Test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact

Abstract

The present invention provides a cumulative impact test method and a test method for measuring the P-a curve of a steel anti-collision facility based on the cumulative impact. The anti-collision sample is fixed on a rigid wall, a rigid vehicle is used to impact the anti-collision sample at a certain speed and mass, the collision force between the anti-collision sample and the rigid vehicle is detected, and a deformation time history curve of the anti-collision test is inferred according to the collision force time history curve, and a cumulative impact method is used until the sample is completely crushed; finally, the P-a (impact force-impact depth) curves obtained by multiple impacts are "spliced" to obtain the impact force-impact depth curve of the anti-collision sample at the speed, thereby providing a basis for evaluating the energy dissipation effect of the anti-collision device and improving the accuracy of data collection.

Description

Technical Field

[0001] The invention relates to a method for detecting the performance of a ship anti-collision facility, in particular to a test method for measuring the Pa performance of a steel anti-collision facility based on cumulative impact. Background Art

[0002] The scale and volume of anti-collision facilities are huge. It is technically and cost-ineffective to use full-scale model tests to verify the energy dissipation effect of anti-collision facilities. Since the impact force-deformation curve of the anti-collision device is sensitive to speed, a deformation curve of the impact force-impact depth relationship of the anti-collision device at a certain speed is proposed. The impact force-deformation curve of the anti-collision device is an important indicator for measuring the protection performance, but there are the following difficulties in the determination of this curve: speed response, different impact speeds, materials reflect different dynamic constitutive relationships, especially for steel, under low-speed impact, the mechanical properties of materials at different speeds have significant differences, so the impact force-deformation curve must be determined by dynamic impact test methods; at the same time, since the impact force-deformation curve of the anti-collision device is sensitive to speed, the speed cannot be similarly compared in the test, so the mass of the impactor must be large, but since the mass of the ship is very large, generally 1000DWT, 2000DWT..., under test conditions, the impactor cannot be so large; and there are currently two main technical paths for impact force testing under large impact force impact:

[0003] Solution 1: Arrange an acceleration sensor on the impact body, and obtain the impact force by collecting the acceleration value at the moment of impact, F=ma; the existing problems are: the accelerometers are arranged at different measuring points, and the acceleration values ​​are very different; the instantaneous acceleration value of the impact force is easily overloaded, resulting in sampling distortion; Solution 2: Direct force measurement method, the collection of automobile collision collision force is to arrange a piezoelectric force sensor at the collision position of the vehicle to directly collect the impact force; the existing problems are: the range of a single sensor is limited, and it is difficult to meet the measurement needs for large impacts; therefore, we proposed a test method for the Pa performance determination of steel anti-collision facilities based on cumulative impact. Summary of the invention

[0004] To solve the above problems, the present invention discloses a test method for measuring the Pa performance of steel anti-collision facilities based on cumulative impact, which realizes the direct collection of a large range of impacts and improves the accuracy of data collection; by detecting the direct collision force between the test device and the impact vehicle and detecting the deformation of the test device, the impact force-impact depth curve of the anti-collision device at the speed can be obtained, providing a basis for evaluating the energy dissipation effect of the anti-collision device.

[0005] The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact includes the following steps:

[0006] Step 1: Fix the anti-collision sample on a rigid wall, use a rigid car to hit the anti-collision sample at a certain speed and mass, determine the collision force borne by the anti-collision sample by detecting the reaction force transmitted to the rigid wall by the anti-collision sample, and determine the Pa (Percussive force-strain) curve of the anti-collision sample under a single impact based on the deformation time history curve of the anti-collision sample obtained by reverse calculation of the collision force;

[0007] Step 2: Then use the rigid vehicle to impact the anti-collision specimen multiple times at the same speed and the same mass, and use the cumulative impact method until the specimen is completely crushed; finally, the Pa (impact force-impact depth) curves obtained from multiple impacts are "joined" to obtain the Pa (impact force-impact depth) curve under the crushing of the anti-collision specimen.

