JP2015145866A - Corrosion fatigue composite test apparatus and corrosion fatigue composite test method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion fatigue composite test apparatus that can change the environmental conditions and stress load conditions during the test as needed and efficiently evaluate the corrosion characteristics and fatigue characteristics with high precision, and a corrosion fatigue composite test method using these.SOLUTION: The corrosion fatigue composite test apparatus 10 comprises rotation control means 20 for rotating test pieces A1 and A2 being capable of changing the speed with one end of the bar-like test pieces A1 and A2 to be supported axially rotatable, load control means 30 for loading and unloading the load on the other end of the test pieces A1 and A2, etching fluid control means 40 for dropping and stopping the corrosive solution to the test pieces A1 and A2, environment control means 50 for controlling the test environment exposing the test pieces A1 and A2, cooling means 60 for cooling the test pieces A1 and A2 and control means for individually controlling them.

Description

  The present invention relates to a corrosion fatigue combined test apparatus and a corrosion fatigue combined test method using the same.

  Conventionally, it is known that a metal material undergoes fatigue failure by repeatedly applying a load. Further, it is known that the fatigue characteristics of a metal material are affected by the environment to which the metal material is exposed. For this reason, a fatigue test of a metal material may be performed in an environment that simulates a corrosive environment to which the metal material is exposed.

In the fatigue test of metal materials, methods for simulating the corrosive environment include the method of immersing a test piece in a corrosive liquid, the method of spraying or dripping the corrosive liquid on the test piece, and installing the test piece There is a method of making the atmosphere in the chamber to be a corrosive atmosphere.
Further, as a method of applying stress to the test piece in the fatigue test, there is a method of rotating the test piece on which a bending moment is applied while applying a load to one or both ends of the test piece.

In recent years, there has been an increasing demand for evaluating the fatigue behavior of a test piece in a region where the number of repeated tests is high (high cycle region). When evaluating fatigue behavior in a high cycle region, it is preferable to perform a rotating bending fatigue test in which compression and tensile loads are repeatedly applied to the surface at high speed by rotating the test piece.
As a method for performing the rotational bending fatigue test of a test piece in an environment simulating a corrosive environment, for example, there are techniques described in Patent Documents 1 to 4.

Patent Document 1 describes a corrosion fatigue test apparatus including means for supplying a gas into a chamber for storing a test piece, means for supplying steam into the chamber, and means for applying a load to the test piece. ing.
Patent Document 2 describes a rotating bending corrosion fatigue test apparatus in which a test piece is inserted into a corrosive bath.

Patent Document 3 includes a mounting portion for mounting one end of a test piece, a driving portion for rotating the test piece, a lower portion of a corrosive droplet for dropping a corrosive liquid on the test piece, and a load adding portion for applying a load to the other end of the test piece. Corrosion fatigue testing apparatus comprising:
In Patent Document 4, a mounting member that fixes and supports one end of a test piece so as to be rotatable about a shaft, a load application member that pulls the other end of the test piece vertically downward, and a liquid inlet at a position where liquid can be dropped on the test piece. A fatigue testing device comprising a container provided with a is described. In the fatigue test apparatus described in Patent Document 4, a corrosive environment tank is provided so that the corrosive liquid does not scatter to the apparatus parts or the outside.

JP 59-73751 A JP-A-61-25037 JP-A-8-5532 JP 2012-78106 A

  Conventionally, it has been found that in steel members used in corrosive environments such as automobile suspensions, corrosion pits generated on the surface due to corrosion affect the fatigue behavior of the members. In a member having corrosion pits on the surface, the corrosion pits become a stress concentration source, and fatigue cracks are generated by repeated stress loading, resulting in a fatigue failure due to a complex phenomenon.

In order to evaluate a material that undergoes fatigue failure due to such a complicated phenomenon with high accuracy, it is necessary to individually grasp the progress of corrosion and the progress of fatigue cracks. For this reason, conventionally, when evaluating the corrosion fatigue characteristics of a material used in a corrosive environment, the evaluation has been made by the following method as necessary.
First, conditions for a combined cycle corrosion test (also referred to as cyclic corrosion test, CCT) are set according to the actual environmental conditions of corrosion occurrence. Moreover, the conditions of the rotating bending fatigue test are set according to the actual stress load conditions. Thereafter, the CCT and the rotating bending fatigue test are alternately and repeatedly performed on the test piece a plurality of times using different test apparatuses.

However, when the CCT and the rotating bending fatigue test are repeated alternately using different test apparatuses, it is very troublesome. For this reason, it has been required to be able to efficiently evaluate corrosion characteristics and fatigue characteristics.
In order to meet this requirement, it is conceivable to continuously perform CCT and rotational bending fatigue tests with one apparatus. However, with the conventional fatigue test equipment that can perform the rotating bending fatigue test in an environment simulating a corrosive environment, it is difficult to change the environmental conditions and stress load conditions in which corrosion occurs during the test, The CCT and the rotating bending fatigue test could not be performed continuously. For this reason, the conventional rotating bending fatigue test apparatus cannot accurately evaluate the corrosion characteristics and fatigue characteristics of materials used in a corrosive environment.

Further, when a rotary bending fatigue test of a high-strength steel material is performed using a conventional rotary bending fatigue test apparatus, there is a problem that the variation in evaluation is large. This problem was particularly noticeable when a rotating bending fatigue test was performed on high strength steel having a tensile strength of 1000 MPa or more.
That is, in a high-strength steel material, the stress applied to the test piece is high by performing the rotary bending fatigue test, and the strain of the test piece increases. For this reason, the test piece generates heat during the test and softens, and the fatigue life may be shorter than the original performance. As a result, the variation in evaluation of fatigue characteristics becomes large.

  The present invention has been made in view of such circumstances, and it is possible to change the environmental conditions and stress load conditions during the test as necessary, and the corrosion characteristics and fatigue characteristics with high accuracy and efficiency. It is an object of the present invention to provide a corrosion fatigue composite test apparatus capable of evaluating the above and a corrosion fatigue composite test method using the same.

The gist of the present invention is as follows.
[1] One end of a rod-shaped test piece is supported so as to be axially rotatable, a rotation control means for rotating the test piece in a variable speed manner, and load control for loading and unloading the load to the other end of the test piece. Means, dripping and stopping the corrosive liquid on the test piece, atmosphere control means for controlling the test atmosphere exposing the test piece, cooling means for cooling the test piece, and the rotation A corrosion fatigue combined test apparatus comprising: control means; load control means; corrosive liquid control means; atmosphere control means; and control means for individually controlling the cooling means.
[2] The control means includes mode selection means for controlling the rotation control means, the load control means, the corrosive liquid control means, and the atmosphere control means to switch the operation of the apparatus. The corrosion droplet lowering mode in which the test piece is rotated while dripping the corrosive liquid onto the test piece from which the load has been removed, and the corrosion droplet lowering mode are continuously performed, and the surface of the test piece is dried. The corrosion-fatigue combined test apparatus according to [1], further including: a corrosive liquid drying mode to be performed; and a fatigue mode in which the test piece is rotated while a load is applied to the test piece.
[3] The combined corrosion fatigue testing apparatus according to [2], wherein the cooling means is controlled by the mode selection means, and the test piece is cooled in the fatigue mode.
[4] The rotation control means rotates the test piece at a low speed of less than 5 to 500 rpm in the corrosion droplet lowering mode, and rotates the test piece at a high speed of 500 to 10,000 rpm in the fatigue mode. The combined corrosion fatigue test apparatus according to [2] or [3], wherein
[5] The load control means includes: a load loading means for pulling the other end of the test piece in a vertically downward direction so as to freely rotate the shaft; and a load unloading means for unloading the load applied to the test piece. The corrosion fatigue combined testing apparatus according to any one of [1] to [4], comprising:
[6] The atmosphere control means supplies a chamber to a portion of the test piece that is exposed to the test atmosphere, a temperature / humidity control means for controlling the temperature and humidity of the test atmosphere, and an atmosphere gas to the chamber. A corrosion fatigue combined testing apparatus according to any one of [1] to [5], comprising a gas supply means.

