Cold weld cracking susceptibility of high strength low alloyed (hsla) steel nionikral 70

In view of the importance of high strength low alloy (HSLA) steels, particularly for critical applications such as offshore platforms, pipeline and pressure vessels, this paper reports on an investigation of how to weld this type of steel without cold cracking. Using manual metal arc welding process and Tekken test (Y - Grove test) has been caned Out both to observe the cold cracking phenomenon, and to investigate the influencing factors, such as preheating temperature and energy input, as well as electrode strength and diameter. However the result of the experiments show that there is a risk of cold cracking

Effect of aging on mechanical properties of Al-8Si-8Fe-1.4V/SiCp composites

In this study, Al-8Fe-8Si-1.4V/SiCp composites fabricated by squeeze casting process were age-hardened to study the influence of heat treatment on mechanical properties, such as hardness, bending strength and modulus of elasticity. The cast samples were solid sоluted at 540 °C for one hour, then quenched in water to room temperature, and finally aged at 190 °C for 2, 4, 6, 8 and 10 hours for hardness test and at 195 °C for 2, 6 and 10 hours for bending strength determination

Effect of aging on mechanical properties of Al-8Si-8Fe-1.4V/SiCp composites

In this study, Al-8Fe-8Si-1.4V/SiCp composites fabricated by squeeze casting process were age-hardened to study the influence of heat treatment on mechanical properties, such as hardness, bending strength and modulus of elasticity. The cast samples were solid sоluted at 540 °C for one hour, then quenched in water to room temperature, and finally aged at 190 °C for 2, 4, 6, 8 and 10 hours for hardness test and at 195 °C for 2, 6 and 10 hours for bending strength determination

Crack propagation in 3PB specimen made from welded joint

Crack propagation in 3PB specimen has been investigated experimentally by using Digital Image Correlation (DIC) technique. For this purpose, specimens were taken from butt welded plates, made of P460NL1 micro-alloyed steel. Fatigue pre-crack of 3PB specimens was introduced in the weld metal. Specimens were then statically loaded and analyzed using digital image correlation software ARAMIS to assess strain fields and crack propagation paths. Bifurcation of cracks was noticed as the main characteristics of crack prop-agation in the analyzed case

Fatigue life prediction of casing welded pipes by using the extended finite element method

The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to verify numerical results with the experimental ones. After successful verification, the XFEM was used to simulate fatigue crack growth, position axially in the pipe, and estimate its remaining life

Effect of aging on mechanical properties of Al-8Si-8Fe-1.4v/SiCp composites

In this study, Al-8Fe-8Si-1.4V/SiCp composites fabricated by squeeze casting process were age-hardened to Study the influence of heat treatment on mechanical properties, such as hardness, bending strength and modulus of elasticity. The cast samples were solid sоluted at 540 °C for one hour, then quenched in water to room temperature, and finally aged at 190 °C for 2, 4, 6, 8 and 10 hours for hardness test and at 195 °C for 2, 6 and 10 hours for bending strength determination

Effect of aging on mechanical properties of Al-8Si-8Fe-1.4v/SiCp composites

In this study, Al-8Fe-8Si-1.4V/SiCp composites fabricated by squeeze casting process were age-hardened to Study the influence of heat treatment on mechanical properties, such as hardness, bending strength and modulus of elasticity. The cast samples were solid sоluted at 540 °C for one hour, then quenched in water to room temperature, and finally aged at 190 °C for 2, 4, 6, 8 and 10 hours for hardness test and at 195 °C for 2, 6 and 10 hours for bending strength determination

Fatigue life prediction of casing welded pipes by using the extended finite element method

The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to verify numerical results with the experimental ones. After successful verification, the XFEM was used to simulate fatigue crack growth, position axially in the pipe, and estimate its remaining life

Micromechanical Coupled Study of Crack Growth Initiation Criterion in Pressure Vessel Steel

We present results of the combined design-theoretical investigation of the mechanism of crack growth at the onset of ductile fracture of NPP reactor pressure vessels. Micromechanical approach to the prediction of ductile fracture has been applied, according to which the volume fraction of voids in the deformed material is determined by finite-element method. On the basis of CT-specimen tests and known damage parameters, obtained on smooth spherical specimens, we obtained micromechanical criterion of crack growth initiation for ductile fracture.Представлены результаты комплексного расчетно-экспериментального исследования механизма распространения трещины на начальном этапе вязкого разрушения корпусных сталей АЭС. Использован микромеханический подход к прогнозированию вязкого разрушения, согласно которому объемное содержание пор деформируемого материала определяется методом конечных элементов. На основании проведенных испытаний образцов СТ с трещиной и имеющихся данных о параметрах разрушения гладких сферических образцов установлен микромеханический критерий начала развития трещины в условиях вязкого разрушения материала.Представлено результати комплексного розрахунково-експериментального дослідження механізму розповсюдження тріщини на початковому етапі в’язкого руйнування корпусних сталей АЕС. Використовується мікромеха- нічний підхід до прогнозування в ’язкого руйнування, згідно з яким об’ємний вміст пор деформівного матеріалу визначається методом скінченних елементів. На основі проведених випробувань зразків СТ із тріщиною та відомих даних про параметри руйнування гладких сферичних зразків установлено мікромеханічний критерій початку розвитку тріщини в умовах в ’язкого руйнування

Integrity and life estimation of turbine runner cover in a hydro power plant

This paper presents integrity and life estimation of turbine runner cover in a vertical pipe turbines,Kaplan 200 MW nominal output power, produced in Russia, and built in six hydro-generation units ofhydroelectric power plant „Đerdap 1” in Serbia. Fatigue and corrosion-fatigue interaction have been taken intoaccount using experimentally obtained material properties, as well as analytical and numerical calculations ofstress state, to estimate appropriate safety factors. Fatigue crack growth rate, da/dN, was also calculated,indicated that internal defects of circular or elliptical shape, found out by ultrasonic testing, do not affect reliableoperation of runner cover