Failure Analysis of Redundant Escalator Chain Pin Retention Mechanisms

2011 ◽  
Author(s):  
Richard W. Klopp
Keyword(s):  
Failure Analysis ◽  
Driving Force ◽  
Lateral Force ◽  
Ring Groove ◽  
Side Plate ◽  
Interference Fit ◽  
Light Interference ◽  
Retaining Ring ◽  
Walking Mechanism ◽  
Rotation Sequence

The pins in new escalator chains were observed to have drifted laterally out of the chain side plates within a few hours of startup. The force driving this movement was sufficient to overcome a light interference fit and retaining rings intended to restrain the pins. Neither pins with heavy interference fit nor connector pins with sliding fits exhibited this tendency to drift. A failure analysis showed that even if the pins and side plates had been manufactured with a heavy interference fit, the sharp edge of the retaining ring groove acted as a broaching tool during assembly, shaving out and enlarging the side plate hole, and destroying the intended fit. The driving force for pin drift was traced to the hysteretic force and rotation sequence as the chain traveled around the escalator sprockets, which led to a walking mechanism that imparted a lateral force sufficient to move the pins and overcome the retaining rings.

Fitness for Service Evaluation of Ring Joint Groove Cracking

1999 ◽  
Vol 122 (1) ◽  
pp. 72-75
Author(s):  
R. G. Brown ◽  
G. M. Buchheim ◽  
D. A. Osage ◽  
J. L. Janelle
Keyword(s):  
Driving Force ◽  
High Stress ◽  
Service Evaluation ◽  
Small Sample ◽  
Crack Advance ◽  
Ring Groove ◽  
Stress Region ◽  
Fracture Assessment ◽  
Inherent Problem ◽  
Pressure Hydrogen

Cracking of ring joint style flanges has been a recurring problem in the petrochemical industry, particularly in high-pressure hydrogen processing vessels. The cracking of the ring joint groove region is an inherent problem with the design. The ring groove is subjected to high stresses from the wedging action of the gasket and the ring groove radii are not substantial enough to effectively reduce the stress concentrating effect. A fitness for service assessment was conducted for a hydrogen processing vessel containing cracks in the ring groove radius region of a ring joint style flange. The flange was forged 2-1/4Cr-1Mo material with a Type 347 SS overlay. Results of an elastic-plastic numerical fracture mechanics assessment showed that the driving force for crack propagation was high for a very localized region near the ring groove radius. However, the driving force decreased significantly for deeper cracks as the crack tip became removed from the very localized high stress region of the ring groove. The assessment also showed that the highest stresses occurred during the bolt-up operation. Metallurgical tests were performed on a small sample removed from the flange. The chemistry, grain size, microstructure, and hardness of the material indicated that the probability that this material had very low resistance to hydrogen-assisted crack growth during downtime was quite small and that the resistance to crack advance during service was good. Therefore, the combined results of the fracture assessment and metallurgical testing were used to justify continued operation without repair of the cracks present in the flange. [S0094-9930(00)01901-6]

The Use of an Interference-Fit Bush to Improve the Fatigue Life of a Pin-Jointed Connection

1962 ◽  
Vol 13 (3) ◽  
pp. 275-284 ◽  
Author(s):  
T. H. Lambert ◽  
R. J. Brailey
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Interference Fit ◽  
Light Interference ◽  
Maximum Benefit ◽  
High Degree

SummaryThe fatigue life of a pin-jointed connection can be optimised by using a moderately high degree of interference between the loading pin and plate. Where a joint has to be assembled in confined conditions, difficulty may be experienced in inserting the interference-fit pin and one possible solution is to use a pre-assembled interference-fit bush in the plate, leaving only a light interference-fit pin to be pressed in on assembly of the joint. It is shown that a relatively thick bush of diametral ratio 4/3 will give a reduction in shear stress concentration factor for the plate comparable with that obtained with a solid pin, but that maximum benefit is not obtained with a thinner bush of diametral ratio 8/7. Where thin bushes are essential in order to maintain the ultimate tensile and fatigue strengths of the plate and /or the ultimate and fatigue strengths of the pin, the shear stress concentration factor for the plate is reduced as the modular ratio of bush to plate is increased and as the interference fit of the loading pin in the bush is increased.

The Effect of Longitudinal Force on Bias and Radial Tires

1976 ◽  
Vol 4 (3) ◽  
pp. 155-168
Author(s):  
B. D. A. Phillips
Keyword(s):  
Driving Force ◽  
Lateral Force ◽  
Longitudinal Force ◽  
Radial Tire ◽  
Pressure Distributions ◽  
Braking Force ◽  
Force Characteristics

Abstract Tests were carried out to compare the effect of longitudinal force on the lateral force and aligning moment produced by a bias and a radial tire for different slip angles. Small differences occurred in the lateral force-driving force characteristics at low slip angles. Large differences occurred between the aligning moment-longitudinal force characteristics of the two tires, when the bias but not the radial tire exhibited a negative aligning moment upon the application of a braking force. These differences were caused mainly by differences in the pressure distributions in the contact patches of the two tires.

scholarly journals Contact stress analysis of disc cutter peg-hole with interference fit

