JPWO2011024743A1 - Bow structure - Google Patents

Abstract

The bow structure includes a plurality of steel plates in which the outer shell member of the Barbasse bow has a linear heating portion that has undergone linear heating processing and a non-linear heating portion that has not undergone linear heating processing, Yield obtained by dividing the yield strength YP (LH, RT) at room temperature of the linear heating part in the steel sheet by the yield strength YP (AR, RT) at room temperature of the non-linear heating part. The intensity ratio α is 1.2 or less.

Description

The present invention relates to a bow structure that has a buffering effect that can prevent damage to a partner ship that collides due to deformation of itself during a collision, thereby improving collision safety.
This application claims priority based on Japanese Patent Application No. 2009-193476 filed in Japan on August 24, 2009, the contents of which are incorporated herein by reference.

  Today's large ships are equipped with a Barbasse bow (spherical bow) under the bowline to reduce any energy loss due to wave resistance during navigation. In order to produce a curved plate having a large curvature used for this Barbasse bow, bending by linear heating, that is, linear heating, is frequently used in the molding process.

  This linear heating process is a processing method that utilizes a phenomenon in which a steel plate surface is locally heated linearly using a gas burner or the like, and the heated portion is thermally expanded and plastically deformed by restraint from the periphery. In this linear heating process, water cooling is generally performed immediately after heating in order to increase work efficiency, and the steel sheet after the linear heating process is baked into the heated part and locally The yield strength has increased.

  For this reason, the Barbasu bow using such a curved plate has nonuniform strength along the surface and is not easily deformed. When a ship equipped with such a Barbus bow collides with another ship, for example, as shown in FIG. 9A, the bow 200a of the own ship 200 (first ship) is placed on the hull 201a of the other ship 201 (second ship). There was a risk that the hull 201a would be broken and the hull 201a was broken, and further, the broken portion 201b was enlarged and the hull was perforated (the hull was broken). In the present invention, “own ship” means a ship equipped with a Barbus bow, and “other ship” means a ship that collides with the “own ship”.

  Conventionally, as a means (structure) for improving the collision safety of a ship, examination from the hull structure aspect such as a double hull structure has been mainly performed. However, in recent years, it has been studied to apply a steel material excellent in energy absorption performance at the time of collision.

  As an example, in Patent Document 1 below, the product of the yield stress σy and the uniform elongation εu (σy × εu) is given to the outer skin of the ship, etc., compared to the conventional standard material of the International Classification Society Association (IACS). Steel material increased by 20% or more, or steel material whose energy absorption up to the uniform elongation εu in the tensile test was increased by 20% or more, or the yield stress σy was equal or higher and the uniform elongation εu was increased by 20% or more. A hull structure to which steel material is applied is disclosed. With this configuration, it is possible to increase the amount of energy that can be absorbed before a breakage occurs in the hull, while maintaining the hull structure that is not different from the conventional one.

  However, if the ship's bow collides with the hull of another ship, even if the ship's bow does not deform, even if the ship uses a steel plate that has improved energy absorption by 50% or more, the other ship There is a risk of penetrating the ship's hull. In that case, there is a problem that the increase in the amount of absorbed energy cannot be expected.

In order to solve such a problem, it is also considered to design a bow portion that exhibits a buffering effect even when the bow of the ship collides with another ship.
For example, Patent Literature 2 below discloses a bow portion having a flexible structure in which the bow portion is constructed using a material softer than a steel material used for general hull construction.
However, this Patent Document 2 only shows an aluminum material that is difficult to apply to a large ship as a soft material, and does not particularly disclose obtaining a flexible structure using a steel material.

  Further, Patent Document 3 below discloses a bow structure in which a low strength portion made of a low yield point steel having a yield stress of 235 MPa or less is provided on the outer plate of the base portion of a spherical protrusion (valve portion) in Barbus Bau. Yes. In this structure, the bending strength in the lateral direction of the base portion is reduced and the bow portion is bent by the reaction force of the collision, so that the bow portion of the collision ship is prevented from biting into the flank of another ship.

