Gép, 1990 (42. évfolyam, 1-12. szám)

1990-01-01 / 1. szám

GÉP SCIENTIFIC SOCIETY OF MECHANICAL ENGINEERING Vol. 42 No. 1. 1—40. Jan. 1990. INTERPRESS Publishing House of the International Organisation of Journalists, H—1525 Budapest, P. O. B. 100. Tel.: 122-7448, 142-1513. Tx.: 22-5080. HUNGEXPO Advertising Agency, H-1441 Budapest, P. O. B, 44. Tel.: 122-5008, Tx.: 22-4525 hexpo, MH—Advertising, H-1818, Budapest, P. O. B. Tel.: 118-3630. Tx.: 22-5341 mahir. MAGYAR MÉDIA Advertising, H-1392 Budapest, P. O. B. 279. Tx.: 22-3040 Subscriptions from abroad through KULTÚRA Foreign Trade Co. (H-1389 Budapest, P. O. B. 149). Subscription price to be paid either by cheque along with the order, or simultaneously by remittance in favour of the account No. 024-7 of KULTÚRA with the Hungarian National Bank (H-1850, Budapest). Subscription price: US S 12 for a year. Kazinczy, Ferenc: Notions on the unification of quality attestations in Europe .................................. 2 Difficulties are often caused in international commerce in consequence of the fact that im­porting countries would not accept official quali­ty attestations of the exporting country, con­sequently proceeding for own — lengthy and expensive — supervision. With a view to prec­­ludong such cases, the competent commisions of the Europen Economic Community have been carying on negoeiations since several years al­ready. The paper furnishes a survey of these emdeavoura. Tóth Dr., Ferenc: Analogies between the operatio­nal ability of technical and economical structures 4 There exist many analogies in respect of techni­cal and economical structures. A parallelt build - -up enhances supply and information flow, a series formation degrades them. The mathemati­cal manoevrability of the system decreases when the number of variables or the size of the system is enlarged. The effectiveness of the system may be improved by analysing and then reducing losses. Fenton, R. G.: Theoretical fundamentals of determi­ning positive forces occurring with clamping, supposed there exist rough surfaces and point contacts............................................................................. 11 These bases describe the possible combinations of contact forces that self equilibrate. The deriva­tion is first performed for a grasp formed from two pf (point-friction) contacts. The results are extended to grasps formed from multiple pf contacts, considering contact paires. The derived bases are utilized in the contact force solution for two and three point friction grasps. Grasp uni­directional normal force feasibility is examined in detail for the three point friction grasp. Petrik Dr., Olivér: Effect of micro-electronics upon the design of mechanical equipment......................... 18 The development of micro-electronics created so small circuits as can readily be inserted into mechanical devices. The so resulting complex „meehatronical” units lend themselves for sol­ving many new tasks. When planning mechatro­nical units receiving and „integrating” electro­nics there must be taken into consideration many novel conditions. Earlier principles have lost validity, new ones developed. The present paper endeavours to survey them. Pásztor Dr., Endre: Examining the friction and wear of combustion-pistonengines, accelerated testing method of their tearing off ......................... 23 Author elaborated a process for determining the friction mean pressure of combustion-piston en­gines and for an accelerated testing method of their tearing off. The test engine is operated without combustionprocese, turning it round Advertisements: from outside in a closed work cycle. Accordingly the engine intakes from an air vessel and exhaust gets into the same vessel. Frictional losses can he determined from the power requirement of rota­ting the experimental engine by means of speci­fic measuring and computation processes with very high accuracy i. e. ±0,6—0,7 %. It is im­possible to determine frictional losses with such an accuracy on an engine operating at actual operational conditions. The feasibility of an accele­rated testing of tearing off is ensured through the fact that an increase of pressure within the air vessel similarly involves higher mean pressure of the working process, and consequently higher mechanical strain on the engine. In this way there increases the wear of engine parts slipping one upon another, as well as the probability of fatigue failures of engine parts. With this process the time requirement of long-term test (according to actual results) amounts to only 15—20 % as compared to the conventional method (actual operational state). Ziaja Dr., György: Critical conditions of processes in plastic deformation .................................................. 28 The most up-to-date method of planning pro­cesses of plastic deformation is the computer-ai­ded simulation. The paper calls the attention to that simulation processes based on continuum­­-mechanical models require completion with a module for monitoring the critical condition. This is to supervise the condition of the process and the material in respect of avoiding the oc­currence of global, diffuse and local instabilities as reasons of waste, as well as breakage pheno­menons. The module will stop the running simu­lation programme in due time. The paper de­monstrated examples in the field of plastic cold deformation of sheet and rod material. Réda, Gyula: Continuum-mechanics and the practi­ce of mechanical engineers ......................................... 34 In up-to-date continuum-mechanics there exist such all-embracing formulae as permit far reaching expansion of technical computations — provided the up-to-date computer engineering now awailable in our country as well is utilized. In this context not our computer engineering facilities, but rather our knowledge of mechani­cal and physical science may be the impediment of the evolution of up-to-date machine design and technology. Bodor, János—Kozák Dr., Imre: Strength testing of pressure-tight vessels provided with heating or cooling channel in the chemical industry.............. 36 To describe stress and deformation conditions of the structure a mob oeoque construction modell is used, which suits a meridian-loop curve, gyration-symmetric build-up and load. Based upon examples the paper suggests alterations of the actual regulating prescriptions.

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