A strain-pattern-based spherical indentation method for simultaneous uniaxial tensile residual stress and flow property determination

2020 ◽  
Vol 56 (1) ◽  
pp. 50-64
Author(s):  
Tairui Zhang ◽  
Jianzhang Guo ◽  
Weiqiang Wang
Keyword(s):  
Residual Stress ◽  
Plastic Zone ◽  
Flow Property ◽  
Tensile Residual Stress ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Strain Pattern ◽  
Loading Direction ◽  
Finite Element Calculations ◽  
Zone Radius

In this study, a strain-pattern-based method was proposed to simultaneously determine the uniaxial tensile residual stress and flow property from a single-cycle spherical indentation test. The variation of the plastic zone radius (at the specimen surface) with uniaxial tensile residual stress was analytically investigated by the expanding cavity model. The analysis proved that the circular plastic boundary will be elliptical under the action of uniaxial residual stress (with a shrunken plastic zone radius along the loading direction and an extended plastic zone radius vertical to the loading direction), and this difference can be used to calibrate the magnitude of the residual stress. The analytical result was verified and modified through finite element calculations, after which a set of regression functions for Holloman hardening metals was established for load compensation, proportional limit correction, and hardening exponent calculation. The effectiveness of the method was verified through finite element calculations of spherical indentation tests on 16 Holloman hardening and 6 metals used in engineering applications at different residual stress levels. The verification proved that maximum errors for strength and residual stress calculations are about 10% and 15%, respectively, and the potential of the new proposed method was validated.

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.

Improving the tensile property calculations with plastic zone radius measurements in depth-sensing spherical indentation tests

2021 ◽  
pp. 030932472110439
Author(s):  
Tairui Zhang ◽  
Jianxun Li ◽  
Xun Sun ◽  
Xiandong Shang ◽  
Weiqiang Wang
Keyword(s):  
Plastic Zone ◽  
Tensile Property ◽  
Measurement Errors ◽  
Displacement Measurement ◽  
Image Correlation ◽  
Spherical Indentation ◽  
Depth Sensing ◽  
Indentation Tests ◽  
Strain Threshold ◽  
Zone Radius

Depth-sensing spherical indentation tests (SITs) have been widely used in tensile property calculations, but the accuracy and reproducibility of calculations may be significantly influenced by displacement measurement errors. Taking two representative tensile property calculation methods as examples, namely the analytical and numerical methods, the rationale as to why accurate and reproducible tensile property calculations cannot be expected from the depth-sensing SITs was discussed in detail. Subsequently, the proportional limit σ0 calculation from plastic zone radius rp measurements, which was analytically developed in the expanding cavity model (ECM) and experimentally measured by digital image correlation (DIC), was introduced to enhance the accuracy and reproducibility of the two representative methods. Principles for setting the strain threshold εth were established, and factors influencing the σ0 calculation from rp measurements were investigated through the optical system, the friction condition, the hardening behaviors of specimen materials, and the indentation depth. Through finite element calculations, it was proven that tensile property calculations at the existence of displacement measurement errors, particularly the constant error from the origin correction, can be significantly improved with the introduction of rp measurements. Similar findings were also observed in experiments on four metals that exhibited different hardening behaviors.

Analysis of Plastic-Zone Radius Influenced by Mechanical Parameters in Tunnel Excavation and Support

2012 ◽  
Vol 238 ◽  
pp. 787-790
Author(s):  
Zhong Ming Su ◽  
Rui Liu
Keyword(s):  
Plastic Zone ◽  
Axial Force ◽  
Analytical Formula ◽  
Mechanical Parameters ◽  
Circular Tunnel ◽  
Tunnel Excavation ◽  
Dynamic Design ◽  
Elastic Plastic ◽  
Zone Radius ◽  
Plastic Theory

According to the elastic-plastic theory, the analytical formula of plastic zone radius is established for circular tunnel in its excavation and support, and the effect of anchor support is verified based on the radius of plastic zone from the perspective of measured axial force. The influences to plastic zone by the variations of mechanical parameters and resistance of support are quantitatively analyzed. The result is of great significance to the monitoring measurement and the dynamic design and construction of tunnel.

