An Improved Analytical Method for Life Prediction of Bolting

2000 ◽  
Vol 123 (1) ◽  
pp. 70-74 ◽  
Author(s):  
F. V. Ellis ◽  
D. R. Sielski ◽  
R. Viswanathan
Keyword(s):  
Stress Relaxation ◽  
Creep Strain ◽  
Life Prediction ◽  
Prediction Method ◽  
Uniaxial Stress ◽  
Life Assessment ◽  
Flow Rule ◽  
Creep Equation ◽  
Strain Limit ◽  
History Of

A research project was conducted to develop and validate an improved, analytical life prediction method for high-temperature turbine and valve studs/bolts. The life prediction method used the two-parameter creep equation, an incremental calculation procedure and a strain hardening flow rule. The failure criterion was an accumulated inelastic or creep strain limit of 1 percent. The life prediction procedure recommends the use of the service history of operating temperature, number/stress level of tightenings, cycle time, etc., to calculate the stress relaxation behavior. Life assessment uses the measured bolt length to calculate the accumulated creep strain. The link between the current condition, i.e., accumulated creep strain, and the remaining creep life, i.e., time to accumulate 1 percent strain, is obtained by a prediction of the future creep strain accumulation under the intended loading cycle(s) imposed during future operation. In order to validate the approach, the calculated results were compared to the results of uniaxial stress relaxation testing, bolt model testing, and service experience. The analytical procedure coupled with other industry wide NDE and measurement procedures is expected to provide broad guidelines to utilities for bolting life assessment.

Calculation of Stress Relaxation Properties for Type 422 Stainless Steel

1999 ◽  
Vol 122 (1) ◽  
pp. 66-71 ◽  
Author(s):  
F. V. Ellis ◽  
Sebastian Tordonato
Keyword(s):  
Stainless Steel ◽  
Stress Relaxation ◽  
Uniaxial Stress ◽  
Rupture Time ◽  
Flow Rule ◽  
Time Data ◽  
Creep Equation ◽  
Relaxation Properties ◽  
Two Parameter ◽  
Rupture Strain

Analytical life prediction methods are being developed for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial stress relaxation testing, bolt model testing, and service experience. Long time creep, creep-rupture, and stress relaxation tests were performed by the National Research Institute for Metals of Japan (NRIM) for 12 Cr-1 Mo-1 W-1/4V, Type 422 stainless steel bolting material, at 500, 550, and 600°C. Based on these results and limited tests for a service-exposed bolt, the creep behavior can be described using a two-parameter material model: ε/εr=1−1−t/trm+1δ where εr is the rupture strain, tr is the rupture time, and m and δ are material constants. For comparison with the measured uniaxial stress relaxation properties, the stress relaxation was calculated using the two-parameter creep equation and a strain-hardening flow rule. The rupture time data was correlated using time-temperature parameter methods. A power law was used for the rupture strain versus rupture time relationship at each temperature. The calculated stress versus time curves were in good agreement with the measured at all temperatures and for initial strain levels of 0.10, 0.15, 0.20, and 0.25 percent. [S0094-9930(00)01701-7]

scholarly journals Numerical Simulation of Creep Damage and Life Prediction of Superalloy Turbine Blade

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Donghuan Liu ◽  
Haisheng Li ◽  
Yinghua Liu
Keyword(s):  
Creep Strain ◽  
Turbine Blade ◽  
Life Prediction ◽  
Damage Model ◽  
Prediction Method ◽  
Creep Damage ◽  
Model Material ◽  
Life Assessment ◽  
Damage Effect ◽  
Superalloy Turbine Blade

Creep caused failure is an important failure mode of the turbine blade. A numerical approach of life assessment of the superalloy turbine blade is proposed in the present paper based on the Lemaitre-Chaboche creep damage model. Material damage is introduced into each element based on the ANSYS APDL function, and the creep damage effect is considered through the modification of Young’s modulus. At last, the strength life and stiffness life of the blade can be obtained through the maximum damage and maximum creep strain criterion, respectively. The present method can not only consider the effect of creep damage, but also give the time histories of the element stresses, damage, and creep strain. The above life prediction results based on the proposed method are compared with theθprojection method, and the results suggest that the present life prediction method of turbine blade is feasible and turbine blade’s life in the present study is determined by creep fracture rather than creep deformation.

Calculation of Stress Relaxation Properties for 1CrMoV Bolt Material

2003 ◽  
Author(s):  
Fred V. Ellis ◽  
Sebastian Tordonato
Keyword(s):  
Stress Relaxation ◽  
Power Law ◽  
Uniaxial Stress ◽  
Flow Rule ◽  
Creep Equation ◽  
Relaxation Properties ◽  
Stress Levels ◽  
Long Time ◽  
Power Law Creep ◽  
Good Agreement

Analytical life prediction methods have been developed for high temperature turbine and valve bolts. For 1CrMoV steel bolt material, long time creep-rupture and stress relaxation tests were performed at 450°C, 500°C, and 550°C by the National Research Institute for Metals of Japan. Based on analysis of their data, the isothermal creep behavior can be described using a power law: ε=Kσn(t)m+1 where ε is the creep strain, t is the time, σ is the stress, K, n, and m are material constants. The time power is a primarily a function of temperature, but also depends slightly on stress. To obtain the value for the time power typical of low stress, the creep equation constants were found in two steps. The time power was found using the lower stress data and a heat-centered type regression approach with the stress levels taking the place of the heats in the analysis. The heat constants were then calculated at all stress levels and regression performed to obtain the stress dependence. For comparison with the measured uniaxial stress relaxation properties, the relaxed stress as a function of time was calculated using the power law creep equation and a strain hardening flow rule. The calculated stress versus time curves were in good agreement with the measured at initial strain levels of 0.10%, 0.15%, and 0.20% for all temperatures except 500°C. At 500°C, good agreement was found using the creep properties typical of a stronger (within heat variation) material.

