JP2012068190A - Impact strength evaluation device, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a product impact strength evaluation device capable of easily evaluating impact strength of an object with high accuracy.SOLUTION: A product impact strength evaluation device includes: storage means 21 that stores time series acceleration data corresponding to impact strength at a damaged portion of an object which can be obtained from an impact test for each of two impact pulses having different waveforms; eigen frequency acquisition means 23 that calculates an impact response spectrum for each impact pulse by using the time series acceleration data and acquires the eigen frequency at the damaged portion from the two impact response spectra; and Damage Boundary Curve (DBC) derivation means 24 that calculates transmission acceleration at the damaged portion by using the acquired eigen frequency and derives a damage boundary curve at the damaged portion from the eigen frequency and the transmission acceleration.

Description

  The present invention relates to an impact strength evaluation apparatus, method, and program, and more particularly to an impact strength evaluation apparatus, method, and program for evaluating impact strength of various products such as home appliances, large machines, and medical equipment.

  In order to evaluate the impact strength of a product, a product damage boundary curve (DBC) is derived as specified in JIS Z0119 “Product Impact Strength Test Method for Packaging and Product Design”. In the past, it has been used for buffer packaging design and product design. In addition, as a conventional method for evaluating product impact strength, Non-Patent Document 1 categorizes DBC evaluation methods for deriving DBC. For example, the allowable acceleration or allowable speed change of a product and the natural frequency are calculated. “Ac · fc method” and “ΔVc · fc method” for measuring and deriving DBC based on the measurement result have been proposed. Non-Patent Document 2 discloses that an improvement guideline for a product is created by drawing a DBC for each damaged part of the product.

Nakashima Takakatsu, “Study on Evaluation of Product Impact Strength for Transport Packaging”, Kobe Mercantile University Doctoral Dissertation, (2003) Takakatsu Nakajima, “Efforts for Revision of Product Impact Strength Test-Creation of Product Improvement Guidelines by DBC by Damaged Sites”, Journal of Japan Packaging Society, Vol. 19, no. 2 (2010)

  However, since the damaged part of the product becomes apparent only after being damaged by an impact test, there is a problem that it is difficult to derive DBC with the conventional impact evaluation method that requires the natural frequency of the damaged part in advance. .

  For example, in the allowable speed change test of JIS Z0119, the effective action time of the shock pulse is required to be equal to or less than the reference value calculated according to the natural frequency of the easily damaged part of the specimen. If the natural frequency of the damaged part remains unknown, there is a possibility that the evaluation cannot be performed accurately. That is, in the permissible speed change test, the effective action time De (ms) of the shock pulse must satisfy De ≦ 1000 / (2πfc) (fc is the natural vibration of the easily damaged part of the EUT) Number (Hz)), and the value of fc is not known until the test is completed, so there is a possibility that the effective action time cannot be set appropriately.

  Further, in the method disclosed in Non-Patent Document 1 in which DBC is obtained by measuring the natural frequency fc, it is difficult to predict in advance the part that is actually damaged. When there are many of them, the work is complicated and time-consuming.

  Furthermore, in the allowable acceleration test of JIS Z0119, it is necessary to set the drop height of the impact table so that the speed change is 1.6 times or more of the allowable speed change obtained by the allowable speed change test. When the speed change becomes a large value, there is a possibility that the speed change may exceed the specifications of the impact tester or may deviate from the actual speed change, and there is a problem that DBC cannot be derived with high accuracy. In the allowable acceleration test, it is also required to use a trapezoidal shock pulse that is as close to a square wave as possible, but it is impossible to actually apply an ideal square wave shock pulse. Was also a factor that caused a drop in evaluation accuracy.

  Therefore, an object of the present invention is to provide a product impact strength evaluation apparatus, method, and program capable of easily and accurately evaluating the impact strength of an object.

