KR101376686B1 - An unstiffened composite thick cylinder subjected to hydrostatic pressure and an ultimate strength design method using the estimation of collapse pressure therefor - Google Patents

Abstract

The present invention relates to an unstiffened composite thick plate cylinder of an underwater vehicle subject to hydraulic pressure, and a final strength design method using collapse strength estimation thereof. The unstiffened composite thick plate cylinder of an underwater vehicle is made of longitudinal fibers and helical fibers, and can be rapidly designed by simplifying a design formula for the final collapse strength of a thick plate cylinder. Therefore, the unstiffened composite thick plate cylinder of an underwater vehicle subject to hydraulic pressure, and a final strength design method using collapse strength estimation thereof can design a deep-sea composite underwater vehicle with excellent strength and reliability. The unstiffened composite thick plate cylinder of an underwater vehicle subject to hydraulic pressure comprises: multiple longitudinal fibers which are formed by being overlapped in a shear direction to the longitudinal direction of the cylinder; and multiple helical fibers which are formed by being overlapped in the helical direction to the cylinder.

Description

An Unstiffened composite thick cylinder subjected to hydrostatic pressure and An Ultimate strength design method using the estimation of collapse pressure therefor}

The present invention relates to a method of designing the final strength of a non-reinforced composite thick plate cylinder of submersible submerged under water pressure and its collapse strength estimation method, the final of the thick plate cylinder as a non-reinforced composite thick plate cylinder composed of longitudinal fiber and spiral fiber Simplified submerged composite heavy plate cylinder design by simplifying the design of collapse strength, and this design method allows the submerged non-reinforced composite heavy plate to design a stronger and more reliable deep sea composite submersible. Cylindrical and its ultimate strength design method by estimating its collapse strength.

In general, aquatic robots such as Autonomous Underwater Vehicles (AUVs) or Remotely Operated Vehicles (ROVs) can be used in physiologically exceeding human diving limits and contaminated areas, such as in deep seabeds. Replace or provide for research and academic purposes for exploring various marine ecological environments such as the topography of the seabed, water temperature and salinity, and for dangerous work that is expected to cause loss of life and equipment such as detecting and removing explosives such as mines. It was developed for a variety of purposes, including military purposes, such as enemy underwater reconnaissance.

Submersibles that are not very deep have mainly consisted of metal hulls. Recently, however, the depth of diving has reached thousands of meters for deep sea marine environment research and military purposes, and thick composite cylinders are often used to withstand deep sea pressures. Figure 1 shows an example.

When the thickness of the composite cylinder is thin, elastic buckling (hereinafter referred to as the first mode) dominates the collapse of the cylinder, but when the thickness is thick, not only the elastic buckling of the cylinder but also the failure of the cylindrical material (hereinafter referred to as the second mode) is affected. do.

Section 10, Section X Fiber-reinforced plastic pressure vessels, Boiler, by the American Society of Mechanical Engineers, boiler and pressure hull regulation, published recently in 2007, which is widely used in the design of hydraulic cylinders. & Pressure Vessel Code) allows the allowable pressure to be estimated by the following equation.

&Quot; (1) "

Where D ₀ Is the outer diameter of the cylinder (in.) And E _at Is the axial tensile modulus (psi), E _hf Is the circumferential bending factor (psi), F is the safety factor of 5, and KD is the knock-down factor of 0.84. Where L is the length of the cylinder (in), P _a is the allowable pressure (psi), t _s is the thickness of the cylinder (in), and v _x and v _y are the axial and circumferential bending poisson's ratios ( Poisson's ratio. r is a reduction factor that reflects the experimental results. If Z _p is less than or equal to 100, and is greater than 100, then Z _p follows <Equation 2>.

&Quot; (2) &quot;

Where E _d is the axial deflection coefficient (psi).

As can be seen from Equation 1, the design equation derives the relevant experimental results through direct regression analysis using design variables, and uses the safety factor (F) 5 in all cases. Therefore, the mutual interference between the elastic buckling (first mode) and the fracture (second mode) of the material cannot be effectively considered by this equation, and the accuracy of estimating the collapse pressure is not high.

Therefore, there is a need for a new design method capable of quickly and easily calculating the collapse strength while considering all of the mutual influences between the first and second modes.

The present invention is to solve the problems of the prior art as described above, the object of the present invention is the fiber in the longitudinal direction in the shear direction and the inclined fiber in the spiral direction as a non-reinforced composite in the thick plate cylinder of submersible To provide an unreinforced composite thick plate cylinder of submersible with high final strength against collapse strength.

Still another object of the present invention is to improve the collapse strength of composite thick plate cylinders subjected to hydraulic pressure in order to design the final strength of the submersible thick plate cylinder, taking into account the mutual interference effect of each collapse mode, to calculate the strength more accurately and quickly. To provide a new method of designing collapse strength.

