Assessment of Notches in Ceramic Components

1995 ◽  
Vol 117 (3) ◽  
pp. 413-416 ◽  
Author(s):  
A. Bru¨ckner-Foit ◽  
A. Heger ◽  
D. Munz
Keyword(s):  
Stress Concentration ◽  
Failure Probability ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Notch Root ◽  
Stress Gradient ◽  
Ceramic Components ◽  
Weibull Theory

The failure probability of notched tensile bars is calculated using the multi-axial Weibull theory. The influence exerted by the stress concentration factor, the stress gradient in the notch root, and the Weibull exponent is analyzed.

scholarly journals Assessment of Notches in Ceramic Components

1994 ◽  
Author(s):  
A. Brückner-Foit ◽  
A. Heger ◽  
D. Munz
Keyword(s):  
Stress Concentration ◽  
Failure Probability ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Notch Root ◽  
Stress Gradient ◽  
Ceramic Components ◽  
Weibull Theory

The failure probability of notched tensile bars is calculated using the multiaxial Weibull theory. The influence exerted by the stress concentration factor, the stress gradient in the notch root, and the Weibull exponent is analysed.

Elastic Stress Concentration Factors (Kt) by Stress Gradient Method Using FEA

1996 ◽  
Author(s):  
Ajay Garg ◽  
Ravi Tetambe
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Maximum Stress ◽  
Elastic Stress ◽  
Stress Gradient ◽  
Nominal Stress ◽  
Element Analysis

Abstract The elastic stress concentration factor, Kt, is critical in determining the life of machines, especially in the case of notched components experiencing high cycle fatigue. This Kt is defined as the ratio of the maximum stress (σmax) at the notch to the nominal stress (σnom) in the region away from the notch effect. For simple geometries such as, plate with a hole, calculation of Kt from either closed form solution or from making simple but valid assumptions is possible [1,2]. However, for complex machine components such data is usually not available in the literature. Using Kt values from the simple geometries may lead to either over or under estimation of the real Kt for such complex geometries. Such error can then further lead to a substandard product or a product which is overdesigned and expensive. Present paper outlines a methodology for computing reasonably accurate elastic stress concentration factor, Kt, using finite element analysis (FEA) tool. The maximum stress (σmax) is readily available from the finite element analysis. The nominal stress (σnom) near the stress concentration is however can not be directly extracted from the FEA results. A novel approach of estimating reasonably accurate σnom is presented in this paper. This approach is based on selecting the correct path at the stress concentration region, post processing the stress and the stress gradient results along that path and identifying the cut of point where stress concentration effect begins to take place. This methodology is first validated using two examples with known Kt and later applied to a real world problem.

Notcheffect on J and Amplification of Anisotropic Stress Concentration Factor in a Laminated Plate Subjected to Tensile Load

2015 ◽  
Vol 1105 ◽  
pp. 381-385
Author(s):  
Djamel Ouinas ◽  
Bel Abbès Bachir Bouiadjra ◽  
A. Albedah ◽  
Mohamed Sahnoun
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fibre Orientation ◽  
Notch Root ◽  
Tensile Load ◽  
Homogeneous Material ◽  
Laminated Plate ◽  
Stress Concentrations ◽  
Anisotropic Stress

Several analytical, numerical and experimental techniques are available to study the stress concentration around the notches. The stress distribution in a rectangular composite laminated plate with a central notch was studied using the finite element method. The objective of this study is to analyze the fibre orientation effect on the variation of stress concentrations at the notch root and the J-integral at the crack-tip emanating from this notch in a plate subjected to tensile loading. The results show that the anisotropic stress concentration factor can be higher or lower than that of a homogeneous material. The area of maximum normal and tangential stresses could shift with fibre orientation with respect to the loading axis. The interaction effect between a crack located on the ligament of the plate and the circular notch of radius is considered.The results indicate that fold sequence influences appreciably the acceleration or the retardation of the crack propagation.

Practical Criterion for Estimation of Notch Fatigue Strength: Fatigue Diagrams and Material-Dependency of Notch Effects

2005 ◽  
Author(s):  
Hiroshi Matsuno ◽  
Yoshihiko Mukai
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Stress Ratio ◽  
Notch Root ◽  
Equivalent Stress ◽  
Reduction Factor ◽  
Strength Reduction Factor ◽  
Fatigue Criterion

