THE NEED FOR QUALITY The first thing that we need to consider, in any organization, is that quality is the most important thing. The quality of your work defines you.  Whoever you are,  Whatever you do,  I can find the same products and services cheaper somewhere else. But your quality is your signature. Developing and delivering high quality products and services means that you are doing things correctly from the beginning. As a consequence, you are reducing the need for additional services, from verification to warranty.

Total quality management.

Structural systems often show nonlinear behavior under severe excitations generated by natural hazards. In that condition, the restoring force becomes highly nonlinear showing significant hysteresis. The hereditary nature of this nonlinear restoring force indicates that the force cannot be described as a function of the instantaneous displacement and velocity. Accordingly, many hysteretic restoring force models were developed to include the time dependent nature using a set of differential equations. This survey contains a review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures.

The Hysteresis Bouc-Wen Model, a Survey

During the last few decades, magnetorheological (MR) elastomers have attracted a significant amount of attention for their enormous potential in engineering applications. Because they are a solid counterpart to MR fluids, MR elastomers exhibit a unique field-dependent material property when exposed to a magnetic field, and they overcome major issues faced in magnetorheological fluids, e.g. the deposition of iron particles, sealing problems and environmental contamination. Such advantages offer great potential for designing intelligent devices to be used in various engineering fields, especially in fields that involve vibration reduction and isolation. This paper presents a state of the art review on the recent progress of MR elastomer technology, with special emphasis on the research and development of MR elastomer devices and their applications. To keep the integrity of the knowledge, this review includes a brief introduction of MR elastomer materials and follows with a discussion of critical issues involved in designing magnetorheological elastomer devices, i.e. operation modes, coil placements and principle fundamentals. A comprehensive review has been presented on the research and development of MR elastomer devices, including vibration absorbers, vibration isolators, base isolators, sensing devices, and so on. A summary of the research on the modeling mechanical behavior for both the material and the devices is presented. Finally, the challenges and the potential facing magnetorheological elastomer technology are discussed, and suggestions have been made based on the authors’ knowledge and experience.

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A state-of-the-art review on magnetorheological elastomer devices

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=3667&context=eispapers

MR damper and its application for semi-active control of vehicle suspension system

Due to the inherent nonlinear nature of magnetorheological (MR) dampers, one of the challenging aspects for developing and utilizing these devices to achieve high performance is the development of models that can accurately describe their unique characteristics. In this review, the characteristics of MR dampers are summarized according to the measured responses under different conditions. On these bases, the considerations and methods of the parametric dynamic modelling for MR dampers are given and the state-of-the-art parametric dynamic modelling, identification and validation techniques for MR dampers are reviewed. In the past two decades, the models for MR dampers have been focused on how to improve the modelling accuracy. Although the force–displacement behaviour is well represented by most of the proposed dynamic models for MR dampers, no simple parametric models with high accuracy for MR dampers can be found. In addition, the parametric dynamic models for MR dampers with on-line updating ability and the inverse parametric models for MR dampers are scarcely explored. Moreover, whether one dynamic model for MR dampers can portray the force–displacement and force–velocity behaviour is not only determined by the dynamic model itself but also determined by the identification method.

https://iopscience.iop.org/article/10.1088/0964-1726/20/2/023001/pdf

Magnetorheological fluid dampers: a review of parametric modelling

A linear magnetorheological (MR) damper, supplied by Lord Corporation, was tested and modeled. Under dynamic conditions, the effects of displacement amplitude, frequency, and magnetic fields on the mechanical properties of MR damper, such as damping force, equivalent-damping capability, were experimentally studied with an INSTRON test machine. A viscoelastic-plastic model is proposed to model the MR behavior. It is shown that the damper response can be satisfactorily predicted with this model.

https://iopscience.iop.org/article/10.1088/0964-1726/9/1/310/pdf

Testing and steady state modeling of a linear MR damper under sinusoidal loading

Vibration reliability characterization of PBGA assemblies

Vibration testing of plastic ball grid array (PBGA) assemblies to assess the reliability of the solder joints under external vibration excitations was reported in this paper. The test vehicle was an assembly with four 256 I/Os PBGA modules assembled on a printed circuit board (PCB). During the test, the assembly was clamped at two opposite sides to a vibration shaker. It was found that the dynamic displacement of the assembly under external out-of-plane sinusoidal vibration excitations was highly nonlinear. In order to determine the reliability of the solder joints, the resistance of each module was continuously monitored during the test. Under an out-of-plane sweep sinusoidal excitation with a constant acceleration amplitude of 2.5 G within a narrow frequency band around the fundamental resonant frequency of the assembly, the first-time-to-failure and mean-time-to-failure of the solder joints were found to be 0.46 and 6.19 million vibration cycles respectively. The failed solder joints were at the corners of the PBGA module. Most failures were due to cracks near the copper pad on the PCB side.

Fook Fah Yap

Papers

MR damper and its application for semi-active control of vehicle suspension system

Testing and steady state modeling of a linear MR damper under sinusoidal loading

Vibration reliability characterization of PBGA assemblies

Reliability of PBGA assemblies under out-of-plane vibration excitations

Shock analysis of a head actuator assembly subjected to half-sine acceleration pulses