Wyniki wyszukiwania - BazTech

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FEM design of composite - metal joint for bearing failure analysis

Puchała K., Szymczyk E., Jachimowicz J.

Przegląd Mechaniczny

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2015

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nr 2

33--41

PL

Stałe dążenie do uzyskania jak najmniejszej masy samolotu jest powodem stosowania w konstrukcjach lotniczych materiałów o wysokiej wytrzymałości i sztywności właściwej. Wysokowytrzymałe stale, stopy tytanu lub stopy aluminium (np. 2024T3) oraz laminaty kompozytowe (np. CFRP, Glare) są przykładami takich materiałów. Stosowanie różnorodnych materiałów na struktury lotnicze wymusza konieczność łączenia części metalowych z kompozytowymi. Stosuje się różne techniki łączenia pokryć płatowca z elementami usztywniającymi: mechaniczne (połączenia nitowane, śrubowe), adhezyjne (klejenie, okazjonalnie zgrzewanie), hybrydowe (w którym zastosowano kombinacje dwóch różnych metod). W przypadku połączeń mechanicznych konieczne jest wykonywanie otworów, które stanowią miejsca silnych koncentracji naprężeń decydujących o wytrzymałości całej konstrukcji. Połączenia mechaniczne jako stosowane od dziesięcioleci odznaczają się wysokim poziomem niezawodności. Połączenia mechaniczne można wykonywać oraz użytkować w trudnych warunkach środowiskowych. Celem pracy jest projekt mechanicznego połączenia metal-kompozyt oraz analiza niszczenia elementu kompozytowego. Analizowano dwucięte połączenie śrubowe. Przeprowadzono obliczenia analityczne oraz numeryczne.

EN

The constant attempt to obtain as low aircraft mass as possible is the reason for using material of high specific strength (or stiffness) in the aerospace industry. High strength steels, titanium or aluminium alloys (e.g. 2024T3) and composite laminates (e.g. CFRP or Glare) are the examples of such materials. Dissimilar materials in aircraft structures provide a necessity of composite and metallic components joining. Various techniques are used to connect the skin with the stiffening elements: mechanical (riveting, bolting), adhesive (bonding and occasionally welding) and hybrid (where both above mentioned methods are used). Making holes is a necessity for mechanical joints. The holes are the areas of high stress concentrations and they determine load capability of the whole structure. However, mechanical joints used for decades are proved to be reliable. They can be assembled and applied in very rough conditions since they are less sensitive to environmental effects. The goal of the work is development of a mechanical metal-composite joint and failure analysis of the composite part. The double-shear joint is analysed. Both analytical and numerical calculations are performed.

2

Modelowanie wytrzymałościowe i analiza masowo-materiałowa dźwigara skrzydła samolotu rolniczego

Jachimowicz J., Szymczyk E., Łukasiński Ł., Puchała K.

Logistyka

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2015

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nr 4

3726--3733, CD 2

PL

W artykule przedstawiono metodologię obliczeń wytrzymałościowych mającej na celu zamianę dźwigara metalowego na kompozytowy na przykładzie rolniczego samolotu PZL-106 Kruk. Zilustrowano przypadki obciążeniowe oraz wskazano przypadek wymiarujący z odpowiednim rozkładem obciążeń. Pokazano modele wytrzymałościowe segmentu dźwigara. Wykonano obliczenia analityczne oraz analizy numeryczne. Przedstawiono analizę sztywnościowo-masową przykładowych rozwiązań , z analizy których wynika m.in. , że stosując kompozyt węglowy jako materiał dźwigara można zmniejszyć masę o około 69%.

EN

The paper presents a strength analysis methodology intended for replacing the metallic wing spar with a composite one on the example of PZL-106 Kruk agriculture aircraft. Loading cases are presented and dimensioning case with appropriate load distribution is selected. Static strength models of wing spar are studied. Analytical and numerical calculations are performed. The strength-mass analysis for exemplary configurations is presented. This analysis shows that mass of the spar can be reduced by 69% if the D16TN aluminum alloy is replaced with CFRP composite of appropriate configuration.

