SEM Validation Technique for FEA of Small Specimens

2007 ◽  
Author(s):  
Kelly Pike ◽  
Z. C. Lin ◽  
Alan Tahran
Keyword(s):  
Fatigue Test ◽  
Before And After ◽  
Surface Measurements ◽  
Small Test ◽  
Individual Specimen ◽  
Validation Technique

The use of the SEM to make direct surface measurements on small test specimens enables the FEA analyst to construct and validate an individual specimen model. The technique is also valuable to engineers so that they can calibrate their fatigue test samples before and after fatigue test regimes.

scholarly journals Stability of external and internal implant connections after a fatigue test

2013 ◽  
Vol 07 (03) ◽  
pp. 267-271 ◽  
Author(s):  
Paulo Cesar Pinheiro Feitosa ◽  
Ana Paula Barbosa de Lima ◽  
Laís Regiane Silva-Concílio ◽  
William Cunha Brandt ◽  
Ana Christina Claro Neves
Keyword(s):  
Mechanical Testing ◽  
Fatigue Test ◽  
Analysis Of Variance ◽  
Mechanical Cycling ◽  
Before And After ◽  
Lower Variation

ABSTRACT Objective: The objective of this study was to compare the torque and detorque values of screw intermediates of external hexagon, internal hexagon, and Morse taper implants in single restorations before and after mechanical cycling. Materials and Methods: The study sample was divided into three groups (n = 10) as follows: group EH - external hexagon implant, group IH - internal hexagon implant, and group MT - Morse taper implant. Universal abutments were screwed on the implants, and metal crowns were cemented onto the abutment. The samples were submitted to a mechanical testing of 1 million cycles, with a frequency of 8 cycles per second under a 400 N load. The application and registration of the screw torque (T0) and detorque (T1) values of the intermediate were performed before and after the test. The results were statistically evaluated by analysis of variance (ANOVA) and Tukey′s test (α = 0.05). Results: There was no difference between the values of T0 and T1 in the intra-group samples. However, the inter-group difference in T0 between the EH (12.8 N cm) and MT (18.6 N cm) groups and in T1 between the EH (10.4 N cm) and IH (13.8 N cm), EH and MT (19.4 N cm), and MT and IH (P = 0.001) groups were significant. The MT group showed a lower variation of T0 and T1. Conclusion: The internal implants, particularly MT, showed better stability in these cases when used for single restorations.

scholarly journals Training Model for Attacking in Football of 16 Years Old

2019 ◽  
Vol 5 (1) ◽  
pp. 8-18
Author(s):  
Valentino Hary ◽  
Bahtiar Firdiansyah
Keyword(s):  
Motor Skills ◽  
Quantitative Data ◽  
Qualitative Data ◽  
Exercise Program ◽  
Training Model ◽  
P Value ◽  
School Students ◽  
Before And After ◽  
Small Test ◽  
The Difference

The aim of this research is to produce a training model for attacking football and also to refute its effectiveness for children aged 16 years. As for the steps in developing the research, the Borg and Gall steps involved 15 subjects for the small test and 60 for the large test. Qualitative data were obtained from observations, documentation and interviews; meanwhile, for the quantitative data using the effectiveness test. The trial of this study used pre and post tests with 10 opposing criteria. In mathematical calculations the significance of the difference t-count = -28.971, db = 43 and p-value = 0.00 <0.05, which means it contains significance before and after giving treatment. It can be concluded that the model is applied effectively to improve the ability for attacking amongst school students aged 16 years. Thus, representing the differences in motor skills highlights the principle of specificity for attacking training at the age of 16 must be considered that the load of portions in the exercise program can be maximized.  

scholarly journals Improvement of mechanical properties and fatigue life by shot peening process on ASTM A516 Grade 70 steel

2018 ◽  
Vol 14 (4) ◽  
pp. 440-442
Author(s):  
Mohd Rashdan Isa ◽  
Omar Suliman Zaroog ◽  
Kalaikathir Murugan ◽  
Sharif Osman Kabashi Guma ◽  
Fareg Saeid Ali
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Test ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Industrial Sector ◽  
Low Intensity ◽  
Before And After

