Matt A Davies

Matt A Davies
University of North Carolina at Charlotte | UNC Charlotte · Department of Mechanical Engineering and Engineering Science

About

55
Publications
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Publications

Publications (55)
Article
The resulting surface integrity of (100)Ge subjected to off-axis single point diamond turning was investigated. Feedrate was varied using 9 and 20 μm/rev at 10 μm nominal depth of cut. Surface topography was measured with coherence scanning interferometry and atomic force microscopy. The resulting near surface lattice disorder was investigated with...
Article
(This article is open access and can be readily downloaded at https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-13-15252) The convex reflective diffraction grating is an essential optical component that lends itself to various applications. In this work, we first outline the design principles of convex diffraction gratings from wavefront qua...
Article
Freeform optics facilitate a revolutionary approach to optical design. Ultra-precision diamond machining is an enabling technology for the manufacture of freeform optics. However, optical designs require tight tolerances across spatial wavelengths ranging from micro-roughness to overall form. To manufacture freeform optics to the necessary toleranc...
Article
Full-text available
Infrared-transparent chalcogenide glasses are important for the manufacturing of optics for thermal imaging. These brittle materials can be diamond machined, but material removal rates are often limited by the occurrence of surface/subsurface damage. In this paper, the cutting mechanics of orthogonal cutting, orthogonal flycutting and ball-milling...
Article
Full-text available
Slow tool servo remains a preferred method for ultraprecision manufacture of freeform optics with millimeter-scale departures from an axisymmetric surface. A methodology has been developed for pre-process mapping of, and compensation for, predictable error sources such as tool waviness and machine misalignment, reducing necessity for typical post-p...
Article
Full-text available
Freeform germanium optics produced by single crystal diamond milling are important for infrared (IR) imaging applications. However the mechanics of interrupted cutting of germanium is not fully understood. This paper presents new findings from cutting experiments including: (1) uninterrupted orthogonal cutting and (2) interrupted flycutting of germ...
Article
Germanium is commonly used for optical components in the infrared, but the high refractive index of germanium causes significant losses due to Fresnel reflections. Anti-reflection (AR) surfaces based on subwavelength “moth’s eye†gratings provide one means to significantly increase optical transmission. As found in nature, these gratings are c...
Article
We present experimental results from variable output refractive beam shapers based on freeform optical surfaces. Two freeform elements in close proximity comprise a beam shaper that maps a circular Gaussian input to a circular 'flat-top' output. Different lateral relative shifts between the elements result in a varying output diameter while maintai...
Article
Polycrystalline ZnSe specimens were diamond turned using a range of feed rates and depths of cut. Confocal Raman spectroscopy was used to estimate the residual stress and resulting crystal quality based on changes in the LO mode spectral center and peak width, respec-tively. Spatial mapping of the LO mode spectral center and peak width indicated va...
Article
Single crystal diamond milling of optical materials opens up new design degrees-of-freedom for optical engineers. However, parameters for milling of many optical materials have not been investigated, understood, or documented. This paper focuses on the milling of germanium to fabricate a freeform “Alvarez lens” in the mid-wave infrared (MWIR). Whil...
Conference Paper
Ethnographic research is used to reveal the nature of collaborative optical engineering work between team members of different backgrounds. Observations in an academic environment are combined data derived from interviews with industry professionals.
Conference Paper
We discuss the application of diamond machining to the fabrication of freeform infrared optical components and structures. Fabrication approaches, challenges, and experimental results are presented for several novel optical designs.
Article
High quality imaging spectroscopy data is useful for both military and civilian applications. State-of-the-art spectrometers incorporate spherically concentric, axially symmetric and telecentric optical design. However, these designs require a diffraction grating operating in reflection that is manufactured on a convex, spherical or possibly freefo...
Article
While Alvarez lens prototypes have recently been manufactured and tested for visible wavelengths, there is little discussion of these types of components for infrared applications in the published literature. We present and characterize a germanium Alvarez lens for infrared imaging. Mathematical analysis for determining the required cubic surfaces...
Article
The success of metal bearings is dependent on several parameters. The effects of in vivo forces on the deformation of monoblock acetabular components have yet to be determined. The purpose of our study was to assess the amount of deformation with press-fit fixation of 1-piece metal acetabular components. Four manufacturers provided 1-piece metal ac...
Article
In 1967, Luis Alvarez introduced a novel concept for a focusing lens whereby two transmitting elements with cubic polynomial surfaces yield a composite lens of variable focal length with small lateral shifts. Computer simulations have demonstrated the behavior of these devices, but fabricating the refractive cubic surfaces of the types needed with...
