Tilting cracks: the evolution of fracture surface topology in brittle solids

1993 ◽  
Vol 62 (2) ◽  
pp. 119-138 ◽  
Author(s):  
Derek Hull
Keyword(s):  
Fracture Surface ◽  
Surface Topology ◽  
Brittle Solids

Intercalated clay nanocomposites: Morphology, mechanics and fracture behavior

2000 ◽  
Vol 661 ◽  
Author(s):  
Adam S. Zerda ◽  
Alan J. Lesser
Keyword(s):  
Fracture Toughness ◽  
Fracture Surface ◽  
Failure Mechanism ◽  
Fracture Behavior ◽  
Surface Topology ◽  
Clay Nanocomposites ◽  
Compressive Behavior ◽  
Modified Montmorillonite ◽  
Montmorillonite Clays ◽  
Curing Agents

ABSTRACTIntercalated nanocomposites of modified montmorillonite clays in a glassy epoxy were prepared by crosslinking with commercially available aliphatic diamine curing agents. These materials are shown to have improved Young's modulus but corresponding reductions in ultimate strength and strain to failure. These results are consistent with most particulate filled systems, The macroscopic compressive behavior is unchanged, although the failure mechanism in compression varies from the unmodified samples. The fracture toughness of these materials is investigated and improvements in toughness values of 200% over unmodified resis are demonstrated. The fracture surface topology is examined using SEM and tappin-mode AFM and showm to be related to the clay morphology of the system.

scholarly journals Biomechanical Behavior of a Variable Angle Locked Tibiotalocalcaneal Construct

2020 ◽  
Vol 7 (1) ◽  
pp. 27
Author(s):  
Farah Hamandi ◽  
Gerard Simon ◽  
Richard Laughlin ◽  
Tarun Goswami
Keyword(s):  
Fracture Surface ◽  
Surface Topology ◽  
Cannulated Screws ◽  
Stainless Steel 316L ◽  
Biomechanical Behavior ◽  
System A ◽  
Variable Angle ◽  
Failure Conditions ◽  
Beach Marks ◽  
Corrosion Pits

This paper examines the mechanics of the tibiotalocalcaneal construct made with a PHILOS plating system. A failed device consisting of the LCP plate and cortical, locking, and cannulated screws was used to perform the analysis. Visual, microstructure, and fractographic examinations were carried out to characterize the fracture surface topology. These examinations revealed the presence of surface scratching, inclusions, discoloration, corrosion pits, beach marks, and cleavage and striations on the fracture surface. Further examination of the material crystallography and texture revealed an interaction of S, Ni, and Mo-based inclusions that may have raised pitting susceptibility of the device made with Stainless Steel 316L. These features suggest that the device underwent damage by pitting the corrosion-fatigue mechanism and overloading towards the end to fail the plate and screws in two or more components. The screws failed via conjoint bending and torsion fatigue mechanisms. Computer simulations of variable angle locking screws were performed in this paper. The material of construction of the device was governed by ASTM F138-8 or its ISO equivalent 5832 and exhibited inconsistencies in chemistry and hardness requirements. The failure conditions were matched in finite element modeling and those boundary conditions discussed in this paper.

scholarly journals Peridynamic analysis of dynamic fracture: influence of peridynamic horizon, dimensionality and specimen size

2021 ◽  
Author(s):  
Sahir N. Butt ◽  
Günther Meschke
Keyword(s):  
Dynamic Fracture ◽  
Fracture Process ◽  
Three Dimensional ◽  
Specimen Size ◽  
Surface Topology ◽  
Linear Elastic ◽  
Brittle Solids ◽  
Non Local ◽  
Elastic Fracture ◽  
Three Dimensional Simulations

AbstractIn peridynamic models for fracture, the dissipated fracture energy is regularized over a non-local region denoted as the peridynamic horizon. This paper investigates the influence of this parameter on the dynamic fracture process in brittle solids, using two as well as three dimensional simulations of dynamic fracture propagation in a notched plate for two loading cases. The predicted crack speed for the various scenarios of the initially stored energy, also known as the velocity toughening behavior as well as characteristics of the crack surface topology obtained in different crack propagation regimes in 3D computational simulations are compared with the experimentally observed crack velocity and fracture surfaces for Polymethyl Methacrylate (PMMA) specimens. In addition, we investigate the influence of the specimen size on the dynamic fracture process using two dimensional peridynamic simulations. The fracture strengths and the velocity toughening relationship obtained from different specimen sizes are compared with the Linear Elastic Fracture Mechanics (LEFM) size effect relationship and with results from experiments, respectively.

