KR20130081724A - Bow structure - Google Patents

Abstract

The bow structure has a curvature provided by the outer shell member of the bulbous bow by linearly heat-processing at a maximum surface temperature of 600 ° C. or higher on the heating side. The yield strength at room temperature is 120 MPa to 220 before the linear heat-processing. It is MPa, and it consists of steel sheets whose yield strength in 600 degreeC is 0.6 times or less of the yield strength in room temperature.

Description

Player structure {BOW STRUCTURE}

The present invention relates to a bow structure that has a buffering effect that can prevent damage to an opponent's ship that has collided by being deformed at the time of a collision, thereby improving collision safety.

This application claims priority in August 24, 2009 based on Japanese Patent Application No. 2009-193475 for which it applied to Japan, and uses the content for it here.

The current large vessel is equipped with a bulbous bow (spherical bow) under the bower's line in order to reduce the energy loss by the wave resistance at the time of navigation even a little. In order to manufacture the curvature with a large curvature used for this bulbous bow, the bending process by linear heating, ie, the linear heating process, is used abundantly in the shaping | molding process.

This linear heating process is a processing method of locally heating a steel plate surface so that the high temperature achieved temperature of a heating side surface may be about 600 to 1100 degreeC using a gas burner etc .. In this linear heating operation, a phenomenon in which the heated portion is thermally expanded and plastically deformed by restraint from its surroundings is used. In addition, in this linear heat processing, in order to improve work efficiency, water cooling is performed immediately after heating, and the steel plate after linear heat processing is quenched, and the yield strength rises locally.

Therefore, the bulbous bow using such a curved sheet has a nonuniform strength along the surface and is difficult to deform. When a ship provided with such a bulbous bow collides with another ship, for example, as shown in FIG. 10A, the bow 200a of the own ship 200 is the ship 201a of the other ship 201. ), The ship 201a is destroyed, and furthermore, the destruction site 201b is enlarged, and there is a possibility that a hole is opened (the ship is broken).

Conventionally, as a means (structure) which improves the collision safety of a ship, examination is mainly carried out from the surface of a ship body structure, such as double structure of a hull. However, in recent years, the application of the steel material which is excellent in the energy absorption performance at the time of a collision is examined.

As an example, the following Patent Document 1 discloses a steel material obtained by increasing the product (σy × εu) of the yield stress σy and the uniform elongation εu by 20% or more, in comparison with the unified standard material of the conventional International Association of Classification Societies (IACS). In addition, a hull structure is disclosed in which a steel material in which the amount of energy absorption up to a uniform elongation εu is increased by 20% or more in the tensile test, or a steel material in which the yield stress σy is equal or more and the uniform elongation εu is increased by 20% or more is disclosed. In this structure, it is possible to increase the amount of energy that can be absorbed until the breakage occurs in the hull even though the hull structure is similar to the conventional one.

However, if a ship of a ship collides with another ship's ship, even if the ship uses a steel plate whose energy absorption is improved by 50% or more, for example, if the ship of the ship is not deformed, the ship may be able to penetrate the ship's ship. There is concern. In that case, there exists a problem that the increase of the amount of absorption energy mentioned above cannot be expected.

In order to solve such a problem, even when a ship of a ship collides with another ship, the design of the bow which exhibits a buffer effect is also considered.

For example, Patent Literature 2 below discloses a bow portion having a research tank in which a bow portion is dried using a material that is more flexible than a steel material used for general shipbuilding.

However, this patent document 2 only discloses an aluminum material which is difficult to apply to a large ship as a flexible material, and it does not specifically disclose about obtaining a research tank using steel materials.

In addition, Patent Document 3 discloses a bow structure in which a low strength part made of a resistive stress point steel having a yield stress of 235 MPa or less is provided on an outer plate of a root portion of a spherical protrusion (bulb part) in a bulbous bow. In this structure, the bending strength in the transverse direction of the root portion is reduced, and the bow portion is bent by the reaction force of the collision, whereby the bow portion of the collision ship is prevented from digging into the ship of the other ship.

