The Experts below are selected from a list of 33 Experts worldwide ranked by ideXlab platform
Jürgen Rudolph - One of the best experts on this subject based on the ideXlab platform.
-
Qualification of the Notch Stress Approach for the Fatigue Assessment of Welded Pressure Equipment and Power Plant Components
Volume 1B: Codes and Standards, 2017Co-Authors: Jürgen Rudolph, Ralf Trieglaff, René Stößlein, Fabian HauserAbstract:The fatigue assessment of welded joints in different engineering disciplines is usually based on nominal, structural or notch stresses on one hand (elastic concept using component fatigue curves of Load Controlled Test data) and local strains on the other hand (elasto-plastic concept using material fatigue curves of strain-Controlled push-pull Test data of un-notched and polished standard specimens). The concepts of the first mentioned group are implemented in widespread standards and recommendations such as [1] to [3]. The fatigue assessment procedure of the European standard for unfired pressure vessels (EN 13445-3, Clause 17 & 18 and related annexes) [4] is currently under revision with one focus on the elaboration of user friendly fatigue assessment options for welded components [5]. The current state of the art focuses on the application of an adapted structural hot spot stress approach to the fatigue assessment of welded pressure equipment [5]. Although this is a significant step forward, the implementation of a notch stress approach can furtherly increase the fatigue assessment options by detailed weld seam analysis. The paper focuses on respective methodological proposals and application examples of typical welded joints. The finite element analysis as part of the procedure has to be harmonized with the requirements of the assessment procedure. Of course, the compatibility of the hot spot stress approach and a notch stress approach has to be guaranteed for individual examples. The direct comparison of the different approaches allows for a qualitative evaluation of methods. The application of an appropriate master fatigue curve FAT100 and the limitations with regard of stress/strain ranges in the low cycle fatigue (LCF) regime as well as the fatigue assessment of welded joints with mild weld toe notches is the subject of special considerations. The laTest recommendations of German Welding Society (DVS) [6] constitute a reference for the last two subjects raised.
-
Discussion of Fatigue Data for Austenitic Stainless Steels
Volume 1: Codes and Standards, 2014Co-Authors: Paul Wilhelm, Paul Steinmann, Jürgen RudolphAbstract:The first results of a detailed fatigue model for austenitic stainless steels in general and for the grades 1.4541 and 1.4550 are presented to describe the effect of the light water reactor (LWR) coolant environments on the fatigue life. The statistical evaluations are based on strain (and Load) Controlled Test series from different institutions. The compiled fatigue data include not only results from America (Keller (1971), Conway (1975), Hale (1977), and Argonne National Laboratory (ANL)(1999–2005)), but also from Europe (Solin (2006), Le Duff (2008–2010), De Baglion (2011, 2012), Huin (2013),…) and Japan (Kanasaki (1997)). The fatigue life is defined as the number of cycles necessary for tensile stress to drop 25 percent from its peak value. Fatigue lives defined by other failure criteria are normalized to the Load reduction of 25 percent, before the statistical analysis is performed. The fatigue data are expressed in terms of the Langer equation and the parameter “material variability and data scatter” is quantified.Additionally, fatigue data in air of roughened specimens are compiled and discussed. A reduction factor of 2.5 on number of cycles is derived to cover the maximum allowed surface roughness.Based on the derived best-fit curves, design-curves in air and, in a second step, environmentally assisted fatigue (EAF) curves for LWR environments, which consider temperature, strain rate, dissolved oxygen content, and hold-time effects, will be incorporated in the detailed fatigue model in the future.Copyright © 2014 by ASME
-
Derivation of Design Fatigue Curves for Austenitic Stainless Steel Grades 1.4541 and 1.4550 Within the German Nuclear Safety Standard KTA 3201.2
Volume 1B: Codes and Standards, 2013Co-Authors: Xaver Schuler, Karl-heinz Herter, Jürgen RudolphAbstract:Titanium and niobium stabilized austenitic stainless steels X6CrNiTi18-10S (material number 1.4541, correspondent to Alloy 321) respectively X6CrNiNb18-10S (material number 1.4550, correspondent to Alloy 347) are widely applied materials in German nuclear power plant components. Related requirements are defined in Nuclear Safety Standard KTA 3201.1. Fatigue design analysis is based on Nuclear Safety Standard KTA 3201.2. The fatigue design curve for austenitic stainless steels in the current valid edition of KTA 3201.2 is essentially identical with the design curve included in ASME-BPVC III, App I (ed. 2007, add. July 2008 respectively back editions).In the current code revision activities of KTA 3201.2 the