The Experts below are selected from a list of 6 Experts worldwide ranked by ideXlab platform

P. Frank Pai - One of the best experts on this subject based on the ideXlab platform.

  • Acoustic metamaterial plates for elastic wave absorption and structural vibration suppression
    International Journal of Mechanical Sciences, 2014
    Co-Authors: Hao Peng, P. Frank Pai
    Abstract:

    This article presents the design and modeling techniques and design guidelines, and reveals the actual working mechanism of acoustic metamaterial plates for elastic wave absorption and structural vibration suppression. Each of the studied metamaterial plates is designed by integrating two (or one) isotropic plates with distributed discrete mass-spring-damper subsystems that act as local vibration absorbers. For an infinite metamaterial plate, its stopband is obtained by dispersion analysis on an analytical unit cell. For a finite metamaterial plate with specific boundary conditions, frequency response analysis of its full-size finite-element model is performed to show its stopband behavior, and the stopband behavior is further confirmed by transient analysis based on direct numerical integration of the finite-element equations. Influences of the vibration absorbers' local resonant frequencies and damping ratios and the plate's damping, boundary conditions, and natural frequencies and mode shapes are thoroughly examined. The concepts of negative effective mass and spring and acoustic and optical wave modes are explained in detail. The working mechanism of acoustic metamaterial plates is revealed to be based on the concept of conventional vibration absorbers. An absorber's resonant vibration excited by the incoming elastic wave generates a concentrated inertial Force to work against the plate's Internal Shear Force, straighten the plate, and attenuate/stop the wave propagation. Numerical results show that the stopband's location is determined by the local resonant frequency of absorbers, the stopband's width increases with the (absorber mass)/(unit cell mass) ratio, and increase of absorbers' damping significantly increases the stopband's width and reduces low-frequency vibration amplitudes. However, too much damping may deactivate the stopband effect, and the plate's material damping is not as efficient as absorbers' damping for suppression of low-frequency vibrations.

Hao Peng - One of the best experts on this subject based on the ideXlab platform.

  • Acoustic metamaterial plates for elastic wave absorption and structural vibration suppression
    International Journal of Mechanical Sciences, 2014
    Co-Authors: Hao Peng, P. Frank Pai
    Abstract:

    This article presents the design and modeling techniques and design guidelines, and reveals the actual working mechanism of acoustic metamaterial plates for elastic wave absorption and structural vibration suppression. Each of the studied metamaterial plates is designed by integrating two (or one) isotropic plates with distributed discrete mass-spring-damper subsystems that act as local vibration absorbers. For an infinite metamaterial plate, its stopband is obtained by dispersion analysis on an analytical unit cell. For a finite metamaterial plate with specific boundary conditions, frequency response analysis of its full-size finite-element model is performed to show its stopband behavior, and the stopband behavior is further confirmed by transient analysis based on direct numerical integration of the finite-element equations. Influences of the vibration absorbers' local resonant frequencies and damping ratios and the plate's damping, boundary conditions, and natural frequencies and mode shapes are thoroughly examined. The concepts of negative effective mass and spring and acoustic and optical wave modes are explained in detail. The working mechanism of acoustic metamaterial plates is revealed to be based on the concept of conventional vibration absorbers. An absorber's resonant vibration excited by the incoming elastic wave generates a concentrated inertial Force to work against the plate's Internal Shear Force, straighten the plate, and attenuate/stop the wave propagation. Numerical results show that the stopband's location is determined by the local resonant frequency of absorbers, the stopband's width increases with the (absorber mass)/(unit cell mass) ratio, and increase of absorbers' damping significantly increases the stopband's width and reduces low-frequency vibration amplitudes. However, too much damping may deactivate the stopband effect, and the plate's material damping is not as efficient as absorbers' damping for suppression of low-frequency vibrations.

Seyed Mohammad - One of the best experts on this subject based on the ideXlab platform.

