scholarly journals Process of Identifying Stress Fields from Strain Fields in the Specimen with a Hole

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Michaela Štamborská ◽  
Miroslav Kvíčala ◽  
Vratislav Mareš
Keyword(s):  
Tensile Tests ◽  
Image Correlation ◽  
Stress Fields ◽  
Uniaxial Tensile ◽  
Main Attention ◽  
Identification Procedure ◽  
Complex State ◽  
Strain Fields ◽  
State Of Stress ◽  
Correlation System

The paper is focused on the process of identifying stress fields from strain fields in the specimen with a hole. The experiment was realized on the specimen with a hole made from anisotropic material. The main attention is paid to the analysis of deformation in the areas of stress (near the hole). That geometry generates a heterogeneous strain field which has been measured during the test using a digital image correlation system. The advantage of using heterogeneous strain fields in the identification procedure is that a complex state of stress-strain can be analyzed at the same time. On the other hand the stress field cannot be directly computed from the test and a suitable identification procedure has to be developed. Here, the virtual fields method (VFM) adapted for plastic strain has been used to identify the hardening behaviour and the anisotropy of the material. The values obtained by the VFM have been compared with the results coming from a standard identification made with uniaxial tensile tests.

scholarly journals Measurement and Analysis of Heterogeneous Strain Fields in Uniaxial Tensile Tests for Boron Steel Under Hot Stamping Conditions

2020 ◽  
Vol 60 (9) ◽  
pp. 1289-1300
Author(s):  
R. Zhang ◽  
Z. Shao ◽  
J. Lin ◽  
T. A. Dean
Keyword(s):  
Temperature Gradient ◽  
Hot Stamping ◽  
Tensile Tests ◽  
Gauge Length ◽  
Image Correlation ◽  
Effect Of Temperature ◽  
Uniaxial Tensile ◽  
Boron Steel ◽  
Strain Fields ◽  
Dog Bone

Abstract Background A significant amount of uniaxial tensile tests has been carried out using Gleeble systems to investigate the viscoplastic deformation of boron steel (22MnB5) under hot stamping conditions. However, due to heat loss through the end clamps, a temperature gradient in the reduced parallel section of dog-bone shaped specimens is inevitable. Objective In the work reported in this paper, the effect of temperature gradient on measured outcomes is examined. Methods Uniaxial tensile tests on 1.5 mm thick boron steel specimens are carried out, under hot stamping conditions and strain fields are quantified using the digital image correlation (DIC) technique. The effect of gauge length on the properties of boron steel, as calculated from observed test results, is determined. Results Compared with the test at room temperature, a bell-shaped strain distribution occurs within the gauge length even before the appearance of the maximum load. Also, average strain within the gauge length, especially in the later stages, changes with gauge length within the investigated range, and thus, different engineering stress-strain curves and fracture strains are determined. In addition, normalized strain rate is significantly dependent on gauge length, which results in over 16% difference among the computed flow stresses by using a unified constitutive model. Conclusions The characterized properties of the material are dependent on gauge length and thus, a testing standard for measuring thermal-mechanical data of materials by using a Gleeble need to be defined.

scholarly journals Robust Filtering Options for Higher-Order Strain Fields Generated by Digital Image Correlation

2020 ◽  
Vol 1 (4) ◽  
pp. 174-192
Author(s):  
Nedaa Amraish ◽  
Andreas Reisinger ◽  
Dieter H. Pahr
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Tensile Tests ◽  
Image Correlation ◽  
Field Strain ◽  
Strain Fields ◽  
Full Field ◽  
Low Pass ◽  
Discrete Measurement ◽  
Mean Filtering

