Tool-Life Distributions—Part 2: Multiple-Injury Tool-Life Model

1977 ◽  
Vol 99 (3) ◽  
pp. 523-528 ◽  
Author(s):  
S. Ramalingam
Keyword(s):  
Tool Life ◽  
Multiple Injury ◽  
Linear Wear ◽  
Life Distribution ◽  
Subsequent Work ◽  
Tool Failure ◽  
Linear Wear Rate ◽  
Life Model ◽  
Life Distributions ◽  
Log Normal

The single-injury tool-life model developed in Part 1 of this paper is extended to the case of tool failure due to a multitude of injuries. The expected tool-life distribution in the case of tool failure from multiple injuries due to constant, time-independent stochastic hazards is shown to be a gamma distribution. The result obtained is based on a linear wear-rate assumption. The model is further extended to ensure applicability in the nonlinear wear region. It is shown that the expectation of a log-normal tool-life distribution when tool failure is due to crater wear is not unrealistic. No specific mechanism of tool wear is used to develop the model. The nature of the hazards and the wear mechanisms that are consistent with the multiple-injury tool-life model will be discussed in a subsequent work.

Tool Life Distributions—Part 3: Mechanism of Single Injury Tool Failure and Tool Life Distribution in Interrupted Cutting

1978 ◽  
Vol 100 (2) ◽  
pp. 193-200 ◽  
Author(s):  
S. Ramalingam ◽  
Y. I. Peng ◽  
J. D. Watson
Keyword(s):  
Tool Life ◽  
Hazard Function ◽  
Rational Design ◽  
Tool Material ◽  
Distribution Functions ◽  
Life Distribution ◽  
Tool Failure ◽  
Interrupted Cutting ◽  
Life Distributions ◽  
Machining Lines

Tool life distribution under production machining conditions must be suitably accounted for in any rational design of large volume or automated machining lines. Reliable data on the type of distributions likely to be encountered are, however, unavailable. To remedy this, using relevent physical arguments, probabilistic models of tool failure which produce distribution functions germane to tool life scatter have been proposed and developed in earlier parts of this paper. An arbitrarily introduced hazard function was used to predict the life distributions likely to be obtained. The details of the mechanisms giving rise to tool failure were, however, not examined. Mechanistic questions connected with the single-injury tool failure (tool fracture) are examined in this part. The arbitrarily introduced hazard function is shown to have a physical basis. It is shown that the hazard function is determined by the interaction between the characteristics of the environment in which the tool operates and the mechanical properties of the tool material. The concepts outlined and the mechanistic model of tool failure proposed have been tested experimentally in interrupted cutting. It is shown that the predicted Weibull-distributed tool life is obtained when tool failure is due to a single injury and that the parameters of the Weibull distribution are governed by the properties of the tool material as well as those of the machining system.

Tool-Life Distributions—Part 1: Single-Injury Tool-Life Model

1977 ◽  
Vol 99 (3) ◽  
pp. 519-522 ◽  
Author(s):  
S. Ramalingam ◽  
J. D. Watson
Keyword(s):  
Tool Life ◽  
Manufacturing Systems ◽  
Rational Design ◽  
Probabilistic Models ◽  
Probabilistic Approach ◽  
Distribution Functions ◽  
Automated Manufacturing Systems ◽  
Tool Failure ◽  
Life Model ◽  
Life Distributions

The statistical variability of tool life in production machining must be accounted for in any rational design of large-volume or automated manufacturing systems. The probabilistic approach needed for such a design is presently limited by lack of data on tool-life distributions and by lack of knowledge of the underlying causes giving rise to tool-life scatter. Given these circumstances, on the basis of relevant physical arguments one may construct probabilistic models that produce distribution functions germane to the problem of tool-life scatter. This paper is concerned with such a study. This first part presents the results obtained on the assumption that the useful life of a tool is terminated by a single, catastrophic injury. Cases where resistance to tool failure is time-independent and time-dependent are examined. The case of tool failure caused by multiple injuries will be presented in Part 2.