In order to achieve the above-mentioned object, the present invention will be realized by an embodiment having the following constitution as a preferred embodiment. The present invention provides the following technical constructions to solve the above problems.

According to one embodiment of the present invention, the submersible thick plate cylinder of the present invention is a non-reinforced composite thick plate cylinder subjected to the hydraulic pressure of the submersible, longitudinal fiber formed by overlapping a plurality of shear in the longitudinal direction of the cylinder; And a spiral fiber formed by overlapping a plurality of spirals with respect to the cylinder.

According to another embodiment of the present invention, in designing the final strength against the collapse pressure for the non-reinforced composite material of the thick plate cylinder of the submersible, the collapse strength estimation to obtain a result by a very simple and accurate calculation The final strength design method is provided.

INDUSTRIAL APPLICABILITY As described above, the present invention can achieve the following effects according to the above-described problem solving means and the construction and operation to be described later.

In the submersible under the pressure of the present invention, the composite thick-walled cylinder is composed of longitudinal fibers in the shear direction of the cylinder and inclined fibers in the helical direction so that the final strength of the collapse strength is increased to increase durability. do.

The final strength design method of the composite thick plate cylinder in the hydraulic submersible of the present invention can more accurately estimate the collapse strength of the composite thick plate cylinder subjected to hydraulic pressure by considering mutual interference between two modes affecting the collapse strength.

In addition, the submersible composite thick plate cylindrical design method of the present invention can be designed faster than the existing design by simplifying the design formula, it is possible to design a stronger and more reliable deep sea composite submersible.

1 is a view showing a deep sea unmanned submersible made of a composite thick plate of the present invention,
Figure 2 shows a thick plate composite cylinder of the present invention.
Figure 3 shows the collapse shape of a thick plate composite cylinder collapsed by hydraulic pressure of the present invention.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the method of designing the final strength by estimating the collapse strength of the non-reinforced composite thick plate cylinder and its collapse according to the present invention will be described in detail.

Prior to this, terms and words used in the present specification and claims should not be construed as being limited to ordinary or dictionary terms, and the inventor should appropriately define the concept of the term to describe its invention in the best way The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

Hereinafter, a non-reinforced composite thick plate cylinder of the submersible under the present invention and the method of designing the collapse strength of such a cylinder will be described with reference to FIGS.

1 is a view showing a deep sea unmanned submersible made of a composite thick plate of the present invention, Figure 2 is a view showing a thick plate composite cylinder of the present invention, Figure 3 is a thick plate composite cylinder collapsed by the hydraulic pressure of the present invention It is a figure which shows the collapse shape.

Accordingly, the present invention, in the non-reinforced composite thick plate cylinder subjected to the hydraulic pressure of the submersible 10, the thick plate cylinder 300, the longitudinal fiber (Fc) formed by overlapping a plurality of shear in the longitudinal direction of the cylinder; And a spiral fiber (Fh) formed by overlapping a plurality of spirals with respect to the cylinder.

2, in the present invention, the non-reinforced composite thick plate cylinder 300 of the submersible 10 is formed of a cylindrical non-reinforced composite material having a predetermined thickness, and the non-reinforced composite is fiber, and the shear of the cylinder It consists of a composite of fibers (Fc) in the longitudinal direction with respect to the direction and a helical fibers (Fh) with respect to the cylinder.

The thick plate cylinder 300 of the submersible in the present invention has a constant cylinder outer diameter (Do), and has an average radius (Rm) from the center of the thickness (t _s ) of the cylinder to the center of the cylinder.

Here, the predetermined thickness t _s of the cylinder 300 is composed of an unreinforced composite organized by the longitudinal fibers Fc and the spiral fibers Fh.

The submersible thick plate cylinder of the present invention is a new method of designing the collapse strength of the composite thick plate cylinder subjected to hydraulic pressure in order to calculate the strength more accurately and quickly in consideration of mutual interference effects for each collapse mode. It can be produced through.

를 <수학식 4>를 사용하여 치환하는 단계; 및 상기 기본식의 각 변수들에 해당하는 수치를 대입하여 붕괴압력(Pc) 를 산출하는 단계;를 포함하는 것을 특징으로 한다.
According to the present invention, the method of designing the final strength of a composite thick plate cylinder of a submersible receiving a hydraulic pressure includes the steps of setting <Equation 3> as a basic formula; Reduction Factor of this Basic Formula

Replacing with Equation 4; And the decay pressure (Pc) by substituting numerical values corresponding to the variables of the basic formula. Computing; characterized in that it comprises a.

