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.

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.

Application of Instrumented Indentation Technique to Small-Scale Testing of Pressure Vessels and Piping Systems

2009 ◽  
Author(s):  
Kug-Hwan Kim ◽  
Seung-Kyun Kang ◽  
Min-Jae Choi ◽  
Kwang-Ho Kim ◽  
Dongil Kwon
Keyword(s):  
Residual Stress ◽  
Pressure Vessels ◽  
Small Samples ◽  
Uniaxial Tensile ◽  
Small Scale ◽  
Specimen Preparation ◽  
Instrumented Indentation ◽  
Flow Properties ◽  
Indentation Technique ◽  
Piping Systems

The instrumented indentation technique (IIT) is a powerful tool for measuring mechanical properties by analyzing the load-penetration depth curve. It differs from conventional test methods such as tensile testing, CTOD, etc., in being applicable to small samples and to localized sections where material properties change rapidly. It also has the significant advantage of simplicity in specimen preparation and experimental procedure. Analytic models and procedures are presented here for evaluating flow properties and stress state using IIT; the flow properties are treated by defining the representative stress and strain underneath a spherical indenter and the residual stress by using a stress-insensitive contact hardness model. Flow properties of 5 steel materials were measured by IIT and compared with those from uniaxial tensile tests. The residual stress states of a welded joint were evaluated and compared with those measured by mechanical saw cutting. Examples of the application of IIT to small-scale materials and localized sections of pressure vessel and piping systems in situ are also presented.

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 Nondestructive Instrumented Indentation Technique in Small-Scale Testing of Pressure Vessel and Piping Systems

2008 ◽  
Author(s):  
Kyung-Woo Lee ◽  
Kug-Hwan Kim ◽  
Kwang-Ho Kim ◽  
Young-Hwan Choi ◽  
Hae-Dong Chung ◽  
...  
Keyword(s):  
Residual Stress ◽  
Nondestructive Method ◽  
Small Scale ◽  
Specimen Preparation ◽  
Instrumented Indentation ◽  
Destructive Testing ◽  
Indentation Technique ◽  
Piping Systems ◽  
Testing Techniques ◽  
Hardness Model

Most small-scale testing techniques are essentially scaled-down versions of conventional testing techniques: they use specimens of similar geometry applied in a similar manner to estimate properties equivalent to those obtained for larger specimens. However, using these techniques for safety assessment of structures and piping systems requires general agreement about the techniques and validation of their results. In addition, these techniques all require destructive testing. In this study we adopt a new nondestructive method to measure the mechanical properties using the instrumented indentation technique. This technique can be applied directly in small-scale and localized sections because of its high spatial resolution. It also has the significant advantage of simplicity of specimen preparation and experimental procedure. During instrumented indentation testing, the load and penetration depth of an indenter tip driven into the sample are monitored, and material properties such as strength, fracture toughness and residual stress are evaluated from this information: the tensile properties by defining a representative stress and strain underneath a spherical indenter; the residual stress values near weldments by using the stress-insensitive contact hardness model.

Tailoring of Mechanical Properties in Microlaminates

1993 ◽  
Vol 308 ◽  
Author(s):  
M. Vill ◽  
D. P. Adams ◽  
S. M. Yalisove ◽  
J. C. Bilello
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Tensile Testing ◽  
Testing Machine ◽  
Thick Layer ◽  
Thin Layers ◽  
Uniaxial Tensile ◽  
Strong Phase ◽  
Uniaxial Tensile Testing ◽  
And Tungsten

ABSTRACTA multiscalar approach is used to demonstrate the ability to control strength and toughness in microlaminates composed of molybdenum and tungsten. Here, two different thickness scales are utilized; an alternating stack of molybdenum and tungsten layers having thicknesses on the nanometer scale are combined with a layer of molybdenum having a thickness on the micron scale. The stack of thin layers acts as a strong phase and the thick layer acts as a tough phase. Multilayers of two configurations were fabricated which had total thicknesses of 31μm and 50μm. The tough phase thickness was 5μm for the 31μm multilayer and 1μm for the other. The strong phase contained a stack of 29 alternating 4nm thick layers of molybdenum and tungsten. Uniaxial tensile testing was performed using a standard Instron tensile testing machine, followed by optical analysis of specimen fracture surfaces. Fracture toughness ranged from 2.4 to 9.5MPa(m)1/2, and tensile strengths were observed from 126MPa to 883MPa. Control of mechanical properties was demonstrated by an increase in the upper bound fracture toughness from 2.7 to 9.5MPa(m)1/2 when the tough layer thickness was increased from 1μm to 5μm.

