Predicting Acoustical Noise Generation in Complex Mechanical Systems

1979 ◽  
Vol 101 (2) ◽  
pp. 199-209 ◽  
Author(s):  
N. D. Perreira ◽  
S. Dubowsky
Keyword(s):  
Analytical Procedure ◽  
Mechanical Systems ◽  
Design Guidelines ◽  
Noise Generation ◽  
Noise Levels ◽  
Fundamental Study ◽  
Acoustic Design ◽  
System A ◽  
Modal Power ◽  
Complex Mechanical Systems

A fundamental study of noise generation in complex mechanical systems is undertaken. The objective of the study is the development of design guidelines for the prediction of mechanical system noise levels. Recently developed dynamical procedures are used to obtain the motions of linked mechanical systems with elastic elements and connection clearances. An analytical procedure for modeling the acoustical noise generated by complex mechanical systems is applied to a typical linked system, a four-bar mechanism. The far field acoustic pressure distribution is calculated and shown to be a function of many of the parameters under the control of the system designer. To aid the designer in producing quieter systems, acoustic design functions are developed. In particular, the system sound power and modal power efficiencies are found to be promising design tools.

Energy Method for Determining Dynamic Characteristics of Mechanisms

1949 ◽  
Vol 16 (3) ◽  
pp. 283-288
Author(s):  
B. E. Quinn
Keyword(s):  
Dynamic Characteristics ◽  
Energy Method ◽  
Mechanical Systems ◽  
Direct Approach ◽  
Graphical Methods ◽  
Applied Forces ◽  
Complex Mechanical Systems

Abstract Two types of problems are dealt with in the paper which are involved in the design of mechanisms required to have specified dynamic characteristics: (1) Determination of applied forces required to produce specified dynamic characteristics. (2) Determination of the dynamic characteristics which will result from the application of known forces. While graphical methods may be used in the solution of type (1) problems involving more or less complex mechanical systems, they do not afford a direct approach to type (2) problems. The energy method which will be outlined can be applied in either case, although this paper will be primarily concerned with the determination of the dynamic characteristics which result when a known force is applied to a given mechanism.

A Form Verification System for the Conceptual Design of Complex Mechanical Systems

1993 ◽  
Author(s):  
Jonathan S. Colton ◽  
Mark P. Ouellette
Keyword(s):  
Conceptual Design ◽  
Process Model ◽  
Mechanical Systems ◽  
Data Representation ◽  
Design System ◽  
Complex Data ◽  
Graphical Display ◽  
Design Environment ◽  
Blackboard System ◽  
Complex Mechanical Systems

Abstract This paper presents a summary of research into the development and implementation of a domain independent, computer-based model for the conceptual design of complex mechanical systems (Ouellette, 1992). The creation of such a design model includes the integration of four major concepts: (1) The use of a graphical display for visualizing the conceptual design attributes; (2) The proper representation of the complex data and diverse knowledge required to design the system; (3) The integration of quality design methods into the conceptual design; and (4) The modeling of the conceptual design process as a mapping between functions and forms. Using the design of an automobile as a case study, a design environment was created which consisted of a distributed problem solving paradigm and a parametric graphical display. The requirements of the design problem with respect to data representation and design processing were evaluated and a process model was specified. The resulting vehicle design system consists of a tight integration between a blackboard system and a parametric design system. The completed system allows a designer to view graphical representations of the candidate conceptual designs that the blackboard system generates.

scholarly journals Degrading systems availability analysis: analytical semi-Markov approach

2021 ◽  
Vol 23 (1) ◽  
pp. 195-208
Author(s):  
Varun Kumar ◽  
Girish Kumar ◽  
Rajesh Kumar Singh ◽  
Umang Soni
Keyword(s):  
Steady State ◽  
Degradation Mechanism ◽  
Continuous Process ◽  
Mechanical Systems ◽  
Embedded Markov Chain ◽  
Steady State Probability ◽  
Opportunistic Maintenance ◽  
System Availability ◽  
Availability Analysis ◽  
Complex Mechanical Systems

This paper deals with modeling and analysis of complex mechanical systems that deteriorate with age. As systems age, the questions on their availability and reliability start to surface. The system is believed to suffer from internal stochastic degradation mechanism that is described as a gradual and continuous process of performance deterioration. Therefore, it becomes difficult for maintenance engineer to model such system. Semi-Markov approach is proposed to analyze the degradation of complex mechanical systems. It involves constructing states corresponding to the system functionality status and constructing kernel matrix between the states. The construction of the transition matrix takes the failure rate and repair rate into account. Once the steady-state probability of the embedded Markov chain is computed, one can compute the steady-state solution and finally, the system availability. System models based on perfect repair without opportunistic and with opportunistic maintenance have been developed and the benefits of opportunistic maintenance are quantified in terms of increased system availability. The proposed methodology is demonstrated for a two-stage reciprocating air compressor with intercooler in between, system in series configuration.