In Patent Document 3, while decreasing the structural strength in the horizontal direction of the bulbous bow while sufficiently securing the strength in the vertical direction of the bulbous bow, as illustrated in FIG. 10B, the bulbous bow 300a is subjected to a collision. The base portion 300b is easily deformed in the hull width direction to increase the contact area of the collision portion 300c. This structure prevents the breaks (the generation of holes) on both the collision line (charity vessel) 300 and the collision line (other vessel) 301 by increasing this contact area. However, bending of the root portion 300b is caused by local deformation of the site using the resistive point steel, and collision energy is not sufficiently absorbed by the bending of the root portion 300b.

Further, by bending the bulbous bow 300a, the ship vessel 300 and the other vessel 301 come closer to each other, so that the distance between them becomes smaller without involving a sufficiently large energy absorption. As a result, as shown in FIG. 10B, the bow portion 300d of the collision line 300 may contact the collision line 301 to penetrate the line 301a of the collision line 301. There is a possibility that the damage caused by a collision accident may be further increased.

Therefore, after the bulbous bow 300a is deformed, it is necessary to increase the absorption amount of the collision energy even while the bow portion 300d of the ship 300 is brought into contact with the ship of the other ship 301. have.

10B shows the position of the bulbous bow 300a before the collision line 300 collides with the collision line 301.

Japanese Patent Application Laid-Open No. 2002-087373 Japanese Patent Application Laid-open No. Hei 7-329881 Japanese Patent Application Laid-open No. 2004-314825

This invention is made | formed in view of the said situation, The part of the bow's bow bow of a bow is used by the steel plate which linearly heat-processed under normal heating conditions (maximum heating temperature of a heating side: 600-1100 degreeC), and given predetermined curvature. For the purpose of clarifying the conditions of the bow structure, when the ship collides, the bulb part of the bulbous bow is deformed as uniformly as possible as a whole, and the large energy absorption amount at the time of deformation is realized. do. It is also an object of the present invention to provide a bow structure with a cushioning effect that can effectively prevent damage to other ships during a collision without changing the hull structure design.

In order to solve the said subject, in one aspect of the present invention, the following bow structure is set.

(1) The bow structure excellent in the collision energy absorption capacity is given curvature by the outer shell member of the bulbous bow to be linearly heat-processed at the heating surface's highest surface temperature of 600 degreeC or more, and before the said linear heat processing, The yield strength is less than 120 MPa to less than 200 MPa, and the yield strength at 600 ° C. is made of steel sheet having 0.6 times or less of the yield strength at room temperature.

(2) In the bow structure excellent in the collision energy absorption ability as described in said (1), in the said steel plate which comprises the said shell member of the said bulbous bow, the bending angle will be 120 degree | times with the highest surface temperature of the said heating side at 600 degreeC or more. In the case where the linear heating process was carried out until then, the yield strength YP (LH, RT) at room temperature of the linear heating part was divided by the yield strength YP (AR, RT) at room temperature of the nonlinear heating part. It may be.

(3) In the bow structure excellent in the collision energy absorption ability as described in said (1) or (2), the angle of 45 degrees or less with respect to the hull length horizontal direction with respect to the said shell member and internal component which comprise the said bulbous bow The yield strength of the L member which has a may be lower than the yield strength of the W member which has an angle larger than 45 degree with respect to a ship body horizontal direction.

According to the present invention, in the event that a player of a vessel having a bulbous bow collides with the ship's overturning, the bulb side of the bulbous bow on the collision side (the vessel side) is more uniformly buckled. By doing so, it is possible to greatly absorb the collision energy. In addition, the collision surface is crushed while absorbing the collision energy, thereby making it possible to minimize the damage of the collision ship (other ship), thereby contributing to the prevention of marine pollution by sinking the collision ship and oil leakage. have.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the yield strength and test temperature of a steel plate.
It is a figure which shows the steel plate bent until the bending angle is 120 degree | times by linear heating.
It is a figure which shows the test piece produced from the said steel plate bent until the bending angle is 120 degree | times by linear heating.
Fig. 3 is a graph showing the relationship between the ratio YP (AR, 600 ° C) / YP (AR, RT) of the yield strength at 600 ° C of the steel sheet to the yield strength at room temperature of the steel sheet.
It is a figure explaining the test method for examining buckling property of the steel plate which received linear heating.
It is a figure which shows the relationship between the magnitude | size P of the load and the displacement (DELTA) of a block when a load is added to the steel plate which received linear heating.
It is a figure which shows the relationship between the EA ratio (ratio with absorption energy when (alpha) is 1.0) in the test shown in FIG. 4, and the value of (alpha).
It is a figure which shows the structural model of the ship side in the collision simulation of a bow structure and a ship structure.
Fig. 8 is a diagram showing the transition of the penetration amount and the relative energy absorption capacity absorbed by the bulbous bow when the bow structure penetrates into the ship side structure.
It is a figure which shows the relationship between (alpha) and the ratio of the energy absorbing power divided by the energy absorbing power of the steel plate when a reference example ((alpha) = 1) to the energy absorption ability of a steel plate.
It is a schematic diagram which shows the deformation | transformation of each of a collision line and a collision line in the case where the ship which does not have a buffer effect in a bow structure collides.
It is a schematic diagram which shows the deformation | transformation of each of a collision line and a collision line in the case where the ship which has a buffer effect to a bow structure collided.
It is a schematic diagram which shows the deformation | transformation of each of a collision line and a collision line when the ship which has the buffering effect of this invention collided with a bow structure.
11A is a longitudinal sectional view showing an outline of the internal structure of a bow with a bulbous bow.
11B is a perspective view illustrating an outline of an internal structure of a player having a bulbous bow.

