Neutron Diffraction Residual Stress Measurements in Electron Beam Welded Compact Tension Specimens

2014 ◽  
Vol 777 ◽  
pp. 99-104
Author(s):  
Priyesh Kapadia ◽  
Catrin M. Davies ◽  
Thilo Pirling ◽  
David W. Dean ◽  
Kamran M. Nikbin
Keyword(s):  
Residual Stress ◽  
Electron Beam ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Compact Tension ◽  
Diffraction Measurement ◽  
Machining Processes ◽  
Residual Stresses And Strains

In a study to investigate the effect of residual stress relaxation on Creep Crack Growth (CCG) a novel fracture mechanics specimen has been designed. Compact Tension, C(T), specimens are fabricated from blocks with Electron Beam (EB) welds such that residual stresses induced during welding are retained in the specimen. Finite element analyses of EB welding and machining processes have been developed to predict the stresses in such C(T) specimens which will drive crack growth in future CCG studies. The residual stresses and strains in these samples have been quantified using the neutron diffraction measurement technique at various stages of the fabrication process and have been used to validate numerical simulations of the fabrication processes.

Measurements of Residual Stresses in 316 Stainless Steel Weldments

2010 ◽  
Author(s):  
C. M. Davies ◽  
D. Hughes ◽  
R. C. Wimpory ◽  
David W. Dean ◽  
K. M. Nikbin
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Stress Distributions ◽  
Tension Specimen ◽  
Creep Crack ◽  
Term Creep

Neutron diffraction measurements have been performed to quantify the residual stresses distributions in austenitic type 316 stainless steel Manual Metal Arc (MMA) weldment sections, which are similar to those used in creep crack growth testing. Measurements have been taken along the expected crack path in these samples to determine the influence of residual stresses on high temperature crack growth. The influence of EB welding extension pieces onto the weldments sections, in order to increase specimen size, and sample cutting for compact tension specimen manufacture are also examined. Similar stress distributions have been measured in nominally identical MMA weldments sections, where peak stresses of up to 120 MPa have been shown. The effects of the EB weld used to attach extension pieces to the weldments sections dominate over the MMA weldments residual stress distributions in these samples, and increases the peak stresses by up to a factor of three. Significant stress relaxation takes place during compact tension specimen manufacture, and in addition creep strain accumulation will further relax these residual stresses. Residual stress effects are therefore considered to only influence the creep crack initiation period in short-term creep crack growth tests. However, in long-term creep crack growth tests, the residual stresses may also influence subsequent creep crack growth behaviour.

Numerical Simulation of Residual Stresses Induced in Compact Tension Specimens Using Electron Beam Welding

2012 ◽  
Author(s):  
P. Kapadia ◽  
C. M. Davies ◽  
D. W. Dean ◽  
K. M. Nikbin
Keyword(s):  
Residual Stress ◽  
Electron Beam ◽  
Residual Stresses ◽  
Mechanical Model ◽  
Elevated Temperatures ◽  
Electron Beam Welding ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Compact Tension ◽  
Eb Welding

In welded components residual stresses on the order of yield magnitude can exist, allowing creep damage and cracking to occur under secondary stresses at elevated temperatures. A method of inducing residual stresses in compact tension, C(T), specimens is proposed using Electron Beam (EB) welding, which is simulated using a sequential thermal-mechanical model. The thermal model has been verified by comparison to thermocouple measurements obtained from instrumented EB welding experiments on blocks made of ex-service Type 316H stainless steel. Residual stress measurements, obtained by the neutron diffraction technique, have also been used to verify the mechanical model. It has been found that in the proposed EB welding method plasticity is localised and limited to just a few millimetres away from the notch whilst at the same time exhibiting a near yield level residual stress at the crack tip. Thus this technique may allow the effects of residual stresses on creep crack growth to be investigated by the EB welding technique without material property changes due to crack tip plasticity influencing the results.

