Machine Systems and Working Principles

The machine consists of two parts: the main unit and the dynamometer, which are connected by oil pipes.

(I) Main Unit

The main unit consists of two parts: a height-adjustable support frame (composed of the base, lead screw, and moving crossbeam) and the working frame (composed of the working cylinder, piston, worktable, smooth rod, and upper crossbeam).

Its working principle involves supplying oil from a high-pressure oil pump to the working cylinder. Through the movement of the piston, the worktable and upper crossbeam are pushed upward to perform tensile or compression tests on specimens. Tensile tests are conducted between the upper crossbeam and the moving crossbeam of the main unit, while compression tests are performed between the worktable and the moving crossbeam of the main unit. The adjustment of the test space is mainly achieved by driving the mechanism to raise or lower the moving crossbeam.

1. Working Cylinder and Piston

The working cylinder and piston are the main components of the unit. The cylinder is fixed on the base, and a spherical head is set between the piston and the worktable. The return stroke relies on the self-weight of the piston to press it back. The sealing of the pressure oil is achieved through the oil film between the cylinder and the piston, with the inner surface of the cylinder serving as a guide. Due to the self-aligning effect of the spherical head, friction between the cylinder and piston caused by lateral forces is reduced.

2. Moving Crossbeam and Drive Mechanism

The moving crossbeam is supported on the lead screw via a transmission nut. The lead screw can rotate in both forward and reverse directions, driven by a mechanism installed at the bottom. The drive mechanism consists of a geared motor, sprockets, and chains. The geared motor drives the two lead screws to rotate synchronously through the sprockets and chains.

3. Piston Stroke Limiting Device

(1) Worktable

(2) Limit Pull Plate

(3) Limit Switch

(4) Trip Rod

(5) Cylinder, Piston

(6) Base

A limit switch (3) is installed between the worktable (1) and the base (6). When the piston rises, it drives the limit pull plate (2) upward. If the trip rod (4) contacts the spring rod of the limit switch, the oil pump power is cut off, achieving a safety protection function.

1. Lead Screw

2. Large Sprocket

3. Adjusting Idler

4. Drive Sprocket

5. Piston, Cylinder

6. Chain

1) A reduction mechanism is installed on the base, where (4) is the drive sprocket that drives the chain movement, (1) are symmetrical lead screws, (2) are large sprockets mounted on the lead screws, (3) is an adjusting idler for tension adjustment, (5) is the piston cylinder, and (6) is the chain.

2) The chain installation and adjustment have been set at the factory, and users do not need to readjust.

3) Special attention: When starting the movement of the moving crossbeam, ensure that it is not used for applying force. The moving crossbeam is only for raising and lowering under no-load conditions.

(II) Dynamometer

This testing machine uses a digital force indicator. The force measurement part consists of a digital display, pressure sensor, microcomputer, and printer. For specific usage, refer to the force display control instrument manual.

(III) Hydraulic Control System

The hydraulic control system consists of the high-pressure oil pump, feed valve, return valve of the dynamometer, and the working cylinder and piston of the main unit. During testing, oil flows from the oil pump’s outlet pipe into the feed valve. When the handwheel of the feed valve is closed, due to oil pressure, when the handwheel is opened, oil is throttled by the feed valve and then enters the working cylinder via the feed pipe. Under pressure, the working piston moves upward, driving the main unit’s worktable, smooth rod, and upper crossbeam to load the specimen. Simultaneously, pressure oil enters the return valve through the return pipe, then flows into the pressure sensor. After calculation and processing by the microcomputer, the results are displayed digitally or printed.

1. High-Pressure Oil Pump

The high-pressure oil pump is an axial piston pump with a flow rate of 1L/min to 3L/min. It forms a pump station together with the tank motor.

2. Feed Valve

This feed valve, also known as an overflow throttle valve, is a key component for controlling load and loading speed. During testing, the valve opening can be adjusted according to actual needs to control flow and pressure.

3. Return Valve

This is essentially an on-off valve. During loading, the handle should be tightened to seal the outlet from the working cylinder, cutting off the oil return path to the tank. During unloading, the handle is loosened to allow oil to return to the tank. Another oil path in the valve leads to the pressure sensor, which outputs an electrical signal.