or between 0.15 and 0.35 mm for method B. In this a 5 mm diameter hardened steel ball is pressed into the test surface under a specified load so that the indentation is between 0.07 and 0.10 mm for method A. #Ball indenter irhd isois the ball indentation hardness test, which is standardized in ISO 2039. Ī test more frequently found in Continental Europe than in the U.K. In the Rockwell test the difference in size between the. In 1920 Rockwell developed a number of tests, including the B, E, F and G scales, in which the indenter is steel, and the A, C and D scales, using a conical diamond indenter with a spherical tip (Figures 10.23b and 10.23c). This was suitable only for metals softer than steel. The first of these, described in 1900, was the Brinell test, using a 10 mm steel ball indenter (Figure 10.23a), giving the Brinell hardness number, BHN. There are four major indentation hardness tests, which differ from each other in the shape of the indenter (Figure 10.23). īS 2782 Method 365D, Determination of Hardness by Ball Indentation Method, London (1978). Unhke other Rockwell scales, Rockwell parameter, R, correlates with the hardness as determined by ball indentation. Typical microhardness values for polymers are summarized by Boor (1947). The scratch test is used where indentation microhardness tests cannot be made close enough to determine local variations. Static-ball indenter correspond directly. This is a typical situation in which the elastic-viscoelastic analogy is, in general, no longer applicable. Let us consider first a rigid ball that does not roll but indents a viscoelastic half-space this analysis will be extended to a rolling ball. Now we consider roller ball indentations. In fact, the impacting cylinder can be considered to represent a circular pillar and the viscoelastic medium the solid upon which it rests. This problem is also interesting from the point of view of soil mechanics, particularly in the theory of the safety of foundations. To gain some insight into this problem, we consider the simple case of a flat circular cylindrical indentor, which presents a relatively simple solution. One of the simplest pieces of equipment used in the experiments is the scleroscope, in which a rigid metallic ball indents the surface of the material. The assessment of mechanical properties of materials by means of indentation experiments is an important issue in polymer physics. Indentation problems are an important subset of contact problems (17,18). įigure 16.13 Resistance against environmental stress cracking by 2-propanol (ball indentation test ISO 4600,1 h exposure).Ĭontact problems have their origins in the works of Hertz (1881) and Boussinesq (1885) on elastic materials. Polymer Izod impact strength (j/m) 7f> (K) hard ness Ball indentation hardness (107 N/m2) Shore D hardness Friction coefficient (-) resistance (ASTM- D1044) (Taber) (mg/lOOOc) Abrasion loss factor (DIN 53516) (mg) Polymer ref. Izmerenie tverdosti po metodu vdavlivaniya sharika ( Hardness Measurements by Ball Indentation Method). This range can be extended upward to HBN 500 by using special cold work-hardened steel balls and to as high as HBN 627 by using special tungsten carbide balls. The Brinell test range is limited, by the capability of the hardened steel ball indenters used, to HBN 444. A modification of this device employs impact loading by a hammer to achieve similar results. Load is controlled by a built-in shear pin. The pin Brinell tester takes the form of a large C damp with the ball indenter on the end of the screw. ISO 2039-1 2001 Plastics - Determination of hardness - Part 1 Ball indentation method ISO 2039-2 1987 Plastics - Determination of hardness - Part 2 Rockwell hardness ISO 2439 1997 Flexible cellular polymeric materials - Determination of hardness (indentation technique). However, Vickers microhardness is more satisfactory for monitoring degradation of rigid materials. The standard methods are given in ISO 868 (Shore) and ISO 2039 (Ball indentation and Rockwell). For plastics, the term hardness refers to resistance to indentation but depending on the test method the measurement is made either with the indentation load applied or after its removal when elastic recovery has taken place. Hardness is essentially a measure of stiffness and in principle can be related to modulus.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |