Universal testing machine
The universal testing machine , also called testing machine , is used to determine stress-strain diagrams or characteristic values from them for materials . Specifically, can tensile tests , compression tests , shear tests and bending tests are carried out, with tensile tests are most common.
Tensile testing machines are special testing machines that are suitable for displaying one-dimensional motion sequences in a force-displacement diagram or in a stress-strain diagram .
The classic application is the tensile test, in which a sample is subjected to increasing tensile loads until it finally breaks. The force-displacement diagram created during this test provides information about the load-bearing capacity, elasticity and plastic deformation of the material sample.
construction
The tensile testing machine generally consists of a fixed and a moving crossbeam , which is driven electrically or hydraulically by means of one or two spindles .
The crossbeam is moved in one direction at a defined speed (depending on the test specification) in order to tear the tensile specimen , which is held between the crossbeams by the specimen holder. The deformation of the specimen via the traverse path or a strain sensor (also called an extensometer ) and the required force are recorded with a force transducer . With the help of the specimen dimensions, the stresses and strains can be calculated. The safe and precise measurement of elongation when testing highly extensible, highly elastic and touch-sensitive samples is expediently carried out using non-contact optical measuring systems. To measure the forces, force transducers in accordance with the accuracy classes according to ISO 7500-1 with very large measuring ranges are preferred.
In addition to these static materials testing machines, they are also becoming increasingly important
- automated test systems as well
- Testing machines for dynamic and fatigue testing and
- Systems for tests under temperature and climatic influences.
conditions
According to the requirements, universal testing machines are offered from inexpensive, single-column table models with 3 kN to double spindle models with 50 kN up to hydraulic high-load machines from 300 - 2000 kN.
The requirements for tensile testing machines are u. a. defined under the following standards :
Norms
- DIN 51220 General information on the requirements for materials testing machines and their testing and calibration
- DIN EN ISO 6892-1: Metallic materials - Tensile test - Part 1 (formerly EN 10002)
- EN ISO 7500-1 Metallic materials - Testing of testing machines for static uniaxial loading - Part 1: Tensile and compression testing machines - Testing and calibration
- ISO 5893 test equipment for rubber and plastics
