scholarly journals Reliability design of mechanical systems subjected to repetitive stresses

2021 ◽  
Vol 349 ◽  
pp. 03009
Author(s):  
Seong-woo Woo ◽  
Dennis L. O’Neal ◽  
Yimer Mohammed Hassen
Keyword(s):  
Life Stress ◽  
Failure Modes ◽  
Plastic Material ◽  
Action Plan ◽  
Mechanical Systems ◽  
Life Time ◽  
Design Parameters ◽  
Repeated Impact ◽  
Reliability Design ◽  
Reliability Method

To enhance the design of mechanical systems, parametric Accelerated Life Testing (ALT) as a systematic reliability method is proposed as a way to evaluate the design of mechanical systems subjected to repeated impact stresses. It requires: (1) a parametric ALT scheme shaped on system BX lifetime, (2) a load inspection, (3) parametric ALTs with the associated design modifications, and (4) an assessment of whether the revised product design(s) reach the targeted BX life-time. We propose using a general life-stress model and sample size equation. A test example using both market data and parametric ALT was the redesign of a hinge kit system (HKS) in a refrigerator. To conduct parametric ALTs, a force and moment balance analysis was utilized. The mechanical impact loadings of the HKS were evaluated for an working refrigerator door. For the first ALT, the HKS failure happened in the crack/fracture of the kit housing and oil spilled from the damper when the HKS was disassembled. The failure modes and mechanisms constructed in the 1st ALT were similar to those of the unsuccessful samples found from the marketplace. The missing design parameters of the HKS included stress raisers such as corner roundings and the rib of the housing in HKS, the seal in the oil damper, and the material of the cover housing. In the second ALT, the cover housing fractured. The design defect of the cover housing in the HKS was the plastic material. As a corrective action plan, the cover housing was modified from plastic to aluminium. After the second ALT, the lifetime of the modified HKS was reassured to be B1 life 10 years with a yearly failure rate of 0.1%.

scholarly journals Reliability Design of Mechanical Systems Such as Compressor Subjected to Repetitive Stresses

2021 ◽  
Vol 3 (1) ◽  
pp. 14
Author(s):  
Seongwoo Woo ◽  
Dennis L. O’Neal ◽  
Samson Mekbib Atnaw ◽  
Muluneh Mekonnen Tulu
Keyword(s):  
Fatigue Failure ◽  
Life Stress ◽  
Failure Modes ◽  
Action Plan ◽  
Mechanical Systems ◽  
Valve Plate ◽  
Pressure Loading ◽  
Reliability Design ◽  
Mechanical Products ◽  
Reed Valve

This paper suggests parametric accelerated life testing (ALT) as a systematic reliability technique to generate the reliability quantitative (RQ) specification such as mission cycle for identifying design flaws in mechanical systems as exerting the accelerated load, defined as the reverse of stress ratio, R. Parametric ALT therefore is a procedure to improve the fatigue for mechanical products subjected to repetitive loading. It includes: (1) a system BX lifetime shaped on the parametric ALT plan; (2) a fatigue failure and design; (3) tailored ALTs with alternatives; and (4) an assessment of whether the design(s) of the product attains the targeted BX lifetime. A BX life ideas, a life-stress model, and a sample size formulation for parametric ALT are proposed. A reciprocating compressor in a domestic refrigerator is utilized to explain this methodology. The compressor was subjected to repetitive impact loading due to the pressure difference between condenser and evaporator, which results in the compressor field failure. To analyze and conduct parametric ALTs, as mass/energy balance was utilized on the vapor-compression refrigerating cycle, a simple pressure loading of the compressor in operating the refrigerator was investigated. At the first ALT, the compressor was locked due to the fractured suction reed valve made of Sandvik 20C carbon steel (1 C, 0.25 Si, 0.45 Mn). The dominant failure modes of the suction reed valve in the parametric ALTs were established to be very close to that of the fractured product from the marketplace. The root cause of the fatigue failure of the suction reed valve was an amount of overlap between the suction reed valve and the valve plate in combination of repeated pressure loading in the compressor. To supply sufficient mechanical strength, the design faults were altered by the trespan dimensions tumbling process, a ball peening and brushing process for the valve plate. At the second ALT, a compressor was locked due to the intrusion between the crankshaft and the thrust washer. The corrective action plan was to give heat treat the surface of crankshaft made of cast iron (0.45 C, 0.25 Si, 0.8 Mn, 0.03 P). After these alternations, there were no issues at the third ALT. The lifetime of the compressor was ensured to have B1 life 10 years.

scholarly journals Reliability Design of Mechanical Systems Such as Compressor Subjected to Repetitive Stresses

