The role of moisture diffusion and matrix plasticisation on the environmental stress corrosion of grp

1989 ◽  
Vol 24 (4) ◽  
pp. 223-233 ◽  
Author(s):  
F R Jones
Keyword(s):  
Fracture Mechanics ◽  
Environmental Stress ◽  
Stress Corrosion ◽  
Fibre Composite ◽  
Moisture Diffusion ◽  
Compact Tension ◽  
Acoustic Microscopy ◽  
Two Phase ◽  
Controlled Fracture ◽  
Crack Blunting

An environmental stress corrosion limit can be postulated from the results of a fracture mechanics study of an E-glass fibre composite fabricated from an isophthalic polyester resin. Both the rates of nucleation and crack growth indicated a diffusion controlled fracture mechanics mechanism. The fracture processes in the resin have been quantified using compact tension specimens. The effect of moisture on the values of K1ci and K1ca for crack initiation and arrest for the completely dried resin has demonstrated how the crack blunting processes occur. The moisture diffusion into the resin is characterised by a two-phase microstructure, which has been confirmed by scanning acoustic microscopy. A mechanism which involves a non-uniform stress distribution between the phases, has been developed. The proposed hypothesis may also explain the mechanism of microcavitation required for the transport of acidic environments through stressed resins as reported by Caddock et al. (7).

UNILOY 326

Alloy Digest ◽  
1970 ◽  
Vol 19 (7) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Physical Properties ◽  
Stress Corrosion ◽  
Tensile Properties ◽  
High Strength ◽  
Heat Treating ◽  
Distinct Advantage ◽  
Two Phase ◽  
Stress Corrosion Resistance

Abstract UNILOY 326 is a two-phase, ferromagnetic stainless steel characterized by high strength and very good general and stress corrosion resistance. It has distinct advantage for the fastener industry. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-241. Producer or source: Cyclops.

Interfacial Delamination in Plastic Encapsulated Integrated Circuits (Pics)

1996 ◽  
Vol 445 ◽  
Author(s):  
Nickolaos Strifas ◽  
Aris Christou
Keyword(s):  
Integrated Circuits ◽  
Failure Analysis ◽  
Stress Corrosion ◽  
Integrated Circuit ◽  
Point Of View ◽  
Acoustic Microscopy ◽  
Electrical Performance ◽  
Premature Failure ◽  
Interfacial Delamination ◽  
Die Surface

AbstractThe reliability of plastic packaged integrated circuits was assessed from the point of view of interfacial mechanical integrity. It is shown that the effect of structural weaknesses caused by poor bonding, voids, microcracks or delamination may not be evident in the electrical performance characteristics, but may cause premature failure. Acoustic microscopy (C-SAM) was selected for nondestructive failure analysis of the plastic integrated circuit (IC) packages. Integrated circuits in plastic dual in line packages were initially subjected to temperature (25 °C to 85 °C) and humidity cycling (50 to 85 %) where each cycle was of one hour duration and for over 100 cycles and then analyzed. Delamination at the interfaces between the different materials within the package, which is a major cause of moisture ingress and subsequent premature package failure, was measured. The principal areas of delamination were found along the leads extending from the chip to the edge of the molded body and along the die surface itself. Images of the 3-D internal structure were produced that were used to determine the mechanism for a package failure. The evidence of corrosion and stress corrosion cracks in the regions of delamination was identified.

Strategies for Treating Weld Residual Stresses in Probabilistic Fracture Mechanics Codes

2011 ◽  
Author(s):  
Frederick W. Brust ◽  
R. E. Kurth ◽  
D. J. Shim ◽  
David Rudland
Keyword(s):  
Fracture Mechanics ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Degradation Mechanism ◽  
Welding Process ◽  
Corrosion Cracking ◽  
Uncertainty Sources

Risk based treatment of degradation and fracture in nuclear power plants has emerged as an important topic in recent years. One degradation mechanism of concern is stress corrosion cracking. Stress corrosion cracking is strongly driven by the weld residual stresses (WRS) which develop in nozzles and piping from the welding process. The weld residual stresses can have a large uncertainty associated with them. This uncertainty is caused by many sources including material property variations of base and welds metal, weld sequencing, weld repairs, weld process method, and heat inputs. Moreover, often mitigation procedures are used to correct a problem in an existing plant, which also leads to uncertainty in the WRS fields. The WRS fields are often input to probabilistic codes from weld modeling analyses. Thus another source of uncertainty is represented by the accuracy of the predictions compared with a limited set of measurements. Within the framework of a probabilistic degradation and fracture mechanics code these uncertainties must all be accounted for properly. Here we summarize several possibilities for properly accounting for the uncertainty inherent in the WRS fields. Several examples are shown which illustrate ranges where these treatments work well and ranges where improvement is needed. In addition, we propose a new method for consideration. This method consists of including the uncertainty sources within the WRS fields and tabulating them within tables which are then sampled during the probabilistic realization. Several variations of this process are also discussed. Several examples illustrating the procedures are presented.

