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Engineering Mechanics Corporation Of Columbus

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Shim D.-J.,Engineering Mechanics Corporation Of Columbus | Wilkowski G.M.,Engineering Mechanics Corporation Of Columbus | Rudland D.L.,U.S. Nuclear Regulatory Commission
International Journal of Pressure Vessels and Piping | Year: 2011

One of the ways that the ASME Section XI code incorporates elastic-plastic fracture mechanics (EPFM) in the Section XI Appendix C flaw evaluation procedures for circumferential cracks is through a parameter called Z-factor. This parameter allows the simpler limit-load (or Net-Section-Collapse) solutions to be used with a multiplier from EPFM analyses. This paper shows how 3-D finite element (FE) analyses were employed to investigate the sensitivity of the crack-driving force as a function of crack location (i.e., crack in the center of weld, or closer to the stainless or low alloy steel sides) in an Alloy 182 dissimilar metal weld (DMW), and how an appropriate (or equivalent) stress-strain curve was determined for use in the J-estimation schemes. The J-estimation schemes are then used to cover a wider range of variables, i.e., pipe diameters, cracks lengths, and also incorporate crack growth by ductile tearing. The Z-factor equations as a function of pipe diameter were calculated using the LBB.ENG2 J-estimation scheme along with the most conservative equivalent stress-strain curve from the FE analyses. The proposed Z-factor approach was then validated against an Alloy 182 DMW full-scale pipe test that had a circumferential through-wall crack in the fusion line. The predicted EPFM maximum load showed excellent agreement with the experimental result. Furthermore, it was shown that the proposed Z-factor equation is not sensitive to the location of the crack. © 2011 Elsevier Ltd.


Rudland D.,U.S. Nuclear Regulatory Commission | Csontos A.,U.S. Nuclear Regulatory Commission | Shim D.-J.,Engineering Mechanics Corporation Of Columbus
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2010

Typical ASME Section XI subcritical cracking analyses assume an idealized flaw shape driven by stress intensity factors developed for semi-elliptical shaped flaws. Recent advanced finite element analyses (AFEA) conducted by both the United States Nuclear Regulatory Commission (U.S.NRC) and the nuclear industry for long circumferential indications found in the pressurizer nozzle dissimilar metal welds at the Wolf Creek power plant suggest that the semi-elliptical flaw assumption may be overly conservative in some cases. The AFEA methodology that was developed allowed the progression of a planar flaw subjected to typical stress corrosion cracking (SCC)-type growth laws by calculating stress intensity factors at every nodal point along the crack front, and incrementally advancing the crack front in a more natural manner. Typically, crack growthanalyses increment the semi-elliptical flaw by considering only the stress intensity factor at the deepest and surface locations along the crack front, while keeping the flaw shape semi-elliptical. In this paper, a brief background to the AFEA methodology and the analyses conducted in the Wolf Creek effort will be discussed. In addition, the predicted behavior of surface cracks under normal operating conditions (plus welding residual stress) using AFEA will be investigated and compared with the semi-elliptical assumption. Conclusions on the observation of when semi-elliptical flaw assumptions are appropriate will be made. These observations will add insight into the conservatism of using an idealized flaw shape assumption. Copyright © 2009 by ASME.


Rudland D.,U.S. Nuclear Regulatory Commission | Csontos A.,U.S. Nuclear Regulatory Commission | Zhang T.,Engineering Mechanics Corporation Of Columbus | Wilkowski G.,Engineering Mechanics Corporation Of Columbus
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2010

At the end of 2006, defects were identified using ultrasonic testing in three of the pres- surizer nozzle dissimilar metal (DM) welds at the Wolf Creek nuclear power plant. Understanding welding residual stress is important in the evaluation of why and how these defects occur, which in turn helps to determine the reliability of nuclear power plants. This paper presents analytical predictions of welding residual stress in the surge nozzle geometry identified at Wolf Creek. The analysis procedure in this paper includes not only the pass-by-pass welding steps, but also other essential fabrication steps of pressurizer surge nozzles. Detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. Case studies were carried out to investigate the change in the DM main weld stress fields resulting from different boundary conditions, material strength, weld sequencing, as well as simulation of the remaining piping system stiffness. A direct comparison of these analysis methodologies and results has been made in this paper. Weld residual stress results are compared directly to those calculated by the nuclear industry. Copyright © 2010 by ASME.


Shim D.-J.,Engineering Mechanics Corporation Of Columbus | Wilkowski G.,Engineering Mechanics Corporation Of Columbus
Proceedings of the Biennial International Pipeline Conference, IPC | Year: 2014

The bulging factor for an external constant-depth axial surface crack in a pipe was calculated by 3D FE simulations. This was done in a manner consistent with Folias's original work for the axial through-wall-cracked pipe bulging factor (MT ), but was evaluated in the elastic to full-plastic conditions. The results demonstrated that the actual surface-cracked pipe bulging factor is considerably lower than the bulging factor empirically derived by Maxey/Kiefner (Mp ) back in the 1970s. Based on the results of the present study, it is suggested that Mp function in the Ln-Secant equation is not truly a bulging factor for axial surface crack. Rather it is an empirically developed equation with many correction factors embedded in it to apply the Dugdale model for prediction of maximum pressure of axial surface-cracked pipes. However, due to this empiricism, this method becomes invalid (or overly conservative) when it is applied in predicting the crack-driving force using the J-based Ln-Secant equation. Copyright © 2014 by ASME.


