Research of replication accuracy in some elastomer materials with different Young’s modulus

In this work we observed three different elastomeric materials with different Young’s modulus: Silastic T-4, Plat Set 30, and Lasil-C. Their usage makes it possible to overlap the range of rigidity obtained for Silgard under different curing conditions, without high temperatures and long curing time. The results obtained during the replicas formation using a brass master mold with micro-sized structures for these elastomers were presented. The quality of the replication in materials with low Young’s modulus turned out to be better than for Silgard, and for the hard Silastic T-4 – it is comparable to it.

Vibration Analysis on a Thin Walled Structure

A vibration analysis performed on thin walled open beam section. The influence of the vibration is studied for different thickness and different critical load conditions. A FEM model is applied to the thin wall sections like beams. For the different young’s modulus, critical load and thickness of the flange the mode shapes are analyzed. The free vibrations of the channel unsymmetrical thin-walled beam of length 80, breadth of the flange is 37.81e-3, thickness of the flange, over all lengths of the flange at λ = (7.5, 10,12.5,15,17.5,20), for e= 10,20.3040,G= rigidity of modulus also been analyzed..

Crimped Fiber Printing via E-Jetting for Tissue Engineering

A regular pattern called crimp is an essential morphological feature of collagen fibers in native tendon. In this study, the direct crimp writing (DCW) and zig-zag pattern writing (ZPW) were developed based on electrohydrodynamic jet printing (E-jetting) process to fabricate the crimped fibers. For the DCW process, the fibers were deposited with the linear movement of stage, and the crimps (crimp angle: ∼ 46°; crimp length: ∼630 μm; fiber diameter: ∼100 μm) were formed from the spinning of fibers. For the ZPW process, the fibers was printed via the zig-zag moving path, and the effects of a vital process parameter (i.e. dwell time) on the fiber characteristics were investigated to obtain controllable and regular crimped fibers. The result of mechanical testing showed that the ZPW fibers exhibited the “toe” and linear regions with different Young’s modulus (4 ± 1 MPa and 23 ± 4 MPa, respectively), while DCW fibers were found only with linear region. Compared with DCW process, the ZPW process was able to fabricate crimped fibers in a more controllable pathway. The human tenocytes were also seeded on the ZPW fibers to investigate the cellular alignment. This study suggested that ZPW process was capable of printing crimped fibers which mimicked the fiber profile in human tendon, and has the potential in scaffold fabrication for tendon tissue engineering.

Numerical analysis of the influence of sample stiffness and plate shape in the Brazilian test

Due to the heterogeneity of rocks, their tensile strength is around 10% of their compressive strength, which means that breakage is mainly caused by tensile stress. The measure of tensile stress is very difficult due to rock fragility, so it has usually been measured by indirect measurement methods , including the Brazilian test. However, recent works indicate that the tensile strength values obtained through the Brazilian test must be increased by almost 26%. To understand this divergence, indirect tensile tests have been monitored. The aim is to know the material deformation and load increase by means of stepwise regression. Stress fields in slightly deformed samples are analyzed and modeled (3D finite differences) with loads applied on flat and curved plates and different Young's modulus. Finally, the results are analyzed and compared with strength values reported using Timoshenko theory and Hondros' approximation.

