JP4869094B2 - Impact property prediction method for marine steel - Google Patents

Description

  The present invention relates to a method for predicting or evaluating impact characteristics (absorbed energy at the time of collision) until a marine vessel collides with a rock or the like and is grounded, and a marine steel material having excellent grounding resistance. It relates to the selection method.

  When a ship collides with rocks and lands and breaks, the outer plate of the ship is torn and fuel and other oil leaks, causing serious environmental pollution and secondary damage such as fire due to equipment damage. It may lead to disaster.

  Therefore, various investigations have been made to provide marine steel materials having excellent grounding resistance (impact resistance) in which a ship collides with rocks and the like, and the ship is not damaged even if it is stranded. For example, in Patent Document 1 and Patent Document 2 shown below, the idea that “to provide a marine steel material with excellent grounding resistance, it is only necessary to increase the amount of energy absorbed until the ship breaks”. Based on the stress-strain diagram (Stress-strain diagram, hereinafter referred to as “SS diagram” in some cases) shown in FIG.

  Specifically, Patent Document 1 describes a steel plate excellent in impact resistance absorption (synonymous with grounding resistance) that can absorb the energy at the time of collision and prevent destruction of the ship. Here, (a) In order to increase the absorbed energy at the time of a collision, it is necessary that the steel materials for marine use have both excellent elongation characteristics (breaking elongation: EL) and strength characteristics (yield stress YP, tensile strength TS). (B) In general, the energy absorption EA until the steel sheet breaks is expressed by EA = [(YP + TS) × EL / 2] (where YP is the yield stress and TS is the tensile strength) , EL is elongation at break). Here, the breaking elongation EL is synonymous with the total elongation shown in FIG.

Further, Patent Document 2 describes a steel material having a high uniform elongation and excellent in collision resistance, which is effective in suppressing damage such as when a ship collides. The uniform elongation is the uniform elongation (elongation at the highest load point) shown in FIG. Here, (a) In order to provide a steel material with excellent impact resistance, it is necessary to absorb a large amount of energy at the time of collision in the steel material itself. (A) Conventionally, energy absorption at the time of collision Is evaluated as the product of the strength-ductility balance of steel (the average of yield stress and rupture stress relaxation layer) and total elongation, and the absorption energy is increased by improving both strength and total elongation. However, the evaluation of absorbed energy by total elongation does not necessarily lead to an evaluation of the safety of the hull structure, and is not appropriate when discussing impact resistance, that is, compared to the gauge distance in a tensile test. In order to evaluate the elongation deformation of the hull outer plate supported by the stiffener with a long span that does not become a failure, the evaluation of the total elongation including the local elongation affected by the shape of the specimen is not suitable. Sucking When considering the energy that should be evaluated in uniform elongation of correlation with elongation characteristics of hull is determined to be high, it is described.
Japanese Patent Laid-Open No. 11-193438 JP 2001-262272 A

  As described above, the above-described technologies for improving the collision resistance of marine steel materials in the patent literature all consider only the SS diagram and based on the viewpoint that the energy absorption amount of the material (marine steel material) may be increased. It has been proposed.

  However, in reality, the area where the ship is greatly deformed by stranding is concentrated in the collision part (a part of the ship), and the entire test piece is deformed as when a tensile test is performed using a tensile test piece. is not. Therefore, in view of the actual collision mode, it is insufficient to consider only the above-mentioned “energy absorption amount of material” in providing marine steel materials having excellent collision resistance. Naturally, the size of the region where the steel material for the ship is greatly deformed, that is, the “size of the deformation region of the collision part” should be taken into consideration, but the latter requirement is also taken into consideration. No technology has yet been proposed to improve impact resistance (ground resistance).

  The present invention has been made in view of the above circumstances, and its purpose is to accurately and accurately measure the impact characteristics (absorbed energy at the time of collision) until the ship collides with rocks and lands and breaks down. Another object of the present invention is to provide a marine steel impact property prediction method, marine impact property evaluation method, and marine steel material selection method excellent in grounding resistance, which can be easily predicted or evaluated.