[7] Using the combined corrosion fatigue test apparatus according to any one of [1] to [6], performing a step of accelerating the corrosion of the test piece and a step of accelerating the fatigue of the test piece. Characteristic corrosion fatigue combined test method.
[8] The combined corrosion fatigue test method according to [7], wherein the test piece is a high-strength steel having a tensile strength of 1000 MPa or more.
[9] The step of accelerating the fatigue includes a step of cooling the test piece and rotating the test piece while applying a load to the other end of the test piece. 8] The corrosion fatigue combined test method according to [8].
[10] In the step of accelerating the fatigue, the corrosion solution is dropped on the test piece and / or a load is applied to the other end of the test piece in a test atmosphere having a relative humidity of 30 to 100%. The corrosion fatigue combined test method according to [7] or [8], including a step of rotating the test piece.

[11] In the step of accelerating the corrosion, the test piece is rotated at a low rotational speed of less than 5 to 500 rpm while dropping the corrosive liquid onto the test piece from which the load has been removed, and the surface of the test piece is rotated. The method includes a step of setting an average film thickness of the formed corrosion liquid film to 20 μm to 2 mm, and setting a variation in the film thickness of the corrosion liquid film in the circumferential direction of the test piece to 5% or less of the average film thickness. The corrosion fatigue combined test method according to any one of [7] to [10].
[12] The step of accelerating the corrosion is performed continuously after the corrosive liquid coating process in which the test piece is rotated while dripping the corrosive liquid onto the test piece from which the load has been removed, and the corrosive liquid coating process. A combination of a drying treatment for drying the surface of the test piece and a wetting treatment for making the surface of the test piece wet after the drying treatment one or more times, the corrosive liquid The corrosion solution according to any one of [7] to [11], wherein a corrosion liquid film formed on the surface of the test piece in the coating treatment is dried at a reduction rate of 200 μm / s or less by the drying treatment. Fatigue composite test method.

  Since the corrosion fatigue combined test apparatus of the present invention includes a rotation control means, a load control means, a corrosive liquid control means, an atmosphere control means, a cooling means, and a control means for individually controlling these, the control means It is possible to change the environmental conditions and stress loading conditions during the test as required. Therefore, the process of accelerating the corrosion of the test piece and the process of accelerating the fatigue of the test piece can be performed continuously with one apparatus. For example, the CCT and the rotating bending fatigue test are performed using separate apparatuses. Compared with the case where it carries out, a corrosion fatigue characteristic can be evaluated efficiently.

  Moreover, when performing the process of accelerating the corrosion of the test piece and the process of accelerating the fatigue of the test piece using the combined corrosion fatigue test apparatus of the present invention, the corrosion fatigue test is performed in an environment simulating a certain corrosive environment. Compared with the case of performing, the corrosion fatigue characteristics of the test piece can be evaluated with higher accuracy under conditions corresponding to actual environmental conditions and stress load conditions. Therefore, the corrosion fatigue combined test apparatus of the present invention can be suitably used when evaluating the corrosion fatigue characteristics of materials used in a corrosive environment such as a suspension spring for automobiles.

  Moreover, since the corrosion fatigue combined testing apparatus of the present invention includes the cooling means, the test piece can be cooled as necessary during the test, and the heat generation of the test piece can be suppressed. For example, when testing a high-strength steel material, it is possible to prevent the test piece from being heated and softened during the test, and to reduce variation in evaluation. Therefore, the corrosion fatigue combined test apparatus of the present invention evaluates the corrosion fatigue characteristics of high strength steel materials used for, for example, automobile suspension springs having a tensile strength of about 1800 MPa and high strength bolts having a tensile strength of about 1200 MPa. It can be suitably used for

FIG. 1 is a schematic perspective view for explaining an example of the corrosion fatigue combined test apparatus of the present invention. FIG. 2 is an explanatory diagram for explaining a part of the corrosion fatigue combined test apparatus shown in FIG. 1, and is an explanatory diagram showing a rotation control means. FIG. 3 is an explanatory diagram for explaining a part of the corrosion fatigue combined test apparatus shown in FIG. 1, and is an explanatory diagram showing a load control means. FIG. 4 is an explanatory diagram for explaining a part of the corrosion fatigue combined test apparatus shown in FIG. 1, and is an explanatory diagram showing an atmosphere control means. FIG. 5A is a schematic diagram of one of the atmosphere control means shown in FIG. 4 and the cooling means connected thereto as viewed from above. FIG. 5B is a schematic view of one of the atmosphere control means shown in FIG. 4 and the corrosive liquid control means and the cooling means connected thereto as viewed from the side.

  Hereinafter, a corrosion fatigue combined test apparatus and a corrosion fatigue combined test method of the present invention will be described in detail with reference to the drawings. Each figure shown below is a schematic diagram for explaining the present invention, and the shape, dimensional ratio, etc. described in each figure may be different from the actual ones, and the following explanation and known techniques are taken into consideration. The design can be changed as appropriate.

"Corrosion fatigue combined testing equipment"
FIG. 1 is a schematic perspective view for explaining an example of the corrosion fatigue combined test apparatus of the present invention. 1 is disposed on both sides of the rotation control means 20 so as to sandwich the rotation control means 20 between the main body 10a having a substantially rectangular parallelepiped shape, the rotation control means 20 installed on the main body 10a. And an atmosphere control means 50. As will be described later, the atmosphere control means 50 includes a chamber 51, a temperature / humidity control means (not shown), and a gas supply means 52 connected to the temperature / humidity control means. As shown in FIG. 1, a load control means 30, a corrosive liquid control means 40, and a cooling means 60 are attached to the atmosphere control means 50.
In FIG. 1, only the portion connected to the atmosphere control means 50 is shown for the corrosive liquid control means 40 and the cooling means 60 in order to facilitate the explanation of the overall configuration of the corrosion fatigue combined test apparatus 10.

  Further, the corrosion fatigue combined test apparatus 10 shown in FIG. 1 includes control means (non-control means) for individually controlling the rotation control means 20, the load control means 30, the corrosive liquid control means 40, the atmosphere control means 50, and the cooling means 60. (Shown) is provided. Each of the rotation control means 20, the load control means 30, the corrosive liquid control means 40, the atmosphere control means 50, the cooling means 60, and the control means are individually connected by wiring not shown. The control means controls the rotation control means 20, load control means 30, corrosive liquid control means 40, atmosphere control means 50, and cooling means 60, and mode selection means (not shown) for switching the operation of the corrosion fatigue combined test apparatus 10. have. The mode selection means controls these individually and switches the operation of the apparatus as will be described later.

  The corrosion fatigue combined test apparatus 10 shown in FIG. 1 can test four bar-shaped test pieces simultaneously. FIG. 1 shows four round bar-shaped test pieces having a circular cross section perpendicular to the longitudinal direction and a constant outer diameter in the longitudinal direction (in FIG. 1, two of the four test pieces A1, Only the end portion attached to the load control means 30 of A2 is shown.) Shows the state attached to the corrosion fatigue combined test apparatus 10. All four test pieces attached to the corrosion fatigue combined test apparatus 10 extend in the Y-axis direction shown in FIG.

  In the present embodiment, a method for testing a round bar-shaped test piece having a circular cross-sectional view and a constant outer diameter in the longitudinal direction using a corrosion fatigue combined test apparatus will be described as an example. The shape may be a rod shape and is not limited to the shape of the test piece of the present embodiment. For example, it may be an hourglass shape having a circular shape in cross section and a constricted portion having a smaller outer diameter than both end portions in the central portion in the longitudinal direction, or a constant shape having a circular shape in cross section and smaller than both end portions. The shape may have a parallel portion extending in the length direction with an outer diameter. The shape of the cross section perpendicular to the longitudinal direction may not be circular. For example, the cross sectional shape perpendicular to the entire longitudinal direction or a part of the longitudinal direction may be a polygon such as a rectangle or a hexagon. . Specifically, the shape of the cross section perpendicular to the longitudinal direction may be, for example, a circle at the center and a polygon at both ends.

