Stop Device Research Articles

On the Mechanics of Chip Segmentation In Machining

The mechanics of chip segmentation, during machining of a cold rolled steel has been investigated from a phenomenological point of view using a high speed movie camera and an explosive quick stop device. The latter was used for obtaining chip root samples at various stages of segmentation for subsequent examination in the Optical and Scanning Electron Microscope (SEM). The chip segmentation process is found to arise as a result of instabilities in the cutting process and is further augmented by the dynamic response of part of the machine tool structure. This process involves a slow forward movement of the plastic boundary in the primary shear zone forming a ramp on the free surface of the chip followed by a rapid return of the plastic boundary back towards the tool forming a step on the chip segment as a result of partial fracture at the free surface. This process is characterized by large strains, low shear angles that oscillate cyclically and stick-slip friction on the rake face. The instability in the cutting process is proposed to be due to the negative stress—strain characteristics of certain materials at large strains, as Walker and Shaw [1] proposed, involving void formation around second phase particles, their propagation into microcracks in the primary shear zone and coalescence of these cracks leading to partial fracture. Evidence for this has been obtained in this investigation.

Elastic Deflections in Grinding

Besides affecting the wheel-workpiece interaction to a large extent, the local contact deflections play a major role in establishing the size accuracy of the ground surface. The increasing interest in this aspect of grinding in recent times has resulted in some hypotheses and models but no complete understanding has yet been achieved. This paper is a review of the work carried out by various investigators and presents a comprehensive picture of the current understanding of local elastic deflections. It extends from the first “grain mounted on springs” model of Hahn, to the most recent studies using holographic interferometry, high acceleration quick stop devices and the Monte Carlo simulation of grinding. The paper also includes a brief reference of some new experimental techniques and results obtained in an elastic deflection study using single grits on actual grinding wheels.

砥粒切削機構の塑性学的解析(第2報)

The paper presents the experimental examination of propriety of the proposed cutting models and the energy method which enables to predict the deformation and the three components of cutting force. The model tool, which has a triangular rake face and is made of sintered carbide, was used in turning experiment. The geometrical constitution of the models is first examined and proved to be true by comparing with the actual deformation obtained by a quick stop device. The cutting force components FH and FV, which are parallel to cutting speed and feed rate respectively, are next measured and further the transition state between the models are observed by changing the inclination and normal rake angles of the tool. The measured results are in good agreement with the analytical results except for the transition from the model [I] to [II] and the normal force in the case of model [II]. In order to dissolve this lack of agreement, some improvements are suggested to be introduced for the estimation of the internal energy dissipation of the model [II].

The mechanism of metal removal by an abrasive tool

To study the basic mechanism of metal removal with abrasive tools, the cutting action of a simulated tool was arrested by a quick stop device. The material behavior ahead of the tool face during cutting was observed by examining the cross section along the cutting groove microscopically. Variation of the stagnant region during the metal removal process was observed. It was found that the initial position of the stagnant tip determined whether or not chips were produced and the chip size.

Design of a metal skinning energy absorber for the U.S. capitol subway system

The design of a metal skinning emergency overshoot stopping device for the U.S. Capitol Subway System is discussed. The kinetic energy of the vehicle is dissipated by pulling a round rod through a circular cutting tool. The design procedure used in the selection of critical components is reviewed and a systematic method for their selection is shown. Photographs of the final design hardware are shown. A subway collision test was conducted and the results of the test are shown to agree well with predictions.

