Residual Stresses in Ultrafine‐Grained Laminated Metal Composites Analyzed by X‐ray Diffraction and the Hole‐Drilling Method

Abstract

Accumulative roll bonding is an advanced manufacturing process, which is capable of simultaneously refining the grain size into the nanometer regime and bonding different metallic sheet materials. Herein, homogenous aluminum/aluminum as well as heterogeneous aluminum/steel laminated metal composite (LMCs) are fabricated. The residual stresses are experimentally determined by X‐ray diffraction and the hole‐drilling method. Generally, a complex residual stress profile is found in all LMCs. The level of residual stress strongly depends on the bonded materials. Compressive residual stresses are induced in all sheets in the near surface area. These stresses range from −5 MPa in aluminum to −240 MPa in steel. In the homogenous aluminum/aluminum LMCs, compressive stresses up to −26 MPa in the softer layers and tensile stresses up to 30 MPa in the stronger layers are built up. This is different to heterogeneous aluminum/steel LMCs, where tensile stresses up to 40 MPa in the softer aluminum layers and compressive stresses up to −72 MPa in the inner harder steel layers are present. Based on the results obtained it is possible to directly design the material combination or stacking architecture of ultrafine‐grained LMCs to tailor the residual stress profile.

Experimental Analysis of Residual Stresses in CFRPs through Hole-Drilling Method: The Role of Stacking Sequence, Thickness, and Defects

“…Considerable differences in residual stresses were found, in particular in the two first hole depth increments with a 50% deviation. Recently, Kümmel et al [19] adopted the HDM to measure the residual stresses in ultrafine-grained laminated metal composites, where steel layers were positioned at the top and bottom surface of the sample, and an aluminum layer was positioned in the middle. When the aluminum core was not considered for the calculation of the calibration coefficients, assuming that composite is a homogeneous material, the evaluated residual stresses were overestimated by about 50% compared with the model of the actual structure.…”