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1261
Author(s):  
Seongwoo Woo ◽  
Dennis L. O’Neal
Keyword(s):  
Life Stress ◽  
Failure Modes ◽  
Action Plan ◽  
Valve Plate ◽  
Pressure Loading ◽  
Reliability Design ◽  
Mechanical Products ◽  
Reed Valve ◽  
Repetitive Impact ◽  
Design Defects

This study demonstrates the use of parametric accelerated life testing (ALT) as a way to recognize design defects in mechanical products in creating a reliable quantitative (RQ) specification. It covers: (1) a system BX lifetime that X% of a product population fails, created on the parametric ALT scheme, (2) fatigue and redesign, (3) adapted ALTs with design alternations, and (4) an evaluation of whether the system design(s) acquires the objective BX lifetime. A life-stress model and a sample size formulation, therefore, are suggested. A refrigerator compressor is used to demonstrate this method. Compressors subjected to repetitive impact loading were failing in the field. To analyze the pressure loading of the compressor and carry out parametric ALT, a mass/energy balance on the vapor-compression cycle was examined. At the first ALT, the compressor failed due to a cracked or fractured suction reed valve made of Sandvik 20C carbon steel (1 wt% C, 0.25 wt% Si, 0.45 wt% Mn). The failure modes of the suction reed valves were similar to those valves returned from the field. The fatigue failure of the suction reed valves came from an overlap between the suction reed valve and the valve plate in combination with the repeated pressure loading. The problematic design was modified by the trespan dimensions, tumbling process, a ball peening, and brushing process for the valve plate. At the second ALT, the compressor locked due to the intrusion between the crankshaft and thrust washer. The corrective action plan specified to perform the heat treatment to the exterior of the crankshaft made of cast iron (0.45 wt% C, 0.25 wt% Si, 0.8 wt% Mn, 0.03 wt% P). After these design modifications, there were no troubles during the third ALT. The lifetime of the compressor was secured to have a B1 life of 10 years.

scholarly journals Improving the Fatigue of Newly Designed Mechanical System Subjected to Repeated Impact Loading

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 139
Author(s):  
Seongwoo Woo ◽  
Dennis L. O’Neal ◽  
Dereje Engida Woldemichael ◽  
Samson Mekbib Atnaw ◽  
Muluneh Mekonnen Tulu
Keyword(s):  
Fatigue Failure ◽  
Impact Loading ◽  
Life Stress ◽  
Action Plan ◽  
Momentum Balance ◽  
Material Strength ◽  
Repeated Impact ◽  
Domestic Refrigerator ◽  
Reliability Method ◽  
Mechanical Products

This paper develops parametric accelerated life testing (ALT) as a systematic reliability method to produce the reliability quantitative (RQ) specifications—mission cycle—for recognizing missing design defects in mechanical products as applying the accelerated load, expressed as the inverse of stress ratio, R. Parametric ALT is a way to enhance the prediction of fatigue failure for mechanical systems subjected to repeated impact loading. It incorporates: (1) A parametric ALT plan formed on the system BX lifetime, (2) a fatigue failure and design, (3) customized ALTs with design alternatives, and (4) an assessment of whether the last design(s) of the system fulfills the objective BX lifetime. A BX life concept with a generalized life-stress model and a sample size equation are suggested. A domestic refrigerator hinge kit system (HKS), which was a newly designed mechanical product, was used to illustrate the methodology. The HKS was subjected to repeated impact loading resulting in failure of the HKS in the field. To conduct ALTs, a force and momentum balance was utilized on the HKS. A straightforward impact loading of the HKS in closing the refrigerator door was examined. At the first ALT, the housing of the HKS failed. As an action plan, the hinge kit housing was modified by attaching inside supporting ribs to the HKS to provide sufficient mechanical strength against its loading. At the second ALT, the torsional shaft in the HKS made with austenitic ductile iron (18 wt% Ni) failed. The cracked torsional shaft for the 2nd ALTs came from its insufficient rounding, which failed due to repeated stress. As an action plan, to have sufficient material strength for the repetitive impact loads, the torsional shaft was reshaped to give it more rounding from R0.5 mm to R2.0 mm. After these modifications, there were no problems at the third ALT. The lifetime of the HKS in the domestic refrigerator was assured to be B1 life 10 years.

