Academic literature on the topic 'Multi-joint isometric strength testing'
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Journal articles on the topic "Multi-joint isometric strength testing"
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Kenville, Rouven, Tom Maudrich, Dennis Maudrich, Arno Villringer, and Patrick Ragert. "Cerebellar Transcranial Direct Current Stimulation Improves Maximum Isometric Force Production during Isometric Barbell Squats." Brain Sciences 10, no. 4 (April 14, 2020): 235. http://dx.doi.org/10.3390/brainsci10040235.
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Maximum voluntary contraction force (MVC) is an important predictor of athletic performance as well as physical fitness throughout life. Many everyday life activities involve multi-joint or whole-body movements that are determined in part through optimized muscle strength. Transcranial direct current stimulation (tDCS) has been reported to enhance muscle strength parameters in single-joint movements after its application to motor cortical areas, although tDCS effects on maximum isometric voluntary contraction force (MIVC) in compound movements remain to be investigated. Here, we tested whether anodal tDCS and/or sham stimulation over primary motor cortex (M1) and cerebellum (CB) improves MIVC during isometric barbell squats (iBS). Our results provide novel evidence that CB stimulation enhances MIVC during iBS. Although this indicates that parameters relating to muscle strength can be modulated through anodal tDCS of the cerebellum, our results serve as an initial reference point and need to be extended. Therefore, further studies are necessary to expand knowledge in this area of research through the inclusion of different tDCS paradigms, for example investigating dynamic barbell squats, as well as testing other whole-body movements.
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Warneke, Konstantin, Martin Hillebrecht, Klaus Wirth, Stephan Schiemann, and Michael Keiner. "Correlation between Isometric Maximum Strength and One Repetition Maximum in the Calf Muscle in Extended and Bended Knee Joint." IJASS(International Journal of Applied Sports Sciences) 34, no. 1 (June 30, 2022): 61–71. http://dx.doi.org/10.24985/ijass.2022.34.1.61.
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Previous research points out high relevance of maximal strength measurement in the diagnostics of different populations. However, there is inconsistency in procedures of maximum strength measurements. Thus, it must be questioned whether the results from different studies are actually comparable. Due to the aforementioned problems in standardization, the aim of this study was to assess correlations between and reproducibility of isometric and dynamic strength testing. Since there are many studies investigating maximal strength in the calf muscles, this study will examine the plantar flexors. For this purpose, 87 active participants were recruited (m: 52, f: 35, age: 28.3 ± 5.5 years, range 18-38 years, height: 178.3 ± 6.6 cm, weight: 81.5 ± 7.4 kg) who performed maximal isometric strength testing and dynamic 1RM testing in plantar flexion both with extended and bended knee joint. Pearson correlation as well as concordance correlation coefficient (CCC) were determined. In literature, CCC is used to determine reproducibility between two different testing methods. There were correlation coefficients of r = 0.63 – 0.77 and <i>ρ<sub>c</sub></i>=0.62 ‒ 0.77. Results are comparable with correlations between maximal isometric strength and 1-RM in previous studies in different movements. In consideration of CCC, isometric strength testing and 1RM seem to not measure the same parameter, therefore comparison of results measured with different procedures seems difficult. Our results exhibit a high influence of isometric maximal strength on 1RM performance. However, 1RM tests cannot be replaced by isometric strength testing. Care must be taken due to standardization of procedure when comparing results from different studies and, especially, if 1RM testing should be replaced with isometric strength measurement.
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Legg, Hayley S., Jeff Spindor, Reanne Dziendzielowski, Sarah Sharkey, Joel L. Lanovaz, Jonathan P. Farthing, and Cathy M. Arnold. "The reliability and validity of novel clinical strength measures of the upper body in older adults." Hand Therapy 25, no. 4 (September 22, 2020): 130–38. http://dx.doi.org/10.1177/1758998320957373.