  One end of each of the four test pieces is supported by the rotation control means 20 so that the shaft can rotate freely. Two of the four test pieces (test piece A1 and test piece A2 shown in FIG. 1) extend from one side of the rotation control means 20 through the atmosphere control means 50 along the Y-axis direction. Exist. The remaining two of the four test pieces have the atmosphere control means 50 along the Y-axis direction from the other side surface of the rotation control means 20 to the side opposite to the test pieces A1 and A2. It extends through. In the corrosion fatigue combined test apparatus 10 shown in FIG. 1, the four test pieces are arranged symmetrically two by two around the rotation control means 20. The adapter 3 (load load means) of the load control means 30 is attached to the other end of each test piece (in FIG. 1, only the test piece A1 and the test piece A2 are shown).

FIG. 2 is an explanatory diagram for explaining a part of the corrosion fatigue combined test apparatus shown in FIG. 1, and is an explanatory diagram showing the inside of the case 20a of the rotation control means 20 to which no test piece is attached.
The rotation control means 20 supports one end of a rod-shaped test piece so that the shaft can rotate freely, and rotates the test piece so as to be capable of shifting. In the case 20a of the rotation control means 20 shown in FIG. 1, as shown in FIG. 2, two rotation driving units 22 are provided at both ends of the rotation driving unit 22 in the rotation axis direction (Y-axis direction). And the four collet chucks 2a (only one is shown in FIG. 2) attached to the gripping part 21.

  Each rotation drive unit 22 is rotated at a predetermined speed about the Y direction as an axis by being controlled by the control means. In the corrosion fatigue combined test apparatus 10 shown in FIG. 1, the test pieces supported respectively at both ends of each rotation drive unit 22 in the Y direction are interlocked with each rotation drive unit 22 rotating at a predetermined speed. It is designed to rotate at a predetermined speed around the axis.

  The two rotation driving units 22 are driven by an electric motor shaft (not shown) installed below the rotation driving unit 22. By using a common motor shaft for driving the two rotation driving units 22, the four test pieces can be rotated at the same rotational speed. In addition, the motor shafts that drive the two rotation driving units 22 are separated from each other, and the rotation speeds of the respective rotation driving units 22 are made different so that four test pieces are rotated at two different rotation speeds. May be.

  The rotation control unit 20 can rotate the test piece by rotating the rotation driving unit 22, for example, at a low speed of a rotation speed of less than 5 to 500 rpm or a high speed of a rotation speed of 500 to 10,000 rpm.

  At both ends of each rotation drive unit 22, a gripping part 21 for gripping the collet chuck 2a is provided. The collet chuck 2a has a cylindrical shape having a hole 2b into which one end of the test piece is inserted at the center. The collet chuck 2a is configured such that the inner diameter of the hole 2b into which the test piece is inserted is changed by increasing or decreasing the interval between the cuts formed radially from the side surface of the hole 2b. By attaching the test piece to the gripping part 21 of the rotation drive unit 22 using the collet chuck 2a, vibration of the rotating test piece can be suppressed, variation in evaluation can be reduced, and the test piece can be rotated easily and reliably. The drive unit 22 can be attached and detached.

  FIG. 3 is an explanatory view for explaining a part of the corrosion fatigue combined test apparatus shown in FIG. 1, and is an explanatory view separately showing each member of the load control means 30 to which no test piece is attached. The load control means 30 performs loading and unloading of the load to the other end of the test piece. As shown in FIGS. 1 and 3, the load control means 30 includes an adapter 3 (load load means), a weight base 4, an adapter cradle 5, and a cylinder 6 (load unload means). .

The adapter 3 (load loading means) is for pulling the other end of the test piece vertically downward so that the shaft can rotate. As shown in FIG. 3, the adapter 3 includes a test piece attachment portion 3a attached to the other end of the test piece, a pedestal attachment portion 3b to which the weight pedestal 4 is attached, a test piece attachment portion 3a, and a pedestal attachment portion 3b. And a hinge 3c to be connected.
The test piece attachment portion 3a is a rectangular plate, and a bearing 3d is disposed at the center. A hole to which the other end of the test piece is attached is provided inside the bearing 3d. The bearing 3d does not move in the rotational axis direction (Y direction in FIG. 1) of the test piece, and operates freely in the rotational direction of the test piece.

As shown in FIG. 3, the upper part 3f of the base attaching part 3b has a substantially U-shape, and is formed so as to surround both side surfaces and the lower face of the test piece attaching part 3a. Further, the lower part 3g of the pedestal attaching part 3b has a plate-like shape having a width that is aligned with that of the upper part 3f and narrower than the upper part 3f. A hole 3e for attaching the weight base 4 is formed at the center in the width direction of the lower part 3g of the base attaching part 3b.
The hinges 3c are provided on both side surfaces of the adapter 3, respectively. The hinge 3c connects the side surface of the test piece attachment portion 3a and the wall surface of the base attachment portion 3b facing the side surface of the test piece attachment portion 3a. The hinge 3c supports the pedestal mounting portion 3b with respect to the test piece mounting portion 3a so as to be rotatable about the X direction in FIG.

  In the corrosion fatigue combined test apparatus 10 shown in FIG. 1, a pedestal mounting portion 3b is connected to a test strip mounting portion 3a of an adapter 3 to which a test strip is mounted by a hinge 3c. And the weight base 4 is attached to the base attachment part 3b. Therefore, in the combined corrosion fatigue test apparatus 10 shown in FIG. 1, a predetermined weight can be placed on the weight base 4 and a vertically downward bending load can be applied to the test piece via the weight base 4 and the adapter 3. Therefore, in the corrosion fatigue combined test apparatus 10 shown in FIG. 1, the rotation control means 20 rotates the test piece while applying a vertically downward bending load to the test piece, and makes one rotation in the direction of the rotation axis of the surface of the test piece. Each time, compression and tension loads can be applied repeatedly. In the corrosion fatigue combined test apparatus 10 shown in FIG. 1, since the adapter 3 has the bearing 3d and the hinge 3c, the other end of the test piece is not affected by the deflection of the test piece by rotation or bending load. Can always be loaded vertically downward.

As shown in FIG. 3, the weight base 4 includes a hook 4a attached to the hole 3e of the base attachment part 3b of the adapter 3, a base 4c on which the weight is placed, and a shaft member 4b that connects the hook 4a and the base 4c. Have. The pedestal 4c has a substantially circular shape in plan view, and the shaft member 4b is connected to the substantial center of the pedestal 4c and substantially perpendicular to the pedestal 4c.
The weight base 4 shown in FIG. 3 is attached to the adapter 3 by hooking the hook 4a into the hole 3e of the adapter 3. For this reason, the weight base 4 can easily apply a vertically downward load to the adapter 3.

As shown in FIGS. 1 and 3, a cylinder 6 (load unloading means) is disposed on the lower surface of the weight base 4. The cylinder 6 can be expanded and contracted vertically by being controlled by the control means.
When the cylinder 6 is extended upward and the upper surface 6 a of the cylinder 6 is brought into contact with the lower surface of the pedestal 4, the weight pedestal 4 loaded on the adapter 3 and the weight load placed on the weight pedestal 4 are applied to the cylinder 6. Moving. As a result, the load applied to the test piece from the adapter 3 is unloaded.

Further, when the cylinder 6 is contracted downward and the upper surface 6a of the cylinder 6 and the lower surface of the pedestal 4 are separated, the load of the weight pedestal 4 loaded on the cylinder 6 and the weight loaded on the weight pedestal 4 is Move to adapter 3. As a result, a load is applied from the adapter 3 to the test piece.
Therefore, by controlling the cylinder 6 by the control means and extending and contracting the cylinder 6 up and down to change the position of the upper surface 6a, the load on the other end of the test piece and the load on the other end of the test piece are changed. Can be switched to unloading.

  As shown in FIGS. 1 and 3, the adapter cradle 5 is a plate-like member. The adapter cradle 5 shown in FIG. 3 protrudes from the mounting portion 5c fixed on the main body 10a of the corrosion fatigue combined testing apparatus 10 shown in FIG. 1 and the edge on the main body 10a of the corrosion fatigue combined testing apparatus 10. It has the overhang | projection part 5a supported in the state. A hole 5b penetrating the adapter cradle 5 is provided at the center of the overhang portion 5a. As shown in FIG. 3, the planar shape of the hole 5b is larger than the cross-sectional shape of the lower part 3g of the base mounting part 3b of the adapter 3, and smaller than the cross-sectional shape of the upper part 3f.

