CWB Level 2 MODULE 7 RESIDUAL STRESS & DISTORTION ALREADY PASSED

CWB Level 2 MODULE 7 RESIDUAL STRESS & DISTORTION ALREADY PASSED Define Compression ? To reduce in volume, or the state of being compressed. To force together or into less space Define Contraction? To become reduced in size. To pull together, shrink or wrinkle. Define Distortion? The act of distorting. A physical change in shape by bending, twisting or warping. Define Ductility? Capability of being easily molded or shaped Define Expansion? Enlargement or increase. Increase in the dimension of a body Define Intermittent Welding ? Welding that is not continuous over the length of the joint Define Lateral Shrinkage? The process of being drawn together parallel to the line of the joint Define Longitudinally? Running lengthwise or pertaining to length Define Neutral Axis? Occupying a middle position of symmetrical shape. Through the center of gravity. Define Peening? The act of inducing compression into the surface layers of an object. Often performing by striking the surface of a metal object with a ball shaped device, i.e ball-peen hammer, or blasting with specific procedures, i.e shot peening. Define Periphery? The outer part of an object or area Define Residual Stresses? Stresses remaining after a process has been completed. Stress present in a material that is free of external forces or thermal gradients. Define Permanent Deformation ? Shape change that is not reversible by the removal of the forces (plastic deformation) that caused it. Define Restrain? To prevent or limit movement Define Restraint? The act of holding back Define Shrinkage Force? An internal force exerted on a component due to uneven dimensional change during heating and cooling Define Strain? A shape change produced by stress Define Stress? An internal force or system of forces that tend to strain or deform an object or body. Force per unit area. Define Symmetrical? Exactly uniform in shape about a dividing line or about a center or axis. Define Transverse? Situated or lying across Define Tensile Stress? A stress that tends to cause elongation or extension Define Upset? To make shorter or thicker EXAM QUESTION Section 1-4 Describe or sketch what happens when a bar is gripped at both ends so that neither expansion nor contraction is allowed to take place, and heat is then applied. a)Causing upsetting, b)upsetting remains on cooling and bar stretches or EXAM QUESTION Section 1-4 Weld metal shrinkage is not proportional to the amount of weld metal. True/False False EXAM QUESTION Section 1-4 Longitudinal residual stress may be as high as the yield stress of the base metal. True/False True EXAM QUESTION Section 1-4 There is no residual stress in a steel plate with mill rolled edges without any additional heat treatment? True/False False EXAM QUESTION Section 1-4 Oxy-fuel gas cutting along rectangular steel plates always causes distortion True/False False Exam Question Section 1-4 What is the formula or application of a Transverse shrinkage-butt welds Exam Question Section 1-4 What is the formula or application for Longitudinal shrinkage-butt welds Exam Question- Section 5 In seam welding, what is the simplest form of distortion control? Start the weld some distance from the end of the joint, making a short weld first Exam Question- Section 5 Where plating and stiffeners are combined as in ship bulkhead work, the butt and seam welds in plating should be welded before the stiffeners? True/False True Exam Question- Section 5 In filling up a weld joint, the number of weld passes does not affect distortion True/False False Exam Question- Section 5 Arc travel speed does not affect the amount of distortion True/False False Exam Question- Section 5 The heat distribution around the welding arc is the same regardless of its travel speed. True/False False Exam Question- Section 6 & 7 Distortion may be partially or fully controlled by mechanical means using: a) rigid clamping or fixturing b) pre-bending or setting c) pre-welding heat treatment d) post weld heat treatment e) sub-assembly a, b , and c Exam Question- Section 6 & 7 In the welded assembly with both groove and fillet welds, the fillet welds should be completed first and then the groove welds. True/False False Exam Question- Section 6 & 7 What is the advantages of intermittent fillet welds? Less distortion Exam Question- Section 6 & 7 What is the advantage of using sub-assemblies when feasible? Reduces cumulative tolerances, easy to handles for large structures Exam Question- Section 6 & 7 Balancing welds about the neutral axes can reduce distortion True/False True Exam Question- Section 6 & 7 Reducing the root opening of a groove joint can reduce shrinkage. True/ False True Exam Question- Section 6 & 7 Is rigid alignment and complete joint restraint by strong backs, clamps and similar devices a recommended practice? Yes/No No Exam Question- Section 6 & 7 Excessive root face in plate edge preparation should be avioded. True/False True Exam Question - Section 8 The contraction effects in the weld metal that are of greater magnitude and, therefore, more serious are: a) longitudinal b) transverse b) transverse Exam Question - Section 8 What is the maximum temperature in heat straightening or forming of low alloy steels? 