Abstract
This paper addresses the issues related to designing and estimating the strength of solid-alloy elements in the deforming broaches of significant diameter (exceeding 150 mm) for the developed process of discrete broaching. The tool limit condition was assessed based on two strength criteria: the specific potential energy of shape change and the maximum tangent stresses. Numerical modeling using the finite element method has made it possible to derive the distribution of equivalent stresses in the tool elements and the contact stresses at the surface of the contact between a solid-alloy insert and the body, which enabled the analysis of tool strength under loading. The simulation was performed under a single normal load, which ensured the versatility of the calculation for any contact pressure values. We have derived formulae to calculate the acceptable contact pressure depending on unit load. The effect of the insert protrusion height over the body on the strength of tool elements has been established. We have derived engineering dependences that determine the required magnitude of insert protrusion over the body depending on the ultimate load. An example of calculating the strength of a prefabricated deforming element in the machining of a sleeve made from gray modified cast iron of hardness HB230 has been considered. Our calculations have shown that the deforming element designed for the new technological process corresponds to the conditions of strength, provided the ratio h 1 /h=0.15 is maintained (where h 1 is the insert height above the body, h is the insert height). The results obtained could be used in engineering calculations when designing the prefabricated tool for discrete deformation, as well as to assess the strength of prefabricated tools, such as cutters, core drills, reamers, when refining external loads
Highlights
One of the main tasks of modern machine building is to devise and implement resource-saving technologies to improve the quality of articles [1]
Our study into the stressed-strained state (SSS) of a prefabricated deforming elements (DE) for discrete broaching when applying unit load provides the versatility of strength calculation for any values of contact loads, including for articles made from different machined materials
The versatility of the calculation is implemented by the product of the values of equivalent stresses obtained under unit load and the actual value of contact pressure corresponding to a particular case and calculated using an algorithm
Summary
One of the main tasks of modern machine building is to devise and implement resource-saving technologies to improve the quality of articles [1]. DBR is applied in engineering production when machining precise holes with low roughness and for draft operations to adjust pipe blanks made from various materials before further treatment [3,4,5]. Scientists from the Institute of Super-Solid Materials of the Ukraine’s National Academy of Sciences devised an effective technological process for machining holes in the sleeves of internal combustion engines (ICE) made from gray modified cast irons [8, 9]. This process is implemented on the basis of a combined broaching operation. The machining involves a broaching tool, which includes the sequentially placed deforming and cutting elements and a group of deforming elements behind them [8, 9]
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