Analysis of Tension and Bending Response to Characterize Elastic-Plastic Material Behavior

2017 ◽  
Author(s):  
Don Metzger ◽  
Wolf Reinhardt
Keyword(s):  
Plastic Material ◽  
Load Capacity ◽  
Material Behavior ◽  
Material Degradation ◽  
Load Curve ◽  
Bending Mode ◽  
Elastic Plastic Material ◽  
Component Loading ◽  
The Relationship ◽  
Bending Response

The integrity of components can be affected by certain material degradation mechanisms that cause a loss of ductility. In cases where the component loading is primarily in bending, a loss of ductility can significantly reduce the load capacity. Material degradation may be determined by component testing involving the bending mode. In such cases, characterizing the material response in terms of yield stress, ultimate stress and failure strain is complicated by the nature of the load curve due to bending. The objective of this work is to examine in detail the relationship between tensile and bending response, with particular attention to the condition of decreasing ductility.

Fatigue Evaluation in Mixing Zones: Comparison of Different Criteria of Fatigue

2008 ◽  
Author(s):  
J. M. Stephan ◽  
C. Gourdin ◽  
J. Angles ◽  
S. Quilici ◽  
L. Jeanfaivre
Keyword(s):  
Fatigue Damage ◽  
Thermal Stresses ◽  
Plastic Material ◽  
Material Behavior ◽  
Damage Evaluation ◽  
Elastic Plastic ◽  
Different Types ◽  
Elastic Plastic Material ◽  
Fatigue Evaluation

The distribution of unsteady temperatures in the wall of the 6" FATHER mixing tee mock-up is calculated for a loading configuration: The results seem realistic even if they are not still very accurate (see paper PVP2005-71592 [11]). On this basis, thermal stresses are evaluated for elastic and elastic-plastic material behavior. Then, different types of fatigue criteria are used to evaluate the fatigue damage. The paper develops a brief description of the criteria, the corresponding fatigue damage evaluation and attempts to explain the differences.

A Continued Evaluation of the Role of Material Hardening Behavior for the NeT TG1 and TG4 Specimens

2014 ◽  
Author(s):  
David J. Dewees ◽  
Phillip E. Prueter ◽  
Seetha Ramudu Kummari
Keyword(s):  
Structural Integrity ◽  
Plastic Material ◽  
Critical Factor ◽  
Material Model ◽  
Standard Test ◽  
Material Behavior ◽  
Weld Residual Stress ◽  
Hardening Models ◽  
Elastic Plastic Material

Modeling of cyclic elastic-plastic material behavior (hardening) has been widely identified as a critical factor in the finite element (FE) simulation of weld residual stresses. The European Network on Neutron Techniques Standardization for Structural Integrity (NeT) Project has provided in recent years both standard test cases for simulation and measurement, as well as comprehensive material characterization. This has allowed the role of hardening in simulation predictions to be isolated and critically evaluated as never before possible. The material testing information is reviewed, and isotropic, nonlinear kinematic and combined hardening models are formulated and tested. Particular emphasis is placed on material model selection for general fitness-for-service assessments, as it relates to the guidance for weld residual stress (WRS) in flaw assessments of in-service equipment in Annex E of the FFS standard, API 579-1/ASME FFS-1.

Stress and Buckling of Internally Pressurized, Elastic-Plastic Torispherical Vessel Heads—Comparisons of Test and Theory

1977 ◽  
Vol 99 (1) ◽  
pp. 39-53 ◽  
Author(s):  
D. Bushnell ◽  
G. D. Galletly
Keyword(s):  
Mild Steel ◽  
Large Deflection ◽  
Plastic Material ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Test Results ◽  
Elastic Plastic ◽  
State Of Stress ◽  
Elastic Plastic Material ◽  
Good Agreement

Several aluminum and mild steel torispherical heads were tested by Galletly and by Kirk and Gill and subsequently analyzed by Bushnell with use of the BOSOR5 computer program. The thinnest specimens buckled at pressures for which part of the toroidal knuckle was stressed well beyond the yield point. The analysis includes large deflection effects, nonlinear material behavior, and meridional variation of the thickness. The calculated strains in the thicker specimens agree reasonably well with the test results, but the calculated prebuckling strains in the thinnest specimens are generally greater than the values measured in the torodial knuckle after the onset of plastic flow. Reasonably good agreement between test and theory is obtained for the buckling pressures of aluminum specimens, but the calculated buckling pressures for mild steel specimens are much lower than the observed values, a discrepancy that is attributed to circumferentially varying thickness and possible inability of the analytical model of the elastic-plastic material to predict accurately the state of stress in the toroidal knuckle where loading is nonproportional once yielding has occurred.

