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We focus on applications from the automotive industry, on mechanical components submitted to vibration loads. On one hand, the characterization of loading for dimensioning new structures in fatigue is enriched and updated by customers data analysis. In a second hand, the loads characterization also aims to provide robust specifications dedicated to the simulation or test rigs. We aim to provide vibration specifications that are adapted to a calculation time or physical test durations in accordance with the pace imposed by the projects timeframe. The vibration specifications need to be robust by taking care of the diversity of vehicles and markets considered in the projects. In the trucks industry, the dynamic behavior can vary significantly from one configuration to another. For non-stiff structures, the lifetime depends, among other things, on the frequency content of the loads, as well as the interactions between the components of the multi-input loads. In this context, this paper proposes to compare sets of multi-input loads applied on the non-stiff structure, i.e for which the frequency content of loads impacts the damage. [ABSTRACT FROM AUTHOR]

Quasi-axisymmetric structural components are very common in any mechanical equipment containing rotating components, such as turbo machinery. Identifying and exploiting symmetric properties in these components is key to simplify the creation of FE volume meshes. In this paper, a novel approach is proposed to detect exact cyclic symmetries, in order to decompose a quasi-axisymmetric CAD component for FEA. Starting from a B-Rep CAD model, axisymmetric and cyclic repeated sectors are automatically identified to generate a subdivided representation, which can then be used to produce a good quality mesh. Using this new component structure, the resulting decomposition produces a reduced number of mesh-able sub-domains. Symmetry properties can then be inferred to generate the full component mesh from meshes on the individual sub-domains. The approach shows a major reduction of the geometry to be meshed leading to less manual intervention from the user. [ABSTRACT FROM AUTHOR]

In seismic codes, the acceleration demand of nonstructural components is commonly expressed in terms of floor response spectra and estimated by means of simple predictive equations. By using the latter, response-history analysis of the structure is not required, being floor spectra calculated directly from the peak ground acceleration expected at the site. The price for this simplicity in the method used for the estimation of floor spectra is the generally poor approximation of the obtained predictions. Codes’ equations, in fact, do not explicitly account for important factors influencing floor spectra, such as the contribution of the higher modes of vibration of the structure and the actual value of the nonstructural components’ damping ratio. Alternative spectrum-to-spectrum methods for direct generation of floor spectra have been proposed, which include these factors and improve the accuracy of the predictions. Different approaches have been used and several methods developed. Despite large research effort, however, a comparative evaluation of the currently available proposals is still lacking. The objective of this paper is to fill this gap, by reviewing selected proposals representative of practice-oriented spectrum-to-spectrum methods. A case study consisting in a six-story frame is analyzed and predictions obtained with the investigated methods are compared with exact floor spectra derived from time-history analyses of the structure, as well as spectra calculated using the Eurocode 8 equation. [ABSTRACT FROM AUTHOR]

Multi-storey buildings may have a valuable inventory consisting of objects that can be damaged during an earthquake causing unacceptable losses. Building contents are often modelled as equivalent rocking rigid blocks, while their dynamic response depends on the geometry of the object, the characteristics of the building and the storey that the object is located. We discuss the vulnerability, risk and loss assessment of the contents of multi-storey buildings. This is a complicated task, since the response of the block and the structure are coupled, the former being acceleration-sensitive and the latter drift-sensitive. We first discuss a performance-based seismic assessment framework for rocking block objects. Our risk assessment framework is based on nonlinear response history analysis, while simplified approaches using nonlinear static pushover methods are also possible. [ABSTRACT FROM AUTHOR]

Giga-cycle fatigue (10 7 ˂ N ˂ 10 10 cycles) is subject of interest of the most important research centres in the world. This interest is involved by existing fatigue fractures of real mechanical parts after more than billions cycles and with growing demands on reliability and safety of structural components. Stainless austenitic steels are used in transport devices which are operated for long time at high temperatures. During operation at higher temperatures in these steels can occur microstructural changes, as result of sensitisation which can cause embrittlement. Authors present their own experimental results about fatigue resistance of sensitised austenitic stainless steel AISI 316L in the very high cycle region (N = 2×10 6 ÷ N = 5×10 9 cycles). Fatigue tests were carried out on the ultrasonic fatigue testing machine (f = 20 kHz) with symmetrical push-pull loading (R = -1) and at temperature 20±5 °C. In the very high cycle region was observed continuous decrease of fatigue strength and there was no effect of sensitisation recorded on the fatigue properties. [ABSTRACT FROM AUTHOR]