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Introduction Research investigating psychometric properties of multi-joint upper body strength assessment tools for older adults is limited. This study aimed to assess the test–retest reliability and concurrent validity of novel clinical strength measures assessing functional concentric and eccentric pushing activities compared to other more traditional upper limb strength measures. Methods Seventeen participants (6 males and 11 females; 71 ± 10 years) were tested two days apart, performing three maximal repetitions of the novel measurements: vertical push-off test and dynamometer-controlled concentric and eccentric single-arm press. Three maximal repetitions of hand-grip dynamometry and isometric hand-held dynamometry for shoulder flexion, shoulder abduction and elbow extension were also collected. Results For all measures, strong test–retest reliability was shown (all ICC > 0.90, p < 0.001), root-mean-squared coefficient of variation percentage: 5–13.6%; standard error of mean: 0.17–1.15 Kg; and minimal detectable change (90%): 2.1–9.9. There were good to high significant correlations between the novel and traditional strength measures (all r > 0.8, p < 0.001). Discussion The push-off test and dynamometer-controlled concentric and eccentric single-arm press are reliable and valid strength measures feasible for testing multi-joint functional upper limb strength assessment in older adults. Higher precision error compared to traditional uni-planar measures warrants caution when completing comparative clinical assessments over time.
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Wang, Xiao Ming, Sheng Zhu, Zhi Hao Zhao, Qi Wei Wang, and Xiao Dong Zhao. "Effect of Micro-Alloyed Treatment for 5183 Welding Wire on Microstructure and Tensile Property of Welded Joint." Applied Mechanics and Materials 633-634 (September 2014): 821–25. http://dx.doi.org/10.4028/www.scientific.net/amm.633-634.821.
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5183 welding wire micro-alloyed using Sc, Zr, Er and automatic MIG welding system applied to weld 7A52 aluminum alloy. Optical microscope and universal tensile testing machine utilized to investigate microstructure and tensile property of welded joint, respectively. The results indicated that welded zone and fused zone was composed of uniform isometric crystal and tiny isometric dendrite crystal when the welded joint was fabricated by using 5183 welding wire micro-alloyed via rare earth element, respectively. Tensile strength and specific elongation of welded zone was improved utmostly when the 5183 welding wire micro-alloyed treatment via single Sc or Zr, respectively. Owing to mirco-alloyed treatment of 5183 welding wire by using Sc, Zr or Er, a large number of Al3Sc, Al3Zr, Al3Er granules had generated in micro-poll, which played heterogeneous nucleation role and refined microstructure of welded zone. Meanwhile, there emerged nanoscaled A13Sc, A13Zr, Al3Er strengthening phase dispersed in welded zone, which had led welded joint to exhibit exclent tensile strength.
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Thompson, Brennan, Morgan Whitson, Eric Sobolewski, and Matt Stock. "Effects of Age, Joint Angle, and Test Modality on Strength Production and Functional Outcomes." International Journal of Sports Medicine 39, no. 02 (November 17, 2017): 124–32. http://dx.doi.org/10.1055/s-0043-121149.
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AbstractThis study investigated the impact of age, knee joint angle, and strength testing modality on lower body maximal and rapid strength production and assessed the transferability of these characteristics to mobility-related function. Twenty young (age=21.9 yrs) and eighteen elderly (71.1 yrs) adults performed single-joint and multiple-joint isometric maximal voluntary contractions at three knee angles. Outcome measures included peak torque (PT), rate of torque development (RTD), jump height, power, 10 and 400 m walk, and timed chair stand. Older adults exhibited greater reductions in RTD for the multiple-joint (45%) than for the single-joint mode (18%). The 10 m walk was best predicted by multiple-joint RTD at 90°, the 400 m walk by jump height, and the chair stand by single-joint PT at 20°. Single-joint strength tests may underestimate age-related rapid strength impairments, likely due to requirements to exert muscular force in excess of one’s body mass in an upright position.
