scholarly journals Prediction of Crack Formation for Cross Wedge Rolling of Harrow Tooth Preform

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2287 ◽  
Author(s):  
Zbigniew Pater ◽  
Janusz Tomczak ◽  
Tomasz Bulzak ◽  
Jarosław Bartnicki ◽  
Arkadiusz Tofil
Keyword(s):  
Crack Formation ◽  
Experimental Testing ◽  
Critical Value ◽  
Cross Wedge Rolling ◽  
Laboratory Conditions ◽  
University Of Technology ◽  
Material Fracture ◽  
Damage Criteria

The article presents the issue of material fracture during the process of cross-wedge rolling (CWR). The object of the research was the process of forming a harrow tooth preform. In the conducted analysis nine damage criteria were applied. The critical value of damage was determined with a new calibrating test, basing on rotational compression of a sample in a channel. The results of calculations were compared to the results of experimental testing performed in laboratory conditions in Lublin University of Technology. On the basis of the obtained results an assessment of the applied damage criteria and their applicability in the analysis of CWR processes was conducted.

scholarly journals Determination of the Critical Value of Material Damage in a Cross Wedge Rolling Test

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1586
Author(s):  
Zbigniew Pater ◽  
Andrzej Gontarz ◽  
Janusz Tomczak ◽  
Tomasz Bulzak ◽  
Łukasz Wójcik
Keyword(s):  
Test Piece ◽  
Finite Element Method Simulation ◽  
Fracture Initiation ◽  
Critical Value ◽  
Material Damage ◽  
Cross Wedge Rolling ◽  
Calibration Test ◽  
Axial Crack ◽  
Material Fracture ◽  
Critical Damage

This study investigates the problem of material fracture in cross wedge rolling (CWR). It was found that this problem could be analysed by means of well-known phenomenological criteria of fracture that are implemented in commercial FEM (Finite Element Method) simulation programs for forming processes. The accuracy of predicting material fracture depends on the critical damage value that is determined by calibration tests in which the modelled and real stresses must be in good agreement. To improve this accuracy, a new calibration test is proposed. The test is based on the CWR process. Owing to the shape of the tools and test piece used in CWR, the forming conditions in this process deteriorate with the distance from the centre of the test piece, which at a certain moment leads to fracture initiation. Knowing the location of axial crack initiation in the specimen, it is possible to determine the critical value of material damage via numerical simulation. The new calibration test is used to determine the critical damage of 42CrMo4 steel subjected to forming in the temperature range of 900–1100 °C. In addition, 12 criteria of ductile fracture are employed in the study. The results show that the critical damage significantly increases with the temperature.

scholarly journals Rotational Compression of Cylindrical Specimen As a New Calibrating Test for Damage Criteria

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 740 ◽  
Author(s):  
Zbigniew Pater ◽  
Janusz Tomczak ◽  
Tomasz Bulzak ◽  
Łukasz Wójcik ◽  
Patrycja Walczuk-Gągała
Keyword(s):  
Accurate Determination ◽  
Cylindrical Sample ◽  
Damage Function ◽  
Actual Process ◽  
Limit Values ◽  
University Of Technology ◽  
Fracture Damage ◽  
Material Fracture ◽  
Fracture Of Materials ◽  
Damage Criteria

The subject-matter of the article is the ductile fracture of materials—A phenomenon occurring in numerous metal forming processes. In order to prognosticate the possibility of a fracture, damage criteria are employed. Their effectiveness, however, depends on the accurate determination of the critical values of damage. These values are obtained through calibrating tests, where the stress state has to be as similar to the actual process as possible. The currently employed calibrating tests do not enable one to determine the limit values of the damage function when the Mannesmann effect occurs. Therefore it was not possible to effectively prognosticate the material fracture in the processes of cross- and skew-rolling. A new calibrating test, based on rotational compression of a cylindrical sample, in which the fractures are caused by the Mannesmann effect, was developed at the Lublin University of Technology. This test was discussed in the article, with a particular focus on the stress and strain state in the sample. A practical use of the test was presented on the example of C45 grade steel, formed in the temperature equal 1150 °C. In the research ten material damage criteria were adopted.

Cross-Wedge Rolling of Driving Shaft from Titanium Alloy Ti6Al4V

2016 ◽  
Vol 687 ◽  
pp. 125-132 ◽  
Author(s):  
Zbigniew Pater ◽  
Tomasz Bulzak ◽  
Janusz Tomczak
Keyword(s):  
Titanium Alloy ◽  
Numerical Analysis ◽  
Process Parameters ◽  
Axial Symmetry ◽  
Cross Wedge Rolling ◽  
University Of Technology ◽  
The Subject ◽  
Titanium Alloy Ti6al4v ◽  
Rolling Technology ◽  
Made In