Brust F.W.,Engineering Mechanics Corporation Of Columbus | Punch E.,Engineering Mechanics Corporation Of Columbus | Kurth E.,Engineering Mechanics Corporation Of Columbus
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

PWR nuclear power plants have dissimilar metal (DM) welds at many junctions between the vessels and the piping. The DM welds are made with Alloy 82 filler materials between carbon steel and stainless steel. These are potentially susceptible to Primary Water Stress Corrosion Cracking (PWSCC). PWSCC is mainly driven by the tensile weld residual stresses (WRS) that develop during fabrication of the piping system. In particular, weld repairs that often occur during the weld fabrication process also play a strong role in the development of the weld residual stress state in and near the DM welds. Most weld residual stress analyses performed to date in order to characterize the weld residual stress state in DM welds for PWSCC crack growth, leakage, and subsequent failure used axis-symmetric assessments. The purpose of this work is to provide direct assessment of the appropriateness of this axis-symmetric assumption on the WRS by comparison with full three dimensional analyses of several nozzles. In particular, weld start stop effects on the original weld will be assessed. In addition, the effect of partial arc weld repairs will be included. Repair cases considered include 15% and 50% deep repairs of length 48-degree and 96-degree of the circumference, along with the baseline case with no repair. The more complex three dimensional WRS state from the three dimensional analyses are compared to the corresponding axissymmetric solutions and guidelines regarding the appropriateness of 2D solutions are discussed. Finally, some limited calculations of stress intensity factors at locations along the repair are presented. Copyright © 2015 by ASME.


Brust F.W.,Engineering Mechanics Corporation Of Columbus | Punch E.,Engineering Mechanics Corporation Of Columbus | Kurth E.,Engineering Mechanics Corporation Of Columbus
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

NASA has numerous non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Since replacement costs of the tanks would be high an assessment of the pressure vessels' capabilities for continued use is desired. Layered tanks typically consists of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. The number of thinner layers required depends on the thickness required for the complete vessel. All cylindrical layers are welded longitudinally with staggered welds so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header (or nozzle) to complete the tank construction. This paper presents computational weld residual stress (WRS) modeling results of two representative layered tanks; (i) a small 4-layer tank and (ii) a large 14-layer tank. Contact between the layers must be considered which led to some convergence difficulties that were overcome. These predictions are compared with the corresponding monolithic tanks (non-layered) of the same size and thickness along with comparing to some compiled API-579 [1] WRS solutions. In general, the WRS fields in layered tanks are quite different from those in corresponding monolithic tanks and the effect of layering is necessary to include in the modeling. In addition, since the toughness of some aged tanks can be low the effect WRS on cracks may important. This is examined by introducing cracks into the tanks at locations where cracking may occur using the finite element alternating method (FEAM). Comments about the effect of WRS fields on fracture are also made. Copyright © 2015 by ASME.


Wilkowski G.M.,Engineering Mechanics Corporation Of Columbus | Shim D.-J.,Engineering Mechanics Corporation Of Columbus
Proceedings of the Biennial International Pipeline Conference, IPC | Year: 2012

Recently, there have been a few failures with brittle fractures occurring during hydrostatic or pneumatic proof testing in pipe fittings that rekindled the need for paying attention on how to specify the toughness for pipe fittings and other components such as valves. This paper shows how an analysis procedure called the "Master Curve of Fracture Transition Temperatures" can be used to specify a Charpy shear area percent at some target temperature so that ductile initiation behavior occurs for either a surface or through-wall cracks in fittings, components or pipe material at the minimum design temperature. Due to differences in thickness, loading rate, and constraint conditions, the Charpy test transition temperature will not be at the same temperature as the minimum design temperature. In addition to the background and summary of prior efforts, several examples of full-scale pipe and fitting/valve fracture tests on different materials will be presented to show that the methodology works well. It is also possible from this method to specify the Charpy shear area percent at some temperature to ensure that brittle fracture propagation will not occur. There are some limits on this methodology for some newer steels that have very high Charpy energy values, and those conditions are also summarized. Copyright © 2012 by ASME.


