Tensile Strength Coefficient Research Articles

Application of the modified Hoek-Brown criterion in the analysis of the ultimate bearing capacity at the tip of a pile in inclined rocks

To calculate the ultimate bearing capacity at the tip of a pile in inclined and highly fractured rocks (GSI≤ 25), the exponent “a” is incorporated in the resolution approach to generalize the formulation of the original Hoek-Brown failure criterion. This exponent, with values close to 0.5 for good geomechanical qualities of the rock mass, has significantly higher values for GSI less than 25. An analytical formulation was developed that allows a suitable understanding of the geomechanical behavior. Thus, different exponent “a” and tensile strength coefficient will lead to the development of different failure modes of piles. Presented here are the mathematical equations obtained to resolve the bearing capacity and the charts used to determine the bearing capacity factor based on the slope angle of the rock and the exponent “a”. In addition, it is demonstrated that to get the same ultimate bearing capacity at the pile tip, the pile embedment ratio increased with an increasing rate as the exponent a of modified Hoek-Brown increased. Through this research it is shown that the modified Hoek-Brown criterion can be applied to highly fractured media of rock mass efficiently to estimate the bearing capacity of piles in inclined slope.

Nano-materials on the strength of ultra-high performance concrete

Traditional concrete can no longer meet people's needs for construction quality in terms of quality. This study mainly discusses the effect of nanomaterials on the strength of ultra-high performance concrete. In response to people's concerns, this study improves the performance of concrete filled with nanomaterials from two indicators: the bending strength of concrete after being doped with nanomaterials and the tensile strength of concrete. When studying the flexural strength of concrete filled with nanomaterials, take nanomaterials with masses of 10 g, 20 g, 30, 40 g, 50 g, and 60 g, and fill them with high-performance concrete with a mass of 500 g. In the experiment, the bending strength of the concrete pier was measured. The experimentally measured that when the mass of the nanomaterial is 50 g, the concrete pier has the best bending strength coefficient, and the bending rate is 90%. When studying the tensile strength of concrete filled with nano-materials, nano-materials with diameters of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm were used to fill high-performance concrete with a mass of 500 g. In the experiment, the tensile strength of the concrete pier was measured. The experimentally measured that when the diameter of the nanomaterial is 1 mm, the tensile strength coefficient of the concrete pier is 88%. During the experiment, the amount of nanomaterials and the individual particle diameter of nanomaterials were controlled. The experimental results show that when the amount of nanomaterials is 50 g and the diameter is 1 mm, the ultra-high performance concrete has the best strength. Nano-materials are of great significance in the use of concrete.

Polyvinylidene Fluoride-Added Ceramic Powder Composite Near-Field Electrospinned Piezoelectric Fiber-Based Low-Frequency Dynamic Sensors.

In this study, near-field electrospinning (NFES) is used to fabricate BaxSr1–xTiO3 (BST)/poly(vinylidene fluoride) (PVDF) piezoelectric fiber composites with excellent mechanical properties and chemical properties. BST ceramic powder is blended with PVDF solution uniformly to prepare a solution of appropriate conductance. The parameter for BST/PVDF fiber processing is based on PVDF fibers. Scanning electron microscopy, differential scanning calorimetry, microtensile testing, Fourier transform infrared spectroscopy, and electricity test of the blends of BST/PVDF fibers are incorporated. Mechanical properties of the fibers are then measured by microtensile testing. Effects of distinct ratios of Ba/Sr and the content of Ba0.7Sr0.3TiO3 ceramic powder on BST/PVDF piezoelectric fibers are discussed. Finally, BST/PVDF piezoelectric fiber composites are patterned on a poly(ethylene terephthalate) (PET)-based structure with an interdigital electrode as a BST/PVDF flexible energy harvester to capture ambient energy. The results show that the BST ceramic powder is ∼58–93 nm, and the diameters of piezoelectric fiber composites are ∼6.8–13.7 μm. The tensile strength of piezoelectric fiber composites is ∼74.92 MPa, and the Young’s coefficient tensile strength is ∼3.74 GPa. Mechanical properties are 2–3 times higher than those of pure PVDF piezoelectric fibers. The maximum open-circuit voltage and closed-loop current of BST/PVDF fibers reached ∼1025 mV and ∼391 nA, respectively. The electromechanical energy conversion efficiency of the BST/PVDF energy harvester is found to be 1–2 times higher than that of the PVDF energy harvester. It is confirmed and validated that the addition of BST ceramic powder could effectively increase the piezoelectric constant of PVDF piezoelectric fibers.

Study on the Effect of Energy-Input on the Joint Mechanical Properties of Rotary Friction-Welding

The objective of the present study is to investigate the effect of energy-input on the mechanical properties of a 304 stainless-steel joint welded by continuous-drive rotary friction-welding (RFW). RFW experiments were conducted over a wide range of welding parameters (welding pressure: 25–200 MPa, rotation speed: 500–2300 rpm, welding time: 4–20 s, and forging pressure: 100–200 MPa). The results show that the energy-input has a significant effect on the tensile strength of RFW joints. With the increase of energy-input, the tensile strength rapidly increases until reaching the maximum value and then slightly decreases. An empirical model for energy-input was established based on RFW experiments that cover a wide range of welding parameters. The accuracy of the model was verified by extra RFW experiments. In addition, the model for optimal energy-input of different forging pressures was obtained. To verify the accuracy of the model, the optimal energy-input of a 170 MPa forging pressure was calculated. Three RFW experiments in which energy-input was equal to the calculated value were made. The joints’ tensile strength coefficients were 90%, 93%, and 96% respectively, which proved that the model is accurate.

Study of Effect Add of Nanoparticals Zirconiam Oxide with Yttrium (ZrO2Y2O3) and Zirconiam Oxide (ZrO2) on the Mechanical Properties of Unsaturated Polyester

Nano composite polymeric - based polymers of thermosets material consisting of two groups of Nano composite polymeric, first: is unsaturated polyester resin (UP) which being considered the base material that supported with Zirconium oxide with Nano yttrium ( ZrO2Y2O3), that has granular size (83.98nm), and other group consist of unsaturated polyester resin (UP) that supported with Nano Zirconium oxide (ZrO2 ) that has granular size (47.23nm), where the study include impact of selected volume fraction with (0.5% , 1% , 1.5% , 2% , 2.5% , 3%) all separately and for every material support, Also through this study number of mechanical tests have been carried out and these includes (Tensile, Compression Strength, Hardness) which all tests were conducted at room temperature by Hand Lay-up method. The results show that (tensile strength coefficient, Compression Strength, hardness), where it increase with the increase of volume fraction of nanoparticle for both polymeric Nano composites material, while (tensile strength ) decreased with increasing of volume fraction of nanoparticle for both polymeric Nano composites material too. The polymer mixture of polyester basis which supported with Zirconium only shows that it has higher mechanical and physical properties than the polymer mixture supported by Zirconium particles with Nano yttrium.