  • Mechanical performance of v-ribbed belt drives
    1996
    Co-Authors: Tabatabaei Lofty, Seyed Mohammad
    Abstract:

    The design and shape of a v-ribbed belt affects its radial movement in the pulley grooves. When rib bottom/ groove tip contact occurs the wedge action decreases. The beginning of the contact depends on belt tension, fit between rib and groove, wear and material properties. For the first time a non-contact laser displacement meter has been used for dynamic measurements of the radial movement of a v-ribbed belt (type 3PK) around the arc of wrap running on a belt testing rig. Accurate and repeatable results are possible. By the help of this device, the radial movement and the beginning of the rib bottom/groove tip contact around the arc of wrap have been determined experimentally for tested v-ribbed belts. This point plays an important role in the mechanical performance of v-ribbed belt drives. Two sizes of standard pulleys were used for mechanical testing. These were paired with nominal effective diameters, de =45 mm and de =80 mm. Tests were carried out at the speed of c.o =2000 RPM and two different values of total belt tensions (F, + F,) for three different types of rib bottom/groove tip contact. (i) Without contact (ii) With contact (iii) Mixed contact. Slip, torque loss and maximum torque capacity have been measured experimentally during the tests. A v-ribbed belt is assumed to be a combination of a flat belt and a v-belt with the same radial movement of the two parts. Based on these assumptions a new theory is developed for the mechanical performance of v-ribbed belt drives, which gives a new modification to Euler's equation (capstan formula). By the help of Maple V (mathematical standard library software) numerical solutions for theoretical modelling give the variation of non-dimensional values of v-ribbed belt tension, flat belt part of v-ribbed belt tension, v-belt part of v-ribbed belt tension, radial movement and sliding angle with the length of active arc. This theory has been developed to obtain expressions for speed loss (slip) in linear and non-linear zones. The experimental and theoretical results show that the radial movement and slip of the v-ribbed belt with rib bottom I groove tip contact is slightly less than the values without contact. However, in spite of more or less apparent similar performance of v-ribbed belt with and without rib bottom contact, it is found experimentally and theoretically that the compressed rubber of the belt (between cord and pulley) is subjected to a variable Internal Shear Force around the pulley after contact

Tabatabaei Lofty - One of the best experts on this subject based on the ideXlab platform.

  • Mechanical performance of v-ribbed belt drives
    1996
    Co-Authors: Tabatabaei Lofty, Seyed Mohammad
    Abstract:

    The design and shape of a v-ribbed belt affects its radial movement in the pulley grooves. When rib bottom/ groove tip contact occurs the wedge action decreases. The beginning of the contact depends on belt tension, fit between rib and groove, wear and material properties. For the first time a non-contact laser displacement meter has been used for dynamic measurements of the radial movement of a v-ribbed belt (type 3PK) around the arc of wrap running on a belt testing rig. Accurate and repeatable results are possible. By the help of this device, the radial movement and the beginning of the rib bottom/groove tip contact around the arc of wrap have been determined experimentally for tested v-ribbed belts. This point plays an important role in the mechanical performance of v-ribbed belt drives. Two sizes of standard pulleys were used for mechanical testing. These were paired with nominal effective diameters, de =45 mm and de =80 mm. Tests were carried out at the speed of c.o =2000 RPM and two different values of total belt tensions (F, + F,) for three different types of rib bottom/groove tip contact. (i) Without contact (ii) With contact (iii) Mixed contact. Slip, torque loss and maximum torque capacity have been measured experimentally during the tests. A v-ribbed belt is assumed to be a combination of a flat belt and a v-belt with the same radial movement of the two parts. Based on these assumptions a new theory is developed for the mechanical performance of v-ribbed belt drives, which gives a new modification to Euler's equation (capstan formula). By the help of Maple V (mathematical standard library software) numerical solutions for theoretical modelling give the variation of non-dimensional values of v-ribbed belt tension, flat belt part of v-ribbed belt tension, v-belt part of v-ribbed belt tension, radial movement and sliding angle with the length of active arc. This theory has been developed to obtain expressions for speed loss (slip) in linear and non-linear zones. The experimental and theoretical results show that the radial movement and slip of the v-ribbed belt with rib bottom I groove tip contact is slightly less than the values without contact. However, in spite of more or less apparent similar performance of v-ribbed belt with and without rib bottom contact, it is found experimentally and theoretically that the compressed rubber of the belt (between cord and pulley) is subjected to a variable Internal Shear Force around the pulley after contact