The Evaluation of Deformation and Fracture of Gilsocarbon Graphite Subject to Service Environments: Experimental and Modelling

2017 ◽  
Vol 754 ◽  
pp. 91-94 ◽  
Author(s):  
B. Šavija ◽  
G.E. Smith ◽  
P.J. Heard ◽  
E. Sarakinou ◽  
J.E. Darnbrough ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reactor Core ◽  
Fracture Characteristics ◽  
Service Environment ◽  
Deformation And Fracture ◽  
Wide Range ◽  
Radiolytic Oxidation ◽  
Service Environments ◽  
Induced Defects ◽  
Irradiation Induced Defects

Commercial graphites are used for a wide range of applications. For example, Gilsocarbon graphite is used within the reactor core of Advanced Gas Cooled Reactors (UK) as a moderator. In service, the mechanical properties of the graphite are changed as a result of neutron irradiation induced defects and porosity arising from radiolytic oxidation. In this paper, we discuss measurements undertaken of mechanical properties at the micro-length-scale for virgin and irradiated material. These data provide the necessary inputs to an experimentally-informed model that predicts the deformation and fracture properties of Gilsocarbon graphite at the centimetrelength-scale. The results provide an improved understanding of how the mechanical properties and fracture characteristics of this type of graphite change as a result of exposure to the service environment.

The Role of Replicated Service Atmosphere on Deformation and Fracture Behaviour of Carburised AISI Type 316H Steel

2019 ◽  
Vol 827 ◽  
pp. 318-323
Author(s):  
A.D. Warren ◽  
P.J. Heard ◽  
P.E.J. Flewitt ◽  
T.L. Martin
Keyword(s):  
Nuclear Reactor ◽  
Fracture Behaviour ◽  
Temperature Deformation ◽  
Heat Transfer Medium ◽  
Fracture Characteristics ◽  
Service Environment ◽  
Aisi Type ◽  
Deformation And Fracture ◽  
The Uk

The UK Advanced Gas Cooled nuclear reactor fleet adopted CO2 gas as the heat transfer medium. Over the plant service life carbon diffuses into the stainless steel components as part of the overall oxidation process. This carbon enrichment promotes carbide precipitation and changes overall microstructure, thereby altering temperature deformation and fracture behaviour. Due to difficulties of replicating the high temperature/high pressure CO2 service environment, many tests are conducted under simulated CO2 conditions. We compare the role of a range of surrogate atmospheres on steel test specimens to one which failed in service to establish the influence of testing atmosphere on creep deformation and fracture characteristics.

scholarly journals Wide range temperature-dependent deformation and fracture mechanisms for 8701 under dynamic and static loading

RSC Advances ◽  
2018 ◽  
Vol 8 (26) ◽  
pp. 14293-14299 ◽  
Author(s):  
Hong-fu Guo ◽  
Yan-qing Wu ◽  
Feng-lei Huang
Keyword(s):  
Mechanical Properties ◽  
Wide Temperature Range ◽  
Static Loading ◽  
Test System ◽  
Fracture Mechanisms ◽  
Temperature Dependent ◽  
Temperature Range ◽  
Deformation And Fracture ◽  
Wide Range ◽  
Hydraulic Servo

The mechanical properties of 8701 were tested over a wide temperature range of −125 °C to 100 °C using the MTS Landmark hydraulic servo test system and SHPB.

Surface mechanical properties of aluminum implanted nickel and co-evaporated Ni–Al on nickel

1990 ◽  
Vol 5 (8) ◽  
pp. 1668-1683 ◽  
Author(s):  
Gary S. Was
Keyword(s):  
Mechanical Properties ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Surface Condition ◽  
Beam Surface ◽  
Hardness Increase ◽  
Nickel Substrates ◽  
Lower Maximum ◽  
Induced Defects ◽  
Irradiation Induced Defects

Implantation of Al into nickel and co-evaporation of Ni–Al films onto nickel substrates followed by ion irradiation was conducted in order to investigate the mechanical properties of ion beam surface modifications and their relation to the composition and microstructure of the surface. Implantations were made using 400 keV Al+ to doses from 1 × 1015 to 6 × 1017 cm−2 at room temperature. Nickel films with 0–25% Al were co-evaporated onto nickel substrates and mixed using the same irradiation conditions but to a lower maximum dose. Hardness was measured using ultra-low load indentation, and residual stress was measured by the bending beam method. Results indicate that the primary contributor to the hardness increase of as-implanted surfaces is the irradiation-induced defects. The effect of Al in solution (γ phase) or Al in γ′ (Ni3Al) in either implanted or co-evaporated and mixed surfaces is evident only upon thermal treating to remove radiation damage. The high inherent hardness of the co-evaporated films is due to the small grain size of the film. The magnitude of the hardness in Al implanted nickel is very sensitive to the surface condition of the substrate. The observed hardness effects are all directly relatable to microstructure or phases present. Residual stresses change from tensile to compressive as a result of damage from low dose irradiation and heat treatment.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

scholarly journals A Slot-Die Technique for the Preparation of Continuous, High-Area, Chitosan-Based Thin Films