  In this patent document 3, while maintaining the strength of the vertical direction of the barbasse bow sufficiently, the structural strength in the horizontal direction of the barbusbau is reduced, so that the root part 300b of the barbusbau 300a is aligned in the hull width direction as shown in FIG. To easily increase the contact area of the collision part 300c. This structure prevents the breakage (occurrence of holes) of both the collision ship (own ship) 300 and the collision ship (other ship) 301 due to the increase in the contact area, but the bending of the root part 300b is a low yield point. It is caused by local deformation of the site where steel is used, and the amount of energy absorbed when it is bent is not large.

Further, when the barbus bow 300a is bent, the own ship 300 and the other ship 301 come closer to each other, and the distance between the two becomes smaller without significant energy absorption. As a result, as shown in FIG. 9B, the tip portion 300d of the collision ship 300 may come into contact with the collision ship 301 and penetrate into the hull 301a of the collision ship 301, which may further increase the damage due to the collision accident. There is also sex.
Accordingly, it is necessary to increase the amount of collision energy absorbed until the barbus bow 300a is deformed and the tip portion 300d of the ship 300 contacts the other ship 301.
9B indicates the position of the Barbus bow 300a before the collision ship 300 collides with the ship to be collided 301.

By the way, the normal linear heat processing is performed by the highest ultimate temperature on the steel plate surface being about 600-1100 degreeC. However, there are cases where the processing accuracy decreases and the heating time becomes long. Thus, in recent years, as disclosed in Patent Document 4 below, a method of repeatedly performing linear heating at a low temperature of about 500 ° C. has been proposed. In a ship in which a bow portion is formed using a bent plate bent under such conditions, a bow having a high shock absorption effect due to a large amount of energy absorption at the time of collision is required.
In addition, in order to improve the workability of bending work by linear heating, a thick steel plate with a large amount of bending deformation under conditions where the heating time is increased and the heating time is shortened (low temperature condition where the maximum temperature reaches 400 to 600 ° C.). Is required. As such a thick steel plate, Patent Document 5 discloses a thick steel plate having a yield strength at room temperature of 235 MPa or more, a yield strength at 400 ° C. of 180 MPa or less, and a Charpy average absorbed energy at 0 ° C. of 100 J or more. Yes.

JP 2002-087373 A Japanese Patent Laid-Open No. 7-329881 JP 2004-314825 A JP 2006-205181 A Japanese Patent No. 4308312

  The present invention has been made in view of the above circumstances, and a ship collides with a ship in which a portion of the barbasse bow of the bow is constructed using a steel plate that is linearly heated and given a predetermined curvature. The purpose of this is to clarify the conditions of the bow structure in which the valve portion of the Barbus Bau is deformed as uniformly as possible as a whole, and a large amount of energy can be absorbed during the deformation. It is another object of the present invention to provide a bow structure having a buffering effect that can effectively prevent damage to the other ship in the event of a collision without changing the hull structure design.

In order to solve the above-described problem, in one aspect of the present invention, the following bow structure is provided.
(1) The bow structure includes a plurality of steel plates in which the outer shell member of the Barbasse bow has a linear heating part that has undergone linear heating and a non-linear heating part that has not undergone linear heating. For each steel plate, it is obtained by dividing the yield strength YP (LH, RT) at room temperature of the linear heating part in the steel plate by the yield strength YP (AR, RT) at room temperature of the non-linear heating part. The yield strength ratio α is 1.2 or less.
(2) In the bow structure as described in said (1), the said steel plate which comprises the said outer shell member of the said Barbus Bau is good also as a steel plate whose yield strength in the room temperature before linear heat processing is 235 MPa-470 MPa.
(3) In the bow structure according to the above (1) and (2), the steel plate constituting the outer shell member of the Barbasse bow is subjected to linear heating processing with a maximum surface temperature on the heating side of less than _Ac1 point. It is good also as a steel plate which a curvature is provided by and the yield strength in 400 degreeC before the said linear heat processing is 150 Mpa or less.

  According to the present invention, when a situation occurs in which the bow of the own ship having the Barbus bow collides with the hull of another ship, the valve side surface of the Barbus bow on the collision ship side (own ship side) is more uniformly buckled and deformed. Thus, the collision energy can be greatly absorbed. In addition, by colliding the collision surface while absorbing the collision energy, it is possible to reduce the damage of the ship to be collided (other ships) as much as possible, thereby contributing to the prevention of marine pollution due to the sinking of the ship and the oil spill. be able to.

