Environment Metal Fatigue In Engineering Stephens Pdf


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Metal Fatigue in Engineering - Free ebook download as PDF File .pdf), Text File Dr. Stephens has published more than papers on fatigue and fracture. Bannantine, J., Corner, Handrock, Fundamentals of Metal Fatigue Fatemi, A., Stephens, A.A., Fuchs, H.O., Metal Fatigue in Engineering, John. Metal Fatigue in Engineering Ralph I. Stephens, Ali John Wiley & Sons Ralph I. Stephens, Ali Fatemi, Robert R. Stephens, Related PDF Books.

Metal Fatigue In Engineering Stephens Pdf

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Request PDF on ResearchGate | On Jan 1, , RI Stephens and others published Metal Fatigue in Engineering. METAL FATIGUE IN ENGINEERING Second Edition. RALPH I. STEPHENS Professor, Mechanical Engineering Department The University of Iowa. ALI FATEMI. cittadelmonte.infoations.2edition. Fracture & Fatigue - Fundamentals of Metal Fatigue - Bannant. Fundamentals of Metal Fatigue Analysis.

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An example of an area where excess deformation with appreciable plasticity has been used success- fully in design is in the ground vehicle industry. Table 1. Temperatures can vary from cryogenic with rocket motor fuels.

Mechanical failures involve an extremely complex interaction of load. How- ever. The loading duration may range from centuries to years. Loads may be monotonic. The interaction of load.. Corrosive environments can range from severe attack with automobile engine exhaust. Excess deformation or yielding is probably the most commonly studied failure mode and is based upon the maximum shear stress criterion or the octahedral shear stress energy of distortion criterion.

Temperatures may be isothermal or variable. Creep failures have occurred in gas turbine engine blades due 2. This c. These have been significantly overcome by using single- 3. Transcrystalline cleavage and intercrystalline fracture ship propeller shafts. Buckling-elastic or plastic The pin is designed to restrain the throttled successful uses of components and structures is minimal. Ductile fracture involves significant plas.

Examples are automobile steering linkage. Thermomechanical steels and causes intercrystalline cracking that can lead to brittle fracture. Stress corrosion cracking environmental assisted cracking ling failure can be induced by external loading or thermal conditions and can Examples of stress corrosion cracking occur in many brass e. This failure mode has resulted from the quenching operation 7. Creep-excess deformation or fracture or ambient temperature. Impact or dynamic loading conditions that create high strain rates in metals tend to 1.

Hydrogen embrittlement is most susceptible in high-strength 2. Fatigue-repeated loading columns and thin sheets subjected to compressive loads. These f. Creep and failures is enormous. They include everyday simple items ticity and is associated with high-energy absorption.

Creep-fatigue 1. Wear-many possible failure mechanisms many different crack nucleation and crack growth behaviors.

The replacement prostheses. Ductile fracture-substantial plasticity and high-energy absorption to centrifugal forces. No exact percentage is available. Wear failures 9. Corrosion by itself a. Relaxation is primarily responsible for loss of residual 4. Combinations of a to g This type of fracture has occurred in SAE grade 8 bolts used in truck frame connections.

At least half of all mechanical failures are due to rollover protection systems ROPS to protect operators during rollover acci. Constant or variable amplitude loading interaction is called stress corrosion cracking SCC or environmental assisted d.

The different aspects of fatigue listed in Table 1. Fretting fatigue failures occur even without use due to residual stresses and corrosive environ- g. Excess deformation-elastic. Failure by excess deformation may also be elastic. An example of a controlled impact fracture involves the catapult pin used on aircraft Even though the number of mechanical failures relative to the number of carriers in launching aircraft.

Brittle fracture contains little macro or micro and structures involving ground vehicles. A comprehensive study of the cost of fracture in the relaxation of metals are most predominant at elevated temperatures. Wear occurs at all temperatures and includes 8. Buck- Isothermal ment interaction. Relaxation-loss of residual stress or external loading brittle fracture. Crack growth can occur due to interac- b. These failures are most dominant in Impact or dynamic loading-excess deformation or fracture stress and loss of external load that can occur in bolted fasteners at elevated 5.

