Abstract

This guide covers how to understand and minimize the errors associated with data acquisition in fatigue and fracture mechanics testing equipment. This guide is not intended to be used instead of certified traceable calibration or verification of data acquisition systems when such certification is required. The output of the fatigue and fracture mechanics data acquisition systems described is essentially a stream of digital data. Such digital data may be considered to be divided into two types: Basic Data, which are a sequence of digital samples of an equivalent analog waveform representing the output of transducers connected to the specimen under test, and Derived Data, which are digital values obtained from the Basic Data by application of appropriate computational algorithms. In its most basic form, a mechanical testing system consists of a test frame with grips which attach to a test specimen, a method of applying forces to the specimen, and a number of transducers which measure the forces and displacements applied to the specimen. The output from these transducers may be in digital or analog form, but if they are analog, they are first amplified and filtered and then converted to digital form using analog-to-digital converters (ADCs). The resulting stream of digital data may be digitally filtered and manipulated to result in a stream of output Basic Data which is presented to the user in the form of a displayed or printed output, or as a data file in a computer. Various algorithms may be applied to the Basic Data to derive parameters representing, for example, the peaks and valleys of the forces and displacements applied to the specimen, or the stresses and strains applied to the specimen and so forth. Such parameters are the Derived Data. The whole measurement system may be divided into three sections for the purpose of verification: the mechanical test frame and its components, the electrical measurement system, and the computer processing of data. oeability, which are performed on the top coat only.

This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

1. Scope

1.1 This guide covers how to understand and minimize the errors associated with data acquisition in fatigue and fracture mechanics testing equipment. This guide is not intended to be used instead of certified traceable calibration or verification of data acquisition systems when such certification is required. It does not cover static load verification, for which the user is referred to the current revision of Practices E 4, or static extensometer verification, for which the user is referred to the current revision of Practice E 83. The user is also referred to Practice E 467.

1.2 The output of the fatigue and fracture mechanics data acquisition systems described in this guide is essentially a stream of digital data. Such digital data may be considered to be divided into two types- Basic Data, which are a sequence of digital samples of an equivalent analog waveform representing the output of transducers connected to the specimen under test, and Derived Data, which are digital values obtained from the Basic Data by application of appropriate computational algorithms. The purpose of this guide is to provide methods that give confidence that such Basic and Derived Data describe the properties of the material adequately. It does this by setting minimum or maximum targets for key system parameters, suggesting how to measure these parameters if their actual values are not known.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

E4 Practices for Force Verification of Testing Machines

E83 Practice for Verification and Classification of Extensometer Systems

E467 Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System

E1823 Terminology Relating to Fatigue and Fracture Testing

Keywords

bandwidth; data acquisition; data rate; data skew, drift; fatigue; filter; fracture mechanics; noise; phase shift; quantization; sample rate; signal conditioning; step response;

ICS Code

ICS Number Code 19.060 (Mechanical testing)

DOI: 10.1520/E1942-98R10E01

ASTM International is a member of CrossRef.

ASTM E1942