  The object of the present invention is to store time series acceleration data corresponding to the impact strength of a damaged part of an object obtained by an impact test for each of two impact pulses having different waveforms, and the time series acceleration. Using the data, the impact response spectrum for each impact pulse is calculated, the natural frequency acquisition means for acquiring the natural frequency of the damaged part from the two impact response spectra, and the acquired natural frequency This is achieved by an impact strength evaluation apparatus comprising DBC deriving means for calculating a transmission acceleration of a damaged part and deriving a damage boundary curve of the damaged part from the natural frequency and the transmission acceleration.

  Further, the object of the present invention is to provide time series acceleration data corresponding to the impact strength of the damaged part of the object obtained by the impact test from the storage means for storing each of the two impact pulses having different waveforms. Reading acceleration data, calculating an impact response spectrum for each impact pulse, obtaining the natural frequency of the damaged site from the two impact response spectra, and using the acquired natural frequency, the damaged site And a step of deriving a damage boundary curve of the damaged portion from the natural frequency and the transmission acceleration.

  The object of the present invention is achieved by an impact strength evaluation program for causing a computer to execute the impact strength evaluation method.

  ADVANTAGE OF THE INVENTION According to this invention, the impact strength evaluation apparatus of the product, method, and program which can evaluate the impact strength of a target object easily with high precision can be provided.

It is a schematic block diagram of the impact strength evaluation apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the test result of an allowable speed change test and an allowable acceleration test. It is the conceptual diagram which modeled the target object. It is a graph for demonstrating the method of acquiring a natural frequency. It is a figure which shows an example of the display screen of a damage boundary curve and additional information.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an impact strength evaluation apparatus according to an embodiment of the present invention. As shown in FIG. 1, the impact strength evaluation apparatus 1 includes an impact pulse generator 10 and an evaluation apparatus body 20.

  The shock pulse generator 10 is a free-falling impact tester, and can adopt, for example, the configuration disclosed in JIS Z0119 (2002). The shock pulse generator 10 can drop the shock base 13 along the guide 12 standing on the upper surface of the cradle 11, and the object W such as a product to be evaluated is fixed to the shock base 13 and desired. An impact pulse can be applied to the object W by dropping from the height. An impact waveform generator 14 is provided on the upper surface of the cradle 11, and a desired type of impact pulse such as a sine half wave or a trapezoidal wave can be generated on the impact base 13. The acceleration applied to the object W can be detected in real time by the acceleration pickup 15 fixed to the impact table 13, and can be stored in the storage unit 21 of the evaluation apparatus body 20 as time-series acceleration data. The shock pulse generator 10 can generate two or more shock pulses with different waveforms, such as different pulses such as sine half wave, trapezoidal wave, square wave, and sawtooth wave, or even the same type of pulse, but with different action times. If it is a simple structure, you may provide the impact generation | occurrence | production mechanism different from this embodiment. Specifically, a vibration tester can be used in addition to various impact testers such as a forced drop type, a cylinder type, and a pendulum type.

  The evaluation apparatus body 20 is configured by a computer such as a personal computer, a portable information terminal, or a PDA, and includes an input unit 22, a natural frequency acquisition unit 23, a DBC derivation unit 24, and an output unit 25 in addition to the storage unit 21 described above. ing. Examples of the input unit 22 include a keyboard and a mouse, and examples of the output unit 25 include a display and a printer. The natural frequency acquisition unit 23 acquires the natural frequency of the damaged portion of the object W from the time-series acceleration data of the object W stored in the storage unit 21, and the DBC derivation unit 24 calculates the natural frequency from the acquired natural frequency. A damage boundary curve of the damaged part is derived. The natural frequency acquisition unit 23 and the DBC derivation unit 24 can be realized by a calculation unit such as a CPU. Each of the components of the evaluation apparatus main body 20 may be configured to be partially realized by external hardware.

