在分析多轴疲劳几种常用非比例度定义的基础上,提出了一种非比例度定义方法,进而以American Society of Mechanical Engineers(ASME)规范案例中非比例加载多轴疲劳设计准则采用的应变参量作为基本损伤参量,发展了一种新的多轴疲劳寿命...在分析多轴疲劳几种常用非比例度定义的基础上,提出了一种非比例度定义方法,进而以American Society of Mechanical Engineers(ASME)规范案例中非比例加载多轴疲劳设计准则采用的应变参量作为基本损伤参量,发展了一种新的多轴疲劳寿命预测模型.结果表明:1所提出的非比例度定义可以描述任意已知轮廓的、非周期的、变幅的非比例加载路径;2与两种常用的多轴非比例加载疲劳寿命模型的预测结果对比可知,新的寿命预测模型对14种比例和非比例加载路径下304不锈钢材料的寿命预测与试验吻合更好,预测结果基本位于2倍分散带以内.展开更多
Purpose The purpose of this work is to study the pulse shape,energy resolution,non-proportionality of energy response for gamma-rays,and time characteristics of CeBr_(3) detector.Method The time and energy responses o...Purpose The purpose of this work is to study the pulse shape,energy resolution,non-proportionality of energy response for gamma-rays,and time characteristics of CeBr_(3) detector.Method The time and energy responses of two CeBr_(3) detectors were characterized by an analog method and a digital method using a set of standardγ-ray sources.The pulse shape,energy resolution and non-proportionality(nPR)of energy response forγ-rays were characterized using the analog method.For the analog method,the high voltage applied to PMTs,parameters of walk and external delay of constant fraction discriminator were optimized.For the digital method,a CEAN 1729A digitizer with sampling frequency of 2 GS/s and resolution of 11 bit,and a digital constant fraction discrimination technique were used to study the time performance of the two CeBr_(3) detectors.Then,the coincidence time resolutions of the CeBr_(3) detectors for the gamma peaks of ^(22)Na and ^(60)Co were measured using the two methods.Results The t_(rise),lifetimeτ,t_(fall) for CeBr_(3)21^(#)and 22^(#)are 11.2 ns,23.8 ns,50.2 ns,and 10.4 ns,26.5 ns,58.6 ns,respectively.The measured non-proportionality of CeBr_(3)21^(#)and 22^(#)are 1.08%and 2.22%,respectively.The time resolutions of the two CeBr_(3) detectors are 244±2 ps and 248±3 ps at the energy peaks of ^(60)Co source,and 336±2 ps and 335±3 ps at 511 keV for the analog and the digital methods.Conclusions The time resolutions obtained by the analog method and the digital method are almost identical.The CeBr_(3) detector is a good option in the applications such as half-life measurements,ToF-PET and high counting rate conditions.Furthermore,it is a goodγ-ray spectrometer owing to the preferable energy resolution and non-internal activity.展开更多
文摘在分析多轴疲劳几种常用非比例度定义的基础上,提出了一种非比例度定义方法,进而以American Society of Mechanical Engineers(ASME)规范案例中非比例加载多轴疲劳设计准则采用的应变参量作为基本损伤参量,发展了一种新的多轴疲劳寿命预测模型.结果表明:1所提出的非比例度定义可以描述任意已知轮廓的、非周期的、变幅的非比例加载路径;2与两种常用的多轴非比例加载疲劳寿命模型的预测结果对比可知,新的寿命预测模型对14种比例和非比例加载路径下304不锈钢材料的寿命预测与试验吻合更好,预测结果基本位于2倍分散带以内.
基金supported by the National Science Founda-tion of China(Grant No.11575165 and 11775200)
文摘Purpose The purpose of this work is to study the pulse shape,energy resolution,non-proportionality of energy response for gamma-rays,and time characteristics of CeBr_(3) detector.Method The time and energy responses of two CeBr_(3) detectors were characterized by an analog method and a digital method using a set of standardγ-ray sources.The pulse shape,energy resolution and non-proportionality(nPR)of energy response forγ-rays were characterized using the analog method.For the analog method,the high voltage applied to PMTs,parameters of walk and external delay of constant fraction discriminator were optimized.For the digital method,a CEAN 1729A digitizer with sampling frequency of 2 GS/s and resolution of 11 bit,and a digital constant fraction discrimination technique were used to study the time performance of the two CeBr_(3) detectors.Then,the coincidence time resolutions of the CeBr_(3) detectors for the gamma peaks of ^(22)Na and ^(60)Co were measured using the two methods.Results The t_(rise),lifetimeτ,t_(fall) for CeBr_(3)21^(#)and 22^(#)are 11.2 ns,23.8 ns,50.2 ns,and 10.4 ns,26.5 ns,58.6 ns,respectively.The measured non-proportionality of CeBr_(3)21^(#)and 22^(#)are 1.08%and 2.22%,respectively.The time resolutions of the two CeBr_(3) detectors are 244±2 ps and 248±3 ps at the energy peaks of ^(60)Co source,and 336±2 ps and 335±3 ps at 511 keV for the analog and the digital methods.Conclusions The time resolutions obtained by the analog method and the digital method are almost identical.The CeBr_(3) detector is a good option in the applications such as half-life measurements,ToF-PET and high counting rate conditions.Furthermore,it is a goodγ-ray spectrometer owing to the preferable energy resolution and non-internal activity.
