Low Cycle Fatigue Analysis of after Treatment Device Induced due to Thermal Load by Using Finite Element Analysis

2014 ◽  
Vol 592-594 ◽  
pp. 1104-1108 ◽  
Author(s):  
Swapnil Vitthal Kumbhar ◽  
Vilas Kulkarni ◽  
R.M. Tayade
Keyword(s):  
Crack Initiation ◽  
Thermal Fatigue ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Analysis ◽  
Von Mises Stress ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Von Mises

Cyclic thermal loading causes cyclic thermal stress and thermal fatigue in the component. The goal of this paper is to characterize the thermal fatigue behavior of after-treatment (AT) device, i.e. Exhaust Gas Processor (EGP) and prediction of crack initiation cycles. The paper contains transient thermal analysis to map temperature on EGP model. By taking temperature distribution as input, Elasto-plastic structural analysis is done. Based on stress-strain data and fatigue material property, crack initiation cycles are estimated. For low cycle fatigue analysis, strain based approach, i.e. Brown-Miller Criteria with Morrow mean stress correction factor [1] is used. The von-Mises stress and crack initiation cycles are investigated and S-N curve and Ɛ-N curve are compared with standard graphs.

Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Adrian Willuweit ◽  
Steffen Bergholz ◽  
Christian Philippek ◽  
Jevgenij Kobzarev
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hybrid Approach ◽  
Combined Cycle ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Constitutive Material Model ◽  
Standard Design ◽  
Creep Fatigue

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.

Factors Affecting the Low Cycle Fatigue Behavior around the Weak Axis of Welded I-Section Bracing Members

2006 ◽  
Vol 324-325 ◽  
pp. 959-962
Author(s):  
Yao Chun Zhang ◽  
Wei An Lian ◽  
Wen Yuan Zhang
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Crack Initiation ◽  
Surface Crack ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Loading History ◽  
Energy Dissipation Capacity ◽  
Surface Crack Initiation

The low cycle fatigue behavior and energy dissipation capacity around the weak axis of the welded I-section bracing members are investigated by 35 pinned-pinned bracing specimen tests under the axial cyclic loading with different characteristics. Particular attention is paid to the effects of loading amplitude, loading history and geometry properties of these members. It is found that the fatigue damage propagating to fracture in the flanges of the bracing members can be divided into 3 stages involving the macroscopic surface crack initiation, the penetrated crack formation and the penetrated crack propagation. Some empirical formulas to estimate the fatigue life and cyclic energy dissipation capacity of the bracing members are also presented based on the experimental data. The statistical analysis indicates that the fatigue life to surface crack initiation significantly depends on the inelastic local buckling and will increase with decreasing width-thickness ratio of the flanges and increasing slenderness ratios of the bracing members. Besides, it is found that the low cycle fatigue and energy dissipation of these members also depends on loading amplitude and loading history, and the effects of overloads and mean compression amplitude can improve the fatigue performance of bracing members. The test results show that the bracing members with better low-cycle fatigue resistance have the better energy dissipation capacities.

scholarly journals Effect of LCF Pre-Damage on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy

2017 ◽  
Author(s):  
Nie Baohua ◽  
Zhao Zihua ◽  
Ouyang Yongzhong ◽  
Chen Dongchu ◽  
Chen Hong ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Mechanism Analysis ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

The effect of low cycle fatigue (LCF) pre-damage on the subsequent very high cycle fatigue (VHCF) behavior is investigated in TC21 titanium alloy. LCF pre-damage is applied under 1.8% strain amplitude up to various fractions of the expected life and subsequent VHCF properties are determined using ultrasonic fatigue tests. Results show that 5% of LCF pre-damage insignificantly affects the VHCF limit due to the absent of pre-crack, but decreases the subsequent fatigue crack initiation life estimated by Pairs’ law. Pre-cracks introduced by 10% and 20% of LCF pre-damage significantly reduce the subsequent VHCF limits. The crack initiation site shifts from subsurface-induced fracture for undamaged and 5% of LCF pre-damage specimens to surface pre-crack for 10% and 20% of LCF pre-damage specimens in very high cycle region. The fracture mechanism analysis indicate that LCF pre-crack will re-start to propagate under subsequently low stress amplitude when stress intensity factor of pre-crack is larger than its threshold. Furthermore, the predicted fatigue limits based on EI Haddad model for the LCF pre-damage specimens well agree with the experimental results.

scholarly journals Establishment of new design criteria for GlidCop® X-ray absorbers

2017 ◽  
Vol 24 (2) ◽  
pp. 402-412
Author(s):  
Jeff T. Collins ◽  
Jeremy Nudell ◽  
Gary Navrotski ◽  
Zunping Liu ◽  
Patric Den Hartog
Keyword(s):  
Thermal Fatigue ◽  
Research Program ◽  
Thermal Loading ◽  
Fatigue Behavior ◽  
Parametric Models ◽  
Beam Power ◽  
Design Criteria ◽  
Element Analysis ◽  
X Ray ◽  
Fatigue Model

