JPH03189538A - Corrosive environment cracking progress testing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technology for measuring the propagation rate of cracks such as corrosion cracks, and in particular, measures the crack length online using the DC potential method. The crack growth rate is calculated from the time change of The present invention relates to a device suitable for determining .

[Conventional technology]

Conventionally, the crack growth rate in a corrosive environment has been determined by the compliance method, which measures the displacement of the notch in a CT specimen used for crack growth tests, or by the compliance method, which first lowers the temperature of the pressure vessel and A CT specimen was taken out, its surface was polished, and the crack length was measured using a metallurgical microscope.

[Problem to be solved by the invention]

These methods are extremely inefficient because the accuracy of crack length measurement is not good, or it takes about 10 hours to measure the crack length twice.Also, because the number of measurements is limited, it is difficult to measure the crack growth. The drawback was that the speed accuracy was not good.

The purpose of the present invention is to measure the crack length of a C'F specimen in a corrosive environment online using the DC potential method, and to automatically calculate the relationship between the crack growth rate and stress intensity factor. Our goal is to provide equipment that can.

[Means to solve the problem]

The above purpose is to install a corrosion tester that can apply hydraulic loads, a stabilized DC power supply, a current polarity switching device, a multiplexer,
Micropotentiometer, water quality monitor, load detector, GP-IB
A measurement device consisting of an interface and a computer is provided, and a DC power supply placed outside the pressure vessel, a minute potentiometer, and a CT test piece placed inside the pressure vessel are connected via lead wires. This is achieved by measuring the potential difference between two locations and simultaneously measuring the corrosive environment using a water quality monitor. That is, calculation of the potential difference ratio from the data of the measured potential difference and the corrosive environment, conversion to crack length using a mathematical model of a master curve of the relationship between the potential difference ratio and crack length determined in advance using the finite element method, etc., and calculation of the crack length. Calculation of crack growth rate from time change, conversion of load detector signal to load, calculation of stress intensity factor from load and crack length.

This is achieved by running a program on a computer that has functions such as calculating the relationship between crack growth rate and stress intensity factor, and calculating the relationship between crack growth rate and corrosive environment.

[Effect]

The potential difference of the CT specimen, the corrosive environment signal, and the load signal are measured by controlling the measuring device using a computer, and the data is processed to determine the crack length.

By providing a program function to evaluate crack growth rate and stress intensity factor, it is possible to automatically and accurately determine the relationship between crack growth rate and stress intensity factor, as well as the relationship between crack growth rate and corrosive environment. It can be calculated.

〔Example〕

An embodiment of the present invention will be described below. FIG. 1 shows the corrosive environment crack propagation test apparatus of the present invention. In order to apply a tensile load to the CT specimen 2 in high-temperature pure water, high-temperature and high-pressure pure water is passed from a pure water production bag M4 to a pressurized heating bag @6 to the pressure vessel 3 of the environmental load loading device @1. Water is provided.

Pure water is heated to almost a predetermined temperature by a pressure heating device 6 whose water quality such as dissolved oxygen concentration is controlled by a control device 5.
is heated to and maintained at a predetermined temperature by a temperature controller 8 by a heater 7 provided outside. The plurality of CT test pieces 2 are connected to each other by a connecting jig 9', one end is fixed to the pressure vessel 3 via a holding jig 9', and the other end is fixed to the pressure vessel 3 via another holding jig 9. The load detector 21 is connected to the load detector 21, and the load detector 21 is attached to the tip of the piston rod of the hydraulic cylinder 11. Pressure gauge 1
A stop valve 14 and an accumulator 12 are provided in the middle of a pipe 13 from a hydraulic pump 16 having a hydraulic pump 16 to a hydraulic cylinder 11. When applying a load to the CT test piece 2, the hydraulic pump 16 is used to set a predetermined pressure or load, and then the stop valve 14 is closed. However, as the crack progresses, the bag opening of the CT test piece increases and the piston position of the hydraulic cylinder 11 moves, causing the pressure to drop and the load applied to the CT test piece to decrease. Make sure it doesn't drop. In this way, when a hydraulic system is used during load application, the mechanism is simpler and more compact than the conventional cantilever type static load application method.

