Vytvorené v rámci KEGA 054TUKE-4/2016 Inovácia výučby predmetov so zameraním na automatizáciu v reakcii na požiadavky priemyslu a služieb.
Študijný materiál k predmetom PAR1 a PAR2 určený pre študijný program Automatizácia a riadenie strojov a procesov.
Garant predmetu: Katedra automatizácie, riadenia a komunikačných rozhraní
The textbook Kinematics is for students of the Bachelor’s study programs Mechanical Engineering (study branch Mechanical Engineering), Management of Technical and Environmental Risk in Mechanical Engineering (study branch Mechanical Engineering), Automobile Production Technology (study branch Production Technology), Management and Innovations of Mechanical Engineering Production (study branch Production Technology), and Prosthetics and Orthotics (study branch Biomedical Engineering) for a full-time and also part-time study of the subject Kinematics and Technical Mechanics.
The textbook covers the main areas of the subject. Each chapter begins with a survey of the topic followed by sample problems and their solutions.
The textbook is divided into six chapters. Each of the chapters contains appropriate and useful sample problems. The students are expected to have a thorough understanding of Statics, and related parts of Physics and Mathematics. The explanations and the concepts of kinematics are adjusted to the content of the following textbook – Dynamics. The individual chapters deal with kinematics of a point, body, systems of bodies, and kinematics of synchronous motions.
The textbook aims not only to provide students with a theoretical base of Kinematics, but also to learn them how to apply it in the basic cases of engineering practice.
In this publication are grouped the basic knowledge of fluid mechanics and thermodynamics that enable students to understand basic processes in liquids and gases.
Chapter describes definition of biomedical engineering, its subdisciplines and potential
activities of biomedical engineer. Second half of the chapter includes current clinical and research
progress and prognosis for the future in this field.
Although what is included in the field of biomedical engineering is considered by many to be
quite clear, there are some disagreements about its definition. For example, consider the terms
biomedical engineering, bioengineering, and clinical (or medical) engineering which have been defined
in Pacela's Bioengineering Education Directory [Quest Publishing Co., 1990]. While Pacela defines
bioengineering as the broad umbrella term used to describe this entire field, bioengineering is usually
defined as a basic research-oriented activity closely related to biotechnology and genetic engineering,
i.e., the modification of animal or plant cells, or parts of cells, to improve plants or animals, or to
develop new microorganisms for beneficial ends. In the food industry, for example, this has meant the
improvement of strains of yeast for fermentation. In agriculture, bioengineers may be concerned with
the improvement of crop yields by treatment of plants with organisms to reduce frost damage. It is
clear that bioengineers of the future will have a tremendous impact on the quality of human life. The
potential of this specialty is difficult to imagine.
In reviewing the above-mentioned terms, however, biomedical engineering appears to have the most
comprehensive meaning. Biomedical engineers apply electrical, mechanical, chemical, optical, and
other engineering principles to understand, modify, or control biologic (i.e., human and animal)
systems, as well as design and manufacture products that can monitor physiologic functions and
assist in the diagnostics and treatment of patients. When biomedical engineers work within a hospital
or clinic, they are more properly called clinical engineers.
Biomedical engineering is a discipline that advances knowledge in engineering, biology and medicine,
and improves human health through cross-disciplinary activities that integrate the engineering
sciences with the biomedical sciences and clinical practice. It includes:
1. The acquisition of new knowledge and understanding of living systems through the innovative
and substantive application of experimental and analytical techniques based on the
2. The development of new devices, algorithms, processes and systems that advance biology
and medicine and improve medical practice and health care delivery.
The notion "culture" comes from Latin, and it means a summary of material and spiritual results of human activity. Therefore, if we talk about "culture safety, it will mean a summary of all human activities, which create conditions for safe work, and life, in the Man - Machine - Environment system. A prerequisite to implement safety culture is the creation of such conditions, when safety and health protection means a joint task of employers and employees on any level of business management. Accepting this principle has to be conditioned by the fact that health protection has the highest priority in any society and in any sphere of people's life. Safety culture in society also includes safety of technical devices. Great achievements have been recently seen in this field. It is not possible to separate workplace safety from safety of technical devices. Both of these fields are managed from the same place, which deliver together with management of environment protection by a synergic effect the significant economic contribution for the business. Let this be held - Safety is the preferred goal or Safety first.
