Wyniki wyszukiwania - Biblioteka Nauki

1

Texture and residual stresses in Ti-Al and Ti-Al-Nb alloy subjected to severe plastic deformation

100%

Mizera J. , Pakieła Z. , Kurzydłowski K. J.

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tom Vol. 50, iss. 2

395-402

EN

The paper presents an analysis of the residual stresses and texture in two alloys of the Ti-Al and Ti- Al-Nb systems (in the Ti3Al phase, which predominated in these alloys), before and after subjecting them to severe plastic deformation. In the as-received state, the texture of the Ti-Al alloy is relatively weak. The Ti-Al-Nb alloy texture has a similar character but contains a well-marked <001> component. After deformation, the texture of the Ti-Al alloy can be described by a single axial <012> component, deflected by 25š from the <001> axis, whereas the texture of the Nb-enriched alloy is much less pronounced than before deformation (in the as-received state). This can be interpreted as a result of its destruction during the deformation process. The magnitudes of the compressive residual stresses in the as- received samples ranged from 5 MPa (Ti-Al) to 15 MPa (Ti-Al-Nb). However, these results contain a relatively large error due to the large grain size. In the as-received state, the alloys are practically free of stresses. After deformation, the residual stresses were found to be again compressive and near 660 MPa in the Ti-Al alloy and 420 MPa in the Ti-Al-Nb alloy.

PL

W pracy przedstawiono analizę zmian naprężeń szczątkowych i tekstury w dwóch stopach na osnowie faz międzymetalicznych z układu Ti-Al i Ti-Al-Nb przed i po dużym odkształceniu plastycznym. Analiza tekstury nie odkształconych próbek wykazała, że w stopie Ti — Al ma ona charakter osiowy o zróżnicowanym stopniu ukształtowania. Podobny charakter ma tekstura stopu Ti-Al-Nb jednakże z wyraźną składową typu <001>. Po odkształceniu tekstura próbek stopu Ti-Al daje się opisać jedna bardzo wyraźna składowa osiowa <012>, która jest odchylona o około 25 stopni od osi <001>. Natomiast stop z dodatkiem Nb jest znacznie słabiej steksturowany w porównaniu ze stanem wyjściowym, co można zinterpretowac jako “niszczenie” tekstury w procesie odkształcania. Wartość naprężeń własnych w nie odkształconych próbkach badanych stopów wahała się stosunkowo dużym błędem ze wzgledu na dużą wielkość ziarna, wobec czego należy przyjąć, że w stanie wyjściowym stopy te są praktycznie pozbawione naprężeń mierzalnych zastosowaną metodą. Z kolei w próbkach odkształconych stwierdzono obecność naprężeń ściskających: -600 MPa i –420 MPa, odpowiednio dla stopu Ti-Al i Ti-Al-Nb.

2

Relief of residual stress in Al2O3/Nb joints brazed with Ag-Cu-Ti/Cu/Ag-Cu-Ti composite interlayer

84%

Zhao Y. , Wang Y. , Yang Z. , Wang D.

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2019

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tom Vol. 19, no. 1

1--10

EN

Ag-Cu-Ti/Cu/Ag-Cu-Ti composite interlayer was successfully designed to braze Al2O3 ceramic and Nb. The effect of the addition of Cu interlayer with various thicknesses on the microstructure, residual stress and mechanical properties of the brazed joints was investigated by finite element modeling (FEM) computation combined with experimental verification. The results showed that the layered Ag-Cu-Ag solid solution structure formed in the Al2O3/Nb brazed joints when the composite interlayer was used. Moreover, the thickness of TiO + Ti3Cu3O reaction layers adjacent to the Al2O3 ceramic substrate did not change obviously regardless of the Cu foil thickness. The maximum residual stress in the whole brazed joint always appeared in the Al2O3 ceramic substrate nearby the interlayer, but it was reduced from 384 MPa to 119 MPa when a 150 μm thick Cu foil was added. The variation of calculated residual stresses as a function of Cu foil thickness, which was verified by X-ray measurement, exhibited a consistent with Al2O3 ceramic strain energy. Thus, the calculation of Al2O3 ceramic strain energy could be a good criterion to evaluate the joint shear strength because the fracture occurred in the Al2O3 ceramic. The reduction of detrimental residual stress was primarily attributed to the increased plastic strain energy of Cu interlayer. The FEM and experiment results indicated that the ability of plastic deformation of the interlayer played a key role in determining the residual stress in the brazed joint, providing a method for improving the bonding properties of ceramic and metal.