3

Analiza dwuzakładkowego połączenia adhezyjnego metal–kompozyt

Szymczyk E., Puchała K., Jachimowicz J.

Mechanik

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2014

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R. 87 nr 11

946--949

PL

Omówiono metody łączenia różnorodnych materiałów. Wskazano ich wady oraz zalety. Przedstawiono mechanizm przenoszenia obciążenia pozwalający na zwiększenie wytrzymałości elementu kompozytowego w miejscach połączeń. W oparciu o analogię do połączenia klejowego, przystąpiono do analizy naprężeń stycznych w połączeniu dwuzakładkowym metal–metal oraz metal– –kompozyt. Przedstawiono dwa podejścia stosowane w modelowaniu kompozytu.

EN

Methods of various materials joining are presented. Their benefits and drawbacks are pointed out and analyzed. The load transfer mechanism resulting in increase of the composite material strength in the joint area is presented. Analysis of the shear stress in double-lap in metal-to-metal and in metal-to-composite adhesive joints was carried out by analogy to the adhesive joint. The paper presents two approaches in the composite material modeling.

4

Analysis of selected parameters influence on failure in metal-composite mechanical joint

Puchała K.

Journal of KONES

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2014

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Vol. 21, No. 1

223--232

EN

The never-ending attempt to obtain as low mass as possible is the reason for using material of high specific strength (stiffness) in the aerospace industry. High strength titanium or aluminium alloys (e.g. 2024T3) and composite laminates (e.g. CFRP or Glare) are the examples of such materials. Despite a large number of composite types, fibre reinforced composites in the form of laminates are commonly used in aircraft structures. One-half of modern aircrafts is made of composites. However, the second one is still made of metallic alloys. The usage of different materials in aircraft structures results in the necessity of joining composite and metallic components. There are three connection methods for aircraft primary structures: mechanical (riveting, bolting), adhesive (bonding) and hybrid where both mentioned methods are used. The paper deals with metal-composite mechanical joint. Although fibre reinforced composites have high tensile strength, the load transfer in mechanical joints of such components is limited. Strength of composite laminates is dependent on the joint geometry; however, it is strongly influenced by laminate lay-up. There are five global failure modes for mechanically fastened composite laminates: tension, bearing, shear-out, cleavage and pull-through. The bearing failure mechanism is a safe progressive mechanism not leading to catastrophic failure and therefore it is acceptable. Problems with strength assessment of composite mechanical joints are drawn. Some geometrical (joint width), material (bolt material, stacking sequence) as well as numerical parameters (failure criterion) are analysed.

5

Analysis of load transfer into composite structure

Szymczyk E., Jachimowicz J., Puchała K.

Applied Computer Science

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2014

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Vol. 10, no 3

86--94

EN

The paper presents advantages and disadvantages of metal foils insertion between composite layers. Composites are complex materials of aniso-tropic structure leading to various failure mechanisms. Mechanism of compressive load transfer into composite laminates by shear of the matrix is analysed. The method of improvement compressive strength of laminates is presented according to literature and analysed for a sele-cted case. Simplified models of a laminate structure modified using various metal foils configurations are analysed with MSC.Marc code. Axial stress in prepreg layers and shear stress in adhesive layers are studied.

6

Wpływ długości nitu na naprężenia własne w połączeniu nitowym

Szymczyk E., Puchała K.

Przegląd Mechaniczny

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2012

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nr 7-8

59-64

PL

Wytrzymałość połączeń nitowych zależy od czynników konstrukcyjnych, technologicznych i materiałowych. Nity tak jak wszystkie części mechaniczne produkowane są z określoną tolerancją, a ich wymiary zawierają się w ustalonych granicach. W artykule przedstawiono analizę wpływu czynnika technologicznego, jakim jest długość nitu, na naprężenia własne w połączeniu. Obliczenia wykonano dla blach ze stopu aluminium 2024T3, stosowanego na pokrycia lotnicze, łączonych nitami z materiału PA25 o podwyższonej wytrzymałości. Analiz´ stanu naprężenia przeprowadzono dla trzech długości nitu. Zwrócono uwagę na naprężenia styczne, które mogą powodować pękanie zakuwek.