Full Size Internal Pressure Creep Test for Welded P91 Hot Reheat Piping

2004 ◽  
Author(s):  
Isamu Nonaka ◽  
Takuya Ito ◽  
Fumio Takemasa ◽  
Kensuke Saito ◽  
Yoshikazu Miyachi ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Damage Detection ◽  
Creep Test ◽  
Life Prediction ◽  
Prediction Method ◽  
Creep Damage ◽  
Assessment Method ◽  
Life Assessment ◽  
Full Size ◽  
Test Component

In order to establish the life assessment method for the welded modified 9Cr-1Mo steel hot reheat piping, an internal pressure creep test is conducted with a full size test component. As a result, the fracture mode of the component is clarified and the life prediction method is established. Furthermore, the creep damage detection procedures are proposed.

Full Size Internal Pressure Creep Test for Welded P91 Hot Reheat Elbow

2004 ◽  
Author(s):  
Isamu Nonaka ◽  
Takuya Ito ◽  
Fumio Takemasa ◽  
Kensuke Saitou ◽  
Yoshikazu Miyachi ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Damage Detection ◽  
Creep Test ◽  
Life Prediction ◽  
Prediction Method ◽  
Creep Damage ◽  
Assessment Method ◽  
Life Assessment ◽  
Full Size ◽  
Test Component

In order to establish the life assessment method for the welded modified 9Cr-1Mo steel hot reheat elbow, an internal pressure creep test is conducted with a full size test component. As a result, the fracture mode of the component is clarified and the life prediction method is established. Furthermore, the creep damage detection procedures are proposed.

Hybrid remaining useful life prediction method. A case study on railway D-cables

2021 ◽  
pp. 107746
Author(s):  
Yu Zang ◽  
Wei Shangguan ◽  
Baigen Cai ◽  
Huasheng Wang ◽  
Michael. G. Pecht
Keyword(s):  
Life Prediction ◽  
Prediction Method ◽  
Remaining Useful Life ◽  
Useful Life

Remaining useful life prediction method for machine tools based on meta-action theory

2021 ◽  
pp. 1748006X2110025
Author(s):  
Zongyi Mu ◽  
Yan Ran ◽  
Genbao Zhang ◽  
Hongwei Wang ◽  
Xin Yang
Keyword(s):  
Machine Tools ◽  
Life Prediction ◽  
Action Theory ◽  
Prediction Method ◽  
Operational Reliability ◽  
Remaining Useful Life ◽  
Practical Application ◽  
Dynamic Prediction ◽  
Degradation Model ◽  
Useful Life

Remaining useful life (RUL) is a crucial indictor to measure the performance degradation of machine tools. It directly affects the accuracy of maintenance decision-making, thus affecting operational reliability of machine tools. Currently, most RUL prediction methods are for the parts. However, due to the interaction among the parts, even RUL of all the parts cannot reflect the real RUL of the whole machine. Therefore, an RUL prediction method for the whole machine is needed. To predict RUL of the whole machine, this paper proposes an RUL prediction method with dynamic prediction objects based on meta-action theory. Firstly, machine tools are decomposed into the meta-action unit chains (MUCs) to obtain suitable prediction objects. Secondly, the machining precision unqualified rate (MPUR) control chart is used to conduct an out of control early warning for machine tools’ performance. At last, the Markov model is introduced to determine the prediction objects in next prediction and the Wiener degradation model is established to predict RUL of machine tools. According to the practical application, feasibility and effectiveness of the method is proved.

Micromechanics Method to Evaluate Fatigue Life of Ni-Based Superalloys during Morphological Evolution

2008 ◽  
Vol 385-387 ◽  
pp. 221-224
Author(s):  
Wen Ping Wu ◽  
Ya Fang Guo ◽  
Yue Sheng Wang
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Life Prediction ◽  
Morphological Evolution ◽  
Mean Field ◽  
Prediction Method ◽  
Field Method ◽  
External Stress ◽  
Equivalent Inclusion ◽  
Evolution Of Precipitates

A quantitative life prediction method has been proposed to evaluate fatigue life during morphological evolution of precipitates in Ni-based superalloys. The method is essentially based on Eshelby’s equivalent inclusion theory and Mori-Tanaka’s mean field method. The shape stability and life prediction are discussed when the external stress and matrix plastic strain are applied. The calculated results show that the fatigue life is closely related with microstructures evolution of precipitates. The magnitude and sign of the external stress and matrix plastic strain have an important effect on fatigue life of Ni-based superalloys during the morphological evolution of precipitates.

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