THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Advances in soft robotics, materials science, and stretchable electronics have enabled rapid progress in soft grippers. Here, a critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures. Soft gripping can be categorized into three technologies, enabling grasping by: a) actuation, b) controlled stiffness, and c) controlled adhesion. A comprehensive review of each type is presented. Compared to rigid grippers, end-effectors fabricated from flexible and soft components can often grasp or manipulate a larger variety of objects. Such grippers are an example of morphological computation, where control complexity is greatly reduced by material softness and mechanical compliance. Advanced materials and soft components, in particular silicone elastomers, shape memory materials, and active polymers and gels, are increasingly investigated for the design of lighter, simpler, and more universal grippers, using the inherent functionality of the materials. Embedding stretchable distributed sensors in or on soft grippers greatly enhances the ways in which the grippers interact with objects. Challenges for soft grippers include miniaturization, robustness, speed, integration of sensing, and control. Improved materials, processing methods, and sensing play an important role in future research.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201707035

Soft Robotic Grippers.

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

Topology optimization has become an effective tool for least-weight and performance design, especially in aeronautics and aerospace engineering. The purpose of this paper is to survey recent advances of topology optimization techniques applied in aircraft and aerospace structures design. This paper firstly reviews several existing applications: (1) standard material layout design for airframe structures, (2) layout design of stiffener ribs for aircraft panels, (3) multi-component layout design for aerospace structural systems, (4) multi-fasteners design for assembled aircraft structures. Secondly, potential applications of topology optimization in dynamic responses design, shape preserving design, smart structures design, structural features design and additive manufacturing are introduced to provide a forward-looking perspective.

Topology Optimization in Aircraft and Aerospace Structures Design

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

Development of a New Dynamic Hysteresis Model for Magnetorheological Dampers with Annular-Radial gaps Considering Fluid Inertia and Compressibility

In this study the finite element formulation for the dynamics of a bridge traversed by moving vehicles is presented. The vehicle including the driver and the passenger is modeled as a half-car-planner model with six degrees of freedom, traveling on the bridge with constant velocity. The bridge is a uniform with simply supported end conditions, and it obeys the Timoshenko beam theory. The equations of motion are derived using the extended Hamilton’s principle, and transformed to the finite element form using the weak-form formulation. Newmark’s method is applied to solve the governing equations and the results are compared with those available in the literature. Also, the maximum deflections in Timoshenko and Euler-Bernoulli beams have been compared. The results illustrated that as the velocity of the vehicle increases, the difference between the maximum beam deflection in two beam models becomes more significant.

Finite Element Approach for Vehicle-Structure Interaction of a Uniform Timoshenko Bridge

The crack-induced changes in the vertical transient response of a rotating shaft–disc system, Jeffcott rotor, are investigated for transverse crack detection. The crack is considered as a breathing crack. A novel breathing function is proposed, in which the partially open–closed crack breathing behavior is interpolated between the fully open and closed crack behaviors. The breathing crack excites superharmonic response components of the transient as well as the subharmonic components. A Hilbert–Huang transform based on an improved empirical mode decomposition algorithm is subsequently formulated to evaluate the time–frequency representation of the vertical transient response of the rotor to detect the crack. The results show that the proposed breathing function can effectively reduce the computational effort without sacrificing the accuracy of the crack breathing behavior in the presence of small cracks. It is shown that time–frequency representations based on an improved empirical mode decomposition algorithm can lead to the detection of smaller cracks compared with those based on the empirical mode decomposition algorithm.

/pdf/vertical-transient-response-analysis-of-a-cracked-jeffcott-3d4fjm07.pdf

Vertical Transient Response Analysis of a Cracked Jeffcott Rotor Based on Improved Empirical Mode Decomposition

A modified Distributed Tuned Mass Damper (DTMD) design approach was proposed in this study. In the traditional DTMD or TMD design, the general approach is to focus on the attached spring (s) and damper (s) under predefined mass (distribution). In this study, the DTMD design approach is to focus on the attached masses in the DTMD system. The numerical examples will be presented to illustrate the validity and effectiveness of the proposed DTMD design approach.

A Modified Distributed Tuned Mass Damper Design Approach

This study aims to investigate the effect of using magnetorheological elastomer (MRE)-based adaptive tuned vibration absorbers (ATVA) on the sound transmission in an elastic plate. Sound transmission loss (STL) of an elastic circular thin plate is analytically studied. The plate is excited by a plane acoustic wave as an incident sound and the displacement of the plate is calculated using corresponding mode shapes of the system for clamped boundary condition. Rayleigh integral approach is used to express the transmitted sound pressure in terms of the plate’s displacement modal amplitude. In order to increase sound transmission loss of the plate, the MRE-based ATVA is considered. The basic idea is to be able to change the stiffness of the ATVA by varying magnetic field in order to reduce the transmitted acoustic energy of the host structure in a wide frequency range. Here, a MRE-based ATVA under the shear mode consisting of an oscillator mass, magnetic conductor, coils and MRE is investigated. In order to predict the viscoelastic characteristics of the field-dependent MRE based on the applied magnetic field, the double pole model is used. Finally, MRE-based ATVAs are integrated with the plate to absorb the plate energy with the aim of decreasing the transmitted sound power. Results show that plate with integrated MRE-based ATVAs suppresses the axisymmetric vibration of the plate and thus considerably improves the STL. Parametric studies on the influence of the position of MRE-based ATVAs and the effects of applied current on their performance are also presented.

Ramin Sedaghati

Papers

Development of a New Dynamic Hysteresis Model for Magnetorheological Dampers with Annular-Radial gaps Considering Fluid Inertia and Compressibility

Finite Element Approach for Vehicle-Structure Interaction of a Uniform Timoshenko Bridge

Vertical Transient Response Analysis of a Cracked Jeffcott Rotor Based on Improved Empirical Mode Decomposition

A Modified Distributed Tuned Mass Damper Design Approach

Investigation on the effect of MR elastomer based adaptive vibration absorbers on the radiated sound from circular elastic plates