What happens when metals are heated? Metal heating leads to several consequences at once, here are the main ones. 1.The metal expands thermally in all directions, i.e. its length, width and surface area increase. When a metal is heated, its atoms and molecules begin to move faster, interatomic bonds weaken, which leads to an increase in the distance between them and an increase in the volume of the metal. When cooled, the dimensions are restored. 2.The vast majority of metals and alloys increase their ductility with increasing temperature, including iron, steel, copper, aluminum and its alloys, magnesium, brass, and others. At the same time, these metals acquire the ability to be forged, i.e., to change shape without breaking under the influence of an external force. For example, steel heated to 700°C (1292°F) requires 4.5 times the forging force as steel heated to 1200°C (2192°F). Other metals and alloys, such as gray cast iron, tin bronze, and zinc alloys, do not deform when heated; they are brittle and fracture on impact.Metal crystals usually have a regular structure, with atoms arranged in a certain order. However, when a metal is heated, the atoms become more mobile and the metal becomes more ductile. Heating a metal can also cause a change in the type of its crystal structure. Changing the structure will lead to a decrease or increase in ductility, because the type of structure has a decisive influence on the properties of metals. This explains why the effect of plasticity changes during heating is observed differently for different metals. 3.The thermal radiation of metals when heated causes the dark cherry glow of steel, which is noticeable already when heated to 550°C (1022°F), and at 850°C (1562°F) it turns into bright red, and then into orange (950°C, 1742°F), yellow (1000°C, 1832°F), and white (1300°C, 2372°F and above).As you can see, the spectrum of thermal radiation depends on temperature, so observing the colors of quenching can be used to estimate the temperature of the metal, which is often used in heat treatment and forging, especially before the invention of non-contact thermometers. Names of glow colors: "red heat", "white heat", are often still used by metallurgists instead of determining the exact temperature.The change in radiation color is due to an increase in the energies of internal interactions, excitation and relaxation of metal atoms, with increasing temperature. The higher the temperature, the more intense this radiation. Its spectrum is gradually enriched with short-wave radiation resulting from interactions with increased energy. Therefore, the main contribution of infrared radiation at low temperatures changes with increasing temperature to the visible light range and to ultraviolet radiation at very high temperatures. 4.An increase in temperature can cause oxidation of metal surface and the formation of an oxide layer on it. In the case of steel, such a layer can form a thin transparent metal film that remains when the temperature drops to room temperature. In this case, the surface of the metal acquires a rainbow colors. This is due to the fact that the surface is covered with a thin transparent layer and works like a mirror. When this layer is very thin, it reflects only certain colors from daylight, which is the result of interference.Before the advent of pyrometers, this effect was also used as an indicator of the heating temperature of iron and steel. The colors were used to judge the heating temperature of steel chips and, consequently, the cutter during drilling and cutting operations. In modern times, it is used to create markings on the surfaces of ferrous metals and titanium by localized heating, including laser annealing. 5.If the steel is heated further, above 1300 °C (2372 °F, the specific temperature depends on the steel grade), melting of the metal can begin. Melting occurs because atoms acquire high energy and interatomic bonds are destroyed, and atoms lose their static positions in crystals and can travel around the material volume. This leads to the loss of the original shape and should be prevented during heat treatment of metals.So we have briefly reviewed the obvious processes that occur with a metal when it is heated. However, changes in the properties of metals caused by heat treatment are due to a number of not so obvious reasons. These changes are due to changes in the metal structure, and we will discuss this in more detail.  