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Van Every, Derrick W., Max Coleman, Daniel L. Plotkin, Hugo Zambrano, Bas Van Hooren, Stian Larsen, Greg Nuckols, Andrew D. Vigotsky, and Brad J. Schoenfeld. "Biomechanical, Anthropometric and Psychological Determinants of Barbell Bench Press Strength." Sports 10, no. 12 (December 5, 2022): 199. http://dx.doi.org/10.3390/sports10120199.
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The purpose of this study was to improve our understanding of the relative contributions of biomechanical, anthropometric, and psychological factors in explaining maximal bench press (BP) strength in a heterogeneous, resistance-trained sample. Eighteen college-aged participants reported to the laboratory for three visits. The first visit consisted of psychometric testing. The second visit assessed participants’ anthropometrics, additional psychometric outcomes, and bench press one repetition maximum (1RM). Participants performed isometric dynamometry testing for horizontal shoulder adduction and elbow extension at a predicted sticking point joint position. Multiple linear regression was used to examine the relationships between the biomechanical, anthropometric, and psychological variables and BP 1RM. Our primary multiple linear regression accounted for 43% of the variance in BP strength (F(3,14) = 5.34, p = 0.01; R2 = 0.53; adjusted R2 = 0.43). The sum of peak isometric net joint moments from the shoulder and elbow had the greatest standardized effect (0.59), followed by lean body mass (0.27) and self-efficacy (0.17). The variance in BP 1RM can be similarly captured (R2 = 0.48) by a single principal component containing anthropometric, biomechanics, and psychological variables. Pearson correlations with BP strength were generally greater among anthropometric and biomechanical variables as compared to psychological variables. These data suggest that BP strength among a heterogeneous, resistance-trained population is explained by multiple factors and is more strongly associated with physical than psychological variables.
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Lee, Yung-Hui, and Yi-Lang Chen. "An Isometric Predictor for Maximum Acceptable Weight of Lift for Chinese Men." Human Factors: The Journal of the Human Factors and Ergonomics Society 38, no. 4 (December 1996): 646–53. http://dx.doi.org/10.1518/001872096778827242.
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The aim of this study was to examine the practicality of the modified isometric strength tests to predict the maximum acceptable weight of lift (MAWL) of Chinese men. The modified strength tests allow the participant to pull on the load cell in front of the body and to apply force in a functional free posture. Both the modified and the standard strength data of each participant were used as predictors for the MAWLs. The prediction models were constructed and evaluated under task conditions of two lifting ranges, two box sizes, and three lifting frequencies. To realize the effect of modifications, testing posture was recorded and the joint angles were calculated. A stepwise multiple regression analysis indicated that modified composite strength (MCS), chest circumference, and acromial height accounted for 86% to 91% of the variance. Because the strength of the upper extremity body was also recruited in the test, the weak upper extremity strength of the Chinese participants would therefore be better reflected. Evidence for the existence of a close match between MAWL and MCS values, as well as the task conditions for its existence, suggest that a simple isometric strength measure is a good predictor for the MAWL.
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Leggett, S. H., J. E. Graves, M. L. Pollock, D. M. Carpenter, D. Foster, B. Holmes, C. Fix, M. Shank, J. Tuccl, and M. Fulton. "115 EFFECT OF ORDER OF MULTIPLE JOINT ANGLE TESTING FOR THE QUANTIFICATION OF ISOMETRIC LUMBAR EXTENSION STRENGTH." Medicine & Science in Sports & Exercise 22, no. 2 (April 1990): S20. http://dx.doi.org/10.1249/00005768-199004000-00115.
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Michaelides, Marcos A., Koulla M. Parpa, and Anthos I. Zacharia. "Assessment of Lower Body and Abdominal Strength in Professional Soccer Players." Journal of Human Kinetics 70, no. 1 (November 30, 2019): 15–23. http://dx.doi.org/10.2478/hukin-2019-0035.
