scholarly journals Selection of fiber orientation around geometric discontinuities in designing against failure of GFRP laminates

2018 ◽  
Vol 188 ◽  
pp. 01010
Author(s):  
Roselita Fragoudakis
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Fiber Orientation ◽  
Failure Theory ◽  
Geometric Discontinuities ◽  
Lamination Theory ◽  
Failure Theories ◽  
Maximum Stresses ◽  
Minimum Moment ◽  
Selection Of

Determining fiber orientation around geometric discontinuities is challenging and simultaneously crucial when designing laminates against failure. This study presents an approach for selecting the fiber orientations in the vicinity of a geometric discontinuity. Maximum stresses in the discontinuity region are calculated using Classical Lamination Theory and the stress concentration factor. The use of the Tsai-Hill and Tsai-Wu failure theories estimate the minimum moment to cause failure in a lamina. Fiber orientations around the discontinuity are obtained using the Tsa-Hill failure theory.

A numerical approach to determine fiber orientations around geometric discontinuities in designing against failure of GFRP laminates

2019 ◽  
Vol 10 (3) ◽  
pp. 371-379 ◽  
Author(s):  
Roselita Fragoudakis
Keyword(s):  
Stress Concentration ◽  
Plastic Zone ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Load Condition ◽  
Content Type ◽  
Geometric Discontinuities ◽  
Failure Theories ◽  
Laminated Structures ◽  
Minimum Moment

Purpose Determining fiber orientations around geometric discontinuities is challenging and simultaneously crucial when designing laminates against failure. The purpose of this paper is to present an approach for selecting the fiber orientations in the vicinity of a geometric discontinuity; more specifically round holes with edge cracks. Maximum stresses in the discontinuity region are calculated using Classical Lamination Theory (CLT) and the stress concentration factor for the aforementioned condition. The minimum moment to cause failure in a lamina is estimated using the Tsai–Hill and Tsai–Wu failure theories for a symmetric general stacking laminate. Fiber orientations around the discontinuity are obtained using the Tsai–Hill failure theory. Design/methodology/approach The current research focuses on a general stacking sequence laminate under three-point bending conditions. The laminate material is S2 fiber glass/epoxy. The concepts of mode I stress intensity factor and plastic zone radius are applied to decide the radius of the plastic zone, and stress concentration factor that multiplies the CLT stress distribution in the vicinity of the discontinuity. The magnitude of the minimum moment to cause failure in each ply is then estimated using the Tsai–Hill and Tsai–Wu failure theories, under the aforementioned stress concentration. Findings The findings of the study are as follows: it confirms the conclusions of previous research that the size and shape of the discontinuity have a significant effect on determining such orientations; the dimensions of the laminate and laminae not only affect the CLT results, but also the effect of the discontinuity in these results; and each lamina depending on its position in the laminate will have a different minimum load to cause failure and consequently, a different fiber orientation around the geometric discontinuity. Originality/value This paper discusses an important topic for the manufacturing and design against failure of Glass Fiber Reinforced Plastic (GFRP) laminated structures. The topic of introducing geometric discontinuities in unidirectional GFRP laminates is still a challenging one. This paper addresses these issues under 3pt bending conditions, a load condition rarely approached in literature. Therefore, it presents a fairly simple approach to strengthen geometric discontinuity regions without discontinuing fibers.

Isogeometric Analysis Prediction of Stress Concentration Factor of Trivariate NURBS-Based Rectangular Plate with Central Elliptical Hole

2014 ◽  
Vol 556-562 ◽  
pp. 742-746
Author(s):  
Yusuf Olatunbosun Tafa ◽  
Gang Zhao ◽  
Wei Wang
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Isogeometric Analysis ◽  
Concentration Factor ◽  
Three Dimensional ◽  
Elliptical Hole ◽  
The Body ◽  
Geometric Discontinuities ◽  
Trivariate Nurbs ◽  
Good Agreement

Experimental, analytical and finite element techniques are commonly known methods used in determining highly localized stress occurring in the body under loading as a result of geometric discontinuities. In this study, we use NURBS-based isogeometric analysis (IGA) to investigate the stress concentration factor (SCF) on three-dimensional geometry with discontinuity feature. The results show that IGA technique is in good agreement with analytical values, thus providing a more effective realistic way of determining SCF.

scholarly journals Stress Concentration Resulting from Irregular Shape of Explosively Cladded Materials Connections - Fem Simulation

2014 ◽  
Vol 8 (2) ◽  
pp. 103-106 ◽  
Author(s):  
Andrzej Kurek ◽  
Adam Niesłony ◽  
Marta Kurek
Keyword(s):  
Numerical Analysis ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Fem Simulation ◽  
Interface Zone ◽  
Joint Zone ◽  
Explosive Cladding ◽  
Constituent Material ◽  
Actual Profile ◽  
Maximum Stresses

Abstract The paper contains a numerical analysis of interface zone steel-titanium bimetal obtained by explosive cladding method. Due to the waviness of the zone, and various properties of the constituent material of the materials type contain structural notch. Therefore it is important inter alia in terms of presentation of the results of fatigue are the maximum stresses that occur just in the area of the zone. In the paper the stress concentration factor and the proposed method of modelling the joint zone of a sinusoidal profile, characterized by the same coefficient of stress concentration at the actual profile.

