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.

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 Discussion of fracture surface using beach marks on fatigue test data with large scale piping

2019 ◽  
Vol 19 ◽  
pp. 64-72
Author(s):  
Masaru Bodai ◽  
Yuichiro Nomura ◽  
Daiki Takagoshi ◽  
Seiji Asada ◽  
Kentaro Hayashi
Keyword(s):  
Fracture Surface ◽  
Fatigue Test ◽  
Test Data ◽  
Large Scale ◽  
Beach Marks

Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology

2021 ◽  
pp. 095440622110431
Author(s):  
Madjid Shamsarjmand ◽  
Saeed Adibnazari
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Crack Size ◽  
Fatigue Tests ◽  
Az31 Magnesium Alloy ◽  
Surface Topology ◽  
Nacl Solution ◽  
New Model ◽  
Proposed Model ◽  
Corrosion Pits

This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The fatigue life of 1-4-hour pre-corroded AZ31 specimens could be predicted accurately by this new model. The Levenberg-Marquardt and curve-fitting methods were used to obtain the constant parameters. The relative error between the crack size corresponding to the immersion time and the virtual crack size calculated by the proposed model was less than 1%.

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.

scholarly journals Blade Lock Ring of 4th Stage Compressor Rotor: Failure Investigation

2019 ◽  
Vol 4 (3) ◽  
pp. 85-95
Author(s):  
Ashok Kumar Singh ◽  
Aginaparru Sambasiva Rao
Keyword(s):  
Stainless Steel ◽  
Fracture Surface ◽  
Martensitic Stainless Steel ◽  
Tempered Martensite ◽  
Near Surface ◽  
Compressor Rotor ◽  
Failure Investigation ◽  
Metallic Inclusions ◽  
Corrosion Pits ◽  
Lock Ring

Present work describes the failure investigation of blade lock ring of 4th stage compressor rotor. The lock ring is fabricated from martensitic stainless steel. The microstructure of failed lock ring is tempered martensite. It shows non-metallic inclusions with three distinct shapes namely, elongated (MnS), globular (Al2O3) and complex shaped (oxy-sulphide). The corrosion pits and corrosion debris are observed in un-etched microstructure and fracture surface, respectively. The tree like branching cracks has observed at several places near surface. These cracks have initiated from the corrosion pits and then propagated inside the material. The interface of inclusions and matrix has also acted as crack initiator.  The lock ring has initially suffered pitting corrosion in service and then cracks have propagated inside the material by stress corrosion cracking.

New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

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).

Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

1995 ◽  
Vol 53 ◽  
pp. 512-513
Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf
Keyword(s):  
Sample Preparation ◽  
Milling Time ◽  
High Density ◽  
Low Density ◽  
Ion Milling ◽  
High Quality ◽  
Variable Angle ◽  
Major Disadvantage ◽  
Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

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