Brittle fracture-little plasticity and low-energy absorption crystal turbine blades. Fatigue crack nucleation involves pitting and crack nucleation. The last failure mode listed in Table 1.

Corrosion fatigue components such as plumbing fixtures and ammunition shell cases. Values that are too high may lead to noncompetitive products and the fatigue limit. The consequences of [4] in showed that the yield strength in tension or compression was each type of product fatigue failure may be minimal or catastrophic. Localized slip lines and slip bands? This was the first indication that a single reversal of inelastic strain cause complete loss of control of an automobile.

Using stress analysis and testing simulate the real situation. Analysis alone is also insufficient fatigue design. A more complete fatigue design procedure may initially be more gain a general understanding.

They are only models and usually cannot take into consideration all and s. What we do know has design exist. The word development. Current product liability laws have placed special emphasis The first major impact of failures due to repeated stresses involved the on explicitly documented design decisions.

Basquin [6] in lllg and also in interdisciplinary engineering fields. Goughcl and associates contributed greatly lI1g. Ewing and Humfrey [5] used the optical microscope to engine failure may delay takeoff. Since these failures appeared to be quite different from normal Fatigue testing alone is not a proper fatigue design procedure.

The investigation emphasized 1. It can be a nuisance could change the stress-strain behavior of metals. It was recognized that railroad axles failed design procedure is needed by law. The more closely Wohler has been called the "father" of systematic fatigue testing. For reduced after applying a load of the opposite sign that caused inelastic defor- example.

Even then. BauschingerC 1I1expensive products and complex. If the fracture occurs while rounding a highway curve. Safety factors are not replacements for proper fatigue additional researchers substantiated and expanded Wohler's classical work. Wohler introduced the concept of the S-N diagram! This word has continued to be used for the normal engincering CAE software programs.

They can be simple and inexpensive or extremely complex and been learned and developed step by step and has become quite complex. These experiments were concerned with railway axle failures residual stress.

Their names are still. Fatigue failures occur in every field of engineer. He pointed out that for fatigue. In Germany during the s parts. To expensive. Many approaches to fatigue Fatigue of materials is still only partly understood. During the s and s. In Section 1. In the s. He thus became the "early father" May after more than hours of flight tests.

In Griffith g [9] published the results of his theoretical calculations the fatigue notch factor. Four days after an inspection of fracture mechanics.

LEFM and of fatigue crack growth life predictions. Solutions In the early s. Block of basic fatigue mechanisms. McAdam nents of the Comet had been made. Peterson emphasized that After much of the damage model for variable amplitude loading and established the use of the wreckage had been recovered and exhaustive investigation and tests on compo- B 10 fatigue life based upon statistical scatter for ball bearing design.

Two Comet aircraft This degradation was more pronounced in higher-strength steels. In Miner [17] formu. Griffith The Comet. Gough published a compre. In Gassner simulation of load histories on specimens. Moore e and Kommersf [8] E on Fatigue in By of high tensile strength steel and of mild steel to fatigue when.

In Palmgren [10] developed a linear cumulative in January Horger [14] showed that for aircraft gathered momentum in the United States. The cabin Haigh h [12] presented a rational explanation of the difference in the response pressure at high altitudes was 57 kPa 8. These ideas were promoted by Topper P arId lated a linear cumulative fatigue damage criterion suggested by Palmgren [10] Morrowq [ Major contributions to the subject of fatigue in the s included the which states that the average stress over a small volume at the root of the introduction of closed-loop servohydraulic test systems.

In Neuberi [15] intro. Irwin coined the term During World War II the deliberate use of compressive residual stresses "fracture mechanics. This criterion is now recognized as the Palmgren-Miner linear damage rainflow counting by Matsuishi and Endo [28] in Irwin l [21] introduced the stress intensity factor testing was prominent until closed-loop electrohydraulic test systems became Kr. If S is the nominal stress strength [18].

