In this video I take a detailed look at Poisson's ratio, a really important material property which helps describe how a material will deform under loading.
Young's modulus is a crucial mechanical property in engineering, as it defines the stiffness of a material and tells us how much it will deform for an applied stress. In this video I take a detailed look at Young's modulus, starting with tensile tests and stress-strain curves, all the way through to what is happening at the atomic scale.
Strength, ductility and toughness are three very important, closely related material properties. The yield and ultimate strengths tell us how much stress a material can withstand, and are often used to define failure. Ductility tells us how much plastic deformation a material undergoes before fracture. Brittle materials fracture at very small strains, and can fail catastrophically. Toughness tells us how much energy a material can absorb before fracture. It is closely linked to both strength and ductility.
Fatigue failure is a failure mechanism which results from the formation and growth of cracks under repeated cyclic stress loading, leading to fracture. It can result in failure at stress levels well below the material yield or ultimate strengths. In this video I discuss the mechanisms behind fracture, and how S-N curves can be used to predict the fatigue life of a component.
In this video I take a look at plane stress, an assumption used in solid mechanics to simplify the analysis of a component by turning a 3D problem into a 2D one. In the video I look at three examples of plane stress - a thin perforated plate, thin-walled pressure vessels, and thin gears.
In this video, we're going to take a look at stress transformation and Mohr’s circle. Stress transformation is a way of determining the normal and shear stress components acting at a specific location within a body, as we rotate the coordinate system we are using to observe the stresses. And Mohr's circle is a very simple but powerful technique we can use to represent stress transformation graphically.
How are things made? In this video I take a look at the different types of manufacturing processes - forming, casting, molding, machining, joining and additive manufacturing - which are used to create the everyday objects that surround us. Using animations, the video explores a number of different specific manufacturing techniques, like rolling, injection molding, investment casting, sand casting, and 3D printing, and gives an overview of the pros and cons of each, to help better understand how to select the correct manufacturing process.
This video is an introduction to shear force and bending moment diagrams. Shear forces and bending moments are resultants which are used to conveniently represent the internal forces that develop within a beam when external loads are acting on it. The internal forces that exist within the beam will depend on how the beam is loaded, and how it is supported. Beams are typically loaded by concentrated forces, distributed forces, and concentrated moments. Typical beam supports include pinned supports, roller supports, and fully fixed supports.
This video is an introduction to stress and strain, which are fundamental concepts that are used to describe how an object responds to externally applied loads. Stress is a measure of the distribution of internal forces that develop within a body to resist these applied loads. Strain is a measure of the displacements that occurs within a body. Again we have both normal and shear stresses.
In this video we will explore torsion, which is the twisting of an object caused by a moment. It is a type of deformation. A moment which tends to cause twisting is called torque. Some of the things covered in this video include how circular bars deform under torsion, how we can calculate the angle of twist, and how we can calculate the stresses and strains that are generated in a circular bar as a result of torsion. We will also discuss internal torque diagrams, and why torsional failure is different for brittle and for ductile and materials.
Did you know that the typical stress-strain curve obtained from a uniaxial tensile test is just an approximation? It doesn't consider the fact that the dimensions of the test specimen change throughout the duration of the tensile test. In this video I cover the interesting topic of true stress and true strain.
The area moment of inertia (also called the second moment of area) defines the resistance of a cross-section to bending, due to the shape of the cross-section. It is a key parameter for the analysis of beams and columns. In this video I take a detailed look at the area moment of inertia, how's it calculated, and how it's used. I also cover key related topics, including the polar moment of inertia, the parallel axis theorem and Mohr's circle for moments of inertia.
In this video we'll take a detailed look at trusses. Trusses are structures made of up slender members, connected at joints which can be approximated to pinned connections. It is important for engineers to be able to determine the axial force in the members of a truss, so that they can be designed appropriately. In this video I cover the two main methods for doing this, which are the Method of Joints and the Method of Sections.
Failure theories are used to predict when a material will fail due to static loading. They do this by comparing the stress state at a point with material properties that can be easily determined from testing, like the yield or ultimate strengths of the material determined from a uniaxial test. In this video I cover some of the main theories for ductile and for brittle materials - Rankine (maximum principal stress theory), Tresca (maximum shear stress theory), von Mises (maximum distortion energy theory) as well as the Coulomb-Mohr and Modified Mohr theories.
In this video we explore bending and shear stresses in beams. A bending moment is the resultant of bending stresses, which are normal stresses acting perpendicular to the beam cross-section. We can easily derive an equation for these bending stresses by observing how a beam deforms for a case of pure bending. This equation is known as the flexure formula. Next we look at shear stresses, which act parallel to the beam cross-section, and can be represented by a shear force. These vertical shear stresses can cause horizontal shear failure in beams, because they result in complementary horizontal shear stresses, which develop to maintain equilibrium. Finally we look at how we can apply the shear stress equation to thin-walled open sections like the I beam, and how shear stress appears to "flow" through the cross-section.