Numerical Modelling of Plasticity Induced Crack Closure with Rough Fracture Surfaces

2019 ◽  
Vol 827 ◽  
pp. 7-12
Author(s):  
Aleš Materna ◽  
Hynek Lauschmann ◽  
Jan Ondráček
Keyword(s):  
Fatigue Crack ◽  
Fracture Surface ◽  
Element Model ◽  
Surface Topology ◽  
304 Stainless Steel ◽  
Surface Fatigue ◽  
Shaped Crack ◽  
Surface Fatigue Crack ◽  
Crack Faces ◽  
Plasticity Induced Crack Closure

A two-dimensional elastic-plastic finite element model was built to simulate the closure of a long fatigue crack with arbitrarily shaped crack faces. The model growth is simulated by the successive mesh splitting along the crack path defined by element edges. To obtain a realistic morphology of the fracture surface, fatigue crack growth experiments with CT specimen made from AISI 304 stainless steel were performed and fracture surface topology was determined using a single camera and a depth-from-focus method. Simulated closing loads and closure lengths for the cracks with rough and smooth faces and for plane-stress and plane-strain conditions are compared. A mismatch of rough crack faces, resulting in an additional contact, is visualized.

scholarly journals Fracture surface formation of notched 2017A-T4 aluminium alloy under bending fatigue

2021 ◽  
Author(s):  
Wojciech Macek
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Surface ◽  
Crack Initiation ◽  
Aluminium Alloy ◽  
Crack Growth ◽  
Surface Topology ◽  
Surface Measurement ◽  
Bending Fatigue ◽  
Fracture Surfaces

AbstractThe effect of cyclic loading on facture surface topology in notched components made by aluminium alloys is not completely clear. Fractography and fracture mechanics can help to understand this interdependency. This paper aims to study the distribution of the fracture surface roughness of notched 2017A-T4 aluminium alloy after bending fatigue using an optical focus-variation surface measurement technique by applying the fracture zone concept. The effects of stress level at the notch root and the load ratio on fatigue crack growth and fracture surfaces are analysed. Profile and areal surface parameters of four fracture surface regions were investigated at incremental crack lengths of the specimens. Studies have confirmed that the surface areas associated with the main stages of fatigue phenomenon (i.e. crack initiation, crack propagation, and final rupture) have significant differences in roughness which can be explained by the different loading scenarios. Overall, fatigue fracture surfaces have smallest roughness values at the crack initiation stage and a gradual increase during the fatigue crack growth stage.

Processing of human melanoma cells for correlative TEM, LVSEM, and LM

1991 ◽  
Vol 49 ◽  
pp. 106-107
Author(s):  
Marek Malecki ◽  
J. Victor Small ◽  
James Pawley
Keyword(s):  
Electron Microscopy ◽  
Low Voltage ◽  
Fluorescent Microscopy ◽  
Blood Stream ◽  
Surface Topology ◽  
Integrin Receptors ◽  
Transmission Electron ◽  
Develop Technology ◽  
Voltage Scanning ◽  
Mechanisms Of Adhesion

The relative roles of adhesion and locomotion in malignancy have yet to be clearly established. In a tumor, subpopulations of cells may be recognized according to their capacity to invade neighbouring tissue,or to enter the blood stream and metastasize. The mechanisms of adhesion and locomotion are themselves tightly linked to the cytoskeletal apparatus and cell surface topology, including expression of integrin receptors. In our studies on melanomas with Fluorescent Microscopy (FM) and Cell Sorter(FACS), we noticed that cells in cultures derived from metastases had more numerous actin bundles, then cells from primary foci. Following this track, we attempted to develop technology allowing to compare ultrastructure of these cells using correlative Transmission Electron Microscopy(TEM) and Low Voltage Scanning Electron Microscopy(LVSEM).

Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

Warm and freeze-fracture of cotton seed radicles

1987 ◽  
Vol 45 ◽  
pp. 984-985
Author(s):  
E. L. Vigil ◽  
E. F. Erbe
Keyword(s):  
Thin Film ◽  
Water Vapor ◽  
Fracture Surface ◽  
Membrane Structure ◽  
Room Temperature ◽  
Freeze Fracture ◽  
Longitudinal Axis ◽  
Fracture Plane ◽  
Cotton Seeds ◽  
Condensed Water

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.

On impact upon brittle solids

2000 ◽  
Vol 10 (PR9) ◽  
pp. Pr9-281-Pr9-286 ◽  
Author(s):  
N. K. Bourne ◽  
J. C.F. Millett
Keyword(s):  
Brittle Solids
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