  Next, a method for evaluating the impact strength of the object W using the impact strength evaluation apparatus 1 will be described. First, the impact test of the object W is performed for each of two impact pulses having different waveforms by the impact pulse generator 10. Examples of shock pulses having different waveforms include different types of pulses such as a sine half wave, trapezoidal wave, square wave, and sawtooth wave, and pulses having different action times even if they are the same type of pulse. In this embodiment, a sine half wave and a trapezoidal wave are used as two shock pulses, and an allowable speed change test and an allowable acceleration test are performed in accordance with JIS Z0119.

  In the allowable speed change test, the speed change applied to the object W by the shock pulse is gradually increased to check whether the object W is damaged. In the present invention, since the natural frequency of the damaged part can be obtained by calculation as will be described later, the damage boundary curve is obtained as a function of the operation time of the shock pulse and can be corrected. Therefore, it is not necessary to consider in particular the conditions relating to the effective action time defined in JIS Z0119. The acceleration of the object W detected in real time by the application of the shock pulse is input to the evaluation apparatus body 20 and stored in the storage unit 21. If any part of the object W is damaged, the operator can input the time-series acceleration data of the speed change that was last applied by the input operation of the input unit 22 to show the impact strength of the damaged part. Corresponding to this, it is stored in the storage unit 21 in association with the damaged part. If there are multiple parts that may be damaged, continue the test until the speed change becomes sufficiently large without ending the test even if one part is damaged. Is stored in the storage unit 21 in association with the damaged site.

  In the allowable acceleration test, the acceleration applied to the object W by the shock pulse is gradually increased. The acceleration of the object W detected in real time by the application of the shock pulse is input to the evaluation apparatus body 20 and stored in the storage unit 21. Every time the damaged part is damaged in the above-described allowable speed change test, the operator uses the input operation of the input unit 22 to input the time-series acceleration data of the acceleration that was last applied without any damage to the impact of the damaged part. The information corresponding to the strength is stored in the storage unit 21 in association with the damaged portion. In the present invention, as defined in JIS Z0119, the condition that the speed change is at least 1.6 times the allowable speed change test is not necessarily satisfied.

  Thus, the storage unit 21 stores time-series acceleration data corresponding to the impact strength of each damaged portion of the object W for each of two impact pulses (sine half-wave and trapezoidal impact pulses) having different waveforms. Is done. As the time-series acceleration data corresponding to the impact strength, it is preferable to select time-series acceleration data in which no breakage occurs as in the present embodiment, but it is also possible to select time-series acceleration data at the time of breakage. .

  FIG. 2 shows an example of a display screen that displays test results of the allowable speed change test and the allowable acceleration test. As shown in FIG. 2, in both the allowable speed change test and the allowable acceleration test, six tests (No. 1 to No. 6) are performed, and the acceleration calculated based on the time-series acceleration data (maximum shaped acceleration) ), Action time and speed change are displayed. In this example, four parts (parts A to D) are damaged after the test is completed, and “◯” or “X” is displayed for each damaged part as to whether or not each part was damaged in each test. For example, the part A is the No. of the allowable speed change test. No. 5 in the allowable acceleration test. No. 4 in the allowable speed change test as time-series acceleration data corresponding to the impact strength of the part A. 4 and allowable acceleration test no. Each time-series acceleration data of 3 is stored in the storage unit 21. In this example, since there are four damaged parts, four display columns A to D are provided, but the number of the columns increases or decreases according to the number of actually damaged parts.

  Next, the natural frequency acquisition unit 23 calculates an impact response spectrum for each impact pulse by performing SRS analysis (impact response spectrum analysis) on the time-series acceleration data stored in the storage unit 21. For example, when the number of broken parts is four, each broken part A to D can be assumed to be a set of one-degree-of-freedom systems with respect to the object W as shown in the conceptual diagram of FIG. Has a frequency. According to the present invention, as will be described later, the natural frequency of each damaged part can be obtained by calculation from the acquired impact response spectrum.

