Drop hammer acceleration measurement method

Abstract

The application provides a drop hammer acceleration measurement method, which can be used for calibrating dynamic force measurement of a drop hammer structure. The method comprises the following steps: firstly, designing the drop hammer structure through finite element simulation, analyzing the impact process of the drop hammer, and calculating the average acceleration of the drop hammer at the force peak value; secondly, arranging points on the upper surface of the drop hammer through an impact experiment, measuring the acceleration of any group of points on the upper surface of the drop hammer at the force peak value by using an acceleration sensor, then performing weight summation calculation on the arranged acceleration, and obtaining the weighted acceleration of different points by repeating the above operation; finally, comparing the average acceleration and the weighted acceleration, and the smaller the error between the average acceleration and the weighted acceleration, the more accurate the acceleration measurement result of the drop hammer. The application has high measurement precision, low cost, and wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of dynamic measurement, in particular to a method for measuring the acceleration of a falling weight. Background Art

[0002] With the modernization of my country's economy, especially the rapid development of industrial technologies such as mechanical design and manufacturing, aerospace, etc., there is an increasing demand for dynamic measurement such as calibration of dynamic force. Taking mass as the intermediate quantity, the use of laser interferometry to measure the acceleration of a falling hammer is becoming a key means to improve the accuracy of dynamic impact force measurement. For example, in patent CN102252803A - a laser absolute method dynamic force calibration device, it is proposed to use a laser interferometer to measure the acceleration of a falling hammer. However, the laser interferometer is easily affected by external environments such as light, and is costly and has a long preparation period, making it difficult to promote. Installing an acceleration sensor at the characteristic point of the falling hammer to measure its acceleration is an attempt. For example, in patent CN201120462537 - a portable dynamic force calibration device, it is proposed to use only one acceleration sensor to measure the acceleration of the falling hammer. However, the falling hammer is not an absolute rigid body. During the impact process, due to the uneven distribution of acceleration, the acceleration of the falling hammer center point measured alone is used to represent the overall acceleration of the falling hammer, which has a large error. At present, there is no method for measuring the acceleration of a falling weight with high precision, low cost and convenient application in dynamic measurement technology. Therefore, studying a method for measuring the acceleration of a falling weight has important practical engineering value. Summary of the Invention

[0003] The present invention provides a method for measuring the acceleration of a falling weight, which has high measurement accuracy and low cost and has broad application prospects.

[0004] The present invention adopts the following technical solutions.

[0005] A drop hammer acceleration measurement method can be used to calibrate the dynamic force measurement of a drop hammer structure. The method first designs the drop hammer structure through finite element simulation, analyzes the impact process of the drop hammer, and calculates the average acceleration of the drop hammer at the peak force. Secondly, through an impact experiment, points are distributed on the upper surface of the drop hammer, and the acceleration of any group of points on the upper surface of the drop hammer at the peak force is measured using an acceleration sensor. The accelerations of the distributed points are then weighted and summed. By repeating the above operation, weighted accelerations of different distributed points are obtained. Finally, the average acceleration and the weighted acceleration are compared. The smaller the error between the two, the more accurate the drop hammer acceleration measurement result.

[0006] The method comprises the following steps:

[0007] Step S1: Based on finite element analysis, the drop hammer structure is designed and the drop hammer is meshed.

[0008] Step S2: Modeling is performed according to actual test conditions, and finite element simulation is performed on the impact process of the drop hammer.

[0009] Step S3: Select all nodes on the drop hammer from the simulation results and extract the acceleration of the nodes at the peak force. The calculation formula is: Where m is the number of all nodes on the falling hammer, a i is the acceleration of each node on the falling weight, is the average acceleration of all nodes on the falling weight;

[0010] Step S4: Select several nodes on the upper surface of the falling weight from the simulation results, perform weighted processing on the acceleration of the selected nodes, and calculate: Where n is the number of nodes selected on the upper surface of the drop weight, a j is the acceleration magnitude of each selected node, c j The weight ratio of the acceleration of each selected node, and satisfy a' is the weighted acceleration of the selected node;

[0011] Step S5: During the actual test, based on the nodes selected by simulation analysis, points are distributed on the upper surface of the drop hammer, and several acceleration sensors are installed at the locations of the distribution points. Through impact experiments, the acceleration magnitude of the distribution points at the peak force is obtained, and its weighted acceleration is calculated.