  As shown in FIGS. 1 and 3, the adapter cradle 5 is fixed substantially horizontally on the main body 10 a of the corrosion fatigue combined test apparatus 10 using bolts, nuts, or the like. A lower portion 3 g of a base mounting portion 3 b of the adapter 3 is inserted into the hole 5 b of the adapter receiving base 5. In the present embodiment, the adapter cradle 5 and the adapter 3 are arranged so that the adapter cradle 5 and the adapter 3 are not in contact between the start of the fatigue test and the test piece breaking. Is adjusted. Therefore, the adapter cradle 5 and the adapter 3 are in contact with each other during the test, and a part of the load applied to the adapter 3 is not loaded on the adapter cradle 5, and the test can be performed with high accuracy. it can.

  The adapter cradle 5 performs a fatigue test using the corrosion fatigue combined test apparatus 10 and receives the adapter 3 when the test piece breaks, and supports the broken test piece. By providing the adapter cradle 5, it is possible to prevent the broken test piece and the adapter 3 attached to the test piece from falling from the corrosion fatigue combined test apparatus 10, and prevent the fracture surface of the test piece from being damaged. it can. Accordingly, by observing the fracture surface of the test piece, the form of the fracture surface, the starting point of the fracture, and the like can be evaluated with high accuracy.

  In order to prevent the adapter cradle 5 from coming into contact with the adapter 3, the distance between the upper surface of the adapter cradle 5 and the upper portion 3 f of the base mounting portion 3 b of the adapter 3 should be 5 mm or more apart. preferable. Moreover, it is preferable that the space | interval of the upper surface of the adapter stand 5 and the upper part 3f of the base attachment part 3b of the adapter 3 is 200 mm or less so that the adapter 3 can be reliably received when a test piece fractures | ruptures.

  FIG. 4 is an explanatory view for explaining a part of the corrosion fatigue combined test apparatus shown in FIG. 1, and is an explanatory view showing an atmosphere control means 50 to which no test piece is attached. In FIG. 4, only the connection portion with the atmosphere control means 50 is shown for the corrosive liquid control means 40 and the cooling means 60 in order to make the drawing easy to see. Parts other than the connection part of the cooling means 60 will be described with reference to FIGS. 5 (a) and 5 (b). Moreover, parts other than the connection part of the corrosive liquid control means 40 will be described with reference to FIG.

  FIG. 5A is a schematic diagram of one of the atmosphere control means 50 shown in FIG. 4 and the cooling means 60 connected thereto as viewed from above. FIG. 5B is a schematic schematic view of one of the atmosphere control means 50 shown in FIG. 4 and the corrosive liquid control means 40 and the cooling means 60 connected thereto as viewed from the side. 5 (a) and 5 (b), symbols A1 and A2 indicate test pieces, and in FIGS. 5 (a) and 5 (b), the atmosphere in which the test pieces A1 and A2 are installed is shown. The control means 50 is shown.

In the combined corrosion fatigue test apparatus shown in FIG. 1, two atmosphere control means 50 are provided as shown in FIGS. As shown in FIG. 1, the two environment control means 50 are arranged symmetrically with the rotation control means 20 in between.
The atmosphere control means 50 controls the test atmosphere to which the test pieces A1 and A2 are exposed by being controlled by a control means (not shown). As shown in FIG. 4, FIG. 5A and FIG. 5B, the atmosphere control means 50 includes a chamber 51, temperature / humidity control means (not shown), and gas supply means connected to the temperature / humidity control means. 52 (supply port 55 and discharge port 56).

  The chamber 51 shown in FIG. 4 is a box having a quadrangular prism shape, and as shown in FIG. 5A, the chamber 51 is exposed to the test atmosphere in the two test pieces A1 and A2 penetrating the chamber 51. It covers the part. Therefore, in the corrosion fatigue combined test apparatus 10 shown in FIG. 1, the portions of the test pieces A <b> 1 and A <b> 2 installed in the chamber 51 can be tested as a controlled test atmosphere in the chamber 51.

On the side surface (see FIG. 4) of the rotation control means 20 side (inner side) of the chamber 51, as shown in FIG. 5A, an opening 54 for allowing the test pieces A1 and A2 to penetrate is formed in the chamber 51. ing. An opening 53 is formed at a position facing the opening 54 on the side surface (see FIG. 4) of the chamber 51 on the load control means 30 side (outside).
As shown in FIG. 5A, an O-ring 57 is arranged at a portion where the edge of the opening 53, 54 on the inner surface side of the chamber 51 and the test piece A1, A2 rotating during the test are slid. ing. In the present embodiment, the O-ring 57 has a diameter of about 0.5 mm smaller than the diameter of the columnar test pieces A1 and A2.

  As shown in FIG. 5A, the O-ring 57 is formed by installing test pieces A1 and A2 in the chamber 51, so that the edges of the openings 53 and 54 on the inner surface side of the chamber 51 are formed by the test pieces A1 and A2. Pressed against the part. Further, the O-ring 57 rotates together with the test pieces A1 and A2 under test, and slides on the edge of the openings 53 and 54 on the inner surface side of the chamber 51. In the present embodiment, as shown in FIG. 5A, the O-ring 57 is disposed at a portion where the openings 53 and 54 of the chamber 51 and the test pieces A1 and A2 are slid together. Leakage of test atmosphere from is prevented.

The test atmosphere can be determined according to the purpose of the test, and is not particularly limited. For example, a predetermined amount of air is adjusted to a predetermined temperature and humidity, or air is adjusted to a predetermined temperature and humidity. What added the corrosive gas etc. can be used.
The temperature / humidity control means controls the temperature and humidity of the test atmosphere by being controlled by a control means (not shown). The temperature / humidity control means adjusts the atmospheric gas serving as a test atmosphere supplied via a pipe (not shown) to a predetermined temperature and humidity within a range of a temperature of 20 to 80 ° C. and a relative humidity of 20 to 100%. It is preferable that the gas supply means 52 is supplied via a pipe (not shown). The temperature / humidity control means is not particularly limited, and for example, a device having a dehumidifying device, a humidifying device, a heating device such as a heater, or a cooling device can be used.

  The gas supply means 52 is controlled by a control means (not shown) to supply an atmosphere gas serving as a test atmosphere supplied from the temperature / humidity control means to the chamber 51 at a predetermined flow rate using a compressor or the like and discharge it. Is. The gas supply means 52 has a supply port 55 and a discharge port 56 as shown in FIGS. 4, 5 (a) and 5 (b). The supply port 55 is provided on one side surface provided in a direction substantially orthogonal to the side surface of the chamber 51 on the rotation control means 20 side. The discharge port 56 is provided on the side surface opposite to the side surface on which the supply port 55 is provided. The exhaust port 56 is preferably provided with a damper.

  A pipe (not shown) connected to the temperature / humidity control means is connected to the supply port 55, and atmospheric gas whose temperature and humidity are adjusted by the temperature / humidity control means is supplied. The atmospheric gas supplied at a predetermined flow rate through the supply port 55 fills the chamber and is used as a test atmosphere, flows toward the discharge port 56, and is discharged from the exhaust port 56 to the outside of the chamber 51. .

  When the exhaust port 56 is provided with a damper, the damper is closed when changing the temperature and / or humidity of the test atmosphere, and when the temperature and / or humidity in the chamber 51 becomes substantially constant, the damper is closed. Can be opened. Thus, when the test atmosphere in the chamber 51 is changed, the time during which the test atmosphere is in an unsteady state can be shortened, which is preferable.

  The corrosive liquid control means 40 performs dripping and stopping of the corrosive liquid on the test pieces A1 and A2 by being controlled by a control means (not shown). As shown in FIG. 5 (b), the corrosive liquid control means 40 includes a nozzle 41 attached to the upper surface of the chamber 51, a tube pump 43, and a tube 42 made of a resin that connects the nozzle 41 and the tube pump 43. And a tank 44, and a tube 45 connecting the tube pump 43 and the tank 44.

