Papers by Keyword: Ceramic

Abstract: The paper presents a numerical study of a double layer composite panels impacted by a AP (Armor Piercing) 51WC projectile. The standard panel is built with aluminum and Al2O3 ceramic continuum layers while the studied model consists of the same aluminum plate but the front one is built with a set of hexagonal ceramic bars. The bar width and the impact position influence on the ballistic resistance are analyzed and compared with the reference solution. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile Tungsten Curbide and aluminum plate material were described by Johnson-Cook model and ceramic target by Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by a rigid wall. The obtained results show interesting properties of the examined structures considering their ballistic resistance. All tests has given clear results about ballistic protection panel response under WC projectile impact. Panels consisting of sets of hexagonal ceramic bars are slightly easier to penetrate, reference model is stronger by 19% for smaller bars and by only 7% for bigger rods. Despite this fact, the ceramic layer is much less susceptible to overall destruction what makes it more applicable for the armor usage. Furthermore, little influence of the projectile impact point and consequently a part of the bar which is first destroyed is proved.

Abstract: Numerical investigations were performed to determine the influence of the spherical convex shape ceramic - alumina composite in reference to the standard double layer panel. All versions of the target were verified in an impact test including influence upon the position of the AP (Armor Piercing) 7,62x51HHS impact. The crucial parameter which was used for this verification was change in time of the PROJECTILE kinetic energy. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile’s core made of HHS and aluminum plate material were described by Johnson-Cook model and ceramic target with Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by rigid wall. The obtained results show interesting properties of the new structures considering their ballistic resistance. However only certain places were chosen for tests, the protection ability against projectile attack is in general higher than the reference model. What is particularly interesting during the 6.6mm from the sphere center impact the sphere surface trajectory deviation effect is present. A projectile is not stopped here by material strength but the front layer shape. Moreover it can be assumed that this phenomenon will take place on majority of points on the sphere surface. Despite this fact, a ceramic multi sphere layer is less susceptible to overall destruction, depending on the impact point. The results of those numerical simulations can be used for designing of modern armor protection systems against hard kinetic projectiles.

Abstract: Preparation of high wear-resistant ceramic parts was studied in this paper. The mechanical property was measured by the three-point bending tester, and the microstructures were analyzed with the scanning electronic microscope (SEM). The experimental results showed that vitrified bond CM2 was suitable for the preparation of high wear-resistant ceramic parts because of its lower refractoriness, and higher bonding strength sintering at 850oC. Moreover, containing 8- 12μm CBN abrasive grains, the ceramic parts reached higher strength and higher wear resistance than other samples.

Abstract: The friction and wear behavior of cutting tool materials keeps an issue. In this study, an high temperature tribometre (UMT-2) was used to investigated the tribology properties and mechanism of two kinds of typical cutting tool materials. Commonly used cemented carbide (ZU5) and ceramic (AT) were chosen. The characteristics as to wear rate, friction coefficient and worn surface were studied. From the results, we found that the ceramic had better wear resistance than the cemented carbide. The friction coefficient of cemented carbide decreased with the increase of ambient temperature while the ceramic exhibited an inverse tendency. Finally, the probable wear mechanism was discussed.

Abstract: By means of Adaptive Neural-Fuzzy Inference Systems(ANFIS), the prediction model of surface roughness of zirconia toughened alumina ceramics (ZTA ceramics) under ultrasonic assisted grinding is established, and the model may obtain the higher forecast precision (81.25%) by dealing with nonlinear problem among grinding parameters, and fuzzy rule curved face formed by prediction model showed four input factors have different influence on surface roughness Ra, and they are abrasive grain size, grinding method, grinding depth, axial feed and speed of worktable from top to bottom. So the prediction model provides a new and efficient method for intelligent information processing, and it could be applied in modeling and real-time control etc, and it is possible to be widely applied in engineering.

Abstract: Cast iron and steel rolls used in the continuous pickling line must be changed frequently because the continuous acid wash equipment induces wear on the roll surface in a short period. The damage portions are usually repaired by using the flame spray coating. Recently, ceramics materials are planed to be introduced to prevent the damage because of their high abrasion and corrosion resistances. In this study new roll structure is considered where a ceramics sleeve is connected with steel shafts at both ends by shrink fitting. Here, the ceramics sleeve may provide a longer lifetime and reduces the cost for the maintenance. However, attention should be paid to the maximum tensile stresses appearing between the ceramics sleeve, spacer rings and steel shafts because the fracture toughness, plasticity and fatigue strengths of ceramics are extremely lower than the values of steel. In this study, finite element method analysis is applied to the new structure, and the maximum tensile stress and stress amplitude have been investigated with varying the dimensions of the structure. Fatigue strengths of ceramics are also considered under several geometrical conditions.

Abstract: Developing easy cleaning and antibacterial ceramics is the key to actualize the ceramics with functionalized, high-quality and band established in china. This paper which combined with research status from home and broad analysed the performance influence of ceramic glaze with different processing methods and discussed the way and methods which can improve the quality of ceramics.

Abstract: Nanometer far-infrared materials (NFIM) were doped into ceramic glazes to prepare easy-to-clean ceramic glazes，and the effect of NFIM on the cleanability properties was investigated. Static contact angle measurements were used to describe the surface hydrophilic property and calculate the surface free energy. The effect of far-infrared radiance measured by Fourier Transform Infrared Spectrometer on the O/W interface tension was tested by a Dynamic Contact Angle Meter and Tensiometer. The cleanability was estimated by the ultraviolet spectrophotometry technique using oleic acid as soiling agent. It was shown that the better cleanability of the ceramic glazes, the higher surface free energy and its polar contribution. The experiments were carried out on detachment of oleic acid drop from the easy-to-clean ceramic glazes. The three-phase contact line shrinked spontaneously, and eventually the oil drop detached from the surface. The spontaneous detachment of a drop corresponded to two different driving factors: (1) the decrease of oil-water interfacial tension caused by the far-infrared radiation of the glazes, (2) the spontaneous advancement of aqueous meniscus owing to the penetration of water between the oil and super hydrophilic glaze surfaces.

Abstract: Glass/ zirconia laminated material is the most commonly used material in the field of dental restoration, although the biocompatibility of such material has been subject to lots of research and the mechanical compatibility and durability have not been deeply researched. This paper, by the research on the contact stress of static and dynamic surfaces of the ceramic material, reveals the physical meaning of damage and fatigue at the interface of material; through contacting with the sphere indentation test and by the investigation of fatigue and damage of the surface and interface of such material in the corresponding time scale as well as by the use of acoustic emission monitoring for detecting the damage process and crack propagation process within the detection layer and the laminated ceramic surface, the time of occurrence and corresponding load can be obtained, which plays an importantly practical role in resolving the forecasting of the changes in material damage and the analysis of fatigue.

Abstract: Micro-hardness is one of the most important mechanical properties for bullet-proof ceramics. The micro-hardness of typical and commercial available bullet-proof ceramics alumina, silicon carbide and boron carbide were studied in this paper. The result indicated that the high ballistic performance (protection coefficient) was mostly attributed to the high micro-hardness of the ceramics. The ballistic protection mechanics of the ceramics was analyzed based on the ceramics’ hardness, structures and protection coefficients.