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.  

The benefits of heat treatment of metals Heat treatment can make the final product more efficient in performing its tasks and more resistant to wear, and therefore more competitive. So below we list the benefits of heat treatment of metals. 1. Increase in strength and toughness Heat treatment can change the microstructure of a metal, reduce grain size and increase grain number; under certain conditions, the crystal structure of the grains can also change (polymorphic transformation), which leads to changes in the mechanical properties of the metal. For example, during quenching, a metal is heated to a high temperature and then rapidly cooled. This leads to crystal size and the formation of martensite, a microstructure with densely packed atoms that is the basis of hardened metal alloys. This structure provides greater hardness and strength of the metal. Another way to increase metal strength is to temper it. After quenching, the metal is heated to a certain temperature and then cooled. This process reduces the excessive stiffness of the metal that can occur after quenching and preserves its strength. There are also many other heat treatment methods that can affect the microstructure of the metal and its mechanical properties. For example, the heating and cooling cycle can be changed to achieve the desired result. The result of properly applied heat treatment processes can increase the tensile strength of steel by up to 50%. 2. Heat treatment can make steel softer There is nothing paradoxical here. Changing the modes in the heating and cooling cycle can have a significant impact on the final result, so it is clear that levers of influence on the material structure can be applied in such a way as to achieve lower metal strength if this is the desired outcome. An example of this is hardening the surface of the metal while allowing the metal deeper in the product to remain soft. thus creating a thin layer of hard metal on the outside. This soft core makes the part resistant to breakage, absorbing stresses without cracking, while providing adequate wear resistance to the surface of the part. 3. Increased flexibility, reduced brittleness One of the heat treatment methods for increasing the flexibility of metal is tempering. It is usually performed after metal hardening to reduce its rigidity and increase its flexibility. During quenching, the metal is heated to a high temperature and cooled rapidly to change its microstructure and increase its strength. However, this process can also make the metal brittle and easily breakable. Tempering is accomplished by heating the metal to a moderate temperature (typically 300 °C or 572 °F) and holding it at that temperature for a period of time. This process reduces the stiffness and increases the flexibility, ductility, and strength of the metal sample. Tempering is used in applications where it is important to have a metal that has a certain level of strength but is flexible and ductile enough to avoid tearing or brittleness during service. This procedure can also relieve stress and facilitate further machining. 4. Increased wear resistance Gears, shafts, cutters, bearings, car body parts, tools, such as jackhammers, are just a short list of products where hardened metal adds extra strength and wear resistance, allowing them to operate under high stress without losing their functional properties. Heat treatment operations increase resistance to fatigue, allowing such steel components to work more efficiently over a longer period of time. Extremely hard steels are often used as cutting tools that require sharp edges - heat treatment here is a critical operation to achieve long service life and shape retention. As noted, hard surfaces with ductile base materials can also be produced by heat treatment. Therefore, heat treatment returns a significant economic benefit due to the long service life of the resulting products. 5. Surface modification In the process of heat treatment of metal, the surface may come into contact with air or other external gases and coolants at different temperatures. This inevitably leads to changes in its properties, which is also used in metalworking. In the case hardening process, metal is heated to high temperatures in an atmosphere of gas containing carbon (endothermic gas, natural gas, etc.) or nitrogen (ammonia), which react with the metal's surface to harden it. This process results in a hard, wear-resistant surface layer that also improves corrosion and abrasion resistance, while the core is relatively strong, allowing the steel to withstand impact loads. 6. Changes in thermal conductivity The smaller the grain, the greater the thermal conductivity. An increase in the thermal conductivity of a metal is usually a side effect of heat treatment aimed at increasing the hardness of the metal. However, when thermal conductivity is a key property, quenching can be used to improve it in a targeted manner. For aluminum alloys used in the creation of radiators, the method of secondary phase hardening - planar hardening - is used. This method involves heat treatment of the alloy in such a way that secondary phases are formed in it, arranged in the form of flat dislocation walls. These walls provide excellent thermal conductivity of the material. 7. Changes in electrical conductivity Reducing the grain size in general also improves electrical conductivity. Therefore, quenching and tempering methods are used in the creation of wires, contacts, soldering irons, electronic components, and other products where high electrical conductivity is important. Additionally, heat treatment processes are used in the production of electronic components to improve electrical and oxidation resistance or to produce thermocouples, where the accuracy of temperature measurement is important, which depends on the electrical conductivity of the metal. 8. Magnetic properties Heat treatment can change the magnetic properties of metals. For the manufacture of permanent magnets, special materials are used that are heat-treated to improve their magnetic properties. Heat treatment can also be used to reduce the magnetic permeability of metals, which is important in electrical devices where magnetic fields can cause undesirable effects such as inductance and magnetic losses. 9. Repair heat treatment Heat treatment can be used to restore the structure of a metal after it has been worn or damaged. Metal wear is a complex process that results in a decrease in the strength and stability of parts due to external factors such as friction, corrosion, impacts, and others. In addition, during the operation of metal products made of hardened steel, a gradual destruction of the martensite structure can occur, which leads to a decrease in strength. The process of restorative heat treatment may include quenching, normalizing, tempering, etc. It is used to restore metal products such as gears, shafts, pump wheels, and other complex parts that are subject to wear or damage due to operation. The rational use of this method can significantly increase the durability and reliability of long-term operation of metal products. 10. Variability of procedures and combinations of methods Heat treatment of metals provides a variety of approaches that seem innumerable. However, they can be customized to achieve specific results. In addition, this process is well combined with other methods, such as mechanical or chemical processing. In some cases, a metal part may undergo several heat treatment procedures and other types of processing. The choice of the ideal method, however, really depends on the type of metal and the properties required, but in any case, it is necessary to test these properties to assess the effect of heat treatment on the mechanical properties of materials.  

