scholarly journals Scalable En Echelon Shear‐Fracture Aperture‐Roughness Mechanism: Theory, Validation, and Implications

2019 ◽  
Vol 124 (1) ◽  
pp. 957-977 ◽  
Author(s):  
Luke P. Frash ◽  
J. William Carey ◽  
Nathan J. Welch
Keyword(s):  
Shear Fracture ◽  
Fracture Aperture ◽  
Mechanism Theory

scholarly journals Mechanical properties, deformation and fracture mechanisms of bimodal Cu under tensile test

2021 ◽  
Vol 60 (1) ◽  
pp. 15-24
Author(s):  
Silu Liu ◽  
Yonghao Zhao
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Tensile Specimen ◽  
Deformation Mechanisms ◽  
Fracture Mechanisms ◽  
Fracture Angle ◽  
Area Reduction

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83∘ and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70∘, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

scholarly journals Design of Self-Reconfigurable Multiarm Robot Mechanism Based on Deployable Kinematic Chains

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Fu-Qun Zhao ◽  
Sheng Guo ◽  
Hai-Jun Su ◽  
Hai-Bo Qu ◽  
Ya-Qiong Chen
Keyword(s):  
Parallel Mechanism ◽  
Parallel Mechanisms ◽  
Kinematic Chains ◽  
Assembly Method ◽  
Operation Modes ◽  
Object Based ◽  
Switch Operation ◽  
Storage Area ◽  
Mechanism Theory

Abstract As the structures of multiarm robots are serially arranged, the packaging and transportation of these robots are often inconvenient. The ability of these robots to operate objects must also be improved. Addressing this issue, this paper presents a type of multiarm robot that can be adequately folded into a designed area. The robot can achieve different operation modes by combining different arms and objects. First, deployable kinematic chains (DKCs) are designed, which can be folded into a designated area and be used as an arm structure in the multiarm robot mechanism. The strategy of a platform for storing DKCs is proposed. Based on the restrictions in the storage area and the characteristics of parallel mechanisms, a class of DKCs, called base assembly library, is obtained. Subsequently, an assembly method for the synthesis of the multiarm robot mechanism is proposed, which can be formed by the connection of a multiarm robot mechanism with an operation object based on a parallel mechanism structure. The formed parallel mechanism can achieve a reconfigurable characteristic when different DKCs connect to the operation object. Using this method, two types of multiarm robot mechanisms with four DKCs that can switch operation modes to perform different tasks through autonomous combination and release operation is proposed. The obtained mechanisms have observable advantages when compared with the traditional mechanisms, including optimizing the occupied volume during transportation and using parallel mechanism theory to analyze the switching of operation modes.

Robust characterization of anisotropic shear fracture strains with constant triaxiality using shape optimization of torsional twin bridge specimen

CIRP Annals ◽  
2021 ◽  
Author(s):  
Yongnam Kim ◽  
Shunying Zhang ◽  
Vincent Grolleau ◽  
Christian C. Roth ◽  
Dirk Mohr ◽  
...  
Keyword(s):  
Shape Optimization ◽  
Shear Fracture

Shear fracture in bulk metallic glass composites

2021 ◽  
pp. 116963
Author(s):  
Devashish Rajpoot ◽  
R. Lakshmi Narayan ◽  
Long Zhang ◽  
Punit Kumar ◽  
Haifeng Zhang ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Shear Fracture ◽  
Glass Composites ◽  
Bulk Metallic Glass Composites

Virtual-mechanism-based analysis of cooperative manipulation

2005 ◽  
Vol 219 (3) ◽  
pp. 315-323
Author(s):  
H Liu ◽  
J S Dai ◽  
H Y Xu ◽  
H Li
Keyword(s):  
Trajectory Planning ◽  
Manipulation Planning ◽  
End Points ◽  
New Approach ◽  
Cooperative Manipulation ◽  
Hypothetical Mechanism ◽  
End Effectors ◽  
Cooperative Manipulators ◽  
Mechanism Theory

This paper proposes a new approach for analysing cooperative manipulation in which cooperative manipulators form a mechanism closure that allows a virtual-mechanism-based analysis to take place. The method is based on the geometry of manipulators during manipulation and converts the cooperative manipulation problem into the analysis of a hypothetical mechanism so that the mechanism theory can be used for the manipulation. This mechanism is hence generated by the fact that the end points (or geometric centres of respective grippers) of cooperative manipulators coincide with a virtual joint during cooperative manipulation. The analysis not only generates positions and orientations of the end effectors of cooperative manipulators but also produces corresponding link configurations that can be used for manipulation planning. The approach is further used for the orientation-based trajectory planning with two different cases. Simulations and discussions are made with respect to cooperative manipulations using two 2R manipulators and one 2R manipulators and one 3R manipulator.

