scholarly journals Failure mechanisms for internally pressurized thin-wall tubes and their relationship to fuel-element failure criteria.

1972 ◽  
Author(s):  
F.L. Yaggee ◽  
C.Y. Li
Keyword(s):  
Fuel Element ◽  
Failure Mechanisms ◽  
Failure Criteria ◽  
Thin Wall ◽  
Element Failure

Finite Element Analysis of X-Cor Sandwich's Compressive Strength

2011 ◽  
Vol 306-307 ◽  
pp. 733-737
Author(s):  
Xu Dan Dang ◽  
Xin Li Wang ◽  
Hong Song Zhang ◽  
Jun Xiao
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compressive Strength ◽  
Failure Modes ◽  
Failure Mechanisms ◽  
Element Model ◽  
Failure Criteria ◽  
Stiffness Degradation ◽  
Element Analysis ◽  
Finite Element Software

In this article the finite element software was used to analyse the values for compressive strength of X-cor sandwich. During the analysis, the failure criteria and materials stiffness degradation rules of failure mechanisms were proposed. The failure processes and failure modes were also clarified. In the finite element model we used the distributions of failure elements to simulate the failure processes. Meanwhile the failure mechanisms of X-cor sandwich were explained. The finite element analysis indicates that the resin regions of Z-pin tips fail firstly and the Z-pins fail secondly. The dominant failure mode is the Z-pin elastic buckling and the propagation paths of failure elements are dispersive. Through contrast the finite element values and test results are consistent well and the error range is -7.6%~9.5%. Therefore the failure criteria and stiffness degradation rules are reasonable and the model can be used to predict the compressive strength of X-cor sandwich.

Assessment of contact-induced damage mechanisms in thick-walled composite cylinders

2020 ◽  
Vol 39 (17-18) ◽  
pp. 679-699
Author(s):  
Ruben AJ Weerts ◽  
Olivier Cousigné ◽  
Klaas Kunze ◽  
Marc GD Geers ◽  
Joris JC Remmers
Keyword(s):  
Damage Tolerance ◽  
Numerical Study ◽  
Failure Mechanisms ◽  
Pressure Vessels ◽  
Thick Wall ◽  
Thin Wall ◽  
Fiber Failure ◽  
Damage Mechanisms ◽  
Filament Wound ◽  
Composite Cylinders

In order to unravel the damage mechanisms occurring in composite-overwrapped pressure vessels (COPVs) subjected to crash conditions, a combined experimental-numerical study has been performed. For the purpose of generality and simplicity, quasi-static contacts on filament-wound cylinders are considered in this paper, as a precursor for geometrically complex impacts on COPVs. Rings with different wall thicknesses are tested to assess how failure mechanisms change when transitioning from thin-wall to thick-wall cylinders. The experimental results are used to identify, which mechanisms occur, and the numerical model is subsequently exploited to analyze the corresponding mechanisms. Based on the understanding of the mechanisms, a method to improve the damage tolerance of thick cylinders is presented. The rings are locally pre-delaminated during manufacturing to promote the growth of these pre-delaminations instead of the initiation of fiber failure.

Failure Mechanisms on Exhaust Systems of Naval Gas Turbines

2008 ◽  
Vol 587-588 ◽  
pp. 946-950 ◽  
Author(s):  
Rui F. Martins ◽  
Carlos M. Branco ◽  
António M. Gonçalves-Coelho ◽  
Edgar C. Gomes
Keyword(s):  
Crack Propagation ◽  
Gas Turbines ◽  
Failure Mechanisms ◽  
Plate Thickness ◽  
Exhaust System ◽  
System Structure ◽  
Surface Finishing ◽  
Thin Wall ◽  
Welding Processes ◽  
Exhaust Systems

