JP3292789B2 - High-temperature damage durability evaluation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating durability against high-temperature damage, and more specifically, to evaluate the life of a device such as a heat exchanger in which a heating operation and a rest state are repeated, against high-temperature damage. To a method and apparatus for doing so.

[0002]

2. Description of the Related Art At a development site of various equipment to be heated, for example, a heat exchanger, work is performed according to a procedure as shown in a flowchart of FIG. That is, in the design (steps S1 and S2) stage, various numerical values are determined based on empirical rules from before. At that time, it is general to adopt a so-called over-spec design in consideration of safety. The reason why the design is performed based on empirical rules is that it is extremely difficult to theoretically analyze the life, especially for fatigue failure, and it is impossible to make a quantitative judgment by calculation.

After the design is completed (YES in step S2), an environment in which the designed heat exchanger is used is predicted, and a durability test corresponding to the environment is performed (step S3). For example, in the case of a heat exchanger used in a general household water heater, the operation / stop is repeated 100,000 times at intervals of 1 minute at the maximum output temperature (the required period is about 5 months). Further, in the case of a heat exchanger used for commercial equipment, the number of operation / stop repetitions is 30.
10,000 times. If there is no problem as a result of the durability test (Yes in step S4), the development is completed (step S5).

[0004]

However, in the conventional development procedure, in particular, the life can be determined only by trial and error based on an empirical rule. Therefore, the heat exchanger is logically or rationally determined based on quantitative determination. Is impossible to develop.

[0005] As long as a design based on an empirical rule is performed, it is impossible to perform a novel design that cannot make use of past experience. As a result, only a heat exchanger that is the same as the past is designed.

In the conventional development procedure, the evaluation of the durability test is very important. However, the enormous cost and time required for the durability test (for a heat exchanger used in a home water heater, about 5 Months) are spent.

[0007] Furthermore, the reliability of the durability test is not perfect because the life cannot be quantitatively evaluated conventionally. Therefore, when designing
The design had to be over-spec with ample room for strength.

On the other hand, it is desired to introduce a high-temperature damage durability simulation by a computer. However, the analysis of the combustion and its thermal effects is so complex that a perfect simulation was not possible.

The present invention has been proposed in view of the above-mentioned problems of the prior art, and has a high-temperature damage durability capable of quantitatively evaluating the life of a heated device such as a heat exchanger. It is intended to provide an evaluation method and an apparatus.

[0010]

SUMMARY OF THE INVENTION A method for evaluating high-temperature damage durability according to the present invention comprises the steps of: preparing a simulation model for a device for which high-temperature damage durability is to be evaluated; Measuring,
A heat conduction analysis step of substituting the temperature data for the corresponding part of the created simulation model to determine the temperature distribution, and performing a tensile test on a piece of material constituting each part of the device and performing a stress / A step of substituting into a corresponding part of the simulation model created by obtaining the strain data, and a thermal stress analysis step of determining a temperature distribution obtained by the heat conduction analysis step and a stress distribution in a heating state from the stress / strain data. And a step of quantitatively evaluating the high-temperature damage durability of the device using the stress distribution in the heated state of the device obtained in the thermal stress analysis step and the high-temperature damage data of the device.

In this specification, the term "simulation model" preferably means, for example, a finite element method model (hereinafter, referred to as "FEM model"). However, the model is not limited to the FEM model, and any model that can be used in a simulation that is effectively performed using a so-called computer is applicable. That is, the present invention can be applied not only to analysis using the finite element method but also to various analysis methods.

The term “non-heated state” means a so-called “rest state” after heating when the material piece is made of a non-linear material, and “the equipment is heated when it is made of a linear material. Before heating (unheated state: initial state) ".

In the case where the material piece is made of a non-linear material, a step of obtaining a temperature distribution in a resting state after heating, and a step of obtaining the temperature distribution (in the resting state) and the thermal stress obtained in the thermal stress analysis step. It is preferable to include a step of obtaining a stress distribution in a rest state from the stress distribution in a heating state, and a step of obtaining a stress amplitude from the stress distribution in the heating state and the stress distribution in the pause state.