A Methodical Approach to Accelerated Screening of Card Assemblies, Static Burn-In Case

1985 ◽  
Vol 28 (2) ◽  
pp. 42-47
Author(s):  
Igor Pugacz-Muraszkiewicz
Keyword(s):  
Critical Parameters ◽  
Small Samples ◽  
Maximum Temperature ◽  
Life Distribution ◽  
Statistical Life ◽  
Methodical Approach ◽  
Life Tests ◽  
One Step ◽  
Life Distributions ◽  
Log Normal

The methodical approach presented for screening cards establishes values of critical parameters, such as apparent activation energy and maximum temperature hence shortest time for screening, and statistical life distributions of assemblies. We conducted one step-stress and two life tests at 120°C (248°F) and 135°C (275°F) using relatively small samples of 40 and 50 cards per test, which, nonetheless, gave us the desired information. The approximate screening parameters that resulted have been successfully used to tailor the stress screening of card assemblies. In our experiments, a trimodal, log-normal life distribution has been revealed, which seems to suggest that the traditional bathtub curve of a life distribution is not applicable to card assemblies.

Tool Life Distributions—Part 4: Minor Phases in Work Material and Multiple-Injury Tool Failure

1978 ◽  
Vol 100 (2) ◽  
pp. 201-209 ◽  
Author(s):  
S. Ramalingam ◽  
J. D. Watson
Keyword(s):  
Tool Life ◽  
Volume Fraction ◽  
Production Systems ◽  
Carbon Steels ◽  
Multiple Injury ◽  
Analytical Models ◽  
Minor Phase ◽  
Tool Failure ◽  
Steel Making ◽  
Work Material

Distributed tool life under production machining conditions results in the need for unplanned tool changes. In the case of large volume or automated production systems, such production interruptions invariably lead to higher manufacturing costs. When the distribution in tool life is known, logical operating strategies can be devised to minimize the costs associated with unforeseen production interruptions. To facilitate this, analytical models for tool life have been developed and presented in the first two parts of this paper. These stochastic models portray tool failure as resulting from injuries due to damage producing encounters in the course of machining. In Part 3 of this paper, a physically consistent model for damage producing encounters which result in tool fracture has been identified and validated for single-injury tool failure. The case of multiple-injury failure is considered here with emphasis on the tool life scatter due to the variations in minor phase content of the work material (nonsulphide, nonmetallic inclusion content). The role and significance of the oxygen-rich nonmetallics to tool wear and machinability in unalloyed carbon steels is examined. It is shown that given a steel, the chemistry and volume fraction of oxygen-rich nonmetallics in it may well determine the tool life (machinability) and tool life scatter. If this be the case, details of the steel making process can be varied to limit and control the detrimental effects of the oxygen-rich, nonmetallic phases to the tool life. Some such techniques that allow machinability enhancement by steel making process modifications are discussed to illustrate the validity of the concepts postulated here. The analysis suggests that the tool life (or machinability) can be improved by limiting the frequency of damaging encounters. But since the minor phase is dispersed and the encounters are stochastic, the tool life improvement will have to be accompanied by an increase in scatter in agreement with previously reported results.

Diffusion Theory Applied to Tool-Life Stochastic Modeling Under a Progressive Wear Process

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Marcello Braglia ◽  
Davide Castellano
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficient ◽  
Tool Life ◽  
Diffusion Theory ◽  
Planck Equation ◽  
Life Distribution ◽  
Wear Process ◽  
Life Distributions ◽  
Useful Life ◽  
Fokker Planck

In this paper, a novel approach to the derivation of the tool-life distribution, when the tool useful life ends after a progressive wear process, is presented. It is based on the diffusion theory and exploits the Fokker–Planck equation. The Fokker–Planck coefficients are derived on the basis of the injury theory assumptions. That is, tool-wear occurs by detachment of small particles from the tool working surfaces, which are assumed to be identical and time-independent. In addition, they are supposed to be small enough to consider the detachment process as continuous. The tool useful life ends when a specified total volume of material is thus removed. Tool-life distributions are derived in two situations: (i) both Fokker–Planck coefficients are time-dependent only and (ii) the diffusion coefficient is neglected and the drift is wear-dependent. Theoretical results are finally compared to experimental data concerning flank wear land in continuous turning of a C40 carbon steel bar adopting a P10 type sintered carbide insert. The adherence to the experimental data of the tool-life distributions derived exploiting the Fokker–Planck equation is satisfactory. Moreover, the tool-life distribution obtained, when the diffusion coefficient is neglected and the drift is wear-dependent, is able to well-represent the wear behavior at intermediate and later times.