ASTM A516 Grade 70 is widely used in the industrial sector as it provides very good mechanical properties in tough conditions. The main usage of this material is in moderate and low operating services. This paper focuses on the effect of shot peening process on ASTM A516 Grade 70 on improving the mechanical properties and fatigue life of the material. Samples have been shot peened with steel shot to induce compressive residual stress. Hardness, tensile and fatigue test as well as microstructure were done on the samples before and after shot peening process to study the effects on mechanical properties. The result shows that there is an increment in every test after shot peening process. There is a slight increment of 0.47% in hardness value, 0.39% increment in tensile strength and 6.78% increment in fatigue life of the material after shot peening process applied. The slight increment in every result was due to the low intensity of the shot peening process. Result also shows that the shot peening process compressed the molecules closer to each other as can be seen under SEM. Therefore it was proven that in this study, there is a very significant improvement in mechanical properties and fatigue life by shot peening process on ASTM A516 Grade 70 Steel.

Salivary Cortisol Responses and Session Ratings of Perceived Exertion to a Rugby Match and Fatigue Test

2017 ◽  
Vol 124 (3) ◽  
pp. 649-661 ◽  
Author(s):  
P. C. Caetano Júnior ◽  
M. L. Castilho ◽  
L. Raniero
Keyword(s):  
Fatigue Test ◽  
Salivary Cortisol ◽  
Perceived Exertion ◽  
Cortisol Response ◽  
Ratings Of Perceived Exertion ◽  
Perceived Effort ◽  
Significant Difference ◽  
Before And After ◽  
Cortisol Responses ◽  
Rugby Players

This study compared the effects of an official rugby match and a fatigue test on the salivary cortisol responses of 13 rugby players. We also examined the relationship between this cortisol response and session ratings of perceived exertion (session-RPE). We collected saliva before and after the match and fatigue test and assessed physical effort intensity via session-RPE using a CR-10 scale. We measured cortisol concentration by enzyme-linked immunosorbent assays. Results were greater session-RPE and cortisol concentrations for the rugby match, compared with the fatigue test. There was a significant difference between cortisol concentrations obtained pre- and postmatch ( p < .022) and significant correlations between cortisol response and session-RPE sampling in both the rugby match ( r = .81; p < .001) and fatigue test ( r = .91; p < .001). This study provides evidence of greater perceived effort and higher cortisol concentrations in actual competition versus a fatigue test. Our data further support session-RPE as a relatively inexpensive close correlate of a stress biomarker (cortisol response). Thus, session-RPE can be used by coaches as a valid indication of training loads and adequate recovery time after exertion.

Effects of Muscle Fatigue Induced by Countermovement Jumps on Efficacy Parameters of Instep Ball Kicking in Soccer

2017 ◽  
Vol 33 (2) ◽  
pp. 105-111 ◽  
Author(s):  
Víctor Torreblanca-Martinez ◽  
Fernando M. Otero-Saborido ◽  
José A. Gonzalez-Jurado
Keyword(s):  
Muscle Fatigue ◽  
Fatigue Test ◽  
Young Male ◽  
Soccer Players ◽  
Maximal Velocity ◽  
Jump Height ◽  
Significant Difference ◽  
Before And After ◽  
Instep Kick ◽  
Efficacy Parameters

The purpose was to study the effects of muscle fatigue induced by countermovement jumps (CMJ) on instep kick foot velocity in young male soccer players. Fifteen under-18 soccer players from a professional club performed maximal velocity instep kicks before and after a fatigue protocol that consisted of continuous CMJ. Foot velocity at impact without fatigue, foot velocity at impact with fatigue, CMJ height without fatigue, maximum jump height in fatigue test, and CMJ height change in fatigue test on a dynamometric platform were measured. There was a significant difference between jump height with and without fatigue (P = .00; ES = 0.8), but there were no significant differences between kicking with fatigue and without fatigue (P = .580, ES = 0.10). In conclusion, although the protocol was intense enough to generate fatigue in the muscles involved in CMJ, there were no significant differences in kicking velocity under fatigue conditions with respect to kicking without fatigue in the soccer players studied.