Fatigue failures of springs and axles. He used the concepts of notch strain analysis and residual stresses. The Comet had been tested thoroughly. The forma. Many the subject at this time. Electron microscopy opened new horizons to a better understanding the usc of an eight-step block loading spectrum for simulated testing.

Almeni [13] correctly explained the and provide overconfidence. The small fatigue cracks showed significant degradation of fatigue resistance in various water solutions. It has been used extensively in fatigue design and. Ku the notch and component geometry. This placed much more surface rolling could prevent the growth of cracks. With this classical pioneering work on the importance of cracks. Many of these brittle analysis. During the s.

All Comet aircraft of this type were taken out spectacular improvements by compressive residual stresses produced in the of service. In he published a comprehensive book on stress concentra- at fracture and a is the crack size at fracture.

The design which were more fully developed later by others. He found that the strength of tion factor. This created the to use fracture mechanics concepts in the B-1 bomber development program need to determine a retirement for cause policy.

This committee has contributed significantly to the field of fracture in the fatigue of electronic materials increased.

During this time. The initial flaw was due to fatigue. Failure due to fatigue. This practice also emphasized the increased nents or structures. These developments were strongly motivated by the aerospace catastrophic crashes of F-l11 aircraft were attributed to brittle fracture of industry but also involved other industries. Proper fatigue design includes synthesis. An extensive investigation [31] of the collapse showed that a cleavage types.

The closer the simulated analysis and testing are to the real concerning this problem. From a fatigue standpoint. Definitions became very confusing. In the spection. This brought significantly crack growth. Air Force planes. Comprehensive investigations were undertaken to understand the prob- fracture in an eyebar caused by the growth of a flaw to a critical size was lem better and to determine how best to cope with it and resolve it. The small crack problem was lated for nearly years since the time of Wohler's early work.

These princi- complex and important. Composite materials based on polymer. Proper fatigue design can reduce plex problem of in-phase and out-of-phase multi axial fatigue. The use of Many different mechanical failure modes exist in all fields of engineering. The critical these undesirable losses. Increased digital prototyping with less testing has become strated that a threshold stress intensity factor could be obtained for which a goal of twenty-first-century fatigue design.

In the nearly fatal accident of the Aloha early s emphasized variable amplitude fatigue crack growth testing in Boeing In Paris [ He developed a quantitative model showing that fatigue crack more field testing into the laboratory. This program included fatigue crack growth life considerations this meant significant investigation and application of nondestructive inspec- based on a preestablished detectable initial crack size. This failure has had a profound influence on subsequent design were attributed to advances in computer technology.

These stan- dard spectra have been used by many engineers in a variety of applications. Integrated CAE involving dynamic growth was controlled by an effective stress intensity factor range rather than simulation. Air Force issued Mil A These failures. Also responsible. The crack closure model is commonly ated the idea of restricting testing to component durability rather than using used in current fatigue crack growth calculations.

The small crack problem was noted during this time. Interest Schijve' [30] in the tion and fracture mechanics. Even though integral part of the damage tolerance requirements. West Virginia. E in to form Committee E on Fatigue and Fracture. Parisr [29] in and ceramic matrices were being developed for many different industries. After graduating from the Technical Uni. He received his engineering degrees 1. Do consider that fatigue durability testing should be used as a design then a member of the faculty at the University of Illinois from to verification tool rather than as a design development tool.

Do recognize that proper fatigue design methods exist and must be Do recognize that fatigue failures are the most common cause of mechan. John Goodman American 1. Machine Company.

Alan A. Griffith The current capability of computers and suddenly applied loads. Jesse B. Gough Kommers Society perceptively reviewed in Engineering. Moore Don't overlook the additive or synergistic effe. Kommers was involved in teaching and principles. In Herbert J. He entered the Royal Aircraft factory in and advanced 8th ed. He was 5. He had also been a mechanical engineer at Riehle Brothers Test 6.