MEANS TO SOLVE THE PROBLEM The present inventors fully consider the case where the bow of the ship which has a bulbous bow had an accident, such as colliding with the ship's ship, and as shown to FIG. 10C, the bulb part of the bulbous bow 100a ( If 100b) was able to buckling more uniformly, knowledge was obtained that more collision energy could be absorbed. As illustrated in FIG. 10C, the impact force due to the collision is alleviated by the buckling deformation of the bulbous bow 100a of the collision line 100. As a result, local breakage and damage of the line 101a of the collision line 101 can be avoided, and generation of breakage can be prevented. 10C shows the position of the bulbous bow 100a before the collision line 100 collides with the collision line 101.

The bulb part of the bulbous bow is comprised using the steel plate which linearly heat-processed and provided the curvature as mentioned above. By this linear heat processing, yield strength becomes high in the part which received the heat of the steel plate. As a result, nonuniformity arises in the yield strength of a steel plate in the part to which heat is locally applied, and the part which is not provided.

When such a steel plate is used, the bulb bow deforms unevenly at the time of collision. Therefore, there exists a possibility that the energy absorbing power of the structural member using this steel plate may fall compared with the structural member using the steel plate uniform in yield strength. Therefore, there is a possibility that a sufficient amount of collision energy absorption cannot be expected to avoid local breakage or breakage of the collision line at the time of collision.

Therefore, it is necessary to prevent bending by bending deformation like FIG. 10B. Therefore, the inventors examined a structure in which the bulbous bow 100a is buckled uniformly along the hull length horizontal direction as shown in Fig. 10C.

In order to deform a bulbous bow at the time of a collision, the member arrange | positioned along the hull length horizontal direction which is a collision direction needs to be comprised with the steel material which is easy to deform | transform. In order to uniformly buckle the bulbous bow, it is effective to restrain the deformation of the member arranged along the longitudinal direction of the hull by the member arranged in a direction crossing the longitudinal direction of the hull to prevent bending of the bulbous bow. Do.

Although the shape and internal structure of the bulbous bow vary, it is constituted by an outer structural member and an outer curvature member having a curvature. Moreover, this internal structural member forms the skeleton of a bulbous bow, and is generally comprised by the combination of a longitudinal rib and a transverse rib.

11A and 11B schematically show an example of the structure of the bulbous bow. The internal structural member 111 constituting the bulbous bow has a plurality of members arranged in parallel or perpendicular to the hull length horizontal direction with respect to the hull length horizontal direction as the hull collision direction, and with respect to the hull longitudinal direction. It is comprised by the some member arrange | positioned at an angle.

Specifically, the plurality of members constituting the internal structural member are classified into either one of the members arranged in parallel to the ship length horizontal direction or the members arranged at right angles. That is, the internal structural member 111 which comprises a bulbous bow is classified into the L member 111b and the 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 length horizontal direction. In addition, the W member 111a is a member having an angle larger than 45 degrees with respect to the hull length horizontal direction.

The L member 111b is a member that is deformed at the time of a collision, and the W member 111a is a member that restrains the deformation of the L member 111b. In order for the L member 111b to deform | transform, it is preferable to use the steel material of yield strength lower than the yield strength of the W member 111a for the L member 111b. As a result, the W member 111a can be prevented from being easily deformed with respect to the L member 111b.

