On the high-stress region stress exponent during creep

1995 ◽  
Vol 32 (11) ◽  
pp. 1889-1893 ◽  
Author(s):  
Z.F. Zhou ◽  
B.A. Parker
Keyword(s):  
Stress Exponent ◽  
High Stress ◽  
High Stress Region ◽  
Stress Region

The Crack Arrest Capability of 9-Percent Ni Steels (ASTM 553, Type 1) LNG Storage Tanks

1991 ◽  
Vol 113 (3) ◽  
pp. 380-384
Author(s):  
P. B. Crosley ◽  
E. J. Ripling
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
High Stress ◽  
Crack Arrest ◽  
Storage Tanks ◽  
Membrane Stress ◽  
High Stress Region ◽  
Fast Running ◽  
Stress Region

Safety of structures can be assured, even if cracks initiate in localized regions of abnormally low toughness, and/or abnormally high stress (LT/HS), if the materials from which they are fabricated have a high enough crack arrest fracture toughness. When this requirement is met, fast-running cracks that initiate in LT/HS regions arrest when their tip encounters material having normal toughness and stresses. The work described in this paper was carried out to determine the crack arrest capability of LNG storage tanks by determining the longest LT/HS region in which a crack could initiate and still arrest when it leaves this region. The determination consisted of relating a fracture analysis with the measured full-thickness crack arrest fracture toughness of three 9-percent Ni plates which were reported in reference [1]. The calculations used a residual stress pattern, produced by welding, superimposed on a typical membrane stress. The residual stress was selected as an example of a localized high stress region. It was found that tanks built from the poorest of the three tested plates could arrest cracks about 3/4 m long, while tanks built from the two tougher plates could arrest cracks almost 2 m long.

Creep and Fracture Mechanisms in an Oxide-Dispersion Strengthened Ni3Al-Based Alloy Between 649°C and 982°C

1994 ◽  
Vol 364 ◽  
Author(s):  
Ralph P. Mason ◽  
Nicholas J. Grant
Keyword(s):  
Stress Exponent ◽  
High Stress ◽  
Oxide Dispersion Strengthened ◽  
Fracture Mechanisms ◽  
Oxide Dispersion ◽  
Creep Tests ◽  
Creep Mechanisms ◽  
Stress Region ◽  
Power Law Creep ◽  
Reported Data

AbstractAn oxide-dispersion strengthened (ODS) Ni3Al-based alloy has been fabricated and creep tested. Previously reported data for minimum creep rate as a function of stress indicated that two creep mechanisms operate at intermediate temperatures of 732 and 816°C [1]. This paper reports the results of recent interrupted creep tests and fractographic studies which serve to identify the two creep mechanisms. Creep at low stresses or low creep-rates occurs by constrained growth of cavities on transverse grain boundaries. In this low stress region an apparent stress exponent of 5.1 is observed. Creep at high stresses or high creep-rates results from the bulk deformation of grains by power law creep with a much smaller contribution due to grain boundary cavitation. The stress exponents of 13 and 22 observed in this high stress region are typical of ODS alloys. In both regions fracture is observed to be mixed mode with a large transgranular component due to the high grain aspect ratio developed in this material. Limited data at 982°C indicate the occurrence of only one mechanism which can be described by a stress exponent of 9.1. It was not possible, based on fractographic studies, to associate the creep mechanism at 982°C with either of those observed at the intermediate temperatures. No fractographic studies were performed at 649°C due to lack of valid specimens; however, the stress exponent of 13.5 observed at 649°C suggests that creep occurs by deformation of the grains.

Effect of Electroless Ni-P Plating on the Fatigue Strength of Dilute Al-Si Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 290-295
Author(s):  
Norihito Nagata ◽  
Teruto Kanadani ◽  
Minoru Fukuhara ◽  
Makoto Hino ◽  
Koji Murakami
Keyword(s):  
Fatigue Strength ◽  
High Stress ◽  
Aging Treatment ◽  
Hydrogen Gas ◽  
Breaking Elongation ◽  
High Stress Region ◽  
Stress Region ◽  
Electroless Ni ◽  
Clear Increase ◽  
Strength And Ductility

In this study, the effect of electroless Ni-P plating on the fatigue strength of dilute Al-Si alloys was investigated. As results, the following points were clarified. Fatigue strength of the specimen subjected to zincate treatment only after furnace cooling treatment was almost the same as the furnace cooling only. Fatigue strength of the specimen subjected to Ni-P plating after furnace cooling treatment, was reduced overall, except for high-stress region, rather than one of non-processing materials. Fatigue strength of the specimen subjected to Ni-P plating after aging treatment showed a clear increase in comparison with one of non-processing materials. Breaking elongation of the specimen subjected to Ni-P plating after aging treatment showed no significant changes in comparison with one of non-processing materials. On the other hand, breaking elongation of the specimen subjected to Ni-P plating after furnace cooling treatment reduced by half in comparison with one of non-processing materials. Especially, it seems that poor fatigue strength and ductility of plating materials are mainly caused due to interaction between surface precipitates and hydrogen gas.