scholarly journals Modeling and Validation of Fatigue and Recovery of Muscles for Manual Demolition Tasks

2022 ◽  
Vol 19 (2) ◽  
pp. 930
Author(s):  
Cannan Yi ◽  
Fan Tang ◽  
Kai-Way Li ◽  
Hong Hu ◽  
Huali Zuo ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Fatigue Test ◽  
Perceived Exertion ◽  
Recovery Test ◽  
Work Related ◽  
Before And After ◽  
Recovery Models ◽  
Human Participants ◽  
Forceful Exertion ◽  
Fatigue Recovery

Manual demolition tasks are heavy, physically demanding tasks that could cause muscle fatigue accumulation and lead to work-related musculoskeletal disorders (WMSDs). Fatigue and recovery models of muscles are essential in understanding the accumulation and the reduction in muscle fatigue for forceful exertion tasks. This study aims to explore the onset of muscle fatigue under different work/rest arrangements during manual demolition tasks and the offset of fatigue over time after the tasks were performed. An experiment, including a muscle fatigue test and a muscle fatigue recovery test, was performed. Seventeen male adults without experience in demolition hammer operation were recruited as human participants. Two demolition hammers (large and small) were adopted. The push force was either 20 or 40 N. The posture mimicked that of a demolition task on a wall. In the muscle fatigue test, the muscle strength (MS) before and after the demolition task, maximum endurance time (MET), and the Borg category-ratio-10 (CR-10) ratings of perceived exertion after the demolition task were measured. In the muscle fatigue recovery test, MS and CR-10 at times 1, 2, 3, 4, 5, and 6 min were recorded. Statistical analyses were performed to explore the influence of push force and the weight of the tool on MS, MET, and CR-10. Both muscle fatigue models and muscle fatigue recovery models were established and validated. The results showed that push force affected MET significantly (p < 0.05). The weight of the tool was significant (p < 0.05) only on the CR-10 rating after the first pull. During the muscle fatigue recovery test, the MS increase and the CR-10 decrease were both significant (p < 0.05) after one or more breaks. Models of MET and MS prediction were established to assess muscle fatigue recovery, respectively. The absolute (AD) and relative (RD) deviations of the MET model were 1.83 (±1.94) min and 34.80 (±31.48)%, respectively. The AD and RD of the MS model were 1.39 (±0.81) N and 1.9 (±1.2)%, respectively. These models are capable of predicting the progress and recovery of muscle fatigue, respectively, and may be adopted in work/rest arrangements for novice workers performing demolition tasks.

scholarly journals Effect of 9.3 μm CO2 and 2.94 μm Er:YAG Laser vs. Bur Preparations on Marginal Adaptation in Enamel and Dentin of Mixed Class V Cavities Restored With Different Restorative Systems

2021 ◽  
Vol 2 ◽  
Author(s):  
Clara Isabel Anton y Otero ◽  
Enrico Di Bella ◽  
Ivo Krejci ◽  
Tissiana Bortolotto
Keyword(s):  
Fatigue Test ◽  
High Speed ◽  
Er:Yag Laser ◽  
Marginal Adaptation ◽  
Class V ◽  
Significant Difference ◽  
Before And After ◽  
Universal Adhesives ◽  
Almost All ◽  
Post Hoc

