جستجوی مقالات مرتبط با کلیدواژه « Fracture » در نشریات گروه « مواد و متالورژی »

Several extensive researches are being carried out in the field of 3D printing. Polymer matrices, such as High-Density Polyethylene (HDPE), are less explored in particular on the microstructure and mechanical properties of HDPE composites developed via Fused Deposition Modelling (FDM) process. Very scarce amount of works is devoted to study HDPE’s reinforced with carbon nano-tubes (CNT’s) . In the present work, we report on the mechanical properties of  HDPE composites prepared via FDM process. Varying proportions of CNTs ( 0.5, 1, 1.5 and 2%) are used as reinforcements. It is found that increasing CNT content enhances impact and tensile strength, with HDPE/2.0%CNT outperforming pure HDPE by approximately 71.6% and 25.4%, respectively. HDPE/2.0%CNT composite also showed Young's modulus approximately 49.2% higher than pure HDPE. According to fracture analysis, pure HDPE failed near ductile, whereas composites failed brittle. CNTs occupy the free positions in the polymeric chains, and their tendency to restrict chain mobility causes HDPE to lose ductility and begin to behave brittle. The use of CNTs as reinforcement successfully improved the mechanical properties of HDPE.

Mill pellets are most used in cement, steel and copper industries and its role in crushing and production of materials and products with optimal grain size and as a mineral production agent in metal and non-metallic mineral processing industries including cement factories, stone mines Iron and copper mines are required. On the other hand, it is used to a limited extent in some defense industries and heavy metal mines. in this study, the factors affecting the failure of steel balls produced from continuous casting ingots with 70Cr2 material during the quenching process in water have been investigated. The samples are 2 destroyed balls and a healthy ball that the destroyed balls, during the production process and before being put into operation (some balls immediately after the quenching process and some others have failed after the tempering process. In order to investigate the causes of destruction, visual inspection, emission spectroscopy, metallography, hardness and scanning electron microscopy studies were performed along with EDS analysis. The high hardness of the sample is due to improper heat treatment and cracking during cooling and when hitting the bullets from the place of forging defects and below the surface in the place of grains, defects and impurities.

Thin perforated Steel Plate Shear (SPS) Walls are among the most common types of energy dissipating systems. The applied holes reduce the shear strength of the plate and allow to decrease the profile size of the members at the boundary of the panel when these systems are used in the typical design of structures. On the other hand, the different fracture locations of these panels are visible when considering the different perforation patterns. This paper reports on the results obtained from the experimental study under cyclic loading of the effect of different hole patterns on the seismic response of the systems and the location of the fracture. According to this, two perforated specimens by different patterns were considered. In addition, a plate without holes for a better comparison of the fracture location was chosen. The results showed that changing the pattern of the holes causes a change in the fracture location. Moreover, in perforated specimens, the amount of shear strength did not reduce suddenly after the fracture phenomenon. In the specimen which was perforated around the web plate, the pinching force was more than any other in the low cycle of the drifts. For this reason, the energy dissipation and initial stiffness were more than up to 3% drift. The experimental specimens were then simulated with a Finite Element (FE) method using the ABAQUS. Finally, a parametric FE analysis on different series of perforated panels, by changing the diameter of the holes and the plate thickness, has been carried out.

In this paper a new method to determine the fracture properties and strain energy release rate for carbon-polyester composite has been introduced. Fracture characteristics such as: critical stress intensity factor and critical strain energy release rate for mode I, mode II and mixed mode loading were determined using Arcan type specimen. 130 layers of carbon fiber polyester woven composite with each of 0.2mm thickness were put on each other. Theoretical studies to determine strain energy release rate were done using three Corrected Beam Theory (CBT), Compliance Calibration Method (CCM), Virtual Crack Closure Technique (VCCT), and results were recorded and compared with the results from experimental and numerical attempts. Critical loads were recorded through experimental attempts then applied to the finite element software. Results were recorded and compared with each other to determine the best method. Results show that CCM and VCCT determine strain energy release rate value closer to J-integral in comparison with corrected beam theory. Finally, the fracture surfaces were examined by scanning electron microscope to gain insight intothe failure responses that shows the fracture surface for mode II is rougher than the fracture surface for mode I and mixed mode.