JP2008224632A - Method for measuring impact absorption energy using dropping weight type impact testing machine, and dropping weight type impact testing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for testing impact of dropping weight type that measures impact absorption energy and is suited for a DWTT test especially, in conformance with API standards, and a machine for testing impact of dropping weight used for it. <P>SOLUTION: The method for measuring impact absorption energy using the machine for testing impact of dropping weight, measures the impact absorption energy of a test specimen by using the kinetic energy when a dropping weight is freely fallen without colliding the weight to the test specimen and the kinetic energy after the weight is collided to the test specimen and the test specimen is broken. The machine comprises the weight, a dropping weight guidance mechanism having a mechanism for moving and holding the weight in the vertical direction, a speed detector for detecting the speed of the weight that falls, and a speed detection mechanism having a pass-detection sensor for detecting that the weight felt on the lower side of the stand of the test specimen. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for measuring the impact absorption energy of a material in a drop weight type impact test method and a drop weight type impact tester used therefor, and particularly to a suitable one for a DWTT test according to API standards.

  An impact fracture test method in which an impact is applied to a sample by a falling weight and its strength and toughness are measured is used as a material evaluation test in various fields.

  For example, a drop weight type impact tester such as a commercially available drop weight type DWTT tester is used in the steel field, and in the semiconductor field, as a method for measuring the strength of a disk of a hard magnetic disk device, an impact fracture test is performed according to Patent Document 1. Proposed.

  Patent Document 2 relates to a “dynamic load measuring device” and proposes a method of measuring the dynamic deformation characteristics of an automobile impact absorbing member by causing a falling weight to collide with a test body.

  In a commercially available drop weight type DWTT tester, a drop weight displacement measuring device is attached to a portion of the test machine excluding the drop weight, and a force sensor is attached to the drop weight, and the collision occurs from the time (t1) when the drop weight collides with the test piece. The displacement of the falling weight (x (t)) and the force (F (t)) received by the falling weight until the completion time (t2) are measured at the same time every minute, and the integral value E is the shock absorption energy. It is said.

特許文献１記載の「衝撃破壊試験方法及び装置」は、ハード磁気ディスク装置のディスクに衝突直前の落錘速度(ｖ1)と衝突完了時の速度(v2)から落錘の運動量変化ｍ(v1−ｖ2)を計算し(ｍは落錘の質量)、得られた値を落錘が試験片につけた圧痕の体積Ｖで除した単位体積当たり運動量変化を衝撃強さとして定義し測定している。
特開平０８−１３６４２９号公報 特開２００６−２８４５１５号公報

The “impact fracture test method and apparatus” described in Patent Document 1 is based on the weight drop velocity (v1) immediately before the collision and the velocity (v2) at the time of collision completion on the disk of the hard magnetic disk device. v2) is calculated (m is the mass of the falling weight), and the change in the momentum per unit volume obtained by dividing the obtained value by the volume V of the indentation on the test piece by the falling weight is defined and measured as the impact strength.
Japanese Patent Laid-Open No. 08-136429 JP 2006-284515 A

  By the way, in the impact fracture test method using a falling weight, the speed at which the falling weight collides with the test piece is large, and depending on the shape of the falling weight, the reflection of elastic waves due to the impact external force received at the time of collision is the test force. This will affect the accuracy of the detector.

  Therefore, in Patent Document 2, the ratio of the diameter D and the length L of the cylindrical load detector is limited to the range of 0.3 ≦ L / D ≦ 3 with respect to the elastic wave reflection.

  For example, in the case of a DWTT test according to the API standard, the speed at which the falling weight collides with the test piece is as high as 9 m / s. In a commercially available falling weight type DWTT tester, the falling weight is about to collide with the test piece. The impact absorption energy is calculated by integrating the force x minute displacement based on the displacement and force of the displacement measuring instrument and the force sensor within a minute time of 10 ms. Since a displacement measuring instrument and a dynamometer having high resolution and time response are required, the cost is high.

  2. In order to integrate and calculate force x minute displacement from each displacement and force of the displacement measuring instrument and the force sensor within a minute time, a computer having a high storage capacity and time response is required and the cost is high.

  3. Since the energy obtained with dynamic measurements has no absolute standard to prove that it is correct, the energy obtained with these measurements has to be a relative comparison within the same tester.

  Furthermore, it is generally considered that the measurement uncertainty increases as the number of processes from measurement to calculation increases. Therefore, when a DWTT test according to the API standard is performed with a commercially available drop weight type DWTT tester, the measurement instrument and the computer Requires a lot of labor to calibrate and maintain accuracy.

