An Evaluation of the Neuber and Glinka Relations for Monotonic Loading

1992 ◽  
Vol 59 (2S) ◽  
pp. S50-S56 ◽  
Author(s):  
W. N. Sharpe ◽  
C. H. Yang ◽  
R. L. Tregoning
Keyword(s):  
Plane Strain ◽  
Plane Stress ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Strain Range ◽  
Local Strain ◽  
Strain Response ◽  
Cycle Fatigue ◽  
Stress Concentrations ◽  
Strain Model

The Neuber relation is widely used to compute elastoplastic stresses and strains at stress concentrations, but a newer relation has been developed by Glinka. Prediction of local strain response is important because low cycle, fatigue life models are based on the strain range. The effects of notch root constraint on the response have been difficult to predict or measure. This paper evaluates the abilities of six models of notch root behavior by comparing them with experimental results over a range of constraints. The models are: the Neuber model, the Neuber model as modified by Walker, the Glinka models for plane stress and for plane strain, and two modifications of the Glinka models that are presented in this paper. Comparisons are made with strains measured at the roots of notches by resistance gages or by laser-based interferometry; data come from previous works as well as some new results of the authors. The constraints vary from plane stress to plane strain with several intermediate cases. Conclusions must take into account the fact that elastoplastic strain measurements have scatter arising from the gage length relative to the grain size. But, in general, one can say that the Neuber model is best for plane stress and the Glinka plane-strain model is best for very large constraint. Response for intermediate amounts of constraint are predicted better by one of the other models.

Life Prediction for Notched Components in Nonproportional Low Cycle Fatigue: Experiment and FEM Analysis

2004 ◽  
Author(s):  
Masao Sakane ◽  
Tsuneo Itoh ◽  
Tomoshige Susaki ◽  
Yoshiyasu Kawazoe
Keyword(s):  
Crack Initiation ◽  
Linear Models ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Fem Analysis ◽  
Local Strain ◽  
304 Stainless Steel ◽  
Cycle Fatigue ◽  
Notched Specimens ◽  
Strain Paths

This paper studies the low cycle fatigue of circumferential notched specimens of type 304 stainless steel in nonproportional loading. Strain controlled tension-torsion low cycle fatigue tests were carried out using the notched specimens under 15 strain paths. Crack initiation lives detected by a d.c. potential method were discussed in relation to the strain concentration factors and strain histories. Finite element analyses were carried out for evaluating the local strain at the notch root using elastic-perfectly plastic and bi-linear models. The maximum principal strain and nonproportional strain ranges conservatively estimated the crack initiation lives of the notched specimens.

scholarly journals THE EFFECT OF NOTCHES ON THE FATIGUE LIFE OF A NICKEL-BASE GAS TURBINE DISK MATERIAL

2018 ◽  
Vol 20 ◽  
pp. 34-42 ◽  
Author(s):  
Robert Eriksson ◽  
Johan Moverare ◽  
Zhe Chen ◽  
Kjell Simonsson
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Strain Range ◽  
Compact Tension ◽  
Critical Distance ◽  
Cycle Fatigue ◽  
Plastic Strain Range ◽  
Life Model

Gas turbine disks carry significant load under high temperatures and may be subject to fatigue failure. Disks contain several notches in the form of the fir tree blade attachments. Low cycle fatigue tests were performed on blunt notch compact tension specimens made from alloy 718. The results indicated that notch support needed to be incorporated not to cause an overly conservative life prediction. The notch support diminished as the plastic strain range decreased, indicating that notch support is only present in the low cycle fatigue regime. A critical distance approach was applied to account for the notch support. An equation relating the critical distance to the notch root stress was derived. The chosen life model was formulated in terms of a variation on the Smith–Watson–Topper (SWT) parameter. The modified SWT parameter taken at the critical distance was used in a life model calibrated for smooth specimens to successfully predict the fatigue life of notched specimens.

Low Cycle Fatigue Analysis of Marine Structures

2006 ◽  
Author(s):  
Xiaozhi Wang ◽  
Joong-Kyoo Kang ◽  
Yooil Kim ◽  
Paul H. Wirsching
Keyword(s):  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Prediction Method ◽  
Local Stress ◽  
Cyclic Plasticity ◽  
Cycle Fatigue ◽  
Stress Concentrations ◽  
Damage Prediction ◽  
Marine Structure ◽  
Number Of Cycles

There are situations where a marine structure is subjected to stress cycles of such large magnitude that small, but significant, parts of the structural component in question experiences cyclic plasticity. Welded joints are particularly vulnerable because of high local stress concentrations. Fatigue caused by oscillating strain in the plastic range is called “low cycle fatigue”. Cycles to failure are typically below 104. Traditional welded joint S-N curves do not describe the fatigue strength in the low cycle region (< 104 number of cycles). Typical Class Society Rules do not directly address the low cycle fatigue problem. It is therefore the objective of this paper to present a credible fatigue damage prediction method of welded joints in the low cycle fatigue regime.

