Wyniki wyszukiwania - BazTech

1

Sandwich panel subjected to blast wave impact and accelerated fragments

Studziński Robert, Sumelka Wojciech, Malendowski Michał, Gajewski Tomasz, Al-Rifaie Hasan, Sielicki Piotr

Eksploatacja i Niezawodność

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2024

|

Vol. 26, no. 2

art. no. 183698

EN

The article presents sandwich panels subjected to blast wave impact and accelerated fragments. The research discusses results obtained from original experimental setups that fill a gap in the area of investigation of the mechanical response of sandwich panels used in civil engineering applications under accidental design situations such as blast wave impact and/or fragment penetration. In field experiments, a high-speed camera was used to record both the fragment trajectory and the deflection of the sandwich panel. The authors proposed the equivalent static load for both the global analysis of the sandwich panel and the calibration of the numerical model. In FE modelling, CONWEP algorithm was used to simulate blast wave impact, and ductile damage model material to allow perforation of the sandwich panel faces. The convergence of mesh size was analyzed. For the validated numerical model, an evaluation of the effect of the size of the fragment (diameter/mass) on the outlet velocity and the size of the inlet andoutlet holes was carried out.

2

Belki zespolone aluminiowo-drewniane łączone za pomocą wkrętów lub śrub - podsumowanie i wnioski z badań własnych

Chybiński Marcin, Polus Łukasz

Przegląd Budowlany

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2023

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R. 94, nr 5-6

56--60

PL

Artykuł przedstawia przegląd badań własnych dotyczących belek zespolonych aluminiowo-drewnianych oraz ich połączeń. Zespolenie aluminiowych dwuteowych belek z płytami z drewna klejonego warstwowo z fornirów ma wiele zalet. W badaniach zaobserwowano wzrost nośności oraz sztywności belek aluminiowych oraz ich niewrażliwość na zwichrzenie po zespoleniu z drewnianymi płytami. Jako łączniki ścinane wykorzystano wkręty z łbem sześciokątnym oraz śruby. Zaproponowano wykorzystanie pierścieni zębatych jako elementów wzmacniających połączenia ścinane i oceniono skuteczność tego rozwiązania.

EN

This paper presents a review of the author’s own tests conducted on aluminium-timber composite beams and their connections. Significant benefits were gained by joining aluminium beams and laminated veneer lumber slabs. It provided for the increase of the load-bearing capacity and stiffness, and eliminated the problem of lateral-torsional buckling of aluminium beams. The composite action was assured by the use of bolts or hexagon head wood screws as shear connectors. The use of toothed plate connectors as reinforcement in aluminium-timber connections was suggested and evaluated.

3

Fracture Mechanism of Hard Main Roof and Determining the Width of Coal Pillars when Extracting Flat-lying Coal Seams

Le Quang Phuc, Dao Van Chi, Nguyen Phi Hung, Vu Thai Tien Dung

Inżynieria Mineralna

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2023

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no. 2, vol. 1

271--280

EN

In underground coal mining, the stability of roadways and gob-side entry depends on the coal pillar width. An unreasonable width of the coal pillar will cause the roadway to be in a dangerous zone of influence of the abutment pressure, leading to severe roadway deformation. This paper studies the fracture mechanism of the hard main roof and reasonable coal pillar width to protect the stability of gob-side entry driving. The research results show that when mining a coal seam under a hard main roof, the console of the main roof on the edge of the coal seam has the form of hinge structure. The great load of the roof layers and the rotation of the console are the main causes leading to the variation of the stress field in the coal seam. According to the development law of the stress field, after the main roof completes the collapse process, the peak of the maximum stress will move deep into the solid coal seam, and on the edge of the coal seam it will form a low-stress zone. Research results from the case of Seam #11 of Khe Cham coal mine, Vietnam show that the gob-side entry will be well stabilized when the narrow coal pillar between it and the boundary of the gob is 4–5 m.

