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Indentation plastometry is the idea of using an indentation-based procedure to obtain (bulk) mechanical properties (of metals) in the form of stress-strain relationships in the plastic regime (as opposed to hardness testing, which gives numbers that are only semi-quantitative indicators of the resistance to plastic deformation).
The J-integral represents a way to calculate the strain energy release rate, or work per unit fracture surface area, in a material. [1] The theoretical concept of J-integral was developed in 1967 by G. P. Cherepanov [2] and independently in 1968 by James R. Rice, [3] who showed that an energetic contour path integral (called J) was independent of the path around a crack.
In fracture mechanics, a crack growth resistance curve shows the energy required for crack extension as a function of crack length in a given material.For materials that can be modeled with linear elastic fracture mechanics (LEFM), crack extension occurs when the applied energy release rate exceeds the material's resistance to crack extension .
The other method, namely the secant method, uses the compliance-crack length equation given by ASTM standard to calculate effective crack length from an effective compliance. Compliance at any point in Load vs displacement curve is essentially the reciprocal of the slope of the curve that ensues if the specimen is unloaded at that point.
The figure on the right shows the plot of an external force vs. the load-point displacement , in which the area under the curve is the strain energy. The white area between the curve and the P {\displaystyle P} -axis is referred to as the complementary energy.
In the Knoop test, only the longer diagonal is measured, and the Knoop hardness is calculated based on the projected area of the indent divided by the applied force, also giving test units in kgf/mm 2. The Vickers microindentation test is carried out in a similar manner welling to the Vickers macroindentation tests, using the same pyramid.
This is not true since the actual area will decrease while deforming due to elastic and plastic deformation. The curve based on the original cross-section and gauge length is called the engineering stress–strain curve, while the curve based on the instantaneous cross-section area and length is called the true stress–strain curve. Unless ...
The value of σ g determines the slope of the least-squares regression curve. α: Relative standard deviation or degree of polydispersity. This value is also determined mathematically. For values less than 0.1, the particulate sample can be considered to be monodisperse. α = σ g /D 50. Re (P) : Particle Reynolds Number. In contrast to the ...