1,721,073 research outputs found
Editorial: bolted joints and mechanical connections of components
No full textThis special issue, dedicated to bolted joints and mechanical connections, offers an attractive selection of the recent and modern findings on mechanical fastening and their products. It is widely demonstrated that fastening systems play a fundamental role for all engineered products especially because they are, nowadays, driven by the continuously pursuit of highest strength to weight ratios. Structural components are getting lighter by taking advantage of the favorable features offered by high strength steels, titanium, aluminum and magnesium alloys as well as fiber reinforced plastics. Among the wide range of fastening systems, which have to withstand increased thermal, mechanical and environmental impacts, threaded components are the most common and dominant solution for structural joining of different materials. Bolted joints have to be considered as important machine elements which will also play a major role for efficient products in future
Adhesives: Mechanical properties, technologies and economic importance
No full textIn this book, some interesting technologies and applications dedicated to adhesives are presented and discussed. First, the interference fitted and adhesively bonded joints are extensively studied as an effective means to increase the transferable load while reducing both the weight and the stress level of the joined components. In such type of joints, the influence of the assembly technique on the shear strength of the joints has been investigated. Therefore, the shear strength of hybrid joints realized by �press fitting�, by �shrink fitting� or by �cryogenic fitting� were compared in order to suggest the best way of joining both for technological and economic importance. Then, some design aspects for practical application (for instance in the automotive steel wheel) were analyzed. The adhesive and interference contributions to the resultant resistance of the hybrid joint were carried out with particular attention to the phenomena occurring at the interface. The effect of the adhesive nature, its curing technology and its mechanical response were strongly related to the type of adhesive exploited. Also, the static and fatigue strength properties of press fitted and adhesively bonded joints was studied by considering their Engagement Ratio, which is the ratio between the coupling length and the coupling diameter. Coupling and decoupling tests have been performed both on press-fitted and adhesively bonded specimens and on pin-collar samples, considering four different levels for the Engagement Ratio. The study shows that the Engagement Ratio has a negligible effect on the shear strength of the adhesive and also on the relationship between the decoupling and the coupling forces. Then, the assessment of the adhesive performance of two binders for reassembling fragment porous stones and, more specifically, the effect of nano-titania in the hydration and carbonation of the derived mortars was investigated. The mechanical characterization indicated that the mortars with the nano-titania addition showed improved mechanical properties when compared to the specimens without nano-titania. This property can be exploited in the fabrication of mortars for reassembling fragments of porous limestones from monuments, where the presence of humidity controls the mortar setting and adhesion efficiency. Based on the physico-chemical and mechanical characterization of the studied adhesive mortars with nano-titania, binders of metakaolin-lime and natural hydraulic lime have been selected as the most appropriate formulations for the adhesion of fragment porous stones in restoration applications. Furthermore, the adhesive crack propagation was investigated for some load bearing applications. It was determined that fatigue cracks, either induced by defects or by applied stresses, may appear and propagate, thus becoming potentially harmful for the structural integrity of a part or a whole structure. Case studies are presented and discussed for adhesively bonded single lap joint (SLJ). Finally, a numerical method able to reproduce three-dimensionally the fatigue debonding and/or delamination evolution in bonded structures is proposed in this book in order to improve their performances. The cohesive zone model previously developed by the authors to simulate fatigue crack growth at interfaces in 2D geometries is extended to 3D cracks under mixed-mode I/II loading
Motorbike equilibrium
No full textThis chapter aims at defining the equations that govern the motorbike equilibrium and are useful for designing the front and the rear suspensions. Such equations are, in some case, non-linear and implicit so that they can be solved by recursive methods applied and presented in the Chap. 3 of this book. The mathematical models can be applied to different types of motorbike but they are developed for the peculiar case of those that adopt a single braking disk installed on front suspension and with a unique arm for the rear suspension
The front suspension
No full textIn this chapter, the authors introduce the telehydraulic fork, which has become, across the years, the most common kind of front suspension for motorbikes. In chronological order, some noteworthy patents are presented, which help the reader following the main steps of the technical evolution which gave front motorbike suspensions their current shape. Then, the behaviour of some key structural elements of the fork is examined, under the assumption that the fork is subject to a bending moment acting on the front wheel mid-plane. Such a noteworthy loading condition is frequently encountered during the life cycle of a motorbike: consider, for instance, an emergency braking manoeuvre. Tests which simulate the effect of a hard braking on the fork are also part of the product validation programmes of the main motorbike producers. It is illustrated an analytical model useful for calculating the stress state of the fork legs under said loading condition. Such a model takes into account some architectural configurations as well as some characteristic geometrical parameters of the fork and of the motorbike. The model was validated referring to some production forks, both by finite element analyses and by experimental tests on the road. In the case of forks equipped with a single brake disc, the load unevenness between the legs during braking is analysed, and some strategies aimed at reducing such loading unbalance are suggested. The model presented herein could be helpful for designers who are developing new fork models, because it allows foreseeing critical issues due to legs dimensioning since the early phase of product development, when FEA techniques may be difficult to implement