The lead wire 31 for DC current supply and potential difference measurement spot welded to the CT test piece 2 is led out to the outside of the pressure vessel 3 via a hermetic seal or the like, and wired to the potential difference measurement water quality monitoring device 29 .

A method of wiring the lead wire 31 to the CT test piece 2 will be described later. The polarity of the DC current supplied from the plurality of DC power supplies 32, 32' is intermittently switched by a current polarity switching device 33, and is supplied to the CT test piece 2 via the DC current supply lead wire 31. The potential difference measurement lead wires 31', 31' are connected to a minute potentiometer 35 with the measurement position switched by a multiplexer 34, and the potential difference is measured. The measured potential difference is GP-I
It is transferred to the computer 37 via the B interface 39. The current polarity switching device 33 and multiplexer 34 are connected to the computer 37 via an interface 40.
controlled by.

The load applied to the CT test piece 2 can be determined from the reading on the pressure gauge 15 during loading, but in order to input it into the computer 37 as digital data, the signal from the load detector 21 is amplified via the amplifier 22 and AD converted. The loaded load data is transferred to the computer 37 via the interface 39 or 40.

The water quality in the pressure vessel 3 is confirmed using the dissolved oxygen concentration meter and electrical conductivity meter attached to the pure water production equipment 4, but since the temperature inside the pressure vessel is high and may differ from room temperature, a CT test specimen is used. 2, an ECP sensor 26 is installed inside the pressure vessel 3 to measure the corrosion potential.
is installed and connected to the water quality monitor 30, and the data is transferred to the computer 37.

When the computer 37 starts the corrosion test, the CT
The crack length of the test piece 2 is calculated by the method described later, and at the same time, the corrosion potential is recorded from the output of the ECP sensor 26. Then, a crack growth curve is determined, the crack growth rate is calculated from its slope, and the relationship between the applied load and the stress intensity factor calculated from the crack length is determined and displayed on the CRT screen or printed. Output to 36.

The specific functions of the corrosion progress testing device are shown below.

FIG. 2 is a flowchart of the entire corrosion crack growth test. In step (1), initial conditions such as mounting the C'F test piece, setting the temperature and quality of pure water, etc. are set. In step (2), high pressure is applied to the hydraulic cylinder 11 by the hydraulic cylinder 16 to apply a load to the CT test piece 2. When the test is started in step (3), a clock for measuring test time is started in step (4). CT in step (5)
Measure the potential difference of specimen 2 and calculate the crack length a/W.

During the test, step (6) determines the water quality as the test condition.

The temperature, pressure, load, etc. are checked, and if any abnormality is found, an alarm is output in step (7) and the test is stopped in step (8). If the test conditions are normal in step (6), check whether the measurement is completed or not in step (9).
If the test is ongoing, step (10) determines the crack length a
/W is 0.9 or more, and 0.9
If it is smaller, return to step (5) and measure the potential difference again to measure the crack length. Repeat this and
The test is continued until the crack length a/W reaches 0.9.

FIG. 3 shows a method for measuring the crack length of the CT specimen 2 using the DC potential method. Lead wires 31 for supplying direct current are attached to the CT test piece 2 near both ends of the notch side, for example, by spot welding or the like. This lead wire 31 is drawn out of the pressure vessel 3 and connected to a plurality of DC power sources 32, 32' provided in the potentiometric water quality monitoring device 29. The polarity of the supplied DC current is intermittently switched by a current polarity switching device 33 controlled by a computer 37 via an interface 40.

Of the potential differences to be measured, the lead wires 31' for measuring the reference potential difference are attached near both ends of the end face in front of the crack of the CT test piece, and the lead wires 31' for measuring the potential difference for measuring the crack length are
1 is installed on both sides of the notch. The potential differences Vo and V at the two locations are connected to a minute potentiometer 35 and measured by switching the measurement positions by a multiplexer 34.