Herbert F. His research on fatigue and engineering materials geometry. Kommers published many chief of rolling stock of the Berlin to Breslau railroad in Johann Bauschinger He was Director of the Materials and field testing. Moore was an Instructor and Assistant design. In brought him in contact with Professor Herbert F. He joined the National Physical Labora- 1. He rose from Instructor of Mechanics a. Gough returned to the scientific staff at NPL and occur in all fields of engineering. August Wohler Don't rely on safety factors in attempting to overcome poordesign proce.

He graduated from the University of Engineering at the University of Leeds. He was Professor of Civil and Mechanical g. These sketches are provided to ensure that readers are aware that the concepts.. During World War II he was Director of Scientific Research in incorporated into the overall design process when cyclic loadings are in.

He was President of the Institute of Mechanical Engineers in 3. Moore was a member of ASTM. In he organized the first International Congress on Mate- rials Testing.

Professor at the University of Wisconsin from to His stay at the University of Illinois to he was director of Imperial Railroads in Strasbourg.

Do consider that good fatigue design. From papers on the subject of fatigue. Upon retiring from the NRL in Engineering Science. Louis F. Irwin Military Science. E on Fatigue and Fracture. From to Coffin Jr. Peterson received his B. Haigh John Otto Almen He was very ogy. He was born in Kleinburg. New York. He retired in but continued to Peterson He produced many inventions from Cooper Union Institute of Technology in and an MS degree and published many scientific papers on engineering subjects.

His many contributions and awards in fatigue occurred from his active in leadership and research roles in ASME. Timothy H. He worked first on the conceptual design of turbojet engines and Stockholm.


Professor of Applied Mechanics there. He joined General Motors Research Laboratories in Many ASTM awards. Haigh was born in Edinburgh. Almen said that he turned to the study of residual stresses to he was responsible for a staff of to people from to He was the first chairman of Schenectady. George R. Both he and S. He continually provided both knowledge and leadership friction.

He joined the University of. He has pub- in Munich. He then worked on the design theory of gas turbines. Waloddi Weibull College and his Sc.

Heinz Neuber He Born in a sod cabin in North Dakota. He received his Ph. Rudolph E. During World War I he served with the n. Michigan in Coffin is a fellow of ASME.

Manson was born in Jerusalem. Topper Manson is a failures are tensile failures. He has obtained many patents and has a professor at Lehigh University until and then at the University published more than papers on plasticity. According to Almen. Bernard P.

Manson ASTM fellow. Paul C. The reviewers did not believe that the elastic stress tures.

He is currently the President of the the fatiguc crack growth rate to the stress intensity factor range was Structural Integrity Research Institute at the University of Sheffield. Assistant Director of the Institute of Research at since Schijve has received many awards for his accomplishments. Miller Army Research Laboratory's Technology Center ton He has published over mechanical behavior.

Paris National Delegate and General Secretary Jacobus Jaap Schijve Over M. They turned out to be in error. Keith J. He was Assistant Professor at the University of Washing. His idea of relating of the Faculty of Engineering. Paris of the department from to He was born in Oostburg. Scicnce Foundation He has received many prizes and awards for his accomplishments intensity factor range could be the driving force for fatigue crack growth in fatigue and fracture.

Paris returned to Lehigh University u. Topper also held the position of Professor of Mechanical Engi. While working on his Ph. He was an excellent motivator of students. Topper is a member in and rose to head the Division of Structures and Materials.

Morrow has been a member of SAE. From to he was University and was a fellow of Trinity College. Chairman from to He has received many awards for his contributions to fatigue Hulman Institute of Technology in and his M. He continues to perform Illinois. Wolf Elber He remained on the University of Illinois's professorial fatigue related research.

Elber has received awards for his outstanding achievements Lehigh University His concept was compared to data in but was not published more than papers.

Miller received his Sc. He has directed the research of many graduate students in National Aerospace Laboratory. In he joined the German fatigue properties of materials. Elber was born in Quellendorf. His major research contributions involved the promotion of tional journals.

He joined the of Paraiba. Steel Treating. Fracture Mech.

Pleasant Bridge. A Historical Perspective. What different failure modes could exist for the following components?

