Out-of-plane deformation reduction via inelastic hinges in fibrous metamaterials and simplified damage approach

The mechanical behavior of fibrous metamaterials is mainly determined by the interactions between the fibers composing the architecture. These interactions are usually of two different kinds: those directly depending on the positions of the fibers and those that need mediators, usually consisting of hinges, either inelastic or perfect, inducing restrictions on the kinematics of the fiber joints. In cases of interest, it has been observed that hinges can either have a certain torsional stiffness or behave as perfect joints, simply ensuring that the fibers remain interconnected, but not applying any constraint on the relative rotations between them. Here the effect of torsional stiffness of inelastic hinges is studied in two shear tests for a selected fibrous metamaterial. It is shown that the stiffness of hinges can be tailored to avoid, or at least reduce, out-of-plane deformations. Moreover, it is shown that, after reaching a threshold, permanent deformations are observed. This phenomenon is treated in a simplified way, by introducing damage in the continuum model.

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

In the concept of the process signature, the relationship between a material load and the modification remaining in the workpiece is used to better understand and optimize manufacturing processes. The basic prerequisite for this is to be able to measure the loads occurring during the machining process in the form of mechanical deformations. Speckle photography is suitable for this in-process measurement task and is already used in a variety of ways for in-plane deformation measurements. The shortcoming of this fast and robust measurement technique based on image correlation techniques is that out-of-plane deformations in the direction of the measurement system cannot be detected and increases the measurement error of in-plane deformations. In this paper, we investigate a method that infers local out-of-plane motions of the workpiece surface from the decorrelation of speckle patterns and is thus able to reconstruct three-dimensional deformation fields. The implementation of the evaluation method enables a fast reconstruction of 3D deformation fields, so that the in-process capability remains given. First measurements in a deep rolling process show that dynamic deformations underneath the die can be captured and demonstrate the suitability of the speckle method for manufacturing process analysis.

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

In the concept of the process signature, the relationship between a material load and the modification remaining in the workpiece is used to better understand and optimize manufacturing processes. The basic prerequisite for this is to be able to measure the loads occurring during the machining process in the form of mechanical deformations. Speckle photography is suitable for this in-process measurement task and is already used in a variety of ways for in-plane deformation measurements. The shortcoming of this fast and robust measurement technique based on image correlation techniques is that out-of-plane deformations in the direction of the measurement system cannot be detected and increases the measurement error of in-plane deformations. In this paper, we investigate a method that infers local out-of-plane motions of the workpiece surface from the decorrelation of speckle patterns and is thus able to reconstruct three-dimensional deformation fields. The implementation of the evaluation method enables a fast reconstruction of 3D deformation fields, so that the in-process capability remains given. First measurements in a deep rolling process show that dynamic deformations underneath the die can be captured and demonstrate the suitability of the speckle method for manufacturing process analysis.

BRB system stability considering frame out-of-plane loading and deformation zone

A simple and economical design approach is described for a BRB system, consisting of a BRB within a steel frame, subject to in-plane and out-of-plane seismic displacements. The approach avoids out-of-plane system or brace instability while allowing large frame out-of-plane deformations and desirable BRB axial performance. It also limits the compressive/tension force ratio. It is based on the simple concept that a brace will be stable with two moment-releases (hinges) but that an out-of-plane buckling mechanism may occur with more than two. The hinges are detailed as specified deformation zones (SDZs) at the brace ends. The hinges use a plate which can yield about its weak axis during out-of-plane movement. Simple methods to assess the stability of the brace itself (between hinges) are developed, an example is provided illustrating how the monotonic deformation demand of the simple plate hinge can be assessed, and detailing recommendations are made to restrict the deformation of the boundary elements at the brace ends.