In performing the method for evaluating high-temperature damage durability according to the present invention, a step of performing a strain measurement test of an apparatus for which high-temperature damage durability is to be evaluated and actually measuring the strain of the entire apparatus;
Comparing the stress distribution in the heating state of the device obtained by the thermal stress analysis process with the measured strain of the entire device to verify the validity of the analysis result of the thermal stress analysis process. Is preferred.

In the step of measuring the temperature data, there are a part performed by the radiation thermometer and a part performed based on other temperature data. In the heat conduction analysis step, the measurement result and the Preferably, the required temperature distribution is displayed on the screen of the display.
More specifically, the measurement of the temperature data performed by the radiation thermometer preferably uses a so-called “thermoviewer”. And the measurement of the temperature data performed based on other temperature data measures, for example, fins, internal gas temperature, etc. as other temperature data, calculates a coefficient related to heat transfer from the measurement result, and uses the coefficient. It is preferably performed by determining the temperature of the other parts.

The apparatus for evaluating high-temperature damage durability according to the present invention includes a means for creating a simulation model for an apparatus for which high-temperature damage durability is to be evaluated, and a method for converting the temperature data of each part of the apparatus obtained by a combustion experiment of the apparatus to the simulation. Heat conduction analysis means for substituting the temperature distribution by substituting the temperature into a corresponding part of the model, and performing the simulation on the stress / strain data of each material piece obtained by a tensile test of the material piece constituting each part of the device. Means for determining the stress distribution in the unheated state of the device by substituting into a model, thermal stress analysis means for determining the stress distribution in the heated state from the temperature distribution and the stress distribution in the unheated state, and the thermal stress means. Evaluation of evaluating the high-temperature damage durability of the device based on the obtained stress distribution after heating of the device and the high-temperature damage data of the device Stage, and includes the capital.

Here, the measured strain of the entire device obtained by the strain measurement test of the device to be evaluated for high-temperature damage durability and the stress distribution after heating of the device obtained by the thermal stress analysis means are described. In comparison, it is preferable to include verification means for verifying the validity of the analysis result of the thermal stress analysis means.

[0018]

According to the present invention having the above-described structure,
Equipment to be evaluated for high temperature damage durability (eg heat exchanger)
A simulation model (for example, FEM model) is created for. Next, a combustion experiment of the device is performed to measure temperature data in each part of the device, and the temperature data is substituted into a corresponding portion of the created simulation model. Here, for the portion where the measurement of the temperature data is performed by the radiation thermometer, the measurement result may be directly displayed on the screen of the display. On the other hand, for a part that cannot be measured by the radiation thermometer, a coefficient relating to heat transfer is obtained, and the temperature of the part that cannot be measured is calculated based on the coefficient.

The substitution of the temperature data can be performed by superimposing the measurement result obtained as described above and the simulation model on a display, or by manual input. Then, if all the temperature data is substituted into the simulation model (for example, F
When the EM model is used, the temperature distribution over the entire device for which the high-temperature damage durability is to be evaluated is determined.

After the temperature distribution is determined, the stress distribution in the non-heated state of the device to be evaluated is determined. Therefore, a piece of material constituting each part of the device on which the combustion experiment was performed was sampled, and a tensile test was performed on the material piece to obtain a stress-
Create a strain diagram. Then, the data of the stress obtained from the stress-strain diagram of the material piece of each part is substituted into the corresponding part of the simulation model. This allows
The input of the stress data of the device is completed.

Then, based on the temperature distribution and the stress data at the time of heating, the stress distribution at the time of heating the equipment to be evaluated for high-temperature damage durability (or life) is estimated or analyzed (thermal stress analysis). Process). Here, by performing a strain measurement test of the entire device and actually measuring the strain of the entire device, and comparing the measured strain with the stress distribution in the heated state of the device obtained in the thermal stress analysis step, the thermal The validity of the analysis result of the stress analysis process can be verified.

