which were randomized clinical trials and 6 were carried out on transplant patients. The most commonly assessed outcome was functional capacity, followed by muscle strength and quality of life, and ending with an assessment of fatigue. Studies have shown positive results for patients, especially those that combine resistance and aerobic exercise protocols. An exercise protocol for patients with onco-hematological diseases can improve the outcomes analyzed. Aerobic and resistance exercises should be performed, but more studies are needed to assess the time and doses required for each activity.

Characterization of Inclusion Size Distributions in a Large Forged Shaft Using X‐ray Micro‐Computed Tomography Imaging

The presence of nonmetallic inclusions in steel considerably affects the material's properties. This study investigates these effects by sampling six locations along the radial direction of a large forged shaft to analyze the distribution characteristics of inclusions. Scanning electron microscopy and optical microscopy are used to identify the types and morphologies of the inclusions. X‐ray micro‐computed tomography scanning provides detailed distribution data, including the length, width, equivalent diameter, and shape of the inclusions. This approach allows for a comprehensive understanding of the radial distribution characteristics of inclusions in the forged shaft. The results reveal that both the quantity and size of inclusions in the large forged shaft increase progressively from the edge toward the center. Additionally, the fatigue strength is estimated based on the inclusion distribution at various locations. The prediction shows a relative error exceeding 15%, indicating that the heterogeneity of the components considerably affects their fatigue performance. Finally, a novel method for predicting the maximum inclusion size within the heterogeneous large forged shaft is introduced.

Physical Activity and Fitness Level of Healthcare Workers in a Tertiary Teaching Hospital

Background and Objectives. Physical activity (PA) and fitness level are considered key factors in public health promotion, and as such, healthcare workers (HCW) need to be physically well because they are not only responsible for themselves, but of their clients as well. Therefore, we aim to determine the PA and health-related fitness (HRF) level of HCW in a tertiary hospital, disaggregated to age, sex, work assignments, and job tenure. Methods. A cross-sectional research design was utilized to assess HCW from the administrative, medical, nursing, and paramedical cohorts. ALPHA-FIT Test Battery was used to assess cardiorespiratory fitness, muscular strength, lower extremity power and strength, upper body muscle endurance, balance, and body composition. Results. Our study concurred with the results of previous studies on HCW yielding lower PA levels compared with the general population. We tested 282 participants (administrative: 97; medical: 36; nursing: 55; paramedical: 94), mean age 37.4 years, 64.54% females, 52.13% perceived average health status. Ninety percent of the HCW had PA levels below the World Health Organization’s recommended levels. The ALPHA-FIT mean score per category revealed: one-legged stance, 2.67/3; figure-of-8 run, 2.45/3; shoulder-neck mobility, 4.58/5; modified push-up, 2.05/4; hand-grip strength, 2.5/5; jump and reach, 4/4; dynamic sit-up, 2.62/3; six-minute walk test, 475.38 meters covered. There were no significant differences in PA and HRF levels across cohorts except for modified sit-ups (p<0.001) and figure-of-8 run (p=0.012). The results showed significant inverse correlation between balance and shoulder-neck mobility and age (p<0.001), and modified push ups (p=0.004). Males had significantly higher sit-up scores (p<0.001), one-legged stance scores (p=0.001), and faster figure-of-8 run (p=0.011), while females had better jump and reach scores (p<0.001). Conclusion. Physical activity levels of HCW did not meet the World Health Organization’s recommended PA levels. Healthcare professionals who are expected to be aware of the benefits of PA and HRF have shown low to midfit levels of grip strength, upper extremity endurance, core strength, and cardiorespiratory endurance. Information on PA and HRF may aid in policy making on employee wellness that could highly impact health service delivery.

