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1
Content available Deformation failure analysis and identification method of zoning type of actual tunnel surrounding rock
Jing Wei, Gao Yunlong, Jin Rencai, Jing Laiwang
Archives of Civil Engineering
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2023
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Vol. 69, nr 4
549--571
EN
The research on deformation zoning mechanism of tunnel surrounding rock is of great significance for ensuring safe production and disaster prevention in coal mines. However, the traditional deformation zoning theory of tunnel surrounding rock uses the ideal strain softening model as the criterion for judging the zoning type of all tunnel surrounding rock, ignoring the difference between the deformation zoning type of a specific actual tunnel and the basic zoning type of surrounding rock. In order to study the method for determining the actual deformation zoning type of tunnel surrounding rock, the formation mechanism of the actual deformation zoning of tunnel surrounding rock has been revealed. Combined with engineering examples, a method for determining the actual deformation zoning type and boundary stress of specific tunnel surrounding rock has been proposed. The results show that the boundary stress and position of the actual deformation zone are determined by the peak strength fitting line, residual strength fitting line, support strength line, and the position of the circumferential and radial stress relationship lines of each deformation zone. The actual boundary stress of each zone of tunnel surrounding rock is ultimately only related to the basic mechanical properties of the tunnel surrounding rock and the in-situ stress field. The research results can provide reference for disaster management of underground engineering, stability evaluation of surrounding rock, and support scheme design.
2
Content available remote A review on the deformation mechanism and formability enhancement strategies in incremental sheet forming
Ullah Sattar, Li Yanle, Li Xiaoqiang, Xu Peng, Li Dongsheng
Archives of Civil and Mechanical Engineering
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2023
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Vol. 23, no. 1
art. no. e55, 2023
EN
The process formability of incremental sheet forming (ISF) is better than the conventional forming processes. Stretching, through-thickness-shear, bending-under-tension (BUT), and compressive forces are the proposed deformation mechanisms for improved formability; however, researchers have not corroborated (on consensus) the relative significance of any one among these. Similarly, researchers observed abrupt fractures (brittle fracture) and fractures preceded by necking (ductile fracture) for different case studies, which initiated a new debate and is still unanswered. Besides, researchers have extended the ISF to energy-assisted ISF to improve the process formability further for materials having a high strength-to-weight ratio. Three prominent energy-assisted ISF are (a) Electric-assisted ISF (E-ISF) works on the principle of lowering the yield stress by raising the temperature and has shown promise for Magnesium and Titanium alloy. (b) The ultrasonic vibration-assisted (UV-ISF) process works on the principle of acoustoplastic softening effect and thus far improved the room temperature material formability while reducing the forming forces. (c) Electromagnetic-assisted ISF (EM-ISF) is a non-contact, high-speed process that utilizes the pulsed magnetic field to apply inertial force, which improves formability by dislocation slips. The EM-ISF and UV-ISF have shown promise to counter the challenges during aluminum alloy forming; however, the work in this regard is still in the initial phase and has not explored its full potential. This study updates the potential research on the current status of the energy-assisted ISF. Different customized testing equipment is discussed that help understand the process mechanism. Microstructural changes in the material occur at normal ISF and with energy-assisted ISF are discussed in detail. Discussion and future work are presented based on the insight from various articles at the end.
3
Content available remote Investigating the capability of the Lemaitre damage model to establish the incremental sheet forming process
Kumar Pavan, Tandon Puneet
Archives of Civil and Mechanical Engineering
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2022
|
Vol. 22, no. 2
art. no. e66, 1--18
EN
This paper presents the numerical and experimental investigation of the incremental sheet forming (ISF) process with the Lemaitre damage model to incrementally form parts of conical shapes. The Lemaitre damage model was prepared as a material subroutine (VUMAT) and linked to Abaqus/Explicit. The elastic–plastic parameters for the simulation were identified through tensile testing of the ASTM E8 specimen. The digital image correlation (DIC) was performed during the tensile testing to identify the damage parameters of the Lemaitre damage model. Scanning electron microscopy (SEM)-based area method was used to identify the area fraction vis-a-vis the variation of the strain. Thereafter, the identified area fractions with respect to strains have been calibrated to obtain the damage parameters through an inverse analysis approach. The identified parameters were used to form conical objects of Al1050 H14 sheets of 2 mm thickness through finite element (FE) simulation. The results obtained through FE simulation were compared with the experimental outcomes to investigate the efficiency of the Lemaitre damage model to simulate the ISF process. The responses obtained through FE simulation and experiments have been discussed in terms of limiting wall angle and forming depth, damage evolution, deformation mechanism, forming limit diagram, geometrical accuracy, forming forces, thickness distribution, and surface roughness.
4
Content available Determination of additional tension in towed streamer cable triggered by collision with underwater moving object
Blintsov Vladimir S., Trunin Konstantin S., Tarełko Wiesław
Polish Maritime Research
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2020
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nr 2
58--68
EN
The paper deals with issues connected with the behaviour of a streamer cable towed by a survey seismic vessel when the cable undergoes a strike triggered by collision with an underwater moving object. The consequences of such collisions may be both threat to the life of marine animals or damage to underwater units and large economic losses suffered by vessel owners. The risk of such collisions has increased over the last years as a result of increased offshore seismic survey operations. Therefore, a towed streamer should be very robust. To assure its robustness, we should know the deformation mechanism of a single streamer cable. This in turn requires the development of an appropriate mathematical model of such a phenomenon. In particular, the paper presents the characteristics of seismic survey vessels and streamers; an analysis of collisions that have occurred in the past; a statement of the problem, and a computer-aided system supporting simulation of the cable behaviour. To obtain all the necessary design parameters regarding the deformation mechanism of a streamer cable, we set up a dedicated computer-aided system that supports their calculation.
