Identification of material properties of orthotropic composite plate using hybrid non-destructive evaluation approach

Identification of material properties is one of the key issues in composite materials research. The mechanical properties of composite materials depend on diverse factors such as configuration of the laminates, constituent materials used and production method adopted. Conventional testing approach tends to be time-consuming, expensive and destructive. As an alternative, a rapid, inexpensive, hybrid and non-destructive evaluation approach which utilises experimental modal analysis and finite element analysis is proposed. Experimental modal data which consist of natural frequencies and mode shapes of an orthotropic composite plate are utilised for correlation purpose with its finite element model. This finite element model of the composite plate is continuously updated and achieves less than 5% in difference of natural frequencies and over 70% in modal assurance criterion. Material properties such as Young's moduli, inplane shear modulus and Poisson ratio of the composite plate are then successfully determined using the well-correlated FE model

Condition monitoring and diagnostic of an extruder motor and its gearbox vibration problem

Reliable production plants are vital in today's economy as they have a direct impact on the productivity, profitability and overall prosperity of industrial nations, the income of which depends on their industries and the products they create and export. Reliability depends on regular condition monitoring and plant maintenance and, more importantly, the tools and technologies being designed, developed and used. Excess vibration is one source of plant failure and this can have many root causes, ranging from dynamic incompatibility between different elements of machinery or their foundations to other causes resulting from general wear and tear. Prediction or detection of the source or causes of these unwanted problems is challenging and requires sophisticated tools and theories as well as experience and expertise. Moreover, classical vibration monitoring on its own cannot predict the root causes of failures that are due to operating conditions, especially when severe or abnormal service conditions are present. Under such conditions, the systems may behave in a completely different or unpredictable manner: active excitation forces/loads and the resulting displacements can make the system behave in a non-linear fashion. Here, an industrial case study that involves the non-destructive evaluation of an extruder motor due to excessive vibration is presented. A novel dynamic design verification (DDV) procedure for non-destructive monitoring and resonant vibration identification, which relies on a combination of experimental modal analysis (EMA), operating deflection shapes (ODS) and linear elastic finite element analysis (FEA), is used to assess the structural integrity and dynamic behaviour of an extruder motor and associated subsystems. The analyses conclude that the root cause of the high vibration is not the result of wear and tear of the motors but is due to a weakness in the motor support structures and concrete foundation supporting the extruder motor. Based on the performed analyses, structural dynamic modifications (additional supports) applied to the non-drive end of the motor have been considered and their effects on the system are analysed. It was concluded that this modification shifted the lowest natural frequency away from the operating speed and effectively reduced vibration to a safe level

Space-charge dynamics of polymethylmethacrylate under electron beam irradiation

10.1088/0953-8984/9/23/026Journal of Physics Condensed Matter9235027-5031JCOM

The effect of Al3+, Na+ and Li+ impurities on the charging ability of single-crystalline quartz under electron beam irradiation

Materials Science and Engineering B52112-1

Secondary and backscattered electron yields of polymer surface under electron beam irradiation

Applied Surface Science1191-2169-175ASUS

Insulator size effect on electron-irradiated quartz

10.1109/94.590873IEEE Transactions on Dielectrics and Electrical Insulation4188-91ITDI

The trapping and distribution of charge in polarized polymethylmethacrylate under electron-beam irradiation

10.1088/0022-3727/30/11/004Journal of Physics D: Applied Physics30111561-1565JPAP

A time-resolved current method for the investigation of charging ability of insulators under electron beam irradiation

Journal of Applied Physics7997123-7128JAPI

Dynamics aspects of the charging behaviour of polymers under focused electron beam irradiation

10.1088/0953-8984/9/43/013Journal of Physics Condensed Matter9439289-9298JCOM