Creep of particle and short fibre reinforced polyurethane rubber

Tensile stress–strain testing and creep testing have been carried out on a polyurethane rubber, at three temperatures, with and without either particulate or short fibre alumina reinforcement. A previous paper reported concerning composites with particulate reinforcement and the present work is focused on the effect of the fibres. The samples were made via a blending and extrusion process that produced a certain degree of fibre alignment (along the direction of loading). Prior milling procedures were used to produce fibres with two different ranges of aspect ratio (with averages about 10 and 16). When expressed as true stress–strain relationships, all materials exhibit approximately linear responses. The dependence of stiffness on the volume fraction and aspect ratio of the reinforcement was found to conform well to the Eshelby model predictions. Moreover, the creep behaviour of all of the materials can be captured well by a Miller–Norton formulation, using the average matrix stress predicted by the Eshelby model. A striking conclusion is that it is both predicted and observed that short fibres are much more effective in reducing the creep rate than is the case with particles.

Research and Application of Stress and Strain Testing Method for Plain Concrete Pile

At present, the stress-strain test of pile body mainly focuses on precast pile and cast-in-place pile with reinforcement, and this is mainly because the pre-assembly of test components can be carried out in the pile body or reinforcement cage before the prefabricated pile is formed. When the pile is formed, it could be embedded together with the pile body or reinforcement cage. But for the cast-in-place plain concrete pile field test research report is rare. In view of the shortcomings of the existing test methods in the test of plain concrete piles, the resistance strain gauge and inclinometer are improved to realize their application in the field test of plain concrete piles, which is employed for the deformation characteristics test of plain concrete pile under horizontal load. The test results show the applicability of the improved test method, which provides useful references for similar research.

Surface Acoustic Wave Sensors for Temperature and Strain Measurements

It is highly desired to develop an inexpensive, wireless embedded sensor system that can provide high-bandwidth measurements of temperature and pressure inside a pipeline for rocket propulsion test applications. The fuel is generally liquid hydrogen and liquid oxygen, which must be kept at cryogenic temperatures. The environment places additional requirements on the design of sensors that is beyond the scope of most available products. Surface acoustic wave (SAW) technology has received considerable attention for harsh environment applications. The ultimate goal of our research is to develop a SAW sensor system for temperature and pressure sensing in the cryogenic environment. In this paper, the temperature testing of the SAW sensor was finished from 30 to 80°C. The strain testing was performed at room temperature. The results have shown that the temperature coefficient of the delay (TCD) at the room temperature is around 74.4 ppm/°C. The Strain coefficient of delay (SCD) of the testing result is 0.38 ppm/με at room temperature.

The Effect of Different Thawing Rates on Cryopreserved Human Iliac Arteries Allograft’s Structural Damage and Mechanical Properties

Introduction. The rate of thawing of cryopreserved human iliac arteries allografts (CHIAA) directly affects the severeness of structural changes that occur during this process. Method. The experiment was performed on ten CHIAA. The 10% dimethylsulphoxide in 6% hydroxyethyl starch solution was used as the cryoprotectant; all CHIAA were cooled at a controlled rate and stored in the vapor phase of liquid nitrogen (-194°C). Two thawing protocols were tested: (1) placing the CHIAA in a water bath at 37°C, and (2) the CHIAA were thawed in a controlled environment at 5°C. All samples underwent analysis under a scanning electron microscope. Testing of the mechanical properties of the CHIAA was evaluated on a custom-built single axis strain testing machine. Longitudinal and circumferential samples were prepared from each tested CHIAA. Results. Ultrastructural analysis revealed that all five CHIAA thawed during the thawing protocol 1 which showed significantly more damage to the subendothelial structures when compared to the samples thawed in protocol 2. Mechanical properties: Thawing protocol 1—longitudinal UTS 2,53±0,47 MPa at relative strain 1,27±0,12 and circumferential UTS 1,94±0,27 MPa at relative strain 1,33±0,09. Thawing protocol 2—longitudinal ultimate tensile strain (UTS) 2,42±0,34 MPa at relative strain 1,32±0,09 and circumferential UTS 1,98±0,26 MPa at relative strain 1,29±0,07. Comparing UTS showed no statistical difference between thawing methods. Conclusion. Despite the significant differences in structural changes of presented thawing protocols, the ultimate tensile strain showed no statistical difference between thawing methods.

Production of 3D Printed Flexible Strain Sensors

3D printing technologies have advanced significantly in recent years allowing for additive manufacturing of new structured materials, expanding the range, function, and capabilities of manufactured components. In this work, flexible capacitors were produced using additive manufacturing and compared to commercially available capacitance sensors in strain testing. The sensors utilize thermoplastic polyurethane (TPU) printed using fused filament fabrication methods as a dielectric substrate and a combination of flexible inks for production of the conductive surface. Flexible inks were printed using syringe based deposition methods on a custom designed printer using the TPU substrate. Results demonstrated successful capacitor production with capacitance values ranging from 2–70 pF depending on geometry, material, and printing conditions. The 3D printed flexible capacitors were characterized over a frequency range of 100 Hz to 10 kHz and compared to commercial roll-to-roll produced capacitors. Strain testing was conducted from 0–50% strain using a mechanical testing machine for the range of sensors and final capacitance post strain was measured to calculate deviation from original capacitance values. The sensors exhibited a relatively linear increase in capacitance when strained and returned to a resting position upon release of strain with minimal hysteresis effects, demonstrating their utility as 3D printed sensors.

You get what you screen for: on the value of fermentation characterization in high-throughput strain improvements in industrial settings

While design and high-throughput build approaches in biotechnology have increasingly gained attention over the past decade, approaches to test strain performance in high-throughput have received less discussion in the literature. Here, we describe how fermentation characterization can be used to improve the overall efficiency of high-throughput DBTAL (design-build-test-analyze-learn) cycles in an industrial context. Fermentation characterization comprises an in-depth study of strain performance in a bioreactor setting and involves semi-frequent sampling and analytical measurement of substrates, cell densities and viabilities, and (by)products. We describe how fermentation characterization can be used to (1) improve (high-throughput) strain design approaches; (2) enable the development of bench-scale fermentation processes compatible with a wide diversity of strains; and (3) inform the development of high-throughput plate-based strain testing procedures for improved performance at larger scales.