It is a figure which shows the steel plate bent to the bending angle of 120 degree | times by linear heating. It is a figure which shows the test piece produced from the said steel plate bent to the bending angle of 120 degree | times by linear heating. It is a figure explaining the test method for investigating the buckling property of the steel plate which received the linear heating. It is a figure which shows the relationship between the magnitude | size P of the load at the time of applying a load to the steel plate which received the linear heating, and the displacement (DELTA) of a block. It is a figure which shows the relationship between EA ratio (ratio with absorbed energy in case (alpha) is 1.0) and the value of (alpha) in the test shown in FIG. The yield strength YP (AR, 400 ° C.) of the steel sheet at 400 ° C. and the yield strength YP (LH, RT) of the linear heating part at room temperature are the yield strength YP (AR, RT) of the non-linear heating part at room temperature. It is a figure which shows the relationship with ratio YP (LH, RT) / YP (AR, RT) divided by). It is a figure which shows the structural model of the ship side in the collision simulation of a bow structure and a ship side structure. It is a figure which shows transition of the amount of penetration and the relative energy absorptivity absorbed by Barbus Bau when a bow structure penetrates into a ship side structure. It is a figure which shows the relationship between (alpha) and the ratio of the energy absorptivity divided by the energy absorptivity of the steel plate in the case of a reference example ((alpha) = 1). It is a schematic diagram which shows each deformation | transformation of a collision ship and a ship to be collided when the ship which does not have a buffering effect collides with the bow structure. It is a schematic diagram which shows each deformation | transformation of a collision ship and a ship to be collided when the ship which has a buffer effect collides with the bow structure. It is a schematic diagram which shows a deformation | transformation of each of a collision ship and a ship to be collided when the ship which has the buffer effect of this invention collides with the bow structure. It is a longitudinal cross-sectional view which shows the outline of the internal structure of the bow which has a Barbus bow. It is a perspective view which shows the outline of the internal structure of the bow which has a Barbus bow.

  The present inventors have fully studied the case where an accident occurs in which the bow of a ship having a Barbus bow collides with the hull of another ship, and as shown in FIG. 9C, the valve portion 100b of the Barbus bow 100a becomes more uniform. It was found that more buckling energy can be absorbed if buckling deformation is possible. Hereinafter, the findings of the present inventors will be specifically described. As shown in FIG. 9C, the impact force due to the collision is alleviated by the buckling deformation of the Barbus bow 100a of the collision ship 100. As a result, local breakage and breakage of the hull 101a of the ship 101 can be avoided, and the occurrence of breakage can be prevented. 9C indicates the position of the Barbus bow 100a before the collision ship 100 collides with the collision ship 101.

  The valve portion of the Barbus Bau is configured using a steel plate that has been linearly heated and provided with a curvature as described above. Therefore, even if it is constructed using a low-yield point steel as used in Patent Document 3, the yield strength after processing becomes high at the portion that receives heat from the steel sheet. As a result, the yield strength of the steel sheet is non-uniform between the part to which heat is locally applied and the part to which heat is not applied.

  When such a steel plate is used, the Barbasse bow deforms unevenly during a collision. Therefore, there is a concern that the energy absorbing ability as a structural member is lower than that of a steel plate whose yield strength is uniform inside the steel plate. Therefore, there is a possibility that a sufficient amount of collision energy absorption cannot be expected in order to avoid local breakage or damage of the ship to be collided.

Therefore, the following experiment was conducted.
First, in mass%, C: 0.02 to 0.15%, Si: 0.05 to 0.3%, Mn: 0.5 to 1.8%, Al: 0.004 to 0.05% Various steel plates 1 were produced in which the yield strength at room temperature and 400 ° C. was changed using steel containing P and S as impurities, and P: 0.03% or less and S: 0.05% or less. . These steel plates 1 had a substantially square shape, and the dimensions were about 500 mm on a side and about 10 mm in thickness. As shown in FIG. 1A, under the condition that the maximum heating temperature is 500 ° C., the steel plates were repeatedly bent by linear heating until the bending angle considered to be the maximum bending angle on an actual ship reached 120 degrees.

