scholarly journals Experimental and Numerical Investigations of the Development of Residual Stresses in Thermo-Mechanically Processed Cr-Alloyed Steel 1.3505

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 480 ◽  
Author(s):  
Bernd-Arno Behrens ◽  
Jörg Schröder ◽  
Dominik Brands ◽  
Lisa Scheunemann ◽  
Rainer Niekamp ◽  
...  

Residual stresses in components are a central issue in almost every manufacturing process, as they influence the performance of the final part. Regarding hot forming processes, there is a great potential for defining a targeted residual stress state, as many adjustment parameters, such as deformation state or temperature profile, are available that influence residual stresses. To ensure appropriate numerical modeling of residual stresses in hot forming processes, comprehensive material characterization and suitable multiscale Finite Element (FE) simulations are required. In this paper, experimental and numerical investigations of thermo-mechanically processed steel alloy 1.3505 (DIN 100Cr6) are presented that serve as a basis for further optimization of numerically modeled residual stresses. For this purpose, cylindrical upsetting tests at high temperature with subsequently cooling of the parts in the media air or water are carried out. Additionally, the process is simulated on the macroscale and compared to the results based on the experimental investigations. Therefore, the experimentally processed specimens are examined regarding the resulting microstructure, distortions, and residual stresses. For the investigation on a smaller scale, a numerical model is set up based on the state-data of the macroscopic simulation and experiments, simulating the transformation of the microstructure using phase-field theory and FE analysis on micro- and meso-scopic level.

2011 ◽  
Vol 681 ◽  
pp. 133-138 ◽  
Author(s):  
Wulf Pfeiffer ◽  
Christof Koplin ◽  
Eduard Reisacher ◽  
Johannes Wenzel

Experimental and numerical investigations have been performed on the relationships between coating parameters, residual stresses, micro-cracks and the near surface strength of electrochemically deposited hard chromium coatings. The experimental investigations included: X-ray measurements of residual and externally-applied stresses; crack density measurements using microscopy; and load-bearing measurements using ball-on-plate tests. The numerical investigations in combination with analytical conclusions focused on the influence of different crack lengths and densities on the effective elastic modulus of the chromium coating and the stress-enhancing or shielding effect of micro-crack networks respectively. The results show that the residual stresses and crack networks are influenced by the current density used during deposition. Coatings with high tensile residual stresses have low crack densities. This correlation is associated with stress relaxation by formation of micro-cracks and, to a lesser extent, to a direct reduction in residual stresses due to the deposition process. The load bearing capacity is dominated by the crack density and can be significantly increased by shot-peening-induced compressive residual stresses. Thus, optimization of hard chromium deposition parameters for applications needing high surface strength should predominantly focus on minimizing the crack density.


Author(s):  
Christian Steinfelder ◽  
Johann Acksteiner ◽  
Christina Guilleaume ◽  
Alexander Brosius

AbstractClinching is a joining process that is becoming more and more important in industry due to the increasing use of multi-material designs. Despite the already widespread use of the process, there is still a need for research to understand the mechanisms and design of clinched joints. In contrast to the tool parameters, process and material disturbances have not yet been investigated to a relatively large extent. However, these also have a great influence on the properties and applicability of clinching. The effect of process disturbances on the clinched joint are investigated with numerical and experimental methods. The investigated process variations are the history of the sheets using the pre-hardening of the material, different sheet thicknesses, sheet arrangements and punch strokes. For the consideration of the material history, a specimen geometry for pre-stretching specimens in uniaxial tension is used, from which the pre-stretched secondary specimens are taken. A finite element model is set up for the numerical investigations. Suitable clinching tools are selected. With the simulation, selected process influences can be examined. The effort of the numerical investigations is considerably reduced with the help of a statistical experimental design according to Taguchi. To confirm the simulation results, experimental investigations of the clinch point geometry by using micrographs and the shear strength of the clinched joint are performed. The analysis of the influence of difference disturbance factors on the clinching process demonstrate the importance of the holistic view of the clinching process.