酸素噴射の方向が切削現象におよぼす影響

This paper describes the results of an investigation into the directions and effects of an oxygen jet in certain cutting operations conducted at cutting speeds between 8m/min and 200m/min. The oxygen is respectively jetted for a cutting point from the four directions along the side rake face, side relief face, side cutting edge and front relief face. In this experiment, by using a newly developed high-sensitivity cutting tool dynamometer and a quick stop device for observing chip forming mechanism, medium carbon steel S43C (JIS) are turned with carbide tool P30 (JIS). To see from what direction the oxygen jet should be supplied in order to obtain the highest possible effect, the cutting phenomena.is experimentally compared with that of the conventional dry cutting. The experimental results obtained are as follows. The jetting methods other than the method of supplying oxygen jet in the direction along the side rake face, compared with the conventional dry cutting, are seen to show an advantageous effect to some extent in the cutting phenomena only in low feed range. On the other hand, in the case of the method of supplying oxygen jet along the side rake face, the effect is found to be especially excellent in the whole range of feed, and moreover, the range of the effective cutting speed is found to be extended about twice toward the high speed. Thus, the method of supplying oxygen jet in the direction along the side rake face is proved to be the best of four jetting methods.

Device at the casing bottom to prevent impact collision of cementing plug with stopping device

Device at the casing bottom to prevent impact collision of cementing plug with stopping device

Impact tolerance of mammals

Correlation of experimental data on human impact tolerance, treating the test subject as a typical structural element, has led to the conclusion that impacts at velocities below about 80 ft/sec are tolerable regardless of the peak deceleration. The present paper is concerned with the empirical verification of the theory adopted in this study of human acceleration resistance, using mice as test specimens. Impact tests were performed using a drop tester capable of velocity changes up to about 90 ft/sec, with various stopping devices for shaping the acceleration-time pulses. The practical ranges of impact parameters for the mouse “impact sensitivity curve” were covered by varying the impact duration from less than 0·5 msec to about 2 msec and peak accelerations from about 500 g to about 10,000 g. The effects of acceleration, impact duration and velocity change were evaluated. The conclusions reached in this mouse impact study, when extended to larger mammals and humans by thorough experimentation, will have immediate application in the establishment of a simple design criterion for manned satellites and space vehicles on landing impact.

An Improved Automatic Stopping Device for MacKenzie Type Tester of Single Fibers

An Improved Automatic Stopping Device for MacKenzie Type Tester of Single Fibers

Stopping devices for 400-cycle motors

BECAUSE of its large size and complexity, the modern airplane requires many kinds of remotely or automatically controlled positioning systems.

裝置の自働化の研究 (第2報)

An automatic stopping device, a pusher-type burette, and a spark-type automatic recorder, were experimentally manufactured and used for the automatization of potential titration apparatus.

Month in the Patent Office

In aircraft engines, the explosion pressures are maintained within safe limits at low altitudes by means of a stop device which is automatically adjusted according to the altitude by an aneroid device operating through a relay. The control lever a moves in a slotted member f2 adjustable by a rod f1 connected to a relay e controlled by an aneroid device d. In a modification, the control lever simultaneously adjusts the throttle and the ignition timing, only the latter being subject to the aneroid control. Fig. 3 shows an aneroid device h connected by a lever h2 to the relay comprising a valve j1 controlling the action of the lubricating‐oil pressure on a piston k1 connected to the ignition control by a lever f and rod f1. When the aneroid chamber h expands, the valve j1 is raised to allow oil admitted at l to pass by way of passages j2, k4 to the underside of the piston. When the piston is raised sufficiently, the oil pressure passes through a port k5 to the upper side of the piston, which is then lowered again by a spring m1. Instead of oil pressure, the engine suction or the pressure in the water‐cooling system may be used to actuate the relay. Specification 247,304, [Class 7 (iv), Internal‐combustion engines, Igniting in], is referred to.

