Research On Key Materials For Intelligent Vehicle Detection Sensors

Traffic accident decreases efficiency of road traffic system.With development of Economic and social,continuous increasement of vehicle overload the road traffic system.That lead to high probability of traffic accidnet.Moreover,traffic accidents occun-in highway or key road section of urban road system may weaken traffic capacity of them,or cause the interruption of traffic.Reducing traffic accident is significant to maintain normal traffic order.The occurance of traffic accident decides by many factors,including mental status of drivers,speed and running route of vehicles,weather,weight of vehicles,and traffic condition et al.For running vehicles in a road section,an appropriate speed limit and driving route trestrict due to the weather,traffic condition,and road design parameters(slop and curvature,type of pavement meaterial) will decrease the traffic accident.Financial supported by Hi-teeh Research and Development Program of China (2006AA11Z117),based on the traffic accident control,a multi-function intelligent vehicle detection sensor,which can monitor the speed,running route,structure parameters,and weight of vehicles,was designed in this paper.Sensitive materials, package materials,and protection materials were researched and developed.Two type of senosrs,based on PZT ceramics and PLMN ceramics,were preapred and output behavior was measured.The main work and compliments are listed as follow.1.A Cr³⁺ doping sensitive material for intelligent vehicle detection sensor with decade aging rate of 1.18%was prepared,which sintered at 960℃by adding KCl.(1) Pinning effect of Cr³⁺ on domain wall hamper the polarization of sensitive material.Due to the acceleartion of Cr³⁺ on sintering of sensitive material,the piezoelectric constant of sensitive material increase with the increasement of content of Cr₂O₃ when weight content of Cr₂O₃ is lower than or equer to 0.3%.In sensitive material with a Cr₂O₃ wight content more than 0.3%,Cr³⁺ hamper the growing of sensitive material grain.That lead to a large area of crystal boundary and spontaneous polarization in sensitive material grain was restrained.A Higher content of Cr₂O₃ will reduce the piezoelectric constat of sensitive material.The optimum weight content of Cr₂O₃ is 0.3% (2) KCL melt at 770℃and accelerat the sintering of senstive material.Sintering temperature of sensitive material decrease a lot.Simultaneously,replacing of cation by K⁺ decrease the stability of part of electric domain,which promote the stability of piezoelectric constant of sensitive material after thermal processing.(3) Thermal processing promote the stability of piezoelectric constant of sensitive material a lot.An appropriate heat treatment will reduce the decad aging rate to 1.8%.2.An Al₂O₃ package table,which sintered at 1550℃by using cation doping and lower temperature liquid sintering together,was prepared with a bulk resistivity more than 9×10¹²Î©Â·m,and a water absorption close to zero.(1) An Al₂O₃ package table sintering by using cation doping and lower temperature liquid sintering together have a low sintering temperature.The water absorption of it is near zero.Weight loss under chemical attack is low,and bulk resistivity is high.(2) A TiO₂ doping sintering Al₂O₃ package table has a higher water absorption and lower bulk resistivity than which sintered by using cation doping and lower temperature liquid sintering together.Moreover,mechanical properties of package table sintered at higher temperature drop sharply due to abnormal growth of grains. Properties of lower temperature liquid sintering package table affected greatly by mix propertion,and water absorption of it is high,and bulk resistivity is low.(3) Microstructure,density,water absorption,flexural strength of package table change little with the increasement of sintering time.Weight loss under acid attack and water attack essentially constant and weight loss under alkali attack decreases sharply and then changes slightly with the increasement of sintering time.Bulk resistivity increases rapidly and then changes slightly with the increasement of sintering time.3.Research on mechanical properties,freezing-thawing resistance,chloride corrosion resistance,acid attack resistance of protection material were conducted.A novel method for flexural toughness assement of protection material was putforwad.(1) Coarse polymer fiber could promote the mechanical properties of concrete which equivalent with steel fiber.As the modulus of coarse polymer fiber is 1/7-1/9 of that of steel,it works after the failure of concrete. (2) Because of the "deflection spring-back" in coarse polymer fiber reinforced concrete,present methods for flexural toughness assessment for fiber reinforced concrete do not fit it.In this paper mean square of stress ratio of "deflection spring-back" to peak point and deflection ratio of "deflection spring-back" to peak point is suggested as the evaluation index.(3) Coarse polymer fiber could promote the freezing-thawing resistance of concrete.However,the reinforce effect of coarse polymer fiber is lower than steel fiber.Otherwise,the resistance of coarse polymer fiber reinforced concrete to cholirde and acik attack is higher than the concrete reinforced by steel fiber.4.Intelligent vehicle detection sensors base PZT and PLMN ceramics were prepared.Output behavior of the sensors were investigated under various pressure, load time,temperature.Output behavior before and after fatigure load were investigated also.(1) Output-pressure curve of intelligent vehicle detection sensor based PZT ceramic has good linearity within pressure limits from 0.1MPa to 2MPa,whereas Output-pressure curve of intelligent vehicle detection sensor based PLMN ceramic was linear only within pressure limits from 0.1MPa to 1.5MPa.(2) Output to pressuer ration of intelligent vehicle detection sensor based PZT ceramic change little when load time is shorter than 0.1 s and it will decreae with the increasement of load time.Output to pressuer ration reduce with the reducing of pressure in the same load time.Output to pressuer ration of intelligent vehicle detection sensor based PZT ceramic decreaes with the increasement of load time.(3) Output of intelligent vehicle detection sensors based PZT and PLMN ceramics increase at first and then decrease and linearity of output-pressure curve deteriorate with the rise of temperature in the temperature range from-20℃to 60℃.(4) Fatigure load have little impact on output of intelligent vehicle detection sensors based PZT and PLMN ceramics.