Fracture and Fatigue Testing of Micro-Sized Materials for MEMS Applications

2005 ◽  
Author(s):  
Kazuki Takashima ◽  
Timothy P. Halford ◽  
Yakichi Higo
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Amorphous Alloy ◽  
Crack Initiation ◽  
Crack Growth ◽  
Testing Machine ◽  
Fatigue And Fracture

We have developed a new type of mechanical testing machine for micro-sized specimens, which can apply a small static or cyclic load, and have investigated fracture and fatigue crack growth behavior of micro-sized specimens. Cantilever beam type specimens (10 μm × 10 μm × 50 μm), with notches were prepared from thin films of a Ni-P amorphous alloy by focused ion beam machining. Fatigue and fracture toughness tests were carried out in air at room temperature using the mechanical testing machine. Fatigue and fracture testing was completed successfully for micro-sized cantilever specimens. Once fatigue crack growth occurs, rapid sample failure was observed in these micro-sized specimens. This indicates that the fatigue life of micro-sized specimens is mainly dominated by crack initiation. This also suggests that even a micro-sized surface flaw can be a fatigue crack initiation site which will shorten the fatigue life of micro-sized specimens. As a result of fracture toughness tests, plane strain criteria for small scale yielding were not achieved for this amorphous alloy. Plane stress and plane strain dominated regions were clearly observed on the fracture surfaces and their sizes were consistent with those estimated by fracture mechanics calculations. This suggests that fracture mechanics is still valid for such micro-sized specimens.

A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application

2005 ◽  
Vol 128 (4) ◽  
pp. 889-895 ◽  
Author(s):  
K. S. Chan ◽  
M. P. Enright
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Growth ◽  
Model Development ◽  
Fatigue Crack Initiation ◽  
Crack Size ◽  
Crack Initiation Life ◽  
Variability Model

This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MICROFAVA (micromechanical fatigue variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α+β Ti-alloy Ti-6Al-4V.

Effect of Sour Acidizing Treatments on the Fatigue Crack Growth and Fracture Toughness Behavior of C-Mn Line Pipe Steels

2016 ◽  
Author(s):  
Weiwei Yu ◽  
Jonathan Bowman ◽  
Apurva Batra ◽  
Ramgopal Thodla ◽  
Colum Holtam ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Compact Tension ◽  
Pipe Steels ◽  
Production Environment ◽  
Line Pipe ◽  
Fatigue And Fracture ◽  
Girth Welds

Acidizing treatments are typically performed intermittently during the life of a well. However, more recently there has been a desire to perform an increased number of acidizing treatments in order to improve production. The acidizing treatments typically involve highly corrosive acids, such as hydrofluoric (HF), hydrochloric (HCl) and acetic acid, which are known to cause significant corrosion. In the presence of hydrogen sulfide (H2S), these acidizing treatments could cause environmentally assisted fatigue and fracture (i.e. increased fatigue crack growth rates and reduced fracture toughness). A test program is underway to evaluate and quantify the effect of sour acidizing treatments on the fatigue and fracture behavior of welded C-Mn line pipe steels. This paper describes the preliminary findings from fatigue crack growth rate (FCGR) and fracture toughness (FT) tests on as-welded (i.e. unstrained) pipe. All tests were conducted at room temperature (RT) using compact tension (CT) specimens notched in the parent pipe (PP). Frequency scan FCGR tests were performed in the following sour acid conditions: simulated production environment (PE), spent acid without inhibitor and spent acid with residual corrosion inhibitor. The PE consisted of a simulated brine with pH = 4.5 and partial pressure of H2S (pH2S) = 0.21psia. FCGRs in the sour PE were of the order of 20 times faster than in air. The pH2S was the same for the tests in spent acid environments, but the pH was lower (approximately 3.5). As would be expected, the FCGRs were much higher in the low pH environment. The highest FCGRs were observed in the inhibited sour spent acid environment and were up to 100 times faster than in air. Sour FT tests were also conducted in the PE and in spent acid with and without inhibitor. In all cases, the measured FT values were significantly lower than in air. The test in PE exhibited higher FT than in the sour acidizing environment. The lowest FT values were observed in spent acid with inhibitor. Future work will investigate the effect of reeling on the fatigue and FT performance of pipe girth welds in sour acidizing environments.

