Effect of Loading Condition on Stress Intensity Factor for Threaded Fasteners Under Helix Angle Condition

2015 ◽  
Author(s):  
Suresh Kumar Sundaram ◽  
Raghu V. Prakash
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Loading Condition ◽  
Helix Angle ◽  
Elliptic Crack ◽  
Published Data ◽  
Far Field ◽  
Loading Conditions ◽  
Deep Crack

The effect of loading condition on the stress intensity factor (SIF) solution for a metric threaded bolt with helix angle consideration is investigated. Available SIF solutions for a nut loaded bolt do not consider the effect of helix angle of thread. Various loading conditions such as: (i) far field loading, (ii) thread face loading without helix angle, (iii) thread face loading with helix angle and (iv) nut loading with helix angle are considered in the present study. 3-D contact analysis is carried out to observe the stress distribution between the bolt and nut interface. A crack was introduced at the first thread of the bolt so that the crack faces experience opening mode of fracture under nut loading condition. The SIF estimated by each loading condition was compared with the SIF values computed taking into consideration the nut loading with helix angle. SIF solutions obtained under far field loading condition are lower than those obtained under other loading conditions at short crack depths (a/d = 0.1); at deep crack depths (a/d = 0.5), SIF obtained under nut loading condition are lower than those obtained under other loading conditions. At deep crack depths (a/d = 0.5) the effect of loading condition on SIF is more pronounced for an elliptic crack (a/c = 0.2) than semi circular crack (a/c = 1). Due to the combined effect of mode II and mode III fracture which is caused by helix angle, non symmetric distribution of SIF was observed along the crack front. It is noted that, crack growth rate derived from SIF under nut loading condition is lower than published data at the middle region (P/P0 = 0).

A Review of K-Solutions for Through-Thickness Flaws in Cylinders and Spheres

2007 ◽  
Author(s):  
Ali Mirzaee Sisan ◽  
Isabel Hadley ◽  
Sarah E. Smith ◽  
Mike Smith
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Loading Conditions ◽  
Wide Range ◽  
Cylinders And Spheres

This paper reviews different stress intensity factor solutions for a wide range of configurations and loading conditions for a cylinder with axial and circumferential through thickness cracks and a sphere with through thickness meridional (equatorial) cracks. The most appropriate solutions to use are identified.

System for Determining the Critical Range of Stress-Intensity Factor Necessary for Fatigue-Crack Propagation

1973 ◽  
Vol 15 (4) ◽  
pp. 271-273 ◽  
Author(s):  
K. Jerram ◽  
E. K. Priddle
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Critical Stress Intensity Factor ◽  
Published Data ◽  
Critical Range ◽  
A New Technique

A new technique is described for determining the critical stress intensity factor required for fatigue crack propagation to occur. It enables data to be obtained more rapidly and with fewer testpieces than existing techniques. Initial results obtained for En 3A mild steel are in excellent agreement with published data.

scholarly journals Fracture Mechanics Approach to Creep Crack Growth in Welded IN738LC Gas Turbine Blades

1991 ◽  
Author(s):  
Wan-P’ng Foo ◽  
Rafael Castillo
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Gas Turbine ◽  
Crack Growth ◽  
Turbine Blades ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Loading Conditions ◽  
Creep Crack

Microcracks caused by hot cracking or strain age cracking mechanisms are very likely to be discovered in the weld repair zone of precision cast IN738LC gas turbine blades. The possibility of crack propagation under the operating conditions of the gas turbine thereby becomes a crucial issue for gas turbine designers. The creep crack growth rate in air of the hipped and fully heat treated IN738LC was measured at the service temperature experienced by the first stage turbine blade tip. The corresponding growth behaviour was also studied. The creep crack growth rate, da/dt, versus crack tip stress intensity factor, K1, a relation which exhibits the typical primary, secondary and tertiary behaviour, supports the applicability of K1 as an appropriate correlating parameter for the creep crack growth of this Ni-based superalloy under the loading conditions used in this study. Microstructural examination illustrated that the creep crack growth of IN738LC principally takes place by the nucleation, growth, coalescence and link-up of grain boundary microvoids and microcracks. An excellent approximation of the stress intensity factor under service loading conditions in the vicinity of the crack tip was obtained by using the Westinghouse WECAN finite element analysis. It is shown that the crack tip stress intensity factor under normal loading conditions will not be able to drive the transverse through-the-wall-thickness blade tip crack in this study.

