KR101064097B1 - Impact tester - Google Patents

Abstract

The present invention relates to an experimental apparatus for predicting and evaluating mechanical damage of structures such as floors or walls caused by impacts of falling objects in ships, offshore structures, or other industrial structures, and does not perform impact tests on actual structures to be tested. The present invention relates to an impact test apparatus configured to perform an impact test simply under the same conditions as an actual impact environment.

In the present invention, in order to predict and evaluate the degree of impact caused by falling objects, etc. applied to ships, offshore structures and other industrial structures, a compressor for supplying compressed air, a pressure chamber that one side is connected to the compressor and accumulates pressure; An impact test apparatus comprising a barrel connected to the other side of the pressure chamber and configured to launch a projectile loaded in the barrel by an operation of a discharge valve connected to the barrel.

Drop impacts, bolts and nuts are combined, pipe supports, LNG carriers, cargo holds, walls, floors, primary and secondary barriers, compressors, compressed air, inlet valves, pressure chambers, discharge lines, discharge valves, barrels, guide rails, Vertical support, barrel support, target structure, signal detector, wire

Description

A testing device for a damage due to impacts}

The present invention relates to an impact test apparatus, and more particularly, to an impact test apparatus for predicting, evaluating and managing the degree of damage caused by impacts on ships, offshore structures and various other industrial structures.

In recent years, the consumption of natural gas is rapidly increasing worldwide, both at home and abroad. In Korea, natural gas is used as a main heating energy source. Recently, it is used as a fuel for buses to reduce the environmental pollution caused by diesel cars. Attempts are being made actively.

As such, natural gas has many demands and various uses, but in Korea, where the resources are scarce, the total amount of natural gas depends on imports. Natural gas is liquefied, stored in natural gas transportation vessels, transported to Korea, and supplied to each customer through gas pipelines on land or sea.

Dedicated vessels that carry natural gas in the form of liquefied natural gas (LNG) are commonly referred to as LNG carriers. LNG carriers use natural gas at a cryogenic temperature of about -163 ° C. By cooling, the volume is reduced to approximately 1/600, allowing for long distance transport by sea. The LNG storage tank installed inside the LNG carrier can be classified into an independent type tank and a membrane type tank depending on whether the load of the cargo is directly applied to the insulation.

Due to the nature and risks of LNG, the contents of LNG storage tanks (cargo hold), the structural design and strength of cargo hold must be evaluated first. If the leakage of liquefied natural gas occurs anywhere in the cargo hold, it can not only guarantee the safety of LNG carriers but also cause irreversible accidents. However, in case of such an LNG carrier, bolts, nuts, and pipe supports may fall on walls such as the bottom of the cargo hold, and such falling objects may form dents due to drop impacts on the walls of the hull. Mechanical damage will occur. In some cases, the impact caused by falling objects may cause fatal damage such as holes in the bottom plate, and thus, gas loaded inside the cargo hold may leak.

The problem of mechanical damage to structural materials due to impacts such as falling objects is not limited to LNG carriers but also occurs in other offshore structures and industrial structures. In particular, if the height is several tens of meters, such as LNG carriers or other offshore structures, damage caused by the impact on the bottom of the hull, even if a small bolt falls, can be fatal. Therefore, it will be very important to predict, evaluate, and manage the mechanical damage caused by the impact of such falling objects.

1 is a photograph showing an example of the actual structure of the cargo hold of the LNG Carrier. That is, the picture shown shows the internal structure of the cargo hold of the LNG carrier of the 150 Km 3 Mark III type.

2 is a schematic cross-sectional view showing the structure of the cargo hold inner wall of FIG. As shown, the inner wall 10 of the cargo hold has a primary barrier 11, a plywood 13a, a plywood, a primary insulation wall 14a, a RPUF panel, and a secondary barrier 12. The secondary insulation wall 14b, the RPUF panel, the plywood 13b, and the mastic 15 are sequentially stacked on the inner hull 16. The primary barrier 11 is a primary membrane formed mainly of a stainless metal plate such as STS 304, so that the cargo is in direct contact with the temperature of about -160 ° C. The secondary barrier 12 functions to prevent leakage of cargo for a certain period of time when the primary barrier 11 is broken. The primary and secondary insulation walls 14a and 14b are made of polyurethane foam to prevent heat from penetrating into the cargo hold, which is a storage tank. The plywoods 13a and 13b help to receive a constant load on the barrier by the uniform arrangement of the thermal insulation walls, and to mitigate the displacement caused by the load in the vertical direction. The mastic 15 serves to transfer the load of the storage tank to the hull.