Comparative Analysis of the Physical, Tactical, Emotional, and Mood Characteristics of Under-13 Soccer Players by Performance Level

Background and Objectives: Soccer is a sport characterized by various unpredictable situations in which physical abilities are associated with athletic performance. There are several capabilities that young soccer players must develop to adapt to the needs of the competition. This study analyzes the physical characteristics, tactical knowledge, emotional intelligence, and mood states of youth soccer players at different competitive levels. Materials and Methods: The sample consisted of 36 male soccer players with an average age of 12.65 ± 0.48 years, weight of 44.92 ± 7.49 kg, and height of 157.2 ± 0.08 cm. A cross-sectional correlational study design was selected. Inferential analysis was conducted via the RV coefficient to assess relationships between groups. Two-sample tests (Student’s t test or the Mann–Whitney U test) were used to assess the distribution of the samples. Standardized mean differences (i.e., Cohen’s d) were calculated as effect sizes. Results: For the yo-yo intermittent endurance test level 1, the Premier category showed higher speed (p = 0.01, d = 0.40) and superior estimated VO2max (p = 0.01, d = −0.91). The statistically significant variables included the hamstring strength exercise of the hamstrings for the angle of rupture (p = 0.04, d = −0.04, d = −0.72), the COD-Timer 5-0-5 for contact time—5-0-5 (ms) (p = 0.04, d = 0.69) and 10 m—5-0-5 (s) (p = 0.02, d = 0.79), tactical knowledge of in-game performance (p = 0.01, d = −1.19), support level (p = 0.01, d = −1.27), decision-making ability (p = 0.01, d = 0.59), melancholy (p = 0.01, d = 0.59), confusion (p = 0.01, d = 0.56), and emotional intelligence (p = 0.04, d = 0.77). The Premier category presented slightly higher averages than did category A. In the assessment of running-based anaerobic sprint test power (p < 0.05, d = 0.83) and mood states (p < 0.05, d = 0.59), players in category A presented higher results. Conclusions: The performance capacity of youth soccer players encompasses a multidimensional complexity that includes physical, tactical, emotional, and psychological aspects, which vary among players of the same age.

Machining Characteristics During Short Hole Drilling of Titanium Alloy Ti10V2Fe3Al

The single-phase titanium ß-alloy Ti10V2Fe3Al (Ti-1023) has been widely used in the aerospace industry due to its unique mechanical properties, which include high fatigue strength and fracture toughness, as well as high corrosion resistance. On the other hand, these unique properties significantly hinder the cutting processes of this material, especially those characterized by a closed machining process area, such as drilling. This paper is devoted to the study of the short hole drilling process of the above-mentioned titanium alloy using direct measurements and numerical modeling. Measurements of the cutting force components in the drilling process and determination of the resultant cutting force and total cutting power were performed. The macro- and microstructure of chips generated during drilling were analyzed, and the dependence of the chip compression ratio and the distance between neighboring segments of serrated chips on cutting speed and drill feed was determined. Experimental studies were supplemented by determining the temperature on the lateral clearance face of the drill’s outer cutting insert in dependence on the cutting modes. For the modeling of the drilling process using the finite element model, the parameters of the triad of component submodels of the numerical model were determined: the machined material model, the model of contact interaction between the tool and the machined material, and the fracture model of the machined material. The determination of these parameters was performed through the DOE sensitivity analysis. The target values for performing this analysis were the total cutting power and the distance between neighboring chip segments. The maximum deviation between the simulated and experimentally determined values of the resulting cutting force is no more than 25%. At the same time, the maximum deviation between the measured values of the temperature on the lateral clearance face of the drill’s outer cutting insert and the corresponding simulated values is 26.1%.

Analytical study on deposits of the aircraft engine piston

Purpose This study aims to provide data references for deposit cleaning, fuel formulation and lubricant formulation. Design/methodology/approach The engine disassembly procedure was carried out based on the IO540 operation manual part number 60297-10-1-7 document. Except for the normal disassembly and assembly of the engine and the measurement of parts, the main test contents included break-in run operation, cylinder pressure test, oil consumption run, pretest calibration run, post-test calibration test and the most critical endurance test. The Lycoming IO-540-V4V5 engine and the customized Hartzell CK319 propeller were selected for the test run. Findings The deposits were mainly composed of C, O, B, Al, Br and Pb, which were mainly sourced from fuel, lubricating oil and body materials. XPS analysis showed that the presence of O determined the richness of the deposit components, giving the deposit structure with organic and inorganic components. Originality/value This work provides certain data support and reference for subsequent aircraft maintenance, fuel formula and lubricating oil formula. The long-term stability and safety of the aircraft run can be ensured through continuous research, improvement and optimizing the operating of the engine. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2024-0300/

