M. Ulbin and T.K. Hellen
Finite element meshes can today be used to represent very complex structures because of high performance hardware and software. Although a very successful contributor to modern…
Abstract
Finite element meshes can today be used to represent very complex structures because of high performance hardware and software. Although a very successful contributor to modern engineering analysis, such techniques are prone to certain classes of numerical analysis errors which have been long recognized and widely investigated. A more recently recognized source of error has, however, received the attention of analysts, being due to the shape distortion effects of popular types of element, such as isoparametric elements. A mesh scanning program, BERQUAL, part of the BERSAFE system, highlights such potential sources of error, but a more precise assessment is only possible from the final results since element performance depends on the stress gradients in each element. Hence additional error checking using certain stress error measures has been devised and implemented in the post‐processing program PLOTTER, part of the BERSAFE system, to enable rapid, interactive, screen diagnosis. The error measures and implementation details are described and illustrated with suitable examples of progressive shape distortion effects.
Yves Gourinat and Vincent Lapoujade
The nonlinear dynamic modelling of safety net systems is approached at different scales. For this purpose, the fundamental rope dynamic tests are the reference for two basic…
Abstract
The nonlinear dynamic modelling of safety net systems is approached at different scales. For this purpose, the fundamental rope dynamic tests are the reference for two basic tools. One hand an analytical bidimensional model with explicit geometrical nonlinearity and bilinear material law is proposed for preliminary design. On the other hand, a nonlinear explicit finite element is defined for numerical modelling of net systems. Semi‐scale and full scale dynamic tests are performed to validate complete finite element models, suitable for global qualification of safety systems. The direct applications of these tools deal with explicit certification of safety systems for high‐speed sport, such as downhill competitions.
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Follows a presentation at a symposium in 1993 where the authors presented an experimental investigation on a fluttering membrane for use in a wind‐tunnel. Analyses the fluttering…
Abstract
Follows a presentation at a symposium in 1993 where the authors presented an experimental investigation on a fluttering membrane for use in a wind‐tunnel. Analyses the fluttering of an object by a theoretical method. Compares the experimental results with those of the theoretical and discusses their effectiveness. States that the present analysis is effective for approximate investigations.
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Genaro Rico-Baeza, Enrique Cuan-Urquizo, Gerardo I. Perez-Soto and Karla A. Camarillo-Gomez
The purpose of this paper is the study of flexural properties of architected lattice beams composed of modified body-centered cubic (BCC) structures when such are additively…
Abstract
Purpose
The purpose of this paper is the study of flexural properties of architected lattice beams composed of modified body-centered cubic (BCC) structures when such are additively manufactured with the liquid crystal display method. The BCC topology was modified by grading the dimensions of the cross-sections of the struts that compose them and their targeted distribution within the lattice beam.
Design/methodology/approach
Six gradations of strut cross-sections were proposed, and their effective stiffness was evaluated in compression finite element (FE) simulations. These were compared and categorized according to their stiffness. Then, these were distributed and arranged in a targeted manner, following two approaches: longitudinal and transversal. Experimental three-point bending tests and FE simulations were performed to characterize their effective flexural properties. The properties of targeted distributions were contrasted with those of uniform distributions.
Findings
Although the structures with longitudinal and transverse distribution presented the same relative density, they demonstrated different stiffness and strength. Beams with longitudinal distribution were 77% stiffer than those with transverse distribution. The method proposed here demonstrates how the effective mechanical properties and failure modes can be tailored by modifying the material arrangement in engineered structures while keeping the amount of material used constant.
Originality/value
The flexural properties of lattice beams with two types of grading and unit cell arrangements were studied. The literature has not deeply studied such a double degree of matter distribution and arrangement in structures.
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Zoran Stjepanovic and Helena Strah
Selection of suitable sewing needle is one of the most important parameters for ensuring an effective and fault‐free sewing process. This task requires good knowledge of basic…
Abstract
Selection of suitable sewing needle is one of the most important parameters for ensuring an effective and fault‐free sewing process. This task requires good knowledge of basic characteristics of a sewing needle, i.e. needle type, point shape and needle fineness. Also good knowledge of sewing materials is required. The contribution presents an analysis of important parameters that influence the sewing needle selection in women’s underwear production. The importance of those parameters in ensuring the appropriate seam quality is described. The selection of a suitable sewing needle was carried out on the basis of analysis of influential sewing parameters with application of machine learning from examples.
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Uğur Kemiklioğlu, Sermet Demir and Caner Yüksel
Adhesively bonded joints are used in many fields, especially in the automotive, marine, aviation, defense and outdoor industries. Adhesive bonding offers advantages over…
Abstract
Purpose
Adhesively bonded joints are used in many fields, especially in the automotive, marine, aviation, defense and outdoor industries. Adhesive bonding offers advantages over traditional mechanical methods, including the ability to join diverse materials, even load distribution and efficient thermal-electrical insulation. This study aims to investigate the mechanical properties of adhesively bonded joints, focusing on adherends produced with auxetic and flat surfaces adhered with varying adhesive thicknesses.
Design/methodology/approach
The research uses three-dimensional (3D)-printed materials, polyethylene terephthalate glycol and polylactic acid, and two adhesive types with ductile and brittle properties for single lap joints, analyzing their mechanical performance through tensile testing. The adhesion region of one of these adherends was formed with a flat surface and the other with an auxetic surface. Adhesively bonded joints were produced with 0.2, 0.3 and 0.4 mm bonding thickness.
Findings
Results reveal that auxetic adherends exhibit higher strength compared to flat surfaces. Interestingly, the strength of ductile adhesives in auxetic bonded joints increases with adhesive thickness, while brittle adhesive strength decreases with thicker auxetic bonds. Moreover, the auxetic structure displays reduced elongation under comparable force.
Originality/value
The findings emphasize the intricate interplay between adhesive type, bonded surface configuration of adherend and bonding thickness, crucial for understanding the mechanical behavior of adhesively bonded joints in the context of 3D-printed materials.