Models for Material Damping of Powders in Additively Manufactured Metal Parts

Brigham Young University, Provo UT

Investigators

Abstract

This award supports research that looks to design and manufacture 3D printed parts that absorb considerably more vibration than existing metals, thereby promoting the progress of science, and advancing prosperity and welfare. Additive manufacturing has recently gained popularity for producing metal parts. Using this process, parts are created one layer at a time from a bed of metal powder by using a laser to melt and fuse the metal at certain locations. Any powder that is not fused is typically washed from the finished parts. However, metal materials that can be used for additive manufacturing have very low vibration damping. This limits the performance that can be achieved when dynamic loads or acoustic performance is important. This project will solve this challenge by designing parts such that they retain pockets of trapped metal powder, which can be designed to increase the parts ability to absorb vibration, reducing stresses and the noise that they generate. This can dramatically increase the life of parts used in automotive, aerospace or consumer applications, improving safety for passengers and end users. The ability to tailor damping on demand could also enable engineers to design systems with unprecedented acoustic performance, improving the competitiveness of domestic products. Beyond technology advancement, this method is expected to be readily adopted by industry through the offering of short courses to practicing engineers. This research aims to make fundamental contributions to expand our understanding of the ability of trapped powders to dissipate energy within additively manufactured parts. The work includes both an experimental component and a modeling component. In the experimental component, various parts will be created and tested to understand what shapes produce the most vibration absorption and the conditions under which they absorb vibration. Both linear and nonlinear dynamic testing methods will be used to characterize the linear modal characteristics of the parts as well as nonlinear behaviors that change the apparent stiffness and damping of the various modes. In the modeling component, a multi-faceted campaign will be conducted to identify a modeling framework for metal powders and methods to determine the effective material properties. The powders of interest contain billions of particles that are governed by complicated and unknown interaction laws, and hence modeling them using first principles is not currently feasible. This work plans to derive an equivalent, homogenized model for metal powders, so they can be treated as elastic or plastic solids within a finite element model of the part of interest, with a focus on capturing the effective stiffness and damping of the powders. This simplifies the material model and makes it feasible to deduce the properties of the powder from simple test coupons that exercise powder pockets in elongation and shear in multiple directions. Measurements of the vibration amplitude-dependent stiffness and damping of the test coupons will be correlated with finite element models that include either linear viscoelastic or nonlinear plastic powder material behavior. Computations will be dramatically accelerated by using quasi-static modal analysis, which allows for dynamic properties to be inferred from a few carefully chosen nonlinear static load-displacement curves. This project is jointly funded by the Dynamics, Control and Systems Diagnostics (DCSD) program, and the Advanced Manufacturing (AM) program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.