A study on the initial crack curving angle of isotropic/orthotropic bimaterial

2002 ◽  
Vol 16 (12) ◽  
Author(s):  
Jai-Sug Hawong ◽  
Dong-Chul Shin ◽  
Ouk-Sub Lee
Keyword(s):  
Initial Crack ◽  
Crack Curving

A Fracture Mechanics Based Parametric Study of the Copper-to-Copper Direct Thermo-Compression Bonded Interface Using Finite Element Method

2013 ◽  
Author(s):  
Ah-Young Park ◽  
Satish Chaparala ◽  
Seungbae Park
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parametric Study ◽  
Initial Crack ◽  
Bonding Interface ◽  
Interface Condition ◽  
Large Temperature ◽  
Bonded Interface ◽  
The Impact ◽  
Element Method

Through-silicon via (TSV) technology is expected to overcome the limitations of I/O density and helps in enhancing system performance of conventional flip chip packages. One of the challenges for producing reliable TSV packages is the stacking and joining of thin wafers or dies. In the case of the conventional solder interconnections, many reliability issues arise at the interface between solder and copper bump. As an alternative solution, Cu-Cu direct thermo-compression bonding (CuDB) is a possible option to enable three-dimension (3D) package integration. CuDB has several advantages over the solder based micro bump joining, such as reduction in soldering process steps, enabling higher interconnect density, enhanced thermal conductivity and decreased concerns about intermetallic compounds (IMC) formation. Critical issue of CuDB is bonding interface condition. After the bonding process, Cu-Cu direct bonding interface is obtained. However, several researchers have reported small voids at the bonded interface. These defects can act as an initial crack which may lead to eventual fracture of the interface. The fracture could happen due to the thermal expansion coefficient (CTE) mismatch between the substrate and the chip during the postbonding process, board level reflow or thermal cycling with large temperature changes. In this study, a quantitative assessment of the energy release rate has been made at the CuDB interface during temperature change finite element method (FEM). A parametric study is conducted to analyze the impact of the initial crack location and the material properties of surrounding materials. Finally, design recommendations are provided to minimize the probability of interfacial delamination in CuDB.

scholarly journals Dynamic Crack Curving under Mixed-Mode Loading.

1994 ◽  
Vol 60 (571) ◽  
pp. 720-727
Author(s):  
Akira Simamoto ◽  
Makoto Kosai ◽  
Albert Kobayashi S.
Keyword(s):  
Mixed Mode ◽  
Dynamic Crack ◽  
Mixed Mode Loading ◽  
Crack Curving

Determination of Initial Crack Strength of Silicon Die Using Acoustic Emission Technique

2015 ◽  
Vol 44 (7) ◽  
pp. 2497-2506 ◽  
Author(s):  
Pei-Chi Chen ◽  
Yen-Fu Su ◽  
Shin-Yueh Yang ◽  
Steven Y. Liang ◽  
Kuo-Ning Chiang
Keyword(s):  
Acoustic Emission ◽  
Initial Crack ◽  
Acoustic Emission Technique

scholarly journals In-situ SEM and optical microscopy testing for investigation of fatigue crack growth mechanism under overload

2018 ◽  
Vol 165 ◽  
pp. 13013
Author(s):  
Wei Zhang ◽  
Liang Cai
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Optical Microscopy ◽  
Crack Growth ◽  
Load Condition ◽  
Crack Tip ◽  
Initial Crack ◽  
Crack Growth Behavior ◽  
Single Overload

In this paper, the in-situ scanning electron microscope (SEM) and optical microscopy experiments are performed to investigate the crack growth behavior under the single tensile overload. The objectives are to (i) examine the overload-induced crack growth micromechanisms, including the initial crack growth acceleration and the subsequent retardation period; (ii) investigate the effective region of single overload on crack growth rate. The specimen is a small thin Al2024-T3 plate with an edge-crack, which is loaded and observed in the SEM chamber. The very high resolution images of the crack tip are taken under the simple variable amplitude loading. Imaging analysis is performed to quantify the crack tip deformation at any time instant. Moreover, an identical specimen subjected to the same load condition is observed under optical microscope. In this testing, fine speckling is performed to promote the accuracy of digital imaging correlation (DIC). The images around the crack tip are taken at the peak loads before, during and after the single overload. After that, the evolution of local strain distribution is obtained through DIC technique. The results show that the rapid connection between the main crack and microcracks accounts for the initial crack growth acceleration. The crack closure level can be responsible for the crack growth rate during the steady growth period. Besides that, the size of retardation area is larger than the classical solution.