Safety is defined as a feature of an object, e.g., machine, technology, activity not threatening people, nor the environment. Analyses used to evaluate the complete safety of an object take into account both the aspects of safety of technical systems, and occupational health and safety. This definition allows us to clearly formulate goals and tasks in the field of occupational safety management. These include all activities related to carrying out and stating the threat extent. When assessing threat extent, as a negative event, it is necessary to state the possibility of its occurrence and assess the extent of possible consequences due to the effect of a negative event, i.e. assess the risk. Then it is necessary to assess if the risk lies within an acceptable extent. In case the risk is higher than the acceptable risk, then it is necessary to execute measures to decrease it or to completely eliminate. The complex of these activities might be included in the occupational safety management system as its subsystem of risk control, risk management.
Progress in the field of occupational health and safety.
New technologies and designs of machines are distinguished by a high level of complexity and get constantly more complex. Nevertheless, things such as their effect on the environment, ergonomic requirements and technical solutions to eliminate a breakdown of human factor are taken into account.
Development trends in technology as a part of an intensifying progress of society in the world do not expect to use only new management systems, shared functional interconnection of classic engineering constructions with IT, and therefore new machine designs, new materials (especially nonmaterial’s) but, naturally, their safe utilization having regard for the environment. It often happens that as early as at the stage of development and design of new types of machines new solutions which might cause damage during operation, i.e., bear risks, come up due to the lack of information about actual operational conditions as well as due to a missing detailed risk analysis.
Stabilized condition of the natural environment that existed millions of years before the first forerunners of man appeared on the earth, are slightly starting to change as unstabilized, now. Natural natural equilibrium is disturbed by human activities. The man has the strongest and most productive tool - his brain and the ability to think. This human ability is further enhanced by a highly effective mutual communication between people. Thus, the fruits of intellectual labor of man as an individual spread faster and realize quicker. Unlike other animals and plants he does not draw from their surroundings just as much dire need for your life, but he has created for himself great demands, that is called as living standard.
As part of standard of living man puts on his environment requirements, which would be like an animal - as a part of the natural environment - not has to ask. This includes technical stuff (cars, electronics, etc.) and various instruments, apparatus,which can enable and facilitate to human an existence in the man-made environment. One also calls for the provision of its affairs and services, increasing the comfort of living and housing - apartments, furniture, white goods, home appliances, financial services and advisory nature, government services, which are related to the demographic jurisdiction.
The basic point of functioning of such an artificial environment and human civilization is the ability to produce for themselves the objects, used for satisfy/meeting of their demands and needs. This ability is important from the reason that the civilization is actually parasited on the nature of the planet, which is not able to meet all the requirements of civilizationin in its perfection.
Human society after this finding has created the ability to produce and started abusing nature only as "the infinite reservoir of raw materials and energy." Only in the recent decades, people came to that the nature has in many ways has reached a stage where, unable to regenerate itself. The resilience of nature is perfect, but it is also adapted to the rapidly changing and wide-ranging adverse effects. Nature is able to regenerate, but it needs a longer time that the dynamic human society is unable to provide.
The creating of a new "green" attitude of human to environment is very difficult, but it is necessary task to be understood as a long-term process, which must be touch by each individual and his personality. This process is closely linked with the social and economic life of society, that requires theoretical and emotional adaptation, as well as practical creative activity. It touches not only the attitudes of man to nature, but also to an artificial environment and other people. Attitudes to the reality are changing and creating at every person in the course of his lifetime, depending on the situation changes in the environment. Education for environmental protection must therefore have a lifelong character. If it must be established a harmonious relationship in the future between man and his environment, it is necessary to prepare the basic assumptions today.
To enable us to develop our own ideas and our relationship to nature and to living, it is necessary to know the basic ecological and environmental terms, to have knowledge of relations between individuals, populations and communities of living organisms and environmental influences on the formation and time for creating of equilibria and for these complex relationships. All this knowledge include inside the subject "Introduction to Environmental Science". Graduated student of technical university should has be familiar with the ecological substance of the contemporary world's global approach. The task of the subject is to show the connection with an ecological patterns with the study branch and the principles of the global and systemic substance of the contemporary world, based on mutual relations, structures. The result of subject studymust be applying of obtained knowledge into engineering solutions, so that the human population shoule be protected from the adverse effects of the environment and at the same time to ensure the sustainable development of the world. This condition requires not only legislation and the need for global action to protect the environment, but also ensure of harmonization, the stability of the natural environment and man in it.
