High-accuracy compliance correction for nonlinear mechanical testing: Improving Small Punch Test characterization

Mechanical Properties Study of Miniature Steel Specimens Based on the Small Punch Test and Simulation Methods

“…However, the reasonableness of the analytical results for the curves in Figure 9 needs to be further investigated by applying the compliance calibration of the loading system to the experimentally obtained force–displacement curves. It is worth noting that regarding the compliance calibration of the loading system, different compliance calibration methods are used by researchers [ 27 , 28 , 32 , 39 , 40 , 46 , 49 ]. The displacement ( δ upper ) on the upper face of the specimen can be derived from the displacements ( δ ext ) through an appropriate correction of the respective elastic compliances involved, referred to as C ext [ 28 , 32 , 39 , 40 ].…”

“…The displacement ( δ upper ) on the upper face of the specimen can be derived from the displacements ( δ ext ) through an appropriate correction of the respective elastic compliances involved, referred to as C ext [ 28 , 32 , 39 , 40 ]. Some researchers [ 27 , 43 , 46 ] believe that a linear calibration of the force–displacement ( δ ext ) response can be achieved with the compliance calibration curve obtained by this method. However, other researchers have argued that the effective contact area with the punch, the applied stress, and the strain field obtained during the SPT are neither constant nor uniform and continuously vary during the test.…”

“…Although SPT is widely developed in the last decades, the standardization of this method is still in progress [ 21 , 22 , 23 , 24 , 25 ]. An important factor affecting the results that need to be considered is the accuracy of the correlation results between SPT and the uniaxial tensile test (UTT), which is highly dependent on the sensitivity of the test equipment [ 26 , 27 , 28 ]. This result makes it difficult to transfer the procedures related to the evaluation of mechanical parameters ( σ YS and σ UTS ) by different researchers [ 29 , 30 ].…”

“…Hähner et al [ 40 ] also pointed out that the initial stage curves of force–displacement in SPT are affected by using the non-contact displacement transducers. The results of Ávila et al [ 27 ] showed that this factor leads to a deviation between SPT tests and FE simulations, and attributed this uncertainty to the large effect of elastic displacement associated with the low stiffness of the device setup. Although the LVDT sensor is recommended to obtain relatively accurate displacement results through direct contact with the bottom of the specimen in the current standard [ 21 ], this displacement measurement system is not used by all researchers.…”

Experimental and Numerical Small Punch Tests of the 14Cr ODS Ferritic Steel

“…During SPT, when the displacement is measured as the displacement of the punch, the elastic displacement of the device and sample are added to the readings. Therefore, the elastic component of the total displacement in the raw load-displacement curves comprises both the material's and the machine's elastic response [27]. To take this error into account, the compliance correction of SPT system was performed, accordingly to procedures described in the literature [28], which is a common practice carried out for tensile and compression tests [29].…”