Low-Cycle Strength of Elements of Constructions

2018 ◽  
Author(s):  
Alexander Zvorykin ◽  
Roman Popov ◽  
Mykola Bobyr ◽  
Igor Pioro
Keyword(s):  
Stress State ◽  
Plane Stress ◽  
Low Cycle Fatigue ◽  
Plane Stress State ◽  
Structural Elements ◽  
Cycle Fatigue ◽  
Kinematic Equation ◽  
Effective Coefficients ◽  
Operational Life ◽  
Cycle Loading

Analysis of engineering approach to the operational life forecasting for constructional elements with respect to the low-cycle fatigue is carried out. Applicability limits for a hypothesis on existence of generalized cyclic-deforming diagram in case of complex low-cycle loading (deforming) are shown. It is determined, that under condition of plane-stress state and piecewise-broken trajectories of cycle loading with stresses and deformation checking the cyclic deforming diagram is united in limits of deformations, which are not exceeded 10 values of deformation corresponding material yield point. Generalized kinematic equation of material damageability is described. The method of damageability parameter utilization for increasing of accuracy calculation of structural elements low-cycle fatigue by using the effective coefficients of stresses and deformations taking into account the damageability parameter is given.

scholarly journals Stress-strain response in gears tooth root due to low cycle fatigue

2019 ◽  
Vol 287 ◽  
pp. 02002
Author(s):  
Marina Franulovic ◽  
Kristina Markovic ◽  
Zdravko Herceg
Keyword(s):  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Material Model ◽  
Strain Response ◽  
Tooth Root ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Main Research ◽  
Damage Initiation

Gears are mechanical components which experience high dynamic loading during their exploitation period. Therefore, their load carrying capacity together with life expectancy are often the main research interest in various studies. The research presented in this paper is focused on the materials response in spur gears tooth root, with the attention given to the repeated overloads during gears operation. In order to simulate low cycle fatigue by using numerical modeling of stress - strain relationship within material, the material model which takes into account isotropic and kinematic hardening is used here. Material response of specimens produced out of steel 42CrMo4 in different loading conditions is used for the calibration of material model, which is then applied to simulate damage initiation and materials stress - strain response in gears tooth root. The results show that materials response to the given loading conditions non-linearly change through the loading cycles.

Low Cycle Fatigue Test of Lead Free Solders Using Small Sized Specimen

2017 ◽  
Vol 734 ◽  
pp. 194-201 ◽  
Author(s):  
Yutaka Konishi ◽  
Takamoto Itoh ◽  
Masao Sakane ◽  
Fumio Ogawa ◽  
Hideyuki Kanayama
Keyword(s):  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Testing Machine ◽  
Strain Range ◽  
Fatigue Tests ◽  
Lead Free ◽  
Cycle Fatigue ◽  
Bulk Specimen ◽  
Free Solder ◽  
Lead Free Solders

This paper investigates the fatigue results in low cycle fatigue region obtained from a miniaturized specimen having a 6mm gage length, 3mm diameter and 55mm total length. Fatigue tests were performed for two type lead-free solders using horizontal-type electrical servo hydraulic push-pull fatigue testing machine. Materials employed were Sn-3.0Ag-0.5Cu and Sn-5Sb. The results from Sn-3.0Ag-0.5Cu were compared with those obtained using a bulk specimen in a previous study. Relationship between strain range and number of cycles to failure of the small-sized specimen agreed with those of the bulk specimens. The testing techniques are applicable to Sn-5Sb following the Manson-Coffin law. These results confirm that the testing technique proposed here, using small-sized specimen, is suitable to get fruitful fatigue data for lead-free solder compounds.

Simulation of Piping Ratcheting Experiments Using Advanced Plane-Stress Cyclic Elastoplasticity Models

2019 ◽  
Author(s):  
Konstantinos Chatziioannou ◽  
Yuner Huang ◽  
Spyros A. Karamanos
Keyword(s):  
Finite Element ◽  
Numerical Integration ◽  
Plane Stress ◽  
Numerical Scheme ◽  
Large Scale ◽  
Low Cycle Fatigue ◽  
Structural Response ◽  
Material Behavior ◽  
Repeated Loading ◽  
Cycle Fatigue

Abstract Industrial steel piping components are often subjected to severe cyclic loading conditions which introduce large inelastic strains and can lead to low-cycle fatigue. Modeling of their structural response requires the simulation of material behavior under strong repeated loading, associated with large strain amplitudes of alternate sign. Accurate numerical predictions of low-cycle fatigue depend strongly on the selection of cyclic-plasticity model in terms of its ability to predict accurately strain at critical location and its accumulation (referred to as “ratcheting”). It also depends on the efficient numerical integration of the material model within a finite element environment. In the context of von Mises metal plasticity, the implementation of an implicit numerical integration scheme for predicting the cyclic response of piping components is presented herein, suitable for large-scale structural computations. The constitutive model is formulated explicitly for shell-type (plane-stress) components, suitable for efficient analysis of piping components whereas the numerical scheme has been developed in a unified manner, allowing for the consideration of a wide range of hardening rules, which are capable of describing accurately strain ratcheting. The numerical scheme is implemented in a general-purpose finite element software as a material-user subroutine, with the purpose of analyzing a set of large-scale physical experiments on elbow specimens undergoing constant-amplitude in-plane cyclic bending. The accuracy of three advanced constitutive models in predicting the elbow response, in terms of both global structural response and local strain amplitude/accumulation, is validated by direct comparison of numerical results with experimental data, highlighting some key issues associated with the accurate simulation of multiaxial ratcheting phenomena. The very good comparison between numerical and experimental results, indicates that the present numerical methodology and, in particular, its implementation into a finite element environment, can be used for the reliable prediction of mechanical response of industrial piping elbows, under severe inelastic repeated loading.

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