3

Superficial integrity analysis in a super duplex stainless steel after turning

84%

Bordinassi E. C. , Stipkovic M. F. , Batalha G. F. , Delijaicov S. , Lima de N. B.

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tom Vol. 18, nr 1-2

335--338

EN

Purpose: Purpose of this paper was to study the main effects of the turning in the superficial integrity of the duplex stainless steel ASTM A890-Gr6A. Design/methodology/approach: The focus of the work was the finishing operations and a complete factorial planning was used, with 2 levels and 5 factors. The tests were conducted on a turning center with carbide tools and the main entrances variables were: tool material class, feed rate, cutting depth, cutting speed and cutting fluid utilization. The answers analyzed were: micro structural analysis by optical microscopy and x-ray diffraction, cutting forces measurements by a piezoelectric dynamometer, surface roughness, residual stress by x-ray diffraction technique and the micro-hardness measurements. Findings: The results do not showed any changes in the micro structural of the material, even when the greater cutting parameters were used. All the other answers were correlated with the cutting parameters and its better combination was founded for the best superficial integrity. The smaller feed rate (0.1 mm/v), smaller cutting speed (110 m/min) and the greater cutting depth (0.5 mm) provided the smaller values for the tensile residua stress, the smaller surface roughness and the greater micro-hardness. Research limitations/implications: The correlation between all the answers was very difficult to analyze because there was great interaction between the factors, but for some data group it was possible. Originality/value: The paper contribute for the study of the super duplex stainless steel, considering that no one researches was founded for the studied topics in this material in witch presents different behavior in machining when compared with another stainless steels.

4

Formability and forming of welded semi-finished parts from corrosion resistant steel

84%

Bilik J. , Sugarova J. , Kusy M. , Tittel V.

Hutnik, Wiadomości Hutnicze

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2017

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tom Vol. 84, nr 8

359--363

EN

The paper is focused on study of formability of welded semi-finished parts from SAF 2507 corrosion resistant steel. The formability is evaluated on the base of tensile test and Erichsen cup test of test samples without weld and welded test samples. The paper mentions also the results of cup test for determination of maximum drawing ratio and results of drawn parts residual stress measurements.

PL

Niniejszy artykuł opisuje badania odkształcalności spawanych półfabrykatów ze stali odpornej na korozję SAF 2507. Odkształcalność była oceniana na podstawie próby rozciągania oraz próby tłoczności wg. Erichsena – oceniano zarówno próbki bez spawu oraz próbki spawane. Praca prezentuje wyniki próby tłoczenia w celu ustalenia maksymalnego współczynnika ciągnienia oraz wyniki pomiarów naprężenia szczątkowego elementów ciągnionych.

5

Elastic-plastic stress analysis of symmetric reinforced thermoplastic matrix laminated beams under a bending moment

84%

Callioglu H. , Aksoy S. , Topcu M. , Arman Y.

International Journal of Applied Mechanics and Engineering

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2003

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tom Vol. 8, no 4

559-575

EN

In this study, an elastic-plastic stress analysis is carried out on symmetric steel fiber reinforced high density polyethylene thermoplastic matrix laminated beams under a bending moment. The Bernoulli-Euler theory is used. The orientation angles are chosen as (90o/0o)2, (30o/-30o)2, (45o/-45o)2 and (60o/-60o)2. The composite material is assumed to be linearly hardening. The stress component 'sigma'x is to be maximum at the upper and lower surfaces in the elastic-plastic solution. The residual stress component 'sigma'x is found to be highest at the upper and lower surfaces. However, when the plastic region is further expanded the residual stress component 'sigma'x is found to be the highest at the elastic and plastic boundaries. The plastic flow is to be maximum at the upper and lower surfaces for the (30o/-30o)2 orientation. The transverse displacement is obtained to be highest at the free end for the (90o/0o)2 orientation.

6

Contact interaction of resilient and cylindrical dies with initial (residual) tension

84%

Yaretska N.