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1566
Author(s):  
Oliver J. Pemble ◽  
Maria Bardosova ◽  
Ian M. Povey ◽  
Martyn E. Pemble
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
High Volume ◽  
Mechanical Anisotropy ◽  
Diverse Range ◽  
Direction Parallel ◽  
High Area ◽  
Wide Range ◽  
Slot Die ◽  
Potential Applications

Chitosan-based films have a diverse range of potential applications but are currently limited in terms of commercial use due to a lack of methods specifically designed to produce thin films in high volumes. To address this limitation directly, hydrogels prepared from chitosan, chitosan-tetraethoxy silane, also known as tetraethyl orthosilicate (TEOS) and chitosan-glutaraldehyde have been used to prepare continuous thin films using a slot-die technique which is described in detail. By way of preliminary analysis of the resulting films for comparison purposes with films made by other methods, the mechanical strength of the films produced was assessed. It was found that as expected, the hybrid films made with TEOS and glutaraldehyde both show a higher yield strength than the films made with chitosan alone. In all cases, the mechanical properties of the films were found to compare very favorably with similar measurements reported in the literature. In order to assess the possible influence of the direction in which the hydrogel passes through the slot-die on the mechanical properties of the films, testing was performed on plain chitosan samples cut in a direction parallel to the direction of travel and perpendicular to this direction. It was found that there was no evidence of any mechanical anisotropy induced by the slot die process. The examples presented here serve to illustrate how the slot-die approach may be used to create high-volume, high-area chitosan-based films cheaply and rapidly. It is suggested that an approach of the type described here may facilitate the use of chitosan-based films for a wide range of important applications.

scholarly journals Effects of a Twin-Screw Extruder Equipped with a Molten Resin Reservoir on the Mechanical Properties and Microstructure of Recycled Waste Plastic Polyethylene Pellet Moldings

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1058
Author(s):  
Hikaru Okubo ◽  
Haruka Kaneyasu ◽  
Tetsuya Kimura ◽  
Patchiya Phanthong ◽  
Shigeru Yao
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Value Added ◽  
Industrial Applications ◽  
Twin Screw Extruder ◽  
Screw Extruder ◽  
Polymer Properties ◽  
Wide Range ◽  
Twin Screw ◽  
Recycled Plastics

Each year, increasing amounts of plastic waste are generated, causing environmental pollution and resource loss. Recycling is a solution, but recycled plastics often have inferior mechanical properties to virgin plastics. However, studies have shown that holding polymers in the melt state before extrusion can restore the mechanical properties; thus, we propose a twin-screw extruder with a molten resin reservoir (MSR), a cavity between the screw zone and twin-screw extruder discharge, which retains molten polymer after mixing in the twin-screw zone, thus influencing the polymer properties. Re-extruded recycled polyethylene (RPE) pellets were produced, and the tensile properties and microstructure of virgin polyethylene (PE), unextruded RPE, and re-extruded RPE moldings prepared with and without the MSR were evaluated. Crucially, the elongation at break of the MSR-extruded RPE molding was seven times higher than that of the original RPE molding, and the Young’s modulus of the MSR-extruded RPE molding was comparable to that of the virgin PE molding. Both the MSR-extruded RPE and virgin PE moldings contained similar striped lamellae. Thus, MSR re-extrusion improved the mechanical performance of recycled polymers by optimizing the microstructure. The use of MSRs will facilitate the reuse of waste plastics as value-added materials having a wide range of industrial applications.

scholarly journals Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1851
Author(s):  
Hye-Seon Park ◽  
Chang-Kook Hong
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Crystallization Behavior ◽  
Mechanical Analysis ◽  
X Ray Diffraction ◽  
Nucleation Agent ◽  
Scanning Calorimetry ◽  
Nucleation Sites ◽  
Wide Range ◽  
Degree Of Crystallization

Poly (l-lactic acid) (PLLA) is a promising biomedical polymer material with a wide range of applications. The diverse enantiomeric forms of PLLA provide great opportunities for thermal and mechanical enhancement through stereocomplex formation. The addition of poly (d-lactic acid) (PDLA) as a nucleation agent and the formation of stereocomplex crystallization (SC) have been proven to be an effective method to improve the crystallization and mechanical properties of the PLLA. In this study, PLLA was blended with different amounts of PDLA through a melt blending process and their properties were calculated. The effect of the PDLA on the crystallization behavior, thermal, and mechanical properties of PLLA were investigated systematically by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized optical microscopy (POM), dynamic mechanical analysis (DMA), and tensile test. Based on our findings, SC formed easily when PDLA content was increased, and acts as nucleation sites. Both SC and homo crystals (HC) were observed in the PLLA/PDLA blends. As the content of PDLA increased, the degree of crystallization increased, and the mechanical strength also increased.

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