Next, the difference between the stress in the heated state and the stress in the unheated state in each part of the device is determined from the stress distribution in the heated state and the stress distribution in the unheated state. This stress difference is the difference between the stress in the operating state (heating) and the stress in the stopped state (non-heating) of the heat exchanger, and is the stress amplitude when the operation / stop is repeated. By using the characteristics of this stress amplitude and the number of repetitions of operation / stop (that is, stress amplitude-lifetime curve), in the obtained stress amplitude, how many repetitions (life limit repetition times) at which the life is reached is obtained. Is determined.

The stress distribution in the non-heating state required for determining the stress amplitude is as follows. If the material piece is a linear material, the stress in the non-heating state of the material piece is the stress (initial stress) before heating. be equivalent to. Therefore, if the material is a linear material, the stress distribution in the non-heated state can be directly obtained from the stress data obtained by the above-described tensile test. On the other hand, in the case of a non-linear material, the stress before heating is not the same as the stress in the rest state after heating. Therefore, it is necessary to obtain the stress in the rest state as the stress in the non-heating state. The stress in the rest state in the case of the non-linear material is obtained from the stress distribution in the heated state analyzed in the thermal stress analysis step and the temperature distribution of the device in the rest state. Then, the stress amplitude is calculated from the difference between the obtained stress in the resting state and the stress in the overheated state obtained in the thermal stress analysis step.

If the stress amplitude is determined in this manner, the number of uses set in the design of the heat exchanger (for example, 100,000 times for a general home heat exchanger, 3 times for a commercial use).
Is less than or equal to the limit number of repetitions, it is determined that the heat exchanger has sufficient high temperature damage durability. It is determined that the durability is insufficient. As a result, the life or high-temperature damage durability, which has conventionally been qualitatively determined by an empirical rule, is quantitatively determined. Therefore, the reliability of the determination of the life or high temperature damage durability is dramatically improved.

Further, since the data to be substituted are all actual experimental results, the accuracy is significantly higher than that of various conventional simulations. Similarly, it is possible to determine the life or high-temperature damage durability in consideration of the difference depending on the material, so that the present invention can be applied to material development.

In addition, since a durability test is not required,
The financial or time costs spent on it are saved. In other words, development of a device to be heated such as a heat exchanger in a short time at a low price is completed.

Furthermore, since a quantitative evaluation is performed without being based on an empirical rule, a novel design that is not restricted to past cases is possible.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this embodiment, the equipment to be designed is a heat exchanger, and an FEM model is used as a simulation model.

First, the FEM model creating means 14 (FIG. 1) for creating a simulation model for the equipment for which the high-temperature damage durability is to be evaluated is a heat exchanger (see FIG. An FEM model of an actual machine (not shown) is created (Step S in FIG. 2)
1). Here, the FEM model creation means 14 is composed of a pre / post workstation (reference numeral 12 in FIG. 1) for preparing various analyzes to be performed in the present invention and for processing results. It is shown as part of the station 12.

Next, a combustion test of the actual heat exchanger is performed (step S2 in FIG. 2), and for the locations where the temperature data of each part of the heat exchanger can be measured by the radiation thermometer, the measurement results are displayed on a display screen. It is displayed above (steps S31 and S32 in FIG. 6). In this embodiment, as shown in FIG. 1, thermal image data is sent to a terminal 18 having a display by a thermoviewer 17, processed by a thermal image data processing means 20 of the terminal 18, and indicated by reference numeral 22 in FIG. Such thermal image data is created.

On the other hand, the parts of the heat exchanger which cannot be measured by the radiation thermometer are thermocouples, temperature gauges,
Using a data logger or the like, other data such as fins and internal gas temperature are measured (FIG. 6: step S33),
A coefficient related to heat transfer is calculated from the data (step S34), and the temperature is estimated or analyzed using the coefficient and the temperature of a location measured by a radiation thermometer or the like.
In some cases, the data obtained in step S33 may be used as it is to determine the temperature distribution.