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tom R. 105, z. 3-M

213-216

EN

The article deals with a mixed type task of measuring pressure of an elastic cylinder die upon a layer with initial stresses within the framework of linear elasticity theory. In general, the research was carried out for the theory of great initial (ultimate) deformations and different variants of the theory of small initial deformations with arbitrary structure of elastic potential.

PL

W artykule podjęto zagadnienie pomiaru ciśnienia w elastycznej formie cylindrycznej w obecności wstępnych naprężeń, wykorzystując teorię sprężystości. Ogólnie, badania były prowadzone na podstawie teorii dużych odkształceń początkowych oraz różnych wariantów teorii małych odkształceń początkowych przy dowolnej wartości potencjału sprężystości.

7

Residual stresses evolution and process route optimization of TC4 profiled rolled rings incorporating thermal bulging

84%

Lv N. , Liu D. , Wang J. , Rao H. , Nan J.

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tom Vol. 23, no. 3

art. no. e200, 2023

EN

The thermal processing of rolled rings inevitably generates and accumulates massive residual stresses, as quenching residual stresses produced by water cooling treatment. Non-uniformly distributed residual stresses would seriously affect the structural strength, dimensional stability and service life of the component. In the traditional rolling process of titanium alloy rings, the quenching residual compressive stresses introduced by solution treatment could reach – 400–600 MPa, for which effective control of the stresses is an urgent issue to be solved. In this research, the stress control efficiency of rolling rings under different process routes was explored according to the thermal bulge stress relief technique. The FEM model of the stress evolution in the whole process of the rolled ring was established. The residual stresses on the ring surface are characterized by the hole-drilling method, while the microstructures are characterized by electron backscatter diffraction. The results indicated that the optimized process incorporating the thermal bulging stress relief technique reduced the levels of stress values to within about ± 50 MP and the stress homogenization index by approximately 60–90%.

8

84%

Kumar A. , Pandey S. M. , Pandey C.

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tom Vol. 23, no. 1

art. no. e54, 2023

EN

A dissimilar joint of martensitic grade P92 and Ni-based Inconel 617 (IN617) alloy are employed commonly in advanced ultra-supercritical (AUSC) units to fabricate thick section components such as steam pipes and turbine rotors. This study investigated the weldability of the IN617 alloy and P92 steel dissimilar welds. Ni-based superalloy ERNiCrMo-3 filler was used to attempt the dissimilar joining for conventional V groove and narrow groove design by employing the gas tungsten arc welding (GTAW) process. The weld metal for the capping pass, backing pass, and near the interface showed the columnar and cellular grains while equiaxed grains are observed corresponding to root and filling passes. The energy dispersive spectroscopy and Electron probe micro-analyzer (EMPA) study confirmed the segregation of the Nb and Mo particles in inter-dendritic spaces and resulted in the formation of the Nb-rich NbC and laves phases and Mo-rich phases. The EDS line map and EPMA study of the P92 interface showed a sharp increase in Cr, Mo, and Ni concentration and a steep decrease in Fe concentration as moving from P92 base metal to weld metal. A negligible diffusion from filler weld to IN617 or vice versa across the IN617 interface was detected. The microhardness gradient along the weldments indicated a sharp rise in hardness value near the P92 fusion boundary due to the formation of the unmixed zone of lower hardness and the P92 coarse-grained heat-affected zone of higher hardness. The weld metal hardness results showed a great variation with an average hardness value for V groove and narrow groove welds of 227 and 262 HV, respectively. The mechanical tests were conducted at the ambient temperatures and data obtained for the weldments were compared with the base metals. The room temperature tensile tests showed the failure from the region of the P92 BM or the interface of P92 BM/weld metal, with joint strength of 646 ± 6 MPa and 747 ± 4 MPa in AW conditions for V groove and narrow groove, respectively. The Charpy impact test (CIT) also showed the variation in impact toughness along the weldments, and the ERNiCrMo-3 filler weld was identified as the weakest region of the welded joint in terms of impact toughness for both the groove designs. The residual stress variation along the thickness of the weld plate was measured using the deep hole drilling (DHT) methods, and the results indicated the peak magnitude of the residual stress for the V groove welded joint. The test results indicated that welded joint produced using ERNiCrMo-3 filler was safe for AUSC power plants' boiler applications for both the groove weld while optimum mechanical properties were measured for narrow groove weld.

9

A theoretical analysis of vibrational stress relief in AISI 1008 as a mechanical treatment

84%

Vardanjani M. J. , Senkara J.