As shown in FIG. 1B, each of the part (linear heating part) 2 that has undergone linear heating of the bent steel sheet 1 and the part (non-linear heating part) 3 that has not undergone linear heating, as shown in FIG. Each test piece 4 including the steel plate surface was cut out from the steel plate surface on the side subjected to the shape heating. By this processing, the NKU No. 1 tensile test piece (Nick Nippon Kaiji Kyokai) (Nippon Kaiji Kyokai) Steel Ship Rules and Inspection Procedures (K-knitted materials), which is half the thickness of the steel plate 1, is 5 mm thick. U1 test piece).
Each test piece was subjected to a tensile test at room temperature to determine the yield strength. The yield strength of the linear heating part at room temperature is YP (LH, RT), and the yield strength of the non-linear heating part at room temperature is YP (AR, RT). The ratio α was α = YP (LH, RT) / YP (AR, RT), and the difference in yield strength between the linear heating part and the non-linear heating part was evaluated. Moreover, about the non-linear heating part, the yield strength YP (AR, 400 degreeC) in 400 degreeC was also calculated | required.

Next, the condition of α for the barbasse bow to buckle uniformly when using a steel plate at the bow was examined.
Using various steel plates with different values of α (side of about 500 mm and thickness of about 10 mm), test pieces having a bending angle of 120 degrees made in the same manner as described above were prepared, as shown in FIG. The load P was applied from one side while restraining with the block 5. The relationship between the magnitude of the load and the block displacement Δ was measured. FIG. 3 shows a measurement example of three test pieces having an α value of 1.0, 1.2, and 1.4.
In addition, in order to eliminate the influence of plastic deformation after α-1.0 steel plate is mechanically bent to a bending angle of 120 degrees without applying linear heating. Tempering is performed to such an extent that the yield strength does not change.

When α was 1.4, since the yield strength of the linearly heated portion of the steel sheet was high, strain was concentrated just outside the region. Since bending occurred at the strain concentration portion, the displacement Δ increased without the load P sufficiently rising. Therefore, as shown in FIG. 3, the energy absorption capacity of the steel sheet was lowered.
When α was 1.2, the steel sheet showed a load-displacement curve similar to that when α was 1.0. Therefore, as shown in FIG. 3, the steel sheet had sufficient energy absorption capability.

  The area formed by the load P and the displacement Δ shown in FIG. 3 (the area formed by the load curve and the displacement axis) is defined as absorbed energy EA (TP), and the value of EA (TP) when α is 1.0. Was used as a reference value. The relationship between α and EA (TP) is shown in FIG. From this figure, if α of the steel sheet is 1.2 or less, even if a portion having a non-uniform yield strength is formed on the steel sheet by linear heating, high energy absorption is achieved as in the deformation of the steel sheet with a uniform yield strength. It was found that Noh can be expected.

  In order to make the yield strength ratio α of the non-linear heating part the yield strength of the linear heating part to 1.2 or less, a steel plate in which the change in the yield strength of the linear heating part due to the linear heating process is as small as possible is used. It is desirable to use it.

As a result of the study, the inventors have found that the amount of bending deformation is large even under conditions where the maximum temperature of the linear heating part is low in order to minimize the change in the yield strength of the linear heating part due to the linear heating process. It discovered that the steel plate as described in the literature 5 could be used. Furthermore, when the maximum temperature of the steel sheet surface is repeatedly linear heating process is less than A _c1 point, as shown in FIG. 5, the bending yield strength at 400 ° C. of the steel sheet by a linear heating processability and good correspondence between I found out. The diamonds in the middle coat in FIG. 5 are data under conditions where the maximum heating temperature is 500 ° C., and the hollow circles in FIG. 5 are data under conditions where the maximum heating temperature is directly under _{Ac 1} . That is, when linear heating is performed at a maximum heating temperature of 500 ° C. or more and less than A _c1 point, the value of the ratio α corresponds to the hatched portion in FIG. From FIG. 5, when using a steel sheet having a yield strength at 400 ° C. of 150 MPa or less, and when the steel sheet is repeatedly linearly heat-processed with a maximum temperature of less than _{Ac 1} point, It has been found that the ratio α between the yield strength and the yield strength of the non-linear heating part can be reliably managed to 1.2 or less.

