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 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 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 Composite Material Damage Processes

2020 ◽  
Vol 3 (3) ◽  
pp. 307-323
Author(s):  
Davor Bolf ◽  
Albert Zamarin ◽  
Robert Basan
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Material Structure ◽  
Material Damage ◽  
Shipbuilding Industry ◽  
Vast Number ◽  
Damage And Fracture ◽  
Control Procedures ◽  
Material Fracture ◽  
Damage Processes

Composite materials are in use in the shipbuilding industry for a long period of time. Composites appear in vast number of fibre – matrix combinations and can be produced with several different production processes. Due to the specific nature of the composite material structure, the selection of the production process and the limitations in the quality control procedures, composite materials will always be subject to defects and imperfections which may, under certain circumstances, lead to the appearance and propagation of cracks. The size and the shape of the crack, the load type and the stress field in the material surrounding the crack will be crucial for crack growth and crack propagation. This paper reviews the composite material damage processes especially relevant for shipbuilding. The basic principles of composite material fracture mechanics are briefly explained, and finally, mechanisms responsible for the development of damage and fracture of composite materials are presented. This paper has emerged from the need to summarize information about composite material fracture and failure mechanisms and modes relevant for the shipbuilding industry.

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.

Failure Analysis of 12 Inch Pipeline Riser

2014 ◽  
Author(s):  
Frank Gareau ◽  
Alex Tatarov
Keyword(s):  
Internal Surface ◽  
Fracture Initiation ◽  
Slag Inclusion ◽  
Ground Movement ◽  
Simultaneous Action ◽  
Additional Stress ◽  
Contributing Factors ◽  
Element Analysis ◽  
Material Fracture ◽  
Corrosion Pits

A rupture and an explosion occurred on a 12.75 inch OD high pressure gas pipeline after 40 years in service. The force of the explosion broke the riser off and sent two large pieces of the riser flying into the surrounding forest. The failure occurred as a result of the simultaneous action of several contributing factors: • The weld had a non-specified profile (a step) and contained a large slag inclusion at the location of fracture initiation. • Corrosion pits were growing from the internal surface close to the weld root. • Dewpoint corrosion took place on the internal surface of the riser close to massive flanges. • The dehydrator at the compressor station was not removing the target amount of moisture. • Low temperatures contributed to the failure by decreasing material fracture toughness. • Ground movement could have created additional stress required for the failure to occur. Several of the above listed factors (pitting corrosion, ground movement, malfunctioning of the dehydrator) developed with time, which explains the delayed mode of failure. The conclusions were supported by Finite Element Analysis and Fracture Mechanics calculations.

scholarly journals Novel Damage Calibration Test Based on Cross-Wedge Rolling

2021 ◽  
Author(s):  
Zbigniew Pater ◽  
Janusz Tomczak ◽  
Tomasz Bulzak ◽  
Patrycja Walczuk-Gągała
Keyword(s):  
Cross Wedge Rolling ◽  
Calibration Test

Role of Ozone in Dynamic Cut Growth of Rubber

1966 ◽  
Vol 39 (4) ◽  
pp. 1053-1064
Author(s):  
G. J. Lake ◽  
P. B. Lindley
Keyword(s):  
Natural Rubber ◽  
Test Piece ◽  
Critical Value ◽  
Rate Of Growth ◽  
Tearing Energy

Abstract The effect of ozone on the growth of cuts in rubber strips subjected to repeated tensile deformations has been investigated. At tearing energies below a critical value ozone accounts for all the cut growth, and in this region the rate of growth is substantially independent of tearing energy. At higher tearing energies, cut growth also occurs due to mechanico-oxidative rupture, the rate of this type of growth increasing rapidly with increasing tearing energy so that the effects of ozone are normally slight. For vulcanizates of natural rubber and SBR unprotected by anti-ozonant, the characteristics of dynamic ozone cut growth can be deduced from static measurements. If a natural rubber test piece is not allowed to relax to zero strain on each cycle, the effects of ozone are important over a wider range of tearing energy.

Fracture Finite Element Analysis for Roll Forming of U Section Parts of TRIP 600 Steel

2012 ◽  
Vol 249-250 ◽  
pp. 874-880 ◽  
Author(s):  
Yan Zhi Guan ◽  
Qiang Li ◽  
Yu Yan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Damage Evolution ◽  
Fracture Initiation ◽  
Roll Forming ◽  
Element Analysis ◽  
Material Fracture ◽  
Set Up ◽  
Explicit Dynamic ◽  
The Relationship

By applying the shear damage criteria, facture occurrence for roll forming of U Section parts of TRIP 600 steel is analyzed with nonlinear finite element. In accordance with the maximum value of steel sheet of plastic strains for the fracture initiation and with the application of the element deletion technology of the ductile fracture, the calculation of the damage evolution parameters of the material fracture is successfully set up. By applying the explicit dynamic solution method, the fracture finite element analysis of TRIP600U type section roll forming is realized, and the relationship among the stress, strain, energy density as well as damage evolution and material fracture is obtained.

scholarly journals Ductile Fracture Prediction in Cross-Wedge Rolling of Rail Axles

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6638
Author(s):  
Tomasz Bulzak
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Effective Strain ◽  
Thermal Conditions ◽  
Ductile Fracture Criterion ◽  
Fracture Criteria ◽  
Cross Wedge Rolling ◽  
Fracture Force ◽  
Advantages And Disadvantages ◽  
Material Fracture

In the process of cross-wedge rolling, axial-symmetric forgings are formed using wedge tools. These tools may be flat- or roll-shaped. This article presents two methods of cross-wedge rolling of rail axles, traditional and multi-wedge, as well as their advantages and disadvantages. Two cross-wedge rolling processes are modelled numerically using Simufact Forming. Numerical results are then verified by experiments performed on a flat wedge rolling mill. Results obtained with the two rolling methods are compared in terms of material fracture, force parameters, effective strain and thermal conditions during rolling. Results show that material fracture poses a serious problem in these rolling processes. It is found that the Cockcroft–Latham ductile fracture criterion does not predict material fracture correctly. Results demonstrate that the fracture of railway axles in cross-wedge rolling can be best predicted by the fracture criteria developed by Ayada, Brozzo, Ko, Rice and Tracey.

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