a machine used to determine the mechanical properties of materials and to test machine parts, assembly units, and manufactured items by damaging or destroying them. A tension testing machine has a loading device and measuring instruments. Tension testing machines are classified according to their loading device as hydraulic or mechanical. The mechanical loading device can be lever-type, single-spindle, or multiple-spindle.
Tension testing machines with one or several constant strain rates are used to test elastic materials, such as metals, wood, rubber, polymers, and fabrics, while tension testing machines with a constant load rate are used to test brittle materials. Depending on the direction of their tensile force, tension testing machines are divided into vertical and horizontal types. The loading device, whether mechanical or hydraulic, applies repeated
cyclic loads. The measuring instruments record the forces and the strains at various stages of the tests. The force-measuring instruments may be mechanical—lever-type, lever-and-pendulum-type, or spring-operated—or hydraulic. The use of electronic circuits makes possible the automatic reproduction of a specific testing routine.
Tension testing machines designed for testing materials at high or low temperatures are fitted with furnaces and cryostats.
Tension testing machines that can be used to test not only for elongation but also for compression, bending, creep, long-term strength, and relaxation are called universal tension testing machines. A kinematic diagram of the Soviet R-5 universal tension testing machine is presented in Figure 1. Universal tension testing machines have a recorder that graphs the process in “load-strain,” “load-time,” and “strain-time” coordinates. Strain is recorded by means of a moving clamp or an extensometer mounted on the specimen.
The maximum force of the loading devices of tension testing machines is 105 newtons (N), or 104 kilograms-force (kgf), for nonmetals, 5 × 105N (5 × 104kgf) for metals, and more than 3 × 107N(3 × 106kgf) for manufactured items. The error in the readings of the force-measuring instruments is ± 1 percent, and the error of the recorder is ± 2 percent.
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