Next, the analysis workstation 24 (FIG. 1) performs a heat conduction analysis step for determining the temperature distribution of the heat exchanger (step S4 in FIG. 2). Here, in FIG. 1, the heat conduction analyzing means 26
4 is shown. And step S4
3 and FIG. 4 show node 1 of FEM model 16.
6-1, 16-2, 16-3, and 16-4 represent thermal image data 22-1, 22-2, 22-3, and 22-4 of corresponding portions of the thermal image data indicated by reference numeral 22. It can be performed by substituting, or can be performed manually. More specifically, thermal image data is substituted into the nodes of the FEM model by superimposing and synthesizing the measurement result displayed on the display screen on the thermoviewer 17 and the FEM model 16. For simplicity of FIG. 1, the data flow is represented by line SL-1, LAN
-1, LAN-2.

When the temperature distribution of the heat exchanger is determined (Step S4 is completed), a tensile test is performed on the material pieces constituting each part of the heat exchanger by the tensile tester 28 (FIG. 1) (Step of FIG. 2). S5), sending the test result to the tensile test result processing means 30 via the signal transmission line SL-2,
A stress-strain diagram is created for each part (step S6) to obtain stress / strain data. Then, the stress / strain data of each part is substituted into the corresponding part of the FEM model 16. Here, if the material piece is a linear material and the stress behavior is considered to be linear when determining high-temperature damage, the stress distribution of the heat exchanger in the non-heated state is determined from the stress / strain data. You.

Next, using the stress data in step S6 and the temperature distribution determined in step S4, the analysis workstation 14 (the thermal stress analysis means 30 is shown as a part of the workstation 14 in FIG. 1). Then, the stress distribution in the heating state is determined (step S7).

The stress distribution in the heating state determined in step S7 is not obtained by measuring the stress of each part in a state where the actual machine is heated, but is obtained by simulation from the temperature distribution in the heating state and the stress distribution in the non-heating state. It is estimated. Therefore, it is difficult to guarantee that this is the same as the stress distribution in the actually heated heat exchanger at the stage of completion of step S7. In other words, it is necessary to check whether or not the stress distribution in the heating state determined in step S7 is reliable. Therefore, the strain tester 32
Performs a strain test on the heated exchange (step S8), and transmits the test result to the signal transmission line SL.
-2 to the strain test result processing means 34 via
The distortion of the heated real machine is detected (step S9).
Here, using the stress-strain diagram created in step S6, the strain is calculated from the stress distribution in the heated heat exchanger determined in step S7. By comparing this strain with the strain detected in step S9, if there is no significant difference between them, the validity of the stress distribution in the heated heat exchanger obtained in step S7 is proved (step S10). .

By comparing the stress distribution in the non-heated state with the stress distribution in the heated state as a result of step S7, the difference between the stress before and after the heating is obtained. This difference is the fluctuation caused by heating,
This corresponds to the stress fluctuation or the stress amplitude (maximum stress amplitude) when the pause is repeated. In other words, the maximum stress amplitude is obtained from this (step S11).

If the material piece is a linear material, the stress before the heating or the initial stress is the same as the stress in the non-heated state as described in connection with step S6. That is, in FIG. 7, when the initial state before heating is denoted by reference numeral “1”, the heating state is denoted by reference numeral “2”, and the resting state after heating is denoted by reference numeral “3”, the initial state 1 and the rest state 3 are completely different. And the stresses σ1 and σ3 are equal. Therefore, the stress in the non-heating state is uniquely derived from the stress / strain data in step S6.

