A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the tem...A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.展开更多
In the phase of the normalized COVID-19 prevention and control,non-contact temperature measurement is one of the most efficient and convenient methods for initial screening of suspected cases.In the year of 2020 in Wu...In the phase of the normalized COVID-19 prevention and control,non-contact temperature measurement is one of the most efficient and convenient methods for initial screening of suspected cases.In the year of 2020 in Wuhan,such non-contact equipment was urgently demanded,standards development in the traditional way cannot satisfy the market needs.So,the research and development of this standard for infrared intelligent body temperature measurement system was carried out in a rapid way.展开更多
The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established t...The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.展开更多
为分析高地温水工隧洞衬砌结构温度应力特性,基于拉普拉斯变换推导出衬砌结构瞬态温度场的解析解,并借助弹性抗力法推导出衬砌结构的弹性温度应力分量。依托新疆布伦口水电站监测数据对衬砌结构瞬态温度场及应力场进行计算分析,并采用...为分析高地温水工隧洞衬砌结构温度应力特性,基于拉普拉斯变换推导出衬砌结构瞬态温度场的解析解,并借助弹性抗力法推导出衬砌结构的弹性温度应力分量。依托新疆布伦口水电站监测数据对衬砌结构瞬态温度场及应力场进行计算分析,并采用抗拉强度准则和裂缝尖端强度因子对衬砌结构破坏进行分析,提出合理的温控防裂措施。结果表明:1)衬砌温度场前期整体温度迅速上升,在第7天左右达到最大值,其中衬砌内壁温度可达到37℃,外壁温度可达到56℃。2)衬砌结构外墙环向应力可达到2.2 MPa,体现为拉应力状态;径向应力可达到2.7 MPa,呈现为压应力状态。3)衬砌结构强度的破坏主要受温度及结构本身稳定性2方面影响,可通过采用低热水泥、控制混凝土的入模温度以及严格监控施工过程来提高衬砌的稳定性。其中,采用低热水泥可降低衬砌结构的温升值,混凝土的最终水化热每降低50 k J/kg,衬砌结构内外壁的温差可降低1.85℃左右;适当提高入模温度可缩短水化热的放热周期及降低衬砌内外壁温差。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50779010)
文摘A three-dimensional finite element program for thermal analysis of hydration heat in concrete structures with a plastic pipe cooling system is introduced in this paper. The program was applied to simulation of the temperature and stress field of the Cao＇e Sluice during the construction period. From the calculated results, we can find that the temperaiure and stress of concrete cooled with plastic pipes are much lower than those of concrete without pipes. Moreover, plastic pipes could not be corroded by seawater. That is to say, a good effect of temperature control and cracking prevention can be achieved, which provides a useful reference for other similar nearshore concrete projects.
文摘In the phase of the normalized COVID-19 prevention and control,non-contact temperature measurement is one of the most efficient and convenient methods for initial screening of suspected cases.In the year of 2020 in Wuhan,such non-contact equipment was urgently demanded,standards development in the traditional way cannot satisfy the market needs.So,the research and development of this standard for infrared intelligent body temperature measurement system was carried out in a rapid way.
文摘The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.
文摘为分析高地温水工隧洞衬砌结构温度应力特性,基于拉普拉斯变换推导出衬砌结构瞬态温度场的解析解,并借助弹性抗力法推导出衬砌结构的弹性温度应力分量。依托新疆布伦口水电站监测数据对衬砌结构瞬态温度场及应力场进行计算分析,并采用抗拉强度准则和裂缝尖端强度因子对衬砌结构破坏进行分析,提出合理的温控防裂措施。结果表明:1)衬砌温度场前期整体温度迅速上升,在第7天左右达到最大值,其中衬砌内壁温度可达到37℃,外壁温度可达到56℃。2)衬砌结构外墙环向应力可达到2.2 MPa,体现为拉应力状态;径向应力可达到2.7 MPa,呈现为压应力状态。3)衬砌结构强度的破坏主要受温度及结构本身稳定性2方面影响,可通过采用低热水泥、控制混凝土的入模温度以及严格监控施工过程来提高衬砌的稳定性。其中,采用低热水泥可降低衬砌结构的温升值,混凝土的最终水化热每降低50 k J/kg,衬砌结构内外壁的温差可降低1.85℃左右;适当提高入模温度可缩短水化热的放热周期及降低衬砌内外壁温差。
