scholarly journals Application of Macro-Instrumented Indentation Test for Superficial Residual Stress and Mechanical Properties Measurement for HY Steel Welded T-Joints

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2061
Author(s):  
Junsang Lee ◽  
Kyungyul Lee ◽  
Seungha Lee ◽  
Oh Min Kwon ◽  
Won-Ki Kang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Arc Welding ◽  
Volume Fraction ◽  
Indentation Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Indentation Testing ◽  
Instrumented Indentation ◽  
Flux Cored Arc Welding

HY-80 and HY-100 steels, widely used in constructing large ocean vessels and submarine hulls, contain mixed microstructures of tempered bainite and martensite and provide high tensile strength and toughness. Weld integrity in HY steels has been studied to verify and optimize welding conditions. In this study, the T-joint weld coupons, HY80 and HY100, were fabricated from HY-80 and HY-100 steel plates with a thickness of 30 mm as base metals by submerged-arc welding. Flux-cored arc welding was performed on an additional welding coupon consisting of HY-100 to evaluate the effect of repair welds (HY100RP). Microstructures in the heat-affected zones (HAZ) were thoroughly analyzed by optical observation. Instrumented indentation testing, taking advantage of local characterization, was applied to assess the yield strength and the residual stress of the HAZ and base regions. The maximum hardness over 400 HV was found in the HAZ due to the high volume fraction of untempered martensite microstructure. The yield strength of the weld coupons was evaluated by indentation testing, and the results showed good agreement with the uniaxial tensile test (within 10% range). The three coupons showed similar indentation residual stress profiles on the top and bottom surfaces. The stress distribution of the HY100 coupon was comparable to the results from X-ray diffraction. HY100RP demonstrated increased tensile residual stress compared to the as-welded coupon due to the effect of the repair weld (323 and 103 MPa on the top and bottom surfaces). This study verifies the wide applicability of indentation testing in evaluating yield strength and residual stress.

A Method for Estimating Uncertainty of Indentation Tensile Properties in Instrumented Indentation Test

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Eun-chae Jeon ◽  
Joo-Seung Park ◽  
Doo-Sun Choi ◽  
Kug-Hwan Kim ◽  
Dongil Kwon
Keyword(s):  
Tensile Strength ◽  
Yield Strength ◽  
Tensile Test ◽  
Tensile Properties ◽  
Indentation Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Estimation Model ◽  
Instrumented Indentation Test

The instrumented indentation test, which measures indentation tensile properties, has attracted interest recently because this test can replace uniaxial tensile test. An international standard for instrumented indentation test has been recently legislated. However, the uncertainty of the indentation tensile properties has never been estimated. The indentation tensile properties cannot be obtained directly from experimental raw data as can the Brinell hardness, which makes estimation of the uncertainty difficult. The simplifying uncertainty estimation model for the indentation tensile properties proposed here overcomes this problem. Though the influence quantities are generally defined by experimental variances when estimating uncertainty, here they are obtained by calculation from indentation load-depth curves. This model was verified by round-robin test with several institutions. The average uncertainties were estimated as 18.9% and 9.8% for the indentation yield strength and indentation tensile strength, respectively. The values were independent of the materials’ mechanical properties but varied with environmental conditions such as experimental instruments and operators. The uncertainties for the indentation yield and tensile strengths were greater than those for the uniaxial tensile test. These larger uncertainties were caused by measuring local properties in the instrumented indentation test. The two tests had the same tendency to have smaller uncertainties for tensile strength than yield strength. These results suggest that the simplified model can be used to estimate the uncertainty in indentation tensile properties.

Instrumented Indentation Testing to Evaluate High-Temperature Material Properties

2011 ◽  
Author(s):  
Chan-Pyoung Park ◽  
Kug-Hwan Kim ◽  
Seung-Kyun Kang ◽  
Won-Je Jo ◽  
Dongil Kwon
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Material Properties ◽  
Indentation Test ◽  
Temperature Deformation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Indentation Testing ◽  
Instrumented Indentation ◽  
Uniaxial Tensile Testing

Mechanical properties must be evaluated at high temperatures to predict high-temperature deformation and fracture behavior, since high-temperature properties differ greatly from those at room temperature. A high-temperature uniaxial tensile test, a representative high-temperature test, is generally used, but it has the limitation of obtaining merely the average material properties. Recently an advanced method for evaluating tensile properties has been developed: the instrumented indentation test (IIT), which simultaneously applies a load and measures displacement. Here we use instrumented indentation testing to evaluate the flow properties (yield strength, ultimate tensile strength, etc.) of heat-resistant steel at high temperature. The contact-area determination algorithm and representative stress-representative strain approach are applied for high temperatures. We compare our experimental results to those of conventional high-temperature uniaxial tensile testing to assess the high-temperature performance of the instumented indentation test.