[0008] Furthermore, in step 1, after the impacted sample is compressed and deformed, the impact force is transmitted to the reaction wall, and the impact force acts on the force collecting plate, and multiple piezoelectric force sensors are distributed between the force collecting plate and the reaction wall; through the data acquisition system, the data signals of each force sensor are synchronously collected, and the complete impact force time domain signal is obtained after time domain superposition;

[0009]

[0010]

[0011] Where: P d (t): time domain signal of the impact force

[0012] Time domain signal of the impact force borne by a single sensor

[0013] M: impact vehicle mass (T)

[0014] V: initial impact velocity (m / s)

[0015] a(t): Time domain signal of anti-collision specimen deformation (m)

[0016] t: impact time (s).

[0017] Furthermore, the step 2 is specifically as follows: while keeping the impact speed unchanged, the entire impact process is cut into multiple sections, and the required impact mass is divided into multiple times, M=n*m1, N is the number of impacts; N times of impacts of M mass are used to replace one impact of M mass; through multiple loading and unloading of the anti-collision test, a complete impact force-impact depth curve can be obtained, which makes one impact of a large mass object have the same effect as multiple impacts of a small mass, and by "splicing" the impact force-deformation curves obtained from multiple impacts of a small mass, finally the impact force-deformation curve of the entire anti-collision device is obtained.

[0018] Furthermore, the range of N values ​​is: when the engineering error is allowed within 10%, n is 10; when the engineering error is allowed within 15%, n is 12; when the engineering error is allowed within 10%, the impact speed should be greater than 3.8m / s.

[0019] Furthermore, the specific steps for “joining” the impact force-deformation curve are as follows:

[0020] Step a: Split the Pa curve obtained from a single impact into a loading segment and a recovery segment, where the loading segment refers to the deformation curve a i (t)P when the value increases i (t) The value corresponding to the curve, the recovery section refers to the deformation curve a i (t) P when the value decreases i (t) The value corresponding to the curve; after the splitting is completed, the data of the loading segment Pa is assigned to the newly created array;

[0021] Step b: Then continue to split the next Pa curve according to the order of impact, and still only keep the loading segment data, among which the deformation data a i All data in (t) + previous paragraph a i-1 (t) The maximum value in the array, a i (t), P i (t) The data is assigned to the newly created array; all the Pa curve data are “merged” in sequence, and finally the complete Pa curve of the anti-collision specimen can be obtained.

[0022] Beneficial effects of the present invention:

[0023] 1. Ensure that the impact vehicle is in equivalent uniform motion before impact, ensure measurement accuracy, and ensure that the test results are not affected by the traction force of the steel rope;

[0024] 2. The impact force measurement method proposed in the solution of the present invention realizes the direct collection of a large range of impacts; through the data acquisition system, the data signals of each force sensor are synchronously collected, and the complete impact force time domain signal is obtained after time domain superposition.

[0025] 3. The impact force-deformation curve is obtained by dynamic impact test. The impact force-deformation curves obtained by multiple impacts of small masses are combined to obtain the overall impact force-deformation curve of the anti-collision device, which provides a basis for evaluating the energy dissipation effect of the anti-collision device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 , a flow chart of the present invention;

[0027] Figure 2 , a schematic diagram of the decoupling designed by the present invention;

[0028] Figure 3 , a flow chart of "joining" the impact force-deformation curve of the present invention;

[0029] Figure 4 , The Pa curves obtained by impacting 12t four times before and after splicing are compared with the Pa curve of 48t impact once. DETAILED DESCRIPTION

[0030] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0031] like Figure 1 As shown, a test method for measuring the Pa performance of a steel anti-collision facility based on cumulative impact in this embodiment is to fix the anti-collision sample on a rigid wall, use a rigid vehicle to impact the anti-collision sample at a certain speed and mass, and detect the direct collision force between the anti-collision sample and the impact vehicle and infer the deformation time history curve of the anti-collision test according to the collision force time history curve. The Pa (impact force-impact depth) curve of the anti-collision device at the speed can be obtained, which provides a basis for evaluating the energy dissipation effect of the anti-collision device, and includes the following steps:

[0032] Step 1: Design the impact force measurement and acquisition system;