This paper deals with the issue of the helicopter SW4 rear gear driving shaft forming. It was assumed that this shaft will be made from titanium alloy Ti6Al4V and it will be formed by means of cross-wedge rolling technology (CWR). It was also assumed that rolling will be realized in double configuration, which will guarantee axial symmetry of forming forces. The conception of tools guaranteeing the CWR process realization and numerical analysis results verifying the assumed CWR process parameters of the subject shaft were presented. Tests of shaft rolling in laboratory conditions at Lublin University of Technology were made, in the result of which the possibility of forming by means of CWR of a driving shaft, manufactured from titanium alloy Ti6Al4V, of the helicopter SW4 rear gear was verified.

scholarly journals Determination of the critical value of damage in a channel-die rotational compression test

2019 ◽  
Vol 13 (6) ◽  
pp. 993-1002
Author(s):  
Z. Pater ◽  
J. Tomczak ◽  
T. Bulzak ◽  
Ł. Wójcik ◽  
P. Walczuk
Keyword(s):  
Finite Element Method ◽  
Critical Value ◽  
Material Damage ◽  
The Finite Element Method ◽  
Axial Zone ◽  
Compression Process ◽  
Skew Rolling ◽  
Damage Criteria ◽  
Critical Damage

AbstractThis article describes the problems involved in modelling material cracking in skew rolling processes. The use of the popular damage criteria is impossible because of the lack of a calibration test that would make it possible to determine the critical value of material damage under conditions similar to those found in skew rolling. To fill this gap, a test called channel-die rotational compression was proposed. It consisted of rolling a disk-shaped specimen in a cavity created by two channels of cooperating tools (flat dies), which had heights smaller than the diameter of the specimen. When the rolling path was sufficiently long, a crack formed in the axial zone of the specimen. In this test, modelling using the finite element method made it possible to determine the critical values of material damage. As an illustration, the test was used to determine the critical damage value when conducting a rotational compression process on 50HS steel (1.5026) specimens formed in the temperature range of 950–1200 °C. The analysis was conducted using the Cockcroft–Latham damage criterion.

scholarly journals Assessment of Skid Resistance of Asphalt Mixtures in Laboratory Conditions

2012 ◽  
Vol 58 (4) ◽  
pp. 521-534 ◽  
Author(s):  
W. Gardziejczyk ◽  
M. Wasilewska
Keyword(s):  
Asphalt Concrete ◽  
Laboratory Tests ◽  
Asphalt Mixtures ◽  
Road Surface ◽  
Skid Resistance ◽  
Mastic Asphalt ◽  
Laboratory Conditions ◽  
University Of Technology ◽  
Road Surfaces ◽  
Stone Mastic Asphalt

AbstractThe aggregate applied for the wearing course has a significant influence on skid resistance of road surfaces. However, it is difficult to evaluate the behaviour of road surface in use on the basis of the Polished Stone Value (PSV) determined for the aggregate according to the so called ‘British method’. The British method, which is currently used in many countries, does not allow to determine the influence of neither the grain size of the aggregate nor the type of the wearing course on skid resistance of road surface. The present paper suggests a method for evaluation of the British Pendulum Number (BPN) for road surfaces in laboratory conditions. The authors assumed the BPN for polished slabs, made from asphalt mixtures, as the criterion. The index was measured with the British Pendulum Tester. The simulation of the process was conducted on research stand (called slab polisher) built at Bialystok University of Technology (BUT). The results of laboratory tests indicate that surfaces from asphalt concrete (AC) have slightly higher values of BPN in comparison with the values determined for surfaces made from stone mastic asphalt (SMA).

A rotary compression test for determining the critical value of the Cockcroft–Latham criterion for R260 steel

2019 ◽  
Vol 29 (6) ◽  
pp. 874-886 ◽  
Author(s):  
Tomasz Bulzak ◽  
Zbigniew Pater ◽  
Janusz Tomczak ◽  
Łukasz Wójcik
Keyword(s):  
Numerical Modeling ◽  
Compression Test ◽  
Experimental Tests ◽  
Critical Value ◽  
Cross Wedge Rolling ◽  
Damage Criterion ◽  
Second Stage ◽  
State Of Stress ◽  
The Moment ◽  
Two Stages

A method for determining the critical value of the Cockcroft–Latham damage criterion is presented using the example of R260 railway steel. The determinations were performed using a rotary compression test specially developed for that purpose. The main object of the proposed test was to provide the best possible representation of the state of stress generated by cross-wedge rolling. The rotary compression test was performed in two stages: in the first stage, experimental tests were conducted to establish the moment of cracking of the specimen, and in the second stage, numerical modeling was used to determine the critical value of the Cockcroft–Latham criterion for the experimentally established cracking moment. The critical value of the Cockcroft–Latham criterion was determined under hot forming conditions.