The measured potential difference is transferred to the computer 37 via the GP-IB interface 39. The reason why both the reference potential difference Vo and the potential difference V are measured in this way is because the specific resistance of the CT test piece 2 related to the potential difference measurement value is affected by temperature, so the potential difference is made dimensionless in order to cancel that effect. It is. Another reason is to eliminate the effect if the current supplied from the DC power supply fluctuates for some reason. On the other hand, when measuring the potential difference by switching the polarity of the DC current, the material of the CT test piece 2 is different from that of the lead wires 31' and 31', and if there is some temperature distribution in the CT test piece 2, the difference between the lead wire and CT Since thermoelectromotive force is generated between the test pieces, the influence of thermoelectromotive force can be eliminated by switching the polarity of the current and measuring the amplitude of the potential difference. Furthermore, if a highly sensitive micropotential meter 35 is used, drift cannot be avoided. In order to eliminate this influence, it is effective to switch the polarity of the current and measure the amplitude of the potential difference. In addition, the lead wires 31', 31
' is installed at a location determined to have optimal sensitivity based on electric field analysis of a CT test piece using the finite element method.

FIG. 4 shows a flowchart of potential difference measurement.

In step (11), the number of measurements is reset as n=o. In step (12), for example, the potential difference Vo(+) and V(+) when 10 currents are applied is measured. Step (
In step 13), the polarity of the current is switched by the current polarity switching device 33, and in step (14), the potential difference Vo(-) and ■(-) when a negative current flows is measured. Step (15
) to switch the polarity of the current and return it to the original polarity. In step (16), 1 is added to n, and in step (17) it is determined whether the number of measurements has exceeded a predetermined number of times, for example, 10. If the number of measurements has not yet reached 10, step (12) is performed. Return to If the number of times reaches 10, it is determined whether the potential difference measurement value is normal or not in step (18). If there is an abnormality, the measurement is re-measured in step (19), and the process proceeds to step (11). return.

FIG. 5 is a flowchart of a potential difference measurement value determination subroutine. When the potential difference is measured according to the flowchart of FIG. 4 in step (21), the amplitude of the potential difference V i = ((V o (+) - V (-)) is determined in step (22).
/2 and Voi = ((VO(+) VO()). In step (23), the potential difference ratio V / Voi
==Vj/Voi is calculated. In step (24), the maximum potential difference ratio and the second from the maximum potential difference ratio, and the minimum potential difference ratio and the second potential difference ratio from the minimum are excluded in consideration of variations in potential difference measurement. Then, in step (25), the average potential difference ratio V/Vom=Σ(V
Calculate i/Voi)/6.

In step (26), the standard deviation σ of the potential difference ratio is calculated, and in step (27), for example, if it is 0.005
If it is larger than , it is determined that there is a measurement abnormality and step (28
) and then returns to step (21).

Figure 6 shows a master curve for crack length determination obtained by electric field analysis using the finite element method. The vertical axis is the potential difference ratio V
/Vo, the horizontal axis is the crack length a/W normalized by the plate width W of the CT test piece. When the crack length a/W becomes larger than about 0.35, the potential difference ratio V/Vo decreases almost in proportion to the crack length a/W. Therefore, the conversion from the potential difference ratio to the crack length is a/W=0.2 to 0.26. a/W
=0.26~0.36. a/W=0.36-0. ．． The calculation was performed using a linear approximation formula within a range of 9.

FIG. 7 shows a flowchart for determining crack length.

In step (31), the potential difference ratio V/Vo is read.

In step (32), as an initial determination, a potential difference ratio measurement error check is performed to determine whether V/Vo<5,689. If V/Vo>5.689, a/W
< 0, 2, and the crack length is impossible to exist, so it is determined that re-measurement is required in step (33), and step (33) is determined to be remeasured.
Return to 11). If V/Vo<5.689, it is a normal measurement value, and in the next step (34) V/Vo>
If it is 5.623, it is determined that a/W = 0.2 to 0.26, and a/W = 5.3718-0.9091V/V in step (35).

