June 1st, 2018
Tensile tests are tests which are performed for number of reasons. The results of tensile tests are used in selecting materials for various applications. Tensile properties frequently are included in material specifications to ensure quality of the product. Tensile properties are measured during development of new materials and processes, so that different materials and processes can be compared.
Tensile Specimens and Testing Machines
Let us consider the typical tensile specimen having enlarged ends or shoulders for gripping and the important part of the specimen is the gage section. Cross-sectional area of the gage section is reduced relative to that of the remainder of the specimen so that deformation and failure will be localized in this region. The gage length is the region over which measurements are made and is centered within the reduced section. The distances between the ends of the gage section and the shoulders should be good enough so that the larger ends do not constrain deformation within the gage section, and the gage length should be great relative to its diameter. Otherwise, the stress state will definitely be more complex than simple tension.
Testing machines tests materials in tension, compression, or bending. They are either electromechanical or hydraulic. The key difference is the method by which the load is applied. Electromechanical machines are based on a variable-speed electric motor; a gear reduction system; and one, two, or four screws that move the crosshead up or down. This motion loads the specimen in tension or compression. Crosshead speeds can be changed by changing the speed of the motor.
A microprocessor-based closed-loop system is implemented to accurately control the speed of the crosshead. On the contrary, hydraulic testing machines are based on either a single or dual-acting piston that moves the crosshead up or down.
A torsion test is a test which is conducted on most materials to find the torsional properties of the material.
Why do we perform a Torsion Test?
Various products are subjected to torsional forces during their operation. Few devices that subject to such torsional stresses are tubing, switches, fasteners, and automotive steering columns. Manufacturers are able to simulate real life service conditions, check product quality, verify designs, and ensure proper manufacturing techniques after testing these products in torsion
Torsion Tests and its types:
Torsion tests are tests which are performed by applying only a rotational motion or by applying both axial (tension or compression) and torsional forces. It can usually be classified as failure, proof, or
product operation testing but it may vary from product to product.
- Axial-Torsion: Axial-Torsion is done by applying both axial and torsional forces to the test specimen.
- Failure Testing: Failure testing is done by twisting the product, component, or specimen until failure. It can be classified as either a physical break or a kink/defect in the specimen.
- Proof Testing: Proof Testing is done by applying a torsional load and holding torque load for a fixed amount of time.
- Operational Testing: It means testing complete assemblies or products such as bottle caps, switches, or dial pens to verify that the product performs as expected under torsion loads.
It has of an optical system and an illumination system. The optical system consists of an eyepiece lens, relay system and the objective lens.
Its applications are grain sizing, inclusion counts, layer thickness assessment and phase determination. Some metallurgical microscope models have special facilities such as darkfield and DIC which produce improved observation techniques for some classes of specimen.
There are three main types of metallurgical microscope:
- Upright Microscopes – where the objectives are above the specimen – this is the most commonly used type
- Inverted Microscopes – where the objectives are beneath the specimen, permitting larger specimens to be observed
- Semiconductor (upright and inverted) where the stage is especially large to accommodate whole wafers
100 Ton Testing Bed
Test beds are used to proof test wire rope, fiber rope, chain, lifting slings and other types of lifting gear.These tester machines are extremely heavy-duty and have proven themselves in years of rugged, real world industrial and military environments. Load force has to be specified by the customer. Test beds performs proof load testing, destructive testing, cycle testing and long term fatigue testing (depending on options) at the specified load capacity.
The test beds come standard with fully enclosed test bed frames (ends, top, bottom) are built with hydraulically operated safety guards for operator safety and full capacity/full length break testing.
In chemical lab, the wire rope is coated with zince to prevent it from corrosion. Galvanized wire is also known as thermal zinc plated gal. wire or HDG wire. Electro-galvanized wire is also called electroplating wire or cold galvanized wire. The zinc applied for plating is ZINC WITH 99.995% purity. Hot dip galvanized wire and electro galvanised wire rope both can be used extensively as weaving wire, tying wire, staple wire and fencing wire. Similar wire diameters applied to them.
The major differences lies in three aspects: the zinc coating processing method, the zinc coating quantity and the wire properties.
Electroplating is achieved by placing the zinc ingots, zinc wire in a liquid bath energized at a current. Under the magnetic field, the zinc atoms lose electrons to become ions, free out of the zinc block, gradually adsorbed onto the steel wire object to be plated.
Thermal zinc plating or hot dip plating is made by placing the steel wire immersed in a liquid bath of hot melt zinc. The zinc layer is formed through intense high-temperature chemical reaction process. Hence, the electroplating is also called cold plating and the later hot dip plating.