The nozzle 41 drops a corrosive liquid on the test pieces A1 and A2. As shown in FIG. 5B, the nozzle 41 is provided at a position overlapping the position where the test pieces A <b> 1 and A <b> 2 are arranged in a plan view of the upper surface of the chamber 51.
As shown in FIG. 5B, the tank 44 contains a corrosive liquid. One end of a tube 45 made of resin or the like is inserted below the level of the corrosive liquid stored in the tank 44. One end of the tube 45 is set at the bottom of the tank 44 by its own weight.

The tube pump 43 supplies the corrosive liquid dropped from the nozzle 41 to the test pieces A1 and A2 to the tube 42 at a preset supply amount and dropping time by being controlled by a control means (not shown). By switching “ON” and “OFF” of the tube pump 43 by the control means, the dripping of the corrosive liquid from the nozzle 41 to the test pieces A1 and A2 is “started” and “stopped”.
The corrosive liquid can be determined according to the purpose of the test, and is not particularly limited. For example, it can be a salt solution for test defined in JIS Z2371.

  As shown in FIGS. 4, 5 (a), and 5 (b), a nozzle 61 of a cooling means 60 that cools the test pieces A 1 and A 2 is provided in the center of the upper surface of the chamber 51 in plan view. Yes. The nozzle 61 is connected to a cooling gas supply means (not shown) installed outside the chamber 51. The cooling gas supply means supplies a cooling gas having a predetermined temperature and flow rate to the nozzle 61. For example, as the cooling gas supply means, one that supplies the cooling gas to the nozzle 61 using a compressor can be cited.

The cooling gas can be determined according to the purpose of the test and is not particularly limited. For example, cooling air can be used. The temperature of the cooling gas can be determined according to the material of the test piece, the type of the cooling gas, and the purpose of the test, and is not particularly limited.
The temperature and flow rate of the cooling gas are preferably controlled so that the temperature of the test piece under test is in the range of 10 ° C. or more and less than 250 ° C. The temperature and flow rate of the cooling gas during the test can be changed by the control means as required.

  If the temperature of the test piece under test is less than 250 ° C, the material of the test piece will change (soften) due to overaging, recovery, recrystallization, etc. if the test piece is made of steel. Can be prevented. Moreover, since it takes cost to set the temperature of the test piece under test to less than 10 ° C., the temperature of the test piece under test is preferably 10 ° C. or higher.

  As shown in FIGS. 5 (a) and 5 (b), the nozzle 61 is branched into two in the chamber 51, and sprays in the vicinity of the two test pieces A 1 and A 2 installed in the chamber 51. A branch nozzle 62 having an outlet is provided. Since the cooling means 60 of the present embodiment has the branch nozzle 62, the cooling gas can be efficiently supplied to each of the two test pieces A1 and A2 installed in the chamber 51.

  Moreover, it is preferable that the nozzle 61 equips an inside with the dry filter (not shown) which dries cooling gas. When air is used as the cooling gas, the heat transfer coefficient of the cooling gas tends to become unstable because the humidity of the cooling gas varies due to changes in the atmospheric humidity due to the season or weather. By passing the drying filter in the nozzle 61 and drying the cooling gas, a cooling gas with stable humidity can be obtained. Therefore, when air is used as the cooling gas, it is possible to reduce the influence on the cooling capacity of the cooling gas due to changes in the humidity in the atmosphere, and it is possible to evaluate the corrosion fatigue characteristics with higher accuracy.

  1 controls the rotation control means 20, the load control means 30, the corrosive liquid control means 40, the atmosphere control means 50, and the cooling means 60 to control the corrosion fatigue composite test apparatus. The mode selection means (not shown) which switches 10 operation | movement is provided. In the corrosion fatigue combined test apparatus 10 shown in FIG. 1, the rotation speed of the test piece, loading / unloading of the load on the test piece, dripping / stopping of the corrosive liquid, and the test are performed according to the control signal sent from the mode selection means to the control means. The temperature / humidity of the atmosphere and whether or not the specimen is cooled are individually changed. These control functions by the mode selection means are realized by the operation of a program stored in a RAM (Random Access Memory) or ROM (Read Only Memory) of the computer.

Examples of the operation switched by the mode selection means include the following four modes.
(1) Corrosion droplet lowering mode in which the test piece is rotated while dripping the corrosive liquid onto the test piece from which the load has been removed.
(2) A corrosive liquid drying mode that is performed continuously after the corrosive droplet lowering mode is performed, and dries the surface of the test piece.
(3) A fatigue mode in which the specimen is rotated while a load is applied to the specimen.
(4) Wetting mode in which the surface of the test piece is wet before the fatigue mode.

  The operation switched by the mode selection means may be the same for all the four test pieces, or if the test pieces arranged in the same chamber have the same test atmosphere, the test may be performed with different operations.

(Corrosion drop mode)
In the corrosive liquid drop mode, the test piece is rotated while dripping the corrosive liquid onto the test piece from which the load has been removed. In the corrosion drop mode, the corrosion solution is uniformly applied to the test piece. In the corrosion drop mode, since the load is unloaded, it does not affect the generation and propagation of fatigue cracks.
In the corrosive droplet mode, in order to prevent variations in evaluation due to local concentration of corrosive components in the corrosive liquid drying mode, which will be described later, a corrosive liquid film formed on the surface of the test piece is uniformly attached in the circumferential direction. It is preferable. For this reason, in the corrosion droplet lowering mode, it is preferable to set the rotation speed of the test piece to a low speed corresponding to the viscosity of the corrosion liquid.

Specifically, in the corrosion droplet lowering mode, it is preferable to rotate the test piece at a low speed of less than 5 to 500 rpm by the rotation control means 20, and a more desirable rotation speed is 50 to 200 rpm. When the rotation speed of the test piece is set to a low speed of less than 500 rpm, the corrosive liquid can be stably attached to the test piece in a thin film state. Further, when the rotation speed of the test piece is set to 5 rpm or more, it is possible to prevent gravity from acting on the corrosive liquid, which is a fluid, and dripping the corrosive liquid downward from the surface of the test piece. Therefore, the corrosive liquid can be stably attached in the circumferential direction of the test piece.
Therefore, for example, when artificial seawater is used as the corrosive liquid and the rotation speed of the test piece is in the above range, the average film thickness of the corrosive liquid film formed on the surface of the test piece easily becomes 20 μm to 2 mm, and the test piece Variation of the thickness of the corrosive liquid film in the circumferential direction is 5% or less of the average film thickness.

  When the rotation speed of the test piece is 500 rpm or more, the centrifugal force due to the rotation of the test piece tends to be stronger than the adhesion force of the corrosive liquid that is rotating together with the test piece due to the viscous force. It becomes easy to detach from and to scatter. Moreover, when the rotational speed is less than 5 rpm, the corrosive liquid hangs down from the surface of the test piece, the variation in the film thickness of the corrosive liquid film in the circumferential direction of the test piece increases, and the environmental conditions of the occurrence of corrosion in the test piece. Tends to be non-uniform.

The average film thickness of the corrosive liquid film and the variation in the film thickness of the corrosive liquid film in the corrosive liquid drop mode are calculated by the following method.
First, from the Z direction (upper direction) shown in FIG. 1, the position of the surface of the test piece (the center part in the longitudinal direction in the round bar-shaped test piece, the test part having the smallest outer diameter and the parallel part in the hourglass type test piece. The parallel part is photographed in advance optically. Next, the corrosive liquid drop mode is started, and the position of the outer surface of the corrosive liquid film that is optically continuously photographed every 50 ms at the same position as the position of the specimen is measured. Is calculated as the thickness of each liquid film. Then, the average film thickness of the corrosive liquid film is obtained by averaging all 3000 points of individual liquid film thicknesses for any one minute in the corrosive liquid drop mode. Further, in the data of 3000 points of individual liquid film thickness, the difference between the maximum value and the minimum value is defined as the variation of the corrosive liquid film.