Moreover, by this structure, local deformation of the L member 111b such as simple bending can be prevented, and the bulbous bow is deformed along the hull length horizontal direction.

Similarly, the shell member 110 can also be classified into an L member and a W member, and it is preferable that a steel material having a yield strength lower than the yield strength of the W member is used for the L member. In this way, the yield strength of the L member having an angle of 45 degrees or less with respect to the hull length horizontal direction with respect to the shell member and the internal structural member constituting the bulbous bow is an angle greater than 45 degrees with respect to the hull length horizontal direction. It is preferable that it is designed so that it might become lower than the yield strength of the W member which has.

In addition, in order for the bulbous bow to be buckled and deformed uniformly, the outer shell member 110 constituting the 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 sheet whose yield strength does not significantly change even after linear heat processing.

Hereinafter, it demonstrates on the assumption that the yield strength of L member is lower than W member.

In the case of using a steel sheet having a curvature of the bulbous bow and having a curvature obtained by linearly heating the surface at a heating surface of 600 ° C. or higher, a change in the yield strength of the linear heating portion accompanying the linear heating processing is possible. It is preferable to use one small steel sheet. As a result, since the amount of energy that can be absorbed by the shell member 110 increases, the bulbous bow can absorb a sufficient amount of collision energy. In order to make the change of the yield strength of the linear heating part accompanying linear heating as small as possible, the steel plate which can be processed to a predetermined curvature by giving as little heat as possible is preferable.

Therefore, the yield strength of the steel plate in high temperature was investigated in order to examine the ease of processing (linear heat processing characteristic) by application of local heat.

Although the yield strength at room temperature is the same grade steel, the steel plate used as the sample was produced using two types of steels A and B which differ in yield strength at high temperature. The difference in yield strength at high temperatures of these steel sheets is because the content of stable fine precipitates is different even at high temperatures. Using these steel sheets, tensile tests were conducted at various temperatures.

The relationship between the yield strength of a steel plate and the test temperature which performed the tensile test in FIG. 1 is shown. The yield point or the value of 0.2% yield strength was used for yield strength in each test temperature. In addition, instead of the yield strength of the steel sheet, the value obtained by dividing the measured value YP (AR, test temperature) at the test temperature by the measured value YP (AR, RT) at room temperature was used.

As shown in Fig. 1, when the test temperature is increased, the yield strength becomes zero at a certain temperature. The temperature is defined as the mechanical melting temperature.

In normal linear heat processing with the highest achieved temperature of about 1000 ° C., it is considered that the mechanical melting temperature affects the linear heating characteristics. However, the mechanical melting temperature cannot be easily measured.

From FIG. 1, it was confirmed that the value of the yield strength in 600 degreeC which is the temperature lower than the mechanical melting temperature in both steels A and B correlates with mechanical melting temperature. Therefore, focusing on the yield strength at 600 degreeC as an index for evaluating the workability by linear heating, the following experiment was performed.

In a steel containing, in mass%, C: 0.1%, Si: 0.3%, Mn: 1.0%, Al: 0.005%, and limited P and S as impurities to P: 0.03% or less and S: 0.01% or less. The content of Cr and Nb which raises high temperature strength was adjusted, and the various steel sheets 1 which changed the yield strength in room temperature and 600 degreeC were produced. These steel sheets 1 were substantially square-shaped, and the dimension was about 500 mm one side and about 10 mm thickness. In addition, also in FIG. 1, the steel plate produced by the same method (steel plate composition and dimensions) is used. As shown in FIG. 2A, linear heat processing (maximum heating temperature of 1000 degreeC on the heating side) was repeated to those steel plates until the bending angle became 120 degree | times.

For each of the portion (linear heating portion) 2 and the portion (non-linear heating portion) 3 not subjected to linear heating of the bent steel sheet 1, as shown in FIG. 2B The test piece 4 containing the steel plate surface was cut out from the steel plate surface of the side which heated. By this processing, it is prescribed by NKU No. 1 tensile test piece (Foundation Corporation Japan Maritime Association (NK; Nippon Kaiji Kyokai) steel wire rule, copper inspection method (K piece material) of plate thickness 5mm which is half of the thickness of steel plate 1). U1 test piece] was prepared.