In addition to actual measurement, this _Ac1 point can be easily obtained by the following equation (1) as a function of composition, for example.
A _c1 (° C.) = 750.8−26.6 [C] +17.6 [Si]
-11.6 [Mn] -22.9 [Cu] -23 [Ni]
+24.1 [Cr] +22.5 [Mo] -39.7 [V]
-5.7 [Ti] +232.4 [Nb] -169.4 [Al]
-894.7 [B] (1)
Here, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], [Ti], [Nb], [Al], [B] Respectively show the content (mass%) of C, Si, Mn, Cu, Ni, Cr, Mo, V, Ti, Nb, Al, and B in steel.
The lower limit of the maximum temperature reached on the steel sheet surface is not specified. However, if the linear heating temperature is too low, the steel sheet has sufficient rigidity, so that almost no deformation occurs. Therefore, it is preferable that it is 300 degreeC or more in order to ensure the deformation amount of a steel plate.

In the above, the conditions of the steel plate for uniformly buckling deformation of the bow on the collision ship side have been described. In order for the bow on the collision ship side to buckle and deform, basically, it is necessary to make the yield strength of the steel plate used for the bow smaller than the yield strength of the ship to be collided.
However, the yield strength of steel plates used in ships must meet the unified standard of the International Classification Societies Association (IACS). In addition, in a bow structure having a conventional inner bone structure, the steel sheet needs to have strength to withstand wave shock. Furthermore, if the strength of the steel sheet is lowered too much, a large energy absorption effect during deformation cannot be expected.

Considering the above points, the yield strength of the steel sheet is preferably 235 MPa or more. In addition, the upper limit of the yield strength of the steel sheet is usually preferably 400 MPa or less as judged from the yield strength of the steel sheet used in the ship. Furthermore, 320 MPa or less is more desirable in order for the Barbasu bow to buckle and deform more reliably during a collision.
Therefore, it is preferable to use a steel plate having a yield strength at room temperature of 235 MPa or more and 470 MPa or less for a portion (outer shell member) having a Barbasse bow curvature before linear heat processing. In this case, the yield strength of the portion (non-linear heating portion) that has not been subjected to linear heating of the steel sheet that has been given a curvature by linear heating is also the same as the above.
In addition, even if the yield strength of the steel plate is less than 235 MPa, means for ensuring the strength as a hull may be adopted by another measure such as increasing the plate thickness. Even in such a case, the yield strength of the steel sheet is preferably 100 MPa or more from the viewpoint of economy.

As a steel plate satisfying the above conditions, it is desirable to use a steel plate shown in Patent Document 5. However, the steel plate provided with the curvature used for the outer shell member is not limited to the steel plate obtained by the combination of the steel plate shown in Patent Document 5 and the linear heating condition. If the ratio α can satisfy 1.2 or less, other steel plates or linear heating conditions may be used. For example, even when a steel sheet having a small change in strength due to linear heat processing is repeatedly subjected to linear heat processing on the condition that the maximum temperature reached on the surface of the steel sheet is equal to or higher than the _Ac1 point, a steel sheet having a ratio α of 1.2 or less is produced. Good. The yield strength of this steel sheet at room temperature is not particularly limited. For example, the yield strength at room temperature of the steel sheet may be less than 235 MPa or 235 MPa or more and 470 MPa or less.

  It is necessary to prevent bending by bending deformation as shown in FIG. 9B. Therefore, a structure in which the Barbus bow 100a buckles uniformly along the hull longitudinal horizontal direction as shown in FIG. 9C was examined.

  In order for the Barbus bow to be deformed at the time of a collision, the member arranged along the hull longitudinal horizontal direction, which is the collision direction, needs to be made of a steel material that is easily deformed. In order for the Barbus bow to buckle uniformly, the deformation of the members arranged along the longitudinal direction of the hull is restrained by the members arranged in the direction intersecting with the longitudinal direction of the hull to prevent the Barbus bow from being bent. It is effective.

