Development of a Residual Stress Evaluation Technique by the Combined Use of Surface Strain Measurements Under the Spherical Indentation Method

2013 ◽  
Author(s):  
Norihiko Ozawa ◽  
Tomoaki Yoshizawa ◽  
Yutaka Watanabe ◽  
Tetsuo Shoji
Keyword(s):  
Residual Stresses ◽  
Elastic Strain ◽  
Fem Analysis ◽  
Indentation Load ◽  
Surface Strain ◽  
Spherical Indentation ◽  
Maximum Pressure ◽  
Strain Measurements ◽  
Combined Use ◽  
Compressive Residual Stresses

In this research, a technique was developed for quantitatively evaluating the amount and distribution of tensile and compressive residual stresses by the combined use of strain measurements under the spherical indentation loading together with the finite element method (FEM). When the spherical indentation is applied to the top surface of a welded plate, the elastic strain at an optimized position near the indentation is measured by strain gauges, where the residual and applied indentation stresses are largely superposed. In order to analyze the residual stresses, FEM analysis was conducted to establish the relationship between the elastic strain adjacent to the indentation and the indentation pressure for plates subjected to various uniform tensile and compressive stresses. The critical indentation load was identified, which maximizes the difference between the tensile and compressive residual stresses. A strain energy term (U*) is newly introduced by integrating along the trajectory between the indentation pressure and the elastic strain in a range from 0 to maximum pressure. The application of this technique could contribute to improved reliability in welded parts.

Post Autofrettage Thermal Treatment and Its Effect on Re-Yielding of High Strength Pressure Vessel Steels

2009 ◽  
Author(s):  
E. Troiano ◽  
J. H. Underwood ◽  
A. P. Parker ◽  
C. Mossey
Keyword(s):  
Thermal Treatment ◽  
Low Temperature ◽  
Plastic Strain ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Lower Amount ◽  
Isotropic Hardening ◽  
Maximum Pressure ◽  
Compressive Residual Stresses

The autofrettage process of a thick walled pressure vessel involves applying tensile plastic strain at the bore of the vessel which reverses during unloading and results in favorable compressive residual stresses at the bore and prolongs the fatigue life of the component. In thick walled pressure vessels this process can be accomplished with either a hydraulic or mechanical overloading process. The Bauschinger effect, which is observed in many of the materials used in thick walled pressure vessels, is a phenomenon which results in lower compressive residual stresses than those predicted with classic ideal isotropic hardening. The phenomenon is a strong function of the amount of prior tensile plastic strain. A novel idea which involves a multiple autofrettage process has been proposed by the present authors. This process requires a low temperature post autofrettage thermal treatment which effectively returns the material to its original yield conditions without affecting its residual stress state. Details of this low temperature thermal treatment are proprietary. A subsequent second autofrettage process generates a significantly lower amount of plastic strain during the tensile re-loading and results in higher compressive residual stresses. This paper reports the details of exploratory tests involving tensile and compressive loading of a test coupon, followed by a low temperature post plastic straining thermal treatment, and subsequent re-loading in tension and compression. Finally results of a full scale Safe Maximum Pressure (SMP) test of pressure vessels are presented; these tests indicate a significant increase (11%) in SMP.

Effects of Simulation Parameters on Residual Stresses of Inconel Alloy 600 in Finite Element Laser Shock Peening Analysis

2012 ◽  
Author(s):  
Ju Hee Kim ◽  
Ji Soo Kim ◽  
Yun Jae Kim ◽  
Hong Yeol Bae ◽  
Joung Soo Kim
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Pulse Duration ◽  
Laser Shock Peening ◽  
Maximum Pressure ◽  
Alloy 600 ◽  
Laser Shock ◽  
Inconel Alloy ◽  
Shock Peening ◽  
Compressive Residual Stresses