The method for predicting the impact characteristics of a marine steel material according to the present invention, which has solved the above-mentioned problems, includes a step (a) of preparing marine steel material surrounded by a reinforcing member, and a tensile property parameter of the marine steel material. TS: Tensile strength (MPa), YP: Yield stress (MPa), and UE: Uniform elongation (%) are obtained (b), and a hard sphere simulating a rock that collides with a ship (c) When have E1 that will be calculated based on the below formula (I), the the step (d) of the absorbed energy of the marine steel, the gist at the inclusion.
E1 = 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)
In the formula, TS: tensile strength (MPa),
YP: Yield stress (MPa),
UE: uniform elongation (%),
b: Short side size (mm) of marine steel material,
t: plate thickness (mm) of marine steel,
φ: Diameter of a hard sphere (mm).

In addition, the ship impact property evaluation method according to the present invention that has solved the above problems includes a step (a) of preparing a marine steel material surrounded by a reinforcing member, and a tensile property parameter of the marine steel material. TS: Tensile strength (MPa), YP: Yield stress (MPa), and UE: Uniform elongation (%) are obtained (b), and a hard sphere simulating a rock that collides with a ship (c) If, on the basis of the above equation (I) to Ru is calculated have based E1, and step (d) of the absorbed energy of the marine steel, the E 1 that will be calculated by the above formula (I), the ship design And the step (e) of comparing with the reference value E2 of the absorbed energy of the marine steel material determined in this way.

In addition, the method for selecting a marine steel material with excellent grounding resistance according to the present invention that has solved the above-mentioned problems includes a step (a) of preparing a marine steel material surrounded by a reinforcing member and the marine vessel. Step (b) for obtaining TS: tensile strength (MPa), YP: yield stress (MPa), and UE: uniform elongation (%), which are the tensile property parameters of steel materials, and a hard sphere that simulates a rock that collides with a ship the step of preparing the (c), the above equation (I) to Ru is calculated have based E1, and step (d) of the absorbed energy of the marine steel, the E 1 that will be calculated by the above formula (I) The absolute value (E0) of the difference (E1-E2) between the step (e) and the E1 and the E2 is compared with the reference value E2 of the absorbed energy of the marine steel determined based on the design of the vessel. When super, the E1 is equal to the E2, so that And the step (f) of changing TS, YP, and UE, which are tensile property parameters of the marine steel material.

In addition, the method for selecting a marine steel material with excellent grounding resistance according to the present invention that has solved the above-mentioned problems includes a step (a) of preparing a marine steel material surrounded by a reinforcing member and the marine vessel. Step (b) for obtaining TS: tensile strength (MPa), YP: yield stress (MPa), and UE: uniform elongation (%), which are the tensile property parameters of steel materials, and a hard sphere that simulates a rock that collides with a ship the step of preparing the (c), the above equation (I) to Ru is calculated have based E1, and step (d) of the absorbed energy of the marine steel, the E 1 that will be calculated by the above formula (I) The absolute value (E0) of the difference (E1-E2) between the step (e) and the E1 and the E2 is compared with the reference value E2 of the absorbed energy of the marine steel determined based on the design of the vessel. When super, the E1 is equal to the E2, so that The gist of the invention includes the step (g) of changing the short side size b (mm) and the plate thickness t of the marine steel material.

  According to the marine steel material impact property prediction method of the present invention, as shown in the above formula (I), the absorbed energy of the marine steel material is expressed by the tensile property parameters (TS, YP, UE) and structural parameters that take into account the “size of the deformation region of the collision part” (short-side size and thickness of the marine steel, the diameter of a hard sphere that simulates a rock that collides with the marine steel) Therefore, the absorption energy (E1) of the marine steel material predicted by the above formula (I) reflects the shock absorption energy of the marine steel material at the time of actual collision (at the time of grounding) more accurately. It will be.

  Therefore, if the absorbed energy (E1) of the marine steel material calculated by the above formula (I) is used, the impact characteristics when the marine steel material during navigation is stranded will be more accurately and accurately evaluated. Can do.

  Furthermore, if the absorbed energy (E1) of the marine steel material calculated by the above formula (I) is used, the marine steel material development guideline (development guideline from tensile properties, structure Development guidelines from the aspect) can also be provided. Specifically, the absorbed energy (E1) calculated by the above formula (I) is normally provided from the manufacturer's side (E2, the reference value of the absorbed energy of the marine steel material that is appropriately set based on the ship design guidelines. If E1 does not coincide with E2 (E1 ≠ E2), the tensile properties (TS, YP, UE) of the marine steel material may be changed as appropriate so that they may coincide with each other. It is possible to provide development guidelines such as appropriately changing the structural characteristics (b, t) of the steel material. This will enable the development of marine steel materials to be further improved because it is possible to reliably select the marine steel material that is most suitable for the ship manufacturer's design guidelines and has extremely high grounding resistance and is extremely safe. It is done.