  Although the shape and internal structure of the Barbus bow are various, it is comprised by the outer shell member and internal structure member which have a curvature. Furthermore, this internal structural member forms the skeleton of Barbus Bau and is generally constituted by a combination of longitudinal ribs and lateral ribs.

  FIG. 10A and FIG. 10B schematically show an example of the structure of the Barbasse bow. The internal structural member 111 that constitutes the Barbassau has an angle with respect to the longitudinal direction of a number of members arranged parallel to or at right angles to the horizontal direction of the hull, considering the horizontal direction of the hull, which is the hull collision direction. It is comprised by the one part member arrange | positioned.

  Therefore, the members arranged at an angle with respect to the hull longitudinal horizontal direction are classified as either members arranged parallel or perpendicular to the hull longitudinal horizontal direction. That is, the internal structural member 111 constituting the Barbus bow is classified into an L member 111b and a W member 111a defined as follows. The L member 111b is a member having an angle of 45 degrees or less with respect to the hull longitudinal horizontal direction. The W member 111a is a member having an angle larger than 45 degrees with respect to the horizontal direction of the hull.

The L member 111b is given a deformation at the time of collision, and the W member 111a is given a function of restraining the deformation. In order to give deformation to the L member 111b, it is preferable to use a steel material having a yield strength lower than the yield strength of the W member 111a for the L member 111b. As a result, it is possible to prevent the W member 111a from being easily deformed with respect to the L member 111b.
Furthermore, with this structure, the L member 111b can be prevented from being deformed so as to collapse due to hip breakage, and the barbass bow is deformed along the horizontal direction of the hull longitudinal direction.
Similarly, the outer shell member 110 can also be classified into an L member and a W member, and a steel material having a yield strength lower than the yield strength of the W member is preferably used for the L member. As described above, regarding the outer shell member and the internal structural member constituting the Barbasse bow, the yield strength of the L member having an angle of 45 degrees or less with respect to the hull longitudinal horizontal direction is larger than 45 degrees with respect to the hull longitudinal horizontal direction. It is preferable to design so that it may become lower than the yield strength of W member which has these.

Further, in order for the Barbasu bow to be uniformly buckled and deformed, the outer shell member 110 constituting the outer shell needs to be buckled and deformed in a bellows shape. In addition, since the outer shell member 110 needs to be uniformly deformed, it is necessary to use a steel plate whose yield strength does not change greatly even after linear heat processing.
Thereafter, it is assumed that the L member has a lower yield strength than the W member.

  Although the embodiments of the present invention have been described above, the effects of the present invention will be specifically described by way of examples.

  As a steel plate used for the bow structure, a steel plate having a component composition of Examples 1 to 8 and Comparative Examples 1 to 6 shown in Table 1 and having a side of about 500 mm and a plate thickness of about 10 mm was prepared. Each steel plate was subjected to a tensile test at room temperature and a tensile test at 400 ° C. to obtain a yield strength YP (AR, RT) at room temperature and a yield strength YP (AR, 400 ° C.) at 400 ° C. . Furthermore, the linear heating process was repeated for each steel plate under the condition that the maximum heating temperature on the heating side surface was 500 ° C., taking into account the maximum bending angle on an actual ship until the bending angle reached 120 degrees. Test pieces similar to those described above were cut out from the portions of these bent steel sheets that had undergone linear heating. These test pieces were subjected to a tensile test at room temperature, and yield strengths YP (LH, RT) were obtained.

Table 2 shows YP (AR, RT), YP (LH, RT), YP (AR, 400 ° C.), YP (AR, RT) and YP for the steel plates of Examples 1-8 and Comparative Examples 1-6. The value of the ratio α with (LH, RT) is shown.
In the steel plates of Examples 1 to 8, α was 1.2 or less. In addition, these steel sheets had a YP (AR, RT) of 235 to 400 MPa and a YP (AR, 400 ° C.) of 170 MPa or less. Moreover, (alpha) of the steel plate of Comparative Examples 1-6 was more than 1.2.