[0033] Step 2: Design the impact vehicle traction and automatic unhooking system; when the impact vehicle is towed, a towing hook must be provided at the front end, and a towing steel rope must be hung on the towing hook. Before the impact vehicle hits the specimen, the steel rope must be disconnected from the impact vehicle, and an unhooking system must be designed to ensure that the impact vehicle is in equivalent uniform motion before the impact;

[0034] Step 3: Design a curve for the impact force-deformation measurement of the anti-collision device based on cumulative impact. In step 1, the impacted sample is compressed and deformed, and then transmits the impact force to the reaction wall. The impact force acts on the force collecting plate, and multiple piezoelectric force sensors are distributed between the force collecting plate and the reaction wall. The data signals of each force sensor are synchronously collected through the data acquisition system, and the complete impact force time domain signal is obtained after time domain superposition.

[0035]

[0036]

[0037] Where: P d (t): time domain signal of the impact force

[0038] Pd i (t): time domain signal of the impact force borne by a single sensor

[0039] M: impact vehicle mass (T)

[0040] V: initial impact velocity (m / s)

[0041] a(t): Time domain signal of anti-collision specimen deformation (m)

[0042] t: impact time (s).

[0043] In the step 2: when the impact vehicle is towed, a towing hook must be designed at the front end, and a towing steel rope must be hung on the towing hook. Before the impact vehicle hits the sample, the steel rope must be disconnected from the impact vehicle to ensure that the impact vehicle is in equivalent uniform motion before the impact, to ensure measurement accuracy, and to ensure that the test results are not affected by the traction force of the steel rope; if the steel rope cannot be disconnected in time, the instantaneous impact of the impact vehicle after the impact will cause the steel rope to shake violently, causing safety risks.

[0044] Therefore, the step 2 is specifically as follows:

[0045] Step 2.1: During construction, ensure that the horizontal movement distance of the impact vehicle is always greater than the falling distance of the drop weight by controlling the length of the track, drop weight and steel rope; the difference between the two should be greater than 5 meters;

[0046] Step 2.2: An inverted hook is set at the front end of the impact vehicle. When the heavy hammer falls to the ground first, the traction rope loses the traction force of horizontal movement, and the impact vehicle continues to move due to inertia. The steel rope can automatically fall off from the inverted hook to achieve unhooking. Figure 2 As shown;

[0047] Step 2.3: At the unhooking position, a sand pit is set under the track. The traction steel rope falls into the sand pit to avoid affecting the operation of the impact vehicle on the track.

[0048] The step 3 is specifically as follows: while keeping the impact speed unchanged, the entire impact process is divided into multiple sections, and the required impact mass is divided into multiple times, M=n*m1, N is the number of impacts; N times of impacts of M mass are used to replace one impact of M mass; through multiple loading and unloading of the anti-collision test, a complete impact force-impact depth curve can be obtained, which makes one impact of a large mass object have the same effect as multiple impacts of a small mass, and by "joining" the impact force-deformation curves obtained from multiple impacts of a small mass, finally the impact force-deformation curve of the entire anti-collision device is obtained.

[0049] like Figure 3 As shown in the figure, the specific steps of “joining” the impact force-deformation curve are:

[0050] Step a: Split the Pa curve obtained from a single impact into a loading segment and a recovery segment, where the loading segment refers to the deformation curve a i (t)P when the value increases i (t) The value corresponding to the curve, the recovery section refers to the deformation curve a i (t) P when the value decreases i (t) The value corresponding to the curve; after the splitting is completed, the data of the loading segment Pa is assigned to the newly created array;

[0051] Step b: Then continue to split the next Pa curve according to the order of impact, and still only keep the loading segment data, among which the deformation data a i All data in (t) + previous paragraph a i-1 (t) The maximum value in the array, a i (t), P i (t) The data is assigned to the newly created array; all the Pa curve data are “merged” in sequence, and finally the complete Pa curve of the anti-collision specimen can be obtained.

