Crack Strength and Crack Propagation Characteristics of High Strength Metals

Item

Title
Crack Strength and Crack Propagation Characteristics of High Strength Metals
Description
The purpose of this program has been to obtain engineering data on the4 crack propagation and residual strength characteristics of structural materials suitable for use in aerospace systems. Results of a fracture testing program for high strength sheet metals are presented. More than 500 sheet stock panels ranging in width from one to 18 inches and in thickness from 0.20" to.100" were tested. These panels contained centrally located cracks which were generated principally by fatigue loading at various exposure times under a variety of environments. In general the fatigue crack is shown to be a more sever stress raiser than any manufactured notch yet investigated. Fracture strengths of the cracked panels were determined for rupturing temperatures ranging from -340°F to 2,500°F.

The experimental results were studied analytically. A semi-empirical expression for residual strength is derived. This expression is based on a modification of the formula given by Crichlow for the effective width of the plastic zone. An expression for the rate of crack propagation also is presented. The crack rate formula is based on the plastic zone concept, and accounts for the observed approach to infinite cracking rates as the crack length approaches critical. These formulas are shown to agree well with test results and are suitable for design applications.

A digital analysis of the elastic and plastic stress and strain distribution in the cracked plate was performed. The analytical method is discussed and results are presented.
Index Abstract
Contrails only
Photo Quality
Incomplete
Report Number
ASD TR 61-207
Index Price
$0.00
Report Availability
Full text available by request
Creator
Christensen, R. H.
Denke, P. H.
Date
1962
Extent
258
Laboratory
Directorate of Materials & Processes
Identifier
AD0275395
AD0275395
Contract
AF 33(616)-7444
DoD Project
7381
DoD Task
738103
Distribution Conflict
No
Access Rights
OTS
Distribution Classification
1
Corporate Author
Douglas Aircraft Company, Inc.
Date Issued
1962-01
Abstract
The purpose of this program has been to obtain engineering data on the4 crack propagation and residual strength characteristics of structural materials suitable for use in aerospace systems. Results of a fracture testing program for high strength sheet metals are presented. More than 500 sheet stock panels ranging in width from one to 18 inches and in thickness from 0.20" to.100" were tested. These panels contained centrally located cracks which were generated principally by fatigue loading at various exposure times under a variety of environments. In general the fatigue crack is shown to be a more sever stress raiser than any manufactured notch yet investigated. Fracture strengths of the cracked panels were determined for rupturing temperatures ranging from -340°F to 2,500°F.

The experimental results were studied analytically. A semi-empirical expression for residual strength is derived. This expression is based on a modification of the formula given by Crichlow for the effective width of the plastic zone. An expression for the rate of crack propagation also is presented. The crack rate formula is based on the plastic zone concept, and accounts for the observed approach to infinite cracking rates as the crack length approaches critical. These formulas are shown to agree well with test results and are suitable for design applications.

A digital analysis of the elastic and plastic stress and strain distribution in the cracked plate was performed. The analytical method is discussed and results are presented.
Provenance
Bombardier/Aero
Type
report
Subject
High Strength Alloys
Crack Propagation
Mechanical Properties
Aluminum Alloys
High Temperature
Deformation
Elastic Properties
Stainless Steel
Molybdenum
Steel
Fracture (Mechanics)
Sheets
Creep
Plastic Properties
Fatigue (Mechanics)
Nickel Alloys
Iron Alloys
Cryogenics
Titanium Alloys
Molybdenum Alloys
Cobalt Alloys
Chromium Alloys
Vanadium Alloys
Stresses
Propagation
Publisher
Wright-Patterson Air Force Base, OH : Directorate of Materials & Processes, Aeronautical Systems Division, Air Force Systems Command, United States Air Force
Format
xiv, 258 pages : ill. ; 28 cm.
AD Number
AD 275395
Cover Price
$4.00
DTIC Record Exists
Yes