The Effect of Extrinsic Factors on the Mechanical Behavior and Structure of Elastic Dental Ligatures and Chains

Force provided by elastomers used in orthodontics can be affected by several factors present in the oral cavity. The aim of our study was to investigate the role of mouthwashes, toothbrushing, and smoking in the force decay of such elastomers. Tensile strength, changes in the force continuously exerted, and force decay of elastic chains (Ortho Organizer and Masel Short Power Chain) and elastic ligatures (Dentaurum and Masel) by two separate manufacturers were measured. Measurements were initially made on untreated elastics, followed by exposure to different environmental factors including cigarette smoke, toothbrushing (mechanical plaque control), and two different mouthwashes (chemical plaque control). Changes on the surface of the elastics were studied with scanning electron microscopy (SEM). Untreated Masel elastic ligature showed lower tensile strength than Dentaurum elastic ligature (2339 cN vs. 3660 cN), while significantly higher tensile strength was measured for Ortho Organizer elastic chains than Masel chains (2639 cN vs. 1324 cN). The decrease in the elastic force of Masel ligature was greater in response to all external factors compared to Dentaurum. Although brushing with toothpaste and toothbrush impacted the force of both Masel and Ortho organizer ligatures negatively, force degradation was more apparent in the case of the Ortho organizer. Surface changes were more visible when applying Curasept mouthrinse, however force decay was higher in the Corsodyl group. Mechanical and chemical plaque control can influence the tensile strength and force decay of orthodontic elastomers, which should be considered by selecting the elastomers or determining their changing interval for the practice.

Utilization of Soybeans as Bio-Catalyst in Calcite Precipitation Method for Repairing Cracks in Concrete

Concrete is a material that has high compressive strength. However, concrete has a lower tensile strength than its compressive strength. As a result, the concrete often cracks and allows the entry of harmful substances such as dan causing corrosion of the reinforcement. Therefore, the repair method began to shift from the conventional way to the concept of self-healing concrete which involves the deposition of CaCO3. Precipitation can be done by the enzymatically – induced carbonate precipitation (EICP) method through a combination of urease, urea, and CaCl2 into a solution. This research used soybean extract as a substitute for pure urease enzyme. Variations in the concentration of soybean flour used as injection solution were variations in the content of soybean flour 15 g/L because it produced an optimum calcite mass of 2.62 grams. As a result, there was an increase in the compressive strength of BI against BR. In addition, there was a decreased value of permeability and porosity and the number of injections carried out. The increase in compressive strength, decrease in permeability, and decrease in porosity in concrete is due to CaCO3 deposition in the concrete which can cover the pores and cracks in the concrete.

Investigation of optimal lamination condition of CFRTP by compression molding method and a comparison of mechanical properties with CFRTS

The variables of die temperature, pressure, time, lamination method, and forming count are applied to fabricate thermosoftening CFRP (CFRTP) with compression molding method. The mechanical properties of CFRTP are compared with those of thermosetting CFRP (CFRTS). The first lamination method is that one hotmelt is inserted into carbon fiber (five carbon fibers and four hotmelts). The optimal lamination conditions are the die temperature of 220°C, pressure of 6 MPa, and pressurization time for 10 min. The tensile strength of CFRTP of this lamination method is 400 MPa. For higher tensile strength value, the second lamination method was applied. CFRTP prepreg was prepared with one hotmelt and one carbon fiber by applying die temperature at optimal lamination conditions. Five CFRTP prepregs were laminated under the same conditions. When the CFRTP sheet was three formings, the tensile strength of 494 MPa could be obtained. CFRTS are prepared by laminating the epoxy prepregs at 140°C with the compressive pressure of 0.5 MPa for 30 min. CFRTP sheet has the lower tensile strength than CFRTS sheet by 223 MPa, but the flexural strength was higher by 61 MPa and by 1.0 J/cm2 for Charpy impact test.

Tensile Strength of Single Fiber of Antheraea pernyi Cocoon Prepared by Various Protocols

The cocoon of Antheraea pernyi was grown in the laboratory with tropical artificial conditioning. The caterpillar was fed with Lantana camara leaf. They are 3 protocols provided to yield single fiber from the cocoon. The first protocol developed in this work was based on the single fiber drawing directly from the live caterpillar during cocoon stage establishment (forcibly silking). The single fiber was gently pulled and rolled up manually. The second protocol was conducted by degumming the cocoon with boiling in 5%NaoH solution. The cocoon was boiled in 5% NaOH solution and gently stirred. When the fiber was found detached from the cocoon, the boiling process was stopped, and the fiber obtained was washed with water and dried in the oven. The third protocol was simple boiling of the cocoon with water and gently stirring until the cocoon disintegrated to become a fiber. The fiber obtained was washed and dried in the oven. The first protocol by forcibly silking produced fiber with highest tensile strength of average value of 149.251 MPa. The other protocols introduced in this work resulted in lower tensile strength. Alkali treatment provided average tensile strength of 43.833 MPa and boiling in water resulted in tensile strength 52.571 MPa.