  The dripping amount of the corrosive liquid in the corrosive liquid drop mode is determined according to the environmental conditions in which the product made of the material of the test piece is actually used. In order to make the environmental conditions of the occurrence of corrosion in the test piece uniform, it is preferable that the amount of dripping of the corrosive liquid is 0.1 to 30 mL / min by the corrosive liquid control means 40. When the dripping amount of the corrosive liquid is within the above range, the corrosive liquid can be stably attached to the test piece in a thin film state. By setting the dripping amount of the corrosive liquid to 0.1 mL / min or more, the corrosive liquid can be uniformly attached over the entire circumferential direction of the test piece. Moreover, it can suppress that the usage-amount of corrosive liquid increases more than necessary by making dripping amount of corrosive liquid 30 mL / min or less.

(Corrosive liquid drying mode)
The corrosive liquid drying mode is continuously performed after the corrosive liquid drop mode is performed. In the corrosive liquid drying mode, the surface of the test piece from which the load is removed is dried. In the corrosive liquid drying mode, a corrosive component (for example, chloride in artificial seawater) contained in the corrosive liquid is concentrated on the surface of the test piece.
In the corrosive liquid drying mode, it is preferable to rotate the test piece within the range of the rotation speed of 5 to 500 rpm by the rotation control means 20, and a more desirable rotation speed is 10 to 100 rpm. By rotating the test piece in the corrosive liquid drying mode, drying of the test piece is promoted. In the corrosive liquid drying mode, since the load is unloaded, it is not necessary to consider the phenomenon caused by the load.

  In the corrosive liquid drying mode, the atmosphere control means 50 preferably sets the test atmosphere in the chamber 51 to a dry state at a high temperature of 40 to 50 ° C., a relative humidity of 20 or more and less than 30%. As a result, the rate of decrease of the corrosive liquid film is 10 μm / s or more and 200 μm / s or less in the corrosive liquid drying mode while maintaining the state of the corrosive liquid film having a uniform circumferential film thickness formed in the corrosive droplet lowering mode. It can be. Thereby, it can prevent that a drying nonuniformity arises in a test piece. Therefore, local variation in concentration of corrosive components on the surface of the test piece can be suppressed, and the test can be performed efficiently.

When the test atmosphere in the chamber 51 is set to a temperature exceeding 50 ° C. and a relative humidity of 20% or less in the corrosive liquid drying mode, the rate of decrease of the corrosive liquid film is likely to exceed 200 μm / s, and uneven drying of the test piece is likely to occur. Become.
In addition, the lower limit of the rate of decrease of the corrosive liquid film in the corrosive liquid drying mode is not particularly specified in terms of function, but by setting it to 10 μm / s or more, it takes too much time to dry the corrosive liquid film, thereby improving the test efficiency. It can be prevented from lowering.

The rate of decrease of the corrosive liquid film in the corrosive liquid drying mode was investigated by the following method.
That is, in the same manner as the measurement of the average film thickness of the corrosive liquid film calculated in the corrosive liquid drop mode, the average film thickness every minute after the start of the corrosive liquid drying mode is continuously measured for 30 minutes. The average reduction rate of the corrosive liquid film was determined from the 30 points of data.

(Wet mode)
The wet mode is continuously performed after performing the corrosive liquid drying mode, if necessary. In the wet mode, the surface of the test piece from which the load has been removed after the corrosive liquid drying mode is in a wet state. In the wet mode, the corrosion components concentrated on the surface of the test piece by the corrosive liquid drying mode are ionized by moisture to promote the generation and growth of corrosion pits on the surface of the test piece.
In the wet mode, the atmosphere control means 50 preferably makes the test atmosphere in the chamber 51 a wet state with a low temperature of 20 to 40 ° C. and a relative humidity of 30 to 100%. This promotes the formation and growth of corrosion pits on the surface of the specimen. In the wet mode, since the load is unloaded, it is not necessary to consider the phenomenon caused by the load.

  By repeating the combination of the corrosive liquid drop mode, the corrosive liquid drying mode, and the wet mode successively in this order one or more times, for example, the progress of corrosion and the penetration of hydrogen into the specimen And the corrosion of the specimen is further accelerated.

(Fatigue mode)
In the fatigue mode, the test piece is rotated while applying a load to the test piece. In the fatigue mode, the fatigue of the specimen is accelerated. In the fatigue mode, it is preferable to rotate at a higher speed than in the corrosive droplet lowering mode. Specifically, in the fatigue mode, it is preferable to rotate the test piece at a high speed of 500 to 10,000 rpm. When the rotational speed is 10,000 rpm or less, it is possible to prevent the occurrence of unexpected vibration of the test piece due to the attachment of the test piece during the test. Moreover, a fatigue test can be efficiently performed by setting a rotational speed to 500 rpm or more.

  For example, when a test piece made of high-strength steel having a tensile strength of 1000 MPa or more is evaluated by performing the fatigue mode, it is preferably performed while cooling the test piece by the cooling means 60. Specifically, for example, the cooling means 60 is controlled by the mode selection means, and the test piece is cooled by spraying a cooling gas such as cooling air from the nozzle 61 of the cooling means 60 to the load-loading portion of the test piece. preferable. In the fatigue mode, the test piece is cooled by the cooling means 60 and the heat generation of the test piece is suppressed, whereby softening due to heating of the test piece made of high-strength steel can be prevented. When the test piece is cooled by the cooling unit 60, the cooling gas from the cooling unit 60 affects the test atmosphere in the chamber 51, so that the test atmosphere need not be controlled by the atmosphere control unit 50.

  When a test piece made of a high-strength steel material is evaluated by performing the fatigue mode without cooling the test piece by the cooling means 60, the test piece generates heat, the oxide film on the surface of the test piece becomes thick, and the gold color Or may turn blue (tempered color). In the test piece on which the temper color is attached, the temperature of the test piece under test rises to 300 to 500 ° C., and the test piece is softened, so that the fatigue life may be shorter than the original performance. For this reason, the dispersion | variation in the evaluation of a test piece becomes large. In particular, in test pieces made of high-strength steel having a tensile strength of 1000 MPa or more, the variation in evaluation becomes significant.

When the test piece is cooled by the cooling means 60 in the fatigue mode, even if the test piece is made of a high-strength steel material, softening due to heating of the test piece can be prevented, so that variation in evaluation can be reduced.
Moreover, when evaluating the test piece which consists of high-strength steel materials by performing fatigue mode, the rotation speed of a test piece shall be 500-10000 rpm, and it is slower than the case where the tensile strength of a test material is low, for example, 700 rpm or less, More preferably, it is good also as 550 rpm or less. In this case, heat generation of the test piece can be suppressed, and softening due to heating of the test piece made of high-strength steel can be prevented.

  When the test material has a low tensile strength (for example, a tensile strength of 700 MPa or less), even when the fatigue mode is performed, the stress applied to the test piece is low, so the distortion of the test piece is small. Therefore, even if the test piece is not cooled, the temperature rise of the test piece due to the fatigue mode is small, the temper color is not attached to the surface, and the variation in evaluation is sufficiently reduced.

Further, the fatigue mode may be performed while the surface of the test piece is in a wet state without performing the wet mode after the corrosive liquid drying mode, depending on the purpose of the fatigue test. In this case, fatigue of the test piece is accelerated and corrosion of the test piece is also accelerated.
More specifically, in the fatigue mode, the corrosive component concentrated on the surface of the test piece by the corrosive liquid drying mode is ionized by moisture in the atmosphere to promote the generation and growth of corrosion pits on the surface of the test piece. When the fatigue mode is performed while the surface of the test piece is in a wet state, the atmosphere in the chamber 51 may be set to a low temperature of 20 to 40 ° C. and a wet state of 30 to 100% relative humidity by the atmosphere control means 50. preferable. This promotes the formation and growth of corrosion pits on the surface of the specimen.

  Moreover, you may perform fatigue mode, dripping a corrosive liquid to a test piece according to the objective of a fatigue test.