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Abstract The purpose of this study was to evaluate abdominal strength in professional soccer players and compare the findings to their lower body strength. An observational design was used to examine abdominal and lower body strength using two functional performance tests (a lower body isokinetic test and an isometric abdominal test, respectively). One hundred and thirty-two professional male soccer players from Cyprus’s first and second divisions participated in this study. Testing included three and twenty-five maximal concentric flexion and extension repetitions at angle speeds of 60°/s (degrees/second) and 300°/s, respectively. On a separate occasion, participants completed two trials on an isometric device (ABTEST Gen. 3 system) for evaluation of abdominal strength. At both isokinetic speeds of 300°/s and 60°/s, abdominal strength had low to moderate significant correlations (p < .05) with quadriceps and hamstring strength. Coefficients of determination (R2) demonstrated that the variability in isokinetic variables accounted for only 14-16% of the variability of abdominal strength. Abdominal strength appears to be high in professional soccer players, but is not dependent on the sports level and/or a playing position. The results of this study demonstrate that abdominal strength and knee joint strength need to be evaluated separately.
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Kozinc, Žiga, Darjan Smajla, and Nejc Šarabon. "The relationship between lower limb maximal and explosive strength and change of direction ability: Comparison of basketball and tennis players, and long-distance runners." PLOS ONE 16, no. 8 (August 18, 2021): e0256347. http://dx.doi.org/10.1371/journal.pone.0256347.
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Change-of-direction (CoD) ability is an important determinant of athletic performance. Muscle strength is among the most important determinants of CoD ability. However, previous studies investigating the relationship between CoD ability and muscle strength focused mostly on flexor and extensor muscle groups, or used multi-joint exercises, such as jumps, squats or mid-thigh pull. The purpose of the present study was to investigate the relationship between CoD ability and strength of ankle, knee, hip and trunk maximal and explosive strength. The participants (n = 327), consisting of male and female basketball players, tennis players and long-distance runners completed isometric strength assessments and CoD testing (90° and 180° turn tests). The times of both CoD tests were associated with muscle strength (peak torques and the rate of torque development variables), with correlation coefficients being mostly weak to moderate (r = 0.2–0.6). Strength variables explained 33%, 62% and 48% of the variance in the 90° turn task, and 42%, 36% and 59% of the variance in the 180° turn task, in basketball players, long-distance runners and tennis players, respectively. Hip and trunk muscle strength variables were the most prevalent in the regression models, especially hip adduction and abduction strength. Our results suggest that the strength of several lower limb muscles, in particular of the hip abductors and adductors, and trunk muscles, but also hip rotators, extensors and flexors, as well as knee and ankle flexors and extensors should be considered when aiming to improve CoD performance.
Dissertations / Theses on the topic "Multi-joint isometric strength testing"
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Noorkoiv, Marika. "Neuromuscular adaptations of joint angle-specific force change after isometric training." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/531.
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Increases in force production in response to isometric training typically occur at or around the joint angles adopted during the training, but the mechanisms underpinning this have not yet been fully elucidated. This PhD thesis project investigated the mechanisms underpinning joint angle-specific strength changes after isometric training, focussing on muscle region-specific cross-sectional area (CSA), muscle fascicle length (Lf) and muscle activation adaptations. For this, the validity and reliability of a two-dimensional extended-field-of-view ultrasonography (EFOV) method for measuring muscle CSA (Study 1) and Lf (Study 2) were examined. Small standard errors of measurement (SEM) and high intra-class correlations (ICCs) were found for CSA measurements (0.6-1.2% and 0.95-0.99, respectively) at proximal and mid-thigh (30, 40 and 50% of the distance from the superior border of the patella to the medial aspect of anterior superior iliac spine) but not distal sections and CSA measurements were very similar to those obtained using computed tomography scanning. Small SEMs and high ICCs were also obtained for Lf measurements (0.8% and 0.95, respectively), and they were accurate when compared to directly-measured swine muscle fascicles. Nonetheless, because of the time required for EFOV CSA scanning and its unreliability for the distal quadriceps (despite a high ICC, the 95% CI of ICC at 20% section = -0.04-0.99), MRI was used for CSA measurement in the subsequent study.
