Creep Rupture Bending Test of 20 Percent Cold-Prestrained Ni-Fe-Cr Alloy Straight Tubes at 1100 F(593 C)

1981 ◽  
Vol 103 (4) ◽  
pp. 337-344 ◽  
Author(s):  
H. H. Woo ◽  
R. H. Ryder ◽  
K. H. Holko ◽  
R. F. Stetson
Keyword(s):  
Crack Initiation ◽  
Creep Rupture ◽  
Bending Test ◽  
Strain History ◽  
Test Results ◽  
Local Material ◽  
Initiation And Propagation ◽  
Nonuniform Stress Field ◽  
Point Bend ◽  
Four Point Bend Test

A four-point bend test was performed on 20 percent cold-prestrained Ni-Fe-Cr alloy tubes at 1100 F (593 C) to verify that creep rupture damage can be used to predict failure in a nonuniform stress field. Deflection control and acoustic emission techniques were used to detect crack initiation, strain gages were employed to record the strain history in the specimen, and a scanning electron microscrope was utilized to check crack initiation and propagation. Stress analyses were made using simplified and finite element methods. Comparison of test results and analyses concluded that creep rupture damage can be used to predict local material failure for structural components under multiaxial nonuniform loading conditions.

Crack Initiation Process for Semi-Circular Notched Plate in Fatigue Test at Elevated Temperature

2008 ◽  
Author(s):  
Bopit Bubphachot ◽  
Osamu Watanabe ◽  
Nobuchika Kawasaki ◽  
Naoto Kasahara
Keyword(s):  
Elevated Temperature ◽  
Crack Initiation ◽  
Fatigue Test ◽  
Video Camera ◽  
Test Results ◽  
Structural Components ◽  
Crack Initiation And Propagation ◽  
Propagation Process ◽  
Initiation Process ◽  
Initiation And Propagation

Crack initiation and propagation process of fatigue test in semi-circular notched plates at elevated temperature were observed by the CCD video camera. Test specimens are made of SUS304 stainless steel, and temperature is kept to be 550°C, and geometry of semi-circular notched plate specimens are changed by diameter size of the circular hole. Photographs in all cycles were recorded to investigate crack initiation process in structural components having stress concentration and obtain number of cycle of crack initiation (Nc). The test results were compared with predictions by Stress Redistribution Locus (SRL) method and Neuber’s rule’s method.

Fatigue Crack Growth Behavior of Threaded Pipe Couplings

2011 ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Patrick De Baets ◽  
Wim De Waele
Keyword(s):  
Fatigue Crack ◽  
Fracture Surface ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Crack Opening ◽  
Bending Test ◽  
Crack Initiation And Propagation ◽  
Accurate Knowledge ◽  
Initiation And Propagation

Threaded couplings are used in various applications to connect steel pipes. To maintain a secure connection, such couplings are preloaded and during service additional dynamic loads can act on the connections. The coupling’s threads act as stress raisers, initiating fatigue cracks, which can cause the connection to fail in time. Accurate knowledge of the fatigue behavior, taking into account crack initiation and propagation is necessary to understand the fatigue mechanisms involved. In this study, the fatigue behavior of tapered couplings with NPT threads is studied. This is done by analyzing the results of an experimental four-point bending test. The fatigue crack propagation is monitored using an optical dynamic 3D displacement measurement device and LVDTs to measure the crack opening. At certain times during the test, the load ratio is changed to apply a number of beach marking cycles. This way a fine line is marked in the fracture surface. These marked crack shapes are used as input for a finite element model. The measured deflection and crack opening are compared to the results of the numerical simulations. Using this methodology a distinction is made between fatigue crack initiation and propagation. By analyzing the fracture surface it was observed that once the crack is initiated, it propagates over a wide segment of the pipe’s circumference and subsequently rapidly penetrates the wall of the pipe. The observed crack growth rates are confirmed by a fracture mechanics analysis. Since the appearing long shallow crack is difficult to detect at an early stage the importance is demonstrated of accurate knowledge of the fatigue behavior of threaded connections in order to define acceptable flaw sizes and inspection intervals.

scholarly journals Hydrogen enhanced cracking studies on Fe–3wt%Si single and bi-crystal microcantilevers

