切屑自然卷曲机理的探索

通过建立切削过程的传热学模型，推导出切屑内部的温度分布，指出切屑内的温度场是一非均匀场，该温度场对切削自然自然卷曲机理有重要影响。     

切削刃法剖面曲线刃口微观形貌对切削加工应力的影响

为了研究切削加工时刀具切削刃法剖面不同曲线刃口微观形貌对刀具切削应力和铁屑的影响,采用切削仿真软件Third Wave Advant Edge进行了2D切削仿真试验,分析了不同刃口微观形貌对镍基合金inconel718进行直角自由切削时的切削应力变化,总结了在切削过程中不同刃口微观形貌的刀具应力和接触面应力变化规律以及铁屑卷曲的形成。     

PTT弹性纤维性能研究

系统对比分析了PTT、PA、PTT/PET、PTT/PBT以及高收缩PET 5种纤维的定伸长反复拉伸回弹性、卷曲性及沸水收缩性。实验表明,PTT纤维具有优良的弹性回复率,PTT/PET、PTT/PBT纤维的卷曲性和沸水收缩性更为优异。     

超高层建筑用大直径厚壁钢管加工新技术

随着我国经济的高速发展,超高层建筑越来越多,超高层建筑结构采用带巨型斜撑、巨型柱、巨型框架结构的钢结构及钢管混凝土结构体系的也越来越多,这类建筑对钢结构构件技术要求及加工精度要求非常高。阐述了超高层建筑大直径厚壁钢管的加工新工艺、新技术要求;提出防止焊接裂纹及振动时效消除焊接应力的措施。     

Non-linear curling of wide single-flange steel panels

An original analytical model to study the non-linear flange curling in wide single-flange panels is presented in this paper. Flange curling phenomenon is the tendency of the wide thin flanges (in compression or tension) to move towards the neutral axis, when thin-walled members are subjected to bending. Despite the simplicity of the formula developed in earlier works of Winter to account for the flange curling effects, which is used in current steel codes, recent work has showed that this expression is rather restrictive and does not apply for all cases. The analytical expressions reported here are rather general since they (i) consider the restraining effect provided by the web, (ii) account for the shift of the neutral axis due to curling, (iii) incorporate the decrement of the second moment of area due to curling, and (iv) are fully analytical, thus avoiding iterative techniques. The analytical model is applied to study the curling behaviour of profiled steel decks and cassette-wall panels and is validated by means of comparisons with experimental results available in the literature. Since the EC3 rules state that the tensioned wide flange in liner trays should be reduced if the curling displacement is higher than 5% of the web height, approximate expressions to evaluate the reduced width of the wide thin flange under curling are proposed.     

An Analysis of the Curling Phenomenon in Viscoelastic Bimaterial Strips

A mathematical analysis is performed to obtain relations for the radius of curvature and flexural moments for initially stretched bimaterial strips in which at least one of the materials exhibits viscoelastic behavior. One practical application of this analysis is for pressure sensitive tapes. Consequently, the radius of curvature and flexural moment relations are obtained as functions of backing and adhesive thicknesses and moduli for typical pressure sensitive tapes. The analysis shows that the flexural moment decreases as the backing thickness and/or backing modulus increase. Furthermore, the flexural moment decreases as the adhesive thickness and/or adhesive modulus decreases.     

Winter Olympic Buildings,Vancouver 2010

Visiting Vancouver in advance of the 2010 Winter Olympics, David Littlefield discovered that the city was pressing two architectural agendas particularly hard: legacy and timber – the Canadian Northwest's principal natural resource. Copyright © 2010 John Wiley & Sons, Ltd.     

超精密切削机理的流体力学分析模型

随着加工硬件性能的提高 ,有色金属的超精密加工技术已相对成熟。但是对微小切削深度时的加工过程还没有建立起比较满意的模型 ,因为还没有深刻了解超精密加工机理。本文提出了基于流体力学的超精密切削模型 ,考虑了切削刀具几何形状 (包括切削刃半径 )、后刀面工件材料弹性回复的影响。使用该模型可以预测超精密加工过程中刀具刃口的影响、尺寸效应、切削力以及切屑的卷曲半径和刀 -屑的接触长度等。     

微形电机机壳16工步连续级进弯曲模结构设计

针对微形电机机壳采用板料卷圆生产的工艺要求,设计了一种7工位连续冲裁、6工位连续弯曲冲裁、单工位落料的16工步的360°卷圆成形连续级进模。模具整体工序包括连续冲裁、连续弯曲冲裁和冲裁落料3道工序。针对壳件的成形特征,采用1个工位冲出定位孔,6个工位对壳体上的9个特征进行连续冲裁成形及倒角成形;针对壳件的弯曲成形,采用6个工位对冲裁壳体进行连续弯曲成形,工步中设置了3个弯曲成形机构,分别为仿形凹模机构、楔紧块驱动的双侧滑块挤压弯曲机构及接口压入成形机构,来实现壳件的360°卷圆成形;为保证后续弯曲工步载料及内圆成形,将内圆成形件设计成一种可以跟随弯曲凹模做小距离的向上浮动的成形构件。最终成形的壳件由单冲头落料,并由气缸驱动的接件圆柱进行接料转移。模具结构整体布局设计简单合理,机构设置巧妙,可为同类壳件的生产提供有益借鉴。     

Finite element modeling of environmental effects on rigid pavement deformation

In this study, finite element (FE)-based primary pavement response models are employed for investigating the early-age deformation characteristics of jointed plain concrete pavements (JPCP) under environmental effects. The FE-based ISLAB (two-and-one-half-dimensional) and EverFE (three-dimensional) software were used to conduct the response analysis. Sensitivity analyses of input parameters used in ISLAB and EverFE were conducted based on field and laboratory test data collected from instrumented pavements on highway US-34 near Burlington, Iowa. Based on the combination of input parameters and equivalent temperatures established from preliminary studies, FE analyses were performed and compared with the field measurements. Comparisons between field measured and computed deformations showed that both FE programs could produce reasonably accurate estimates of actual slab deformations due to environmental effects using the equivalent temperature difference concept.