scholarly journals Stress Rupture Life Prediction Method for Notched Specimens Based on Minimum Average Von Mises Equivalent Stress

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 68
Author(s):  
Dawei Ji ◽  
Xianming Hu ◽  
Zuopeng Zhao ◽  
Xu Jia ◽  
Xuteng Hu ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Rupture Life ◽  
Equivalent Stress ◽  
Constitutive Models ◽  
Concentration Coefficient ◽  
Creep Tests ◽  
Notched Specimens ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Stress Concentration Coefficient

Creep tests were carried out on notched plate specimens of nickel-based superalloy GH4169 with different stress concentration coefficients. It was found that the duration of the first stage of the creep curve increases with the increase of stress concentration coefficient, while the fracture ductility decreases with the increase of stress concentration coefficient. To predict the life of notched plate specimens, four constitutive models were used to analyze the stress and strain of the notches. It was found that the average Von Mises equivalent stress (AVES) on the minimum notch section first decreases and then increases with the creep time, resulting in a minimum value. The minimum average Von Mises equivalent stress (MAVES) is considered as the characteristic stress of notched specimens in this paper. The creep life equation is fitted according to the results of creep tests of smooth specimens, and then the predicted life of notched specimens is obtained by substituting the minimum average Von Mises equivalent stress of notched specimens into the creep equation. The prediction results of the four constitutive models are within 2 times the dispersion band, and the three-stage model is within the 1.5 times dispersion band.

The prediction of stress rupture life of notched specimens in the beta-processed titanium alloy Ti5331s

1987 ◽  
Vol 22 (3) ◽  
pp. 145-153 ◽  
Author(s):  
P S Webster ◽  
A C Pickard
Keyword(s):  
Titanium Alloy ◽  
Notch Root ◽  
Rupture Life ◽  
Equivalent Stress ◽  
Stress Rupture ◽  
High Rate ◽  
Stress Rupture Life ◽  
Notched Specimen ◽  
Notched Specimens ◽  
Von Mises

Methods of predicting notched bar stress rupture behaviour are reviewed. Two very different types of notched specimens are analysed using the finite element method; one being a circumferentially V-notched test piece, the other having two semi-circular notches in a plane section. A prediction based on the Von Mises equivalent stress distribution is proposed. Predictions using this method are compared with notched specimen test results in a commercially available titanium alloy, Ti5331s, tested at 600°C. The correlation is good for the semi-circular notched specimen and for the V-notched specimen at low stress, long life and can be improved at high stresses by making allowance for time independent plasticity and for the initial high rate of creep strain accumulation at the notch root.

Creep Void Formation and Rupture Lifetime in Multiaxial Stress States

2019 ◽  
Vol 795 ◽  
pp. 159-164
Author(s):  
Masao Sakane ◽  
Hiroki Kobayashi ◽  
Ryohei Ohki ◽  
Takamoto Itoh
Keyword(s):  
Equivalent Stress ◽  
Void Formation ◽  
Creep Rupture ◽  
Triaxial Stress ◽  
Multiaxial Stress ◽  
Creep Tests ◽  
Triaxial Creep ◽  
Stress States ◽  
Von Mises Equivalent Stress ◽  
Von Mises

This paper discusses creep void formation and rupture lifetimes in multiaxial stress states for a SUS 304 stainless steel at elevated temperatures. Biaxial and triaxial tension creep tests were performed using a cruciform and a cubic specimen, respectively. These two types of the specimens were designed to achieve uniform equi-biaxial and equi-triaxial stress distributions by a finite element analysis in the gage parts. Void formation at grain boundaries was observed by intermitting biaxial creep tests and by interrupting triaxial creep tests. Creep rupture lifetimes were also obtained in biaxial and triaxial creep tests. Biaxial stresses increase the void formation but give a little influence on a creep rupture lifetime in the correlation with von Mises equivalent stress. Triaxial stresses also increase the void formation and drastically reduce a creep rupture lifetime in the correlation with von Mises equivalent stress. Evident void formation in an equi-triaxial stress condition demonstrates that von Mises equivalent stress is not a suitable measure to evaluate creep damage development in multiaxial stress states. A new equivalent stress is proposed to evaluate creep rupture lifetimes in biaxial and triaxial stress states.