Figure 3 is a photograph showing an example of the actual structure of the inner wall of the cargo hold of the LNG Carrier, Figure 4 is an enlarged photograph of the primary barrier (11) intersecting small wrinkles and large wrinkles, Figures 5a and 5b is a drop impact An example of water is a combination of bolts and nuts and a pipe support. Mechanical damage to the membrane structure such as the primary barrier 11 on the bottom surface when the combination 21 or pipe support 22 of the illustrated bolt 21a and nut 21b falls at a height of 27m, the height of the cargo hold. Will be coated. Therefore, an evaluation and prediction process for damage of the cargo hold wall structure due to the drop impact by the drop impact object is required. By the way, it is very difficult and inadequate to carry out the impact test by falling objects etc. in the cargo hold of an actual LNG carrier. This is because during the test, it will inevitably damage the walls of expensive LNG carriers, and high cost and time will be required to repair these damaged parts.

Due to the above-mentioned problems, it is urgently required to develop a system for predicting and evaluating the degree of damage to the wall structure due to the impact material falling inside the cargo hold without damaging the cargo hold of the actual LNG carrier. In addition, the necessity of the pre-impact test by such a falling object is not only limited to the vessel, but also requested in the offshore structure and various other industrial structures.

An object of the present invention is to perform a simple impact test under the same conditions without actually performing the impact test on the structure of the ship, such as LNG carriers, structures such as offshore structures and various other industrial structures directly on the structure. To provide a means. Therefore, by predicting and evaluating the damage caused by drop impacts on structures such as cargo holds of expensive LNG carriers in advance, it is possible to safely maintain the facilities.

In order to solve the above technical problem, in the present invention, to predict and evaluate the degree of impact caused by falling objects applied to ships, offshore structures and other industrial structures, etc., a compressor for supplying compressed air, and one side is connected to the compressor. And a pressure chamber for accumulating pressure and a barrel connected to the other side of the pressure chamber, and an impact test apparatus for launching a projectile loaded in the barrel by operation of a discharge valve connected to the barrel. do.

Here, the barrel is preferably installed so as to be movable back, front, left, and right on the base frame.

It is preferable that a hydraulic body having a cross-sectional shape corresponding to the cross-sectional shape of the barrel is inserted behind the position where the projectile is loaded in the barrel.

A discharge tube may be coupled between the other side of the pressure chamber and the barrel, and the discharge valve may be formed on the discharge tube.

Through-holes are formed at two points on the end side of the barrel from which the projectile is to be fired, and a wire is inserted into each of the through-holes so as to be connected to a signal detector capable of measuring resistance or voltage.

According to the present invention, even if the impact object is dropped or impacted directly in a facility such as a cargo hold or a marine structure or other industrial structure of a ship, the experiment is not performed on the damage of the floor or the wall. The same impact test can be carried out under the conditions, which is advantageous in terms of time and cost.

In addition, since the impact test by falling objects and the like can be performed accurately and simply under actual conditions, it is possible to accurately predict and evaluate the extent of damage to the floor or wall due to the falling of the impact object or the impact.

Hereinafter, with reference to the accompanying drawings will be described in more detail the configuration and operation of the present invention.