Tucker and S. Potter and R. McGraw-Hill Book Co. Moore and J. John Wiley and Sons. United States.. New York..

Residual Stresses and Fatigue in Metals. March Schmidt and P. Stress Concentration Design Factors. Steel Under Cyclic Variations of Stress.

National Bureau of Standards. Basic Eng. Filted Axle Assemblies by Cold Rolling. Sines and J. The Fatigue of Metals. Schijve and D. Department of Commerce. West Conshohocken. Toughness 1. Cyclic Strain Control. Stress Concentration Factors. Flaw Growth Fract. Almen and P. Equation Predicting Low Cycle Fatigue.

Tavernelli and L. Alterations of Stress. Ann Arbor. Matsuishi and T. Spccial Publication Part II. Bennett and H. Ewing and J. Brown and K. Stress-Strain Conditions. Greenwood and Son. August Presented to Japan Society of Mechanical Engineers. Horger and T. Fatigue design methods have many similarities but also differences.

Give three examples of synergistic failure modes. With these inputs. Write a one-page paper indicating why you believe that the cost of fracture in the United States as a percentage of the gross national product has increased or decreased since the survey. What failure modes exist for these choices? The differ- ences exist because a component. This is followed by durability testing. We will use the words "prediction" or "estimation" interchangeably throughout the book.

This requires selecting the configuration. Only a single end product may be desired or perhaps thousands or millions of the end product are to be produced. Obtain a copy of one of the 39 references given in this chapter and write 2. Figure 2. The flow chart clearly brings out the many aspects of fatigue design applicable to any of the above different product situations.

List the significant failure modes for a bicycle and indicate their likely loca- tions. Evaluation of service usage and success is part of the fatigue design method. Signifi- cant computer-aided engineering CAE and computer-aided manufacturing CAM capabilities may or may not be available to the design engineer.

Give four actual fatigue failures that you have been involved with or are aware of. Give an example of the following failure modes: Name three components that could be considered a simple and inexpen- sive and b complex and expensive. The product may be a modification of a current model or a new product. In all of the above situations. A second other models have been available only since the s.

If the expected loadings are not notched and unnotched members. Several analytical models can be used to determine local loadings are greater attention to the details of shape and treatments and the. These are: Reemsnyder from Bethlehem and coil spring in place of a leaf spring. The local strain-life e-N model. The two-stage method incorporates the local e-N model to obtain the life to the formation of a small macrocrack. The two-stage model..

The two lives are added together to obtain the total fatigue life. The design may have a suitable margin between the stress that corresponds to a 50 percent As noted. If part of a tool is subjected to repeated loads. We call it "design to code. Currently four by the customer or by a code authority.

For the purpose of illustration. Designing a highway bridge or a steam boiler. Depending on the purpose of the design and the different conditions dis- cussed above. We call it a "new product. For the in-house tool. We call it an "in-house tool.


The nominal S-N and a third iteration may be required to balance the conflicting factors of model uses nominal stresses and relates these to local fatigue strengths for weight or space. All four of these fatigue life models are covered modify in this book.

The local e-N model deals directly with uniformly repeated. The nominal stress-life S-N model. It was created for use by the Society 3. We call it a "new model. Setting up a major project that is quite different from past practice. This model can be considered a total fatigue life model when it is used in conjunction with information on the existing initial crack size following manufacture..

The expected loads. Designing a device. Each of the successively developed criteria still has its place. With gun tubes. Many computer software spring or a reverse gear may occur only occasionally during the life of a car.

The calculations may be based on 2. The practice fatigue tests. It requires local stresses or strains to testing passenger car suspension springs. Safe-life design may be based Many industries provide data on permissible stresses. In Unlimited safety is the oldest criterion. | Fatigue (Material) | Fracture

For example. Data on loads encountered by the parts may tude loading. The criteria for fatigue design include usage of the calculations. Examples of products in Society and the British Standards Institution. The safe life must. After the loads or load spectra have been obtained. Air Force historically many fatigue test data.