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.

Application of Instrumented Indentation Technique to Evaluate Residual Stress and Stress Directionality

2008 ◽  
Vol 385-387 ◽  
pp. 889-892
Author(s):  
Min Jae Choi ◽  
In Geun Kang ◽  
Kwang Ho Kim ◽  
Dong Il Kwon
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Indentation Load ◽  
Hole Drilling ◽  
Specimen Preparation ◽  
Instrumented Indentation ◽  
Promising Alternative ◽  
Indentation Technique ◽  
Ultrasonic Methods ◽  
Process Characterization

The instrumented indentation technique (IIT) is a powerful method for evaluating mechanical properties of materials such as elastic modulus, tensile strength, fracture toughness and residual stress. Especially, IIT is a promising alternative to conventional methods of residual stress measurement such as hole drilling, saw cutting, X-ray/neutron diffraction, and ultrasonic methods because of its various advantages of nondestructive specimen preparation, easy process, characterization of material properties on local scales and measurement of in-service structures. Evaluation of residual stress using IIT is based on the key concepts that the deviatoric-stress part of the residual stress affects the indentation load-depth curve and that the quantitative residual stress in a target region can be evaluated by analyzing the difference between the residual stress-induced indentation curve and residual stress-free curve. To verify the applicability of the suggested technique, indentation tests were performed on the welded zone.

Reducing Residual Stress in 7050 Aluminum Alloy Die Forgings by Heat Treatment

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
J. S. Robinson ◽  
D. A. Tanner
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Aluminum Alloy ◽  
Residual Stresses ◽  
Boiling Water ◽  
Hole Drilling ◽  
Subsequent Aging ◽  
Stress Relieving

Aerospace aluminum alloy forgings can have the residual stresses arising from heat treatment reduced by modification to the quench cooling rates and subsequent aging treatments. A series of propeller hubs usually made from the alloy 2014 have been closed die forged from the less quench sensitive alloy 7050. These forgings have been subjected to various quenching and aging treatments in an attempt to improve the balance of mechanical properties with the residual stress magnitudes. These forgings were not amenable to stress relieving by cold compression or stretching. Warm water (60°C) and boiling water quenches are investigated in addition to quenching into molten salt (200°C) and uphill quenching from −196°C. Various dual aging treatments including retrogression and reaging have been evaluated in an attempt to optimize low residual stress magnitudes with mechanical properties. Residual stresses determined by the center hole-drilling strain-gauge method are reported in addition to electrical conductivity, stress corrosion cracking, fracture toughness, initiation fatigue, and tensile mechanical property variations. It was found that quenching into boiling water and salt at 200°C did substantially reduce the residual stress but had only a small detrimental effect on the majority of the properties measured. However, the influence of quench rate on fracture toughness was much more significant. This is attributed to both coarse grain boundary precipitation and heterogeneous precipitation of η on Al3Zr dispersoids within the grains, which promotes easier crack propagation.

SUPERSTON 40

Alloy Digest ◽  
1965 ◽  
Vol 14 (4) ◽  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Shear Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
Aluminum Bronze

Abstract SUPERSTON 40 is an aluminum bronze containing 12% manganese and has good casting properties and excellent mechanical properties. It is recommended for any application where extreme corrosion resistance is required and where weldability is desired, such as propellers and marine equipment. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and compressive and shear strength as well as fracture toughness, creep, and fatigue. It also includes information on corrosion resistance as well as casting, forming, heat treating, and machining. Filing Code: Cu-150. Producer or source: H. Kramer & Company.

VIRGO 17.4 PH

Alloy Digest ◽  
2013 ◽  
Vol 62 (5) ◽  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Precipitation Hardening ◽  
Heat Treating

Abstract Virgo 17.4 PH is a 17Cr-4Ni-3Cu-0.3% Cb alloy that is precipitation hardening. It is martensitic and combines high mechanical properties with corrosion resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-1145. Producer or source: Industeel USA, LLC.

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