The tensile response, the low cycle fatigue （LCF） resistance, and the creep behavior of an aluminum （A1） cast alloy are studied at ambient and elevated temperatures. A non-contact real-time optical extensometer ba...The tensile response, the low cycle fatigue （LCF） resistance, and the creep behavior of an aluminum （A1） cast alloy are studied at ambient and elevated temperatures. A non-contact real-time optical extensometer based on the digital image correlation （DIC） is developed to achieve strain measurements without damage to the specimen. The optical extensometer is validated and used to monitor dynamic strains during the mechanical experiments. Results show that Young＇s modulus of the cast alloy decreases with the increasing temperature, and the percentage elongation to fracture at 100 ℃ is the lowest over the temperature range evaluated from 25 ℃ to 300 ℃. In the LCF test, the fatigue strength coefficient decreases, whereas the fatigue strength exponent increases with the rising temperature. The fatigue ductility at 100 ℃. As expected, the resistance to and changes from 200 ℃ to 300 ℃. coefficient and exponent reach maximum values creep decreases with the increasing temperature展开更多
A series of transparent casting polyurethane resins (TCPU) were synthesized from cycloaliphatic diisocyanate (IPDI or H_(12)MDI), polyol, chain extender, crosslinking agents, catalyst and special aids (T),which were c...A series of transparent casting polyurethane resins (TCPU) were synthesized from cycloaliphatic diisocyanate (IPDI or H_(12)MDI), polyol, chain extender, crosslinking agents, catalyst and special aids (T),which were characterized by FTIR. The thermal stabilities of the obtained TCPU were examined by DSC and TGA, the glass transition temperature (T_g) was in the range of 95-110 ℃, the initial decomposition temperature (5% weight loss) was 250-265 ℃, and 10% weight loss at the temperature was in the range of 260-286℃ in nitrogen atmosphere. The morphologies of the fractured surfaces of TCPU were revealed by a scanning electron microscope (SEM). The crystalline-amorphous characters of TCPU were studied by WAXD, the result shows that TCPU possesses amorphous glassy characters. The optical properties of TCPU were studied by a UV-7500 visible light absorbance measurement. All the samples exhibited excellent optical properties and possessed light transmittance in the range of 91%-93%.展开更多
灌注桩是最常见的桩基础形式之一,开展灌注桩桩身变形测量,对研究其桩身承载特性及分析桩身质量非常重要。采用目前国际上最为先进的光频域反射光纤传感技术(optical frequency domain reflectometer,OFDR),开展了灌注桩桩身变形高精度...灌注桩是最常见的桩基础形式之一,开展灌注桩桩身变形测量,对研究其桩身承载特性及分析桩身质量非常重要。采用目前国际上最为先进的光频域反射光纤传感技术(optical frequency domain reflectometer,OFDR),开展了灌注桩桩身变形高精度测量现场试验,获得了灌注桩在加载和卸载过程中的桩身变形、桩身轴力及桩身侧摩阻力分布情况,分析了加载和卸载过程中灌注桩桩身变形特征及荷载传递规律。试验结果表明:加载阶段光纤测得的桩身应变随荷载逐级增加,卸载阶段光纤测得的桩身应变随荷载逐级减小,卸载结束后桩身有一定应力残余;同时,通过对比加载、卸载过程中桩身轴力分布曲线,发现桩身轴力在卸载后存在时间滞后效应;结果显示OFDR技术能够实现对灌注桩桩身变形的高精度测量,并能精细化掌握桩身变形特征。展开更多