The rear suspension equilibrium
No full textThis chapter aims at defining the equations that govern the rear suspension in term of the overall equilibrium and loads applied for different conditions of the motorbike motion. The formulae are useful for designing a rear suspension made by a unique arm which connects the frame pin with the wheel axle. The equations are non-linear and implicit so that they can be solved by recursive methods applicable in a calc sheet. The mathematical models can be applied to different types of rear suspension but they are developed for the peculiar case of those equipped with an articulated mechanism which leads to a progressive stiffness of a single arm rear suspension
Example of loads and stresses acting on the rear suspension
No full textIn this chapter is presented an example (case study) of calculations and definitions of loads and stresses obtained by applying the formulae discussed in the Chaps. 1 and 2. The results are obtained using a calc sheet in order to solve the recursive problem caused by the implicit function of the equilibrium equation associated to the rear suspension and in order to produce the diagrams of loads and stresses. Loads and stresses have been calculated depending on some fixed and variable parameters while results are presented in tables and diagrams so that it is possible to highlight their trend and their maximum values
Special Issue Editorial
No full textThis special issue promotes the understanding of both fundamentals of engineering science and its application in the field of the Wood Engineering. It offers an attractive selection of recent and modern findings devoted to some smart solutions of challenges and problems in wood products and their applications
Fatigue strength of a fork-pin equivalent coupling in terms of the local strain energy density
No full textThe fork-pin coupling of the front suspension of a motorbike is very important for the reliability and the safety of the entire vehicle. One of the more important causes of failure of the component is fatigue under fully reversed bending load. In this work, the fatigue behaviour of fork-pin equivalent couplings made of 39NiCrMo3 steel is analysed by means of simplified specimens obtained by the interference of a cylindrical pin in a hollow cylinder reproducing the same static stresses present on the contact surfaces of the real component. The contact of the two bodies is modelled by means of Ansys (R) 9.0 and the stress field due to the interference is analysed and compared with that obtained by a strain gauge located on the external surface of the equivalent hub during the press-fit operation. By means of the same three-dimensional model, the local strain energy density (SED) averaged in a control volume, defined under mode I loading and surrounding the critical zone of the pin, is evaluated to summarize all fatigue strength data. The data, expressed in terms of the local energy, fall in the same scatter band with some other new data from plain and V-notched specimens made of the same material subjected to tension loading. Altogether about 60 new fatigue results are now available and presented in the paper
Fatigue strength of a fork-pin equivalent coupling in terms of the local Strain Energy Density
No full textThe fork-pin coupling of the front suspension of a motorbike is very important for the reliability and the safety of the entire vehicle. One of the more important causes of failure of the component is fatigue under fully reversed bending load. In this work, the fatigue behaviour of fork-pin equivalent couplings made of 39NiCrMo3 steel is analysed by means of simplified specimens obtained by the interference of a cylindrical pin in a hollow cylinder reproducing the same static stresses present on the contact surfaces of the real component. The contact of the two bodies is modelled by means of Ansys 9.0 and the stress field due to the interference is analysed and compared with that obtained by a strain gauge located on the external surface of the bush during the press-fit operation. By means of the same three-dimensional model, the local Strain Energy Density (SED) averaged in a control volume, defined under mode I loading and surrounding the critical zone of the pin, is evaluated to summarise all fatigue strength data. The data, expressed in terms of local energy, fall in the same scatter band with some other new data from plain and V-notched specimens made of the same material subjected to tension loading. Altogether about sixty new fatigue results are now available and presented in the paper
Special issue on new trends in mechanical design and product development
Full text linkThis special issue is devoted to a special selection of the best papers presented at the Mechanics and Materials in Design International Conference (M2D 2019) held in Bologna (Italy) in 2019. The M2D 2019 was the eighth international meeting of the M2D series, gathering hundreds of scientists and engineers interested in the fields of mechanics, engineering design, advanced materials, energy harvesting, reliability, quality, and safety engineering. It was held between 4th and 6th of September 2019. Almost 160 contributions in the fields of Mechanics, Materials and Design at varied length scales, as well as Biomechanics and Experimental and Computational Mechanics applied to Mechanical, Aeronautical, Automotive, Biomedical, Environmental, and Nuclear Engineering were submitted to the Scientific board. The best 100 of those papers were selected for an oral presentation with the goal to enable engineers, researchers and scientists to exchange ideas on the following and other derivative topics
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