The measurement of micro-hardness with loads between 0.09807 N and 0.9807 N has been carried out in direct mode (appraiser measured the dimensions of indentations with a measuring device fitted to the micro-hardness tester, a part of microscope) and in modified remote modes. The reference block – certified reference material with defined specified hardness and its uncertainty was used as a spec...

The nanoindentation experiment was carried out to estimate nanomechanical characteristics of polycarbonate polymer films. Hardness, effective elastic modulus and contact stress–strain rate curve were obtained. The results showed that the effective elastic modulus and the hardness decreased as the applied load was increased. As the hold time was increased, the effective elastic modulus and the h...

A new concept, the strength of bond, and a new form expressing the hardness of covalent and ionic crystals are presented. Hardness is expressed by means of quantities inherently coupled to the atomistic structure of matter, and, therefore, hardness can be determined by first-principles calculations. Good agreement between theory and experiment is observed in the range of 2 orders of magnitude. ...

We conducted the measurement of the hardness-depth relationship of NiTi shape memory alloy with a sharp Berkovich indenter. Different from most ductile metals, NiTi reacts to the mechanical load of indentation through phase transition underneath the indentation tip. We found that the hardness decreases rapidly with the increase of the indentation depth and eventually approaches a constant. To u...

Modern nanoindentation devices are capable of dynamic experimentations, which allow us to exploit instrumented hardness tests extensively. Beside the assets of recording mechanical properties continuously over displacement, there are ongoing debates whether the superimposed force alters the material's hardness. We will show for a broad range of materials that significant hardness differences ar...

Scissors are used to determine the hardness of fresh insects of different size and taxa. Our results indicate a strong relationship between the size of an insect and its hardness, which can be expressed as log(Fmax) = 0.65 × log(V) + α . Fmax is the maximal force needed to cut the insect and is our measure of insect hardness. V is the volume of the insect and a is a constant that can be derived...

Global optimization process can often be divided into two subprocesses: exploration and exploitation. The tradeoff between exploration and exploitation (T:Er&Ei) is crucial in search and optimization, having a great effect on global optimization performance, e.g., accuracy and convergence speed of optimization algorithms. In this paper, definitions of exploration and exploitation are first give...

AIM To evaluate the effect of successive cycles of disinfection in different denture cleansers on the surface roughness and the Vickers hardness of two layers of acrylic resin (base-BL and enamel-EL) of two commercial cross-linked artificial teeth. MATERIALS AND METHODS The occlusal surfaces of 60 acrylic resin denture posterior teeth (Trilux-TLX and SR Orthosit PE-SRO) embedded in autopolyme...

Treated effluent discharge from uranium (U) mines and mills elevates the concentrations of U, calcium (Ca), magnesium (Mg), and sulfate (SO4 (2-) ) above natural levels in receiving waters. Many investigations on the effect of hardness on U toxicity have been experiments on the combined effects of changes in hardness, pH, and alkalinity, which do not represent water chemistry downstream of U mi...

I nstrumented indentation testing (IIT) is a technique for measuring the mechanical properties of materials. It is a development of traditional hardness tests such as Brinell, Rockwell, Vickers, and Knoop. IIT is similar to traditional hardness testing in that a hard indenter, usually diamond, is pressed into contact with the test material. However, traditional hardness testing yields only one ...