High-Frequency Thin-Film AlN-on-Diamond Lateral–Extensional Resonators

In this paper, low-impedance lateral–extensional microresonators are fabricated on a stack of aluminum nitride (AlN) directly deposited on a polished ultrananocrystalline diamond (UNCD) film. The large acoustic velocity of UNCD is utilized to extend the frequency of such resonators beyond 1 GHz while the frequency-defining features are not reduced excessively. In order to promote the growth of a <jats:formula formulatype="inline"><jats:tex Notation="TeX">$c$</jats:tex> </jats:formula>-plane piezoelectric AlN film, the surface of the UNCD film is polished after deposition. Three different UNCD films with different Young's modulus values were prepared, and frequencies up to two times that of similar devices fabricated on silicon have been achieved. The finite-element analysis is employed to evaluate the effect of various physical parameters on the performance of the thin-film piezoelectric-on-substrate resonators in order to achieve very low motional resistance <jats:formula formulatype="inline"><jats:tex Notation="TeX" >$(R_{m})$</jats:tex></jats:formula>. Several resonators were designed with various lateral dimensions and different numbers of support tethers to evaluate the propositions. The lowest <jats:formula formulatype="inline"><jats:tex Notation="TeX" >$R_{m}$</jats:tex></jats:formula> was measured from a multitethered 29th-order thin-film piezoelectric-on-diamond (TPoD) resonator (22 <jats:formula formulatype="inline"><jats:tex Notation="TeX"> $Omega$</jats:tex></jats:formula>) and <jats:formula formulatype="inline"><jats:tex Notation="TeX">$fcdot Q$</jats:tex></jats:formula> product of <jats:formula formulatype="inline"><jats:tex Notation="TeX">$2.72 ast 10^{12}$</jats:tex></jats:formula> at 888 MHz. The temperature coefficient of frequency of this TPoD resonator is measured to be <jats:formula formulatype="inline"><jats:tex Notation="TeX">$-9.6 hbox{ppm}/^{circ} hbox{C}$</jats:tex></jats:formula>, which is much lower than that of the devices fabricated on silicon. Also, this device can withstand input powers up to <jats:formula formulatype="inline"><jats:tex Notation="TeX">$+$</jats:tex></jats:formula>27 dBm, leading to a delivered power density per unit area of <jats:formula formulatype="inline" ><jats:tex Notation="TeX">$sim!!2.9 muhbox{W}/muhbox{m}^{2}$</jats:tex> </jats:formula>.<jats:formula formulatype="inline"><jats:tex Notation="TeX" >$hfill$</jats:tex></jats:formula>[2012-0099]

Damping Properties of Viscoelastic Stiffened Laminated Cylindrical Shells with an Unconstrained Fiber-Reinforced Layer

By use of the mixed layerwise theories and the interpolation functions of displacements and transverse stress, the dynamics equations of viscoelastic stiffened laminated cylindrical shells with an unconstrained fiber-reinforced layer were derived. The predicted vibration frequency and loss factor show the good agreement with the A.Okazaki’ experimental results for the two-layer cylindrical shells. The non-dimensional frequencies and loss factors were computed for different Young’s modulus and thickness of viscoelastic layer. The results show that using a higher module and thickness viscoelastic layer can effectively increase the loss factors; moreover, using a circular-reinforced viscoelastic layer has little effect on the non-dimensional frequencies, but can effectively increase the model loss factors.

THE DYNAMICS OF AN OSCILLATING BUBBLE NEAR BIO-MATERIALS

The simulation of an oscillating bubble near various bio-materials (brain and cornea) using the Boundary Element Method (BEM) is presented. The bio-materials are modeled as an elastic fluid with different Young's modulus and density. It is found that the bubble tends to split into two or more bubbles when it is oscillating near soft bio-materials (such as brain). The bubble will collapse with a high speed jet (about 100 m/s) near hard bio-materials (such as cornea). It is found from simulation that under certain conditions (light and soft elastic material), the oscillating bubble will jet away from the elastic boundary similar to a bubble near a free surface. An experiment using a laser generated bubble is carried out to confirm this phenomenon.

Mechanical Property Determination for Supported Polymer Films using Double Bending Beams

ABSTRACTA double-bending-beam technique has been developed to determine the mechanical properties (e.g., the elastic stiffness parameter and the in-plane coefficient of thermal expansion) of thin polymer films during thermal cycling. The mechanical properties of poly(methyl methacrylate) and a polyimide have been determined from the combined stress-temperature relationships of identical polymer films coated on two rigid beams (each with a distinctly different Young's modulus and coefficient of thermal expansion). The measured mechanical properties were found to agree with data obtained using conventional techniques. The double-bending-beam technique can be applied to a wide variety of dry and wet processing situations involving thin polymer films.

A note on the elastic stress in tunnel linings

A circular tunnel lining is idealized as a perfectly elastic annulus either keyed to, or a sliding fit in a hole in an infinite elastic medium of different Young's modulus, the system being under stress at infinity. The solution to this problem is used to give a qualitative discussion of two situations: 1 The resistance of a tunnel lining is limited amongst other things by its inability to withstand tensile stress. It is shown that in the above idealization, the more flexible the lining the less likely are tensions to arise. Such flexibility might be achieved by allowing the lining freedom to slide relative to the surrounding rock rather than by keying it to the walls, by making it of laminated construction or by lowering its Young's modulus. Increasing the thickness may increase the liability to tension. 2 As a means of estimating the load on a lining, gauges may be placed to measure circumferential strain, and from these measurements the load is deduced by assuming that the lining behaves like a bending beam. A difficulty in interpreting such measurements is pointed out in the case of a keyed lining, when the shearing stresses are very large.