  As described above, the simulation method according to the present invention is highly expected as being able to evaluate the impact characteristics of a ship in operation with high accuracy, accuracy, and simplicity.

  In order to provide marine steel with excellent grounding resistance, technology that can accurately and accurately predict impact characteristics (absorbed energy at the time of collision) until the ship breaks (specifically, marine steel) Establishment of absorption energy calculation means is extremely important. If a highly accurate technology is constructed, it can be used to evaluate the impact resistance (safety) of a vessel while navigating, and it is most suitable for ship manufacturers' design guidelines. This is because it is possible to select (sort) steel materials.

  However, as described above, the conventional marine steel material absorption energy calculating means is only determined in consideration of the SS diagram, and has a great influence on the calculation of absorption energy. No consideration is given to “size”. Therefore, it cannot be said that the conventional method reflects the actual situation, and is insufficient in terms of accuracy and precision.

Based on such a viewpoint, the present inventor has further studied. As a result, as the absorbed energy of the marine steel material, as shown in the following formula (I), the structural parameters (t, TS, YP, UE) and the structural parameter (t , B, φ) and E1 calculated based on the above , it was found that the intended purpose was achieved, and the present invention was completed.
E1 = 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)
In the formula, TS: tensile strength (MPa),
YP: Yield stress (MPa),
UE: uniform elongation (%),
b: Short side size (mm) of marine steel material,
t: plate thickness (mm) of marine steel,
φ: Diameter of a hard sphere (mm).

  As described above, the greatest feature of the present invention is that “absorbed energy of marine steel”, which is an important evaluation standard for providing marine steel excellent in grounding resistance, is expressed by the tensile property parameter (marine steel of marine steel). TS, YP, UE) and structural parameters that take into account the “size of the deformation area of the collision part” (short side size b of the steel for boats, thickness t, (Diameter φ).

  Hereinafter, the present invention will be described in detail based on the basic experiment that led to the identification of the above formula (I).

(1) Model for predicting absorbed energy of marine steel materials In the present invention, in order to accurately and easily predict the absorbed energy of marine steel materials, an analysis model simulating a ship collision shown in FIG. 1 was used. There is a feature in the point.

  This analysis model was created in consideration of the actual situation of ship grounding that “the region where the ship is deformed by the collision is concentrated not on the entire ship but on the collision part, which is a part of it,” FIG. 1 and FIG. As shown in FIG. 2, the hard sphere 2 is pressed against a part of the flat plate 1 having a finite area. By using an analysis model using such a hard sphere, not only the absorption energy of the analysis material (marine steel), but also the material (marine for marine use) that takes into account the size of the region that greatly deforms due to a collision (dimension of the collision part) It is possible to determine the amount of energy absorbed until the steel material is damaged.

  Hereinafter, the analysis model used in the present invention will be described in detail with reference to FIGS. 1 and 2.

  FIG. 1 simulates the situation when a ship collides with a rock, and schematically shows the situation when a hard sphere 2 collides with the vicinity of the center of a flat plate 1. Here, the flat plate 1 simulates the outer plate of a ship and is a rectangular parallelepiped composed of a long side a, a short side b, and a plate thickness t. The periphery (outer periphery) of the flat plate 1 is surrounded by the reinforcing member 3. This is because the outer plate of a ship is usually reinforced (completely constrained) in a lattice shape. The hard sphere 2 simulates a rock that collides with a ship.

  FIG. 2A is a diagram schematically showing a state in which the hard sphere 2 is pushed into the flat plate 1 and the flat plate 1 is deformed, and FIG. 2B is a view from the A direction of FIG. 2A. It is a figure shown typically.

  That is, in the present invention, “the absorption energy of the marine steel material is the smallest (that is, the marine vessel is most easily damaged) when the rock collides with the central portion of the flat plate 1 surrounded by the reinforcing member”. In consideration of this, the analysis model shown in FIG. 1 is determined as a model under conditions where damage is most likely to occur. In other words, the analysis model shown in FIG. 1 is created with the highest importance on safety, and the impact characteristic prediction method of the present invention based on the analysis model minimizes damage caused by a ship collision accident. Is considered to be a possible method.