Digital image correlation (DIC) systems have been used in many engineering fields to obtain surface full-field strain distribution. However, noise affects the accuracy and precision of the measurements due to many factors. The aim of this study was to find out how different filtering options; namely, simple mean filtering, Gaussian mean filtering and Gaussian low-pass filtering (LPF), reduce noise while maintaining the full-field information based on constant, linear and quadratic strain fields. Investigations are done in two steps. First, linear and quadratic strain fields with and without noise are simulated and projected to discrete measurement points which build up strain window sizes consisting of 6×5, 12×11, and 26×17 points. Optimal filter sizes are computed for each filter strategy, strain field type, and strain windows size, with minimal impairment of the signal information. Second, these filter sizes are used to filter full-field strain distributions of steel samples under tensile tests by using an ARAMIS DIC system to show their practical applicability. Results for the first part show that for a typical 12×11 strain window, simple mean filtering achieves an error reduction of 66–69%, Gaussian mean filtering of 72–75%, and Gaussian LPF of 66–69%. If optimized filters are used for DIC measurements on steel samples, the total strain error can be reduced from initial 240−300 μstrain to 100–150 μstrain. In conclusion, the noise-floor of DIC signals is considerable and the preferable filters were a simple mean with s*¯ = 2, a Gaussian mean with σ*¯ = 1.7, and a Gaussian LPF with D0*¯ = 2.5 in the examined cases.

scholarly journals Determination of Strain and Stress Fields in Welded Joints of S960-QC Steel

2017 ◽  
Vol 62 (4) ◽  
pp. 2081-2087 ◽  
Author(s):  
T. Pała ◽  
I. Dzioba
Keyword(s):  
Welded Joints ◽  
Experimental Studies ◽  
Welding Process ◽  
Tensile Tests ◽  
Stress Fields ◽  
Uniaxial Tensile ◽  
Displacement Fields ◽  
The Individual ◽  
Computational Part

Abstract The paper presents the results of two butt welded joints by conventional method. The welding process was performed using a variety of linear welding energy. The studies included experimental and computational part. In experimental studies determined the distribution of hardness and mechanical properties of the individual analyzed sections of welded joints. The data obtained were intended to determine the extent of zones in the welded joints that have certain strength characteristics. Also conducted uniaxial tensile tests of welded joints with the registration of displacement fields on the surface of specimens by means of Aramis video-system what the final result are images of strain fields map on the surface of welded joints. The resulting strain values were compared with the results of numerical computations FEM.

scholarly journals Strain Distribution of Intact Rat Rotator Cuff Tendon-to-Bone Attachments and Attachments With Defects

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Ryan C. Locke ◽  
John M. Peloquin ◽  
Elisabeth A. Lemmon ◽  
Adrianna Szostek ◽  
Dawn M. Elliott ◽  
...  
Keyword(s):  
Area Under The Curve ◽  
Tensile Tests ◽  
Biomechanical Properties ◽  
Defect Group ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Transverse Strain ◽  
Intact Group ◽  
Deformation Patterns ◽  
Insight Into

Abstract This study aimed to experimentally track the tissue-scale strains of the tendon–bone attachment with and without a localized defect. We hypothesized that attachments with a localized defect would develop strain concentrations and would be weaker than intact attachments. Uniaxial tensile tests and digital image correlation were performed on rat infraspinatus tendon-to-bone attachments with defects (defect group) and without defects (intact group). Biomechanical properties were calculated, and tissue-scale strain distributions were quantified for superior and inferior fibrous and calcified regions. At the macroscale, the defect group exhibited reduced stiffness (31.3±3.7 N/mm), reduced ultimate load (24.7±3.8 N), and reduced area under the curve at ultimate stress (3.7±1.5 J/m2) compared to intact attachments (42.4±4.3 N/mm, 39.3±3.7 N, and 5.6±1.4 J/m2, respectively). Transverse strain increased with increasing axial load in the fibrous region of the defect group but did not change for the intact group. Shear strain of the superior fibrous region was significantly higher in the defect group compared to intact group near yield load. This work experimentally identified that attachments may resist failure by distributing strain across the interface and that strain concentrations develop near attachment defects. By establishing the tissue-scale deformation patterns of the attachment, we gained insight into the micromechanical behavior of this interfacial tissue and bolstered our understanding of the deformation mechanisms associated with its ability to resist failure.

