Research

creative engineering

I worked on conceptual design, analytical/numerical analysis and experiments of energy absorbing structures for my DPhil. Specifically, I investigated extensively the relationship between geometry and corresponding reaction response in large deformation, and then came up with geometrical solutions for better energy absorbing performance. My current interest moves to other various applications and also researches tie more closely to specific engineering problems with multidisciplinary context.

 

 

Origami Bending Devices (Finished)

 

A series of novel bending devices of beams, panels, arches, and shells using origami technique were developed. These bending devices use origami techinique and spot-welding to eliminate section-height reduction problem during large deformation. This improvement enables structures for more constant bending resistance and overall higher energy absorption than conventional open section beam. Numerical simulations and experiments were used to validate these designs, which showed that properly designed origami bending devices can achieve 23.0%-40.0% increase of energy absorption and 12.7%-20.7% lower load uniformity than those of conventional beam. One pair of comparison of conventional and origami beams is presented below.

Li, Y., You, Z. (2014) Thin Walled Open-Section Origami Beams for Energy Absorption. In Proceedings of the ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 17-21 August 2014, Buffalo, NY, USA.

Thin Corrugated Tubes for Inversion (Finished)

 

Thin-walled tubes with corrugated cross-section instead of traditional circular tubes were proposed for tube inversion. Comparing to circular tubes, the introduction of corrugation not only increases specific buckling force and reduces imperfection-sensitivity of tubes, but also decreases load needed for inversion process due to less circumferential stretching. In consequence, thin corrugated tubes can be inverted significantly more reliably, and even allow practical frictional contact and geometric imperfection, which was not achieved or claimed before for tube inversion. A comprehensive numerical, experimental, and theoretical analysis was carried out on thin circular and corrugated tubes inversion, and validated the effectiveness of the new design. Thin corrugated tube inversion also reaches the theoretical limit of energy absorption. Experimental deformations of cirular and corrugated tubes inverison are presented below.

Li, Y., You, Z. (2015) Corrugated Tube Inversion for Energy Absorption. In Proceedings of the ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, August 2-5, 2015 in Boston, Massachusetts, USA.

Origami Concave Tubes (Finished)

 

Origami initiators were added to tubes with concave cross-sections. This new type of geometries, named as origami concave tubes, successfully triggered reliable progressive buckling failure which is uncommon for tubes with concave cross-sections, and achieved ultra-high energy absorption and relatively low peak force. A comprehensive numerical, experimental, and theoretical analysis was conducted on square, traditional concave, and origami concave tubes, which showed origami concave tubes achieved 3.3 times of specific energy absorption of square tubes. Additional to the huge improvement, it was illustrated that origami concave tubes can approach the theoretical limit of energy absorption with progressive buckling failure. Deformation of one type of origami concave tube and its reaction comparison to square tube are shown below.

Three Types of New Cores of Sandwich Panels for Energy Absorption

 

Sandwich panels, which consist of light core structure in middle and two outside skins, have been widely used for load bearing and energy absorption. Recently, origami foldcores, which can be used as light core structures in sandwich panels, are of interest of many for their open-channel design, continuous manufacturing process, and abundant number of design parameters in comparison with honeycomb and foams. However, one main drawback of origami foldcores is their relatively low energy absorbing capacity. I proposed three types of new designs for enhancing performance.

 

Type 1

 

Miura pattern has been usd for foldcore of sandwich panel and gives good performance. However, it always only folds once when crushed, which gives it high peak force and low mean crush force. The solution we proposed is D3-2, shown in figure below, is to add a higher order origami fold at one end of the foldcore as an initiator, which can trigger progressive buckling and lead to three times folding. This leads to 76.2% higher mean crush force than Miura foldcore.

 

Type 2

 

I proposed a new origami foldcore design, which is based on a zigzag origami pattern known as Miura pattern. The new design has a multi-corrugated shape as its cross-section, and asymmetric dents in it. It triggers failure mechanism containing both shell buckling and inversing modes, and doubles the energy absorption of Miura pattern foldcore.

Crushing process

Li, Y., You, Z. (2015) Multi-corrugated Indented Foldcore Sandwich Panel for Energy Absorption. In Proceedings of the ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, August 2-5, 2015 in Boston, Massachusetts, USA.

 

 

Type 3

 

One main hinderance for higher energy absorption of honeycomb structure is the difficulty of increasing ratio between thickness and width without increasing mass. Higher thickness to width ratio generally indicates higher energy absorption. My new design origami honeycomb structures can increase thickness width ratio per unit mass, and have stable progressive failure mode, which shall largely increase specific energy absorption of traditional honeycomb structures. Details and results will be presented soon.

 

Current Research Focus

 

Theoretical modelling of mechanics in wrapping folded sheet.

 

Mechanism analysis and design of thick origami panels.

 

Future Research Interest

 

Generally I am very open to researches on all sorts of problems and applications. I am specifically confident in conceptual design, as well as numerical, theoretical, and experimental analysis in structure and mechanism related topics. My planed future research topics are listed below.

 

 

Energy Absorbing Structures using Composite Material (idea orientated)

 

- Adopt composite material with relatively weaker matrix for making existent structures which utilize ductility

- Develop new designs of structures to coordinate composite materials commonly used

 

 

Origami Metamaterial for Various Reaction-displacement Curves (idea orientated)

 

- Fundamentally establish relationship between geometry and reaction curve

- Develop several charactermatic tunable modules, and achieve any desired reaction curve with combination of those modules

- Utilize reprogrammability to realize several desired reaction curves by only one initial geometry.

 

 

Use of Algorithm for Optimization or Developing New Conceptual Designs of Structures

 

- Very interested in this approach for the possibility of optimizing targeted non-linear behaviour of structures

 

 

Project Orientated Research

 

- Solving specific engineering problems in multidisciplinary context

- Corporation with people in different fields

- Specifically interested in space related research and project

 

 

Yang Li

DPhil Candidate

Department of Engineering Science

University of Oxford

 

Mobile: +44 (0)7478343695

Email: yang.li@eng.ox.ac.uk