5
Content available Deformacionnyj mehanizm uplotneniăstrukurnogo tela
Protasenya O. N., Larchenkov L. V., Protasenya M. L., Jakubowski A.
Technical Issues
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2017
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nr 1
46--52
EN
Application of agricultural technique for preparation (loosening) of soil to sowing of agricultural cultures has an ambivalent character: from one side, elimination of weeds, and from the other mechanical destruction by the eyelids of the folded structure of soil profiles. The questions of compression of structure of soil are considered in the process of her forming and influence of the external loading without substantial violation of the structure.
6
Content available Deformation of semicrystalline polymers – the contribution of crystalline and amorphous phases
Bartczak Z.
Polimery
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2017
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T. 62, nr 11-12
787--799
EN
The plastic deformation process of semicrystalline polymers and the micromechanisms involved are discussed. The particular attention is paid to the dependence of deformation on structure and mutual influence of deformation of crystalline and amorphous components. Deformation of a semicrystalline polymer appears a complex series of continuous processes, involving mostly crystallographic deformation mechanisms operating in the crystalline phase. However, a very important role in that sequence is played by the deformation of amorphous interlamellar layers, partially reversible on unloading, which produces not only the high orientation of amorphous component but also influences deeply and supports the deformation of crystalline phase since crystalline lamellae and amorphous interlamellar layers, intimately connected through covalent bonds of chains crossing the interface, can deform only simultaneously and consistently. In particular, an influence of the topology of the amorphous phase, including the density of the molecular network of entangled chains and number of chains connecting adjacent crystalline and amorphous layers, on deformation instabilities of crystalline component in polyethylene are discussed. The induced instabilities of crystallographic slip lead to formation of lamellar kinks and frequently to an extensive fragmentation of lamellae. These transformations of crystalline structure together with restructurization of amorphous phase at high strains influence deeply the formation of the final highly oriented structure of the deformed semicrystalline polymer.
PL
Rozważano przebieg procesu odkształcenia plastycznego polimerów semikrystalicznych i zaangażowane w nim mikromechanizmy, zwracając szczególną uwagę na zależność deformacji od struktury materiału oraz na wzajemny wpływ odkształcenia fazy amorficznej i krystalicznej. Deformacja polimeru semikrystalicznego obejmuje szereg ciągłych procesów, w których zaangażowane są głównie krystalograficzne mechanizmy deformacji, aktywne w fazie krystalicznej. Bardzo ważną rolę w procesie odgrywa też częściowo odwracalne odkształcenie amorficznych warstw międzylamelarnych, które nie tylko prowadzi do wysokiego stopnia orientacji molekularnej w fazie amorficznej, ale wpływa również na deformację fazy krystalicznej. Lamele krystaliczne i amorficzne warstwy międzylamelarne, ściśle połączone wzajemnie wiązaniami kowalencyjnymi w łańcuchach przekraczających granice międzyfazowe, mogą deformować się tylko jednocześnie i spójnie. Omówiono także wpływ topologii fazy amorficznej, w tym gęstości sieci molekularnej splątanych łańcuchów i liczby łańcuchów łączących sąsiednie warstwy krystaliczne i amorficzne, na niestabilności deformacji fazy krystalicznej w polietylenie. Pojawiające się niestabilności poślizgów krystalograficznych prowadzą do powstawania załamań lamel, a często nawet do ich rozległej i silnej fragmentacji. Takie transformacje struktury fazy krystalicznej wraz z restrukturyzacją fazy amorficznej przy dużych odkształceniach wpływają istotnie na końcową, silnie zorientowaną, strukturę zdeformowanego polimeru semikrystalicznego.
7
Wpływ pasm ścinania na teksturę i własności mechaniczne walcowanej miedzi
Stalony-Dobrzański F., Bochniak W.
Rudy i Metale Nieżelazne
|
2006
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R. 51, nr 1
11-25
PL
Wykazano związek pomiędzy zjawiskami strukturalnymi a teksturą i własnościami mechanicznymi miedzi poddanej jednokierunkowemu i krzyżowemu walcowaniu oraz próbie rozciągania. W szczególności, ujawniono dominującą rolę mechanizmu zlokalizowanego plastycznego płynięcia w pasmach ścinania po zmianie drogi odkształcenia wywołanej rozciąganiem próbek w kierunku prostopadłym do kierunku walcowania. Znalazło ono również odzwierciedlenie w obrazach tekstury odkształcanej miedzi oraz dwukrotnie wyższej wartości współczynnika Lankforda w porównaniu z wartością określoną z próbek poddanych rozciąganiu w kierunku zgodnym z kierunkiem walcowania.
EN
Relationship between structural phenomena, texture and mechanical properties of copper subjected to non-reversing rolling, alternate longitudinal and cross rolling and to a tensile test, has been proved. In particular, the dominant role of a mechanism of localized plastic flow in the shear bands after the change of a strain path caused by tension applied perpendicularly to the rolling direction has been revealed. This phenomenon has also been reflected in the images of a texture of copper under deformation and in twice higher value of a Lankford’s coefficient compared to that determined for the samples subjected to the tensile test in the direction consistent with the rolling direction.
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