Archive of Mechanical Engineering

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2021

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tom LXVIII, nr 4

353--374

EN

Vibrational stress relief (VSR) treatment as a method of stress relief is currently performed on different alloys and sizes as an appropriate alternative for thermal stress relief (TSR) method. Although many studies have been performed to extend the knowledge about this process, analytical studies in the field of VSR process seems to require wider efforts to introduce the concept more clearly and extensively. In this study, a theoretical model is proposed based on an analytical equation. The proposed equation was modified in terms of required variables including frequency, amplitude, and vibration duration to encompass more practical parameters compared to the previous models. Thus, essential VSR parameters including the number of cycles as a representative of treatment duration, strain rate as a representative of frequency, and the amplitude were embedded in the model to make it comprehensively practical. Experimental tests were also performed and residual stress distribution was measured by X-ray diffractometry (XRD) method for certain points to compare the experimental results with the theoretical output. An acceptable range of conformation was observed between theoretical and experimental results.

10

Study on effect of weld groove geometry on mechanical behavior and residual stresses variation in dissimilar welds of P92/SS304L steel for USC boilers

67%

Dak G. , Pandey C.

Archives of Civil and Mechanical Engineering

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2022

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tom Vol. 22, no. 3

art. no. e140

EN

This research article reports the correlation between microstructure, mechanical properties, and residual stresses of dissimilar weld joints (DWJs) between P92 martensitic steel and 304L austenitic stainless steel (ASS). The groove geometry plays a vital role in DWJs. Thus the effect of groove geometry on mechanical and microstructural properties was also investigated. The V-shape and narrow shape groove profile were implemented for P92/304L SS DWJs. The microstructural characteristic, tensile strength, micro-hardness, Charpy impact toughness and residual stresses were evaluated for both the groove geometry in as-weld (AW) and post-weld heat treatment (PWHT) (760 °C, 2 h) state. Microstructural observations performed using an optical microscope (OM), and scanning electron microscope (SEM) showed that high temperature during the weld thermal cycle leads to the formation of the coarse grain heat-affected zone (CGHAZ), fine grain HAZ (FGHAZ), and inter-critical HAZ (ICHAZ) across the P92 HAZ. The ERNiFeCr-2 (Inconel 718) welding consumable wire (filler rod) of diameter 2.4 mm was used for this investigation. The ERNiFeCr-2 weld fusion zone showed a fully austenitic microstructure with the formation of the secondary phases due to the solidification segregation. The EDS and SEM area mapping results indicated that the secondary phases in the inter-dendritic region contain a higher amount of the Mo and Nb than the matrix region. The ultimate tensile strength (UTS) of the as-weld and PWHT tensile specimen of the P92/304L SS DWJs was 630 and 621 MPa, respectively, for V-groove geometry specimens and 620 and 629 MPa, respectively, for narrow groove geometry specimens. The tensile fracture was experienced at the interface between weld metal and 304L base metal, and the UTS value of DWJs was very close to the UTS of the 304L SS. The abrupt variation in the micro-hardness value of the CGHAZ (456HV0.5), FGHAZ (375HV0.5), and ICHAZ (221HV0.5) was noticed in the as-weld state due to their distinguish microstructure characteristics. After PWHT, the micro-hardness value of the CGHAZ (255HV0.5), FGHAZ (236HV0.5), and ICHAZ (207HV0.5) was below the maximum allowable value of 265HV0.5 for P92 material because of the tempering of the martensite. The Charpy impact test indicated that the ERNiFeCr-2 weld fusion zone has a low toughness value of 33 J (AW) and 25 J (PWHT) for V-groove design and 35 J (AW) and 28 J (PWHT) for narrow groove design than that of the P92 and 304L parent metal. The impact toughness of the ERNiFeCr-2 filler weld was below the minimum requirement of 47 J (EN ISO 3580:2017). The tensile residual stresses were generated in the weld fusion zone due to the volumetric contraction during the solidification. The residual stresses developed in the case of the narrow groove design were less than that for the V-groove design due to the less quantity of weld metal available for volumetric contraction in the case of the narrow groove geometry. From comparing mechanical and microstructural properties obtained for V-groove and narrow groove geometry DWJs, it was found that narrow groove design reduces the overall heat affected zone span, and it requires less welding time and less heat input.