Gunshot missile caliber and type estimation using superposition method by exit gunshot cranial vault fracture

A case of missile group identification by comparative examination using the image superposition method is presented. Identification was carried out using a skeletonized body vault exit gunshot fracture. The exit gunshot buttonhole fracture shape and dimensions reflected the bullet caliber and its flank profile. The entrance injury located on the anterior arch of the first cervical vertebra and the basilar part of the occipital bone, in this case, had no identification significance.

Numerical Simulation for Fracture Propagation in Elastoplastic Formations

Current hydraulic fracture models are mainly based on elastic theories, which fail to give accurate prediction of fracture parameters in plasticity formation. This paper proposes a fluid–solid coupling model for fracture propagation in elastoplastic formations. The rock plastic deformation in the model satisfies the Mohr-Coulomb yield criterion and plastic strain increment theory. The extended finite-element method (XFEM) combined with the cohesive zone method (CZM) is used to solve the coupled model. The accuracy of the model is validated against existing models. The effects of stress difference, friction angle, and dilation angle on fracture shape (length, width), injection pressure, plastic deformation, induced stress, and pore pressure are investigated through the model. The results indicate that compared with elastic formation, fracture propagation in elastoplastic formation is more difficult, the breakdown pressure and extending pressure are greater, and fracture shape is wider and shorter. The plastic deformation causes the fracture tip to become blunt. Under the condition of high stress difference or low friction angle formation, it is prone to occur large plastic deformation zones and form wide and short fracture. Compared with friction angle, dilation angle is less sensitive to plastic deformation, fracture parameters, and fracture geometry. For the formation with high stress difference and friction angle, the effect of plasticity deformation on fracture propagation should not be ignored.

Application of Extended Finite Element Method in Fracture Propagation Simulation of Plastic Formation

Current hydraulic fracture models are mainly based on elastic theories, which fail to give accurate prediction of fracture parameters in plasticity formation. This paper proposed a fluid–solid coupling model for fracture propagation in elastoplastic formations. The rock plastic deformation in the model satisfied the Mohr-Coulomb yield criterion and plastic strain increment theory. The coupled model is solved by using extended finite-element method(XFEM) and the cohesive zone method (CZM). The accuracy of the model is verified by comparing the calculated results with existing models. The influences of stress difference, friction angle and dilation angle on fracture shape (length, width), injection pressure, plastic deformation, induced stress and pore pressure are investigated. The results indicate that compared with elastic formation, fracture shape in elastoplastic formation is wider and shorter and fracture propagation is more difficult with greater breakdown pressure and extending pressure. Plastic deformation also cause blunt fracture tip. High stress difference or low friction angle formations tend to occur large plastic deformation area and form wide and short fracture. Compared with friction angle, dilation angle is less sensitive to plastic deformation and fracture parameters and geometry. For the formation with high stress difference and friction angle, plasticity effects on fracture propagation should not be ignored.

Finite Element Analysis of Double-Bolt Shear-Out Fracture Failure

This paper presents the finite element (FE) analysis of double-bolt shear-out (DBSO) fracture failure. The DBSO fracture shape consists of two oppositely: inclined outer main shear fractures, inner main shear fracture, outer shear lips, and curved inner curved fractures. The DBSO begins with two outer main shear fracture initiations under shear, vertical compressive bending, and sideways bending deformations/stresses followed by the two inner main shear fracture initiations under shear and vertical compressive bending deformations. The outer shear lips occurred under vertical compression bending, shear, and sideways tensile bending stresses/deformations while the two inner curved fractures occur under rotational deformation.

Effect of cooling distance on DC-LSND treatment on weld defects and weld fractures of A-36 steel

Control of weld defects and weld fractures in the welding construction should be done to provide the quality assurance of the welding products and to provide a positive assessment of construction to meet technical and economic requirements. The objective of this study is to investigate the effect of the cooling distance on DC-LSND (dynamic controlled low stress no distortion) treatment on weld defects and weld fractures to obtain the best characteristic of the treatment. In this research, DC-LSND treatment was performed by cooling the both sides near weld line applied in welding process. The cooling media used cryogenic liquid nitrogen sprayed by nozzle. The nozzle was placed at a various distance behind the weld torch. Weld defect was investigated by radiograph test. Tensile strength was tested by servo pulser machine and weld fracture was examined by macro structure and SEM. Results showed that the DC-LSND treatment with a cooling nozzle that is too close to the weld torch has the potential to cause weld imperfections. Porosity and initial welding defect lead to the decrease in the tensile strength of the weld metal and the brittle fracture based on the fracture shape. SEM fractography shows that DC-LSND treatment tends to increase the number of inclusions that have an effect on increasing hardness.

