Stephen A. Batzer

A numeric investigation of the rake face stress distribution in orthogonal machining

Abstract An analysis of the normal and shear stress distribution on the rake face of an orthogonal cutting tool is presented. A research-licensed version of DYNA3D finite element package was used to model the cutting process based upon mechanistic experiments that provided the empirical parameters of the Johnson–Cook constitutive model. The Johnson–Cook model uses strain, strain rate, and temperature to predict the material’s stress response. The computer model gave predictions for the normal and shear stresses on the rake lace that qualitatively agree with the experimentally determined stress distributions determined by other researchers.

Modeling Vibratory Drilling Dynamics

The dynamic behavior of deep-hole vibratory drilling is analyzed. The mathematical model presented allows the determination of axial tool and workpiece displacements and cutting forces for significant dynamic system behavior such as the engagement and disengagement of the cutting tool into the workpiece material and tool breakthrough. Model parameters include the actual rigidity of the tool and workpiece holders, time-varying chip thickness, time lag for chip formation due to tool rotation and possible disengagement of drill cutting edges from the workpiece due to tool and/or workpiece axial vibrations. The main features of this model are its nonlinearity and inclusion of time lag differential equations, which require numeric solutions. The specific cutting conditions (feed, tool rotational velocity, amplitude and frequency of forced vibrations) necessary to obtain discontinuous chips and reliable removal are determined. Calculated bifurcation diagrams make it possible to derive the relevant domain of user-specified system parameters along with the determination of optimal cutting conditions.

Nonlinear dynamics of a machining system with two interdependent delays

Abstract The dynamics of turning by a tool head with two rows, each containing several cutters, is considered. A mathematical model of a process with two interdependent delays with the possibility of cutting discontinuity is analyzed. The domains of dynamic instability are derived, and the influence of technological parameters on system response is presented. The numeric analysis show that there exists specific conditions for given regimes in which one row of cutters produces an intermittent chip form while the other row produces continuous chips. It is demonstrated that the contribution of parametric excitation by shape roughness of an imperfect (unmachined) cylindrical workpiece surface is not substantial due to the special filtering properties of cutters that are uniformly distributed circumferentially along the tool head.

Study of Airborne Dust Emission and Process Performance During Dry Machining of Aluminum-Silicon Alloy with PCD and CVD Diamond-Coated Tools☆

The generation of a fine mist of cutting fluid during conventional wet machining and the associated environmental and operator health concerns make environmentally benign machining and manufacturing a major research thrust both in the scientific and manufacturing communities. In this context, high-speed machining in combination with environmentally benign methods makes diamond-coated tooling a unique candidate for dry machining. Diamond coating research in the past few decades has resulted in new products, one of them being diamond-coated carbide tooling. Diamond in polycrystalline diamond (PCD), chemical vapor deposited (CVD) thin-film (polished and unpolished) and thick-film forms offers unique advantages for dry machining. This paper presents the correlation between diamond tool morphology, machining parameters, nonferrous workpiece properties, and particulate emission in dry machining. These findings provide an important benchmark to gauge the true benefit of diamond tools for dry machining.

A Preliminary Study of Chemical Solubility of Ultra-Hard Ceramic AlMgB14 in Titanium: Reconciliation of Model with Experiment

Abstract This article investigates the chemical wear behavior of the ultra-hard ceramic AlMgB14 and cemented tungsten carbide for machining aerospace alloys. The chemical interdiffusivity of AlMgB14 against pure Ti and Ti-6Al-4V, in comparison with cemented carbide (WC-6%Co) cutting tool was investigated by means of diffusion couple experiments. The chemical composition profiles of various tool-workpiece combinations were determined by electron probe microanalysis after exposing the couples to 1000°C for 120 h in vacuum. Thermodynamic calculations of the chemical solubility of AlMgB14 show that the experimental diffusion results are in reasonable agreement with the predicted behavior. It is shown that AlMgB14 is significantly less soluble in titanium under static diffusion conditions, and therefore, shows considerable promise as a potential cutting tool for machining Ti alloys.