Study on Reliability Design of the Domestic Compressor Subjected to Repetitive Internal Stresses by Parametric Accelerated Life Testing

2022 ◽  
pp. 241-266
Author(s):  
Seongwoo Woo ◽  
Dennis L. O'Neal ◽  
Yimer Mohammed Hassen
Keyword(s):  
Life Stress ◽  
Failure Modes ◽  
Action Plan ◽  
Accelerated Life Testing ◽  
Valve Plate ◽  
Life Testing ◽  
Accelerated Life ◽  
Mechanical Products ◽  
Reed Valve ◽  
Design Defects

This chapter explains the parametric accelerated life testing (ALT) to recognize design defects in mechanical products. A life-stress model and a sample size formulation are suggested. A compressor is used to demonstrate this method. Compressors were failing in the field. At the first ALT, the compressor failed due to a fractured suction reed valve. The failure modes were similar to those valves returned from the field. The fatigue of the suction reed valves came from an overlap between the suction reed valve and the valve plate. The problematic design was modified by the trespan dimensions, tumbling process, a ball peening, and brushing process for the valve plate. At the second ALT, the compressor locked due to the intrusion between the crankshaft and thrust washer. The corrective action plan performed the heat treatment to the exterior of the crankshaft made of cast iron. After the design modifications, there were no troubles during the third ALT. The lifetime of compressor was secured to have a B1 life 10 years.

Reliability Design and Case Study of a Refrigerator Compressor Subjected to Repetitive Loads

2007 ◽  
Author(s):  
Seong-Woo Woo ◽  
Dennis L. O’Neal ◽  
Yongchan Kim
Keyword(s):  
Failure Modes ◽  
Design Parameters ◽  
Refrigeration Cycle ◽  
Life Testing ◽  
Reliability Design ◽  
Analysis And Design ◽  
Reliability Parameters ◽  
Design Changes ◽  
Field Failure

A newly designed crank shaft of a compressor for a side-by-side (SBS) refrigerator was studied. Using standard mass and energy conservation balances, a variety of compressor loads typically found in a refrigeration cycle were analyzed. The laboratory failure modes and mechanisms were compressor locking and crank shaft wear. These were similar to those of the failed samples in the field. Failure analysis, accelerating life testing (ALT), and corrective action were used to identify the key reliability parameters and their level. The design parameters of the crank shaft included the hole locations and the groove of the crank shaft used for oil lubrication, crank shaft hardness, and thrust washer interference. Based on the analysis and design changes, the B1 life of the new design is now over 10 years with a yearly failure rate of 0.01 percent. A procedure was recommended for refrigerator parts design which included five steps.

Vulnerability-Based Design of Sliding Concave Bearings for the Seismic Isolation of Steel Storage Tanks

2016 ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri ◽  
Phuong Hoa Hoang
Keyword(s):  
Liquid Steel ◽  
Seismic Isolation ◽  
Failure Modes ◽  
Fragility Curves ◽  
Time History ◽  
Probability Of Failure ◽  
Design Parameters ◽  
Economic Losses ◽  
Storage Tanks ◽  
Isolation System

Liquid steel storage tanks are strategic structures for industrial facilities and have been widely used both in nuclear and non-nuclear power plants. Typical damage to tanks occurred during past earthquakes such as cracking at the bottom plate, elastic or elastoplastic buckling of the tank wall, failure of the ground anchorage system, and sloshing damage around the roof, etc. Due to their potential and substantial economic losses as well as environmental hazards, implementations of seismic isolation and energy dissipation systems have been recently extended to liquid storage tanks. Although the benefits of seismic isolation systems have been well known in reducing seismic demands of tanks; however, these benefits have been rarely investigated in literature in terms of reduction in the probability of failure. In this paper, A vulnerability-based design approach of a sliding concave bearing system for an existing elevated liquid steel storage tank is presented by evaluating the probability of exceeding specific limit states. Firstly, nonlinear time history analyses of a three-dimensional stick model for the examined case study are performed using a set of ground motion records. Fragility curves of different failure modes of the tank are then obtained by the well-known cloud method. In the following, a seismic isolation system based on concave sliding bearings is proposed. The effectiveness of the isolation system in mitigating the seismic response of the tank is investigated by means of fragility curves. Finally, an optimization of design parameters for sliding concave bearings is determined based on the reduction of the tank vulnerability or the probability of failure.

