scholarly journals Anti-fatigue-fracture hydrogels

2019 ◽  
Vol 5 (1) ◽  
pp. eaau8528 ◽  
Author(s):  
Shaoting Lin ◽  
Xinyue Liu ◽  
Ji Liu ◽  
Hyunwoo Yuk ◽  
Hyun-Chae Loh ◽  
...  
Keyword(s):  
Fatigue Fracture ◽  
Unit Area ◽  
Mechanical Load ◽  
Single Layer ◽  
Polymer Chains ◽  
Fatigue Threshold ◽  
Single Cycle ◽  
Mechanical Loads ◽  
Fracture Properties ◽  
Multiple Cycles

The emerging applications of hydrogels in devices and machines require hydrogels to maintain robustness under cyclic mechanical loads. Whereas hydrogels have been made tough to resist fracture under a single cycle of mechanical load, these toughened gels still suffer from fatigue fracture under multiple cycles of loads. The reported fatigue threshold for synthetic hydrogels is on the order of 1 to 100 J/m2. We propose that designing anti-fatigue-fracture hydrogels requires making the fatigue crack encounter and fracture objects with energies per unit area much higher than that for fracturing a single layer of polymer chains. We demonstrate that the controlled introduction of crystallinity in hydrogels can substantially enhance their anti-fatigue-fracture properties. The fatigue threshold of polyvinyl alcohol (PVA) with a crystallinity of 18.9 weight % in the swollen state can exceed 1000 J/m2.

scholarly journals Fatigue Fracture Properties of Wood Plastic Composites

2015 ◽  
Vol 71 (12) ◽  
pp. 339-344 ◽  
Author(s):  
Nordin M. N. A. ◽  
Yuta Makino ◽  
Koichi Goda ◽  
Hirokazu Ito
Keyword(s):  
Fatigue Fracture ◽  
Wood Plastic Composites ◽  
Fracture Properties ◽  
Plastic Composites

scholarly journals Beyond Trees: Analysis and Convergence of Belief Propagation in Graphs with Multiple Cycles

2020 ◽  
Vol 34 (05) ◽  
pp. 7333-7340
Author(s):  
Roie Zivan ◽  
Omer Lev ◽  
Rotem Galiki
Keyword(s):  
Graphical Models ◽  
Belief Propagation ◽  
Optimization Problems ◽  
Optimal Solution ◽  
Damping Factor ◽  
Constraint Optimization ◽  
Single Cycle ◽  
Distributed Constraint Optimization ◽  
Multiple Cycles ◽  
Constraint Optimization Problems

Belief propagation, an algorithm for solving problems represented by graphical models, has long been known to converge to the optimal solution when the graph is a tree. When the graph representing the problem includes a single cycle, the algorithm either converges to the optimal solution or performs periodic oscillations. While the conditions that trigger these two behaviors have been established, the question regarding the convergence and divergence of the algorithm on graphs that include more than one cycle is still open.Focusing on Max-sum, the version of belief propagation for solving distributed constraint optimization problems (DCOPs), we extend the theory on the behavior of belief propagation in general – and Max-sum specifically – when solving problems represented by graphs with multiple cycles. This includes: 1) Generalizing the results obtained for graphs with a single cycle to graphs with multiple cycles, by using backtrack cost trees (BCT). 2) Proving that when the algorithm is applied to adjacent symmetric cycles, the use of a large enough damping factor guarantees convergence to the optimal solution.

Advanced Ferroelectric MFC Actuators: The Effect of Ferro-Elastic Domain Switching

2008 ◽  
Author(s):  
Uri Kushnir ◽  
Oded Rabinovitch
Keyword(s):  
Nonlinear Response ◽  
Domain Switching ◽  
Mechanical Load ◽  
Fiber Composite ◽  
Beam Element ◽  
Mechanical Loads ◽  
Active Structure ◽  
Elastic Domain ◽  
Macro Fiber Composite ◽  
Fiber Segment