The Spherical Indentation Approach for Fracture Toughness Evaluation: A Study Based on the Energy Release Rate

2018 ◽  
Author(s):  
Tairui Zhang ◽  
Weiqiang Wang ◽  
Aiju Li
Keyword(s):  
Fracture Toughness ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Damage Mechanism ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Material Damage ◽  
Fracture Tests

In this study, we investigated the drawbacks of previous studies regarding the evaluation of fracture toughness from spherical indentation tests (SITs). This was achieved by an examination of the material damage mechanism during indentation tests, uniaxial tensile tests, and Mode I/II fracture tests. A new approach based on the energy release rate was proposed in this study to evaluate the fracture toughness of ductile metals. Scanning electron microscope (SEM) observations revealed that the mechanism for material damage during an indentation test was different with the material damage in uniaxial tensile tests and Mode I fracture tests, but similar to that in Mode II fracture tests. Thus, the energy release rate during SITs should be correlated with JIIC. Compared with previous studies, this new proposed method was more consistent with the actual damage mechanism and did not rely on the specific critical damage values. Experiments on SA508, SA533, 15CrMoR, and S30408 revealed that the maximum error from this energy release rate-based approach was no more than 13% when compared with their conventional counterparts (compact tension tests), and thus can meet the precision requirement of engineering applications.

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.

Modeling and Prediction of Residual Stresses in Additive Layer Manufacturing by Microplasma Transferred Arc Process Using Finite Element Simulation

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Sagar H. Nikam ◽  
N. K. Jain
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Temperature Distribution ◽  
Residual Stresses ◽  
Substrate Material ◽  
Tensile Residual Stress ◽  
Additive Layer Manufacturing ◽  
Element Simulation ◽  
Layer Manufacturing ◽  
Transferred Arc

Prediction of residual stresses induced by any additive layer manufacturing process greatly helps in preventing thermal cracking and distortion formed in the substrate and deposition material. This paper presents the development of a model for the prediction of residual stresses using three-dimensional finite element simulation (3D-FES) and their experimental validation in a single-track and double-track deposition of Ti-6Al-4V powder on AISI 4130 substrate by the microplasma transferred arc (µ-PTA) powder deposition process. It involved 3D-FES of the temperature distribution and thermal cycles that were validated experimentally using three K-type thermocouples mounted along the deposition direction. Temperature distribution, thermal cycles, and residual stresses are predicted in terms of the µ-PTA process parameters and temperature-dependent properties of substrate and deposition materials. Influence of a number of deposition tracks on the residual stresses is also studied. Results reveal that (i) tensile residual stress is higher at the bonding between the deposition and substrate and attains a minimum value at the midpoint of a deposition track; (ii) maximum tensile residual stress occurs in the substrate material at its interface with deposition track. This primarily causes distortion and thermal cracks; (iii) maximum compressive residual stress occurs approximately at mid-height of the substrate material; and (iv) deposition of a subsequent track relieves tensile residual stress induced by the previously deposited track.

A study on determination of tensile properties of metals at elevated temperatures from spherical indentation tests

2019 ◽  
Vol 54 (5-6) ◽  
pp. 331-347
Author(s):  
Tairui Zhang ◽  
Shang Wang ◽  
Weiqiang Wang
Keyword(s):  
Tensile Properties ◽  
Analytical Model ◽  
Elevated Temperatures ◽  
Regression Function ◽  
Maximum Error ◽  
Analytical Models ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Material Parameters ◽  
Indentation Tests

In this study, spherical indentation tests were used to determine the uniaxial tensile properties of metals at elevated temperatures (200 °C, 400 °C, and 600 °C). Taking the difference between spherical indentation tests at room and elevated temperatures into consideration, the incremental and analytical models were used to determine material parameters ( σ0, Ep, and n) and thermal softening parameters ( Eeff and m) in the Johnson–Cook constitutive equation, respectively. A discussion on the stability of the analytical model proved that despite in relative complicated forms and with three intercoupling material parameters, the analytical model is still effective for tensile property calculation. From the investigation on the relationship between pm and pi, it was found that correlating coefficient ξ is actually a function of both indentation depth and material parameters, and thus, a regression function was proposed for a more accurate description of ξ. Effectiveness of the spherical indentation tests was verified through experiments on three steels, SA508, 15CrMoR, S30408, and one titanium alloy, TC21, which proved that the spherical indentation tests can provide both proof and tensile strength calculations with a maximum error around 15% at room temperature and within 20% at elevated temperatures, and thus satisfy the demands for engineering applications.

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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