Article
High-speed milling is used across industries from aerospace to electronics. Tool wear can be affected by cutting interruptions in milling that lower tool–chip interface temperatures but also cause thermal and stress cycling. Micro-thermal imaging was used to determine the temperature during interrupted cutting of titanium alloy Ti6Al4V and AISI 414...
Article
Full-text available
Despite the clinical success of modern metal-on-metal articulations, concerns with wear-related release of metal ions persist. Evidence suggests metal ion release is related to the effective coverage of the head in the metal shell (the cup's functional articular arc). A recent study suggests a reduced functional articular arc is associated with inc...
Article
Micro-thermal imaging was used to determine the amount of heat flowing into the tool, chip and workpiece during orthogonal cutting at speeds up to 400 m min−1. Two AISI 4140 steels with different machinability ratings and three types of tools were compared: (i) uncoated with 0° rake angle, (ii) coated with −6° rake angle and (iii) coated with chip...
Article
The micro-scale temperature fields in the cutting of two AISI 4140 steels with different machinability ratings were measured. A custom infrared microscope was constructed; each pixel was calibrated separately to reduce measurement uncertainty. Orthogonal cutting experiments were performed on a high speed machining center with surface speeds up to 5...
Article
Full-text available
While mechanical ruling and single point diamond turning has been a mainstay of optical fabrication for many years, many types of micro-optical devices and structures are not conducive to simple diamond turning or ruling, such as, for example, microlens arrays, and optical surfaces with non-radial symmetry. More recent developments in machining tec...
Article
Because it is key to understanding the performance of material removal processes and resultant workpiece quality, the measurement of temperature during material removal is done extensively. We review several widely used temperature measurement methods and show how they can be applied to temperature monitoring during material removal. Since there is...
Article
Articulating cervical disk implants have been proposed as an alternative to disk fusion in the treatment of cervical disk disease. To examine the mechanical effect of articulating cervical disk implants (ACDI) versus simulated cervical disk fusion, a mechanical test device was constructed and cadaveric tests were carried out. While results show lit...
Article
A custom thermal microscope was constructed using a high-bandwidth thermal imaging system (40 megapixels/sec). The microscope was attached to a high-speed machining centre (20 thousand RPM/18.5 kW spindle) that was operated as a high-speed lathe to measure temperature distributions during orthogonal cutting of AISI 1045 steel at surface speeds of u...
Article
Time finite element analysis (TFEA) is used to determine the accuracy, stability, and limit cycle behavior of the milling process. Predictions are compared to traditional Euler simulation and experiments. The TFEA method forms an approximate solution by dividing the time in the cut into a finite number of elements. The approximate solution is then...
Article
Infrared microscopic measurements of the temperature fields at the tool-chip interface in steady-state, orthogonal, machining of AISI 1045 steel are presented for a range of chip thicknesses The measurements are verified using an energy balance method and simple finite difference calculations (see [14]) These results are compared to the predictions...
Article
Chatter in milling and other interrupted cutting operations occurs at different combinations of speed and depth of cut from chatter in continuous cutting. Prediction of stability in interrupted cutting is complicated by two facts: (1) the equation of motion when cutting is not the same as the equation when the tool is free; (2) no exact analytical...
Article
Traditional regenerative stability theory predicts a set of optimally stable spindle speeds at integer fractions of the natural frequency of the most flexible mode of the system. The assumptions of this theory, become invalid for highly interrupted machining, where the ratio of time spent cutting to not cutting (denoted rho) is small. This paper pr...
Article
Full-text available
We compare the repeated adiabatic shear band formation that takes place at sufficiently large cutting speeds in a number of materials during high-speed machining operations with the more well-known formation of a single shear band that often takes place at sufficiently large strain rates in dynamic torsion tests on these materials. We show that the...
Article
Stability prediction and chatter avoidance in high-speed machining requires knowledge of the tool point dynamics. In this paper, three advances toward the rapid identification of the tool point frequency response and corresponding stable cutting parameters are described: 1) stable speeds determination using non-contact periodic impulsive excitation...
Article
Full-text available
The implementation of high-speed machining for the manufacture of discrete parts re- quires accurate knowledge of the system dynamics. We describe the application of recep- tance coupling substructure analysis (RCSA) to the analytic prediction of the tool point dynamic response by combining frequency response measurements of individual compo- nents...
Conference Paper
Chatter in milling and other interrupted cutting operations occurs at different combinations of speed and depth of cut from chatter in continuous cutting. Prediction of stability in interrupted cutting is complicated by two facts: (1) the equation of motion when cutting is not the same as the equation when the tool is free; (2) no exact analytical...
Article
Aluminum bronze C95800 is used extensively for the manufacture of propellers because of its mechanical strength and corrosion resistance. Typically these components are machined from large castings and then hand ground and polished. In this work, we demonstrate the possibility of using high speed machining with tungsten carbide tooling to significa...
