Joining of CFRT-steel hybrid parts via hole-forming and subsequent pin caulking

In times of increasing global warming, the awareness of the necessity for significant CO2 reduction is growing. Especially in the transport and aerospace sector, lightweight construction has potential to achieve emission reduction goals by reducing the overall vehicle weight. Thereby, adding lightweight fibre-reinforced composites to materials such as steel and aluminium is used to achieve weight savings. Furthermore, continuous-fibre-reinforced thermoplastics (CFRTs) begin to replace more traditional thermoset thermoplastics due to their easier bulk production and uncomplicated storage. Hybrid parts often consist of a CFRT and a higher strength metal component. Here, the joining process poses the main challenge, due to different chemical and physical properties of the components. In the current state of the art, riveted and bolted joints are commonly used, leading to increased weight due to auxiliary elements and requiring precise bolt holes often destroying load-bearing fibres. Joining with cold formed pin structures is an innovative and versatile joining process, which avoids the need for auxiliary elements. These pins are subsequently inserted in warm formed holes in the CFRT component and then caulked to create a form-fitting hybrid joint. To obtain a fundamental understanding of this joining process, hole-forming and pin-caulking, are investigated in this study. First, the hole-forming with IR-radiation is investigated with regard to suitable process parameters and resulting fibre morphology. The formed holes are consequently mechanically characterized. Second, the caulking-process is investigated by iteratively upsetting a pin and subsequently measuring the geometry. Based on these findings two different suitable caulking degrees are defined and samples for mechanical as well as microscopic investigations are manufactured. The created joints are first investigated via micro-sections and reflected light microscopy to identify possible damage in the CFRT component, which can result from the pin caulking process. Second, a mechanical characterisation under shear load as well as pin extraction loads normal to the sample surface is conducted and the normal load tests are compared with the bearing strength of CFRT samples.

Prediction of the Delamination at the Steel and CFRP Interface of Hybrid Composite Part

The purpose of this study was to predict the adhesive behavior of steel and carbon-fiber-reinforced plastic (CFRP) hybrid parts based on the cohesive zone model (CZM). In this study, the steel sheet and CFRP were joined by epoxy resin in the CFRP prepreg during the curing process, which could generate delamination at their interface because of the springback of steel or the thermal contraction of the CFRP. First, double cantilever beam (DCB) and end-notched flexure (ENF) tests were performed to obtain various adhesion properties such as the critical energy release rate of mode I, mode II (GI, GII), and critical stress (σmax). A finite element (FE) simulation was performed to predict delamination using CZM, which was also used to describe the interfacial behavior between the steel sheet and the CFRP. Finally, a U-shape drawing test was performed for the steel/CFRP hybrid parts, and these results were compared with analytical results.

Fatigue Behavior of Hybrid Components Containing Maraging Steel Parts Produced by Laser Powder Bed Fusion

This investigation concerns about of fatigue behavior under controlled loading and under strain control for hybrid specimens with parts produced with conventional processes in steel AISI H13 and the stainless steel AISI 420 and the rest part produced by laser powder bed fusion in AISI 18Ni300 steel. The controlled loading tests were performed in constant and variable amplitude. Fatigue failure of hybrid samples occurs mostly in laser-melted parts, initiated around the surface, in many cases with multi-nucleation and propagated predominantly between the deposited layers. Fatigue strength of hybrid parts, tested under displacement control is similar, but for specimens tested under load control the fatigue strength the fatigue strength of hybrid specimens is progressively lesser than laser powder bed fusion samples. Despite a tendency to obtain conservative predictions, Miner’s law predicts reasonably the fatigue lives under block loadings. The interface between materials presented an excellent joining and fatigue strength because the fatigue failure of hybrid samples occurred mostly in laser melted parts out of the interface.