It is converted into crack length a/W by Then step (
36), the raw crack length is corrected to a. Step (34)
If V/Vo<5.623, then step (37
) and if V/Vo>5.225, a/W = 0
, 26-0, 36, and step (38)
and a/W=1.6729-0.2513V/V.

It is converted into crack length a/W by Step (37)
If V/Vo<5.225, then step (3
9), if V/Vθ>2.169, a/W =
0, 36-0, 9, and step (40)
So a/W=1.2831 0.1767V/V.

It is converted into crack length a/W by Step (39)
If V/Vo<2.169, then a/W>0.9, so the test ends.

After completing a series of crack growth tests, the next data processing is required. The corrosion testing machine shown in FIG. 1 is all controlled by a computer 37, and data processing is also possible.

Therefore, we created a crack growth curve.

It has functions such as calculating crack growth rate. Figure 8 shows the crack growth curve. The vertical axis is the crack length, and the horizontal axis is the test time. The crack gradually grows as the test time increases, and the longer the crack becomes, the faster the crack grows. In step (41), the computer 37 displays a crack growth curve as shown in FIG. 8 on the screen of the CRT 38 based on the crack length data obtained from the built-in clock and potential difference measurement according to the flow chart shown in FIG. to be displayed. At the same time, in step (42), from the crack length a and the test time t, a=Ao+At
The crack growth curve is approximated by the method of least squares using an n-dimensional equation such as t+Azt2+Aat3+.=-.(t). Next, in step (43), from the crack length a and the test time t, t=Bo+Bxa+Bza"+Baa3+-...(2)
The inverse function of the crack growth curve is approximated by the method of least squares using the n-dimensional equation as follows. In step (44), the crack growth curve is differentiated and d a/d t=AI+2Azt+3Ast 2+-・
-----(3) Create an evaluation formula for crack growth rate. In step (45), the crack length a(1
) as a(i)=ao+n・Δa...
Obtain from (4) and substitute it into equation (2), a
Calculate t (i) corresponding to (i). Here, ao is the initial crack size, which is usually about 0.1 mm. n
is an integer. In step (46), the obtained t(i
) into equation (3) to obtain the crack growth rate da/dt(i)
Calculate. Next, in step (47), the crack length a (
i) and the load measured by the load detector 21, a (
Calculate the stress intensity factor K (i) for i). By the above operations, the stress intensity factor K(i) and the crack growth rate da
Since the relevant data of /dt(i) has been collected, in step (48), K(i) and da/d as shown in FIG.
A diagram of the relationship between t(i) is created and displayed on the screen of the CRT 38. In step (49), K(i) and da/dt(i
) is expressed as d a/d t=c-K”
Since it is approximated by Paris law like ・=(5),
For K, the approximation range is: Kwin≦≦Kmax da/dt For t, da/dtmtn≦da/d t≦da/dt+
Set it like sax. Usually 10-6+no+/c
It is approximated in a range such as ≦da/dt≦10-2re/c. Once the approximation range is specified, in step (50), approximation is performed using the least squares method as shown in equation (5), and the coefficient C and index m are determined. In step (51), step (48)
An approximated curve is drawn on the drawing of the relationship between K and d a / d t created in , and an approximate formula is displayed.

In step (52), the test time t(i), the crack length a(
i), stress intensity factor K (i) and crack growth rate da/d
The list of t(i) is output to the printer 36.

Of course, the crack growth curve displayed on the CRT screen, K and d
The a/dt relationship allows the printer 38 to print a hard copy.

FIG. 11 shows an example of a crack length measuring device.

A constant voltage DC power supply 51 is used to drive the entire system. The constant voltage current supplied from the constant voltage DC power supply 52 is turned into a stabilized constant current by the floating constant current circuit 53.

The polarity of the current is switched at regular intervals by a polarity switching device 54, and the current is supplied to a current terminal 56 of the input/output boat 55. This current terminal and the CT test piece 2 of the pressure vessel 3 are connected by a Riet wire 31. Lead wire 31' for potential difference measurement
32'' is connected to the potential difference terminal 57, and the multiplexer 5
8 switches the terminal to be measured, and the potential difference is measured by the direct Jε amplifier 59. The potential difference is A/D converted by an A/D converter 60 and transferred to a computer 62 via a bus buffer 61. Around the computer 62 is a CRT or liquid crystal display 63. Printer 64. A floppy disk drive 65 or the like is connected and used for data processing, data storage and two-screen display, etc.