4

Wybrane aspekty stosowania nitów zrywalnych w jednostronnych połączeniach do płyt warstwowych

Studziński Robert, Piekarczuk Artur

Inżynieria i Budownictwo

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2023

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R. 79, nr 9-10

494--498

PL

W artykule przedstawiono koncepcję zastosowania nitów zrywalnych do mocowania elementów infrastruktury budowlanej do płyt warstwowych. Połączenie takie nie wymaga podkonstrukcji oraz nie przyczynia się do powstania lokalnych mostków termicznych. Brak wytycznych normowych i literaturowych ogranicza możliwość stosowania takich połączeń. Wskazane zostały parametry definiujące, zdaniem autorów artykułu, nośność i niezawodność połączenia. Omówione w artykule stanowiska badawcze i możliwe do wystąpienia mechanizmy zniszczenia mogą posłużyć za punkt wyjścia do określenia zależności analitycznych pozwalających na szybką ocenę zakresu stosowania połączenia.

EN

The article presents the concept of using blind rivets to attach building infrastructure components to sandwich panels. Such a connection does not require a substructure and does not cause local thermal bridges. The lack of standard and literature guidelines limits the possibility of using such connections. The parameters that define, according to the authors of the article, the load-bearing capacity and reliability of the connection are indicated. The testbeds discussed in the article, as well as the possible failure mechanisms, can serve as a starting point for determining analytical relationships that allow a quick assessment of the scope of application of the connection.

5

Bending Failure Behavior of the Glass Fiber Reinforced Composite I-Beams Formed by a Novel Bending Pultrusion Processing Technique

Zhu Lvtao, Cao Shengbin, Zhang Xiaofeng, Li Lei

Autex Research Journal

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2022

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Vol. 22, no. 2

172--176

EN

The glass fiber reinforced resin matrix composite I-beams were designed and formed via a type of novel bending pultrusion processing technique, and the three-point bending tests were carried out to analyze the mechanical bending performances. The obtained results show that the main failure mode of the composite I-beam under the bending load is the upper structure (top flange) cracks along the length direction of the fibers, and the cracks simultaneously propagate downwards in the vertical direction. The bifurcated cracks can be found at the junction area between the top flange and web. In addition, the main bending failure mechanism of the composite I-beam includes the matrix cracking, propagation of cracks, and final fracture failure. In particular, noting that when the crack reaches the I-shaped neck position, the lateral bifurcation occurs, and the resulting secondary cracks further extend in two directions, which leads to the serious damage between the top flange and web, and the ultimate fracture failure occurs.

6

Experimental investigation of sandwich panels supported by thin-walled beams under various load arrangements and number of connectors

Ciesielczyk Katarzyna, Studziński Robert

Archives of Civil Engineering

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2022

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Vol. 68, nr 4

389--402

EN

In the paper there the laboratory tests of interaction between thin-walled beams of the Z crosssection and the sandwich panels with PIR foam core are presented. The different numbers of connectors (0, 4, and 8) were used to connect the sandwich panels with the thin-walled beams. Furthermore, the parallel and perpendicular to the longitudinal axis of the thin-walled beam load arrangement was analysed. The research provides a qualitative and quantitative comparison of the mentioned experiments using the ultimate capacity, the deformation capacity, and the stiffness. In the second part of the paper, the numerical analysis of the thin-walled beam was also performed. The beam was modelled as a shell element and loaded in two ways, which corresponded to the loading scenario during laboratory tests (uniformly distributed and concentrated loads). The results of the numerical calculations of the beam without lateral stabilization were compared with the laboratory results of the beam stabilized by the sandwich panels.