"Corrosion fatigue combined test method"
Next, as an example of the combined corrosion fatigue test method of the present invention, the corrosion fatigue combined test apparatus 10 shown in FIG. 1 is used to perform a step of accelerating the corrosion of the test piece and a step of accelerating the fatigue of the test piece. The method will be described as an example.
In this embodiment, after performing the step of accelerating the corrosion of the test piece, the step of accelerating the fatigue of the test piece, and then the step of accelerating the corrosion of the test piece until the test piece breaks and the test piece The process of accelerating fatigue is repeated alternately.
In the present embodiment, all four test pieces may be tested under the same conditions, and if the test pieces placed in the same chamber have the same test atmosphere, the tests may be performed under different conditions. Good.

(Process to accelerate corrosion)
The step of accelerating the corrosion of the test piece is not particularly limited as long as it can accelerate the corrosion of the test piece, but it is a step of rotating the test piece while dripping the corrosion solution onto the test piece from which the load has been removed. It is preferable that the step shown in the following (a1) or (a2) is more preferably performed in a preset time. The step of accelerating the corrosion of the test piece may be a step in which the following (a1) and (a2) are combined.

(A1) A step of rotating the test piece at a low speed of less than 5 to 500 rpm while dropping the corrosive liquid on the test piece from which the load has been removed. In this step, the average thickness of the corrosive liquid film formed on the surface of the test piece is 20 μm to 2 mm, and the variation in the thickness of the corrosive liquid film in the circumferential direction of the test piece is 5% or less of the average film thickness. . The step shown in (a1) is preferably combined with the step including (b2) described later.
(A2) a corrosive solution coating process in which the test piece is rotated while dripping the corrosive liquid on the test piece from which the load has been removed, and a drying process for drying the surface of the test piece that is continuously performed after the corrosive solution coating process; A corrosive liquid formed on the surface of the test piece in the corrosive liquid coating process, including a step of performing one or a plurality of times a combination with a wet process in which the surface of the test piece is continuously wetted after the drying process. The film is dried by a drying process at a decreasing rate of 200 μm / s or less to concentrate the corrosive component, and the corrosive component concentrated by the wet process is ionized. The step shown in (a2) is preferably combined with the step including (b1) described later.

The process shown in (a1) above is performed by switching the operation of the apparatus to the “corrosive droplet lowering mode” by the mode selection means.
In the step shown in (a2), the mode selection means switches the operation of the apparatus to the “corrosive droplet lowering mode”, then switches to the “corrosive liquid drying mode”, and then switches to the “wetting mode”. Do it once or multiple times.

(Process to accelerate fatigue)
The step of accelerating fatigue is not particularly limited as long as it can accelerate the fatigue of the test piece, but is preferably a step of rotating the test piece while applying a load to the test piece. It is preferable to perform any of the steps shown in (b1) to (b3) for a preset time. In addition, when a test piece is high strength steel with a tensile strength of 1000 MPa or more, it is preferable to perform the process shown in the following (b1). Moreover, the process of accelerating the corrosion of the test piece may be a process in which two or more of the following (b1) to (b3) are combined. For example, the following (b1) and (b3) Or a combination of the following (b2) and (b3).

(B1) A step of rotating the test piece while applying a load to the other end of the test piece and cooling the test piece.
(B2) A step of rotating the test piece while applying a load to the other end of the test piece in a test atmosphere having a relative humidity of 30 to 100%.
(B3) A step of rotating the test piece while dropping a corrosive liquid onto the test piece and applying a load to the other end of the test piece.
The steps shown in the above (b1) to (b3) are performed by switching the operation of the apparatus to the “fatigue mode” by the mode selection means.

In the present embodiment, the step shown in the above (a1) or (a2) and the steps shown in (b1) to (b3) may be performed in any combination, such as the material of the test piece and the purpose of the test. Can be determined according to
In the present embodiment, the step of accelerating the corrosion of the test piece and the step of accelerating the fatigue of the test piece are performed in a preset time, respectively, to accelerate the corrosion of the test piece and accelerate the fatigue. However, the step of accelerating fatigue after the step of accelerating the corrosion of the test piece may be continuously performed only once until the test piece breaks.

  In the process shown in (b1) described above, a cooling gas for cooling the test piece is supplied into the chamber 51. For this reason, it becomes difficult to control the test atmosphere in the chamber 51 in the step shown in (b1). Therefore, it is preferable not to control the test atmosphere in the chamber 51 by the atmosphere control means 50 in the step shown in (b1).

In the step shown in (b2), when the test piece is cooled, the relative humidity tends to become unstable due to the cooling gas. For this reason, it is preferable not to cool a test piece in the process shown to (b2).
Moreover, it is preferable to perform the process shown to (b2) after the process shown to (a1) or (a2). In this case, the solute component in the corrosive liquid is crystallized uniformly on the surface of the test piece when performing the step shown in (b2). Therefore, in the step shown in (b2), when the test atmosphere in the chamber 51 is set to a low temperature of 20 to 40 ° C. and a wet state of a relative humidity of 30 to 100%, corrosion pits are generated and fatigue cracks are promoted. .

  Further, when the test piece is cooled while dripping the corrosive liquid onto the test piece, the application of the corrosive liquid to the surface of the test piece tends to become unstable. For this reason, it is preferable not to perform dripping of the corrosive liquid to a test piece, and cooling of a test piece simultaneously.

  The corrosion fatigue combined test method of the present invention may be any method that uses the corrosion fatigue combined test apparatus of the present invention to perform the step of accelerating the corrosion of the test piece and the step of accelerating the fatigue of the test piece. The method is not limited to the method exemplified in the above embodiment.

  The corrosion fatigue combined test apparatus 10 of this embodiment includes a rotation control means 20, a load control means 30, a corrosive liquid control means 40, an atmosphere control means 50, and a cooling means 60, and includes a control means for individually controlling these. Since it is provided, it is possible to change environmental conditions and stress load conditions during the test as required by the control means. Therefore, the process of accelerating the corrosion of the test piece and the process of accelerating the fatigue of the test piece can be performed continuously with one apparatus. For example, the CCT and the rotating bending fatigue test are performed using separate apparatuses. Compared with the case where it carries out, a corrosion fatigue characteristic can be evaluated efficiently.

  Further, in the corrosion fatigue combined test apparatus 10 of the present embodiment, the process of accelerating the corrosion of the test piece and the process of accelerating the fatigue can be performed with one apparatus. Compared with the case where the corrosion fatigue test is performed at, the corrosion fatigue characteristics can be evaluated with higher accuracy under conditions corresponding to actual environmental conditions and stress load conditions.

  Moreover, since the corrosion fatigue combined test apparatus 10 of this embodiment is provided with the cooling means 60, the test piece under test can be cooled and the heat generation of the test piece can be suppressed. As a result, for example, when testing a high-strength steel material, it is possible to prevent the test piece from generating heat and softening during the test, and to reduce variation in evaluation.

  In this embodiment, the corrosion fatigue combined test apparatus 10 that can efficiently test four test pieces simultaneously has been described as an example. However, in the corrosion fatigue combined test apparatus, the number of test pieces that can be tested simultaneously is particularly large. It is not limited. For example, only one test piece may be tested.

Further, in this embodiment, a case where a part of the rotation control means, the atmosphere control means, the corrosive liquid control means and the cooling means is provided for two test pieces is taken as an example. Although described, all of these may be provided individually for each test piece.
Even if the rotation control means provided in the corrosion fatigue combined test apparatus of the present invention rotates four test pieces at the same rotational speed, the four test pieces are rotated at different rotational speeds by two. It may be a thing, and all the test pieces may be rotated at different rotational speeds.

  Next, an Example is shown and this invention is demonstrated concretely. It should be noted that the scope of the present invention is not limited by the following examples, and can be implemented with appropriate modifications without departing from the scope of the present invention.

No. shown in Table 1 and Table 2. 1-No. Under the conditions of 10, the corrosion fatigue combined test was performed on the hourglass test pieces having the tensile strength shown in Table 3. As an hourglass-type test piece, a test piece having a circular shape in cross section, an outer diameter of 10 mm at both end portions, and an outer diameter of 4 mm at the smallest outer diameter portion at the central portion in the longitudinal direction was used.
No. 1-No. Rotation speed of test piece in each step (process) of 10 conditions, loading / unloading of load on test piece, dripping (flow rate) / stop of corrosive liquid, temperature / humidity of air as test atmosphere, Table 1 and Table 2 show the presence / absence of cooling, the test time, and the operation mode.

