Duroscope

A duroscope is a measuring device used in non-destructive material testing to determine the hardness of materials.

Working principle

The duroscope is a forgotten tool that works according to a dynamic hardness test method and principles similar to those of the rebound hammer (Schmidt hammer) or that of a scleroscope . It can be used to test the hardness of rock surfaces or metals in order to detect small fluctuations in strength.

Testing of rock surfaces

In a test method rebound values at selected lithologies , such as porous limestone , travertine , microcrystalline limestone, marble , andesite - tuff and basalt measured. The rebound values of the values determined by the duroscope were then compared with 4 types of Schmidt hammers (N-34, L-9, Digi-Schmidt and PT). In order to be able to test the influence of weathering on the strength of the rock, not only fresh, but also weathered surfaces were measured. The rebound values determined were then compared with the standardized laboratory results of the same lithologies and presented as the relationship between Duroskop rebound values and the Schmidt impact values. The values obtained from both principles could now be correlated with one another. The advantage of the duroscope is that it allows minor changes in the surface strength to be recognized. The disadvantage is the greater sensitivity to surface irregularities.

Working method on metal surfaces

With the duroscope, which is also similar to that of a scleroscope in its mode of action, a pendulum strikes against a vertical surface to be tested, so that the pendulum bounces back again. The hardness of the test object can be inferred from the maximum height of the rebounding pendulum. The end of the duroskop pendulum has a steel ball with a diameter of 3 mm. The pendulum is moved from a defined position, e.g. B. 70 °, dropped onto the flat surface of the test object. Here part of the physical casework is used to create a permanent spherical impression, while the elastically absorbed work drives the hammer back up again. The rebound height or the rebound height corresponds to the "duroscope hardness" and is indicated by a drag pointer on a display with circular graduation. The ratio of the initial height to the recessed height is used as a measure of the hardness (hardness number).

In order to be able to test small or difficult-to-access test pieces, a new addition was brought to the interposition of a firing pin under preload between the drop hammer and the test piece. The so-called Brinell duroscope analysis , on the other hand, allows the hardness and dynamic properties of carbon steels to be determined . In contrast to the other methods, the ball of the pendulum hammer is tested depending on the metal from 3 to 20 blows on the same point on the surface of the test piece. From the resulting change in the point change in hardness, conclusions can be drawn about the behavior of the material in the event of intermittent loading.

Web links

Structural mapping to analyze the state of weathering on the outer walls of Buda Castle (Budapest, Hungary)

Individual evidence

↑ ^a ^b ^c ^d Non-destructive Surface Strength Test — Duroskop a Forgotten Tool; Comparison to Schmidt Hammer Rebound Values of Rocks, In: Link Springer
↑ Return hardness (PDF), In: Link Springer
↑ Deutsche Chemischen Gesellschaft (Ed.): Iron: Part C - Delivery 1. Hardness test method (= Gmelin Handbook of Inorganic and Organometallic Chemistry . No. 59 ). Springer, Berlin, Heidelberg 1974, ISBN 3-662-07543-1 ( limited preview in the Google book search).

[D-1] Non-destructive Surface Strength Test — Duroskop a Forgotten Tool; Comparison to Schmidt Hammer Rebound Values of Rocks, In: Link Springer

[2] Return hardness (PDF), In: Link Springer

[3] Deutsche Chemischen Gesellschaft (Ed.): Iron: Part C - Delivery 1. Hardness test method (= Gmelin Handbook of Inorganic and Organometallic Chemistry . No. 59 ). Springer, Berlin, Heidelberg 1974, ISBN 3-662-07543-1 ( limited preview in the Google book search).