Stress Corrosion Cracking Behavior of Uranium Alloys

CORROSION ◽  
1974 ◽  
Vol 30 (5) ◽  
pp. 181-189 ◽  
Author(s):  
W. F. CZYRKLIS ◽  
M. LEVY
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Threshold Stress ◽  
Crack Extension ◽  
Corrosion Cracking ◽  
Nacl Solution ◽  
Cracking Behavior ◽  
Linear Elastic ◽  
Elastic Fracture

Abstract The stress corrosion cracking (SCC) behavior of U-3/4% Ti, and uranium alloys 3/4% Quad, 1% Quad, and 1% Quint have been studied utilizing a linear elastic fracture mechanics approach. The threshold stress intensities for stress corrosion crack propagation for these alloys have been determined in distilled H2O and NaCl solutions containing 50 ppm Cl− and 21,000 ppm Cl−. All of the alloys studied may be classified as very susceptible to SCC in aqueous solutions since they exhibit SCC in distilled H2O (<1 ppm Cl−) and have low KIscc values in NaCl solutions. Crack extension in all of the alloys in all environments was transgranular and failure occurred by brittle quasicleavage fracture in NaCl solution.

Crack Propagation Simulation: A Local Deformation-Based Mesh Mapping Method for Crack Modeling and a Direct Method for Residual Stress Representation in Welds

2011 ◽  
Author(s):  
Heqin Xu ◽  
Samer Mahmoud ◽  
Ashok Nana ◽  
Doug Killian
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Crack Front ◽  
Direct Method ◽  
Local Deformation ◽  
Front Shape ◽  
A Direct Method ◽  
Mesh Mapping

Cracks found in a nuclear power plant reactor coolant system (RCS), such as primary water stress corrosion cracking (PWSCC) and intergranular stress corrosion cracking (IGSCC), usually have natural crack front shapes that can be very different from the idealized semi-elliptical or rectangular shapes considered in engineering handbooks and other analytical solutions based on limited shapes. Simplifications towards semi-elliptical shape or rectangular shape may potentially introduce unnecessary conservatism when the simplified shape has to contain the actual crack shape. On the other hand, it is very time-consuming to create a three-dimensional (3D) finite element (FE) model to simulate crack propagation in a natural shape using existing public-domain software like ABAQUS or ANSYS. In this study, a local deformation-based mesh-mapping (LDMM) method is proposed to model cracks with a natural front shape in any 3D structures. This methodology is first applied to model circumferential surface cracks with a natural crack front shape in the cross-sectional plane of a cylinder. The proposed new method can be applied to simulate both shallow and deep cracks. Also discussed in this paper is a direct method to reproduce welding residual stresses in the crack model using temperature fields combined with other sustained loads to predict crack propagations. With this novel LDMM method, natural crack fronts and non-planar crack faces can be easily modeled. The proposed new method can be used to generate a high-quality finite element model that can be used for both linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) analyses. The study case illustrates that the proposed LDMM method is easy to implement and more efficient than the existing commercial software.

scholarly journals Stress corrosion cracking of two-phase (.ALPHA./.BETA.)-brass bicrystals.

1985 ◽  
Vol 34 (384) ◽  
pp. 1051-1056
Author(s):  
Takuro MIMAKI ◽  
Nobuo UEDA ◽  
Satoshi HASHIMOTO ◽  
Sei MIURA
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Two Phase ◽  
Alpha Beta

Experimental evaluation of fracture properties of bovine hip cortical bone using elastic–plastic fracture mechanics

2021 ◽  
pp. 1-10
Author(s):  
Waseem Ur Rahman ◽  
Rafiullah khan ◽  
Noor Rahman ◽  
Ziyad Awadh Alrowaili ◽  
Baseerat Bibi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Cortical Bone ◽  
Elastic Deformation ◽  
Compact Tension ◽  
J Integral ◽  
Elastic Plastic ◽  
American Society ◽  
Fracture Specimens

BACKGROUND: Understanding the fracture mechanics of bone is very important in both the medical and bioengineering field. Bone is a hierarchical natural composite material of nanoscale collagen fibers and inorganic material. OBJECTIVE: This study investigates and presents the fracture toughness of bovine cortical bone by using elastic plastic fracture mechanics. METHODS: The J-integral was used as a parameter to calculate the energies utilized in both elastic deformation (Jel) and plastic deformation (Jpl) of the hipbone fracture. Twenty four different types of specimens, i.e. longitudinal compact tension (CT) specimens, transverse CT specimens, and also rectangular unnotched specimens for tension in longitudinal and transverse orientation, were cut from the bovine hip bone of the middle diaphysis. All CT specimens were prepared according to the American Society for Testing and Materials (ASTM) E1820 standard and were tested at room temperature. RESULTS: The results showed that the average total J-integral in transverse CT fracture specimens is 26% greater than that of longitudinal CT fracture specimens. For longitudinal-fractured and transverse-fractured cortical specimens, the energy used in the elastic deformation was found to be 2.8–3 times less than the energy used in the plastic deformation. CONCLUSION: The findings indicate that the overall fracture toughness measured using the J-integral is significantly higher than the toughness calculated by the stress intensity factor. Therefore, J-integral should be employ to compute the fracture toughness of cortical bone.

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