Distribution function in terms of quality means adjusting the structure of supply to demand structure. The functions include: transport, storage, business processing (sorting, packing), process changes of production assortment to trade assortment, sale of products to dealers and other users or consumers.
The other distribution functions result from its perception as a dynamic marketing element. To a certain level neutral element – distribution apparatus influenced by technology, economy and demographic changes and legislation factors seems to be an active element. Nowadays, distribution, besides classical functions has to have innovative function, too. This function is linked to the classical functions by application of new technical and commercial view, new methods and conceptions. New methods are related to various distribution fields, mainly [ ]:
technology and technique equipment of material processing, resp. application of logistics rules into the real practice of economic life, e.g. containerization, palleting, supplies optimization, shops and interims building,
techniques of products and material fractioning, grouping and treatment which means packaging, protective films, new methods of packing,
sales methods – sales over the phone, catalogue sale,
market conditions survey, study of business activities means with the use of research panels of advertising, publicity, public relations, brands creating, information about customers,
coordinating techniques, use of coordinating new methods supply and warehouses, checking and financial coordination.
From the above mentioned the basic functions of distribution logistics can be defined:
spatial balancing – overcome the distance between supplier and buyer,
time balancing – eliminate the disbalance caused by demand changes,
amount balancing – commissioning, resp. products completion for expedition to the customer,
assortment balancing – so called cross-docking.
In general, the objective of logistics is optimization of costs-performance relations. In relation to distribution, the main objective of logistics is to minimize the costs related to distribution along with sustaining high quality of customer service. The objective can further be specified in the following points:
meet the customer needs to the maximum – delivery flexibility,
deliver the product to the proper place,
invoice adequate price,
provide excellent customer service,
meet delivery dates – delivery reliability,
provide delivery readiness and promptness,
minimize costs of distribution system operation.
The students are assumed to have a thorough understanding of Statics, Kinematics, and
connected parts of Physics and Mathematics. Individual chapters deal with particle dynamics, rigidbody
dynamics, dynamics of systems of rigid bodies and vibration of systems of rigid bodies.
The textbook is aiming not only to provide the students with the theoretical base of Dynamics,
but also to learn them how to apply it in the basic cases of engineering practice.
mass property. It exists in two forms - substance and field of force. Mass is meant as objective reality, independent for consciousness.
Operation of energetics equipments are connected with converting one form of energy or one type of energy to another form or type of energy.
In general, we can consider for each specific machine properly configured system mechanisms that allows to transform input energy into mechanical work, part of which will be used in the form of useful work to implement certain specific activities.
Production machines are machines designed to process materials, respectively, semi-finished products into the desired shape, dimensions and surface quality of various physical, chemical, thermal and other processes. The production machine is usually replaced human energy needed to draw relevant motion drives. The hallmark of the production machine is guiding the tool mechanism.
Intermediate product may be casting, forging, molding, clipping, etc. Processing of materials or semi-finished products or components for the manufacture of machinery concerned mostly metal or plastic parts and products and runs either without separation of parts of the material, or separating parts of the material, possibly adding additional material, semi-finished products or components.
Summary and sequence of movements necessary for production machines processing one product (part number) or several products (components) at the same time is called the duty cycle. If this duty cycle controlled automatically, it is an automatic working cycle.
In order to have a production machine immediately processed material (the blank ) to a specific component or product often requires a range of extra facilities , such as facilities for loading blanks and tools to production machines, equipment for replacement (the operational handling equipment ) equipment for the elimination of technological waste and the like. Together with them, constitutes a production machine the technological workplace.
Production machines can be divided in several respects. Basic Classification is clear from the very nature of the processing material into the desired shape, dimensions and surface quality. From this perspective, we divide production machines:
Foundry machines, which process the material in molds. This includes machines for free (including gravity) casting, die casting machines and machines for processing plastics.
Welding machines, which process raw or adding material components in their coupled or burning, or firing in separating parts.
