Research on Mechanical Model and Fatigue Crack of Tubular Joint

2012 ◽  
Vol 446-449 ◽  
pp. 278-282
Author(s):  
Diao Yan
Keyword(s):  
Mechanical Model ◽  
Fatigue Cracks ◽  
Axial Direction ◽  
Mechanical Analysis ◽  
Fatigue Tests ◽  
Computational Formula ◽  
Analysis Model ◽  
Mechanical Models ◽  
Tubular Joint ◽  
Intersection Line

When the tubular joint is under stress, the stressed conditions on the intersection line are rather complicated. This article proposes to establish a cylindrical coordinated system for the stress on a tubular joint with axial direction, radical direction and circumferential direction as directions of coordinate axis. The system resolves the stress on points of the line of intersection along those three directions and establishes a mechanical analysis model for the stress on the tubular joint based on that. Besides, with combination of conditions of fatigue cracks of tubular joint, effective tensile stress specific to I-shape cracks are put forward and relevant mechanical formula are deduced accordingly. By taking fatigue tests of tubular joints of CaoEJiang Bridge as examples, the article also works out the position of the maximum geometrical value of stress on the line of intersection of tubular joint with applications of mechanical models and computational formula presented in the paper and compares the position with the result of test to explain the result of test.

Design of Space Sliding Rails and Mechanical Analysis

2014 ◽  
Vol 624 ◽  
pp. 207-212
Author(s):  
Fu Pei Liu ◽  
Jian Zhong Shang ◽  
Zi Rong Luo ◽  
Tao Zhang ◽  
Nai Hui Yu
Keyword(s):  
Carrying Capacity ◽  
Simulation Analysis ◽  
Mechanical Analysis ◽  
The State ◽  
Mechanical Models ◽  
Design Requirements

Unlike commercial sliding rails, space sliding rails need to meet complex mechanical requirements in the state of ground tooling, launch and on-orbit. The former could slide smoothly while their carrying capacity is low. As a result, they cannot be applied directly to the space stations, manned spacecrafts and other space probes. Hence, it is necessary to design a kind of full-pulling sliding rails which can be suitable for three completely different mechanical conditions. In this paper, we firstly built the mechanical models of the ground tooling, launch and on-orbit state, then a kind of sliding rails is designed according to the mechanical models, finally, a simulation analysis was carried out on the designed sliding rail. The result shows that this kind of sliding rails meets all the design requirements, which verifies the validity of the models.

On the Direction of Fatigue Cracks in Polycrystalline Ingot Iron

1952 ◽  
Vol 19 (1) ◽  
pp. 54-56
Author(s):  
F. A. McClintock
Keyword(s):  
Statistical Analysis ◽  
Shear Failure ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Tensile Failure ◽  
Bending Fatigue ◽  
Polycrystalline Iron

Abstract A statistical analysis is developed to show how a microscopic shear failure can result in the apparent tensile failure of polycrystalline iron in rotary bending fatigue tests.

Study of Sand Production Using Geomechanical and Hydro-Mechanical Models

2018 ◽  
Vol 876 ◽  
pp. 181-186
Author(s):  
Son Tung Pham
Keyword(s):  
Production Rate ◽  
Mechanical Model ◽  
Failure Criteria ◽  
Sand Production ◽  
Geomechanical Model ◽  
Strength Failure ◽  
Rate Versus ◽  
Mechanical Models ◽  
Rock Mechanical Properties ◽  
Bottomhole Pressure

