Duration of load and probability of failure in wood. Part II. Constant, ramp, and cyclic loadings

1978 ◽  
Vol 5 (4) ◽  
pp. 515-532 ◽  
Author(s):  
J. D. Barrett ◽  
R. O. Foschi
Keyword(s):  
Cyclic Load ◽  
Constant Load ◽  
Probability Of Failure ◽  
Strength Distribution ◽  
Generalized Model ◽  
Cycle Amplitude ◽  
Short Term Strength ◽  
Wood Part ◽  
Duration Of Load ◽  
Snow Loading

A generalized model for damage accumulation is used to study the probability of failure of a wood member in bending for different load histories. The variability in time-to-fracture corresponding to a given load history is accounted for in the generalized model. Four types of loads are considered: (1) a constant load, (2) a ramp load, (3) a cyclic load of constant cycle amplitude, and (4) a cyclic load of random cycle amplitude. In each case, the probability of failure is studied as a function of the factor [Formula: see text] which, in the design equation, is applied to the 5th percentile of the short-term strength distribution to obtain the design stress. Snow loading is considered as an example of cyclic load with random cycle amplitude.

Effects of Constant Load on Autograft Healing Compared with Those of Cyclic Load

1994 ◽  
pp. 347-352
Author(s):  
Takeshi Muneta ◽  
Shunich Murakami ◽  
Youichi Ezura ◽  
Shintaro Asahina ◽  
Kazuo Takakuda ◽  
...  
Keyword(s):  
Cyclic Load ◽  
Constant Load

A Direct Method on the Evaluation of Ratchet Limit

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Haofeng Chen ◽  
Alan R. S. Ponter
Keyword(s):  
Cyclic Load ◽  
Mechanical Load ◽  
Low Cycle Fatigue ◽  
Direct Method ◽  
Numerical Technique ◽  
Load Condition ◽  
Numerical Procedure ◽  
Constant Load ◽  
Inelastic Analysis ◽  
Additional Constant

This paper describes a new linear matching method (LMM) technique for the direct evaluation of the ratchet limit of a structure subjected to a general cyclic load condition, which can be decomposed into cyclic and constant components. The cyclic load history considered in this paper contains multiload extremes to include most complicated practical applications. The numerical procedure uses the LMM state-of-the-art numerical technique to obtain a stable cyclic state of component, followed by a LMM shakedown analysis, to calculate the maximum constant load, i.e., the ratchet limit, which indicates the load carrying capacity of the structure subjected to a cyclic load condition to withstand an additional constant load. This approach is particularly useful in conjunction with the evaluation of the stable cyclic response, which produces the cyclic stresses, residual stresses, and plastic strain ranges for the low cycle fatigue assessment. A benchmark example of a holed plate under the combined action of cyclic thermal load and constant mechanical load is presented to verify the applicability of the new ratchet limit method through a comparison with published results by a simplified method assuming a cyclic load with two extremes. To demonstrate the efficiency and effectiveness of the method for a complicated cyclic load condition with multiload extremes, a composite thick cylinder with a radial opening subjected to cyclic thermal loads and a constant internal pressure is analyzed using the proposed ratchet limit method. Further verification by the ABAQUS step-by-step inelastic analysis demonstrates that the proposed new method provides a general-purpose technique for the evaluation of the ratchet limit and has both the advantages of programming methods and the capacity to be implemented easily within a commercial finite element code Abaqus.

scholarly journals Calculation of Failure Probability of Constantly Loaded Cantilever Beam by Monte Carlo Method

2014 ◽  
Vol 17 (3) ◽  
pp. 80-82
Author(s):  
Dušan Páleš ◽  
Milada Balková ◽  
Ingrid Karandušovská
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Cantilever Beam ◽  
Probability Distributions ◽  
Probabilistic Approach ◽  
Constant Load ◽  
Probability Of Failure ◽  
The Subject ◽  
Individual Variables ◽  
The Mathematical Model

Abstract In this paper, we demonstrate a probabilistic approach to the design of structures on a cantilever beam with constant load. Individual variables in the mathematical model are not represented deterministically by their specifc values but randomly by probability distributions. Normal distribution is used for all random variables. The resulting probability of failure is calculated using a simple Monte Carlo method, for which a brief overview is also provided in this article. Such a probabilistic proposal is the subject matter of newly emerging feld Reliability of Structures.

Duration of load tests for shear strength

1986 ◽  
Vol 13 (2) ◽  
pp. 188-195 ◽  
Author(s):  
R. A. Spencer ◽  
Borg Madsen
Keyword(s):  
Shear Strength ◽  
Stress Ratio ◽  
Control Sample ◽  
Term Strength ◽  
Short Term ◽  
Current Design ◽  
Short Term Strength ◽  
Load Effects ◽  
Duration Of Load

