Types of Stresses – Stress and Strain – Strength of Materials


Hello friends here in this video we are going to see what is meant by types of stresses the types of stresses in this the first type is called as tensile stress next compressive stress then shear stress next torsional sheer stress and then bending stress so these are the kinds of stresses which we are going to see in the subject of strength of material so let us understand them one by one starting with tensile stress tensile stress for that I have to draw a diagram in this diagram again Here I am drawing a rod next year I have the axis of the rod let me say that D is the diameter of the rod and its length is L so now when I am applying load which is in the upward direction and another load which is there in the downward direction so because of the action of these two opposite values of load which is passing through the axis because for tensile stress here the load has to pass through the axis and when it is passing through this then this load will try to pull the rod and this pulling action is called as tensile and the stress which is developed in the material would be called as tensile stress so your in tensile stress I can write down it is stress produced in a member because of pull type of loading next tensile stress it is denoted by Sigma T where T is the suffix indicating tensile stress so tensile stress will result in pulling action and when there is pulling action the diameter will reduce and length of the member will go on increasing so this is called as the tensile stress next is compressive stress in case of compressive stress here again we have a rod having the same diameter D and same length of L next here I have excess of this rod so when I am applying a load instead of pulling the rod here in case of compressive stress we are going to push the rod in both the directions so because of this action I can write down it is the stress produced in a member because of push type of loading and because of this push kind of loading the diameter of the member will go on increasing and length will go on decreasing so compressive stress it results in decrease in diameter and it results in increase in diameter and decrease in length and I can say that compressive stress it is denoted by Sigma suffix C where C is the suffix for compressive stress next after understanding tensile in compressive stress here we have the third kind of stress which would be called as shear stress for shear stress first let me draw a diagram for that so that we can understand it in a more clear way here in this diagram we have two plates which are connected with the help of a pin or we can say it is a rivet this is the cross-section of the upper plate similarly we have the cross section for the lower plate now here the load will be tangential one load is acting on the upper plate towards left other load is acting on the bottom plate acting towards right now because of the action of these two opposite forces there are chances of this plate to slide this one plate will move in its direction towards left another plate will try to move towards right and because of that this pin can break at the junction so here I’ll write down shear stress it is the stress produced in a member when the load is tangential to the cross-sectional area so here I have written the definition of shear stress that it is the stress produced in a member when the load is tangential to the cross sectional area your shear stress is denoted by tau or F of S which means shear stress now as I have told shear stress it is denoted by tau or FS next if the pin which I have at the center which is connecting these two plates if it gets sheared then how it looks like Here I am drawing the broken section of the rivet now so when this rivet will break it will look like this breaking into two halves and here I will get the cross-section area which is the breaking area another area would be here so now I can say that if the diameter of the rivet is small D then this cross-sectional area capital A will be PI by 4 into B Square and as we can see in this diagram that the cross sectional area and load they are tangential so that is why the effect is of shear now suppose if in case of two plates we have three plates I will draw the diagram and explain Here I am drawing the diagram for three plates which are connected with the help of pin or rivet Here I am drawing the section for the plates now suppose I am applying load on the upper plate towards left load on the lower plate that is also towards left and load on the middle plate that is towards right so because of this action what can happen previously we have seen when there were two plates pin was breaking into two parts now when we are having three plates in that case the pin will break into three parts and if I see the cross sectional area here I will be getting one area and here another area so this is called as double shear this case is of double shear and when we have double shear in that case area will be twice of PI by 4 into d square and here previously we have seen this area it was corresponding to single shear so this was regarding shear stress next torsional shear stress this is the next type of stress torsional shear stress in this case suppose we have a rotating member or we can say a rotating shaft which will be supported inside a bearing now I say that this is a shaft and here is the bearing so when this shaft will start rotating as we are giving shaft is a rotating member then torque would be given to this shaft and when this torque is given this shaft will start rotating and suppose for an example that when the shaft is starting to rotate bearing is a member which is stationary and shaft is rotating inside a member which is fixed so because of this what can happen that when the shaft is rotating at that time bearing will try to rotate the shaft or stop its motion or move it in the opposite direction that is if the shaft tries to rotate in the clockwise direction bearing will opposite and it will offer a motion in anti-clockwise direction that is it would offer another torque in anti-clockwise direction and because of this what can happen there can be a shaft which gets twisted and when it twists there are chances of the layers of the shaft to come out for example like this this layer has come out that is it has been sheared because of torsion so your torsional shear stress it is a stress which exists in rotating members like shafts then torsional shear stress it is denoted by again as it is shear stress we can denote it by tau or we can denote it by FS then after studying torsional shear stress the last type of stress which we have it is called as bending stress in case of bending stress this I can explain with a diagram of a beam which is fixed at one end and free at the other end now when the load will be acting on this beam there are chances of this beam to bend and it will Bend in such a fashion in the direction of load so this is the bending pattern so I can see that bending stress it is a stress which causes elongation of a member as we can see from this diagram when this load is applied this beam will try to move in the downward direction the bottom layers they are compressed and the top layers they are elongated so this is an example of bending like even if I am bending this pin then the length of this will go on increasing and finally when it is bending there is stress developed inside the pin and that stress is called as bending stress it is denoted by Sigma suffix B B stands for bending bending stress so bending stress mostly we would be saying in case of beams which are fixed at one and three at the other than other kinds of beam which are supported at both the ends called as simply supported beam so here in this video we have seen what are meant by types of stresses each stresses we have seen in detail with their description

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