Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coeffic...Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coefficients of super Gauss vibration stress and temperature stress. Then, by applying these coefficients, an accelerated reliability qualification testing curve was obtained from the standard tests. Finally,the actual experiment on a digital marine control device was carried out under the proposed testing method.The experiment result shows that the proposed method can reduce the total experiment time and improve the efficiency of the reliability qualification test.展开更多
With the rapid development of transportation industry in China, fire accidents frequently happen in railway tunnels. Fire accidents that happened in railway tunnels can be roughly divided into three types: fire accide...With the rapid development of transportation industry in China, fire accidents frequently happen in railway tunnels. Fire accidents that happened in railway tunnels can be roughly divided into three types: fire accidents of passenger trains; those of freight trains; and those of oil tank trains. The most inflammable and dangerous among them is the fire accidents of oil tank trains, since oil has extremely great danger--it keeps burning long and extensively after it catches fire and the temperature rises fast with a highest temperature of the central flame over 1 000℃ and in some part the temperature goes as high as 1 200℃-1 600℃, which makes it rather difficult to extinguish fire, and thus leads to great damage to tunnel lining. From 1976 to 1998, there have been 8 serious tank train fires accident happened in railway tunnel in China, train traffic had been held up for 2 500 hours and more than 300 person injured (115 person died). As a result, the direct economic loss exceeded RMB30 million and the indirect economic loss was inestimable. Aimed at existing problems in research of fire accident in railway tunnel at present in China, in this paper, following contents have been focused on: 1 The Test and Study of Damage Degree of Tunnel Lining under Different Burning Temperature Grades Adopting the experimental means of really burning down for concrete material and members of tunnel lining under different fire temperature and different ablating time, the rule of change of mechanics behavior and damage degree of lining structure after withstanding high temperature is analyzed, and the empirical curves are obtained. The contents include: (1)The test method, measuring process, and instrument and equipment used. (2)The variety regulation of damage degree (thickness of burn, loosen, shelling) of lining concrete under different fire temperature and different ablating time. (3)The rule of change of compress strength of lining concrete under different fire temperature and different ablating time, as well as the different rules of change and relation of corresponding compress strength between surface burnt and surface borne. (4)The rule of change of tensile strength of lining concrete under different fire temperatures and different ablating time, as well as the corresponding relation between compress strength and tensile strength. (5)Based on the result of the above research, a divide standard of damage classification of lining structure under different burning temperature grade is presented and enduring fire critical time of the tunnel lining caused by fire accident is discussed. 2 Detection Test of Fire Damage Degree of Lining Members The relation between physical mechanical change and ultrasonic wave velocity after the tunnel lining structure damage due to high fire temperature are analyzed with the application of the ultrasonic detection technology. Also discussed is the tunnel fire damage. The relation includes the following: (1)The change of rule of ultrasonic wave velocity under different fire temperature field with different detection means. (2)The relation between remained compress strength and ultrasonic wave velocity of the damaged tunnel lining concrete after high temperature. (3)The relation between remained tensile strength and ultrasonic wave velocity of the damaged tunnel lining concrete after high temperature. (4)The relation between damage deepness and ultrasonic wave velocity of the damaged tunnel lining concrete after high temperature. (5)According to change of ultrasonic wave velocity, the calculation method of depth of the fire damage to lining structure and its practicality are also presented. 3 Damage Mechanism of Tunnel Lining after the Action of High Temperature On the basis of electron scanning microscope observation for lining material before and after being burnt down, the rule of change of microstructure of tunnel lining concrete effected by high temperature is analyzed, and damage mechanism of lining structure under different fire temperatures is discussed. Furthermore,展开更多
文摘Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coefficients of super Gauss vibration stress and temperature stress. Then, by applying these coefficients, an accelerated reliability qualification testing curve was obtained from the standard tests. Finally,the actual experiment on a digital marine control device was carried out under the proposed testing method.The experiment result shows that the proposed method can reduce the total experiment time and improve the efficiency of the reliability qualification test.
文摘With the rapid development of transportation industry in China, fire accidents frequently happen in railway tunnels. Fire accidents that happened in railway tunnels can be roughly divided into three types: fire accidents of passenger trains; those of freight trains; and those of oil tank trains. The most inflammable and dangerous among them is the fire accidents of oil tank trains, since oil has extremely great danger--it keeps burning long and extensively after it catches fire and the temperature rises fast with a highest temperature of the central flame over 1 000℃ and in some part the temperature goes as high as 1 200℃-1 600℃, which makes it rather difficult to extinguish fire, and thus leads to great damage to tunnel lining. From 1976 to 1998, there have been 8 serious tank train fires accident happened in railway tunnel in China, train traffic had been held up for 2 500 hours and more than 300 person injured (115 person died). As a result, the direct economic loss exceeded RMB30 million and the indirect economic loss was inestimable. Aimed at existing problems in research of fire accident in railway tunnel at present in China, in this paper, following contents have been focused on: 1 The Test and Study of Damage Degree of Tunnel Lining under Different Burning Temperature Grades Adopting the experimental means of really burning down for concrete material and members of tunnel lining under different fire temperature and different ablating time, the rule of change of mechanics behavior and damage degree of lining structure after withstanding high temperature is analyzed, and the empirical curves are obtained. The contents include: (1)The test method, measuring process, and instrument and equipment used. (2)The variety regulation of damage degree (thickness of burn, loosen, shelling) of lining concrete under different fire temperature and different ablating time. (3)The rule of change of compress strength of lining concrete under different fire temperature and different ablating time, as well as the different rules of change and relation of corresponding compress strength between surface burnt and surface borne. (4)The rule of change of tensile strength of lining concrete under different fire temperatures and different ablating time, as well as the corresponding relation between compress strength and tensile strength. (5)Based on the result of the above research, a divide standard of damage classification of lining structure under different burning temperature grade is presented and enduring fire critical time of the tunnel lining caused by fire accident is discussed. 2 Detection Test of Fire Damage Degree of Lining Members The relation between physical mechanical change and ultrasonic wave velocity after the tunnel lining structure damage due to high fire temperature are analyzed with the application of the ultrasonic detection technology. Also discussed is the tunnel fire damage. The relation includes the following: (1)The change of rule of ultrasonic wave velocity under different fire temperature field with different detection means. (2)The relation between remained compress strength and ultrasonic wave velocity of the damaged tunnel lining concrete after high temperature. (3)The relation between remained tensile strength and ultrasonic wave velocity of the damaged tunnel lining concrete after high temperature. (4)The relation between damage deepness and ultrasonic wave velocity of the damaged tunnel lining concrete after high temperature. (5)According to change of ultrasonic wave velocity, the calculation method of depth of the fire damage to lining structure and its practicality are also presented. 3 Damage Mechanism of Tunnel Lining after the Action of High Temperature On the basis of electron scanning microscope observation for lining material before and after being burnt down, the rule of change of microstructure of tunnel lining concrete effected by high temperature is analyzed, and damage mechanism of lining structure under different fire temperatures is discussed. Furthermore,