The third study aimed to examine joint angle-specific neuromuscular adaptations in response to isometric knee extension training at short (SL; !knee = 38.1 ± 3.7°) versus long (LL; !knee = 87.5 ± 6.0°) muscle lengths. Sixteen men trained three times a week for six weeks at a knee angle at which peak muscle force (i.e. quadriceps torque/moment arm) was 80% of the peak force obtained at the optimum joint angle. Clear joint angle specificity was seen in SL (force increased 13.4 ± 2.4% at 40°), which was associated with an increase in VL EMG around the training (40°; 26.4 ± 15.5%) and adjacent (50°; 22.5 ± 14.9%) angles, without a shift in the electrically evoked force-angle relationship or changes in muscle size. In contrast, increases in force in LL occurred at angles further from the training angle and varied between subjects. Also, muscle volume and CSA increased significantly and the changes in CSA of specific muscle regions were correlated with the changes in peak force produced at both 30° and at 100°. This occurred with small changes in vastus lateralis (VL) and rectus femoris (RF) muscle EMG activity and no detectable change in coactivation, thus selective regional muscle hypertrophy was most associated with the direction of shift in the force-length relationship. A small (5.4 ± 1.4%) and similar increase in Lf was found in both groups, which was not associated with angle-specific force changes. The effect of isometric training on the concentric torque-velocity relationship was examined in Study 4 to determine whether the isometric training influenced dynamic force production. Isokinetic torque at seven velocities (30, 60, 90, 120, 180, 240 and 300°"s-1) was assessed at weeks 0, 3 and 6. Torque increased only in LL, and only at slow angular velocities (30 - 120°"s-1). The change in torque correlated well with changes in VL, VM and RF CSA, although there was little relationship with Lf. There was no change in angle of peak isokinetic torque.
These results reveal a different mechanism of joint angle–specific adaptation between training at short versus long muscle lengths; neural adaptations underpinned changes after training at short quadriceps lengths but muscular (hypertrophic) changes predominated after training at long lengths. Importantly, clear angle specificity was only observed after training at the short length, although muscle mass acquisition and improvements in dynamic muscle force production were elicited only after training at longer lengths. Thus, although specificity is reduced, greater functional benefit appears to be derived after training at longer lengths. Further research is required to determine why some individuals improved force production at shorter muscle lengths after training only at longer muscle lengths and whether such ‘nonspecificity’ can be predicted before training.
Books on the topic "Multi-joint isometric strength testing"
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P, Wilmington Robert, and United States. National Aeronautics and Space Administration., eds. Astronaut candidate strength measurement using the Cybex II and the LIDO multi-joint II dynamometers. [Washington, DC: National Aeronautics and Space Administration, 1992.
Find full textConference papers on the topic "Multi-joint isometric strength testing"
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Santos, Wanderson, Vitor Marques, Naiany Silva, Gabriel Siqueira, Raquel Schincaglia, and Carlos Vieira. "HANDGRIP STRENGTH AND ISOMETRIC BILATERAL BENCH PRESS FOR UPPER INTERLIMB STRENGTH ASYMMETRY IN BREAST CANCER WOMEN, WITH OR WITHOUT LYMPHEDEMA." In Abstracts from the Brazilian Breast Cancer Symposium - BBCS 2021. Mastology, 2021. http://dx.doi.org/10.29289/259453942021v31s2058.
