JPH07111392B2 - Material testing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a material testing machine capable of accurately determining load-displacement characteristics of a test piece per the same production unit (lot).

B. Conventional Technology Conventionally, for example, as shown in FIG. 5, a pair of screw rods 2 are erected on a table 1, a crosshead 3 is horizontally mounted on the table, and a screw 4 is rotated by a motor 4. Cross head 3
A material testing machine is known in which a specimen TP is loaded by moving up and down. The load cell 5 and the extensometer 6 (or the pulse encoder 7) are used to sample the displacement of the sample TP with respect to the load while compressing or tensioning the sample TP at predetermined time intervals, and the sample is provided based on the sampled load and displacement data. The load-displacement characteristic of the sample is measured.

C. Problem to be Solved by the Invention However, in the above-mentioned conventional material testing machine, when obtaining an average value of load-displacement characteristics of a plurality of specimens in the same production unit, the same sampling order is used with the sampling order number as a common reference. The average of the load-displacement characteristics of the specimen in the same production unit is obtained by averaging the displacement and load data in the numbers. For this reason, when the increase rate of the displacement amount varies even in the same production unit, the displacement value of the same sampling order number varies, and the average value of the load for the displacement in the same production unit cannot be accurately measured. There was a point. In addition, the load for each specimen −
Averaging the load for any given displacement from the displacement curve does not match the data obtained with the above method.

A technical problem of the present invention is to accurately measure an average value of load-displacement characteristics of a test piece in the same production unit.

D. Means for solving the problem The present invention is a load mechanism for loading a test piece, a load detection means for detecting a load applied to the test piece, and a displacement detection means for detecting a displacement of the test piece under load. , A means for measuring a load-displacement curve based on the detection data of both detection means sampled at a predetermined time interval. The above-mentioned technical problem is determined by determining means for determining whether or not load or displacement detection data exceeds a plurality of predetermined values, and it is determined that the detection data exceeds each of the predetermined values. Storage means for storing detection data of load and displacement, interpolation calculation means for performing interpolation calculation of the other detection data for one predetermined detection data by the sequential detection data stored in the storage means, and a plurality of storage means. The problem can be solved by including an average calculation means for calculating an average value of the interpolation calculation results for the same load or the same displacement of the sample.

E. Action For example, the displacement and load detection data are stored every time the displacement sampled at a predetermined time interval exceeds a predetermined displacement, and the predetermined displacement is determined based on the displacement and load detection data stored in this order. Is calculated by interpolation, and the average value of the loads of the interpolation calculation results for the same displacement of a plurality of specimens is calculated. Therefore, the average value of load-displacement characteristics for each lot can be accurately measured.

F. Embodiment FIG. 1 is a block diagram showing an embodiment of the data processing unit of the material testing machine to which the present invention is applied. Basically, a load cell 11 for measuring the load acting on the specimen, an extensometer 12 for measuring the strain of the specimen, AD converters 13 and 14, a central processing unit (CPU) 15,
It is composed of a memory 16, a CRT display device 17, and a printer 18. Further, a pulse encoder 19 for detecting the stroke of the crosshead and a stroke counter 20 for inputting the stroke value of the crosshead to the central processing unit 15 by counting the output pulse of the pulse encoder 19 are provided.

First, the normal measurement operation of the load-displacement characteristic of the test piece will be described.

When a load is started to be applied to the sample (not shown), the load is detected by the load cell 11 and the displacement (elongation) of the sample due to the load is detected by the extensometer 12. Since the detected load signal and displacement signal are analog signals, they are converted into digital values by the AD converters 13 and 14, respectively. The load and displacement as digital values are sampled by the central processing unit 15 at predetermined time intervals and stored in the memory 16 in the order of sampling. The load and displacement data stored in the memory 16 is read out at the stage when the test is completed, and is displayed as a load-displacement characteristic in a graph on the CRT display device 17, and is printed out by the printer 18 as necessary. To be done.

Next, the operation of measuring the average value of the load-displacement characteristics of the test piece in the same production unit will be described. In this case, the central processing unit 15 performs the sampling operation as shown in the flowchart of FIG. 2 and the data processing as shown in the flowchart of FIG.

