Theoretical stress concentration factors for short flat bars with opposite U-shaped notches subjected to in-plane bending

Troyani, Nando; Hernández, S. I.; Villarroel, G.; Pollonais, Y.; Gomes, Carlos J.

doi:10.1016/j.ijfatigue.2004.04.007

Cited by 19 publications

(8 citation statements)

References 9 publications

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“…Although extensive analytical and experimental studies focused on the determination of the SCFs of cylindrical shells, plates, and round bars with periodic notches or grooves [ 22 , 23 , 24 ], most were restricted to static or quasi-static scenarios. Such approaches may not be able to determine the SCFs of materials that undergo large deformations and high strain rate, such as warhead explosions and hypervelocity impacts.…”

Section: Numerical Simulationmentioning

confidence: 99%

Dynamic Disintegration of Explosively-Driven Metal Cylinder with Internal V-Grooves

Zhou

Wan

et al. 2021

Materials

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Machining V-shaped grooves to the internal surface of cylindrical shells is one of the most common technologies of controlled fragmentation for improving warhead lethality against targets. The fracture strain of grooved shells is a significant concern in warhead design. However, there is as yet no reasonable theory for predicting the fracture strain of a specific grooved shell; existing approaches are only able to predict this physical regularity of non-grooved shells. In this paper, through theoretical analysis and numerical simulations, a new model was established to study the fracture strain of explosively driven cylindrical shells with internal longitudinal V-grooves. The model was built based on an energy conservation equation in which the energy consumed to create a new fracture surface in non-grooved shells was provided by the elastic deformation energy stored in shells. We modified the energy approach so that it can be applicable to grooved shells by adding the elastic energy liberated for crack penetration and reducing the required fracture energy. Cylinders with different groove geometric parameters were explosively expanded to the point of disintegration to verify the proposed model. Theoretical predictions of fracture strain showed good agreement with experimental results, indicating that the model is suitable for predicting the fracture strain of explosively driven metal cylinders with internal V-grooves. In addition, this study provides an insight into the mechanism whereby geometric defects promote fracturing.

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Section: Numerical Simulationmentioning

confidence: 99%

Dynamic Disintegration of Explosively-Driven Metal Cylinder with Internal V-Grooves

Zhou

Wan

et al. 2021

Materials

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“…Troyani et al, (Troyani 2004) investigated the effect on SCF of varying low ratios of beam length (L) to plate thickness, (H). Often SCF graphs presented in books and journals do not include the "L/H" ratio because the graphs were either derived theoretically with the assumption that L was much larger than H, or derived empirically with specimens that had long L to H ratios.…”

Section: Strength Testingmentioning

confidence: 99%

Die Separation Strength for Deep Reactive Ion Etched Wafers

Porter

2011

Conference Proceedings of the Society for Experimental Mechanics Series

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In the electronic and microfabrication industry, die separation is one of the most critical steps in producing an undamaged, stand-alone micro-scale device. For silicon based devices, it is the predominant step governing resistance to die failure by mechanical fracture. Traditional separation methods include the use of dicing saws and/or backside grinding to dice-by-thinning. Excessive forces, vibrations, and surface contact involved with these methods can cause undesirable side-wall chipping and microcracking, which often translates to inoperable devices. Deep Reactive Ion Etching (DRIE) offers an alternative technique for die separation with less mechanical force. The DRIE process may be used to either introduce notches in one uniform step that allow for die separation via fracture in three-point bending, or to directly separate the dies by etching completely through the substrate. This work presents an analysis of the stress concentrations due to DRIE etched notches and the bending stress required to achieve die separation. The defect rate and die strength associated with DRIE-based die separated is compared with traditional saw methods for a variety of notch depths. Results indicate that the DRIE-based separation technique offers modest advantages over the traditional methods, but can also greatly reduce strength if the protective mask is over etched. It will also show that shallow trenches formed by a mechanical dicing saw resulted in stronger die than deeper trenches. vi TABLE OF CONTENTS

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“…It is extremely difficult to take account of this phenomenon in strength computations, especially while using analytical solutions expected to comprise its 3D nature, a complicated shape of the notch, and the effect of boundary conditions. Determination of actual stress and strain levels in the region of fatigue crack initiation would considerably facilitate interpretation of phenomena that go together with the process, and often affords any description of fatigue cracking of tested members with stress concentrators in the form of suitably cut crack initiator [5][6][7][8]. Application of a numerical method offers a chance to find some approximate solution to the above-described problem, however, with some limitations.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Theoretical Investigations of Fatigue Crack Growth in D16 Alloy

Śnieżek

2009

Fatigue of Aircraft Structures

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Experimental and Theoretical Investigations of Fatigue Crack Growth in D16 AlloyIn this work the arising and development of fatigue crack in aluminium alloy D16, taking into consideration the influence of notch in the form of hole with incisions which were done on its sides were tested. The process of working out of tests' programme was preceded by numeric analysis of stresses pattern and strains distribution in the zone of notch's influence which was focused on determination of stresses' face values. To examine stress and strain distributions, the specialised FEM software (MSC. Patran and MSC. Nastran) was applied. Findings have been presented in the form of a statement of σmax and εmax values, and functions of the following factors: aσ, aε, and ak, computed on the grounds of these values for both different distances from the bottom of the notch and assumed levels of loading the specimens. Theoretical analysis has been supplemented with experimental investigation into the microstructure of fatigue-fracture surfaces in the area of crack initiation and that of fatigue of a propagating crack. The paper has been intended to present a model of the probabilistic estimation of fatigue life of structural members. The model has been based on the deterministic description of the cracking. Analyzed were components with notches in the form of centrally located holes with side cuts. In the method of probabilistically approaching the crack propagation, some dependences have been used that take account of the presence of areas showing plastic strains in front of crack tips. It has been assumed that the cracking can be modeled on the grounds of some general-purpose quantity used to describe the energy state in the area of the crack tip, i.e. the Rice's integral (J). The formulated computational model has been used to estimate fatigue life of model components made of D16 alloy. Experimental work was carried out using some flat specimens with centrally positioned holes. They were exposed to flat bending at R = 0. Analytical and experimental results have shown pretty good conformity.

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Theoretical stress concentration factors for short flat bars with opposite U-shaped notches subjected to in-plane bending

Cited by 19 publications

References 9 publications

Dynamic Disintegration of Explosively-Driven Metal Cylinder with Internal V-Grooves

Dynamic Disintegration of Explosively-Driven Metal Cylinder with Internal V-Grooves

Die Separation Strength for Deep Reactive Ion Etched Wafers

Experimental and Theoretical Investigations of Fatigue Crack Growth in D16 Alloy

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