The strength of wood falls with time under load, and in current design codes the short-term strength of wood is reduced by about 40% to account for duration of load effects. This figure is based on tests made on small bending specimens. In this paper are described tests made on wooden torque tubes to investigate the effect of duration of load on shear strength. A control sample was tested to establish a curve for short-term strength, and four groups of 80 specimens each were then tested under various levels of constant long-term load. Stress ratio at failure was estimated by assuming that the short-term strength of each group could be represented by the control curve, and that under long-term loading specimens would fail in the order of their short-term strength. In each group the stress ratio at failure fell with time under load, and this reduction appears to be related to that predicted by a viscoelastic plastic model. It is concluded that the Madison curve presently used to predict duration of load effects may be conservative at normal levels of applied stress. Key words: wood, shear, long-term loading, duration of load.

scholarly journals Ratchet Analysis of Structures Under a Generalised Cyclic Load History

2014 ◽  
Author(s):  
Michael Lytwyn ◽  
Haofeng Chen ◽  
Michael Martin
Keyword(s):  
Cyclic Load ◽  
Mechanical Load ◽  
Low Cycle Fatigue ◽  
Limit Load ◽  
Constant Load ◽  
Load History ◽  
Matching Method ◽  
Additional Constant ◽  
Thermal Ratcheting ◽  
Linear Matching Method

This paper introduces a new approach based upon the Linear Matching Method in order to obtain the ratchet limit of structures subjected to an arbitrary thermo-mechanical load history. This method varies from the traditional Linear Matching Method ratchet analysis, where the cyclic load history is decomposed into cyclic and constant components, instead calculating the ratchet limit with respect to a proportional cyclic load variation, as opposed to an additional constant load. The shakedown and limit load boundaries are initially obtained for the given structure, followed by the utilisation of a bisection procedure in order to calculate an approximate ratchet boundary based upon a predefined magnitude of ratchet strain per cycle. The method also yields the total and plastic strain ranges based upon perfect plasticity, for low-cycle fatigue post-processing considerations. The effects of analysing the ratcheting mechanism of structures undergoing a cyclic primary load that varies proportionally with a cyclic secondary load can be seen to lead to modified and less conservative ratchet boundaries compared to the traditional Bree solution in which the thermal ratcheting requirement (NB-3222.5) of ASME III is based upon. This paper introduces the theory, numerical implementation and verification of the proposed method via a series of example problems.

Study on temperature rise distribution of contact surface under cyclic load

2020 ◽  
Vol 235 (1) ◽  
pp. 138-148
Author(s):  
Ling Li ◽  
Haifei Tian ◽  
Qiangqiang Yun ◽  
Wei Chu
Keyword(s):  
Contact Surface ◽  
Temperature Rise ◽  
Cyclic Load ◽  
Thermal Structure ◽  
Constant Load ◽  
Contact Center ◽  
Tangential Load ◽  
Cycle Number ◽  
Load Amplitude ◽  
Depth Direction

A large amount of heat is generated during the friction of joint surfaces, which has a significant influence on the contact characteristics of surfaces, causing deformation or failure of key components. A two-dimensional friction-thermal structure coupling contact model of cylinder/plane was established in ABAQUS. The effects of roughness under different fractal parameters, tangential load amplitude and cycle number on the temperature rise distribution of a contact surface under normal cyclic loading were studied. The results show that with the increase of roughness and tangential load amplitude, the area of thermal effect becomes more obvious and the temperature rise of the contact surface increases. It is also found that the heat affected zone is mainly distributed near the surface of the contact area with a high-temperature field generated, while the temperature rise amplitude decreases gradually along the depth direction. In addition, the contact surface nodes have a similar temperature rise distribution process and the farther away from the contact center ( x = 0.3 mm), the smaller the temperature rise, which is consistent with the simulation results of the published literature. For the same tangential load amplitude, the surface temperature rise amplitude under the normal cyclic load is lower than that of the normal constant load. The temperature rise of the surface increases with the increase of the number of fretting cycles.

A Hybrid Procedure for Ratchet Boundary Prediction

2009 ◽  
Author(s):  
Michael Martin ◽  
David Rice
Keyword(s):  
Nuclear Power ◽  
Cyclic Load ◽  
Hybrid Approach ◽  
Limit Load ◽  
Constant Load ◽  
Hybrid Procedure ◽  
Cyclic Response ◽  
Shakedown Theory ◽  
Load Component ◽  
Yield Capacity

Methods exist in today’s published literature which establish proximity to the ratchet boundary of a given load set by decomposing a cyclic load history into constant and cyclic components. Such methods operate by calculating the utilisation of yield capacity throughout the structure in response to the cyclic load. The remaining yield capacity is then available to support the constant load. In this paper, a hybrid procedure is described which uses established finite element techniques to obtain a stable response to the cyclic load component, followed by a limit load analysis based on the remaining yield capacity, to calculate the maximum primary load. This approach is particularly useful in conjunction with Fourier based cyclic procedures which, although capable of predicting the existence of a stable cyclic response, are not based on classical shakedown theory and are therefore unable to predict proximity to ratchet, unless a search procedure is used. The hybrid approach provides the combined benefit of an efficient cyclic response calculation scheme with a measure of proximity to the ratchet boundary. In this paper, the hybrid method is applied to the Bree case before application to a more complex thermo-mechanical transient, typical of nuclear power plant loading. The generation of interaction diagrams for both cases is considered.

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