Multiscale Mapping of Mechanical Properties by Instrumented Indentation Test

2010 ◽  
Vol 654-656 ◽  
pp. 2316-2321
Author(s):  
Kug Hwan Kim ◽  
Young Cheon Kim ◽  
Seung Kyun Kang ◽  
Kwang Ho Kim ◽  
Dong Il Kwon
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Indentation Test ◽  
Uniaxial Tensile ◽  
Material Surface ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Flow Properties ◽  
Residual Stress State ◽  
Instrumented Indentation Test

The instrumented indentation test (IIT) is a mechanical testing method to determine the hardness and elastic modulus of materials by putting an indenter into a material surface. This technique has now gone beyond normal hardness tests by evaluating additional properties of materials and by allowing testing at much lower forces and indentation depths (micro/nano ranges). This study presents analytic models and procedures for evaluating tensile flow properties and residual stress state using IIT; the tensile flow properties are treated by defining a representative stress/strain beneath a spherical indenter and the residual stress by using a stress-insensitive contact hardness model. The IIT results are compared with those from conventional methods such as uniaxial tensile test and X-ray diffraction. In addition, IIT can be used as a multiscale mapping tool for the mechanical properties of composite materials and constituent phases by using macro/micro/nano indentation system: we made a hardness map of multiphase steel and measured the strength/residual stress distributions of welded pipeline.

Evaluation of Mechanical and Fracture Characteristics Using Instrumented Indentation Technique

2007 ◽  
Vol 539-543 ◽  
pp. 2210-2215
Author(s):  
Jung Suk Lee ◽  
Kwang Ho Kim ◽  
Jae Hwan Han ◽  
Dong Il Kwon
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Material Characterization ◽  
Damage Mechanics ◽  
Evaluation Method ◽  
Flow Property ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Indentation Technique

The material characterization on the weak points of the structural systems is essential to evaluate safety accurately. However, general material characterization methods such as uniaxial tensile test and CTOD (crack tip opening displacement) test are destructive, therefore, it cannot be applied to the system in use. To overcome this problem, the material characterization using instrumented indentation technique was developed. However, current researches on instrumented indentation technique focus on the hardness measurement. The evaluation of flow property, residual stress and fracture toughness using instrumented indentation technique is not sufficiently performed. In this paper, we introduce the evaluation method of the flow property, the residual stress near the weldment and the fracture toughness developed from damage mechanics. The algorithm of flow property evaluation, the residual stress evaluation model and the fracture toughness model by using indentation were verified comparing with the experimental results.

Application of Instrumented Indentation Technique for Small Scale Testing

2007 ◽  
Author(s):  
Kug-Hwan Kim ◽  
Kyung-Woo Lee ◽  
Ju-Young Kim ◽  
Dongil Kwon ◽  
Kwang-Ho Kim
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Tensile Properties ◽  
Pressure Vessel ◽  
Uniaxial Tensile ◽  
Small Scale ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Indentation Technique

Instrumented indentation technique (IIT) is a novel tool to estimate mechanical properties such as tensile properties, residual stress and fracture toughness by analyzing indentation load-depth curve measured during loading-unloading of indentation. It can be applied directly in small-scale and localized sections of pressure vessel and pipeline since the preparation of specimen is very easy and the experimental procedure is feasible and nondestructive. We present the principles developed for measuring mechanical properties using IIT; the tensile properties by defining the representative stress and strain underneath a spherical indenter, the residual stress near the weldments using the stress-insensitive contact hardness model, and the fracture toughness of ductile metal based on critical indentation energy model. The experimental results from IIT were verified by comparing the results from the conventional methods such as uniaxial tensile test for tensile properties, mechanical saw-cutting and hole-drilling methods for residual stress, and CTOD test for fracture toughness. In particular, the applications of IIT in small scale materials and localized sections of the pressure vessel and pipeline in-use and in-fields are presented.