This study aimed to compare marginal adaptation in enamel and dentin before and after aging of laser vs. bur-prepared mixed class V cavities restored by different restorative systems. Seventy two caries-free human molars were distributed to nine experimental groups; cavities were prepared using two different lasers: a handpiece -integrated 2.94 μm Er:YAG laser at 4.5 W, 300 mJ, and 0.75 W, 50 mJ with 15 Hz (LiteTouch, Light Instruments, Israel) and a novel CO2 laser at 12.95 W, 19.3 mJ, and 4.1 W, 6.11 mJ with 671 Hz (Solea 9.3 μm, Convergent Dental, USA). Cavities prepared with conventional diamond burs (Intensiv, Switzerland) in a red contra angle at high speed under maximal water cooling served as control. Cavities were prepared under simulation of dentinal fluid and restored using three different self-etching universal adhesives in combination with three nanohybrid composites, applied in two layers: Scotchbond Universal with Filtek Supreme XTE (3M, USA), G-Premio BOND with Essentia Universal (GC, Japan), and OptiBond Universal with Harmonize Universal (Kerr, USA). After restorations' polishing and simultaneous thermal (5–50°C, 2 min each) and mechanical loading (max. 49 N; 200,000 cycles), replicas of restoration margins were examined under SEM at × 200 magnification. Percentages of continuous margins (CMs) were quantified before and after the fatigue test and statistically compared (two-way ANOVA with Fisher's least significant difference [LSD] post hoc test). Significant differences were found in almost all groups between the results before and after the fatigue test, as well as between the different preparation tools and restorative materials (p &lt; 0.05). Traditional bur preparations are confirmed as gold standard in enamel and dentin, as all three tested restorative systems provide results of marginal adaptation of more than 80% CM after loading. Er:YAG laser preparations can be equally effective in combination with SBU/Filtek Supreme XTE. CO2 laser ablation could not provide convincing results with the tested self-etching restorative systems. Marginal adaptation has been highly dependent on the substrate and showed impaired adhesion, especially in enamel. Scotchbond Universal/Filtek Supreme XTE showed the highest and most stable values of CM. The other two restorative systems were highly dependent on the preparation device of the substrate.

scholarly journals DEVELOPMENT OF A GEO-ANALYTICS PLATFORM FOR POST-DISASTER GROUND ASSESSMENT

2021 ◽  
Vol XLIII-B3-2021 ◽  
pp. 685-692
Author(s):  
K. Atasoy ◽  
S. Kocaman
Keyword(s):  
Natural Hazard ◽  
3D Visualization ◽  
Database Management System ◽  
High Complexity ◽  
Web Based ◽  
Before And After ◽  
Surface Measurements ◽  
Accessibility Issues ◽  
Spatial Database Management System ◽  
Post Disaster

Abstract. Earthquake is a frequently encountered natural hazard and can cause losses of lives and assets. In order to understand the nature of seismic hazards and the risks sourced from them, careful investigations are needed by using diverse geoinformation types. Thanks to the availability of multi-platform and high-resolution geospatial datasets, vast amount of geodata can be collected and analyzed for obtaining timely information on land’s surface before and after an earthquake event; and to assist the disaster management authorities and first responders for supporting the mitigation efforts. On January 24, 2020, an earthquake with Mw 6.8 occurred in Elazig Province, Turkey; caused 41 deaths and damaged the buildings and infrastructure. Although various geodatasets could be collected and processed by the geomatics experts, their utilization by other stakeholders, such as geoscientists, local authorities, and citizens remained limited due to the accessibility issues, and high complexity in their visualization, processing and interpretation. In this study, a web-based platform called EQ4D was designed and implemented to present the multi-sensor and multi-platform 4D data to the stakeholders, and to allow for basic geo-analytical processes such as change detection, 3D surface measurements, etc. Cesium JS and Potree libraries were employed for 3D visualization. PostGIS spatial database management system was used for storing and managing the data, and for performing spatial queries. Currently EQ4D is suitable for the use of geoscientists, and can be further customized for generic use at similar geohazards and developed for the use of inexperienced users, such as citizen scientists.

