The invention discloses a method for predicting an influence of the sample size on fatigue life. The method comprises the steps that by means of a function relationship between the fatigue life and stress, the fatigue life under different stress levels are converted into the fatigue life under the same stress level; statistical analysis is conducted on the fatigue life under the same stress level, and the most obedient probability distribution from is determined; the control volume of a small sample and the control volume of a big sample are calculated, and the control volume ratio of the big sample to the small sample is determined; the fatigue life N of the big sample is obtained through n times of Monte Carlo simulation of the fatigue life N of the small sample under the same stress, that is, N =min{N1, N2,..., Nn}; multiple fatigue life data of the big sample under the same stress are obtained; the fatigue life data of the big sample under different stress is obtained; statistical analysis is conducted on the obtained big sample fatigue life data, and a P-S-N curve is obtained. The defect that for big sample fatigue tests, the time and energy are wasted is effectively overcome.

Method for predicting influence of sample size on fatigue life

A fatigue limit rapid prediction method based on strain increment belongs to the field of rapid prediction of material fatigue limit. The invention discovers that under gradient stress load, the variation rule of strain capacity is very similar to the variation rule of temperature. Since the Luong method can use corresponding stable temperature rise value under gradient load to predict the fatigue limit, the strain capacity under gradient load can theoretically be used for rapid prediction of fatigue limit. The method utilizes a fatigue testing machine and an extensometer thereof (no dependence on expensive high-precision thermal infrared imager), and theoretically only uses one specimen to rapidly and economically predict a reliable fatigue limit of the material or a simple member in a day time according to variation rule of strain capacity under gradient load. The traditional lifting method and grouping method spend a few months and consume a large amount of human and financial resources, therefore the present invention has high engineering practical value and significant economic benefits.

Fatigue limit rapid prediction method based on strain increment

The invention discloses a usage life monitoring device used for a high and middle pressure cylinder of a frequently rapid start and stop combined cycle steam turbine. Strain changes of a high and middle pressure cylinder are sensed by strain gages, and strain values are transmitted to the strain gauges to conduct observation. A data logger is used to carry out recording and storing. A life evaluation server carries out real time processing on the measured strain information, and converts the information into stress information of key positions of the high and middle pressure cylinder. A temperature sensor and a pressure sensor are utilized to sense changing information of the temperature and the pressure of the high and middle pressure cylinder, and provide the information for the life evaluation server to calculate a temperature field and a stress field of the high and middle pressure cylinder in real time. With consideration given to stress distribution measured by the foil gauges of the high and middle pressure cylinder and stress field distribution obtained through value calculating, and according to a creep deformation life curve and a fatigue life curve of materials of the high and middle pressure cylinder, the real-time life consumption rate of the high and middle pressure cylinder of the frequently rapid start and stop combined cycle steam turbine and an accumulative life consumption real-time monitoring curve of the high and middle pressure cylinder are obtained.

A usage life monitoring device used for a high and middle pressure cylinder of a frequently rapid start and stop combined cycle steam turbine

The invention discloses a method of adopting a strain sensor to monitor the fatigue of nuclear grade pipelines. At first, a strain sensor (a strain sheet or a strain meter) is used to monitor the strain of the external surface of a nuclear grade pipeline; then according to the external surface strain of the nuclear grade pipeline, the properties of the material of the nuclear grade pipeline, and information of an existed monitoring device of the nuclear power plant, the strain of the internal wall of the nuclear grade pipeline can be determined; then alternation amplitude in strain circulations and corresponding circulation times can be determined; according to a preset epsilon-N curve, the fatigue use coefficient is calculated; then according to the pipeline strain history, the reasonable environmental influence coefficient (Fen) is determined, the fatigue use coefficient is corrected; finally, the fatigue use coefficient is output on the display terminal of the master-control room, and an accumulated fatigue use coefficient curve, which changes along the time, can be outputted and can be used to evaluate the change trend of accumulated fatigue use coefficient of a monitored position.

Method of adopting strain sensor to monitor fatigue of nuclear grade pipelines

A system for determining a remaining useful life of a cooling component operatively connected to a prime mover. A controller performs a thermal strain analysis that includes determining the power output of the prime mover based upon sensor signals, determining a temperature output of the prime mover based upon the power output, determining a temperature at each of the plurality of analysis locations based upon the temperature output, determining a temperature difference based upon the temperature at each respective one of the plurality of analysis locations, and determining a thermal strain based upon the temperature difference. The controller repeats the thermal strain analysis at time intervals over a period of time, determines an accumulated damage for the cooling component based upon the thermal strain from each thermal strain analysis, and determines a remaining useful life of the cooling component based upon the material characteristics and the accumulated damage.

Useful life prediction system for cooling components

The invention relates to a boiler wall temperature and stress measurement device and a boiler fatigue life measurement method. Two thermoelectric couples and two strain gauges are stuck onto the outer wall and the inner wall of an upper barrel of a boiler; the thermoelectric couples are connected with a temperature data acquisition instrument by leads; the strain gauges are connected with a stress meter by leads. The device is characterized by being provided with a conduit and a sleeve, wherein the two ends of the conduit are provided with a flange (1) and a flange (2) respectively; the flange (1) is connected with a connecting flange of the upper barrel of the boiler in a sealing way; the bottom end of the sleeve is provided with a flange (3); the flange (2) is connected with the flange (3); the flange (3) is provided with small holes; the leads of the thermoelectric couple and the strain gauge which are arranged on the inner wall of the upper boiler barrel pass through the small holes; the flange (3) is welded with a thermoelectric couple metal shell to form a whole body so as to be sealed; a junction box is connected to the sleeve; the leads of the thermoelectric couple and the strain gauge which are arranged on the inner wall of the upper boiler barrel enter the junction box through the conduit and the sleeve.

Boiler wall temperature and stress measurement device and boiler fatigue life measurement method

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Boiler wall temperature and stress measurement device and boiler fatigue life measurement method