PL

W pracy przedstawiono wyniki badan eksperymentalnych układów konstrukcyjnych składających się z płyt warstwowych i belek cienkościennych o przekroju Z ułożonych niesymetrycznie względem siebie. W oparciu o europejskie rekomendacje oraz wcześniejsze badania autorów zakłada się, że w analizowanym układzie belki są stabilizowane bocznie przez płyty warstwowe. Wykonano 11 badań laboratoryjnych, które różniły się między sobą liczbą łączników oraz sposobem przyłożenia obciążenia. W celu połączenia płyt warstwowych z belką cienkościenną użyto 0, 4 lub 8 łączników. Obciążenie przypadające na układ było przyłożone równolegle do belek cienkościennych powodując obciążenie równomiernie rozłożone a prostopadle do belek cienkościennych powodując obciążenie punktowe. Przeprowadzone badania wykazały znaczącą wrażliwość układu na sposób przyłożenia obciążenia względem analizowanych układów konstrukcyjnych. Wykazano, że obciążenie realizowane jako równoległe do długości belki podpierającej płytę pozwala analizowanemu układowi na przeniesienie ponad dwukrotnie większego obciążenia niż w przypadku obciążenia realizowanego w sposób prostopadły do długości belki. Dodatkowo omówiono w pracy mechanizmy zniszczenia układu w zależności od sposobu jego obciążenia. Zbadano również wpływ liczby łączników na całkowitą nośność analizowanego układu. Wykazano znaczący wzrost nośności układu przy zwiększającej się liczbie łączników. Zwiększenie liczby łączników łączących belki cienkościenne z płytami warstwowymi wiązało się również z powstaniem złożonym mechanizmami zniszczenia układu. Uzupełnieniem przeprowadzonych badań eksperymentalnych było wykonanie symulacji numerycznych belek cienkościennych niestężonych poszyciem. Belki zamodelowane zostały jako elementy powłokowe obciążone na dwa sposoby: obciążeniem równomiernie rozłożonym na pasie górnym belki oraz siłą skupioną w środku rozpiętości belki. Otrzymane wyniki oraz mechanizmy zniszczenia porównano z wynikami laboratoryjnymi belki stężonej płytą warstwową. Wykazano, że belka niestężona płytą warstwową wykazuje prawie dwukrotnie niższą nośność niż belka stężona.

7

Damage mechanism of conventional joints and proposal of a novel joint for hollow-core slab bridges

Cui Yujun, Xue Xingwei, Yao Hao, Hua Xudong, Huang Yuanming

Archives of Civil Engineering

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2022

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Vol. 68, nr 4

571--590

EN

The prefabricated hollow-core slab bridge is a common bridge. In prefabricated hollow-core slab bridges, joints play an important role in connecting prefabricated slabs and ensuring the integrity of the bridge. However, as the service time of the bridge increases, conventional joints have a large number of typical diseases that affect the safety and durability of bridges. In this study, a three-dimensional finite element model of the entire construction phase is established to investigate the development difference of shrinkage and creep between joints and hollow-core slabs. The effects of vehicle load and temperature gradient on joints were analysed, the failure mechanism of joints was explored, and a novel joint was proposed. The results of a nonlinear analysis showed that the novel joint can effectively improve the mechanical performance of joints and cracks can be effectively controlled. Moreover, the novel joint solves the problem in that the conventional novel joint cannot be vibrated effectively.

8

Experimental and numerical study on the indentation behavior of TBM disc cutter on hard-rock precutting kerfs by high-pressure abrasive water jet

Cheng Jian‑Long, Yang Sheng‑Qi, Han Wei-Feng, Zhang Zuo-Ru, Jiang Zi-Hao, Lu Jun-Fu

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e37, 2022

EN

Tunnel boring machine (TBM) excavation of high strength or highly abrasive rock strata has some limitations, such as slow advance speed, low rock-breaking efficiency, and significant increase in the disc cutter changes and construction cost. To improve the rock boreability, a novel breakage method for hard rocks using a TBM disc cutter penetrating into kerfs precut by a high-pressure abrasive water jet is explored. With a confining pressure of 5 MPa, a series of cutter indentation tests and particle flow simulations of granite with two precutting kerfs are carried out to investigate the indentation behavior and the breaking efficiency. The effects of the kerf depth and the kerf spacing on the normal indentation force, rock chip volume, and specific energy are studied. The initiation, propagation, and coalescence modes of the surface and internal cracks and the failure mechanism are analyzed. The results show that the average peak force decreases significantly with the increase of the kerf depth, and the maximum rock chip volume and minimum specific energy are obtained at a kerf depth of 18.14 mm. The failure mode of kerf specimens after two indentations could be divided into the flat and slow shallow failure, one-sided inclined failure, and two-sided inclined failure. The micro-crack distribution of a single shallow kerf under low confining pressure is similar to that of intact rocks, while it is oblate and semi-elliptical under high confining pressure. However, for a single deep kerf, the breakage consists of a wedge-shaped crushed zone, a failure zone, and a damage zone around the kerf boundary and the bilateral inclined cracks, which are almost not affected by the confining pressure.