FIG. 12 shows another embodiment. The method for measuring the potential difference is basically the same as the method shown in Figure 3, but in order to improve the measurement accuracy, measure multiple potential differences at the same potential difference measurement position and calculate the average potential difference ratio. By determining this, the attachment of the lead wires 31'31' attempts to compensate for errors. That is, for both the reference potential difference Vo and the potential difference V, the CT test piece 2 is attached by spot welding lead wires at three locations: at the center of the plate thickness and, for example, between the center of the plate and the end surface. is measured, and the crack length is evaluated from the ratio of their potential differences. FIG. 13 shows the flowchart.

Step (61) 1' Potential difference V (1) , V (2
), V (3).

Vo(1), Vo(2), and Vo(3) are measured, and in step (62), the average potential difference ratios V/Vo(1), V/Vo(
2) Calculate V/Vo(3). Then, in step (63), the average potential difference ratio V of the three measurement positions is
/Vo is determined, and in step (64), the potential difference ratio V/V as shown in FIG. 6 is determined.

The crack length is determined using a master curve of the relationship between crack length a/W.

FIG. 14 shows another embodiment. A direct current is applied near both ends of the CT test piece 2 on the notch side, and the reference potential difference is measured as the potential difference between the upper and lower surfaces parallel to the notch. Its position is
In the case of a CT test piece with w=50-, the optimum value is around 30 to 35+a++ from the surface opposite to the notch. FIG. 14 shows a master curve of the potential difference ratio V/V o and the crack length a/W, which are determined using the potential difference at the position of 32.5a++ as a reference potential difference. The resulting potential difference ratio V/V
When converting o to crack length a/W, a/W=0.2 to 0.26, similar to that shown in FIG. a/W
=0.26-0.36. The measurement was performed using a linear approximation formula within the range of a/W=0.36-0.9.

The measuring method shown in FIG. 3 has good sensitivity and accuracy when using a material with a high specific resistance, while the measuring method shown in FIG. 14 has good accuracy when using a material with a large specific resistance.

FIG. 15 shows another embodiment. DC current was applied while switching the polarity from the lead wires spot-welded to both ends of the notch side of the CT test piece, and the potential difference ■ measured at the position sandwiching the notch and the side opposite to the notch The potential difference Vo across the notch was measured by applying a DC current while switching the polarity from the lead wires spot welded to both ends of the
The crack length is measured from the ratio of Therefore,
In order to realize this method, the polarity of the current supplied from the DC power supply 32 is switched by a current polarity switching device 33, and furthermore, the polarity of the current supplied from the DC power supply 32 is switched by a current multiplexer 41.
It is possible to switch the current supply destination to the test piece. FIG. 16 shows a potential difference measurement system for the measurement method of FIG. 15. A constant voltage current supplied from the constant voltage DC power supply 52 is supplied by a floating constant current circuit 53.

Stabilized constant current. The polarity of the current is determined by a polarity switching device 54.
The current is switched at regular intervals by the current multiplexer 66, and the current supply destination is switched by the current multiplexer 66, and the current is supplied to the current terminal 56 of the input/output port 55. This current terminal and the CT test piece 2 of the pressure vessel 3 are connected by a lead wire 31. The lead wire 31' for potential difference measurement is connected to the potential difference terminal 57.
The DC amplifier 59 measures the potential difference. The potential difference is A/D converted by the A/D converter 60,
The data is transferred to the computer 62 through the bus buffer 61.