Forming machines, which work either without separation of parts of the material, or it separates cutting or die cutting. Forming can be carried out either hot or cold. Critical temperature by re-crystallization the molded metal is crucial. Forming may be volume or area. According to the movement of the tool, method of work and type of drive is forming machines divided further:
• Mechanical presses that work with rectilinear movement of the tool, peaceful pressure and which is usable strength depends on the tool path;
• Hydraulic presses that work a peaceful pressure as straight line motion of the instrument; usable power is not dependent on the tool path;
• Hammers and other machine tools working with the energy of each census strokes (strokes) and the straight line motion of the instrument;
• Machines with rotary motion (rolling mills, bending, bending and straightening machines, forging rolls, rolling the volume forming, thread rolling machines;
• Scissors that work with either rectilinear or rotary movement of the tool;
• Special forming machines, such as machines with straightforward pulsating effect active members in the radial forming, pulse machines operating at very high speeds active member riveting machines for joining of parts and the like.
Metal cutting machines that separate the material in the form of chips. Depending on how a tool machine tool works can be divided into:
• Machine tool with a certain geometry, where we include machine tools with the main rotary cutting motion (lathes, drilling machines, boring machines, milling machines) and machine tools with the main cutting motion rectilinear (planing and shaping machines, broaching machines and transfer);
• Machine tool with an indefinite geometry tool, where we include especially machine tools for finishing operations (grinding, honing, lapping);
• Machine tool with non-conventional machining method, which include, for example super finishing machines, EDM machines, electrochemical equipment, and machines working with electron beam, laser, plasma, water jet, etc.
The manufacturing machine could meet the needs of its users , it must have a certain technical level , work relatively long time without faults and all at an affordable price. Therefore, the essential requirements that are imposed on production machines in general are : • Productivity - the amount paid in respect of production machine for a certain time unit , • Working accuracy - the closeness of the machine built in part with the theoretically flawless model (drawings),
• Reliability - ability to perform a specified period required functions while maintaining operating parameters according to technical conditions,
• Economic efficiency - the ability of the minimum input (capital) and operating (energy, maintenance, repair, etc.) cost more than meet the needs of the customer in meeting its production goals.
Meet these basic requirements is subject to the other partial requirements that must be met to the maximum extent possible production machinery manufacturers.
The current global economic situation carries with it many risks and changes even across a broad spectrum of engineering production . Many manufacturing programs completely disappeared and production facilities built for their implementation becomes redundant. Newly emerging manufacturing programs are adopted by today's investors with feelings of significant risks and uncertainties. This is also evident from the ever more rapidly advancing globalization, which leads to liquidation of many local traditional products and transferring them to other regions with new terms and conditions. Therefore, today's investors put such emphasis on flexibility, re-configurability technological landscape and new production vehicles and regrouping within manufacturing cells, flexible manufacturing systems and lines.
The decreasing number of pieces required production machinery and total precarious economic situation influencing the technological requirements for newly developed machines and their structural design. Individual requirements overlap, but nevertheless we have specified the ones that currently have a general application which affect trends in manufacturing construction machinery.
Machines and machinery specified for material transport and handling are the representatives of an important and attractive part of the mechanical engineering. Design of these machines integrates knowledge and skills from the various areas of the mechanical engineering, as well as from other industrial branches.
The transport and handling machines are representing a specific area in the framework of the whole large spectrum of the engineering production. Machines and machinery belonging to the transport and handling technology create an unavoidable integrated part of all branches in the industrial production. There is one special characteristic feature of these machines: despite of a fact that they are occurring in almost all operations of technological processes, in production and assembly procedures within the frame of a global production chain in the various industrial branches (e.g. in the engineering, building, chemistry, food processing, metallurgy, mining, power supply, etc), the transport machines are not able to increase the qualitative characteristics or operational properties of the final products, neither the value in use of them. However, an implementation of the transport and handling procedures into the manufacturing process is resulting in rising of the investment and production costs, as well as other expenditures. The statement of this fact seems to be a paradoxical phenomenon at a first sight, but this relevant reality emphasizes importance of a reasonable choice of the suitable transport and handling equipment, together with a correct decision-making in relation to the selection of a concrete material handling application. The choice of a concrete material handling technology is influencing not only the design and technological dispositions of a certain production process, but it is impacting also the economical aspects of the industrial production, namely the investment and operational costs and as a final result, the ultimate price of the given product.
There is well-known a statistical fact, which is presented often among the professional community, that almost one third of all employees, who are working in the industrial area, is employed in the branch of material transport or handling and one fifth of the total input production costs are spent for realisation of the transport or handling operations. These facts are typical for economies in the countries with a well-developed, advanced industrial production. Of course, such numerical data are presented only for guidance; they are varying according to the concrete kind of the industrial branch, but in some way or other they underline significantly a relevancy of the transport and handling machinery taking into consideration the technical and operational aspects together with the economical criteria.