Comparison of water uptake behavior on tensile property of epoxy impregnated continuous basalt and slag filament composites

Slag fiber has economic and environmental advantages in that it converts a low-value-added material to a high-value-added material. However, although the slag fiber has a chemical composition similar to basalt fiber, its competitiveness in the fiber industry is significantly lower. Moreover, the slag fiber remains in the pre-commercial stage due to the uncertainty and instability of the basic properties. Therefore, in this study, the slag fiber customized through the fiberization process was compared with the existing basalt fiber to analyze the effect of the similarity of chemical composition on the environmental degradation characteristics and mechanical properties under tensile loading. As a result, the slag filament composites showed lower tensile strength due to the weaker interfacial bonding strength with the epoxy matrix than the basalt filament composites, but the difference in decreased tensile strength rate was not significant. In addition, long-term moisture absorption in fresh water and seawater demonstrated excellent moisture absorption resistance.

Concomitant Outcomes due to the Alterations of Process Parameters During the Friction Stir Welding of T-Joint Between Dissimilar Aluminium Alloys

Dissimilar Friction Stir Welded T-joints gives auxiliary strength to engineering structures, keeping insignificantbody weight. Due to the stronger material being away from the heat source, the T-joint between AA8011 and AA5754 is very vulnerable to formation of defects which results in lower tensile strength along the skin and stringer. In this paper, two aluminium alloys, namely AA5754 and AA8011 were friction stir welded in the Tjoint configuration, and the roles of welding parameters such as the tool transverse speed, tool rotational speed, and tool shoulder diameter on the tensile strength along skin and stringer was analyzed and discussed. The relative importance of the three process parameters was also analyzed. The tool shoulder diameter is found to be the most dominant factor for the strength along the skin, whereas, tool transverse speed is found to be the most important for the strength along stringer.

The Fracture Behavior and Mechanical Properties of a Support Structure for Additive Manufacturing of Ti-6Al-4V

In the laser powder bed fusion processes for metal additive manufacturing, a support structure is needed to fix the part to the base plate and to support overhanging regions. Currently the importance of support structure for a successful build process is often underestimated and some effects are not yet well understood. Therefore, this study investigates the fracture behavior and mechanical properties of thin additive manufactured struts using the titanium alloy Ti-6Al-4V and specific machine parameters for support structures. Tensile tests were performed for different strut diameters and the fracture surfaces were analyzed using a laser microscope and a scanning electron microscope. Additionally, the porosity was examined with micro-CT scans. The results were compared with a different set of parameters used for solid parts. The experiments revealed that struts produced with support parameters had no significantly lower tensile strength than the comparative parts. Despite that, some porosity and around two percent of defects on the fracture surface for parts using the solid parameter set have been found. Parts with support parameters show no porosity, even though the energy density is around 30% lower compared to the solid parameter set.

Mechanical properties of low-density paper

For the mechanical properties of paper, tensile testing has been widely used. Among the tensile properties, the tensile stiffness has been used to determine the softness of low-density paper. The lower tensile stiffness, the greater softness of paper. Because the elastic region may not be clearly defined in a load-elongation curve, it is suggested to use the tensile modulus which is defined as the slope between the two points in the curve. The two points which provide the best correlation with subjective softness evaluation should be selected. Low-density paper has a much lower tensile strength, but much larger elongation at the break. It undergoes a continuous structural change during mechanical testing. The degree of the structural change should depend on tensile conditions such as the sample size, the gauge length, and the rate of elongation. For low-density paper, the tensile modulus and the tensile strength should be independent of each other. The structure efficiency factor (SEF) is defined as a ratio of the tensile strength to the tensile modulus and it may be used a guideline in developing superior low-density paper products.

Effect of Lipase Enzyme on Physical and Dyeing Properties of Cellulose Acetate Fabric

: Cellulose acetate fabric was bio-treated by lipase enzyme. Afterwards, untreated and bio-treated fabrics were dyed with direct and disperse dyes in conventional methods. Enzymatic deacetylation of cellulose acetate fibers led to an improvement in hydrophilicity. The whiteness index of cellulose acetate fabric slightly decreased from 95.81 to 95.79 after bio-pretreatment. Lipase pre-treatment also caused an increase in fiber diameter up to 54.80%. Bending length decreased from 1.95 to 1.80 cm after enzymatic treatment while number of threads per centimeter and fabric thickness increased. Bio-treated fabric showed lower tensile strength in comparison to untreated fabric almost 52.48%. Change in morphology of fibers was observed by SEM after enzymatic deacetylation. Bio-treated fabric showed an increase in color strength in comparison to untreated fabric. The lipase pretreatment increased the color strength by 19.04 % and 18.50 % for direct and disperse dyes respectively.

Pearlite Spheroidization and Its Relationship with Tensile Strength in Hypoeutectoid Steels

One steel containing 0.6 wt pct C, 0,78 wt pct Mn, and 0.32 wt pct Cr was austenitized at 840 °C for 1 hour and cooled at two rates. Microstructural evaluation by light optical and scanning electron metallography showed a change in the pearlite microstructure. Cooling in air as compared to furnace cooling reduced the pearlite interlamellar spacing and increased the hardness. The slower cooling resulted in a lower tensile strength, higher tensile elongation, and a different fracture appearance.