2016 ◽  
Vol 2 (2) ◽  
pp. 129
Author(s):  
Urtak Hamiti

Barbaric, savage, horrific-these were terms to define the decision of the Islamic State of Iraq and Syria (ISIS) to murder its captured Jordanian pilot by burning him alive inspired a thesaurus of horror and revulsion. The men who did it, the perpetrators were described by the media as mad men, thugs, monsters. To most of the people, the act itself seemed inexplicable and without sense. However, behind the choreographed and videotaped violence lies a calculated horrible cold logic. Although, ISIS is often portrait as a mighty force on the ground in Syria and Iraq, facts state that they control mainly communications between various provinces in both countries, and, as most guerrilla armies, are militarily weak by conventional measure. ISIS has little or almost none defense against the bombing campaign that is facing now, while US has formed a coalition that is confronting them on the ground as well, after President Barack Obama published the “New Security Doctrine” which includes degrading and finally destroying ISIS. ISIS, however, have proven to be very organized in promoting dramatic acts of violence against their enemies and promoting them two achieve two goals: use terror tactics as a psychological weapon against all those facing them and all those that are to face them in combat. Secondly, through usage of social network platforms to promote killings and executions, the aim of ISIS is to encourage recruits from out of Syria and Iraq, and elsewhere, to join them in their cause. Online operations of ISIS fall under a production group called the Al Hayat Media Center. The Center was created to seduce Westerners into joining the ranks of ISIS and also to distribute propaganda through social and media platforms. It is difficult to assess the success of this operation, but solid sources provided by US military and intelligence estimate that at least 300 Americans are fighting in the ranks of ISIS (at least two Americans have been killed fighting for ISIS in Iraq/Syria region) while the number of Europeans is in thousands. The US Response to this psychological kind of warfare came when President Barack Obama established the Center for Strategic Counterterrorism Communications (CSCC) aiming to combat terrorist propaganda. The main strategy of CSCC is not directly to confront ISIS operatives, but rather than that to deal with the people they are trying to recruit. Now, with almost entire international public opinion on their side, it is time for US to more actively respond to ISIS especially in the manner of psychological warfare since it is obvious that operations of “winning hearts and minds” of people in Iraq and Syria are not enough compared to ruthless tactics of ISIS which “winning hearts and minds” by brute force, terror, and vivid violent images. The online propaganda war is a new component to conflicts of 21st century that allows enemies to reach one another’s home fronts directly. ISIS might seem not so strong on the ground but it has captured one fundamental flaw of the media of 21st century-the one that bad news is always good news and that televised violence will always have an audience. ISIS has proclaimed that its goal is to create a caliphate of 21st century but its psychological warfare and propaganda is inspiring individuals throughout the West to commit horrible terrorist crimes. Could this be another mind game set up by ISIS, it remains to be seen. However one thing is for certain, US and its allies must tackle ISIS not only by planes and other military means, but also by a strategy that would eliminate its influence in spreading their propaganda.


2007 ◽  
Vol 329 ◽  
pp. 761-766 ◽  
Author(s):  
Y. Zhang ◽  
Masato Yoshioka ◽  
Shin-Ichiro Hira

At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.


Author(s):  
Stefan Schmid ◽  
Rudi Kulenovic ◽  
Eckart Laurien

For the validation of empirical models to calculate leakage flow rates in through-wall cracks of piping, reliable experimental data are essential. In this context, the Leakage Flow (LF) test rig was built up at the IKE for measurements of leakage flow rates with reduced pressure (maximum 1 MPA) and temperature (maximum 170 °C) compared to real plant conditions. The design of the test rig enables experimental investigations of through-wall cracks with different geometries and orientations by means of circular blank sheets with integrated cracks which are installed in the tubular test section of the test rig. In the paper, the experimental LF set-up and used measurement techniques are explained in detail. Furthermore, first leakage flow measurement results for one through-wall crack geometry and different imposed fluid pressures at ambient temperature conditions are presented and discussed. As an additional aspect the experimental data are used for the determination of the flow resistance of the investigated leak channel. Finally, the experimental results are compared with numerical results of WinLeck calculations to prove specifically in WinLeck implemented numerical models.


Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2077
Author(s):  
Oliver Zeman ◽  
Michael Schwenn ◽  
Martin Granig ◽  
Konrad Bergmeister

The assessment of already installed anchorages for a possible exceeding of the service load level is a question that is gaining more and more importance, especially in building maintenance. Bonded anchors are of particular interest here, as the detection of a capacity reduction or load exceedance can cause damage to the concrete-bonded mortar behavior. This article investigates the extent to which ultrasonic methods can be used to make a prediction about the condition of anchorages in concrete and about their load history. A promising innovative assessment method has been developed. The challenges in carrying out the experimental investigations are the arrangement of the transducers, the design of the test set-up and the applicability of direct, indirect or semidirect ultrasonic transmission. The experimental investigations carried out on a test concrete mix and a bonded anchor system show that damage to the concrete structure can be detected by means of ultrasound. The results indicate the formation of cracks and therefore a weakening of the response determined by means of direct, indirect and semidirect ultrasonic transmission. However, for application under non-laboratory conditions and on anchors with unknown load history, the calibration with a reference anchor and the identification of the maximum load is required. This enables a referencing of the other loaded anchors to the unloaded conditions and allows an estimation of the load history of individual anchors.


Author(s):  
Efim I. Pivovar ◽  

The article covers the activities of the Association called Business Centre for Economic Development of the Commonwealth of Independent States. The author examines in detail the twenty-year history of this organisation, its creation, goals and objectives, features of the structure, participants and partners, and the formation of competence areas. The article emphasises that over the years of its existence, the Association has become an important and effective platform for interaction among business structures, industry associations, banking and financial institutions, entrepreneurs, the expert and scientific community as well as the media of the Commonwealth countries. Considering the Association’s key areas and forms of activity the author highlights the annual International Economic Forums involving business leaders of the Commonwealth member states, which contribute to the strengthening and development of multilateral economic relations in the post-Soviet space. The article examines in great detail the work of each Forum, its participants (both individuals and legal entities), the topics of discussions and speeches of individual speakers from various Commonwealth countries, which, in the author’s opinion, are of crucial importance for the activities of the Association called Business Centre for Economic Development of the Commonwealth of Independent States and the entire Commonwealth, as well as for the development of Eurasian integration. In addition, the article focuses on the final documents of the Forums: the author studies their main provisions with the set up in them goals, tasks, proposals and priorities.


2022 ◽  
Vol 327 ◽  
pp. 272-278
Author(s):  
Elisa Fracchia ◽  
Federico Simone Gobber ◽  
Claudio Mus ◽  
Yuji Kobayashi ◽  
Mario Rosso

Nowadays, one of the most crucial focus in the aluminium-foundry sector is the production of high-quality castings. Mainly, High-Pressure Die Casting (HPDC) is broadly adopted, since by this process is possible to realize aluminium castings with thin walls and high specific mechanical properties. On the other hand, this casting process may cause tensile states into the castings, namely residual stresses. Residual stresses may strongly affect the life of the product causing premature failure of the casting. Various methods can assess these tensile states, but the non-destructive X-Ray method is the most commonly adopted. Namely, in this work, the residual stress analysis has been performed through Sinto-Pulstec μ-X360s. Detailed measurements have been done on powertrain components realized in aluminium alloy EN AC 46000 through HPDC processes to understand and prevent dangerous residual stress state into the aluminium castings. Furthermore, a comparison with stresses induced by Rheocasting processes is underway. In fact, it is well known that Semi-Solid metal forming combines the advantages of casting and forging, solving safety and environmental problems and possibly even the residual stress state can be positively affected.


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