Sinostar MACH Company, all cast products need to undergo strict tensile testing of materials.

In the production, research and development, and quality control of metal products, tensile testing is a crucial experiment. It is like a precise ruler that can accurately measure the mechanical properties of metal materials under stress, providing a key basis for material selection, process optimization, and product safety and reliability assessment. 

Basic Principles of Tensile Testing

The principle of tensile testing is based on the mechanical response of materials when subjected to axial tension. When a gradually increasing tensile force is applied to a metal specimen, the specimen will deform. As the tensile force continues to increase, the specimen undergoes elastic deformation, plastic deformation, and may eventually break. By measuring the relationship between tension and specimen deformation, we can obtain a series of important mechanical performance indicators. 

Tensile Test Experimental Process

Specimen Preparation:

The preparation of the specimen is the primary link in the tensile test, and its shape, size, and processing accuracy have a direct impact on the test results. Common tensile specimen shapes include circular cross-section and rectangular cross-section. Taking a circular cross-section specimen as an example, it is usually made of metal bars or wires. It is necessary to ensure that the surface of the specimen is smooth, free of defects such as scratches and cracks, and the two ends are processed flat for easy clamping. The size of the specimen must be processed strictly in accordance with relevant standards. For example, parameters such as gauge length (specific length used to measure deformation) and diameter are clearly specified. 

For casting products, specimen preparation is more critical. Due to its special molding process, castings may have defects such as pores and shrinkage. When preparing tensile specimens, it is necessary to avoid these defective areas as much as possible to ensure that the specimen can truly reflect the mechanical properties of the casting material. For example, when casting complex castings such as automobile engine cylinders, samples are taken from different parts to prepare specimens, and their mechanical properties are compared and analyzed to evaluate the overall casting quality. 

Experimental Equipment

Tensile testing is mainly carried out by universal material testing machines. The equipment consists of three parts: loading system, measurement system and control system. The loading system can provide stable and precisely controllable tension, usually using hydraulic or electric drive; the measurement system includes force sensors and displacement sensors. The force sensor is used to measure the tension applied to the specimen in real time, and the displacement sensor is used to measure the deformation of the specimen; the control system is responsible for the automation of the entire experimental process, such as loading speed control, data collection and processing, etc.

Experimental steps

Install the sample: Install the prepared sample accurately in the fixture of the testing machine to ensure that the axis of the sample is consistent with the loading direction to avoid inaccurate test results due to installation deviation.

Set parameters: According to the experimental requirements and material properties, set the appropriate loading speed in the control system of the testing machine. The selection of loading speed must follow relevant standards. Too fast loading speed may lead to high test results, while too slow loading speed may make the experiment time too long. For example, for some high-strength metal materials, too slow loading speed may cause the sample to age harden during loading, affecting the test results.

Start the experiment: Start the testing machine, and the loading system begins to apply tension to the sample. During the loading process, the measurement system records the data of tension and sample deformation in real time, and transmits these data to the control system for storage and processing.

Observation and recording: The experimenter needs to closely observe the deformation and fracture of the sample. When the sample breaks, the testing machine automatically stops loading and records the maximum tensile force value at the time of fracture.

Data analysis: After the experiment, the collected data is analyzed and processed. According to the recorded tension-deformation curve, important mechanical performance indicators such as tensile strength, yield strength, elongation and cross-sectional shrinkage of the material can be calculated.

Important indicators and significance of tensile test

Tensile strength

Tensile strength refers to the maximum stress that a metal material can withstand in a tensile test, which reflects the material's ability to resist fracture. The higher the tensile strength, the less likely the material is to break when subjected to tension. For structural parts that withstand large tensile forces, such as bridge cables and crane hooks, metal materials with higher tensile strength need to be selected. In the field of castings, such as cast steel anchor chains for large ships, their tensile strength is directly related to the safe anchoring of ships in harsh sea conditions, and tensile tests must be performed to ensure that their tensile strength meets the design requirements.

Yield strength

Yield strength is the stress at which a material begins to produce obvious plastic deformation. When the stress on a material exceeds the yield strength, the deformation will continue to increase even if the stress no longer increases. Yield strength is an important basis for material design and selection. For example, in the design of mechanical parts, in order to ensure that the parts do not undergo obvious plastic deformation during use, the working stress should be lower than the yield strength of the material. For cast automobile transmission shafts, its yield strength determines whether it will be excessively deformed when transmitting torque, affecting transmission efficiency and service life.

Elongation

Elongation refers to the percentage of the increment of the gauge length after the specimen breaks to the original gauge length, which reflects the plastic deformation capacity of the material. The greater the elongation, the better the plasticity of the material, and it can absorb energy through greater plastic deformation when subjected to force, thereby improving the safety of the structure. For example, in the design of automobile collision safety, metal materials with higher elongation need to be selected to ensure that the vehicle can absorb collision energy through deformation during collision and protect the safety of passengers. For cast automobile bumpers, its elongation determines whether it can effectively buffer the impact force during collision.

Sectional reduction

Sectional reduction refers to the percentage of the maximum reduction in the cross-sectional area at the necking after the specimen breaks to the original cross-sectional area, and is also an important indicator for measuring the plasticity of the material. Together with the elongation, it fully reflects the plastic deformation characteristics of the material during the stretching process. 

The tensile test of metal products is a rigorous and important experiment. Through precise tensile testing, we can gain an in-depth understanding of the mechanical properties of metal materials, provide a scientific basis for the rational selection of materials, process optimization and improvement, and product quality control, thereby ensuring the safety and reliability of metal products in various engineering applications. 

In terms of ensuring product quality, our Sinostar MACH company's tensile equipment plays an important role. Our tensile equipment is manufactured with advanced technology and exquisite craftsmanship, and has the characteristics of high precision, high stability and high reliability. Its loading system can provide precise tension control, the measurement system can collect data in real time and accurately, and the control system realizes the automation and intelligence of the experimental process. Whether it is for common metal products or products with special process requirements such as castings, our tensile equipment can provide reliable test results to protect product quality.