2017 ◽  
Vol 375 (2098) ◽  
pp. 20160410 ◽  
Author(s):  
T. Hajilou ◽  
Y. Deng ◽  
N. Kheradmand ◽  
A. Barnoush
Keyword(s):  
Stress Concentration ◽  
Crack Initiation ◽  
The Other ◽  
Bending Test ◽  
Propagation Path ◽  
Transgranular Fracture ◽  
Post Mortem ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation

Hydrogen (H) enhanced cracking was studied in Fe–3wt%Si by means of in situ electrochemical microcantilever bending test. It was clearly shown that the presence of H causes hydrogen embrittlement (HE) by triggering crack initiation and propagation at the notch where stress concentration is existing. Additionally, the effect of carbon content and the presence of a grain boundary (GB) in the cantilever were studied. It was shown that in the presence of H the effect of carbon atom on pinning the dislocations is reduced. On the other hand, the presence of a GB, while the chemical composition of material kept constant, will promote the HE. Crack initiation and propagation occur in the presence of H, while the notch blunting was observed for both single and bi-crystalline beams bent in air. Post-mortem analysis of the crack propagation path showed that a transition from transgranular fracture to intragranular fracture mechanism is highly dependent on the position of the stress concentration relative to the GB. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

scholarly journals Numerical modelling strategies using implicit and explicit methods to simulate quasi-static and dynamic three-points bend fracture tests of a ductile steel

2021 ◽  
Vol 250 ◽  
pp. 02033
Author(s):  
Frédéric Nozères ◽  
Hervé Couque ◽  
Rémi Boulanger ◽  
Yann Quirion ◽  
Patrice Bailly ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Fracture Tests ◽  
Point Bend ◽  
Dynamic Loading Conditions ◽  
Implicit And Explicit ◽  
Static And Dynamic Loading

Three-point bend fracture tests have been conducted at different loading rates with a quadratic martensitic steel. The failure energy has been found to increase with loading rate. To get insights in this increase a numerical investigation has been undertaken with different strategies using ABAQUS and IMPETUS softwares in order to address quasi-static and dynamic loading conditions. Simulations were conducted with the ABAQUS software in order to carry out a comparative analysis of both implicit and explicit approaches. In addition to standard Finite Element Method (FEM) applied to quasi-static and dynamic conditions, the eXtended-Finite Element Method (X-FEM) was applied to quasistatic conditions. In both approaches, implicit and explicit, crack initiation and propagation were governed by a critical plastic strain threshold combined with a displacement-based damage evolution criterion. Simulations conducted with the IMPETUS software use an explicit approach and second order elements for both quasi-static and dynamic loading conditions. A node-splitting method using an energy-based damage criterion was employed to simulate the crack initiation and propagation. Experimental data and numerical results have been compared, allowing to determine the ability of these two softwares to simulate accurately three-point bend fracture tests.

Crack Initiation Process for Semi-Circular Notched Plate in Creep-Fatigue Test at Elevated Temperature

2008 ◽  
Author(s):  
Osamu Watanabe ◽  
Bopit Bubphachot ◽  
Nobuchika Kawasaki ◽  
Naoto Kasahara
Keyword(s):  
Stainless Steel ◽  
Elevated Temperature ◽  
Crack Initiation ◽  
Fatigue Test ◽  
Video Camera ◽  
Test Results ◽  
Crack Initiation And Propagation ◽  
Initiation Process ◽  
Initiation And Propagation ◽  
Creep Fatigue

Crack initiation and propagation in creep-fatigue test were observed on semi-circular notched plates at elevated temperature by the CCD video camera. Test specimens are made of SUS304 stainless steel, and temperature is kept to be 550°C, and geometry of the semi-circular plate specimens are changed by diameter size of the hole. Photographs of all cycles were recorded to investigate crack initiation process in structural component having stress concentration and obtain number of cycle of crack initiation (Nc). The test results were compared with predictions by the Stress Redistribution Locus (SRL) method and the Neuber’s rule’s method.