The size of (1a) plate-plate 1 is depending on the type of ship to be applied can be changed as appropriate, generally, the long side a: 1000~2000 m m × short side b: 1000 to 10,000 m It is preferable to be within the range of m.

  In the above formula (I), only the short side b of the flat plate 1 is defined, and the long side a of the flat plate 1 is not defined. This is because it is considered sufficient to define only the short side b of the flat plate 1 in consideration of the fact that the short side is closer to the restraining portion than the long side, and that large stress is likely to occur.

  Moreover, although the board thickness t of the flat plate 1 can be suitably changed according to the kind of ship etc. which are applied, it is preferable that it exists in the range of 5-20m in general.

(1b) Hard sphere In this invention, the hard sphere 2 is used simulating the rock which collides with a ship. “Hard sphere” generally means a sphere having rigidity (small dimensional change with respect to bending or torsional force), but in the present invention, a diameter sufficiently larger than the plate thickness (generally, roughly). Means a solid sphere having 10 times or more). In the present invention, the above-mentioned hard sphere is used in order to provide the safest evaluation means / prediction means.

  In the present invention, the reason for the “sphere” as described above is not technical, and it is easy to compare materials when selecting materials using the evaluation method according to the present invention. It is based on “simpleness”. Actually, the shape of the rock is not spherical, but is composed of polyhedrons having various planar shapes. For example, it is possible to consider the shape of the rock. The comparison when selecting a material suitable for the manufacturer's design guidelines is complicated, and it is difficult to say that it is a simple evaluation method. Therefore, for the sake of convenience, it was decided to be “sphere”.

  In addition, when a database on the shape, size, material, etc. of rocks can be obtained from a ship manufacturer, the shape of the rigid body can be changed with reference to the database. Thereby, more quantitative evaluation becomes possible.

  The size of the hard sphere 2 can be appropriately changed in consideration of the assumed rock size in accordance with the type of ship to be applied, but it is generally preferable that the diameter is in the range of 500 to 1000 mm.

  The ratio of the size of the hard sphere 2 to the flat plate 1 is preferably, for example, that the ratio of the short side size b of the flat plate 1 to the diameter φ of the hard sphere 2 is 1 or more.

  The hard sphere 2 used in the present invention may be a hard sphere that satisfies the above requirements, and other requirements such as the weight of the hard sphere 2 and the speed at which the hard sphere 2 collides with the flat plate 1 may not be considered. . The weight of the hard sphere 2 is usually considered insignificant in determining the impact properties of the material. In reality, it is considered that the speed at the time of the collision may be neglected considering that the speed at which the ship collides with the rock is almost zero.

(2) Calculation of tensile property parameters (TS, YP, UE of marine steel materials) The present invention also calculates tensile property parameters (TS, YP, elongation properties) based on the SS diagram shown in FIG. The above formula (I) is set using the obtained parameters. In the present invention, in particular, (a) UE (uniform elongation) is used as an elongation index, and an SS diagram taking into account up to plastic deformation is set. (A) YP (yield stress) is The smaller the smaller, the smaller the absorbed energy of the ship.

  Among these, (a) is also described in Patent Document 2 described above. The reason why uniform elongation is used instead of total elongation is based on almost the same viewpoint as that of Patent Document 2 described above, and when the strain of the material exceeds the uniform elongation, local elongation occurs and almost absorbs energy. It is thought that it will be impossible. Therefore, in the present invention, the time when the maximum value of the equivalent plastic strain in the flat plate reaches uniform elongation is set as the “material fracture point”.

  On the other hand, the above knowledge (a) has been found for the first time by the present inventors. In any of the above-mentioned patent documents, as shown below, the opposite to the above knowledge is described.

  That is, all of the methods disclosed in the above-mentioned patent literatures are described as follows: “In order to obtain marine steel having excellent grounding resistance, elongation properties [breaking elongation (= total elongation) in Patent Literature 1; uniform in Patent Literature 2] It is proposed based on the viewpoint that “the sum (YP + TS) of the yield stress YP and the tensile strength TS, which is a strength characteristic, may be increased while ensuring the elongation (= uniform elongation)”. In other words, in order to increase the absorbed energy of the marine steel material and obtain the marine steel material excellent in grounding resistance, the larger the UE, TS, and YP, the better.

  However, according to the basic experiment of the present inventor shown below, surprisingly, among the above tensile property parameters (UE, TS, YP), only YP shows a completely opposite tendency, and the above formula (I) As shown in Fig. 5, it is clear that the UE should be rather small, which increases the absorbed energy of the marine steel. This knowledge cannot be obtained with conventional evaluation methods, and is a matter to be noted.

