Stress and Fracture Analyses of Solar Silicon Wafers During Suction Process and Handling

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
S. Saffar ◽  
S. Gouttebroze ◽  
Z. L. Zhang
Keyword(s):  
Fracture Mechanics ◽  
Dynamic Fracture ◽  
Maximum Load ◽  
Structural Defects ◽  
J Integral ◽  
Impact Time ◽  
Static And Dynamic Analysis ◽  
Mechanics Analysis ◽  
Optimum Suction ◽  
The Impact

Solar wafer/cell breakage depends on the combination of the stresses generated in the handling and the presence of structural defects such as cracks. Suction process is a common loading during silicon wafer handling. This paper presents a systematic static and dynamic analysis of the suction process. Optimum suction pad diameter and locations are obtained by minimizing the stress distribution under both static and dynamic loading, and the effect of the impact time on the crack driving force is also investigated in this optimum situation. The results show that the four pads configuration with diameter of 20 mm placed in a rhombus shape with 18 and 38 mm diagonal lengths yields lowest maximum principle stress among the cases analyzed. In the dynamic fracture analyses, the maximum J integral appears at 800 and 1400 μs for continued holding and unloading cases after reaching the maximum load, respectively. The J integral for the unloading cases are always smaller than the holding cases. It has been found that when the impact time is longer than 3 s and 5600 μs the dynamic fracture mechanics analysis of the suction impact process can be replaced by a static fracture mechanics analysis for the holding and unloading cases, respectively.

Dynamic Steady-State Stress Field in a Web During Slitting

2005 ◽  
Vol 72 (2) ◽  
pp. 157-164 ◽  
Author(s):  
C. Liu ◽  
H. Lu ◽  
Y. Huang
Keyword(s):  
Steady State ◽  
Fracture Mechanics ◽  
Stress Field ◽  
Dynamic Fracture ◽  
Dynamic Stress ◽  
Razor Blade ◽  
Dynamic Fracture Mechanics ◽  
Mechanics Analysis ◽  
Dynamic Stress Field ◽  
The Web

Based on a dynamic fracture mechanics analysis, the stress field in a continuous film (called a web) during slitting (or cutting) is investigated. For a homogeneous, isotropic and linearly elastic web, the steady-state dynamic stress field surrounding the slitter blade can be related to the interacting traction between the moving web and the blade, and to the far-field tension that is parallel to the slitting direction. The interaction between the moving web and the blade also includes friction that is considered to be a Coulomb type. By solving an integral equation, the normal traction between the web and the blade can be expressed as a function of the blade profile and the web speed. Numerical calculations are performed for an ideal razor blade with the wedge shape. The analysis presented in this study indicates that the contact between the moving web and the blade does not start at the tip of the blade but rather starts at some distance behind the blade tip. Moreover, it is found that the distance from the point where the web begins to separate to the point where the blade and the web start to have contact, is controlled by the toughness of the web material and also by the web speed. Some characteristic nature of the dynamic stress field surrounding the slitter blade is investigated based on the dynamic fracture mechanics analysis results.

Effects of Negative Biaxial Loadings and Notch on Failure Assessment Diagrams

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
K. Ragupathy ◽  
K. Ramesh ◽  
D. Hall
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Biaxial Loading ◽  
Failure Criteria ◽  
Small Scale ◽  
J Integral ◽  
Element Analysis ◽  
Worst Case ◽  
Failure Assessment ◽  
The Impact