Bending moment calibration for rotational bending fatigue testing machine based on strain measurement

Abstract Rotational bending fatigue testing is an important method to evaluate the fatigue of metal materials under cyclic loading. Specifically, the fatigue strength is evaluated through repeated rotational bending under complex loads with the accuracy affected by the bending moment. Here, a method based on strain measurements is proposed for calibrating the bending moment of rotational bending fatigue testing machines. Specifically, the strain of a metal sample under loading with resistance strain gauges was recorded using a strain acquisition system to measure the bending moment. The positions of strain gauges were designed according to the principle of strain measurements to establish a calibration program. Three metal samples of different sizes were tested on two types of rotational bending fatigue testing machines, and the measurement uncertainty was evaluated and verified. The experimental results showed that the proposed method measured and calibrated the bending moment of rotational bending fatigue testing machines rapidly, conveniently, and accurately. The results also provide a practical reference for research and application in related fields.

A correlation study of weak core muscles with hamstring muscles flexibility in young adults

Abstract Background Hamstring, being a two-joint muscle, tends to shorten over time, resulting in tightness, affecting performance in daily activities and is also capable of generating exaggerated posterior pelvic tilt, leading to decreased lumbar lordosis. Weak core muscles have been associated with hamstring tightness, and strengthening the core has been attempted in an effort to relax the hamstring tightness. It is believed that the hamstrings overact and over a period of time tightens, when the core is weak, to compensate for postural stability. Method Thirty-three subjects, both male and females with and without hamstring tightness, were assessed for their core endurance through McGill’s core endurance test battery. It was followed by active knee extension test to determine degree of hamstring tightness on both sides. Correlation between the two variables was statistically analyzed. Results Pearson’s correlation was used to analyze the collected data. A moderate positive but significant correlation (p = 0.02) was found between flexor endurance test and active knee extension (both sides). A weak positive but significant correlation (p = 0.05) was found between extensor endurance test and active knee extension (both sides). Correlation between the right and left lateral bridge with their respective side hamstring flexibility was negative and not significant (p = 0.916 (right lateral torso endurance); p = 0.339 (left lateral torso endurance)). Conclusion Since there is a moderate positive but significant correlation between the flexion torso endurance test and both side hamstring flexibility and a weak positive but significant correlation between extension torso endurance test and both side hamstring flexibility, the core (flexor, extensor, and lateral) should be thought of as a whole unit when strengthening in order to maintain and improve hamstring flexibility.

Identifying Variations in Motor Fitness Components among Upper Primary and Secondary School Male Students

Background. Motor fitness helps students develop academically and socially. The students are more engaged in fitness activities with classmates of similar skills. Therefore, motor fitness programs should address kids’ capacity to increase physical activity. Objectives. The study aimed to ascertain variations in upper primary and secondary school male students with respect to selected motor fitness components, i.e. strength (standing broad jump), speed (50-meter sprint) and endurance (800-meter run). Materials and methods. A total of 150 male students, aged 12 to 16, from five schools in Delhi, India, participated in this study. The students were divided into five groups, each consisting of 30 students from both private and government schools. The study assessed three motor fitness components: strength (measured by the standing broad jump), speed (measured by a 50-meter sprint), and cardiovascular endurance (measured by an 800-meter run). The one-way ANOVA was used to identify significant differences among the groups, with post hoc LSD tests performed for pairwise comparisons. A significance level of p < 0.05 was applied to all analyses. Results. The analysis revealed statistically significant differences among the groups in all three motor fitness components: speed (F(4,145) = 27.07, p < 0.05), strength (F(4,145) = 16.93, p < 0.05), and cardiovascular endurance (F(4,145) = 75.46, p < 0.05). Post hoc analysis using the LSD test further indicated that students in each group differed significantly in strength, speed, and cardiovascular endurance when compared to one another. Conclusions. The study concludes that male students in grades nine and ten demonstrate significantly higher levels of strength, speed, and cardiovascular endurance compared to students in grades six, seven, and eight. Therefore, motor fitness programs targeting these components should be tailored differently for upper primary and secondary school students to address their distinct developmental needs.

