scholarly journals Investigation of the mechanical properties of steel plates with artificial pitting and the effects of mutual pitting on the stress concentration factor

2019 ◽  
Vol 14 ◽  
pp. 102520
Author(s):  
Xiangzhou Liang ◽  
Jie Sheng ◽  
Kun Wang
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Steel Plates

scholarly journals Reduction of the Local Stress Field around Holes through Porous Shaped Structures

2018 ◽  
Vol 20 (3) ◽  
pp. 36-41
Author(s):  
Stefano Monti
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Stress Field ◽  
Present Article ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Laser Cutting ◽  
Local Stress ◽  
Hole Boundary ◽  
Local Stress Field

Geometrical discontinuities in mechanical components are detrimental for the mechanical properties of the product itself. Actually, in proximity of such features, the stress increases due to the stress concentration factor, that in the case of a circular hole is equal to 3. Several solutions have been proposed to reduce the stress concentration value. In the present article, the application of a particular porous pattern that can be obtained by laser cutting with the appropriate finishing requirements is introduced in order to modify the local stress field and reduce the stress concentration value near the hole boundary.

Analysis of strain and stress concentrations in micro-lattice structures manufactured by SLM

2019 ◽  
Vol 26 (2) ◽  
pp. 370-380 ◽  
Author(s):  
Laura Boniotti ◽  
Stefano Foletti ◽  
Stefano Beretta ◽  
Luca Patriarca
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Content Type ◽  
Lattice Materials ◽  
Geometrical Imperfections

Purpose Additive manufacturing (AM) enables the production of lightweight parts with complex shapes and small dimensions. Recent improvements in AM techniques have allowed a significant growth of AM for industrial applications. In particular, AM is suitable for the production of materials shaped in lattice, which are very attractive for their lightweight design and their multi-functional properties. AM parts are often characterised by geometrical imperfections, residual porosity, high surface roughness which typically lead to stress/strain localisations and decreasing the resistance of the structure. This paper aims to focus on the study of the effects of geometrical irregularities and stress concentrations derived from them. Design/methodology/approach In this paper, several technique were combined: 3D tomography, experimental tests, digital image correlation and finite elements (FE) models based on both the as-designed and the as-manufactured geometries of lattice materials. The Digital Image Correlation technique allowed to measure local deformations in the specimen during the experimental test. The micro-computed tomography allowed to reconstruct the as-manufactured geometries of the specimens, from which the geometrical quality of the micro-structure is evaluated to run FE analyses. Findings Experimental and numerical results were compared by means of a stress concentration factor. This factor was calculated in three different specimens obtained from three-different printing processes to compare and understand their mechanical properties. Considering the as-designed geometry, it is not possible to model geometrical imperfections, and a FE model based on an as-manufactured geometry is needed. The results show that the mechanical properties of the printed samples are directly related to the statistical distribution of the stress concentration factor. Originality/value In this work, several techniques were combined to study the mechanical behaviour of lattice micro-structures. Lattice materials obtained by different selective laser melting printing parameters show different mechanical behaviours. A stress concentration factor can be assumed as a measure of the quality of these mechanical properties.

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.

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.

Fracture of Inoculated Iron Under Biaxial Stresses

1955 ◽  
Vol 22 (2) ◽  
pp. 172-174
Author(s):  
I. Cornet ◽  
R. C. Grassi
Keyword(s):  
Cast Iron ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Gray Cast Iron ◽  
Energy Criterion ◽  
Gray Cast ◽  
Published Data ◽  
Thin Wall ◽  
As Stress

Abstract Data are presented on the fracture of inoculated-iron thin-wall tubes, investigated under various ratios of axial to tangential stress, ranging from pure tension to pure compression. These data are consistent with published data on gray cast iron. It may be assumed that in cast-iron, plates of friable graphite in an iron matrix, act like solid iron with respect to compressive stresses, but they act as stress-concentrating cavities with respect to tensile stresses. This gives a stress-concentration factor, which is easily determined experimentally. Stress-concentration factors obtained were 3.2–3.3 for gray cast iron, and 2.4–2.5 for inoculated cast iron. A distortion-energy criterion for fracture, modified by this stress-concentration factor, is consistent with the experimental data. It appears that the concentration of the dispersed graphite, and the shape and size of this brittle phase, affect the fracture strength under combined stresses.

The Flow and Fracture of a Brittle Material

1950 ◽  
Vol 17 (3) ◽  
pp. 233-248
Author(s):  
L. F. Coffin
Keyword(s):  
Cast Iron ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Gray Cast Iron ◽  
Gray Cast ◽  
Residual Tensile Stress ◽  
Two Dimensional ◽  
Combined Stress ◽  
Plastic Stress

Abstract The mechanism of flow and fracture of a gray cast iron can be understood if one considers the microstructure to consist of a ductile structure with a random dispersion of cracks due to the graphite flakes following the concept of Fisher. A notch effective stress can be calculated for a critically situated crack by a knowledge of the external stresses, a plastic stress-concentration factor of 3, and a residual tensile stress at the sharp edge of the crack, based upon either the “maximum-shear” theory or the “distortion-energy” theory. This allows the formulation of generalized plastic stress-strain relationships and renders gray cast iron applicable to the many known solutions for plastic flow of ductile metals. Fracture in the region of tension-tension and tension-compression can be evaluated by a similar analysis, using the same stress-concentration factor and the same residual stress. A combined stress-testing program is described wherein thin-walled cast-iron tubes are subjected to two-dimensional states of combined stress covering the complete two-dimensional field.

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