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Demolition
Published in Erik K. Lauritzen, Construction, Demolition and Disaster Waste Management, 2018
Demolition by chopping or crushing requires small machines to be lifted by crane to the top and placed on a climbing platform, which can be lowered successively in time with the progress of the demolition work. Section-wise dismantling needs horizontal cuts in the structure. Usually, the cuts are performed by an abrasive saw or wire tool, which also need a mobile work platform to place the cutting tool. The cuts might be provided by handheld chopping or Mini Blasting.
Experimental Investigation on Micro-Electrical Discharge Machining process for heat treated Nickel-based Nimonic 80A
Published in Materials and Manufacturing Processes, 2023
Piyush Pant, Pushpendra S. Bharti
Machining nickel-based alloys was acknowledged to be a very challenging task.[4] Numerous criteria such as the surface roughness generated, tool life, temperature generated during machining, and the force required, form the basis for judgment of machinability. While machining Nimonic alloys, various situations are confronted which lead to lower value of material removal rate and accelerated tool wear. Superior temperatures result in work hardening of the Nimonic alloys and this contradicts the non-elastic deformation, which is otherwise vital for the generation of chips. Thermal stresses increase as a consequence of small thermal diffusivity. Subsequently, at the nose of the cutting tool, intense heat is set up, leading to an accelerated rate of tool loss. The fracturing of the gross inset edge happens as a result of the loss due to notches at the nose of the tool. Abrasive saw-toothed edged chips can join with the material of the cutting tool due to adhesive forces and localization of shear and hence, resulting in the constitution of built-up edges. The degradation of the tool is also accelerated due to the existence of carbides in the work sample. The management of the swarf of abrasive saw-toothed edged chips is also a concern. For a steel workpiece under the similar circumstances, the attained normal stresses in material removal are halved in analogy to the material removal for Nimonic alloys.[5,6] In respect of the aforementioned situations, these alloys are tagged as difficult to cut and Electrical Discharge Machining (EDM) is among the most befitting approach for material removal.
Investigation of abrasive saw kickback
Published in International Journal of Occupational Safety and Ergonomics, 2022
Steven Burcat, Brian Yue, Alexander Slocum, Tal Cohen
For abrasive saws, dangerous kickback most frequently occurs on construction sites during pipe-cutting operations, particularly when the pipe is in an excavated trench. However, when abrasive saws were tested in a machine analogous to a woodcutting saw kickback machine described by ANSI Standard No. B175.1-2012 [6], similar levels of kickback were not observed by Wu [7], despite reports of kickback in the field. A recent study by Yue [8] theorized that this result is due to abrasive saws primarily experiencing a different mode of kickback whereby the cutting element is pinched in the kerf of the cut, rather than being frontally engaged by the workpiece. To investigate abrasive saw kickback, a kinetics model was developed which treats the abrasive cutting engagement as a sudden frictional engagement. This model predicts the resultant motion of the saw, given assumed engagement parameters, allowing for a prediction of the resultant energy transferred to the saw's motion during a kickback event.
Temperature evolution associated with dynamic phase transformation in shape-memory TiNi alloys
Published in Phase Transitions, 2019
The material considered in this study is a commercial polycrystalline TiNi alloys with a nominal composition of 50.9 at.% Ni balanced with Ti (Nitinol Devices & Components, USA). Cylindrical specimens of 8.04 mm diameter by 6.08 mm long were sliced from a heat-treated Nitinol rod with a water-jet cooled abrasive saw. Chilled water was continuously sprayed on the contact area of the cutting blade and the Nitinol bar to keep the temperature low in the NiTi alloy during machining. Before being clamped the samples were heated in boiling water for 15 min, so that TiNi alloy was completely in austenite phase, then cooled to room temperature naturally. Because the room temperature (24.4°C) was higher than the Ms (11.4°C), as shown in Table 1. Thus, the initial microstructure of the sample was entirely austenitic and exhibits shape-memory behavior. Optical micrograph of an SME TiNi indentation sample depicting its microstructure is shown in Figure 1. The figure reveals a uniform equiaxed grain structure, with an average grain size of 30 μm.