• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.6
• /
• pp.16-23
• /
• 2018

A polymer porous sheet, which can be applied to diverse wearable devices, has some advantages such as light-weight, high flexibility, high elongation, and so many others. In order to fabricate a porous sheet, water-soluble particles like sugar were utilized frequently, and there has been great advances. However, with our best knowledge, there are not enough reports on the mechanical behavior of porous sheets having different porosity. So, in this work, we tried to find out the relationship between porosity and mechanical deformation of a porous sheet. The process parameters such as a particle size, sheet thickness and PDMS mixing ratio with curing agent were analyzed on the effect of increasing the porosity of a sheet. Also, mechanical deformation of a sheet was tested using a tensile experiment. Through the experimental results, we make a conclusion that a highly porous sheet with thin thickness has high flexibility, and it deformed nearly double elongation comparing to worst one among nine cases.

• Journal of the Microelectronics and Packaging Society
• /
• v.31 no.3
• /
• pp.91-98
• /
• 2024

This study reveals the feasibility and effectiveness of sinter bonding using an Ag nano-porous sheet at the lowest "theoretically" possible temperature of 145 ℃. By uniform pressure of 10 MPa for bonding times of 5 min and 10 min at 145 and 175 ℃, we achieved bonding strengths exceeding approximately 20 MPa with a only 5 min of bonding time at 145 ℃. In particular, it is interesting to note that in the pressure sintering bonding process at 145 ℃, bonding times of 5 and 10 min had no significant difference in strength. Even with a bonding temperature of 175 ℃, the difference in average bonding strength between bonding times of 5 min (i.e., 37.6 MPa) and 10 min (i.e., 43.0 MPa) was only 5 MPa. The bonding strength was fundamentally attributed to the thickness of the Ag sintered neck in the Ag sintered layer. Microstructural analysis revealed that as the bonding temperature increased to 175 ℃, the fraction of CSL Σ3 boundaries within the Ag sintered layer increased, indicating greater coalescence of Ag particles. This study systematically investigated the mechanism of bonding strength in extremely low-temperature pressure Ag sinter bonding, considering the relationship between microstructures and mechanical behaviors.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.2
• /
• pp.79-86
• /
• 2022

Numerous fabrication techniques have been used to mimic cylindrical natural tissues, such as blood vessels, tendons, ligaments, and skeletal muscles. However, most processes have limitations in achieving the biomimetic properties of multilayered and porous architectures. In this study, to embrace both features, a novel self-assembly method was proposed using electrospun microfibrous sheets. A bilayer microfibrous structure, comprising two sheets with different internal stresses, was fabricated by electrospinning a polycaprolactone (PCL) sheet on a uniaxially stretched thermoplastic polyurethane (TPU) sheet. Then, by removing the stretching tension, the sheet was rolled into a hollow cylindrical structure with a specific internal diameter. The internal diameter could be quantitatively controlled by adjusting the thickness of the PCL sheet against that of the TPU sheet. Through this self-assembly method, biomimetic cylindrical structures with multilayer and porous features can be manufactured in a stable and controllable manner. Therefore, the resulting structures may be applied to various tissue engineering scaffolds, especially vascular and connective tissues.

• Steel and Composite Structures
• /
• v.32 no.6
• /
• pp.753-767
• /
• 2019

Vibration control in mechanical equipments is an important problem where unwanted vibrations are vanish or at least diminished. In this paper, free vibration active control of the porous sandwich piezoelectric polymeric nanocomposite microbeam with microsensor and microactuater layers are investigated. The aim of this research is to reduce amplitude of vibration in micro beam based on linear quadratic regulator (LQR). Modified couple stress theory (MCST) according to sinusoidal shear deformation theory is presented. The porous sandwich microbeam is rested on elastic foundation. The core and face sheet are made of porous and three-phase carbon nanotubes/resin/fiber nanocomposite materials. The equations of motion are extracted by Hamilton's principle and then Navier's type solution are employed for solving them. The governing equations of motion are written in space state form and linear quadratic regulator (LQR) is used for active control approach. The various parameters are conducted to investigate on the frequency response function (FRF) of the sandwich microbeam for vibration active control. The results indicate that the higher length scale to the thickness, the face sheet thickness to total thickness and the considering microsensor and microactutor significantly affect LQR and uncontrolled FRF. Also, the porosity coefficient increasing, Skempton coefficient and Winkler spring constant shift the frequency response to higher frequencies. The obtained results can be useful for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.9
• /
• pp.22-29
• /
• 1997