Significance and Benefits of Tensile Testing The performance and strength data measured by tensile testers are important in the selection of design and materials, purchase and sale of products, development of new products, quality control, and safety of equipment. During the research stage of product development, tensile testing is crucial in choosing the most appropriate materials. A tensile test machine can verify whether candidate materials pass the required strength and elongation requirements for a certain product. In the metals industry, tensile testing provides an opportunity to discover new alloys, their qualities, and the possible uses they might have. This can lead to improved materials, which are beneficial to both manufacturers and end users. The use of a tensile strength tester in the quality control of products is also crucial. It provides manufacturers a way to identify whether there are problems in their manufacturing line. It also ensures that what they deliver to customers is safe, of high quality, and adheres with industry and international standards. The cost of not complying with industry standards may not only be monetary. At worst, it could involve human cost. Performing regular tensile testing usually costs far less than the consequences brought about by using inappropriate materials or sale of substandard products. Therefore, carrying out reliable and accurate tensile tests should be a priority.

Types of Tensile Tests One of the most significant and widely used types of mechanical testing of a material is the tensile or tension test. With the use of a tensile tester machine,a pulling force or tension is applied to a material until it fails or breaks and its response to the stress is measured. Through this test, the strength of the material can be determined, and the amount of force needed to elongate it can be measured.   There are several types of tensile test, which include the following: 1.  Adhesion or Bond Strength Test This type of tensile stress test measures the strength of the bond of a coating to a surface or item. This test is commonly associated with adhesives, laminates, tapes, sealants, electronics, and general packaging seal strength. 2.  Crimp Pull-off Test Also known as crimp pull testing, this test uses a tensile testing equipment to measure how much tensile force is needed to remove a crimped ferrule, connector, or terminal from a wire. This is usually done in the production line, as part of lifespan assessment, or together with electrical integrity for electrical wiring. 3.  Peel Test A peel or peeling test is conducted to determine the strength of adhesion or stickiness between two materials bonded with an adhesive. This measures the resistance to detachment from one another after the application of adhesive to the tensile test samples. The assessed value determines whether the bond is sufficient or too much for the intended application or whether another adhesive or bonding method should be used. 4.  Tear Resistance Test This test uses a tensile test apparatus to apply a force to an item that already has an initial tear until it completely fails or breaks. This test measures the tear resistance or the ability of tensile testing samples to resist the progress of a partial tear. This is often used in flexible materials, which are more vulnerable to accidental tears and holes. Such materials include fabrics, textiles, polymers, rubbers, elastomers, packaging, and paper products.  

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. 