(3) About the above formula (I) Based on the above background, in the present invention, the analysis model shown in FIG. 1 is used, and the tensile properties (TS, YP, UE) was measured and the above formula (I) was specified.
Hereinafter, basic experiments that have reached the above formula (I) will be described in detail.

(3a) Basic experiment (analysis)
First, various steel flat plates made of a rectangular parallelepiped having a long side a = 2000 to 20,000 mm , a short side b = 2.5 to 10 m, and a plate thickness t = 5 to 20 mm, and a diameter φ = 0.5 to 2 m Various steel hard balls 2 are prepared. The periphery of the flat plate 1 is all covered with a reinforcing member 3 (YP: 350 to 500 MPa material) having a plate thickness of about 100 mm and a plate width of about 1 m.

  Next, as shown in FIG. 2, the hard sphere 2 was pushed near the center of the flat plate 1 at a sufficiently low speed of 1 mm / min or less to deform the flat plate 1.

  The tensile properties (TS, YP, UE, EL) at this time were measured under the following conditions. Based on the “metal material tensile test method” defined in JIS Z2241, using a No. 14 test piece (parallel part diameter is 10 mm) defined in JIS Z2201 from the plate thickness 1/4 part of the flat plate, TS, YP, UE, and EL were measured. The test speed during the tensile test was 0.5 mm / second. In addition, although the measurement of EL is unnecessary in the method of the present invention, the measurement was performed here in order to make a comparison with the conventional method as described below.

  Furthermore, the absorption energy E (actual value, N · m) until the flat plate 1 was broken was calculated. The absorbed energy E was obtained as a diagram area until the flat plate 1 was broken in the indentation load-indentation displacement diagram.

  The obtained results are shown in Tables 1 and 2. Table 1 shows the tensile characteristic parameters and structural parameters constituting the formula (1), and Table 2 shows the tensile characteristic parameters constituting the absorbed energy calculation formula described in Patent Document 1 described above.

3 to 8 are graphs created based on the results of the above table. Among these, FIGS. 3 to 5 are graphs in which any one of TS, YP, and UE, which are tensile property parameters, is taken on the horizontal axis, and the actual measurement value E of the absorbed energy is taken on the vertical axis. FIG. 8 is a graph in which any one of the short side b of the flat plate, the thickness t, and the diameter φ of the hard sphere is taken as the structural parameter on the horizontal axis, and the measured value E of the absorbed energy is taken on the vertical axis. .

  From these figures, the tensile properties of TS and UE and the structural properties of b, t, and φ all have a positive correlation with the absorption energy of the flat plate (FIGS. 3, 5 to 8). On the other hand, the tensile property of YP shows a negative correlation with the absorption energy of the flat plate (see FIG. 4), and only the tensile property of YP has a behavior different from other parameters. I understand that.

Specifically, FIG. 3 shows that YP = 350 MPa, UE = 0. 3 is a graph showing the relationship between TS (tensile strength) and measured value E of absorbed energy at 3 %, b = 2.5 m, t = 9 mm, and φ = 1 m. As shown in FIG. 3, TS and E almost showed a positive correlation, and based on the least square method, TS ² and E had a high correlation.

FIG. 4 shows that TS = 500 MPa, UE = 0. 3 is a graph showing the relationship between YP (yield stress) and the measured value E of absorbed energy at 3 %, b = 2.5 m, t = 9 mm, and φ = 1 m. As shown in FIG. 4, YP and E almost show a negative correlation, and based on the least square method, it can be seen that YP ⁻¹ and E have a high correlation. It was.

FIG. 5 is a graph showing the relationship between UE (uniform elongation) and measured value E of absorbed energy when TS = 500 MPa, YP = 350 MPa, b = 2.5 m, t = 9 mm, and φ = 1 m. As shown in FIG. 5, UE and E almost show a positive correlation, and based on the least square method, it was found that UE ^1.5 and E have a high correlation. .

FIG. 6 is a graph showing the relationship between b (the short side length of the flat plate) and the measured value E of the absorbed energy when TS = 500 MPa, YP = 400 MPa, UE = 0.2 %, t = 9 mm, and φ = 1 m. It has become. As shown in FIG. 6, it was found that b and E almost showed a positive correlation, and based on the least square method, b ^0.5 and E had a high correlation. .