Macro Fiber Composite (MFC) actuators, which are commonly integrated in modern smart structures, may be subjected to high levels of mechanical loads. Opposed to the electrical actuation, these loads are not always controlled or anticipated by the user. Thus, they may yield a response that is beyond the linear range due to a stress induced ferro-elastic domain switching. In this paper, the phenomenon of domain switching and mechanical depolarization in the MFC actuator and the resulting degradation of the actuation capabilities are investigated. As an illustrative numerical example, the response of MFC layers in an active beam element is analyzed. Emphasis is placed on the location of the fiber segment along the active beam with a distinction between the compressed and the tensed layers. The results highlight the range of effects associated with the potential nonlinear response of the active structure under high levels of mechanical load.

scholarly journals Numerical Investigation of the Fracture Properties of Pre-Cracked Monocrystalline/Polycrystalline Graphene Sheets

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 263 ◽  
Author(s):  
Xinliang Li ◽  
Jiangang Guo
Keyword(s):  
Fracture Toughness ◽  
Grain Boundary ◽  
Misorientation Angle ◽  
Strain Energy ◽  
Unit Area ◽  
Crack Tip ◽  
Mode I ◽  
Fracture Properties ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness

The fracture properties of pre-cracked monocrystalline/polycrystalline graphene were investigated via a finite element method based on molecular structure mechanics, and the mode I critical stress intensity factor (SIF) was calculated by the Griffith criterion in classical fracture mechanics. For monocrystalline graphene, the size effects of mode I fracture toughness and the influence of crack width on the mode I fracture toughness were investigated. Moreover, it was found that the ratio of crack length to graphene width has a significant influence on the mode I fracture toughness. For polycrystalline graphene, the strain energy per unit area at different positions was calculated, and the initial fracture site (near grain boundary) was deduced from the variation tendency of the strain energy per unit area. In addition, the effects of misorientation angle of the grain boundary (GB) and the distance between the crack tip and GB on mode I fracture toughness were also analyzed. It was found that the mode I fracture toughness increases with increasing misorientation angle. As the distance between the crack tip and GB increases, the mode I fracture toughness first decreases and then tends to stabilize.

Fracture properties of hybrid woven bamboo/woven e-glass fiber composites

2018 ◽  
Vol 9 (4) ◽  
pp. 491-519
Author(s):  
Aidy Ali ◽  
Wei Kuan Ng ◽  
Faiz Arifin ◽  
Kannan Rassiah ◽  
Faiz Othman ◽  
...  
Keyword(s):  
Unsaturated Polyester ◽  
Single Layer ◽  
Good Alternative ◽  
Compact Tension ◽  
Fiber Composites ◽  
Content Type ◽  
Fracture Properties ◽  
Glass Fiber Composites ◽  
Fracture Tests

Purpose The purpose of this paper is to investigate the fracture properties of hybrid woven bamboo (WB)/woven e-glass (EG) fiber composites with various layer arrangements. This paper utilized a specific type of bamboo species named Gigantochloa Scortechinii (Buluh Semantan). Design/methodology/approach In these experiments, unsaturated polyester, woven EG and WB fibers were prepared through the hand lay-up technique. The composite bamboo strips were prepared in 1.5 mm thickness. The strips are woven to make a single layer. The layer was then laminated into several thicknesses. The specimens were then characterized using compact tension fracture tests. Findings The fracture toughness of 12–14 MPa was obtained. These findings suggest that this hybrid bamboo composite provides superior fracture strength that is equivalent with steel alloy and is extremely a good alternative for reinforcing fibers to combat fracture failures of materials and structures. Originality/value In this paper, experimental determination of newly developed composite made of WB and woven EG is presented.

scholarly journals Effect of Injection-Molded Speed on Fatigue Fracture Properties of Polypropylene.

2000 ◽  
Vol 66 (650) ◽  
pp. 1855-1863 ◽  
Author(s):  
Jianhui QIU ◽  
Makoto KAWAGOE ◽  
Wataru MIZUNO ◽  
Mikio MORITA
Keyword(s):  
Fatigue Fracture ◽  
Fracture Properties ◽  
Injection Molded
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