Grinding Characteristics of MoS_(2)-Coated Brazed CBN Grinding Wheels in Dry Grinding of Titanium Alloy

As an important green manufacturing process,dry grinding has problems such as high grinding temperature and insufficient cooling capacity.Aiming at the problems of sticking and burns in dry grinding of titanium alloys,grinding performance evaluation of molybdenum disulfide(MoS_(2))solid lubricant coated brazed cubic boron carbide(CBN)grinding wheel(MoS_(2)-coated CBN wheel)in dry grinding titanium alloys was carried out.The lubrication mechanism of MoS_(2)in the grinding process is analyzed,and the MoS_(2)-coated CBN wheel is prepared.The results show that the MoS_(2)solid lubricant can form a lubricating film on the ground surface and reduce the friction coefficient and grinding force.Within the experimental parameters,normal grinding force decreased by 42.5%,and tangential grinding force decreased by 28.1%.MoS_(2)lubricant can effectively improve the heat dissipation effect of titanium alloy grinding arc area.Compared with common CBN grinding wheel,MoS_(2)-coated CBN wheel has lower grinding temperature.When the grinding depth reaches 20μm,the grinding temperature decreased by 30.5%.The wear of CBN grains of grinding wheel were analyzed by mathematical statistical method.MoS_(2)lubricating coating can essentially decrease the wear of grains,reduce the adhesion of titanium alloy chip,prolong the service life of grinding wheel,and help to enhance the surface quality of workpiece.This research provides high-quality and efficient technical support for titanium alloy grinding.

Experimental Research on Performances of Dry-grinding Fine Cement for Grouting

The performances of dry grinding fine cement (DFC) in grouting procedure were experimentally studied.The measurement of its fineness and simulated test for injectability showed that this DFC could be used to inject rock mass with micro fissure.In order to improve the grouting quality,the water cement ratio and discarding time of slurry should be controlled precisely.If the water cement ratio is over 2∶1 in slurry that is made from DFC,it is not suitable to grout.Finally,the influence of different mixing times on strength of hydrated cement made from the DFC is explained by microstructure analysis with SEM.

Cooling and lubrication techniques in grinding:A state-of-the-art review,applications,and sustainability assessment

Grinding technology is an essential manufacturing operation,in particular,when a component with a superfinishing and an ultra-resolution is yearned.Meeting the required strict quality checklist with maintaining a high level of productivity and sustainability is a substantive issue.The recent paper outlines the lubrication and cooling technologies and mediums that are used for grinding.Furthermore,it provides a basis for a critical assessment of the different lubrication/cooling techniques in terms of machining outputs,environmental impact,hygiene effect,etc.Meanwhile,the paper put light on the sustainability of different cooling/lubrication strategies.The sustainability of machining aims to get the product with the best accuracy and surface quality,minimum energy consumption,low environmental impact,reasonable economy,and minimum effect on worker’s health.The paper revealed that despite some cooling/lubrication mediums like mineral oils and semisynthetic,afford sufficient lubrication or cooling,they have a significant negative impact on the environment and public health.On the other hand,emulsions can overcome environmental problems but the economy and the energy consumption during grinding are still a matter of concern.Biodegradable and vegetable oils are considered eco-friendly oils,but they suffer from a lack of thermal stability which affects their ability of efficiently cooling.Using the cooling medium with the lowest amount can achieve the goal of the economy but it may be reflected negatively on the machinability.Furthermore,cryogenic lubrication doesn’t provide sufficient lubrication to reduce friction and hence energy consumption.The research described in the paper is such a comprehensive compilation of knowledge regarding the machinability and machining performance under different cooling and lubrication systems that it will aid the next generation of scientists in identifying current advancements as well as potential future directions of research on ecological aspects of machining for sustainability.