9

Experiment and validation of local bearing capacity for reactive powder concrete confined with high-strength spirals

Li Sheng, Zheng Wenzhong, Zhou Wei, Jiang Zhisheng, Wang Ying

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e40, 2022

EN

In this study, ten reactive powder concrete (RPC) specimens confined by high-strength spirals loaded over a limited area are used to investigate their behaviour and determine their local bearing capacity. The crack, wedge, and failure characteristics of RPC are discussed based on tests and simulation. The index of pressure versus deformation is used to evaluate the loading stages. The ratio of the cracking load to the ultimate load varies from 34 to 60%. A wedge pyramid is formed ahead of the bearing plate when approaching the ultimate load; thereafter, it slips downward, splitting the concrete below. The high-strength spirals did not yield even under the ultimate load. According to the test data, all the existing models for predicting the local bearing capacity are nonconservative. In this case, the effect of the actual stress caused by high-strength spirals is considered to further modify the existing calculation models when high-strength spirals are used, and a simple empirical equation for calculating the local bearing capacity of the RPC is developed. The equation and the models modified as described are verified experimentally.

10

An investigation of longwall failure using 3D numerical modelling – A case study at a copper mine

Nguyen Phu Minh Vuong, Olczak Tomasz, Rajwa Sylwester

Studia Geotechnica et Mechanica

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2021

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Vol. 43, nr 4

389--410

EN

It is well-known that the longwall mining method (with roof caving) is widely used in underground mining extraction for bedded deposits (e.g. coal) due to its numerous advantages. Generally, this method is not commonly applied for ore deposits such as copper deposit. In Poland, the longwall mining method has been tested for thin copper deposits at the Polkowice-Sieroszowice copper mine (KGHM). Various failure modes were observed during longwall operation in the 5A/1 panel. This paper aims to examine these occurred failures. To do so, an analysis has been conducted using 3D numerical modelling to investigate the failure mode and mechanism. Based on the 3D numerical modelling results with extensive in situ measurements, causes of failure are determined and practical recommendations for further copper longwall operations are presented.

11

Zginanie muru w płaszczyźnie prostopadłej do powierzchni ściany – obciążenia i mechanizmy zniszczenia

Piekarczyk Adam

Materiały Budowlane

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2021

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nr 2

27--29

PL

Artykuł jest pierwszą częścią cyklu omawiającego przypadek ścian murowanych zginanych w płaszczyźnie prostopadłej do płaszczyzny muru. Opisano w nim obciążenia prostopadłe do powierzchni ścian, które wywołują omawiany przypadek pracy konstrukcji murowanej. Zaprezentowano mechanizmy zniszczenia muru w dwóch ortogonalnych płaszczyznach oraz ich warianty.

EN

The article is the first part of the cycle discussing the case of bending masonry walls in a plane perpendicular to the masonry plane. Loads and actions perpendicular to the wall surfaces, which cause the discussed case of masonry structure work, are described. The mechanisms of wall failure in two orthogonal planes and their variants were presented.

12

Zginanie muru w płaszczyźnie prostopadłej do powierzchni ściany - wytrzymałość na zginanie

Piekarczyk Adam

Materiały Budowlane

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2021

|

nr 3

29--31

PL

Artykuł jest drugą częścią cyklu omawiającego przypadek zginania ścian murowanych w płaszczyźnie prostopadłej do powierzchni muru. Przedstawiono informacje teoretyczne dotyczące wytrzymałości na zginanie określanej w dwóch ortogonalnych płaszczyznach, w tym w przypadku uwzględnienia wypełnienia i niewypełnienia spoin pionowych w murze wraz z odpowiednimi zależnościami. Podano również sposoby określania wytrzymałości na zginanie, w tym tzw. wytrzymałości zastępczej uwzględniającej czynniki pozytywnie wpływające na obliczeniową nośność muru zginanego.

