A New Prediction Method for the Ultimate Tensile Strength of Steel Alloys with Small Punch Test

Abstract

The load–deflection curve acquired from the Small Punch Test (SPT) is used to obtain the mechanical properties of materials using different correlation methods. The scattering level of these regressions tends to be high when a wide set of materials is analyzed. In this study, a correlation method based on a specific slope of the SPT curve was proposed to reduce scattering. Assuming the Ramberg–Osgood hardening law, the dependence of the SPT curve slope on the yield strength and the hardening coefficient is demonstrated by numerical simulations (FEM). Considering that the ultimate tensile strength could be obtained from the hardening coefficient, a response surface of the ultimate tensile strength with the yield strength and SPT curve slope, along with its equation, is presented for steel alloys. A summary of steel mechanical properties, based on the Boiler and Pressure Vessel Code (BPVC) and limited to yield strengths lower than 1300 MPa, is shown to select a set of experimental tests (tensile tests and SPTs) for which the range is completely covered. This experimental analysis validates the previous FEM analyses and the validity of the proposed correlation method, which shows more accurate correlations compared to the current methods.

Quantitative Representation of Mechanical Behavior of the Surface Hardening Layer in Shot-Peened Nickel-Based Superalloy

“…where K is the strength coefficient shown the ability to resist plastic deformation. n is the exponent of the strain hardening effect of the material, reflected by the differential slope of the plastic strain and stress curve of the material [35,36].…”

A systematic FEM analysis of the influence of mechanical properties in the reliability of the correlation methods in the small punch test

“…To obtain the Slope UL , Slope ini and Slope min in the SPT's, the same process introduced in previous research is used to follow a standardized method [8,16,20].…”

“…In order to improve the accuracy of the ultimate tensile strength, an alternative correlation method, known as the Slope min method, was introduced [20]. This method used the minimum slope of the zone III of the SPT curve (Slope min ) instead of the punch loads P m or P i used in the previous methods, and it showed a good accuracy.…”

An Improved Correlation for the Estimation of the Yield Strength from Small Punch Testing

“…Recently, a European standard was published [6]. Thus far, the SP test has been successfully used to estimate (i) the ductile-tobrittle transition temperature where SP tests at different temperatures are used to derive the SP energy as function of test temperature [1,2,7]; (ii) tensile properties, in particular the yield strength (YS) and ultimate tensile strength (UTS) [8][9][10][11][12]; (iii) fracture and damage parameters [3,13,14]; and (iv) creep properties [15][16][17][18][19][20][21][22]. In the European standard [6], the associated methods are described in informative, non-mandatory annexes.…”