The Nonlinear Dynamics of Coupled Structures and Interfaces (ND-CSI) Summer Program

The 2018 ND-CSI Call for Applications

The 2018 Nonlinear Dynamics of Coupled Structures and Interfaces (NDCSI) Summer Program, hosted by Imperial College London, is open to graduate students and early career researchers from the US and international communities. The goal of this program is to bring together participants with diverse technical backgrounds from around the world to work in small teams on projects germane to interfacial mechanics and the dynamics of coupled structures. It is our hope that this program will help form lasting collaborations and make significant progress towards solving several of the major challenges in these research areas. The program is scheduled to last for six weeks, from July 4th through August 10th, 2018, in London, UK. Funds are potentially available through Imperial College London to cover some expenses associated with attending the program. There is no registration fee or other fees for participating in the program itself, though there are several expenses associated with Imperial sponsoring visas for international students.

The steering committee, Matthew Brake (Rice), Christoph Schwingshackl (Imperial), and Malte Krack (Stuttgart), are seeking 16 graduate students or postdocs to participate on this year’s projects:

Project 1: Evolution of Wear and Joint Behavior

Wear can have a significant impact on the dynamic behaviour of joints due to the changes of the interface conditions. This project will experimentally assess potential connections between the evolution of the hysteretic properties of the joint materials and the evolution of joint properties due to wear in the interface, and attempted to define some metric that will allow to quantify the damage.

Project 2: Suitability of Asymptotic Numerical Method for Friction Damping

The Asymptotic Numerical Method (ANM) provides an embedded framework for the continuation of solutions of the Harmonic Balance method, offering good advantages of more traditional continuation methods, but also introducing new challenges. In this project, a comparison of the ANM with the conventional Alternating Frequency-Time (AFT) method will be conducted for a friction-damped system (MDOF system with elastic Coulomb friction) to quantify the advantages and disadvantages of ANM.

Project 3: High Speed Camera DIC to Monitor Joint Behaviour

This project will develop an approach to measure localised joint behaviour in a lab joint during a vibration cycle (bending and torsion modes) with the help of High Speed Cameras and Digital Image Correlation techniques. The main challenge thereby will be to capture the separation at the interface and link it to the global motion, in order to provide an understanding of the underlying mechanism at the joint.

Project 4: Continuation Method for Bladed-Disk Vibration with Contact and Friction

The purpose of this project is to prepare a general nonlinear dynamic test case for the community, based on a real bladed-disk geometry in order to assess different continuation solver. The project will focus initially on preparing different finite element meshes of the test case, running static analysis in different finite element package, and produce reduced order models for nonlinear vibration analysis. The provided test case can then be used to carry out initial nonlinear analysis, either by student provided tools, or some basic in-house solvers.

To submit an application for participating in the program, please email Matthew Brake (brake at rice.edu) a copy of your CV and a cover letter detailing your research interests, project preference, and a statement about what funding your home institution can provide. Applications are due by March 2, 2018. For more information, please contact a steering committee member.



Background Information

The ND-CSI, hosted by Rice University, was founded by Prof. Brake, and is directed by a steering committee consisting of three faculty members: Matthew Brake, Christoph Schwingshackl (Imperial College London), and Malte Krack (University of Stuttgart). The ND-CSI is open for any graduate student to apply to participate. The 16 participants each year are selected by the steering committee based on the students’ applications as well as the fit and needs of each of the four projects that will be hosted in the ND-CSI each summer. There are no fees or costs associated with participating in the ND-CSI. The aims of the ND-CSI are 1) to promote collaboration amongst graduate students who are planning on embarking on a research career so that they have a professional network to support them beyond graduate school, 2) to develop a solid foundation in nonlinear dynamics and joint mechanics for newer graduate students, 3) to conduct scoping research that motivates larger research problems, and 4) to synthesize new research techniques from the varied backgrounds of the participants and mentors. The previous incarnation of the ND-CSI has been instrumental in advancing the state of the art for joints modeling, with an average of 1.5 conference papers per project per year, and one journal paper for each project that spans multiple years, in addition to the adoption of new metrics and hardware throughout the community (such as the use of the Brake-Reuß beam by approximately two dozen institutions as a benchmark system for joints research).

The ND-CSI is a six week long research collaboration that has two components associated with it: graduate student research and STEM outreach. The graduate component of the ND-CSI additionally includes 1.5 months of preparation before students come on site, and approximately 2 months of work following the conclusion of the summer research during which students complete a paper on their project. The STEM outreach program is open to any high school student who wishes to apply, and there are no fees or other costs associated with attending. For more information about the STEM program, please visit the RSTEM webpage.

In 2017, the first ND-CSI summer program was hosted at Rice University. The four projects from this first edition of the program resulted in four conference papers and three journal papers that are in progress. The projects are briefly described below:

Project 1: Interfacial Contact Pressure – In Situ Measurements and Numerical Modeling

Understanding the mechanisms that leads to a nonlinear dynamic response of a bolted lap joint is of great importance when it comes to the correct prediction of the dynamics of an assembled structure. This project will use a newly developed technique to measure, in situ, the contact pressures internal to a jointed interface during dynamic excitation. Numerical studies conducted in tandem with the experiments are expected to elucidate new understanding to the physics of interface dynamics.

Project 2: Nonlinear System Identification for Joints Including Modal Interactions

Even with the best available simulation tools, it is still not possible to predict the effective stiffness and damping of bolted interfaces. This project proposes to study methods that can experimentally capture the dynamics of interfaces in the important case in which multiple modes of the structure interact. Initially, finite element models for a jointed structure with a discrete nonlinearity will be used to test the proposed techniques. The most promising approaches will then be validated on measurements from real structures.

Project 3: The Effect of Non-Flat Interfaces on System Dynamics

Jointed systems have long been known to exhibit high part-to-part variability. To better understand the high part-to-part variability, this research will focus on the role that local geometric effects have on part-to-part variability through a combined numerical and experimental investigation. The ultimate goal of this research is to both determine what portion of part-to-part variability can be explained by surface curvature and to propose interface designs that are robust against this variability.

Project 4: Comparison of Nonlinear Modal Testing Methods for Jointed Structures

This project addresses the extraction of nonlinear modal characteristics, i.e., modal frequency, damping and deflection shape of a jointed structure as a function of the vibration level. Multiple methods are applied to a simple structure with a friction joint. The quality of the metrics is assessed by testing their ability to reconstruct the steady-state frequency response and the free decay for different loading and initial conditions.