FIG. 7 shows the relationship between t (the thickness of the flat plate) and the measured value E of the absorbed energy when TS = 500 MPa, YP = 400 MPa, UE = 0.2 %, b = 1 m, and φ = 0.5 m. Is a graph. As shown in FIG. 7, it was found that t and E almost showed a positive correlation, and that t and E had a high correlation based on the least square method.

FIG. 8 is a graph showing the relationship between φ (the diameter of a hard sphere) and the measured value E of absorbed energy when TS = 500 MPa, YP = 400 MPa, UE = 0.2 %, b = 1 m, and t = 9 mm. Is. As shown in FIG. 8, it was found that φ and E have a substantially positive correlation, and that φ ² and E have a high correlation based on the least square method. .

From the above table and the results of FIGS. 3 to 8, the absorption energy E1 (predicted value) of the flat plate is determined using the tensile property parameters (TS, YP, UE) and the structural parameters (b, t, φ). Is expressed as the following formula (I).
Absorption energy of marine steel E 1
= 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)

  FIG. 9 is a graph showing the relationship between the absorption energy E1 (predicted value) of the above formula (I) derived as described above and the actual measurement value E of the absorption energy. As shown in FIG. 9, since E1 and E have a high correlation, if the above equation (I) is used, the absorbed energy (actually measured value) of the flat plate can be predicted and accurately accurately. Can be evaluated.

  For reference, FIG. 10 shows the absorption energy EA (EA = [(YP + TS) × EL / 2] calculated in consideration of only the tensile properties of the material described in Patent Document 1 described above, The relationship between EL = total elongation) and the absorption energy (measured value) of the flat plate is shown in a graph.

  As shown in FIG. 10, it can be seen that the absorption energy EA predicted by the conventional calculation method has an extremely low correlation with the actual measurement value E.

  As described above, the predicted value E1 of the absorbed energy according to the above formula (I) derived by the present invention has an extremely high correlation with the actual measurement value E as compared with the conventional calculation method. Was also confirmed.

(4) Application Example Using the above Formula (I) Furthermore, the predicted value E1 of the absorbed energy calculated by the above formula (I) can be applied to the following modes, for example. Included within the scope of the present invention.

(4a) Ship Safety Evaluation Method The predicted value E1 of the absorbed energy of the marine steel calculated by the above equation (I) is the reference value E2 of the absorbed energy of the marine steel determined based on the design of the marine vessel. By comparing, it is possible to indirectly evaluate the safety of the ship.

  Here, the reference value E2 of absorbed energy may be provided from, for example, each ship manufacturer. Normally, ship manufacturers often adopt their own absorbed energy calculation method for each manufacturer based on the ship design guidelines, and even use the “absorbed energy reference value E2” as a safety index. In many cases, each manufacturer sets its own safety standards according to past histories and achievements. The present invention does not include the determination of the reference value E2 of the absorbed energy that can be arbitrarily set by each manufacturer. E2 uses the value provided by each manufacturer as it is, and this E2 By comparing E1 derived from the present invention with E1, the safety of the ship is easily evaluated.

  Specifically, when the predicted value E1 obtained by the method of the present invention is provided to a ship manufacturer, for example, and compared with the reference value E2 of the absorbed energy in the ship manufacturer, the provided analysis model (steel steel for ships) ) Can be easily and accurately evaluated as to whether or not it conforms to the design guidelines of the ship manufacturer, that is, whether it is a steel material for ships that meets the safety standards of the ship manufacturer. .

For example, the predicted value E1 = 60 0 of absorbed energy calculated by the above formula (I), the time the reference value E2 = 600 kN · m of absorbed energy by ship manufacturers, since it is E1 = E2, the prediction value It can be evaluated that a material satisfying E1 (marine steel) conforms to the design guidelines of the ship manufacturer and is extremely safe with excellent grounding resistance.

Similarly, for example, the predicted value E1 = 70 0 of absorbed energy calculated by the above formula (I), the time the reference value E2 = 600 kN · m of absorbed energy by ship manufacturers, because it is E1> E2, A material that satisfies the predicted value E1 can sufficiently satisfy the design guidelines of the ship manufacturer, and can be evaluated as being extremely excellent in safety.

In contrast, the predicted value E1 = 50 0 of absorbed energy calculated by the above formula (I), the time the reference value E2 = 600 kN · m of absorbed energy by ship manufacturers, because it is E2> E1, the It can be evaluated that the material satisfying the predicted value E1 does not satisfy the design guideline of the ship manufacturer, is inferior in grounding resistance, and has low safety.