What Is Mechanical Testing: Different Types of Mechanical Testing of Materials Mechanical testing is a series of tests used in product design and part manufacturing for material identification, characterization, selection, and validation of products. As a result, manufacturers can ensure proper material utilization, safety during production, and cost-effectiveness. This article will introduce the series of tests and their applications in product design and part manufacturing.     What is Mechanical Testing? Mechanical testing is a series of standardized tests used to determine a material’s physical and mechanical properties and suitability for its proposed applications. It is a huge requirement in product design and part manufacturing due to the need to achieve standards set by organizations such as ASTM and ISO. These tests allow manufacturers to distinguish materials of less quality and choose the right material for their products.  Tensile Testing Tensile testing is a fundamental mechanical strength test used to determine material properties such as stress, strain, and yield deformation. It involves subjecting a material to a force on opposite ends and pulling till it breaks. Testing occurs in a tensile testing machine that is either hydraulic or electric. The operator subjects the material to different forces and records the data. Afterward, they plot the data to get the stress-strain curve in a graph. Common standards for the tensile test include ASTM D638 / ISO 527-2 (for reinforced plastics), ASTM D412 / ISO 37 (vulcanized rubber and thermoplastic elastomers), and ASTM E8 / ASTM A370 / ISO 6892 (metals and other metallic materials).   Torsion Testing   Torsion testing is another form of mechanical testing that evaluates a material’s behavior when subjected to stress at an angular displacement. As a result, it gives information about the material’s shear modulus of elasticity, shear yield strength, shear strength, shear modulus of rupture, and ductility. In contrast to tensile testing, torsion testing applies to materials and products. Furthermore, there are several types explained below. Torsion only: Applying only torsional load to the material Axial-torsion Applying axial (tension/compression) and torsional force to a material. Failure testing: Twisting the product or material until it breaks or there is a visible defect. Proof testing Applying a torsional load to the material and holding the torque for a certain time. Functional testing: Final testing to verify a material’s behavior under torsional forces and loads.   According to ASTM and ISO, common standards for torsional testing are ASTM A938/ ISO 7800 (Torsion Testing of Metallic Wire). Fatigue Testing   Fatigue mechanical testing determines how a material behaves under fluctuating loads applied axially, in torsion, or flexure. It involves subjecting the material to a mean load and an alternating load. As a result, the material will experience fatigue (i.e., when the material breaks). The data will be presented from the test in an S-N diagram – a plot of the number of cycles to cause failure against the amplitude of cyclical stress (which can be stress amplitude, max stress, or min stress). Fracture Mechanics Testing   Fracture mechanics testing allows manufacturers to determine the energy it will take to break material with an existing crack into two. Furthermore, it allows the manufacturer to ascertain the material’s ability resist fracturing using the intrinsic stress factor. From the data, manufacturers can analyze the brittle fracture and examine its grain size, case depth, etc. Common standards for the test are BS 7448, NS-EN 10225, ASTM E1820, and EEMUA pub. 158. Compressive Testing Compressive testing is another fundamental mechanical engineering test determining the material’s behavior when subjected to crushing loads. As a  result, it is very important in part manufacturing because materials pass through different phases. It is suitable for a wide variety of testing materials such as metals, plastics, ceramics, or other users in load-bearing capacity. Common standards for compressive testing are ASTM D3574 (flexible cellular materials) ASTM D695-15 (Rigid Plastics), AITM 0010, ASTM C109 (2-Inch Concrete Cubes), ISO 844 (Rigid Cellular Plastics). Creep Testing   Creep testing or stress-relaxation test involves subjecting the material to constant stress at high temperatures and recording the deformation at a specific time interval. Afterward, operators plot the creep against the time on a graph to get the creep rate (slope of the graph). This test allows manufacturers to determine a material’s tendency to deform under constant stress at constant temperatures (to incorporate thermal expansion or shrinkage). It is important for materials such as metal workings, springs, and soldered joints.

Is Industrial Mechanical Testing Important? Structural integrity is an important part of part manufacturing for ensuring safety and economic feasibility. As the set of tests aims to ascertain a product’s structural integrity, it is an important part of the following: Manufacturers For quality, mechanical engineering tests are important to every manufacturer. Aside from that, these tests allow manufacturers to maintain their reputation, reduce production costs, and avoid product failure. Few manufacturing companies have the required machines for these tests. Therefore, you should ensure you outsource to one with the necessary machines. Material Dealers Dealers in materials should ensure proper adherence to international standards because they are the major point of material acquisition. This gives credibility to the dealers. Customers/Clients Every customer and client associated with product manufacturing should ensure that mechanical testing takes place on material and products before, during, and after production. As a result, they can improve product quality and reduce product failure. Conclusion Mechanical testing is a series of test methods used in analyzing products and materials to ensure safety during production, proper utilization of materials, and cost-effectiveness. It is a critical part of every design and manufacturing industry.