[0052] Furthermore, in step 3: while keeping the impact speed unchanged, the entire impact process is cut into multiple sections, and the required impact mass is divided into multiple times, M=n*m1, N is the number of impacts; N times of M1 mass impacts are used to replace one M mass impact; through multiple loading and unloading of the anti-collision test, a complete impact force-impact depth curve can be obtained, which makes one impact of a large mass object equal to multiple impacts of a small mass, and by "joining" the impact force-deformation curves obtained by multiple impacts of a small mass, finally the overall impact force-deformation curve of the anti-collision device is obtained;

[0053] M=N*m1

[0054] M: Equivalent impact mass of the fortified ship type

[0055] M1: The mass of the impactor at a low mass

[0056] The range of N values ​​is: when the engineering error is allowed to be within 10%, n is 10; when the engineering error is allowed to be within 15%, n is 12; when the engineering error is allowed to be within 10%, the impact speed should be greater than 3.8m / s.

[0057] This embodiment also provides a verification method for the accuracy of the experimental method. It is assumed that the collision test can crush the test with a mass of M in one collision. However, due to the limitation of conditions in the test, the impact vehicle is changed to M / n, which is divided into N cumulative collisions. Since the rigid vehicle itself does not absorb energy, the kinetic energy is transferred to the collision test specimen. Therefore, the energy transferred to the collision test specimen by a rigid vehicle with a mass of m and a rigid vehicle with a mass of m / n after n collisions is the same.

[0058] The sample is hit again with the same mass and the same speed. The difference between this and the original mass impact is the change in speed. The difference between the split impact and the single impact is that in the split impact, the speed of each impact is the same initial speed, while in the single impact, the speed of each impact point corresponding to the split impact is gradually attenuated. The following discusses the change in impact force caused by the difference in speed.

[0059] The reaction force of any structure can be decomposed into elastic force and damping force (Equation 3). At the same time, since steel satisfies the Cowper-Symonds constitutive relation (Equation 4), P s (t) and P d (t) also satisfies formula (5)

[0060] P d (t) = P s (t)+P v (t) (3)

[0061]

[0062]

[0063] Where P s (t) has nothing to do with speed, but only with impact depth. Therefore, when the impact depth is constant:

[0064]

[0065] therefore:

[0066] Where: P s (t): time domain signal of elastic force of anti-collision specimen

[0067] P v (t): Time domain signal of the damping force of the anti-collision specimen

[0068] Time domain signal of the impact force borne by a single sensor

[0069] Impact speed

[0070] a0: initial size of the impact specimen

[0071] The collision velocity of the sample under the nth impact

[0072] C and D are constant values, C = 40.4s -1 and D=5

[0073] Therefore, the error in the impact force obtained by using a rigid car with mass m / n for n collisions and a rigid car with mass m for one collision can be estimated by equation 7. Due to the multiple collisions, the initial impact velocity can be controlled constant, so You can take a fixed value, It can be calculated back based on the energy (because the impact vehicle and the anchor wall are both rigid, each impact of the impact vehicle transfers energy to the anti-collision specimen), therefore:

[0074] Among them, E n =E / n

[0075] m is the mass of a single impact;

[0076] Example: The initial speed of the rigid vehicle is 4m / s. The impact force of a 120t rigid vehicle hitting once and a 12t rigid vehicle hitting 10 times are compared. The results show that compared with a single impact, the impact mass is divided into 1 / 10. After ten impacts, the error of the impact force gradually increases, and the maximum error is 9%, which meets the requirements of engineering detection.

[0077]

[0078] At the same time, the error under different impact speeds was compared. The analysis showed that the greater the speed, the smaller the error. Under the impact number of about 10 times, this test method is suitable for the impact speed of 3-5m / s.

[0079]

[0080] Therefore, by using the cumulative calculation method, the error is within a controllable range, and the stress-strain curve of the sample can be obtained by cumulative energy.

[0081] like Figure 4 The Pa curves obtained by 12t impact 4 times before and after splicing are compared with the Pa curves obtained by 48t impact once; Figure 4 (a) before splicing; Figure 4 (b) After splicing.

[0082] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above technical features.