The transmission acceleration ac i of the broken portion i corresponding to damage the strength of the broken portion _i, the input acceleration A _i of the object W, when the transmission rate of the shock and Tr _i, Tr _i is unique broken portion i Since it can be expressed by a function of fc _i · T _i , which is the product of the frequency fc _i and the shock pulse action time T _i , the following Equation 1 is established.

[Equation 1]
_{ac i / A i = Tr i} (fc i · T i)

In the present embodiment, two impact response spectra can be calculated from two time-series acceleration data at each breakage site i acquired by the allowable speed change test and the allowable acceleration test. Since it is considered that these two impact response spectra have the same transmission acceleration ac _i and natural frequency fc _i of the damaged part i, the following formula 2 is derived from the above formula 1.

[Equation 2]
_AiAc / _AiΔVc = _TriΔVc (fc _i · T _iΔVc ) / _TriAc (fc _i · T _iAc )

In the above formula 2, the suffixes ΔVc and Ac represent the allowable speed change test and the allowable acceleration test, respectively. Equation 2 _{A iAc, A iΔVc, T iΔVc} , T iAc, Tr iΔVc, Tr iAc , since the both obtained from time series acceleration data, unknown is only fc _i. Therefore, fc _i can be searched from Equation 2. When the function of fc _i is a multimodal function and a multimodal solution exists, the minimum fc _i is the natural frequency. For example, when the relationship between fc and _{Tri_ΔVc} / _{Tri_Ac} is expressed as shown in FIG. 4, fc in the case of _{Tri_ΔVc} / _{Tri_Ac} = 1.25 is about 200 Hz. fc _i can be searched by a linear search in which plot data is traced in order from the smallest frequency, but is known as an algorithm for searching for a solution of a multimodal function such as a binary search, a depth-first search, and a breadth-first search. Things can also be used.

Thus, if the natural frequency fc _{i at} the damaged part i is clarified, the transmission acceleration ac _i of the damaged part i can be obtained from the above equation 1. The DBC deriving unit 24 derives a damage boundary curve (DBC) from fc _i and ac _i by a known method based on the type of shock pulse selected by the operator via the input unit 22. For example, when a sine half-wave shock pulse is selected, the damage boundary curve of the damaged site i can be drawn by the following equations 3 and 4.

[Equation 3]
A _i (T) = ac _i / Tr _HS (fc _i · T)
[Equation 4]
ΔV _i (T) = (2 / π) · A _i (T) · T

Here, Tr _HS is an impact response spectrum when the impact pulse has an ideal waveform of a half sine wave. The shock response spectrum of an ideal waveform shock pulse is disclosed in, for example, JIS Z0119 (2002). The shock response spectrum of various ideal waveform shock pulses such as a sine half wave and a square wave is stored in advance in the storage unit 21 or the like. Can be stored. T is the operating time of a sine half-wave shock pulse. When the selected shock pulse is a square wave, the damage boundary curve of the damaged site i can be drawn by the following equations 5 and 6 (Tr _SQ is the case where the shock pulse is an ideal waveform of a square wave) Impact response spectrum).

[Equation 5]
A _i (T) = ac _i / Tr _SQ (fc _i · T)
[Equation 6]
ΔV _i (T) = A _i (T) · T

  The output unit 25 displays the damage boundary curve created by the operator's selection on the screen or prints it on a paper medium or the like. In this way, a damage boundary curve corresponding to the type of shock pulse assumed for the object W can be obtained depending on the presence or absence of the buffer material that protects the object W, and can be used for buffer packaging design, product design, and the like. it can.

  As described above, according to the impact strength evaluation method of the present embodiment, even if the portion of the object W that may be damaged is unknown, an impact test is performed using two impact pulses having different waveforms. The natural frequency of the damaged part can be obtained by calculation using the shock response spectrum of the shock pulse. As the waveforms of the two shock pulses, it is preferable to use a sine half wave and a trapezoidal wave as in this embodiment from the viewpoint of facilitating the impact test and the calculation of the natural frequency, but other waveforms that can calculate the natural frequency are used. It may be a combination of shapes. According to the present invention, since the evaluation accuracy can be ensured even if the shock pulse applied in the impact test is not an ideal square wave, the test method specified in JIS and the measurement of the natural frequency of the damaged part are required. Compared to conventional evaluation methods, workability is improved and impact strength can be evaluated with high accuracy.

