SUBSTANTIATION OF THE TEST LOAD RELEASE ALTITUDE IN DYNAMIC STRENGTH TESTS OF EMERGENCY DESCENDING DEVICES

Purpose: To examine the relationships between different loading intensities and movement velocities in the bench-press exercise (BP) in Paralympic powerlifters. Methods: A total of 17 national Paralympic powerlifters performed maximum dynamic strength tests to determine their BP 1-repetition maximum (1RM) in a Smith-machine device. A linear position transducer was used to measure movement velocity over a comprehensive range of loads. Linear-regression analysis was performed to establish the relationships between the different bar velocities and the distinct percentages of 1RM. Results: Overall, the correlations between bar velocities and %1RM were strong over the entire range of loads (R2 .80–.91), but the precision of the predictive equations (expressed as mean differences [%] between actual and predicted 1RM values) were higher at heavier loading intensities (∼20% for loads ≤70% 1RM and ∼5% for loads ≥70% 1RM). In addition, it seems that these very strong athletes (eg, 1RM relative in the BP = 2.22 [0.36] kg·kg−1, for male participants) perform BP 1RM assessments at lower velocities than those previously reported in the literature. Conclusions: The load–velocity relationship was strong and consistent in Paralympic powerlifters, especially at higher loads (≥70% 1RM). Therefore, Paralympic coaches can use the predictive equations and the reference values provided here to determine and monitor the BP loading intensity in national Paralympic powerlifters.

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Repeatability of Dynamic Strength Tests

Proceedings of the Human Factors Society Annual Meeting ◽

10.1177/154193128502900525 ◽

1985 ◽

Vol 29 (5) ◽

pp. 517-520 ◽

Cited By ~ 2

Author(s):

Krishna K. Menon ◽

Andris Freivalds

Keyword(s):

Dynamic Strength ◽

Dynamic Tests ◽

Strength Measurement ◽

Strength Tests ◽

Good Repeatability ◽

Coefficients Of Variations

The repeatability of dynamic strength tests was examined by calculating coefficients of variations (CV) for the forces exerted on lifting tests using the legs, torso and arms. Static strengths were also measured and compared to dynamic strengths. The CV for dynamic strengths, was in fact slightly lower than for static strengths, 9.79% vs. 10.6%. The correlations between the two types of strength measurements were large (r=.8l) and significant, indicating that along with good repeatability dynamic tests are an acceptable form of employee strength measurement.

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Material Characterization Results for a Selected Graphite Fiber/Epoxy Composite

ASME 1969 Gas Turbine Conference and Products Show ◽

10.1115/69-gt-114 ◽

1969 ◽

Author(s):

G. E. Molter ◽

E. A. Rothman

Keyword(s):

Injection Molding ◽

Epoxy Matrix ◽

Material Characterization ◽

Room Temperature ◽

Epoxy Composite ◽

Dynamic Strength ◽

Graphite Fiber ◽

Strength Tests ◽

Laminar Shear ◽

Inherent Tendency

Static and dynamic strength tests and modulus data are reported for a uniaxial graphite yarn reinformcement impregnated with an epoxy matrix by the vacuum injection molding technique. All testing was done at room temperature. An inherent tendency to fracture in inter-laminar shear was observed.

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Simulation-Based Methodology for Determining the Dynamic Strength of Tire Inflation Restraining Devices

Energies ◽

10.3390/en13040991 ◽

2020 ◽

Vol 13 (4) ◽

pp. 991 ◽

Cited By ~ 1

Author(s):

Jacek Karliński ◽

Mariusz Ptak ◽

Leszek Chybowski

Keyword(s):

Permanent Deformation ◽

Equivalent Stress ◽

Dynamic Strength ◽

Strength Criteria ◽

Contour Lines ◽

Simulation Based ◽

Strength Tests ◽

Principal Tool ◽

Plastic Displacement ◽

Operator Safety

The article suggests and supports a simulation-based methodology for determining whether the dynamic strength of tire inflation restraining devices for tire inflation meet quality requirements and ensure operator safety during a potential tire explosion. Dynamic strength tests using an NM-600 safety shield and NK-0728 safety cage during a 29.5 R25X tire explosion at a pressure of 10 bar were presented as an example application of this methodology. The shield was subjected to destructive tests involving the use of a 2200 kg impactor, dropping it so that the minimum kinetic energy reached 20 kJ at the time of impact. Analyzed devices were constructed of S355 steel in accordance with EN 10025. The Cowper–Symonds model of material for strain rate phenomena was used in the calculations. Simulations of a 20 kJ ring impact against the cage were performed. The equivalent stress distribution was determined, and displacement contour lines for the maximum dynamic deformation value and plastic deformation were calculated. The plastic displacement obtained in numerical tests was equal to the permanent deformation recorded in the experimental test. Further, the simulations showed that the examined cage met the assumed strength criteria. The conducted tests confirmed the usefulness of the proposed methodology for assessing the dynamic strength of safety cages and shields for tire inflation. The full-scale, physical cage testing is difficult to implement because it requires placing a ring impacting the cage wall. This is a major boundary for closed cages, as considered in this publication. Thus, simulation-based methods are becoming a principal tool for safety assessment of tire inflation restraining devices.

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Experience in ensuring the strength of the supporting structures of locomotives and electric multiple units

Vestnik of the Railway Research Institute ◽

10.21780/2223-9731-2019-78-2-67-73 ◽

2019 ◽

Vol 78 (2) ◽

pp. 67-73

Author(s):

V. V. KOCHERGIN ◽

A. A. BUKHANTSEV ◽

I. G. PANKRATOVA ◽

O. A. RUSANOV

Keyword(s):

Fatigue Strength ◽

Fatigue Testing ◽

Dynamic Strength ◽

The Body ◽

Rolling Stock ◽

Load Bearing ◽

Cyclic Stresses ◽

Strength Tests ◽

Cis Countries ◽

Multiple Units

To ensure fatigue strength of metal structures in mechanical engineering, various approaches are practiced. One of them allows for the appearance of cyclic stresses in details with amplitudes exceeding the fatigue limit. Typically, this approach is justified where the loads are fairly regular and ample opportunities for fatigue testing exists, but the requirement of a minimum metal consumption is critically important as well. Another approach to ensuring fatigue strength does not allow the possibility of cyclic stresses with amplitudes exceeding its endurance limit in the designed structure. With regard to the supporting elements of locomotives and electric multiple units (EMU) to ensure the fatigue resistance characteristics in Russia and the CIS countries, the second of these approaches has been implemented and successfully practiced for many years. Its purpose is to ensure the absence of fatigue damage in the parts of the carriage and the body during the designated service life. Relevant requirements for strength and dynamic qualities for these types of rolling stock, as well as the method of conducting dynamic strength tests are currently formalized in the standards. The article presents the main provisions of the methodology currently used on the railways of the Russian Federation and CIS countries to control the strength requirements of load-bearing structures of locomotives and EMUs, as well as the admission of these types of rolling stock to operation. Types of dynamic strength tests are described, strength indicators are listed, methods for their determination are indicated. Today, this technique successfully solves the problem of the strength of load-bearing structures of traction rolling stock.

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