Assembly Reliability Evaluation Method (AREM)

This paper introduces an effective new Design For Quality tool called the Assembly Reliability Evaluation Method (AREM) that visualizes assembly fault potential. The distinctive features of AREM are: (1) visualization of parts and operations having a high fault probability; (2) evaluation of shop reliability, as well as product reliability and, (3) easy data input by symbol selection as well as simultaneous assemblability evaluation; can be evaluated quantitatively. The method can be integrated with other DFX tools such as the Assemblability Evaluation Method (AEM), and the Recyclability/Disassemblability Evaluation Method (REM/DEM) to realize a comprehensive production design evaluation system.

Dynamic Response of Cracked Cylindrical Shells With Internal Pressure

Sub-surface cracks in pipelines with internal pressure may severely affect their dynamic response. The extreme cases of these cracks are when these cracks go through the thickness of the pipes. Dynamic responses of cracked and un-cracked pipes with fixed ends and under various internal pressures were evaluated experimentally and theoretically. In the experimental part, the effects of pipe internal pressure on the resonant frequencies and damping of the pipe were evaluated. In the theoretical part, finite element analyses were performed to find dynamic response of pipes with various crack length and orientation respect to the axis of the pipe. The experimental results showed resonant frequencies of the pipe are little sensitive to the pipe internal pressure. Similar results were obtained from the theoretical investigations. An axial crack had little effect on the pipe resonant frequencies. In contrast, cracks oriented at an angle to the axis of the pipe had a pronounced effect on some of the resonant frequencies of the pipe. This depended on the crack location in a particular mode shapes. For frequencies where the nodal point of the mode shape was located on the crack region, the frequencies were not significantly affected by the presence of the crack in the pipe. Furthermore, it was observed that the pipe internal pressure had little effect on the resonant frequencies of the cracked pipes.

On Double Frequency Vibration of a Generator-Bearing System With Asymmetrical Stiffness

A finite element model for a generator-bearing system with asymmetrical stiffness is developed for investigation of the double frequency vibration. The modal reduction method is used for reducing the degrees of freedom system to improve computing efficiency, and the Newmark direct integration method is employed to solve the reduced motion equations. The two-modal interaction vibration is induced when the rotation speed is half a critical speed of the system due to asymmetry and gravity force of the generator. Such a phenomena is observed in the practical test.

Dynamic Response Control of Piezoelastic Laminated Cylindrical Shells Under Hydrostatic Pressure

Based on classical laminated plate theory and Navier solutions, the control of the piezoelastic laminated cylindrical shell’s dynamic response under hydrostatic pressure is discussed in this paper. Considering the direct and inverse piezoelectric effects of piezoelectric materials and from Hamilton’s principle, the nonlinear dynamic equations of the piezoelastic laminated cylindrical shell are derived first. Using close circuit method, the charge enclosed in the piezoelectric sensor layer can be measured. Furthermore, the voltage applied on the actuator layer can be obtained based on the closed-circuit charge signal of the sensor and velocity negative feedback control algorithm. An active dynamic response control model of simply supported laminated cylindrical shells with piezoelectric sensor/actuator under various dynamic loads is established in this paper at last. Three types of loading conditions, namely sinusoidal distributed load, line load and moving point load, are considered in numerical examples to investigate the performance of the control model. The numerical results show that the active control model presented in this paper can suppress the vibration of the structure under dynamic loading effectively.

Periodic Behavior of a Nonlinear Third Order Vibrating System

In modeling of dynamical systems, differential equations, either ordinary or partial, are a common outcome of the modeling process. The basic problem becomes the existence of solution of these deferential equations. In the early days of the solution of deferential equations at the beginning of the eighteenth century the methods for determining the existence of nontrivial solution were so limited and developed very much on an ad hoc basis. Most of the efforts on dynamical system are related to the second order systems, derived by applying Newton equation of motion to dynamical systems. But, behavior of some dynamical systems is governed by equations falling down in the general nonlinear third order differential equation x″′+f(t,x,x′,x″)=0, sometimes as a result of combination of a first and a second order system. It is shown in this paper that these equations could have nontrivial solutions, if x, x′, x″, and f(t,x,x′,x″) are bounded. Furthermore, it is shown that the third order differential equation has a τ-periodic solution if f(t,x,x′,x″) is an even function with respect to x′. For this purpose, the concept of Green’s function and the Schauder’s fixed-point theorem has been used.

