Narrow Results

Geometrical analysis, numerical simulation and experiment were conducted to investigate wrinkling behavior in hydroforming of unsymmetrical tubular part. The influence of wrinkle parameters on the average thickness reduction rate was demonstrated using geometrical analysis. The wrinkling process and forming results of different loading paths were analyzed especially by means of FE simulation. It is shown from the experiment and simulation results that the unsymmetrical tubular part could be formed through the method of useful wrinkles. The thickness of the sound part is not uniform along the axial direction in the forming area. The internal pressure is the key factor to form the useful wrinkle. The axial stress is near zero in the expanding zone for useful wrinkles. By the method of useful wrinkle, process window of unsymmetrical tubular part can be enlarged for tube hydroforming.

Liquid meniscuses were prepared by spraying silicone oil drops with different sizes onto clean glass slides. Metal (iron) films with varied thicknesses were then deposited on the liquid meniscuses by direct current magnetron sputtering. The fracture and wrinkle behaviors of the films resulting from residual stresses are investigated in detail. It is found that cracks nucleate and propagate in the film during deposition owing to the thermal expansion of the liquid substrate. Subsequent cooling of the system creates a high compressive stress, resulting in the formation of various wrinkles in the film. The initiation and shape of the cracks are closely related to the film thickness and oil drop size. The wrinkle morphologies are dependent on the stress anisotropy induced by the liquid meniscus and crack edge.

Controlled surface morphologies of stiff films on compliant substrates possess a variety of applications, ranging from stretchable electronics, surface engineering to biomimics. Here, we report on the morphological evolutions of silver films deposited on prestretched compliant PDMS substrates by tuning the film strain in unloading, reloading and further stretching processes. It is found that the silver films generate transverse (perpendicular to the loading direction) wrinkles and longitudinal (parallel to the loading direction) cracks during the unloading process. On the contrary, longitudinal wrinkles and transverse cracks can be observed during the further stretching process. The morphological characteristics, evolution behaviors and mechanical mechanisms of the crack and wrinkle patterns are investigated in detail. The report in this work could promote a better understanding of the morphological evolutions of stiff films on compliant substrates by tuning the mechanical strain.

The generation of overall wrinkles on garment surfaces can be achieved by either introducing accurate cloth models with full collision response or by providing geometric wrinkle functions. Small wrinkles such as rippled appearance along seam lines have not been fully studied. Boundaries between different panels are often excluded from most garment draping simulations resulting in unrealistic appearance. This paper describes a new method to model realistic wrinkles on clothes via seams. The proposed seam model of tension pucker is simple and is easy to incorporate into a mass spring model with improvements over wrinkled appearance. We present a method that automatically constructs a seam surface along an arbitrary path on the surface of an irregular mesh. As an extension of modeling of seam pucker, we also apply the seam model to 3D garments.

In the present study, the initiation and evolution mechanisms of wrinkles in a square single layer graphene sheet (SLGS) under gradient tensile displacements are investigated based on molecular dynamics (MD) simulations. The mechanism of wrinkling process is elucidated by studying the atomic out-of-plane displacements development of the key atoms in SLGS. It reveals that the loading and boundary conditions play dominant roles in the wrinkling deformation of graphene. The dependences of the wrinkling amplitude, wavelength, out-of-plane displacement, direction angle and wrinkling area ratio on the applied gradient tensile displacements are obtained. The effects of temperature, size of graphene and loading grads on graphene wrinkling are investigated.

Quantum optics and photonic quantum-information technologies require emitters that have good stability and brightness, coupled with fabrication scalability and on-chip integrability. Most quantized emitters are presently based on 1D and 3D sources. Recently, monolayer transition metal dichalcogenides (TMDCs) hosting spatially localized excitons with narrow linewidths have garnered great interest. Advantages such as large binding energies and long room-temperature lifetimes of intralayer excitons suggest that TMDCs are promising candidates for use in optical devices. Here, we propose an emitter based on a 2D WSe₂ semiconductor monolayer integrated with a periodic 3D Si-based wrinkled pattern. Carriers confined within the wrinkled pattern can be electrically and optically pumped, and funneled, to boost emission from the 2D WSe₂ layer. This in turn acts as a monochromated quantum light source for the Si or any Si-based quantum optic and photonic information technologies. The brightness of the emission is enhanced by a factor greater than 40 compared with monolayer WSe₂ on conventional flat SiGe. Moreover, these monolayer 2D/3D semiconductor composite heterostructures are fully scalable and promisingly efficient chip-integrated emitters.