[0012] Step S6: Compare the average acceleration and the weighted acceleration, and calculate the error between the two: The smaller Δa is, the more accurate the acceleration measurement of the falling weight is.

[0013] The drop hammer structure in step S1 includes a drop hammer, and the specific shape and size of the drop hammer are designed according to specific requirements.

[0014] In step S4, the method of selecting nodes on the upper surface of the drop weight includes a method of distributing nodes along the four sides or along the radial direction, and when selecting feature points of the distribution, it includes selecting the center point and the symmetrical point.

[0015] In step S4, the Δa value is calculated according to the point distribution method along the periphery or the point distribution method along the radial direction, and the point distribution method of the nodes is selected according to the method with the smaller Δa.

[0016] The acceleration sensor in step S5 is used to synchronously and in real time measure the acceleration of any group of points on the upper surface of the falling weight.

[0017] The drop hammer structure is based on a dynamic force calibration device, which includes a guide mechanism, a base, a force sensor, a buffer pad and several acceleration sensors; the guide mechanism is vertically arranged, and the drop hammer is placed on the guide mechanism.

[0018] A force sensor (3) is placed on the base (2); the buffer pad (4) is placed centrally on the force sensor (3); the guide mechanism (1) is used to lift and release the drop hammer (5), and can adjust the release height of the drop hammer; the acceleration sensor (6) is fixedly mounted on the drop hammer; after being released by the guide mechanism, the drop hammer performs free fall motion and impacts the force sensor via the buffer pad at the end of the fall.

[0019] The drop hammer is a cylinder.

[0020] The drop hammer has an aspect ratio of 3:1, a mass of 50 kg, and a release height of 500 mm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The original information of the method provided by the present invention is easy to obtain, the analysis is convenient and the operability is strong.

[0023] 2. The acceleration sensor device used in the present invention is cheaper and has a great cost advantage.

[0024] 3. The present invention uses a combination of multiple acceleration sensors, which has higher measurement accuracy than installing only one acceleration sensor on the drop weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0026] Attachment Figure 1 is a schematic diagram of the device structure of an embodiment of the present invention;

[0027] Attachment Figure 2 is a schematic diagram of a finite element model of a drop hammer impact process according to an embodiment of the present invention;

[0028] Attachment Figure 3 Schematic diagram of radial acceleration of a node on the upper surface of a falling weight according to an embodiment of the present invention;

[0029] Attachment Figure 4 Schematic diagram of the distribution of points along the periphery of the upper surface of the drop hammer according to an embodiment of the present invention;

[0030] Attachment Figure 5 Schematic diagram of radial distribution of points on the upper surface of the drop weight according to an embodiment of the present invention;

[0031] In the figure: 1-guide mechanism, 2-base, 3-force sensor, 4-buffer pad, 5-drop weight, 6-acceleration sensor. DETAILED DESCRIPTION

[0032] As shown in the figure, a drop hammer acceleration measurement method can be used to calibrate the dynamic force measurement of the drop hammer structure. The method first designs the drop hammer structure through finite element simulation, analyzes the impact process of the drop hammer, and calculates the average acceleration of the drop hammer at the peak force. Secondly, through the impact experiment, points are distributed on the upper surface of the drop hammer, and the acceleration sensor is used to measure the acceleration of any group of points on the upper surface of the drop hammer at the peak force. Then, the acceleration of the distributed points is weighted and summed. By repeating the above operation, the weighted acceleration of different distribution points is obtained. Finally, the average acceleration and the weighted acceleration are compared. The smaller the error between the two, the more accurate the acceleration measurement result of the drop hammer.

[0033] The method comprises the following steps:

[0034] Step S1: Based on finite element analysis, the drop hammer structure is designed and the drop hammer is meshed.

[0035] Step S2: Modeling is performed according to actual test conditions, and finite element simulation is performed on the impact process of the drop hammer.