Each test piece was subjected to a tensile test at room temperature to yield yield strength, respectively. The yield strength of the linear heating section at room temperature is YP (LH, RT), and the yield strength of the nonlinear heating section at room temperature is YP (AR, RT). By setting the ratio α to α = YP (LH, RT) / YP (AR, RT), the difference in yield strength between the linear heating portion and the nonlinear heating portion was evaluated. In addition, the yield strength YP (AR, 600 degreeC) in 600 degreeC was also calculated | required about the nonlinear heating part.

In Fig. 3, the ratio α of the yield strength of the linear heating portion and the non-linear heating portion of the steel sheet and the yield strength of the steel sheet at 600 ° C. and the yield strength at room temperature of the steel sheet YP (AR, 600 ° C.) / YP (AR, RT) represents the relationship.

As a result, as shown in FIG. 3, when the yield strength at 600 ° C. is 0.6 times or less the yield strength at room temperature, the value of α representing the difference between the yield strengths of the linear heating portion and the nonlinear heating portion can be suppressed to 1.2 or less. there was.

Next, when the steel plate was used for a bow, the conditions of (alpha) for bulging the bulbous bow uniformly were investigated.

Using various steel plates having different values of α (about 500 mm on one side and about 10 mm on thickness), a test piece having a bending angle of 120 degrees manufactured as described above was produced, and both ends were blocked as shown in FIG. 4. The load P was applied from one side while restraining by (5). The relationship between the magnitude of the load at that time and the displacement Δ of the block was measured. The measurement example of three test pieces whose values of (alpha) are 1.0, 1.18, 1.4 is shown in FIG.

In addition, for a steel plate with α = 1.0, the bending process is performed mechanically without applying a linear heat treatment to a bending angle of 120 degrees, and then tempering to the extent that the yield strength does not change in order to exclude the influence of plastic deformation. The process is performed.

In the case where α is 1.4, since the yield strength of the linear heating portion of the steel sheet is high, deformation was concentrated just outside of the region. Since bending occurred at the deformation concentration portion, the displacement Δ became large without the load P sufficiently increasing. Therefore, as shown in FIG. 5, the energy absorption ability of the steel plate was reduced.

When α was 1.18, the steel plate exhibited a load-displacement curve similar to that when α was 1.0. Therefore, as shown in FIG. 5, the steel plate had sufficient energy absorption capacity.

The area (the area formed by the load curve and the displacement axis) formed by the load P and the displacement Δ shown in FIG. 5 was defined as absorbed energy EA (TP), and the value of EA (TP) when α was 1.0 was used as the reference value. And the relationship between α and EA (TP) is shown in FIG. From this drawing, if α of the steel sheet is 1.2 or less, even if a portion where the yield strength is nonuniform is formed on the steel sheet by a linear heating process in which the maximum surface temperature on the heating side is 600 ° C. or higher, the yield strength is as high as that of the steel sheet with uniform uniformity. Energy absorption capacity can be expected. Therefore, it is preferable that (alpha) is 1.2 or less when linearly heat-processing until the bending angle becomes 120 degree | times in the highest surface temperature of the heating side at 600 degreeC or more.

From the results of FIGS. 3 and 6 described above, when producing a steel sheet (curved plate) having a curvature for the bulbous bow by linear heating at a temperature of 600 ° C. or higher, the yield strength at 600 ° C. is equivalent to the yield strength at room temperature. Use a steel plate that is 0.6 times or less. If the curved board which the said value of (alpha) becomes 1.2 or less is produced from such a steel plate, the curved board will become nonuniform in the yield strength in a curved board. It was confirmed that the bulbous bow comprised of such curved boards can be buckled uniformly at the time of a collision, and can exhibit a large collision energy absorption ability.

In the above, the conditions of the steel plate for making the bow of the collision line side buckling uniformly were demonstrated. In order for the bow on the collision line to be buckled, the yield strength of the steel sheet used for the bow is basically smaller than the yield strength of the collision line.

However, the yield strength of the steel plate used for a ship needs to satisfy the IAA standard. Moreover, in the bow structure which has a conventional endothelial structure, the steel plate requires the intensity | strength which can endure a wave impact. In addition, when the strength of the steel sheet is excessively reduced, a large energy absorption effect at the time of deformation cannot be expected.

In view of the above, the yield strength of the steel sheet needs to be 120 MPa or more. In addition, in order for bulging bow to buckling deform reliably at the time of a collision, the yield strength of a steel plate needs to be 220 Mpa or less. In order to make the buckling deformation of a bulbous bow more reliable, less than 200 Mpa is preferable.

