基于切削建模的螺旋铣孔刀具角度优化

针对钛合金螺旋铣孔过程中的刀具角度优化问题,固定切削参数,通过一系列实验,得到了螺旋角和前角不同的刀具产生的轴向切削力.利用遗传算法,结合Matlab程序对实验数据建立切削力模型,分析了刀具螺旋角和前角对切削力的影响,并对角度参数进行了优化.     

金刚石圆盘锯锯石特点与锯机参数的选定

通过对金刚石圆盘锯锯割石材的实际观察和试验研究,根据石材在静、动载作用下的破碎过程,阐明了圆锯片锯割石材时碎石的一些特点。还对锯机设计中主要性能参数驱动功率和锯片圆周线速度问题进行了较深入的讨论。     

Failure criterion for soft rocks considering intermediate principal stress

The significant differences between hard rocks(more brittle) and soft rocks(more ductile) may suggest the use of different failure criteria. A strength criterion for soft rocks that includes intermediate principal stress was proposed. The new criterion includes two independent parameters: the uniaxial compressive strength(rci), which can be obtained from common laboratory tests or indirectly estimated by alternative index tests in the laboratory or field; and f(joint), which is used to characterize the rock mass quality and can be easily estimated. The authors compared the predictive capabilities of the new criterion with other criteria using the database of soft rocks under two conditions: with and without triaxial data. For the estimation of triaxial and true-triaxial strengths, the new criterion generally produced a better fit. The proposed criterion is practical for an approximate first estimation of rock mass strength, even without triaxial data, as it balances accuracy(lower prediction error) and simplicity(fewer independent parameters).     

不同定义下的带角圆回转铣刀的优劣

回转铣恨是加工复杂曲面的重要工具,目前流行多种刃口曲线设计方法,因此比较其优劣具有工程价值,通过介绍不同定义下的螺旋角对应的带角圆的柱状回转铣刀在刃口曲线、二轴联动NC加工中的进给速度等问题的不同之处,指出了与经线成等角的定义下这种铣刀设计、NC加工及使用均具有明显优点。     

灌孔速成墙抗压强度的试验研究

新型灌孔速成墙体是一种在新型轻质玻璃纤维石膏空心板内灌入混凝土而形成的墙体。本文对12块试件进行了竖向荷载下的抗压试验,研究了该种新型灌孔速成墙板在竖向荷载作用下的变形性能,并分析其在竖向荷载下的破坏机理,得出其应力—应变曲线,并推导出抗压强度的计算公式。     

不同螺旋角螺旋折流板换热器壳侧传热性能研究

对两种不同螺旋角的螺旋折流板换热器进行传热测试,利用测得试验数据,根据Kern法推导出这两种螺旋折流板换热器壳程传热系数的近似计算公式.     

盾构切刀切削混凝土过程中的动态响应试验

为探究盾构切刀与混凝土的相互作用规律,开展室内切削试验,验证切削的实质是刀具与试件反复碰撞、挤压、切削和剥落的循环过程.通过切削力测试系统得到刀具前后角、刀具形状、切削深度和试件强度等因素对刀具法向切削力Fn与切向切削力Ft的影响规律,并分析得到各影响因素作用下Fn、Ft及切削合力Fc的波动范围.结果表明:刀具切削混凝...     

基于单颗磨粒划切试验的SiCp/Al复合材料表面去除机理研究

碳化硅颗粒增强铝基（SiCp/Al）复合材料中含有不规则碳化硅颗粒使得材料内部形成大量非理想截面,为材料表面的有效去除带来困难. 为了揭示材料去除机理,进行SiCp/Al 复合材料单颗磨粒变切深划切的表面去除仿真分析和试验验证. 研究结果表明,界面破坏对表面创成有重要影响,存在铝合金基体撕裂、界面分离,碳化硅颗粒裸露、裂纹扩展、破碎脱落、压入铝合金基体、碎片滑擦材料表面等去除过程,碳化硅颗粒中部大面积破碎脱落形成凹坑,并在刀具推挤作用下对材料进行二次切削,使铝合金基体表面形成非连续裂纹. SiCp/Al复合材料中由于铝合金基体的存在,实际划切深度小于名义切削深度. 研究可以为SiCp/Al复合材料去除机理与加工研究提供一定借鉴.     