Minimal distributions in a stochastic partial ordering and bounds for Gaussian processes

1983 ◽  
Vol 20 (03) ◽  
pp. 529-536
Author(s):  
W. J. R. Eplett
Keyword(s):  
Gaussian Process ◽  
Gaussian Processes ◽  
Partial Ordering ◽  
Boundary Crossing ◽  
Conditional Probabilities ◽  
Life Distribution ◽  
Life Distributions ◽  
Bounded Below ◽  
Crossing Probabilities

A natural requirement to impose upon the life distribution of a component is that after inspection at some randomly chosen time to check whether it is still functioning, its life distribution from the time of checking should be bounded below by some specified distribution which may be defined by external considerations. Furthermore, the life distribution should ideally be minimal in the partial ordering obtained from the conditional probabilities. We prove that these specifications provide an apparently new characterization of the DFRA class of life distributions with a corresponding result for IFRA distributions. These results may be transferred, using Slepian's lemma, to obtain bounds for the boundary crossing probabilities of a stationary Gaussian process.

Fatigue Reliability Functions in Semilogarithmic Coordinates

1991 ◽  
Author(s):  
Vladimir A. Avakov
Keyword(s):  
Fatigue Life ◽  
Coordinate System ◽  
Strength Distribution ◽  
Fatigue Reliability ◽  
Life Distribution ◽  
Similar Transformation ◽  
Asymptotic Type ◽  
Life Distributions ◽  
Strength Distributions

Abstract In the previous publication [2], the transformation between fatigue life and strength distribution was established using double-logarithmic coordinate system (lnN-lnS). Here, a similar transformation is established using a semi logarithmic (lnN-S) coordinate system. With the aid of the developed orthogonal relations, lognormal, Weibull and three-parameter logweibull life distributions have been transformed into normal, asymptotic type 1 of smallest value, and three-parameter Weibull strength distributions, respectively. This procedure may be applied to other types of fatigue life distribution.

Tool life model for end milling steel (190 BHN)

1997 ◽  
Vol 68 (1) ◽  
pp. 50-59 ◽  
Author(s):  
M. Alauddin ◽  
M.A. El Baradie
Keyword(s):  
Tool Life ◽  
End Milling ◽  
Life Model

scholarly journals The Ringloc liner compared with the Hexloc liner in total hip arthroplasty

2009 ◽  
Vol 1 (1) ◽  
pp. 16 ◽  
Author(s):  
Olof Sköldenberg ◽  
Mats Salemyr ◽  
Olle Muren ◽  
Åke Johansson ◽  
Torbjörn Ahl ◽  
...  
Keyword(s):  
Survival Rate ◽  
Penetration Rate ◽  
Osteolytic Lesion ◽  
Femoral Stem ◽  
Clinical Results ◽  
Linear Wear ◽  
Osteolytic Lesions ◽  
Linear Wear Rate ◽  
Head Penetration ◽  
Pelvic Osteolysis

The aim of this study was to compare the 10-year survival rate, pelvic osteolysis frequency and linear head penetration rate of the Hexloc and Ringloc liners used together with a partially threaded porous and hydroxyapatite coated cup and the Bi-Metric uncemented femoral stem. The 15-year results for the cup with the Hexloc liner are also reported. We included 332 consecutive hips (166 Hexloc and 166 Ringloc) on 281 patients in the study. Revisions of prosthesis components were recorded and pelvic osteolytic lesions were assessed using radiographs and computed tomography. The linear head penetration rate was measured using the Martell method. The 10-year survival rate of the liner with revision due to liner wear and/or osteolysis as endpoint was 88% for the Hexloc liner and 98% for the Ringloc liner. The 15-year survival rate of the Hexloc liner was 67%. Pelvic osteolysis was found in 27% of the Hexloc and 19% of the Ringloc hips. After 15 years, 53% of the Hexloc hips had developed an osteolytic lesion. The linear head penetration rate was 0.16 mm/year for the Hexloc liner and 0.12 mm/year for the Ringloc liner. This paper is the first to describe the rapidly deteriorating survival up to 15 years with the old generation gamma-in-air sterilized polyethylene used in Hexloc liners. The newer Ringloc liner with the ArCom™ polyethylene has superior clinical results but a linear wear rate and frequency of osteolytic lesions that is higher than expected.

Sign in / Sign up

Export Citation Format

Share Document