An Analysis of Filament Overwound Toroidal Pressure Vessels and Optimum Design of Such Structures

2002 ◽  
Vol 124 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Shuguang Li ◽  
John Cook
Keyword(s):  
Optimum Design ◽  
Equivalent Stress ◽  
Mechanical Damage ◽  
Stress Rupture ◽  
Optimization Procedure ◽  
Pressure Vessels ◽  
Thickness Variation ◽  
Von Mises Equivalent Stress ◽  
Metal Liner ◽  
Von Mises

This paper is concerned with the membrane shell analysis of filament overwound toroidal pressure vessels and optimum design of such pressure vessels using the results of the analysis by means of mathematical nonlinear programming. The nature of the coupling between overwind and linear has been considered based on two extreme idealizations. In the first, the overwind is rigidly coupled with the liner, so that the two deform together in the meridional direction as the vessel dilates. In the second, the overwind is free to slide relative to the linear, but the overall elongations of the two around a meridian are identical. Optimized designs with the two idealizations show only minor differences, and it is concluded that either approximation is satisfactory for the purposes of vessel design. Aspects taken into account are the intrinsic overwind thickness variation arising from the winding process and the effects of fiber pre-tension. Pre-tension can be used not only to defer the onset of yielding, but also to achieve a favorable in-plane stress ratio which minimizes the von Mises equivalent stress in the metal liner. Aramid fibers are the most appropriate fibers to be used for the overwind in this type of application. The quantity of fiber required is determined by both its short-term strength and its long-term stress rupture characteristics. An optimization procedure for the design of such vessels, taking all these factors into account, has been established. The stress distributions in the vessels designed in this way have been examined and discussed through the examples. A design which gives due consideration of possible mechanical damage to the surface of the overwind has also been addressed.

Biomechanical Behavior of All-Ceramic Crowns with Variable Thicknesses of Zirconia Frameworks

2016 ◽  
Vol 835 ◽  
pp. 97-102
Author(s):  
Liliana Porojan ◽  
Florin Topală ◽  
Sorin Porojan
Keyword(s):  
Mechanical Behavior ◽  
Equivalent Stress ◽  
The Finite Element Method ◽  
Static Loads ◽  
Biomechanical Behavior ◽  
All Ceramic ◽  
Ceramic Crowns ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Posterior Restorations

Zirconia is an extremely successful material for prosthetic restorations, offering attractive mechanical and optical properties. It offers several advantages for posterior restorations because it can withstand physiological posterior forces. The aim of the study was to achieve the influence of zirconia framework thickness on the mechanical behavior of all-ceramic crowns using numerical simulation. For the study a premolar was chosen in order to simulate the mechanical behavior in the components of all-ceramic crowns and teeth structures regarding to the zirconia framework thickness. Maximal Von Mises equivalent stress values were recorded in teeth and restorations. Due to the registered maximal stress values it can be concluded that it is indicated to achieve frameworks of at least 0.5 mm thickness in the premolar area. Regarding stress distribution concentration were observed in the veneer around the contact areas with the antagonists, in the framework under the functional cusp and in the oral part overall and in dentin around and under the marginal line, also oral. The biomechanical behavior of all ceramic crowns under static loads can be investigated by the finite element method.

Influence of Stress Concentration on Fatigue Property of Welded Joints of 5083 Aluminum Alloy

2013 ◽  
Vol 456 ◽  
pp. 451-455
Author(s):  
Jun Yang ◽  
Bo Li ◽  
Qiang Jia ◽  
Yuan Xing Li ◽  
Ming Yue Zhang ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Aluminum Alloy ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Welded Joints ◽  
Weld Zone ◽  
Fatigue Property ◽  
Concentration Coefficient ◽  
5083 Aluminum Alloy ◽  
Stress Concentration Coefficient

Fatigue test of the welded joint of 5083 aluminum alloy with smooth and height of specimen and the weld zone than the high test measurement and theoretical stress concentration coefficient calculation, the weld reinforcement effect of stress concentration on the fatigue performance of welded joints. The results show that: Smooth tensile strength of specimens for 264MPa, fatigue strength is 95MPa, the tensile strength of the 36%. Higher tensile strength of specimens for 320MPa, fatigue strength is 70MPa, the tensile strength of the 22%. Higher specimen stress concentration coefficient is 1.64, the stress concentration to the weld toe becomes fatigue initiation source, and reduces the fatigue strength and the fatigue life of welded joints.

scholarly journals Stress strain state of elastic plate with elliptical cut-out

2020 ◽  
pp. 3-8
Author(s):  
E.E. Deryugin ◽  
Keyword(s):  
Plastic Deformation ◽  
Stress Concentration ◽  
Driving Force ◽  
Strain State ◽  
Mechanical State ◽  
Concentration Coefficient ◽  
Stress Strain ◽  
Crack Driving Force ◽  
Stress Strain State ◽  
Stress Concentration Coefficient

The article considers a crack in the form of a narrow cut with a certain cfn at the cut out in an unbounded plate. The characteristics of the mechanical state of this system under uniaxial loading are determined: the stress concentration coefficient, the crack-driving force, and the energy of a solid with a crack. The elastic energy expenditure during crack propagation is determined. The general regularities of the mechanical state of a solid with a crack, not necessary having the form of an ellipse, are revealed. An important parameter of a crack is the curvature at the tip. It is shown that the Griffiths crack does not actually have a singularity at the tip. The stress strain state of the plate with an elliptical crack is identical to the same of the plate with a focus of homogeneous plastic deformation.