6 is a block diagram of an impact test apparatus according to the present invention. The impact test apparatus 100 of the present invention is largely composed of a compressor 110, a pressure chamber 120, a barrel (133) and a base frame 150. A compressor 110 is connected to an inlet pipe 131 provided at one side of the pressure chamber 120 by a compressor cable 111, and an inlet valve for intermitting the inflow of compressed air on the inlet pipe 131. 134 is installed. A discharge tube 132 is connected to the other side of the pressure chamber 120, and a barrel 133 is connected to an end of the discharge tube 132 by fittings such as a pipe connecting member 136. Here, although the discharge pipe 132 and the barrel 133 may be formed integrally, it is preferable to configure so as to be separated or coupled to each other by the pipe connecting member 136 as shown. This is because, when it is necessary to change the diameter of the barrel 133, it is easy to replace the barrel with a different diameter by loosening the pipe connecting member 136. On the discharge pipe 132, a discharge valve 135 for controlling the discharge of the compressed air accumulated in the pressure chamber 120 is installed. The discharge valve 135 serves as a trigger of the impact test apparatus 100 and may be configured in the form of a solenoid valve that is manually operated or electronically controlled.

The pressure chamber 120 is equipped with a pressure gauge 121 for measuring the air pressure accumulated in the pressure chamber 120. The pressure chamber 120 is installed on the base frame 150 by vertical supports 141 and 142. The vertical support is composed of an outer support 141 and the inner support 142 inside the outer support 141, the outer support 141 is configured to slide up and down on the outer surface of the inner support 142. This is to adjust the height of the barrel 133 up and down to accurately hit the projectile at the target point of the target structure 200, which will be described later.

First and second guide rails 151 and 152 may be formed on the base frame 150 to allow the vertical supports 141 and 142 to slide forward, backward, left and right. That is, the inner supporter 142 may be mounted to slidably move left and right on the first guide rail 151, and the first guide rail 151 may be mounted to slidably move forward and backward on the second guide rail. have. The guide rails 151 and 152 may adopt any type as long as the structure is slidable, and in the embodiment of the drawing, the inner supporter 142 and the first guide along the guide grooves 151a and 152a on the guide rails 151 and 152. The rail 151 is made to slide.

A barrel support 153 having a long hole 152a is mounted in front of the base frame 150, and the barrel support 153 may be slidably moved from side to side on the base frame 150.

FIG. 7 is a cross-sectional view of the barrel showing a case in which a combination of a bolt and a nut, which is a projectile, is loaded in the barrel, and FIG. 8 is a longitudinal cross-sectional view of the barrel in which the projectile is loaded. As shown in the barrel 133, a projectile such as a combination 21 of the bolt 21a and the nut 21b is loaded. Since the barrel 133 is a kind of barrel and has a hollow hollow tube shape, the barrel 21 is inserted into the joint 21 of the bolt and nut, which is a projectile, through an opening (muzzle) at the end side of the barrel, and is then twisted (not shown). If you push back into the barrel 133, the preparation for launch is completed. Here, loading of the projectile may be performed much more easily by opening a part of the side portion of the barrel 133 to inject the projectile into the side and then installing a door (not shown) that may seal the opening.

At this time, when the inner diameter of the barrel 133 and the diameter of the bolt 21a or the nut 21b are different from each other and the projectile is not in close contact with the inner wall of the barrel 133, the pressure of the compressed air is properly applied to the projectile in the launching step to be described later. There can be problems with delivery. Therefore, in this case, as shown in the rear of the coupling body 21, which is the projectile, when the disc-shaped hydraulic body 23 is mounted, the air pressure opened from the pressure chamber 120 is transmitted to the projectile without loss. It becomes possible. The hydraulic member 23 may be made of rubber or other resin material. When the hydraulic member 23 has a circular cross-sectional shape of the barrel 133, it is preferable that the hydraulic body 23 has a circular cross-sectional shape or a cylindrical shape, but is not limited thereto. That is, it is sufficient that the hydraulic body 23 is formed so that its cross-sectional shape corresponds to the cross-sectional shape of the barrel 133.