Residual Stresses in Steel and Zirconium Weldments

1997 ◽  
Vol 119 (2) ◽  
pp. 137-141 ◽  
Author(s):  
J. H. Root ◽  
C. E. Coleman ◽  
J. W. Bowden ◽  
M. Hayashi
Keyword(s):  
Residual Stress ◽  
Electron Beam ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Prolonged Exposure ◽  
Electron Beam Welding ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Outer Diameter ◽  
Stress Relieving

Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5Nb plate have shown that heat treatment at 530°C for 1 h reduces the longitudinal residual strain by 60 percent. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclear reactor.

Quantification of Residual Stresses Induced by Prior Loading at High Temperatures

2011 ◽  
Author(s):  
Ali N. Mehmanparast ◽  
Catrin M. Davies ◽  
Robert C. Wimpory ◽  
Kamran M. Nikbin
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Residual Stresses ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Crack Plane ◽  
Residual Stress Field ◽  
Compression Direction ◽  
Fracture Specimen

High temperature components generally undergo cyclic loading conditions. Prior tensile/compressive loading of a fracture specimen can induce compressive/tensile residual stress fields at the crack tip. These residual stresses will influence the subsequent fracture behaviour of the cracked body. This work forms part of a project to examine the influence of creep induced damage at a crack tip on subsequent fatigue crack growth and fracture toughness properties of austenitic type 316H stainless steel. Creep damage is introduced local to the crack tip of a fracture specimen by interrupting a creep crack growth test, performed at 550 °C. Prior to testing, the material was pre-compressed in order to strain harden the material. The compact tension, C(T), specimen geometry has been considered in this work. Since residual stresses are known to influence fatigue and fracture toughness properties of a cracked body, it is important that the residual stress levels at the crack tip are quantified. Neutron diffraction (ND) measurements have therefore been performed to quantify the extent of residual stress in these samples after initial loading, and compared to finite element model predictions. Two specimens have been considered with the crack plane orientated in parallel and perpendicular to the pre-compression direction. Compressive residual stresses of around 100 MPa have been measured directly ahead of the crack tip. Reasonable predictions of the principal residual stress distributions have been obtained by the simplified FE analysis. Though the tensile properties differ significantly in for specimens orientated parallel and perpendicular to the pre-compression direction, no significant differences in the residual stress field are predicted in the C(T) specimens orientated in both directions.

Neutron Diffraction Measurement and Numerical Simulation to Study the Effect of Repair Depth on Residual Stress in 316L Stainless Steel Repair Weld

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Wenchun Jiang ◽  
Yun Luo ◽  
BingYing Wang ◽  
Wanchuck Woo ◽  
S. T. Tu
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
316L Stainless Steel ◽  
Diffraction Measurement ◽  
Transverse Stress ◽  
Longitudinal Stress ◽  
Hardening Model ◽  
Mixed Hardening

Welding is often used to repair the defects in pressure vessels and piping, but residual stresses are generated inevitably and have a great effect on structure integrity. According to the defect size, different repair depth will be carried out, which leads to different stress state. In this paper, the effect of repair depth on residual stress in 316L stainless steel repair weld has been studied by neutron diffraction measurement and finite element modeling (FEM). The results show that the residual stresses in the deep repair are larger than those in shallow repair weld, because the deep repair involves multipass welding and brings a serious work hardening. In the weld metal, the longitudinal stress has exceeded the yield stress, and increases slightly with the increase of repair depth. In contrast to the longitudinal stress, the transverse stress is more sensitive to the repair depth. With the increase of repair depth, the transverse stress increases and even exceeds the yield strength as the repair depth is 45% of the plate thickness. At the bottom surface of the plate and heat affected zone (HAZ), both the longitudinal and transverse stresses increase as the repair depth increases. It also shows that the mixed hardening model gives the best agreement with the measurement, while isotropic and kinematic hardening models cause an overestimation and underestimation, respectively. Therefore, the mixed hardening model is recommended for the prediction of residual stresses.