The Emergency Stops of the Gearless Traction Elevator at the Terminal Landings: Performance and Limitation of the Emergency Terminal Stopping Devices; Calculation of the Required Overhead Clearances

Abstract The present paper is confined to an investigation of the oil buffer and the limit switch. Part I is a short description of these and allied devices. Part II gives of a theory of the oil buffer, developed by the author, that part which bears on the subject matter of this paper, namely the complete calculation of the properties of a given buffer if struck by a free weight at a given speed. It is shown that this theory applies when a buffer is suitable for service with an elevator. On the other hand it is a fact, not as yet fully recognized, that a buffer satisfactory when engaged by a free weight may be wholly objectionable if the same weight instead of being free is the car or counterweight of an elevator. In Part III a very useful and simple concept is introduced under the name of “the equivalent system,” by means of which the problems in Part IV are quickly disposed of with no greater difficulties than the application of first principles. Part IV is divided into four sections. The first is an investigation of the stop of an elevator when a limit switch is opened. It is found that the limit switch alone is inadequate as an emergency terminal stopping device unless the top and bottom clearances are exorbitant. The second is an investigation of the stop of an elevator when brought about by the action of the buffer alone. It is shown that an intimate relation exists between the buffer and the particular elevator it is to serve and two requirements are deduced which a suitable buffer must satisfy. One of these relates to the force it must exert on the member engaging it and the other to the stroke. It is further shown that a well-designed buffer is always an excellent terminal stopping device for the descending member of the elevator but not, in general, for the ascending member, unless the buffer stroke and the top clearance are considerable. This part also includes a discussion of the present buffer testing in the field and in particular of what is involved if such tests are conduced at governor tripping speed — as some codes now specify — with buffers of the usual stroke. Having to abandon the accepted notion that in the oil buffer and in the limit switch there are two independent emergency terminal stopping devices, each capable of bringing the elevator to a safe stop within the usual clearances, there is next investigated the case when both of these devices become simultaneously effective. The results are gratifying although they plainly indicate that the coöperation of both devices is necessary. They further show that the location of the limit switches is a matter of major importance. The third section investigates the stop of the elevator with buffer and limit switch coöperating in the usual sequence of practice. One of the outstanding results of Part IV is the proof that the required amount of top clearance can be readily calculated for any given emergency. Vice-versa, it is shown that a given top clearance provides for certain definite emergencies only. The author shows how to calculate the required top clearance and, upon a consideration of the accumulated experience, specifies the emergency upon which the calculation is based. It is shown in Part IV that the selection of the buffer stroke not only depends on the speed but also on the particular details of the elevator and location of the limit switches. The author further discusses which of a number of buffers of the same stroke but with different graduations is suitable for service with a given elevator. Since the emergency stops at high speed are generally associated with slack hoist rope, Part V develops the formulas for determining the stresses upon the subsequent fall of the ascending member to pick up the slack. In it will be found the reason why present methods of field testing are so frequently accompanied by a failure of the shaft of the machine and often make a re-alignment necessary.

Discussion: “The Emergency Stops of the Gearless Traction Elevator at the Terminal Landings: Performance and Limitation of the Emergency Terminal Stopping Devices; Calculation of the Required Overhead Clearances” (Hymans, F., 1926, Trans. ASME, 48, pp. 1095–1161)

Discussion: “The Emergency Stops of the Gearless Traction Elevator at the Terminal Landings: Performance and Limitation of the Emergency Terminal Stopping Devices; Calculation of the Required Overhead Clearances” (Hymans, F., 1926, Trans. ASME, 48, pp. 1095–1161)

Speed control and stopping devices : Anon. (Safety Standards of the Industrial Board, Pennsylvania Department of Labor and Industry, Electric Code, vol. I, No. 21, p. 59.)

Many small wind turbines operate at high tip speed ratio and this gives rise to situations where compressibility may influence performance. The most important example is runaway, the operating point for an unloaded turbine where the rotational speed of the blades is maximised. Because compressibility significantly increases drag through the action of “shock-stall”, it may provide an inherent mechanism for overspeed protection. This possibility is tested computationally for a turbine with a high optimum tip speed ratio, having an aerofoil section (NACA 0012) whose behaviour in compressible flow is well known. Calculations of turbine performance for differing windspeeds, and hence Mach numbers, show that compressibility effects occur too slowly to prevent overspeeding. However, it is suggested that aerofoils could be designed to maximise the onset of shock stall.