改进的微铸造技术利用Bi2O3代替Si O2作为浸润层,以提升X射线吸收光栅中铋的填充率.通过源光栅发现,铋填充率很大程度上取决于初始浸润材料Bi(NO3)3的覆盖程度.提出使用超声的方法,使丙酮携带Bi(NO3)3进入高深宽比分析光栅结构内部,并...改进的微铸造技术利用Bi2O3代替Si O2作为浸润层,以提升X射线吸收光栅中铋的填充率.通过源光栅发现,铋填充率很大程度上取决于初始浸润材料Bi(NO3)3的覆盖程度.提出使用超声的方法,使丙酮携带Bi(NO3)3进入高深宽比分析光栅结构内部,并覆盖在侧壁表面,待Bi(NO3)3高温分解为Bi2O3后,利用Bi2O3与铋的浸润性使铋完全进入分析光栅结构内部.实验结果表明,相比不使用和使用频率如40、120及170 k Hz的超声,80 k Hz的超声更有助于提高铋的填充率,同时还表明超声具备向高深宽比结构内辅助填充物质的能力.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11372173,11672347,and 11727804)the Science and Technology Development Foundation of Shanghai Automobile Industry(No.1514)
文摘The tensile response, the low cycle fatigue （LCF） resistance, and the creep behavior of an aluminum （A1） cast alloy are studied at ambient and elevated temperatures. A non-contact real-time optical extensometer based on the digital image correlation （DIC） is developed to achieve strain measurements without damage to the specimen. The optical extensometer is validated and used to monitor dynamic strains during the mechanical experiments. Results show that Young＇s modulus of the cast alloy decreases with the increasing temperature, and the percentage elongation to fracture at 100 ℃ is the lowest over the temperature range evaluated from 25 ℃ to 300 ℃. In the LCF test, the fatigue strength coefficient decreases, whereas the fatigue strength exponent increases with the rising temperature. The fatigue ductility at 100 ℃. As expected, the resistance to and changes from 200 ℃ to 300 ℃. coefficient and exponent reach maximum values creep decreases with the increasing temperature
文摘A series of transparent casting polyurethane resins (TCPU) were synthesized from cycloaliphatic diisocyanate (IPDI or H_(12)MDI), polyol, chain extender, crosslinking agents, catalyst and special aids (T),which were characterized by FTIR. The thermal stabilities of the obtained TCPU were examined by DSC and TGA, the glass transition temperature (T_g) was in the range of 95-110 ℃, the initial decomposition temperature (5% weight loss) was 250-265 ℃, and 10% weight loss at the temperature was in the range of 260-286℃ in nitrogen atmosphere. The morphologies of the fractured surfaces of TCPU were revealed by a scanning electron microscope (SEM). The crystalline-amorphous characters of TCPU were studied by WAXD, the result shows that TCPU possesses amorphous glassy characters. The optical properties of TCPU were studied by a UV-7500 visible light absorbance measurement. All the samples exhibited excellent optical properties and possessed light transmittance in the range of 91%-93%.
文摘灌注桩是最常见的桩基础形式之一,开展灌注桩桩身变形测量,对研究其桩身承载特性及分析桩身质量非常重要。采用目前国际上最为先进的光频域反射光纤传感技术(optical frequency domain reflectometer,OFDR),开展了灌注桩桩身变形高精度测量现场试验,获得了灌注桩在加载和卸载过程中的桩身变形、桩身轴力及桩身侧摩阻力分布情况,分析了加载和卸载过程中灌注桩桩身变形特征及荷载传递规律。试验结果表明:加载阶段光纤测得的桩身应变随荷载逐级增加,卸载阶段光纤测得的桩身应变随荷载逐级减小,卸载结束后桩身有一定应力残余;同时,通过对比加载、卸载过程中桩身轴力分布曲线,发现桩身轴力在卸载后存在时间滞后效应;结果显示OFDR技术能够实现对灌注桩桩身变形的高精度测量,并能精细化掌握桩身变形特征。
文摘改进的微铸造技术利用Bi2O3代替Si O2作为浸润层,以提升X射线吸收光栅中铋的填充率.通过源光栅发现,铋填充率很大程度上取决于初始浸润材料Bi(NO3)3的覆盖程度.提出使用超声的方法,使丙酮携带Bi(NO3)3进入高深宽比分析光栅结构内部,并覆盖在侧壁表面,待Bi(NO3)3高温分解为Bi2O3后,利用Bi2O3与铋的浸润性使铋完全进入分析光栅结构内部.实验结果表明,相比不使用和使用频率如40、120及170 k Hz的超声,80 k Hz的超声更有助于提高铋的填充率,同时还表明超声具备向高深宽比结构内辅助填充物质的能力.