〔Effect of the invention〕

According to the present invention, in a crack propagation test using a CT specimen in a corrosive environment in high-temperature water, potential differences at several locations on the CT specimen are measured online using the DC potential method, and in advance using the finite element method. Using the obtained master curve of the relationship between potential difference ratio and crack length, convert it to crack length, approximate the crack growth curve with an n-th equation, create a crack growth rate evaluation formula, and further calculate the stress intensity factor. Since the relationship between the crack growth rate and the stress intensity factor can be calculated by calculating the relationship between the crack growth rate and the stress intensity factor, it is possible to calculate the crack growth rate in a corrosive environment in a much shorter time and with higher accuracy than with conventional methods.

[Brief explanation of drawings]

Figure 1 is a block diagram of the crack growth test equipment in a high-temperature corrosion environment, Figure 2 is a flowchart of the entire corrosion test, Figure 3 is a block diagram of the potential difference measurement system for measuring crack length,
FIG. 4 is a flowchart for measuring potential difference, FIG. 5 is a flowchart for determining abnormality in potential difference measurement values, FIG. 6 is a characteristic diagram of the relationship between potential difference ratio and crack length, and FIG. 7 is a flowchart for determining crack length. Figure 8 is a crack growth explanatory diagram, Figure 9 is a flowchart for calculating the crack growth rate and creating a diagram.
Fig. 10 is an explanatory diagram of the relationship between crack growth rate and stress intensity factor, Fig. 11 is a block diagram of the potential difference measurement system, and Fig. 12
The figure shows the arrangement of lead wires for measuring the potential difference of CT test pieces.
Figure 3 is a flowchart of potential difference measurement, Figure 14 is a characteristic diagram of the relationship between potential difference ratio and crack length, Figure 15 is a block diagram of the potential difference measurement system for crack length measurement, and Figure 16 is a block diagram of the potential difference measurement system. It is a diagram. 1...Environmental medium weight loading device, 2...CT test piece, 3
... Pressure vessel, 4 ... Pure water production device, 5 ... Pure water production device control device, 6 ... Pressure heating device, 7 ... Heater, 11 ... Hydraulic cylinder, 12. ...Accumulator, 13...Hydraulic piping, 14...Stop valve, 15...Pressure gauge, 16...Hydraulic pump, 21...
・Load cell, 22... Load amplifier, 26... Water quality sensor, 29... Potential difference measurement water quality monitoring system,
30...Water quality monitor 32...DC power supply, 33...
・Current polarity switching device, 34... multiplexer,
35...Minute potentiometer, 36...Printer, 37.
...Computer, 38...CRT, 40...Interface, 41...GP-IB interface, 51...DC power supply, 53...Floating constant current circuit, 58...Multiplexer, 59...・DC amplifier, 60...A/D converter, 61...Bus buffer, 62...Computer, 63...Display device, 64...Printer, 65...Floppy 260 Figure 2 Porridge diagram Tin diagram Figure 6 (12 (L3 (140+5 (160-
7 (180-9 Crack length &/W Relationship between potential difference ratio and crack length Fig. 8 Time Fig. 7 Fig. 9 Fig. 10 Fig. 10 Stress intensity factor 12 Fig. 11 Fig. 3 Fig. Potential difference ratio and Fig. 14 The length of the bag is related to the length of the long bag.

Claims (1)