Moreover, as a steel plate used for the bow structure, a steel plate having a component composition of Examples 9 and 10 shown in Table 1 and having a side of about 500 mm and a plate thickness of about 10 mm was prepared. About each steel plate, the room temperature tensile test and the 600 degreeC tensile test were implemented, and the yield strength YP (AR, RT) in room temperature and the yield strength YP (AR, 600 degreeC) in 600 degreeC were calculated | required. Here, in order to perform linear heating at the _Ac1 point or higher, the yield strength YP (AR, 600 ° C.) at 600 ° C. is obtained instead of the yield strength YP (AR, 400 ° C.) at 400 ° C. ( * In Table 2). Furthermore, the linear heating process was repeated for each steel plate under the condition that the maximum heating temperature on the heating side surface was 1000 ° C., taking into account the maximum bending angle on an actual ship until the bending angle reached 120 degrees. Test pieces similar to those described above were cut out from the portions of these bent steel sheets that had undergone linear heating. These test pieces were subjected to a tensile test at room temperature, and yield strengths YP (LH, RT) were obtained.

In Table 2, for the steel plates of Examples 9 and 10, YP (AR, RT), YP (LH, RT), YP (AR, 600 ° C.) (see * in the column of YP (AR, 400 ° C.)), YP ( The value of the ratio α between AR, RT) and YP (LH, RT) is shown.
In the steel plates of Examples 9 and 10, α was 1.2 or less. In addition, these steel sheets had a YP (AR, RT) of less than 235 MPa.

Next, the energy absorptivity in the case where Barbusbau was constituted using the steel plates shown in Tables 1 and 2 was determined by simulation.
FIG. 6 shows a 1/4 simulation model in the center of the hull in the longitudinal direction of the hull longitudinal structure of the ship side structure of the crude oil tanker. A transverse partition wall 12 corresponding to the partition structure of the oil cargo portion is disposed along the BB ′ portion in the ship side structure. Since the collision positions A and D in the ship side structure are set at the center position of the oil cargo portion, the model is symmetric with respect to the collision center 13 in the longitudinal direction of the hull. A portion along the CC ′ portion is a heel side thick plate portion 11 which is the most important member in the hull structure. The AA ′ portion indicates the vertical direction of the collision position, and the DD ′ portion indicates the horizontal direction of the collision position.

  When the deformation caused by the collision increases, plastic deformation occurs not only in the D-D 'and A-A' portions close to the collision portion but also in the C-C 'portion far from the collision center 13. Therefore, the heel side thick plate portion 11 which is the most important member of the hull structure is plastically damaged. As a result, the fracture resistance of the steel material is significantly reduced, and there is a risk of causing large-scale damage to the hull structure. Therefore, using the above model, the energy absorption capacity of Barbusbau when the entire collision part deformed and collided was calculated. The energy absorption ability is originally indicated by the unit (J) indicating energy, but is a non-dimensional value here for numerical calculation.

In FIG. 7, when the bow structure provided with the barbus bow composed of the steel plates of Example 1 and Comparative Example 1 is collided with the ship side structure of the model of FIG. The relationship with relative energy absorption ability is shown. The amount of penetration of the bow indicates the amount that Barbus Bau has deformed and penetrated after colliding with the ship side of the ship to be collided.
Regarding Example 1, it was assumed that α of each steel plate used in the bow structure was 1.2 or less and displaced as shown in FIG. 9C. Moreover, the yield strength of the outer shell member of the Barbasse bow was 240 MPa, which corresponds to 60% of the yield strength of the steel used in the ship side structure.
For Comparative Example 1, it was assumed that the characteristics of each steel plate used in the bow structure were the strength characteristics shown in Table 2.
In the simulation, the calculation result of the relative energy absorption capacity under the condition that both the yield strength of the linearly heated portion and the yield strength of the non-linearly heated portion is 220 MPa was used as a reference example (ref). . The reduction ratio from the reference example with respect to the relative energy absorption capacity of each of the examples and comparative examples is shown by EA / EA (ref) in Table 2.

  When α of the steel plate on the bow structure side is 1.2 or less and the yield strength of this steel plate is lower than the yield strength on the boat side structure side, the bow structure buckles as shown in FIG. 9C. Therefore, in the first embodiment, the collision surface with the ship-side structure and the energy absorption amount at the outer shell member are larger than those in the first comparative example, so that the energy absorption capability is dramatically improved as shown in FIG.

