MODEL INVESTIGATION OF EXPLOSIONS IN PRESTRESSED MEDIA

Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 633-651 ◽  
Author(s):  
W. H. Kim ◽  
C. Kisslinger
Keyword(s):  
Stress Field ◽  
Energy Release ◽  
Strain Energy ◽  
Strain Energy Release ◽  
Direct Consequence ◽  
Rupture Propagation ◽  
S Wave ◽  
Elastic Zone ◽  
Radiation Fields ◽  
Aluminum Sheets

Seismic effects of explosions and rupture propagation in prestressed two‐dimensional models (Plexiglas, aluminum) as well as anisotropy produced by the stress field are investigated. An explosion in a prestressed medium releases a portion of the stored strain energy by one or more of the following mechanisms: (1) formation of directional cracking, especially in brittle materials, (2) release of strain energy in the elastic zone outside the cavity, and (3) rupture propagation. Phenomena associated with all of these mechanisms were observed in the present investigation. Explosions in prestressed Plexiglas produce cracks in preferred directions, the intensity of which increases with the applied stress. Explosions in prestressed aluminum sheets do not cause fracturing but rather plastic deformation about the explosion. Straight and branching modes of moving cracks initiated from explosions in prestressed Plexiglas can be explained on the basis of stress distribution ahead of the crack tips. Observed radiation patterns resulting from explosions in prestressed media indicate asymmetrical radiation fields which are a direct consequence of strain energy release for the case of aluminum and by the combined effects of directional cracking and energy release in the elastic zone for the case of Plexiglas. Explosions in prestressed media generate shear waves. The observed S‐wave magnitude increases sharply with the level of the existing stress field for a given amount of strain energy release. It is concluded that this phenomenon is attributable to the effective conversion of energy release to seismic radiation at high ambient stress fields. In other words, the effectiveness of S‐wave generation is governed by the rapidity with which the existing strain energy is released. A definite anisotropy effect was observed in prestressed models, but this effect is not large enough to affect wave propagation in the range of the tensile loads applied.

Influence of Ply Sequence and Thermoelastic Stress Field on Asymmetric Delamination Growth Behavior Emanating From Elliptical Holes in Laminated FRP Composites

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Brajabandhu Pradhan ◽  
Poosa Ramesh Babu
Keyword(s):  
Stress Field ◽  
Energy Release ◽  
Strain Energy ◽  
Thermoelastic Stress ◽  
Strain Energy Release ◽  
Growth Behavior ◽  
Delamination Growth ◽  
Elliptical Holes ◽  
Delamination Front ◽  
Thermoelastic Stress Field

The present study encompasses the influence of ply sequence and thermoelastic stress field on asymmetric delamination growth behavior emanating from elliptical holes in laminated fiber reinforced polymeric composites. Results, emphasizing the effect of thermal residual stresses on delamination growth behavior of the composite laminates subjected to two different loading conditions, i.e., in-plane tensile and compressive loadings, are presented. Two sets of full three-dimensional finite element analyses have been performed to calculate the displacements and interlaminar stresses along the delaminated interfaces responsible for the delamination onset and propagation. Modified crack closure integral methods based on the concepts of linear elastic fracture mechanics have been followed to evaluate the individual modes of strain energy release rates along the delamination front. In each case, the delamination is embedded at a different depth along the thickness direction of the laminates. It is observed that the fiber orientation of the plies bounding the delamination front significantly influences the distribution of the local strain energy release rate. Also, the residual thermal stresses have a detrimental effect on the laminates subjected to compressive loading and more so in the case of laminates with delaminations existing closer to the top and bottom surfaces of the laminate.

On the Axial Rigidity of a Perforated Strip and the Strain Energy Release Rate in a Centrally Notched Strip Subjected to Uniaxial Tension

1964 ◽  
Vol 86 (4) ◽  
pp. 693-697 ◽  
Author(s):  
R. G. Forman ◽  
A. S. Kobayashi
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Uniaxial Tension ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Theoretical Studies ◽  
Correction Factors ◽  
Elasticity Solutions

This paper presents theoretical studies on the axial rigidities in strips with circular and elliptical perforations and subjected to uniaxial tension. Greenspan’s original derivations on these axial rigidities [2] were improved by using the elasticity solutions by Howland [6] and Ishida [7] for infinite strips with circular and elliptical perforations, respectively. Finally, the correction factors for centrally notched strips subjected to uniaxial tension were rederived from the above results following the energy approach by Irwin and Kies [3].

Nonlinear Approach for Strain Energy Release Rate in Micro Cantilevers

2010 ◽  
Author(s):  
Arash Kheyraddini Mousavi ◽  
Seyedhamidreza Alaie ◽  
Maheshwar R. Kashamolla ◽  
Zayd Chad Leseman
Keyword(s):  
Surface Roughness ◽  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Rigid Substrate ◽  
Micro Cantilever

An analytical Mixed Mode I & II crack propagation model is used to analyze the experimental results of stiction failed micro cantilevers on a rigid substrate and to determine the critical strain energy release rate (adhesion energy). Using nonlinear beam deflection theory, the shape of the beam being peeled off of a rigid substrate can be accurately modeled. Results show that the model can fit the experimental data with an average root mean square error of less than 5 ran even at relatively large deflections which happens in some MEMS applications. The effects of surface roughness and/or debris are also explored and contrasted with perfectly (atomically) flat surfaces. Herein it is shown that unlike the macro-scale crack propagation tests, the surface roughness and debris trapped between the micro cantilever and the substrate can drastically effect the energy associated with creating unit new surface areas and also leads to some interesting phenomena. The polysilicon micro cantilever samples used, were fabricated by SUMMIT V™ technology in Sandia National Laboratories and were 1000 μm long, 30 μm wide and 2.6 μm thick.

Influence of Loading History on Delamination in Multilayered Beam with Creep

2021 ◽  
Vol 1046 ◽  
pp. 23-28
Author(s):  
Victor Iliev Rizov
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Time Dependent ◽  
External Loading ◽  
Loading History ◽  
Multilayered Beam

The present paper deals with an analytical study of the time-dependent delamination in a multilayered inhomogeneous cantilever beam with considering of the loading history. The multilayered beam exhibits creep behaviour that is treated by using a non-linear stress-strain-time relationship. The material properties are continuously distributed along the thickness and length of the layers. The external loading is applied in steps in order to describe the loading history. The analysis reveals that during each step of the loading, the strain energy release rate increases with time. The influences of crack length and location on the time-dependent strain energy release rate are also investigated.

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