Referring to the impact test using the impact test device 100 having the above-described configuration as follows. First, the compressor 110 is operated and the inlet valve 134 is opened to raise the internal pressure of the pressure chamber 120 to a desired level. When the internal pressure of the pressure chamber 120 reaches a predetermined level, the discharge valve 135 may be opened to launch the projectile loaded in the barrel 133 toward the target structure 200. In this case, when the target point to which the projectile is to be impacted does not match the muzzle position of the barrel 133, the operation of precisely aiming the target point by slidingly moving back, front, left, and right on the guide rail on the base frame 150 should be preceded. The target structure 200 is a target object that is intended to observe whether damage by an impact material. In this embodiment, the above-described inner wall of the cargo hold of the LNG Carrier is implemented as it is, and the experiment is performed using the target structure 200. It was.

However, the impact test apparatus 100 is for predicting and evaluating in advance whether or not mechanical damage applied to the bottom surface of a cargo hold of an LNG carrier by various impacts such as dropping impacts, etc. This should be done. In other words, when various mechanical elements fall inside the cargo hold, for example, when the bolt or nut actually falls from the falling height of the cargo hold, the projectile must be launched at the same speed as the speed of reaching the ground, which is the speed just before hitting the ground. Experimental results close to can be obtained.

In general, when an object falls freely under the gravitational field, the ground reaching speed (v) is expressed by the following equation.

Equation 1.

Where v is the ground reaching speed, h is the drop height, and g is the acceleration of gravity.

If the drop height h = 27m inside the cargo hold,

Becomes

Thus, the projectile must also impact the target structure 200 at a launch rate of 23.02 m / s. By the way, the launch rate of the projectile is proportional to the internal pressure of the pressure chamber 120, and it is necessary to determine what value the projectile has the desired speed. Therefore, in the present invention, the speed of the projectile is precisely adjusted in the following manner.

9 is a configuration diagram of a signal detection device for determining the relationship between the speed of the projectile and the internal pressure of the pressure chamber, FIG. 10 is a graph of 'voltage vs time' obtained using the signal detection device of FIG. FIG. 11 is a graph of 'projector velocity vs. internal pressure of the pressure chamber' determined using the signal detection device of FIG. 9.

As shown in FIG. 9, a signal is obtained by inserting two wires 161 and 162 through two points P1 and P2 at a predetermined distance L at a side close to the exit of the barrel 133 loaded with the projectile. To the detector 160. At this time, the internal pressure of the pressure chamber 120 is measured and recorded. Next, when the discharge valve 135 is opened, the projectile is fired from the barrel 133 and the first wire 161 is cut off and then the second wire 162 is cut off. At this time, the waveform of the voltage (or resistance) of the signal detector 160 as shown in Figure 10 occurs. The first waveform in the graph is obtained by the disconnection of the first wire 161, and the second waveform is due to the disconnection of the second wire 162. Thus, by reading the distance between the x coordinate axis (time axis), which is the time difference between the two waveforms, the time it takes for the projectile to pass through points P1 and P2 can be known. In the above embodiment, the experiment was performed with the distance L between the points P1 and P2 as 150 mm.

Therefore, since the moving distance (distance between P1 and P2) and the required time ΔT of the projectile can be known, the launching speed v ₁ of the projectile can be calculated using the following equation.

Equation 2.

(Where L = 0.15m)

Such experiments are performed several times by varying the internal pressure of the pressure chamber 120, and then the calculated firing speed v ₁ and the pressure are displayed on the coordinates of 'pressure vs speed' and connected in a line. A graph between 'pressure vs speed' is shown as shown. Therefore, it can be seen from the graph of FIG. 11 that the internal pressure of the pressure chamber should be about 1.5 bar to obtain the speed of the projectile satisfying the ground reaching speed calculated by Equation 1, v = 23.02 m / s. .

12 is an experimental photograph showing the impact position in the target structure to perform the impact test of the projectile, Figure 13 is a photograph showing the experimental results after hitting the projectile at the impact test position of Figure 12, Figure 14 is an angle of FIG. The photograph shows an enlarged view of the mechanical damage applied to the impact test location.

In Figures 12 and 13, B1 is the intersection of the large and small wrinkles, B2 is the floor portion of the small wrinkles, B3 is the bottom surface of the membrane sheet, B4 is the weld portion of the membrane sheet, B5 is the weld portion of the small wrinkles The floor portion, B6, represents a large corrugated floor portion, respectively, and was selected for the impact test of the combination 21 of bolts and nuts. In addition, the selected large corrugated floor section S1 and the membrane sheet bottom surface S2 were selected for the impact test of the pipe support 22.