compatibility of laTest in air fatigue data for austenitic stainless steels with the above mentioned grades were examined in detail. The examinations were based on statistical evaluations of 149 strain Controlled Test data at room temperature and 129 data at elevated temperatures to derive best-fit mean data curves. Results of two additional Load Controlled Test series (at room temperature and 288°C) in the high cycle regime were used to determine a technical endurance limit at 107 cycles. The related strain amplitudes were determined by consideration of the cyclic stress strain curve. The available fatigue data for the two austenitic materials at room temperature and elevated temperatures showed a clear temperature dependence in the high cycle regime demanding for two different best-fit curves. The correlation of the technical endurance limit(s) at room temperature and elevated temperatures with the ultimate strength of the materials is discussed.Design fatigue curves were derived by application of the well known factors to the best-fit curves. A factor of SN = 12 was applied to Load cycles correspondent to the NUREG/CR-6909 approach covering influences of data scatter, surface roughness, size and sequence. In terms of strain respectively stress amplitudes in the high cycle regime, for elevated temperatures (>80°C) a factor of Sσ = 1.79 was applied considering and combining in detail the partial influences of data scatter surface roughness, size and mean stress. For room temperature a factor of Sσ = 1.88 shall be applied.As a result, new design fatigue curves for austenitic stainless steel grades 1.4541 and 1.4550 will be available within the German Nuclear Safety Standard KTA 3201.2. The fatigue design rules for all other austenitic stainless steel grades will be based on the new ASME-BPVC III, App I (ed. 2010) design curve.Copyright © 2013 by ASME
Jurg Dual - One of the best experts on this subject based on the ideXlab platform.
-
Load Controlled Test apparatus for snow
Cold Regions Science and Technology, 2010Co-Authors: Ingrid Reiweger, Jurg Schweizer, Robert Ernst, Jurg DualAbstract:Abstract Natural dry-snow slab avalanches start with a failure at a weak snow layer. In order to understand the mechanical behaviour and the failure mechanism, we designed an experimental setup to perform Loading experiments with homogeneous and layered snow samples under Controlled conditions in a cold laboratory. We here present our Loading apparatus where the snow sample can be tilted by a “slope angle” and is Loaded by an increasing weight analogous to a snowfall. The force and the global displacement are measured with a force and two displacement sensors, respectively. The local displacement can be computed with a particle image velocimetry algorithm (PIV). Additionally, we record acoustic emissions (AE) to monitor the damage (breaking of bonds) in the snow sample before catastrophic failure. To demonstrate the capability of the system we present preliminary results with both homogeneous and layered snow samples. The AE count rate increased before fracture, as the samples progressively weakened. For the layered samples we measured a concentration of strain within the weak layer.
Paul Wilhelm - One of the best experts on this subject based on the ideXlab platform.
-
Discussion of Fatigue Data for Austenitic Stainless Steels
Volume 1: Codes and Standards, 2014Co-Authors: Paul Wilhelm, Paul Steinmann, Jürgen RudolphAbstract:The first results of a detailed fatigue model for austenitic stainless steels in general and for the grades 1.4541 and 1.4550 are presented to describe the effect of the light water reactor (LWR) coolant environments on the fatigue life. The statistical evaluations are based on strain (and Load) Controlled Test series from different institutions. The compiled fatigue data include not only results from America (Keller (1971), Conway (1975), Hale (1977), and Argonne National Laboratory (ANL)(1999–2005)), but also from Europe (Solin (2006), Le Duff (2008–2010), De Baglion (2011, 2012), Huin (2013),…) and Japan (Kanasaki (1997)). The fatigue life is defined as the number of cycles necessary for tensile stress to drop 25 percent from its peak value. Fatigue lives defined by other failure criteria are normalized to the Load reduction of 25 percent, before the statistical analysis is performed. The fatigue data are expressed in terms of the Langer equation and the parameter “material variability and data scatter” is quantified.Additionally, fatigue data in air of roughened specimens are compiled and discussed. A reduction factor of 2.5 on number of cycles is derived to cover the maximum allowed surface roughness.Based on the derived best-fit curves, design-curves in air and, in a second step, environmentally assisted fatigue (EAF) curves for LWR environments, which consider temperature, strain rate, dissolved oxygen content, and hold-time effects, will be incorporated in the detailed fatigue model in the future.Copyright © 2014 by ASME
Ingrid Reiweger - One of the best experts on this subject based on the ideXlab platform.
