Slide 1

Alternating Current Potential Drop ProbeAlternating Current Potential Drop Probe

Alternating current potential drop (ACPD) testing is a relative newcomer to the area ofnondestructive evaluation (NDE). Developed in the 1980’s, ACPD testing currently usestwo point probes for single frequency (typically 5kHz) measurements of crack depths,crack growth, and material properties. Although this type of testing is effective, there areseveral limitations, including the need to perform the tests over a wide range offrequencies. To counter these problems, the intent of this project will be to design fourfour-point ACPD probes. Two probes will be used for lower frequencies (1 Hz to 10 kHz)and the others for higher frequencies (100 kHz to 10MHz). As a result of producingthese probes, it will be easier for users to test materials more efficiently, accurately, andeffectively.

Abstract

Project Team Information

DESIGN TEAM MAY05-17

Jacob Chatterton (EE)

Jennifer Johnson (EE)

Jonathan O’Dell (EE)

Jordan Vos (EE)

FACULTY ADVISORS

Dr. John Bowler

Dr. Nicola Bowler

CLIENT:

Center for Nondestructive Evaluation1915 Scholl Road111 ASC IIAmes, Iowa 50011-3042

Project Requirements

Design Objectives

•Build the in-line and square head probes for each frequency range

Functional Requirements

 Ability to work over a wide range of frequencies

 Capability to control the effect of the inductive pick-up

 Easy to maintain and service as needed

Design Constraints

 Must be handheld and portable

 Voltage pin connections must be durable and long-lasting

 Construction of four prototype probes (December 2004)

 Performance testing of prototypes (January 2005)

 Finish user’s manual and technical report (April 2005)

Approach and Considerations

Proposed Approach

 Analyze commercially available probes

 Build and test prototype probes in lab and compare with theory

 Revise probe design until satisfactory

Technologies Considered

 Square Head Design

 In-Line Design

Testing Considerations

 Compare laboratory tests to theory to check accuracy

 Provide and reference voltage to the injected current

 Provide effective control or regulation of the inductive pick-up

Estimated Resources and Schedule

Problem Statement

Develop four probes that can be used for two bands of frequencies as well asdifferent alignments.

Solution Approach

 Research ACPD theory and probe technologies currently used in the field

 Perform laboratory tests on all design prototypes

 Investigate the material properties of different types of steels

Intended Uses and Users

 Assessment of steel vehicle shafts and case-hardened components

 Observation/characterization of cracks and defects in aircraft engine disks

 Probe will be operated by trained technicians

Operating Environment

 Probes will be used in a laboratory testing setting

 Probes will also be used in production line environment

End Product and Other Deliverables

 Four probes: two for each frequency range with two different head designs(square and in-line)

 User’s manual with usage, calibration, and repair instructions

Assumptions

 The developed theory will be accurate

 Probe materials and machining will be available

 Laboratory testing time and equipment will be available

Limitations

• Probes built for two different frequency ranges

• Low frequency: 1 Hz to 10 kHz

• High frequency: 100 kHz 10MHz

• Voltage pin connections must be made close to test surface

• Probes must be robust and portable

Introduction

Closing Summary

Alternating current potential drop (ACPD) measurement and testing withinthe area of nondestructive evaluation (NDE) is a rapidly growing field.Currently, the probes used in the field are limited by their size andoperating frequencies. By the end of this project, the team will havecreated four hand-held probes, which will be capable of takingmeasurements over a vast range of frequencies. These new probes willaid in the advancement of ACPD testing within the area of NDE.

Milestones

Project Schedule

Personnel Effort

Financial Resources