Re: Why RP? Stress Analysis....

From: Thomas G. Loebig (
Date: Fri Jul 25 1997 - 02:09:11 EEST

Is it feasible? This past spring, I completed a study using SLA for
three-dimensional, frozen-stress, photoelastic testing of a human femur
validated against strain gage testing of the cadaver femur that was used to
generate the SLA model (used Materialise software demo). Results from these
studies were in EXCELLENT AGREEMENT. I presented the results at the 1997 ASME
Summer Bioengineering Conference.

To summarize the study:
1. Photoelastic tests were performed at Measurements Group Headquarters in
Raleigh, North Carolina, USA with the guidance of Tom Corby and Bob Kochie.
2. Strain gage tests were performed at my lab.
3. Four stacked strain gage rosettes were placed on the inside (medial) part
of the femur for comparison to the SLA-photoelastic data.
4. The stress-to-load ratios (principal stresses, plane-strain with Poisson
correction) computed for three of the four strain gages were within 3% of the
data from the SLA model. This ratio at the fourth strain gage location, the
most superior (highest), was not so good due to dimensional simplifications of
complex geometry made in producing the SLA model (SLA data 4 times that of
strain gage, ie, 4kPa/N vs. 1kPa/N).

We concluded that SLA/photoelastic stress analysis is very accurate when
applied correctly, i.e., correct dimensional similarity.

I could send you copies of my results and the proceedings from the 1995 IFSTRP
meeting if you like.

Best Regards,

 ------ From: Christian Antoniutti, Wed, Jul 23, 1997 ------

Hi to all RP Community members,

I am doing some research on mechanical behaviour (stress and strain
measurement) of RP models compared to the original parts.
I wondered if this topic has been investigated...
I noticed that the mayor concern of RP People is to get better materials
and to achieve the best Rapid Tooling...
I thought it could be possible to create RP parts in materials that are
different from the real part and do experimental testing (strain gages,
SPATE or others, photoelasticity, etc.) and compare the results, without
the aim of having the same (or similar) material, but considering that
you have different material.

Anyone has some experience in this field, or some opinion that convinces
me that this is not feasible??

Thank you all

*    Christian Antoniutti

Thomas G. Loebig, MSME Biomechanics Research Lab Allegheny University of the Health Sciences 320 E. North Avenue, 10th Floor South Tower Pittsburgh, PA 15212 412.359.6773 FAX: 412.359.3387

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