-
Load Controlled Test apparatus for snow
Cold Regions Science and Technology, 2010Co-Authors: Ingrid Reiweger, Jurg Schweizer, Robert Ernst, Jurg DualAbstract:Abstract Natural dry-snow slab avalanches start with a failure at a weak snow layer. In order to understand the mechanical behaviour and the failure mechanism, we designed an experimental setup to perform Loading experiments with homogeneous and layered snow samples under Controlled conditions in a cold laboratory. We here present our Loading apparatus where the snow sample can be tilted by a “slope angle” and is Loaded by an increasing weight analogous to a snowfall. The force and the global displacement are measured with a force and two displacement sensors, respectively. The local displacement can be computed with a particle image velocimetry algorithm (PIV). Additionally, we record acoustic emissions (AE) to monitor the damage (breaking of bonds) in the snow sample before catastrophic failure. To demonstrate the capability of the system we present preliminary results with both homogeneous and layered snow samples. The AE count rate increased before fracture, as the samples progressively weakened. For the layered samples we measured a concentration of strain within the weak layer.
Xaver Schuler - One of the best experts on this subject based on the ideXlab platform.
-
Derivation of Design Fatigue Curves for Austenitic Stainless Steel Grades 1.4541 and 1.4550 Within the German Nuclear Safety Standard KTA 3201.2
Volume 1B: Codes and Standards, 2013Co-Authors: Xaver Schuler, Karl-heinz Herter, Jürgen RudolphAbstract:Titanium and niobium stabilized austenitic stainless steels X6CrNiTi18-10S (material number 1.4541, correspondent to Alloy 321) respectively X6CrNiNb18-10S (material number 1.4550, correspondent to Alloy 347) are widely applied materials in German nuclear power plant components. Related requirements are defined in Nuclear Safety Standard KTA 3201.1. Fatigue design analysis is based on Nuclear Safety Standard KTA 3201.2. The fatigue design curve for austenitic stainless steels in the current valid edition of KTA 3201.2 is essentially identical with the design curve included in ASME-BPVC III, App I (ed. 2007, add. July 2008 respectively back editions).In the current code revision activities of KTA 3201.2 the compatibility of laTest in air fatigue data for austenitic stainless steels with the above mentioned grades were examined in detail. The examinations were based on statistical evaluations of 149 strain Controlled Test data at room temperature and 129 data at elevated temperatures to derive best-fit mean data curves. Results of two additional Load Controlled Test series (at room temperature and 288°C) in the high cycle regime were used to determine a technical endurance limit at 107 cycles. The related strain amplitudes were determined by consideration of the cyclic stress strain curve. The available fatigue data for the two austenitic materials at room temperature and elevated temperatures showed a clear temperature dependence in the high cycle regime demanding for two different best-fit curves. The correlation of the technical endurance limit(s) at room temperature and elevated temperatures with the ultimate strength of the materials is discussed.Design fatigue curves were derived by application of the well known factors to the best-fit curves. A factor of SN = 12 was applied to Load cycles correspondent to the NUREG/CR-6909 approach covering influences of data scatter, surface roughness, size and sequence. In terms of strain respectively stress amplitudes in the high cycle regime, for elevated temperatures (>80°C) a factor of Sσ = 1.79 was applied considering and combining in detail the partial influences of data scatter surface roughness, size and mean stress. For room temperature a factor of Sσ = 1.88 shall be applied.As a result, new design fatigue curves for austenitic stainless steel grades 1.4541 and 1.4550 will be available within the German Nuclear Safety Standard KTA 3201.2. The fatigue design rules for all other austenitic stainless steel grades will be based on the new ASME-BPVC III, App I (ed. 2010) design curve.Copyright © 2013 by ASME