变参数激光三维加工方法及试验

介绍了在一次走刀中连续改变加工参数的激光加工新方法，研究变加工条件对切口几何尺寸的影响。在试验切割过程中，调整激光移动速度、输入功率和相对试件表面的焦点位置，来模拟激光三维切割实际状态，进一步分析得出变参数激光加工材料的去除规律。试验参数设计分为线性和二次方两种输入方式，证明了该方法的有效性。     

Investigation on the cutting quality characteristics of abrasive water jet machining of AA6061-B4C-hBN hybrid metal matrix composites

Aluminum metal matrix composites (AMMCs) explicitly show better physical and mechanical properties as compared to aluminum alloys and results in a more preferred material for a wide range of applications. The addition of reinforcements embargo AMMCs employment to industry requirements by increasing order of machining complexity. However, it can be machined with a high order of surface integrity by nonconventional approaches like abrasive water jet machining. Hybrid aluminum alloy composites were reinforced by B₄C (5–15?vol%) and solid lubricant hBN (15?vol%) particles and fabricated using a liquid metallurgy route. This research article deals with the experimental investigation on the effect of process parameters such as mesh size, abrasive flow rate, water pressure and work traverse speed of abrasive water jet machining on hybrid AA6061-B₄C-hBN composites. Water jet pressure and traverse speed have been proved to be the most significant parameters which influenced the responses like kerf taper angle and surface roughness. Increase in reinforcement particles affects both the kerf taper angle and surface roughness. SEM images of the machined surface show that cutting wear mechanism was largely operating in material removal.     

电火花线切割加工铜钨合金切缝宽度及加工精度影响因素研究

铜钨合金是一种广泛应用于精密及难加工材料电火花成形加工的低损耗电极材料。在窄缝、清棱清角、高纵横比等结构的电极加工中,低速走丝电火花线切割加工较传统加工方法具有一定的优势。通过单因素实验研究了电火花线切割加工参数对铜钨合金粗加工切缝宽度、加工速度及表面粗糙度的影响规律,为实际加工提供理论指导。     

三峡工程兴山峡口移民区滑坡防治与利用方案研究(续)

从粉末冶金的压型理论入手 ,分析热压法制造薄壁金刚石钻头的胎体压制过程中的受力情况 ,指出了平底唇面设计存在的不足 ,在分析薄壁金刚石钻头胎体密度和硬度分布及钻进过程的前提下 ,提出了薄壁金刚石钻头的唇面应采用类似半圆形。     

淹没磨料水射流切缝形貌研究

分析研究了淹没磨料水射流对花岗岩切割所成的切缝,发现淹没状况下切缝断面存在一宽度常数区;利用Hurst指数和R/S分析法得出了切缝形成过程中的时间相关性与随机性,得出切缝底部不仅存在时间相关性,且随着进给速度的减小,随机性增强、相关性减弱的结论。     

切缝加锚杆综合措施在金圆公司的应用

施工中应用巷道围岩切缝法的岩石力学理论分析 ,采用锚杆支护法解决底板臌起现象 ,收到良好效果。     

From magnesite directly to lightweight closed-pore MgO ceramics: The role of Si and Si/SiC

Partial/full replacement of traditional dense refractory aggregates (for furnace lining) with lightweight aggregates is considered to be an effective and promising strategy for energy saving and emission reduction. In this work, lightweight magnesia refractory ceramics with tailored closed porosity were prepared by one-step sintering at 1600 °C from high-purity magnesite added with silicon kerf waste in different ratios, with the emphasis on the evolution of their phase compositions, micromorphologies, and various properties. With the addition of additives, Mg_2–xFe_xSiO₄ solid solution was formed at the grain boundaries of the MgO matrix, and then the volumetric expansion effect (interfacial reaction) and activated sintering effect (vacancy defect) promote the decrease of apparent porosity and the increase of closed porosity, respectively. Consequently, MgO ceramics with apparent/closed porosity of 0.6%/6.5%, bulk density of 3.25 g cm⁻³, and lightweight index of 7.8% were successfully prepared, suitable for the working lining of metallurgical furnaces.     

WEDM of layered composite: analyzing material removal and cut quality issues

The use of cladded bimaterial composites has grown in the recent past as they offer a combination of properties at low cost. But the heterogeneity which is the inherent attribute of these composites makes it challenging to accurately cut via conventional means. Therefore, thermal cutting is commonly employed for their cutting which not only produce poor cut quality and deeper heat affected zones but also demand subsequent finishing operations. Wire electric discharge cutting (WEDM) is a proficient alternate but low material removal (MRR) and widen kerf slot (KW) due to sideways sparking limit its application. Moreover, both layers of material have different thermoelectric properties and are subjected to simultaneous cutting by a single moving wire electrode which lead to produce different spark strength against both layers. In this regard, the present study aims to investigate the cutting potential of WEDM for cladded bimaterial with a prior focus on both the aforesaid issues, i.e. MRR and KW. Considering the thermoelectric nature of the WEDM, workpiece-related parameters like orientation of work surface and layer thickness of each layer are taken as control variables in addition to the WEDM process parameters. Experimental results are thoroughly analyzed using statistical and SEM analysis.     

激光切割过程中的光程补偿与切割质量

基于激光切割加工大型板材时光束的传输路径长度差异导致切缝切割质量的下降,提出了采用高精度位移电机来实时补偿光束的路径长度并在切割过程中保持光束焦点形状一致的方法,经过切割10mm厚板材的实验分析,切割质量得到了提高。     

超高压水力割缝技术在低渗透特厚煤层中的应用

为增大煤层透气性系数,提高煤层瓦斯抽采效果,通过超高压水力割缝技术,增大煤体暴露面积,给煤层内部卸压、瓦斯释放和流动创造了良好的条件,缝槽上下的煤体在一定范围内得到较充分的卸压,增大了煤层的透气性。结果表明:水力割缝钻孔组瓦斯抽采浓度、纯流量、百米瓦斯抽采纯流量及瓦斯抽采率是对比钻孔的2~4倍,远远大于对比钻孔组,割缝钻孔瓦斯抽采效果显著。研究为其他类似矿井提供借鉴。