Cladding of Wear-Resistant Layers in Metallurgy and Engineering

2016 ◽  
Vol 862 ◽  
pp. 41-48
Author(s):  
Ján Viňáš ◽  
Miroslav Greš ◽  
Tomáš Vaško
Keyword(s):  
Arc Welding ◽  
Experimental Testing ◽  
Gas Metal Arc Welding ◽  
Metallographic Analysis ◽  
Cored Wire ◽  
Laboratory Conditions ◽  
Metal Arc Welding ◽  
The Impact ◽  
Welding Processes ◽  
Cladding Layers

The paper presents the application of weld layers used in renovations of functional surfaces of components that are exposed to several tribodegradation factors in operation of metallurgical and engineering industries. Surfaces of selected components are renovated using arc welding processes, namely: (MMAW) Manual Metal Arc Welding, (SAW) Submerged Arc Welding methods, (GMAW) Gas metal arc welding and (FCAW) Flux cored wire metal arc welding without gas shield. Claddings were made always three-layered directly on the surfaces of renovated components using dedicated cladding machines in operations and laboratory conditions respectively. Their quality was assessed using non-destructive tests, namely (VT) visual testing by STN EN ISO 17637 and (UT) Ultrasonic testing STN EN ISO 11666. Within the destructive tests the quality of claddings was evaluated using the metallographic analysis conducted on a light microscope Olympus BX and electron microscope Jeol where the impact of mixing the weld metal as well as heat treatment after cladding on the final structure of claddings was observed. Using the Shimadzu HMV 2 device the microhardness of cladding layers was evaluated on metallographic samples by STN EN ISO 9015-2. In laboratory conditions the resistance of cladding layers to abrasive wear was verified on the device Di-1. Experimental testing of the claddings confirmed that the selected additives and cladding parameters witting individual technology were chosen correctly as in cladding layers no presence of internal defects was observed.

AN ATTEMPT AT IDENTIFYING THE INFLUENCE OF TEST HEAD ASSEMBLY STIFFNESS ON THE RESULTS OF A TRIBOLOGICAL EXPERIMENT CONDUCTED UNDER MICRO-OSCILLATION CONDITIONS

Tribologia ◽  
2016 ◽  
Vol 268 (4) ◽  
pp. 79-89
Author(s):  
Rafał GAWARKIEWICZ
Keyword(s):  
Computer Simulation ◽  
Finite Elements ◽  
Computer Model ◽  
Experimental Testing ◽  
Reciprocating Motion ◽  
Test Rig ◽  
Full Control ◽  
University Of Technology ◽  
Bearing Materials ◽  
Head Assembly

The outcome of experimental research on a group of dry bearing materials carried out under small oscillation conditions and using a test rig designed and made at Gdansk University of Technology inspired the decision to find out if the stiffness of test head elements influenced the generated results. Therefore, a computer model utilising finite elements was devised and used to simulate the workings of the test head. The model enabled full control of the head’s geometry, and loading and boundary conditions at every stage of simulation. Moreover, the simulation includes the preparation of test head elements, fixings, and the specimen loading, and executes the displacement of the counter-face during full-cycle reciprocating motion. Finally, the results of computer simulation are compared with those produced by experimental testing.

Innovative Metal Forming Techniques Developed at the Lublin University of Technology

2015 ◽  
Vol 237 ◽  
pp. 209-214 ◽  
Author(s):  
Zbigniew Pater ◽  
Janusz Tomczak ◽  
Tomasz Bulzak
Keyword(s):  
Metal Forming ◽  
Light Metal ◽  
Metal Alloys ◽  
Cross Wedge Rolling ◽  
University Of Technology ◽  
Innovative Techniques

This study presents innovative metal forming techniques that have been developed at the Lublin University of Technology in Lublin, Poland, including rotary compression, cross wedge rolling and roll forging. Dozens of Polish patents and several European patents have been granted for inventions based on the use of the above forming techniques. This study gives an overview of applications of these innovative techniques for producing stepped axes and shafts (including hollow and gear shafts) that are made of steel and light metal alloys (aluminium, titanium). It also presents prototype machines for forming metals and metal alloys.

scholarly journals A New Methodology for Predicting Brittle Fracture of Plastically Deformable Materials: Application to a Cold Shell Nosing Process

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1593
Author(s):  
Jae Gun Eom ◽  
Sang Woon Byun ◽  
Seung Won Jeong ◽  
Wan Jin Chung ◽  
Man Soo Joun
Keyword(s):  
Brittle Fracture ◽  
Bauschinger Effect ◽  
Effective Strain ◽  
Critical Value ◽  
Quantitative Agreement ◽  
Maximum Principal Stress ◽  
Traditional Theory ◽  
Brittle Fractures ◽  
Deformable Materials ◽  
Damage Criteria

The traditional theory of ductile fracture has limitations for predicting crack generation during a cold shell nosing process. Various damage criteria are employed to explain fracture and failure in the nose part of a cold shell. In this study, differences in microstructure among fractured materials and analysis of their surfaces indicated the occurrence of brittle fractures. The degree of “plastic deformation-induced embrittlement” (PDIE) of plastically deformable materials affects the likelihood of brittle fractures; PDIE can also decrease the strength in tension due to the Bauschinger effect. Two indicators of brittle fracture are presented, i.e., the critical value of PDIE and the allowable tensile strength (which in turn depends on the degree of PDIE or embrittlement-effective strain). When the maximum principal stress is greater than the latter and the PDIE is greater than the former, our method determines the likelihood of brittle fracture. This approach was applied to an actual cold shell nosing process, and the predictions were in good quantitative agreement with the experimental results.

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