A Methodology for Computed Tomography-Based Non-Destructive Geometrical Evaluations of Lattice Structures by Holistic Strut Measurement Approach

Abstract

The presence of lattice structures is increasing in the manufacturing domain especially in the air/spacecraft and biomedical applications due to their advantages of high strength-to-weight ratios, energy absorption, acoustic and vibrational damping etc. Dimensional accuracy of a lattice structure is one of the most important requirements to meet the desired functionality as there could be significant deviations in the as-produced part from the designed one. Evidently, an approach (non-destructive) to evaluate the dimensional accuracy of all the elements and eventually the lattice quality is of great significance. X-ray computed tomography (CT) has emerged as a promising solution in the field of industrial quality control over the last few years due to its non-destructive approach. In this work, we propose a methodology for geometrical evaluations of a lattice structure by measuring the deviation in shape and size of its strut elements holistically. The acquired CT data of the complete lattice is extracted in the form of a point cloud and then segmented and stored as single strut element with unique identification so that measurements can be performed on strut individually. As demonstrated with a metallic BCCz type lattice structure, the methodology helps in critical evaluation of its quality and the correlation with spatial position of the individual struts; e.g. the lattice exhibits large variations of shape among the inclined struts while the vertical struts possess consistency in their shape.

Progress toward the Definition of X-ray Computed Tomography Accuracy in the Characterization of Polymer-Based Lattice Structures

“…Single-strut measurements are also used [41] for a general characterization of the complete part, in which the orientation of the strut is evaluated as a parameter. Zanini et al [42] explored the application of two different methods for uncertainty calculation in lattice structures, with both using an additional calibrated reference standard as a test object along with a lattice part.…”

Geometrical Imperfections in Lattice Structures: a Simulation Strategy to Predict Strength Variability

“…Surface determination process is followed to extract a point cloud representation of the entire structure. The segmentation of this point cloud allows to build a point cloud representation of each micro-beam of the structure [7,8]. The CT workflow is represented in figure 1.…”

“…The scanned object can be treated and determined its surface as cloud points. Numerically, the cloud points can be extracted and segmented to individual struts to compute specific geometric defects such as shape defects (elliptic shape) [7,8].…”

Analysis of Correlation Between Manufacturing Parameters and Mechanical Strength Followed by Uncertainty Propagation of Geometric Defects in Lattice Structures

“…Geometric defects can be characterized by elliptic shape obtained by ellipse fitting of the lattice cell strut cloud point projection on the plan orthogonal to the strut axis as shown in figure 3 [5]. The elliptic shape of each strut can be obtained in our platform LATANA (LATtice ANAlyis) which is developed in a project framework at Institut de Recherche Technologique Systemx.…”

“…During the manufacturing process of a lattice structure, geometric defects are inevitably generated [5]. The defects can cause high impact on overall structural mechanical strength.…”