Some exhaust systems of naval gas turbines have been periodically repaired due to thermal-fatigue crack propagation after entering into service. Those structures were made of austenitic stainless steel grade AISI 316L in thin wall plates, which were bent in rolling machines and welded with longitudinal and circumferential joints by means of shielded metal arc, TIG or MIG/MAG welding processes. The plate thickness is about 3.7 mm and the temperature on the exhaust system is approximately 500°C and 350°C in the critical zones, which are located in the lower and intermediate regions of the exhaust system.Several cracks were detected at the critical regions, near the weld toe of butt and T-welded joints. The stress concentration factors induced by the weld angle, toe radius and rolled surface finishing diminishes the fatigue life strength. Some cracked material samples were taken out from the exhaust system structure and were analysed with a Scanning Electron Microscope (SEM/EDS), in order to determine the failure mechanisms involved in the crack propagation process. Those results are presented in the paper. Several high temperature fatigue and creep tests were performed with CT specimens. The mechanisms of crack propagation on the CT specimens were studied by SEM and compared with the fracture surfaces obtained from the samples taken out from the structure. The carbide precipitation on the grain boundaries was also studied.

Failure Prediction for Textile Composites Via Micromechanics

Materials ◽  
2003 ◽  
Author(s):  
Brian Cox ◽  
Qingda Yang
Keyword(s):  
Single Point ◽  
Failure Mechanisms ◽  
Material Constant ◽  
Local Stress ◽  
Failure Criteria ◽  
Textile Composites ◽  
Local Damage ◽  
Stress Components ◽  
Definition Of ◽  
2D And 3D

The question of failure criteria for textile composites is taken up, with reference to the micormechanics of known failure mechanisms in broad classes of 2D and 3D textile composites. Of primary importance is the definition of the measure of local stress or strain that should be compared against a putative material constant to predict local damage. In most prior work, some combination of strain or stress components evaluated at a single point has been used. Due to the complexity and inevitahle irregularity of textile composites, this approach is not favoured. Instead, micromechanical considreations recommend using strains averaged over gauge volumes whose dimensions are greater than or equal to approximately half the width dimensions of a single tow. Engineering tests that can be used for calibration are suggested but remain to be proven repeatable and consistent.

Thermal-hydraulics analysis during fuel element failure in an operating PWR

2015 ◽  
Vol 85 ◽  
pp. 694-700 ◽  
Author(s):  
Wenzhen Chen ◽  
Lei Yang ◽  
Hongguang Xiao ◽  
Zhiyun Chen
Keyword(s):  
Fuel Element ◽  
Thermal Hydraulics ◽  
Element Failure

γ-Ray spectral analysis method for real-time detection of fuel element failure

2019 ◽  
Vol 133 ◽  
pp. 221-226 ◽  
Author(s):  
Guoxiu Qin ◽  
Qimin Wang ◽  
Youning Xu ◽  
Xilin Chen ◽  
Fan Li ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Fuel Element ◽  
Real Time ◽  
Analysis Method ◽  
Spectral Analysis Method ◽  
Element Failure ◽  
Γ Ray ◽  
Real Time Detection

Application of a multisurface discrete crack model for clear wood taking into account the inherent microstructural characteristics of wood cells

Holzforschung ◽  
2016 ◽  
Vol 70 (9) ◽  
pp. 845-853 ◽  
Author(s):  
Markus Lukacevic ◽  
Josef Füssl
Keyword(s):  
Building Materials ◽  
Load Capacity ◽  
Failure Mechanisms ◽  
Failure Criteria ◽  
Failure Behavior ◽  
Crack Model ◽  
Clear Wood ◽  
Discrete Crack ◽  
Splitting Test ◽  
Definition Of

Abstract A more accurate prediction of the mechanical behavior of wood is needed to increase its ability to compete with other building materials. Especially, when it comes to estimate failure loads, the lack of appropriate prediction tools becomes obvious. The present work contributes to this goal in two different ways: First, a damage concept for wood is revisited, which allows for transferring information about failure processes through different scales of observation. In this concept, the failure behavior of clear wood is linked to the different characteristic of earlywood and latewood layers in softwoods. This reduces the number of empirically determined strength parameters, while the definition of multisurface failure criteria is still possible. Secondly, it will be demonstrated that the combination of these models with discrete crack modeling based on the extended finite element method provides a numerical simulation tool capable to describe failure mechanisms more realistically than existing approaches. The results obtained by numerical calculations and experiments by means of a micro wedge splitting test show very good agreement, especially, if the load capacity and failure mechanisms are in focus. The presented approach shows a much better performance compared to linear elastic or elastoplastic simulations.

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