Papers by Keyword: Penetration Depth

Abstract: In 4H-SiC crystals, Frank type dislocations are created through the deflection of threading screw/mixed dislocations onto the basal plane. Grazing-incidence X-ray topographs are often used to evaluate the density of such dislocations and a knowledge of the effective penetration depth is therefore essential. In this study, a systematic analysis is performed to investigate the effective penetration depth, which is the depth from which contrast from the dislocation is still discernible. This is achieved by comparison between observed topographic images and detailed ray tracing simulations. Simulations shows no significant contrast difference between a deflected TSD and a deflected TMD with the same line direction since the large c component is the dominant contributor to the effective misorientation, whereas the effect of a component is rather negligible. Therefore, this effective penetration depth study uses ray tracing simulation images of deflected TSDs with photoelectric absorption applied to compare with all topographically observed Frank type dislocations. Analysis first reveals that the effective penetration depth varies with the line direction of a Frank type dislocation, and the effective penetration depth is significantly deeper compared to that of a BPD. Further, the effective penetration depth on ray tracing simulations with absorption applied matches well with experimentally measured depth. The study also evaluated the effectiveness of a simplified model based on an approximate expression for the effective misorientation of a dislocation modulated by photoelectric absorption. This was also found to yield satisfactory results and can be used as a universal method to determine the effective penetration depth for Frank type dislocations with c component of Burgers vector.

Abstract: Understanding the depth from which contrast from dislocations is still discernible (the effective penetration depth of the X-rays) in grazing-incidence synchrotron monochromatic beam X-ray topography is of great interest as it enables three-dimensional dislocation configuration analysis and accurate density calculations. To this end, systematic analysis has been performed of topographic and ray-tracing simulated contrast of basal plane dislocations with different Burgers vector and line direction combinations, and a universal method to determine the effective penetration depth based on ray tracing has been developed. This study reveals that the observable dislocation contrast depends on the effective misorientation associated with the dislocation modulated by the photoelectric absorption effect. The dislocations with larger effective misorientation tend to have longer projected length and correspondingly deeper effective penetration depths.

Abstract: This paper, with the simplified concrete damage plasticity (SCDP) model, studying the penetration depth of steel projectile in the concrete block by Abaqus software. Comparing the results calculated by Abaqus software with the Modified NDRC formula to check the reliability of the computational model and material model. From there, studying the effect of concrete strength on penetration depth in concrete B20, B30, B40, B50.

Abstract: Practical work and is devoted to the study of the rheological and deformative properties of Geofip aluminosilicate glue, obtained on the basis of an alkaline aluminosilicate binder composition Na₂O Al₂O₃×6SiO₂×20H₂O, modified with 5% Cr₂O₃, when gluing wooden trusses in the field. The rheological and deformative properties of an aluminosilicate adhesive based on an alkaline aluminosilicate binder composition of Na₂O×Al₂O₃×6SiO₂×20H₂O modified with 5% Cr₂O₃ have been investigated. It is noted that the dynamic viscosity of the adhesive slurry in the speed range from 0.1 to 0.8 RPM varies from 147600 to 144600 cP, and the average plastic viscosity in the same speed range is 87.39 cP. It was found that at shear rates from 0.021 to 0.168 1/s, an increase in shear force from 31 to 242.9 dyne/cm² is observed due to the stabilization and uniformity of the dispersion phase particle distribution in the dispersion medium of the adhesive. It is shown that the aluminosilicate adhesive at a surface tension value of 88.1 mN/m is characterized by coefficients of wetting (s = 0.648) and fluidity (f = -62.02 mN/m), which ensures the uniformity of its application to the pine substrate. The average thickness of the adhesive layer was 1.25 mm, and the average depth of penetration of the aluminosilicate adhesive into the wood substrate, respectively, 0.12 mm. The destruction of the adhesive seam occurred at shear stresses of 515 MPa. The relative shear deformations were 162.5×10^-5 mm.

Abstract: The paper deals with hard cutters of drill bits for drilling rocks. The research on geometry of hard alloy and steel cutters of bits that work either under conditions of shockless loads was carried out in this work. The rationale of tungsten carbide and cobalt composition according to their hardness and robustness is provided. Different alloys were suggested to be used for tools working either under conditions of shockless loads or under shock loads for drilling rocks of high hardness. The rock deformation process was identified to occur by cutting and shearing forces. The highest influence on the cutting process is exerted by the acuity angle and back rake angle. Peculiarities of work of cutters with positive, negative and neutral back rake angles were determined as part of the main research. The dependence of penetration depth on the back rake angle of the cutter was obtained. Indicators of wearing identified in the research are including the type and properties of interacting surfaces characterized by the roughness of cutting bit surface, the hardness of materials in contact zone, friction mode that depends on unit pressure, movement rate, the nature of load application, and the rate of interaction of working parts of bit.