[Claims] 1. A plurality of compact test pieces are installed in a pressure vessel that is supplied with high-temperature pure water through a pressure heating device from a pure water production device that can control water quality, and a load is applied to the test pieces. One end of the jig for loading is connected to a hydraulic cylinder via a load detector provided outside the pressure vessel, and high pressure is supplied to the hydraulic cylinder from a hydraulic pump through hydraulic piping with an accumulator provided in the middle. Several pairs of lead wires are attached to the test piece and connected to a DC power source and a micropotentiometer provided outside the pressure vessel to measure the potential differences at multiple locations on the test piece, and the potential differences at the multiple locations are measured. A crack growth testing device in a corrosive environment, characterized in that the crack length of the test specimen is determined from the ratio of the crack length, and the relationship between the stress intensity factor of the crack determined from the load crack length and the crack growth rate is automatically measured. 2. Claim 1 provides a DC constant voltage power supply, a floating constant current circuit, a multiplexer, a DC amplifier, an A/D converter, a bus buffer, an interface, a liquid crystal display, a floppy disk drive, a printer, and A crack growth testing device in a corrosive environment, characterized by being equipped with a crack length measuring device configured with a computer. 3. In the product described in claim 1 or 2, a direct current is applied from lead wires spot-welded to both ends of the initial notch side of the test piece while switching the polarity, and the notch is sandwiched. A corrosive environment crack growth testing device characterized by measuring the potential difference at the position where the notch is located and the potential difference at both ends opposite the notch through a spot welded lead wire, and measuring the crack length from the ratio of the two. 4. In the product described in claim 1 or 2, a direct current is applied from the lead wires spot-welded to both ends of the initial notch side of the test piece while switching the polarity, and the notch is sandwiched. The potential difference at the position where the cutout is located and the potential difference between the two surfaces parallel to the notch are measured via spot welded lead wires.
A crack growth test device in a corrosive environment, which measures the crack length from the ratio of the two. 5. In the item described in claim 3 or 4, the ratio of the potential difference at the positions sandwiching the notch to the potential difference at both ends opposite to the notch or the potential difference between two surfaces parallel to the notch. A corrosive environment crack growth testing device characterized in that the crack length is determined from the measured potential difference ratio by approximating the relationship between the time and the crack length using an n-th equation or a polylinear formula. 6. In the item described in claim 3 or 4, the potential difference between the positions sandwiching the notch is a potential difference measured via a lead wire spot welded to the center of the plate thickness, or a potential difference between the plates between each other. A crack growth test device in a corrosive environment characterized by using a potential difference measured at a position oblique to the center of the plate thickness through lead wires spot welded from both ends of the plate thickness. 7. In the item described in claim 6, the potential difference between the positions sandwiching the notch is a potential difference measured via a lead wire spot welded to the center of the plate thickness, and a potential difference measured from both ends of the plate thickness. A crack growth test in a corrosive environment characterized by using the average value of the potential differences at two locations, which are measured at diagonal positions with respect to the center of the plate thickness through lead wires spot welded to the plate. Device. 8. In the product described in claim 1 or 2, measurement is performed by applying a direct current while switching the polarity from lead wires spot welded to both ends of the test piece on the initial notch side of the compact test piece. The ratio of the potential difference across the notch and the potential difference across the notch measured by applying DC current while switching the polarity from lead wires spot welded to both ends on the opposite side of the notch. A corrosive environment crack growth test device characterized by measuring crack length. 9. In the item described in claim 1 or 2, the cut is measured by applying a direct current while switching the polarity from the lead wire spot welded to both ends of the compact test piece on the initial notch side. The crack length is calculated from the ratio of the potential difference between the positions that sandwich the notch and the potential difference between both ends of the notch side, which is measured by applying a direct current while switching the polarity from the lead wire spot welded to both ends of the opposite side of the notch. A corrosion environment crack growth test device characterized by measuring. 10. In the items described in claims 1 to 9, the crack length of the test piece is determined from the ratio of the potential difference between two places on the compact test piece, and the relationship between the crack length and the number of repetitions is determined. Corrosion characterized by approximating it with an n-th order equation, calculating the crack growth rate from its first-order differential equation, and automatically measuring the relationship between the crack stress intensity factor and the crack growth rate determined from the load and crack length. Environmental crack growth test equipment. 11. In the product described in claim 10, the relationship between the crack length and the time or the number of repetitions obtained from the ratio of the potential differences at two locations of the compact test piece is approximated by an n-th equation, and its first derivative is calculated. A method for crack growth in a corrosive environment characterized by calculating the crack growth rate from a formula for a constant crack length increment or a constant stress intensity factor increment, and automatically measuring the relationship between the stress intensity factor and the crack growth rate. Crack growth test device. 12. In the claims 1 to 11, the relationship between the crack length obtained from the ratio of the potential differences at two locations of the compact test piece to time or the number of repetitions, and the stress intensity factor and crack growth. A corrosion environment crack growth testing device characterized by being capable of displaying speed relationships on a liquid crystal display and outputting a hard copy of the same to a printer.