Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for +publisher:"Cornell University" +contributor:("Sachse, Wolfgang H"). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


Cornell University

1. Tan, Danielle. Sound From Sand.

Degree: PhD, Theoretical and Applied Mechanics, 2012, Cornell University

Various methods of producing sound from 'sounding' sand in the laboratory are explored. Low amplitude sound with frequency similar to that of 'booming' during spontaneous avalanches was produced in a small inclined chute and rotating flask. Shearing of dried sand with a stylus, and pouring from buckets or shaking in a jar produced loud sound in 200-500Hz range. Dryness of the sand and flowrate have significant effect on the produced sound. A model based on kinetic theory is proposed to explain the production of oscillations in avalanching flows. The avalanching layer behaves like a breathing mode with infinite wavelength, and perturbations in volume fraction allow oscillatory behaviour to be sustained in the inclined shear flow. Finally, a phase transition model is used to explain the presence, and characteristics, of oscillations observed in numerical simulations of inclined flows near their stopping angle. Advisors/Committee Members: Jenkins, James Thomas (chair), Sachse, Wolfgang H (committee member), Cohen, Itai (committee member).

Subjects/Keywords: granular material; sound production; kinetic theory

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Tan, D. (2012). Sound From Sand. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/29283

Chicago Manual of Style (16th Edition):

Tan, Danielle. “Sound From Sand.” 2012. Doctoral Dissertation, Cornell University. Accessed October 28, 2020. http://hdl.handle.net/1813/29283.

MLA Handbook (7th Edition):

Tan, Danielle. “Sound From Sand.” 2012. Web. 28 Oct 2020.

Vancouver:

Tan D. Sound From Sand. [Internet] [Doctoral dissertation]. Cornell University; 2012. [cited 2020 Oct 28]. Available from: http://hdl.handle.net/1813/29283.

Council of Science Editors:

Tan D. Sound From Sand. [Doctoral Dissertation]. Cornell University; 2012. Available from: http://hdl.handle.net/1813/29283


Cornell University

2. Zhou, Rachel. Effects Of Crimp And Slip On Laminar And Woven Fabrics Subjected To Ballistic Impact.

Degree: PhD, Mechanical Engineering, 2014, Cornell University

In the past decade, there has been growing interest and research on improving the performance of soft body armor materials subjected to high-speed ballistic impact. One "by-product" of the production process for these high strength polymer fibers, which are bundled into yarns, is the existence of undulation or waviness in the yarns, known as crimp. While this has always been treated as undesirable, few comprehensive studies have been done on the true effects of crimp in conjunction with yarn slip in ballistic fabrics. We first develop an in-house Finite-Difference (FD) numerical model to study the post-impact but pre-failure behavior of crimped fabrics made with Dyneema┬« yarns. While there has been past literature that attempted to numerically model crimp in ballistic fabrics, we note that the results provided little insight regarding the strain profile of individual yarns, the growth and evolution of tension and cone waves, and the yarn de-crimping process. Our first fabric model has laminar geometry with outof-plane zigzag crimp, and we validate our results through comparison with previous analytical models developed by the Cornell Phoenix Group. We present the following findings: (i) the peak strain attained by yarns in the fabric is lowered with increase in crimp, but with small sacrifices in terms of velocity deceleration and out-of-plane projectile displacement, (ii) yarn strain build-up towards its maximum value can vary significantly depending on projectile mass and size dimensions, (iii) tension and cone waves' velocities and shapes are influenced by various parameters including [ETA], the rocking viscosity coefficient, and (iv) allowing for frictional slip between the projectile and the yarns beneath it causes a shock wave effect, which changes the very early response behavior of the fabric post-impact. With our first fabric model, we also ensure that local strain concentrations and other dynamic artifacts resulting from the discretization of the structure are suppressed or smoothed. Since most fabrics in reality are woven with interlaced, over-under yarn structure, we develop a second crimp model with woven geometry. In addition to the forces from our first model, we introduce six new forces to describe the contact motion between weft and warp yarns in-plane (viscoelastic), and out-of-plane (allowing for compression but imposing a "Hertzian" condition). Correspondingly, we introduce six new parameters to control for yarn slip, crossover forces, and restoring forces. Comparing our two models, we observe that the second model provides greater flexibility and is more realistic in its ability to accurately portray the phenomenon of crimp interchange. Within the woven crimp model, we find many of the same trends in results provided in (i)-(iv) from the laminar model. We also discover that most of these parametric effects are not independent of each other, and provide case studies to show that varying combinations of multiple parameter values can in some cases produce nearly identical simulation behavior, but… Advisors/Committee Members: Phoenix, Stuart Leigh (chair), Hui, Chung-Yuen (committee member), Sachse, Wolfgang H (committee member).

Subjects/Keywords: ballistic impact; crimp; yarn slip

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zhou, R. (2014). Effects Of Crimp And Slip On Laminar And Woven Fabrics Subjected To Ballistic Impact. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/36160

Chicago Manual of Style (16th Edition):

Zhou, Rachel. “Effects Of Crimp And Slip On Laminar And Woven Fabrics Subjected To Ballistic Impact.” 2014. Doctoral Dissertation, Cornell University. Accessed October 28, 2020. http://hdl.handle.net/1813/36160.

MLA Handbook (7th Edition):

Zhou, Rachel. “Effects Of Crimp And Slip On Laminar And Woven Fabrics Subjected To Ballistic Impact.” 2014. Web. 28 Oct 2020.

Vancouver:

Zhou R. Effects Of Crimp And Slip On Laminar And Woven Fabrics Subjected To Ballistic Impact. [Internet] [Doctoral dissertation]. Cornell University; 2014. [cited 2020 Oct 28]. Available from: http://hdl.handle.net/1813/36160.

Council of Science Editors:

Zhou R. Effects Of Crimp And Slip On Laminar And Woven Fabrics Subjected To Ballistic Impact. [Doctoral Dissertation]. Cornell University; 2014. Available from: http://hdl.handle.net/1813/36160

.