An engineering research program has been conducted at the Advanced Photon Source (APS) in order to determine the thermomechanical conditions that lead to crack formation in GlidCop®, a material commonly used to fabricate X-ray absorbers at X-ray synchrotron facilities. This dispersion-strengthened copper alloy is a proprietary material and detailed technical data of interest to the synchrotron community is limited. The results from the research program have allowed new design criteria to be established for GlidCop® X-ray absorbers based upon the thermomechanically induced fatigue behavior of the material. X-ray power from APS insertion devices was used to expose 30 GlidCop® samples to 10000 thermal loading cycles each under various beam power conditions, and all of the samples were metallurgically examined for crack presence/geometry. In addition, an independent testing facility was hired to measure temperature-dependent mechanical data and uniaxial mechanical fatigue data for numerous GlidCop® samples. Data from these studies support finite element analysis (FEA) simulation and parametric models, allowing the development of a thermal fatigue model and the establishment of new design criteria so that the thermomechanically induced fatigue life of X-ray absorbers may be predicted. It is also demonstrated how the thermal fatigue model can be used as a tool to geometrically optimize X-ray absorber designs.

Comparative Low-Cycle Fatigue Behavior of HAYNES 244 Alloy and Waspaloy

2021 ◽  
Author(s):  
Michael G. Fahrmann
Keyword(s):  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Axial Strain ◽  
Fatigue Crack Initiation ◽  
High Strength ◽  
Cyclic Hardening ◽  
Cycle Fatigue ◽  
Softening Behavior

Abstract HAYNES® 244® alloy was chiefly developed to address the need for high-strength, low coefficient of thermal expansion (CTE) alloys for seal rings and cases in advanced gas turbine engines. In addition to these attributes, adequate resistance to low-cycle fatigue (LCF) due to cyclic thermal and mechanical loading during service is critical for such applications. The isothermal LCF performance of commercially produced 0.5” (12.5 mm) thick, fully heat treated plate products of 244 alloy was evaluated by means of axial strain-controlled (R = −1) LCF tests covering total strain ranges up to 1.25 % (without dwells), at temperatures ranging from 800–1400°F (427–760°C). In addition, the comparative LCF performance of Waspaloy, a well-established alloy for turbine cases, was evaluated under selected, nominally identical test conditions. S-N curves were constructed and fitted by the Coffin-Manson equation, allowing the delineation of regimes controlled by the elastic and plastic response of the material. Fracture surfaces were examined in the scanning electron microscope to identify fatigue crack initiation sites and crack propagation modes. Differences between the alloys are discussed in terms of tensile strength and cyclic hardening/softening behavior. Implications for fatigue performance of these alloys under cyclic thermal loading conditions are discussed as well.

Low-Cycle Fatigue Behavior Under Biaxial Strain Distribution

1969 ◽  
Vol 91 (1) ◽  
pp. 23-31 ◽  
Author(s):  
J. L. Mattavi
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Biaxial Strain ◽  
Cyclic Life ◽  
Aluminum Casting ◽  
Strain Mode ◽  
Damage Theory ◽  
Von Mises ◽  
Elastic Strains

This paper presents a linear cumulative damage theory considering macroscopically both elastic and plastic straining to define behavior in the low-cycle fatigue region of the classic S-N curve. A combined strain mode was considered throughout the study with biaxiality effects accounted for through the von Mises theory. An experimental evaluation was conducted to determine the validity of the theory. The biaxial strain mode was provided by centrifugally loading 6-in-dia rotors. Experimentation on SAE 4340 steel alloy supported the damage theory and confirmed the existence of exponential relationships between equivalent elastic strains with cyclic life and equivalent plastic strains with life similar to those contained in the literature for uniaxially loaded specimens. A limited evaluation of an aluminum casting material, C 355-T61, also supported this exponential dependency.

