Measuring Thin Film Fracture Toughness Using the Indentation Sinking-in Effect and Focused Ion Beam

1999 ◽  
Vol 594 ◽  
Author(s):  
Ting Y. Tsui ◽  
Young-Chang Joo
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Crack Tip ◽  
Bending Moment ◽  
Hard Metal ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Extension Force

AbstractA new experimental technique is developed to measure the fracture toughness of a hard metal thin film deposited on a soft substrate. A pre-crack was fabricated in the thin film by using the advanced focused ion beam (FIB) milling techniques. The crack extension force was generated by means of the indentation sinking-in effect. The effect creates a bending moment and tensile stress on the hard thin film near the indentation, which promotes crack growth. The amount of crack tip blunting prior to the critical failure was measured from the FIB cross-sectioned micrographs. By using the crack tip opening displacement model (CTOD), the fracture toughness of the thin film was calculated. The results show the nickel phosphorus (NiP) thin film fracture toughness is at least 15.0MPa√m. The finite element method (FEM) was used to understand the modes of mixity near the crack tip. The results indicate the crack tip modes of mixity are dominated by the Mode I opening, provided the indentation is sufficiently far from the pre-crack or the indentation depths is small when compared with the film thickness.

Characterisation of Fracture and HAC Resistance of an Individual Microstructural Constituent with Micro-Cantilever Testing

2016 ◽  
Vol 713 ◽  
pp. 66-69
Author(s):  
Walter Costin ◽  
Olivier Lavigne ◽  
Andrei G. Kotousov
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Plastic Hinge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Ferrous Alloys ◽  
Microstructural Constituent ◽  
Macro Scale ◽  
Micro Cantilever ◽  
Hinge Model

This paper focuses on the application of miniaturized fracture tests to evaluate the fracture and hydrogen assisted cracking (HAC) resistance of a selected microstructural constituent (acicular ferrite, AF) which only occurs in microscopic material volumes. Site-specific Focused Ion Beam (FIB) micro-machining was used to fabricate sharply notched micro-cantilevers into a region fully constituting of AF. The micro-cantilevers were subsequently tested under uncharged and hydrogen charged conditions with a nanoindenter. The load displacement curves were recorded and analysed with a simplified plastic hinge model for the uncharged specimen, as AF demonstrated an essentially ductile behaviour. The simplified model assisted with FE simulations provided values of the critical plastic crack tip opening displacement (CTOD). A value of the conditional fracture toughness was thereby determined as 12.1 MPa m1/2. With LEFM, a threshold stress intensity factor, Kth, to initiate hydrogen crack propagation in AF was found to range between 1.56 MPa m1/2 and 4.36 MPa m1/2. All these values were significantly below the corresponding values reported for various ferrous alloys in standard macro-tests. This finding indicates that the fracture and HAC resistance at the micro-scale could be very different than at the macro-scale as not all fracture toughening mechanisms may be activated at this scale level.

Impact of Metallic Foam’s Microstructure to its Mechanical Property

2013 ◽  
Vol 634-638 ◽  
pp. 2808-2812
Author(s):  
Zhu Feng Sun ◽  
Ling Yun Xie
Keyword(s):  
Fracture Toughness ◽  
Cell Structure ◽  
Crack Tip ◽  
Metallic Foam ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Metal Material ◽  
Loading Mode ◽  
Foam Metal ◽  
Material Fracture

Explored the influence of pore structure of foam metal material on mechanical behavior of fracture. Discuss fracture toughness of several different micro geometric structure of foam metal material with finite element method. The author's calculations showed, microstructure and loading mode has an important effect on the fracture toughness of the foam metal material. due to ignoring the effects of cell structure on the mechanical properties of materials, the classic fracture toughness criterion -crack tip opening displacement (COD) is incomplete, it would be more efficient to take opening displacement change rate of the crack-tip as the parameter to characteristic the metallic foam material fracture toughness.

Fracture Toughness of Titanium - Titanium Nitride Multi-Layer Thin Film

2008 ◽  
Author(s):  
Mohan Prasad Manoharan ◽  
Amit Desai ◽  
Amanul Haque
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Titanium Nitride ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
New Class ◽  
Tin Coatings ◽  
Film Specimen ◽  
Cantilever Bending ◽  
Layer Thin Film

Thin film specimens of titanium - titanium nitride multilayer erosion resistant coating were prepared using liftout technique in Focused Ion Beam - Scanning Electron Microscope (SEM). The fracture toughness of the thin film specimen was measured in situ using a cantilever bending experiment in SEM to be 11.33 MPa/m0.5, twice as much as conventional TiN coatings. Ti–TiN multi-layer coatings are part of a new class of advanced erosion resistant coatings and this paper discusses an experimental technique to measure the fracture toughness of these coatings.