Subsurface fracture surveys using a borehole television camera and acoustic televiewer

1987 ◽  
Vol 24 (4) ◽  
pp. 499-508 ◽  
Author(s):  
J. S. O. Lau ◽  
L. F. Auger ◽  
J. G. Bisson
Keyword(s):  
Rapid Assessment ◽  
Cost Effective ◽  
Fracture Aperture ◽  
Computer Data ◽  
Fracture Characteristics ◽  
Television Camera ◽  
Strip Chart ◽  
Data Record ◽  
Magnetic North ◽  
Apparent Orientation

Borehole television survey and acoustic televiewer logging provide rapid, cost-effective, and accurate methods of surveying fractures and their characteristics within boreholes varying in diameter from 7.6 to 15.3 cm. In the television survey, a camera probe is used to inspect the borehole walls. Measurements of location, orientation, infilling width, and aperture of fractures are made on the television screen and recorded on computer data record sheets. All observations are recorded on video cassette tapes. With the acoustic televiewer, oriented images of fractures in the borehole walls are recorded on a strip–chart log and also on video cassette tapes. The images are displayed as if the walls were split vertically along magnetic north and spread out horizontally. Measurements of fracture characteristics are made on the strip–chart log, using a digitizing table and a microcomputer, and the data recorded on floppy diskettes. In both surveys, an inclined fracture is displayed as a sinusoidal curve, from which the apparent orientation of the fracture can be measured. Once the borehole orientation is known, the true orientation of the fracture can be computed from its apparent orientation. Computer analysis of the fracture data, provides a rapid assessment of fracture occurrence, fracture aperture, and statistically significant concentrations of fracture orientations. Key words: borehole, television survey, acoustic televiewer logging, fractures, distribution, orientation, aperture.

Effects of diagenesis (cement precipitation) during fracture opening on fracture aperture-size scaling in carbonate rocks

2012 ◽  
Vol 370 (1) ◽  
pp. 187-206 ◽  
Author(s):  
J. N. Hooker ◽  
L. A. Gomez ◽  
S. E. Laubach ◽  
J. F. W. Gale ◽  
R. Marrett
Keyword(s):  
Carbonate Rocks ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Size Scaling ◽  
Fracture Opening

Mechanisms of Synchronous Belt Tooth Failure due to Fatigue Shear Fracture

2011 ◽  
Vol 86 ◽  
pp. 566-569
Author(s):  
Jian Hua Guo ◽  
Hong Yuan Jiang ◽  
Dong Sheng Li
Keyword(s):  
Conformal Mapping ◽  
Compressive Stress ◽  
Shear Fracture ◽  
Complex Function ◽  
Fatigue Cracking ◽  
Plane Elasticity ◽  
Mapping Method ◽  
Tooth Surface ◽  
Tooth Root ◽  
Shear Cracking

Conformal mapping with complex function based on plane elasticity mechanics is an analytical method for resolving stress and displacement at any point of a half-plane domain. Using complex function conformal mapping method in this article we investigated the relationship between load on tooth surface and maximum stress at tooth root for calculating the maximum compressive stress on the opposite side of working flank and maximum tensile stress on working flank side when loads are applied to tooth top and root of working flank side, respectively. The maximum tensile and compressive stress at the tooth root are the main forces that cause fatigue cracking of the tooth root, which may extend along the elastomer compound-cord interface resulting in shear cracking of the belt tooth. The results of our calculation reveal the mechanisms whereby tooth shear cracking causes fatigue failure of synchronic belt, which are consistent with the experimental research results of Lizuka.

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