Modeling of the materials superplasticity based on damage summation theory

2018 ◽  
Author(s):  
Daniel Sawicki ◽  
Volodymyr O. Kraievskyi ◽  
Volodymyr M. Mykhalevych ◽  
Olga Ostapenko
Keyword(s):  
Damage Summation

The generalized regularities of damageability and integrity in estimations of the endurance in conditions of variability of loading regimes

2019 ◽  
Vol 85 (9) ◽  
pp. 61-65
Author(s):  
N. A. Makhutov
Keyword(s):  
Life Time ◽  
Cyclic Strength ◽  
Laboratory Diagnostics ◽  
Methodological Issues ◽  
Break Points ◽  
Number Of Cycles ◽  
Cyclic Damage ◽  
Damage Summation ◽  
Temperature Factors

We consider and analyze general methodological issues regarding the strength and endurance (life-time) of the materials and structure elements under a combined effect of various force, deformation and temperature factors. The Journal "Zavodskaya laboratoriya. Diagnostika materialov" (Industrial laboratory. Diagnostics of materials) has launched systematic publications on this problematic since 2018. For many decades, domestic and foreign laboratory studies have gleaned to a traditional methodology for obtaining initial curves of the long-term and cyclic strength that related the breaking stresses with time or number of cycles. These curves, with the characteristic sections and break points, separating the areas of elastic and inelastic (plastic strain or creep strain) strain, are used in analysis of long-term and cyclic damage. Using the elementary linear law of damage summation, it is possible to calculate at a first approximation the strength and endurance under varying conditions of loading. Stepping up the requirements to the accuracy of calculations necessitates a transition from force fracture criteria (at stresses a) to deformation criteria (in elastic and inelastic deformations e). Thus, it becomes possible to construct and use a unified expression for the curve of the long-term cyclic fracture (taking into account the temporal x and cyclic N factors) and a long-term cyclic damage. With such approach it is possible to remain the linear law of damage summation though those damages are obviously nonlinear. The goal of the study is to continue and support the discussion of the most complex problems of a comprehensive assessment of the strength, resource, survivability and safety of high-risk engineering equipment within the journal pages.

Creep Failure Simulations for 316H at 550°C

2012 ◽  
Author(s):  
Nak Hyun Kim ◽  
Yun Jae Kim ◽  
Catrin M. Davies ◽  
Kamran M. Nikbin ◽  
David W. Dean
Keyword(s):  
Experimental Data ◽  
Damage Model ◽  
Creep Damage ◽  
Inelastic Strain ◽  
Compact Tension ◽  
Creep Failure ◽  
Creep Ductility ◽  
Summation Rule ◽  
Creep Damage Model ◽  
Damage Summation

In this work a method to simulate failure due to creep is proposed using finite element damage analysis. The creep damage model is based on the creep ductility exhaustion concept. Incremental damage is defined by the ratio of incremental inelastic (plastic & creep) strain and multi-axial ductility. A simple linear damage summation rule is applied. When accumulated damage becomes unity, element stresses are reduced to almost zero to simulate progressive crack growth. The model is validated through comparison with experimental data on various sized compact tension, C(T), specimens of 316H stainless steel at 550 °C. The influence of the inelastic strain rate on the uniaxial ductility is considered. Good agreement is found between the simulated results and the experimental data.

Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Hélder F.S.G Pereira ◽  
Abílio M. P. De Jesus ◽  
Alfredo S. Ribeiro ◽  
António A. Fernandes
Keyword(s):  
Fatigue Damage ◽  
Structural Component ◽  
Stress Ratio ◽  
Sequence Effect ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Load Sequence ◽  
Stress Ratios ◽  
Remote Stress ◽  
Damage Summation

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren–Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope stress-life curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as nonconservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two-block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely, R=0, R=0.15, and R=0.3. Also, constant amplitude fatigue data are generated for the investigated structural component. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels, and stress ratios. In particular, a clear load sequence effect is verified for the two-block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is nonlinear. This suggests an important effect of the stress ratio on fatigue damage accumulation.

scholarly journals USING THE LINEAR DAMAGE SUMMATION HYPOTHESIS IN THE FATIGUE TESTS ANALYSIS OF TITANIUM ALLOY PIECES

2021 ◽  
pp. 1-6
Author(s):  
Evgeniya Gnatyuk ◽  
Arkadiy Skvortsov ◽  
Svetlana Kuleshova
Keyword(s):  
Titanium Alloy ◽  
Endurance Limit ◽  
Linear Regression Analysis ◽  
High Strength ◽  
Fatigue Tests ◽  
Test Pieces ◽  
Operational Testing ◽  
Strength Material ◽  
Number Of Cycles ◽  
Damage Summation

This paper presents the results of fatigue tests of titanium alloy, and also describes the use of the hypothesis of linear damage summation when processing the results of fatigue tests. On the basis of the experiments, the endurance limit of the titanium alloy was determined, which lies in the range from 460 to 480 MPa with the number of cycles from 105 to 108. The purpose of the experiment was to determine the endurance limit of high strength material, as well as a mathematical measurement of the expected destruction. In this study, empirical methods were used such as indirect observation of the object under study, description and measurement of technical influences exerted on it by an artificial means, as well as linear regression analysis to establish the relationship between stress and durability. As a result of the experiment, fatigue curves were obtained for various probabilities, which give grounds to conclude that the use of the linear damage summation hypothesis in processing the results of fatigue tests entails a satisfactory practical accuracy of the calculation of endurance limit. This experiment is aimed at improving metal production by studying the quality of titanium alloy test pieces and performing mathematical analysis of possible problems arising in the process of its operational testing.

scholarly journals Two Approaches to the Problem of High-cycle Fatigue of Materials and Structures

2019 ◽  
Vol 253 ◽  
pp. 01004 ◽  
Author(s):  
Vladimir Mironov ◽  
Lukashuk ◽  
Dmitriy Ogorelkov
Keyword(s):  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Material Degradation ◽  
Metallic Structures ◽  
New Methods ◽  
Vibration Decrement ◽  
Fatigue Of Materials ◽  
Notable Increase ◽  
Foam Filled ◽  
Damage Summation

Creation of new types of materials and development of new methods aimed at extending the lifetime of structures are two interconnected approaches to solve the problem of metallic structures fatigue. The paper considers a method for estimating the efficiency of damping implemented in metallic structures by means of energy-intensive materials. The results of comparative calculation are given on the ultimate number of transverse vibration cycles in bridge girders. The calculation uses a linear hypothesis of fatigue-caused damage summation and a model of cyclic material degradation. Notable increase of the vibration decrement for foam-filled metallic structures is predicted, with the lifetime of products lengthening as a result.

Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading

2007 ◽  
Author(s):  
He´lder F. S. G. Pereira ◽  
Abi´lio M. P. De Jesus ◽  
Anto´nio A. Fernandes ◽  
Alfredo S. Ribeiro
Keyword(s):  
Fatigue Damage ◽  
Structural Component ◽  
Stress Ratio ◽  
Sequence Effect ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Load Sequence ◽  
Stress Ratios ◽  
Remote Stress ◽  
Damage Summation

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren-Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope S-N curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as non-conservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely R = 0, R = 0.15 and R = 0.3. Also constant amplitude fatigue data is generated for the investigated structural detail which is applied for indirect damage calculations. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels and stress ratios. In particular, a clear load sequence effect is verified for the two block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is non-linear. This suggests an important effect of the stress ratio on fatigue damage accumulation.

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