EN

The article is the second part of the series discussing the case of masonry bent in a plane perpendicular to the wall plane. This section presents theoretical information on the flexural strength determined in two orthogonal planes, including the filling and unfilling of vertical joints in the wall, along with the appropriate relationships. Methods of determining the flexural strength, including the so-called apparent strengths, taking into account factors positively influencing the design load-bearing capacity of a bending wall, are also given.

13

Wpływ zbrojenia spoin wspornych w ścianach z otworami, wykonanych z silikatowych elementów murowych, na morfologię zarysowań i mechanizm zniszczenia

Jasiński Radosław

Materiały Budowlane

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2021

|

nr 4

11--14

PL

W artykule przedstawiono wyniki badania ścian niezbrojonych i zbrojonych, z otworami różnych kształtów, wykonanych z silikatowych elementów murowych. Podstawowym celem przeprowadzonych eksperymentów było określenie wpływu zastosowanego zbrojenia na morfologię zarysowań oraz mechanizm zniszczenia. Wszystkie ściany wykonano z silikatowych elementów murowych z pionowymi drążeniami (grupa I wg PN-EN 1996-1-1:2013). Zbadano 12 ścian o zewnętrznych wymiarach l = 4,45 m, h = 2,45 m, t = 180 mm z otworami zróżnicowanymi pod względem kształtu i wymiarów. Do zbrojenia zastosowano stalowe kratowniczki typu EFZ 140/Z 140 type (typ Z1) oraz siatki z tworzywa sztucznego (typ Z2). Wykazano, że rozwój zarysowań zależał od wielkości otworu. W ścianach zbrojonych propagacja zarysowań była istotnie ograniczana.

EN

The article presents the results of tests of unreinforced and reinforced walls with openings of various shapes made of calcium silicate masonry units. The main aim of the conducted experiments was to determine the influence of the applied reinforcement on the cracking morphology and the failure mechanism. All walls are made of calcium silicate masonry elements with vertical traverses (group I according to PN-EN 1996-1-1:2013). 12 walls with external dimensions of l = 4,45 m, h = 2,45 m, t = 180 mm with openings of different shape and dimensions were constructed and tested. Steel trusses of the EFZ 140/Z 140 type (type Z1) and plastic meshes (type Z2) were used for reinforcement. It was shown that the development of cracking depended on the size of the opening. In reinforced walls, the propagation of scratches was significantly limited.

14

A Study on the Durability of Dimensionally Stable Electrode in High-Rate Electroplating Process Condition Using Accelerated Life Test

Park Sung Cheol, Jung Yeon Jae, Koo Seokbon, Lee Kee-Ahn, Son Seong Ho

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

675--678

EN

In order to the long-term stability of DSE for electroplating process, the lifetime equations were calculated from the results of the accelerated life testing, and the lifetime of DSE was predicted. The nano-embossing pre-treatment led to 2.65 times in the lifetime of DSE. The degradation mechanism of DSE with a thick metal oxide layer for applied highly current density process condition was identified. The improvement of durability of DSE seems to be closely related to adhesion between titanium plate and mixed metal oxide layer.

15

Penetration behaviour of TBM disc cutter assisted by vertical precutting free surfaces at various depths and confining pressures

Cheng Jian‑Long, Wang Yong‑Xing, Wang Lian-Guo, Li Yuan-Hai, Hu Bo, Jiang Zi-Hao

Archives of Civil and Mechanical Engineering

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2021

|

Vol. 21, no. 1

375--392

EN

The ability to improve rock-breaking efficiency of tunnel boring machines in hard rock stratum is significant to improve driving speed and reduce construction cost and time. The undercutting method has been used to improve the rock-breaking efficiency of disc cutters, including the design of curved and multistage cutterheads. The limited radian of curved cutterheads and the number of multistage cutterheads, however, are restricted by the current manufacturing level. We explored mechanical response and rock-breaking efficiency assisted by water jet kerfs as the vertical free surface. We conducted a quasi-static penetration test of the disc cutter considering four kerf depths and three groups of confining pressures. We analysed the surface crack propagation and fractures inside the sample using acoustic emission and computed tomography scanning. We studied the influence of confining pressure and cutting depth of the water jet on penetration force, rock chips, and specific energy. We analysed the failure evolution and stress field of kerf specimens using numerical simulation. The results showed that increasing cutting depth relieved restraint stress and the resulting influence of the confining pressure on removed rock volumes and specific energy was not remarkable. We recommended a kerf depth of greater than 18 mm to reduce penetration force and significantly improve rock-breaking efficiency.

