Modeling and stress analysis of wire ropes with parametric equations

Tel halat geometrisi imalat tarzından dolayı karmaşık bir yapıdadır. Halatın temel öğelerinden birisi halatın özünü oluşturan Bağımsız Tel Halat Çekirdeği (BTHÇ)’dir. BTHÇ ise ortasında yedi telden oluşan basit düz bir demet ve onu çevreleyen altı adet helisel sarılmış demetten oluşmaktadır. BTHÇ’nin merkez demeti ile dış demetinde yer alan helisel tellerin geometrileri arasında önemli bir fark vardır. Merkez demetin dış telleri tek helisel yapıya sahip iken, dış demeti oluşturan dış teller çift helisel yapıdadır. Bu sebepten ötürü dış demete ait dış çift helisel tellerin modellenmesi özel yöntemlerin kullanılmasını zorunlu kılmaktadır. Bu makalenin amacı, BTHÇ ile tel halatların modellenmesi için yeni bir tekniğin tanıtılması ve bu teknik ile elde edilecek sonuçların literatürde mevcut bulunan sonuçlarla karşılaştırılmasıdır. Öncelikle BTHÇ’nin merkezinde bulunan basit düz tel demetinin modeli oluşturularak modelin doğruluğu kanıtlanmıştır. Ardından BTHÇ’nin dış demetindeki dış tellerin çift helisel geometrisi incelenerek modellenme tekniği üzerinde durulmuştur. Farklı sarım teknikleri ile modellenmesi yapılan BTHÇ’lerin modelleri anlatılmıştır. BTHÇ’nin sonlu elemanlar kullanılarak analizleri sonucunda tel bazında elde edilen sonuçların analitik sonuçlarla mukayesesi yapılmıştır. En son olarak BTHÇ’nin öz olarak kullanıldığı Seale tipi tel halatların modellenmesi ve analizi yapılmıştır. Elde edilen sonuçlar literatürde bulunan analitik ve test sonuçlarıyla karşılaştırılmış ve iyi uyum sağladıkları görülmüştür. Sonuç olarak tanıtılan yeni modelleme tekniği kullanılarak kolay ve daha efektif bir biçimde sayısal analiz yapma olanağı sağlanmıştır. Aynı zamanda uygulanan yöntem daha basit ve daha pratiktir.  Anahtar Kelimeler: Tel demet, bağımsız tel halat çekirdeği, çift helisel geometri, Seale tipi halat modelleme.Loads and moments over an helical wire geometry is the fundamental starting point of the wire rope theory. The equilibrium equations are derived from the equilibrium of this wire and it has been presented by Love (1944) in his well-known treatise. Solution of the equilibrium equations under axial loading and pure bending is presented by Love (1944). Frictional and contact effects are not included in the theorethical investigations of the problem due to the complicated geometry. Without taking into account the frictional effects, nonlinear problem of wire rope theory is solved using linearization of the equilibrium equations. A simple wire strand is composed by a straight wire which is wrapped by six outer single helical wires. An independent wire rope core (IWRC) is composed by a simple straight strand as a core strand which is wrapped around by six outer helical strands. The outer wires of the core strand is helical shaped wires while the outer wire of the outer strands is double or nested helical wires. Double or nested helical wire geometry is not included in the analytical solution procedures during the development of the theory of wire ropes. Superposition theory is used for the solutions of the IWRC which takes into account core strand as a straight wire while the outer strands as a single helical wire. IWRCs are widely used as a core for more complicated wire ropes at present. Most of the well known structures are Seale and Warrington IWRC. IWRCs are preferred when the wire rope is run under large lateral compressive loads and additional axial loading capacity is required (Velinsky, 1989). During the literature survey, the first analytical analysis are done by Hruska (1951, 1952, 1953). Hruska did not take into account the frictional effects due to contacts while solving the equilibrium equations given by Love (1944). Only geometrical aspects, axial loading and pure bending are discussed during the early studies. Since then Costello (1990), and later, Utting and Jones (1987) have followed a more fundamental approach. They treat each wire of wire rope as a helically curved rod but make differing assumptions relative to the rope geometry or the interwire contacts. The different theories produce results, which remain close to the experimental values presented by Utting and Jones (1987), but the question of the actual relative displacements and forces within a rope is nevertheless still open. Early studies of the wire ropes under axial loading condition obtained by using finite element analysis are given by Jiang and Henshall (1999). Then this study is extended to three layered strand by Jiang et.al. (1999,2000). These analysis are based on a simple sector of 1/12 or 1/6 of the wire rope cross-section, an arc length or a percentage of the pitch length is taken into account generally. Meanwhile during the literature survey, analytical models conducted for IWRC have not mentioned double helical wire geometry until 2004. Most of the analitical analysis rely on homogenization process except theoretical studies of Elata et.al. (2004), Usabiaga and Pagalday (2008). In this article, wire rope geometry is modelled in a more realistic manner taking into account the double or nested helical geometry of the outer wires of the outer strands for IWRC. To accomplish this, a code is generated named Wire Rope Skeleton (WRS) which creates the centerline of the specified wire in a strand, IWRC or Seale IWRC. Proposed modeling scheme considers each wire with its real solid behaviour. Thus analysis over the wire rope with proposed structure gives more realistic results. To model long wire rope models in 3-D is a cumbersome issue due to the irregularities encountered on the surface of the wires while meshing. The proposed modeling scheme solves the meshing problems of long wire ropes. Also the interactions between wires are defined by contact definitions and friction is taken into account. Realistic material properties are defined and analytical results, test results available in the literature and the finite element analysis results are compared simultaneously. It has been concluded that the proposed modeling procedure works for a wire strand and its development to IWRC and Seale IWRC also gives reasonable results. This analysis technique gives more information about the interwire contacts. As this face this modeling scheme and analysis methodology gives oppurtunity for the future analysis. Keywords: Wire strand, independent wire rope core, double helical geometry, Seale type rope modeling.

