Elastomers

In this study, we experimentally investigated the effect of shoes on gait with new elastomer-embedded flexible joint (EEFJ). We designed the EEFJ to support plantar flexion moments on ankle joints. A strength test was conducted for the EEFJ. According to the results of the test, moments in plantar flexion were significantly stronger than those in dorsiflexion. We prototyped gait support shoes with the EEFJ. The weight of the EEFJ unit for a single foot was 32.5 g. We also conducted gait experiment on a healthy subject with and without the shoes. The results showed reductions in electromyograms of the tibialis anterior muscle in the initial phases of gait.

Distributed manufacturing even at the household level is now well established with the combined use of open source designs and self-replicating rapid prototyper (RepRap) 3-D printers. Previous work has shown substantial economic consumer benefits for producing their own polymer products. Now flexible filaments are available at roughly 3-times the cost of more conventional 3-D printing materials. To provide some insight into the potential for flexible filament to be both technically feasible and economically viable for distributed digital manufacturing at the consumer level this study investigates 20 common flexible household products. The 3-D printed products were quantified by print time, electrical energy use and filament consumption by mass to determine the cost to fabricate with a commercial RepRap 3-D printer. Printed parts were inspected and when necessary tested for their targeted application to ensure technical feasibility. Then, the experimentally measured cost to DIY manufacturers was compared to low and high market prices for comparable commercially available products. In addition, the markup and potential for long-term price declines was estimated for flexible filaments by converting thermoplastic elastomer (TPE) pellets into filament and reground TPE from a local recycling center into filament using an open source recyclebot. This study found that commercial flexible filament is economically as well as technically feasible for providing a means of distributed home-scale manufacturing of flexible products. The results found a 75% savings when compared to the least expensive commercially equivalent products and 92% when compared to high market priced products. Roughly, 160 flexible objects must be substituted to recover the capital costs to print flexible materials. However, as previous work has shown the Lulzbot Mini 3-D printer used in this study would provide more than a 100% ROI printing one object a week from hard thermoplastics, the upgrade needed to provide flexible filament capabilities can be accomplished with 37 average substitution flexible prints. This, again easily provides a triple digit return on investment printing one product a week. Although these savings, which are created by printing objects at home are substantial, the results also have shown the savings could be further increased to 93% when the use of a pellet extruder and TPE pellets, and 99% if recycled TPE filament made with a recyclebot is used. The capital costs of a recyclebot can be recovered in the manufacturing of about 9 kg of TPE filament, which can be accomplished in less than a week, enabling improved environmental impact as well as a strong financial return for heavy 3-D printer users.

This study deals with two new generation smart high damping rubber bearings (HDRBs) incorporated with shape memory alloy (SMA) wires. Due to the superelastic effect and the re-centering capability of SMAs, the residual deformation in SMA-based elastomeric isolators is reduced. Two different configurations of SMA wires incorporated in rubber bearings are compared by changing the aspect ratio of base isolator, the type of SMA, the thickness of wires, and the pre-strain in wires where the isolator is subjected to a vertical pressure and unidirectional cyclic lateral displacement. A performance-based design flowchart is also provided along with a design example for determining the pre-strain and the radius of cross section of wires in the SMA wire-based rubber bearings. Results demonstrated that using ferrous SMA wires (FeNCATB) with 13.5% superelastic strain in the cross configuration leads to the best performance since the strain induced in wires is significantly decreased. Seismic performance evaluation of a three-span continuous bridge isolated by smart HDRBs shows that using SMA wires with cross configuration leads to the highest energy dissipation during earthquake. However, implementing SMA wires into HDRBs has negligible effect and in some cases no effect on the pier displacement and peak deck acceleration. It was also observed that neither of the HDRBs nor the SMA-HDRBs experienced any residual deformations when they were subjected to three different ground motions scaled by Vancouver design response spectrum.

The photooxidation of hydrogenated poly [styrene-b-butadiene-b-styrene] or poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), has been studied using a variety of analytical and spectroscopic methods including yellowness, luminescence and FTIR spectroscopy coupled with crosslinking and hydroperoxide analysis in order to understand the nature of the processes involved. FTIR and luminescence analysis show complex oxidation processes with distinct features associated with each phase. Rates of photooxidation measured by carbonyl growth and discolouration show that low molecular weight samples are more photostable than those with high molecular weight. Oxidation primarily due to the aliphatic part occurs with a predominant absorption associated with terminal carboxylic acid groups at 1712 cm −1 .

In Part I of this paper a new metric, titled the ''blade sharpness index" or ''BSI", for quantifying the sharpness of a straight edge blade when cutting soft solids was derived from first principles and verified experimentally by carrying out indentation type cutting tests with different blade types cutting different target or substrate materials. In this Part II companion paper, a finite element model is constructed to examine the effect of different blade variables including tip radius, wedge angle and blade profile on the BSI developed in Part I. The finite element model is constructed using ABAQUS implicit and experiments are performed to characterise the non-linear material behaviour observed in the elastomeric substrate. The model is validated against the experiments performed in Part I and a suitable failure criterion is determined by carrying out experiments on blades with different tip radii. The paper finds that a simple maximum stress criterion is a good indicator for predicting the onset of cutting. The validated model is then used to examine blade geometry. It is shown that finite element analysis is an important tool in helping to understand the mechanics of indentation. Furthermore, the study finds that all the blade geometric variables have an influence on the sharpness of a blade, with the BSI being most sensitive to tip radius. Increasing the tip radius and wedge angle decreases the sharpness of the blade.

Graphene oxide (GO)-reinforced acrylonitrile-butadiene rubber (NBR) nanocomposite are prepared via solution mixing. The morphology and structure of the GO was studied and its successful dispersion within the rubber matrix was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and x-ray diffraction (XRD).

Our objective was to investigate the effect of archwire cross-section increases on the levels of force applied to teeth during complex malalignment correction with various archwire-bracket combinations using an experimental biomechanical setup. The study comprised 3 types of orthodontic brackets: (1) conventional ligating brackets (Victory Series [3M Unitek, Monrovia, Calif] and Mini-Taurus [Rocky Mountain Orthodontics, Denver, Colo]), (2) self-ligating brackets (SmartClip, a passive self-ligating bracket [3M Unitek]; and Time3 [Rocky Mountain Orthodontics, Denver, Colo] and SPEED [Strite Industries, Cambridge, Ontario, Canada], both active self-ligating brackets), and (3) a conventional low-friction bracket (Synergy [Rocky Mountain Orthodontics]). All brackets had a nominal 0.022-in slot size. The brackets were combined with 0.014-in and 0.016-in titanium memory wires, Therma-Ti archwires (American Orthodontics, Sheboygan, Wis). The archwires were tied to the conventional brackets ...