Fatigue Life Estimation Method Considering Inelastic Behavior of Ni-Based Directionally Solidified Superalloy With Multiple Holes

2012 ◽  
Author(s):  
Takashi Yokoyama ◽  
Masaru Sekihara
Keyword(s):  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Estimation Method ◽  
Inelastic Strain ◽  
Maximum Tensile Stress ◽  
Fatigue Tests ◽  
Inelastic Behavior ◽  
Cycle Fatigue ◽  
Directionally Solidified ◽  
Element Analysis

Low cycle fatigue tests at high temperature were conducted on test specimens with small holes made of a Ni-based directionally solidified superalloy, which are intended as the cooling structures formed in the components in the fossil fuel power plant. The tests included those cases with and without a strain holding process, i.e., fatigue creep interaction (FCI) tests and low cycle fatigue (LCF) tests, respectively. The number of LCF crack initiation cycles of the one- and seven-hole specimens decreased compared to that of the smooth one. The number of FCI crack initiation cycles of a compressive hold case for the seven-hole specimen decreased compared to that of the LCF test, while that of a tensile hold case decreased further. The test results were evaluated based on the inelastic behavior around the center hole of the specimens, where the most serious inelastic strain occurred, using finite element analysis that takes into account the inelastic anisotropy of material properties. The number of crack initiation cycles of the LCF and the compressive FCI tests correlated with the maximum tensile stress around the hole, while that of all the tests correlated with the frequency-modified strain energy. We propose a method for evaluating cyclic inelastic behavior around a hole using cyclic Neuber’s rule for anisotropic materials to simply evaluate the failure life of actual components.

scholarly journals Failure Investigation of Plastic Shredding Machine’s Flange Coupling Based on Mechanical Analysis

2017 ◽  
Vol 2 (2) ◽  
pp. 124 ◽  
Author(s):  
Ignatius Pulung Nurprasetio ◽  
Bentang Arief Budiman ◽  
Farid Triawan
Keyword(s):  
Crack Initiation ◽  
Dynamic Load ◽  
Cast Steel ◽  
Hardness Test ◽  
Mechanical Analysis ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Failure Investigation ◽  
Critical Stresses ◽  
Von Mises

This paper presented the investigation of failure mechanism of plastic shredding machine’s flange coupling which is made of cast steel. The machine unexpectedly stalled a few minutes after High-Density Polyethylene (HDPE) plastic bottles were fed into the machine. It was discovered afterward that the flange broke with the large crack surface. Finite element analysis (FEA) was performed to find the position and value of the critical stresses in the flange during operating condition. Subsequently, hardness test was conducted on the flange body to determine the Brinell hardness which was then converted into the approximate ultimate tensile strength (σu). As a result, a maximum Von Mises stress of 287 MPa was confirmed from the FEA to be concentrated in the flange’s keyway. Although this was found to be lower than the approximate σu obtained from hardness testing i.e. 449 MPa, the critical stress indicated an unstable condition which may induce a crack initiation any time when vibration or dynamic load occurs. Based on these analyses, it was concluded that the failure had been initiated by dynamic rather than static loading generated during machine stall condition. The dynamic load caused crack initiation at a stress concentration point of the keyway. The crack then propagated rapidly, breaking the flange body.

Optimization of Turbine Disk Profiles by Metamorphic Development

2002 ◽  
Vol 124 (2) ◽  
pp. 192-200 ◽  
Author(s):  
Jing-Sheng Liu ◽  
Geoffrey T. Parks ◽  
P. John Clarkson
Keyword(s):  
Hoop Stress ◽  
Thermal Loading ◽  
Axial Stress ◽  
Optimization Method ◽  
Geometric Constraints ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Metamorphic Development ◽  
Turbine Disks ◽  
Von Mises

A novel topology/shape optimization method, Metamorphic Development, is applied to an axisymmetric thermo-elasticity design problem. Based on solid modeling and finite element analysis, optimal profiles of minimum mass turbine disks are sought by growing and degenerating simple initial structures subject to both response and geometric constraints. Radial stress, axial stress, hoop stress and von Mises stress are analyzed throughout the optimization and a constraint is imposed on von Mises stress everywhere in the disk. The optimal structures are developed metamorphically in specified infinite design domains using both quadrilateral and triangular axisymmetric finite elements. Comparisons are made of the results obtained for different optimization scenarios: (a) with and without thermal loading; (b) with and without centrifugal body forces; (c) with and without a fit pressure on the inner surface of the hub; and (d) operating at different rotational speeds.

Notch Effect on Low Cycle Fatigue of Sn–3.5Ag Solder

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Mineo Nozaki ◽  
Masao Sakane ◽  
Yutaka Tsukada
Keyword(s):  
Stress Concentration ◽  
Crack Initiation ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Elastic Stress ◽  
Low Cycle Fatigue ◽  
Notch Effect ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Cycles To Failure

This paper studies the notch effect on low cycle fatigue of Sn–3.5Ag solder. Strain controlled push-pull low cycle fatigue tests were carried out using three circumferential notched specimens at 313K. Cycles to crack initiation were measured by an a.c. potential method, and cycles to failure and for crack propagation were also determined in experiments. Cycles to failure, to crack initiation, and for propagation decreased with elastic stress concentration factor but cycles to crack initiation were most sharply reduced with elastic stress concentration factor. Prediction methods of cycles to crack initiation, for propagation, and to failure were discussed from the data fitting and the local strain approach utilizing finite element analysis.

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