Different Types Of Chips Research Articles

Development of a new theory of cutting 7. Mathematical description of the formation of different chips, pulsation of the cutting force, and contact parameters of the machined billet surface and the rear cutter surface

Using the new theory, the formation of different types of chips is mathematically explained, the cutting-force pulsation is described, and the upheaval of the machined material behind the cutter tip is determined.

Effects of workpiece thermal properties on machining-induced residual stresses - thermal softening and conductivity

Workpiece material properties play a key role in controlling the cutting process, and consequently residual stresses. Different materials may behave totally differently under the same cutting conditions; they may produce different types of chip, surface finish, residual stress, etc. The current work examines the effects of two workpiece thermal properties, specifically thermal conductivity ( k) and thermal softening exponent ( m), on machining-induced residual stresses, in order to understand their role in controlling the residual stresses induced in different materials, when cut using the same cutting conditions. Finite element analysis was used to model the process of orthogonal dry cutting, using the arbitrary-Lagrangian-Eulerian technique, and then predict the induced residual stresses. In order to isolate the effects of the examined properties ( k and m), only one material (stainless steel AISI 316L) was used as the base workpiece material, and different values were assigned to its k and m, one at a time. Values up to four times the original magnitudes were used, covering almost all commercial steels and stainless steels. All other material properties and cutting conditions were kept constant. Surface tensile residual stresses were induced in all cases, and a strong effect was found for both properties, k has mainly affected the thickness of the tensile layer, where higher k resulted in thicker layers; it has also induced higher surface tensile residual stresses. On the other hand, higher m (lower softening effects) has significantly increased the magnitude of surface tensile residual stresses, with almost no effect on the thickness of the tensile layer.

Chaotic Phenomena Induced by the Fast Plastic Deformation of Metals During Cutting

In the present study the examination of chip formation is focused on the primary shear zone, which is divided into two layers, and the variation of shear stress and temperature in time are given by two mechanical balance equations and three energy equations. All the five evolution differential equations are autonomous and nonlinear. The material characteristics are determined by an exponential constitutive equation. The mathematical model is suitable for the qualitative description of different types of chips, such as continuous chips and periodic or aperiodic shear localized chips, which is demonstrated by the general structure and typical solutions of the equation system.

Rosenhain and Sturney revisited: The ‘tear’ chip in cutting interpreted in terms of modern ductile fracture mechanics

Rosenhain and Sturney in 1925 identified the ‘tear’ chip, in addition to the well-known types of chip found in metal cutting, namely continuous with or without a built-up edge and discontinuous. Tear chips occur at deep uncut chip thicknesses and, since their formation results in undesirable surface finish, they have been largely ignored in subsequent analyses of machining. A recent paper by Atkins shows that metal cutting is from the class of ductile fracture problems where there is complete plastic collapse in the formation of the chip. It was demonstrated that incorporation of significant work of surface separation (ductile fracture toughness), in analyses of machining with continuous chip formation, explains many features of metal cutting which traditional ‘plasticity and friction only’ treatments cannot, in particular why the primary shear plane angle is material dependent. It also explained why finite element simulations of machining have to employ a ‘separation criterion’ at the tool tip. The new model is extended in this paper to predict quantitatively the conditions under which the tear chip forms. The production of other well-known types of chip is also considered, and the results are applied to diagrams relating combinations of tool rake angle and uncut chip thickness at which different types of chip are formed. It is demonstrated that the analysis has general applicability to the cutting of other materials such as plastics and wood for which similar diagrams exist.

411 砥粒切削機構の解析的検討(OS14 切削加工の最前線)

The mechanisms of abrasive grain machining processes are investigated based on thermo-elastic-plastic finite element simulations of orthogonal cutting with a negative rake. When machining of a steel of SK-5 with negative rake at low, intermediate, or fast cutting speed, bulge-type, ribbon-like, or serrated chips are formed, respectively. First, changes in the equivalent stress, temperature, plastic strain, and plastic strain rate observed at a spatially fixed point during a serrated chip formation are clarified. This indicates that a adiabatic shear occurred in the serrated chip formation. Next, changes in these cutting state parameters at some convective points of different types of chips are clarified. This shows the conditions of transition from a type of chip formation.

Progress in methodology and standards in European molecular genetics laboratories

The enormous expansion in the application of the technologies of molecular and cell biology with the objective of resolving medical problems is discussed, as well as the problems arising due to this revolution. Progress in methodology is also reported paying special attention to chip technology. The different types of chips, strategies for readout, and applications are described. The difficulties in achieving common standards in Molecular Genetics are analysed as well as the need to develop European networks of genetic testing laboratories. Forensic genetics is a particular field where the progress in technical and procedural standards has been considerable in European labs. Molecular genetic laboratories with other medical applications could benefit from the progress in standards in the forensic field.

Allocation of Chips to Wafers in a Production Problem of Semiconductor Kits

The problem of maximizing the production of good sets of semiconductor chips under random yield is reexamined in this paper. (A set of semiconductor chips is called a semiconductor kit.) This problem has been considered by Avram and Wein (Avram, F., L. Wein. 1992. A product design problem in semiconductor manufacturing. Opns. Res. 40(5) 986–998.) and Singh et al. (Singh, M. R., C. T. Abraham, R. Akella. 1988. Planning for production of a set of components when yield is random. Fifth IEEE CHMT Internat. Electronic Manufacturing Technology Proc.). To solve this problem we show that under certain combinations of assumptions the production process can be replaced by a black box. The use of the black box model considerably simplifies the analysis and reduces the simulation effort required for carrying out parametric analysis of the proposed solution procedure. The model includes that of Avram and Wein, and we extend their results to more general settings and strengthen their conclusions. Using the black box model, it is shown that the strategy of placing different types of chips on a single wafer gives larger yield of kits in a stochastic sense than the traditional method of placing single types of chips on a wafer. We compare the production of kits under different chip design and lot release policies and also carry out a parametric analysis with respect to factors such as set proportions and yield.