Effect of Helix Angle on the Stress Intensity Factor of a Cracked Threaded Bolt

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
S. Suresh Kumar ◽  
Raghu V. Prakash
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Depth ◽  
Helix Angle ◽  
Mode Ii ◽  
Mode Iii ◽  
Aspect Ratios ◽  
Depth Ratio ◽  
Crack Depth Ratio

The fracture behavior of a crack in a threaded bolt depends on the stress intensity factor (SIF). Available SIF solutions have approximated the threaded bolt as a circular groove, thus, the SIF predominantly corresponds to the opening mode, mode-I. As a thread in a bolt has a helix angle, the crack propagates under mixed mode conditions (opening, sliding and tearing), esp. when the crack sizes are small. This paper presents the results of SIF solutions for a part-through crack emanating from a Metric threaded bolt. A 3D finite element model with preexisting flaws was generated to calculate the SIF values along the crack front. Crack aspect ratios in the range of (0.2 < (a/c) < 1) and crack depth ratios in the range of (0.1 < (a/d) < 0.5) (where “a” is crack length, “c” is semi major axis of ellipse and “d” is minor diameter of the bolt) were considered along the crack plane for the SIF estimation. The SIF values at the midregion decreases with an increase in aspect ratio (a/c), and SIF increases when the crack depth ratio (a/d) increases in the midregion. Close to the free edges, higher SIF values was observed for crack depth and aspect ratios ranging between 0.2 and 0.6 compared to midregion. In the crack surface region, up to a crack depth ratio of 0.25, significant influence of mode-II and mode-III fracture was noted for shallow cracks (a/c < 0.2). Significant influence of mode-II and mode-III fracture was observed for semicircular cracks (a/c = 1) beyond the crack depth ratio of 0.3.

Crack Growth Behavior of Aluminum Alloys Tested in Liquid Mercury

1986 ◽  
Vol 108 (1) ◽  
pp. 37-43 ◽  
Author(s):  
J. A. Kapp ◽  
D. Duquette ◽  
M. H. Kamdar
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Intensity Factor ◽  
Crack Growth ◽  
Static Loading ◽  
Fatigue Loading ◽  
Loading Conditions ◽  
Fixed Load

Crack growth rate measurements have been made in three mercury embrittled aluminum alloys each under three loading conditions. The alloys were 1100-0, 6061-T651, and 7075-T651. The loading conditions were fixed displacement static loading, fixed load static loading, and fatigue loading at two frequencies. The results showed that mercury cracking of aluminum was not unlike other types of embrittlement (i.e. hydrogen cracking of steels). Under fixed load static conditions no crack growth was observed below a threshold stress intensity factor (KILME). At K levels greater than KILME cracks grew on the order of cm/s, while under fixed displacement loading, the crack growth rate was strongly dependent upon the strength of the alloy tested. This was attributed to crack closure. In the fatigue tests, no enhanced crack growth occurred until a critical range of stress intensity factor (ΔKth) was achieved. The ΔKth agreed well with the KILME obtained from the static tests, but the magnitude of the fatigue growth rate was substantially less than was expected based on the static loading results. Observations of the fracture surfaces in the SEM suggested a brittle intergranular fracture mode for the 6061-T651 and the 7075-T651 alloys under all loading conditions. The fractographic features of the 1100-0 alloy under fixed load and fatigue loading conditions were also brittle intergranular. Under fixed displacement loading the cracks grew via a ductile intergranular mode.

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