SEM Imaging of In Situ Tensile Testing of 27CrNiMoV Steel

2020 ◽  
Vol 405 ◽  
pp. 60-65
Author(s):  
Martin Bystrianský ◽  
Ludmila Kučerová ◽  
Zbyněk Bunda
Keyword(s):  
Tensile Testing ◽  
Tensile Load ◽  
Strain Curve ◽  
Tensile Tests ◽  
Gauge Length ◽  
Whole Body ◽  
Initial State ◽  
Dog Bone ◽  
Gauge Section

In-situ tensile testing of a 27CrNiMoV alloy which is used for steam turbine rotors was carried out using scanning electron microscope (SEM). Deformation and crack formation and propagation were examined with this test. Small (45 × 10 × 1.5 mm, with gauge length of 20 mm), flat samples based on dog-bone shape were prepared from the steel. The material in its initial state contained high number of defects in form of microcracks. A comparison of behaviour at tensile tests of samples without visible defect and with crack in the gauge section was performed. Apparently, the presence of defect in the initial state showed direct influence on properties like lower tensile strength. The sample, its necking and propagated crack is displayed at different stages of the tensile load. In-situ testing reveals differences in the sample deformation. The defect-free sample is affected in its whole body and regular necking can be observed, whereas the presence of the crack in the defect samples concentrates stress to a smaller area and also changed the shape of the stress-strain curve.

The Effect of Specimen Dimensions on Obtained Tensile Properties of Sheet Metals

2009 ◽  
Vol 410-411 ◽  
pp. 481-491 ◽  
Author(s):  
Li Han ◽  
Neil Reynolds ◽  
I. Dargue ◽  
G. Williams
Keyword(s):  
Tensile Properties ◽  
Strain Curve ◽  
Gauge Length ◽  
Mapping Technique ◽  
Test Machine ◽  
Test Procedures ◽  
Strain Mapping ◽  
Aluminium Sheet ◽  
Dog Bone ◽  
2D Strain

A pilot study has been carried out to examine the effect of specimen dimensions on the obtained tensile properties of aluminium and steel sheet. The materials used were DP600 grade steel and AA5754 grade aluminium sheet. Four types of dog-bone samples with varying dimensions were tested for both materials. Standard tensile test procedures were performed using a universal test machine together with contacting extensometry. The GOM Aramis photogrammetric 2D strain mapping technique was also applied. The results suggest that for both steel and aluminium sheet materials, differing specimen dimensions have little effect on the obtained mechanical properties. Depending on the gauge length of extensometer chosen and the position at where necking occurred on the sample, the extensometry results and 2D strain mapping results slightly differed towards to the end of stress-strain curve. The failure mode between the chosen grades of steel and aluminium samples was observed to differ, as did the percentage of failures that occurred within the gauge length. All steel samples fractured across the specimen perpendicularly to the test direction; whilst fracture of aluminium samples occurred approximately 30 degrees from the perpendicular.

scholarly journals The influence of sample geometry and size on porcine aortic material properties from uniaxial tensile tests using custom-designed tissue cutters, clamps and molds

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0244390
Author(s):  
Ming Pei ◽  
Donghua Zou ◽  
Yong Gao ◽  
Jianhua Zhang ◽  
Ping Huang ◽  
...  
Keyword(s):  
Material Properties ◽  
Tensile Testing ◽  
Tensile Tests ◽  
Optimal Choice ◽  
The Other ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Uniaxial Tensile Testing ◽  
Dog Bone ◽  
Weibull Theory

The aim of this study was to identify the influence of specimen geometry and size on the results of aortic uniaxial tensile tests using custom-designed tissue cutters, clamps and molds. Six descending thoracic aortas from pigs were used for rectangular sample tests, in which the circumferential and axial specimens had widths of 6 mm, 8 mm and 10 mm. The other six aortas were used for the dog-bone-shaped sample tests and were punched into circumferential, axial and oblique specimens with widths of 2 mm, 4 mm and 6 mm. We performed uniaxial tensile tests on the specimens and compared the test results. The results showed that mid-sample failure occurred in 85.2% of the dog-bone-shaped specimens and in 11.1% of the rectangular samples, which could be caused by Saint-Venant’s principle. Therefore, rectangular specimens were not suitable for aortic uniaxial tensile testing performed until rupture. The results also showed that the size effect of the aorta conformed to Weibull theory, and dog-bone-shaped specimens with a width of 4 mm were the optimal choice for aortic uniaxial tensile testing performed until rupture.

scholarly journals An in situ synchrotron study of the localized B2↔B19′ phase transformation in an Ni–Ti alloy subjected to uniaxial cyclic loading–unloading with incremental strains

2020 ◽  
Vol 53 (2) ◽  
pp. 335-348
Author(s):  
Xiaohui Bian ◽  
Ahmed A. Saleh ◽  
Peter A. Lynch ◽  
Christopher H. J. Davies ◽  
Azdiar A. Gazder ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Strain Curve ◽  
Transformation Strain ◽  
Gauge Length ◽  
Stress Strain ◽  
Macroscopic Stress ◽  
Residual Strains