Towards Failure-Free Design: Reducing Dimensionality in Function-Failure Similarity Analysis for Large Databases

When designing products, it is crucial to assure failure and risk-free operation in the intended operating environment. Failures are typically studied and eliminated its much as possible during the early stages of design. The few failures that go undetected result in unacceptable damage and losses in high-risk applications where public safety is of concern. Published NASA and NTSB accident reports point to a variety of components identified as sources of failures in the reported cases. In previous work, data from these reports were processed and placed in matrix form for all the system components and failure modes encountered, and then manipulated using matrix methods to determine similarities between the different components and failure modes. In this paper, these matrices are represented in the form of a linear combination of failures modes, mathematically formed using Principal Components Analysis (PCA) decomposition. The PCA decomposition results in a low-dimensionality representation of all failure modes and components of interest, represented in a transformed coordinate system. Such a representation opens the way for efficient pattern analysis and prediction of failure modes with highest potential risks on the final product, rather than making decisions based on the large space of component and failure mode data. The mathematics of the proposed method are explained first using a simple example problem. The method is then applied to component failure data gathered from helicopter accident reports to demonstrate its potential.

Nonlinear Free Vibration of a Cable Against a Straight Obstacle

The purpose of this study is to investigate the nonlinear effect of gravity on the free vibration of a cable against a straight obstacle. The cable model is expressed in terms of nonlinearly coupled transverse and axial displacements. The penalty method is used to simulate the obstacle, which is equivalent to inserting a stiff elastic foundation. The first symmetric frequencies are obtained when the depth of the obstacle is 1/2 and 1/3 of the initial transverse displacement. The effects of varying amplitude and equilibrium curvature are investigated.

The Periodic Impact Responses of Human-Body in a Vehicle Traveling on the Rough Terrain

The human-body in a vehicle traveling on the rough terrain is modeled through the lumped mass approach and its periodic impact motions and stability are investigated through a linear model of vehicle and passenger systems. The linear model assumes the motion response of vehicle is very small compared to passenger’s rotational motion since the vehicle chassis has a very large mass and moment of inertia. The period-1 impact motion for two impacts respectively on two walls for a specific number of periods is predicted analytically and numerically. The stability and bifurcation of such a period-1 impact motion are developed analytically. The phase planes of the periodic impact motions are illustrated for a better understanding of the human-body impacting motion in the vehicle.

Nonlinear Delay Equations With Fluctuating Delay: Application to Regenerative Chatter

The mathematical models representing machine tool chatter dynamics have been cast as differential equations with delay. The suppression of regenerative chatter by spindle speed variation is attracting increasing attention. In this paper, we study nonlinear delay differential equations with periodic delays which models the machine tool chatter with continuously modulated spindle speed. The explicit time-dependent delay terms, due to spindle speed modulation, are replaced by state dependent delay terms by augmenting the original equations. The augmented system of equations is autonomous and has two pairs of pure imaginary eigenvalues without resonance. We make use of Lyapunov-Schmidt Reduction method to determine the periodic solutions and analyze the tool motion. Analytical results show both modest increase of stability and existence of periodic solutions close to the new stability boundary.

Design of Horizontal Mechanical Presses for Deep Drawing and Ironing Process

This paper addresses the kinematics design and analysis of a special class of mechanical presses used for deep drawing and ironing process. The key design objectives are to obtain a longer stroke and a quicker punch return. From the kinematics equations, it is shown that the horizontal quick return mechanism exhibits the preferred characteristics. The behavior of the press is studied based on the placement of the links. The kinematics constraints are observed and the placement of press components to achieve better performance is summarized.