Method of predicting deterioration and damage of structural member and prediction apparatus for use with the method

• US 5,455,777 A
• Filed: 11/19/1993
• Issued: 10/03/1995
• Est. Priority Date: 11/20/1992
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Fujiyama, Kazunari, Yoshioka, Yomei, Okabe, Nagatoshi, Murakami, Itaru
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): NOORI, MAX H
• Application Number:
  US08/154,543
• Time in Patent Office: 683 Days
• Field of Search: 73/799, 73/804, 73/866.4, 364/507, 364/508
• US Class Current: 702/34
• CPC Class Codes: G01N 17/00 Investigating resistance of materials to the weather, to corrosion, or to light
• CPC Class Codes: G07C 3/00 Registering or indicating the condition or the working of machines or other apparatus, other than vehicles

Abstract

An apparatus for predicting a deterioration and damage in a structural member of a prime mover or the like has a use condition monitoring unit for monitoring a condition of use of the structural member, an inspection unit for inspecting a deteriorated and damaged state of the structural member, a use condition setting unit for setting a use condition by being supplied with use condition data of the structural member from the use condition monitoring unit, a simulation unit for forming a model of the deterioration and damage in the structural member on the basis of the use condition of the structural member and a result of inspection of the structural member at a preceding time, and for simulating the advancement of the deterioration and damage in the structural member on the basis of the deterioration/damage model, and an inverse analysis unit for correcting a simulation model formed by the simulation unit by comparing the simulation model with a result of inspection of the structural member at the present time. The simulation unit is arranged to predict a future deterioration and damage in the structural member by using the corrected simulation model and the result of present inspection. By a deterioration/damage prediction apparatus of the invention using this apparatus, the deterioration and damage in the structural member can be accurately predicted using a simulation and an inverse-problem analysis method with respect to use conditions and results of inspection of the structural member, i.e., information actually available.

Claims

1. A method of predicting deterioration and damage in a structural member operated under a high temperature condition for a long period of time, the method comprising the steps of:

inspecting information regarding a number, position, shape, and length of micro cracks existing in the structural member;

forming a structural model of a set of lattice points and providing said information to the structural model as respective lattice points;

providing the respective lattice points with material resistances against various operating conditions such as temperature, stress, strain, crack initiation and crack growth as information, the material resistances being previously calculated in accordance with operating conditions of said structural member;

determining crack initiation and growth occurring at respective lattice points at each time when operating conditions such as pressure and temperature of the structural member are changed during an operation period, the crack initiation and growth being determined on the basis of a calculation of a damage function which is defined as a function of stress, strain, and material resistances; and

predicting an amount of time until a length of the crack growth will extend to a limit value by determining the crack growth due to coalescence of respective micro cracks.

2. A method of predicting deterioration and damage in a structural member operated under a high temperature condition for a long period of time, the method comprising the steps of:

inspecting information regarding a number, position, shape, and length of micro cracks existing in the structural member;

converting the information into numerical parameters of crack number, crack average length, and crack dispersion, and memorizing the numerical parameters;

presenting variation trends of the numerical parameters, with respect to a number of start/stop times or an operating time of the structural member, as an optimal approximation formula;

predicting future variation trends of the numerical parameters of crack number, crack average length, and crack dispersion on the basis of the optimal approximation formula;

predicting a maximum length or an overall length of a crack to be grown due to coalescence of the micro cracks, and setting the maximum length or the overall length of a limit value; and

predicting an amount of time until a current crack length extends to the limit value and the structural member is brought to breakdown due to growth and coalescence of the micro cracks distributed in the structural member.

3. A method of predicting deterioration and damage in a structural member operated under a high temperature condition for a long period of time, wherein the prediction is performed by predicting an amount of time until the structural member is brought to breakdown due to increase of an injurious compound phase therein, the injurious compound phase being not formed at a manufacturing time of the structural member but then initiated and grown by diffusion and chemical combination of elements constituting the structural member to thereby cause micro-structural degradation, the method comprising the steps of:

inspecting information regarding a distribution of the elements constituting the structural member and temperatures of respective portions of the structural member;

forming a structural model of a set of lattice points and providing the information to the structural model as respective lattice points;

calculating initiation and growth of the injurious compound phase promoted by diffusion of the elements constituting said structural member, the calculation being performed in such a manner that diffusion rates of the elements at respective lattice points are irregularly distributed using random numbers and diffusion analysis;

displaying a geometrical shape and a distribution of the injurious compound phase on the lattice points of the structural model; and

predicting an amount of time until the injurious compound phase extends to a critical state and the structural member is brought to breakdown due to micro-structural degradation of the structural member.