JP2570842B2 - Damping composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vibration-damping composite material having a light weight and high vibration damping ability.

[Prior Art] Pollution due to vibration and noise has been attracting attention as one of the serious social problems, and the use of vibration-proof alloys has been considered as the most aggressive and drastic one of the countermeasures. An anti-vibration alloy is obtained by imparting high damping ability to a metal material itself, which is a constituent material of a machine or a structure that generates vibration and noise.

On the other hand, an aluminum alloy used as a material for mechanical structures in a wide range of fields due to its large feature of being light is known to have the extremely low damping ability (damping coefficient = 0.3%). Of course, among the aluminum alloys, the Al-78Zn alloy which is practically used as the above vibration damping alloy has the next highest damping ability (damping coefficient = 30%) next to the Mg alloy,
Since a large amount of Zn having a specific gravity of about 2.6 times that of Al is contained, there is a problem in that the original lightweight characteristics are lost.

[Problem to be Solved by the Invention] As described above, a vibration damping material having both excellent lightweight properties and economic practicality has not been reported yet.

The present invention is to solve the technical problem to solve the problem of creating a vibration damping material utilizing the properties of an aluminum alloy as a matrix metal and compensating for a decrease in strength that occurs in inverse proportion to the provision of damping ability by a composite technology with reinforcing fibers. It is assumed that.

[Means for Solving the Problems] To solve the above problems, the present invention is a vibration damping composite material obtained by combining a ceramic fiber assembly holding phosphorous graphite and an aluminum alloy, and has a volume of phosphorous graphite. Rate 2
A new configuration of ~ 8% is adopted.

The ceramic fibers used in the present invention include long fibers,
Either short fiber or whisker can be used, and its volume fraction is
About 10 to 20% is preferable. Phosphorous graphite is a fine powder of about 1 to 50 μm ground and classified from a graphite ore, and is finely held between fine fibers formed as an aggregate and is uniformly dispersed in an aluminum alloy.

The outline of the manufacturing method of the above-mentioned vibration damping composite material is as follows. If necessary, a small amount of a surfactant is added to the required ceramic fiber and phosphorous graphite, if necessary, dispersed in a liquid medium (eg, water), and formed into an integrated body by a known compression forming method. dry. Thereafter, the fiber assembly is preheated and set in a preheated mold, and the aluminum alloy is infiltrated by high-pressure solidification casting and cooled and solidified.

[Test Example 1] Alumina-silica fiber and phosphorous graphite were dispersed in water, formed into an aggregate by a compression molding method, and dried. In this case, the volume ratio of the fibers at the time of compounding with the matrix metal was adjusted about 15% in advance and the volume ratio of the phosphorous graphite was adjusted to about 4%. Thereafter, the fiber assembly was preheated to about 350 ° C. in a nitrogen gas atmosphere, and set in a mold also preheated to about 250 ° C. Then, an aluminum alloy (Al-6Cu-0.5Zr) was infiltrated by high-pressure solidification casting, cooled and solidified, and then a test piece 1 having a width of 10 mm, a thickness of 2 mm and a length of 70 mm was cut out.

Test Example 2 Test pieces 2 to 4 were cut out under the same conditions as in Test Example 1 except that earth graphite, graphite whisker, and activated carbon were used instead of phosphorous graphite.

[Test Conditions] As shown in FIG. 1, two yarns 12 are stretched between supports 10 which are spaced apart from each other, and the test piece P is placed thereon. Impact vibration was applied, and the vibration attenuation type at that time was detected by a laser Doppler vibrometer.

The total amplitude Xn is set to 10 by the vibration damping waveform shown in FIG.
The relationship between the point reading and the number of vibration repetitions n and logeXn was calculated by the least square method, and the logarithmic decay rate (△) was obtained.

In the above test, Fc25, Al-56Zn
(Cosmar), and test pieces 5 to 7 similarly cut out from each material of Al-6Cu-0.5Zr were added and evaluated.

As can be understood from the test results obtained by the vibration damping waveform shown in FIG. 3 and the evaluation shown in Table 1, the test piece 1 according to the present invention generally has a high vibration damping ability and is used for a bed of a machine tool. The results were as good as those of ordinary cast iron (Fc25).

[Test Example 3] Next, in order to observe the effect of the volume fraction of phosphorous graphite on the vibration damping capacity and strength, the volume fraction of the fiber was fixed at 10%.
Several kinds of test pieces were cut out under the same conditions as test piece 1 except that only the volume ratio of phosphorous graphite was changed stepwise. In addition,
The test piece dimensions used for the bending test were 4 mm wide, 2 mm thick, and
The test was performed with a span of 30 mm and a load speed of 1 mm / min.

As can be seen from the results of the test, the logarithmic decay rate increases in proportion to the volume fraction of the phosphorous graphite, as shown in FIG.
As shown in the figure, the bending strength tends to decrease in inverse proportion to the volume fraction of the phosphorous graphite. This is due to the fact that phosphorous graphite itself has poor wettability with aluminum alloys and low interfacial bonding strength between them, but when vibration is applied, internal friction occurs at the interface,
Vibration energy is converted to heat energy and dissipated, and in particular, the large surface area of the finely powdered phosphorous graphite is accompanied by the expansion of the energy loss interface, and conversely the damping ability is effectively increased. Therefore, from the above test results, it was found that the volume fraction of phosphorous graphite which can be sufficiently used practically is 2 to 8%.

[Effect of the Invention] As described above, the present invention is a composite of a ceramic fiber assembly holding a specific amount of phosphorous graphite and an aluminum alloy. While maintaining the high vibration damping ability, the ceramic fiber and the phosphorous graphite have the other-side effect, and can also have excellent wear resistance, seizure resistance, and self-lubrication.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of a vibration damping test method, and FIG. 2 shows a method of obtaining a logarithmic damping rate, where (a) shows a vibration damping waveform and (b) shows a relationship between wave number and amplitude. FIG. 3 is a diagram comparing the vibration attenuation waveforms of the test pieces, FIG. 4 is a diagram illustrating the relationship between the volume ratio of phosphorous graphite and logarithmic decrement, and FIG. 5 is a diagram illustrating phosphorous graphite. It is a diagram which shows the relationship between volume ratio and bending strength.

Claims (1)

(57) [Claims] 1. A composite material comprising a ceramic fiber assembly holding phosphor graphite and an aluminum alloy, wherein the volume ratio of the phosphor graphite is 2 to 8%. Vibration composite materials.