The effect of vibrations on the mechanical properties of laminations

This study aims to increase the mechanical properties of the composite material manufactured by the lamination process. In this study, the lamination process will be implemented in two ways, and mechanical properties are compared between the two methods. The first method covers the lamination process under the influence of vacuum pressure only, while in the second method lamination process is achieved by the influence of vacuum pressure and vibrate by shaker device. The results showed that the endurance stress of fatigue increased by 18.18% for the material manufactured by the lamination process under the influence of vibration, while the yield stress and ultimate stress values remained roughly constant for both methods.

Effect of Different Exercise Stressors on Soldier’s Psychophysiological Response and Marksmanship

Background: Authors have proposed that depending on the type of fatigue, either central or peripherical, as well as previous training and experience, shooting impairment may occur in different gradients. However, the effects of different stressor stimuli on fine motor skills as shooting is yet not fully understood.Methods: The present research aimed to analyze the effect of endurance and resisted physical stressors on the psychophysiological response and pistol marksmanship of soldiers, and the possible differences by gender and weigh. Variables of heart rate, isometric hand strength, rated of perceived exertion and pistol marksmanship were analyzed in 86 soldiers in basal, endurance and resisted stress protocols moments.Results: Isometric hand strength, HR and RPE were significantly higher in both resisted and endurance physical stress protocols than in basal sample. Gender differences were seen, among strength, cardiovascular and RPE values. Also, soldiers with larger BMI presented significantly higher isometric hand strength and higher marksmanship in all moments evaluated. Conclusions: An endurance stress protocol produced a higher cardiovascular and perceived exertion than a resisted one, not affecting hand strength, shooting heart rate and marksmanship. Females presented lower hand strength marksmanship and higher rated of perceived exertion and heart rate during the endurance and resisted stress protocols than males. Overweight soldiers have higher heart rate during both protocols, higher hand strength and marksmanship, and similar hear rate while shooting than normoweight soldiers.

Evaluation of Physiological Parameters in Response to Endurance Exercise of Zanskar Ponies Adapted to High Altitude of Ladakh Region

Zanskar pony, a native horse breed of Ladakh mainly used for transportation in Trans-Himalayan region of India, is well adapted to high altitude hypobaric hypoxia environment. Due to extreme conditions of the Ladakh region, better endurance of these ponies under hypoxic and extreme cold conditions is of utmost concern for their recruitment in Indian Army. In the present study, 12 young trained Zanskar ponies were evaluated during endurance exercise at an altitude of 3292 meter above mean sea level. The animals were subjected to carriage transport with 65-70Kg load or riding on a track of 5-6 Km. Physiological parameters <em>viz</em>., pulse rate (PR), heart rate (HR), rectal temperature (RT), respiratory rate (RR) and oxygen saturation (SaO₂) were recorded in Zanskar ponies during pre-exercise (T₀), post- exercise (T₁) and post recovery (T_2,2 hours post resting) stages. Results showed marked increase in PR, HR, RR and RT post exercise time points. The mean values of PR increased from 49.83±4.62 to 73.67±21.54 per minute, HR from 48±13.60 to 75±15.82 beats/min, RR from 37.83±9.70 to 57.67±13.48 per min and RT from 99.62±0.34 101.04±0.53 °F from pre stress to post endurance stress. The mean SaO₂level reduced significantly (88.58±6.75 at T₀ versus 64.00±18.70 at T₁ and 54.42±14.79 at T₂) post exercise. This indicated limited availability of arterial oxygen for tissues which could be vital factor for adverse change in some of physio-biochemical parameters. Though the trend of physiological response was similar for all the 12 animals, still variation at individual animal level was observed during endurance stress. In future, some of these physiological parameters along with biochemical and molecular parameters could be evaluated as potential biomarkers in selecting ponies with superior endurance trait specifically under hypoxic conditions.