EN

The load carrying capacity of riveted joints depends on many structural, manufacturing and material factors. Rivets, like all mechanical parts, are produced with certain tolerance, therefore their dimensions are enclosed in fixed limits. The paper presents an influence of such a technological factor as a rivet length on a residual stress state in the riveted joint. Numerical calculations were performed for sheets made of 2024T3 alloy commonly used in aircraft fuselages joined together with rivets of high-strength PA25 alloy. The analysis of residual stresses is performed for three different rivet lengths. The shear stress field which tends to cause cracking of the formed rivet head is taken into account.

7

Some aspects of dynamic riveting simulations

Szymczyk E., Jachimowicz J., Puchała K.

Journal of KONES

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2012

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Vol. 19, No. 1

423-430

EN

Riveting is a commonly used (especially in aircraft structures) method of joining metal and composite components. The methods of forming solid shank rivets can be classified in two types: static and dynamic. The static method is the most efficient one. Regrettably, its application is limited. A popular upsetting tool used in an aircraft is a pneumatic riveter. The rivet driving requires a few hammer strokes. The total stress in a riveted joint depends on the residual and applied stress. Residual post-riveting stress fields are widely accepted to have a beneficial influence on the fatigue life of aircraft structures. The analysis is carried out for a solid mushroom rivet (made of PA25 alloy) joining two sheets (made of 2024T3 alloy). Nonlinear dynamic simulations of the upsetting process are carried out. Simulation of the riveting process is significantly influenced by a material model. The numerical calculations are performed for three different cases of upsetting described by the formed rivet head diameters 1.4d, 1.5d and 1.6d, respectively. The rivet head diameter and, consequently, the residual stress state depend on hammer stroke energy. It has a significant influence on a plastic region around the rivet hole, whereas the influence of a number of strokes can be neglected. The strain rate in both local and global (average) formulation is analysed in the paper. For one hammer stroke, the global strain rate of the rivet shank is about 1.0 thousand per second. The local strain rate is about two times greater than the global one, so a strain rate factor has an effect on the residual stress state. For a few hammer strokes, the strain rate is lower than for one stroke; however, it increases a little in each stroke. The hole deformation can be treated as a function of the internal energy of the sheet. The lower total energy of the part the greater influence of the strain rate on the internal energy is observed.

8

About mechanical joints design in metal - composite structure

Puchała K., Szymczyk E., Jachimowicz J.

Journal of KONES

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2012

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Vol. 19, No. 3

381-390

EN

Riveting is still one of the main joining methods of thin-walled aircraft structures. Such features as simplicity of implementation, possibility of two different material connection (e.g. metallic with non-metallic ones) and the fact that is it a well-known (reliable) method causes popularity of riveting. The never-ending attempt to obtain as low mass as possible (mainly to reduce fuel consumption) is the reason for using material of high specific strength in the aerospace industry. High strength titanium or aluminium alloys (e.g. 2024T3) and composite laminates (e.g. CFRP or Glare) are examples of such materials. The article deals with methods of connecting various materials. The paper presents advantages and disadvantages of different/selected connection types. Strength prediction and failure modes of mechanical joints are described for metallic as well as for composite components. Composites are complex materials having an anisotropic structure (and anisotropic mechanical properties) leading to various failure mechanisms. Main principles for appropriate joint design of composite laminate panels (laminate configuration and typical/specific geometrical dimensions) are indicated/specified. The bearing failure mechanism is accepted to be a safe progressive one. Mechanism of bearing (generally compressive) load transfer into composite laminates by shear of the matrix is analysed. Some examples of improvement bearing strength of laminates are presented according to literature. On the base of presented examples and bearing load transfer analysis, some conclusions for an appropriate solution of this problem are drawn.