The spectral variability of the transported materials depends on their mechanical and physical properties primarily with respect to the state of matter of them and afterwards the additional material attributes are specified according to other criteria in details.
A sufficient amount of information describing important characteristic features of the transported material enables to propose an optimal transport-handling machine or machinery, which is suitable for the given purpose, considering all relevant constructional and operational aspects or which is able to optimise projection process of the global transport-handling chain in the given real situation.
It is also necessary to dispose of a large information database covering the whole extensive spectrum of the machines and machinery specified for the transport and handling purposes in order to undertake qualified decisions in the projection process of the transport and handling systems.
The practical everyday experiences are providing a lot of very expensive lessons for many designers and developers about an uncompromising fact that an inconsequent knowledge or neglecting of the mechanical and physical properties of the transported materials, as well as disrespect of the operational and constructional characteristics of the transport machines can doom the project already in its preparative phase. Afterwards, the final calamitous result is realisation of an incorrect final technical solution. The real consequence of such unfavourable situation is a partial or total malfunction of the transport-logistic chain, together with following economical losses.
We would like to express our gratitude to prof. František Trebuňa for his support and to our colleagues Ing. Róbert Huňady and Ing. Martina Znamenáková for their help in drawing illustrations.
Metal forming includes a large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces. Deformation results from the use of a tool, usually called a die in metal forming, which applies stresses that exceed the yield strength of the metal. The metal therefore deforms to take a shape determined by the geometry of the die. Metal forming dominates the class of shaping operations as the deformation processes.
Stresses applied to plastically deform the metal are usually compressive. However, some forming processes stretch the metal, while others bend the metal, and still others apply shear stresses to the metal To be successfully formed, a metal must possess certain properties, Desirable properties for forming include low yield strength and high ductility, These properties are affected by temperature. Ductility is increased and yield strength is reduced when work temperature is raised. The effect of temperature gives rise to distinctions between cold working, warm working, and hot working. Strain rate and friction are additional factors that affect performance in metal forming. We examine all of these issues in this chapter, but first let us provide an overview of the metal forming processes.
Mechanical engineering production is currently characterized by increasing complexity of products, greater variability of the products, increasing competition and shortening of innovation cycles. The main objective of mechanical engineering is to deliver a high quality product to the market in the shortest time with low total costs, which is determined by using the various technologies in the production of these components. This textbook describes the technology of casting, welding and surface treatment, which are the fundamental processes of mechanical engineering technologies. In these production processes the effect of mechanical and thermal energy change the materials into final products or semi-products for further processing.
The technological casting processes are the manufacturing processes, during which the use of the heat energy changes the input metal materials on semi-products and then the cutting operations are used to finish them in to the final products. The production of difficult shaped products of machinery and technological equipment by classical mechanical machining, forming, welding etc. becomes unprofitable from today's perspective of the consumption of expensive materials, energy and high labour content. It is therefore an effort to replace these technologies casting parts.
Welding is a technology of joining two or more meltable materials with a local melting, mixing and subsequent cooling. Welding is a non-demountable joining method of materials with using a focused heat source or the pressure, with or without using of the filler material, usually with similar composition as the joined materials. Among the welding process we also include welding-on, brazing and soldering, which are modifications of welding. The welding may be used for production of difficult appliances, which cannot be realized by other technology at all. Renovation and repairing of components, improving of their properties and extending the lifetime of products by welding-on brings the large economic impact to the industry.
The surface treatment is a summary of work procedures, which a surface part is cleaned, polished or improved by deposition of layers and coatings. It is the last finishing process in the processing of engineering materials. The task of surface treatment is to protect and extend the lifetime of components and products or provide their aesthetic and hygienic properties.
This textbook contains and provides the basic information to students about mechanical engineering technologies such as casting, welding and surface treatment used in the production of components. It is destined to foreign and domestic students of study programs at the engineering faculties and students of other faculties with study programs containing mechanical engineering technology.
Elasticity and strength is a part of mechanics, which is the oldest branch of science. Mechanics was developed in the frame of physics and it was a fundament for development of physical sciences. The knowledge attained in this scientific branch was applied also in other scientific branches and vice-verse in the elasticity and strength the knowledge of philosophy, mathematics etc. is used. Philosophy served and still serves primarily the function of specialized general theory and scientific methodology and it is a theoretically-methodological base of elasticity and strength.