Production of Hybrid Joints by Selective Laser Melting of Maraging Tool Steel 1.2709 on Conventionally Produced Parts of the Same Steel

Joining additively manufactured (AM) complex shaped parts to larger conventionally produced parts can lead to innovative product designs. Another alternative is direct deposition on a conventional semi-product. Therefore, similar joints of maraging tool steel 1.2709 were produced by AM deposition of powder of this steel on a bulk conventionally manufactured steel part. The resulting hybrid parts were solution annealed and precipitation hardened. Solution annealing at 820 °C for 20 min was followed by furnace cooling. Precipitation hardening was performed at 490 °C for 6 h. The mechanical properties of the samples were characterised using tensile testing and hardness measurement across the joint. Metallographic analysis was also carried out. The tensile properties of the AM and conventionally produced steel after equivalent heat treatments were also determined as the reference values. The mechanical properties of the hybrid parts are close to the properties of both steels. The hybrid parts in the as-built condition had a tensile strength of 1029 MPa and a total elongation of 14%. Solution annealing did not change these properties significantly, except for yield strength, which decreased by approximately 150 MPa. After precipitation annealing, the strength was higher, 2011 MPa, and total elongation dropped to 5%.

Fiber Orientation Mechanism of Continuous Fiber Reinforced Thermoplastics Hybrid Parts Joined with Metallic Pins

Continuous Fiber Reinforced Thermoplastic (CFRT) hybrid parts offer interesting possibilities for lightweight application, which can exceed the capabilities of mono material metal or CFRT parts. In this case, the joining technology oftentimes is the limiting factor. This study investigates a joining operation with metal pin structures which are additively manufactured via powder bed fusion featuring different diameters and tip geometries, which are inserted into the locally infrared heated CFRT part. The resulting fiber rearrangement is assessed using transmitted light microscopy, confocal laser scanning microscopy as well as micro-computer-tomography. It could be shown that for all assessed pin variants a similar distinct fiber displacement can be seen and that the pin diameter has a significant effect on the resulting fiber orientation with smaller pin diameters being advantageous because of gentle fiber displacement and reduced undulation. The tip geometry has only minor effect on the fiber orientation. Especially in the X/Y plane no systematic influence of the tip geometry on the fiber displacement could be observed. Based on the gained insights a three-stage model of the fiber orientation processes is proposed.

CASE GOVERNMENT OF VERBAL NOUNS IN POLISH AND UKRAINIAN

The purpose of the article is to perform the comparative analysis of case government (rekcja) of Polish and Ukrainian verbal nouns. The fulfilment of this purpose requires describing the status of verbal nouns in linguistics, clarifying the terminological apparatus, proving the verbal nature of these formations, comparing case government in Polish and Ukrainian, in particular, due to the existence of categories of transitivity and valence as well as establishing common and distinctive features.Methods. The application of the comparative and typological method allows to compare the semantic and syntactic features of verbal nouns of two related languages. Methods of deduction and induction were used to systematize, describe and generalize the identified features and differences.Results. Verb nouns ending with -nie, -cie // -ння, ття possess a pronounced verbal nature, as evidenced by the preservation of the case government, namely: the form of the governed noun dependent on the verbal noun denotes the object to express certain syntactic relations like the one dependent on the verb. The case government of verb nouns ending with -nie, -cie // -ння, ття is expressed by the categories of transitivity and valence. At the level of syntagmatics, the semantics of transitive / intransitive action of verbal nouns affects their compatibility and becomes a defining feature for distinguishing components of the semantic paradigm of a polysemous verbal noun. VNs generally have the same valence as the root verb (with or without a preposition), but there are a number of differences, particularly in prepositional government. In contrast to Ukrainian, a number of Polish verbs can be used with an object in the form of a verbal noun due to the fact that Poles perceive the world more ‘object-based’, and Ukrainians have an organic ability to see life in dynamics, movement and convey it using verbs.Conclusions. Hybrid parts of language are a little-studied and relevant aspect in modern linguistic research, in particular in the context of structural and semantic differences against the background of Slavic languages. Verbal nouns are a clear example of hybridity as they combine categories typical for different classes of words, such as verbal grammatical categories of aspect, voice, mood, and transitivity / intransitivity as opposed to noun categories of gender and case.Key words: valence, transitivity / intransitivity, case government, semantics. Метою статті є зіставний аналіз сполучуваності (рекції) польських та українських дієслівних іменників. Реалізація поставленої мети передбачає опис статусу дієслівних іменників у мовознавстві, вияснення термінологічного апарату, дове-дення дієслівного характеру цих утворень, порівняння дієслівної рекції у польській та українській мові, зокрема завдяки наявності категорій перехідності та валентності, встановленню спільних та відмінних ознак.Методи. Застосування зіставно-типологічного методу дало змогу порівняти семантико-синтаксичні особливості дієслів-них іменників двох споріднених мов. З метою систематизації, опису та узагальнення виявлених особливостей та відмінностей використовувалися методи дедукції та індукції.Результати. Дієслівні іменники на -nie, -cie // -ння, ття мають виражений дієслівний характер, про що свідчить зокрема і збереження дієслівної рекції, а саме: залежна від дієслівного іменника форма керованого іменника позначає об’єкт, як і при дієслові для вираження певних синтаксичних відношень. Рекція дієслівних іменників на -nie, -cie // -ння, ття виражається за допомогою категорії перехідності та валентності. Семантика перехідності / неперехідності дії віддієслівних іменників на рівні синтагматики впливає на їх сполучуваність і стає диференційною ознакою розрізнення компонентів семантичної парадигми багатозначного віддієслівного іменника. ДІ здебільшого мають таку саму валентність, як і твірне дієслово (з прийменником чи без), проте є ряд відмінностей, зокрема в прийменниковому керуванні. Низка польських дієслів може вживатися з додатком у формі дієслівного іменника, на відміну від української мови, що пов’язане з тим, що поляки сприймають світ більш ‘опред-мечено’, а українці мають органічну здатність бачити життя в динаміці, русі й передавати це дієсловом.Висновки. Малодослідженим та актуальним аспектом у сучасних мовознавчих дослідженнях є гібридні частини мови, зокрема в контексті структурно-семантичних відмінностей на тлі слов'янських мов. Дієслівні іменники є яскравим прикладом гібридності, оскільки поєднують у собі категорії, характерні різним класам слів, як наприклад, дієслівні граматичні категорії виду, стану та способу протиставляються іменниковим категоріям роду та відмінка.Ключові слова: валентність, перехідність / неперехідність, дієслівне керування, семантика.