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Purpose: The aim of this study is to compare upper interlimb strength asymmetry in breast cancer women (BCW), with or without lymphedema, using the handgrip strength test and the isometric bilateral bench press (IBBP) test. Methodology: Twenty-two BCW (age 52.04±8.62 years) were enrolled in a cross-sectional study, with a single-day testing. Ten participants with self-reported breast cancer – related lymphedema (BCRL) and 12 participants without BCRL were evaluated for the interlimb strength asymmetry. The average of the best three of four attempts of the handgrip strength and the IBBP was used to compare the maximal voluntary isometric contraction of each limb. To calculate the interlimb strength asymmetry, we used the following formula as a percentage: the modulus of left minus right side divided by the average between sides, then multiplied by 100. For the statistical analysis, we used the nonparametric Mann–Whitney U test for the handgrip strength and the independent t-test for IBBP. Results: The handgrip strength in BCW with lymphedema (27.62%±15.5%) showed a higher interlimb strength asymmetry than BCW without lymphedema (12.37%±16.29%; p=0.021). However, there was no difference in IBBP (with lymphedema 8.89%±5.81% versus without lymphedema 9.84%±7.98%, p=0.759). Conclusion: BCW with lymphedema might have higher interlimb strength asymmetry assessed by the handgrip strength test compared with BCW without lymphedema, but not in a multi-compound movement such as IBBP. More studies are necessary to confirm our findings.
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Mustafa, Irfan, and Tsz-Ho Kwok. "Development of Intertwined Infills to Improve Multi-Material Interfacial Bond Strength." In ASME 2021 16th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/msec2021-63965.
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Abstract Recently the availability of various materials and ongoing research in developing advanced systems for multi-material additive manufacturing (MMAM) have opened doors for innovation in functional products. One major concern of MMAM is the strength at the interface between materials. This paper hypothesizes overlapping and interlacing materials to enhance the bonding strength. To test this hypothesis, we need a computer-aided manufacturing (CAM) tool that can process the overlapped material regions. However, existing computational tools lack key multi-material design processing features and have certain limitations in making full use of the material information, which restricts the testing of our hypothesis. Therefore, this research also develops a new MMAM slicing framework that efficiently identifies the boundaries for materials to develop different advanced features. By modifying a ray tracing technology, we develop layered depth material images (LDMI) to process the material information from computer-aided design (CAD) models for slicing and process planning. Each sample point in the LDMI has associated material and geometric properties that are used to identify the multi-material regions. Based on the material information in each slice, interlocking joint (T-Joint) and interlacing infill are generated in the regions with multiple materials. Tensile tests have been performed to verify the enhancement of mechanical properties by the use of overlapping and interlacing materials.
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McClure, Matthew R., A. Mehran Shahhosseini, Todd Alberts, and Phillip Cochrane. "Effects of Joint Preparation Angle of Single-Vee Butt Welds on the Tensile Strength of ASTM A36 Carbon Steel." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63757.
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Welding is a multi-faceted procedure of manufacturing and can occur at any point during the creation of a product. Quality issues in welding can have disastrous, or even deadly, consequences. The issue of weld preparation angle is one of several different elements that have a direct correlation on the quality of a welded joint. The purpose of this research centers on resultant tensile strength of a single-vee butt joint in carbon steel with various preparation angles. Preparation angles were machined on twenty-six pieces of ASTM A36 carbon steel in 5° increments in order to produce thirteen samples with included preparation angles ranging from 0° to 120°. Test samples were developed using an automated welding process that remained consistent for all of the welds. Each sample was plasma cut into ten coupons, which were machined to have a uniform cross section of the welded joint and surrounding parent material using a computer numerically controlled machining center. This yielded a total population of 130 coupons, which were tested to failure using a United Testing Systems stress/strain tensile tester. The empirical data were analyzed via the use of SPSS 18 statistical software. Initially, the level of population variance was assessed within groups and between groups by use of a one-way ANOVA test at the .05 alpha level. The result showed a statistically significant difference of the sample population. Secondly, a comparison of the data at various preparation angles to that of the industry standard angle of 60° was assessed using a Bonferroni multiple comparisons at the .05 alpha level, which resulted in one angle being statistically significant compared to the industry standard.