&Quot; (3) &quot;

는 강도저하계수로 <수학식 4>를 사용하여 구할 수 있다. 또한 P_m 는 수압을 받는 복합재 원통의 탄성좌굴압력으로 <수학식 6>을 사용하여 구할 수 있고, P_f 는 파단압력으로 <수학식 8>에 의해 구한다.
Equation 3 is a Merchant-Rankine formula utilized as a basic formula of the present invention, and shows the collapse pressure as a secondary combination of elastic buckling pressure and breaking pressure. Where P _c is the collapse pressure

Can be obtained using Equation 4 as the strength reduction factor. In addition, P _m can be obtained using Equation 6 as the elastic buckling pressure of the composite cylinder subjected to hydraulic pressure, and P _f is calculated by Equation 8 as the breaking pressure.

&Quot; (4) &quot;

는 강도저하계수이고, t_a 는 경사방향 복합재 두께이며, t_s 는 원통의 전체 두께이다. 그리고 (E_x)_h 와 (E_y)_h 는 각각 경사방향 복합재의 축방향과 원주방향 탄성계수로 <수학식 5>로 구할 수 있다.
From here

Is the strength decay factor, t _a is the sloped composite thickness, and t _s is the overall thickness of the cylinder. And (E _x ) _h and (E _y ) _h can be obtained from Equation 5 as the axial and circumferential elastic moduli of the inclined composite.

&Quot; (5) &quot;

Where (E _x ) _h and (E _y ) _h are the axial and circumferential elastic moduli of the inclined composite, respectively, and E ₁ and E ₂ are the longitudinal and lateral moduli of the composite material, respectively, and C ₁₂ and v ₁₂ is the in-plane shear modulus and Poisson's ratio of the composite material. And θ is the angle of inclination with the axial direction of the inclined direction composite material.

&Quot; (6) &quot;

이며, n 은 <수학식 6>의 값은 최소화하는 양의 정수이다.
Where p _m is the elastic buckling pressure of the composite cylinder subjected to hydraulic pressure, and E _eq is the equivalent elastic modulus of the composite cylinder. R _m is the average radius of the cylinder,

N is a positive integer that minimizes the value of Equation 6.

&Quot; (7) &quot;

,

로 정해진다. (E_x)_h 와 (E_y)_h 는 <수학식 5>에 의해 구할 수 있고, t_a 는 경사방향 복합재 두께, t_c 는 원주방향 복합재 두께이며, t_s 는 원통의 전체 두께 (= t_a + t_c) 이다
Where E _eq is the equivalent elastic modulus of the composite cylinder, and E _x and E _y are the axial and circumferential moduli of the cylinder, respectively.

,

It is decided. (E _x ) _h and (E _y ) _h are given by Equation 5, where t _a is the sloped composite thickness, t _c is the circumferential composite thickness, and t _s is the total thickness of the cylinder (= t _a + t _c ) is

&Quot; (8) &quot;

Here, p _f is the breaking pressure of the cylinder, which is the smaller of the axial breaking pressure (p _f ) _x and the diagonal breaking pressure (p _f ) _θ . (p _f ) _x and (p _f ) _θ are obtained by the following equation. The suitability of this estimation method can be confirmed by the collapse shape of the composite thick plate cylindrical experimental model shown in FIG.

Where X _T is the breaking strength of the material.

In order to verify the adequacy and accuracy of the design method proposed in the present invention, 21 composite plate cylinders were fabricated and hydraulic collapse tests were performed. Table 1 shows the names and dimensions (length, total thickness, and outer diameter) of the experimental model, and the dimensions of the composite cylinder are shown in <Figure 2>.

Model Height
(mm) Thickness
(mm) Measured outside radius (mm) FW 30 / 90-1 686 8.4 159.5 FW 30 / 90-2 687 8.4 159.8 FW 30 / 90-3 687 8.4 159.2 FW 30 / 90-4 687 8.4 159.2 FW 60-1 686 9.2 159.3 FW 60-2 686 9.2 159.3 FW 60-4 687 9.2 159.5 FW 45 / 90-1 695 8.1 158.1 FW 45 / 90-2 695 8.1 158.1 FW 45 / 90-3 695 8.1 158.1 FW 45 / 90-4 695 8.1 158.2 FW 60 / 90-1 695 7.8 157.8 FW 60 / 90-2 695 7.8 157.8 FW 60 / 90-3 695 7.7 157.7 FW 60 / 90-4 695 7.9 157.9 FWT 45-6-1 695 6.047 156.047 FWT 45-6-2 694 6.171 156.171 FWT 45-6-3 693 6.091 156.091 FWT 45-10-1 693 10.403 160.403 FWT 45-10-2 694 10.364 160.364 FWT 45-10-3 694 10.603 160.603

Table 2 shows the properties of the composite material used in the experimental model. In this table, the longitudinal modulus of fiber E _{1 ,} and the lateral modulus E ₂ And E ₃ , in-plane Poisson's ratio ν ₁₂ and ν ₁₃ and out-of-plane Poisson's ratio ν ₂₃ , in-plane shear modulus G ₁₂ And G ₁₃ , out-of-plane shear modulus G ₂₃ , longitudinal tensile strength X _T , lateral tensile strength Y _T and Z _T , in-plane shear strength S ₁₂ and S ₁₃ , and out-of-plane shear strength S ₂₃ .

