Analysis of macroscopic crack branching patterns in chemically strengthened glass

2008 ◽  
Vol 23 (1) ◽  
pp. 214-225 ◽  
Author(s):  
J.E. Kooi ◽  
R. Tandon ◽  
S.J. Glass ◽  
J.J. Mecholsky
Keyword(s):  
Residual Stress ◽  
Strain Energy ◽  
Tensile Strain ◽  
Exchange Process ◽  
The Body ◽  
Aluminosilicate Glass ◽  
Crack Branching ◽  
Stress Profile ◽  
Branching Patterns ◽  
Macroscopic Crack

Residual stress profiles were introduced in sodium aluminosilicate glass disks using an ion-exchange process. They were fractured in two loading conditions: indentation and biaxial flexure. The fractal dimension of the macroscopic crack branching pattern called the crack branching coefficient (CBC), as well as the number of fragments (NOF) were used to quantify the crack patterns. The fracture surfaces were analyzed to determine the stresses responsible for the crack branching patterns. The total strain energy in the body was calculated. The CBC was a good measure of the NOF. They are directly related to the tensile strain energy due to the residual stress profile for fractures due to indentation loading. However, in general for materials with residual stresses, CBC (or NOF) is not related to the strength or the stress at fracture, or even to the total stored tensile strain energy. Instead, the CBC appears to be related, in a complex manner, to the distribution of stresses in the body. Therefore, in general, the characterization of the CBC of fractured materials cannot be used to ascertain the prior stress distribution.

Effect of Ion-Exchange Chemistry on the Fracture of Chemically Strengthened Sodium Aluminosilicate Glass

2019 ◽  
Author(s):  
Benedict O. Egboiyi ◽  
Trisha Sain
Keyword(s):  
Residual Stress ◽  
Ion Exchange ◽  
Fracture Strength ◽  
Critical Stress Intensity Factor ◽  
Consumer Electronics ◽  
Test Method ◽  
Aluminosilicate Glass ◽  
Ring Test ◽  
Stress Profile ◽  
Sodium Aluminosilicate

Abstract The widespread use of sodium aluminosilicate glass in many critical applications due to its hardness, weight, density and optical properties (transparency, dielectric etc.), instead of metals or plastics has become common in recent years. However, glass which is known to be a brittle material has its own vulnerability to fracture. Processes such as heat treatment (heat tempering) or chemical strengthening, through ion-exchange have been deployed to create residual stress profile on the glass, in a bid to improve its strength for applications such as in the automobile windshield design, consumer electronics mobile communication devices e.g. smartphones and tablet etc. However, failure still occurs which is mostly catastrophic and expensive to repair. Therefore, understanding, predicting and eventually improving the resistance to damage or fracture of chemically strengthened glass is significant to designing new glasses that would be tougher, while retaining their transparency. The relationship between the glass residual stress parameters, compressive stress (CS), depth of layer (DOL), center tension (CT) and fracture strength was investigated in this study using a grit particle blast plus ring on ring test method, based on IEC standard for retained biaxial flexural strength measurements. This technique can be used to measure both the surface and edge fracture strength of the glass. Preliminary results showed that for a reasonable level of CS, and CT, high DOL are beneficial to resisting fracture due to severe surface damage, while a high CS and low CT are beneficial to resisting fractures due to shallower flaws. The correlation of critical stress intensity factor versus DOL and CT for various level of CS were also determined and discussed. These results provide a valuable piece of information in the design of a more robust glass in engineering applications.

