Differences in indentation and wear behaviors between the two sides of thermally tempered soda lime silica glass

Thermal tempering is an industrial process widely used to make soda lime silica (SLS) glass panels stronger and tougher. During the tempering process, the upper and bottom sides of the glass may experience different cooling rates, and thus, their properties could be different. This study characterized changes in surface composition and subsurface glass network structures as well as indentation and wear resistance properties of the air- and tin-sides of 6-mm-thick SLS window panels faced toward the upper and sliding roller sides during thermal tempering. The results showed that although the chemical and structural differences detected with X-ray photoelectron spectroscopy and specular reflection infrared spectroscopy are subtle, there are large differences in nanoindentation behaviors and mechanochemical wear properties of the SLS glass surface. The findings of this study provide further insights into the performance difference between the air- and tin-sides of the SLS glass panel treated with thermal tempering.     

High temperature tensile properties of 316LN stainless steel investigated using automated ball indentation technique

Type 316LN stainless steel (SS) is the principal structural material for the components of sodium cooled fast reactors operating under elevated temperature conditions. In order to assess the degradation in strength of service exposed components using a small specimen testing technique such as automated ball indentation (ABI), it is necessary to carry out prior detailed ABI studies on the virgin material. In this investigation, the tensile behaviour of as-received 316LN SS were investigated at several temperatures in the range 298–973 K using ABI technique. The load-depth of indentation data measured from ABI tests was analyzed using semi-empirical relationships to obtain the tensile properties. The yield stress and the flow curves were determined by correlating ABI results with corresponding uniaxial tensile test results. Trend curve for tensile strength with temperature, as estimated from ABI tests, exhibited a plateau region in the temperature around 823 K, similar to uniaxial tensile tests. The variations of strength coefficient, strain hardening exponent, yield ratio, hardness and uniform ductility with temperature were evaluated from ABI tests. The ABI technique was found to estimate the influence of temperature on tensile properties sensitively.     

Cavitation erosion resistance and ratio of elastic deformation energy to total deformation energy for Ti_3Al and TiNiNb alloys

1　INTRODUCTIONCavitationerosioniscausedbythegrowthandcollapseofvaporcavitiesorbubblesduetolocalpres surefluctuationinaliquid[1] .Itisaseriousprobleminhigh speedcomponentsofhydraulicmachines .Al thoughagreatamountofworkonthecavitationphe nomenahasbeen published ,thecavitationerosionmechanismofmaterialsisstillnotunderstoodcom pletely .Itisgenerallybelieved[2 ,3] thatmechanicalattackisadominantmechanismforcavitationero sion .Manyinvestigations[4 6 ] attemptedtocorrelatethemechanicalproperti…     

Ti—N多层膜的显微结构和压痕行为

研究了Ti/TiN多层膜的显微结构,横截面试样的透射电镜研究和二次离子质谱深度分析均表明,该膜具有周期变化的多层结构,即:基体/FeTi/Ti/Ti_2N/TiN/Ti_2N/Ti/Ti_2N/TiN…Ti/Ti_2N/TiN.制备了压痕试样的断口试样,并用扫描电镜进行了观察.结果表明,多层硬膜在压痕试验时发生形变,出现压痕坑,在其周围形成材料堆积.随着所加载荷的增加,形变区扩大,越过膜/基界面进入基体,引起膜内的层间开裂和在膜/基界面上形成孔洞,研究结果表明,和单层TiN相比,Ti/TiN多层膜具有较好的韧性.     

Microstructural studies of the temperature-dependence of deformation structures around hardness indentations in ceramics

Various light microscopy and SEM techniques have been used to study the temperature dependence of deformation structures around hardness indentations in highly brittle ceramics (including single crystals of silicon and silicon carbide and polycrystalline forms cf SiC, Si₃N₄ and B₄C). Nomarski differential interferometry has enabled slip steps to be resolved around high-temperature indentations, allowing identification of the dominant slip systems and measurement of the extent of surface plasticity as a function of temperature. The occurrence of indentation fracture as a function of both temperature and specimen microstructure was studied by SEM methods (including stereo imaging), Nomarski differential interferometry and polarized reflection light microscopy. Generally, radial and lateral crack sizes increased with increasing temperature, due to increasing residual stresses around indentations caused by increasing indentation plasticity. Examples of microstructural control of crack paths are given for various single crystal and polycrystalline materials.     

Initiation and propagation laws of the glass cracks in specimens subjected to normal loading under the action of symmetric wedges

With more and more applications of glass in advanced fields of science, the demand for glass machining precision has increased greatly. More and more attention is being paid to glass cutting because precise glass parts with various shapes can be obtained at high efficiency and low cost. To improve the machining precision of part surfaces and to facilitate tool design and cutting parameter selection, the initiation and propagation laws of glass cracks in specimens subjected to normal loading by symmetric wedges were investigated. Research results show that initiation and propagation laws are the same with interior symmetric wedge angles of 30°–120°, while the laws are different with interior symmetric wedge angles equal to or more than ≥150°. The relationship between medial crack length and normal loading was also investigated when specimens were indented by symmetrical wedges with interior angles of 30°–120°. __________ Translated from Journal of South China University of Technology (Natural Science Edition), 2004, 32(7) (in Chinese)     

层间增韧复合材料在静压痕力下的损伤阻抗和渐进损伤分析

在复合材料层合板层间植入韧性层是提高复合材料韧性和抗冲击能力的有效方法。为了研究层间增韧对层合板损伤阻抗的改善作用，文中通过准静态压痕试验研究层间增韧复合材料在准静态压痕力下的损伤和破坏行为，利用超声C扫描测量分层损伤面积。试验结果表明，层间增韧复合材料具有较高的分层起始载荷和分层起始能量，损伤阻抗显著提高。在相同的载荷水平下，具有较小的分层损伤面积。文中还采用有限元方法对层间增韧复合材料在静压痕力下的分层和铺层失效进行数值分析，有限元计算结果与试验结果吻合较好。     

A Micro/Macro Impact Test at Controlled Energy for Erosion and Phase-Transformation Simulation

An impact test with energy control has been developed to study the degradation phenomena generally encountered on materials submitted to complex conditions including impacts, for example during erosion. The test permits the material response to single or multiple impacts at a microscopic and a macroscopic scale to be characterized. The energy of each impact is precisely controlled and may reach a value of 100mJ per impact. Experiments have shown that the dynamic loading duration is very short, typically between 100 and 200 s, and deformation speeds on the impacted metals are in the order of magnitude of 10³ s^-1. Indenters of various tip radii have been used and a large range of impacting conditions tested. The high reproducibility of the tests confirms that it permits the simulation of damage phenomena already identified in metallic substrates submitted to erosion wear induced by hard particle impacts.     

辊面裂纹引起的冷轧辊大面积剥落失效分析

针对某产线冷轧工作辊多次出现大面积剥落事故,为了研究其失效原因,从剥落面断口观察、化学成分、工作层组织、淬硬层深度、裂纹扩展等角度对其进行了较为深入的分析研究。结果表明,该轧辊大面积剥落失效为疲劳裂纹扩展所致,裂纹源是轧钢过程中异常压痕产生的辊面裂纹。最后,针对如何预防辊面剥落恶性事故的问题,从轧辊使用、维护和设计制造三个角度提出了相应的建议,确保了近期未再发生类似的事件。