Finite Element Analysis of Heat Production of Metals during Low-cycle Fatigue Process

2013 ◽  
Vol 49 (04) ◽  
pp. 64
Author(s):  
Weiqing WANG
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heat Production ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Fatigue Process

A Nonlinear Dynamic Reduced-Order Model for a Large Gas Turbine Outer Casing Low Cycle Fatigue Prediction

2021 ◽  
Author(s):  
Aditya Dubey ◽  
Rishi Relan ◽  
Uwe Lohse ◽  
Jaroslaw Szwedowicz
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Gas Turbine ◽  
Nonlinear Dynamic ◽  
Low Cycle Fatigue ◽  
Reduced Order Model ◽  
Cycle Fatigue ◽  
Order Model ◽  
Element Analysis ◽  
Reduced Order

Abstract The secondary stresses that result from nonlinear and transient thermal gradients during the start-up and shut down of the large gas turbine engines drive low-cycle fatigue at specific locations of the outer casing. Typical service inspection of the outer casing is primarily based on finite element analysis estimates, considering various safety factors. However, as finite element analysis includes the worst possible combination of loading scenarios and operating conditions any engine may encounter in actual operation, this results in a conservative estimation of the service interval. Therefore, a generic preventive maintenance plan for the whole fleet often underutilises the casing capability and added cost. Hence, this paper proposes a data-driven nonlinear dynamic reduced-order model developed using the temperature data from low-cycle fatigue critical casing locations, ramp rates, and the percentage load of operation to predict the stresses. As a result, a reduced-order model can assess the damage for low-cycle fatigue critical locations in real-time using the operational data and propose an appropriate service intervention plan for each casing in a fleet.

Experimental fatigue characterization and elasto-plastic finite element analysis of notched specimens made of direct-quenched ultra-high-strength steel

2016 ◽  
Vol 231 (22) ◽  
pp. 4209-4226 ◽  
Author(s):  
Mohammad Dabiri ◽  
Matti Isakov ◽  
Tuomas Skriko ◽  
Timo Björk
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Strength Steel ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Cyclic Softening ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Notched Specimens ◽  
Ultra High Strength Steel

The low-cycle fatigue behavior of a direct-quenched ultra-high-strength steel was experimentally characterized and numerically modeled. Fatigue and cyclic parameters were obtained by conducting strain-controlled low-cycle fatigue tests on uniform-gage specimens. Surface residual stresses were minimized and axial deflection eliminated by optimization of machining parameters and post-machining electro-polishing. The steel material showed cyclic softening and decrease in yield strength. Cyclic softening, stabilized response, and the cyclic stress–strain curve were numerically simulated using finite element analysis with a model capable of describing nonlinear kinematic-isotropic hardening. The results showed good agreement with experimental values and validated the model’s ability to simulate the softening and cyclic stabilization of the material under investigation. The same numerical method was then used in elasto-plastic stress–strain analysis of notched specimens made of the same material to make fatigue life predictions. Estimated lives were compared with predictions made by analytical approximations such as the linear rule, Neuber’s rule, and the strain energy density method and verified by experimental data. Finite element analysis using stabilized cyclic response yields the most accurate predictions and, thus, provides an effective tool for the fatigue analysis of this material.

Low Cycle Fatigue Tests and Simulations on Steel Elbows

2013 ◽  
Author(s):  
Patricia Pappa ◽  
George E. Varelis ◽  
Spyros A. Karamanos ◽  
Arnold M. Gresnigt
Keyword(s):  
Finite Element ◽  
Low Cycle Fatigue ◽  
Local Strain ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Out Of Plane ◽  
Strain Gauge Measurements ◽  
Number Of Cycles

In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditions (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data for in-plane bending. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the low-cycle fatigue of elbows, focusing on the stress and strain variations. Strain gauge measurements are compared with finite element models. Upon calculation of local strain variation at the critical location, the number of cycles to fracture can be estimated.

Experimental Verification of a Full-Size Buckling Restrained Brace

2012 ◽  
Vol 166-169 ◽  
pp. 3147-3150 ◽  
Author(s):  
Lin Liu ◽  
Chao Liu ◽  
Xue Jun Yin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Low Cycle Fatigue ◽  
Axial Strain ◽  
Steel Tube ◽  
Test Sequence ◽  
Element Analysis ◽  
Full Size ◽  
Buckling Restrained Brace ◽  
Steel Core

This paper presents experimental and finite element analysis result of a full-size Buckling Restrained Brace (BRB). The brace consists of a steel core encased in a steel tube filled with concrete. The low-cycle fatigue check was incorporated into the cyclic test program. Test results show that the BRB product can develop stable hysteretic responses up to core axial strain of 1.3% and the maximum compressive loads is 1.23 times the actual yield load. The specimen performs well through the whole test sequence. Nonlinear finite element analysis was conducted for a comparison analysis, and contact interactions between the steel core and concrete infill were modeled. The finite element model can reasonably predict the compression behavior and post-yield strength of the specimen.

Impact of Bolt-Nut Interface Modeling Assumptions on the Calculated Low Cycle Fatigue Life of Aircraft Engine Turbine Rotor Bolted Joints

2013 ◽  
Author(s):  
Anil Saigal ◽  
Luke Jensen ◽  
Thomas James
Keyword(s):  
Finite Element ◽  
Stress Analysis ◽  
Low Cycle Fatigue ◽  
Aircraft Engine ◽  
High Energy ◽  
Bolted Joint ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Joint Stress ◽  
Interface Modeling

Finite element analysis is used extensively in the aircraft turbine engine industry to predict stresses to calculate low cycle fatigue (LCF) life of life-limited parts (LLP’s). A failure of an LLP can lead to a potentially catastrophic event such as a noncontainment of high energy debris. Under-predicted stress can cause the life limits to be set too high, which is a safety hazard. Over-predicted stress can cause the life limits to be set too low, which adds cost due to the need to replace expensive engine hardware more frequently. As such, high fidelity stress analysis is necessary to appropriately set LCF life limits. This study focuses on the nut-bolt interface modeling assumptions associated with a rotor bolted joint stress analysis for LCF predictions. A 3D finite element model of an actual aircraft engine rotor bolted joint is created. Different cases are analyzed and compared to investigate how the thread modeling assumptions might affect the calculated life in the mated rotor LLP hardware. Walker-adjusted alternating stress, σ0,alt, is used to measure the affect on life impact. It is shown that elastic versus elastic-plastic nut/bolt materials properties and the inclusion of the helical thread shape have minor impact on the calculated stresses. However, inclusion of contact elements with friction at the thread interface instead of couples has a moderate impact on the calculated stresses and therefore expected life.

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