不同缝合方式对缝合复合材料力学性能的影响研究

缝合技术作为整体成型的制造技术,能有效增强复合材料的层间强度和抗冲击损伤性能。在缝合技术中有不同的缝合方式,目前常用的缝合方式有锁式缝合、链式缝合和临缝三种。不同的缝合方式对复合材料的层间剪切性能、压缩性能、拉伸性能和弯曲性能会产生不同的影响。主要研究了在三种不同的缝合方式下,复合材料的压缩性能、拉伸性能和弯曲性能的变化。

缝合参数对缝合复合材料力学性能的影响研究

缝合复合材料因具有优异的抗冲击性能而在航空航天界得到广泛应用。在缝合时可以设置不同的缝合参数,主要包括缝合压力、针距和行距等。不同的缝合参数对复合材料制件的力学性能影响不同。本文主要研究了临缝和链式缝合两种缝合方式在不同的针距和行距缝合时,对缝合复合材料力学性能的影响,包括拉伸性能、压缩性能和剪切性能,从而来确定临缝和链式缝合的最佳缝合针距和行距。

Measuring crack propagation in reinforced asphalt concretes

Two different reinforcing methodologies are applied：modification of the overlay characteristics by adding chopped glass fibers to the hot mixture asphalt （HMA） and reinforcing asphalt overlay with glass grids.Theory of fracture mechanics （FM） is employed to determine crack growth rates for the suggested anti-cracking overlay systems.Asphalt mixture designing tests,three point bending tests and fatigue crack propagation tests were carried out.The critical stress intensity factors KIC are determined for plain and reinforced asphalt concrete.Depending on the fatigue crack propagation,the crack growth rate is determined for each type of anti-cracking system and the cracking process is also analyzed.One of the significant points in this study is the attempt to give better understanding of the crack propagation for multilayer asphaltic overlay or what are suggested herein to be called composite structure anti-cracking overlay system.The results indicate that the reinforcing materials improve anti-cracking characteristics of the asphalt concrete.Composite structure anti-cracking overlay gives a good solution for the reflective cracking phenomenon over old cracked pavements.

Operative treatment of acromioclavicular joint dislocation：a new technique with suture anchors

Objective：To evaluate clinical outcome of suture anchors in strengthening both acromioclavicular and coracoclavicular ligaments in the surgical treatment of acromioclavicular joint dislocation.Methods：Twenty-eight patients with acute traumatic Rockwood Ⅲ,Ⅳ and Ⅴ dislocations of the acromioclavicular joint surgically treated at our institute between October 2010 and January 2012 were recruited.All patients underwent open reduction combined with suture anchors.Function was evaluated using the ConstantMurley shoulder score.Clinical and radiographic shoulder ratings were evaluated using Taft criteria at 3,6 and 12 months.Results：Two cases with fixation loosening were not included in final statistical analysis.Other patients obtained full joint reposition on immediate postoperative radiographs.Follow-up was performed with an average of 15.6 months （range,12-19）.After early range of motion exercises,96.2％ of the patients （25/26） could abduct and elevate their shoulders more than 90 degrees within postoperative 3 months.There was no infection.Average Constant-Murley score was 96.3 points （range,94-100）and mean Taft shoulder rating was 10.7 points （range,8-12） at 12 months.Conclusion：The suture anchor is a relatively simple technique and can avoid screw removal which is helpful in reconstructing both acromioclavicular and coracoclavicular ligaments in acute traumatic acromioclavicular joint dislocation.

ExExperimental and numerical studies on the prediction of bendability limit of QSTE340 welded tube in NC bending process

For a low carbon steel tube with small wall factor D/t and bending radius R,the over-thinning induced localized necking is one dominant failure in tube numerical control(NC) bending process,which strongly restricts the bendability limit of the tube.In addition,the deterioration of bendability of a tube is increased by the existence of the weak weld region.Therefore,an important issue is how to determinate and predict the welded tube bendability limit.In the present study,a finite element(FE) model with weld and subdivided heat affected zones under ABAQUS platform is employed to explore the deformation behaviors of welded tube NC bending.A localized necking criterion based on the critical thickness thinning is used to predict the critical principal strains,critical bending radius and burst location during the forming process.It is found that the failures always occur at the rigid supporting point of mandrel flexible balls near the tangent point at the outside of the bend,where the wall thickness of the tube is the lowest.The bending limit curves(BLCs) of the QSTE340 welded tube are obtained by shifting the standard shaped forming limit curve to the critical principal strains along the major strain axis.Comparison between the numerical and experimental results has shown that the BLC and critical bending radius predictions agree well with the experimental results.In addition,the effect of weld positions on BLC is discussed,the weld region shows an almost negligible effect on the forming limit at a non-critical location that is far away from the outside of the bend.However,when the weld is at the large tensile deformation region on the outside of the bend,a decrease of the forming limit strains is seen.

Determination of critical slip surface of fractured rock slopes based on fracture orientation data

The critical slip surface of a fractured rock slope tends to extend along the fractures.Thus,fracture orientation plays a critical role in determining the critical slip surface.Based on fracture orientation data,this paper examines the critical slip surfaces of fractured rock slopes.Given that the surface of a fractured rock slope extends along the fracture surfaces,or the wedges,with each composed of two arbitrary fractures,the critical slip surface is determined via stochastic dynamics.In addition,a fracture frequency method is proposed as a means of analyzing the critical slip surface.According to this method,the critical slip surface slips in whichever direction has the lowest fracture frequency.Based on the stochastic dynamics method and the fracture frequency method,the critical slip surface of the slope is finally determined,that is,the critical slip surface takes the form of a plane passing the slope toe with a dip of 120° and a dip angle of 45°.