Interferometric Micropositioning in the Planar Chip Insertion Technique for Multichip Modules (MCMs)

A novel planar insertion technique has been developed at the CNET, Grenoble. This technique, combining laser cutting and, in particular, micropositioning controlled by interferometric vision, allows chip‐to‐substrate interconnection using a microlithography process and also chip insertion into a substrate with no physical contact with the active surfaces. Holes in MCM substrates are made by moving the 15 micron spot of a YAG laser. The chip‐to‐substrate gap of 100 ?m is filled with UV curable epoxy resin in order to bind the chip to the substrate. Chip insertion into these holes is controlled by interferometric vision yielding a planar alignment better than 0.1 µm between the active surfaces (pads) of both chip and substrate; interferometric vision enables simultaneous measurements on many chosen pads of less than 100 µm square in one imaging zone. After epoxy resin curing, this planar alignment remains in the order of 1 µm. The micropositioning by interferometric vision described above has been demonstrated in the fabrication of HDTV modules with 19 chips; on each MCM, six different types of chips from 1 mm2 to 32 mm2 have been micropositioned using interferometric vision. The feasibility of micropositioning optical fibres is also shown.

The Computer Simulation and Experimental Analysis of Chip Monitoring for Deep Hole Drilling

Chip congestion is a long time bottleneck in deep hole drilling. This paper addresses the problem of chip state monitoring in single-edge deep hole drilling by computer simulation and experimental analysis. Two phenomenological models were proposed to interpret the physics of chip discharging in normal and congested states, respectively. Length and diameter of the chip are chosen to represent the geometric features of the chip, and the formation of a chip signal is discussed. Based on the two models different types of chips are used to simulate the monitoring process. Computer simulation shows that the normal chip discharging in a real drilling process can be interpreted by the proposed slug flow model. Also, the experiments with cylindrical form chips confirms model II proposed for a congested chip state in which the diametral effect develops due to chip congestion. The experimental analyses also find out the dependence of pressure signals on the various parameters of chips as well as the cutting process.

A Product Design Problem in Semiconductor Manufacturing

We consider the product design problem of allocating the chip sites on a semiconductor wafer to various types of chips. The manufacturing facility sells chips to its customers in sets (a specified number of several different types of chips), and the objective of the facility is to maximize the average production rate of sets. Variability in the wafer fabrication process, in particular random yield, poses a major obstacle in producing sets in a reliable fashion. A stochastic analysis is employed to develop an effective wafer design, to measure the improvement in performance of the multitype wafer over the traditional single-type wafer, and to determine the cumulative production of sets of nondefective chips as a function of the rate at which lots of wafers are released into the facility. The analysis reveals that multitype wafers regularize the production flow of nondefective chips of each type and cause these flows to be correlated positively, both of which help to improve performance. A numerical example is provided that illustrates the analysis and demonstrates the design's effectiveness.

Zones and boundaries between different types of chip

The machining conditions, speed, feed and depth of cut, as well as the mechanical properties of the machined parts have a marked influence on the mechanics of chip formation. Different types of chip may be produced, namely continuous, partially discontinuous, discontinuous or continuous with either a serrated or a built-up edge. In the present work three different materials, aluminium, mild steel and brass, were machined orthogonally under different cutting conditions. Different types of chip were observed and the variations in the zones of and in the boundaries between types of chip with the machining conditions were determined for the materials used. An analysis for changing from one type of chip to another type is given, and recommended cutting conditions are reported for the different materials tested according to the type of chip produced. The cutting force components were measured in order to determine the mean coefficient of friction on the tool face and to determine the relation between this coefficient of friction and the type of chip produced.

A scanning electron microscope study of fracture phenomena associated with rolling contact surface fatigue failure

In a manufacturing process, studying the removed material called chip, swarf or debris, is the key to understand the process. In micro cutting process, the size effect is a dominant factor for material removal mechanism and chip generation physics. There are different types of chips but a particular type, stands out from the others due to its specificities: the spheroidal chip. It is often found in grinding and tribological tests. This type of chip has no specific classification and there are no reports of it being found in milling or micro milling research. This paper makes a review of this not so well known type of chip, to classify it by its characteristics and to present some examples of spheroidal chips obtained from micro milling operation. Spheroidal chips were obtained when micro milling slots using a 381 µm diameter TiN coated WC tool. The workpiece material was Inconel 718, a high strength refractory superalloy. SEM images were obtained to analyze and classify the chips and observe the machined surface of the slots. In the proposed classification of spherical chip, there are eight major types: Fatigue Sphere, Layer-like Sphere, Thin Plate Sphere, Dendritic-like Sphere, Partially Formed Sphere, Tadpole, Melted sphere and Hollow sphere. The thin chip is submitted to high energy, which is one of the main aspects of size effect that occurs in micro milling. Inconel 718 has low thermal conductivity and high oxidation rates, which makes it an ideal environment for the formation of spherical chip. The spheres formed can be classified as Dendritic Spheres, defined by extremely high rates of oxidation in a thin chip which leads to high heat energy causing its spherical form and dendritic microstructure.