Texture Formation by the Compression Deformation of AA5182 Aluminum Alloy at High Temperatures

2012 ◽  
Vol 715-716 ◽  
pp. 918-923
Author(s):  
Hyeon Mook Jeong ◽  
Kazuto Okayasu ◽  
Hiroshi Fukutomi
Keyword(s):  
Boundary Migration ◽  
High Stress ◽  
Fiber Texture ◽  
Pole Density ◽  
Texture Formation ◽  
High Stress Region ◽  
Stress Region ◽  
Ebsd Technique ◽  
Region 10 ◽  
Main Component

Texture formation of AA5182 for compressive deformation with a range of temperatures from 673K to 823K and strain rates from 5.0×10-4to 5.0×10-2s-1is experimentally investigated by EBSD technique and X-ray diffraction. Fiber textures are observed in all deformation conditions. Stress regions are divided into a low stress region (10~55MPa) and a high stress region (above 55MPa) on the basis of the relationship between stress and grain size. In the low stress region, it is found that the main component of the fiber texture is {001}(compression plane). In this case, the pole density at {001} is increased with increasing temperature at the same stress level. It is concluded that development of {001} component is attributed to grain boundary migration. For the high stress region, the main component of the fiber texture is {011}. It is considered that the formation of {011} component is attributed to the slip deformation by {111}<110> system.

Effect of Boron Addition on Creep Strength in 9Cr-3W-3Co-V-Nb Steels

2007 ◽  
Author(s):  
Nobuyoshi Komai ◽  
Fujimitsu Masuyama
Keyword(s):  
Grain Boundary ◽  
Diffraction Analysis ◽  
Creep Strength ◽  
High Stress ◽  
High Strength Steels ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Boron Addition ◽  
High Stress Region ◽  
Stress Region

Recently, boron is being added to high-strength steels for boilers and turbines in order to raise creep strength. However, there are various points that are not yet fully understood with regard to the creep-strengthening mechanism of boron addition. In order to investigate the influence of boron addition on creep strength, varying the amounts of boron and nitrogen were added in 9Cr-3W-3Co-V-Nb steels tempered two different conditions and investigated. Although creep strengths of all materials converged to become similar in the low-stress region, the materials tempering at 780°C with boron addition which exhibited the lowest strength on the high-stress region is seen to have slightly greater strength on the low-stress region. In analysis of the precipitates and grain boundary of creepruptured material conducted using TEM-EDS and Auger diffraction analysis equipment, the presence of boron could not be detected.

The Effect of Adhesive for Fillet on Stress in Weld-Bonded Joints

2010 ◽  
Vol 450 ◽  
pp. 502-505 ◽  
Author(s):  
Min You ◽  
Jia Ling Yan ◽  
Xiao Ling Zheng ◽  
Nan Feng Xiong ◽  
Ding Feng Zhu
Keyword(s):  
Elastic Modulus ◽  
High Stress ◽  
Bonded Joints ◽  
Longitudinal Stress ◽  
Lap Joint ◽  
Load Bearing Capacity ◽  
High Stress Region ◽  
Single Lap Joint ◽  
Stress Region ◽  
Peak Value

The influence of the fillet with different elastic modulus on the stress distributed in weld-bonded aluminum alloy single lap joint was investigated using elasto-plastic finite element method. The results show that the peak values of the stress along the mid-bondline at the points near the fillet edge were increased as the elastic modulus of the fillet increased. But at points near the both ends of the adherend in over lap zone as well as in the region of the nugget the peak stresses were decreased except longitudinal stress Sx. The peak value of Seqv decreased first, and then it increased again as the elastic modulus in fillet increased. The load-bearing capacity of the whole weld-bonded joints may be improved for the fillet with Adhesive B (825 MPa) for the relative high stress region in nugget was wider and the stress distribution in overlap zone was more uniform.

Optimization of the Compositions of PEG/PMMA Binder System in Ceramic Injection Moulding via Water-Debinding

2013 ◽  
Vol 302 ◽  
pp. 556-560 ◽  
Author(s):  
Xian Feng Yang ◽  
Wei Liu ◽  
Zhi Peng Xie ◽  
Xie Wen Xu
Keyword(s):  
Removal Rate ◽  
High Stress ◽  
Binder System ◽  
Comprehensive Investigation ◽  
Binder Removal ◽  
High Stress Region ◽  
Rate Region ◽  
Stress Region ◽  
Ceramic Injection Moulding ◽  
Injection Region

In this study, we have made a comprehensive investigation on optimization of the compositions of PEG/PMMA binder system for water-debinding. An orthogonal test was designed and L9(33) table was chosen to investigate the influence of the molecular weight of low molecular PEG (L-PEG), high molecular PEG (H-PEG) and the percentage of L-PEG in PEGs on flaws of the injection moulded compacts after water-debinding. In addition, the ratio of PMMA content to PEGs content on flaws is also investigated. Four regions were defined as high stress region, safe debinding region, low binder removal rate region and unavailable injection region respectively. It is believed that our work could provide comprehensive and convincing principles for the manufacturing of injection-moulded ceramic parts via water-debinding.

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