Mechanical properties and cyclic fracture behavior of differently heat-treated steel

Static mechanical, dynamic and resistance to cyclic loading properties obtained for differently heat-treated low carbon steel AISI 4130. Insignificant change of chemical content and heat-treatment change hardness, strength, ductility properties, impact resistance and threshold value of fatigue crack propagation. An analysis of CT specimens’ fractured views performed using SEM shows relationship of material microstructure with cyclic fracture

Struktūros ir mechaninių savybių įtaka ketaus ciklinio irimo rodikliams

This paper presents the study and perform analysis of additional research by measuring limits of cracking threshold at very low speeds (5·10-12 m /cycle). The micro-structure and mechanical properties of cast iron make big influence on crack propagation. Big dispersal of experimental research data unstable propagation of the crack was noticed. The obtained data were used for the calculation of durability of structural elements.Straipsnyje apibendrinami atlikti darbai ir analizuojami papildomi tyrimai, kuriais siekiama nustatyti pleišėjimo slenksčio ribas, esant labai mažiems plyšio plitimo greičiams (5·10-12 m /ciklą). Šiomis sąlygomis plyšio pliti-mui didelę įtaką turi ketaus mikrostruktūra ir mechaninės savybės. Lietuviška santrauka. Pastebėta didesnė eksperimentinių rezultatų sklaida ir nestabilus plyšio plitimas. Gauti duomenys panaudoti konstrukcijų elementų ilgaamžiškumo skaičiavimui

Influence of structure and mechanical properties for cyclic fracture rates of cast iron

This paper presents the study and perform analysis of additional research by measuring limits of cracking threshold at very low speeds (5·10-12 m /cycle). The micro-structure and mechanical properties of cast iron make big influence on crack propagation. Big dispersal of experimental research data unstable propagation of the crack was noticed. The obtained data were used for the calculation of durability of structural elements

The model of bent threaded connection in three segments

For the calculation of load distribution between turns the threaded connection subjected to bending is modeled by three segments. The model gives a possibility to estimate the influence of runouts and of the connection position with respect to bending plane. The equations for the displacements compatibility of threaded joint elements for every segment are constructed. The numerical and approximate analytical solutions for these equations are obtained

Fatigue strength investigation of four type cast irons specimens

In this paper data about four types cast irons chemical composition, microstructure, static mechanical properties, durability and cyclic fracture toughness is given. Ultimate stress obtained using cylindrical specimens of diameters 8-14 mm with circular notch are σu = 403-692 MPa. Endurance limit values of notched specimens are σ0 = 85-96 MPa. The performed analysis of breaks shows that heterogeneities and defects (voids) formation have an influence on static and cyclic fracture, because they change the crack front and shape of final fracture’s zone. The values of cyclic fracture toughness obtained according to the shape of final fracture’s zone are Kc = 10-26 MPa m . The obtained data allows deciding about the suitability of cast irons for structural elements production

High-cyclic failure analysis of welded cast iron plates

The article presents experimental analytical research results of seminatural welded cast iron specimen. It has been determined: the chemical structure of the base and weld material, static mechanical properties, hardness and microstructure. The static loading during the experiment is started from a close to structural elements loading. The investigation starts from a given stress changing programme. The experiment was performed according to the given programme on stress changing. The kinetic fatigue diagram is performed according to the experimental data. For determining the failure conditions an additional fracture analysis has been performed. The investigation was supplemented by cast and normalised CT samples experimental data analysis by applying the crack growth rate versus stress intensity factor range diagram as well as by the crack opening diagram. Values of limiting stress factors Kth and KC have been determined

Strength of mining and building equipment materials subjected to Gigacycle loading

High‐strength cast iron is used for manufacturing the supporting elements of minerals and cement clinker grinding machines. The dross layer remains inside large dimension castings after manufacturing. It has worse mechanical properties and resistance to fatigue crack formation and propagation. In this paper, the results of an experimental investigation of cyclic bending strength of semi‐natural specimens from cast iron with a dross layer of 10–11 mm thickness are presented. The mechanical properties and structures of the base and dross layers differed considerably. Before testing the methods of defectoscopy were applied to detect technology defects. The stress ratio was r = ‐0,62 and the stress alternating range varied from 70 to 280 MPa. To 1*108cycles, crack growth was insignificant. Further crack propagation was controlled. The 1st specimen was broken after 3*108 and the 2nd one after 2*108 cycles. The dependencies of crack propagation on cycle number and stress intensity factor range were estimated. The dross layer stops crack propagation, when crack front passes from dross to base metal. Medžiagų, skirtų malūnų ir uolienų smulkintuvų įrenginiams, atsparumas gigaciklei apkrovai Santrauka Uolienų smulkintuvų ir cemento klinkerio malūnų atraminių mazgų gamybai naudojamas stiprusis ketus. Didelių matmenų detalėse liejimo proceso metu lieka nuodegų ir neaiškių pagrindinio metalo darinių. Jų blogesni mechaninių savybių rodikliai ir geba priešintis plyšio atsiradimui bei plitimui. Straipsnyje pateikiami pusiau natūrinių stačiakampio skerspjūvio bandinių iš ketaus su 10–11 mm storio nuodegų sluoksniu eksperimentiniai ciklinio lenkimo tyrimo rezultatai. Prieš eksperimentą defektoskopijos metodu buvo nustatyti technologiniai defektai. Ciklinio deformavimo asimetrijos koeficientas r = –0,62, įtempių intervalas kito nuo 70 iki 280 MPa. Ciklų plyšiai iki 1·108 didėjo nežymiai. Toliau varginant ir didinant įtempių intervalą, plyšio augimas buvo kontroliuojamas. Pirmasis bandinys suiro po 3·108 , antrasis – po 2·108 ciklų. Eksperimentiškai nustatyta plyšio plitimo rodiklių priklausomybė nuo ciklų skaičiaus ir įtempių intensyvumo koeficiento kitimo intervalo. Plyšio plitimą stabdo tarpinis sluoksnis, pereinant nuo nuodegų sluoksnio į pagrindinį metalą. Raktiniai žodžiai: uolienų trupintuvas, nuovargis, plyšio plitimas, įtempių intensyvumo slenkstis. First Published Online: 14 Oct 201

Suvirintos ketaus plokštės daugiaciklio irimo analizė

The article presents experimental analytical research results of seminatural welded cast iron specimen. It has been determined: the chemical structure of the base and weld material, static mechanical properties, hardness and microstructure. The static loading during the experiment is started from a close to structural elements loading. The investigation starts from a given stress changing programme. The experiment was performed according to the given programme on stress changing. The kinetic fatigue diagram is performed according to the experimental data. For determining the failure conditions an additional fracture analysis has been performed. The investigation was supplemented by cast and normalised CT samples experimental data analysis by applying the crack growth rate versus stress intensity factor range diagram as well as by the crack opening diagram. Values of limiting stress factors Kth and KC have been determined