Why are there different hardness tests?

Why are there different hardness tests?

Different test scales were created to assist engineers in selecting the appropriate metals and hardness for their specific application. To help you understand the different test scales we’ve created a cross-reference table table for three of the most popular hardness tests below.

What is the limitation of Brinell hardness test and why?

Disadvantages of Brinell Hardness Test: The main disadvantage of this test is that it is not suitable for small size objects due to large indentor impression. Slightly inaccurate hardness measurement while testing hard objects as ball indentor deforms. Not suitable for thin objects due to deep penetration.

What is the limit for hardness test?

® Limits: Oral tablets have a hardness of 4 to 10kg ; but, hypodermic and chewable tablets have a hardness of 3 kg and sustained release tablets have about 10-20 kg. Page 9 > Make hardness test on 5 tablets and then take the average hardness.

Why is the hardness test used for material evaluation?

Hardness testing is widely used for material evaluation because of its simplicity and low cost relative to direct measurement of many properties. Specifically, conversion charts from Rockwell hardness to tensile strength are available for some structural alloys, including steel and aluminum.

Why can a hardness test often be substituted for a tensile test?

Common concerns with hardness testing are accuracy and repeatability. Hardness is extrapolated from the depth measured, which then correlates to tensile strength. This indirect route can introduce more error. A tensile test is more accurate because it provides an actual reading of the tensile strength.

Why Brinell hardness test is not suitable for very hard material?

Brinell testing is not suitable for very hard materials since the hardness of the test material approaches that of the steel indentor. As a result there will be a tendency for the indentor to deform.

Why Brinell and Vickers hardness test results show similarities?

Why Brinell and Vickers hardness test results show similarities? Explanation: Brinell test indenter is made of hardened steel. Vickers test indenter is made of diamond. These give geometrically similar indentations so the similar results.

How does hardness affect dissolution?

The dissolution rate constants were determined from the equation of Noyes & Whitney (1897) and a good correlation between the hardness and the dissolution rate constants was obtained. The hardness governed the dissolution over all the stages from tablet to the smallest particles after the breakage by disintegration.

Why is hardness test important in material characteristics?

The application of hardness testing enables you to evaluate a material’s properties, such as strength, ductility and wear resistance, and so helps you determine whether a material or material treatment is suitable for the purpose you require.