Sand production is a complicated physical process depending on rock mechanical properties and flow of fluid in the reservoir. When it comes to sand production phenomenon, many researchers applied the Geomechanical model to predict the pressure for the onset of sand production in the reservoir. However, the mass of produced sand is difficult to determine due to the complexity of rock behavior as well as fluid behavior in porous media. In order to solve this problem, there are some Hydro – Mechanical models that can evaluate sand production rate. As these models require input parameters obtained by core analysis and use a large empirical correlation, they are still not used popularly because of the diversity of reservoirs behavior in the world. In addition, the reliability of these models is still in question because no comparison between these empirical models has been studied. The onset of sand production is estimated using the bottomhole pressure that makes the maximum effective tangential compressive stress equal or higher than the rock strength (failure criteria), which is usually known as critical bottomhole pressure (CBHP). Combining with Hydro – Mechanical model, the main objective of this work aims to develop a numerical model that can solve the complexity of the governing equations relating to sand production. The outcome of this study depicts sand production rate versus time as well as the change of porosity versus space and time. In this paper, the Geomechanical model coupled with Hydro – Mechanical model is applied to calibrate the empirical parameters.

The Influence of Biaxial Mean Stresses on the Failure of Tubes by Fatigue

1961 ◽  
Vol 12 (1) ◽  
pp. 1-33 ◽  
Author(s):  
H. L. Cox ◽  
N. B. Owen
Keyword(s):  
Fatigue Crack ◽  
Mild Steel ◽  
Test Piece ◽  
Fatigue Cracks ◽  
Small Diameter ◽  
Axial Direction ◽  
Gas Pressure ◽  
Modes Of Failure ◽  
Explosive Failure ◽  
Bending Stresses

SummaryThin-walled tubes, in. in diameter, of three hard aluminium alloys and of mild steel have been tested in fatigue under three systems of alternating stresses while subjected to biaxial mean tensions imposed by means of internal pressure. In fatigue under direct or bending stresses the hoop tension in the walls of the aluminium alloy tubes did not seriously reduce the fatigue endurance, but it did markedly affect the mode and rate of crack propagation; cracks initially transverse to the tube axis tended to develop very rapidly in the axial direction. This tendency was present under both fluid and gas pressure, and under gas pressure the cracks propagated so fast that the test piece was often blown to pieces before the gas pressure fell by leakage through the cracks. The gradual taper in wall thickness along the fillets joining the test section to the enlarged ends offered no barrier to propagation of the axial cracks and the whole test piece, including its enlarged ends, was often shattered. Propagation of the axial cracks was preventible by sufficiently reducing the fillet radius, or by a ring glued on. Under alternating torsion, both endurance and mode of failure were affected by internal gas pressure. The initial fatigue crack, either circumferential or axial, often extended over a length comparable with the diameter of the tube, except under low ranges of shear stress when the crack length was sometimes very short. At each end the cracks forked in a characteristic manner and under moderate gas pressure the portions of tHe wall between the prongs of the fork were blown outwards. Under high pressure explosive failure and fragmentation often occurred. Mild steel under alternating torsion with internal gas pressure exhibited the same modes of failure, and two or more fatigue cracks were often formed simultaneously. Under high hoop tension, cracks propagated rapidly and one test piece, after two million cycles endurance, failed by exploding. However, no mild steel test piece was fragmented. A tentative explanation is offered of the reason why, in tubes of small diameter, rather short fatigue cracks may be expected to lead to fast fracture under the static loading. Attention is drawn to the inference that the initial fatigue crack itself must develop very quickly to considerable length.

Investigation of Fracture in Transparent Glass Fiber Reinforced Polymer Composites Using Photoelasticity

2002 ◽  
Author(s):  
Sanjeev K. Khanna ◽  
Marius D. Ellingsen ◽  
Robb M. Winter
Keyword(s):  
Composite Materials ◽  
Fatigue Cracks ◽  
Large Body ◽  
Mechanical Analysis ◽  
Pressure Vessels ◽  
High Ratio ◽  
Material Behavior ◽  
Engineering Structures ◽  
Glass Fiber Reinforced ◽  
Fiber Reinforced Polymer Composites