Stress-Concentration Factors for a Countersunk Hole in a Flat Bar in Tension and Transverse Bending

1978 ◽  
Vol 45 (4) ◽  
pp. 929-932 ◽  
Author(s):  
Y. F. Cheng
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Neutral Plane ◽  
Transverse Bending ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Maximum Stresses

A series of three-dimensional photoelastic experiments was performed to determine the maximum stresses and stress-concentration factors at countersunk holes in a flat bar in tension and transverse bending. In the tension case, the maximum stress was found at the base of the countersunk and the stress-concentration factor was approximately 33 percent higher than those found in a straight hole. In the bending case, the neutral plane was shifted toward the surface containing the straight part of the hole and the stress-concentration factor was practically the same as those found in straight holes.

scholarly journals CALCULATION OF STRESS CONCENTRATION FACTORS OF PLATES UNDER TENSION VIA COMPUTER PROGRAM DEVELOPED

2020 ◽  
Vol 29 (2) ◽  
pp. 568-583
Author(s):  
Raphael Basilio Pires Nonato
Keyword(s):  
Stress Concentration ◽  
Mathematical Modelling ◽  
Computer Program ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Elastic Range ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Maximum Stresses ◽  
Approximate Equations

Stress concentration factors (SCFs) for some set of fixed geometrical and loading cases can be obtained experimentally, analytically, and computationally. In order to accomplish this, tables and charts that relate a geometrical ratio and a specific type of loading with their correspondent stress concentration factor are commonly available. Although these resources are abundantly accessible for the most common cases, their reading and interpretation processes often imply parallax error. To overcome this difficulty, the approximate or interpolated equations may be applied. However, the application of the adequate equation in a non-structured manner can be time consuming when there are several cases to be calculated within the context of a whole design. Thus, the study of two geometrical cases of plates under tension in elastic range enabled the comparison of SCFs obtained from three sources: (a) chart reading; (b) approximate proven equations; and (c) specific computer program developed by the author. In addition, the program provides the user with the nominal and the maximum stresses for both cases. Results provided by the software were then validated through the comparison with the approximate equations applied in the mathematical modelling of the experimental charts.

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.

Scale-Dependent Crack Modeling for Investigation the Effect of Geometrically Necessary Dislocations in Micro/Nano Grain Size of Copper

2016 ◽  
Vol 15 ◽  
pp. 1-16 ◽  
Author(s):  
Amin Zaami ◽  
Ali Shokuhfar
Keyword(s):  
Grain Size ◽  
Stress Concentration ◽  
Strain Gradient ◽  
Stress Concentration Factor ◽  
Size Effects ◽  
Crack Tip ◽  
Length Scale ◽  
State Variables ◽  
Dependent Model ◽  
Homogeneous Strain

In this study, a scale-dependent model is employed to investigate the size effects of copper on the behavior of the crack-tip. This model includes the homogeneous and non-homogeneous strain hardening based on the wavelet interpretation of size effect. Introducing additional micro/nano structural considerations together with decreasing grain size, different size effects can be obtained. As the size dependency is not taken into account in conventional plasticity, an enhanced theory which is related to the strain gradient introduces a length scale will give more realistic representations of state variables near the crack-tip. Accordingly, the contribution of geometrically necessary dislocations (GNDs) activity on strengthening and stress concentration factor is identified in the crack-tip. Finally, the affected zone which is dominated by presence of GNDs is identified

Stress Concentration of Periodic Collinear Square Holes in an Infinite Plate in Tension

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Changqing Miao ◽  
Yintao Wei ◽  
Xiangqiao Yan
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Infinite Plate ◽  
Numerical Approach ◽  
Numerical Examples ◽  
Calculated Stress ◽  
Bueckner’S Principle

A numerical approach for the stress concentration of periodic collinear holes in an infinite plate in tension is presented. It involves the fictitious stress method and a generalization of Bueckner's principle. Numerical examples are concluded to show that the numerical approach is very efficient and accurate for analyzing the stress concentration of periodic collinear holes in an infinite plate in tension. The stress concentration of periodic collinear square holes in an infinite plate in tension is studied in detail by using the numerical approach. The calculated stress concentration factor is proven to be accurate.

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