Grey Model Based Particle Swarm Optimization Algorithm for Anticorrosion Reliability Design of Underground Pipelines

2010 ◽  
Vol 118-120 ◽  
pp. 541-545
Author(s):  
Qin Ming Liu ◽  
Ming Dong
Keyword(s):  
Particle Swarm Optimization ◽  
Optimization Algorithm ◽  
Failure Modes ◽  
Particle Swarm Optimization Algorithm ◽  
Particle Swarm ◽  
Grey Model ◽  
Swarm Optimization ◽  
Reliability Design ◽  
Model Based ◽  
Underground Pipelines

This paper explores the grey model based PSO (particle swarm optimization) algorithm for anti-cauterization reliability design of underground pipelines. First, depending on underground pipelines’ corrosion status, failure modes such as leakage and breakage are studied. Then, a grey GM(1,1) model based PSO algorithm is employed to the reliability design of the pipelines. One important advantage of the proposed algorithm is that only fewer data is used for reliability design. Finally, applications are used to illustrate the effectiveness and efficiency of the proposed approach.

scholarly journals Incorporating Uncertainty in Diagnostic Analysis of Mechanical Systems

2002 ◽  
Author(s):  
Gregory Mocko ◽  
Robert Paasch
Keyword(s):  
Life Cycle ◽  
Failure Modes ◽  
Mechanical Systems ◽  
Fault Tree Analysis ◽  
Joint Probability ◽  
Fault Isolation ◽  
Diagnostic Model ◽  
Component Reliability ◽  
Bayes Formula ◽  
Alternative Designs

The increase in complexity of modern mechanical systems can often lead to systems that are difficult to diagnose, and therefore require a great deal of time and money to return to a normal operating condition. Analyzing mechanical systems during the product development stages can lead to systems optimized in the area of diagnosability, and therefore to a reduction of life cycle costs for both consumers and manufacturers and an increase in the useable life of the system. A methodology for diagnostic evaluation of mechanical systems incorporating indication uncertainty is presented. First, Bayes formula is used in conjunction with information extracted from the Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA), component reliability, and prior system knowledge to construct the Component-Indication Joint Probability Matrix (CIJPM). The CIJPM, which consists of joint probabilities of all mutually exclusive diagnostic events, provides a diagnostic model of the system. The Replacement Matrix is constructed by applying a predetermined replacement criterion to the CIJPM. Diagnosability metrics are extracted from a Replacement Probability Matrix, computed by multiplying the transpose of the Replacement Matrix by the CIJPM. These metrics are useful for comparing alternative designs and addressing diagnostic problems of the system, to the component and indication level. Additionally, the metrics can be used to predict cost associated with fault isolation over the life cycle of the system.

Concrete Fatigue Life Characteristics of the Different Survival Rates in the Lateral Pressure Conditions

2012 ◽  
Vol 600 ◽  
pp. 250-255
Author(s):  
Qiang Cai ◽  
Ji Ming Kong ◽  
Ze Fu Chen
Keyword(s):  
Fatigue Life ◽  
Life Stress ◽  
Failure Modes ◽  
Survival Curve ◽  
Survival Rates ◽  
Life Distribution ◽  
Fatigue Design ◽  
Set Up ◽  
Fatigue Equation ◽  
Two Parameter

Under cyclic loading of concrete structures, fatigue failure is the main failure modes of fatigue, which has become the fatigue design of concrete structure must be considered, then the concrete fatigue studies must clarify the fatigue life of concrete under different survival curve S-N curve. Based on the statistics of the two parameter Weibull distribution theory, obtain the concrete under different survival rates of fatigue life distribution, namely to improve survival, reduce the fatigue life; stress level is reduced, the fatigue life is increased; and has set up more than 50% under different survival rates of concrete fatigue equation.

scholarly journals Percolation Analysis of Brain Structural Network

2021 ◽  
Vol 9 ◽  
Author(s):  
Shu Guo ◽  
Xiaoqi Chen ◽  
Yimeng Liu ◽  
Rui Kang ◽  
Tao Liu ◽  
...  
Keyword(s):  
Failure Modes ◽  
Critical Infrastructure ◽  
Network Reliability ◽  
Brain Connectivity ◽  
Brain Networks ◽  
Structural Features ◽  
Brain Network ◽  
Structure Design ◽  
Reliability Design ◽  
The Brain

The brain network is one specific type of critical infrastructure networks, which supports the cognitive function of biological systems. With the importance of network reliability in system design, evaluation, operation, and maintenance, we use the percolation methods of network reliability on brain networks and study the network resistance to disturbances and relevant failure modes. In this paper, we compare the brain networks of different species, including cat, fly, human, mouse, and macaque. The differences in structural features reflect the requirements for varying levels of functional specialization and integration, which determine the reliability of brain networks. In the percolation process, we apply different forms of disturbances to the brain networks based on metrics that characterize the network structure. Our findings suggest that the brain networks are mostly reliable against random or k-core-based percolation with their structure design, yet becomes vulnerable under betweenness or degree-based percolation. Our results might be useful to identify and distinguish brain connectivity failures that have been shown to be related to brain disorders, as well as the reliability design of other technological networks.

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