Claims

1. The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact is characterized by: The following steps are involved: Step 1: Fix the anti-collision sample on a rigid wall, use a rigid car to hit the anti-collision sample at a certain speed and mass, determine the collision force borne by the anti-collision sample by detecting the reaction force transmitted to the rigid wall by the anti-collision sample, and determine the Pa impact force-impact depth curve of the anti-collision sample under a single impact based on the deformation time history curve of the anti-collision sample obtained by reverse calculation based on the collision force; Step 2: Then the rigid car is used to impact the anti-collision specimen multiple times at the same speed and the same mass, and the cumulative impact method is used until the specimen is completely crushed; finally, the Pa impact force-impact depth curves obtained from multiple impacts are "joined" to obtain the Pa impact force-impact depth curve under the crushing of the anti-collision specimen; The specific steps for "joining" the Pa impact force-impact depth curve are: Step a: Split the Pa impact force-impact depth curve obtained from an impact into a loading section and a recovery section, where the loading section refers to the deformation curve a i (t)P when the value increases i (t) The value corresponding to the curve, the recovery section refers to the deformation curve a i (t) P when the value decreases i (t) The value corresponding to the curve; after the splitting is completed, the data of the loading segment Pa is assigned to the newly created array; Step b: Then continue to split the next Pa impact force-impact depth curve according to the impact order, and still only retain the loading segment data, among which the deformation data a i All data in (t) + previous paragraph a i-1 (t) The maximum value in the array, a i (t), P i (t) Data is assigned to the newly created array; All Pa impact force-impact depth curve data are "merged" in sequence, and finally a complete Pa impact force-impact depth curve of the anti-collision specimen is obtained.

2. The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact according to claim 1 is characterized in that: In the step 1, the impacted sample is compressed and deformed, and then the impact force is transmitted to the reaction wall. The impact force acts on the force collecting plate, and multiple piezoelectric force sensors are distributed between the force collecting plate and the reaction wall. The data signals of each force sensor are synchronously collected through the data acquisition system, and the complete impact force time domain signal is obtained after time domain superposition. Where: P d (t): time domain signal of the impact force Time domain signal of the impact force borne by a single sensor M: Rigid vehicle mass (T) V: initial impact velocity (m / s) a(t): Time domain signal of anti-collision specimen deformation (m) t: impact time (s).

3. The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact according to claim 1 is characterized in that: The step 2 is specifically as follows: while keeping the impact speed unchanged, the entire impact process is divided into multiple impacts, and the required impact mass is divided into multiple parts, M=n*m1, where n is the number of impacts; one impact of M mass is replaced by n impacts of m1 mass; a complete Pa impact force-impact depth curve is obtained by multiple loading and unloading of the anti-collision test; one impact of a large mass object is equal to multiple impacts of a small mass, and the Pa impact force-impact depth curves obtained by multiple impacts of the small mass are "spliced" to finally obtain the overall impact force-impact depth curve of the anti-collision device.

4. The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact according to claim 3 is characterized in that: The range of n values ​​is: when the engineering error is allowed to be within 10%, n is 10; when the engineering error is allowed to be within 15%, n is 12; when the engineering error is allowed to be within 10%, the impact speed should be greater than 3.8m / s.

5. The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact according to claim 1 is characterized in that: When the falling weight is towed by a rigid vehicle, a towing hook must be provided at the front end, and a towing steel rope must be hung on the towing hook. Before the rigid vehicle hits the specimen, the steel rope must be disconnected from the rigid vehicle, and a decoupling system must be designed to ensure that the rigid vehicle is in equivalent uniform motion before the impact.

6. The test method for determining the Pa performance of steel anti-collision facilities based on cumulative impact according to claim 5 is characterized in that: Ensure that the horizontal moving distance of the rigid car is always greater than the falling distance of the drop weight; an inverted hook is set at the front end of the rigid car. When the drop weight falls to the ground first, the traction steel rope loses the traction force for horizontal movement, and the rigid car continues to move due to inertia, and the steel rope automatically falls off from the inverted hook to achieve unhooking; a sand pit is set under the track at the unhooking point, and the traction steel rope falls into the sand pit to avoid affecting the operation of the rigid car on the track.

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