A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed at the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), whose rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the experimental research on the vibrations during the piling process and the analytical analyses of the gained signal. The results will be applied in the VPH control system.
The purpose of modelling a laminated windshield using the FEM is to provide a critical look on the way the adult headform impact tests are conducted in the process of motor vehicle certification. The main aim of the study is to modify the design of a laminated windshield in the context of a vehicle collision with vulnerable road users. The initial phase of the work was to develop a model of the adult headform impactor. The validation consisted in conducting a series of FEM analyses of the impactor certification testing according to the Regulation (EC) 631/2009. Next, the impact of the headform model on a windshield was analysed. The FEM model of laminated glass is composed of two outer layers of glass and an inner layer of polyvinyl butyral. FEM analyses of the impaction were performed at five points of the windshield characterised by various dynamic responses of the impactor and various patterns of glass cracking. In modelling the layers of glass, the Abaqus environment “brittle cracking” model was used. The following material models of PVB resin were considered: elastic, elastic-plastic, hyperelastic, and low-density foam. Furthermore, the influence of the mesh type on the process of glass cracking in a laminated windshield was analysed.
The paper presents a new way of hyperelastic materials specimens testing. For some time now Finite Element Method (FEM) Software allows to calculate stress in this kind of materials which make an engineering work easier. Unfortunately the results of the classical hyperelastic materials tests done so far do not give a possibility to use full abilities of FEM software. Furthermore, the attempts of conversion of classical type of data to FEM expected ones, do not lead to a correct solution. Such input data are accepted by software, but not physically correct. The specimens used for new types of elastomer tests are completely different, they are of different shape, they have to be hold and measured in a different way. These differences are described in the paper. PROBLEM STATEMENT All experiments defined by ISO or ASA are the tests which can deliver a lot of important information. Unfortunately most of this information is not appropriate to apply in mathematical material models used by FEM software. Only few laboratories or manufactures give more data then Shore hardness, IRH hardness, abrasiveness, temperature resistance, fluids resistance, oxidation resistance and others defined by standards. Mathematical models are non-linear models, it means that data in numerical form-as one single number representative-is not usable. Expected data is a set of stress/strain functions in discrete form (Fig. 1). Such tests are provided, but in a different way than expected. Most popular in this group of tests is the simple tension test.
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