利用X线平片分析骨折愈合的等效最弱截面

目的更多地提取X线平片中包含的骨折愈合力学信息,为临床骨折愈合治疗过程定量判断愈合程度提供有效并且简便实用的方法。方法 12只家兔胫骨中部横断造成骨折模型,并穿针进行滑动固定。利用力传感器在胫骨中部体表从前向后横向手动加载。通过安装在滑动固定器上的微位移传感器测量断端活动位移。采用计算机数据采集系统记录加载力值P和滑动架滑动位移ΔL关系曲线。以K=P/ΔL值代表带滑动固定器兔胫骨整体等效抗弯刚性。每周测量1次。采用经过数字化改造的手提X线机每周拍摄正、侧位X线片;在delphi软件开发环境中编写图像处理和计算程序。在X线正、侧位片灰度分析基础上,沿胫骨轴向扫描计算寻找等效最弱截面并计算其等效抗弯截面惯性矩,得到定量的抗弯刚度和断裂强度判据。结果家兔骨折愈合拆架时间分布在29～41 d。在正侧位X线片上获得计算机模拟的等效最弱截面分界线,且得到其抗弯截面惯性矩。最弱抗弯截面惯性矩与最强抗弯截面惯性矩的比值随愈合时间逐渐升高。侧位片比值术后第1周为(0.31±0.17),第2周为(0.34±0.13),第3周为(0.43±0.20),第4周为(0.56±0.23)。正位片位片比值术后第1周为(0.40±0.19),第2周为(0.47±0.16),第3周为(0.56±0.20),第4周为(0.66±0.11)。家兔骨折胫骨在体抗弯刚性测试所得K值术前平均为(3.976±4.986)N.μm-1,术后第1周为(0.679±1.026)N.μm-1,术后第2周为(2.115±3.233)N.μm-1,术后第3周为(3.459±4.723)N.μm-1,术后第4周为(4.788±4.831)N.μm-1。从1～4周愈合过程,X线片计算得到的最弱抗弯截面惯性矩和最强抗弯截面惯性矩的比值与K值之间具有很好的相关性。结论外骨痂生长有较强规律性,并且在普通正侧位X线平片易于辨认。从骨折近端和远端分别生长的骨痂在愈合进程中逐渐合拢,最终弥合。本文所述方法较好地反映了实际读片感觉。

织物马鞍状弯曲试验研究

为更好地表征织物在实际弯曲状态下的力学特性,使用自制的织物马鞍状弯曲测试装置,分别选用两种不同厚度和面密度的纸、塑料薄膜与织物为试样,在马鞍状弯曲情况下采用单因素分析法探讨了织物长度、宽度和加载速度等测试条件对织物受力负荷-位移的影响,并确定出织物马鞍状弯曲测试参数。结果表明当评价指标为抗弯刚性时,在下端距离16mm,试样宽度50mm,加载速度50mm/min条件下,采用马鞍状弯曲测试方法测定织物弯曲性能与采用斜面法测定性能相比,具有较好的一致性。

Bonding Characteristics and Flexural Stiffening Effect of Carbon Fibre Reinforced Plastics Strand Sheets Bonded to Steel Beams

Corrosion of steel structures is unavoidable and the structural performance decreases dramatically due to the corrosion. As a repairing method for corroded steel members, bonding carbon fiber sheets with resin had been developed. The purpose of this study is to propose the flexural strengthening method for steel members by using CFRP （carbon fiber reinforced polymer） strand sheets. In order to clarify the stiffening effect and the debonding characteristics of CFRP strand sheets, and to optimize the strengthening design specifications, the flexural tests using high tension steel beams strengthened with CFRP strand sheets are performed. Two cases of experiments are carried out. In Experiment 1, the result from previous research is reflected in the strengthening design. Moreover in Experiment 2, the debonding characteristics obtained from Experiment 1 are reflected. As a result, it was clarified that CFRP strand sheets have stiffening effect equivalent to the theoretical value and its debonding property is practically high enough when FRP （fiber reinforcement polymer） sheets have an appropriate bonding length.