Values Of Normal Stress Research Articles

External Constraint and Shrinkage of Butt-welded Joints in the Erection of Assemblies on Building Way

As for the degree of external constraint of welded joints in ship construction, various discussions have long been made in connection with the problems of shrinkage and residual stress, but the magnitude of the constraint has been left unknown. On the degree of external constraint we adopted in this paper the following definition ; Degree of external constraint=Average value of transverse stress along weld line necessary to produce average dislocation of 1 mm along weld line, we obtained the magnitude quantitatively by applying two methods. The one is the method of measuring the change of root gap due to external load applied transversely to weld line before welding, and the other is the method of comparing average shrinkage along weld line due to welding with the shrinkage in free welded joint.The main results obtained in this paper are summarized as follows : (a) Degree of external constraint seems to be independent to thickness of plate and total weight of assembly.(b) Degree of external constraint is generally very small. About 60 per cent, of total butt joints measured showed the degree of external constraint less than lkg/sq. mm/mm, and none of them showed more than 10 kg/sq. mm/mm.(c) When the magnitude of degree of external constraint and welding conditions are definite, average locked-in stress increases a little with the increase of the thickness of plate.

Stress Distributions in Rotating Disks Subjected to Creep at Elevated Temperature

Abstract Assuming a creep rate proportional to a power function of the stress, curves of stress distribution as a function of the radius have been calculated for several cases of rotating disks subject to steady-state creep at elevated temperature. The disks are assumed to have central holes and to be uniformly loaded at the periphery (to simulate blade loading in turbine disks). It is also postulated that the Tresca (maximum-shear) criterion and the associated flow rule govern. The following cases are treated: (1) Disk of constant temperature and thickness with various ratios of outside to inside diameter and with various values of the exponent n in the assumed power function stress-creep rate relation. (2) Disk of constant temperature and variable thickness, the thickness at the periphery being equal to half that at the hub, for various n-values. (3) Disk with variable temperature such that the creep rate at the outside diameter is ten times that at the inside diameter for the same stress, various n-values being assumed. Limits of radial peripheral loading beyond which the derived stress-distribution curves are not valid are also determined. The results indicate that a considerable nonuniformity in stress distribution under creep conditions may exist, particularly for the lower n-values; thus creep-rupture strengths of such disks for long-time loading conditions may be lower than would be expected if based on average stress values, particularly for materials having limited ductility in long-time creep-rupture tests.

Strength of Rotating Disks

The criterion for rupture of brittle materials like cast iron is σ=σB, where, σ is mean value of normal tensile stress on the surface of rupture ; the mean is generally a weighted mean, the effectiveness to the load being taken into account, and σB is ultimate tensile strength. The strength, when a rotating disk of brittle material bursts in a diametral section under centrifugal force, can be obtained from the same condition, σ being, in this case, the ordinary average value. For ductile materials the condition of strength may be put σ=σB', where, σB'is tensile strength under uniform stress, or in this case the strength of a rotating ring. The strength calculated from this condition was compared with experiments hitherto carried out.

Experiments for determining the position of the neutral axis of rectangular beams of cast and wrought iron and wood, and also for ascertaining the relative amount of compression and transverse strain

Adding particles and fibers to the adhesive layer in adhesively bonded joints can increase adhesive toughness and improve stress distribution in the adhesive layer. In this paper, geometric and material parameters of metal fibers employed for reinforcement of adhesively bonded single lap joint (SLJ) were studied using experimental investigations and finite element modeling. The experimental results showed that incorporating metal fibers in the adhesive layer of a bonded joint can have considerable influence on the joint strength. This was in correlation with the numerical results predicting improved stress distributions of the adhesive layer when the metal fibers were incorporated in the adhesive layer. The diameter and the stiffness of the fibers and the distance between the fibers were found as three key parameters in design of metal fiber-reinforced adhesive joints. It was found that reducing the distance between the fibers, increasing the fiber diameter and choosing a stiffer material for the fibers improved the stress distribution and reduced the maximum and average stress values in the adhesive layer.