The main objective of strength and elasticity is to investigate state of internal forces and deformations of bodies and their mutual relations as a consequence of external forces. Every body exerted to influence of external forces or change of temperature changes in general its shape and dimensions – it undergoes the deformation. The deformation is result of shifting of individual parts of body. Stabile position of body parts before loading is a result of absence of resulting internal forces that act between them. Internal forces maintaining unloaded body in solid state are not subject of elasticity and strength theory, because they do not depend imminently on external influences. On the other hand, it deals with so-called complement internal forces which under external load acting on the body prevent mutual shifting of body parts and they endeavor to return them to the position they occupy before deformation. Complement internal forces (in the next internal forces) are able to remove or diminish deformations caused by external influences in case they do not act further.
Elasticity is an ability of solid bodies to return to their original shape after removing external loading.
Strength is an ability of structural element to carry out loading without failure.
Stiffness represents the extent of structural element to resist deformation in response to an applied external force.
Stability is ability of structural element to preserve initial state of elastic equilibrium.
The objective of elasticity and strength is determination of relations between external loading and dimensions of carrying element made of material of given properties that ensure its safety with respect to structural damage during operation. The strength has to be ensured during operational loading. The measure of strength is a stress level. Stress is a measure of intensity of internal forces. Choice of material and dimensions has to be in accordance with the conditions of its economical using.
Technical standardization is a main assumption for fluent organization of mass
production, but also it is an easement for unified work of constructers.(is the process
of formulating and applying rules for an orderly approach to a specific activity for the
benefit and the cooperation with all concerned) For this, a constructer does not need
to deal with questions solved by specialists/expert, e.g. surface roughness, material,
tolerance, operation process, service methods, etc.
Technical standardization implements and asserts science results even practical
experiences in a given sphere, that lead to increasing technical and economic level
of production and products.
Technical standards are complex of appropriate provisions designed to be used as a
rule (set o technical definitions and guidelines). They are discussed, approved and
promulgated by prescribed procedure. They specify operations and procedures,
parameters of products, necessary documentations for production and products.
Technical standards deal with raw materials, materials, semi-products, operation
process, physical and other material characteristics, parameters, units, terminology,
symbols, drawings, calculating methods etc. According to application field, technical
standards are divided into:
· International standards: mostly recommendation character; they are
implemented by assuming to national standard.
International interest in technical standardization began in 1926 in Geneva by
establishing of International Standard Association, lately in 1946 it transformed
into International Standard Organization. By International Standards assigned
for worldwide needs/requirements, there are also International Standards
originated by group of states or regional economic organizations (e.g.
standards originated in the EU)
· National standards (STN – Slovak Technical Standard) – national validity;
define products, proceedings and general technical concerns by branches and
departments. They are accredited/approved, promulgated and issued by
ÚNMS SR in Bratislava, that established SÚTN as its part. The main function
of department is creation of new National Standards in Slovak republic.
· Departmental standards: valid for all departmental organizations; define
products, proceedings and general technical concerns by given department. In
Slovak Technical Standard system, they were substituted/replaced by
Corporate standards or National standards.
· Corporate standards: only corporation validity; for chosen and used objects
or proceedings within the corporation.
Structure-sensitive properties like strength, ductility or toughness depend critically on things like the composition of the metal and on whether it has been heated, quenched or cold formed. Alloying or heat treating work by controlling the structure of the metal. Table 1.1 shows the large range over which a material has structure. The bracketed subset in the table can be controlled to give a wide choice of structure-sensitive properties.
When selecting a material for an engineering application, a primary concern is to assure that its properties will be adequate for the anticipated operating conditions. The various requirements of each part or component must first be estimated or determined. These may include mechanical characteristics (strength, rigidity, resistance to fracture, or the ability to withstand vibrations or impacts) and physical characteristics (weight, electrical properties, or appearance), as well as features relating to the service environment (ability to operate under extremes of temperature or resist corrosion).
The selection of an appropriate engineering material is then based on a comparison of the established design requirements and the tabulated or recorded results that describe how common materials responded to various standardized tests. Test data are usually readily available, but it is important that they be used properly. It is important to consider which of the evaluated properties are significant, how the test values were determined, and what restrictions or limitations should be placed on their use. Only by being familiar with the various test procedures, their capabilities, and their limitations can one determine if the data are applicable to any particular problem.