Evaluation of the strength of material characteristics on hydraulic test machines

Conclusions

1.Tests have shown that the moving grip in universal hydraulic test machines can be subjected to considerable forced oscillations in the static loading of samples. The value of these oscillations can be computed theoretically from formula (2), or recorded experimentally on an oscillograph. The forced oscillations of the machine-sample elastic system disrupt the sample's static loading conditions specified by GOST 1497-61. As a result of this the physical conditions for determining the basic strength of materials characteristics are changed and may produce wrong results.

Moreover, the presence of stray forced oscillations in the operating components of the machine lowers its reliability and life, especially since these oscillations cannot be detected by simple recorders such as pointer indicators. 2.The supply elements of hydraulic test machines should consist only of thoroughly tested multipiston pumps which should feed oil to the working cylinder at a highly uniform pressure. It is also advisable to provide special throttling devices. 3.In accepting test machines the State Inspection Laboratories should check the absence of oscillations in the moving grip of the machine at its permanent location.