  In such a case, as shown in (4b) to be described later, the tensile property parameter and the structural parameter of the marine steel are appropriately changed, and the absorbed energy of the marine steel is predicted so that E1 ≧ E2. By increasing the value E1, it is possible to obtain a marine steel material that is suitable for a ship manufacturer's design guideline and excellent in safety.

(4b) Method for selecting marine steel having excellent grounding resistance (4b-1) Method for selecting based on change of tensile property parameter The material selecting method is the absorption of marine steel calculated by the above formula (I). When the energy E1 is compared with the reference value E2 of the absorbed energy of the marine steel material determined based on the design of the ship, and the absolute value (E0) of the difference (E1-E2) between E1 and E2 is greater than 0, TS, YP, and UE, which are tensile property parameters of the marine steel material, are changed so that E1 becomes equal to E2.

Specifically, the predicted value E1 of the absorbed energy calculated by the above formula (I) is 500 , and when the reference value E2 of the absorbed energy by the ship manufacturer is 600 kN · m, E2 ≧ E1 For example, E1 may be increased by increasing TS and UE, or E1 may be increased by decreasing YP.

  It should be noted that the present invention only provides an index of tensile properties and is not intended to provide a material that can satisfy such properties. Accordingly, a steel material manufacturer or the like may appropriately control the steel components and the structure appropriately so as to satisfy the above tensile properties.

(4b-2) Selection method based on change in structure parameter The material selection method described above is for a ship in which the absorbed energy E1 of the steel for ship calculated by the above equation (I) is determined based on the design of the ship. Compared to the standard value E2 of absorbed energy of steel, when the absolute value (E0) of the difference (E1-E2) between E1 and E2 is greater than 0, the short side of the steel for marine is set so that E1 is equal to E2. The size b (mm) and the plate thickness t are changed.

Specifically, the predicted value E1 of the absorbed energy calculated by the above formula (I) is 500 , and when the reference value E2 of the absorbed energy by the ship manufacturer is 600 kN · m, E2 ≧ E1 For example, it is useful to increase E1 by increasing the short side size b and the plate thickness t of the flat plate.

FIG. 1 simulates the situation when a ship collides with a rock, and schematically shows the situation when a hard sphere 2 collides with the vicinity of the center of a flat plate 1. FIG. 2A is a diagram schematically showing a state in which the hard sphere 2 is pushed into the flat plate 1 and the flat plate 1 is deformed, and FIG. 2B is a view from the A direction of FIG. 2A. It is a figure shown typically. FIG. 3 is a graph showing the relationship between TS (tensile strength) and measured value E of absorbed energy when YP = 350 MPa, UE = 0.3 %, b = 2.5 m, t = 9 mm, and φ = 1 m. It is. FIG. 4 is a graph showing the relationship between YP (yield stress) and the actual measured value E of absorbed energy when TS = 500 MPa, UE = 0.3 %, b = 2.5 m, t = 9 mm, and φ = 1 m. It is. FIG. 5 is a graph showing the relationship between UE (uniform elongation) and measured value E of absorbed energy when TS = 500 MPa, YP = 350 MPa, b = 2.5 m, t = 9 mm, and φ = 1 m. FIG. 6 is a graph showing the relationship between b (the short side length of the flat plate) and the measured value E of the absorbed energy when TS = 500 MPa, YP = 400 MPa, UE = 0.2 %, t = 9 mm, and φ = 1 m. It has become. FIG. 7 shows the relationship between t (the thickness of the flat plate) and the measured value E of the absorbed energy when TS = 500 MPa, YP = 400 MPa, UE = 0.2 %, b = 1 m, and φ = 0.5 m. Is a graph. FIG. 8 is a graph showing the relationship between φ (the diameter of a hard sphere) and the measured value E of absorbed energy when TS = 500 MPa, YP = 400 MPa, UE = 0.2 %, b = 2.5 m, and t = 9 mm. It is a thing. FIG. 9 is a graph showing the relationship between the absorbed energy E1 (predicted value) calculated by the formula (I) and the actually measured value E of the absorbed energy. FIG. 10 is a graph showing the relationship between the absorbed energy EA calculated by the formula [(TS + YP) × EL / 2] (where EL = total elongation) and the measured value E of the absorbed energy. FIG. 11 is a diagram (SS diagram) showing the relationship between stress and strain.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flat plate 2 Hard sphere 3 Reinforcement member a Long side of a flat plate b Short side of a flat plate t Thickness of a flat plate φ Diameter of a hard sphere