Finite element modeling of residual stress profile patterns in hard turning

2009 ◽  
Vol 24 (S1) ◽  
pp. S22-S25
Author(s):  
Y. B. Guo ◽  
S. Anurag
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Hard Turning ◽  
Internal State ◽  
Stress Profile ◽  
Surface Residual Stress ◽  
Mechanical Coupling ◽  
Element Modeling ◽  
Stress Profiles

Hard turning, i.e., turning hardened steels, may produce the unique “hook” shaped residual stress (RS) profile characterized by surface compressive RS and subsurface maximum compressive RS. However, the formation mechanism of the unique RS profile is not yet known. In this study, a novel hybrid finite element modeling approach based on thermal-mechanical coupling and internal state variable plasticity model has been developed to predict the unique RS profile patterns by hard turning AISI 52100 steel (62 HRc). The most important controlling factor for the unique characteristics of residual stress profiles has been identified. The transition of maximum residual stress at the surface to the subsurface has been recovered by controlling the plowed depth. The predicted characteristics of residual stress profiles favorably agree with the measured ones. In addition, friction coefficient only affects the magnitude of surface residual stress but not the basic shape of residual stress profiles.

Surface Modification Analysis after Shot Peening of AA 7075 in Different States

2013 ◽  
Vol 768-769 ◽  
pp. 519-525 ◽  
Author(s):  
Sebastjan Žagar ◽  
Janez Grum
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Residual Stresses ◽  
Aluminium Alloy ◽  
Shot Peening ◽  
Fatigue Testing ◽  
Stress Profile ◽  
Treatment Conditions ◽  
Stress Profiles ◽  
Compressive Residual Stresses

The paper deals with the effect of different shot peening (SP) treatment conditions on the ENAW 7075-T651 aluminium alloy. Suitable residual stress profile increases the applicability and life cycle of mechanical parts, treated by shot peening. The objective of the research was to establish the optimal parameters of the shot peening treatment of the aluminium alloy in different precipitation hardened states with regard to residual stress profiles in dynamic loading. Main deformations and main residual stresses were calculated on the basis of electrical resistance. The resulting residual stress profiles reveal that stresses throughout the thin surface layer of all shot peened specimens are of compressive nature. The differences can be observed in the depth of shot peening and the profile of compressive residual stresses. Under all treatment conditions, the obtained maximum value of compressive residual stress ranges between -200 MPa and -300 MPa at a depth between 250 μm and 300 μm. Comparison of different temperature-hardened aluminium alloys shows that changes in the Almen intensity values have greater effect than coverage in the depth and profile of compressive residual stresses. Positive stress ratio of R=0.1 was selected. Wöhler curves were determined in the areas of maximum bending loads between 30 - 65 % of material's tensile strength, measured at thinner cross-sections of individual specimens. The results of material fatigue testing differ from the level of shot peening on the surface layer.

Study on the SCC Growth of Alloy 182 Under Constant Displacement Condition in High Temperature Oxygenated Water

2004 ◽  
Author(s):  
Shunichi Suzuki ◽  
Katsuhiko Kumagai ◽  
Satoshi Namatame ◽  
Masaaki Kikuchi ◽  
Mikiro Itow ◽  
...  
Keyword(s):  
Residual Stress ◽  
Growth Rates ◽  
Loading Condition ◽  
Growth Behavior ◽  
Stress Profile ◽  
Constant Loading ◽  
Compression Region ◽  
Displacement Condition ◽  
Oxygenated Water ◽  
Constant Displacement

SCC initiates and propagates along the fusion line or in the weld metal in BWR and many SCC initiation & propagation studies have been performed so far (Saito, et al. (1997), Kikuchi, et al. (1997), Itow, et al. (1997, 2000), Suzuki (1999), Namatame, et al. (2001)). SCC growth behavior can be evaluated by conjunction of SCC growth rates and the residual stress of the welded component, which consists of tension/compression region. Especially, thick components such as core shrouds have increasing and decreasing tensile stress profile under constant displacement. In general, SCC growth rates are obtained from CT specimens under constant loading condition. This study shows that SCC growth rates depend on dK/dt as well as on K and that their growth rates under constant displacement with decreasing K are lower than those under constant loading condition with increasing K.

scholarly journals Influence of residual stress profile and surface microstructure on fatigue life of a 15-5PH