Enhanced Surface Properties of Carbon Fiber Reinforced Plastic by Epoxy Modified Primer with Plasma for Automotive Applications

Carbon fiber reinforced plastic (CFRP) is currently used as a lightweight material in various parts of automobiles. However, fiber reinforced plastic (FRP) material may be damaged at the time of joining via mechanical bonding; therefore, adhesion is important. When bonding is conducted without surface CFRP treatment, interfacial destruction occurs during which the adhesive falls off along with the CFRP. Mechanical strength and fracture shape were investigated depending on the surface treatment (pristine, plasma treatment times, and plasma treatment times plus epoxy modified primer coating). The plasma treatment effect was verified using the contact angle and X-ray photoelectron spectroscopy. The wettability of the epoxy modified primer (EMP) coating was confirmed through surface morphology analysis, followed by observation of mechanical properties and fracture shape. Based on test data collected from 10 instances of plasma treatment, the EMP coating showed 115% higher strength than that of pristine CFRP. The adhesive failure shape also changed from interfacial failure to mixed-mode failure. Thus, applying an EMP coating during the automotive parts stage enhances the effect of CFRP surface treatment.

Optimization of Sulfur Soaking Water on Mechanical Properties and Physical Properties of Woven Petung Bamboo (Dendrocalamus asper Backer ex Heyne) Strips

There are about 60 species of bamboo belonging to family gramineae found in Indonesia, which is one of them is Petung bamboo (Dendrocalamus asper). Bamboo has the potential to produce environmentally friendly engineering materials. The strength and durability of the material can be increased through the immersion process using chemical or natural solutions, such as sulphur water because it is known to contain carbon elements high enough to support strength increase. The research was started by making thick bamboo slats 1 mm thick, 250 mm long, 10 mm wide, and then woven in plain shapes of 250 mm × 250 mm, then dried at 110 °C for 60 min then immersed in sulfur water. For tensile test using the ASTM D638-02 standart, ASTM D790-02 bending test, ASTM D5942-96 impact test. The test results show the tensile strength increased 89.17 %, bending strength increased 59.90 % and impact strength increased 1.59 %. The highest value of the mechanical test results occurred in sample 1 AB3, while the lowest mechanical test value occurred in 1 TP sample. The microstructure of the 1 TP sample shows a pointed and smooth fracture shape while the sample 1 AB3 has an increasingly blunt fracture shape with fine threads.

Effect of Fluid Compressibility on Toughness-Dominated Hydraulic Fractures With Leakoff

Summary Hydraulic fracturing using supercritical carbon dioxide (CO2) has a recognized potential to grow in importance for unconventional oil and gas reservoirs. It is characterized by higher compressibility than traditional liquid-phase hydraulic-fracturing fluids. Motivated by the larger compressibility of supercritical CO2, this paper considers the problem of a hydraulic fracture in which a compressible fluid is injected at a constant rate to drive a hydraulic fracture in a permeable and brittle rock. The two cases of a plane-strain fracture and a penny-shaped fracture are considered. It is shown that for many practical cases, the formation has a large enough fracture toughness that the propagation is in a regime for which the pressure inside the hydraulic fracture can be treated as spatially uniform (“toughness dominated”). Both numerical simulations and analytical solutions for the relevant limiting regimes show that fluid compressibility affects fracture shape only at the very beginning period, which corresponds to the storage regime, and has little effect on fracture growth in the leakoff regime. Overall, because the transition from the storage regime to the leakoff regime is expected to often take place in a short time after the fracture starts propagating, the influence of compressibility in the storage regime is very brief and can be quickly ignored. Therefore, even relatively sizable fluid compressibility has almost no effect on fracture growth in the toughness-dominated regime when leakoff is taken into account.

Microcrystalline Cellulose/Polyurethane Wood Material Preparation and Properties Research

The microcrystalline cellulose (MCC) was used as the filler to modify the properties of polyurethane (PU) woodlike material. As we can see from the experimental data, with the gradually increase the amount of MCC added, polyurethane fracture shape variable and the maximum tensile force also increase accordingly, but due to its large density effect on the performance of other, So MCC to improve the effect of polyurethane compression performance is not very big; Through before and after the modification of Fourier transform infrared spectroscopy, the modification of polyurethane materials in amino carbonyl ester peak, so that MCC and polyurethane chemical reaction happened.