Universal Testing Machine STM-50
SANTAM Universal Testing Machine is able to test mechanical properties of a wide range of materials such as graphite, metals, wire, cable, ceramics, plastics, tube, pipe, adhesives, bars, belts, and composites. Using this instrument, mechanical properties such as, ring stiffness, tensile, bending, and compression can be measured.
- Tensile Test:
Tensile testing is a fundamental materials science and engineering test in which a sample is subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength, breaking strength, maximum elongation, and reduction in area. From these measurements the Young’s modulus, Poisson’s ratio, yield strength, and strain-hardening characteristics can be determined.
The test process involves placing the test specimen in the testing machine and slowly extending it until it fractures. During this process, the elongation of the gauge section is recorded against the applied force. The data is manipulated so that it is not specific to the geometry of the test sample. The elongation measurement is used to calculate the engineering strain (ε) using the following equation:
where L0 is the initial gauge length, and L is the final length. The force measurement is used to calculate the engineering stress (σ) using the following equation:
where F is the tensile force and A is the nominal cross-section of the specimen. Also, Young’s modulus can be defined by E=Stress/Strain . The machine does these calculations as the force increases, so that the data points can be graphed into a stress–strain curve.
- Compressive Strength Test:
Compression testing is a very common testing method that is used to establish the compressive force or crush resistance of a material and the ability of the material to recover after a specified compressive force is applied and even held over a defined period of time. Compression tests are used to determine the material behavior under a load. Compression testing is often done to a break (rupture) or to a limit. When the test is performed to a break, break detection can be defined depending on the type of material being tested. When the test is performed to a limit, either a load limit or deflection limit is used.
Types of compression testing include flexure/bend, spring testing, and top-load/crush. Common compression testing results are load at rupture, deflection at rupture, work at rupture, maximum load, deflection at maximum load, work at maximum load, stiffness, chord slope, offset yield, and stress.
- Three or Four-Point Bending Flexural Test:
Bend tests deform the test material at the midpoint causing a concave surface or a bend to form without the occurrence of fracture and are typically performed to determine the ductility or resistance to fracture of that material. Unlike in a flexure test the goal is not to load the material until failure but rather to deform the sample into a specific shape. The test sample is loaded in a way that creates a concave surface at the midpoint with a specified radius of curvature according to the standard in relation to which the test is performed. Bending tests are as popular as tensile test, compression test, and fatigue tests.
The three or four-point bending flexural test provides values for the modulus of elasticity in bending Ef, flexural stress σf, flexural strain εf, and the flexural stress-strain response of the material. The main advantage of a three or four-point flexural test is the ease of the specimen preparation and testing.
- Axial Tensile Testing of Single Fibers:
The mechanical and damage properties of single fibers used in fibrous composite have gained tremendous importance in recent years. These properties are used in determination of effective properties of composites by micromechanics. These are also used in the micromechanical damage modeling. Further, these properties are used as an indicator of the excellence of product by manufacturers. Axial tensile testing of single fibers provides values for the axial tensile modulus, ultimate strength and failure strain of single fibers.