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Banu, Mihaela, Mitica Afteni, Alexandru Epureanu, and Valentin Tabacaru. "Prediction of the Stress-Strain Response of the Ultrafine-Grained Materials Using Multi-Scale Analysis." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30871.
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There are several severe plastic deformation processes that transform the material from microsized grains to the nanosized grains under large deformations. The grain size of a macrostructure is generally 300 μm. Following severe plastic deformation it can be reached a grain size of 200 nm and even less up to 50 nm. These structures are called ultrafine grained materials with nanostructured organization of the grains. There are severe plastic deformation processes like equal angular channel, high pressure torsion which lead to a 200 nm grain size, respectively 100 nm grain size. Basically, these processes have a common point namely to act on the original sized material so that an extreme deformation to be produced. The severe plastic deformation processes developed until now are empirically-based and the modeling of them requires more understanding of how the materials deform. The macrostructural material models do not fit the behavior of the nanostructured materials exhibiting simultaneously high strength and ductility. The existent material laws need developments which consider multi-scale analysis. In this context, the present paper presents a laboratory method to obtain ultrafine grains of an aluminum alloy (Al-Mg) that allows the microstructure observations and furthermore the identification of the stress–strain response under loadings. The work is divided into (i) processing of the ultrafine-grained aluminum alloy using a laboratory-scale process named in-plane controlled multidirectional shearing process, (ii) crystallographic analysis of the obtained material structure, (iii) tensile testing of the ultrafine-grained aluminum specimens for obtaining the true stress-strain behavior. Thus, the microscale phenomena are explained with respect to the external loads applied to the aluminum alloy. The proposed multi-scale analysis gives an accurate prediction of the mechanical behavior of the ultrafine-grained materials that can be further applied to finite element modeling of the microforming processes.
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Abdi, Frank, Saber DorMohammadi, Jalees Ahmad, Cody Godines, Gregory N. Morscher, Sung Choi, Rabih Mansour, Steve Gonczy, and Greg Ojard. "Crack Growth Resistance of CMC Attachment Element and Turbine Joint in Aircraft Engines." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-65089.
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A Durability and Damage Tolerance (D&DT) analysis of an S200 Nicalon/SiNC CVI SiC/SiC attachment joint was conducted to determine the CMC components material structural integrity during service loading. A building block validation strategy is proposed that includes: (i) Room, and High Temperature (RT/HT) testing with AE (Acoustic Emission) and ER (Electrical Resistivity) strategies; (ii) Advanced multi-scale modeling; (iii) Interpretation test/model; and (iv) ASTM draft submittal of simplified beam equation supported by FEM/test compliance and round robin exercise. The following building block calibration, verification, validation, and accreditation strategy were performed: 1) Material characterization analysis to determine the damage evolution under uniaxial tensile loads and compared with test; 2) Crack Growth Resistance (CGR) analysis and test of wedge loaded DCB (Double Cantilever Beam) to determine the crack growth length, zig-zag pattern, fracture, shift in failure mechanisms and derivation of fracture energy vs. crack length simple formulation at RT; 3) Joint loading multi scale modeling and comparison with observed test load displacement curve, and determination of fracture energy; and 4) blade structural integrity and response under service loading using Multi-Scale Progressive Failure Analysis (MS-PFA) and determination of contributing damage and delamination types and their locations. FE based MS-PFA of the material and structure studied addressed the critical damage events (damage initiation, damage propagation, fracture initiation, and fracture propagation) as the components were being loaded. All dehomogenized multi scale methods CMC parameters were implemented in the material and structural modeling strategy, such as crack density effects and architecture (2D, 3D orthogonal, and mixed) interphase thickness, and interfacial shear strength. Many parameters that contribute to specimen failure including interface coating thickness, mixed mode failure evolution, interlaminar defects, delamination damage, crack bridging, and fiber fracture were all studied in detail in this work. Several FE-based multi-scale modeling techniques were investigated: a) MS-PFA; b) Virtual Crack Closure Technique (VCCT); and c) integrated damage and fracture evolution methodology using combined MS-PFA and VCCT.