Identification of the Mechanical Properties of High-Strength Steel Using Digital Image Correlation

2014 ◽  
Vol 980 ◽  
pp. 122-126 ◽  
Author(s):  
Michaela Štamborská ◽  
Miroslav Kvíčala ◽  
Monika Losertová
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Digital Image ◽  
High Strength Steel ◽  
Strain Field ◽  
High Strength ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Large Strains ◽  
Identification Procedure

Identification of the mechanical properties of high-strength steel using digital image correlation. In this paper an experimental procedure to identify the plastic behaviour of sheet metals up to large strains using full field measurement is presented. The tests were conducted on notched specimens. This geometry generates a heterogeneous strain field which was measured during the test using a digital image correlation system. The advantage of using a heterogeneous strain field in the identification procedure is that a complex state of stress-strain can be analyzed at the same time and much more information can be obtained in a single test. On the other hand, the stress field cannot be directly computed from the test and a suitable identification procedure must be developed. Here, the virtual fields method (VFM) adapted for large strains and plasticity was used to identify the hardening behaviour and the anisotropy of the material. The values obtained with the VFM were compared with the results from a standard identification made using uniaxial tensile tests.

scholarly journals Study on Retrofitted Masonry Elements under Shear Using Digital Image Correlation

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2122 ◽  
Author(s):  
Benjamín Torres ◽  
Francisco B. Varona ◽  
F. Javier Baeza ◽  
David Bru ◽  
Salvador Ivorra
Keyword(s):  
Digital Image Correlation ◽  
Mechanical Behavior ◽  
Digital Image ◽  
Tensile Tests ◽  
Shear Behavior ◽  
Wind Pressure ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Tension Tests ◽  
Reinforced Masonry

Architectural heritage is usually built with masonry structures, which present problems under lateral in-plane loading conditions, such as wind pressure or earthquakes. In order to improve the shear behavior of masonry, the use of a fabric-reinforced cementitious matrix (FRCM) has become an interesting solution because of its synergy of mechanical properties and compatibility with masonry substrates. For a proper structural evaluation, the mechanical behavior of reinforced masonry and the FRCM itself needs to be characterized. Hence, a numerical model to evaluate the FRCM reinforcement requires some mechanical parameters that may be difficult to obtain. In this sense, the shear behavior of masonry can be evaluated by means of diagonal tension tests on small specimens (71 × 71 cm). In this work, a digital image correlation (DIC) monitoring system was used to control displacements and cracking patterns of masonry specimens under shear stress (induced by diagonal tension with FRCM layers) applied to one or two sides. In addition, the mechanical behavior of FRCM coupons under uniaxial tensile tests was also registered with DIC. The displacement measurements obtained by DIC were validated with the measurements registered with LVDT. Unlike LVDT-based techniques, DIC monitoring allowed us to measure deformations in masonry during the full test, detecting crack initiation even before it was visible to the eye.

Finite Element Modeling of Deformation Behavior of Steel Specimens under Various Loading Scenarios

2015 ◽  
Vol 651-653 ◽  
pp. 969-974 ◽  
Author(s):  
Dilip Banerjee ◽  
Mark Iadicola ◽  
Adam Creuziger ◽  
Tim Foecke
Keyword(s):  
Finite Element ◽  
Deformation Behavior ◽  
Stress Measurement ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Strain Paths

Lightweighting materials (e.g., advanced high strength steels, aluminum alloys etc.) are increasingly being used by automotive companies as sheet metal components. However, accurate material models are needed for wider adoption. These constitutive material data are often developed by applying biaxial strain paths with cross-shaped (cruciform) specimens. Optimizing the design of specimens is a major goal in which finite element (FE) analysis can play a major role. However, verification of FE models is necessary. Calibrating models against uniaxial tensile tests is a logical first step. In the present study, reliable stress-strain data up to failure are developed by using digital image correlation (DIC) technique for strain measurement and X-ray techniques and/or force data for stress measurement. Such data are used to model the deformation behavior in uniaxial and biaxial tensile specimens. Model predictions of strains and displacements are compared with experimental data. The role of imperfections on necking behavior in FE modeling results of uniaxial tests is discussed. Computed results of deformation, strain profile, and von Mises plastic strain agree with measured values along critical paths in the cruciform specimens. Such a calibrated FE model can be used to obtain an optimum cruciform specimen design.