Elastic-Plastic Analysis of Stresses and Initiation of Cracks in a Ceramic Coating Under Indentation by an Elastic Sphere

1998 ◽  
Vol 120 (3) ◽  
pp. 463-469 ◽  
Author(s):  
K. Hayashi ◽  
F. Yuan
Keyword(s):  
Ceramic Coating ◽  
Plastic Material ◽  
Circumferential Stress ◽  
Material Behavior ◽  
Elastic Sphere ◽  
The Finite Element Method ◽  
Elastic Plastic ◽  
Formation Of Cracks ◽  
Elastic Plastic Material ◽  
Radial Cracks

The elastic-plastic contact problem of a ceramic coating on a half-space indented by an elastic sphere is solved by the use of the finite element method under a variety of conditions. An elastic-plastic material behavior with isotropic strain hardening was employed. Results for stresses, during loading and after unloading, on the surface and along the axis of symmetry are presented and formation of cracks is discussed in detail, emphasizing the influence of the thickness of coating. It is shown that the circumferential stress on the surface of the coating is highly tensile so that radial cracks are induced for a sharp indenter. But, for a blunt indenter, the radial stress is tensile and is always larger than the circumferential stress, leading to the formation of circumferential cracks. It is also shown that, in the case of a sharp indenter, radial cracks can be induced during unloading.

Repairing Corrosion Damage the Smart Way: A Story of Vessel Redemption

2014 ◽  
Author(s):  
Michael Turnquist ◽  
Gregory Brown
Keyword(s):  
Corrosion Rate ◽  
Plastic Material ◽  
Internal Surface ◽  
Corrosion Damage ◽  
Lessons Learned ◽  
Material Behavior ◽  
Metal Loss ◽  
Repair Procedure ◽  
Elastic Plastic Material ◽  
Improved Design

The application of emerging fitness-for-service standards in conjunction with advanced modeling and ultrasonic thickness (UT) inspection is demonstrated with the recent assessment and repair of a CO2 absorber vessel. UT inspection discovered four regions of localized metal loss on the internal surface of a CO2 absorber vessel shell. Of the four regions, two were directly adjacent to major structural discontinuities, including two nozzles, one of which contained a reinforcing plate or repad. In order to define the critical locations of metal loss and estimate a corrosion rate, thickness data for the regions of metal loss was provided in the form of 1 inch by 1 inch equally-spaced, rectangular thickness grid from two separate inspection dates. Based on the estimated corrosion rate, and the specified operation interval, the rate of metal loss was determined to be significant enough to require repair. This conclusion was based on the fact that in certain locations, the metal loss was estimated to grow through-wall before the end of the specified operation interval. Computational analysis using guidelines per API 579-1/ASME FFS-1 [1] was used to evaluate an appropriate repair procedure. This included evaluation of repair plate placement and sizing using advanced modeling techniques including elastic-plastic material behavior and contact interaction. The effect of future metal loss was included based the estimated corrosion rate. The result of this assessment was a repair design that provided sufficient protection against excessive plastic deformation and allowed for continued operation through the specified operating interval. Thus, repairing the vessel based on fitness-for-service (FFS) criteria allowed for continued use of the vessel and avoided costly replacement. The lessons learned provide insight into the improved design of vessel repairs.

Plastic Waves of Combined Stresses Due to Longitudinal Impact of a Pretorqued Tube—Part 2: Comparison of Theory With Experiment

1970 ◽  
Vol 37 (4) ◽  
pp. 1113-1120 ◽  
Author(s):  
J. Lipkin ◽  
R. J. Clifton
Keyword(s):  
Strain Rate ◽  
Numerical Solutions ◽  
Plastic Material ◽  
Material Behavior ◽  
Complete Agreement ◽  
Longitudinal Impact ◽  
Final State ◽  
Theoretical Predictions ◽  
Constant State ◽  
Elastic Plastic Material

The strain-time profiles of the experiments described in Part 1 are compared with numerical solutions based on a rate-independent theory for an isotropic work-hardening, elastic-plastic material. As discussed in Part 1, complete agreement between theory and experiment is not possible because the constant state regions predicted by the theory are not observed. In addition, the calculations lead to a final state of shear strain that is considerably greater than the measured value. Also, the magnitude of the observed jump in strain rate at an unloading wave does not agree with the theoretical predictions. The absence of constant state regions and the discrepancy in the jump at unloading waves are shown to be explainable in terms of the inadequacy of the assumption of strain rate-independent material behavior.

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