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.

Prediction and Measurement of Residual Stresses Arising From Quenching of Stainless Steels

2004 ◽  
Author(s):  
S. Hossain ◽  
C. E. Truman ◽  
D. J. Smith ◽  
M. R. Daymond
Keyword(s):  
Stainless Steel ◽  
Residual Stresses ◽  
Stainless Steels ◽  
Numerical Study ◽  
Hole Drilling ◽  
The Core ◽  
Residual Stress State ◽  
Surface Residual Stresses ◽  
Compressive Residual Stresses ◽  
Good Agreement

This paper presents results from an experimental and numerical study examining the creation of highly triaxial residual stresses in stainless steel. This was motivated by a need to model and understand creep in aged power plant. The residual stresses were introduced by rapid spray water quenching of heated solid stainless steel spheres and cylinders. Finite element (FE) simulations predicted high compressive residual stresses around the surface of the specimens and tensile residual stresses near the centre. Surface residual stresses were measured using the incremental centre-hole drilling (ICHD) technique. Neutron diffraction (ND) was used to measure the interior residual stresses. The measurements were in good agreement with FE predictions. The ND measurements confirmed that a highly triaxial residual stress state existed in the core of the specimens.

scholarly journals Analysis of Residual Stress in Stress Harps of Grey Iron by Experiment and Simulation

2014 ◽  
Vol 996 ◽  
pp. 586-591 ◽  
Author(s):  
Pål Schmidt ◽  
Lin Peng Ru ◽  
Vadim Davydov ◽  
Mattias Lundberg ◽  
Maqsood Ahmad ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Casting Process ◽  
Axial Direction ◽  
Hole Drilling ◽  
Fe Simulations ◽  
Stress Relieving ◽  
Compressive Residual Stresses ◽  
Good Agreement ◽  
Grey Iron

Stress harps with bars of different size were used to study residual stresses due to different cooling rate during casting of a grey iron. Finite element (FE) simulations were performed to predict residual stresses from the casting process and the effect of a stress relieving heat treatment. Intended for validating the simulations, neutron diffraction (ND) and hole drilling methods were used to measure the residual stress distribution through the thickness and in a thin surface layer, respectively. Good agreement between the FE simulations and ND measurements is observed for the annealed harp and the normal and transverse directions of the as cast harp. Discrepancy occurs in the axial direction and especially in the side bars of the as cast harp for which the simulation shows much higher compressive residual stresses. The observed difference between the different techniques was discussed with respect to the characteristics of the different methods.

A Numerical and Experimental Study of Distribution of the Residual Stress on the Shot Peened Low Alloy Steel

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Pham Quang Trung ◽  
David Lee Butler ◽  
Sridhar Idapalapati
Keyword(s):  
Residual Stresses ◽  
Shot Peening ◽  
Cold Working ◽  
Experimental Studies ◽  
Element Model ◽  
Working Process ◽  
Factors Affecting ◽  
Properties Of Materials ◽  
Compressive Residual Stresses ◽  
Good Agreement

Shot peening is a cold working process, which is used to enhance the properties of materials, especially the fatigue life as it induces large compressive residual stresses in the subsurface of materials. In this paper, the effect of the shot peening process on the topography of the shot peened surface and the distribution of the residual stresses in the subsurface of the material was systematically investigated. A technique to estimate the shot peening coverage was employed using a finite element model which was further developed using experimental results for increased accuracy. The comparison between the numerical and experimental studies gives a good agreement of the distribution of the residual stresses in the subsurface of the shot peened material. The shot peening pressure and media size are two main factors affecting on the presence of compressive residual stresses in the subsurface of the material.

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.

Electromechanical modelling of piezoelectrically actuated MEMS tunable lenses with geometric nonlinearity

2021 ◽  
pp. 1045389X2110069
Author(s):  
Mahmoud A. Farghaly ◽  
Vladimir Kartashov ◽  
Muhammad Nadeem Akram ◽  
Einar Halvorsen
Keyword(s):  
Residual Stresses ◽  
Nonlinear Model ◽  
Plate Theory ◽  
Variational Model ◽  
Nonlinear Behaviour ◽  
Variational Integrals ◽  
Piezoelectric Coupling ◽  
Tunable Lenses ◽  
Compressive Residual Stresses ◽  
Good Agreement

This article presents a variational model for the geometrically nonlinear behaviour of the piezoelectrically actuated MEMS tunable lenses. Residual stresses during fabrication and larger actuation voltages cause large deflections such that a linear model would provide less accurate approximation. This presses the need for a nonlinear model that can explain the softening and hardening effects exhibited by the lens during its operation and affect its optical performance. Thus, in the view of von Kármán’s plate theory, the presented nonlinear model predicts the lens displacement after solving a cubic nonlinear system of equations. The chosen displacement ansatz fits the problem under study by satisfying the mechanical boundary conditions, and simplifying calculation of the variational integrals and optical representation of the lens’ sag. The model also shows good agreement with FEM simulations over various combinations of tensile and compressive residual stresses. Moreover, it succeeds in fitting measurements when used in a constrained optimization scheme in which the layers’ residual stresses and the e-form piezoelectric coupling coefficient are the fitting parameters.

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 Experimental Methods for Measuring the Viscous Friction Coefficient in Hydraulic Spool Valves

2021 ◽  
Vol 13 (13) ◽  
pp. 7174
Author(s):  
Massimo Rundo ◽  
Paolo Casoli ◽  
Antonio Lettini
Keyword(s):  
Friction Coefficient ◽  
Viscous Friction ◽  
Experimental Tests ◽  
Experimental Methods ◽  
Displacement Transducer ◽  
A Posteriori ◽  
Displacement Control ◽  
Spool Valves ◽  
The University ◽  
Good Agreement

In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.

The Deformation of an Erythrocyte Under the Radiation Pressure by Optical Stretch

2006 ◽  
Vol 128 (6) ◽  
pp. 830-836 ◽  
Author(s):  
Yong-Ping Liu ◽  
Chuan Li ◽  
Kuo-Kang Liu ◽  
Alvin C. K. Lai
Keyword(s):  
Radiation Pressure ◽  
Experimental Situation ◽  
Numerical Data ◽  
Shear Stiffness ◽  
Cell Deformation ◽  
Membrane Properties ◽  
Optimization Approach ◽  
Bending Modulus ◽  
Average Shear ◽  
Good Agreement

In this paper, the mechanical properties of erythrocytes were studied numerically based upon the mechanical model originally developed by Pamplona and Calladine (ASME J. Biomech. Eng., 115, p. 149, 1993) for liposomes. The case under study is the erythrocyte stretched by a pair of laser beams in opposite directions within buffer solutions. The study aims to elucidate the effect of radiation pressure from the optical laser because up to now little is known about its influence on the cell deformation. Following an earlier study by Guck et al. (Phys. Rev. Lett., 84, p. 5451, 2000; Biophys. J., 81, p. 767, 2001), the empirical results of the radiation pressure were introduced and imposed on the cell surface to simulate the real experimental situation. In addition, an algorithm is specially designed to implement the simulation. For better understanding of the radiation pressure on the cell deformation, a large number of simulations were conducted for different properties of cell membrane. Results are first discussed parametrically and then evaluated by comparing with the experimental data reported by Guck et al. An optimization approach through minimizing the errors between experimental and numerical data is used to determine the optimal values of membrane properties. The results showed that an average shear stiffness around 4.611×10-6Nm−1, when the nondimensional ratio of shear modulus to bending modulus ranges from 10 to 300. These values are in a good agreement with those reported in literature.

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.

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