Article
This paper describes the application of high-speed milling to the production of monolithic, metallic, functional prototypes, with special emphasis placed on the applicable process times. An example component is selected and the relevant process times are presented. Fundamental requirements for the use of high-speed milling to produce prototypes in...
Article
Full-text available
This paper presents a nonlinear dynamics approach for predicting the transition from continuous to shear–localized chip formatio in machining. Experiments and a simplified one–dimensional model of the flow both show that, as cutting speed is increased a transition takes place from continuous to shear–localized chip formation in the flowfield of the...
Article
Robust machine tools are changing the role of machining across a wide range of industries. It is believed that high-speed machining requires changes in shop practices to maximize its benefits. This paper presents information most applicable to machines with spindles rated at more than 15 kW, and capable of running at speeds in excess of 10,000 rpm.
Article
Traditional regenerative stability theory predicts a set of spindle speeds with locally optimum stability at integer fractions of the natural frequency of the most flexible mode of the system. The assumptions of this theory become invalid for highly interrupted machining, where the ratio of time spent cutting to not cutting (denoted ρ) is small. Th...
Article
Full-text available
Progress in developing and assessing predictive modeling of machining processes has been hindered by the extremely localized nonlinear physical phenomena that occur in machining and the many different types of models ranging from theoretical to empirical. The difficulty in assessing models has been cited by industry as the major barrier to use of m...
Article
A critical parameter in predicting tool wear during machining and in accurate computer simulations of machining is the spatially-resolved temperature at the tool-chip interface. We describe the development and the calibration of a nearly diffraction-limited thermal-imaging microscope to measure the spatially-resolved temperatures during the machini...
Article
Full-text available
As interest in high-speed machining techniques grows among world manufacturers, efficient methods for obtaining the tool point frequency response (used as input to analytic or numerical chatter prediction/avoidance models) become more important. We describe the application of receptance coupling substructure analysis to the analytic prediction of t...
Article
The authors describe a new approach to modeling chip formation in orthogonal machining. Metal cutting is interpreted as a nonlinear dynamical process with thermomechanical feedback, that is similar in many ways to an open chemical reactor. As the cutting speed is increased, there is a bifurcation from steady-state to periodic oscillatory behavior i...
Article
The stability of interrupted cutting is examined for the case in which the tool is in contact with the work piece for a small, but finite, fraction of the tooth-passing period. A model of a single degree-of-freedom tool excited by intermittent, regenerative cutting forces is analyzed. The equations are transformed into a discrete model by use of th...
Article
A dynamic cutting fixture based on the test rig pioneered by Peters et al. has been developed to aid investigations of cutting process dynamics. This active fixture consists of a flexure-based tool holder with a single dominant modal direction, two voice-coil type actuators for excitation and control, sensors for measuring tool displacement and acc...
Conference Paper
A single-degree-of-freedom active cutting fixture is employed to reveal and analyse the hysteretic nature of the lobed stability boundary in a simple machining experiment. Specifically, the seventh stability lobe of a regenerative cutting process is mapped using experimental, analytical, and computational techniques. Then, taking width of cut as a...
Article
Tool deflections of high length-to-diameter ratio endmills are measured with capacitance probes during high-speed milling and compared with the predictions of regenerative chatter theory. Poincaré sectioning (once per revolution sampling) techniques are introduced as a new means of characterizing and identifying chatter. The regenerative chatter th...
Article
The results of orthogonal cutting tests on electroplated nickel-phosphorus (15% phosphorus) and AISI 52100 bearing steel are presented and compared. For both materials, chips become segmented at relatively low cutting speeds (0.3 m/s to 2 m/s) due to the onset of an oscillation in the material flow that is manifested in the repetitive formation of...
Article
Topography of surfaces produced in finish hard turning using cubic boron nitride (CBN) tools is affected by a large number of factors including tool wear and the mechanics of the chip formation process. This paper shows first that tool wear rates are affected by interactions between the work material and the binder phase of the CBN tool. For finish...
Article
A single-degree-of-freedom dynamic cutting fixture is used to map out a part of the lobed stability boundary in a simple high-speed machining experiment. The experiment reveals the hysteretic nature of the instability. A 1 DOF mechanical model is derived using parameters identified from the experiment. We then show the existence of a subcritical Ho...
Article
Full-text available
The accuracy of simulations for modeling of machining processes is often limited by insufficient knowledge of the material properties during machining, which can involve strain rates on the order of 10 4 per second or higher, plus rapid material heating. By adapting a traditional Kolsky bar (split-Hopkinson pressure bar) to an existing electrical-h...