On the other hand, if the material piece is a non-linear material, the stress exhibits characteristics as shown in FIG. 8, and the state 1 and the state 3 do not coincide with each other. Does not match the stress of Further, as shown in FIG. 9, during the durability test or the like, the next heating is performed before the temperature T3 decreases to the initial temperature T1 during one cycle.
Even in the case of a linear material, the initial stress and the stress in the rest state often do not match. In such a nonlinear material, the difference between the stress in the heated state and the stress in the resting state should be adopted as the stress amplitude which is a criterion for determining durability against high-temperature damage.

Therefore, as shown in FIG. 10, prior to determining the maximum stress amplitude (step S11), the stress distribution in the rest state is obtained in step S20. Specifically, in the same process as steps S3 and S4, the stress distribution of the device in the rest state is determined, and the temperature distribution and
The stress distribution in the rest state is obtained from the stress distribution in the heating state analyzed in the thermal stress analysis step of step S7. Then, if the difference between the stress in the heating state (stress distribution) obtained in step S7 and the stress (stress distribution) in the resting state obtained in step S20 is obtained, the stress amplitude in the case where heating and rest are repeated is obtained. is there.

Once the stress amplitude is determined, the durability of the linear and nonlinear materials to high temperature damage is evaluated in the same process. In this case, the material constituting the components of the heat exchanger is known in advance, and various data are prepared for the characteristic (fatigue curve) between the maximum stress amplitude and the life of the material.
Therefore, for example, a stress amplitude-life curve as shown in FIG. 5 is stored in advance in the analysis preparing means 36 (FIG. 1) (step S12), and the stress amplitude in the heat exchanger to be evaluated is calculated from FIG. Using the characteristic curve indicated by, the limit number of repetitions corresponding to the stress amplitude is obtained. If the limit number of repetitions exceeds 100,000, it can be evaluated that the high-temperature damage durability as a heat exchanger used for household products is sufficient (high-temperature damage durability evaluation process: FIG. Step S13). Such evaluation is performed by the analysis result processing means indicated by reference numeral 38 in FIG.

The step of evaluating high-temperature damage durability in step S13 will be further described. If the stress amplitude is 8.36 kg,
/ Mm ² , a component made of a material having a high-temperature damage characteristic indicated by reference numeral Nf-3 in FIG. 5 can withstand about 320,000 repetitions of operation / pause, so that it is of course for household use. It is evaluated that the heat exchanger used in commercial products has sufficient durability against high-temperature damage. In addition, a component made of a material having a high-temperature damage characteristic indicated by a reference symbol Nf in FIG. 5 can withstand about 650,000 repetitions of operation and suspension, and thus has sufficient high-temperature damage durability for business use. Is evaluated.

On the other hand, in FIG.
In the case of a component made of a material having a high-temperature damage characteristic indicated by, the maximum number of repetitions exceeds 100,000 times, it is determined that the product has sufficient high-temperature damage durability as a household product. , The durability against high temperature damage is evaluated as insufficient for a heat exchanger used for commercial products.

Here, the judgment according to the illustrated embodiment is based on the judgment that the limit number of repetitions obtained from the high-temperature damage curve as shown in FIG. 5 is a predetermined number (for example, 100,000 times for a home heat exchanger, a commercial heat exchanger). Since it is a quantitative determination as to whether or not it exceeds 300,000 times, it is very accurate.

In the illustrated embodiment, the equipment to be designed is a heat exchanger, and the simulation model is F
The analysis by the finite element method using the EM model is described, but it is noted that the purpose is not limited to this.

[0045]

The effects of the present invention are listed below. (1) High-temperature damage durability can be quantitatively evaluated. (2) Since the analysis can be performed using the screen data of the radiation thermometer as it is, the labor required for the analysis is reduced. (3) It is possible to design a heat exchanger or the like based on a high-temperature damage durability evaluation based on a quantified rational judgment. (4) Since the time from trial production to evaluation of high-temperature damage durability is reduced, the time and financial burden involved in development is reduced, and development is facilitated. (5) Development considering the material is possible. (6) Quantitative evaluation facilitates the development of a database for development. (7) A novel design that could not be achieved by conventional development based on empirical rules is possible.