Residual stress model of pre-stressed dry grinding considering coupling of thermal, stress, and phase transformation

Pre-stressed dry grinding can result in a hardened layer on the part surface while the surface residual stress is controlled.Considering the factors of the thermal field,pre-stress,and microstructural transformation,a proximate model of surface residual stress for pre-stressed dry grinding is established using the ANSYS finite element simulation method and verified through experiment.The variation laws and mechanisms of the residual stress along with the grinding parameters are revealed.Under the comprehensive effect of pre-stress and phase transformation,the residual stress of pre-stressed dry grinding is revealed mainly as compressive stress.This increases as the pre・stress and grinding depth increase.Under the coupling effect,pre-stress has larger influence on the residual stress than the grinding depth.The model can analyze and predict the residual stress of pre-stressed dry grinding in general.

基于主成分分析的玉米DDGS物理特性评价

为对玉米DDGS的物理特性进行分析及量化评价,以国内外8个玉米DDGS为试验材料,测定分析其容重、热物理特性、摩擦特性、粉碎特性及色差指标参数,并运用主成分分析法简化物理特性指标,构架评价体系,得到每种样品的综合得分。结果表明:样品各物理特性指标间存在不同程度的差异;各物理特性指标之间存在不同程度的相关性,比热与热导率呈极显著正相关,与导温系数呈极显著负相关;热导率与平均粒径呈显著正相关;导温系数与容重呈极显著负相关;摩擦系数与休止角呈极显著正相关,与平均粒径呈极显著负相关;L*、b*与平均粒径呈极显著正相关;L*与b*呈极显著正相关。通过主成分分析提取了3个主成分,累积方差贡献率达到87.415%;主成分分析的结果表明进口玉米DDGS的物理特性较好。

土壤有机质测定全程质量控制

质量控制是环境监测赖以生存和发展基础,加强全程质量控制才能确保监测数据的准确性和可靠性。结合环境监测工作实际,应用标准分析方法—重铬酸钾容量法《土壤检测第6部分:土壤有机质的测定》(NY/T 1121.6-2006)对土壤有机质测定进行了全程质量控制技术探讨。简介了方法所需仪器与试剂,深入探讨了运用标准法进行土壤中有机质测定全程质量控制技术问题。指出在标准分析方法基础上,选用有效期内质量合格分析纯以上试剂,全面规范样品采集与保存,有序开展样品制备与称取,严格管控消煮操作与滴定过程,准确进行分析结果数据处理,切实加强结果填报规定程式,能够确保大批量、成分复杂土壤样品有机质测定精密度和准确度。

高速钢磨屑直接还原铁冶炼新型模具钢W4Mo3Cr4VRE

在250kg感应炉,利用高速钢磨屑直接还原铁(海绵铁%:0.44C-4.62W-3.27Mo-2.2Cr-0.98V),配加一定含量高速钢车屑废钢(%:0.87C-3.50W-1.30Mo-1.50Cr-0.60V),冶炼成一种新型模具钢W4Mo3Cr4VRE(%:0.78～0.88C、3.50～4.50W、2.50～3.50Mo、3.80～4.40Cr、1.10～1.60V、0.15～0.25RE)再经电渣重熔。检验结果表明,电渣重熔后,该钢1180℃淬火+250℃2次回火,HRC硬度值≥60,冲击韧性≥49J/cm2;当1150℃或1180℃淬火+560℃2次回火时,其HRC硬度值达66。该实验结果证实了采用精选、还原烧结、电炉配料的冶炼工艺对磨屑的回收利用是可行的,生产的新型钢能满足耐火制品模具使用性能的要求。

挤压和超微粉碎对绿豆面条特性的影响

绿豆是亚洲人,特别是中国人经常食用的一种豆类,前期研究表明绿豆具有多种健康功效,然而其食用方法单一,限制了消费量的提升。本研究旨在开发绿豆含量高,加工品质及食用品质好的挂面。为探究粉碎、超微粉碎、挤压膨化3种预处理方式对绿豆添加量4%~50%的面团品质的影响,采用快速黏度分析仪、混合实验仪和质构仪分别测定面粉的淀粉糊化特性、面团流变特性和质构特性。结果表明:超微粉碎和挤压膨化两种加工方式都能改善面条的品质。本研究拓展了绿豆的食用方法,为工业化绿豆挂面的生产提供了理论依据。