The DBC derivation unit 24 may calculate other information that can serve as an improvement guideline for the object W along with the derivation of the damage boundary curve described above. For example, the corrected maximum allowable speed change ΔVc (= ac / (2πfc)) and the set maximum resilience coefficient e (for example, 0.8) without a cushioning material h (= (1/2) × {ΔVc / (1 + e)} ² / g (gravity acceleration)), corrected allowable acceleration Ac (= ac / 2), and the like may be calculated and displayed or printed by the output unit 25. FIG. 5 shows an example of a display screen on which the damage boundary curve and the additional information are displayed at four locations (damage sites A to D) of the object W.

  As shown in FIG. 5, the damage boundary curve is displayed for each broken part (broken parts A to D). For example, when a product designer improves a product, Thus, it is possible to clarify a portion that does not require improvement. Further, as the additional information, the corrected allowable speed change (corrected allowable speed change) ΔVc, the maximum height (allowable drop height) h, and the corrected allowable acceleration (corrected allowable acceleration) Ac are also displayed. Therefore, it can be easily used as an improvement guideline.

  The impact strength evaluation device 1 of the present embodiment includes the impact pulse generator 10 and the evaluation device main body 20, but if time series acceleration data can be acquired by an external impact tester or the like, It is also possible to configure only the evaluation apparatus main body 20. In this case, time series acceleration data is read from an external impact tester into the evaluation apparatus main body 20 by wire or wirelessly, or a recording medium such as a USB memory or a CD-ROM storing time series acceleration data is used as the storage unit 21. Can function. The functions of the natural frequency acquisition unit 23 and the DBC derivation unit 24 can be executed by a computer program. This program can be distributed via a network such as the Internet or recorded on a recording medium. It can be executed by a computer.

DESCRIPTION OF SYMBOLS 1 Impact strength evaluation apparatus 10 Shock pulse generator 20 Evaluation apparatus main body 21 Storage part 22 Input part 23 Natural frequency acquisition part 24 DBC derivation part 25 Output part

Claims (5)

Storage means for storing time-series acceleration data corresponding to the impact strength of the damaged part of the object obtained by the impact test for each of two impact pulses having different waveforms;
A natural frequency acquisition means for calculating a shock response spectrum for each shock pulse using the time-series acceleration data, and acquiring the natural frequency of the damaged part from the two shock response spectra;
An impact strength evaluation device comprising: DBC deriving means for calculating a transmission acceleration of the damaged part using the acquired natural frequency and deriving a damage boundary curve of the damaged part from the natural frequency and the transmission acceleration. The storage means stores the time-series acceleration data of two shock pulses for each of a plurality of damaged portions,
The impact strength evaluation apparatus according to claim 1, wherein the natural frequency acquisition unit acquires a natural frequency for each damaged portion.   The impact strength evaluation apparatus according to claim 1, further comprising an impact pulse generation device that generates the time-series acceleration data by applying an impact pulse to an object. The time-series acceleration data corresponding to the impact strength of the damaged part of the object obtained by the impact test is read from storage means for storing each of the two impact pulses having different waveforms, and each of the impacts is read out. Calculating an impact response spectrum with respect to a pulse, and obtaining a natural frequency of the damaged portion from the two impact response spectra;
An impact strength evaluation method comprising: calculating a transmission acceleration of the damaged part using the acquired natural frequency and deriving a damage boundary curve of the damaged part from the natural frequency and the transmission acceleration.   An impact strength evaluation program for causing a computer to execute the impact strength evaluation method according to claim 4.

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