High-resolution in situ synchrotron X-ray diffraction was applied to study a cold-drawn and solution-treated 56Ni–44Ti wt% alloy subjected to uniaxial cyclic loading–unloading with incremental strains. The micro-mechanical behaviour associated with the partial and repeated B2↔B19′ phase transformation at the centre of the sample gauge length was studied with respect to the macroscopic stress–strain response. The lattice strains of the (110)B2 and different B19′ grain families are affected by (i) the transformation strain, the load-bearing capacity of both phases and the strain continuity maintained at/near the B2–B19′ interfaces at the centre of the gauge length, and (ii) the extent of transformation along the gauge length. With cycling and incremental strains (i) the elastic lattice strain and plastic strain in the remnant (110)B2 grain family gradually saturate at early cycles, whereas the plastic strain in the B19′ phase continues to increase. This contributes to accumulation of residual strains (degradation in superelasticity), greater non-linearity and change in the shape of the macroscopic stress–strain curve from plateau type to curvilinear elastic. (ii) The initial 〈111〉B2 fibre texture transforms to [120]B19′, [130]B19′, [150]B19′ and [010]B19′ orientations. Further increase in the applied strain with cycling results in the development of [130]B19′, [102]B19′, [102]B19′, [100]B19′ and [100]B19′ orientations.

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.

Materials Testing of 3D Printed ABS and PLA Samples to Guide Mechanical Design

2016 ◽  
Author(s):  
Daniel Farbman ◽  
Chris McCoy
Keyword(s):  
Finite Element Analysis ◽  
Tensile Testing ◽  
Mechanical Design ◽  
Tensile Tests ◽  
Design Guidelines ◽  
Materials Testing ◽  
Element Analysis ◽  
Dog Bone ◽  
3D Printed ◽  
Future Work

A set of monotonic tensile tests was performed on 3-D printed plastics following ASTM standards. The experiment tested a total of 13 “dog bone” test specimens where the material, infill percentage, infill geometry, load orientation, and strain rate were varied. Strength-to-weight ratios of the various infill geometries were compared. It was found through tensile testing that the specific ultimate tensile strength (MPa/g) decreases as the infill percentage decreases and that hexagonal pattern infill geometry was stronger and stiffer than rectilinear infill. However, in finite element analysis, rectilinear infill showed less deformation than hexagonal infill when the same load was applied. Some design guidelines and future work are presented.

Axial–Torsional interactions and wire deformation in 19-wire spiral strand

1988 ◽  
Vol 23 (2) ◽  
pp. 79-86 ◽  
Author(s):  
W S Utting ◽  
N Jones
Keyword(s):  
Tensile Load ◽  
Bending Moment ◽  
Tensile Tests ◽  
Gauge Length ◽  
Strain Gauges ◽  
Bending Moments ◽  
Test Results ◽  
Predicted Values ◽  
Fixed End ◽  
Increasing Load

Tensile tests were performed on a straight steel strand of three layer (12/6/1) construction, having a core wire diameter of 3.66 mm and 3.33 mm diameter helical wires, under conditions of full end-fixity, partial restraint, and ends free from torsional restraint. The torque generated under tensile load was recorded as well as the strand extension and rotation over a 600 mm gauge length. Wire tensions and bending moments in the outer layer of helical wires were determined at the mid-strand position from the outputs of strain gauges in groups of three with parallel grids and mounted parallel to the wire axis on the crown of each wire. The rate of strand extension under tensile load was found to be greater in tests with reduced torsional restraint, the greatest rate occurring in the free-end test. The strand rotation rate was also found to be greatest in the free-end test. The greatest difference from the theoretically predicted rates occurred in a free-end test with increasing load; predicted values of extension and rotation underestimated the test results by 12 and 23 per cent, respectively. Displacement of the load-torque plots occurred in the direction of reducing torque as testing proceeded. This appears to indicate the redistribution of the strand load between the layers of wires. Wire tensions showed a more even sharing of load in the fixed-end condition than in the free-end condition. The increase in rate of tension with strand load was less for most wires in tests with reduced torsional restraint, with the lowest tension rates developing in the free-end condition. For most wires, the rate of bending moment change with strand load was greater (in the sense tending to decrease tensile stress on wire crowns) in tests with reduced torsional restraint. However, the bending moment rates varied greatly between wires, the variation being greater in tests with reduced torsional restraint than in fixed-end tests.

scholarly journals A novel method for in situ TEM measurements of adhesion at the diamond–metal interface

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. A. Loginov ◽  
D. A. Sidorenko ◽  
A. S. Orekhov ◽  
E. A. Levashov
Keyword(s):  
Bonding Strength ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
In Situ Tem ◽  
Dog Bone ◽  
Ni Alloy ◽  
Novel Method

AbstractThe procedure for in situ TEM measurements of bonding strength (adhesion) between diamond and the metal matrix using a Hysitron PI 95 TEM Picoindenter holder for mechanical tests and Push-to-Pull devices was proposed. For tensile tests, dog-bone shaped lamellae 280–330 nm thick and ~ 2.5 µm long were used as objects of study. The lamellae were manufactured using the focused ion beam technology from the metal–diamond interface of diamond-containing composite material with a single-phase binder made of Fe–Co–Ni alloy. The experimentally determined bonding strength was 110 MPa.