The “impact fracture test method and apparatus” described in Patent Document 1 calculates the momentum change m (v1−v2) of the falling weight from the falling weight speed (v1) immediately before the collision and the speed (v2) at the time of the completion of the collision ( m is the mass of the falling weight), and the change in momentum per unit volume divided by the volume V of the indentation applied to the test piece by the falling weight is defined and measured as impact strength.
1) It cannot be used for the measurement of shock absorption energy that should be expressed in J units.
2) Since the characteristic value is calculated based on two measured values of speed and indentation, the uncertainty of each measurement affects the uncertainty of the characteristic value. Therefore, it cannot be applied to the DWTT test.

  Conventionally, a method for measuring impact energy absorption by a pendulum impact tester is defined in JIS Z2242 “Metallic material impact test method” and the like.

The pendulum type impact tester calculates the shock absorption energy based on the angle that is one of the statically measurable quantities of the pendulum angle before the test and the pendulum angle after the test. Has the disadvantages listed below.
1) Since the potential energy of the pendulum is determined by the length from the pendulum fulcrum to the pendulum's center of gravity and the mass of the pendulum, it is complicated to independently vary the collision speed and the mass of the collision object, which are variables of the collision phenomenon is there.
2) Since the robustness of the rotary shaft holding function for rotating the pendulum in the vertical plane is important, in the case of the same weighing capacity, a larger apparatus configuration than the falling weight type is required and the cost is high.

  Accordingly, the present invention aims to provide a falling weight type impact test method for measuring the impact absorption energy of a material, such as a DWTT test according to the API standard, and a falling weight type impact test machine used therefor, which solve the above-described problems. To do.

The object of the present invention can be achieved by the following means.
1. This is a method for measuring the impact absorption energy using a drop weight type impact tester, and the kinetic energy when the drop weight is dropped freely without colliding with the test piece, and the drop weight collides with the test piece and breaks it. A method for measuring shock absorption energy using a falling weight type impact tester, characterized in that the impact absorption energy of the test piece is measured using the kinetic energy after the test.
2. A falling weight, a mechanism for moving and holding the falling weight in the vertical direction, a falling weight guide mechanism having a test piece table, a speed detector for detecting the speed of the falling weight, and the falling weight are the test piece table. A falling weight type impact testing machine equipped with a speed detection mechanism having a passage detection sensor for detecting that the vehicle has fallen below.

According to the present invention, for a commercially available falling weight type DWTT tester: The physical quantity to be measured is only the speed, and the measurement accuracy is superior to the method of measuring the displacement and force, which are two physical quantities.
2. Uncertainty factors resulting from smoothing and integrating displacement and force diagrams can be eliminated.
3. There is no restriction on the elastic wave phenomenon in the shape design of the falling weight.
4). A dynamometer having high resolution and time responsiveness and a computer having high storage capacity and time responsiveness are not required and the cost is low.
5. By simply calibrating with reference to the speedometer, the absolute accuracy of the energy can be guaranteed, so the labor involved in calibration and maintaining the accuracy can be reduced, and measured values or pendulum type testers between different test machines can be used. It is also possible to make a relative comparison with the measured value.

  The present invention uses the kinetic energy when the falling weight is allowed to fall freely without colliding with the test piece, and the kinetic energy after the falling weight collides with the test piece and breaks, thereby absorbing the shock of the test piece. It is characterized by measuring energy.

  FIG. 1 shows an example of a drop weight impact tester suitable for implementing the present invention. In the figure, 1 is a drop weight guide mechanism for moving the drop weight in the vertical direction, 2 is a drop weight of mass m, 3 Is a test specimen table, 4 is a test specimen, 5 is a laser Doppler velocimeter, 6 is a passage detection sensor, 7 is a lifting device that raises the falling weight vertically upward, and 8 is a falling weight 2 that has passed through the passage detection sensor 6. And a controller equipped with an arithmetic mechanism for calculating kinetic energy and a display function thereof, 9 for the floor surface, 10 for the center of gravity of the falling weight 2, and 11 for dropping A weight gripping tool, a and b indicate signal lines.

  The illustrated drop weight type impact tester has a structure according to a commercially available drop weight type DWTT tester, and has a platform for holding the drop weight guide mechanism 1 and the laser Doppler velocimeter 5, and the drop weight guide mechanism 1 is a floor. The laser Doppler velocimeter 5 is fixed to the floor 9 via a gantry. The floor surface 9 is rigidly connected to the earth or the earth.

  The falling weight guide mechanism 1 has a column member that stands upright with two intervals, and the column member includes a lifting device 7 for dropping the falling weight 2 and a gripping of the falling weight 2 from above to below. The test piece holder 3 is provided below the test piece holder 3, and a passage detection sensor 6 for detecting that the falling weight 2 has passed is provided with the drop weight 2 and the broken test piece 4 It can be installed at a position that does not interfere.