Property Symbol Value Unit Elastic modulus E _One 149.120 GPa E ₂ = E ₃ 10.558 GPa Poisson's
ratio v ₁₂ = ν ₁₃ 0.253 - v ₂₃ 0.421 - Shear
modulus G ₁₂ = G ₁₃ 4.138 GPa G ₂₃ 3.311 GPa Tensile
Strength X _T 2548 MPa Y _T = Z _T 40 MPa Shear
Strength S ₁₂ = S ₁₃ 55 MPa S ₂₃ 79 MPa

, 경사방향 복합재 두께와 전체 두께의 비

, 발명된 설계법에 의한 추정 붕괴압력 (P_c)_{pred .} 과 실험에 의한 붕괴압력 (P_c)_{exp .} 과 그 비

를 보여주고 있다.
Table 3 shows the ratio of elastic modulus along with the name of the experimental model.

, Ratio of sloped composite thickness to total thickness

, The estimated collapse pressure (P _c ) _{pred .} And decay pressures (P _c ) _{exp .} And its rain

Respectively.

, 즉 <표 3>의 제일 마지막 줄의 값의 평균과 무차원화된 표준편차(COV: Coefficient of Variation)를 계산한 바, 평균은 1.00 이고 COV는 5.71%로 상당히 우수한 결과를 제시하고 있다.
Estimated collapse pressure by the invented design method, (P _c ) _{pred .} And the collapse pressure from the experiment, (P _c ) _{exp .} Rain of

In other words, the average of the values in the last row of <Table 3> and the coefficient of variation (COV) were calculated. The average was 1.00 and the COV was 5.71%, which is quite good.

The above-described embodiment is a method of designing the final strength by the non-reinforced composite thick plate cylinder and the collapse strength estimation thereof that the person skilled in the art (hereinafter referred to as 'an expert') according to the present invention under water pressure according to the present invention The present invention is not limited to the above-described embodiment and the accompanying drawings, which are intended to facilitate the implementation of the present invention. Therefore, the scope of the present invention is not limited thereto. It will be apparent to those skilled in the art that various changes, substitutions, and alterations can be made hereto without departing from the spirit of the present invention, and it is obvious that those parts easily changeable by those skilled in the art are also included in the scope of the present invention.

10: submersible 300: thick plate cylinder
Xh: spiral collapse Xc: longitudinal collapse
Do: Outer plate cylindrical outer diameter of submersible Rm: Average radius of thick plate cylinder
ts: Thickness of the thick plate cylinder θ: Inclined angle of the inclined composite material (Fh) and the longitudinal composite material (Fc)
Fh: spiral fiber Fc: longitudinal fiber

Claims (5)

delete In the design method of composite thick plate cylinder of submersible under water pressure,

Setting the basic expression;
The strength reduction coefficient of the basic formula

Substitution with:
Calculating the collapse strength P _c by substituting the corresponding numerical values of the variables in the basic formula; composite thick plate cylindrical final strength design method of a submersible.
[

Is the strength reduction factor, p _c Is the collapse pressure, p _m is the elastic buckling pressure of the composite cylinder under water pressure, p _f is the breaking pressure of the composite cylinder, t _a is the thickness of the composite in the direction of the slope, t _s is the thickness of the entire cylinder, and (Ex) h is the gradient of the composite. The axial elastic modulus of (Ey) h denotes the circumferential elastic modulus of the warp composite.]
3. The method of claim 2,
The elastic buckling pressure (P _m ) of the composite cylinder is

ego,
The breaking pressure (P _f ) of the composite cylinder is

and

Final strength design method of the composite thick plate cylindrical submersible of the submersible, characterized in that designed by taking a small value.
An unreinforced composite thick plate cylinder of the submersible, designed for the ultimate strength of the heavy plate cylinder of the submersible by the design method of claim 2 or 3. 5. The method of claim 4,
The thick plate cylinder,
Longitudinal fibers formed of a plurality of overlapping shearing directions in the longitudinal direction of the cylinder; And
Spiral fibers formed in a plurality of spirals with respect to the cylinder;
Submerged unreinforced composite thick plate cylinder consisting of a non-reinforced composite consisting of.

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