Dynamic Behavior of FGM Doubly Curved Panel due to Mechanical Loading

2019 ◽  
Vol 950 ◽  
pp. 200-204
Author(s):  
Guang Ping Zou ◽  
Nadiia Dergachova
Keyword(s):  
Mechanical Loading ◽  
Volume Fraction ◽  
Equivalent Stress ◽  
Functionally Graded ◽  
Excitation Mode ◽  
Simply Supported ◽  
Curved Panel ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Doubly Curved

This study presents the dynamic response analyze of a simply supported and isotropic functionally graded (FG) double curved panel under mechanical loading. The aim of the research was to investigate mechanical behavior in a FGM curved panel due to different excitation mode of dynamic loading. The novelty of this research is an investigation of von Mises equivalent stress distribution in double curved panel due to different excitation mode. Computed results are found to agree well with the results reported in the literature. Moreover, influence of volume fraction of the material is studied.

Mechanical Properties and Experimental Study of a Composite Polishing Plate during Super-High Polishing

2010 ◽  
Vol 135 ◽  
pp. 337-342
Author(s):  
Li Zhou ◽  
Shu Tao Huang ◽  
Li Fu Xu
Keyword(s):  
Chemical Reaction ◽  
High Speed ◽  
Equivalent Stress ◽  
Stress Distributions ◽  
Centrifugal Forces ◽  
X Ray ◽  
High Speed Rotation ◽  
Speed Rotation ◽  
Von Mises Equivalent Stress ◽  
Von Mises

A new composite polishing plate for polishing of CVD diamond films has been designed. The displacement and stress distributions of the high speed rotation polishing plate have been investigated due to centrifugal forces, and the polishing mechanism of super-high polishing has been analyzed by using X-ray photo-electron spectroscopy. The results showed that the displacements both in axial and radial increase with the increasing of the rotational speed. When the rotation speed reached to 1200 rad/s, the von Mises equivalent stress is about 242 MPa, which is safe for the composite polishing plate. Additional, the polishing mechanism is mainly the chemical reaction between carbon and titanium during the super-high speed polishing. At elevated temperature, the chemical reaction between oxygen and titanium, oxygen and carbon can also occur.

A new method of measuring the stress concentration coefficient

2012 ◽  
Vol 28 (6) ◽  
pp. 436-440
Author(s):  
Krzysztof Kwieciński ◽  
Robert Jachym ◽  
Krzysztof Krasnowski
Keyword(s):  
Stress Concentration ◽  
New Method ◽  
Concentration Coefficient ◽  
Stress Concentration Coefficient

The effects of shape memory alloys’ tension–compression asymmetryon NiTi endodontic files’ fatigue life

2018 ◽  
Vol 232 (5) ◽  
pp. 437-445 ◽  
Author(s):  
MR Karamooz-Ravari ◽  
R Dehghani
Keyword(s):  
Finite Element ◽  
Shape Memory ◽  
Numerical Models ◽  
Equivalent Stress ◽  
Element Model ◽  
Niti Shape Memory Alloy ◽  
Element Analysis ◽  
Tension And Compression ◽  
Von Mises Equivalent Stress ◽  
Von Mises

Nowadays, NiTi rotary endodontic files are of great importance due to their flexibility which enables the device to cover all the portions of curved canal of tooth. Although this class of files are flexible, intracanal separation might happen during canal preparation due to bending or torsional loadings of the file. Since fabrication and characterization of such devices is challenging, time-consuming, and expensive, it is preferable to predict this failure before fabrication using numerical models. It is demonstrated that NiTi shape memory alloy shows asymmetric material response in tension and compression which can significantly affect the lifetime of the files fabricated from. In this article, the effects of this material asymmetry on the bending response of rotary files are assessed using finite element analysis. To do so, a constitutive model which takes material asymmetry into account is used in combination with the finite element model of a RaCe file. The results show that the material asymmetry can significantly affect the maximum von Mises equivalent stress as well as the force–displacement response of the tip of this file.

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