This paper describes a three dimensional profile measurement method for sheet metal products which have flexible and porous sculptured surfaces. Shadow masks are used as measuring objects for practical implementation or this study. The shadow masks are located inside the fluorescent glasses of monitors for televisions or computers and used to prevent electron guns from interfering between pixels. Three dimen- sional surface profiles are measured by adopting a software autofocusing technique to capture focused images. The experimental results show that the method is very effecive and suitable for sheet meal prod- ucts with flexible and porous surfaces.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.35 no.3
• /
• pp.184-188
• /
• 2013

Post-traumatic enophthalmos is a relatively common problem following orbitozygomatic fractures. Bony-volume expansion and soft tissue atrophy are considered the main etiological causes of this condition. Enophthalmos is corrected mostly through reducing the enlarged orbit volume. Autogenous graft and various alloplastic materials are used for this purpose. Porous polyethylene is highly biocompatible, durable, and remarkably stable. Also, the titanium plate embedded in a porous polyethylene sheet provides radiographic visibility and increased sheet strength and contour retention. We present experiences of titanium reinforced porous polyethylene for correction of the traumatic enophthalmos with literature review.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.24 no.2
• /
• pp.89-96
• /
• 2012

Based on the hydroelastic theory and the matched eigenfunction expansion method(MEEM), the dynamic behavior of the porous flexible net sheet and wave forces have been investigated in monochromatic waves. The net sheet is installed vertically with the submergence depth. Top end of a net sheet is fixed and its lower end is attached by a clump weight. It is assumed that the initial tension is sufficiently large so that the effects of dynamictension variation can be neglected. The boundary condition on the porous flexible net sheet is derived based on Darcy's fine-pore model and body boundary condition. The developed analytic model can be extended to the impermeable/permeable vertical plate and the impermeable flexible membrane. The analytical model was used to study the influence of design parameters(wave characteristics, porosity, submergence depth, initial tension) on the response characteristics and wave load of the net sheet.

• Structural Engineering and Mechanics
• /
• v.77 no.4
• /
• pp.549-557
• /
• 2021

In this study, it is aimed to analyze the bending of porous sandwich plates using the four-variable shear deformation theory. The core of the sandwich plate is assumed to be functionally graded, and face sheets are assumed to be isotropic. The pore distribution of the sandwich plate is considered even and uneven type of porosity distribution. Displacement fields are defined with four variable shear deformation theory. Equilibrium equations of porous sandwich plates are derived from virtual displacement principle. An analytical solution is obtained by Navier's approach. Results are presented for uniformly and sinusoidally distributed loaded porous sandwich plates. Face sheet -core thickness ratio, porosity distribution, amount of porosity is investigated.

• Journal of Sensor Science and Technology
• /
• v.17 no.5
• /
• pp.329-337
• /
• 2008

Simple, small and portable oxygen sensors were fabricated by tape casting technique. Yttria stabilized zirconia containing cordierite ceramics (YSZC) were used as a porous diffused layer of oxygen in pumping cell. Yttria stabilized zirconia (YSZ) solid electrolyte, YSZC porous diffusion layer and heater-patterned ceramic sheets were prepared by co- firing method. Limit current characteristics and the linear relationship of current to oxygen concentration were observed. Viscosity variation of the slurries both YSZ and YSZC showed a similar behavior, but micro pores in the fired sheet were increased with increasing of the cordierite amount. Molecular diffusion was dominated due to the formation of large pores in porous diffusion layer. The plateau range of limit current in porous-type oxygen sensor was narrow than the one of aperture-type oxygen sensor. However limit current curve was appeared in porous-type oxygen sensor even at the lower applied voltage. The plateau range of limit-current was widen as increasing the thickness of porous diffusion layer of the YSZ containing cordierite. Measuring temperature of $600{\sim}650^{\circ}C$ was recommended for limit-current oxygen sensor. Porous diffusion layer-type oxygen sensor showed faster response than the aperture-type one and was stable up to 30 days running without any crack at interface between the layers.

• Steel and Composite Structures
• /
• v.41 no.6
• /
• pp.821-829
• /
• 2021

Nonlinear dynamic response of a sandwich beam considering porous core and nano-composite face sheet on nonlinear viscoelastic foundation with temperature-variable material properties is investigated in this research. The Hamilton's principle and beam theory are used to drive the equations of motion. The nonlinear differential equations of sandwich beam respect to time are obtained to solve nonlinear differential equations by Homotopy perturbation method (HPM). The effects of various parameters such as linear and nonlinear damping coefficient, linear and nonlinear spring constant, shear constant of Pasternak type for elastic foundation, temperature variation, volume fraction of carbon nanotube, porosity distribution and porosity coefficient on nonlinear dynamic response of sandwich beam are presented. The results of this paper could be used to analysis of dynamic modeling for a flexible structure in many industries such as automobiles, Shipbuilding, aircrafts and spacecraft with solar easured at current time step and the velocity and displacement were estimated through linear integration.