The Experts below are selected from a list of 128982 Experts worldwide ranked by ideXlab platform
Hong Zhongyan - One of the best experts on this subject based on the ideXlab platform.
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The fabrication of eccentric stepped-shaft forgings using the process of cross-wedge rolling
Journal of Materials Processing Technology, 1992Co-Authors: Ren Guangsheng, Bai Zhibin, Zhang Chengjian, Hong ZhongyanAbstract:Abstract The technology of fabrication of eccentric stepped-shaft forgings using the process of cross-wedge rolling is proposed in this paper. The geometrical characteristics of the directrix of the working surface on cross-wedge dies to form the eccentric step are analysed and simple directrix equations capable of being used easily in engineering are presented. The maximum eccentric dimension that can be formed with the process is derived on the basis of the rotation conditions of the eccentric deformation. The effects of positional error of the dies on the dimensional and geometrical precision of the eccentric step are investigated. The technology has been used to produce three kinds of eccentric shaft in batch quantities and very good technical and economic benefit has resulted.
Alan Donnelly - One of the best experts on this subject based on the ideXlab platform.
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Changes in human skeletal muscle length during stimulated eccentric muscle actions
The Journal of Physiological Sciences, 2011Co-Authors: Stephen J. Brown, Alan DonnellyAbstract:Following eccentric exercise, increases in muscle length alter the length-tension relation of skeletal muscle. However, its unclear if this change occurs during eccentric exercise. Therefore, 70 eccentric actions of the knee extensors of one leg (with superimposed electrical stimulation) were performed at 100°/s, from full extension to full flexion. Angle-specific eccentric force was recorded throughout. Force decreased at all angles although this was non-uniform. At 70°, force decreased by 25%, whereas at 130°, force decreased by 41%. Initial peak force was recorded at 100° (590 ± 232 N); the exercise bout induced a 21% decrease in peak force and a 10° shift in the position of peak force production to 90°. The rightward shift in the muscle length-tension relation thus occurred during eccentric exercise, where greater force loss at short muscle lengths suggested an eccentric-induced over-stretching of sarcomeres.
David T Bercades - One of the best experts on this subject based on the ideXlab platform.
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eccentric knee flexor torque following anterior cruciate ligament surgery
Medicine and Science in Sports and Exercise, 1995Co-Authors: Louis R Osternig, Charles R James, David T BercadesAbstract:The purposes of this study were to compare eccentric knee flexor torque and muscle activation in the limbs of normal (NOR) subjects and in subjects who had undergone unilateral ACI, autograft surgical reconstruction (INJ) and to assess the effect of movement speed on EMG/ torque ratios and eccentric-concentric actions. Fourteen subjects (7 NOR and 7 INJ) were tested for knee eccentric flexor torque and EMG activity at four isokinetic speeds (15 degrees, 30 degrees, 45 degrees and 60 degrees.s-1). Results revealed that post-surgical limbs (ACL) produced significantly less (P < 0.05) eccentric torque and flexor EMG activity at 60 degrees.s-1 than uninjured (UNI) contralateral limbs. Eccentric torque rose significantly as speed increased from 45 degrees to 60 degrees.s-1 for surgical group uninjured limbs and NOR group left and right limbs. Eccentric flexor torque increased with speed for both groups and approximated equality with concentric extensor torque at 60 degrees.s-1 for INJ group ACL and UNI limbs. Concentric flexor muscle EMG/torque ratios were 30-191% greater than eccentric muscle actions across groups and speeds. The results suggest that ACL dysfunction may result in reduced eccentric flexor torque at rapid movement speeds, that eccentric flexor torque increases with movement speed and may have the capacity to counter forceful extensor concentric torque, and that eccentric muscle actions produce less muscle activation per unit force than concentric actions which may reflect reduced energy cost.
Alain Holeyman - One of the best experts on this subject based on the ideXlab platform.
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Load Transfers During Vibratory Driving
Geotechnical and Geological Engineering, 2012Co-Authors: Valerie Whenham, Alain HoleymanAbstract:The vibratory driving technique consists in applying a vibratory load onto a profile to reduce the ground resistance and allow penetration of the profile under its own weight. The vibratory action is produced by counter-rotating eccentric masses actuated within the exciter block. A proper definition of this mechanical action is fundamental for vibratory driving analyses. The vibratory force transferred from the vibrator onto the pile during vibratory driving is however generally neither well defined nor understood, in particular when using simplified closed form solutions for the analysis of pile driving. Few authors have pointed out the very low ratio observed between the force measured in the pile and the nominal inertial force developed by the Eccentrics, but without offering a theoretical framework to explain and predict this low ratio. The objective of this paper is to develop a better understanding of the so-called ‘efficiency factor’ of the vibratory driving process. Analytical solutions are presented, along with more advanced numerical simulations. Theoretical solutions are illustrated with reference to field measurements collected at different test sites.
Ren Guangsheng - One of the best experts on this subject based on the ideXlab platform.
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The fabrication of eccentric stepped-shaft forgings using the process of cross-wedge rolling
Journal of Materials Processing Technology, 1992Co-Authors: Ren Guangsheng, Bai Zhibin, Zhang Chengjian, Hong ZhongyanAbstract:Abstract The technology of fabrication of eccentric stepped-shaft forgings using the process of cross-wedge rolling is proposed in this paper. The geometrical characteristics of the directrix of the working surface on cross-wedge dies to form the eccentric step are analysed and simple directrix equations capable of being used easily in engineering are presented. The maximum eccentric dimension that can be formed with the process is derived on the basis of the rotation conditions of the eccentric deformation. The effects of positional error of the dies on the dimensional and geometrical precision of the eccentric step are investigated. The technology has been used to produce three kinds of eccentric shaft in batch quantities and very good technical and economic benefit has resulted.