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Mechanical properties

 

Mechanical tests

 

The mechanical tests are tests which make it possible to measure various properties of materials such as: hardness, tensile strength, limits elastic, deformation, ratio compression…

 

Tensile tests

 

The tensile test represents a concrete test of measurement of the properties of material.

 

The mechanical tests are experiments of which the aim is to characterize the laws of behaviors of the materials (mechanics of continuous mediums). The law of behavior establishes a relation between the constraints (pressure=force/surface) and the deformations (unit lengthening without dimensions). One should not confuse a deformation with a displacement.

 

 

Tensil test on a flat wire

 

The test opposite watch a tensile test carried out a flat wire rolled in Phynox (0.145x0.017). The maximum stress measurement (sigma max) makes it possible to define the state of the wire in the level of work hardening and the heat treatment.

 

The tests on wire of small sections is one of our knowledge obtained with the years of works. We are able to make complete studies on good numbers of alloys, in particular those with property arises. The section can be round one rectangular, that not of incidence on the result.

 

Tensile test on a Titanium rod (rank 4)

 

Titanium rank 4 is an alloy used for surgical implants. The test opposite at summer carried out on a bar (diameter 4mm) in order to validate a batch with reception.

 

The standard ISO 6892 definite the shape and the dimension of the tensile specimen to be tested. A test on a bar without machining is also possible.

 

 

Tensile test on a fabric

 

The test opposite at summer carried out on a fabric used in technique of insulation of aeronautical apparatus. The aim of the test is to tear a piece of fabric of known size in order to know its resistance of it. The test will be carried out in theory in two directions X and Y.

 

Vickers hardness test (HV)

 

The measurement of Vickers pyramid hardness is carried out with a pyramidal point standardized out of basic diamond square and of point angle between face of 136°. The perfect print thus has a form of square. One measures of two diagonal d1 and d2 using an optical tool.

 

The median value D is obtained with d1 and d2. The test standardizes also the time of application as well as the load applied to the penetrant. A tabelle data by the standard makes it possible to correlate these parameters with Vickers pyramid hardness.

 

Hardness by micro-print, usually called microhardness calls going upon loads of 5 to 1000g. The utlisation of micro-print makes it possible to locate the point of measurement precisely. We generally use it in parallel of a microstructural analysis.

 

This test has many advantages:

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non-destructive test, no point visible

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local measurement on a defect

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filiation of hardness of surface to heart.

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measure on different phase from an alloy

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measure homogeneity of materials

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measure on a sample coated or not

 

Hardness test Shores A or D

 

The scale of Shore hardness measures the hardness of elastomers, plastics, leathers and wood.

 

This scale was developed with an aim of carrying out measurements except laboratory with a portable Shore durometer (for example to measure the hardness of tires.

 

Measurement is based on the spring deformation according to a known displacement. The quality of the spring thus determines the quality of the apparatus.

 

There exists in fact twelve scales of Shore measurement. Most current are the scales A and D, recognized in particular by the standards ISO 868 and 7619, ASTM D 2240 and DIN 53505:

 

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Shore A (for soft materials);

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Shore D (for hard materials).

 

The geometry of the penetrant differentiates these two scales.

The dial of the durometer is graduated in SHORE degrees from 0 to 100, of slackness to hard.