Research on the cutting performance and the wear mechanism of the cermet cutter in high speed turn-milling

High speed machining not only improves the ma-chining efficiency but also makes the machining preci-sion and surface quality of workpieces greatly better.This is an important development in the machiningfield.With regard to machining revolving workpieceswith high speed cutting,the increase of cutting velocityis limited since the dynamic balance of the lathe spin-dle on which the workpiece is fixed is more difficult toadjust than the milling spindle.Also,when the hightension steel workpieces ar…     

切丝宽度对卷烟烟丝结构和主流烟气的影响

为比较不同切丝宽度对卷烟主流烟气中7种有害成分释放量和卷烟烟丝结构的影响,对两种低焦油规格的卷烟进行切丝宽度试验,分析不同切丝宽度对7种有害成分释放量及烟气危害性指数的影响,并对烟丝结构与烟气危害性指数进行相关分析.研究表明:切丝宽度对卷烟烟气中有害成分的单支和单口释放量均有一定影响; 烟丝长度与烟气危害性指数有正负相关性,两种规格卷烟应适当增加3.35～2.00 mm长度的烟丝比例.     

数控插齿加工的非圆齿轮极径与极角误差分析

研究了用数控插齿方法加工非圆齿轮时,数控插齿机床工艺误差,对被加工非圆齿轮节曲线极径与极角参数的影响.对非圆齿轮的实际数控插齿加工过程进行了计算机模拟仿真,为分析非圆齿轮的误差来源、提高非圆齿轮的加工精度以及对非圆齿轮的误差评定和精度测量方法的研究提供了理论依据.     

岩石强度尺寸效应的研究方法和机理的研究

论述了目前研究岩石强度尺寸效应现象的四种方法,指出了每种方法存在的不足,讨论了岩石强度尺寸效应产生的机理,探讨了岩石强度尺寸效应研究方法今后的发展方向.     

螺栓联结受外压力作用时的力学计算

在螺栓联接的强度计算中 ,绝大多数情况为密封螺栓强度计算 ,此时 ,预紧力和工作载荷对螺栓产生的皆为拉力。在工程应用中 ,存在一种紧固件螺栓 ,工作载荷的作用使螺栓产生压缩 ,整个螺栓最终合力和综合变形都不同于常规密封螺栓。螺栓的最终变形量δ∑ 为预紧变形量δL 减去工作载荷作用下螺栓伸长减少量△δ。而被联接件由原来的预紧压缩量δF 增加△δ,对应变形量的受力计算也相应发生变化。当工作载荷为交变载荷时 ,螺栓在这一压缩交变载荷作用下 ,同样存在疲劳断裂问题。本文就此进行了对比论证和实例计算。     

Comparative evaluation of different statistical tools for the prediction of uniaxial compressive strength of rocks

In this study, uniaxial compressive strength (UCS), unit weight (UW), Brazilian tensile strength (BTS), Schmidt hardness (SHH), Shore hardness (SSH), point load index (Is₅₀) and P-wave velocity (V_p) properties were determined. To predict the UCS, simple regression (SRA), multiple regression (MRA), artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and genetic expression programming (GEP) have been utilized. The obtained UCS values were compared with the actual UCS values with the help of various graphs. Datasets were modeled using different methods and compared with each other. In the study where the performance indice PI_at was used to determine the best performing method, MRA method is the most successful method with a small difference. It is concluded that the mean PI_at equal to 2.46 for testing dataset suggests the superiority of the MRA, while these values are 2.44, 2.33, and 2.22 for GEP, ANFIS, and ANN techniques, respectively. The results pointed out that the MRA can be used for predicting UCS of rocks with higher capacity in comparison with others. According to the performance index assessment, the weakest model among the nine model is P7, while the most successful models are P2, P9, and P8, respectively.     