There are two main types of fluid flow - laminar flow, in which the fluid flows smoothly in layers, and turbulent flow, which is characterised by chaotic motion and large amounts of mixing. In this video we explore the differences between these two flow regimes. We'll cover how Reynolds number can be used to predict which flow regime will occur for a specific set of flow conditions. And we will look at laminar and turbulent flows in pipes, and how the flow regime affects the pressure drop in a pipe. We'll also investigate why it is so difficult to simulate turbulent flow, and we'll look at some of the different Computational Fluid Dynamics methods which can be used to simulate it.
Bernoulli's equation is a simple but incredibly important equation in physics and engineering that can help us understand a lot about the flow of fluids in the world around us. It essentially describes the relationship between the pressure, velocity and elevation of a flowing fluid.
In this video I take a look at five methods that can be used to predict how a beam will deform when loads are applied to it. These are the double integration method, Macaulay's method, the principle of superposition, the moment-area method, and Castigliano's theorem, which is based on strain energy.
Drag and lift are the forces which act on a body moving through a fluid, or on a stationary object in a flowing fluid. We call these aerodynamic forces (if the fluid is a gas) or hydrodynamic forces (if the fluid is a liquid). This video is all about the drag force. There are two main causes of drag - first we have the pressure distribution around the object, which is particularly significant if flow separation occurs. And then we have the shear stresses acting on the object, which are most significant for streamlined bodies.
Humanity has long been obsessed with heavier-than-air flight, and to this day it remains a topic that is shrouded in a bit of mystery. In this video we take a detailed look at lift, starting with how it is linked with the pressure distribution around airfoils. We also cover a few different explanations of lift, including the Bernoulli Principle and Newton's Third Law explanations. Circulation is a key aspect of lift that it is important to grasp to develop a more complete understanding of lift so that's covered too, as is the Kutta condition. Finally we explore how the lift force varies with the angle of attack of the airfoil (which explains why aerobatic aircraft use symmetrical airfoils), and how stalling can result in a dangerous loss of lift.
In this video we take a look at viscosity, a key property in fluid mechanics that describes how easily a fluid will flow. But there's more to it than that! We'll start by defining viscosity using Newton's Law of Viscosity, that describes the linear relationship between the shear stress in the fluid and the strain rate, and how it relates to the dynamic and kinematic viscosities. We'll also explore how viscosity is dependent on temperature - the viscosity of liquids reduces with increasing temperature, but for gases temperature has the opposite effect. We can explain this by looking at what causes viscosity on the molecular level. Another interesting aspect of viscosity that's covered in the video is non-Newtonian fluids, like shear thinning or shear thickening fluids, for which the relationship between the shear stress and the strain rate is non-linear.
The finite element method is a powerful numerical technique that is used in all major engineering industries - in this video we'll explore how it works. We'll look at why it's useful to split the body being analysed into small elements and the different elements types that can be used. We'll also cover the key concept behind the finite element method, which is the stiffness matrix, including how the element stiffness matrices are derived, using techniques like the Galerkin method of weighted residuals. Once we have the element stiffness matrices we can assemble them into a global stiffness matrix that describes how the body will displace for a set of applied loads and boundary conditions.
To be able to use metals effectively in engineering, it's important to have an understanding of how they are structured at the atomic level. In this video we'll explore metals, their microstructure, and various techniques like grain boundary strengthening, solid solution strengthening, precipitation hardening and work hardening that can be used to improve their properties. We'll also cover phase diagrams, focusing on the diagram for Iron-Carbon atoms, that shows us the different phases like ferrite, austenite and cementite that can be found in steels for equilibrium conditions.
Buckling is a failure mode that occurs in columns and other members that are loaded in compression. It is a sudden change in deformation that occurs at a certain critical load. In this video we explore some key topics relating to buckling, including Euler's formula, the effects of end conditions, and other aspects like the effect of column slenderness, inelastic buckling and the buckling of shells and plates.
In this video we take a look at how vibrating systems can be modelled, starting with the lumped parameter approach and single degree of freedom models. We then go on to look at damping, the dissipation of energy that occurs in all real systems, as well as forced vibration, resonance and multiple degree of freedom models.
In this video we'll take a look at thermal radiation, one of the three modes of heat transfer along with conduction and convection. We'll start by covering electromagnetic waves, the Stefan-Boltzmann law, black bodies and emissive power. We'll then talk about emissivity, absorptivity, transmissivity and reflectivity, as well as view factors, all key concepts for being able to calculate the radiative heat transfer between surfaces.
Continuing the heat transfer series, in this video we take a look at conduction and the heat equation. Fourier's law is used to calculate the rate at which heat is transferred through an object due to conduction. But it can only be applied if the temperature distribution within the body is known. To determine the temperature distribution, the heat equation needs to be solved.
This video explores different methods that can be used to amplify a force, and focuses on three types of machine - levers, pulleys and gears. The amplification of a force is called mechanical advantage, and it is useful for a wide range of applications, like lifting heavy loads.