Determination of Residual Stress Directionality by Instrumented Indentation Testing Using Anisotropic Indenter

2018 ◽  
Author(s):  
Sungki Choi ◽  
Jong Hyoung Kim ◽  
Jun Sang Lee ◽  
Kyungyul Lee ◽  
Min-Jae Choi ◽  
...  
Keyword(s):  
Residual Stress ◽  
Indentation Test ◽  
Surface Preparation ◽  
Field Testing ◽  
Indentation Load ◽  
Indentation Testing ◽  
Instrumented Indentation ◽  
Element Analysis ◽  
Knoop Indenter ◽  
Depth Curves

Residual stress is a major factor in failure and fracture in structures or electronic components. Various testing methods are used to measure residual stress: there are saw-cutting, holedrilling, X-ray diffraction and layer-removing methods. In particular, instrumented indentation testing (IIT) has many advantages: it is a simple and non-destructive procedure that can be used for in-field testing. In previous research, we proposed an algorithm for evaluating the magnitude and directionality of residual stress using an asymmetric Knoop indenter with long and short axes in the ratio 7.11:1. Indenting in different directions with a Knoop indenter creates different indentation load-depth curves depending on the residual stress state. In addition, the directionality of the residual stress can be expressed as a function of the load difference ratio calculated from these load-depth curves. However, When the Knoop indentation test is performed at small indentation depths, experimental issues such as surface preparation or indentation normality can become significant as the load difference decreases. In order to solve these issues, we introduce a wedge indenter, that makes it possible to select the edge length independent of indentation depth. We can thus decrease indent size when working in a small testing area. The load difference between the stress-free and stressed state is related to the sensitivity of residual stresses, and a wedge indenter can maximize the sensitivity to residual stress. In this study, we suggest a way to use the wedge indenter and verify the model using cruciform bending specimens and finite element analysis.

Structure Assessment Using Instrumented Indentation: Strength, Toughness and Residual Stress

2018 ◽  
Author(s):  
Dongil Kwon ◽  
Jong Hyoung Kim ◽  
Ohmin Kwon ◽  
Woojoo Kim ◽  
Sungki Choi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Tensile Properties ◽  
Hole Drilling ◽  
Uniaxial Tensile ◽  
Small Scale ◽  
Specimen Preparation ◽  
Instrumented Indentation ◽  
Uniaxial Tensile Testing

The instrumented indentation technique (IIT) is a novel method for evaluating mechanical properties such as tensile properties, toughness and residual stress by analyzing the indentation load-depth curve measured during indentation. It can be applied directly on small-scale and localized sections in industrial structures and structural components since specimen preparation is very easy and the experimental procedure is nondestructive. We introduce the principles for measuring mechanical properties with IIT: tensile properties by using a representative stress and strain approach, residual stress by analyzing the stress-free and stressed-state indentation curves, and fracture toughness of metals based on a ductile or brittle model according to the fracture behavior of the material. The experimental results from IIT were verified by comparing results from conventional methods such as uniaxial tensile testing for tensile properties, mechanical saw-cutting and hole-drilling methods for residual stress, and CTOD test for fracture toughness.

Characterization and Evaluation of Mechanical Properties and Residual Stress in Aluminum-Magnesium Alloys Welded by the FSW Process

2020 ◽  
Vol 1012 ◽  
pp. 349-353
Author(s):  
D.B. Colaço ◽  
M.A. Ribeiro ◽  
T.M. Maciel ◽  
R.H.F. de Melo
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welding Process ◽  
Bending Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Friction Stir ◽  
Aluminum Magnesium Alloys

The demand for lighter materials with suitable mechanical properties and a high resistance to corrosion has been increasing in the industries. Therefore, aluminum appears as an alternative due to its set of properties. The aim of this work was to evaluate residual stress levels and mechanical properties of welded joints of Aluminum-Magnesium alloy AA 5083-O using the Friction Stir Welding process. For mechanical characterization were performed a uniaxial tensile test, Vickers hardness, bending test and, finally, the determination of residual stresses. It was concluded that welding by FSW process with an angle of inclination of the tool at 3o, established better results due to better mixing of materials. The best results of tensile strength and a lower level of residual stresses were obtained using a tool rotation speed of 340 RPM with welding advance speed of 180 mm/min and 70 mm/min.

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