Weld Research Papers - Academia.edu (original) (raw)

Hundreds of kilometers of pipeline, especially the elbows and welded joints in nuclear power plants (NPPs), are susceptible to aging and other types of damage. Therefore, the condition of a piping system requires regular inspection. We... more

Hundreds of kilometers of pipeline, especially the elbows and welded joints in nuclear power plants (NPPs), are susceptible to aging and other types of damage. Therefore, the condition of a piping system requires regular inspection. We propose an automatic damage visualization technique using a laser ultrasonic scanning system and an ultrasonic wave propagation imaging (UWPI) method for the regular inspection process. Ultrasonic wave propagation movies (UWPMs) in thick and complex NPP pipes could be successfully visualized in a straight pipe with a crack, a welded pipe with multiple open and inner cracks at the welds, and an elbow pipe with wall thinning. A UWPM with ultrasonic time information could enable the discrimination of damage-induced wavefields from the wavefield not related to damage by providing the appearance time, source location, wavefront curvature, and propagation direction of the damage-induced wavefield. For the specimens tested, a 1 mm long crack in a 9 mm thick pipe could be localized regardless of the relative orientation of a sensor to the crack direction; 4 mm long 1.5 mm deep inner crack in a 4 mm thick welding bead could be detected despite the presence of the welding bead; wall thinning with gradual property variations could also be detected. In addition, since this method did not require laser focusing or reference data from the undamaged condition, and allows a large laser beam incident angle, it was very advantageous for the automatic scanning of the curved pipe surfaces. This study demonstrated that the proposed laser ultrasonic system equipped with the UWPI method is a useful inspection tool for NPP piping system management.

This paper presents the failure analysis of AISI-304 stainless steel tank that was fabricated by welding and used for the storage of styrene monomers. After about 13 years of satisfactory operation, significant cracking was observed... more

This paper presents the failure analysis of AISI-304 stainless steel tank that was fabricated by welding and used for the storage of styrene monomers. After about 13 years of satisfactory operation, significant cracking was observed adjacent to the weld joints and in base plate near tank foundation. Weld repair was by shielded gas arc welding using AISI 308 stainless steel filler

By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test,... more

By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, the electrochemical behavior of 5083/6082 friction stir welding weld and parent materials were comparatively investigated by gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation. The results indicated that at given processing parameters, the anti-corrosion property of the dissimilar weld was superior to those of the 5083 and 6082 parent materials.

This paper presents a review of creep cavitation and rupture of low Cr alloy and its weldment, particular in the heat-affected zone (HAZ). Creep damage is one of the serious problems for the high temperature industry. One of the... more

This paper presents a review of creep cavitation and rupture of low Cr alloy and its weldment, particular in the heat-affected zone (HAZ). Creep damage is one of the serious problems for the high temperature industry. One of the computational approaches is continuum damage mechanics which has been developed and applied complementary to the experimental approach and assists in the safe operation. However, the existing creep damage constitutive equations are not developed specifically for low stress. Therefore, in order to form the physical bases for the development of creep damage constitutive equation, it is necessary to critically review the creep cavitation and rupture characteristics of low Cr alloy and its weldment.

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle given in terms of the exponential of Gaussian Free Field. We conjecture that our curves are locally... more

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle given in terms of the exponential of Gaussian Free Field. We conjecture that our curves are locally related to SLE(κ) for κ<4.

When there is residual stress in a material, stress intensity factor (SIF) in liner elastic fracture mechanics (LEFM) approach and J-integral in elastic-plastic fracture mechanics (EPFM) approach have not constant values and are path... more

When there is residual stress in a material, stress intensity factor (SIF) in liner elastic fracture mechanics (LEFM) approach and J-integral in elastic-plastic fracture mechanics (EPFM) approach have not constant values and are path dependent parameters. In this paper, we used themodified relations for them that take into account the effects of theresidual stress. These relations have constant values in existing of residual stress and are independent of the path. In this study, we investigated a butt welded plate with through thicknesscrack perpendicular to theweld path. TheSIF and J-integral were numerically calculated for applied and residual stresses.Results have a good agreement with theoretical values obtained by weight function method. Also it was shown that the modifiedSIF and J-integral can be used as fracture parameters to obtain other properties of fractured plates and structures.

New demands often create a need for new evaluation methods. However, there are several pitfalls when choosing those methods that can endanger the expected benefits. This study shows examples from the implementation of a new welding... more

New demands often create a need for new evaluation methods. However, there are several pitfalls when choosing those methods that can endanger the expected benefits. This study shows examples from the implementation of a new welding standard at several sites in the same company. It focuses on possible pitfalls as well as probable causes and potential solutions with a push-and pull-approach. The examples cover the problems with unclear or too simplified demands, lack of evaluation method and incapable evaluation methods. The ability to handle and prevent the described issues is a prerequisite in order to be able to develop the organisation in means of quality assurance for light weight structures.

Residual stress are stresses that remains in an engineering material, especially metallic materials, after the original applied load has been removed. Its measurement will help reveal areas in fabricated materials highly stressed. This... more

Residual stress are stresses that remains in an engineering material, especially metallic materials, after the original applied load has been removed. Its measurement will help reveal areas in fabricated materials highly stressed. This paper presents a design of a portable residual stress measuring device based on the magnetic barkhausen noise principle. This was achieved by using two permanent magnets, a pickup coil, amplifier and an analogue to digital converter to create the hardware. The software was designed using LabVIEW 2019. After fabrication, measuring experiments on mild steel materials were conducted and the results obtained from using the device for measurement were compared to simulated values (Simufact.Weld 6.0) CAD software. Comparing its results with that obtained from Simulation showed an R 2 value of 77.47% with a strong correlation of 0.831and a P-value of 0.0071 which was less than the 0.05 alpha level taken. This device can be adopted in weld residual stress measurement by artisans and roadside welders for effective minimization of residual stress and failures associated with it.

Los electrodos rutilicos impermeabilizados se usan frecuentemente en la soldadura subacuatica por su buen comportamiento tecnologico. Una alternativa para mejorar su comportamiento seria incorporar compuestos quimicos a la capa de barniz.... more

Los electrodos rutilicos impermeabilizados se usan frecuentemente en la soldadura subacuatica por su buen comportamiento tecnologico. Una alternativa para mejorar su comportamiento seria incorporar compuestos quimicos a la capa de barniz. En el presente trabajo se presentan los resultados obtenidos con la adicion de una mezcla pirometalurgica exotermica en la primera capa de barniz de electrodos rutilicos del tipo 6013 y 7024. La mezcla pirometalurgica propuesta proporciona, por etapas, oxigeno al medio,segun la temperatura del revestimiento, alterando asi la presion parcial del hidrogeno del medio circundante. El elemento quimico portador de oxigeno en la mezcla pirometalurgia se reduce hasta su estado elemental, interactuandodespues con el bano de soldadura como desoxidante. Todo este proceso brinda un balance energetico favorable al proceso de soldadura. A 50 metros de profundidad se comparan el comportamiento tecnologico, la cantidad de poros en el metal de soldadura, la estruct...

Las fundiciones presentan poca soldabilidad, sin embargo, bajo ciertos cuidados, estos materiales pueden ser soldados y recuperados siguiendo procedimientos rigurosos y seleccionando electrodos de baja entrada de calor para aumentar la... more

Las fundiciones presentan poca soldabilidad, sin embargo, bajo ciertos cuidados, estos materiales pueden ser soldados y recuperados siguiendo procedimientos rigurosos y seleccionando electrodos de baja entrada de calor para aumentar la soldabilidad. En el cordón de soldadura se ...