Thermal Stress and Fatigue Analysis in Turbine Rotors

1971 ◽  
Vol 93 (1) ◽  
pp. 13-20
Author(s):  
C. L. Chow
Keyword(s):  
Thermal Stress ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Cold Start ◽  
Fatigue Analysis ◽  
Stress Conditions ◽  
Computer Technique ◽  
Detailed Method ◽  
Physical Geometry ◽  
Block Relaxation

A method of thermal stress and fatigue analysis under triaxial stress conditions is presented. A rotor of a marine steam turbine is taken as a typical example to illustrate the detailed method of analysis in assessing the cycle damage life of the rotor. A computer technique of iterative block relaxation is devised for the thermal stress calculation as the physical geometry of the problem under consideration is fairly complex. This technique is particularly advantageous for such a system as (a) damping the magnitude of the oscillation in the solution of the ill-conditioned stress equations and (b) keeping the number of nodal points required in a converging solution to a minimum. Three different operating procedures of starting and loading the marine turbine have been studied with full three-dimensional stress and fatigue considerations. One of the three procedures which is found to be more desirable is recommended with the descriptions of detailed steam history and main features of the cold start throughout its whole operation.

On Comparison of Two Approaches for Steam Turbine Optimizing Start-Up

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chao Dongy ◽  
◽  
Yongjian Sun ◽  
Keyword(s):  
Mathematical Model ◽  
Thermal Stress ◽  
Steam Turbine ◽  
Working Condition ◽  
Cold Start ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Limit Value ◽  
Operating Rules ◽  
Start Up

According to the operating conditions, operating rules and procedures of the steam turbine, a 300MW steam turbine cold start mathematical model was established, and the finite element 3-D modeling and simulation of the 300MW condensing steam turbine rotor was carried out. By using ANSYS. Calculate the stress value of cold start-up according to the cold start curve under standard conditions. The start-up curve design of the initial working condition is inefficient. This paper uses genetic algorithm and particle swarm optimization algorithm to optimize and analyze the turbine mathematical model, draw a new cold start-up curve, and then load the cold start curve into the model. The ANSYS calculates the optimal thermal stress value. After calculating the stress, compare the results on the initial working condition with the results after two optimizations. In contrast, under the premise of ensuring that the thermal stress value of the turbine rotor does not exceed the limit value of the rotor, the startup time is shortened and the economy is improved.

An Advanced Reliability Improvement and Failure Analysis Approach to Thermal Stress Issues in IC Packages

2009 ◽  
Author(s):  
Michael Hertl ◽  
Diane Weidmann ◽  
Alex Ngai
Keyword(s):  
Thermal Stress ◽  
Failure Analysis ◽  
Deformation Measurement ◽  
Stress Conditions ◽  
Analysis Approach ◽  
New Approach ◽  
Reliability Improvement

Abstract A new approach to reliability improvement and failure analysis on ICs is introduced, involving a specifically developed tool for Topography and Deformation Measurement (TDM) under thermal stress conditions. Applications are presented including delamination risk or bad solderability assessment on BGAs during JEDEC type reflow cycles.

Steady-State Formulation for Stress and Distortion of Welds

1994 ◽  
Vol 116 (4) ◽  
pp. 467-474 ◽  
Author(s):  
M. Gu ◽  
J. A. Goldak
Keyword(s):  
Thermal Stress ◽  
Steady State ◽  
Three Dimensional ◽  
Significant Gain ◽  
Free Boundaries ◽  
Flow Lines ◽  
Eulerian Formulation ◽  
Noticeable Reduction ◽  
Computing Speed ◽  
Lagrangian Frame

A steady state formulation has been developed for thermal stress analysis. It uses features from both the Lagrangian formulation and the Eulerian formulation. The mesh sits on an Eulerian frame but deforms as if in the Lagrangian frame. Therefore, it is suitable for steady state problems with free boundaries. History dependent parameters are integrated along flow lines. A significant gain in computing speed and/or spatial resolution over transient analyses has been achieved together with a noticeable reduction for memory requirements. Numerical results are given for a three-dimensional analysis of edge weld.

Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine

2014 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Arne Graßmann
Keyword(s):  
Steam Turbine ◽  
Design Process ◽  
Energy Demand ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Pressure Steam ◽  
Last Stage

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.

THERMAL EXPANSION OF PHASE-CHANGE RANDOM ACCESS MEMORY CELLS

2008 ◽  
Vol 1072 ◽  
Author(s):  
Jianming Li ◽  
L.P. Shi ◽  
H.X. Yang ◽  
K.G. Lim ◽  
X.S. Miao ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Phase Change ◽  
Electrical Power ◽  
Thermal Strain ◽  
Three Dimensional ◽  
Amorphous State ◽  
Random Access ◽  
Random Access Memory ◽  
Access Memory ◽  
Three Dimensional Finite Element

ABSTRACTThree-dimensional finite element method (FEM) is used to solve the thermal strain-stress fields of phase-change random access memory (PCRAM) cells. Simulation results show that thermal stress concentrates at the interfaces between electrodes and phase change layer and it is significantly larger than that within the phase change layer. It has been found that the peak thermal stress is linearly related to the voltage of electrical pulse in the reset process but once amorphous state is produced in the cell, a nonlinear relationship between thermal stress and electrical power exists. This paper reported the change of thermal stress during set process. It was found that the stress decreases significantly due to the amorphous active region during set processes.

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