Aging of High Speed Train Wheelsets and its Quantitative Characteristics Based on Fracture Mechanics for Optimization of In-Service Inspection

2004 ◽  
Vol 261-263 ◽  
pp. 1037-1042 ◽  
Author(s):  
Sung Jae Kwon ◽  
Kazuhiro Ogawa ◽  
Tetsuo Shoji
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
High Speed ◽  
High Speed Train ◽  
Load Rate ◽  
The Impact ◽  
Mechanics Characteristics

The fracture mechanics characteristics in the critical locations of the wheelset for high-speed train have not been studied enough yet despite of severe conditions due to increase in operating speeds. Moreover, the fracture mechanics characteristics with respect to the aging effects of wheelset materials have not been clearly studied. In the present study, the following fracture mechanics characterization tests were carried out in accordance with various locations on the wheelset for high-speed train: fracture toughness depending on load rate, fatigue crack growth rate and fatigue thresholds. The results show that the fatigue crack growth rates in accordance to the locations on wheelset were not remarkably different, and the fatigue threshold in the region of the bolt-hole is lower than that in other regions. The fracture toughness depending on load rate data shows that once the downward curve from quasi-static values was reached, subsequent values showed a slow increase with respect to the impact velocity. This means that dynamic fracture toughness should be considered in the design code of the wheelset material.

Virtual Testing for Fracture Toughness, Fatigue Crack Growth and Fatigue Life Data Estimation of Metallic Components

2013 ◽  
Vol 577-578 ◽  
pp. 177-180
Author(s):  
Michele Pettinà ◽  
Bahram Farahmand ◽  
Filippo Berto ◽  
Frank Abdi
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Strain Curve ◽  
Stress Concentrations ◽  
Damage And Fracture ◽  
Data Estimation ◽  
Total Life

Evaluating fracture and fatigue life properties of structural components involves tests that are costly and time consuming. To estimate total life of engineering parts, high cycle fatigue data (S-N) for the material under study is needed. In many cases the S-N data is not available to the analyst and both the time and budget required for testing prevent engineers to meet the deadline imposed on the program. An analytical combined Progressive Damage and Fracture Mechanics based approach is proposed that estimates the S-N data for components that have stress concentrations. The proposed methodology starts from a full engineering tensile stress-strain curve of the material under study and ends up with the estimation of fracture toughness, fatigue crack growth and fatigue S-N curves.

Evaluation of the Compatibility of High-Strength Aluminum Alloy 7075-T6 to High-Pressure Gaseous Hydrogen Environments

2018 ◽  
Author(s):  
Yuhei Ogawa ◽  
Dain Kim ◽  
Hisao Matsunaga ◽  
Saburo Matsuoka
Keyword(s):  
Fracture Toughness ◽  
High Pressure ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
High Strength ◽  
Gaseous Hydrogen ◽  
Aluminum Alloy 7075

To develop safer and more cost-effective high-pressure hydrogen tanks used in fuel cell vehicles (FCVs), the metallic materials with the following three key properties, i.e. lightweight, high strength and excellent resistance to hydrogen embrittlement should be explored. In this study, the compatibility of high-strength, precipitation-hardened aluminum alloy 7075-T6 was evaluated according to the four types of mechanical testing including slow-strain rate tensile (SSRT), fatigue life, fatigue crack growth (FCG) and fracture toughness tests in high-pressure gaseous hydrogen environments (95 ∼ 115 MPa) at room temperature. Even though numerous publications have previously reported significant degradation of the mechanical properties of 7075-T6 in some hydrogenating environments, such as moist atmosphere, the understanding with regards to the performance of this alloy in high-pressure gaseous hydrogen environments is still lacking. In SSRT tests, the alloy showed no degradation of tensile strength and ductility. Furthermore, fatigue life, fatigue crack growth and fracture toughness properties were also not degraded in hydrogen gas. Namely, it was first demonstrated that the material has big potential to be used for hydrogen storage tanks for FCVs, according to its excellent resistance to high-pressure gaseous hydrogen.

A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application

2005 ◽  
Author(s):  
K. S. Chan ◽  
M. P. Enright
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Growth ◽  
Model Development ◽  
Fatigue Crack Initiation ◽  
Crack Size ◽  
Crack Initiation Life ◽  
Variability Model

This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MicroFaVa (Micromechanical Fatigue Variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α + β Ti-alloy Ti-6Al-4V.

A Study on Fatigue Crack Growth Parameters for Fatigue Life Assessment based on Fracture Mechanics

2017 ◽  
Vol 35 (1) ◽  
pp. 61-67
Author(s):  
Hyeon-Su Kim ◽  
Tae-Jong Park ◽  
Dong-Ju Lee ◽  
Sang-Beom Shin ◽  
Myung-Hyun Kim
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Parameters ◽  
Life Assessment ◽  
Fatigue Life Assessment
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