In the previous paper, authors considered a notch fatigue criterion on the basis of an equivalent stress ratio which was newly proposed as the parameter for the correspondence between cyclic stress conditions of a notched and unnotched specimen. The equivalent stress ratio is represented as a function of a nominal stress ratio and a theoretical stress concentration factor of a notched specimen. It could be derived without difficulty from a hypothesis of plastic adaptation which was newly proposed by the authors and the mechanical models which reflected the hypothesis. In the present paper, in order to confirm the applicability of the equivalent stress ratio, a wide range of published fatigue test data is rearranged on the diagram where the abscissa represents the equivalent stress ratio and the ordinate does the notch-root-concentrated stress range. As a result, the consistent relation proper to material is obtained in spite of the difference of a notch stress concentration factor, a specimen type (a plate or a round-bar) and a loading type (axial, bending, torsional or their combined loading). The relation is formulated in a simple form as an empirical equation. Such a result leads to a notch fatigue criterion that the notch-root-concentrated stress range at the fatigue strength of the notched specimen for any nominal stress ratio is identical with the fatigue strength of the unnotched specimen for the equivalent stress ratio. Moreover, the equation for estimation of a fatigue strength reduction factor can be derived by relating its definition with the notch fatigue criterion. As a result, it is shown that a usually defined fatigue strength reduction factor is represented by multiplying the theoretical stress concentration factor by the unnotched specimen’s fatigue strength ratio which is dependent upon the mean stress. Accordingly, it is clear that the material-dependency of notch effects can be characterized by the steepness of slope of the unnotched specimen’s fatigue strength diagram.

Effect of Thread Form on the Strength of Ceramic Bolts

1995 ◽  
Vol 209 (3) ◽  
pp. 207-214
Author(s):  
N Gane ◽  
F Polivka
Keyword(s):  
Tensile Strength ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Notch Root ◽  
Screw Thread ◽  
Weibull Statistics ◽  
Threaded Connection ◽  
Direct Use ◽  
Safe Working

The strength of various designs of screw thread in partially stabilized zirconia (PSZ) bolts has been measured. It was found that the thread geometry usually used for metal fasteners and connections is not the optimum for a brittle ceramic material such as PSZ. An increase in the flank angle of the thread from the normal 60° to 90° can produce a 40 per cent increase in strength. The results are discussed in terms of the stress concentration factor acting at the notch root of the thread and the tensile strength of PSZ. This stress concentration or notch embrittlement factor reduces the strength of the threaded connection in a brittle material, compared to that of a metal with the same tensile strength. In the present experiments a stress concentration factor of between 2 and 4 was observed. This factor is combined with Weibull statistics to obtain safe working stresses for various designs of screw thread in PSZ. This information should be of direct use to designers interested in using this new engineering material.

Notch Fracture Behavior of Cold-Rolled Ni3Al Foil

2012 ◽  
Vol 602-604 ◽  
pp. 2201-2204
Author(s):  
Chuan Yong Cui ◽  
Toshiyuki Hirano
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fracture Behavior ◽  
Notch Root ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Theoretical Stress ◽  
Local Plastic Deformation ◽  
Theoretical Stress Concentration Factor

Notch effect on the fracture behavior of the Ni3Al foils has been investigated as a function of notch radius and depth. Tensile tests along the rolling direction showed that notch weakening occurred with introduce of notch. The effective stress concentration factor (ke) was much lower than the theoretical stress concentration factor (Kt), which was due to the local plastic deformation at the notch root. Cracks initiated along the shear band in the RD tension.

scholarly journals A novel thread connection structure of slimehole drilling tool in ultra-deep natural gas well

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110264
Author(s):  
Zhang Ying ◽  
Lian Zhanghua ◽  
Gao Anqi ◽  
Yang Kun
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Sensitivity Coefficient ◽  
Notch Sensitivity ◽  
Sensitivity Factor ◽  
Drilling Tool ◽  
Gas Well ◽  
Thread Connection

The thread connection’s root fillet radius of 0.038″ size is the greatest weakness of the API NC type joints and thread. During the slimehole drilling, especially in the deep and ultra-deep gas well, its stress concentration factor and notch sensitivity factor are very high A novel thread connection design (TM) of a drilling tool is proposed to decrease the fatigue failure of the slimehole drilling tool in the deep and the ultra-deep gas well in the Tarim oilfield China. The novelty in the TM thread structure is, reducing the threads per inch, extending the distance from the last engaged thread to the external shoulder of the pin and adding three threads to the conventional connection. The novel thread connection will improve the slimehole drilling tool’s anti-fatigue life due to its improved elasticity and rigidity. Furthermore, the TM can transfer the maximum stress at the connection root to the loaded surface, which can effectively lower the fatigue notch’s sensitivity coefficient. In this paper, the finite element method (FEM) is applied to carry out the detailed comparative analysis of the TM with existing thread connection NC38, TX60 and TH90. The TM has the lowest stress concentration factor and fatigue notch sensitivity coefficient, so its anti-fatigue life is the highest. In addition, TM is manufactured and is tested at Tarim oilfield in China.

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