The strength of materials at high temperatures is related to the duration of load application. The longer the load is applied, the lower the resistance to deformation.

In production, many machine components operate under high temperatures and alternating loads. For example, turbine wheels and blades in steam turbines and gas turbines, as well as exhaust valves in diesel engines, are prone to high-temperature fatigue failure.

This microcomputer-controlled electro-hydraulic servo fatigue testing system, developed by Xi'an Lichuang Material Testing Technology Co., Ltd., is primarily used for high-temperature metal materials, aluminum alloys, stainless steel, titanium alloys, ceramic matrix composites, and their high-temperature service components and structures in aerospace and aviation applications. It performs tests under sine wave, triangular wave, square wave, trapezoidal wave, ramp wave, and program block wave conditions, including:

High-temperature tension-compression fatigue;

High-temperature fatigue failure testing;

High-temperature fatigue life testing;

Fracture toughness testing;

Fatigue crack propagation testing;

Low-cycle fatigue testing;

High-cycle fatigue testing;

Three-point bending fatigue testing;

CT testing, CCT fatigue testing.

Main technical specifications and configurations:

1. Equipped with a 1600°C high-temperature testing system;

2. Equipped with a 2000°C high-temperature vacuum heating testing system.

Metal tubes are typically structural materials that serve under certain temperatures and stresses. Therefore, directly assessing their high-temperature low-cycle fatigue performance, fitting their fatigue curves, and statistically analyzing their low-cycle fatigue test data are of significant importance for the fatigue-resistant design and engineering application of tubes.

Fatigue testing can be categorized by test environment into: room temperature fatigue testing, low-temperature fatigue testing, high-temperature fatigue testing, thermal fatigue testing, corrosion fatigue testing, contact fatigue testing, and fretting wear fatigue testing.

At high temperatures, grain boundaries are relatively weakened, and under external loads, grain boundary sliding occurs. However, since grain boundaries are not straight and smooth and may contain inclusions, if grain boundaries intersect with slip bands or subgrain boundaries, steps may form. As a result, grain boundary sliding will cause stress concentrations at these discontinuous locations and triple junctions, where cracks or voids initiate.

High-temperature fatigue refers to the phenomenon where components fracture after prolonged exposure to alternating loads at high temperatures. This occurs because some components operate at temperatures above room temperature but not excessively high. For fatigue design in such cases, it is sufficient to consider the effect of temperature on the fatigue limit and still apply room-temperature fatigue design methods. Only when the temperature exceeds 0.5Tm (where Tm is the melting point in thermodynamic temperature) or is above the recrystallization temperature, and alternating stresses are applied, does a combined phenomenon of creep and mechanical fatigue occur.