Automotive Materials Testing A Huge Variety of Specialized Challenges Why is materials testing for the automotive industry so challenging? The automotive industry involves complex products that must be carefully engineered to ensure safety and performance across a variety of crucial subsystems. This imperative for meticulous engineering is only amplified by the high level of competition in the industry, which pushes automotive manufacturers to innovate constantly in pursuit of continuous product improvement.   In this context, material testing takes on added importance. Materials need to be specified as precisely as possible to ensure optimal cost, weight, and performance. And testing results need to be of the utmost quality to avoid errors that could drive costly recalls (or worse, safety issues).   Automotive manufacturers face an imperative to maintain reliable, precise, accurate, and repeatable procedures across a huge variety of required tests. We cover some of the most important across several categories below. This list only begins to cover the vast number of tests ultimately required by auto industry manufacturers, but it helps illustrate just how complicated testing requirements are for automotive OEM’s.   Automotive Materials Testing: Body Vehicle bodies are becoming increasingly complex, employing high strength materials including steels, aluminum, and fiber-reinforced plastics. Engineers face a continuous competition to utilize the most lightweight materials possible without compromising passenger safety.   Representative solutions for automotive body testing include machines for testing sheet metal forming properties and crash structures.   Automotive Materials Testing Machines: Chassis An automotive chassis is instrumental for overall vehicle safety, driving comfort, and fuel efficiency. Consequently, they are a particular focus of inspections, and materials need to be engineered meticulously for each and every chassis component.   Representative testing needs for automotive chassis include:   Spring Testing: key spring testing requirements cover compression coil springs, pneumatic springs, and hydraulic shock absorbers. A variety of spring testing capabilities (including force measuring platforms, servo-hydraulic testing machines, and multi-axial testing) are needed to evaluate attributes like friction, wear, and service life.   Testing for Wheels, Rims, and Tires: as the direct link between a vehicle chassis and the road, wheels, rims, and tires transfer all forces and torques experienced by the vehicle. All of these components come with their own testing requirements, ranging from tensile/tear growth tests for tire elastomers, to compression tests for rim flanges and break pads, to tests for the entire wheel assembly.   Steering Systems: steering systems attributes like stick slip effect, maximum torsion angle for steering shafts, and the reliability of steering column height adjustors must all be carefully tested for this safety-critical control system.   Automotive Materials Testing: Interior and Safety Components From seat belts, to headrests, to brake pedals, every part of a vehicle interior needs to be designed for optimal usability, comfort, and safety.  Automakers must navigate testing for a vast array of components including:   Seat and Interior Components: crucial seating components need to perform under extensive long-term use in operating environments that can range from sub-zero arctic temperatures to scorching desert sun. Testing processes need to cover attributes including fatigue strength for seat materials, foam hardness tests for headrests and other cushioned surfaces, and stiffness for headrests.   Safety Components: safety systems including seatbelts (with tests strictly regulated by UN/ECE-R16), air bag fabrics and connectors, and anti-pinch sealing systems for doors/windows all require an extensive array of testing capabilities to ensure reliable operation even after years of use.   Operational Controls: pedals (clutch/brake/gas), emergency break levers, and control switches all need to be precision engineered to ensure ease-of-use with optimal haptic, optical, and acoustic feedback for associated user actions. Doing so successfully requires specialized testing capabilities like curved-force actuators for pedals and specialized servo actuator grips for emergency brake lever testing.   Automotive Materials Testing: Engines and Drives Engines and drive assemblies play an essential role in determining performance, efficiency, and emissions. Auto makers are pressed to design lighter and faster engines, even as features (like supercharging and hybridization) become more complex.   Engine Components: crucial engine component testing capabilities include fatigue tests at a variety of temperatures for connecting rods, crankshafts, and valve springs. Additional testing capabilities are needed for engine-related systems like elastomer bearings, exhaust systems, and catalytic converter mats. Drive Train: drive train testing must capture specific properties at high speeds, torques, and temperatures. Vital drive train testing capabilities include clutch testing, torsion testing on drive shafts, hardness/fatigue tests on gears, and torsion tests on rubber-metal elements. Alternative Drives: as hybrid vehicles proliferate, automotive manufacturers are investing in achieving more efficiency in traction motors, which requires specialized testing capabilities for components like energy/hydrogen storage systems and electromagnetic actuators.