Application of Dic Technique for Monitoring of Deformation Process of Spr Hybrid Joints / Zastosowanie Techniki Dic Do Obserwacji Procesu Deformacji Hybrydowych Połaczen Typu Spr

2013 ◽  
Vol 58 (1) ◽  
pp. 119-125 ◽  
Author(s):  
T. Sadowski ◽  
M. Knec
Keyword(s):  
Deformation Process ◽  
Load Capacity ◽  
Tensile Tests ◽  
Lap Joints ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Specimen Preparation ◽  
Forming Process ◽  
Absorption Increase ◽  
Dic Technique

Digital Image Correlation (DIC) technique gives possibility to observe deformation process in many applications including self-piercing riveting (SPR) hybrid joint. The hybrid SPR joint consists of simple SPR joint made of two adherends, steel tubular rivet (total length of 5 mm) and an adhesive. The adhesive was applied before piercing process. For specimen preparation two different aluminum alloys were used: 2024 and 5005 (2mm thickness both) with tensile strength 400 and 160MPa, respectively. For better understanding of joint forming process and to allow DIC strains observation during the joint creation, a special holder was designed with precisely polished die. The tests were performed by application of the 100kN servo-hydraulic machine, which recorded time, load, displacement and was synchronized with the DIC system. The joint forming process was carried out with 2 mm/min constant speed. During piercing process rivet and upper surface of the adherend were observed and the major strain states were estimated. The uniaxial tensile tests of single lap joints (SLJ) up to the final failure were performed and the displacements and the strains were recorded. In particular the rivet deformation was observed also during the whole loading process. The hybrid SPR joints are very effective, because the load capacity and energy absorption increase more than 1.5 times in comparison to the simple SPR joints.

scholarly journals On mesoscale strain fluctuations in tensile tests on additively manufactured 17-4PH stainless steel

2021 ◽  
pp. 030932472110602
Author(s):  
Mohamed Ali Bouaziz ◽  
Joseph Marae Djouda ◽  
François Hild
Keyword(s):  
Stainless Steel ◽  
Digital Image Correlation ◽  
Characteristic Length ◽  
Tensile Tests ◽  
Processing Parameters ◽  
Image Correlation ◽  
Length Scale ◽  
Characteristic Length Scale ◽  
Strain Fields ◽  
Printing Parameters

Additively manufactured materials usually exhibit mesoscale heterogeneities. Mesoscale fluctuations of strain fields in notched samples made of 17-4PH Stainless steel and loaded in tension are investigated. Regularized digital image correlation enables for the analysis of strain fluctuations at different length scales. Five tests on specimen fabricated with different printing parameters are studied. It is shown that the strain fluctuations have no characteristic length scale and are essentially independent of the probed processing parameters.

Stress Analysis Performed by Photoelasticity and Digital Image Correlation

2015 ◽  
Vol 816 ◽  
pp. 474-481
Author(s):  
Miroslav Pástor ◽  
Martin Hagara ◽  
Ján Kostka
Keyword(s):  
Digital Image Correlation ◽  
Stress Analysis ◽  
Static Analysis ◽  
Experimental Technique ◽  
Basic Principle ◽  
Digital Image ◽  
Image Correlation ◽  
Stress Fields ◽  
Stress Concentrators ◽  
Correlation System

This paper deals with the use of classical experimental technique of photoelasticity as well as modern one – digital image correlation by stress analysis. Both mentioned methods were used to compare the corresponding stress fields obtained on a sample with stress concentrators loaded by bending. The paper contains the basic principle of photoelasticity, methodology of static analysis with polariscope and briefly describes the measurement with low-speed digital image correlation system. Taking into account that the used correlation system does not allow to evaluated stress fields, calculation and visualization of stress fields were realized in program Q-STRESS v.1.0 developed at the authors department.

Sign in / Sign up

Export Citation Format

Share Document