Mechanical properties of granular media, including snow, investigated by a low-frequency forced torsion pendulum

2000 ◽  
Vol 62 (1) ◽  
pp. 982-992 ◽  
Author(s):  
G. D’Anna
Keyword(s):  
Mechanical Properties ◽  
Granular Media ◽  
Low Frequency ◽  
Torsion Pendulum

A Low-Frequency Forced Torsion Pendulum for the Measurement of the Mechanical Properties of Granular Media

2000 ◽  
Vol 627 ◽  
Author(s):  
G. D'Anna
Keyword(s):  
Mechanical Properties ◽  
Granular Media ◽  
Low Frequency ◽  
Glass Beads ◽  
Torsion Pendulum ◽  
Dynamic Moduli ◽  
Small Glass ◽  
Static Mechanical ◽  
Macroscopic Failure ◽  
Static Mechanical Properties

ABSTRACTWe present a forced torsion pendulum designed to measure the dynamic moduli of granular media. In the method, the oscillating probe of the pendulum is immersed into various materials, such as sand, glass beads, snow. The apparatus operates at low-frequency and provides information about the quasi-static mechanical properties of the medium. In particular, a peak in the losses is ascribed to friction and cohesion between the grains, and a measure of the macroscopic failure limit can be obtained. As an example the effect of moisture-induced ageing in small glass beads, and the effect of sintering of ice grains in snow, are shown.

Stress fields in granular material and implications for performance of robot locomotion over granular media

2015 ◽  
Vol 8 (1) ◽  
pp. 2005-2009
Author(s):  
Diandong Ren ◽  
Lance M. Leslie ◽  
Congbin Fu
Keyword(s):  
Mechanical Properties ◽  
Granular Material ◽  
Granular Media ◽  
Rotation Frequency ◽  
Legged Locomotion ◽  
Working Environment ◽  
Navier Stokes ◽  
Maximum Speed ◽  
Sigmoid Curve ◽  
Multi Body

 Legged locomotion of robots has advantages in reducing payload in contexts such as travel over deserts or in planet surfaces. A recent study (Li et al. 2013) partially addresses this issue by examining legged locomotion over granular media (GM). However, they miss one extremely significant fact. When the robot’s wheels (legs) run over GM, the granules are set into motion. Hence, unlike the study of Li et al. (2013), the viscosity of the GM must be included to simulate the kinematic energy loss in striking and passing through the GM. Here the locomotion in their experiments is re-examined using an advanced Navier-Stokes framework with a parameterized granular viscosity. It is found that the performance efficiency of a robot, measured by the maximum speed attainable, follows a six-parameter sigmoid curve when plotted against rotating frequency. A correct scaling for the turning point of the sigmoid curve involves the footprint size, rotation frequency and weight of the robot. Our proposed granular response to a load, or the ‘influencing domain’ concept points out that there is no hydrostatic balance within granular material. The balance is a synergic action of multi-body solids. A solid (of whatever density) may stay in equilibrium at an arbitrary depth inside the GM. It is shown that there exists only a minimum set-in depth and there is no maximum or optimal depth. The set-in depth of a moving robot is a combination of its weight, footprint, thrusting/stroking frequency, surface property of the legs against GM with which it has direct contact, and internal mechanical properties of the GM. If the vehicle’s working environment is known, the wheel-granular interaction and the granular mechanical properties can be grouped together. The unitless combination of the other three can form invariants to scale the performance of various designs of wheels/legs. Wider wheel/leg widths increase the maximum achievable speed if all other parameters are unchanged.

Sound insulation performance of pyramidal truss core sandwich structure with frame

2021 ◽  
pp. 109963622110288
Author(s):  
Yu-Zhou Wang ◽  
Li Ma
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structure ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Insulation ◽  
Geometrical Parameters ◽  
Acoustic Performance ◽  
Truss Core ◽  
Pyramidal Truss ◽  
Wave Angle

Recently, sandwich structures have been widely used in different fields because of their good mechanical properties, but these structures are weak in acoustic performance. In this paper, by combining pyramidal truss core sandwich structure with frame, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the pyramidal truss core sandwich structure with frame is developed to investigate the sound transmission loss (STL) performance. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the incident wave angle and the geometrical parameters on the STL of the structure are discussed.

scholarly journals Torsion-Bar Antenna: A ground-based mid-frequency and low-frequency gravitational wave detector

2019 ◽  
Vol 29 (04) ◽  
pp. 1940003 ◽  
Author(s):  
Tomofumi Shimoda ◽  
Satoru Takano ◽  
Ching Pin Ooi ◽  
Naoki Aritomi ◽  
Yuta Michimura ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Gravitational Wave ◽  
Low Frequency ◽  
Gravitational Wave Detector ◽  
Torsion Pendulum ◽  
Rotational Mode ◽  
Prototype Development ◽  
The Past ◽  
Wave Detector ◽  
Torsion Bar

Expanding the observational frequency of gravitational waves is important for the future of astronomy. Torsion-Bar Antenna (TOBA) is a mid-frequency and low-frequency gravitational wave detector using a torsion pendulum. The low resonant frequency of the rotational mode of the torsion pendulum enables ground-based observations. The overview of TOBA, including the past and present status of the prototype development, is summarized in this paper.

Microstructures and Mechanical Properties of AZ31B Extruded Sheets from Different Casting Processing

2007 ◽  
Vol 546-549 ◽  
pp. 399-402
Author(s):  
Qi Chi Le ◽  
Zi Qiang Zhang ◽  
Jian Zhong Cui
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Electromagnetic Field ◽  
Deformation Process ◽  
Low Frequency ◽  
High Quality ◽  
Refined Microstructure ◽  
Plastic Deformation Process ◽  
Dc Casting ◽  
Microstructures And Mechanical Properties

A novel way producing magnesium billets, LFEC (low frequency electromagnetic casting processing), was developed in Northeastern University in China. The high-quality magnesium billets with less macrosegregation, refined microstructure, and better surface quality were achieved because the temperature field and the flow pattern of magnesium DC casting were improved significantly after applying low frequency electromagnetic field. Extrusion is an important plastic deformation process for magnesium alloys. In this research, the magnesium billets from LFEC were extruded through a special designed die into sheets. The results of investigation on AZ31B indicated that the extrusion velocity has obvious effects on their microstructures and mechanical properties and the sheets from LFEC had finer microstructure and higher mechanical properties than that from conventional DC casting.

EXPERIMENTAL STUDY OF ENERGY ABSORPTION PROPERTIES OF GRANULAR MATERIALS UNDER LOW FREQUENCY VIBRATIONS

2004 ◽  
Vol 18 (17n19) ◽  
pp. 2708-2712
Author(s):  
MAO-BIN HU ◽  
XIANG-ZHAO KONG ◽  
QING-SONG WU ◽  
ZHEN-GANG ZHU
Keyword(s):  
Experimental Study ◽  
Granular Materials ◽  
Energy Absorption ◽  
Vibration Frequency ◽  
Absorption Rate ◽  
Low Frequency ◽  
Vibration Energy ◽  
Torsion Pendulum ◽  
Absorption Properties ◽  
Low Frequency Vibration

The low frequency vibration energy absorption properties of granular materials have been investigated on an Invert Torsion Pendulum (ITP). The energy absorption rate of granular material changes nonlinearly with amplitude under low frequency vibration. The frequency of ITP system increases a little with granular materials in the holding cup. The vibration frequency of ITP system does not change with time.

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