Endurance of leg muscle strength and endurance of arm muscle strength to the ability of swimming speed 200 meters breaststroke

The lack of breaststroke swimming ability among athletes has led to a decline in breaststroke swimming performance in the Solok city swimming association. This problem is thought to be related to the low endurance of leg and arm muscles to the swimming speed of 200 meters breaststroke. This correlational study aims to reveal the contribution of leg muscle endurance, arm muscles, and the joint contribution of both to swimming speed 200 meters breaststroke in athletes coaching achievements in the Solok city swimming association. This study involved 25 swimming athletes in Solok city, with total sampling technique. Data on leg muscle strength endurance was measured through the squat jump test, arm muscle strength endurance through the push up test, and swimming speed through the 200 meter breaststroke swimming test. Data were analyzed using simple and multiple correlations with a significant level of α = 0.05, and the contribution was calculated by the formula r² x 100%. The results of data analysis showed that leg muscle strength endurance contributed 74.65%, while arm muscle strength endurance contributed 70.06%. The combination of both contributed 74.99% to the ability of 200 meters breaststroke swimming speed of athletes coaching achievements in swimming associations in Solok city.

Utilization of coal bottom ash in zero-carbon footprint pavement quality geopolymer concrete

Worldwide demand for natural fine aggregates (NFA) in the construction sector has skyrocketed in recent decades, but NFA supply is becoming scarcer. At the same time, thermal power plants are producing massive quantities of coal bottom ash (CBA) which impacts the environment. As per the latest research, CBA can be used as NFA in concrete preparation. This study examines the fresh and mechanical properties, durability characteristics, and fatigue life of pavement quality geopolymer concrete (PQGPC) mixes prepared with the partial addition of CBA as NFA. Results found that after 28 days of curing, the basic properties like workability, compressive and flexural strength with the addition of 30% CBA-based PQGPC (GPC-30) mix are safe as per the requirement of rigid pavements. Furthermore, compared to the PQGPC mix, GPC-30 has a 2% lower endurance limit against fatigue at 2 million cycles at different stress levels of 0.55, 0.60, 0.65, and 0.70, respectively. Even though GPC-30 possesses 19% lower flexural strength than regular PQGPC, the fatigue life is comparable. So, incorporating CBA in the preparation of green PQGPC pavements not only lessens the reliance on NFA but also mitigates the need for landfills.

Fatigue Behavior of Al/Steel Dissimilar Friction Stir Welds and the Effect of Die‐Press Forming

ABSTRACT6016‐T4 aluminum (Al) alloy plate was butt welded to the cold‐rolled steel plate by a friction stir welding (FSW) technique, and the fatigue properties of Al/steel dissimilar welds were investigated. Some dissimilar welds were die‐press formed to the hat shape, and specimens were sampled from the corners of the hat shape, where severe plastic deformation occurred by the die‐press forming. The die‐press‐formed samples had better tensile strengths and hardness than the as‐welded ones because of the work hardening. It indicates that the die‐press forming is applicable for the Al/steel dissimilar welds. However, large voids were formed around the steel fragments dispersed into Al matrix by die‐press forming. Those voids acted as the fatigue crack nucleation sites, thus reducing the fatigue lives of the die‐press‐formed specimens. When the bottom side of the welds experienced tension plastic deformation, the fatigue strength was the lowest.

Contribution of the Self‐Heating Method in the Characterization of the Fatigue Damage of Materials With Defects Resulting From Additive Manufacturing

ABSTRACTThis paper investigates the ability of the self‐heating method to characterize the fatigue behavior of 316L stainless steel produced by Laser Powder Bed Fusion. Nearly dense cylinders are built vertically using various process parameters corresponding to various volumetric energy densities. Fatigue specimens are then machined from these cylinders and polished. Fully reversed tension–compression fatigue tests (R = −1) are conducted. The self‐heating method is used for the estimation of the fatigue limits. These fatigue limits are compared to results obtained from S‐N curves in the high cycle regime. Whatever the set of process parameters, the self‐heating curves show three distinct domains of heat dissipation. Thanks to microstructure analysis, fractographic observations, and correlations with S–N curves, these domains can be closely linked to damage mechanisms associated or not with defects.

