Permanent ground displacement across earthquake faults, landslides and natural slopes

Permanent ground displacement analysis methods, as very important aspect of the seismic dynamic analysis is explained in the paper. A methodology for probabilistic hazard assessment of permanent displacement across natural slopes and landslides caused by earthquake rupture is presented, compatible with regions with low to moderate seismicity, as well as comparison with the results of the other authors. The results show that for the most cases, in terms of displacement of earthquake faults the displacement hazard is small, in contrast to ground shaking hazard. From the other side, slope displacements (rockfalls landslides, mudflows) as side effects may cause huge consequences during the earthquake

The effect of exploitation conditions on the damage of a roller reducer toothed shaft and its repair

This paper describes repair method of the toothed shaft of roller reducer located in Steelworks Smederevo facility, as well as the effects of exploitation conditions that have led to damage i.e. shaft fracture. After more than 15 years of in-service exploitation the shaft fracture has occurred at the bearing position. The fracture occurred due to blocking on the roller driven by this shaft. In order to restore the working capabilities of the shaft, the repair welding procedure has been established. Additional difficulties during establishing repair procedure were caused by the fact that the base material of the shaft was unknown, so certain assumptions were made (e.g. assumption of base material). Application of repair welding has resulted in significant direct and indirect savings in comparison to the purchasing of a new shaft

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

Influence of multiple defects in welded joints subjected to fatigue loading according to sist en iso 5817: 2014

Structural integrity of pressure vessels is of great importance in ensuring their safe exploitation. Due to this, a number of standards are developed in order to define the criteria according to which materials, technologies and test methods are selected for pressure vessels, particularly when it comes to welded joints. Because of the nature of the welding process, welded joints will typically contain different types of defects, some of which could greatly endanger their integrity. Cracks in particular are the cause of pressure vessel failure. The goal of this paper is to present the standard SIST EN ISO 5817: 2014 and emphasize the changes and additions that are made, compared to the previous version, SIST EN 5817: 2007. The standard includes recommendations and requirements related to the presence of multiple types of defects in welded joints subjected to fatigue loading. Since fatigue crack growth greatly contributes to failure of pressure vessels, for the first time this standard covers a very important topic. Some of the earlier work related to multiple defects in welded joint is also shown in the paper, and used as examples

Integrity assessment of ammonia storage tank by non-destructive testing

Ammonia is a very dangerous fluid, and it is so important that its storage tanks are safe. Fusion welded joints (in further text: welded joints) are the 'weakest' location in some structures, in this case - tanks, and the detection of defects in welded joints during manufacture is also very important, since defects may cause failure with catastrophic events. NDT techniques that have been performed on welded joints show insight into the quality of the performed welding technique, and results imply whether tanks are safe to be put into exploitation. Three different methods are used for testing: visual, penetrant, and ultrasonic (in this case a new method is used). The first two methods show no irregularities, but third NDT method shows the necessity for tank repair. All of these tests are performed in accordance with relevant standards that are discussed, as well as the used NDT methods in general, with their ability and restrictions

Numerical simulation of crack growth in a welded joint with defects

Research presented in this paper involves the numerical simulation of crack growth in a welded joint made of common structural steel S235JR2, but with the presence of a number of different welding defects, which represents a scenario that is not covered by relevant standards, in this case EN ISO 5817. After analysing several defect combinations, which could occur in reality, the one with the least favourable combination of stress concentration and plastic strain was selected as the relevant model. A crack was then introduced in the location where the stresses, caused by tensile loading of the welded joint model, were above the yield stress. The numerical analysis performed in this case involved different combinations of load magnitudes and crack length, in order to determine at which point the initial crack will start propagating

Damages of burner pipes due to the working conditions and its repair welding

Repair welding represents the activity that restores the working capability of machine or construction caused by some damage due to working or environmental condition. Damages of burner pipes, part of the facility "Cold Rolling Mill" Steelwork in Smederevo, which appeared on welded joints during the manufacturing of the burner, and its repairing are presented in this paper. The damages occurred on welded joints along the weld as a result of the working conditions that burner was exposed to. Due to high temperatures that can reach up to 850 degrees C and "explosion" during gas burning, a crack may appear on the inner side of the burner. The base material of the burner pipes is stainless steel X12NiCrSi35-16. Repair welding is preceded by a series of operations, and one of them is the selection of an electrode. It turned out that inadequate selection of the electrode for repair welding had contributed to the occurrence of cracks on welded joints. Selecting a new electrode and examining its characteristics, as well as performing test welding of pipe that is still in exploitation, had confirmed the importance of proper selection of materials for repairing of burner pipes

Integrity assessment of ammonia storage tank by non-destructive testing

Ammonia is a very dangerous fluid, and it is so important that its storage tanks are safe. Fusion welded joints (in further text: welded joints) are the 'weakest' location in some structures, in this case - tanks, and the detection of defects in welded joints during manufacture is also very important, since defects may cause failure with catastrophic events. NDT techniques that have been performed on welded joints show insight into the quality of the performed welding technique, and results imply whether tanks are safe to be put into exploitation. Three different methods are used for testing: visual, penetrant, and ultrasonic (in this case a new method is used). The first two methods show no irregularities, but third NDT method shows the necessity for tank repair. All of these tests are performed in accordance with relevant standards that are discussed, as well as the used NDT methods in general, with their ability and restrictions

Numerical simulation of crack growth in a welded joint with defects

Research presented in this paper involves the numerical simulation of crack growth in a welded joint made of common structural steel S235JR2, but with the presence of a number of different welding defects, which represents a scenario that is not covered by relevant standards, in this case EN ISO 5817. After analysing several defect combinations, which could occur in reality, the one with the least favourable combination of stress concentration and plastic strain was selected as the relevant model. A crack was then introduced in the location where the stresses, caused by tensile loading of the welded joint model, were above the yield stress. The numerical analysis performed in this case involved different combinations of load magnitudes and crack length, in order to determine at which point the initial crack will start propagating

Influence of multiple defects in welded joints subjected to fatigue loading according to sist en iso 5817: 2014

Structural integrity of pressure vessels is of great importance in ensuring their safe exploitation. Due to this, a number of standards are developed in order to define the criteria according to which materials, technologies and test methods are selected for pressure vessels, particularly when it comes to welded joints. Because of the nature of the welding process, welded joints will typically contain different types of defects, some of which could greatly endanger their integrity. Cracks in particular are the cause of pressure vessel failure. The goal of this paper is to present the standard SIST EN ISO 5817: 2014 and emphasize the changes and additions that are made, compared to the previous version, SIST EN 5817: 2007. The standard includes recommendations and requirements related to the presence of multiple types of defects in welded joints subjected to fatigue loading. Since fatigue crack growth greatly contributes to failure of pressure vessels, for the first time this standard covers a very important topic. Some of the earlier work related to multiple defects in welded joint is also shown in the paper, and used as examples