  Similarly, with respect to the steel plates of Examples 2 to 10 and Comparative Examples 2 to 6, the relative energy absorption capacity up to the bow penetration of 6 m shown in FIG. 7 was calculated. As shown in Table 2, in the bow structure using the steel plates of Examples 2 to 10, since α was 1.2 or less, these bow structures had sufficient energy absorbing ability. On the other hand, in the bow structure using the steel plates of Comparative Examples 2 to 6, since α is larger than 1.2, the energy absorption capacity of these bow structures is greatly reduced as compared with Examples 2 to 9.

  Furthermore, the information in Table 2 is summarized, and FIG. 8 shows the relationship between α and EA / EA (ref). As shown in FIG. 8, when α is greater than 1.2, EA / EA (ref) is greatly reduced. This large decrease in the energy absorption capability is considered to be due to the transition of the deformation mode of Barbusbau from FIG. 9C to FIG. 9A or FIG. 9B. Therefore, even if a portion having a non-uniform yield strength is formed on a steel sheet by linear heating, a bow structure having a high energy absorption capacity is obtained by using a steel sheet having an α of 1.2 or less for the outer shell portion of the Barbasse bow. Can be configured.

Based on the above, the bow structure is determined so that the ratio α of the yield strength of the linear heating part and the non-linear heating part is 1.2 or less, using the linearly heated steel plate for the outer shell of the Barbasse bow. By doing so, the energy absorption capacity of the bow side at the time of a collision can be increased, and the serious damage of the other ship can be prevented. Furthermore, as this steel plate, a steel plate having a yield strength at room temperature of 235 MPa or more and 400 MPa or less and a yield strength at 400 ° C. of 170 MPa or less may be used. In this case, regardless of the introduction of dislocations into the ferrite, it is possible to ensure bending workability when the film is linearly heated under a heating condition less than the _Ac1 point to give a curvature. Such a bow structure has a buffering effect due to buckling deformation without causing a change in the hull structure design.

  It is possible to provide a bow structure having a buffering effect that can effectively prevent damage to a partner ship in the event of a collision without causing a change in the hull structure design.

1 Steel plate 2 Part subjected to linear heating (linear heating part)
3 Parts not receiving linear heating (non-linear heating part)
4 specimens 5 blocks

In order to solve the above-described problem, in one aspect of the present invention, the following bow structure is provided.
(1) The bow structure includes a plurality of steel plates in which the outer shell member of the Barbasse bow has a linear heating part that has undergone linear heating and a non-linear heating part that has not undergone linear heating. For each steel plate, it is obtained by dividing the yield strength YP (LH, RT) at room temperature of the linear heating part in the steel plate by the yield strength YP (AR, RT) at room temperature of the non-linear heating part. the ratio of yield strength α is Ri der 1.2, said steel sheet forming the outer shell member of the bulbous bow is the curvature by the maximum surface temperature of the heating side is linear heating process is less than Ac1 point grant was is the yield strength at 400 ° C. before the linear heating processing Ru following steel der 150 MPa.
(2) In the bow structure as described in said (1), the said steel plate which comprises the said outer shell member of the said Barbus Bau is good also as a steel plate whose yield strength in the room temperature before linear heat processing is 235 MPa-470 MPa .

Claims (3)

The outer shell of Barbus Bau
Comprising a plurality of steel plates having a linear heating part that has undergone linear heating and a non-linear heating part that has not undergone linear heating;
For each of the steel plates, the yield strength YP (LH, RT) at room temperature of the linear heating portion in the steel plate is divided by the yield strength YP (AR, RT) at room temperature of the non-linear heating portion. A bow structure having a yield strength ratio α of 1.2 or less. 2. The bow structure according to claim 1, wherein the steel sheet constituting the outer shell member of the Barbasse bow has a yield strength at room temperature before linear heat processing of 235 MPa to 470 MPa. The steel sheet constituting the outer shell member of the Barbasse bow is given a curvature by being linearly heated when the maximum surface temperature on the heating side is less than _Ac1 point, and yield at 400 ° C. before the linear heating process. The bow structure according to claim 1 or 2, wherein the strength is 150 MPa or less.

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