A three-dimensional visualization system was developed to investigate the dynamic state of bridge components using portable sensors located at multiple points. The system utilizes wireless data transfer and real-time signal processing for on-site output of the dynamic oscillation of bridge components. Vibrational modes (bending, twisting, and translation) are determined upon excitation by an external load. In this study, a sensor fusion technique was introduced to enhance the accuracy of motion visualization. An angular velocity sensor and an accelerometer were mounted within each sensor box. The same sensor boxes were prepared, and boxes were placed at 12 positions in all. The performance of the system was checked using a mock-up reinforced concrete beam. In cyclic loading tests of the mock-up, variations in the natural vibration frequency and its mode shape were observed. It was shown that disturbance of the initial motion may be used to detect crack initiation, and that changes in the mode shape may be used to detect the location of the damaged area. [ABSTRACT FROM AUTHOR]

The structural components from structures such as bridge members are subjected to a long operating period of time. The problem of fatigue cracks is more interesting in existing bridge structures with existing cracks. In case of the structures erected at the turn of the 19 th and 20 th centuries, the cracks are natural elements of the old steel metallic structures. The uniaxial fatigue crack growth description lead us often to significant errors in predicting of a residual lifetime. As a good example, it can be a residual lifetime of the riveted joints in such a type of structures. On the other hand, the 19 th century structures were erected with puddled iron or low carbon mild rimmed steel. The experimental results [1,2] obtained by authors, have shown that the fatigue cracks grow much faster than its modern equivalent. This phenomenon is supported by microstructural degradation processes [2] . In this paper some examples of degenerated microstructures have been presented. In order to fill a lack in experimental data in the literature, the results of a mixed mode (I+II) fatigue crack growth have been presented and discussed within the background of Fracture Mechanics models. All the results have been implemented into the Abaqus environment. [ABSTRACT FROM AUTHOR]

Major variables which cause internal fatigue crack initiation are nonmetallic inclusions in high strength steels, surface roughness and notch in structural components and corrosive environments. This paper focused on the effect of stress concentration factor and corrosive environment for internal fatigue crack initiation of structural materials mainly based upon author's experimental results.In the results of conventional and ultrasonic fatigue testing on notched specimens with stress concentration factor of 1.5, 2.0 and 2.5 for 0.65 mass % carbon matrix high speed steel with HRC 60.7, subsurface fatigue crack initiation was observed on all notched specimens at failed number of cycles over than 10 6 . On the contrary fatigue crack initiated from notched specimen surface for powdered high speed steel with HRC 67 with stress concentration factor of 2.0. The fatigue crack initiation mode in notched specimens at high cycle region may be governed by surface hardness of high speed steels. The different effect of corrosive environment on fatigue crack initiation is demonstrated in the plate bending fatigue testing results of 1% carbon steel and13Cr-1Mo steel in refrigeration compressor gaseous environment. For 1% carbon steel fatigue crack initiated from subsurface at lower fatigue life of 5x10 6 cycles,while fatigue crack initiated from surface corrosion pit at higher fatigue life of 5x10 6 cycles. For 13Cr-1Mo steel subsurface fatigue crack initiation was predominantly observed in air and in refrigeration compressor gaseous environment. [ABSTRACT FROM AUTHOR]

Reinforced steel rebar is commonly supplied in one-dimensional stocks and typically designed for and installed in various structural components in civil and industrial construction. Surplus reinforcement constitutes a major fraction of construction generated waste. Cutting one-dimensional stocks to suit construction project requirements results in cutting losses. Therefore, reducing steel waste (or minimizing cutting losses) has long been the focus of academic research in one-dimensional stock design and cutting problems. Previous research developed mathematical models in an attempt to analytically minimize cutting losses based on preliminary engineering designs, but little insight has been provided on how to integrate minimization of cutting losses and engineering design into an integrated optimization problem, let alone considering minimizing total steel rebar installation cost as a parallel objective. The sustainability issue in regard to balancing reinforcement waste and crew installation costs on the basis of optimized engineering design has yet to be addressed. This study introduces a Mixed Integer Programming (MIP) approach to generate optimal cutting patterns, minimum cutting losses and associated total installation cost. A reinforced concrete slab case is adopted as a test to show that the proposed methodology is capable of producing optimal tradeoff solutions in slab reinforcement detailing design, resulting in less wastage and lower crew installation cost. [ABSTRACT FROM AUTHOR]

In this study, a design analysis was performed through non-destructive test by rectangular rosette and uniaxial strain gages with FEA, between a structural aerospace assembled component of aluminium and a proposal part machined in one step with the same geometric characteristics. The analysis showed that the proposal part machined in one step has a trend to obtain less strain (0.5156mɛ@46.44N rectangular rosette strain gage, 0.4796 FEA) than the assembled component (0.7012mɛ@46.44N rectangular rosette strain gage, 0.7793 FEA). These findings indicate that the proposal part is a structural element with greater structural stiffness in comparison to the assembled component. [ABSTRACT FROM AUTHOR]