2019 ◽  
Vol 43 (3) ◽  
pp. 273-282
Author(s):  
Jie Li ◽  
Chao Ma ◽  
Bin Zhang ◽  
Yuanjun Huang ◽  
Jingbo Guo
Keyword(s):  
Thermal Expansion ◽  
Contact Stress ◽  
Contact Length ◽  
Radial Force ◽  
Disc Cutter ◽  
The Finite Element Method ◽  
Interference Fit ◽  
Mating Surface ◽  
Retaining Ring ◽  
Surface Increase

To study the relation of the interference fit between cutter body and cutter ring, a theoretical design of interference fit of the cutter peg-hole is carried out according to the theory of thick-walled cylinders. The finite element method is used to analyzed the mapping relationship between the contact stress of cutter ring and cutter body. Thermal expansion assembly of the cutter ring is simulated, and the temperature of the thermal expansion assembly of the cutter ring is determined. The result shows that the contact length between the cutter body and the cutter ring has little influence on the contact stress of the cutter ring, but with increasing contact length the stress concentration of the retaining ring will increase. The contact stress of the cutter ring is basically the same at the same amount of interference and temperature, but the contact stress of the ring decreases with increasing contact length at high temperature. When the contact length is the same, the contact stress and the radial force of the mating surface increase with increasing amount of interference. The reasonable temperature for thermal expansion assembly of the cutter ring is 160 °C.

scholarly journals Limb swinging in elephants and giraffes and implications for the reconstruction of limb movements and speed estimates in large dinosaurs

Fossil Record ◽  
1999 ◽  
Vol 2 (1) ◽  
pp. 81-90 ◽  
Author(s):  
A. Christian ◽  
R. H. G. Müller ◽  
G. Christian ◽  
H. Preuschoft
Keyword(s):  
Detailed Analysis ◽  
Driving Force ◽  
Stride Length ◽  
Stride Frequency ◽  
Limb Movements ◽  
Eine Analyse ◽  
Fast Walking ◽  
Shoulder Joints ◽  
Walking Mechanism ◽  
Walking Speeds

Abstract. Speeds of walking dinosaurs that left fossil trackways have been estimated using the stride length times natural pendulum frequency of the limbs. In a detailed analysis of limb movements in walking Asian elephants and giraffes, however, distinct differences between actual limb movements and the predicted limb movements using only gravity as driving force were observed. Additionally, stride frequency was highly variable. Swing time was fairly constant, but especially at high walking speeds, much shorter than half the natural pendulum period. An analysis of hip and shoulder movements during walking showed that limb swinging was influenced by accelerations of hip and shoulder joints especially at high walking speeds. These results suggest an economical fast walking mechanism that could have been utilised by large dinosaurs to increase maximum speeds of locomotion. These findings throw new light on the dynamics of large vertebrates and can be used to improve speed estimates in large dinosaurs. Geschwindigkeiten gehender Dinosaurier, die fossile Fährten hinterlassen haben, wurden als Produkt aus Schrittlänge und natürlicher Pendelfrequenz der Beine abgeschätzt. Eine detaillierte Analyse der Beinbewegungen von gehenden Asiatischen Elefanten und Giraffen offenbarte allerdings klare Unterschiede zwischen den tatsächlichen Extremitätenbewegungen und den Bewegungen, die zu erwarten wären, wenn die Gravitation die einzige treibende Kraft darstellte. Zudem erwies sich die Schrittfrequenz als hochgradig variabel. Die Schwingzeit der Gliedmaßen war recht konstant, aber besonders bei hohen Gehgeschwindigkeiten viel kürzer als die halbe natürliche Pendelperiode der Extremitäten. Eine Analyse der Bewegungen der Hüft- und Schultergelenke während des Gehens zeigte, daß das Schwingen der Gliedmaßen durch Beschleunigungen dieser Gelenke beeinflußt wurde, insbesondere bei hohen Gehgeschwindigkeiten. Die Resultate legen einen ökonomischen Mechanismus für schnelles Gehen nahe, der von großen Dinosauriern zur Erhöhung der Höchstgeschwindigkeiten eingesetzt worden sein könnte. Die Ergebnisse werfen neues Licht auf die Dynamik großer Wirbeltiere. Sie können zu Verbesserungen in den Schätzungen der Fortbewegungsgeschwindigkeiten großer Dinosaurier eingesetzt werden. doi:10.1002/mmng.1999.4860020105

Failure Analysis With the Scanning Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 482-483
Author(s):  
John R. Devaney
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Integrated Circuits ◽  
Failure Analysis ◽  
High Reliability ◽  
Military Applications ◽  
Small Structure ◽  
Useful Life ◽  
Insight Into ◽  
Scanning Electron

Occasionally in history, an event may occur which has a profound influence on a technology. Such an event occurred when the scanning electron microscope became commercially available to industry in the mid 60's. Semiconductors were being increasingly used in high-reliability space and military applications both because of their small volume but, also, because of their inherent reliability. However, they did fail, both early in life and sometimes in middle or old age. Why they failed and how to prevent failure or prolong “useful life” was a worry which resulted in a blossoming of sophisticated failure analysis laboratories across the country. By 1966, the ability to build small structure integrated circuits was forging well ahead of techniques available to dissect and analyze these same failures. The arrival of the scanning electron microscope gave these analysts a new insight into failure mechanisms.

Sign in / Sign up

Export Citation Format

Share Document