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Mohr, William, Robin Gordon, and Robert Smith. "Local Strain Accumulation in Pipeline Girth Welds." In 2004 International Pipeline Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ipc2004-0474.
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The majority of existing pipeline design codes are stress based and provide limited guidance on the design and assessment of pipelines that may experience high local strains in service. High strains can occur in service due to ground movement, bending over an unsupported span and seismic loading. In such cases pipelines should be designed based on strain capacity. The rigors of strain-based analyses pose a number of challenges, particularly related to pipeline girth welds and general material behavior. This paper presents a summary of an ongoing multi-year project co-funded by the US Minerals Management Service (MMS) and US Dept of Transportation (DOT) to develop design and assessment guidelines for pipelines that may experience high strains in service. Specific topics to be addressed by the project include: • Parent Pipe specifications (Y/T limits, stress-strain behavior, material toughness, etc.); • Welding specifications (joint design, joint geometry, weld strength mismatch, etc.); • Engineering Critical Assessment (ECA) Methods for strain based loading; • Validation test methods to verify pipeline performance (criteria for full-scale testing).
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Kim, G. G., C. H. Shin, P. R. Jeon, S. G. Lee, H. R. Kim, G. J. Min, S. H. Cho, J. S. Yang, and K. J. Yun. "Laboratory Test on Direct Shear Behavior of Rock Joints Using a Bar Drop Impact System." In 56th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/arma-2022-2318.
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ABSTRACT: For an underground excavation at depth in highly stressful conditions, it is important to mitigate the risk of stress-induced failure, e.g., rockburst, and improve miner safety concerning the stability of underground workplaces and the prevention of fatalities. In general, the cause of rockburst is classified into three categories: strainburst due to stress-induced fracturing, rock ejection by seismic energy transfer, and rockfall associated with mining-induced seismicity. In this study, the Split Hopkinson Pressure Bar (SHPB) modified configuration of bar drop apparatus was developed by attaching a direct shear test box and a long bar. As a result, the modified bar drop system enabled to replicate and control of a seismic velocity that was an incident on the joint rock surfaces installed in the direct shear testing box. The long bar installed in the modified bar drop system provides a longer stress wavelength to overcome the relatively shorter duration of the stress waves in the SHPB system. The dynamic shear test on the jointed rock samples using the bar drop apparatus also provided the information to estimate the rock joint shear strengths. 1. INTRODUCTION The rock structures stability depends on the distribution characteristics and mechanical characteristics of discontinuous surfaces such as faults and joints in the rock. Underground excavation has high-stress conditions, and such workplaces are causing stability and fatalities of underground workplaces due to rockburst. In general, the cause of rockburst is classified into three categories: strainburst due to stress-induced fracturing, rock ejection by seismic energy transfer, and rockfall associated with mining-induced seismicity. In order to understand the behavior and stability of such rock structures, it is necessary to understand the shear characteristics of the joint surfaces. The direct shear test and multi-stage shear test are methods to measure the shear characteristics of the joint surfaces. The direct shear test measures the shear characteristics of a joint surface by generating shear displacement with different load conditions from each specimen and requires samples with the same roughness. However, it is difficult to obtain samples with the same roughness in the field, so a multi-stage shear test is conducted. A constant normal load section is set as a specimen in the multi-stage shear test. The shear characteristics for each normal stress stage are measured by generating shear displacement while increasing the normal load. In the case of the multi-stage shear test, the International Society of Rock Mechanics and Rock Engineering (ISRM, 1981) recommends the discontinuous surface test method for rock. However, it has been pointed out that the joint surface of the specimen is damaged due to an increase in shear load due to the normal load, resulting in a lower shear strength than the direct shear test (Zhao and Zhou, 1992).