Effect of Sandblasting Process on Mechanical Properties of ASTM A516 Grade 70 Steel

2018 ◽  
Vol 765 ◽  
pp. 222-226 ◽  
Author(s):  
Mohd Rashdan Isa ◽  
Omar Suliman Zaroog ◽  
Muhammad Aiman Yunus ◽  
Vignesh Rao Sanny Bavu ◽  
Norzulhilmi Rosmi
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Test ◽  
Industrial Sector ◽  
Time Result ◽  
Before And After ◽  
Test Result ◽  
Significant Increment

Sandbalsting is a method used for surface treatment and at the same time this process also improves the mechanical properties of the material. ASTM A516 Grade 70 is widely used in industrial sector as it provides very good mechanical properties in tough conditions. The main usage of this material is in moderate and low operating services. This paper focus on the effect of sandblasting process on ASTM A516 Grade 70 on improving the mechanical properties and fatigue life of this material. Samples have been blasted with sand grade SAE G-80. The focus of this paper is the result of the microhardness, tensile and fatigue test before and after the sandblasting process to study the improvement in mechanical properties as well as the fatigue life. The research was extent to the microstructure analysis using SEM to study the change in microstructure after sandblasting process and fatigue test. Result shows that the hardness increases with respect to blasting time. Result also shows 2.3% increment in tensile strength after sandblasting and there is significant increment in fatigue life. Result also shows that the sandblasting process decreases the grain size of the material. It was proven that the sandblasting process will increase the hardness and decrease the grain size of the material with respect to sandblasting time. At the same time, there is a significant improvement in mechanical properties and fatigue life by applying sandblasting process on the tested material.

Task and fatigue effects on low-threshold motor units in human hand muscle

1989 ◽  
Vol 62 (6) ◽  
pp. 1344-1359 ◽  
Author(s):  
R. M. Enoka ◽  
G. A. Robinson ◽  
A. R. Kossev
Keyword(s):  
Motor Unit ◽  
Fatigue Test ◽  
Unit Activity ◽  
Muscle Activity ◽  
Index Finger ◽  
Motor Units ◽  
Motor Unit Activity ◽  
First Dorsal Interosseus ◽  
Before And After ◽  
Low Threshold

1. The activity of single motor units was recorded in the first dorsal interosseus muscle of human subjects while they performed an isometric ramp-and-hold maneuver. Motor-unit activity was characterized before and after fatigue by the use of a branched bipolar electrode that was positioned subcutaneously over the test muscle. Activity was characterized in terms of the forces of recruitment and derecruitment and the discharge pattern. The purpose was to determine, before and after fatigue, whether motor-unit activity was affected by the direction in which the force was exerted. 2. Regardless of the task during prefatigue trials, interimpulse intervals were 1) more variable during increases or decreases in force than when force was held constant at the target value (4-6% above the recruitment force), and 2) more clustered around an arbitrary central value than would be expected with a normal (Gaussian) distribution. Both effects were seen during the flexion and abduction tasks. The behavior of low-threshold motor units in first dorsal interosseus is thus largely unaffected by the direction of the force exerted by the index finger. The absence of a task (i.e., a direction of force) effect suggests that the resultant force vector about the metacarpophalangeal joint of the index finger is not coded in terms of discrete populations of motor units, but, rather, it is based on the net muscle activity about the joint. 3. Motor-unit behavior during and after fatigue showed that the relatively homogeneous behavior seen before fatigue could be severely disrupted. The fatiguing protocol involved the continuous repetition, to the endurance limit, of a 15-s ramp-and-hold maneuver in which the abduction target force was 50% of maximum and was held for 10-s epochs (ramps up and down were approximately 2 s each). Motor-unit threshold was assessed by the forces of recruitment and derecruitment associated with each cycle of the fatigue test. Changes in recruitment force during the protocol were either minimal or, when present, not systematic. In contrast, the derecruitment force of all units exhibited a marked and progressive increase over the course of the test. 4. After the fatigue test, when the initial threshold tasks were repeated, the behavior of most motor units changed. These changes included the derecruitment of previously active motor units, the recruitment of additional motor units, and an increased discharge variability of units that remained recruited. The variation in recruitment order seemed to be much greater than that reported previously for nonfatiguing conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

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