Finite Element Analysis of the Hydro-Mechanical Punching Process

2006 ◽  
Vol 505-507 ◽  
pp. 871-876
Author(s):  
Jong Hun Yoon ◽  
Hoon Huh ◽  
Yong Sin Lee ◽  
Seung Soo Kim ◽  
E.J. Kim ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Ductile Fracture ◽  
Sheet Material ◽  
Middle Surface ◽  
Initial Crack ◽  
Fracture Criteria ◽  
Element Analysis ◽  
Final Fracture ◽  
Ductile Fracture Criteria ◽  
Punching Process

This paper investigates the characteristics of a hydro-mechanical punching process. The hydro-mechanical punching process is divided into two stages: the first stage is the mechanical half piercing in which an upper punch goes down before the initial crack is occurred; the second stage is the hydro punching in which a lower punch goes up until the final fracture is occurred. Ductile fracture criteria such as the Cockcroft et al., Brozzo et al. and Oyane et al. are adopted to predict the fracture of a sheet material. The index value of ductile fracture criteria is calculated with a user material subroutine, VUMAT in the ABAQUS Explicit. The hydrostatic pressure retards the initiation of a crack in the upper region of the blank and induces another crack in the lower region of the blank during the punching process. The final fracture zone is placed at the middle surface of the blank to the thickness direction. The result demonstrates that the hydro-mechanical punching process makes a finer shearing surface than the conventional one as hydrostatic pressure increases.

Study on Fiber-Reinforced Laminated Composite Textile Tearing Behavior and Strength Prediction

2014 ◽  
Vol 651-653 ◽  
pp. 1370-1373
Author(s):  
Yun Chao Gu ◽  
Long Bin Liu ◽  
Shuai Cao ◽  
Hou Di Xiao ◽  
Ming Yun Lv
Keyword(s):  
Engineering Application ◽  
Laminated Composite ◽  
Initial Crack ◽  
Strength Prediction ◽  
Deformation Analysis ◽  
Fiber Reinforced ◽  
Mechanics Performance ◽  
Envelope Material ◽  
Safety And Stability ◽  
Tearing Strength

The tearing behavior of fiber-reinforced laminated composite textile plays the key role in the decision of mechanics performance of high altitude airship envelop material, even directly deciding its safety and stability. This paper, based on typical woven fabricated fiber yarns’ characteristics of geometry and mechanics, adopts Euler-displacement deformation analysis to explore yarn bundles deformation effects on tearing behavior and strength of envelope material with prefabricated damage and crack. Also, models with prefabricated crack with different size and textile density are respectively built to find factors that affect tearing behavior and strength of envelope material. From tests, it can be observed that the built models for predicting its tearing strength are in conformity with the experimental data. Nonlinear relationship is reflected between the initial crack width or yarn bundles density with tearing strength. Conclusively, the methods and models adopted in this paper provide an effective and innovative mind on tearing behavior and strength of fiber reinforced envelope material and make the foundation for its engineering application.

Corrosion Fatigue Crack Growth in Clad Low-Alloy Steels—Part I: Medium-Sulfur Forging Steel

1997 ◽  
Vol 119 (3) ◽  
pp. 249-254 ◽  
Author(s):  
L. A. James ◽  
T. A. Auten ◽  
T. J. Poskie ◽  
W. H. Cullen
Keyword(s):  
Fatigue Crack ◽  
Corrosion Fatigue ◽  
Compact Tension ◽  
Initial Crack ◽  
Aqueous Environment ◽  
Low Alloy Steels ◽  
Surface Cracks ◽  
Low Oxygen ◽  
Corrosion Fatigue Crack ◽  
Alloy Steels

Corrosion fatigue crack propagation tests were conducted on a medium-sulfur ASTM A508-2 forging steel overlaid with weld-deposited alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 30.3–38.3 mm, and depths of 13.1–16.8 mm. The experiments were conducted in a quasi-stagnant low-oxygen (O2 < 10ppb) aqueous environment at 243°C, under loading conditions (ΔK, R, and cyclic frequency) conducive to environmentally assisted cracking (EAC) in higher-sulfur steels under quasi-stagnant conditions. Earlier experiments on unclad compact tension specimens of this heat of steel did not exhibit EAC, and the present experiments on semi-elliptical surface cracks penetrating cladding also did not exhibit EAC.

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