Physical and mechanical properties of sandstone containing a single fissure after exposure to high temperatures

In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,and the processed samples were then heated at 5 different temperatures.Indoor uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature,and the deformation,strength and failure characteristics of sandstone containing fissures.The results show that,with increasing temperature,the volume of sandstone increases gradually while the quality and density decrease gradually,and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 ℃;the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25℃and 400℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature,and the mechanical properties of sandstone show obvious deterioration after 400 ℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature;with increasing angle αof the fissure,the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical properties.When the temperature is 800 ℃,the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously weakened.The failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including:tensile crack failure,tensile and shear cracks mixed failure,and shear crack failure.Tensile and shear crack mixed failure occur mainly at low temperatures and small angles;tensile crack failure occurs at high temperatures and large angles.     

高水材料结石体抗压强度环境效应试验研究

借助MTS力学试验系统、SEM电子扫描电镜和X射线衍射等分析设备,对在不同环境下高水速凝结石体的主要物理力学指标、结构特征及内部物质组成进行测试,研究高水结石体强度特征的环境效应。结果表明：高水结石体在不同PH值水环境中强度差异并非由其物质成分变化引起的,PH值主要通过影响结石体的微观结构而使其体现出不同的强度特征;空气环境中,结石体抗压强度值、变形常数及泊松比均大幅减小,力学性质差;水环境中,PH值=5.5时试样的抗压强度值最大,变形常数和泊松比在不同PH值环境中均减小,泊松比呈现随环境酸度或碱度的增大而迅速减小的趋势;不同环境中结石体应力-应变关系曲线相似,应力增长较快且体现蠕变特性。     

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结合江淮汽车厂4DA1型发动机缸体、缸盖的生产实际,对覆膜砂的强度、发气性和溃散性进行了研究。通过对3种覆膜砂性能的检测和比较,得出覆膜砂的固化强度表现为随固化因素改变,先不断升高直至达到最大值,然后再不断下降,以及在覆膜砂常规固化温度(200~250℃)和固化时间(90~140 s)范围内,固化温度和固化时间对覆膜砂型芯发气性的影响不大等基本规律,最终确定制芯工艺指导参数分别为:覆膜砂A 230℃、110 s,覆膜砂B 230℃、120 s,覆膜砂C 220℃、120 s,同时满足了制备型芯的高强度、低发气量和高溃散性的要求。     

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研究了反应离心熔渗法制备高体积比SiCp／Al复合材料的工艺过程及其抗弯强度。结果表明：通过适当的粒度配比，可在低温、低离心力下熔渗制备组织均匀的高体积比SiCp／Al复合材料，SiC颗粒体积分数可达到63％；复合材料的强度在很大程度上依赖于SiC颗粒尺寸及界面反应程度，合适的界面结合及细SiC颗粒的掺入有利于复合材料强度的提高；基体热处理改变了SiC颗粒所受应力状态，提高了复合材料的强度，其最高值可达519MPa。     

冶炼工艺对0Cr15Ni25WMoTi2NbAl合金力学性能的影响

研究了真空感应 电渣和非真空感应 电渣两种工艺冶炼的0Cr1 5Ni2 5WMoTi2NbAl合金的杂质元素含量、组织与性能。因真空感应冶炼过程中晶界偏聚元素Pb得到了有效挥发 ,减轻了晶界的弱化效应 ,因而该合金中高温塑性、持久强度均不同程度提高。随着中温形变速率的降低 (拉伸、大应力持久、小应力持久 ) ,两工艺合金的晶界弱化效应加剧。未发现两者的基本组织以及晶界沉淀相的种类、数量、形貌和分布有明显差异。     

多点成形压力机中基本体群安装模板的有限元分析

应用ANSYS商业软件，对多点成形压力机基本体群安装模板的强度与刚度进行了分析，获得了不同厚度、不同载荷工况下的应力分布规律和变形状况，为多点成形压力机的设计提供了重要的参考依据。     

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阐述高性能低硅铝蠕墨铸铁和球墨铝铸铁的试验工作，介绍采用热循环试验装置测量铸造中内应力的方法，以及硼铝球墨铸铁热挤压变形的试验工作。     

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C20混凝土试块在450℃高温下持续不同时间后自然冷却，再对其进行超声、回弹综合法及标准抗压强度试验，以探讨同一高温不同时间作用后混凝土强度的变化规律，分析无损检测与标准抗压强度试验之间的关系。