Therefore, before linear heat processing, the steel plate whose yield strength at room temperature is 120 Mpa or more and 220 Mpa or less is used for the site | part (shell member) which has the curvature of a bulbous bow. For this reason, the yield strength of the site | part (nonlinear heating part) which is not receiving linear heating of the steel plate with curvature provided by linear heat processing is also the yield strength similar to the above.

Example

As mentioned above, although embodiment of this invention was described, the effect of this invention is concretely demonstrated by an Example.

As a steel plate used for the bow structure, a steel plate having a side composition of about 500 mm and a sheet thickness of about 10 mm having a component composition shown in Table 1 was prepared. Each steel sheet was subjected to a tensile test at room temperature and a tensile test at 600 ° C to yield yield strength YP (AR, RT) at room temperature and yield strength YP (AR, 600 ° C) at 600 ° C. Moreover, linear heating processing was repeated about each steel plate until the bending angle became 120 degree on the conditions which the maximum heating temperature of the heating side surface becomes 1000 degreeC. The test piece similar to the above was cut out from the site | part which received linear heating of these bent steel sheets. That is, NKU No. 1 tensile test piece of 5 mm of plate | board thickness which is half of the thickness of steel plate so that cutting process may be performed about the linear heating part, and to include the steel plate surface of the side which performed linear heating (Foundation Corporation Japan Maritime Association (NK; Nippon) Kaiji Kyokai) U1 Test Specimen prescribed in the Rules for the Classification of Steel Wires and Test Procedures (K-Part Materials)]. These test pieces were subjected to a tensile test at room temperature to yield yield strengths YP (LH, RT), respectively.

In Table 2, YP (AR, RT), YP (LH, RT), YP (AR, 600) for the steel sheets of the first to third reference examples, the steel sheets of the first to third embodiments and the steel sheets of the first to sixth comparative examples. ° C), and the values of these ratios α = YP (LH, RT) / YP (AR, RT) and β = YP (AR, 600 ° C) / YP (AR, RT).

The steel sheets of the first to third reference examples and the first to third examples had YP (AR, RT) of 120 to 220 MPa, α of 1.2 or less, and β of 0.6 or less. In addition, in the 1st-6th comparative examples, (beta) was more than 0.6.

Next, the energy absorbing capacity at the time of forming a bulbous bow using the steel plate of Table 1, Table 2 was calculated | required by simulation.

The quarter simulation model in the center part of the ship body longitudinal direction of the ship side structure of a crude oil tanker is shown in FIG. The horizontal partition 12 corresponding to the partition structure of the oil cargo part is arrange | positioned along B-B 'part in a side structure. Since the collision positions A and D in a ship side structure were set to the center position of the oil cargo part, it becomes a model which is also symmetric also in the ship longitudinal direction with respect to the collision center 13. The portion along the C-C 'portion is the sheath thick plate portion 11 which is the most important member in the hull structure. In addition, A-A 'part has shown the vertical direction of a collision position, and D-D' part has shown the horizontal direction of a collision position.

When the deformation caused by the collision increases, plastic deformation occurs not only in the portion D-D 'or A-A' close to the collision portion, but also in the portion C-C 'separated from the collision center 13. Therefore, the sheath side plate part 11 which is the most important member of a ship body structure is plastically damaged. As a result, the fracture resistance of the steel material is remarkably lowered, and there is a risk of causing massive damage to the hull structure. Therefore, using the model described above, the energy absorbing capacity of the bulbous bow when the entire impact portion was deformed and collided was calculated. In addition, although the energy absorbing power was originally represented by the unit (J) which shows energy, it was set as the dimensionless value here for numerical calculation.

In FIG. 8, the bow penetration amount and the bulbous when the bow structure provided with the bulbous bow formed using the steel plate of the 1st, 2nd reference example and a 1st comparative example collide with the ship side structure of the model of FIG. The relationship of the relative energy absorption capacity at the time of the collision of Bow is shown. The bow intrusion represents the amount in which the bulbous bow is deformed and penetrated in the horizontal direction of the hull length after collision with the ship side of the collision line.