Abstract: Composite peening describes a modified process based on micro shot peening. This process allows the controlled penetration of ceramic particles into areas of metallic matrix materials close to the surface layer. Composite material produced by composite peening promises a high application potential in the fields of lightweight, wear-resistant and durable materials. The use of ceramic reinforcing particles is expected to significantly improve thermal stability compared to conventional surface hardening processes. In addition, composite peening offers the possibility of cost-effectively reinforcing components and can even be applied subsequently in highly stressed surface layers. The material combination selected for this study was technically pure aluminum as model and matrix material and alumina as abrasive respectively reinforcement material. The influence on the particle density and the particle gradient was achieved by varying the process parameters, such as the process temperature and the peening pressure. A maximum penetration depth of almost 30 μm could be observed at high homologous temperatures. In light and scanning electron microscopy it was observed that the ceramic particles might break on impact with the surface of the blasting material. This causes a drastic reduction of the particle size, which initially had a size of 10 μm. This reduction of particle size promises advantages, particularly with cyclic loads.

Abstract: The main objective of this study is to investigate the effect of cementitious capillary crystalline waterproofing (CCCW) material on the water impermeability and microstructure of concrete. The water impermeability of concrete covered with or without CCCW material was tested according to the Chinese standard GB 18445-2012. The results indicate that concretes coated with CCCW material showed much higher water impermeability than blank ones, and the ratio of water impermeability pressure between them reached 275. The samples obtained in various depths of hardened cement paste specimens with or without CCCW coating were analyzed through scanning electron microscopy (SEM) and thermogravimetry-differential scanning calorimetry (TG-DSC), to study the differences in microstructure and hydration products. The results present that after a 28-day standard curing, there were lots of ettringite crystals and CaCO₃ formed in the paste in 1 cm from the coating, but the action depth of the CCCW coating could not reach 3 cm. The ettringite and CaCO₃ is precipitated in the pore structure of cement matrix and filling the voids, which leads to the significant enhancement in water impermeability.

Abstract: The choice of abrasive particle size is crucial to improve the lapping efficiency and surface quality in lapping of sapphire wafer by fixed abrasive (FA) pad. A model for the penetration depth of a single abrasive is developed with fixed abrasive pad. A serious of lapping tests were carried out using FA pads embedded with different size of diamond particles to verify the validity of the developed model. Results show that the penetration depth of abrasive is related not only to the particle size, but to the hardness ratio of the work-piece to the pad as well. The material removal rate of sapphire is proportional to the square of abrasive particle size, while the average surface roughness is proportional to the abrasive particle size.

Abstract: Synchrotron X-ray Topography with grazing incidence geometry is useful for discerning defects at different depths below the crystal surface, particularly for 4H-SiC epitaxial wafers. However, the penetration depths measured from X-ray topographs are much larger than the theoretical values. In order to interpret this discrepancy, we simulate topographic contrast of dislocations based on two of the most basic contrast formation mechanisms – orientation contrast and kinematical contrast. Orientation contrast considers merely the displacement fields associated with dislocations while kinematical contrast also takes the diffraction volume into account. The diffraction volume is defined by the effective misorientation around dislocations and the rocking curve width for particular diffraction vector. Ray Tracing Simulation has been carried out to visualize dislocation contrast for both models, taking into account the photoelectric absorption of X-ray beams inside the crystal. Results show that orientation contrast plays the key role in determining both the contrast and X-ray penetration depths for different types of dislocations.

Abstract: This paper presents the results of an experimental investigation of the impact resistance of UHPFRC slabs. The influence of horizontal and vertical casting of thin slabs against penetration by a projectile is described. The resistance of penetration by a projectile was investigated using projectile with lead core. The results indicate different penetration depths and crater diameters in the target specimens for both kind of casting. Which points on a different arrangement of fibers for horizontal and vertical casting slabs. However, the protective ability is guaranteed in both placement method. Based on the present findings the slabs from ultra-high performance fiber-reinforced concrete casted vertically appear to be most efficient in protection against projectile impact.