6/27/2023 0 Comments Residual stressWhile the residual stresses of the second order are homogeneous over single grains, the residual stresses of the third order are inhomogeneous over smallest areas such as unit cells. The residual stresses of the second and third orders, on the other hand, classify as micro-stresses. They are homogeneous over multiple grains. The residual stresses of the first order are macro-stresses. In general, residual stresses are divided into three orders (Ref 13). Some methods, however, use different variables such as magnetic permeability (Ref 12). In most cases, this calculation is based on measurable strains. Residual stresses in solid materials are quantified through calculation rather than direct measurement (Ref 11). Since components are exposed to various types of heat inputs during manufacturing, the effects of a unilateral as well as a uniform heat input on the residual stress state in the components are of interest. Therefore, the aim of this study is to investigate the requirements for a qualitative or quantitative comparison of various methods. The influences of these differences on the comparability of various residual stress measurement methods are one major aspect that needs to be examined. There are several fundamental differences between the microstructure of the bulk material and the thermally sprayed coatings contains. In an approach to facilitate metallurgical bonding between aluminum and steel during pressure casting, AlZn5.5MgCu is deposited on steel by means of cold spraying. Current research is being conducted to produce hybrid materials by joining aluminum and steel for a lightweight design using pressure casting (Ref 10). AlZn5.5MgCu is another high-strength aluminum alloy. One disadvantage is its tendency to form hot cracks during welding, which can also be caused by residual stress fields. AlCu6Mn is the focus of current research, particularly in additive manufacturing (Ref 9). Strengthening effects are achieved by segregating Al 2Cu. AlCu6Mn represents a high-strength aluminum alloy that is predominantly used in the aerospace industry (Ref 8, 9). The materials used in this study were AlCu6Mn bulk material as well as an AlZn5.5MgCu coating on an S355J2 + N substrate. The used materials and the process technology have a great influence. Endeavors for a cross-comparison between various methods have been made (Ref 6, 7). Destructive methods are based on measuring the surface deformation of a workpiece after the removal of material, while non-destructive methods estimate the amount of residual stresses via the distortion of the crystal structure using diffraction methods. There are various destructive and non-destructive methods for measuring residual stresses (Ref 5). Similarly, additive manufacturing processes combine both aspects: a negative influence in form of thermal distortion as well as an unexpected component failure due to multiaxial stress formation (Ref 3, 4). Residual stresses can have a negative impact on the alternating load resistance. Welding is mainly characterized by thermal distortion. The formation of residual stresses during coating processes may result in cracks or even the delamination of the coating (Ref 2). The distribution and magnitude of the residual stresses play an important role for the correct design of the product and its manufacturing processes as residual stresses can have either a positive or a negative effect on the load-bearing capabilities (Ref 1). Especially the processing of metallic components is often followed by an inhomogeneous thermal heat input leading to the formation of residual stresses. In contrast, cold-spray coatings deposited on construction steel substrate exhibited tensile stresses, which relax over time at room temperature.Ĭoating, welding and additive manufacturing are key manufacturing processes in modern production lines and can be found across a wide field of technical applications. In case of cold spraying, the stresses in the feedstock material are considered negligible. Highest stress levels were found in the mechanically machined specimen, while heat treatment via tempering or deposition welding shows reduced stress levels inside of the specimens. Measurements with both methods were conducted on the same specimens and on the same measurement spots. To compare both methods, aluminum-based specimens (AlCu6Mn, AlZn5.5MgCu) with different processing histories were investigated. Furthermore, the residual stress state of a material is influenced by its processing history. Each stress analysis method has its specific limitations. In this work, the two established residual stress analysis methods x-ray stress analysis and incremental hole-drilling combined with electronic speckle pattern interferometry are compared. The level of residual stresses is of great importance for many applications.
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