Three- and Four-Point Bend Testing for Electronic Packages

2003 ◽  
Vol 125 (4) ◽  
pp. 556-561 ◽  
Author(s):  
Santosh Shetty ◽  
Tommi Reinikainen
Keyword(s):  
Bending Test ◽  
Electronic Packages ◽  
Reliability Model ◽  
Test Results ◽  
Printed Wiring Board ◽  
Reliability Models ◽  
Four Point Bending ◽  
Three Point Bend Test ◽  
Point Bend ◽  
Wiring Board

This study demonstrates the application of three-point and four-point bending tests for evaluating the reliability of chip scale packages under curvature loads. A three-point bend test is conducted on 0.5-mm-pitch chip-scale packages (CSPs) mounted on FR4 (Flame Retardant) substrates. This test is simulated by using the finite element method and the results are calibrated experimentally to formulate a reliability model. A three-point bend scheme is an ideal choice for generating reliability models because multiple packages can be tested under multiple loads in a single test. This reliability model can be used to predict the durability of the packages in the real product under any printed wiring board (PWB) curvature loading conditions. A four-point bending simulation is also demonstrated on the test substrate. Four-point bending test is an ideal method for testing a larger sample size of packages under a particular predefined stress level. This paper describes the bending simulation and testing on packages in a generic sense. Due to the confidentiality of the test results, the package constructional details, material properties, and the actual test data have not been presented here.

scholarly journals In Situ Scanning Electron Microscopy Observation of Crack Initiation and Propagation in Hydroxide Films Formed by Steam Coating on Aluminum-Alloy Sheets

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1238
Author(s):  
Hongmei Li ◽  
Naoki Takata ◽  
Makoto Kobashi ◽  
Ai Serizawa
Keyword(s):  
Crack Initiation ◽  
Amorphous Layer ◽  
Image Correlation ◽  
Bending Test ◽  
Al Alloy ◽  
Crack Initiation And Propagation ◽  
Surface Normal ◽  
Initiation And Propagation ◽  
Hydroxide Film

Hydroxide film was formed on 6061 Al-alloy (Al-1.00Mg-0.62Si(wt.%)) sheets by steam coating with the temperature of 220 °C for 24 h. During bending test of the coated specimens, the crack initiation and propagation processes in the hydroxide film were investigated using in situ SEM observations. The hydroxide film formed exhibited a dual-layer structure composed of an inner amorphous layer and an outer polycrystalline γ-AlO(OH)-phase layer. On the compressively strained surface, lateral cracks are preferentially initiated inside the inner amorphous layer, and propagate either inside this layer or on its interface with the outer γ-AlO(OH) layer. Digital image correlation analyses of the in situ observed SEM images suggested that the concentrated tensile strain along the surface normal localized at some parts of the amorphous layer could contribute to the crack initiation. On the tensile-strained surface, a number of cracks were initiated inside the inner amorphous layer along the surface normal and propagate into the outer γ-AlO(OH) layer. No cracks were found along the interface of the amorphous layer with the Al-alloy substrate. As a result, the anticorrosion hydroxide film adhered on the Al sheet after bending deformation. Such strong adhesion contributes to the excellent corrosion resistance of the Al-alloy parts provided by the steam coating.

Mechanical Properties of 91% Tungsten Alloy

2007 ◽  
Vol 345-346 ◽  
pp. 1625-1628 ◽  
Author(s):  
Wei Dong Song ◽  
Hai Yan Liu ◽  
Jian Guo Ning
Keyword(s):  
Crack Initiation ◽  
Tensile Tests ◽  
Tungsten Alloy ◽  
Test Results ◽  
Bending Tests ◽  
Three Point Bending ◽  
Grain Sizes ◽  
Initiation And Propagation ◽  
Fracture Behaviors ◽  
The Matrix

The tensile tests and the three-point bending tests have been conducted to investigate the crack initiation and propagation and the fracture behavior of 91W-6.3Ni-2.7Fe with three kinds grain sizes of 1~3μm, 10~15μm and 30~40μm. SEM was introduced to analyze the grain sizes, the micro-defects, the deformations and the fracture behaviors of tungsten alloys. The test results show that under the same loading conditions, the crack initiation and the crack propagation are not only related to grain size, but also related to the contiguity of tungsten grains and the interface between the tungsten grains and the matrix.

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