Tensile, flexural and fatigue response of lightweight pumice-reinforced magnesium composite: Experimentation followed by an analytical modelling

Abstract Featherweight material to sustain mountainous loads is an extreme contrast. Still, in reality, the automobile and aerospace industries seek very light materials with high specific strength to survive in global competition. This study offers a timely answer to the problems faced by those sectors. Through the use of a stir-assisted squeeze casting method, the current investigation aims to generate a lightweight magnesium composite that is reinforced with porous low-density pumice particles at weight percentages of 5, 10, and 15 per cent. An examination of the density indicates that there is a downward tendency in conjunction with the growing reinforcement. In comparison to the magnesium alloy in its natural state, the Pumice 15 coupon achieves a tensile strength increment of 47%, flexural strength increment of 35% and a 10-times increment in service cycle at fatigue increase. The micromechanics model is implemented to justify the strengthening process in terms of the adhesion between the filler matrix and the interface shear strength. The property plots that were drafted provide evidence that the suggested material is lightweight while exhibiting a significant amount of strength in tensile, flexural and fatigue. Post-fracture surface morphology analysis exhibits distinct tensile, flexural and fatigue patterns.

Fatigue characterization and life prediction of flexible lattice structures based on DLP processes

This study investigated the effects of cell configuration and relative density on the fatigue performance of truss-like lattice structures. Among the lattice structures examined, simple cube cells exhibited the highest fatigue strength across all relative densities. Numerical simulation results indicated that the S-N curves of the structures demonstrated pronounced power-law behavior as the volume fraction changed. The influence of various geometric factors on the power-law model parameters is discussed in detail. The power-law coefficient is influenced by the unit cell configuration and relative density; however, the power-law index is not affected by relative density and depends solely on the unit cell configuration. A fatigue life prediction model based on the Ashby-Gibson model was proposed. Finally, the reliability of the numerical simulation results was experimentally verified, with the predicted results of the model showing good agreement with the test data.

Evaluating the athletics Athletes' Physical Fitness for PON XXI/2024 Qualification

Maluku's achievements can grow when the human resources of the coaches are enhanced to promote professionalism in the development of the science and technology of sports. Thus, the training process is not solely based on experience but on the science of training, which is studied in depth to support the better development of training athletes in the future. This study aims to determine how well Maluku athletic athletes' physical fitness is prepared for the PON XXI/2024 qualification round held in Solo, Central Java. This study used saturation sampling to study all the population samples. The instruments utilized in this study are the VO2 Max test, local muscle endurance test, biomotor ability test, speed and power tests, and local muscular stamina tests. The results revealed that the athletes' physical fitness to face a national event, in this case, the PON XXI/2024 qualification, is still considered medium, and the physiological condition belongs to the category of good based on the running time achievement that is close to the time achieved on the PON XXI qualification. The results of the study indicate that Maluku's athletic athletes have improved. However, the improvement has not surpassed the PB PASI time record. Despite the improvement in performance during training, the athletes had not reached the target to pass into the PON XXI Qualification. Keywords: evaluation, physical fitness, athletes’ achievement.

Assessment of multiaxially loaded safety components with uniaxial stress state in fatigue critical sites caused by design

AbstractThe focus of this study, using results obtained with hollow specimens of the alloy Al 2024 T3 (AlCuMg2 T3) with a one‐sided bore, was to determine if, under multiaxial loading, the fatigue strength in a notch with a uniaxial stress state can simply be assessed without the application of any multiaxial strength hypothesis. In the fatigue critical location, the bore edge, only a superimposition of normal stress components, resulting from axial loading or/and torsion, occurs. In the case of out‐of‐phase loading, the resulting local uniaxial stress is even lower than the stress under in‐phase loading and leads to an increase of fatigue life to crack initiation under the non‐proportional loading, which is not observed in the case of multiaxial stressing/straining of the material itself. As the local stress state in the crack initiation site is uniaxial, the application of a multiaxial strength hypothesis, for the failure criterion of crack initiation (l=0.2 mm), is not necessary. Furthermore, the benefit of non‐homogenous stress distributions, which allow locally higher stresses than the levels given by the Woehler‐line for unnotched specimens, was underlined by considering highly‐stressed, material‐volume‐related support factors.