2018 ◽  
Vol 213 ◽  
pp. 623-629 ◽  
Author(s):  
F. Valiorgue ◽  
V. Zmelty ◽  
M. Dumas ◽  
V. Chomienne ◽  
C. Verdu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Surface Microstructure ◽  
Stress Profile ◽  
Residual Stress Profile

scholarly journals Cross-Sectional Mapping of Residual Stresses by Measuring the Surface Contour After a Cut

2000 ◽  
Vol 123 (2) ◽  
pp. 162-168 ◽  
Author(s):  
M. B. Prime
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Superposition Principle ◽  
New Method ◽  
Contour Method ◽  
Stress Profile ◽  
Relaxation Methods ◽  
Cross Sectional ◽  
Residual Stress Profile

A powerful new method for residual stress measurement is presented. A part is cut in two, and the contour, or profile, of the resulting new surface is measured to determine the displacements caused by release of the residual stresses. Analytically, for example using a finite element model, the opposite of the measured contour is applied to the surface as a displacement boundary condition. By Bueckner’s superposition principle, this calculation gives the original residual stresses normal to the plane of the cut. This “contour method” is more powerful than other relaxation methods because it can determine an arbitrary cross-sectional area map of residual stress, yet more simple because the stresses can be determined directly from the data without a tedious inversion technique. The new method is verified with a numerical simulation, then experimentally validated on a steel beam with a known residual stress profile.

Quantitative Infrared Photoelasticity of Silicon Photovoltaic Wafers Using a Discrete Dislocation Model

2015 ◽  
Vol 82 (1) ◽  
Author(s):  
T.-W. Lin ◽  
G. P. Horn ◽  
H. T. Johnson
Keyword(s):  
Residual Stress ◽  
Numerical Modeling ◽  
Strain Energy ◽  
Dislocation Model ◽  
Slip Systems ◽  
Inspection Method ◽  
Crystalline Defects ◽  
Discrete Dislocation ◽  
Stress Mapping ◽  
And Performance

Residual stress and crystalline defects in silicon wafers can affect solar cell reliability and performance. Infrared photoelastic measurements are performed for stress mapping in monocrystalline silicon photovoltaic (PV) wafers and compared to photoluminescence (PL) measurements. The wafer stresses are then quantified using a discrete dislocation-based numerical modeling approach, which leads to simulated photoelastic images. The model accounts for wafer stress relaxation due to dislocation structures. The wafer strain energy is then analyzed with respect to the orientation of the dislocation structures. The simulation shows that particular locations on the wafer have only limited slip systems that reduce the wafer strain energy. Experimentally observed dislocation structures are consistent with these observations from the analysis, forming the basis for a more quantitative infrared photoelasticity-based inspection method.

Study of Effect of Repetition Rate on Laser Shock Peening Using Finite Element Modeling

2020 ◽  
Author(s):  
Sai Kosaraju ◽  
Xin Zhao
Keyword(s):  
Shock Wave ◽  
Residual Stress ◽  
Finite Element ◽  
Shock Waves ◽  
Repetition Rate ◽  
High Repetition Rate ◽  
Stress Profile ◽  
Surface Residual Stress ◽  
Residual Stress Profile ◽  
High Repetition

Abstract A two-dimensional finite element model is developed to simulate the interaction between metal samples and laser-induced shock waves. Multiple laser impacts are applied at each location to increase plastically affected depth and compressive stress. The in-depth and surface residual stress profiles are analyzed at various repetition rates and spot sizes. It is found that the residual stress is not sensitive to repetition rate until it reaches a very high level. At extremely high repetition rate (100 MHz), the delay between two shock waves is even shorter than their duration, and there will be shock wave superposition. It is revealed that the interaction of metal with shock wave is significantly different, leading to a different residual stress profile. Stronger residual stress with deeper distribution will be obtained comparing with lower repetition rate cases. The effect of repetition rate at different spot sizes is also studied. It is found that with larger laser spot, the peak compressive residual stress decreases but the distribution is deeper at extremely high repetition rates.

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