ISO 10375:1997 非破壊検査—超音波検査—検索ユニットと音場の特性評価 | ページ 2

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

International Standard ISO 10375 was prepared by Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee SC 3, Acoustical methods.

Introduction

In ultrasonic non-destructive testing, sound pulses are used for detecting and evaluating imperfections or flaws in a material. To obtain reproducible flaw information, the generation, production and reception of the ultrasonic pulses must be properly specified, controlled and characterized. To ensure the accuracy and repeatability of the ultrasonic examination, a knowledge of the characteristics of the search unit or probe (also known as the transducer), as well as the associated sound field and the testing procedures used, is required.

For a complete description or proper selection of an ultrasonic search unit or probe, a commonly accepted set of characteristics of the search unit must be specified. This standard establishes techniques to be used in the laboratory for characterizing ultrasonic search units with parameters such as centre frequency, bandwidth, near-field length, half-angle of beam spread, depth of field, beam diameter and focal length. This standard specifies means for measuring the characteristics of both immersion and contact search units used for the inspection of materials. This standard also provides guides for obtaining parameters measured in the free field and by pulse-echo measurement. Examples of calculations of these parameters are given.

This standard provides techniques and procedures to achieve the following objectives:

• a) to select and specify search unit or probe characteristics;
• b) to check and ensure consistency of search unit performance over its life span;
• c) to facilitate selection of identical search units or equivalent alternatives;
• d) to provide a base for the comparison of results obtained using different instruments, equipment settings, operators, operating times and periods.

1 Scope

This International Standard establishes procedures for specifying certain ultrasonic search unit characteristics and for measuring the associated sound field. The aim is to establish uniformity of testing techniques, to form a basis for the interpretation of results obtained by different laboratories and at different times. Note that this International Standard establishes no acceptance criteria; however, it does establish the technical basis for criteria that may be defined by user parties.

ISO 2400 describes a calibration block used in weld inspection for checking the performance of the ultrasonic instrument and search unit. To further enhance the general ultrasonic inspection capability, information concerning the search unit's time domain response, frequency response (also referred to as frequency spectrum, frequency analysis, spectrum analysis and signature analysis) and sound field must be known before reliable detection and characterization of flaws can be achieved.

The search units discussed herein are straight-beam and angle-beam search units with a nominal ultrasonic frequency from 0,5 MHz to 15 MHz. Surface wave search units are not included in this standard. This standard provides procedures for specifying sound field parameters as well as methods of measurement in immersion tests. This standard does not address sound field measurement in contact tests.

This International Standard describes measurement procedures for evaluating characteristics of ultrasonic search units and describes techniques used for obtaining sound field data produced by electrically pulse-excited search units used in the field or in the laboratory. The characteristic parameters discussed in this standard are the upper, lower and centre frequencies, the wavelength, the bandwidth, the time domain and frequency domain responses, the near-field length, the half-angle of beam spread for search units of different shapes in free field, echo sound measurements, beam profiles, the impedance and the relative sensitivity. Formats for specifying both flat-face and focused search units are given.

To provide baseline information and to check possible performance degradation, the electrical properties of the search unit are measured independently of the ultrasonic instrument. The electrical impedance and sensitivity are measured at specific frequencies selected for each search unit. The electrical impedance corresponds to the complex input impedance of the search unit and the sensitivity of the search unit is a measure of the electroacoustic efficiency of the unit. These procedures are described in 4.6 and 4.7, respectively.

2 Normative reference

The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.