Comparison of Brazed Residual Stress and Thermal Deformation between X-Type and Pyramidal Lattice Truss Sandwich Structure: Neutron Diffraction Measurement and Simulation Study

2016 ◽  
Vol 35 (6) ◽  
pp. 567-574 ◽  
Author(s):  
Wenchun Jiang ◽  
Zhiquan Wei ◽  
Yun Luo ◽  
Weiya Zhang ◽  
Wanchuck Woo
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Sandwich Structure ◽  
Thermal Deformation ◽  
Diffraction Measurement ◽  
Neutron Diffraction Measurement ◽  
Pyramidal Structure ◽  
Transverse Stresses ◽  
Type Lattice

AbstractThis paper uses finite element method and neutron diffraction measurement to study the residual stress in lattice truss sandwich structure. A comparison of residual stress and thermal deformation between X-type and pyramidal lattice truss sandwich structure has been carried out. The residual stresses are concentrated in the middle joint and then decreases gradually to both the ends. The residual stresses in the X-type lattice truss sandwich structure are smaller than those in pyramidal structure. The maximum longitudinal and transverse stresses of pyramidal structure are 220 and 202 MPa, respectively, but they decrease to 190 and 145 MPa for X-type lattice truss sandwich structure, respectively. The thermal deformation for lattice truss sandwich panel structure is of wave shape. The X-type has a better resistance to thermal deformation than pyramidal lattice truss sandwich structure. The maximum wave deformation of pyramidal structure (0.02 mm) is about twice as that of X-type (0.01 mm) at the same brazing condition.

Effect of Residual Stresses Caused by Thermal Treatment on Creep Crack Growth Rate in Aluminium Gas Cylinders

1998 ◽  
Author(s):  
Raafat Ibrahim ◽  
Dmitry Ischenko
Keyword(s):  
Residual Stress ◽  
Growth Rate ◽  
Residual Stresses ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Stress Distributions ◽  
Creep Crack ◽  
Quenching Process ◽  
Creep Crack Growth Rate ◽  
Gas Cylinders

Abstract Aluminum gas cylinders, which are in common use for various purposes, are susceptible to creep crack growth. Residual stresses introduced during the quenching process in aluminum gas cylinders contribute to the development of cracks. This may result in leakage or fracture of the cylinders. Finite element studies were conducted to evaluate the effect of the quenching process on through thickness inelastic strain and the residual stress distributions in the neck area of gas cylinders. Numerical modeling and experimental studies confirmed that a high level of tensile residual stresses exists on the inner surface of aluminum gas cylinders’ neck which is susceptible to cracking. The relationship between the amount of residual stresses and cooling conditions was established. The obtained residual stress distributions were included in the calculation of the creep crack growth rates. It was shown that residual stresses caused by manufacturing processes have a significant effect on the creep crack growth rate.

Determination of Repair Weld Residual Stress in a Tube to Tube-Sheet Joint by Neutron Diffraction and the Finite Element Method

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Yun Luo ◽  
Wenchun Jiang ◽  
Dongfeng Chen ◽  
Robert C. Wimpory ◽  
Meijuan Li ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Diffraction Measurement ◽  
Neutron Diffraction Measurement ◽  
Repair Welding ◽  
Welding Direction ◽  
Element Method

Repair welding is a popular method to repair the leakage zone in tube-to-tubesheet joint of shell-tube heat exchangers. But the repaired residual stresses are generated inevitably and have a great effect on stress corrosion cracking (SCC). In this paper, the effects of repair welding on residual stress were studied by finite element method (FEM) and neutron diffraction measurement. The original weld residual stresses calculated by FEM showed good agreement with neutron diffraction measurement results. After repair welding, the transverse residual stresses change very little while the longitudinal residual stresses are increased in the repair zone. In the nonrepair zone, both the transverse and longitudinal stresses are decreased. The repair welding times have little effect on residual stress distribution. With the increase of welding length and heat input, the residual stresses increase. Repair opposite to the original welding direction is recommended because the opposite welding direction minimizes the residual stresses.

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