I think tensile stress relaxation is governed by particle rearrangement and fluid redistribution. An increased packing density inhibits particle rearrangement and only leaves fluid redistribution as the major process that governs tensile stress relaxation.

Useful link:https://www.nature.com/nature/journal/v217/n5130/pdf/217736a0.pdf

It seems you have to prepare a miniature tensile specimen. I suggest you to make a holder which can be easily clamped by a tensile testing machine.

In order to measure  tensile strength you need a force to apply on a selected area. You can calculate your area and you can selected the value of selected force. When you divide force to area you can achieve tensile strength. Good lucks

If you know hardness of the pellet, you can easily convert to tensile strength. 

I dont know how you have prepared the pellet.... there are some formulas for pellets strength calculation, may be you can adopt this techniques

The surface tensile strength was calculated from the

measured crushing force F and the pellet mean

radius R by using the equation σf = 0.4F/πR2

A texture analyzer may be used to measure the force required to break a pellet. A single pellet is placed under a probe which applies force to the particle. The texture analyzer records the initial diameter

of the particle and the amount of force needed to break it. The texture analyzer data is best reported as tensile strength using above equation. 

First measure the hardness and convert your measurements to stress-strain curve.  It is a new technique.

Best wishes