[0036] Step S3: Select all nodes on the drop hammer from the simulation results and extract the acceleration of the nodes at the peak force. The calculation formula is: Where m is the number of all nodes on the falling hammer, a i is the acceleration of each node on the falling weight, is the average acceleration of all nodes on the falling weight;

[0037] Step S4: Select several nodes on the upper surface of the falling weight from the simulation results, perform weighted processing on the acceleration of the selected nodes, and calculate: Where n is the number of nodes selected on the upper surface of the drop weight, a j is the acceleration magnitude of each selected node, c j The weight ratio of the acceleration of each selected node, and satisfy a' is the weighted acceleration of the selected node;

[0038] Step S5: During the actual test, based on the nodes selected by simulation analysis, points are distributed on the upper surface of the drop hammer, and several acceleration sensors are installed at the locations of the distribution points. Through impact experiments, the acceleration magnitude of the distribution points at the peak force is obtained, and its weighted acceleration is calculated.

[0039] Step S6: Compare the average acceleration and the weighted acceleration, and calculate the error between the two: The smaller Δa is, the more accurate the acceleration measurement of the falling weight is.

[0040] The drop hammer structure in step S1 includes a drop hammer, and the specific shape and size of the drop hammer are designed according to specific requirements.

[0041] In step S4, the method of selecting nodes on the upper surface of the drop weight includes a method of distributing nodes along the periphery or along the radial direction, and when selecting feature points of the distribution, it includes selecting the center point and the symmetrical point.

[0042] In step S4, the Δa value is calculated according to the circumferential distribution method or the radial distribution method, and the node distribution method is selected according to the method with the smaller Δa.

[0043] The acceleration sensor in step S5 is used to synchronously and in real time measure the acceleration of any group of points on the upper surface of the falling weight.

[0044] The drop hammer structure is based on a dynamic force calibration device, which includes a guide mechanism, a base, a force sensor, a buffer pad and several acceleration sensors; the guide mechanism is vertically arranged, and the drop hammer is placed on the guide mechanism.

[0045] A force sensor 3 is placed on the base 2; the buffer pad 4 is placed centered on the force sensor 3; the guide mechanism 1 is used to lift and release the drop hammer 5, and can adjust the release height of the drop hammer; the acceleration sensor 6 is fixedly installed on the drop hammer; after the drop hammer is released by the guide mechanism, it performs free fall motion and impacts the force sensor through the buffer pad at the end of the fall.

[0046] The drop hammer is a cylinder.

[0047] The drop hammer has an aspect ratio of 3:1, a mass of 50 kg, and a release height of 500 mm.

[0048] In this embodiment, step S1 is implemented, and the drop weight 5 is designed to be a cylinder with an aspect ratio of 3:1, a mass of 50 kg, and a release height of 500 mm.

[0049] By implementing step S2, a finite element model of the impact process of the drop hammer 5 can be obtained as follows: Figure 2 shown.

[0050] After executing step S3 and completing the model analysis, the calculation result is a=9040109.135mm / s 2 .

[0051] By implementing step S4, the acceleration weight ratio of any group of points on the upper surface of the falling hammer can be obtained. The acceleration of the upper surface of the falling hammer along the radial direction is as follows: Figure 3 shown.

[0052] In step S5, since the drop hammer 5 is a cylinder, its acceleration is approximately symmetrically distributed during the impact process, and points can be arranged along the four sides of the upper surface of the drop hammer as follows: Figure 4 As shown, the acceleration of each point is a1 = 9164340 mm / s 2 , a2=9176980mm / s 2, a3=9105090mm / s 2 , a4=9108160mm / s 2 , a5=9377870mm / s 2 ; Points can be arranged radially on the upper surface of the falling hammer as follows Figure 5 As shown, the acceleration of each point is a1 = 9164340 mm / s 2 , a2=9176980mm / s 2 , a3=8866350mm / s 2 .

[0053] When the points are distributed along the four sides of the upper surface of the falling hammer, if the acceleration weight ratio of each point is c1 = 0, c2 = 0.5, c3 = 0, c4 = 0.5, c5 = 0, the weighted acceleration a' = 9142570 mm / s 2 , and the error between a and a' is: Δa = 1.13%; Similarly, when the points are distributed along the radial direction on the upper surface of the falling hammer, if the weight of each point is c1 = 0, c2 = 0.5, c3 = 0.5, the weighted acceleration can be obtained as a' = 9021665 mm / s 2 , and the error between a and a' is: Δa = 0.2%. Therefore, it can be considered that the method of measuring the acceleration of the falling weight along the radial distribution method adopted in this embodiment is more accurate than the method of distributing points along the circumference.