650 Celsius Exam Question - Section 8 When a heated members cools non-uniformly, the portions that cool first go into compression and the portions that cool last go into tension. True/False True Exam Question - Section 8 In flaming forming, if the temperature is much higher than 650 Celsius it can cause damage to the base metal. True/ False True Exam Question - Section 8 In flame straightening, if the temperature is too low the member will not be straightened. Why Insufficient to produce upsetting Exam Question - Section 8 In flame straightening or forming of low alloy steel members, what color should be watched for? a dull or cherry red color 1. Exam Question It would be correct to say: a) expansion and contraction are proportional to the dimensions of the heated area b) when a bar is heated under restraint, its stress relieves itself as it cools c) slow cooling of a heated area will provide the greatest amount of shrinkage d) when metal is heated it expands, but it does not shrink back to its original size when it cools a) expansion and contraction are proportional to the dimensions of the heated area 2. Exam Question To reduce the amount of angular distortion you should: a) increase travel speed b) reduce the angle of the preparation c) preheat the metal d) all of the above e) none of the above d) all of the above 3. Exam Question When a structural member has been bent sharply, it can be straightened by heating: a) a vee shaped section of the web underneath the bent area of the flange b) the inside corner of an angle, channel, I-beam, or T-bar c) a vee shaped area at the point of the greatest bend, with the top of the vee at the point of the greatest bend d) all along the edge of the section e) all along the edge opposite to the one which is bent c) a vee shaped area at the point of the greatest bend, with the top of the vee at the point of the greatest bend 4. Exam Question Of the many mechanical means of controlling distortion, the following will have the least residual stress: a) rigid clamping b) sub-assembly of the section c) heavy strong-backs, welded on both sides of the joint d) similar weldments clamped back to back e) pre-set the plates to allow recovery of angular distortion e) pre-set the plates to allow recovery of angular distortion 5. Exam Question Decreasing the number of weld beads in a specific weld will: a) result in annealing the weld area b) give a finer grain structure c) reduce the transverse shrinkage d) increase the transverse shrinkage e) possible crack the root pass c) reduce the transverse shrinkage 6. Exam Question The neutral axis is the the : a) line in which there will be neither tension nor compression when the piece is flexed or bent. b) center-line of the weld bead halfway between the root pass and the face pass c)outside center-line of the web of a channel d) inside corner line of an unequal leg steel angle e)dimensional halfway point of a welded assembly a) line in which there will be neither tension nor compression when the piece is flexed or bent. 7. Exam Question When expansion and contraction are prevented, heating and cooling may cause: a) no residual stresses b) failure due to lamellar tearing c) no permanent deformation or failure d) failure when the metal is highly ductile e) failure when metal is not sufficiently ductile e) failure when metal is not sufficiently ductile 8. Exam Question When heated, unrestrained metal will expand : a) transversely (across the weld) b) volumetrically (in all directions) c) until it upsets d) longitudinally (lengthwise) e) mostly across the width of the weld b) volumetrically (in all directions) 9. Exam Question It would be INCORRECT to say that peening: a) should not be used on the last pass b) puts the surface of the weld in compression c) should not be used on root passes d) can be used to form the surface contour of the weld to the inspectors satisfaction e) should be stopped before the weld surface starts to flake d) can be used to form the surface contour of the weld to the inspectors satisfaction 10. Exam Question To avoid longitudinal bending of a plate when it is being cut to width, you would : a) cool the outer edge with an air blast b) cut both edges at the same time c) dog the plate down away from the cut d) pre-bend the plate away from the cut e) slow down the cutting speed b) cut both edges at the same time