Grant
Agency: Department of Transportation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2015

The US DOT’s PHMSA is exploring technologies and methods which could increase the integrity, reliability and safety of the U.S. pipeline network. Corrosion metal loss is one of the major damage mechanisms to gas transmission pipelines worldwide. Current methods to assess the remaining strength of corroded pipelines, such as the ASME B31G (including the Modified B31G) and RSTRENG models that have been incorporated into the US Code of Federal Regulations may be inadequate and perhaps non-conservative for higher grade line pipe, X65 and above. Also recent work supported by PHMSA has shown that existing methods may be non-conservative. Emc2 proposes to establish the feasibility of a novel mathematical and computational model to assess the remaining strength of pipelines and fittings with natural corrosion type defects and a failure criterion that accounts for the transitional changes from a sharp crack to generally thinned corroded regions. The successful demonstration of the proposed approach “Simulation of Natural Corrosion via Computation” (SNC2) along with carefully selected laboratory experiments will allow appropriate correction factors to the existing methodologies and also provide a high-performance computational tool for reliable prediction of the remaining strength of both line pipe and fittings made with higher grade steels.


Grant
Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2013

The use of virtual design in the fabrication of large structures has enjoyed significant success in the heavy materials industry for almost two decades. Industries that have used virtual design and analysis tools have reduced material parts size, developed environmentally-friendly fabrication processes, improved product quality and performance, and reduced manufacturing costs. The proposed project involves leveraging an existing, state-of-the-art software code VFT used currently to design and model large welded structures prior to fabrication - to a broader range of applications and products for widespread use by small and medium-sized companies. The VFT code helps control distortion, minimize residual stresses, and pre-determine welding parameters such as weld-sequencing, pre-bending, and thermal-tensioning, using material properties, consumable properties, etc. as inputs. By doing this, manufacturing companies avoid costly design changes after fabrication. Emc2 staff developed this software code over a number of years in close cooperation with Caterpillar Inc. (CAT) of Peoria, IL, who currently uses this code exclusively for all fabrication and product design and development activities worldwide. Emc2 has licensed VFT for a number of other applications including the nuclear industry (USNRC), national laboratories (KAPL), shipbuilding (USNAVY), etc. The current limitation of VFT is that it requires the use of a commercially available finite-element software package as its core solver. This makes it prohibitively expensive for use by small and medium-size companies, since there is a significant licensing cost for the solver, over and above the minimal fees for VFT. The proposed project involves adapting VFT so that small and medium-size firms have access to this sophisticated technology and proven methodology that provides a quick, accurate and cost effective tool and is available on-demand to address weld-simulation and fabrication problems prior to manufacture. With the above background the scope of this effort will involve the following tasks:1) Employ an open-source solver (no fee) to replace the commercial code (solver). 2) Improve the graphical user interface (GUI) to a road map style to eliminate the need to be a computational expert to use VFT effectively. 3) Implement adaptive mesh refinement into VFT to enhance computational solution times without compromising accuracy. This will require the use of some codes and algorithms previously developed at several DOE laboratories (and other sources), and 4) Improve hardware architecture so that procurement of HPC assets or small scale clusters is justified and affordable for the small and mid-size firms of interest here. Accomplishing the above objectives in this SBIR project will provide small and mid-size companies access to this high-performance computational (HPC) technology via cloud- computing, either at Emc2 or at a national supercomputing site such as The Ohio Supercomputing Center at the OSU, on a pay-per-use basis.


Grant
Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 1.00M | Year: 2014

Historically, companies that fabricate structural parts/pieces that include welding as part of their fabrication process have relied on an iterative trial-and-error method to establish manufacturing and fabrication processes for new products. This approach is inefficient. A few US Industries that have used virtual design and analysis tools have developed environmentally-friendly fabrication processes, improved quality and performance, and reduced manufacturing costs to remain globally competitive. The Phase II project leverages an existing, state-of-the-art software code Virtual Fabrication Technology (VFT) used currently to design and model large welded structures prior to fabrication - to a broader range of applications and products for widespread use by small and medium-sized companies. This will enable these companies to have on-demand access both to weld modeling training and to low cost weld simulation technology through a cloud-based high performance computing portal. In Phase I the VFT code, which was tied to an expensive commercial solver, was modified to perform efficiently on a high performance open source finite element code called WARP3D. The results from Phase I clearly demonstrated that the software code produces high speed accurate solutions and can enable these fabricators to overcome the barriers to high performance computing using an easy-to-use portal. The Phase II program goal is to complete the adaptation of a (HPC) software code so it is accessible and useable to small and medium sized firms to improve their manufacturing and fabrication processes that yield products that have higher quality at reduced costs. The new software will be hosted on the Manufacturing and Polymer (M & amp;P) Portal within the Ohio Supercomputer Center (OSC) at the Ohio State University. This adapted version results in very rapid solution times and a new menu driven graphical user interface (GUI) so that the user does not have to be an expert in computational methods to use the code effectively. The long term (Phase III) goal is automate the software to permit fatigue and corrosion life prediction, optimization routines to automate the weld design process to design weld strategies that minimize distortions, reduce cost, and result in robust designs.

Loading Engineering Mechanics Corporation Of Columbus collaborators
Loading Engineering Mechanics Corporation Of Columbus collaborators