The gantry holding the laser Doppler velocimeter 5 is fixed to the floor 9 so that the speed of the falling weight 2 on which the laser Doppler velocimeter 5 falls can be measured from above.
Here, FIG. 2 schematically shows the relationship between the height and speed of the falling weight when the test piece is present and when there is no test piece.

Hereinafter, a procedure for measuring the impact absorbing ability of a test piece such as a DWTT test using the falling weight type impact tester illustrated will be described.
1. First, in a state in which the test piece is not placed on the test piece placing table 3, the drop weight 2 is lifted by the lifting device 7 so that the center of gravity 10 of the drop weight 2 is higher than the passage detection sensor 6 by H in the vertical direction. 11 holds the falling weight 2 to maintain the height H.

  2. The gripping state of the falling weight gripping tool 11 and the falling weight 2 is released, and the falling weight 2 is almost freely dropped vertically downward while receiving air resistance and friction from the falling weight guide mechanism 1.

  3. The fact that the falling weight 2 has fallen to the height of the passage detection sensor 6 is transmitted to the controller 8 through the signal line b, and the velocity v1 at that time is measured by the laser Doppler velocimeter 5 and transmitted through the signal line a. Calculate and display kinetic energy.

  When the acceleration of gravity is g, and the energy loss due to air resistance and friction from the drop weight guide mechanism 1 is E1, Equation (1) is established from the mechanical energy conservation law.

mgH-E1 = 1 / 2m (v1) ² (1)
4). Next, the falling weight 2 is lifted by the lifting device 7 so that the center of gravity 10 of the falling weight 2 is higher than the passage detection sensor 6 by H, and the falling weight gripping tool 11 holds the falling weight 2 to increase the height H. 4. After holding, place the test piece 4 on the test piece placing table 3 and release the gripping state between the falling weight gripping tool 11 and the falling weight 2. While the falling weight 2 is subjected to air resistance and friction from the falling weight guide mechanism 1, the drop weight 2 is almost freely dropped downward to break the test piece 4 and drop it again.

  6). The fact that the falling weight 2 has fallen to the height of the passage detection sensor 6 is transmitted to the controller 8 through the signal line b, the speed v2 at that time is measured by the laser Doppler velocimeter 5, and the signal line a is transmitted through the controller 8 Calculate and display kinetic energy.

  Mechanical energy conservation, where g is the gravitational acceleration, E1 is the energy loss due to air resistance and friction from the drop weight guide mechanism 1, and E2 is the energy consumed to destroy the test piece 4, that is, the shock absorption energy of the test piece 4 Equation (2) is established from the law.

mgH-E1-E2 = 1/2 m (v2) ² (2)
Expression (3) is derived from Expression (1) and Expression (2), and the impact absorption energy E2 is expressed by a simple expression having only speed as a variable.

E2 = 1/2 m {(v1) ² − (v2) ² } (3)
As described above, according to the present invention, only the speed of the falling weight is detected, and the kinetic energy when the falling weight is allowed to fall freely without colliding with the test piece, and the falling weight collides with the test piece and breaks. Since the impact absorption energy of the test piece is measured using the kinetic energy after the treatment, an apparatus configuration with excellent measurement accuracy and low cost is possible.

  The present invention can be applied not only to the DWTT test by appropriately changing the arrangement of the passage detection sensor 6 and the laser Doppler velocimeter 5 in the apparatus configuration, but also to various tests for evaluating material properties by using shock absorption energy. is there.

Schematic which shows the structure of the falling weight type impact tester based on one Example of this invention. The figure which shows the relationship between falling weight height and falling weight speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drop weight guide mechanism 2 Drop weight 3 Test piece stand 4 Test piece 5 Laser Doppler velocimeter 6 Passing detection sensor 7 Lifting device 8 Controller 9 Floor surface 10 Center of gravity 11 Drop weight gripping tool a, b Signal line

Claims (2)

  This is a method for measuring the impact absorption energy using a drop weight type impact tester, and the kinetic energy when the drop weight is dropped freely without colliding with the test piece, and the drop weight collides with the test piece and breaks it. A method for measuring shock absorption energy using a falling weight type impact tester, characterized in that the impact absorption energy of the test piece is measured using the kinetic energy after the test.   A falling weight, a mechanism for moving and holding the falling weight in the vertical direction, a falling weight guide mechanism having a test piece table, a speed detector for detecting the speed of the falling weight, and the falling weight are the test piece table. A falling weight type impact testing machine equipped with a speed detection mechanism having a passage detection sensor for detecting that the vehicle has fallen below.

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