Vibrations and Waterborne Noise on Fishery Vessels

1988 ◽  
Vol 32 (02) ◽  
pp. 112-133
Author(s):  
W. Ojak
Keyword(s):  
United Nations ◽  
Noise Generation ◽  
Noise Levels ◽  
Structural Vibrations ◽  
Mechanical Vibrations ◽  
Noise Propagation ◽  
Research Institutes ◽  
Fishery Research ◽  
Elastically Supported ◽  
Agricultural Organization

The Food and Agricultural Organization of the United Nations granted a fellowship to the author to study, at several European ship research institutes, the problem of noise generation and propagation on fishery vessels. He later took part in the design of the fishery research vessel Prof. Siedlecki, which included the implementation of a series of antivibration and antinoise precautions. This paper compares vibration and noise levels on two fishery research vessels—the conventional RV G.O.Sars and RV Prof. Siedlecki. The paper is divided into two parts. In the first part, mechanical vibrations of the elastically supported propeller are dealt with and conditions for minimum vibration response are determined. In the second part, structural vibrations in the ships and noise propagation from the ships to the water are described. The paper concludes with data on structural vibrations and waterborne noise propagation. This paper, and the paper published in the June 1984 issue of JOURNAL OF SHIP RESEARCH [1],2 completes the author's approach to propeller vibrations.

Influence of Alkaline Environments on the Mechanical Properties of FRCM/CRM and their Materials

2019 ◽  
Vol 817 ◽  
pp. 195-201
Author(s):  
Valeria Rizzo ◽  
Antonio Bonati ◽  
Francesco Micelli ◽  
Marianovella Leone ◽  
Maria Antonietta Aiello
Keyword(s):  
Glass Fibers ◽  
Tensile Tests ◽  
Design Guidelines ◽  
Hydraulic Lime ◽  
System A ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites ◽  
Alkaline Environments ◽  
Externally Bonded ◽  
Direct Tensile

Fabric Reinforced Mortar (FRCM) used as Externally Bonded Reinforcements (EBR), provide a sustainable solution for retrofitting and repair of existing masonry structures. They are commonly made by fibrous meshes embedded in a cementitious/hydraulic lime matrix. This technique represents a valid alternative to the well-known FRP (Fiber Reinforced Polymer) composites, which show some limitations in heritage masonry applications. In this scenario, a new system known as CRM (Composite Reinforced Mortar) has been developed in the last years. In this system, a pre-cured FRP grid is utilized as internal reinforcement in a mortar layer. The system reproduces the traditional technique of reinforced plaster, where the steel grid is substituted by a non-metallic one. In masonry applications high compatibility with the substrate, sustainability and removability are commonly required in heritage construction. These goals are not easily achieved by using fibers immersed into a polymeric resin. Moreover, the inorganic matrix ensures the transpiration of substrates and consequently a higher durability of the whole strengthened system is expected. On the other hand, the recent use of these new materials in civil engineering needs appropriate design guidelines. The proposed paper focuses attention on the initial results of a large experimental study on the durability of FRCM/CRM systems and their single components (dry glass fibers, resin, pre-cured FRP grid and mortar). In particular, the influence of three alkaline environments solutions was studied. Exposure conditions were stressed by increasing the temperature of the three aqueous solutions. The mechanical retention of tensile properties was measured by performing direct tensile tests after different exposure times.

Speech and noise levels in classrooms—signal, noise, reverberation levels as a metric for acoustic design for learning

2006 ◽  
Vol 120 (5) ◽  
pp. 3200-3201
Author(s):  
Line Guerra ◽  
Nicolas Teichner ◽  
Sooch San Souci ◽  
Dick Campbell
Keyword(s):  
Noise Levels ◽  
Signal Noise ◽  
Acoustic Design ◽  
Design For Learning

scholarly journals Synaptic mechanisms for motor variability in a feedforward network

2020 ◽  
Vol 6 (25) ◽  
pp. eaba4856
Author(s):  
Guo Zhang ◽  
Ke Yu ◽  
Tao Wang ◽  
Ting-Ting Chen ◽  
Wang-Ding Yuan ◽  
...  
Keyword(s):  
State Transition ◽  
Behavioral Variability ◽  
Noise Levels ◽  
Feedforward Network ◽  
Rhythmic Motor ◽  
System A ◽  
Synaptic Noise ◽  
Variable Activity ◽  
Transition Points ◽  
Synaptic Mechanisms

Behavioral variability often arises from variable activity in the behavior-generating neural network. The synaptic mechanisms underlying this variability are poorly understood. We show that synaptic noise, in conjunction with weak feedforward excitation, generates variable motor output in the Aplysia feeding system. A command-like neuron (CBI-10) triggers rhythmic motor programs more variable than programs triggered by CBI-2. CBI-10 weakly excites a pivotal pattern-generating interneuron (B34) strongly activated by CBI-2. The activation properties of B34 substantially account for the degree of program variability. CBI-10– and CBI-2–induced EPSPs in B34 vary in amplitude across trials, suggesting that there is synaptic noise. Computational studies show that synaptic noise is required for program variability. Further, at network state transition points when synaptic conductance is low, maximum program variability is promoted by moderate noise levels. Thus, synaptic strength and noise act together in a nonlinear manner to determine the degree of variability within a feedforward network.

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