(E)-N-[(2-Ethoxynaphthalen-1-yl)methylidene]-2-ethylaniline

In the title compound, C21H21NO, the dihedral angle between the naphthalene ring system and the benzene ring is 64.61(6)°. The molecular structure is stabilized by an intramolecular C-H?N hydrogen bond

A qualitative and quantitative analysis of Turkish forest policy documents in the rural development scope

The interaction between forest resources and forest villagers has made rural development a privileged component of Turkish forest policy. In this context the main aim of the study was to investigate the framing of rural development issues in national forest policy by using content analysis method. The economic aspect is the most prominent dimension regarding rural development in the context of national forest policy, environmental and socio-cultural factors follow it respectively. Also, the main approach depends on supporting the forest villagers and its development is seen as an essential tool to protect the forest resources

Differences between urban and rural population with respect to demand on forestry aspects, in a case study of the Turkish province of Bal kesir Diferenças entre a população urbana e rural em matéria das suas exigências de silvicultura, estudo de caso da província turca de Bal kesir

Inhabitants of urban and rural areas are important participants in the process of developing and implementing forest policy. Thus, it is essential to determine their demands and attitudes towards forestry issues. In this context, the demands and evaluation of forest functions are investigated in a case study of the Turkish province of Bal kesir. The findings of the case study show that differences in terms of demands among inhabitants of rural and urban areas are related to forest fires fighting, crimes fighting, forestry-tourism integration, forestation and regeneration activities, and the enlargement of forest areas. The main differences among their assessments of forest functions are related to fire wood production, and the provision of flood and erosion control, nature protection, and recreational opportunities. The findings are important for conflict management and for local decision making. By using the findings of similar studies, the provincial organizations should harmonize their priorities with the expectations of relevant interest groups.<br>A política de silvicultura da população urbana e rural é uma participante fundamental no processo de formação e execução das florestas. Portanto, é importante determinar as exigências e as aproximações em matéria da silvicultura. A determinação das exigências da população urbana e rural no âmbito desse processo e a interpretação destinada aos assuntos das funções da floresta foram pesquisadas tendo como base a província turca de Bal kesir. As constatações resultantes do estudo na região demonstraram que as diferenças entre as exigências da população urbana e rural em matéria da silvicultura são a luta contra os incêndios florestais, a luta contra os delitos florestais, a integração de silvicultura-turismo, as atividades de reflorestamento e rejuvenescimento da floresta e a ampliação dos campos florestais. Por outro lado, as diferenças fundamentais entre as constatações feitas em matéria das funções da floresta são a produção de lenha, a prevenção de erosão e inundação, a protecção natural, o projeto de recreação. Os resultados obtidos são importantes para a gestão de estudo e para a tomada de decisões no âmbito local. As instituições locais devem adaptar as suas prioridades e as exigências dos grupos interessados tirando proveito das constatações obtidas em estudos semelhantes