A Proof‐of‐Concept Study of the Use of Complex Borides for Disassembly of Decommissioned Nuclear Reactor Containment Vessels

Tool specimens of hot pressed AlMgB14 were employed in lathe turning tests cutting exterior surface material from 6061 aluminum, 304 stainless steel, Inconel, and concrete at various cutting rates. Performance was measured via analysis of mass change (removal rate), wear mechanisms, surface chemistry (reactivity), and fracture mechanisms. Preliminary results indicate that this new family of ultra‐hard materials exhibits good cutting performance against all four workpiece materials, while combining favorable toughness with an unusual absence of tool heating, leading to minimal wear and anticipation of long life in application for sectioning of ferrous‐based metals and structures such as reinforced concrete containing such metals. The potential value of these new materials for use in disassembly of decommissioned nuclear reactor pressure vessels is discussed.

Thermodynamic, Tribological and Chemical Interdiffusion Study of Ultra-Hard Ceramic AlMgB14 in the Machining of Aerospace Alloys

There has been a growing concern about the reactivity at the tool/work-piece interface during machining, leading to lower tool life. The problem is more severe especially in the case of aerospace alloys such as Ti-6Al-4V and stainless steels. Recently, a new ultra hard ceramic material, AlMgB14 , was reported with properties that show considerable promise as a cutting tool material for machining titanium alloys [1]. This paper investigates the chemical wear behavior of AlMgB14 , in the machining of aerospace alloys. The mechanical properties of AlMgB14 are compared with leading cutting tool materials (WC-Co, Al2 O3 SiCw -TiC and Al2 O3 -TiC), which are used extensively in machining titanium and ferrous alloys. Materials characterization of candidate tool materials shows that AlMgB14 exhibits superior hardness, fracture toughness and abrasive wear resistance as compared to the other cutting tool materials. We also report on a study of chemical reactivity of tool materials (AlMgB14 and WC-6%Co) in machining various alloys such as Ti-6Al-4V and Fe-18Ni-8Cr. The chemical reactivity was investigated using diffusion tests conducted in vacuum at 1000°C for 120 hrs. Transverse sections of couples were characterized using electron probe micro analysis (EPMA), to determine the extent of diffusion zones. The results show that AlMgB14 shows considerably less reactivity with titanium alloys when compared with cemented carbide cutting tools. It was also observed that the boride reacts significantly with the iron based Fe-18Ni-8Cr alloy. The paper also reports on the evaluation of the free energy of formation of AlMgB14 using the thermochemical software program FactSage™.© 2003 ASME

Capstone design project coursework using the industrial short course format

The Creative Project Design sequence is a 2 semester long capstone design project in the University of Arkansas mechanical engineering department. It is split into the CPD I class (primarily lecture), followed by CPD II (all project work; no lecture) the subsequent semester. This course covers project management and the iterative design process, including problem definition, creative thinking and optimization. The lecture portion of the course is split into 3 distinct topical areas: reinforcement of basic technical skills and their integration; engineering professionalism; and materials selection in design. This last topic addresses a need that many working engineers acknowledge; a broader expertise in practical materials science. This course strongly borrows from the industrial short course paradigm using concise, encapsulated lectures using participative learning.

A geometric analysis of semi-spiral chip morphology in orthogonal machining

Continuous, unbroken chips used to be a significant manufacturing problem, creating a hazardous situation for the operator and endangering the machine tool. This problem, however, is now largely solved. At this point, further work is needed to optimize well-broken chips. Once chip initial curl and spiral characteristics can be predicted, they can be optimized as part of the overall cutting process design. This may decrease the need for cutting fluids to flush the chips from the cutting region, thereby facilitating a more environmentally conscious process design. Analytic and experimental work is performed to investigate chip spiral morphology and develop a predictive orthogonal chip model. The analytic semi-spiral chip prediction model of Cook et al., [1] is extended to the constricted envelope case. Numerically developed chips are created to investigate the effects of generalized obstruction geometry. The process inputs that have statistically significant effects on chip morphology are determined to confirm the model.