16

Deformation and failure mechanism of deep cement mixing walls: experimental study using physical model tests

Waichita Siriwan, Jongpradist Pornkasem, Patawanit Pongpeera, Jamsawang Pitthaya, Arangelovski Goran, Likitlersuang Suched

Archives of Civil and Mechanical Engineering

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2021

|

Vol. 21, no. 3

699--715

EN

This article presents the results of experimental research on the behaviour of deep cement mixing (DCM) walls during excavation up to failure. For this purpose, a novel laminar box equipped with a set of springs and a pneumatic loading system were designed and developed to run a total of nine scaled-down model tests at normal gravity on five different testing programs: (1) the wall thickness variation, (2) wall modulus variation, (3) effect of the reinforcement, (4) the bending stiffness (EI) control, and (5) the wall volume control of varying wall slenderness. The responses of the walls were studied through the wall horizontal displacement profile, tensile strains along with wall depth on the retained side, the distribution of strains using photogrammetric analysis and observation of crack initiation at the wall. The experimental results indicate that the behaviours of DCM walls depend strongly on the wall dimensions, particularly the thickness, and the analysis concepts used for conventional retaining walls cannot be directly utilized. The wall-to-excavation shape factor has been proven to effectively distinguish the behaviour mode and characterize the crack location concerning the wall height.

17

On determining the undrained bearing capacity coefficients of variation for foundations embedded on spatially variable soil

Chwała Marcin

Studia Geotechnica et Mechanica

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2020

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Vol. 42, nr 2

125--136

EN

This paper presents an efficient method and its usage for the three-dimensional random bearing capacity evaluation for square and rectangular footings. One of the objectives of the study is to deliver graphs that can be used to easily estimate the approximated values of coefficients of variations of undrained bearing capacity. The numerical calculations were based on the proposed method that connects three-dimensional failure mechanism, simulated annealing optimization scheme and spatial averaging. The random field is used for describing the spatial variability of undrained shear strength. The proposed approach is in accordance with a constant covariance matrix concept, that results in a highly efficient tool for estimating the probabilistic characteristics of bearing capacity. As a result, numerous three-dimensional simulations were performed to create the graphs. The considered covariance matrix is a result of Vanmarcke’s spatial averaging discretization of a random field in the dissipation regions to the single random variables. The matrix describes mutual correlation between each dissipation region (or between those random variables). However, in the presented approach, the matrix was obtained for the expected value of undrained shear strength and keep constant during Monte Carlo simulations. The graphs were established in dimensionless coordinates that vary in the observable in practice ranges of parameters (i.e., values of fluctuation scales, foundation sizes and shapes). Examples of usage were given in the study to illustrate the application possibility of the graphs. Moreover, the comparison with the approach that uses individually determined covariance matrix is shown.

18

Stress evolution mechanism and thermo-mechanical reliability analysis of copper-filled TSV interposer

Chen Yuan, Su Wei, Huang Hong-Zhong, Lai Ping, Lin Xiao-ling, Chen Si

Eksploatacja i Niezawodność

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2020

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Vol. 22, no. 4

705--714

EN

Through silicon via (TSV) has become one of the key emerging trends of three-dimensional (3D) packages, as it can realize vertically interconnect between stacked-dies. Due to large mismatch in thermal expansion coefficients (CTE) between the copper via and the silicon, significant mechanical stresses are induced at the interfaces when TSV structure is subjected to thermal stresses, which would greatly affect the reliability and electrical performance of TSV 3D device. In this paper, the relationship between the state of stresses and failure of TSV had been explored by combining finite element model simulation (FEM) and failure physical analysis. The position of the maximum stress of the TSV structure was obtained by FEM analysis. The relationship of stress and displacement change with temperature was also studied. And a thermal cycling experiment was conducted to validate the simulation results. Physical failure analysis after thermal cycling experiment was used to verify the degradation mechanism predicted by thermo-mechanical simulation.