Abstract 30: Endurance Exercise Induces Cardiac Hypertrophy in Aged Nrf2-/- Mice

Background: Radical forms of oxygen and nitrogen species (ROS/RNS) are highly reactive with nucleic acids, proteins and lipids and promote their oxidation. Normally, cellular ROS/RNS concentrations are tightly controlled by the inducible antioxidant system, which is predominantly regulated by the transcription factor Nrf2 (nuclear erythroid-2 like factor-2) and its cytosolic repressor protein, Keap1. We hypothesized that a decrease or an abrogation of Nrf2 impairs cardiac function and induce hypertrophy upon endurance stress in aging heart. Methods: Age-matched wild-type (WT) and Nrf2-/- (KO) mice (n=12/gp) at 2 and >20 months were subjected to endurance exercise stress (EES; 20 meter/min, 12% grade) and assessed the activation of Nrf2/ARE-dependent transcriptional mechanisms in the heart. Cardiac hypertrophy was determined by echocardiography, heart/body weight ratio and biochemical/molecular marker analyses. Results: Interestingly, both old-WT and Nrf2-/- mice exhibited oxidative stress on EES due to significant decrease or abrogation of Nrf2 nuclear levels, respectively, suggesting that aged-WT is equally susceptible to stress as Nrf2-/- mice. Age-dependent loss of Nrf2 decreased the transcription of Nrf2-dependent antioxidants and thereby elevated ROS levels to cause a more oxidized intracellular environment. Importantly, the loss of Nrf2 induced cardiac hypertrophy upon endurance stress in the aged (>20 mon) mice. At the end of 2-weeks of endurance stress, both the old-WT and Nrf2-/- mice had developed cardiac hypertrophy. Also, qPCR analysis showed significant (p<0.05) upregulation of hypertrophy markers (ANF and BNF) in the old-WT or Nrf2-/- when compared to sedentary WT mice confirmed cardiac hypertrophy due to loss of Nrf2. These results indicate that either a decrease or an abrogation of Nrf2 can increase susceptibility to stress induced hypertrophy in an aging heart. Conclusions: We conclude that enhancing protein levels and stability of nuclear Nrf2 could activate the transcription of major antioxidant enzymes and biosynthesis of key antioxidants. Enhancing protective mechanisms against oxidative stress in the elderly is expected to prevent or delay the onset of age-associated cardiac hypertrophy and cardiomyopathy.

Impulse Testing and Blade Load Simulation Tools to Estimate Cyclic Stress Life in Blades and Impellers

A pragmatic approach for estimating cyclic stresses in rotating airfoils based on impulse testing with strain gauge sensors and application of simplified aerodynamic excitations is presented. The method has been successfully applied to determine the root causes of blade and impeller failures in gas turbines, steam turbines, and industrial compressors. The method provides guidance for quickly determining the natural frequency most responsible for a failure by analyzing experimental stress data at blade resonances, incorporating the Campbell diagram to evaluate frequency margins, and applying the Goodman diagram to evaluate endurance stress margins. The effects of mis-tuned blade responses can be included and operating lifetimes can be evaluated by use of the Palmgren-Miner analysis. Example cases of significant failure analyses for an axial flow gas turbine compressor and a driven industrial compressor are used to illustrate how the method is used.

New Methods for Characterizing Coating Properties at Ambient and Elevated Temperatures

In the paper, innovative methods for characterizing coatings’ properties at ambient and elevated temperatures are introduced based on various experimental procedures. Nanoindentation results, which were obtained at elevated temperatures, are evaluated by FEM algorithms, rendering possible the determination of temperature dependent coating mechanical properties. Impact tests conducted on coated specimens revealed a non-linear film impact resistance versus the temperature. The latter results were evaluated by appropriate FEM supported procedures, to predict the coating fatigue endurance stress versus the temperature. In these investigations, the impact load was induced electromagnetically for a duration of ca. 1ms, depending on the force amplitude. To change the impact load characteristics, such as frequency, impact duration etc., a new test device has been developed, employing a piezoelectric actuator. This device enables the investigation of the impact time effect on the dynamic response of coated surfaces and on the coating fatigue endurance stress. Finally, diffusion phenomena in coatings were examined by a developed convenient experimental setup. A specimen is pressed onto a coated surface at adjustable high temperature and pressure in an inert atmosphere. After this test, the diffusion of characteristic elements into the coating and vice versa is detected by EDX-microanalyses. These results contribute, among others, to the description of diffusion phenomena between coatings and various materials.