####################################################
# Judy Pang <pangj@ornl.gov>
# requesting 7 days, at minimum=5 days
# beamline 34ID-E, Crack tip propagation in Al
# instrument 34ID-E microbeam
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# top:/home/www/beamtime-requests/req01020.txt
# UNICAT Member Beam Time Request  #1020
# created Mon Aug 21 15:02:51 CDT 2006
####################################################

apsrun:
	2006-03

beamline:
	34ID-E

collaboration:
	Yes

collaborator_Wenjun:
	ON

contact:
	pangj@ornl.gov

days:
	7

description:
	Preliminary x-ray microbeam experiment has been made on the deformation zone size of the fatigue crack in Al2024 alloy. An area surrounding the crack with larger peak width is observed. This can be explained by the increased level of plasticity around the crack. 

The challenge for such measurements is the determination of the crack location within the sample. To solve this problem, we will characterize the sample by x-ray tomography with a resolution of 1 µm and a penetration depth of ~ 1mm prior to the microbeam experiment. This will allow the microbeam measurements to be focused on the crack tip region inside the sample. This is particularly important for strain field determination which location of the measurement with respect to the crack tip is critical. 

Based on the experiment on Al2024 alloy, we will begin our study with Al. Fatigued cracked samples will be prepared with difference of stress intensity factor (ÄK). ÄK is a measure of the driving force on a crack and crack propagation is dependent on the K-field. ÄK is used as a basic parameter in all fracture models. Crack will not propagate until ÄK reaches a threshold value. And once the threshold is reached, the propagation rate increases quickly. The specific ÄK values to be used will be determined by the preliminary measurements on the prepared samples. We will select samples of a range of propagation rate. 

Initial EBSD and tomography measurements will be carried out in ORNL to determine the surface conditions and crack locations within the samples. They also serve in the selection of samples for the x-ray microbeam measurements.

equipment_required:
	

experiment:
	Crack tip propagation in Al

foreign_nationals:
	

hazards:
	

instrument:
	34ID-E microbeam

instrument_other:
	

minimumdays:
	5

name:
	Judy Pang

nonmembers:
	

submit:
	Submit

unacceptable_dates:
	Dates before November 1 are not possible.

z34ID_change_undulator:
	no

z34ID_details:
	

z34ID_on_axis:
	no

z34ID_parasitic:
	no

z34ID_taper:
	no


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