No. 1-No. The corrosion fatigue combined test was performed 10 times under the same conditions under 10 conditions, and the variation in the number of rotations of the test piece until the test piece broke (maximum number / minimum number) was examined.
Further, the thickness of the corrosive liquid film in the corrosive liquid drop mode was calculated by the following method.
First, from the Z direction (upward) shown in FIG. 1, the position of the central portion in the longitudinal direction of the test piece was optically photographed in advance. LS-9030 manufactured by Keyence Corporation was used as the photographing apparatus. Next, the corrosive liquid drop mode is started, and the position of the outer surface of the corrosive liquid film that is optically continuously photographed every 50 ms at the same position as the position of the specimen is measured. The difference was calculated as the thickness of each liquid film. Then, the average film thickness of the corrosive liquid film was obtained by averaging all 3000 points of individual liquid film thicknesses for an arbitrary 1 minute in the corrosive liquid drop mode.

Further, for the test piece after the corrosion fatigue combined test, as an evaluation of the presence or absence of abnormal heat generation during the test, whether or not the surface was changed to gold or blue (presence of temper color) was examined visually.
In addition, the presence or absence of vibration of the test piece in the fatigue mode was evaluated by the following method.
The presence / absence (x) or non-existence (O) of the vibration of the test piece in the fatigue mode was evaluated based on the presence or absence of operation noise or the presence or absence of vibration in the case of the rotation control means. The operation sound due to the vibration of the test piece is a very high frequency sound. For this reason, the presence or absence of the operation sound generated by the vibration of the test piece was determined based on whether or not the operation sound was heard without using a measuring instrument. In addition, when no operation sound was heard, the case of the rotation control means was touched, and the occurrence of vibration of the test piece was detected based on the presence or absence of the vibration.

  Table 3 shows the presence / absence of vibration of the test piece, presence / absence of abnormal heat generation, variation in the number of revolutions until breakage, and thickness of the corrosive liquid film in the corrosive liquid drop mode.

As shown in Table 3, no. 1-No. 4, no. 7-No. When the corrosion fatigue combined test was conducted under the conditions of No. 10, 5, no. Compared to 6, the rotational speed variation until breakage was smaller.
This is no. 1-No. 4, no. 7-No. This is because, under the condition No. 10, the rotation speed of the test piece under test was appropriate, and the test piece with high tensile strength was cooled in the fatigue mode.

No. In No. 5, since the rotational speeds in the corrosive droplet lowering mode and the corrosive liquid drying mode were slow, unevenness in formation of corrosion pits was large, and the number of revolutions until the specimen was broken increased.
No. In No. 6, the rotational speed in the fatigue mode was too high, and the test piece vibrated, resulting in a large variation in the number of revolutions until breaking.

  According to the corrosion fatigue combined test apparatus of the present invention and the corrosion fatigue combined test method using the same, the test piece can be evaluated efficiently and with high accuracy. In particular, a test piece made of high-strength steel can be evaluated with high accuracy. Therefore, it is extremely useful industrially, such as promoting the development of high-strength steel.

  A1, A2 Test piece, 2a Collet chuck, 3 Adapter, 3a Test piece mounting part, 3b Base mounting part, 3c Hinge, 3d Bearing, 4 Weight base, 4a Hook, 4b Shaft member, 4c base, 5 Adapter base, 5a Overhang part, 5b hole, 5c attachment part, 6 cylinder, 10 corrosion fatigue combined test apparatus, 10a body, 20 rotation control means, 21 gripping part, 22 rotation drive part, 30 load control means, 40 corrosive liquid control means, 41 nozzle , 43 Tube pump, 42, 45 Tube, 44 Tank, 50 Atmosphere control means, 51 Chamber, 52 Supply means, 53, 54 Opening, 55 Supply port, 56 Discharge port, 57 O-ring, 60 Cooling means, 61 Nozzle, 62 Branch nozzle.

Claims (12)

A rotation control means for rotatably supporting the one end of the rod-shaped test piece and rotating the test piece in a shiftable manner;
Load control means for loading and unloading the load to the other end of the test piece;
Corrosive liquid control means for dropping and stopping the corrosive liquid on the test piece;
Atmosphere control means for controlling a test atmosphere for exposing the test piece;
A cooling means for cooling the test piece;
A corrosion fatigue combined testing apparatus comprising: control means for individually controlling the rotation control means, the load control means, the corrosive liquid control means, and the atmosphere control means. The control means includes mode selection means for controlling the rotation control means, the load control means, the corrosive liquid control means, and the atmosphere control means to switch the operation of the apparatus,
The operation is a corrosive liquid drop mode in which the test piece is rotated while dripping the corrosive liquid onto the test piece from which a load has been removed;
A corrosive liquid drying mode for continuously drying the corrosive liquid drop mode and drying the surface of the test piece;
The corrosion fatigue combined test apparatus according to claim 1, further comprising a fatigue mode in which the test piece is rotated while a load is applied to the test piece. The cooling means is controlled by the mode selection means;
The corrosion fatigue combined test apparatus according to claim 2, wherein the test piece is cooled in the fatigue mode.   The rotation control means rotates the test piece at a low speed of a rotation speed of less than 5 to 500 rpm in the corrosive liquid drop mode, and rotates the test piece at a high speed of a rotation speed of 500 to 10,000 rpm in the fatigue mode. The corrosion fatigue combined test apparatus according to claim 2 or 3, wherein the corrosion fatigue combined test apparatus is characterized in that the apparatus is used. The load control means includes a load loading means for pulling the other end of the test piece vertically downward so as to freely rotate the shaft;
The corrosion fatigue combined testing apparatus according to any one of claims 1 to 4, further comprising load unloading means for unloading a load applied to the test piece. The atmosphere control means includes a chamber covering a portion of the test piece exposed to the test atmosphere;
Temperature and humidity control means for controlling the temperature and humidity of the test atmosphere;
Gas supply means for supplying atmospheric gas to the chamber;
The corrosion fatigue combined test apparatus according to any one of claims 1 to 5, further comprising:   The process for accelerating the corrosion of the test piece and the process for accelerating the fatigue of the test piece are performed using the combined corrosion fatigue test apparatus according to any one of claims 1 to 6. Corrosion fatigue combined test method.   The corrosion fatigue combined test method according to claim 7, wherein the test piece is a high strength steel having a tensile strength of 1000 MPa or more.   The step of accelerating the fatigue includes the step of rotating the test piece while cooling the test piece and applying a load to the other end of the test piece. The combined corrosion fatigue test method described.   The step of accelerating the fatigue is performed by dropping the corrosive liquid onto the test piece and / or applying a load to the other end of the test piece in a test atmosphere having a relative humidity of 30 to 100%. The corrosion fatigue combined test method according to claim 7 or 8, further comprising a step of rotating the piece.   The step of accelerating the corrosion is formed on the surface of the test piece by rotating the test piece at a low rotation speed of less than 5 to 500 rpm while dropping the corrosive liquid on the test piece from which a load has been removed. The method includes a step of setting an average film thickness of the corrosive liquid film to 20 μm to 2 mm and setting a variation of the film thickness of the corrosive liquid film in a circumferential direction of the test piece to 5% or less of the average film thickness. The corrosion fatigue combined test method according to any one of 7 to 10. The test piece in which the step of accelerating the corrosion is performed continuously after the corrosive liquid coating process of rotating the test piece while dropping the corrosive liquid on the test piece from which the load has been removed, and the corrosive liquid coating process. A combination of a drying treatment for drying the surface of the test piece and a wetting treatment for continuously bringing the surface of the test piece into a wet state after the drying treatment,
The corrosive liquid film formed on the surface of the test piece in the corrosive liquid coating treatment is dried at a decreasing rate of 200 μm / s or less by the drying treatment. The combined corrosion fatigue test method described.

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