SHOCK SPECTRUM ANALYSIS METHOD AND APPARATUS

• US 3,842,661 A
• Filed: 03/29/1971
• Issued: 10/22/1974
• Est. Priority Date: 03/22/1968
• Status: Expired due to Term

• Current Assignee: M&R Acquisition Corporation
• Original Assignee: Philip Marshall, William C. Stevens Jr
• Inventors: Marshall, Philip, Stevens, William C. Jr.
• Primary Examiner(s): Gill, James J.
• Application Number:
  US05/128,698
• Time in Patent Office: 1,303 Days
• Field of Search: 73/67,67.2,71.4,67.1,71.5,71.6,71.2 328/127
• US Class Current: 73/576
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G06G 7/48 Analogue computers for specific processes, systems or devices, e.g. simulators
• CPC Class Codes: G06G 7/64 for non-electric machines, e.g. turbine
• CPC Class Codes: G06G 7/68 for civil engineering structures, e.g. beam, strut, girder, elasticity computation

Abstract

A shock spectrum analysis and synthesis method and apparatus which includes the use of a shock spectrum analyzer and a shock spectrum synthesizer. The analyzer is a special purpose analog computer which provides an automatic shock spectrum analysis of both the primary and residual spectrum by solving the equation of motion for a single degree of freedom, mass-spring-damping system and displaying the output signals on an oscilloscope or X-Y recorder. The synthesizer generates a variable transient electrical input to a vibration shaker system by generating a plurality of steady state signals each having a different frequency and gating and summing the signals.

Claims

1. A method of analyzing an input acceleration applied to a test specimen comprising the steps of:

applying a transient force to a test specimen;

sensing the input acceleration of said specimen in response to said force;

providing an electrical signal proportional to said sensed input acceleration;

computing from said electrical signal response signals respresenting acceleration, velocity and displacement of a damped single-degree-of-freedom mass system of a specified natural frequency to said input acceleration;

automatically incrementing the response signals to another natural frequency for analysis and automatically resetting the response signals to their initial conditions after each frequency response has been computed;

gating the computed response signals in such a way as to separate those parts of the response signals defined as primary and residual;

applying the computed acceleration response signals to a peak sampling and holding circuit; and

displaying the peak values of the acceleration response signals.

2. A method in accordance with claim 1 including the additional step of providing the peak value of the response signals for recording.

3. Apparatus for analyzing an input acceleration applied to a test specimen, comprising:

means for applying a transient force to a test specimen;

means for sensing the input acceleration of said specimen in response to said force;

means for providing an electrical signal proportional to said sensed input acceleration;

means for computing from said electrical signal response signals representing acceleration, velocity and displacement of a damped single-degree-of-freedom mass system of a specified natural frequency to said input acceleration;

means for automatically incrementing the response signals to another natural frequency for analysis;

means for automatically resetting the response signals to their initial conditions after each frequency response has been computed;

means for establishing the peak values of the computed acceleration response signals; and

means for displaying the peak values of the acceleration response signals.

4. Apparatus as set forth in claim 3 including:

means for gating the computed responses in such a way as to separate those parts of the response defined as primary and residual.

5. Apparatus as set forth in claim 3 including:

means for recording the peak value of the responses.

6. Apparatus for analyzing an input acceleration applied to a test specimen, comprising:

an electrodynamic shaker for applying a transient force to a test specimen;

means for sensing the input acceleration of said specimen in response to said force;

means for providing an electrical signal proportional to said sensed input acceleration;

a computing loop circuit for computing from said electrical signal response signals representing acceleration, velocity and displacement of a damped single-degree-of-freedom mass system of a specified natural frequency to said input acceleration;

an automatic incrementing circuit for automatically incrementing the response signals to another natural frequency for analysis;

a reset circuit for automatically resetting the response signals to their initial conditions after each frequency response has been computed;

means for gating the computed response signals in such a way as to separate those parts of the response signals defined as primary and residual;

peak circuit means for establishing the peak values of the acceleration response signals;

display means integral with said peak circuit means for displaying the peak values of the acceleration response signals; and

a two axis plotting means for recording the peak values of the acceleration response signals for each natural frequency.

7. Apparatus as seT forth in claim 6 where said automatic incrementing circuitry includes a control circuit for controlling the operation of said computing loop circuit.

8. Apparatus as set forth in claim 6 wherein said automatic incrementing circuitry includes a reset circuit for resetting the computing loop circuit.

9. A method of analyzing an input acceleration applied to a test specimen comprising the steps of:

applying a transient force to a test specimen;

sensing the input acceleration of said specimen in response to said force;

providing an electrical signal proportional to said sensed input acceleration;

computing from said electrical signal response signals representing acceleration, velocity and displacement of a damped single-degree-of-freedom mass system of a specified natural frequency to said input acceleration;

automatically incrementing the response signals to another natural frequency for analysis and automatically resetting the response signals to their initial conditions after each frequency response has been computed;

applying the computed acceleration response signals to a peak sampling and holding circuit; and

displaying the peak values of the acceleration response signals.