Effect of variable load on crack initiation microalloyed steel S 690-QL

The accumulation of damage in the form of initiation and growth of micro-cracks is the first stage of destruction that ends when the merger microcracks form macro cracks. Cracks formed in the cycle number N =104 - 105 are the result of low cycle fatigue. From the need to evaluate low cycle fatigue life was carried out to investigate the low cycle fatigue microalloyed high-strength steel S690QL in the heat-treated

The effect of variable loading onintegrity of a welded joint of high alloy-steel X20

In present paper, experimental investigations have included the effect of exploitation conditions (exploitation time and temperature) on properties of high-cycle fatigue and parameters of fatigue-crack growth of a welded joint of steel X20 CrMoV 12-1 (X20). The effect of exploitation conditions was analysed by testing new pipe and the pipe having been exploited for 116 000 hours. The results obtained by testing and their analysis provide a practical contribution to assessment of quality of a welded joint of steel X20, the aim of which is revitalisation and extension of exploitation life of vital components of thermal power plants manufactured from high-alloy steel for operation at elevated temperatures

Experimental and Numerical Evaluation of a Steamline Behaviour Using Local Approach

Results of the experimental and numerical comparative analysis of steamline pipes have been presented. New pipes and the pipes used for more than 117,000 hours at 540 °C under pressure of 42 bars have been simultaneously tested. This testing has been carried out because frequent failures of the equipment components exposed to elevated temperatures, such as steam pipelines, make it necessary to pay particular attention to the analysis of the materials used. The most frequent failures were those connected with occurrence of cracks, particularly expressed in case of steel 14MoV6 3. Local approach to fracture has been developed for complete understanding of fracture mechanism. This approach combines theoretical, experimental and numerical solution

Influence of temperature and exploitation period on the behaviour of a welded joint subjected to impact loading

Presented in this paper is the analysis of the influence of temperature and exploitation period on the measure of fracture resistance of welded joint constituents in both new and exploited low-alloyed Cr-Mo steel A-387 Gr. B subjected to impact load. Exploited parent material was a part of the reactor mantle in exploitation for over 40 years and is currently in the repair stage, wherein a part of the mantle is being replaced with newly built-in material. Performed are impact tests of a notched specimen of new and exploited parent material (PM), weld metal (WM) and heat affected zone (HAZ), at both the exploited and new PM sides, in order to determine total impact energy, and its components, crack initiation-and crack propagation energy. Based on test results, analysis of tendency toward brittle fracture, i.e. toward an increase of in-service brittleness (ageing) represents the comparison of values obtained for characteristic areas of welded joints and the justification of the selected welding technology

Influence of temperature and exploitation period on the behaviour of a welded joint subjected to impact loading

Presented in this paper is the analysis of the influence of temperature and exploitation period on the measure of fracture resistance of welded joint constituents in both new and exploited low-alloyed Cr-Mo steel A-387 Gr. B subjected to impact load. Exploited parent material was a part of the reactor mantle in exploitation for over 40 years and is currently in the repair stage, wherein a part of the mantle is being replaced with newly built-in material. Performed are impact tests of a notched specimen of new and exploited parent material (PM), weld metal (WM) and heat affected zone (HAZ), at both the exploited and new PM sides, in order to determine total impact energy, and its components, crack initiation-and crack propagation energy. Based on test results, analysis of tendency toward brittle fracture, i.e. toward an increase of in-service brittleness (ageing) represents the comparison of values obtained for characteristic areas of welded joints and the justification of the selected welding technology

The effect of shielding gas composition on the toughness and crack growth parameters of AlMg4,5Mn weld metals

The experiment have been performed using samples of welded joints of the three components aluminium alloy AlMg4,5Mn. The welding was performed with GTAW in the shielded atmosphere of Ar+0,015N2, mixture of the inert gases Ar+50%He+0,015N2 and Ar+70%He+0,015N2. After welding has been completed, the metallographic tests, the tensile test and the tests of the hardness were performed. Also, the weld metal toughness was estimated, using the instrumental Charpy impact testing system, followed by estimating the crack initiation energy, crack growth energy and the fracture mechanics parameters. The goal was to establish the effects of shielding atmosphere composition on the mechanical properties and fracture mechanics parameters of weld metal

Mechanical and magnetic properties of composite materials with polymer matrix

Many of modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. Material property combinations and ranges have been extended by the development of composite materials. Development of Nd-Fe-B/polymer composite magnetic materials has significantly increased interest in research and development of bonded magnets, since particles of Nd-Fe-B alloys are proved to be very suitable for their production. This study investigates the mechanical and magnetic properties of compression molded Nd-Fe-B magnets with different content of magnetic powder in epoxy matrix. Mechanical properties were investigated at ambient temperature according to ASTM standard D 3039-00. The obtained results show that tensile strength and elongation decrease with an increase of Nd-Fe-B particles content in epoxy matrix. The modulus of elasticity increases, which means that in exploitation material with higher magnetic powder content, subjected to the same level of stress, undergoes 2 to 3.5 times smaller deformation. Scanning Electron Microscopy (SEM) was used to examine the morphology of sample surfaces and fracture surfaces caused by the tensile strength tests. The results of SQUID magnetic measurements show an increase of magnetic properties of the investigated composites with increasing content of Nd-Fe-B particles

Experimental and Numerical Evaluation of a Steamline Behaviour Using Local Approach

Results of the experimental and numerical comparative analysis of steamline pipes have been presented. New pipes and the pipes used for more than 117,000 hours at 540 °C under pressure of 42 bars have been simultaneously tested. This testing has been carried out because frequent failures of the equipment components exposed to elevated temperatures, such as steam pipelines, make it necessary to pay particular attention to the analysis of the materials used. The most frequent failures were those connected with occurrence of cracks, particularly expressed in case of steel 14MoV6 3. Local approach to fracture has been developed for complete understanding of fracture mechanism. This approach combines theoretical, experimental and numerical solution

The effects of dynamic load on behaviour of welded joint A-387 Gr. 11 alloyed steel

The in-service behaviour of alloyed steel A-387 Gr. 11 Class 1, for pressure vessels, used for high temperature applications, depends on the properties of its welded joint, with parent metal (BM), heat-affected-zone (HAZ) and weld metal (WM), as constituents. Charpy testing of BM, WM and HAZ, together with, determination of the parameters of fatigue-crack growth and fatigue threshold ΔKth was used, in order to understand, how heterogeneity of structure and different mechanical properties of welded joint constituents affect on crack initiation and propagation