ASTM E292 Conducting Time-for-Rupture Notch Tension Tests of Materials

Introduction

ASTM E292 determines the time-for-rupture of notched specimens under constant force and temperature. The values are in imperial units. The time-for-rupture notch is a qualitative tool that helps compare the material’s suitability for designs that contain accidental stress concentrators. When subjected to multi-axial stress conditions, the sample’s rupture life indicates the material’s ability to deform without cracking.

Scope

ASTM E292 covers the notch test. The notch test determines the time it takes for a notched specimen to rupture or break under pressure. It is not used to make any deformation measurements. A notch is a stress concentrator. A stress concentrator is a place on an object where the stress is significantly greater than the surrounding region. The notched specimen determines the strength of materials with stress concentrators under tension. Rupture life of notched specimens indicates the ability of a material to deform locally without cracking under multi-axial stress conditions, thereby redistributing stresses around a stress concentrator.

Test Procedure

In ASTM E292, the specimen has a notch and a reduced section, a place where it is thinner. The dimensions of the specimen are measured. The technician cleans the specimen and the machine with acetone. A thermocouple is attached to the specimen to measure temperature. The specimen is positioned in the testing machine and extended until it breaks. 

Procedure to load the sample into the machine

Treat the installation of the specimen to avoid the introduction of nonaxial forces. Do not bottom or turn threaded connections to the end of the threads. Lightly load the string of specimen, then manually move it in the transverse direction and center within its range of motion if threads fit loosely. Apply packing to seal the furnace without displacing the pull rods or restricting their movement.

Specimen Size

The specimens should adhere to the requirements. The specimen should have a notch and a reduced section in the middle of the specimen for the break to occur there. As per ASTM E292, the part of the specimen gripped by the machine can be threaded, button-headed, or tapered for a cylindrical specimen. Flat specimens are attached through loading yokes and pins or wedge grips.

Advantages and Disadvantages of Notch Tension Tests

The table below provides the advantages and disadvantages of time-for-rupture notch tension tests.

Data Analysis

Calculations of the notch rupture strength and percent reduction in the area using ASTM E292 are as follows.

Notch Rupture strength: 

The calculation of the notch rupture strength is as follows: 

Notch rupture strength = P/A 0

P = the load applied to the specimen, and 

A 0= the initial area at the notch cross-section.

Percent reduction:

The calculation of the percent reduction in area and true strain at the notch cross-section is as follows:

Percent reduction in area = 

True fracture strain = εN = InA0/Af

Where Af is the final area at the notch section

Result Analysis

ASTM E292 covers the notched test, which determines the time it takes for a notched specimen to rupture or break under pressure.

Conclusion

ASTM E292 offers crucial information regarding the materialize to rupture and notch tensile strength. The data collected is used for material characterization, design and engineering, quality assurance, and material certification. It ensures manufacturers that the material has the required strength and durability under certain loading conditions. The test helps manufacturers detect faults and ensure product quality. Contact us today to get your product tested to climb the ladder of success.

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