Laser shock peening (LSP) is an innovative surface treatment technique, which is successfully applied to improve fatigue performance of metallic components. After the treatment, the fatigue strength and fatigue life of a metallic material can be increased remarkably owing to the presence of compressive residual stresses in the material. Recently, the incidences of cracking in Alloy 600 small-caliber penetration nozzles (CRDM (control rod drive mechanism) and BMI (bottom mounted instrument)) have increased significantly. The cracking mechanism has been attributed to primary water stress corrosion cracking (PWSCC) and has been shown to be driven by welding residual stresses and operational stresses in the weld region. For this reason, to mitigating weld residual stress, preventive maintenance of BMI nozzles was considered application of laser shock peening process. The present study is to predict the residual stresses distribution along the peening surface and the interior of the target (Inconel alloy 600 steel) induced by single and multiple LSP processes using the finite element method. The simulations were accomplished using a commercial finite element package ABAQUS, employing both explicit and implicit methodologies. Effects of parameters related to finite element simulation of laser shock peening process to determine compressive residual stresses of Inconel alloy 600 steel are discussed, in particular parameters associated with the LSP process, such as the maximum pressure, pressure pulse duration, laser spot size and number of shots. It is found that about 2HEL maximum pressure and a certain range of the pulse duration can produce maximum compressive residual stresses near the surface, and thus proper choices of these parameters are important. But plastically affected depth increase with increasing maximum pressure and pulse duration. For the laser spot size, residual stresses are not affected, provided it is larger than a certain size. Magnitudes of the compressive residual stresses and plastically affected depth are found to increase with increasing number of shots, but the effect is less pronounced for more shots. Thus, the amplitude of the initial tensile residual stresses was remarkably changed by LSP. Additionally, In order to evaluate the influence of initial residual stresses in Inconel alloy 600 steel, the initial condition option was employed in the finite element code.

Post-Autofrettage Thermal Treatment and Its Effect on Reyielding of High Strength Pressure Vessel Steels

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
E. Troiano ◽  
J. H. Underwood ◽  
A. P. Parker ◽  
C. Mossey
Keyword(s):  
Thermal Treatment ◽  
Low Temperature ◽  
Plastic Strain ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Lower Amount ◽  
Isotropic Hardening ◽  
Maximum Pressure ◽  
Compressive Residual Stresses

The autofrettage process of a thick walled pressure vessel involves applying tensile plastic strain at the bore of the vessel, which reverses during unloading and results in favorable compressive residual stresses at the bore and prolongs the fatigue life of the component. In thick walled pressure vessels this process can be accomplished with either a hydraulic or mechanical overloading process. The Bauschinger effect, which is observed in many of the materials used in thick walled pressure vessels, is a phenomenon, which results in lower compressive residual stresses than those predicted with classic ideal isotropic hardening. The phenomenon is a strong function of the amount of prior tensile plastic strain. A novel idea, which involves a multiple autofrettage processes, has been proposed by the present authors. This process requires a low temperature post-autofrettage thermal treatment, which effectively returns the material to its original yield conditions with minimal effect on its residual stress state. Details of this low temperature thermal treatment are proprietary. A subsequent second autofrettage process generates a significantly lower amount of plastic strain during the tensile reloading and results in higher compressive residual stresses. This paper reports the details of the exploratory tests involving tensile and compressive loading of a test coupon, followed by a low temperature post-plastic straining thermal treatment, and subsequent reloading in tension and compression. Finally results of a full scale safe maximum pressure (SMP) test of pressure vessels are presented; these tests indicate a significant increase (11%) in SMP.

A Neural Networks Approach to Measure Residual Stresses Using Spherical Indentation

2013 ◽  
Vol 768-769 ◽  
pp. 114-119
Author(s):  
Amir Hossein Mahmoudi ◽  
Mitra Ghanbari-Matloob ◽  
Soroush Heydarian
Keyword(s):  
Residual Stresses ◽  
Error Propagation ◽  
Numerical Data ◽  
Experimental Tests ◽  
Spherical Indentation ◽  
316L Steel ◽  
Indentation Tests ◽  
Artificial Neural Network Ann ◽  
Compressive Residual Stresses ◽  
Good Agreement

In the present study an Artificial Neural Network (ANN) approach is proposed for residual stresses estimation in engineering components using indentation technique. First of all, load-penetration curves of indentation tests for tensile and compressive residual stresses are studied using Finite Element Method (FEM) for materials with different yield stresses and work-hardening exponents. Then, experimental tests are carried out on samples made of 316L steel without residual stresses. In the next step, multi-layer feed forward ANNs are created and trained based on 80% of obtained numerical data using Back-Error Propagation (BEP) algorithm. Then the trained ANNs are tested against the remaining data. The obtained results show that the predicted residual stresses are in good agreement with the actual data.