Claims (4)

A method for predicting impact characteristics of marine steel,
A step (a) of preparing a marine steel material surrounded by a reinforcing member;
Step (b) for obtaining TS: tensile strength (MPa), YP: yield stress (MPa), and UE: uniform elongation (%) which are tensile property parameters of the marine steel material;
A step (c) of preparing a hard sphere simulating a rock colliding with a ship;
The E1 that will be calculated based on the below formula (I), the the step (d) of the absorbed energy of the marine steel,
E1 = 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)
In the formula, TS: tensile strength (MPa),
YP: Yield stress (MPa),
UE: uniform elongation (%),
b: Short side size (mm) of marine steel material,
t: plate thickness (mm) of marine steel,
φ: diameter of a hard sphere (mm),
A method for predicting impact characteristics of marine steel, characterized by comprising: A method for evaluating the impact characteristics of a ship,
A step (a) of preparing a marine steel material surrounded by a reinforcing member;
Step (b) for obtaining TS: tensile strength (MPa), YP: yield stress (MPa), and UE: uniform elongation (%) which are tensile property parameters of the marine steel material;
A step (c) of preparing a hard sphere simulating a rock colliding with a ship;
The E1 that will be calculated based on the below formula (I), the the step (d) of the absorbed energy of the marine steel,
E1 = 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)
In the formula, TS: tensile strength (MPa),
YP: Yield stress (MPa),
UE: uniform elongation (%),
b: Short side size (mm) of marine steel material,
t: plate thickness (mm) of marine steel,
φ: diameter of a hard sphere (mm),
The E 1 that will be calculated by the above formula (I), the the step (e) to be compared with a reference value E2 of the absorption energy of the marine steel is determined based on the ship's design,
A ship impact characteristic evaluation method including A method for selecting marine steel with excellent grounding resistance,
A step (a) of preparing a marine steel material surrounded by a reinforcing member;
Step (b) for obtaining TS: tensile strength (MPa), YP: yield stress (MPa), and UE: uniform elongation (%) which are tensile property parameters of the marine steel material;
A step (c) of preparing a hard sphere simulating a rock colliding with a ship;
The E1 that will be calculated based on the below formula (I), the the step (d) of the absorbed energy of the marine steel,
E1 = 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)
In the formula, TS: tensile strength (MPa),
YP: Yield stress (MPa),
UE: uniform elongation (%),
b: Short side size (mm) of marine steel material,
t: plate thickness (mm) of marine steel,
φ: diameter of a hard sphere (mm),
The E 1 that will be calculated by the above formula (I), the the step (e) to be compared with a reference value E2 of the absorption energy of the marine steel is determined based on the ship's design,
When the absolute value (E0) of the difference (E1-E2) between E1 and E2 is greater than 0, TS, YP, which are tensile property parameters of the marine steel material, so that E1 is equal to E2. And (f) changing the UE;
Of marine steel materials including A method for selecting marine steel with excellent grounding resistance,
A step (a) of preparing a marine steel material surrounded by a reinforcing member;
Step (b) for obtaining TS: tensile strength (MPa), YP: yield stress (MPa), and UE: uniform elongation (%) which are tensile property parameters of the marine steel material;
A step (c) of preparing a hard sphere simulating a rock colliding with a ship;
The E1 that will be calculated based on the below formula (I), the the step (d) of the absorbed energy of the marine steel,
E1 = 0.8 × (TS ² × UE ^1.5 × b ^0.5 × t × φ ² / YP) (I)
In the formula, TS: tensile strength (MPa),
YP: Yield stress (MPa),
UE: uniform elongation (%),
b: Short side size (mm) of marine steel material,
t: plate thickness (mm) of marine steel,
φ: diameter of a hard sphere (mm),
The E 1 that will be calculated by the above formula (I), the the step (e) to be compared with a reference value E2 of the absorption energy of the marine steel is determined based on the ship's design,
When the absolute value (E0) of the difference (E1-E2) between the E1 and the E2 is greater than 0, the short side size b (mm) and the plate of the marine steel material are set so that the E1 is equal to the E2. A step (g) of changing the thickness t;
Of marine steel materials including

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