On the inextensional axial collapse of thin PVC conical shells

Inextensional collapse mechanisms are presented for the axial crumpling of thin-walled circular cones and frusta (truncated circular cones). Shortening of the (thin) shell height is achieved by folding in a non-symmetric diamond mode about stationary circumferential and inclined plastic hinges; collapse proceeds progressively from the narrower end of the conical shell during the passage of a travelling hinge. Expressions for the various mean crushing loads, when collapsing frusta of rigid-perfectly-plastic material, are developed. Theoretical collapse modes and predicted loads are compared with those obtained experimentally by collapsing rigid PVC conical shells of constant axial length, of various wall-thicknesses and semi-apical angles, as well as metal (aluminium alloy and low-carbon steel) conical shells of similar geometry; agreement is found to be good.     

Analysis of failure mechanisms observed in axial collapse of thin-walled circular fibreglass composite tubes

Theoretical analysis of the failure mechanism of the stable mode of collapse of thin-walled fibreglass composite tubes under static axial compression, based on experimental observations and taking into account all possible energy absorbing mechanisms developed during the process, is reported. Crushing loads and the energy absorbed are theoretically predicted. The proposed theoretical model was experimentally verified for various composite materials and tube geometries and proved to be very efficient for theoretically predicting the energy absorbing capacity of the shell.     

Upper- and lower-bounds for rectangular plates transversely loaded

A new technique, the ‘end-fixity coefficients method’, is developed for the prediction of upper- and lower-bound loads to cause the plastic collapse of thin, uniformly loaded rectangular plates of rigid-perfectly plastic material, which is assumed to flow according to the Johansen yield criterion, re-deriving some well-known results and extending the analysis to other cases of loaded plates. The proposed theory has unified application for the analysis of plate bending, under various boundary conditions, taking into consideration the clamping conditions of plate sides.     

Computer-aided selection of ISO manufacturing limits for interference fit joints

Consideration is given to the problem of selecting ISO manufacturing limits to be assigned to parts thats are to be connected via an interference fit joint. Factors such as the functional requirements of the end assembly, the manufacturing capabilities of the manufacturer concerned and the limitations imposed by this very nature of the ISO Limits and Fits system have been considered.An interactive computer program for the selection of ISO interference fits with nominal joint diameter less than 500 mm, written in MBASIC computer language, was developed. The program can run on a desk-top micro-computer and it is believed that its usage in industry will considerably facilitate the interference fit selection procedure.     

On the experimental investigation of crash energy absorption in laminate splaying collapse mode of FRP tubular components

In this experimental work the crash energy absorption of fibre reinforced plastic (FRP) tubular components that collapse in laminate splaying mode is investigated by means of a new testing method, the “curling test”. This test method was used trying rectangular carbon, aramid and glass FRP strips—in which the reinforcing fibres were in the form of reinforcing woven fabric (carbon and aramid FRP specimens) and multi-axial fibre reinforcements (glass FRP specimens). Apart from the analysis of the system of bending and friction forces acting on the specimens during the curling tests in comparison with the forces acting in the case the laminate splaying collapse mode and the observations related to the deformation and crushing induced on the FRP specimens by this force combination, the analysis of the test results focused on the influence of the most important geometric and laminate material properties—such as thickness, flexural rigidity, number of reinforcing fibre layers, laminate stacking sequence and constituent material mechanical properties—on the specific energy absorption and the peak load.     

Crashworthy characteristics of axially statically compressed thin-walled square CFRP composite tubes: experimental

In this paper the results of experimental works pertaining to the crash behaviour, collapse modes and crashworthiness characteristics of carbon fibre reinforced plastic (CFRP) tubes that were subjected to static axial compressive loading are presented in detail. The tested specimens were featured by a material combination of carbon fibres in the form of reinforcing woven fabric in thermosetting epoxy resin, and they were cut at various lengths from three CFRP tubes of the same square cross-section but different thickness, laminate stacking sequence and fibre volume content. CFRP tubes were compressed in a hydraulic press of 1000 kN loading capacity at very low-strain rate typical for static testing. The influence of the most important specimen geometric features such as the tube axial length, aspect ratio and wall thickness on the compressive response and collapse modes of the tested tubes is thoroughly analysed. In addition, the effect of the laminate material properties such as the fibre volume content and stacking sequence on the energy absorbing capability of the thin-wall tubes is also examined. Particular attention is paid on the analysis of the mechanics of the tube axial collapse modes from macroscopic and microscopic point of view, emphasizing on the mechanisms related to the crash energy absorption during the compression of the composite tubes.     

Electromagnetic Forming Tools and Processing Conditions: Numerical Simulation

Finite element (FE) modeling is used to simulate the electromagnetic forming process. Two industrial tools are considered: a four-turn compression coil with a ferromagnetic screen and a stepped field shaper as well as a seven-turn pancake coil with a ferromagnetic outer screen. Details on FE model building are thoroughly discussed. The input load is the current of the coil, which can be experimentally measured. The deformation characteristics of the workpiece as well as the electromagnetic variables of the high-energy rate process (i.e., the magnetic flux density around the conductors and the Lorentz forces acting on the workpiece) are calculated numerically. The effects of the various parameters of the electromagnetic forming process, such as initial charging voltage, workpiece material, and geometry as well as holding devices, are analyzed either theoretically or through FE modeling. In most cases, the dependent variable is the Lorentz force acting on the workpiece. The numerically calculated and analytical electromagnetic results are in good agreement. The present analysis is useful for the practical realization of the electromagnetic forming process, contributing also to a better understanding of its principles.     

Extracting knowledge on the links between the water body stressors and biotic integrity

Multi-metric indices of biological integrity (IBIs) are most frequently created by examining single biological metrics along gradients of environmental degradation, and then combining multiple metrics using "best professional judgment" to characterize and calibrate stressor-response relationships. We aim to provide an efficient data analysis and visualization tool to assess the simultaneous effects of anthropogenic stressors on the fish population through the fish metrics and the associated Index of Biotic Integrity (IBI). Kohonen's self-organizing feature maps (SOM), unsupervised neural networks, are employed to pattern the sampling sites in the state of Ohio based on similar metrics characteristics. Canonical correspondence analysis (CCA) allows us then to draw conclusions about the role of the environmental variables in maintaining the perfect abode for fishes. Different visualizations superimposed with SOM clustering are realized to explore the complex interrelationships in the aquatic system and aid watershed managers to comprehend the effects of the environment on the fish.     

Effect of the workpiece material on the heat affected zones during grinding: a numerical simulation

A simulation of the precision grinding of steel was performed using an implicit finite element code, namely the commercial code MARC, in order to describe the temperature fields developed during the process. The input data required a model obtained via a series of experiments, grinding several steels under the same grinding conditions in order to examine the effect of the workpiece materials on the temperature fields and the depth of the heat affected zones developed during grinding.