摘要
金刚石锯片已被广泛的应用在混凝土切割中,混凝土作为一种常用的建筑材料,其种类繁多,成分及性能复杂,因此金刚石锯片锯切混凝土过程与锯切石材等脆性材料的过程有很大的区别,其中存在诸多问题急待解决,但国内外针对混凝土锯切的研究却相对较少,特别是针对钢纤维和钢丝网混凝土的研究就更少。本文采用4种不同的锯片对不同强度和类型的素混凝土、钢纤维混凝土、钢丝网混凝土进行了大量的锯切实验,在此基础上研究了混凝土的锯切机理、锯切过程中的锯切力、锯片的磨损以及振动和噪声。
采用扫描电镜(SEM)和体视显微镜对混凝土的切屑及混凝土的锯切表面形貌进行了观察分析,结合混凝土的特性,研究了混凝土材料的锯切加工机理。研究表明混凝土在锯片的冲击作用下首先形成宏观裂纹造成其断裂,随后在金刚石颗粒的微切削作用下,石子和砂子等脆性硬骨料成分断裂形成极细的粉屑,钢纤维混凝土中钢纤维一部分被金刚石的微切削刃切削铲除断裂,另外一部分则是在切削力作用下被拔拉而断裂,而钢丝网混凝土中钢丝则完全是被金刚石切削发生塑性变形而断裂。
通过锯切力实验,研究了锯切过程中锯切力的特征以及影响锯切力的主要因素。实验结果表明:锯切过程中锯切力呈平稳波动变化,水平方向锯切力会波动到零值以下。锯切力随着锯切速度的增加而减小,随进给速度的增加而增大,但锯切速度对锯切力的影响没有进给速度明显。锯切力随混凝土强度的提高而增大,强度相同的三种混凝土,钢纤维混凝土的锯切力最大,钢丝网混凝土次之,素混凝土的锯切力最小。锯切混凝土时,钴基节块的锯片锯切力要小于铜基节块的锯片,高钴含量的节块锯切素混凝土时锯切力比低钴含量的小,锯切钢纤维和钢丝网混凝土时适当降低钴含量,增大铁、镍含量可减小锯切力。
锯切过程中由于切屑粘结在节块上,堵塞节块的容屑空间造成锯片磨损加剧。锯切素混凝土和钢纤维混凝土时Co-Fe基节块的磨损率最小。锯切过程冲击较大,节块胎体易破损;锯切素混凝土时,金刚石磨平和局部破碎的颗粒较多,锯切钢纤维混凝土和钢丝网混凝土过程中,整体
广西大学硕_l:学位论文
破碎的金刚石颗粒较多。三种混凝土锯切过程中,Cu一Co基节块中的金
刚石磨平和脱落的较多,Co基节块局部大块破碎和端部破碎的金刚石相
对较多。另外干切削过程中产生的高温易造成锯片烧伤损伤从而降低锯
片寿命。
分析了混凝土锯切过程中的强振动、高噪音的原因,并通过实验研
究了锯切工艺参数对振动与噪音的影响,对一种带波形细槽孔的锯片的
减振降噪效果进行了实验研究,最后提出了一些降低噪音和振动的方法。
锯切工艺参数中,锯切速度、进给速度以及切削深度的增加均会引起振
动与噪声的增大。在锯片基体上开波形细缝能够降低锯切过程中的噪音
和振动,对改善加工环境有一定的作用。
The diamond blades are commonly used in sawing concrete material for the civil engineering industry. With complication compositions and properties of concrete, it is different between concrete sawing and other brittle material just like stone sawing by diamond blades. During sawing process, some problems are to be solved imminently. So far, less research on the sawing process of concrete especially sawing process of steel fiber concrete and ferroconcrete at home and abroad has been published.
Based on vast experiment, sawing mechanism, sawing force, and blade wear of various concrete including cement, steel fiber concrete, ferroconcrete sawing process have been studied systematically in this paper. In addition, the noise and vibration of sawing process have been studied. The noise and vibration of a new type of diamond blade with special structure and those of conventional blade are compared.
The concrete chips and topographies of cutting surface were observed by means of scanning electronic microscope and zoom stereo microscope, conbined with properties of concrete, sawing mechanism of concrete was analyzed. The research results show that concrete form macro crack and crack firstly. Then under micro cutting of diamond grits, rock and sand break up and forming minuteness chips. A part of steel fiber materials were cut by diamond grits micro edge, others were pull out by forces. Steel wire materials were cut with plastic deformation under diamond grits cutting.
By cutting force experiment, the characteristics of cutting forces and the main influences on forces were studied. During sawing process, the curve of cutting forces fluctuates intensely and the values in curves of cutting forces in horizontal didrection dropped to below zero line. The cutting forces increase with the increase of feed speed, in reverse, decrease with the increasing of cutting speed and the influence of cutting speed on cutting forces is not noticeable. When the strength grades of the concrete materials are the same, the cutting forces of ferroconcrete and steel fiber reinforced concrete show the higher value than that of cement concrete. The cutting forces of sawblade with
bronz-cobalt bond are bigger than those of sawblade with cobalt bond in sawing concrete process. Adding cobalt content in matrix, the cutting forces can be decreased when sawing cement concrete. While sawing steel fiber concrete and ferroconcrete, the cutting forces can be decrease by reduction of cobalt content and increase of iron content in matrix.
The concrete chips adhering to segment surface and jaming the space among diamond grits result to acceleratting blade wear during dry cutting concrete process. When sawing cement concrete and steel fiber concrete in experiment, the wear rate of blade with Co-Fe bond segment are the least among four various blades. There existing big impact during sawing process, the segment cracks easily. When sawing cement concrete, the polished and micro fracture diamond grits are the most and the whole fracture diamond grits are the most when sawing steel fiber concrete and ferroconcrete. Among the sawing process of three various kinds of concrete, the polished and pull-out diamond grits of blade with Cu-Co bond segment are the most and the macro frature and end fracture diamond grits of blade with Co bond segment are the most.
The reasons of strong vibration and high noise of concrete sawing have been analyzed. The cutting parameters influence on noise and vibration and the decreasing noise and vibration effect of blade with some "s" slots cut on blade core have been studied by experiment. At last according the theory of noise and vibration and experiment results, some methods of decreasing noise and vibration have been presented.
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