[0054] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A drop weight acceleration measurement method, which can be used to calibrate the dynamic force measurement of a drop weight structure, is characterized by: The method first designs a drop hammer structure through finite element simulation, analyzes the impact process of the drop hammer, and calculates the average acceleration of the drop hammer at the peak force; Secondly, through the impact experiment, points are distributed on the upper surface of the falling hammer. The acceleration of any group of points on the upper surface of the falling hammer at the peak force is measured using an accelerometer. The acceleration of the distributed points is then weighted and summed. By repeating the above operation, the weighted acceleration of different distributed points is obtained. Finally, the average acceleration and the weighted acceleration are compared. The smaller the error between the two, the more accurate the acceleration measurement result of the falling hammer. The method comprises the following steps: Step S1: Based on finite element analysis, design the drop hammer structure and perform mesh division on the drop hammer; Step S2: Modeling based on actual test conditions and performing finite element simulation on the impact process of the drop hammer; Step S3: Select all nodes on the drop hammer from the simulation results and extract the acceleration of the nodes at the peak force. The calculation formula is: Where m is the number of all nodes on the falling hammer, a i is the acceleration of each node on the falling weight, is the average acceleration of all nodes on the falling weight; Step S4: Select several nodes on the upper surface of the falling weight from the simulation results, perform weighted processing on the acceleration of the selected nodes, and calculate: Where n is the number of nodes selected on the upper surface of the drop weight, a j is the acceleration magnitude of each selected node, c j The weight ratio of the acceleration of each selected node, and satisfy a' is the weighted acceleration of the selected node; Step S5: During the actual test, based on the nodes selected by the simulation analysis, several acceleration sensors are installed at the locations of the nodes. Through the impact test, the acceleration of the nodes at the peak force is obtained, and the weighted acceleration is calculated. Step S6: Compare the average acceleration and the weighted acceleration, and calculate the error between the two: The smaller Δa is, the more accurate the acceleration measurement of the falling weight is.

2. A method for measuring falling weight acceleration according to claim 1, characterized in that: The drop hammer structure in step S1 includes a drop hammer, and the specific shape and size of the drop hammer are designed according to specific requirements.

3. The method for measuring falling weight acceleration according to claim 1, wherein: In step S4, the method of selecting nodes on the upper surface of the drop weight includes a method of distributing nodes along the four sides or along the radial direction, and when selecting feature points of the distribution, it includes selecting the center point and the symmetrical point.

4. A method for measuring falling weight acceleration according to claim 3, characterized in that: In step S4, the Δa value is calculated according to the point distribution method along the periphery or the point distribution method along the radial direction, and the point distribution method of the nodes is selected according to the method with the smaller Δa.

5. The method for measuring falling weight acceleration according to claim 1, wherein: The acceleration sensor in step S5 is used to synchronously and in real time measure the acceleration of any group of points on the upper surface of the falling weight.

6. A method for measuring falling weight acceleration according to claim 1, characterized in that: The drop hammer structure is based on a dynamic force calibration device, which includes a guide mechanism, a base, a force sensor, a buffer pad and several acceleration sensors; the guide mechanism is vertically arranged, and the drop hammer is placed on the guide mechanism.

7. A method for measuring falling weight acceleration according to claim 6, characterized in that: A force sensor (3) is placed on the base (2); the buffer pad (4) is placed centrally on the force sensor (3); the guide mechanism (1) is used to lift and release the drop hammer (5), and can adjust the release height of the drop hammer; the acceleration sensor (6) is fixedly mounted on the drop hammer; after being released by the guide mechanism, the drop hammer performs free fall motion and impacts the force sensor via the buffer pad at the end of the fall.

8. The method for measuring falling weight acceleration according to claim 6, wherein: The drop hammer is a cylinder.

9. The method for measuring falling weight acceleration according to claim 6, wherein: The drop hammer has an aspect ratio of 3:1, a mass of 50 kg, and a release height of 500 mm.

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