Study on pick arrangement of shearer drum based on load fluctuation

According to the coal or rock cutting theory, a mechanical model and computing formula for a pick and the drum load fluctuation model were established in order to obtain relationships between pick arrangements and drum fluctuation loads, drum rotary speeds and haulage speeds. Based on a minimum load fluctuation, an optimal mathematical model was established for drum pick arrangements. The effects of pick arrangements (including punnett square, sequence, aberrance Ⅰ and Ⅱ) on the drum load fluctuation coefficient are discussed. The relationships between the pick arrangements of the drum with different start vanes and the cutting load fluctuation coefficient, the drum rotary speed and haulage speed were also studied. The results indicate that the punnett square arrangement has a smaller cutting load fluctuation coefficient than other forms of arrangement and the drum with the 4-start vanes has the smallest coefficient. The drum rotary speed and haulage speed are affected not only by pick arrangements, but also by the number of vanes.     

基于不同面料的裁床切割参数设置

为提高面料的利用率,降低面料损耗,设置裁床的最佳切割参数,以控制面料成本;根据切割面料的不同厚度、紧度、克重和刚度,通过实验分析,获得了裁床切割参数的最佳配置,提高其切割效率,对加快服装裁片生产速度和降低成本有积极的理论意义和现实意义.     

生物酶联合水泥固化淤泥力学性能及机理

为改良淤泥强度,环保、高效解决疏浚淤泥处理问题,采用生物酶联合水泥对淤泥进行固化处理。通过无侧限抗压强度试验、直接剪切试验初步分析了生物酶对水泥固化淤泥强度的影响规律,并通过阳离子交换量试验（CEC）、电动电位试验、扫描电镜测试（SEM）、X射线衍射试验（XRD）和红外光谱试验（FTIR）等手段进一步探究了其协同固化机理。结果表明:生物酶联合水泥固化处理对淤泥强度有明显提升效果,其强度最高可提升73.8%,且生物酶掺量、种类、养护龄期影响其固化效果,但生物酶不和土体内矿物发生化学反应;生物酶和水泥的联合固化作用主要通过促进淤泥内阳离子交换作用,降低土体的电动电位,提高水泥水化产物的胶凝作用,促进活性黏土矿物的胶结以及催化包膜结构的形成实现;各类生物酶中,路易酶的固化效果最好,其水泥固化淤泥7 d无侧限抗压强度达378.8 kPa、黏聚力达307 kPa、内摩擦角达52.3°,相比水泥固化淤泥分别提高73.8%、33.2%和55.2%。     

旋转矩形截面螺旋管内对流传热特性的研究

利用数值计算方法研究了旋转矩形截面螺旋管内的粘性流动，分析了在离心力、科氏力共同作用下曲线管道中的二次流动结构、轴向流速分布、截面温度分布、摩擦系数比以及管道Nusselt系数数比随各参数的变化情况，计算结果表明：对于不同截面的矩形螺旋管道，当旋转方向和主流方向相同时，旋转的作用与增大Germano数的作用相同，使得管道摩擦系数变大，管道换热效果增强；而当旋转方向和主流方向相反时，管道内流动结构变化十分明显，当F≈-1．3时，二次流出现类似于直扭管内的鞍状流动结构，轴向速度类似与静止直管内的流动结构，管道内的摩擦系数近似于静止直管内的磨擦系数，换热效果减至最弱。     

不同槽型的麻花钻切削性能实验

麻花钻螺旋槽的形状直接影响其切削性能,轴向力及扭矩是主要的切削性能指标。本实验介绍了3种常用槽型的硬质合金麻花钻切削铸铁、合金钢、不锈钢的轴向力和扭矩测量。实验结果表明,与直线型、凸型槽比较,凹型槽麻花钻对这几种材料的切削性能最好。     

三维切削确定重叠系数与等效切宽的新方法

针对三维切削再生颤振的重叠系数与等效切宽的现行确定方法存在的问题，提出新的确定方法，给出几种典型切削方式下三种确定方法的结果并进行了比较．新方法避免了现行方法存在的缺陷．