A Membrane Deflection Fracture Experiment to Investigate Fracture Toughness of Freestanding MEMS Materials

2003 ◽  
Vol 795 ◽  
Author(s):  
H. D. Espinosa ◽  
B. Peng
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Mean Value ◽  
Advanced Materials ◽  
Ultrananocrystalline Diamond ◽  
Membrane Deflection

ABSTRACTThis paper presents a novel Membrane Deflection Fracture Experiment (MDFE) to investigate the fracture toughness of MEMS and other advanced materials in thin film form. It involves the stretching of freestanding thin-film membranes, in a fixed-fixed configuration, containing pre-existing cracks. The fracture behavior of ultrananocrystalline diamond (UNCD), a material developed at Argonne National Laboratory, is investigated to illustrate the methodology. When the fracture initiates from sharp cracks, produced by indentation, the fracture toughness was found to be 4.7 MPa m1/2. When the fracture initiates from blunt notches with radii about 100 nm, machined by focused ion beam (FIB), the mean value of the apparent fracture toughness was found to be 7.2 MPa m1/2. Comparison of these two values, using the model proposed by Drory et al. [9], provides a correction factor of 2/3, which corresponds to a mean value of ρ/2x=1/2.

CTOD Fracture Toughness Assessment Under Different Notch Type (Fatigue Pre-Cracking and EDM)

2019 ◽  
Author(s):  
Israel Marines-Garcia ◽  
Aaron Aguilar ◽  
Kristian Carreon ◽  
Philippe Darcis
Keyword(s):  
Fracture Toughness ◽  
Crack Length ◽  
Heat Affected Zone ◽  
Crack Tip ◽  
Fusion Line ◽  
Testing Time ◽  
Pipe Material ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Electro Discharge Machining

Abstract The standardization of any mechanical material characterization is aiming to get homogenization on the testing physical execution by independent laboratories and to drive for accurate material evaluation between different entities. However, from time to time, standard tests may be reconsidered in order to improve their efficacy, execution time and incorporate new testing techniques or technologies without compromising the testing results and consistency. In the present work, fracture toughness crack tip opening displacement (CTOD) testing is addressed and particularly the need to perform fatigue pre-cracking prior monotonic testing. Without the fatigue pre-cracking, CTOD testing time can be significantly reduced during the preparation of specimens, meaning that specimens can be tested as soon as they are machined. Wire electro-discharge machining (EDM) technique allows generating sharp tip notches, and presents a good alternative to the standards specified fatigue pre-cracking [1–2]. In addition, this machining technology reduces the risk of rejecting the specimen testing, particularly when targeting weld heat affected zone/fusion line (HAZ/FL) microstructure on specimens with surface notch DNV-ST-F101 Figure B-9 [3], where it is specified that the crack tip shall be within a narrow distance (0.5 mm) from the fusion line (FL) or assess grain coarsened heat affected zone (GCHAZ) microstructure as indicated in DNV-ST-F101 section B.2.8.7 [3]. Herein, it is presented an assessment carried out in order to identify the notch type effect over the fracture toughness (CTOD) considering notches conditions as standard fatigue pre-crack and wire electro-discharge machining (EDM). Fifteen (15) CTOD specimens were manufactured from plain pipe material (same pipe), 251.3 mm OD × 20.9 mm WT, SMLS 450PD and tested according to ISO 12135 recommendations [1], they were distributed as follow; five (5) specimens according to standard recommendations with fatigue pre-cracking length ≥ 1.3 mm or 2.5%W (whichever is bigger), five (5) specimens with a fatigue pre-cracking length < 1.3 mm (between 0.5 mm to 1 mm), and five (5) specimens without fatigue pre-cracking (EDM notch), additionally, results from five (5) specimens previously tested in a round robin (RR) testing performed internally by Tenaris using the same LP material and standard fatigue pre-crack length. The crack length target (a/W) was kept 0.5 for all cases. Even if the sampling population is relatively small considering the three notch conditions, it seems that EDM might be an alternative to the standard specified fatigue pre-cracking. Thus, this experimental assessment aims to open the discussion on the use of EDM notch as alternative.

Sign in / Sign up

Export Citation Format

Share Document