Alternating Current Potential Drop Probe

1
Alternating Current Potential Drop Probe
Approach and Considerations
Abstract
Alternating current potential drop (ACPD) testing
is a relative newcomer to the area of
nondestructive evaluation (NDE). Developed in
the 1980s, ACPD testing currently uses two point
probes for single frequency (typically 5kHz)
measurements of crack depths, crack growth, and
material properties. Although this type of
testing is effective, there are several
limitations, including the need to perform the
tests over a wide range of frequencies. To
counter these problems, the intent of this
project will be to design four four-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 producing these probes, it will be
easier for users to test materials more
efficiently, accurately, and effectively.

• 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

Introduction

• Problem Statement
• Develop four probes that can be used for two
  bands of frequencies as well as different
  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)
• Users manual with usage, calibration, and
  repair instructions
• Assumptions
• The developed theory will be accurate
• Probe materials and machining will be available

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

Milestones

• Construction of four prototype probes (December
  2004)
• Performance testing of prototypes (January 2005)
• Finish users manual and technical report (April
  2005)

Closing Summary
Alternating current potential drop (ACPD)
measurement and testing within the area of
nondestructive evaluation (NDE) is a rapidly
growing field. Currently, the probes used in the
field are limited by their size and operating
frequencies. By the end of this project, the
team will have created four hand-held probes,
which will be capable of taking measurements
over a vast range of frequencies. These new
probes will aid in the advancement of ACPD
testing within the area of NDE.
Estimated Resources and Schedule
Personnel Effort
Financial Resources
Project Schedule
Project Team Information
FACULTY ADVISORS Dr. John Bowler Dr. Nicola Bowler
CLIENT Center for Nondestructive
Evaluation1915 Scholl Road111 ASC IIAmes, Iowa
50011-3042
DESIGN TEAM MAY05-17 Jacob Chatterton
(EE) Jennifer Johnson (EE) Jonathan ODell
(EE) Jordan Vos (EE)