As for the 1st reference example and the 2nd reference example, (alpha) of the steel plate used for the bow structure is 1.18, and it displaces like FIG. 10C. In the first reference example, the yield strength of the shell member of the bulbous bow was 200 MPa, which corresponds to 50% of the yield strength of the steel material used in the ship side structure. In the second reference example, the yield strength of the shell member of the bulbous bow was 214 MPa, which corresponds to 53.5% of the yield strength of the steel used in the ship side structure.

Regarding the first comparative example, it is assumed that the characteristics of the steel sheet used for the bow structure are the strength characteristics shown in Table 2.

In addition, in the simulation, the calculation result of the relative energy absorption ability in the conditions of both the yield strength of the linearly heated part and the yield strength of the part which is not linearly heated is 220 Mpa as a reference example (ref). The reduction ratio from the reference example for each of the relative energy absorption capacities of the examples and the comparative examples is shown as 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 the steel plate is lower than the yield strength on the ship side structure, the bow structure is buckled as shown in FIG. 10C. Therefore, in the 1st reference example, since the energy absorption amount of the collision surface and a sheath member with a ship side structure is larger than a 1st comparative example, as shown in FIG. 8, energy absorption ability improves dramatically. Also in the case of the 2nd reference example, although the collision area becomes smaller than the 1st reference example, since the energy absorption amount of an outer shell member increases, the energy absorption ability increased compared with the 1st comparative example.

Similarly, relative to the steel sheets of the first to third examples and the second to sixth comparative examples, the relative energy absorption capacity up to 6 m of the penetration amount shown in FIG. 8 was calculated. As shown in Table 2, in the bow structure using the steel sheets of the first to third embodiments, since the YP (AR, RT) is 120 to 220 MPa and β is 0.6 or less, these bow structures have sufficient energy absorption capacity. there was. On the other hand, in the bow structure using the steel plate of the 2nd-6th comparative example, since YP (AR, RT) is more than 220 Mpa or (beta) is more than 0.6, these bow structures are compared with the steel plate of 1st-3rd Example, The energy absorption capacity was greatly reduced.

In addition, the information of Table 2 was put together, and the relationship of (alpha) and EA / EA (ref) was shown in FIG. As shown in FIG. 9, when (alpha) became larger than 1.2, EA / EA (ref) fell large. This large decrease in energy absorption capacity is considered to be because the deformation mode of the bulbous bow shifts from FIG. 10C to FIG. 10A or FIG. 10B. Therefore, even if a part with an uneven yield strength is formed in a steel plate by the linear heating process of 600 degreeC or more, the bow structure which has high energy absorption ability can be comprised by using the steel plate whose alpha is 1.2 or less for the outer shell member of a bulbous bow. .

From the above, the steel plate whose yield strength is 120 Mpa or more and 220 Mpa or less, and the yield strength at 600 degreeC before linear heat processing is 0.6 times or less of the yield strength at room temperature is applied to the outer shell member of a bulbous bow. By using it, the energy absorption capacity of the bow side at the time of a collision can be increased, and the serious damage of the ship of an opponent can be prevented. In addition, in such a steel plate, the ratio (alpha) of the yield strength of the linear heating part and the nonlinear heating part after linear heat processing under normal heating conditions (600 degreeC or more) and giving curvature becomes 1.2 or less. The bow structure using such a steel plate for a shell member has a buffer effect by buckling deformation, without causing a change in the hull structure design.

It is possible to provide a bow structure with a cushioning effect that can effectively prevent damage to a ship of an opponent during a collision without causing a change in the hull structure design.

1: steel plate
2: site subjected to linear heating (linear heating part)
3: site | part which is not receiving linear heating (nonlinear heating part)
4: test piece
5: block

Claims (2)

The outer shell of the bulbous bow,
Curvature is imparted by linearly heat-processing at 600 degreeC or more at the highest surface side of a heating side, and before the said linear heat processing, the yield strength in room temperature is less than 120 Mpa-200 Mpa, and the yield strength in 600 degreeC is room temperature. The bow structure excellent in the collision energy absorption capability characterized by consisting of a steel plate which is 0.6 times or less of the yield strength of the. The yield strength of the L member having an angle of 45 degrees or less with respect to the hull length horizontal direction with respect to the shell member and the internal structural member constituting the bulbous bow is 45 with respect to the hull length horizontal direction. The bow structure excellent in the collision energy absorption capability characterized by being lower than the yield strength of the W member which has an angle larger than degree.

Images