That is, the central processing unit 15 samples the load and displacement data at predetermined time intervals t ₁ , t ₂ , t _3, ... As shown in (a) of the time chart of FIG. Then, as shown in the flowchart of FIG. 2, for example, it is determined in step P1 whether or not the starting load set so as not to take in unnecessary components such as noise in the initial state is exceeded, and if negative, the step P1 is executed. It is repeatedly executed, and if affirmed, load load R ₀ and displacement data S ₀ (see FIG. 4) appearing immediately after that are stored in the memory 16 (procedure P2).
Then, in step P3, it is judged whether or not the displacement interval x specified from the outside has been exceeded, and if the displacement of "S ₁ = S ₀ + x" is exceeded, the load load and displacement data at the sampling time appearing immediately after that. Is stored in the memory 16 (procedure P4). Thereafter, in the same manner, “S ₂ = S ₀ + 2x”, “S ₃ = S ₀ + 3x”, ... “Sn = S ₀ ” until it is determined in step P5 that the data collection is completed.
The load load and displacement data at the sampling time appearing immediately after the detection of the displacement represented by “+ nx” are stored in the memory 16. That is, the central processing unit 15 does not store the load load and displacement data at each sampling time in the memory 16 each time, but the load load and displacement data sampled immediately after the displacement designated from the outside is detected. Are selectively collected and stored in the memory 16. For example,
In the time chart of FIG. 4, sampling time
Data of load loads and displacements of t ₁ , t ₄ , t ₇ , t ₁₀ among t ₀ , t ₁ , t ₂ , ... Tn are selected and stored in the memory 16.

If the data of the designated displacement intervals for each of the plurality of specimens in a certain production unit are stored in the memory 16 in this way, the central processing unit 15 determines the load-displacement characteristic of each specimen as shown in FIG. As shown in the flow chart of
Sampling time _{t 1, t 4, t 7} , t 10 ... load data is linearly approximated or approximate quadratic curve of the interpolating calculation. This allows
The true load value at the specified displacements S _{1 to} Sn is calculated for each specimen. That is, the value R ₁ of the true load applied in each designated displacement _{S 1, S 2, S 3} , and calculates the R _2, R ₃ (Step P10). Next, the average value of the load load in each designated displacement is obtained for each specimen (procedure P11), and the average curve of the load-displacement characteristics of the specimen of the same production unit is displayed on the CRT display device 17 ( Step P12).

Therefore, according to the above procedure, the load-displacement characteristics of each sample in a lot can be obtained from a plurality of sets of load data corresponding to almost equal displacements. Accurate measurement is possible without being affected by speed and other factors. Moreover, since the interval of the displacement for loading the load can be appropriately selected, the measurement can be performed with an arbitrary measurement resolution. This means that the resolution of the memory 16 can be selected according to the capacity.

In the configuration of the above embodiments, the material testing machine main body is a load mechanism, the load cell 11 is a load detecting means, the extensometer 12 is a displacement detecting means, the central processing unit 15 is a load-displacement curve measuring means, and a determining means. The memory 16 constitutes a storage means, as well as an interpolation calculation means and an average calculation means.

The interpolation calculation of the flowchart of FIG. 3 may be performed in real time while measuring the load-displacement characteristics of individual test pieces, or the load-displacement characteristics of all test pieces have been measured. It may be carried out at a different stage. Again,
Although the method of storing the sampling data immediately after the detection of the predetermined displacement value in real time was described, all the data is read and stored in advance at predetermined sampling intervals, and the sampling data immediately after each time the predetermined displacement is exceeded after the test is completed. May be stored to obtain the average value of load-displacement. Further, the displacement and load data sampled at the sampling time immediately after the displacement exceeds the planned value are stored, but it may not be immediately after the error unless there is an error. Furthermore, the case has been described in which a predetermined displacement is designated and the load corresponding thereto is obtained, but the reverse case is also possible. Further, in the above, the method of setting a predetermined displacement value for each predetermined displacement amount x from the reference start displacement S ₀ has been described, but a sequential displacement value is designated in advance, and a displacement and a load are applied each time the displacement is exceeded. Data may be loaded.

G. Effect of the invention Since the present invention is configured as described above, even if the displacement of the specimen in the same production unit and the increasing speed of the load vary, the value of the load or displacement at the same displacement or load Can be collected and the average value can be calculated. Therefore, an accurate average value of load-displacement characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing a load-displacement characteristic sampling operation, FIG. 3 is a flowchart showing an operation for obtaining an average value of the load-displacement characteristic, and FIG. Is a time chart for explaining the operation of calculating the average value of the load-displacement characteristics, and FIG. 5 is a front view for explaining the load mechanism of the material testing machine according to the present invention. 11: Load cell, 12: Extensometer 13, 14: AD converter, 15: Central processing unit 16: Memory, 17: CRT display device 18: Printer

Claims (1)

[Claims] 1. A load mechanism for loading a test piece, a load detecting means for detecting a load applied to the test piece, a displacement detecting means for detecting a displacement of the test piece under load, and sampling at predetermined time intervals. And a means for measuring a load-displacement curve based on the detection data of both detection means, a determination means for determining whether or not the detection data of load or displacement exceeds a plurality of predetermined values. And storage means for storing the load and displacement detection data when it is determined that the detection data exceeds respective predetermined values, and the other detection data for one predetermined detection data is stored in the storage means. An interpolation calculation means for performing an interpolation calculation based on the sequential detected data, and an average calculation means for calculating an average value of the interpolation calculation results for the same load or the same displacement of a plurality of specimens. Material testing machine, characterized by Bei.