Based on flight test data, an identification technology for dynamic loads is proposed in this paper. Thereafter, the assumption, theory, and identification flow-chart are also provided. Taking structural component vibration data of an aircraft during flight test as an example, an engineering application of identifying dynamic loads based on flight test data is offered. The approach presented in this paper is fit for engineering practices, especially for fast evaluation of structural dynamical strength during flight test. It can also be used for predicting or evaluating structural vibration fatigue life [ABSTRACT FROM AUTHOR]

Automobiles are required weight reduction and improvement of collision safety. Additionally, rigidity of vehicle bodies is important performance that affects driving stability. Collision safety and rigidity of vehicles are strongly affected by strength and rigidity of the structural components. Accordingly, they are made of high strength steel / ultra-high strength steel and have closed cross section shapes (closed-profiles). Conventional closed-profile components are currently assembled by spot welding of two press-formed parts. Flanges of press-formed parts are required for spot welding and inhibit weight reduction. In the present situation, a new forming method was developed for closed-profile parts without flanges. The developed method was constituted three forming processes by using conventional mechanical press machines. In the 1st process, a steel sheet was partially stretched for adjustment of the cross section length and formed folds at ridgeline positions of the final shape. In the 2nd process, the formed sheet in 1st process was bent by press forming. In the 3rd process, the formed sheet in 2nd process was closed to hexagonal cross section shape by side tools which were driven transversely by cams. And finally it was added compression in plain by the punch. Trial product by the developed forming method satisfied the target performances (bending and torsion rigidity and collision strength). Weight reduction ratio was 39% by optimization of the cress section shape and removing flanges. [ABSTRACT FROM AUTHOR]

Abstract: The structural behaviour of a bicycle saddle is mainly affected by the shell and the rails properties and by their assembly connections. The knowledge of the stress acting on these components is therefore fundamental for a safe and performing saddle engineering design. The aim of the work was the measurement and analysis of the strain/stress state of shell and rails of a bicycle saddle during real cycling conditions. The shell and the rails of a saddle were instrumented with a total of 16 strain gauge channels, allowing the measurement of the local deformations of shell and rails. Two field test sessions (one for road cycling and one for mountain bike riding) were performed with two professional cyclists different for body height and weight (65 and 76kg). Reported results regard the analysis of rails cyclic stresses due to road pedalling and of stress cumulative spectra obtained during road and mountain bike sessions. Right and the left portions of the rails were loaded symmetrically. The two testers showed large differences in the pedalling style and in the cycling posture. The stress on the front and rear rails portions was mainly influenced by the cyclist posture and pedalling style. An increase of the road slope caused an increment of the stress range and mean values; the damage ratio between mountain bike and road load spectra for an equivalent cycled distance resulted to range between 6 and 9, depending on the tester involved. [Copyright &y& Elsevier]

Abstract: Approximation of structural components by the plane model 2D is most frequently applied in the design practice. This paper presents simple, technical and engineering procedure of modelling flat slab of reinforced concrete slab-column structures and so allows to obtain in the plane model 2D results close to those of the very difficult modelling by solid elements. [Copyright &y& Elsevier]

Abstract: Many structural components are subjected to cyclic loading, fracture being the most common form of failure. Design life assessment and reliability prediction of engineering components for in-service conditions, with the external loads of irregular and random nature, are obviously critical issues. The present work is an investigation of fatigue crack growth rates and design life assessment of the structural components subjected to various types of fatigue loadings. The life prediction has been carried out by linear elastic fracture mechanics (LEFM) principles using commercial package MATLAB(R) and FORTRAN(R) programming language. Modified Wheeler Model (MWM) and Crack Closure Model (CCM) have been applied to evaluate fatigue crack growth and its retardation due to interaction between the materials and various overloads (single, multiple and spectrum). The MWM is based on plasticity induced effects in front and in the wake of an advancing crack and CCM is based on the crack closure effects. Studies on design life assessment of cracked plate panels and other structural members subjected to tensile-compressive overloading-underloading have been carried out for validating these models. Quantitative retardation based on the residual stresses with an effective stress intensity factor has been developed using MWM and applied to the material specimen: plates with center crack-350 WT Steel, 7075-T6 Al- Alloy and plate with edge crack for 6061-T6-Al-Alloy to predict the design life of components under various fatigue loadings. The results obtained have been compared with the experimental results. Various fatigue crack growth rate equations of constant amplitude loading models in conjunction with Wheeler Model have been incorporated in the design life estimation and compared with the experimental data and are in good agreement. [Copyright &y& Elsevier]