# Lateral Strain and Poisson's ratio derived from measurement sphere and gage balls

**URL:** <https://forum.itascainternational.com/t/lateral-strain-and-poissons-ratio-derived-from-measurement-sphere-and-gage-balls/1910>\
**Category:** PFC\
**Created:** [January 23, 2025, 10:49am UTC](https://forum.itascainternational.com/t/lateral-strain-and-poissons-ratio-derived-from-measurement-sphere-and-gage-balls/1910 "2025-01-23T10:49:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Pallavi](https://avatars.discourse-cdn.com/v4/letter/p/3be4f8/32.png) [@Pallavi](https://forum.itascainternational.com/u/Pallavi)\
**Post date:** [January 23, 2025, 10:49am UTC](https://forum.itascainternational.com/t/lateral-strain-and-poissons-ratio-derived-from-measurement-sphere-and-gage-balls/1910/1 "2025-01-23T10:49:07Z")

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Hello everyone,

I was measuring Lateral Strain and thereby Poisson’s ratio of a UCS specimen in PFC2D. It is observed that Lateral Strain derived by measurement sphere is way greater than by using Gage Balls. I have taken the diameter of measurement sphere be the width of the specimen. The code for gage balls I have used is attached below. I would like to know if there is any mistake in my approaches and which approach to be followed to measure lateral strain.

 ![Screenshot (18)](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/2X/d/dae627b62fc4c811c6ce3d48f5285259aa9cea2d.jpeg)  
 ![gage balls derived sphere](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/2X/6/675e7b35454e1336e1b3a3b895ef847e93a06452.png)  
 ![measurement sphere derived strain](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/2X/8/82e62b72c08069724cc21fd7019d7d71a89df9dc.png)

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**Author:** ![BaiQS](https://avatars.discourse-cdn.com/v4/letter/b/f475e1/32.png) [@BaiQS](https://forum.itascainternational.com/u/BaiQS)\
**Post date:** [March 2, 2025, 12:09pm UTC](https://forum.itascainternational.com/t/lateral-strain-and-poissons-ratio-derived-from-measurement-sphere-and-gage-balls/1910/2 "2025-03-02T12:09:37Z")

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It seems that your method and code are right. I recommend the measurement sphere method. My experience is that the Gage ball method may obtain large errors.