Improving the repeatability of flexural testing is the key to ensuring the reliability of material mechanical property testing data, and it requires systematic optimization from three aspects: operating standards, equipment maintenance, and environmental control. The following are specific operational points and equipment maintenance strategies:
1、 Operation points: Standardize processes and reduce human errors
Standardization of sample preparation
Strictly cut the sample according to the standard to ensure dimensional accuracy, with a surface flatness deviation of ≤ 0.1mm, to avoid data fluctuations caused by sample differences.
Sample pretreatment: Before testing, it is necessary to place it in a standard environment (temperature 20 ± 2 ℃, humidity 50% ± 5%) for 24 hours to eliminate the influence of temperature and humidity on material properties.
Accurate control of loading process
Adopting constant speed loading mode, the speed error is controlled within ± 5% (such as standard loading rate of 0.5MPa/s, actual rate of 0.475-0.525MPa/s).
Loading point positioning: Use a specialized fixture to ensure that the distance between the support points is consistent with the span of the specimen, with a deviation of ≤ 0.2mm, to avoid data dispersion caused by eccentric loading.
Data recording and review
Test continuously for more than 3 times, take the average as the final result, and the deviation between a single test result and the average should be ≤ 1%.
Record environmental parameters (temperature and humidity, loading rate) and sample status, and establish a data traceability system.
2、 Equipment maintenance strategy: Ensure stable performance
routine maintenance
Cleaning: Clean the sample debris after each test to prevent it from entering mechanical components and causing jamming.
Lubrication: Apply special lubricating grease to the screw and guide rail every week to reduce wear.
Check: Before starting up daily, check if the sensor connection wire is loose to ensure stable signal transmission.
periodic calibration
Force calibration: Use standard weights (such as 1000N) to calibrate the sensor every month, with an error of ≤ 1/3 of the relative error of the displayed value.
Displacement calibration: Measure the actual displacement of the loading head with a vernier caliper every quarter and compare it with the displayed value, with a deviation of ≤ 0.1mm.
Key component replacement
Sensor: Replace immediately when the force fluctuation exceeds ± 1% or the linearity deteriorates.
Drive belt: Check the belt tension every six months, and adjust or replace it if the looseness exceeds 10%.
3、 Environmental control: eliminate external interference
The laboratory needs to be equipped with a temperature and humidity control system to ensure a stable testing environment.
Avoid placing vibration sources (such as air conditioning and heavy equipment) near the testing machine to reduce mechanical interference.
Electromagnetic shielding: Ground the control cabinet to prevent signal interference.
Implementation effect: Through the above measures, a certain testing institution reduced the repeatability (CV value) of the flexural test from 3.2% to 0.8%, significantly improving the reliability of the data. It is recommended to establish a maintenance file in conjunction with the equipment manual, recording information on each calibration, repair, and component replacement, to provide a basis for long-term quality control.