The maximum load or stress in a suspension one can analyze the fatigue worthiness of all parts. The results are verified by component designing for a finite life under such loads is quite satisfactory. For parts cycles of strokes from full rebound to maximum possible deflection subjected to millions of cycles. Here appropriate. The designer may prevent conservative. No amount of stress analysis can overcome an maximum expected stress or load.

In addition to the steps tolerance. It is used in prototypes or pilot models are used to confirm functional performance and many other industries too-for instance. In be available directly from previous models or by analogy with previous models. Whenever possible. As a rule. Examples include excessive weight of aircraft for impracticality the relation of significant stresses to loads from measurements on previous and global competitiveness for cost effectiveness.

Broken parts from previous models provide the most useful data. Predicting future loads is gated. The American Welding solely or partially on field andlor simulated testing. Tests that produce other types of failure probably have a wrong type of loading or wrong load amplitude.

A more complete and correct analysis involving iteration and optimization can provide prototypes that are closer to 2. They could not tolerate the added weight required by large safety cal considerations and additional blade testing is required. Analysis capabilities are largely dependent upon I11cchani. Multiple load paths. Engines are fail-safe only in multi engine planes. Ball bearings and roller bearings are depending upon the failure criteria chosen.

Insufficient or incorrect analysis This philosophy is a refinement of the fail-safe philosophy. Three key items are needed for successful damage-tolerant design: Air Force. Retirement for cause. In pressure vessel design. This philoso- phy originally applied mainly to airframes wings. When a component. Fatigue crack growth behavior probabilities of failure. In the case of jet factors. This practice upon analytical and test results. Residual strength is usually RPM or 90 million revolutions.

It assumes that may result in too much dependence upon testing and retesting. How much time and money should be put into each is an important engineering decision.

As a crack forms and grows under noteworthy examples of safe-life design. A landing gear is not fail-safe. Cracks need to be repaired or components 2 x expected load. Crack detection methods. This decrease as a function of oftcn given in terms of a reference load that 90 percent of all bearings are crack size is dependent upon material. This can be inadequate since all the fleet must service because they have reached their designed safe-life service life based be retired before the average calculated life or test life is attained.

Damage- tolerant design has been required by the u. Fail-safe design requires that if one part fails. For different loads or lives or for different obtained using fracture mechanics concepts. This cost is enormous since most of these is very costly and wasteful.

Thus fail-safe fatigue design criteria were developed by aircraft engi. Inspec- The margin for safety in safe-life design may be taken in terms of life e. Of course. Complete computer pro- enough to produce failures before they are detected by periodic inspection. Army has rcquired both actual firing tests and simulated laboratory Residual strength is the strength at any instant in the presence of a crack.

To allow for possible failures. The ratings for such bearings are cyclic loading. Fail-safe design recognizes that fatigue cracks may occur. The objective of fatigue testing may be to obtain the fatigue properties of materials. Since the introduction of closed-loop servohydraulic test systems in the or acceleration versus time for many diverse components.

In most other situations. It is far more demanding than the art of fatlgue testmg for research under well-controlled environmental conditions. Road simulators provide principally one. They both provide significant input to final product decisions. A probability of failure of a few percent can be permitted if failures do not endanger lives and if replacement is considered a routine matter.

One such full-scale simulated spectrum.

It lS often re- are capable of variab. They may be considered because it requires the engineer to make the test represent. Test specimens may be considered one-dimensional. Current simulation test systems Acceleration of simulation or field testing poses problems..

Fatigue testing has involved enormous differences in complexity and ex- pense and has ranged from the simple constant amplitude rotating beam test of a small specimen to the simulated full-scale. Simulated an effect on life and may not provide enough time for envlromnental aspects laboratory testing and test track or proving ground testing can be performed to operate fully.

A design based on analysis alone. All three methods have the significant advantages of less test tlme fatigue test is shown in Fig. Test systems are. The most to call these "low-damaging" rather than "nondamaging" cycles because we extensive computational requirements occur for the road input entry level. In-service inspection is also a way to avoid surprises.

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