Influence of Stress States on Forming Hybrid Parts with Sheet Metal and Additively Manufactured Element

Hybrid parts with additively manufactured elements (AME) combine the advantages of two or more manufacturing processes, e.g., forming and additive manufacturing (AM), and thus offer a solution to the increasing demands of industrial trends such as personalized mass production. Despite their advantageous properties, research in this field still lacks in clear classification and process interactions. Due to the strong influence of the AME on the formability of hybrid parts, the combination of laser-based powder bed fusion (PBF-LB) with subsequent sheet metal forming is examined in this paper. Therefore, cylindrical functional elements are built up on sheet metal and the resulting hybrid components are subsequently formed. Common forming processes such as bending, stretch forming and deep drawing are compared in regard to the different stress states. The results show a reduction in formability for hybrid components compared to conventional sheet metal materials. Reasons found are geometrical properties, gradients of mechanical properties and induced stresses. Consequently, requirements for the additive manufacturing process regarding a subsequent forming process are outlined. Namely, the gradient of mechanical properties should be smoothened, residual stresses kept low and the design of AMEs should avoid stress concentration.

Stretch Forming of Ti-6Al-4V Hybrid Parts at Elevated Temperatures

Hybrid components produced by two or more different process technologies grant the possibility to compensate the drawbacks of the used processes. The combination of additive manufacturing (AM) and forming offers geometrical freedom in extensions of geometrical simple parts in a cost-efficient way. Unlike the combination of bulk metal forming and AM, sheet metal forming and AM is less investigated. Especially for Ti-6Al-4V, which is widely used in AM but has a low formability at room temperature, research is still needed. In this study, the formability of hybrid parts made of Ti‑6Al‑V consisting of sheet material and additively manufactured elements (AME) is investigated for a hemispherical punch geometry. Thus, a designed tool for forming of hybrid parts at elevated temperatures is used. First investigations with a specially designed stretch forming tool demonstrate the distinct influence of the additively manufactured bodies on the stretch forming process of hybrid parts made of Ti‑6Al‑4V. Namely, the achievable drawing depth is reduced for hybrid parts as the functional elements are placed in the area of highest stresses, distorting material flow.