Engineering drawings are key tools that engineers use to communicate, but deciphering them isn't always straightforward. In this video we cover the fundamentals, including the different types of views, first and third angle projection methods, dimensioning, tolerancing, best practices when creating drawings, and GD&T (geometric dimensioning and tolerancing).
Geometric dimensioning and tolerancing (GD&T) complements traditional dimensional tolerancing by letting you control 14 different geometric characteristics. It applies tolerances to the form of features, instead of just to their dimensions. This video covers the different geometric characteristics and other key aspects of GD&T including datums, material modifiers (MMC, LMC and RFS), the Envelope Principle (also called GD&T Rule #1), and the Independency Principle.
This video takes a detailed look at bolted joints, and how preload, the tensile force that develops in a joint as it is torqued, can significantly improve the performance of a joint. The video covers tension joints, shear joints, and joints that are subjected to combined tensile and shear loads. It also explores the different methods that can be used to control the amount of preload applied to a joint, including the torque, turn-of-nut and ultrasonic measurement methods.
This video takes a look at composite materials, materials that are made up from two or more distinct materials. Composites are engineered to obtain materials with very useful material properties, tailored for specific applications. In the structure of a typical composite, one material - the dispersed phase - is contained within another - the matrix phase. The dispersed phase usually consists of small particles, or of either short or continuous fibers. CFRP, or carbon fiber-reinforced polymer, is one of the most commonly used engineering composites. But there are many others, including metal-matrix composites and ceramic-matrix composites, that have uses in many different industries and applications.
This video explores the fascinating world of strain gauges, these clever little devices that combine elements of mechanical engineering, electrical engineering, and materials science to give us a way of measuring the deformation on the surface of an object.
Satellite technology is a fascinating field that makes use of some very clever engineering to overcome the challenges of designing for the space environment. This video explores the seven subsystems - the structure, the on-board computer, the electrical power system, the attitude determination and control system, the propulsion system, the communications system and the thermal control system - that make up a typical satellite bus.
In this video we’ll explore what momentum is, why it’s such a fundamental concept in physics and engineering, and how it can be used to understand and analyse the motion of objects - from collisions and explosions to car crashes and rocket launches!
Polymers - what we commonly call "plastics" - are everywhere, but they're anything but ordinary. In this video we'll dive into the surprising science behind plastics, from their unique molecular structure to their unexpected properties.
This video explores the fascinating world of superalloys - highâperformance metals designed to excel in extreme, high-temperature environments. We’ll take a look at how these materials compare to more conventional alloys, and how one such material, Inconel 718, is able to perform at temperatures up to 700°C, thanks to its Nickel-based matrix and precipitate phases.
Pressure vessels are everywhere, from propane tanks to subsea pipelines. Pressurized fluids can exert enormous forces on the walls of the vessels that contain them. In this video we’ll explore how engineers apply simple mechanics principles to ensure pressure vessels can safely contain their contents without risk of catastrophic failure.
Friction plays a role in every mechanical system, from gears and bearings to tires on the road. In this video, we examine what friction is, where it comes from, and why different surfaces interact the way they do. We’ll explore static and kinetic friction, the effect of surface roughness, and how engineers can use friction to their advantage.
This video explores the superpower of steels - heat treatment, the precise heating and cooling of steel that allows the microstructure and so the properties of the material to be finely adjusted. It's one of the main reasons steel is so dominant in engineering.
This video explores one of the most powerful tools in engineering - calculus. By looking at how quantities change and how those changes accumulate, calculus helps describe and predict physical behaviour. In this video we work through the core ideas of calculus, from differentiation and integration through to differential equations and numerical methods, but with an engineering focus, linking the mathematics back to real-world physical behaviours.
Stainless steel has earned its reputation as one of the most corrosion-resistant materials in engineering. But when used in the wrong environment, that reputation can be dangerously misleading. This is exactly what happened in 1985, when the roof of a swimming pool in Uster, Switzerland collapsed without warning, killing 12 people and injuring many others. In this video, we explore the science behind stainless steels - what they are, how they achieve their remarkable corrosion resistance, and the unexpected failure mechanisms that can turn a trusted material into a critical point of failure.
Titanium is widely regarded as one of the more advanced engineering materials in regular use. It’s strong, lightweight, corrosion-resistant, and capable of operating in extreme environments. In this video, we explore the science behind this fascinating material. But we also examine the subtle weaknesses that can arise within titanium alloys, and the rare but critical failure mechanism that played a role in the dramatic engine failure of Air France Flight 066.
In this video we explore the science behind welding, the hidden flaws that can hide within a weld, and how a single fillet weld played a critical role in the sinking of the Alexander L. Kielland platform, in what remains Norway's deadliest industrial disaster.
On September 9, 2010, a pipeline exploded in a residential neighborhood in San Bruno, California, killing 8 people and causing huge amounts of destruction. This video explores fracture mechanics - the main tool engineers use to predict and prevent this type of failure.