(8) Whether the material is a linear material or a nonlinear material, the evaluation can be performed accurately and easily.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a process of evaluating high-temperature damage durability using the embodiment of FIG. 1 in the case of a linear material.

FIG. 3 is a diagram showing an example of an FEM model used in the illustrated embodiment.

FIG. 4 is a diagram showing an example of thermal image data used in the illustrated embodiment.

FIG. 5 is a diagram showing an example of a stress amplitude-lifetime curve used for evaluating the high-temperature damage durability of the illustrated embodiment.

FIG. 6 is a flowchart illustrating a process of measuring temperature data.

FIG. 7 is a stress-strain diagram showing stress characteristics of a linear material.

FIG. 8 is a stress-strain diagram showing stress characteristics of a nonlinear material.

FIG. 9 is a characteristic diagram showing heating characteristics in an endurance test.

10 is a flowchart showing a process of evaluating high-temperature damage durability using the embodiment of FIG. 1 in the case of a nonlinear material.

FIG. 11 is a flowchart showing a development procedure in the related art.

[Explanation of symbols]

12 Pre-post workstation 14 FEM model creation means 16 FEM models 16-1, 16-2, 16-3, 16-4 of heat exchanger (actual machine not shown) ... FEM
Model node 17 ... Thermoviewer 18 ... Terminal 20 ... Thermal image data processing means 22, 22-1, 22-2, 22-3, 22-4 ...
Thermal image data 24: Analysis workstation 26: Thermal conduction analysis means SL-1, SL-2: Signal transmission line LAN-1, LAN-2: LAN line (Signal transmission line) 28 ... tensile tester 30 ... tensile test result processing means 32 ... strain tester 34 ... strain test result processing means 36 ... analysis preparation means 38 ... analysis result processing means

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 3/60 G01M 19/00 G01N 17/00 G01N 25/18 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A step of creating a simulation model for a device for which high-temperature damage durability is to be evaluated; a step of performing a combustion experiment on the device to measure temperature data of each part; A heat conduction analysis step of determining the temperature distribution by substituting into corresponding parts, and a simulation model created by performing a tensile test on a material piece constituting each part of the device and obtaining stress / strain data for each part And a thermal stress analysis step of determining a stress distribution in a heated state from the temperature distribution and the stress / strain data obtained in the heat conduction analysis step, and a temperature distribution obtained in the heat conduction analysis step. Quantifying the high temperature damage durability of the device using the stress distribution in the heated state of the device and the high temperature damage data of the device A high-temperature damage durability evaluation method. 2. A step of performing a strain measurement test of an apparatus to be evaluated for high-temperature damage durability to actually measure the strain of the entire apparatus, and a step of measuring a stress distribution in a heating state of the apparatus obtained by the thermal stress analysis step. 2. The high-temperature damage durability evaluation method according to claim 1, further comprising a step of comparing the measured strain of the entire device with the measured strain to verify the validity of the analysis result of the thermal stress analysis step. 3. A means for creating a simulation model for equipment for which high-temperature damage durability is to be evaluated, and substituting temperature data of each part of the equipment obtained by a combustion experiment of the equipment into a corresponding part of the simulation model. Heat conduction analysis means for determining the temperature distribution, and substituting the stress / strain data of each material piece obtained by a tensile test of the material piece constituting each part of the device into the simulation model, Thermal stress analysis means for determining a stress distribution in a heating state from stress / strain data; and high-temperature damage durability of the equipment based on the stress distribution after heating of the equipment obtained by the thermal stress means and high-temperature damage data of the equipment. A high temperature damage durability evaluation device, comprising: 4. A comparison between the measured strain of the entire device obtained by a strain measurement test of the device to be evaluated for high-temperature damage durability and the stress distribution after heating of the device obtained by the thermal stress analysis means. 4. The high-temperature damage durability evaluation device according to claim 3, further comprising verification means for verifying the validity of the analysis result of said thermal stress analysis means.