Composite materials are widely used in mechanical structures where a high ratio of strength or stiffness to weight is desired. Not only are composite materials widely used in building recreational equipment such as skis, snowboards or even sports cars, but also multiple types of military aircraft are built from composite materials. Airplane bodies are in principle cyclically loaded pressure vessels and are susceptible to the formation of fatigue cracks, and it is necessary to possess knowledge of how the material behaves with a crack present. In fact, all engineering structures have to be designed with the presence of crack like defects in mind. For traditional engineering materials such as steel and aluminum there exists a large body of knowledge regarding material behavior in the presence of a crack. Furthermore, their isotropic nature eases the process of mechanical analysis. Photoelasticity, an optical method, has been widely used to study fracture in isotropic transparent materials (Irwin, 1962, 1980; Dally, 1979; Daniel, 1984; Kobayashi, et al, 1973; Chona, 1987).

scholarly journals Stress Distribution Analysis of DKDT Tubular Joint in a Minimum Offshore Structure

Rekayasa ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 191-199
Author(s):  
Irma Noviyanti ◽  
Rudi Walujo Prastianto ◽  
Murdjito Murdjito
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Axial Force ◽  
Oil And Gas ◽  
Bending Moment ◽  
Out Of Plane ◽  
Tubular Joint ◽  
Plane Bending ◽  
Intersection Line ◽  
Marginal Field

A marginal field defines as an oil and/or gas field that has a short production period, low proven reservoir, and could not be exploited using existing technology. As the demand for oil and gas keeps increasing, one of the solutions to tackle the issues is to build the modified platform which came to be more minimalist to conduct the oil and gas production in the marginal field. Naturally, the minimum offshore structures are cost less but low in redundancy, therefore, pose more risks. Although the study on the minimum structures is still uncommon, there are opportunities to find innovative systems that need to have a further analysis toward such invention. Therefore, this study took the modified jacket platform as a minimum structure, and local stresses analysis by using finite element method is applied for the most critical tubular joint with multiplanarity of the joint is taking into account. The analysis was carried out using the finite element program of Salome Meca with three-dimensional solid elements are used to model the multiplanar joint. Various loading types of axial force, in-plane bending moment, and out-of-plane bending moment are applied respectively to investigate the stress distribution along the brace-chord intersection line of the tubular joint. The results show that the hotspot stress occurred at a different point along each brace-chord intersection line for each loading type. Finally, as compared to the in-plane bending moment or out-of-plane bending moment loading types, the axial force loading state is thought to generate greater hotspot stress.

Structural, technological and Aesthetical Considerations for the Detailing of Steel Tubular Joints

2018 ◽  
Author(s):  
Vasil Georgiev Georgiev ◽  
Dimitar Dakov ◽  
Yavor Mihov
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Civil Engineering ◽  
Fatigue Cracks ◽  
High Stress ◽  
Traffic Sign ◽  
Tubular Joints ◽  
Joint Repair ◽  
Tubular Joint ◽  
Supporting Structures

<p>For the majority of steel outdoor facilities (towers, masts, billboards and traffic-sign supporting structures) wind loading is the governing factor for determining their resistance and stiffness. In many cases fatigue-related issues appear, with cracking and failure in the welded connections of tubular joints or in the parent metal adjacent to the welds.</p><p>Structural detailing of the joints in steel tubular structures subjected to repeated cyclic loading is of great importance for their fatigue strength. Sharp changes in the shape, sharp turns in the welds and notches give rise to high stress concentration. The combined effect of discontinuities and stress concentration is the main cause for the formation and propagation of fatigue cracks. When detailing the erection joints it is also necessary to observe technological requirements related to efficiency of fabrication. For the civil engineering works exposed to public it is indispensable to include additional requirements for the aesthetic appearance of their visible structural parts. The design experience shows that applying aesthetic considerations to steel tubular joint detailing may contribute to satisfying the increased fatigue strength requirements.</p><p>The paper presents a study on the wind action on a specific kind of civil engineering works (traffic- sign supporting structures) and the approach used for its determination. The leading structural, technological and aesthetic criteria to be implemented in the detailing of tubular erection joints are formulated. An example of tubular joint destroyed due to propagation of fatigue crack is given and possible options for the joint repair are proposed. Numerical modeling and analyses of the original and repaired joints have been carried out in order to make conclusions for the advantages and shortcomings of the joint repair options.</p>