Micromechanical Tensile Testing

1996 ◽  
Vol 436 ◽  
Author(s):  
S. Greek ◽  
F. Ericson ◽  
S. Johansson ◽  
J.-Å. Schweitz
Keyword(s):  
Fracture Strength ◽  
Tensile Testing ◽  
Weibull Modulus ◽  
Tensile Tests ◽  
Cross Sectional ◽  
Weibull Statistics ◽  
Electrodeposited Nickel ◽  
The Mean ◽  
Scanning Electron

AbstractA method is described where tensile tests can be performed in situ on micromachined structures. The testing equipment consists of a testing unit mounted on a micromanipulator in a Scanning Electron Microscope (SEM). The fracture loads of micromachined beam structures made from thick and thin film polysilicon as well as from electrodeposited nickel and nickeliron alloy were measured, and the fracture strengths then calculated via measurements of the test structures’ initial cross-sectional areas. The statistical scatter of the polysilicon fracture strength values were evaluated by Weibull statistics. The mean fracture strength and the Weibull modulus, a measure of the scatter, were obtained

Strain measurement and error analysis in thermo-mechanical tensile tests of sheet metals for hot stamping applications

2017 ◽  
Vol 232 (11) ◽  
pp. 1994-2008 ◽  
Author(s):  
Zhutao Shao ◽  
Nan Li ◽  
Jianguo Lin ◽  
Trevor A Dean
Keyword(s):  
Error Analysis ◽  
Hot Stamping ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Gauge Length ◽  
Temperature Gradients ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Heating And Cooling ◽  
Gauge Section

In order to conduct uniaxial tensile tests for hot stamping applications, tests are normally performed by using a Gleeble thermo-mechanical materials simulator so that rapid heating and cooling processes can be obtained. However, temperature gradients in a specimen tested on Gleeble are inevitable due to resistance heating principles and heat loss to grips and water-cooled jaws. In this research, a pair of purpose-built grips made of stainless steel with low thermal conductivity and significantly reduced contacting area for clamping, as well as a flat dog-bone specimen with maximised parallel length (80 mm) were designed, for the purpose of improving the temperature uniformity within the concerned gauge section area of the specimen. Uniaxial tensile tests on AA6082 were performed, after controlled heating and cooling processes, at constant deformation temperatures in the range of 400 ℃–500 ℃ and at constant strain rate in the range of 0.1–4/s, to simulate its hot stamping conditions. The digital image correlation system was adopted to enable strain distributions in specimens to be measured. The temperature distributions in specimens were investigated and an effective gauge length of 14 mm was specified accordingly to ensure temperature gradients less than 10 ℃ within it at all tested temperatures. True stress–true strain curves of AA6082 were obtained based on results of strain measurements along the defined effective gauge length and used to calibrate a set of advanced material model. Error analysis was carried out by using thermo-electrical and thermo-mechanical FE models on ABAQUS, in which the calibrated material constitutive equations were implemented via subroutines. The error of stress–strain curves of AA6082 measured based on the specified gauge length was investigated and quantified by analysing the distribution of axial strain and axial stress.

In Situ SEM study of iodine-induced stress corrosion cracking (ISCC) in Zircaloy-4

1990 ◽  
Vol 48 (4) ◽  
pp. 840-841
Author(s):  
Marthinus P Fick
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Zirconium Alloys ◽  
Tensile Tests ◽  
Gauge Length ◽  
Argon Atmosphere ◽  
Corrosion Cracking ◽  
Outer Diameter ◽  
Mechanism Of Failure

Stress corrosion cracking (SCC) of Zirconium alloys by an abundant fission product, iodine, has been extensively studied in order to understand the mechanism of failure of fuel cladding in nuclear reactors. This study was an attempt to observe the fracture mechanics of ISCC in Zircaloy-4 during in situ scanning electron microscope (SEM) tensile tests.A 200mm long section of a Zircaloy-4 cladding tube with an outer diameter of 9’55mm and a wall thickness of 0,55mm, was bisected and then cold rolled into flat strips 14mm wide and 0,5mm thick. The material was annealed at 680°C for 1 h at a time in an Argon atmosphere between successive cold working steps. Following the final cold roll the material was annealed at 1080°C for 4 h in an Argon atmosphere and air-quenched.Tensile test specimens with a gauge length of 12’5mm and a width of 3’12mm were cut from the sheet metal by spark erosion accordinq to scaled down ANSI/ASTM E8-79a specifications. The specimens had to be lapped and polished to a thickness of 0’16mm in order to obtain a maximum stress of 500MPa without exceeding the 250N limit of the apparatus.

Sign in / Sign up

Export Citation Format

Share Document