Effect of length in rotational autofrettage of long cylinders with free ends

2021 ◽  
pp. 095440622110342
Author(s):  
Rajkumar Shufen ◽  
Uday Shanker Dixit
Keyword(s):  
Plastic Deformation ◽  
Residual Stresses ◽  
Axial Stress ◽  
Fem Analysis ◽  
Longitudinal Axis ◽  
Pressure Vessels ◽  
Stress Changes ◽  
Different Types ◽  
Compressive Residual Stresses ◽  
Spherical Pressure

Thick-walled cylindrical and spherical pressure vessels are often subjected to autofrettage, a process in which the vessel is loaded at the inner wall to cause a partial or complete plastic deformation emanating from the inner wall, followed by unloading. This introduces the beneficial compressive residual stresses in the vicinity of the inner wall. Depending on the type of the loading, there are five different types of autofrettage processes— hydraulic, swage, explosive, thermal and rotational. This article analyzes the rotational autofrettage, in which the cylinder to be autofrettaged is loaded by rotating it about its longitudinal axis. The centrifugal forces cause the required plastic deformation in the cylinder. Hence, when the cylinder is unloaded by bringing it to rest, compressive hoop residual stresses are introduced in the vicinity of its inner wall. When long cylinders are rotated about their axes, the distribution of axial stress changes with length of the cylinder and affects the generation of the residual stresses in the autofrettaged cylinder. This effect is investigated here by a finite element method (FEM) analysis of rotational autofrettage of cylinder made up of A723 gun steel. The FEM analysis using ABAQUS® package reveals the presence of tensile axial residual stresses in the vicinity of the inner wall of the cylinder, which increase with length. The tensile residual stresses can be mitigated by constraining the ends of the cylinder during the rotational autofrettage.

Nonlinear Membrane Direct and Inverse FEM Analysis

2014 ◽  
Author(s):  
Mattia Alioli ◽  
Pierangelo Masarati ◽  
Marco Morandini ◽  
Trenton Carpenter ◽  
Roberto Albertani
Keyword(s):  
Three Dimensional ◽  
Fem Analysis ◽  
Solution Procedure ◽  
General Purpose ◽  
Inverse Solution ◽  
Surface Strain ◽  
Image Correlation ◽  
Direct Solution ◽  
Strain Measurements ◽  
Solution Approach

The analysis of thin structural components integrated within a general-purpose multibody system dynamics formulation is presented. An original inverse finite element solution procedure is developed to reconstruct the deformed shape of a membrane from in-plane membrane strain measurements, and eventually indirectly estimate the distributed loads. A direct solution approach is used in co-simulation with fluid-dynamics solvers to predict the configuration of the system under static and unsteady loads. Numerical validation of the inverse solution is performed considering the results of direct solution analysis. The direct and inverse solutions are validated considering experimental displacement and strain measurements obtained using digital image correlation. Moving Least Squares are used to smooth and remap measurements as needed by the inverse solution meshing. Utilizing surface strain measurements from strain sensors, the methodology enables the accurate computation of the three-dimensional displacement field.

scholarly journals X-ray Determination of Compressive Residual Stresses in Spring Steel Generated by High-Speed Water Quenching

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1154
Author(s):  
Diego E. Lozano ◽  
George E. Totten ◽  
Yaneth Bedolla-Gil ◽  
Martha Guerrero-Mata ◽  
Marcel Carpio ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
High Speed ◽  
Spring Steel ◽  
X Ray Diffraction ◽  
Laboratory Equipment ◽  
X Ray ◽  
Water Chamber ◽  
Hardened Case ◽  
Compressive Residual Stresses