Noise calculation method of deep groove ball bearing caused by vibration of rolling elements considering raceway waviness

2021 ◽  
pp. 095440622110458
Author(s):  
Minjie Sun ◽  
Haojie Xu ◽  
Qi An
Keyword(s):  
Ball Bearing ◽  
Axial Direction ◽  
Rolling Bearing ◽  
Mechanical Analysis ◽  
Machining Accuracy ◽  
Surface Waviness ◽  
Random Surface ◽  
Deep Groove ◽  
Deep Groove Ball Bearing ◽  
Rolling Elements

Raceway waviness error is the main reason to cause rolling elements to vibrate along axial direction and emit noise. In this paper, the mechanical analysis on deep groove ball bearing is carried out. With auto-correlation function, random surface waviness of both inner and outer raceways is simulated. A contact model of rolling elements and raceways considering surface waviness is established. Combining with the theory of acoustic equation, a calculation model is established for the noise caused by vibration of rolling elements and inner ring. The results show that with the decrease of machining accuracy, the noise of rolling elements increases due to axial vibration; with the increase of rotation speed, the noise also increases. Besides, the spectrum of radiation noise of inner raceway with different waviness amplitudes is given. The results indicate that the 3-D waviness on raceway surface has an influence on the vibration and the noise emitted by both rolling elements and inner ring, and provide guidance for sound control in deep groove rolling bearing.

Some Properties of a Mechanical Model of Plasticity

1948 ◽  
Vol 15 (3) ◽  
pp. 222-225
Author(s):  
H. F. Bohnenblust ◽  
Pol Duwez
Keyword(s):  
Plastic Deformation ◽  
Potential Energy ◽  
Work Hardening ◽  
Mechanical Model ◽  
Strain Curve ◽  
Hysteresis Curve ◽  
Plastic Range ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Mechanical Models

Abstract Various mechanical models explaining the plastic deformation of metals have been proposed. One of the present authors has shown that in some cases an analytical expression for the stress-strain curve and the hysteresis curve of a metal in the plastic range can be deduced from such a model. The present investigation is a further analysis of the model leading to the computation of the change in potential energy of the metal due to work-hardening.

scholarly journals Study on the Fracture Law of Inclined Hard Roof and Surrounding Rock Control of Mining Roadway in Longwall Mining Face

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5344
Author(s):  
Feng Cui ◽  
Shuai Dong ◽  
Xingping Lai ◽  
Jianqiang Chen ◽  
Chong Jia ◽  
...  
Keyword(s):  
Energy Release ◽  
Longwall Mining ◽  
Coal Pillar ◽  
High Energy ◽  
Mechanical Analysis ◽  
Engineering Practice ◽  
Analysis Model ◽  
Hard Roof ◽  
Working Face ◽  
The Stability

In the inclination direction, the fracture law of a longwall face roof is very important for roadway control. Based on the W1123 working face mining of Kuangou coal mine, the roof structure, stress and energy characteristics of W1123 were studied by using mechanical analysis, model testing and engineering practice. The results show that when the width of W1123 is less than 162 m, the roof forms a rock beam structure in the inclined direction, the floor pressure is lower, the energy and frequency of microseismic (MS) events are at a low level, and the stability of the section coal pillar is better. When the width of W1123 increases to 172 m, the roof breaks along the inclined direction, forming a double-hinged structure, the floor pressure is increased, and the frequency and energy of MS events also increases. The roof gathers elastic energy release, and combined with the MS energy release speed it can be considered that the stability of the section coal pillar is better. As the width of W1123 increases to 184 m, the roof in the inclined direction breaks again, forming a multi-hinged stress arch structure, and the floor pressure increases again. MS high-energy events occur frequently, and are not conducive to the stability of the section coal pillar. Finally, through engineering practice we verified the stability of the section coal pillar when the width of W1123 was 172 m, which provides a basis for determining the width of the working face and section coal pillar under similar conditions.

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