Some aspects concerning the measuring of forces for deformation diferent profiles of composite materials.

Nedelcu, Dumitru ; Tabacaru, Lucian ; Ciobanu, Romeo-Mihai 等

1. INTRODUCTION

In order to make the gauging, we used an equipment presented in figure 1. In the boring of the bearing (3) of the machine-tool MURF 32 was introduced a shaft (8) similar to that of the machine on which the deforming rollers are fixed, shaft that comes in contact with a prism system (4) fixed on the board (7) mounted with the screws (10) on the arm (5). The bearing (3) is laid on a rigid board (2) that is on three load cells DT 210.00 located at 120[degrees] on the body (9) of the universal machine used for tests of static strength of materials MU200. The pillars (6) are oriented diagonally and serve to guide the arm (5) (that moves via helicoidally transmissions) the function of which is to apply the charge (the static load).

[FIGURE 1 OMITTED]

[FIGURE 2a OMITTED]

[FIGURE 2b OMITTED]

The strain gauges EA-06-125BT-120 are located on the opposite sides (serially linked to these sides) of the bearing (3) forming thus two half decks. The measurement of the mechanic sizes is not without errors owed to disturbing factors that cannot be evaluated by calculation, but only appreciatively (Ciocardia, C et al, 1991).

For gauging, we used two lines of action presented in figure 2, where the figure 2a shows the line to be measured and figure 2b the standard driving line (Cazimirovici, E., et al, 1990). The supplied voltage was [U.sub.a] = 10,0036[V].

We previously gauged the measuring chain so that at the minimal load ([F.sub.min] = 0[daN]) the meter should indicate a value close to zero, and at the nominal load ([F.sub.nom] = 20.000[daN]) the meter indicator should show the maximal value.

Further to the attempts made, the results were passed with values for three test cycles, upon loading and unloading, for variation stages of the load applied of 1000 [daN]. The signal was measured in [[10.sup.-6] V]. The error of repetitiveness is good being lower than 5 units both when loading and when unloading.

[FIGURE 3 OMITTED]

Thus we obtained the gauging chart of figure 3.

2. TECHNOLOGY USE

The acquisition plate will make the acquisition on one channel only, that is the channel 0 (figure 4).

To eliminate the noise, metal-braided cables are used, and the signal will be acquired on integration intervals on which an average of the signal values will be made. The acquired signal will be amplified with a value that will bring it to the output parameters that we need.

The classic meter (Pruteanu, O.V., Nedelcu, D., 1996) of the values of a strain gauge is the electronic tens meter. The electronic tens meter is a device with a limited number of channels, a carrier frequency that cannot be changed and designated directly. The device contains identical measurement channels and a common unit of supply and designation, being able to be connected to any measurement channel. The measurement is made by transforming via a resistive strain gauge, the value to be measured into the variance of an electric parameter.

The disadvantages of the meter appear when we want to make a measurement in a dynamic system. In a dynamic system, we do not have the possibility to read a sufficient number of values on the device scale, as the variance of the value to be measured may be too quick and this prevents the drawing of solid conclusions on the respective phenomenon. What is less convenient is the fact that the read values cannot be memorized. In the dynamic system, there appear problems when the value measurement value varies into values that cannot be comprised in a very precise measurement scale (Cobzaru, P., 2004). Because of these advantages, the use of a virtual meter became a necessity.

When making the virtual tens meter, we used for the interface of the software the programming environment Lab Windows compiled under Borland C++, where the sources for the acquisition system AX5210 were written.

The virtual tens meter has two ways of operating: acquisition in a static system, acquisition in a dynamic system.

Acquisition in a static system: a number of values are read from the strain gauge during the integration intervals, values that will be memorized in a vector. The integration intervals are the intervals on which the read values will be mediated to eliminate any possible noise.

Acquisition in a dynamic system: a number of values are read from the strain gauge during the integration intervals, values that will be memorized in a vector and displayed in a chart. Every integration interval will be displayed and conclusions will be drawn on the signal.

The user, after turning on the program, will see a panel with options for choosing the operating system (static, dynamic), the hard setting of the acquisition plate and the standard curve. In case there is a direct entrance into the operating mode, the settings taken will be the implicit ones.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

The acquisition panel (figure 5) in a statically system contains: indicators of the position of on charts; the control for the selection of the interpolation type; control for the selection of the operating type; control for the bridge balancing; control for starting the measurement; control for the selection of the acquisition time; control for the selection of the measurement rate; control for coming back to the main panel; charts for viewing the standard and the force evolution; As concerns the interpolation time there are two options: linear and polynomial. For the polynomial option, the interpolation is done according to a 14 degree polynomial. This interpolation is achieved by the "Poly Fit" function. The function looks for coefficients that best represent the curve to follow (standard loading curve).

The future research consists of using this equipment for measurement of different profiles made from others material like steel, iron and so on. Also the improvement of this equipment will be the future research.

3. CONCLUSIONS

This equipment has two ways of operating: acquisition in a static system, acquisition in a dynamic system.

This equipment has a very low measurement errors, may be used, after adequate changes.

This equipment can be use to measure forces in entire cold plastic strain area and also in the metal cutting area.

4. REFERENCES

Cazimirovici, E., et al (1990). Teoria si tehnologia deformarii prin tragere, The technology and theory of cold plastic deformation, Technical Publishing, pp. 160, ISBN 97331-0266-0, Bucharest

Ciocardia, C. et al (1991). Tehnologia presarii la rece, The technology of cold plastic deformation, EDP Bucharest, pp. 437, ISBN 973-30-2314-0, Bucharest

Cobzaru, P. (2004). Materiale compozite, Composite material, EDP Bucharest, pp. 34, 38, ISBN 973-30-1445-1, Bucharest

Nedelcu, D., Pruteanu, O.V., (1998). Aspecte ale formarii canelurilor exterioare prin deformare plastica la rece utilizand metoda Taguchi, Some aspects concerning the cold plastic deformation of exterior grooves using Taguchi method, Tehnica-Info Chisinau, pp. 34-38, ISBN 9975-910-96-3, Chisinau

Pruteanu, O.V., Nedelcu, D.,(1996). The stress analysis on deformation roll, Proceedings of 7th International DAAAM Symposium, Katalinik, B. (Ed.), pp. 361-362, ISBN 3-901509-02-X, Vienna, Austria, October 1996, Vienna