The failure assessment diagram (FAD) is a simplified and robust flaw assessment methodology, which simultaneously connects two dominant failure criteria: linear elastic fracture mechanics on one end and plastic collapse on the other end. This interaction is in the realm of elastic-plastic fracture mechanics. It is popularly known as the R6 approach, which graphically characterizes the impact of plasticity on crack driving force. In recent years, there has been continuous interest in using FADs to assess the failure of cracked structures subjected to biaxial loadings. Biaxiality is defined as the ratio of stress applied parallel and normal to the crack. Some pressure loaded aircraft components operate under negative biaxial ratios up to −0.5. In this paper, a detailed study on FAD was conducted using finite element analysis computed J-integral methods to investigate the effect of biaxial loading using different FAD approaches for geometries with notches. Geometries with a crack that emanates at a fillet region were simulated with various biaxial loading ratios from −0.5 to +0.5 using 2014-T6 material. FAD curves were numerically generated for cracks at notched regions subjected to various biaxial loadings using J-integral values from finite element analyses. These results were compared with standard FAD approaches. All comparison studies were made between uniaxial and biaxial loading cases with FAD curves created using four different crack sizes. Under small scale yielding, this study clearly shows that FAD curves are not influenced by negative biaxial loading at low load (up to 40% of yield strength). It was clearly confirmed that the majority of previously developed analytical FAD curves do not effectively account for notch and plasticity effects due to negative biaxiality. Based on this study, tension normal to the crack and compression parallel to the crack is the worst combination, and it has a very pronounced effect on FAD curve shapes. The standard analytical FAD curves are nonconservative compared with the approach recommended here, particularly under the worst case condition. FAD curves developed are shown to predict lower failure loads as compared with the currently accepted analytical FAD approaches defined in existing standards, e.g., R6 and API 579. The impact of negative biaxial loading can be investigated directly using a J-integral FAD approach but can be compared with ease by plotting both approaches in a FAD format.

scholarly journals Applications of adina to viscoplastic-dynamic fracture mechanics analysis

1989 ◽  
Vol 32 (3-4) ◽  
pp. 815-824 ◽  
Author(s):  
B.R. Bass ◽  
J.K. Eeney-Walker ◽  
T.L. Dickson ◽  
C.E. Pugh ◽  
C.W. Schwartz ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Dynamic Fracture ◽  
Dynamic Fracture Mechanics ◽  
Mechanics Analysis

Effects of Negative Biaxial Loadings and Notch on Failure Assessment Diagrams

2008 ◽  
Author(s):  
K. Ragupathy ◽  
K. Ramesh ◽  
Doug Hall
Keyword(s):  
Fracture Mechanics ◽  
Biaxial Loading ◽  
Failure Criteria ◽  
Small Scale ◽  
J Integral ◽  
Worst Case ◽  
Integral Methods ◽  
Failure Assessment ◽  
Cracked Structures ◽  
The Impact

The Failure Assessment Diagram (FAD) is a simplified and robust flaw assessment methodology which simultaneously connects two dominant failure criteria: Linear Elastic Fracture mechanics (LEFM) on one end and Plastic collapse on other end. This interaction is the realm of Elastic Plastic Fracture Mechanics (EPFM.) It is popularly known as the R6 approach which graphically characterizes the impact of plasticity on crack driving force. In the recent years, there has been continuous interest in using Failure Assessment Diagrams (FAD) to assess the failure of cracked structures subjected to biaxial loadings. Biaxiality is defined as the ratio of stress applied parallel and normal to the crack. Some aircraft components operate under negative biaxial ratios up to −0.5. In this paper, a detailed study on FAD was conducted using FEA computed J-integral methods to investigate the effect of biaxial loading using different FAD approaches for geometries with notches. Geometries with a crack that emanates at a fillet region were simulated with various biaxial loading ratios from −0.5 to +0.5 using 2014-T6 material. FAD curves were numerically generated for cracks at notched regions subjected to various biaxial loadings using J-integral values from finite element analyses and validated its practical application. Comparison studies were made between uniaxial and biaxial loading cases with FAD curves created using standard approaches for four different crack sizes. Under small scale yielding, this study clearly shows that FAD curves are not influenced by negative biaxial loading at low load (up to 40% of yield strength). It was clearly confirmed that the majority of previously developed analytical FAD curves do not effectively account for notch and plasticity effects due to negative biaxilaity. Based on this study, tension normal to the crack and compression parallel to the crack is the worst combination and it has a very pronounced effect on FAD curve shapes. The standard analytical FAD curves are non-conservative compared to the approach recommended here, particularly under the worst case condition. The proposed method is expected to predict lower failure loads relative to currently accepted analytical methods.

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