19

Performance degradation comparisons and failure mechanism of silver metal oxide contact materials in relays application by simulation

Wang ZhaoBin, Li WeiYan, Shang Shang, Wang Zhan, Han ChunYang

Eksploatacja i Niezawodność

|

2020

|

Vol. 22, no. 1

86--93

EN

To evaluate the electrical contact behaviors of silver metal oxide contact materials in relays application more accurately, and to guide the selection of contact materials, the test device and testing method for simulating electrical contact performance in relays application were analyzed in this paper. The electrical contact simulation test system was designed and developed, which can easily simulate contact materials. The contact resistance, static force and rebound energy degradation parameters of AgSnO2, AgCdO and AgNi contact materials under the same load conditions were obtained through experimental research, the contact resistance and arcing energy degradation parameters of AgSnO2 under different opening distances were acquired at the same time. The result indicated that accurate data are received by the electrical contact simulation testing method. Finally, based on the test data, the degradation performance of three selected test materials was tested, and the failure mechanism of AgSnO2 materials was analyzed.

PL

W celu dokładniejszej oceny zachowania styków elektrycznych z kompozytów srebra i tlenku metalu stosowanych w przekaźnikach elektromagnetycznych oraz w celu ułatwienia wyboru materiałów stykowych, w niniejszej pracy przeanalizowano urządzenie testowe oraz metodę testowania, które pozwalają na symulację działania styku przekaźnika. Zaprojektowano i zbudowano system testowania styków elektrycznych, który umożliwia łatwą symulację zachowania materiałów stykowych. Parametry degradacji rezystancji zestykowej, siły statycznej oraz energii odbicia materiałów stykowych AgSnO2, AgCdO i AgNi uzyskano w badaniach eksperymentalnych prowadzonych w takich samych warunkach obciążenia. Jednocześnie badano także parametry degradacji rezystancji zestykowej energii łuku AgSnO2 przy różnych odległościach otwarcia styków. Wyniki pokazują, że proponowana metoda badania symulacyjnego styków elektrycznych pozwala na uzyskanie dokładnych danych. W oparciu o dane testowe, przebadano zachowanie degradacyjne trzech wybranych materiałów oraz przeanalizowano mechanizm uszkodzenia styków z kompozytu AgSnO2.

20

Mechanical performances of metal-polymer sandwich structures with 3D-printed lattice cores subjected to bending load

Liu Zhaobing, Chen Hantang, Xing Shuaiqi

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

368--384

EN

In this article, we propose a new class of metal-polymer architected sandwich structures that exhibit different mechanical behaviors. These lightweight sandwich structures have been made of aluminum face sheets and 3D-printed lattice cores with 2D (Bi-grid, Tri-grid, Quadri-grid and Kagome-grid) and 3D (face-centered cubic-like and body-centered cubic-like) topologies. Finite element simulation and experimental tests were carried out to evaluate mechanical performances of the proposed sandwich structures under quasi-static three-point bending load. Specifically, the damage-tolerant capability, energy absorption and failure mechanisms of these sandwich structures were investigated and evaluated through a combination of analytical, numerical and experimental methods. It is found that sandwich structures with 3D face and body-centered cubic-like cores can provide more excellent flexural stiffness, strength and energy absorption performance. These enhanced mechanical features could be further explained by a so-called ‘Stress Propagation’ mechanism through finite element analysis (FEA) that can facilitate sandwich structures with 3D cores, especially body-centered cubic-like one, to transfer bending loads from central lattice units across neighboring ones more efficiently than 2D cores. Furthermore, core cracking is the main failure mode for the proposed sandwich structures, which is primarily caused and dominated by bending-induced tensile stress followed by shear stress. It is worth mentioning that our findings provide new insights into the design of novel lightweight sandwich composites with tailored mechanical properties, which can benefit a wide variety of high-performance applications.