Automotive components manufacturers use the 5160 steel in leaf and coil springs. The industrial heat treatment process consists in austenitizing followed by the oil quenching and tempering process. Typically, compressive residual stresses are induced by shot peening on the surface of automotive springs to bestow compressive residual stresses that improve the fatigue resistance and increase the service life of the parts after heat treatment. In this work, a high-speed quenching was used to achieve compressive residual stresses on the surface of AISI/SAE 5160 steel samples by producing high thermal gradients and interrupting the cooling in order to generate a case-core microstructure. A special laboratory equipment was designed and built, which uses water as the quenching media in a high-speed water chamber. The severity of the cooling was characterized with embedded thermocouples to obtain the cooling curves at different depths from the surface. Samples were cooled for various times to produce different hardened case depths. The microstructure of specimens was observed with a scanning electron microscope (SEM). X-ray diffraction (XRD) was used to estimate the magnitude of residual stresses on the surface of the specimens. Compressive residual stresses at the surface and sub-surface of about −700 MPa were obtained.

scholarly journals Thermal Effects on Surface and Subsurface Modifications in Laser-Combined Deep Rolling

2021 ◽  
Vol 5 (2) ◽  
pp. 55
Author(s):  
Robert Zmich ◽  
Daniel Meyer
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Thermal Loads ◽  
Deep Rolling ◽  
Mechanical Loads ◽  
Thermomechanical Process ◽  
Compressive Stresses ◽  
New Process ◽  
Negative Effect ◽  
Compressive Residual Stresses

Knowledge of the relationships between thermomechanical process loads and the resulting modifications in the surface layer enables targeted adjustments of the required surface integrity independent of the manufacturing process. In various processes with thermomechanical impact, thermal and mechanical loads act simultaneously and affect each other. Thus, the effects on the modifications are interdependent. To gain a better understanding of the interactions of the two loads, it is necessary to vary thermal and mechanical loads independently. A new process of laser-combined deep rolling can fulfil exactly this requirement. The presented findings demonstrate that thermal loads can support the generation of residual compressive stresses to a certain extent. If the thermal loads are increased further, this has a negative effect on the surface layer and the residual stresses are shifted in the direction of tension. The results show the optimum range of thermal loads to further increase the compressive residual stresses in the surface layer and allow to gain a better understanding of the interactions between thermal and mechanical loads.

scholarly journals Additive Manufactured 316L Stainless-Steel Samples: Microstructure, Residual Stress and Corrosion Characteristics after Post-Processing

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 182
Author(s):  
Suvi Santa-aho ◽  
Mika Kiviluoma ◽  
Tuomas Jokiaho ◽  
Tejas Gundgire ◽  
Mari Honkanen ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Sample Surface ◽  
Post Processing ◽  
Magnesium Chloride Solution ◽  
Manufacturing Method ◽  
Four Point Bending ◽  
Traditional Manufacturing ◽  
Processing Steps ◽  
Compressive Residual Stresses

Additive manufacturing (AM) is a relatively new manufacturing method that can produce complex geometries and optimized shapes with less process steps. In addition to distinct microstructural features, residual stresses and their formation are also inherent to AM components. AM components require several post-processing steps before they are ready for use. To change the traditional manufacturing method to AM, comprehensive characterization is needed to verify the suitability of AM components. On very demanding corrosion atmospheres, the question is does AM lower or eliminate the risk of stress corrosion cracking (SCC) compared to welded 316L components? This work concentrates on post-processing and its influence on the microstructure and surface and subsurface residual stresses. The shot peening (SP) post-processing levelled out the residual stress differences, producing compressive residual stresses of more than −400 MPa in the AM samples and the effect exceeded an over 100 µm layer below the surface. Post-processing caused grain refinement and low-angle boundary formation on the sample surface layer and silicon carbide (SiC) residue adhesion, which should be taken into account when using the components. Immersion tests with four-point-bending in the heated 80 °C magnesium chloride solution for SCC showed no difference between AM and reference samples even after a 674 h immersion.

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