 A combination of bolts and nuts 21 and pipe supports 22 were fired at each of the impact test positions described above at a speed of dependent 23 m / s.

In FIG. 14, the photographs of (a) to (h) are photographs showing the degree of mechanical damage at positions B1, B2, B3, B4, B5, B6, S1 and S2, respectively. As a result of the experiment, the damages of B2 and B6, which are the floors of the large wrinkles and the small wrinkles, are more prominent than the other portions. The crushed depths of the B2 and B6 positions were up to about 11 mm, about 18 mmm for S1, but the extent of damage was limited to the primary barrier and no penetrating damage to gas leaks was found. Did. However, it was observed that the plywood panels had some damage in the B3, B4 and S2 positions. This is because the dent depth of the membrane sheet was observed to exceed the thickness of the membrane sheet.

As described above, the impact test apparatus of the present invention accurately predicts the degree of damage of wall structures such as the floor surface caused by the drop impact without actually dropping various mechanical elements such as bolts, nuts or piping materials in cargo holds or offshore structures of ships. Can be evaluated. In addition, according to the present invention, it is possible to predict, evaluate and manage the damage degree due to the impact of an object having a constant speed in advance not only in ships but also in offshore structures and other various industrial structures.

1 is a photograph showing an example of the actual structure of the cargo hold of the LNG Carrier.

Figure 2 is a schematic cross-sectional view showing the structure of the cargo hold inner wall of Figure 1;

3 is a photograph showing the actual structure of the inner wall of the cargo hold of the LNG Carrier.

4 is an enlarged photograph of the primary barrier 11 formed by crossing small wrinkles and large wrinkles.

5A and 5B are photographs of a combination of bolts and nuts and pipe supports, examples of drop impacts.

6 is a block diagram of an impact test apparatus according to the present invention.

Figure 7 is a cross-sectional view showing a case where the combination of the projectile bolt and nut is loaded in the barrel.

8 is a longitudinal sectional view of the barrel with the projectile of FIG. 7 loaded;

9 is a block diagram of a signal detection device for determining the relationship between the speed of the projectile and the internal pressure of the pressure chamber.

10 is a graph of 'voltage vs time' obtained using the signal detection device of FIG.

FIG. 11 is a graph of 'projector velocity vs. internal pressure of the pressure chamber' determined using the signal detection device of FIG.

12 is an experimental photograph showing the impact position in the target structure to perform an impact test of the projectile.

13 is a photograph showing the experimental results after hitting the projectile at the impact test position of FIG.

14 is an enlarged photograph showing mechanical damage applied to each impact test position of FIG. 13.

<Description of the symbols for the main parts of the drawings>

100: impact test apparatus 110: compressor

111: compressor cable 120: pressure chamber

131: inlet pipe 132: discharge pipe

133: barrel 134: inlet valve

135: discharge valve 136: piping connection material

141: outer support 142: inner support

150: base frame 151,152: guide rail

153: barrel support 200: target structure

Claims (5)

In order to predict and evaluate the degree of impact caused by falling objects, etc. applied to ships, offshore structures and other industrial structures, a compressor for supplying compressed air, one side of the pressure chamber connected to the compressor and accumulating pressure, Consists of a barrel connected to the other side, so as to launch the projectile loaded in the barrel by the operation of the discharge valve connected to the barrel, The barrel is installed so as to be movable in front, rear, left and right on the base frame, and the hydraulic test body having a cross-sectional shape corresponding to the cross-sectional shape of the barrel is inserted in the rear of the position where the projectile is loaded in the barrel. delete delete The method of claim 1, And a discharge tube is coupled between the other side of the pressure chamber and the barrel, and the discharge valve is formed on the discharge tube. The method of claim 1, Through-holes are formed at two points on the end side of the barrel from which the projectile is fired, and a wire is inserted into each of the through-holes and connected to a signal detector capable of measuring resistance or voltage. Impact testing device.

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